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1/*
2 * linux/fs/buffer.c
3 *
4 * Copyright (C) 1991, 1992, 2002 Linus Torvalds
5 */
6
7/*
8 * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95
9 *
10 * Removed a lot of unnecessary code and simplified things now that
11 * the buffer cache isn't our primary cache - Andrew Tridgell 12/96
12 *
13 * Speed up hash, lru, and free list operations. Use gfp() for allocating
14 * hash table, use SLAB cache for buffer heads. SMP threading. -DaveM
15 *
16 * Added 32k buffer block sizes - these are required older ARM systems. - RMK
17 *
18 * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de>
19 */
20
21#include <linux/kernel.h>
22#include <linux/syscalls.h>
23#include <linux/fs.h>
24#include <linux/iomap.h>
25#include <linux/mm.h>
26#include <linux/percpu.h>
27#include <linux/slab.h>
28#include <linux/capability.h>
29#include <linux/blkdev.h>
30#include <linux/file.h>
31#include <linux/quotaops.h>
32#include <linux/highmem.h>
33#include <linux/export.h>
34#include <linux/backing-dev.h>
35#include <linux/writeback.h>
36#include <linux/hash.h>
37#include <linux/suspend.h>
38#include <linux/buffer_head.h>
39#include <linux/task_io_accounting_ops.h>
40#include <linux/bio.h>
41#include <linux/notifier.h>
42#include <linux/cpu.h>
43#include <linux/bitops.h>
44#include <linux/mpage.h>
45#include <linux/bit_spinlock.h>
46#include <linux/pagevec.h>
47#include <trace/events/block.h>
48
49static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
50static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
51 unsigned long bio_flags,
52 struct writeback_control *wbc);
53
54#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
55
56void init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
57{
58 bh->b_end_io = handler;
59 bh->b_private = private;
60}
61EXPORT_SYMBOL(init_buffer);
62
63inline void touch_buffer(struct buffer_head *bh)
64{
65 trace_block_touch_buffer(bh);
66 mark_page_accessed(bh->b_page);
67}
68EXPORT_SYMBOL(touch_buffer);
69
70void __lock_buffer(struct buffer_head *bh)
71{
72 wait_on_bit_lock_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
73}
74EXPORT_SYMBOL(__lock_buffer);
75
76void unlock_buffer(struct buffer_head *bh)
77{
78 clear_bit_unlock(BH_Lock, &bh->b_state);
79 smp_mb__after_atomic();
80 wake_up_bit(&bh->b_state, BH_Lock);
81}
82EXPORT_SYMBOL(unlock_buffer);
83
84/*
85 * Returns if the page has dirty or writeback buffers. If all the buffers
86 * are unlocked and clean then the PageDirty information is stale. If
87 * any of the pages are locked, it is assumed they are locked for IO.
88 */
89void buffer_check_dirty_writeback(struct page *page,
90 bool *dirty, bool *writeback)
91{
92 struct buffer_head *head, *bh;
93 *dirty = false;
94 *writeback = false;
95
96 BUG_ON(!PageLocked(page));
97
98 if (!page_has_buffers(page))
99 return;
100
101 if (PageWriteback(page))
102 *writeback = true;
103
104 head = page_buffers(page);
105 bh = head;
106 do {
107 if (buffer_locked(bh))
108 *writeback = true;
109
110 if (buffer_dirty(bh))
111 *dirty = true;
112
113 bh = bh->b_this_page;
114 } while (bh != head);
115}
116EXPORT_SYMBOL(buffer_check_dirty_writeback);
117
118/*
119 * Block until a buffer comes unlocked. This doesn't stop it
120 * from becoming locked again - you have to lock it yourself
121 * if you want to preserve its state.
122 */
123void __wait_on_buffer(struct buffer_head * bh)
124{
125 wait_on_bit_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
126}
127EXPORT_SYMBOL(__wait_on_buffer);
128
129static void
130__clear_page_buffers(struct page *page)
131{
132 ClearPagePrivate(page);
133 set_page_private(page, 0);
134 put_page(page);
135}
136
137static void buffer_io_error(struct buffer_head *bh, char *msg)
138{
139 if (!test_bit(BH_Quiet, &bh->b_state))
140 printk_ratelimited(KERN_ERR
141 "Buffer I/O error on dev %pg, logical block %llu%s\n",
142 bh->b_bdev, (unsigned long long)bh->b_blocknr, msg);
143}
144
145/*
146 * End-of-IO handler helper function which does not touch the bh after
147 * unlocking it.
148 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
149 * a race there is benign: unlock_buffer() only use the bh's address for
150 * hashing after unlocking the buffer, so it doesn't actually touch the bh
151 * itself.
152 */
153static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
154{
155 if (uptodate) {
156 set_buffer_uptodate(bh);
157 } else {
158 /* This happens, due to failed read-ahead attempts. */
159 clear_buffer_uptodate(bh);
160 }
161 unlock_buffer(bh);
162}
163
164/*
165 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
166 * unlock the buffer. This is what ll_rw_block uses too.
167 */
168void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
169{
170 __end_buffer_read_notouch(bh, uptodate);
171 put_bh(bh);
172}
173EXPORT_SYMBOL(end_buffer_read_sync);
174
175void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
176{
177 if (uptodate) {
178 set_buffer_uptodate(bh);
179 } else {
180 buffer_io_error(bh, ", lost sync page write");
181 set_buffer_write_io_error(bh);
182 clear_buffer_uptodate(bh);
183 }
184 unlock_buffer(bh);
185 put_bh(bh);
186}
187EXPORT_SYMBOL(end_buffer_write_sync);
188
189/*
190 * Various filesystems appear to want __find_get_block to be non-blocking.
191 * But it's the page lock which protects the buffers. To get around this,
192 * we get exclusion from try_to_free_buffers with the blockdev mapping's
193 * private_lock.
194 *
195 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
196 * may be quite high. This code could TryLock the page, and if that
197 * succeeds, there is no need to take private_lock. (But if
198 * private_lock is contended then so is mapping->tree_lock).
199 */
200static struct buffer_head *
201__find_get_block_slow(struct block_device *bdev, sector_t block)
202{
203 struct inode *bd_inode = bdev->bd_inode;
204 struct address_space *bd_mapping = bd_inode->i_mapping;
205 struct buffer_head *ret = NULL;
206 pgoff_t index;
207 struct buffer_head *bh;
208 struct buffer_head *head;
209 struct page *page;
210 int all_mapped = 1;
211
212 index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
213 page = find_get_page_flags(bd_mapping, index, FGP_ACCESSED);
214 if (!page)
215 goto out;
216
217 spin_lock(&bd_mapping->private_lock);
218 if (!page_has_buffers(page))
219 goto out_unlock;
220 head = page_buffers(page);
221 bh = head;
222 do {
223 if (!buffer_mapped(bh))
224 all_mapped = 0;
225 else if (bh->b_blocknr == block) {
226 ret = bh;
227 get_bh(bh);
228 goto out_unlock;
229 }
230 bh = bh->b_this_page;
231 } while (bh != head);
232
233 /* we might be here because some of the buffers on this page are
234 * not mapped. This is due to various races between
235 * file io on the block device and getblk. It gets dealt with
236 * elsewhere, don't buffer_error if we had some unmapped buffers
237 */
238 if (all_mapped) {
239 printk("__find_get_block_slow() failed. "
240 "block=%llu, b_blocknr=%llu\n",
241 (unsigned long long)block,
242 (unsigned long long)bh->b_blocknr);
243 printk("b_state=0x%08lx, b_size=%zu\n",
244 bh->b_state, bh->b_size);
245 printk("device %pg blocksize: %d\n", bdev,
246 1 << bd_inode->i_blkbits);
247 }
248out_unlock:
249 spin_unlock(&bd_mapping->private_lock);
250 put_page(page);
251out:
252 return ret;
253}
254
255/*
256 * Kick the writeback threads then try to free up some ZONE_NORMAL memory.
257 */
258static void free_more_memory(void)
259{
260 struct zoneref *z;
261 int nid;
262
263 wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM);
264 yield();
265
266 for_each_online_node(nid) {
267
268 z = first_zones_zonelist(node_zonelist(nid, GFP_NOFS),
269 gfp_zone(GFP_NOFS), NULL);
270 if (z->zone)
271 try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0,
272 GFP_NOFS, NULL);
273 }
274}
275
276/*
277 * I/O completion handler for block_read_full_page() - pages
278 * which come unlocked at the end of I/O.
279 */
280static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
281{
282 unsigned long flags;
283 struct buffer_head *first;
284 struct buffer_head *tmp;
285 struct page *page;
286 int page_uptodate = 1;
287
288 BUG_ON(!buffer_async_read(bh));
289
290 page = bh->b_page;
291 if (uptodate) {
292 set_buffer_uptodate(bh);
293 } else {
294 clear_buffer_uptodate(bh);
295 buffer_io_error(bh, ", async page read");
296 SetPageError(page);
297 }
298
299 /*
300 * Be _very_ careful from here on. Bad things can happen if
301 * two buffer heads end IO at almost the same time and both
302 * decide that the page is now completely done.
303 */
304 first = page_buffers(page);
305 local_irq_save(flags);
306 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
307 clear_buffer_async_read(bh);
308 unlock_buffer(bh);
309 tmp = bh;
310 do {
311 if (!buffer_uptodate(tmp))
312 page_uptodate = 0;
313 if (buffer_async_read(tmp)) {
314 BUG_ON(!buffer_locked(tmp));
315 goto still_busy;
316 }
317 tmp = tmp->b_this_page;
318 } while (tmp != bh);
319 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
320 local_irq_restore(flags);
321
322 /*
323 * If none of the buffers had errors and they are all
324 * uptodate then we can set the page uptodate.
325 */
326 if (page_uptodate && !PageError(page))
327 SetPageUptodate(page);
328 unlock_page(page);
329 return;
330
331still_busy:
332 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
333 local_irq_restore(flags);
334 return;
335}
336
337/*
338 * Completion handler for block_write_full_page() - pages which are unlocked
339 * during I/O, and which have PageWriteback cleared upon I/O completion.
340 */
341void end_buffer_async_write(struct buffer_head *bh, int uptodate)
342{
343 unsigned long flags;
344 struct buffer_head *first;
345 struct buffer_head *tmp;
346 struct page *page;
347
348 BUG_ON(!buffer_async_write(bh));
349
350 page = bh->b_page;
351 if (uptodate) {
352 set_buffer_uptodate(bh);
353 } else {
354 buffer_io_error(bh, ", lost async page write");
355 mapping_set_error(page->mapping, -EIO);
356 set_buffer_write_io_error(bh);
357 clear_buffer_uptodate(bh);
358 SetPageError(page);
359 }
360
361 first = page_buffers(page);
362 local_irq_save(flags);
363 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
364
365 clear_buffer_async_write(bh);
366 unlock_buffer(bh);
367 tmp = bh->b_this_page;
368 while (tmp != bh) {
369 if (buffer_async_write(tmp)) {
370 BUG_ON(!buffer_locked(tmp));
371 goto still_busy;
372 }
373 tmp = tmp->b_this_page;
374 }
375 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
376 local_irq_restore(flags);
377 end_page_writeback(page);
378 return;
379
380still_busy:
381 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
382 local_irq_restore(flags);
383 return;
384}
385EXPORT_SYMBOL(end_buffer_async_write);
386
387/*
388 * If a page's buffers are under async readin (end_buffer_async_read
389 * completion) then there is a possibility that another thread of
390 * control could lock one of the buffers after it has completed
391 * but while some of the other buffers have not completed. This
392 * locked buffer would confuse end_buffer_async_read() into not unlocking
393 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
394 * that this buffer is not under async I/O.
395 *
396 * The page comes unlocked when it has no locked buffer_async buffers
397 * left.
398 *
399 * PageLocked prevents anyone starting new async I/O reads any of
400 * the buffers.
401 *
402 * PageWriteback is used to prevent simultaneous writeout of the same
403 * page.
404 *
405 * PageLocked prevents anyone from starting writeback of a page which is
406 * under read I/O (PageWriteback is only ever set against a locked page).
407 */
408static void mark_buffer_async_read(struct buffer_head *bh)
409{
410 bh->b_end_io = end_buffer_async_read;
411 set_buffer_async_read(bh);
412}
413
414static void mark_buffer_async_write_endio(struct buffer_head *bh,
415 bh_end_io_t *handler)
416{
417 bh->b_end_io = handler;
418 set_buffer_async_write(bh);
419}
420
421void mark_buffer_async_write(struct buffer_head *bh)
422{
423 mark_buffer_async_write_endio(bh, end_buffer_async_write);
424}
425EXPORT_SYMBOL(mark_buffer_async_write);
426
427
428/*
429 * fs/buffer.c contains helper functions for buffer-backed address space's
430 * fsync functions. A common requirement for buffer-based filesystems is
431 * that certain data from the backing blockdev needs to be written out for
432 * a successful fsync(). For example, ext2 indirect blocks need to be
433 * written back and waited upon before fsync() returns.
434 *
435 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
436 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
437 * management of a list of dependent buffers at ->i_mapping->private_list.
438 *
439 * Locking is a little subtle: try_to_free_buffers() will remove buffers
440 * from their controlling inode's queue when they are being freed. But
441 * try_to_free_buffers() will be operating against the *blockdev* mapping
442 * at the time, not against the S_ISREG file which depends on those buffers.
443 * So the locking for private_list is via the private_lock in the address_space
444 * which backs the buffers. Which is different from the address_space
445 * against which the buffers are listed. So for a particular address_space,
446 * mapping->private_lock does *not* protect mapping->private_list! In fact,
447 * mapping->private_list will always be protected by the backing blockdev's
448 * ->private_lock.
449 *
450 * Which introduces a requirement: all buffers on an address_space's
451 * ->private_list must be from the same address_space: the blockdev's.
452 *
453 * address_spaces which do not place buffers at ->private_list via these
454 * utility functions are free to use private_lock and private_list for
455 * whatever they want. The only requirement is that list_empty(private_list)
456 * be true at clear_inode() time.
457 *
458 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
459 * filesystems should do that. invalidate_inode_buffers() should just go
460 * BUG_ON(!list_empty).
461 *
462 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
463 * take an address_space, not an inode. And it should be called
464 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
465 * queued up.
466 *
467 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
468 * list if it is already on a list. Because if the buffer is on a list,
469 * it *must* already be on the right one. If not, the filesystem is being
470 * silly. This will save a ton of locking. But first we have to ensure
471 * that buffers are taken *off* the old inode's list when they are freed
472 * (presumably in truncate). That requires careful auditing of all
473 * filesystems (do it inside bforget()). It could also be done by bringing
474 * b_inode back.
475 */
476
477/*
478 * The buffer's backing address_space's private_lock must be held
479 */
480static void __remove_assoc_queue(struct buffer_head *bh)
481{
482 list_del_init(&bh->b_assoc_buffers);
483 WARN_ON(!bh->b_assoc_map);
484 if (buffer_write_io_error(bh))
485 set_bit(AS_EIO, &bh->b_assoc_map->flags);
486 bh->b_assoc_map = NULL;
487}
488
489int inode_has_buffers(struct inode *inode)
490{
491 return !list_empty(&inode->i_data.private_list);
492}
493
494/*
495 * osync is designed to support O_SYNC io. It waits synchronously for
496 * all already-submitted IO to complete, but does not queue any new
497 * writes to the disk.
498 *
499 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
500 * you dirty the buffers, and then use osync_inode_buffers to wait for
501 * completion. Any other dirty buffers which are not yet queued for
502 * write will not be flushed to disk by the osync.
503 */
504static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
505{
506 struct buffer_head *bh;
507 struct list_head *p;
508 int err = 0;
509
510 spin_lock(lock);
511repeat:
512 list_for_each_prev(p, list) {
513 bh = BH_ENTRY(p);
514 if (buffer_locked(bh)) {
515 get_bh(bh);
516 spin_unlock(lock);
517 wait_on_buffer(bh);
518 if (!buffer_uptodate(bh))
519 err = -EIO;
520 brelse(bh);
521 spin_lock(lock);
522 goto repeat;
523 }
524 }
525 spin_unlock(lock);
526 return err;
527}
528
529static void do_thaw_one(struct super_block *sb, void *unused)
530{
531 while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
532 printk(KERN_WARNING "Emergency Thaw on %pg\n", sb->s_bdev);
533}
534
535static void do_thaw_all(struct work_struct *work)
536{
537 iterate_supers(do_thaw_one, NULL);
538 kfree(work);
539 printk(KERN_WARNING "Emergency Thaw complete\n");
540}
541
542/**
543 * emergency_thaw_all -- forcibly thaw every frozen filesystem
544 *
545 * Used for emergency unfreeze of all filesystems via SysRq
546 */
547void emergency_thaw_all(void)
548{
549 struct work_struct *work;
550
551 work = kmalloc(sizeof(*work), GFP_ATOMIC);
552 if (work) {
553 INIT_WORK(work, do_thaw_all);
554 schedule_work(work);
555 }
556}
557
558/**
559 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
560 * @mapping: the mapping which wants those buffers written
561 *
562 * Starts I/O against the buffers at mapping->private_list, and waits upon
563 * that I/O.
564 *
565 * Basically, this is a convenience function for fsync().
566 * @mapping is a file or directory which needs those buffers to be written for
567 * a successful fsync().
568 */
569int sync_mapping_buffers(struct address_space *mapping)
570{
571 struct address_space *buffer_mapping = mapping->private_data;
572
573 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
574 return 0;
575
576 return fsync_buffers_list(&buffer_mapping->private_lock,
577 &mapping->private_list);
578}
579EXPORT_SYMBOL(sync_mapping_buffers);
580
581/*
582 * Called when we've recently written block `bblock', and it is known that
583 * `bblock' was for a buffer_boundary() buffer. This means that the block at
584 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
585 * dirty, schedule it for IO. So that indirects merge nicely with their data.
586 */
587void write_boundary_block(struct block_device *bdev,
588 sector_t bblock, unsigned blocksize)
589{
590 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
591 if (bh) {
592 if (buffer_dirty(bh))
593 ll_rw_block(REQ_OP_WRITE, 0, 1, &bh);
594 put_bh(bh);
595 }
596}
597
598void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
599{
600 struct address_space *mapping = inode->i_mapping;
601 struct address_space *buffer_mapping = bh->b_page->mapping;
602
603 mark_buffer_dirty(bh);
604 if (!mapping->private_data) {
605 mapping->private_data = buffer_mapping;
606 } else {
607 BUG_ON(mapping->private_data != buffer_mapping);
608 }
609 if (!bh->b_assoc_map) {
610 spin_lock(&buffer_mapping->private_lock);
611 list_move_tail(&bh->b_assoc_buffers,
612 &mapping->private_list);
613 bh->b_assoc_map = mapping;
614 spin_unlock(&buffer_mapping->private_lock);
615 }
616}
617EXPORT_SYMBOL(mark_buffer_dirty_inode);
618
619/*
620 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
621 * dirty.
622 *
623 * If warn is true, then emit a warning if the page is not uptodate and has
624 * not been truncated.
625 *
626 * The caller must hold lock_page_memcg().
627 */
628static void __set_page_dirty(struct page *page, struct address_space *mapping,
629 int warn)
630{
631 unsigned long flags;
632
633 spin_lock_irqsave(&mapping->tree_lock, flags);
634 if (page->mapping) { /* Race with truncate? */
635 WARN_ON_ONCE(warn && !PageUptodate(page));
636 account_page_dirtied(page, mapping);
637 radix_tree_tag_set(&mapping->page_tree,
638 page_index(page), PAGECACHE_TAG_DIRTY);
639 }
640 spin_unlock_irqrestore(&mapping->tree_lock, flags);
641}
642
643/*
644 * Add a page to the dirty page list.
645 *
646 * It is a sad fact of life that this function is called from several places
647 * deeply under spinlocking. It may not sleep.
648 *
649 * If the page has buffers, the uptodate buffers are set dirty, to preserve
650 * dirty-state coherency between the page and the buffers. It the page does
651 * not have buffers then when they are later attached they will all be set
652 * dirty.
653 *
654 * The buffers are dirtied before the page is dirtied. There's a small race
655 * window in which a writepage caller may see the page cleanness but not the
656 * buffer dirtiness. That's fine. If this code were to set the page dirty
657 * before the buffers, a concurrent writepage caller could clear the page dirty
658 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
659 * page on the dirty page list.
660 *
661 * We use private_lock to lock against try_to_free_buffers while using the
662 * page's buffer list. Also use this to protect against clean buffers being
663 * added to the page after it was set dirty.
664 *
665 * FIXME: may need to call ->reservepage here as well. That's rather up to the
666 * address_space though.
667 */
668int __set_page_dirty_buffers(struct page *page)
669{
670 int newly_dirty;
671 struct address_space *mapping = page_mapping(page);
672
673 if (unlikely(!mapping))
674 return !TestSetPageDirty(page);
675
676 spin_lock(&mapping->private_lock);
677 if (page_has_buffers(page)) {
678 struct buffer_head *head = page_buffers(page);
679 struct buffer_head *bh = head;
680
681 do {
682 set_buffer_dirty(bh);
683 bh = bh->b_this_page;
684 } while (bh != head);
685 }
686 /*
687 * Lock out page->mem_cgroup migration to keep PageDirty
688 * synchronized with per-memcg dirty page counters.
689 */
690 lock_page_memcg(page);
691 newly_dirty = !TestSetPageDirty(page);
692 spin_unlock(&mapping->private_lock);
693
694 if (newly_dirty)
695 __set_page_dirty(page, mapping, 1);
696
697 unlock_page_memcg(page);
698
699 if (newly_dirty)
700 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
701
702 return newly_dirty;
703}
704EXPORT_SYMBOL(__set_page_dirty_buffers);
705
706/*
707 * Write out and wait upon a list of buffers.
708 *
709 * We have conflicting pressures: we want to make sure that all
710 * initially dirty buffers get waited on, but that any subsequently
711 * dirtied buffers don't. After all, we don't want fsync to last
712 * forever if somebody is actively writing to the file.
713 *
714 * Do this in two main stages: first we copy dirty buffers to a
715 * temporary inode list, queueing the writes as we go. Then we clean
716 * up, waiting for those writes to complete.
717 *
718 * During this second stage, any subsequent updates to the file may end
719 * up refiling the buffer on the original inode's dirty list again, so
720 * there is a chance we will end up with a buffer queued for write but
721 * not yet completed on that list. So, as a final cleanup we go through
722 * the osync code to catch these locked, dirty buffers without requeuing
723 * any newly dirty buffers for write.
724 */
725static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
726{
727 struct buffer_head *bh;
728 struct list_head tmp;
729 struct address_space *mapping;
730 int err = 0, err2;
731 struct blk_plug plug;
732
733 INIT_LIST_HEAD(&tmp);
734 blk_start_plug(&plug);
735
736 spin_lock(lock);
737 while (!list_empty(list)) {
738 bh = BH_ENTRY(list->next);
739 mapping = bh->b_assoc_map;
740 __remove_assoc_queue(bh);
741 /* Avoid race with mark_buffer_dirty_inode() which does
742 * a lockless check and we rely on seeing the dirty bit */
743 smp_mb();
744 if (buffer_dirty(bh) || buffer_locked(bh)) {
745 list_add(&bh->b_assoc_buffers, &tmp);
746 bh->b_assoc_map = mapping;
747 if (buffer_dirty(bh)) {
748 get_bh(bh);
749 spin_unlock(lock);
750 /*
751 * Ensure any pending I/O completes so that
752 * write_dirty_buffer() actually writes the
753 * current contents - it is a noop if I/O is
754 * still in flight on potentially older
755 * contents.
756 */
757 write_dirty_buffer(bh, REQ_SYNC);
758
759 /*
760 * Kick off IO for the previous mapping. Note
761 * that we will not run the very last mapping,
762 * wait_on_buffer() will do that for us
763 * through sync_buffer().
764 */
765 brelse(bh);
766 spin_lock(lock);
767 }
768 }
769 }
770
771 spin_unlock(lock);
772 blk_finish_plug(&plug);
773 spin_lock(lock);
774
775 while (!list_empty(&tmp)) {
776 bh = BH_ENTRY(tmp.prev);
777 get_bh(bh);
778 mapping = bh->b_assoc_map;
779 __remove_assoc_queue(bh);
780 /* Avoid race with mark_buffer_dirty_inode() which does
781 * a lockless check and we rely on seeing the dirty bit */
782 smp_mb();
783 if (buffer_dirty(bh)) {
784 list_add(&bh->b_assoc_buffers,
785 &mapping->private_list);
786 bh->b_assoc_map = mapping;
787 }
788 spin_unlock(lock);
789 wait_on_buffer(bh);
790 if (!buffer_uptodate(bh))
791 err = -EIO;
792 brelse(bh);
793 spin_lock(lock);
794 }
795
796 spin_unlock(lock);
797 err2 = osync_buffers_list(lock, list);
798 if (err)
799 return err;
800 else
801 return err2;
802}
803
804/*
805 * Invalidate any and all dirty buffers on a given inode. We are
806 * probably unmounting the fs, but that doesn't mean we have already
807 * done a sync(). Just drop the buffers from the inode list.
808 *
809 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
810 * assumes that all the buffers are against the blockdev. Not true
811 * for reiserfs.
812 */
813void invalidate_inode_buffers(struct inode *inode)
814{
815 if (inode_has_buffers(inode)) {
816 struct address_space *mapping = &inode->i_data;
817 struct list_head *list = &mapping->private_list;
818 struct address_space *buffer_mapping = mapping->private_data;
819
820 spin_lock(&buffer_mapping->private_lock);
821 while (!list_empty(list))
822 __remove_assoc_queue(BH_ENTRY(list->next));
823 spin_unlock(&buffer_mapping->private_lock);
824 }
825}
826EXPORT_SYMBOL(invalidate_inode_buffers);
827
828/*
829 * Remove any clean buffers from the inode's buffer list. This is called
830 * when we're trying to free the inode itself. Those buffers can pin it.
831 *
832 * Returns true if all buffers were removed.
833 */
834int remove_inode_buffers(struct inode *inode)
835{
836 int ret = 1;
837
838 if (inode_has_buffers(inode)) {
839 struct address_space *mapping = &inode->i_data;
840 struct list_head *list = &mapping->private_list;
841 struct address_space *buffer_mapping = mapping->private_data;
842
843 spin_lock(&buffer_mapping->private_lock);
844 while (!list_empty(list)) {
845 struct buffer_head *bh = BH_ENTRY(list->next);
846 if (buffer_dirty(bh)) {
847 ret = 0;
848 break;
849 }
850 __remove_assoc_queue(bh);
851 }
852 spin_unlock(&buffer_mapping->private_lock);
853 }
854 return ret;
855}
856
857/*
858 * Create the appropriate buffers when given a page for data area and
859 * the size of each buffer.. Use the bh->b_this_page linked list to
860 * follow the buffers created. Return NULL if unable to create more
861 * buffers.
862 *
863 * The retry flag is used to differentiate async IO (paging, swapping)
864 * which may not fail from ordinary buffer allocations.
865 */
866struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
867 int retry)
868{
869 struct buffer_head *bh, *head;
870 long offset;
871
872try_again:
873 head = NULL;
874 offset = PAGE_SIZE;
875 while ((offset -= size) >= 0) {
876 bh = alloc_buffer_head(GFP_NOFS);
877 if (!bh)
878 goto no_grow;
879
880 bh->b_this_page = head;
881 bh->b_blocknr = -1;
882 head = bh;
883
884 bh->b_size = size;
885
886 /* Link the buffer to its page */
887 set_bh_page(bh, page, offset);
888 }
889 return head;
890/*
891 * In case anything failed, we just free everything we got.
892 */
893no_grow:
894 if (head) {
895 do {
896 bh = head;
897 head = head->b_this_page;
898 free_buffer_head(bh);
899 } while (head);
900 }
901
902 /*
903 * Return failure for non-async IO requests. Async IO requests
904 * are not allowed to fail, so we have to wait until buffer heads
905 * become available. But we don't want tasks sleeping with
906 * partially complete buffers, so all were released above.
907 */
908 if (!retry)
909 return NULL;
910
911 /* We're _really_ low on memory. Now we just
912 * wait for old buffer heads to become free due to
913 * finishing IO. Since this is an async request and
914 * the reserve list is empty, we're sure there are
915 * async buffer heads in use.
916 */
917 free_more_memory();
918 goto try_again;
919}
920EXPORT_SYMBOL_GPL(alloc_page_buffers);
921
922static inline void
923link_dev_buffers(struct page *page, struct buffer_head *head)
924{
925 struct buffer_head *bh, *tail;
926
927 bh = head;
928 do {
929 tail = bh;
930 bh = bh->b_this_page;
931 } while (bh);
932 tail->b_this_page = head;
933 attach_page_buffers(page, head);
934}
935
936static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
937{
938 sector_t retval = ~((sector_t)0);
939 loff_t sz = i_size_read(bdev->bd_inode);
940
941 if (sz) {
942 unsigned int sizebits = blksize_bits(size);
943 retval = (sz >> sizebits);
944 }
945 return retval;
946}
947
948/*
949 * Initialise the state of a blockdev page's buffers.
950 */
951static sector_t
952init_page_buffers(struct page *page, struct block_device *bdev,
953 sector_t block, int size)
954{
955 struct buffer_head *head = page_buffers(page);
956 struct buffer_head *bh = head;
957 int uptodate = PageUptodate(page);
958 sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode), size);
959
960 do {
961 if (!buffer_mapped(bh)) {
962 init_buffer(bh, NULL, NULL);
963 bh->b_bdev = bdev;
964 bh->b_blocknr = block;
965 if (uptodate)
966 set_buffer_uptodate(bh);
967 if (block < end_block)
968 set_buffer_mapped(bh);
969 }
970 block++;
971 bh = bh->b_this_page;
972 } while (bh != head);
973
974 /*
975 * Caller needs to validate requested block against end of device.
976 */
977 return end_block;
978}
979
980/*
981 * Create the page-cache page that contains the requested block.
982 *
983 * This is used purely for blockdev mappings.
984 */
985static int
986grow_dev_page(struct block_device *bdev, sector_t block,
987 pgoff_t index, int size, int sizebits, gfp_t gfp)
988{
989 struct inode *inode = bdev->bd_inode;
990 struct page *page;
991 struct buffer_head *bh;
992 sector_t end_block;
993 int ret = 0; /* Will call free_more_memory() */
994 gfp_t gfp_mask;
995
996 gfp_mask = mapping_gfp_constraint(inode->i_mapping, ~__GFP_FS) | gfp;
997
998 /*
999 * XXX: __getblk_slow() can not really deal with failure and
1000 * will endlessly loop on improvised global reclaim. Prefer
1001 * looping in the allocator rather than here, at least that
1002 * code knows what it's doing.
1003 */
1004 gfp_mask |= __GFP_NOFAIL;
1005
1006 page = find_or_create_page(inode->i_mapping, index, gfp_mask);
1007 if (!page)
1008 return ret;
1009
1010 BUG_ON(!PageLocked(page));
1011
1012 if (page_has_buffers(page)) {
1013 bh = page_buffers(page);
1014 if (bh->b_size == size) {
1015 end_block = init_page_buffers(page, bdev,
1016 (sector_t)index << sizebits,
1017 size);
1018 goto done;
1019 }
1020 if (!try_to_free_buffers(page))
1021 goto failed;
1022 }
1023
1024 /*
1025 * Allocate some buffers for this page
1026 */
1027 bh = alloc_page_buffers(page, size, 0);
1028 if (!bh)
1029 goto failed;
1030
1031 /*
1032 * Link the page to the buffers and initialise them. Take the
1033 * lock to be atomic wrt __find_get_block(), which does not
1034 * run under the page lock.
1035 */
1036 spin_lock(&inode->i_mapping->private_lock);
1037 link_dev_buffers(page, bh);
1038 end_block = init_page_buffers(page, bdev, (sector_t)index << sizebits,
1039 size);
1040 spin_unlock(&inode->i_mapping->private_lock);
1041done:
1042 ret = (block < end_block) ? 1 : -ENXIO;
1043failed:
1044 unlock_page(page);
1045 put_page(page);
1046 return ret;
1047}
1048
1049/*
1050 * Create buffers for the specified block device block's page. If
1051 * that page was dirty, the buffers are set dirty also.
1052 */
1053static int
1054grow_buffers(struct block_device *bdev, sector_t block, int size, gfp_t gfp)
1055{
1056 pgoff_t index;
1057 int sizebits;
1058
1059 sizebits = -1;
1060 do {
1061 sizebits++;
1062 } while ((size << sizebits) < PAGE_SIZE);
1063
1064 index = block >> sizebits;
1065
1066 /*
1067 * Check for a block which wants to lie outside our maximum possible
1068 * pagecache index. (this comparison is done using sector_t types).
1069 */
1070 if (unlikely(index != block >> sizebits)) {
1071 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1072 "device %pg\n",
1073 __func__, (unsigned long long)block,
1074 bdev);
1075 return -EIO;
1076 }
1077
1078 /* Create a page with the proper size buffers.. */
1079 return grow_dev_page(bdev, block, index, size, sizebits, gfp);
1080}
1081
1082static struct buffer_head *
1083__getblk_slow(struct block_device *bdev, sector_t block,
1084 unsigned size, gfp_t gfp)
1085{
1086 /* Size must be multiple of hard sectorsize */
1087 if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
1088 (size < 512 || size > PAGE_SIZE))) {
1089 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1090 size);
1091 printk(KERN_ERR "logical block size: %d\n",
1092 bdev_logical_block_size(bdev));
1093
1094 dump_stack();
1095 return NULL;
1096 }
1097
1098 for (;;) {
1099 struct buffer_head *bh;
1100 int ret;
1101
1102 bh = __find_get_block(bdev, block, size);
1103 if (bh)
1104 return bh;
1105
1106 ret = grow_buffers(bdev, block, size, gfp);
1107 if (ret < 0)
1108 return NULL;
1109 if (ret == 0)
1110 free_more_memory();
1111 }
1112}
1113
1114/*
1115 * The relationship between dirty buffers and dirty pages:
1116 *
1117 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1118 * the page is tagged dirty in its radix tree.
1119 *
1120 * At all times, the dirtiness of the buffers represents the dirtiness of
1121 * subsections of the page. If the page has buffers, the page dirty bit is
1122 * merely a hint about the true dirty state.
1123 *
1124 * When a page is set dirty in its entirety, all its buffers are marked dirty
1125 * (if the page has buffers).
1126 *
1127 * When a buffer is marked dirty, its page is dirtied, but the page's other
1128 * buffers are not.
1129 *
1130 * Also. When blockdev buffers are explicitly read with bread(), they
1131 * individually become uptodate. But their backing page remains not
1132 * uptodate - even if all of its buffers are uptodate. A subsequent
1133 * block_read_full_page() against that page will discover all the uptodate
1134 * buffers, will set the page uptodate and will perform no I/O.
1135 */
1136
1137/**
1138 * mark_buffer_dirty - mark a buffer_head as needing writeout
1139 * @bh: the buffer_head to mark dirty
1140 *
1141 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1142 * backing page dirty, then tag the page as dirty in its address_space's radix
1143 * tree and then attach the address_space's inode to its superblock's dirty
1144 * inode list.
1145 *
1146 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1147 * mapping->tree_lock and mapping->host->i_lock.
1148 */
1149void mark_buffer_dirty(struct buffer_head *bh)
1150{
1151 WARN_ON_ONCE(!buffer_uptodate(bh));
1152
1153 trace_block_dirty_buffer(bh);
1154
1155 /*
1156 * Very *carefully* optimize the it-is-already-dirty case.
1157 *
1158 * Don't let the final "is it dirty" escape to before we
1159 * perhaps modified the buffer.
1160 */
1161 if (buffer_dirty(bh)) {
1162 smp_mb();
1163 if (buffer_dirty(bh))
1164 return;
1165 }
1166
1167 if (!test_set_buffer_dirty(bh)) {
1168 struct page *page = bh->b_page;
1169 struct address_space *mapping = NULL;
1170
1171 lock_page_memcg(page);
1172 if (!TestSetPageDirty(page)) {
1173 mapping = page_mapping(page);
1174 if (mapping)
1175 __set_page_dirty(page, mapping, 0);
1176 }
1177 unlock_page_memcg(page);
1178 if (mapping)
1179 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
1180 }
1181}
1182EXPORT_SYMBOL(mark_buffer_dirty);
1183
1184/*
1185 * Decrement a buffer_head's reference count. If all buffers against a page
1186 * have zero reference count, are clean and unlocked, and if the page is clean
1187 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1188 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1189 * a page but it ends up not being freed, and buffers may later be reattached).
1190 */
1191void __brelse(struct buffer_head * buf)
1192{
1193 if (atomic_read(&buf->b_count)) {
1194 put_bh(buf);
1195 return;
1196 }
1197 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1198}
1199EXPORT_SYMBOL(__brelse);
1200
1201/*
1202 * bforget() is like brelse(), except it discards any
1203 * potentially dirty data.
1204 */
1205void __bforget(struct buffer_head *bh)
1206{
1207 clear_buffer_dirty(bh);
1208 if (bh->b_assoc_map) {
1209 struct address_space *buffer_mapping = bh->b_page->mapping;
1210
1211 spin_lock(&buffer_mapping->private_lock);
1212 list_del_init(&bh->b_assoc_buffers);
1213 bh->b_assoc_map = NULL;
1214 spin_unlock(&buffer_mapping->private_lock);
1215 }
1216 __brelse(bh);
1217}
1218EXPORT_SYMBOL(__bforget);
1219
1220static struct buffer_head *__bread_slow(struct buffer_head *bh)
1221{
1222 lock_buffer(bh);
1223 if (buffer_uptodate(bh)) {
1224 unlock_buffer(bh);
1225 return bh;
1226 } else {
1227 get_bh(bh);
1228 bh->b_end_io = end_buffer_read_sync;
1229 submit_bh(REQ_OP_READ, 0, bh);
1230 wait_on_buffer(bh);
1231 if (buffer_uptodate(bh))
1232 return bh;
1233 }
1234 brelse(bh);
1235 return NULL;
1236}
1237
1238/*
1239 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1240 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1241 * refcount elevated by one when they're in an LRU. A buffer can only appear
1242 * once in a particular CPU's LRU. A single buffer can be present in multiple
1243 * CPU's LRUs at the same time.
1244 *
1245 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1246 * sb_find_get_block().
1247 *
1248 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1249 * a local interrupt disable for that.
1250 */
1251
1252#define BH_LRU_SIZE 16
1253
1254struct bh_lru {
1255 struct buffer_head *bhs[BH_LRU_SIZE];
1256};
1257
1258static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1259
1260#ifdef CONFIG_SMP
1261#define bh_lru_lock() local_irq_disable()
1262#define bh_lru_unlock() local_irq_enable()
1263#else
1264#define bh_lru_lock() preempt_disable()
1265#define bh_lru_unlock() preempt_enable()
1266#endif
1267
1268static inline void check_irqs_on(void)
1269{
1270#ifdef irqs_disabled
1271 BUG_ON(irqs_disabled());
1272#endif
1273}
1274
1275/*
1276 * The LRU management algorithm is dopey-but-simple. Sorry.
1277 */
1278static void bh_lru_install(struct buffer_head *bh)
1279{
1280 struct buffer_head *evictee = NULL;
1281
1282 check_irqs_on();
1283 bh_lru_lock();
1284 if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
1285 struct buffer_head *bhs[BH_LRU_SIZE];
1286 int in;
1287 int out = 0;
1288
1289 get_bh(bh);
1290 bhs[out++] = bh;
1291 for (in = 0; in < BH_LRU_SIZE; in++) {
1292 struct buffer_head *bh2 =
1293 __this_cpu_read(bh_lrus.bhs[in]);
1294
1295 if (bh2 == bh) {
1296 __brelse(bh2);
1297 } else {
1298 if (out >= BH_LRU_SIZE) {
1299 BUG_ON(evictee != NULL);
1300 evictee = bh2;
1301 } else {
1302 bhs[out++] = bh2;
1303 }
1304 }
1305 }
1306 while (out < BH_LRU_SIZE)
1307 bhs[out++] = NULL;
1308 memcpy(this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
1309 }
1310 bh_lru_unlock();
1311
1312 if (evictee)
1313 __brelse(evictee);
1314}
1315
1316/*
1317 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1318 */
1319static struct buffer_head *
1320lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1321{
1322 struct buffer_head *ret = NULL;
1323 unsigned int i;
1324
1325 check_irqs_on();
1326 bh_lru_lock();
1327 for (i = 0; i < BH_LRU_SIZE; i++) {
1328 struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
1329
1330 if (bh && bh->b_blocknr == block && bh->b_bdev == bdev &&
1331 bh->b_size == size) {
1332 if (i) {
1333 while (i) {
1334 __this_cpu_write(bh_lrus.bhs[i],
1335 __this_cpu_read(bh_lrus.bhs[i - 1]));
1336 i--;
1337 }
1338 __this_cpu_write(bh_lrus.bhs[0], bh);
1339 }
1340 get_bh(bh);
1341 ret = bh;
1342 break;
1343 }
1344 }
1345 bh_lru_unlock();
1346 return ret;
1347}
1348
1349/*
1350 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1351 * it in the LRU and mark it as accessed. If it is not present then return
1352 * NULL
1353 */
1354struct buffer_head *
1355__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1356{
1357 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1358
1359 if (bh == NULL) {
1360 /* __find_get_block_slow will mark the page accessed */
1361 bh = __find_get_block_slow(bdev, block);
1362 if (bh)
1363 bh_lru_install(bh);
1364 } else
1365 touch_buffer(bh);
1366
1367 return bh;
1368}
1369EXPORT_SYMBOL(__find_get_block);
1370
1371/*
1372 * __getblk_gfp() will locate (and, if necessary, create) the buffer_head
1373 * which corresponds to the passed block_device, block and size. The
1374 * returned buffer has its reference count incremented.
1375 *
1376 * __getblk_gfp() will lock up the machine if grow_dev_page's
1377 * try_to_free_buffers() attempt is failing. FIXME, perhaps?
1378 */
1379struct buffer_head *
1380__getblk_gfp(struct block_device *bdev, sector_t block,
1381 unsigned size, gfp_t gfp)
1382{
1383 struct buffer_head *bh = __find_get_block(bdev, block, size);
1384
1385 might_sleep();
1386 if (bh == NULL)
1387 bh = __getblk_slow(bdev, block, size, gfp);
1388 return bh;
1389}
1390EXPORT_SYMBOL(__getblk_gfp);
1391
1392/*
1393 * Do async read-ahead on a buffer..
1394 */
1395void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1396{
1397 struct buffer_head *bh = __getblk(bdev, block, size);
1398 if (likely(bh)) {
1399 ll_rw_block(REQ_OP_READ, REQ_RAHEAD, 1, &bh);
1400 brelse(bh);
1401 }
1402}
1403EXPORT_SYMBOL(__breadahead);
1404
1405/**
1406 * __bread_gfp() - reads a specified block and returns the bh
1407 * @bdev: the block_device to read from
1408 * @block: number of block
1409 * @size: size (in bytes) to read
1410 * @gfp: page allocation flag
1411 *
1412 * Reads a specified block, and returns buffer head that contains it.
1413 * The page cache can be allocated from non-movable area
1414 * not to prevent page migration if you set gfp to zero.
1415 * It returns NULL if the block was unreadable.
1416 */
1417struct buffer_head *
1418__bread_gfp(struct block_device *bdev, sector_t block,
1419 unsigned size, gfp_t gfp)
1420{
1421 struct buffer_head *bh = __getblk_gfp(bdev, block, size, gfp);
1422
1423 if (likely(bh) && !buffer_uptodate(bh))
1424 bh = __bread_slow(bh);
1425 return bh;
1426}
1427EXPORT_SYMBOL(__bread_gfp);
1428
1429/*
1430 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1431 * This doesn't race because it runs in each cpu either in irq
1432 * or with preempt disabled.
1433 */
1434static void invalidate_bh_lru(void *arg)
1435{
1436 struct bh_lru *b = &get_cpu_var(bh_lrus);
1437 int i;
1438
1439 for (i = 0; i < BH_LRU_SIZE; i++) {
1440 brelse(b->bhs[i]);
1441 b->bhs[i] = NULL;
1442 }
1443 put_cpu_var(bh_lrus);
1444}
1445
1446static bool has_bh_in_lru(int cpu, void *dummy)
1447{
1448 struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1449 int i;
1450
1451 for (i = 0; i < BH_LRU_SIZE; i++) {
1452 if (b->bhs[i])
1453 return 1;
1454 }
1455
1456 return 0;
1457}
1458
1459void invalidate_bh_lrus(void)
1460{
1461 on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL);
1462}
1463EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1464
1465void set_bh_page(struct buffer_head *bh,
1466 struct page *page, unsigned long offset)
1467{
1468 bh->b_page = page;
1469 BUG_ON(offset >= PAGE_SIZE);
1470 if (PageHighMem(page))
1471 /*
1472 * This catches illegal uses and preserves the offset:
1473 */
1474 bh->b_data = (char *)(0 + offset);
1475 else
1476 bh->b_data = page_address(page) + offset;
1477}
1478EXPORT_SYMBOL(set_bh_page);
1479
1480/*
1481 * Called when truncating a buffer on a page completely.
1482 */
1483
1484/* Bits that are cleared during an invalidate */
1485#define BUFFER_FLAGS_DISCARD \
1486 (1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \
1487 1 << BH_Delay | 1 << BH_Unwritten)
1488
1489static void discard_buffer(struct buffer_head * bh)
1490{
1491 unsigned long b_state, b_state_old;
1492
1493 lock_buffer(bh);
1494 clear_buffer_dirty(bh);
1495 bh->b_bdev = NULL;
1496 b_state = bh->b_state;
1497 for (;;) {
1498 b_state_old = cmpxchg(&bh->b_state, b_state,
1499 (b_state & ~BUFFER_FLAGS_DISCARD));
1500 if (b_state_old == b_state)
1501 break;
1502 b_state = b_state_old;
1503 }
1504 unlock_buffer(bh);
1505}
1506
1507/**
1508 * block_invalidatepage - invalidate part or all of a buffer-backed page
1509 *
1510 * @page: the page which is affected
1511 * @offset: start of the range to invalidate
1512 * @length: length of the range to invalidate
1513 *
1514 * block_invalidatepage() is called when all or part of the page has become
1515 * invalidated by a truncate operation.
1516 *
1517 * block_invalidatepage() does not have to release all buffers, but it must
1518 * ensure that no dirty buffer is left outside @offset and that no I/O
1519 * is underway against any of the blocks which are outside the truncation
1520 * point. Because the caller is about to free (and possibly reuse) those
1521 * blocks on-disk.
1522 */
1523void block_invalidatepage(struct page *page, unsigned int offset,
1524 unsigned int length)
1525{
1526 struct buffer_head *head, *bh, *next;
1527 unsigned int curr_off = 0;
1528 unsigned int stop = length + offset;
1529
1530 BUG_ON(!PageLocked(page));
1531 if (!page_has_buffers(page))
1532 goto out;
1533
1534 /*
1535 * Check for overflow
1536 */
1537 BUG_ON(stop > PAGE_SIZE || stop < length);
1538
1539 head = page_buffers(page);
1540 bh = head;
1541 do {
1542 unsigned int next_off = curr_off + bh->b_size;
1543 next = bh->b_this_page;
1544
1545 /*
1546 * Are we still fully in range ?
1547 */
1548 if (next_off > stop)
1549 goto out;
1550
1551 /*
1552 * is this block fully invalidated?
1553 */
1554 if (offset <= curr_off)
1555 discard_buffer(bh);
1556 curr_off = next_off;
1557 bh = next;
1558 } while (bh != head);
1559
1560 /*
1561 * We release buffers only if the entire page is being invalidated.
1562 * The get_block cached value has been unconditionally invalidated,
1563 * so real IO is not possible anymore.
1564 */
1565 if (offset == 0)
1566 try_to_release_page(page, 0);
1567out:
1568 return;
1569}
1570EXPORT_SYMBOL(block_invalidatepage);
1571
1572
1573/*
1574 * We attach and possibly dirty the buffers atomically wrt
1575 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1576 * is already excluded via the page lock.
1577 */
1578void create_empty_buffers(struct page *page,
1579 unsigned long blocksize, unsigned long b_state)
1580{
1581 struct buffer_head *bh, *head, *tail;
1582
1583 head = alloc_page_buffers(page, blocksize, 1);
1584 bh = head;
1585 do {
1586 bh->b_state |= b_state;
1587 tail = bh;
1588 bh = bh->b_this_page;
1589 } while (bh);
1590 tail->b_this_page = head;
1591
1592 spin_lock(&page->mapping->private_lock);
1593 if (PageUptodate(page) || PageDirty(page)) {
1594 bh = head;
1595 do {
1596 if (PageDirty(page))
1597 set_buffer_dirty(bh);
1598 if (PageUptodate(page))
1599 set_buffer_uptodate(bh);
1600 bh = bh->b_this_page;
1601 } while (bh != head);
1602 }
1603 attach_page_buffers(page, head);
1604 spin_unlock(&page->mapping->private_lock);
1605}
1606EXPORT_SYMBOL(create_empty_buffers);
1607
1608/**
1609 * clean_bdev_aliases: clean a range of buffers in block device
1610 * @bdev: Block device to clean buffers in
1611 * @block: Start of a range of blocks to clean
1612 * @len: Number of blocks to clean
1613 *
1614 * We are taking a range of blocks for data and we don't want writeback of any
1615 * buffer-cache aliases starting from return from this function and until the
1616 * moment when something will explicitly mark the buffer dirty (hopefully that
1617 * will not happen until we will free that block ;-) We don't even need to mark
1618 * it not-uptodate - nobody can expect anything from a newly allocated buffer
1619 * anyway. We used to use unmap_buffer() for such invalidation, but that was
1620 * wrong. We definitely don't want to mark the alias unmapped, for example - it
1621 * would confuse anyone who might pick it with bread() afterwards...
1622 *
1623 * Also.. Note that bforget() doesn't lock the buffer. So there can be
1624 * writeout I/O going on against recently-freed buffers. We don't wait on that
1625 * I/O in bforget() - it's more efficient to wait on the I/O only if we really
1626 * need to. That happens here.
1627 */
1628void clean_bdev_aliases(struct block_device *bdev, sector_t block, sector_t len)
1629{
1630 struct inode *bd_inode = bdev->bd_inode;
1631 struct address_space *bd_mapping = bd_inode->i_mapping;
1632 struct pagevec pvec;
1633 pgoff_t index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
1634 pgoff_t end;
1635 int i;
1636 struct buffer_head *bh;
1637 struct buffer_head *head;
1638
1639 end = (block + len - 1) >> (PAGE_SHIFT - bd_inode->i_blkbits);
1640 pagevec_init(&pvec, 0);
1641 while (index <= end && pagevec_lookup(&pvec, bd_mapping, index,
1642 min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
1643 for (i = 0; i < pagevec_count(&pvec); i++) {
1644 struct page *page = pvec.pages[i];
1645
1646 index = page->index;
1647 if (index > end)
1648 break;
1649 if (!page_has_buffers(page))
1650 continue;
1651 /*
1652 * We use page lock instead of bd_mapping->private_lock
1653 * to pin buffers here since we can afford to sleep and
1654 * it scales better than a global spinlock lock.
1655 */
1656 lock_page(page);
1657 /* Recheck when the page is locked which pins bhs */
1658 if (!page_has_buffers(page))
1659 goto unlock_page;
1660 head = page_buffers(page);
1661 bh = head;
1662 do {
1663 if (!buffer_mapped(bh) || (bh->b_blocknr < block))
1664 goto next;
1665 if (bh->b_blocknr >= block + len)
1666 break;
1667 clear_buffer_dirty(bh);
1668 wait_on_buffer(bh);
1669 clear_buffer_req(bh);
1670next:
1671 bh = bh->b_this_page;
1672 } while (bh != head);
1673unlock_page:
1674 unlock_page(page);
1675 }
1676 pagevec_release(&pvec);
1677 cond_resched();
1678 index++;
1679 }
1680}
1681EXPORT_SYMBOL(clean_bdev_aliases);
1682
1683/*
1684 * Size is a power-of-two in the range 512..PAGE_SIZE,
1685 * and the case we care about most is PAGE_SIZE.
1686 *
1687 * So this *could* possibly be written with those
1688 * constraints in mind (relevant mostly if some
1689 * architecture has a slow bit-scan instruction)
1690 */
1691static inline int block_size_bits(unsigned int blocksize)
1692{
1693 return ilog2(blocksize);
1694}
1695
1696static struct buffer_head *create_page_buffers(struct page *page, struct inode *inode, unsigned int b_state)
1697{
1698 BUG_ON(!PageLocked(page));
1699
1700 if (!page_has_buffers(page))
1701 create_empty_buffers(page, 1 << ACCESS_ONCE(inode->i_blkbits), b_state);
1702 return page_buffers(page);
1703}
1704
1705/*
1706 * NOTE! All mapped/uptodate combinations are valid:
1707 *
1708 * Mapped Uptodate Meaning
1709 *
1710 * No No "unknown" - must do get_block()
1711 * No Yes "hole" - zero-filled
1712 * Yes No "allocated" - allocated on disk, not read in
1713 * Yes Yes "valid" - allocated and up-to-date in memory.
1714 *
1715 * "Dirty" is valid only with the last case (mapped+uptodate).
1716 */
1717
1718/*
1719 * While block_write_full_page is writing back the dirty buffers under
1720 * the page lock, whoever dirtied the buffers may decide to clean them
1721 * again at any time. We handle that by only looking at the buffer
1722 * state inside lock_buffer().
1723 *
1724 * If block_write_full_page() is called for regular writeback
1725 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1726 * locked buffer. This only can happen if someone has written the buffer
1727 * directly, with submit_bh(). At the address_space level PageWriteback
1728 * prevents this contention from occurring.
1729 *
1730 * If block_write_full_page() is called with wbc->sync_mode ==
1731 * WB_SYNC_ALL, the writes are posted using REQ_SYNC; this
1732 * causes the writes to be flagged as synchronous writes.
1733 */
1734int __block_write_full_page(struct inode *inode, struct page *page,
1735 get_block_t *get_block, struct writeback_control *wbc,
1736 bh_end_io_t *handler)
1737{
1738 int err;
1739 sector_t block;
1740 sector_t last_block;
1741 struct buffer_head *bh, *head;
1742 unsigned int blocksize, bbits;
1743 int nr_underway = 0;
1744 int write_flags = wbc_to_write_flags(wbc);
1745
1746 head = create_page_buffers(page, inode,
1747 (1 << BH_Dirty)|(1 << BH_Uptodate));
1748
1749 /*
1750 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1751 * here, and the (potentially unmapped) buffers may become dirty at
1752 * any time. If a buffer becomes dirty here after we've inspected it
1753 * then we just miss that fact, and the page stays dirty.
1754 *
1755 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1756 * handle that here by just cleaning them.
1757 */
1758
1759 bh = head;
1760 blocksize = bh->b_size;
1761 bbits = block_size_bits(blocksize);
1762
1763 block = (sector_t)page->index << (PAGE_SHIFT - bbits);
1764 last_block = (i_size_read(inode) - 1) >> bbits;
1765
1766 /*
1767 * Get all the dirty buffers mapped to disk addresses and
1768 * handle any aliases from the underlying blockdev's mapping.
1769 */
1770 do {
1771 if (block > last_block) {
1772 /*
1773 * mapped buffers outside i_size will occur, because
1774 * this page can be outside i_size when there is a
1775 * truncate in progress.
1776 */
1777 /*
1778 * The buffer was zeroed by block_write_full_page()
1779 */
1780 clear_buffer_dirty(bh);
1781 set_buffer_uptodate(bh);
1782 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1783 buffer_dirty(bh)) {
1784 WARN_ON(bh->b_size != blocksize);
1785 err = get_block(inode, block, bh, 1);
1786 if (err)
1787 goto recover;
1788 clear_buffer_delay(bh);
1789 if (buffer_new(bh)) {
1790 /* blockdev mappings never come here */
1791 clear_buffer_new(bh);
1792 clean_bdev_bh_alias(bh);
1793 }
1794 }
1795 bh = bh->b_this_page;
1796 block++;
1797 } while (bh != head);
1798
1799 do {
1800 if (!buffer_mapped(bh))
1801 continue;
1802 /*
1803 * If it's a fully non-blocking write attempt and we cannot
1804 * lock the buffer then redirty the page. Note that this can
1805 * potentially cause a busy-wait loop from writeback threads
1806 * and kswapd activity, but those code paths have their own
1807 * higher-level throttling.
1808 */
1809 if (wbc->sync_mode != WB_SYNC_NONE) {
1810 lock_buffer(bh);
1811 } else if (!trylock_buffer(bh)) {
1812 redirty_page_for_writepage(wbc, page);
1813 continue;
1814 }
1815 if (test_clear_buffer_dirty(bh)) {
1816 mark_buffer_async_write_endio(bh, handler);
1817 } else {
1818 unlock_buffer(bh);
1819 }
1820 } while ((bh = bh->b_this_page) != head);
1821
1822 /*
1823 * The page and its buffers are protected by PageWriteback(), so we can
1824 * drop the bh refcounts early.
1825 */
1826 BUG_ON(PageWriteback(page));
1827 set_page_writeback(page);
1828
1829 do {
1830 struct buffer_head *next = bh->b_this_page;
1831 if (buffer_async_write(bh)) {
1832 submit_bh_wbc(REQ_OP_WRITE, write_flags, bh, 0, wbc);
1833 nr_underway++;
1834 }
1835 bh = next;
1836 } while (bh != head);
1837 unlock_page(page);
1838
1839 err = 0;
1840done:
1841 if (nr_underway == 0) {
1842 /*
1843 * The page was marked dirty, but the buffers were
1844 * clean. Someone wrote them back by hand with
1845 * ll_rw_block/submit_bh. A rare case.
1846 */
1847 end_page_writeback(page);
1848
1849 /*
1850 * The page and buffer_heads can be released at any time from
1851 * here on.
1852 */
1853 }
1854 return err;
1855
1856recover:
1857 /*
1858 * ENOSPC, or some other error. We may already have added some
1859 * blocks to the file, so we need to write these out to avoid
1860 * exposing stale data.
1861 * The page is currently locked and not marked for writeback
1862 */
1863 bh = head;
1864 /* Recovery: lock and submit the mapped buffers */
1865 do {
1866 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1867 !buffer_delay(bh)) {
1868 lock_buffer(bh);
1869 mark_buffer_async_write_endio(bh, handler);
1870 } else {
1871 /*
1872 * The buffer may have been set dirty during
1873 * attachment to a dirty page.
1874 */
1875 clear_buffer_dirty(bh);
1876 }
1877 } while ((bh = bh->b_this_page) != head);
1878 SetPageError(page);
1879 BUG_ON(PageWriteback(page));
1880 mapping_set_error(page->mapping, err);
1881 set_page_writeback(page);
1882 do {
1883 struct buffer_head *next = bh->b_this_page;
1884 if (buffer_async_write(bh)) {
1885 clear_buffer_dirty(bh);
1886 submit_bh_wbc(REQ_OP_WRITE, write_flags, bh, 0, wbc);
1887 nr_underway++;
1888 }
1889 bh = next;
1890 } while (bh != head);
1891 unlock_page(page);
1892 goto done;
1893}
1894EXPORT_SYMBOL(__block_write_full_page);
1895
1896/*
1897 * If a page has any new buffers, zero them out here, and mark them uptodate
1898 * and dirty so they'll be written out (in order to prevent uninitialised
1899 * block data from leaking). And clear the new bit.
1900 */
1901void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1902{
1903 unsigned int block_start, block_end;
1904 struct buffer_head *head, *bh;
1905
1906 BUG_ON(!PageLocked(page));
1907 if (!page_has_buffers(page))
1908 return;
1909
1910 bh = head = page_buffers(page);
1911 block_start = 0;
1912 do {
1913 block_end = block_start + bh->b_size;
1914
1915 if (buffer_new(bh)) {
1916 if (block_end > from && block_start < to) {
1917 if (!PageUptodate(page)) {
1918 unsigned start, size;
1919
1920 start = max(from, block_start);
1921 size = min(to, block_end) - start;
1922
1923 zero_user(page, start, size);
1924 set_buffer_uptodate(bh);
1925 }
1926
1927 clear_buffer_new(bh);
1928 mark_buffer_dirty(bh);
1929 }
1930 }
1931
1932 block_start = block_end;
1933 bh = bh->b_this_page;
1934 } while (bh != head);
1935}
1936EXPORT_SYMBOL(page_zero_new_buffers);
1937
1938static void
1939iomap_to_bh(struct inode *inode, sector_t block, struct buffer_head *bh,
1940 struct iomap *iomap)
1941{
1942 loff_t offset = block << inode->i_blkbits;
1943
1944 bh->b_bdev = iomap->bdev;
1945
1946 /*
1947 * Block points to offset in file we need to map, iomap contains
1948 * the offset at which the map starts. If the map ends before the
1949 * current block, then do not map the buffer and let the caller
1950 * handle it.
1951 */
1952 BUG_ON(offset >= iomap->offset + iomap->length);
1953
1954 switch (iomap->type) {
1955 case IOMAP_HOLE:
1956 /*
1957 * If the buffer is not up to date or beyond the current EOF,
1958 * we need to mark it as new to ensure sub-block zeroing is
1959 * executed if necessary.
1960 */
1961 if (!buffer_uptodate(bh) ||
1962 (offset >= i_size_read(inode)))
1963 set_buffer_new(bh);
1964 break;
1965 case IOMAP_DELALLOC:
1966 if (!buffer_uptodate(bh) ||
1967 (offset >= i_size_read(inode)))
1968 set_buffer_new(bh);
1969 set_buffer_uptodate(bh);
1970 set_buffer_mapped(bh);
1971 set_buffer_delay(bh);
1972 break;
1973 case IOMAP_UNWRITTEN:
1974 /*
1975 * For unwritten regions, we always need to ensure that
1976 * sub-block writes cause the regions in the block we are not
1977 * writing to are zeroed. Set the buffer as new to ensure this.
1978 */
1979 set_buffer_new(bh);
1980 set_buffer_unwritten(bh);
1981 /* FALLTHRU */
1982 case IOMAP_MAPPED:
1983 if (offset >= i_size_read(inode))
1984 set_buffer_new(bh);
1985 bh->b_blocknr = (iomap->blkno >> (inode->i_blkbits - 9)) +
1986 ((offset - iomap->offset) >> inode->i_blkbits);
1987 set_buffer_mapped(bh);
1988 break;
1989 }
1990}
1991
1992int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
1993 get_block_t *get_block, struct iomap *iomap)
1994{
1995 unsigned from = pos & (PAGE_SIZE - 1);
1996 unsigned to = from + len;
1997 struct inode *inode = page->mapping->host;
1998 unsigned block_start, block_end;
1999 sector_t block;
2000 int err = 0;
2001 unsigned blocksize, bbits;
2002 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
2003
2004 BUG_ON(!PageLocked(page));
2005 BUG_ON(from > PAGE_SIZE);
2006 BUG_ON(to > PAGE_SIZE);
2007 BUG_ON(from > to);
2008
2009 head = create_page_buffers(page, inode, 0);
2010 blocksize = head->b_size;
2011 bbits = block_size_bits(blocksize);
2012
2013 block = (sector_t)page->index << (PAGE_SHIFT - bbits);
2014
2015 for(bh = head, block_start = 0; bh != head || !block_start;
2016 block++, block_start=block_end, bh = bh->b_this_page) {
2017 block_end = block_start + blocksize;
2018 if (block_end <= from || block_start >= to) {
2019 if (PageUptodate(page)) {
2020 if (!buffer_uptodate(bh))
2021 set_buffer_uptodate(bh);
2022 }
2023 continue;
2024 }
2025 if (buffer_new(bh))
2026 clear_buffer_new(bh);
2027 if (!buffer_mapped(bh)) {
2028 WARN_ON(bh->b_size != blocksize);
2029 if (get_block) {
2030 err = get_block(inode, block, bh, 1);
2031 if (err)
2032 break;
2033 } else {
2034 iomap_to_bh(inode, block, bh, iomap);
2035 }
2036
2037 if (buffer_new(bh)) {
2038 clean_bdev_bh_alias(bh);
2039 if (PageUptodate(page)) {
2040 clear_buffer_new(bh);
2041 set_buffer_uptodate(bh);
2042 mark_buffer_dirty(bh);
2043 continue;
2044 }
2045 if (block_end > to || block_start < from)
2046 zero_user_segments(page,
2047 to, block_end,
2048 block_start, from);
2049 continue;
2050 }
2051 }
2052 if (PageUptodate(page)) {
2053 if (!buffer_uptodate(bh))
2054 set_buffer_uptodate(bh);
2055 continue;
2056 }
2057 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
2058 !buffer_unwritten(bh) &&
2059 (block_start < from || block_end > to)) {
2060 ll_rw_block(REQ_OP_READ, 0, 1, &bh);
2061 *wait_bh++=bh;
2062 }
2063 }
2064 /*
2065 * If we issued read requests - let them complete.
2066 */
2067 while(wait_bh > wait) {
2068 wait_on_buffer(*--wait_bh);
2069 if (!buffer_uptodate(*wait_bh))
2070 err = -EIO;
2071 }
2072 if (unlikely(err))
2073 page_zero_new_buffers(page, from, to);
2074 return err;
2075}
2076
2077int __block_write_begin(struct page *page, loff_t pos, unsigned len,
2078 get_block_t *get_block)
2079{
2080 return __block_write_begin_int(page, pos, len, get_block, NULL);
2081}
2082EXPORT_SYMBOL(__block_write_begin);
2083
2084static int __block_commit_write(struct inode *inode, struct page *page,
2085 unsigned from, unsigned to)
2086{
2087 unsigned block_start, block_end;
2088 int partial = 0;
2089 unsigned blocksize;
2090 struct buffer_head *bh, *head;
2091
2092 bh = head = page_buffers(page);
2093 blocksize = bh->b_size;
2094
2095 block_start = 0;
2096 do {
2097 block_end = block_start + blocksize;
2098 if (block_end <= from || block_start >= to) {
2099 if (!buffer_uptodate(bh))
2100 partial = 1;
2101 } else {
2102 set_buffer_uptodate(bh);
2103 mark_buffer_dirty(bh);
2104 }
2105 clear_buffer_new(bh);
2106
2107 block_start = block_end;
2108 bh = bh->b_this_page;
2109 } while (bh != head);
2110
2111 /*
2112 * If this is a partial write which happened to make all buffers
2113 * uptodate then we can optimize away a bogus readpage() for
2114 * the next read(). Here we 'discover' whether the page went
2115 * uptodate as a result of this (potentially partial) write.
2116 */
2117 if (!partial)
2118 SetPageUptodate(page);
2119 return 0;
2120}
2121
2122/*
2123 * block_write_begin takes care of the basic task of block allocation and
2124 * bringing partial write blocks uptodate first.
2125 *
2126 * The filesystem needs to handle block truncation upon failure.
2127 */
2128int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
2129 unsigned flags, struct page **pagep, get_block_t *get_block)
2130{
2131 pgoff_t index = pos >> PAGE_SHIFT;
2132 struct page *page;
2133 int status;
2134
2135 page = grab_cache_page_write_begin(mapping, index, flags);
2136 if (!page)
2137 return -ENOMEM;
2138
2139 status = __block_write_begin(page, pos, len, get_block);
2140 if (unlikely(status)) {
2141 unlock_page(page);
2142 put_page(page);
2143 page = NULL;
2144 }
2145
2146 *pagep = page;
2147 return status;
2148}
2149EXPORT_SYMBOL(block_write_begin);
2150
2151int block_write_end(struct file *file, struct address_space *mapping,
2152 loff_t pos, unsigned len, unsigned copied,
2153 struct page *page, void *fsdata)
2154{
2155 struct inode *inode = mapping->host;
2156 unsigned start;
2157
2158 start = pos & (PAGE_SIZE - 1);
2159
2160 if (unlikely(copied < len)) {
2161 /*
2162 * The buffers that were written will now be uptodate, so we
2163 * don't have to worry about a readpage reading them and
2164 * overwriting a partial write. However if we have encountered
2165 * a short write and only partially written into a buffer, it
2166 * will not be marked uptodate, so a readpage might come in and
2167 * destroy our partial write.
2168 *
2169 * Do the simplest thing, and just treat any short write to a
2170 * non uptodate page as a zero-length write, and force the
2171 * caller to redo the whole thing.
2172 */
2173 if (!PageUptodate(page))
2174 copied = 0;
2175
2176 page_zero_new_buffers(page, start+copied, start+len);
2177 }
2178 flush_dcache_page(page);
2179
2180 /* This could be a short (even 0-length) commit */
2181 __block_commit_write(inode, page, start, start+copied);
2182
2183 return copied;
2184}
2185EXPORT_SYMBOL(block_write_end);
2186
2187int generic_write_end(struct file *file, struct address_space *mapping,
2188 loff_t pos, unsigned len, unsigned copied,
2189 struct page *page, void *fsdata)
2190{
2191 struct inode *inode = mapping->host;
2192 loff_t old_size = inode->i_size;
2193 int i_size_changed = 0;
2194
2195 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2196
2197 /*
2198 * No need to use i_size_read() here, the i_size
2199 * cannot change under us because we hold i_mutex.
2200 *
2201 * But it's important to update i_size while still holding page lock:
2202 * page writeout could otherwise come in and zero beyond i_size.
2203 */
2204 if (pos+copied > inode->i_size) {
2205 i_size_write(inode, pos+copied);
2206 i_size_changed = 1;
2207 }
2208
2209 unlock_page(page);
2210 put_page(page);
2211
2212 if (old_size < pos)
2213 pagecache_isize_extended(inode, old_size, pos);
2214 /*
2215 * Don't mark the inode dirty under page lock. First, it unnecessarily
2216 * makes the holding time of page lock longer. Second, it forces lock
2217 * ordering of page lock and transaction start for journaling
2218 * filesystems.
2219 */
2220 if (i_size_changed)
2221 mark_inode_dirty(inode);
2222
2223 return copied;
2224}
2225EXPORT_SYMBOL(generic_write_end);
2226
2227/*
2228 * block_is_partially_uptodate checks whether buffers within a page are
2229 * uptodate or not.
2230 *
2231 * Returns true if all buffers which correspond to a file portion
2232 * we want to read are uptodate.
2233 */
2234int block_is_partially_uptodate(struct page *page, unsigned long from,
2235 unsigned long count)
2236{
2237 unsigned block_start, block_end, blocksize;
2238 unsigned to;
2239 struct buffer_head *bh, *head;
2240 int ret = 1;
2241
2242 if (!page_has_buffers(page))
2243 return 0;
2244
2245 head = page_buffers(page);
2246 blocksize = head->b_size;
2247 to = min_t(unsigned, PAGE_SIZE - from, count);
2248 to = from + to;
2249 if (from < blocksize && to > PAGE_SIZE - blocksize)
2250 return 0;
2251
2252 bh = head;
2253 block_start = 0;
2254 do {
2255 block_end = block_start + blocksize;
2256 if (block_end > from && block_start < to) {
2257 if (!buffer_uptodate(bh)) {
2258 ret = 0;
2259 break;
2260 }
2261 if (block_end >= to)
2262 break;
2263 }
2264 block_start = block_end;
2265 bh = bh->b_this_page;
2266 } while (bh != head);
2267
2268 return ret;
2269}
2270EXPORT_SYMBOL(block_is_partially_uptodate);
2271
2272/*
2273 * Generic "read page" function for block devices that have the normal
2274 * get_block functionality. This is most of the block device filesystems.
2275 * Reads the page asynchronously --- the unlock_buffer() and
2276 * set/clear_buffer_uptodate() functions propagate buffer state into the
2277 * page struct once IO has completed.
2278 */
2279int block_read_full_page(struct page *page, get_block_t *get_block)
2280{
2281 struct inode *inode = page->mapping->host;
2282 sector_t iblock, lblock;
2283 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2284 unsigned int blocksize, bbits;
2285 int nr, i;
2286 int fully_mapped = 1;
2287
2288 head = create_page_buffers(page, inode, 0);
2289 blocksize = head->b_size;
2290 bbits = block_size_bits(blocksize);
2291
2292 iblock = (sector_t)page->index << (PAGE_SHIFT - bbits);
2293 lblock = (i_size_read(inode)+blocksize-1) >> bbits;
2294 bh = head;
2295 nr = 0;
2296 i = 0;
2297
2298 do {
2299 if (buffer_uptodate(bh))
2300 continue;
2301
2302 if (!buffer_mapped(bh)) {
2303 int err = 0;
2304
2305 fully_mapped = 0;
2306 if (iblock < lblock) {
2307 WARN_ON(bh->b_size != blocksize);
2308 err = get_block(inode, iblock, bh, 0);
2309 if (err)
2310 SetPageError(page);
2311 }
2312 if (!buffer_mapped(bh)) {
2313 zero_user(page, i * blocksize, blocksize);
2314 if (!err)
2315 set_buffer_uptodate(bh);
2316 continue;
2317 }
2318 /*
2319 * get_block() might have updated the buffer
2320 * synchronously
2321 */
2322 if (buffer_uptodate(bh))
2323 continue;
2324 }
2325 arr[nr++] = bh;
2326 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2327
2328 if (fully_mapped)
2329 SetPageMappedToDisk(page);
2330
2331 if (!nr) {
2332 /*
2333 * All buffers are uptodate - we can set the page uptodate
2334 * as well. But not if get_block() returned an error.
2335 */
2336 if (!PageError(page))
2337 SetPageUptodate(page);
2338 unlock_page(page);
2339 return 0;
2340 }
2341
2342 /* Stage two: lock the buffers */
2343 for (i = 0; i < nr; i++) {
2344 bh = arr[i];
2345 lock_buffer(bh);
2346 mark_buffer_async_read(bh);
2347 }
2348
2349 /*
2350 * Stage 3: start the IO. Check for uptodateness
2351 * inside the buffer lock in case another process reading
2352 * the underlying blockdev brought it uptodate (the sct fix).
2353 */
2354 for (i = 0; i < nr; i++) {
2355 bh = arr[i];
2356 if (buffer_uptodate(bh))
2357 end_buffer_async_read(bh, 1);
2358 else
2359 submit_bh(REQ_OP_READ, 0, bh);
2360 }
2361 return 0;
2362}
2363EXPORT_SYMBOL(block_read_full_page);
2364
2365/* utility function for filesystems that need to do work on expanding
2366 * truncates. Uses filesystem pagecache writes to allow the filesystem to
2367 * deal with the hole.
2368 */
2369int generic_cont_expand_simple(struct inode *inode, loff_t size)
2370{
2371 struct address_space *mapping = inode->i_mapping;
2372 struct page *page;
2373 void *fsdata;
2374 int err;
2375
2376 err = inode_newsize_ok(inode, size);
2377 if (err)
2378 goto out;
2379
2380 err = pagecache_write_begin(NULL, mapping, size, 0,
2381 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2382 &page, &fsdata);
2383 if (err)
2384 goto out;
2385
2386 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2387 BUG_ON(err > 0);
2388
2389out:
2390 return err;
2391}
2392EXPORT_SYMBOL(generic_cont_expand_simple);
2393
2394static int cont_expand_zero(struct file *file, struct address_space *mapping,
2395 loff_t pos, loff_t *bytes)
2396{
2397 struct inode *inode = mapping->host;
2398 unsigned blocksize = 1 << inode->i_blkbits;
2399 struct page *page;
2400 void *fsdata;
2401 pgoff_t index, curidx;
2402 loff_t curpos;
2403 unsigned zerofrom, offset, len;
2404 int err = 0;
2405
2406 index = pos >> PAGE_SHIFT;
2407 offset = pos & ~PAGE_MASK;
2408
2409 while (index > (curidx = (curpos = *bytes)>>PAGE_SHIFT)) {
2410 zerofrom = curpos & ~PAGE_MASK;
2411 if (zerofrom & (blocksize-1)) {
2412 *bytes |= (blocksize-1);
2413 (*bytes)++;
2414 }
2415 len = PAGE_SIZE - zerofrom;
2416
2417 err = pagecache_write_begin(file, mapping, curpos, len,
2418 AOP_FLAG_UNINTERRUPTIBLE,
2419 &page, &fsdata);
2420 if (err)
2421 goto out;
2422 zero_user(page, zerofrom, len);
2423 err = pagecache_write_end(file, mapping, curpos, len, len,
2424 page, fsdata);
2425 if (err < 0)
2426 goto out;
2427 BUG_ON(err != len);
2428 err = 0;
2429
2430 balance_dirty_pages_ratelimited(mapping);
2431
2432 if (unlikely(fatal_signal_pending(current))) {
2433 err = -EINTR;
2434 goto out;
2435 }
2436 }
2437
2438 /* page covers the boundary, find the boundary offset */
2439 if (index == curidx) {
2440 zerofrom = curpos & ~PAGE_MASK;
2441 /* if we will expand the thing last block will be filled */
2442 if (offset <= zerofrom) {
2443 goto out;
2444 }
2445 if (zerofrom & (blocksize-1)) {
2446 *bytes |= (blocksize-1);
2447 (*bytes)++;
2448 }
2449 len = offset - zerofrom;
2450
2451 err = pagecache_write_begin(file, mapping, curpos, len,
2452 AOP_FLAG_UNINTERRUPTIBLE,
2453 &page, &fsdata);
2454 if (err)
2455 goto out;
2456 zero_user(page, zerofrom, len);
2457 err = pagecache_write_end(file, mapping, curpos, len, len,
2458 page, fsdata);
2459 if (err < 0)
2460 goto out;
2461 BUG_ON(err != len);
2462 err = 0;
2463 }
2464out:
2465 return err;
2466}
2467
2468/*
2469 * For moronic filesystems that do not allow holes in file.
2470 * We may have to extend the file.
2471 */
2472int cont_write_begin(struct file *file, struct address_space *mapping,
2473 loff_t pos, unsigned len, unsigned flags,
2474 struct page **pagep, void **fsdata,
2475 get_block_t *get_block, loff_t *bytes)
2476{
2477 struct inode *inode = mapping->host;
2478 unsigned blocksize = 1 << inode->i_blkbits;
2479 unsigned zerofrom;
2480 int err;
2481
2482 err = cont_expand_zero(file, mapping, pos, bytes);
2483 if (err)
2484 return err;
2485
2486 zerofrom = *bytes & ~PAGE_MASK;
2487 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2488 *bytes |= (blocksize-1);
2489 (*bytes)++;
2490 }
2491
2492 return block_write_begin(mapping, pos, len, flags, pagep, get_block);
2493}
2494EXPORT_SYMBOL(cont_write_begin);
2495
2496int block_commit_write(struct page *page, unsigned from, unsigned to)
2497{
2498 struct inode *inode = page->mapping->host;
2499 __block_commit_write(inode,page,from,to);
2500 return 0;
2501}
2502EXPORT_SYMBOL(block_commit_write);
2503
2504/*
2505 * block_page_mkwrite() is not allowed to change the file size as it gets
2506 * called from a page fault handler when a page is first dirtied. Hence we must
2507 * be careful to check for EOF conditions here. We set the page up correctly
2508 * for a written page which means we get ENOSPC checking when writing into
2509 * holes and correct delalloc and unwritten extent mapping on filesystems that
2510 * support these features.
2511 *
2512 * We are not allowed to take the i_mutex here so we have to play games to
2513 * protect against truncate races as the page could now be beyond EOF. Because
2514 * truncate writes the inode size before removing pages, once we have the
2515 * page lock we can determine safely if the page is beyond EOF. If it is not
2516 * beyond EOF, then the page is guaranteed safe against truncation until we
2517 * unlock the page.
2518 *
2519 * Direct callers of this function should protect against filesystem freezing
2520 * using sb_start_pagefault() - sb_end_pagefault() functions.
2521 */
2522int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2523 get_block_t get_block)
2524{
2525 struct page *page = vmf->page;
2526 struct inode *inode = file_inode(vma->vm_file);
2527 unsigned long end;
2528 loff_t size;
2529 int ret;
2530
2531 lock_page(page);
2532 size = i_size_read(inode);
2533 if ((page->mapping != inode->i_mapping) ||
2534 (page_offset(page) > size)) {
2535 /* We overload EFAULT to mean page got truncated */
2536 ret = -EFAULT;
2537 goto out_unlock;
2538 }
2539
2540 /* page is wholly or partially inside EOF */
2541 if (((page->index + 1) << PAGE_SHIFT) > size)
2542 end = size & ~PAGE_MASK;
2543 else
2544 end = PAGE_SIZE;
2545
2546 ret = __block_write_begin(page, 0, end, get_block);
2547 if (!ret)
2548 ret = block_commit_write(page, 0, end);
2549
2550 if (unlikely(ret < 0))
2551 goto out_unlock;
2552 set_page_dirty(page);
2553 wait_for_stable_page(page);
2554 return 0;
2555out_unlock:
2556 unlock_page(page);
2557 return ret;
2558}
2559EXPORT_SYMBOL(block_page_mkwrite);
2560
2561/*
2562 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
2563 * immediately, while under the page lock. So it needs a special end_io
2564 * handler which does not touch the bh after unlocking it.
2565 */
2566static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2567{
2568 __end_buffer_read_notouch(bh, uptodate);
2569}
2570
2571/*
2572 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2573 * the page (converting it to circular linked list and taking care of page
2574 * dirty races).
2575 */
2576static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2577{
2578 struct buffer_head *bh;
2579
2580 BUG_ON(!PageLocked(page));
2581
2582 spin_lock(&page->mapping->private_lock);
2583 bh = head;
2584 do {
2585 if (PageDirty(page))
2586 set_buffer_dirty(bh);
2587 if (!bh->b_this_page)
2588 bh->b_this_page = head;
2589 bh = bh->b_this_page;
2590 } while (bh != head);
2591 attach_page_buffers(page, head);
2592 spin_unlock(&page->mapping->private_lock);
2593}
2594
2595/*
2596 * On entry, the page is fully not uptodate.
2597 * On exit the page is fully uptodate in the areas outside (from,to)
2598 * The filesystem needs to handle block truncation upon failure.
2599 */
2600int nobh_write_begin(struct address_space *mapping,
2601 loff_t pos, unsigned len, unsigned flags,
2602 struct page **pagep, void **fsdata,
2603 get_block_t *get_block)
2604{
2605 struct inode *inode = mapping->host;
2606 const unsigned blkbits = inode->i_blkbits;
2607 const unsigned blocksize = 1 << blkbits;
2608 struct buffer_head *head, *bh;
2609 struct page *page;
2610 pgoff_t index;
2611 unsigned from, to;
2612 unsigned block_in_page;
2613 unsigned block_start, block_end;
2614 sector_t block_in_file;
2615 int nr_reads = 0;
2616 int ret = 0;
2617 int is_mapped_to_disk = 1;
2618
2619 index = pos >> PAGE_SHIFT;
2620 from = pos & (PAGE_SIZE - 1);
2621 to = from + len;
2622
2623 page = grab_cache_page_write_begin(mapping, index, flags);
2624 if (!page)
2625 return -ENOMEM;
2626 *pagep = page;
2627 *fsdata = NULL;
2628
2629 if (page_has_buffers(page)) {
2630 ret = __block_write_begin(page, pos, len, get_block);
2631 if (unlikely(ret))
2632 goto out_release;
2633 return ret;
2634 }
2635
2636 if (PageMappedToDisk(page))
2637 return 0;
2638
2639 /*
2640 * Allocate buffers so that we can keep track of state, and potentially
2641 * attach them to the page if an error occurs. In the common case of
2642 * no error, they will just be freed again without ever being attached
2643 * to the page (which is all OK, because we're under the page lock).
2644 *
2645 * Be careful: the buffer linked list is a NULL terminated one, rather
2646 * than the circular one we're used to.
2647 */
2648 head = alloc_page_buffers(page, blocksize, 0);
2649 if (!head) {
2650 ret = -ENOMEM;
2651 goto out_release;
2652 }
2653
2654 block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
2655
2656 /*
2657 * We loop across all blocks in the page, whether or not they are
2658 * part of the affected region. This is so we can discover if the
2659 * page is fully mapped-to-disk.
2660 */
2661 for (block_start = 0, block_in_page = 0, bh = head;
2662 block_start < PAGE_SIZE;
2663 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
2664 int create;
2665
2666 block_end = block_start + blocksize;
2667 bh->b_state = 0;
2668 create = 1;
2669 if (block_start >= to)
2670 create = 0;
2671 ret = get_block(inode, block_in_file + block_in_page,
2672 bh, create);
2673 if (ret)
2674 goto failed;
2675 if (!buffer_mapped(bh))
2676 is_mapped_to_disk = 0;
2677 if (buffer_new(bh))
2678 clean_bdev_bh_alias(bh);
2679 if (PageUptodate(page)) {
2680 set_buffer_uptodate(bh);
2681 continue;
2682 }
2683 if (buffer_new(bh) || !buffer_mapped(bh)) {
2684 zero_user_segments(page, block_start, from,
2685 to, block_end);
2686 continue;
2687 }
2688 if (buffer_uptodate(bh))
2689 continue; /* reiserfs does this */
2690 if (block_start < from || block_end > to) {
2691 lock_buffer(bh);
2692 bh->b_end_io = end_buffer_read_nobh;
2693 submit_bh(REQ_OP_READ, 0, bh);
2694 nr_reads++;
2695 }
2696 }
2697
2698 if (nr_reads) {
2699 /*
2700 * The page is locked, so these buffers are protected from
2701 * any VM or truncate activity. Hence we don't need to care
2702 * for the buffer_head refcounts.
2703 */
2704 for (bh = head; bh; bh = bh->b_this_page) {
2705 wait_on_buffer(bh);
2706 if (!buffer_uptodate(bh))
2707 ret = -EIO;
2708 }
2709 if (ret)
2710 goto failed;
2711 }
2712
2713 if (is_mapped_to_disk)
2714 SetPageMappedToDisk(page);
2715
2716 *fsdata = head; /* to be released by nobh_write_end */
2717
2718 return 0;
2719
2720failed:
2721 BUG_ON(!ret);
2722 /*
2723 * Error recovery is a bit difficult. We need to zero out blocks that
2724 * were newly allocated, and dirty them to ensure they get written out.
2725 * Buffers need to be attached to the page at this point, otherwise
2726 * the handling of potential IO errors during writeout would be hard
2727 * (could try doing synchronous writeout, but what if that fails too?)
2728 */
2729 attach_nobh_buffers(page, head);
2730 page_zero_new_buffers(page, from, to);
2731
2732out_release:
2733 unlock_page(page);
2734 put_page(page);
2735 *pagep = NULL;
2736
2737 return ret;
2738}
2739EXPORT_SYMBOL(nobh_write_begin);
2740
2741int nobh_write_end(struct file *file, struct address_space *mapping,
2742 loff_t pos, unsigned len, unsigned copied,
2743 struct page *page, void *fsdata)
2744{
2745 struct inode *inode = page->mapping->host;
2746 struct buffer_head *head = fsdata;
2747 struct buffer_head *bh;
2748 BUG_ON(fsdata != NULL && page_has_buffers(page));
2749
2750 if (unlikely(copied < len) && head)
2751 attach_nobh_buffers(page, head);
2752 if (page_has_buffers(page))
2753 return generic_write_end(file, mapping, pos, len,
2754 copied, page, fsdata);
2755
2756 SetPageUptodate(page);
2757 set_page_dirty(page);
2758 if (pos+copied > inode->i_size) {
2759 i_size_write(inode, pos+copied);
2760 mark_inode_dirty(inode);
2761 }
2762
2763 unlock_page(page);
2764 put_page(page);
2765
2766 while (head) {
2767 bh = head;
2768 head = head->b_this_page;
2769 free_buffer_head(bh);
2770 }
2771
2772 return copied;
2773}
2774EXPORT_SYMBOL(nobh_write_end);
2775
2776/*
2777 * nobh_writepage() - based on block_full_write_page() except
2778 * that it tries to operate without attaching bufferheads to
2779 * the page.
2780 */
2781int nobh_writepage(struct page *page, get_block_t *get_block,
2782 struct writeback_control *wbc)
2783{
2784 struct inode * const inode = page->mapping->host;
2785 loff_t i_size = i_size_read(inode);
2786 const pgoff_t end_index = i_size >> PAGE_SHIFT;
2787 unsigned offset;
2788 int ret;
2789
2790 /* Is the page fully inside i_size? */
2791 if (page->index < end_index)
2792 goto out;
2793
2794 /* Is the page fully outside i_size? (truncate in progress) */
2795 offset = i_size & (PAGE_SIZE-1);
2796 if (page->index >= end_index+1 || !offset) {
2797 /*
2798 * The page may have dirty, unmapped buffers. For example,
2799 * they may have been added in ext3_writepage(). Make them
2800 * freeable here, so the page does not leak.
2801 */
2802#if 0
2803 /* Not really sure about this - do we need this ? */
2804 if (page->mapping->a_ops->invalidatepage)
2805 page->mapping->a_ops->invalidatepage(page, offset);
2806#endif
2807 unlock_page(page);
2808 return 0; /* don't care */
2809 }
2810
2811 /*
2812 * The page straddles i_size. It must be zeroed out on each and every
2813 * writepage invocation because it may be mmapped. "A file is mapped
2814 * in multiples of the page size. For a file that is not a multiple of
2815 * the page size, the remaining memory is zeroed when mapped, and
2816 * writes to that region are not written out to the file."
2817 */
2818 zero_user_segment(page, offset, PAGE_SIZE);
2819out:
2820 ret = mpage_writepage(page, get_block, wbc);
2821 if (ret == -EAGAIN)
2822 ret = __block_write_full_page(inode, page, get_block, wbc,
2823 end_buffer_async_write);
2824 return ret;
2825}
2826EXPORT_SYMBOL(nobh_writepage);
2827
2828int nobh_truncate_page(struct address_space *mapping,
2829 loff_t from, get_block_t *get_block)
2830{
2831 pgoff_t index = from >> PAGE_SHIFT;
2832 unsigned offset = from & (PAGE_SIZE-1);
2833 unsigned blocksize;
2834 sector_t iblock;
2835 unsigned length, pos;
2836 struct inode *inode = mapping->host;
2837 struct page *page;
2838 struct buffer_head map_bh;
2839 int err;
2840
2841 blocksize = 1 << inode->i_blkbits;
2842 length = offset & (blocksize - 1);
2843
2844 /* Block boundary? Nothing to do */
2845 if (!length)
2846 return 0;
2847
2848 length = blocksize - length;
2849 iblock = (sector_t)index << (PAGE_SHIFT - inode->i_blkbits);
2850
2851 page = grab_cache_page(mapping, index);
2852 err = -ENOMEM;
2853 if (!page)
2854 goto out;
2855
2856 if (page_has_buffers(page)) {
2857has_buffers:
2858 unlock_page(page);
2859 put_page(page);
2860 return block_truncate_page(mapping, from, get_block);
2861 }
2862
2863 /* Find the buffer that contains "offset" */
2864 pos = blocksize;
2865 while (offset >= pos) {
2866 iblock++;
2867 pos += blocksize;
2868 }
2869
2870 map_bh.b_size = blocksize;
2871 map_bh.b_state = 0;
2872 err = get_block(inode, iblock, &map_bh, 0);
2873 if (err)
2874 goto unlock;
2875 /* unmapped? It's a hole - nothing to do */
2876 if (!buffer_mapped(&map_bh))
2877 goto unlock;
2878
2879 /* Ok, it's mapped. Make sure it's up-to-date */
2880 if (!PageUptodate(page)) {
2881 err = mapping->a_ops->readpage(NULL, page);
2882 if (err) {
2883 put_page(page);
2884 goto out;
2885 }
2886 lock_page(page);
2887 if (!PageUptodate(page)) {
2888 err = -EIO;
2889 goto unlock;
2890 }
2891 if (page_has_buffers(page))
2892 goto has_buffers;
2893 }
2894 zero_user(page, offset, length);
2895 set_page_dirty(page);
2896 err = 0;
2897
2898unlock:
2899 unlock_page(page);
2900 put_page(page);
2901out:
2902 return err;
2903}
2904EXPORT_SYMBOL(nobh_truncate_page);
2905
2906int block_truncate_page(struct address_space *mapping,
2907 loff_t from, get_block_t *get_block)
2908{
2909 pgoff_t index = from >> PAGE_SHIFT;
2910 unsigned offset = from & (PAGE_SIZE-1);
2911 unsigned blocksize;
2912 sector_t iblock;
2913 unsigned length, pos;
2914 struct inode *inode = mapping->host;
2915 struct page *page;
2916 struct buffer_head *bh;
2917 int err;
2918
2919 blocksize = 1 << inode->i_blkbits;
2920 length = offset & (blocksize - 1);
2921
2922 /* Block boundary? Nothing to do */
2923 if (!length)
2924 return 0;
2925
2926 length = blocksize - length;
2927 iblock = (sector_t)index << (PAGE_SHIFT - inode->i_blkbits);
2928
2929 page = grab_cache_page(mapping, index);
2930 err = -ENOMEM;
2931 if (!page)
2932 goto out;
2933
2934 if (!page_has_buffers(page))
2935 create_empty_buffers(page, blocksize, 0);
2936
2937 /* Find the buffer that contains "offset" */
2938 bh = page_buffers(page);
2939 pos = blocksize;
2940 while (offset >= pos) {
2941 bh = bh->b_this_page;
2942 iblock++;
2943 pos += blocksize;
2944 }
2945
2946 err = 0;
2947 if (!buffer_mapped(bh)) {
2948 WARN_ON(bh->b_size != blocksize);
2949 err = get_block(inode, iblock, bh, 0);
2950 if (err)
2951 goto unlock;
2952 /* unmapped? It's a hole - nothing to do */
2953 if (!buffer_mapped(bh))
2954 goto unlock;
2955 }
2956
2957 /* Ok, it's mapped. Make sure it's up-to-date */
2958 if (PageUptodate(page))
2959 set_buffer_uptodate(bh);
2960
2961 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2962 err = -EIO;
2963 ll_rw_block(REQ_OP_READ, 0, 1, &bh);
2964 wait_on_buffer(bh);
2965 /* Uhhuh. Read error. Complain and punt. */
2966 if (!buffer_uptodate(bh))
2967 goto unlock;
2968 }
2969
2970 zero_user(page, offset, length);
2971 mark_buffer_dirty(bh);
2972 err = 0;
2973
2974unlock:
2975 unlock_page(page);
2976 put_page(page);
2977out:
2978 return err;
2979}
2980EXPORT_SYMBOL(block_truncate_page);
2981
2982/*
2983 * The generic ->writepage function for buffer-backed address_spaces
2984 */
2985int block_write_full_page(struct page *page, get_block_t *get_block,
2986 struct writeback_control *wbc)
2987{
2988 struct inode * const inode = page->mapping->host;
2989 loff_t i_size = i_size_read(inode);
2990 const pgoff_t end_index = i_size >> PAGE_SHIFT;
2991 unsigned offset;
2992
2993 /* Is the page fully inside i_size? */
2994 if (page->index < end_index)
2995 return __block_write_full_page(inode, page, get_block, wbc,
2996 end_buffer_async_write);
2997
2998 /* Is the page fully outside i_size? (truncate in progress) */
2999 offset = i_size & (PAGE_SIZE-1);
3000 if (page->index >= end_index+1 || !offset) {
3001 /*
3002 * The page may have dirty, unmapped buffers. For example,
3003 * they may have been added in ext3_writepage(). Make them
3004 * freeable here, so the page does not leak.
3005 */
3006 do_invalidatepage(page, 0, PAGE_SIZE);
3007 unlock_page(page);
3008 return 0; /* don't care */
3009 }
3010
3011 /*
3012 * The page straddles i_size. It must be zeroed out on each and every
3013 * writepage invocation because it may be mmapped. "A file is mapped
3014 * in multiples of the page size. For a file that is not a multiple of
3015 * the page size, the remaining memory is zeroed when mapped, and
3016 * writes to that region are not written out to the file."
3017 */
3018 zero_user_segment(page, offset, PAGE_SIZE);
3019 return __block_write_full_page(inode, page, get_block, wbc,
3020 end_buffer_async_write);
3021}
3022EXPORT_SYMBOL(block_write_full_page);
3023
3024sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
3025 get_block_t *get_block)
3026{
3027 struct buffer_head tmp;
3028 struct inode *inode = mapping->host;
3029 tmp.b_state = 0;
3030 tmp.b_blocknr = 0;
3031 tmp.b_size = 1 << inode->i_blkbits;
3032 get_block(inode, block, &tmp, 0);
3033 return tmp.b_blocknr;
3034}
3035EXPORT_SYMBOL(generic_block_bmap);
3036
3037static void end_bio_bh_io_sync(struct bio *bio)
3038{
3039 struct buffer_head *bh = bio->bi_private;
3040
3041 if (unlikely(bio_flagged(bio, BIO_QUIET)))
3042 set_bit(BH_Quiet, &bh->b_state);
3043
3044 bh->b_end_io(bh, !bio->bi_error);
3045 bio_put(bio);
3046}
3047
3048/*
3049 * This allows us to do IO even on the odd last sectors
3050 * of a device, even if the block size is some multiple
3051 * of the physical sector size.
3052 *
3053 * We'll just truncate the bio to the size of the device,
3054 * and clear the end of the buffer head manually.
3055 *
3056 * Truly out-of-range accesses will turn into actual IO
3057 * errors, this only handles the "we need to be able to
3058 * do IO at the final sector" case.
3059 */
3060void guard_bio_eod(int op, struct bio *bio)
3061{
3062 sector_t maxsector;
3063 struct bio_vec *bvec = &bio->bi_io_vec[bio->bi_vcnt - 1];
3064 unsigned truncated_bytes;
3065
3066 maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
3067 if (!maxsector)
3068 return;
3069
3070 /*
3071 * If the *whole* IO is past the end of the device,
3072 * let it through, and the IO layer will turn it into
3073 * an EIO.
3074 */
3075 if (unlikely(bio->bi_iter.bi_sector >= maxsector))
3076 return;
3077
3078 maxsector -= bio->bi_iter.bi_sector;
3079 if (likely((bio->bi_iter.bi_size >> 9) <= maxsector))
3080 return;
3081
3082 /* Uhhuh. We've got a bio that straddles the device size! */
3083 truncated_bytes = bio->bi_iter.bi_size - (maxsector << 9);
3084
3085 /* Truncate the bio.. */
3086 bio->bi_iter.bi_size -= truncated_bytes;
3087 bvec->bv_len -= truncated_bytes;
3088
3089 /* ..and clear the end of the buffer for reads */
3090 if (op == REQ_OP_READ) {
3091 zero_user(bvec->bv_page, bvec->bv_offset + bvec->bv_len,
3092 truncated_bytes);
3093 }
3094}
3095
3096static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
3097 unsigned long bio_flags, struct writeback_control *wbc)
3098{
3099 struct bio *bio;
3100
3101 BUG_ON(!buffer_locked(bh));
3102 BUG_ON(!buffer_mapped(bh));
3103 BUG_ON(!bh->b_end_io);
3104 BUG_ON(buffer_delay(bh));
3105 BUG_ON(buffer_unwritten(bh));
3106
3107 /*
3108 * Only clear out a write error when rewriting
3109 */
3110 if (test_set_buffer_req(bh) && (op == REQ_OP_WRITE))
3111 clear_buffer_write_io_error(bh);
3112
3113 /*
3114 * from here on down, it's all bio -- do the initial mapping,
3115 * submit_bio -> generic_make_request may further map this bio around
3116 */
3117 bio = bio_alloc(GFP_NOIO, 1);
3118
3119 if (wbc) {
3120 wbc_init_bio(wbc, bio);
3121 wbc_account_io(wbc, bh->b_page, bh->b_size);
3122 }
3123
3124 bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
3125 bio->bi_bdev = bh->b_bdev;
3126
3127 bio_add_page(bio, bh->b_page, bh->b_size, bh_offset(bh));
3128 BUG_ON(bio->bi_iter.bi_size != bh->b_size);
3129
3130 bio->bi_end_io = end_bio_bh_io_sync;
3131 bio->bi_private = bh;
3132 bio->bi_flags |= bio_flags;
3133
3134 /* Take care of bh's that straddle the end of the device */
3135 guard_bio_eod(op, bio);
3136
3137 if (buffer_meta(bh))
3138 op_flags |= REQ_META;
3139 if (buffer_prio(bh))
3140 op_flags |= REQ_PRIO;
3141 bio_set_op_attrs(bio, op, op_flags);
3142
3143 submit_bio(bio);
3144 return 0;
3145}
3146
3147int _submit_bh(int op, int op_flags, struct buffer_head *bh,
3148 unsigned long bio_flags)
3149{
3150 return submit_bh_wbc(op, op_flags, bh, bio_flags, NULL);
3151}
3152EXPORT_SYMBOL_GPL(_submit_bh);
3153
3154int submit_bh(int op, int op_flags, struct buffer_head *bh)
3155{
3156 return submit_bh_wbc(op, op_flags, bh, 0, NULL);
3157}
3158EXPORT_SYMBOL(submit_bh);
3159
3160/**
3161 * ll_rw_block: low-level access to block devices (DEPRECATED)
3162 * @op: whether to %READ or %WRITE
3163 * @op_flags: req_flag_bits
3164 * @nr: number of &struct buffer_heads in the array
3165 * @bhs: array of pointers to &struct buffer_head
3166 *
3167 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
3168 * requests an I/O operation on them, either a %REQ_OP_READ or a %REQ_OP_WRITE.
3169 * @op_flags contains flags modifying the detailed I/O behavior, most notably
3170 * %REQ_RAHEAD.
3171 *
3172 * This function drops any buffer that it cannot get a lock on (with the
3173 * BH_Lock state bit), any buffer that appears to be clean when doing a write
3174 * request, and any buffer that appears to be up-to-date when doing read
3175 * request. Further it marks as clean buffers that are processed for
3176 * writing (the buffer cache won't assume that they are actually clean
3177 * until the buffer gets unlocked).
3178 *
3179 * ll_rw_block sets b_end_io to simple completion handler that marks
3180 * the buffer up-to-date (if appropriate), unlocks the buffer and wakes
3181 * any waiters.
3182 *
3183 * All of the buffers must be for the same device, and must also be a
3184 * multiple of the current approved size for the device.
3185 */
3186void ll_rw_block(int op, int op_flags, int nr, struct buffer_head *bhs[])
3187{
3188 int i;
3189
3190 for (i = 0; i < nr; i++) {
3191 struct buffer_head *bh = bhs[i];
3192
3193 if (!trylock_buffer(bh))
3194 continue;
3195 if (op == WRITE) {
3196 if (test_clear_buffer_dirty(bh)) {
3197 bh->b_end_io = end_buffer_write_sync;
3198 get_bh(bh);
3199 submit_bh(op, op_flags, bh);
3200 continue;
3201 }
3202 } else {
3203 if (!buffer_uptodate(bh)) {
3204 bh->b_end_io = end_buffer_read_sync;
3205 get_bh(bh);
3206 submit_bh(op, op_flags, bh);
3207 continue;
3208 }
3209 }
3210 unlock_buffer(bh);
3211 }
3212}
3213EXPORT_SYMBOL(ll_rw_block);
3214
3215void write_dirty_buffer(struct buffer_head *bh, int op_flags)
3216{
3217 lock_buffer(bh);
3218 if (!test_clear_buffer_dirty(bh)) {
3219 unlock_buffer(bh);
3220 return;
3221 }
3222 bh->b_end_io = end_buffer_write_sync;
3223 get_bh(bh);
3224 submit_bh(REQ_OP_WRITE, op_flags, bh);
3225}
3226EXPORT_SYMBOL(write_dirty_buffer);
3227
3228/*
3229 * For a data-integrity writeout, we need to wait upon any in-progress I/O
3230 * and then start new I/O and then wait upon it. The caller must have a ref on
3231 * the buffer_head.
3232 */
3233int __sync_dirty_buffer(struct buffer_head *bh, int op_flags)
3234{
3235 int ret = 0;
3236
3237 WARN_ON(atomic_read(&bh->b_count) < 1);
3238 lock_buffer(bh);
3239 if (test_clear_buffer_dirty(bh)) {
3240 get_bh(bh);
3241 bh->b_end_io = end_buffer_write_sync;
3242 ret = submit_bh(REQ_OP_WRITE, op_flags, bh);
3243 wait_on_buffer(bh);
3244 if (!ret && !buffer_uptodate(bh))
3245 ret = -EIO;
3246 } else {
3247 unlock_buffer(bh);
3248 }
3249 return ret;
3250}
3251EXPORT_SYMBOL(__sync_dirty_buffer);
3252
3253int sync_dirty_buffer(struct buffer_head *bh)
3254{
3255 return __sync_dirty_buffer(bh, REQ_SYNC);
3256}
3257EXPORT_SYMBOL(sync_dirty_buffer);
3258
3259/*
3260 * try_to_free_buffers() checks if all the buffers on this particular page
3261 * are unused, and releases them if so.
3262 *
3263 * Exclusion against try_to_free_buffers may be obtained by either
3264 * locking the page or by holding its mapping's private_lock.
3265 *
3266 * If the page is dirty but all the buffers are clean then we need to
3267 * be sure to mark the page clean as well. This is because the page
3268 * may be against a block device, and a later reattachment of buffers
3269 * to a dirty page will set *all* buffers dirty. Which would corrupt
3270 * filesystem data on the same device.
3271 *
3272 * The same applies to regular filesystem pages: if all the buffers are
3273 * clean then we set the page clean and proceed. To do that, we require
3274 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3275 * private_lock.
3276 *
3277 * try_to_free_buffers() is non-blocking.
3278 */
3279static inline int buffer_busy(struct buffer_head *bh)
3280{
3281 return atomic_read(&bh->b_count) |
3282 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3283}
3284
3285static int
3286drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3287{
3288 struct buffer_head *head = page_buffers(page);
3289 struct buffer_head *bh;
3290
3291 bh = head;
3292 do {
3293 if (buffer_write_io_error(bh) && page->mapping)
3294 mapping_set_error(page->mapping, -EIO);
3295 if (buffer_busy(bh))
3296 goto failed;
3297 bh = bh->b_this_page;
3298 } while (bh != head);
3299
3300 do {
3301 struct buffer_head *next = bh->b_this_page;
3302
3303 if (bh->b_assoc_map)
3304 __remove_assoc_queue(bh);
3305 bh = next;
3306 } while (bh != head);
3307 *buffers_to_free = head;
3308 __clear_page_buffers(page);
3309 return 1;
3310failed:
3311 return 0;
3312}
3313
3314int try_to_free_buffers(struct page *page)
3315{
3316 struct address_space * const mapping = page->mapping;
3317 struct buffer_head *buffers_to_free = NULL;
3318 int ret = 0;
3319
3320 BUG_ON(!PageLocked(page));
3321 if (PageWriteback(page))
3322 return 0;
3323
3324 if (mapping == NULL) { /* can this still happen? */
3325 ret = drop_buffers(page, &buffers_to_free);
3326 goto out;
3327 }
3328
3329 spin_lock(&mapping->private_lock);
3330 ret = drop_buffers(page, &buffers_to_free);
3331
3332 /*
3333 * If the filesystem writes its buffers by hand (eg ext3)
3334 * then we can have clean buffers against a dirty page. We
3335 * clean the page here; otherwise the VM will never notice
3336 * that the filesystem did any IO at all.
3337 *
3338 * Also, during truncate, discard_buffer will have marked all
3339 * the page's buffers clean. We discover that here and clean
3340 * the page also.
3341 *
3342 * private_lock must be held over this entire operation in order
3343 * to synchronise against __set_page_dirty_buffers and prevent the
3344 * dirty bit from being lost.
3345 */
3346 if (ret)
3347 cancel_dirty_page(page);
3348 spin_unlock(&mapping->private_lock);
3349out:
3350 if (buffers_to_free) {
3351 struct buffer_head *bh = buffers_to_free;
3352
3353 do {
3354 struct buffer_head *next = bh->b_this_page;
3355 free_buffer_head(bh);
3356 bh = next;
3357 } while (bh != buffers_to_free);
3358 }
3359 return ret;
3360}
3361EXPORT_SYMBOL(try_to_free_buffers);
3362
3363/*
3364 * There are no bdflush tunables left. But distributions are
3365 * still running obsolete flush daemons, so we terminate them here.
3366 *
3367 * Use of bdflush() is deprecated and will be removed in a future kernel.
3368 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
3369 */
3370SYSCALL_DEFINE2(bdflush, int, func, long, data)
3371{
3372 static int msg_count;
3373
3374 if (!capable(CAP_SYS_ADMIN))
3375 return -EPERM;
3376
3377 if (msg_count < 5) {
3378 msg_count++;
3379 printk(KERN_INFO
3380 "warning: process `%s' used the obsolete bdflush"
3381 " system call\n", current->comm);
3382 printk(KERN_INFO "Fix your initscripts?\n");
3383 }
3384
3385 if (func == 1)
3386 do_exit(0);
3387 return 0;
3388}
3389
3390/*
3391 * Buffer-head allocation
3392 */
3393static struct kmem_cache *bh_cachep __read_mostly;
3394
3395/*
3396 * Once the number of bh's in the machine exceeds this level, we start
3397 * stripping them in writeback.
3398 */
3399static unsigned long max_buffer_heads;
3400
3401int buffer_heads_over_limit;
3402
3403struct bh_accounting {
3404 int nr; /* Number of live bh's */
3405 int ratelimit; /* Limit cacheline bouncing */
3406};
3407
3408static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3409
3410static void recalc_bh_state(void)
3411{
3412 int i;
3413 int tot = 0;
3414
3415 if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
3416 return;
3417 __this_cpu_write(bh_accounting.ratelimit, 0);
3418 for_each_online_cpu(i)
3419 tot += per_cpu(bh_accounting, i).nr;
3420 buffer_heads_over_limit = (tot > max_buffer_heads);
3421}
3422
3423struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3424{
3425 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
3426 if (ret) {
3427 INIT_LIST_HEAD(&ret->b_assoc_buffers);
3428 preempt_disable();
3429 __this_cpu_inc(bh_accounting.nr);
3430 recalc_bh_state();
3431 preempt_enable();
3432 }
3433 return ret;
3434}
3435EXPORT_SYMBOL(alloc_buffer_head);
3436
3437void free_buffer_head(struct buffer_head *bh)
3438{
3439 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3440 kmem_cache_free(bh_cachep, bh);
3441 preempt_disable();
3442 __this_cpu_dec(bh_accounting.nr);
3443 recalc_bh_state();
3444 preempt_enable();
3445}
3446EXPORT_SYMBOL(free_buffer_head);
3447
3448static int buffer_exit_cpu_dead(unsigned int cpu)
3449{
3450 int i;
3451 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3452
3453 for (i = 0; i < BH_LRU_SIZE; i++) {
3454 brelse(b->bhs[i]);
3455 b->bhs[i] = NULL;
3456 }
3457 this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3458 per_cpu(bh_accounting, cpu).nr = 0;
3459 return 0;
3460}
3461
3462/**
3463 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3464 * @bh: struct buffer_head
3465 *
3466 * Return true if the buffer is up-to-date and false,
3467 * with the buffer locked, if not.
3468 */
3469int bh_uptodate_or_lock(struct buffer_head *bh)
3470{
3471 if (!buffer_uptodate(bh)) {
3472 lock_buffer(bh);
3473 if (!buffer_uptodate(bh))
3474 return 0;
3475 unlock_buffer(bh);
3476 }
3477 return 1;
3478}
3479EXPORT_SYMBOL(bh_uptodate_or_lock);
3480
3481/**
3482 * bh_submit_read - Submit a locked buffer for reading
3483 * @bh: struct buffer_head
3484 *
3485 * Returns zero on success and -EIO on error.
3486 */
3487int bh_submit_read(struct buffer_head *bh)
3488{
3489 BUG_ON(!buffer_locked(bh));
3490
3491 if (buffer_uptodate(bh)) {
3492 unlock_buffer(bh);
3493 return 0;
3494 }
3495
3496 get_bh(bh);
3497 bh->b_end_io = end_buffer_read_sync;
3498 submit_bh(REQ_OP_READ, 0, bh);
3499 wait_on_buffer(bh);
3500 if (buffer_uptodate(bh))
3501 return 0;
3502 return -EIO;
3503}
3504EXPORT_SYMBOL(bh_submit_read);
3505
3506void __init buffer_init(void)
3507{
3508 unsigned long nrpages;
3509 int ret;
3510
3511 bh_cachep = kmem_cache_create("buffer_head",
3512 sizeof(struct buffer_head), 0,
3513 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3514 SLAB_MEM_SPREAD),
3515 NULL);
3516
3517 /*
3518 * Limit the bh occupancy to 10% of ZONE_NORMAL
3519 */
3520 nrpages = (nr_free_buffer_pages() * 10) / 100;
3521 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3522 ret = cpuhp_setup_state_nocalls(CPUHP_FS_BUFF_DEAD, "fs/buffer:dead",
3523 NULL, buffer_exit_cpu_dead);
3524 WARN_ON(ret < 0);
3525}
1/*
2 * linux/fs/buffer.c
3 *
4 * Copyright (C) 1991, 1992, 2002 Linus Torvalds
5 */
6
7/*
8 * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95
9 *
10 * Removed a lot of unnecessary code and simplified things now that
11 * the buffer cache isn't our primary cache - Andrew Tridgell 12/96
12 *
13 * Speed up hash, lru, and free list operations. Use gfp() for allocating
14 * hash table, use SLAB cache for buffer heads. SMP threading. -DaveM
15 *
16 * Added 32k buffer block sizes - these are required older ARM systems. - RMK
17 *
18 * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de>
19 */
20
21#include <linux/kernel.h>
22#include <linux/sched/signal.h>
23#include <linux/syscalls.h>
24#include <linux/fs.h>
25#include <linux/iomap.h>
26#include <linux/mm.h>
27#include <linux/percpu.h>
28#include <linux/slab.h>
29#include <linux/capability.h>
30#include <linux/blkdev.h>
31#include <linux/file.h>
32#include <linux/quotaops.h>
33#include <linux/highmem.h>
34#include <linux/export.h>
35#include <linux/backing-dev.h>
36#include <linux/writeback.h>
37#include <linux/hash.h>
38#include <linux/suspend.h>
39#include <linux/buffer_head.h>
40#include <linux/task_io_accounting_ops.h>
41#include <linux/bio.h>
42#include <linux/notifier.h>
43#include <linux/cpu.h>
44#include <linux/bitops.h>
45#include <linux/mpage.h>
46#include <linux/bit_spinlock.h>
47#include <linux/pagevec.h>
48#include <trace/events/block.h>
49
50static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
51static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
52 enum rw_hint hint, struct writeback_control *wbc);
53
54#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
55
56inline void touch_buffer(struct buffer_head *bh)
57{
58 trace_block_touch_buffer(bh);
59 mark_page_accessed(bh->b_page);
60}
61EXPORT_SYMBOL(touch_buffer);
62
63void __lock_buffer(struct buffer_head *bh)
64{
65 wait_on_bit_lock_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
66}
67EXPORT_SYMBOL(__lock_buffer);
68
69void unlock_buffer(struct buffer_head *bh)
70{
71 clear_bit_unlock(BH_Lock, &bh->b_state);
72 smp_mb__after_atomic();
73 wake_up_bit(&bh->b_state, BH_Lock);
74}
75EXPORT_SYMBOL(unlock_buffer);
76
77/*
78 * Returns if the page has dirty or writeback buffers. If all the buffers
79 * are unlocked and clean then the PageDirty information is stale. If
80 * any of the pages are locked, it is assumed they are locked for IO.
81 */
82void buffer_check_dirty_writeback(struct page *page,
83 bool *dirty, bool *writeback)
84{
85 struct buffer_head *head, *bh;
86 *dirty = false;
87 *writeback = false;
88
89 BUG_ON(!PageLocked(page));
90
91 if (!page_has_buffers(page))
92 return;
93
94 if (PageWriteback(page))
95 *writeback = true;
96
97 head = page_buffers(page);
98 bh = head;
99 do {
100 if (buffer_locked(bh))
101 *writeback = true;
102
103 if (buffer_dirty(bh))
104 *dirty = true;
105
106 bh = bh->b_this_page;
107 } while (bh != head);
108}
109EXPORT_SYMBOL(buffer_check_dirty_writeback);
110
111/*
112 * Block until a buffer comes unlocked. This doesn't stop it
113 * from becoming locked again - you have to lock it yourself
114 * if you want to preserve its state.
115 */
116void __wait_on_buffer(struct buffer_head * bh)
117{
118 wait_on_bit_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
119}
120EXPORT_SYMBOL(__wait_on_buffer);
121
122static void
123__clear_page_buffers(struct page *page)
124{
125 ClearPagePrivate(page);
126 set_page_private(page, 0);
127 put_page(page);
128}
129
130static void buffer_io_error(struct buffer_head *bh, char *msg)
131{
132 if (!test_bit(BH_Quiet, &bh->b_state))
133 printk_ratelimited(KERN_ERR
134 "Buffer I/O error on dev %pg, logical block %llu%s\n",
135 bh->b_bdev, (unsigned long long)bh->b_blocknr, msg);
136}
137
138/*
139 * End-of-IO handler helper function which does not touch the bh after
140 * unlocking it.
141 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
142 * a race there is benign: unlock_buffer() only use the bh's address for
143 * hashing after unlocking the buffer, so it doesn't actually touch the bh
144 * itself.
145 */
146static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
147{
148 if (uptodate) {
149 set_buffer_uptodate(bh);
150 } else {
151 /* This happens, due to failed read-ahead attempts. */
152 clear_buffer_uptodate(bh);
153 }
154 unlock_buffer(bh);
155}
156
157/*
158 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
159 * unlock the buffer. This is what ll_rw_block uses too.
160 */
161void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
162{
163 __end_buffer_read_notouch(bh, uptodate);
164 put_bh(bh);
165}
166EXPORT_SYMBOL(end_buffer_read_sync);
167
168void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
169{
170 if (uptodate) {
171 set_buffer_uptodate(bh);
172 } else {
173 buffer_io_error(bh, ", lost sync page write");
174 mark_buffer_write_io_error(bh);
175 clear_buffer_uptodate(bh);
176 }
177 unlock_buffer(bh);
178 put_bh(bh);
179}
180EXPORT_SYMBOL(end_buffer_write_sync);
181
182/*
183 * Various filesystems appear to want __find_get_block to be non-blocking.
184 * But it's the page lock which protects the buffers. To get around this,
185 * we get exclusion from try_to_free_buffers with the blockdev mapping's
186 * private_lock.
187 *
188 * Hack idea: for the blockdev mapping, private_lock contention
189 * may be quite high. This code could TryLock the page, and if that
190 * succeeds, there is no need to take private_lock.
191 */
192static struct buffer_head *
193__find_get_block_slow(struct block_device *bdev, sector_t block)
194{
195 struct inode *bd_inode = bdev->bd_inode;
196 struct address_space *bd_mapping = bd_inode->i_mapping;
197 struct buffer_head *ret = NULL;
198 pgoff_t index;
199 struct buffer_head *bh;
200 struct buffer_head *head;
201 struct page *page;
202 int all_mapped = 1;
203
204 index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
205 page = find_get_page_flags(bd_mapping, index, FGP_ACCESSED);
206 if (!page)
207 goto out;
208
209 spin_lock(&bd_mapping->private_lock);
210 if (!page_has_buffers(page))
211 goto out_unlock;
212 head = page_buffers(page);
213 bh = head;
214 do {
215 if (!buffer_mapped(bh))
216 all_mapped = 0;
217 else if (bh->b_blocknr == block) {
218 ret = bh;
219 get_bh(bh);
220 goto out_unlock;
221 }
222 bh = bh->b_this_page;
223 } while (bh != head);
224
225 /* we might be here because some of the buffers on this page are
226 * not mapped. This is due to various races between
227 * file io on the block device and getblk. It gets dealt with
228 * elsewhere, don't buffer_error if we had some unmapped buffers
229 */
230 if (all_mapped) {
231 printk("__find_get_block_slow() failed. "
232 "block=%llu, b_blocknr=%llu\n",
233 (unsigned long long)block,
234 (unsigned long long)bh->b_blocknr);
235 printk("b_state=0x%08lx, b_size=%zu\n",
236 bh->b_state, bh->b_size);
237 printk("device %pg blocksize: %d\n", bdev,
238 1 << bd_inode->i_blkbits);
239 }
240out_unlock:
241 spin_unlock(&bd_mapping->private_lock);
242 put_page(page);
243out:
244 return ret;
245}
246
247/*
248 * I/O completion handler for block_read_full_page() - pages
249 * which come unlocked at the end of I/O.
250 */
251static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
252{
253 unsigned long flags;
254 struct buffer_head *first;
255 struct buffer_head *tmp;
256 struct page *page;
257 int page_uptodate = 1;
258
259 BUG_ON(!buffer_async_read(bh));
260
261 page = bh->b_page;
262 if (uptodate) {
263 set_buffer_uptodate(bh);
264 } else {
265 clear_buffer_uptodate(bh);
266 buffer_io_error(bh, ", async page read");
267 SetPageError(page);
268 }
269
270 /*
271 * Be _very_ careful from here on. Bad things can happen if
272 * two buffer heads end IO at almost the same time and both
273 * decide that the page is now completely done.
274 */
275 first = page_buffers(page);
276 local_irq_save(flags);
277 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
278 clear_buffer_async_read(bh);
279 unlock_buffer(bh);
280 tmp = bh;
281 do {
282 if (!buffer_uptodate(tmp))
283 page_uptodate = 0;
284 if (buffer_async_read(tmp)) {
285 BUG_ON(!buffer_locked(tmp));
286 goto still_busy;
287 }
288 tmp = tmp->b_this_page;
289 } while (tmp != bh);
290 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
291 local_irq_restore(flags);
292
293 /*
294 * If none of the buffers had errors and they are all
295 * uptodate then we can set the page uptodate.
296 */
297 if (page_uptodate && !PageError(page))
298 SetPageUptodate(page);
299 unlock_page(page);
300 return;
301
302still_busy:
303 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
304 local_irq_restore(flags);
305 return;
306}
307
308/*
309 * Completion handler for block_write_full_page() - pages which are unlocked
310 * during I/O, and which have PageWriteback cleared upon I/O completion.
311 */
312void end_buffer_async_write(struct buffer_head *bh, int uptodate)
313{
314 unsigned long flags;
315 struct buffer_head *first;
316 struct buffer_head *tmp;
317 struct page *page;
318
319 BUG_ON(!buffer_async_write(bh));
320
321 page = bh->b_page;
322 if (uptodate) {
323 set_buffer_uptodate(bh);
324 } else {
325 buffer_io_error(bh, ", lost async page write");
326 mark_buffer_write_io_error(bh);
327 clear_buffer_uptodate(bh);
328 SetPageError(page);
329 }
330
331 first = page_buffers(page);
332 local_irq_save(flags);
333 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
334
335 clear_buffer_async_write(bh);
336 unlock_buffer(bh);
337 tmp = bh->b_this_page;
338 while (tmp != bh) {
339 if (buffer_async_write(tmp)) {
340 BUG_ON(!buffer_locked(tmp));
341 goto still_busy;
342 }
343 tmp = tmp->b_this_page;
344 }
345 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
346 local_irq_restore(flags);
347 end_page_writeback(page);
348 return;
349
350still_busy:
351 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
352 local_irq_restore(flags);
353 return;
354}
355EXPORT_SYMBOL(end_buffer_async_write);
356
357/*
358 * If a page's buffers are under async readin (end_buffer_async_read
359 * completion) then there is a possibility that another thread of
360 * control could lock one of the buffers after it has completed
361 * but while some of the other buffers have not completed. This
362 * locked buffer would confuse end_buffer_async_read() into not unlocking
363 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
364 * that this buffer is not under async I/O.
365 *
366 * The page comes unlocked when it has no locked buffer_async buffers
367 * left.
368 *
369 * PageLocked prevents anyone starting new async I/O reads any of
370 * the buffers.
371 *
372 * PageWriteback is used to prevent simultaneous writeout of the same
373 * page.
374 *
375 * PageLocked prevents anyone from starting writeback of a page which is
376 * under read I/O (PageWriteback is only ever set against a locked page).
377 */
378static void mark_buffer_async_read(struct buffer_head *bh)
379{
380 bh->b_end_io = end_buffer_async_read;
381 set_buffer_async_read(bh);
382}
383
384static void mark_buffer_async_write_endio(struct buffer_head *bh,
385 bh_end_io_t *handler)
386{
387 bh->b_end_io = handler;
388 set_buffer_async_write(bh);
389}
390
391void mark_buffer_async_write(struct buffer_head *bh)
392{
393 mark_buffer_async_write_endio(bh, end_buffer_async_write);
394}
395EXPORT_SYMBOL(mark_buffer_async_write);
396
397
398/*
399 * fs/buffer.c contains helper functions for buffer-backed address space's
400 * fsync functions. A common requirement for buffer-based filesystems is
401 * that certain data from the backing blockdev needs to be written out for
402 * a successful fsync(). For example, ext2 indirect blocks need to be
403 * written back and waited upon before fsync() returns.
404 *
405 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
406 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
407 * management of a list of dependent buffers at ->i_mapping->private_list.
408 *
409 * Locking is a little subtle: try_to_free_buffers() will remove buffers
410 * from their controlling inode's queue when they are being freed. But
411 * try_to_free_buffers() will be operating against the *blockdev* mapping
412 * at the time, not against the S_ISREG file which depends on those buffers.
413 * So the locking for private_list is via the private_lock in the address_space
414 * which backs the buffers. Which is different from the address_space
415 * against which the buffers are listed. So for a particular address_space,
416 * mapping->private_lock does *not* protect mapping->private_list! In fact,
417 * mapping->private_list will always be protected by the backing blockdev's
418 * ->private_lock.
419 *
420 * Which introduces a requirement: all buffers on an address_space's
421 * ->private_list must be from the same address_space: the blockdev's.
422 *
423 * address_spaces which do not place buffers at ->private_list via these
424 * utility functions are free to use private_lock and private_list for
425 * whatever they want. The only requirement is that list_empty(private_list)
426 * be true at clear_inode() time.
427 *
428 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
429 * filesystems should do that. invalidate_inode_buffers() should just go
430 * BUG_ON(!list_empty).
431 *
432 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
433 * take an address_space, not an inode. And it should be called
434 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
435 * queued up.
436 *
437 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
438 * list if it is already on a list. Because if the buffer is on a list,
439 * it *must* already be on the right one. If not, the filesystem is being
440 * silly. This will save a ton of locking. But first we have to ensure
441 * that buffers are taken *off* the old inode's list when they are freed
442 * (presumably in truncate). That requires careful auditing of all
443 * filesystems (do it inside bforget()). It could also be done by bringing
444 * b_inode back.
445 */
446
447/*
448 * The buffer's backing address_space's private_lock must be held
449 */
450static void __remove_assoc_queue(struct buffer_head *bh)
451{
452 list_del_init(&bh->b_assoc_buffers);
453 WARN_ON(!bh->b_assoc_map);
454 bh->b_assoc_map = NULL;
455}
456
457int inode_has_buffers(struct inode *inode)
458{
459 return !list_empty(&inode->i_data.private_list);
460}
461
462/*
463 * osync is designed to support O_SYNC io. It waits synchronously for
464 * all already-submitted IO to complete, but does not queue any new
465 * writes to the disk.
466 *
467 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
468 * you dirty the buffers, and then use osync_inode_buffers to wait for
469 * completion. Any other dirty buffers which are not yet queued for
470 * write will not be flushed to disk by the osync.
471 */
472static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
473{
474 struct buffer_head *bh;
475 struct list_head *p;
476 int err = 0;
477
478 spin_lock(lock);
479repeat:
480 list_for_each_prev(p, list) {
481 bh = BH_ENTRY(p);
482 if (buffer_locked(bh)) {
483 get_bh(bh);
484 spin_unlock(lock);
485 wait_on_buffer(bh);
486 if (!buffer_uptodate(bh))
487 err = -EIO;
488 brelse(bh);
489 spin_lock(lock);
490 goto repeat;
491 }
492 }
493 spin_unlock(lock);
494 return err;
495}
496
497void emergency_thaw_bdev(struct super_block *sb)
498{
499 while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
500 printk(KERN_WARNING "Emergency Thaw on %pg\n", sb->s_bdev);
501}
502
503/**
504 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
505 * @mapping: the mapping which wants those buffers written
506 *
507 * Starts I/O against the buffers at mapping->private_list, and waits upon
508 * that I/O.
509 *
510 * Basically, this is a convenience function for fsync().
511 * @mapping is a file or directory which needs those buffers to be written for
512 * a successful fsync().
513 */
514int sync_mapping_buffers(struct address_space *mapping)
515{
516 struct address_space *buffer_mapping = mapping->private_data;
517
518 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
519 return 0;
520
521 return fsync_buffers_list(&buffer_mapping->private_lock,
522 &mapping->private_list);
523}
524EXPORT_SYMBOL(sync_mapping_buffers);
525
526/*
527 * Called when we've recently written block `bblock', and it is known that
528 * `bblock' was for a buffer_boundary() buffer. This means that the block at
529 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
530 * dirty, schedule it for IO. So that indirects merge nicely with their data.
531 */
532void write_boundary_block(struct block_device *bdev,
533 sector_t bblock, unsigned blocksize)
534{
535 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
536 if (bh) {
537 if (buffer_dirty(bh))
538 ll_rw_block(REQ_OP_WRITE, 0, 1, &bh);
539 put_bh(bh);
540 }
541}
542
543void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
544{
545 struct address_space *mapping = inode->i_mapping;
546 struct address_space *buffer_mapping = bh->b_page->mapping;
547
548 mark_buffer_dirty(bh);
549 if (!mapping->private_data) {
550 mapping->private_data = buffer_mapping;
551 } else {
552 BUG_ON(mapping->private_data != buffer_mapping);
553 }
554 if (!bh->b_assoc_map) {
555 spin_lock(&buffer_mapping->private_lock);
556 list_move_tail(&bh->b_assoc_buffers,
557 &mapping->private_list);
558 bh->b_assoc_map = mapping;
559 spin_unlock(&buffer_mapping->private_lock);
560 }
561}
562EXPORT_SYMBOL(mark_buffer_dirty_inode);
563
564/*
565 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
566 * dirty.
567 *
568 * If warn is true, then emit a warning if the page is not uptodate and has
569 * not been truncated.
570 *
571 * The caller must hold lock_page_memcg().
572 */
573void __set_page_dirty(struct page *page, struct address_space *mapping,
574 int warn)
575{
576 unsigned long flags;
577
578 xa_lock_irqsave(&mapping->i_pages, flags);
579 if (page->mapping) { /* Race with truncate? */
580 WARN_ON_ONCE(warn && !PageUptodate(page));
581 account_page_dirtied(page, mapping);
582 radix_tree_tag_set(&mapping->i_pages,
583 page_index(page), PAGECACHE_TAG_DIRTY);
584 }
585 xa_unlock_irqrestore(&mapping->i_pages, flags);
586}
587EXPORT_SYMBOL_GPL(__set_page_dirty);
588
589/*
590 * Add a page to the dirty page list.
591 *
592 * It is a sad fact of life that this function is called from several places
593 * deeply under spinlocking. It may not sleep.
594 *
595 * If the page has buffers, the uptodate buffers are set dirty, to preserve
596 * dirty-state coherency between the page and the buffers. It the page does
597 * not have buffers then when they are later attached they will all be set
598 * dirty.
599 *
600 * The buffers are dirtied before the page is dirtied. There's a small race
601 * window in which a writepage caller may see the page cleanness but not the
602 * buffer dirtiness. That's fine. If this code were to set the page dirty
603 * before the buffers, a concurrent writepage caller could clear the page dirty
604 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
605 * page on the dirty page list.
606 *
607 * We use private_lock to lock against try_to_free_buffers while using the
608 * page's buffer list. Also use this to protect against clean buffers being
609 * added to the page after it was set dirty.
610 *
611 * FIXME: may need to call ->reservepage here as well. That's rather up to the
612 * address_space though.
613 */
614int __set_page_dirty_buffers(struct page *page)
615{
616 int newly_dirty;
617 struct address_space *mapping = page_mapping(page);
618
619 if (unlikely(!mapping))
620 return !TestSetPageDirty(page);
621
622 spin_lock(&mapping->private_lock);
623 if (page_has_buffers(page)) {
624 struct buffer_head *head = page_buffers(page);
625 struct buffer_head *bh = head;
626
627 do {
628 set_buffer_dirty(bh);
629 bh = bh->b_this_page;
630 } while (bh != head);
631 }
632 /*
633 * Lock out page->mem_cgroup migration to keep PageDirty
634 * synchronized with per-memcg dirty page counters.
635 */
636 lock_page_memcg(page);
637 newly_dirty = !TestSetPageDirty(page);
638 spin_unlock(&mapping->private_lock);
639
640 if (newly_dirty)
641 __set_page_dirty(page, mapping, 1);
642
643 unlock_page_memcg(page);
644
645 if (newly_dirty)
646 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
647
648 return newly_dirty;
649}
650EXPORT_SYMBOL(__set_page_dirty_buffers);
651
652/*
653 * Write out and wait upon a list of buffers.
654 *
655 * We have conflicting pressures: we want to make sure that all
656 * initially dirty buffers get waited on, but that any subsequently
657 * dirtied buffers don't. After all, we don't want fsync to last
658 * forever if somebody is actively writing to the file.
659 *
660 * Do this in two main stages: first we copy dirty buffers to a
661 * temporary inode list, queueing the writes as we go. Then we clean
662 * up, waiting for those writes to complete.
663 *
664 * During this second stage, any subsequent updates to the file may end
665 * up refiling the buffer on the original inode's dirty list again, so
666 * there is a chance we will end up with a buffer queued for write but
667 * not yet completed on that list. So, as a final cleanup we go through
668 * the osync code to catch these locked, dirty buffers without requeuing
669 * any newly dirty buffers for write.
670 */
671static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
672{
673 struct buffer_head *bh;
674 struct list_head tmp;
675 struct address_space *mapping;
676 int err = 0, err2;
677 struct blk_plug plug;
678
679 INIT_LIST_HEAD(&tmp);
680 blk_start_plug(&plug);
681
682 spin_lock(lock);
683 while (!list_empty(list)) {
684 bh = BH_ENTRY(list->next);
685 mapping = bh->b_assoc_map;
686 __remove_assoc_queue(bh);
687 /* Avoid race with mark_buffer_dirty_inode() which does
688 * a lockless check and we rely on seeing the dirty bit */
689 smp_mb();
690 if (buffer_dirty(bh) || buffer_locked(bh)) {
691 list_add(&bh->b_assoc_buffers, &tmp);
692 bh->b_assoc_map = mapping;
693 if (buffer_dirty(bh)) {
694 get_bh(bh);
695 spin_unlock(lock);
696 /*
697 * Ensure any pending I/O completes so that
698 * write_dirty_buffer() actually writes the
699 * current contents - it is a noop if I/O is
700 * still in flight on potentially older
701 * contents.
702 */
703 write_dirty_buffer(bh, REQ_SYNC);
704
705 /*
706 * Kick off IO for the previous mapping. Note
707 * that we will not run the very last mapping,
708 * wait_on_buffer() will do that for us
709 * through sync_buffer().
710 */
711 brelse(bh);
712 spin_lock(lock);
713 }
714 }
715 }
716
717 spin_unlock(lock);
718 blk_finish_plug(&plug);
719 spin_lock(lock);
720
721 while (!list_empty(&tmp)) {
722 bh = BH_ENTRY(tmp.prev);
723 get_bh(bh);
724 mapping = bh->b_assoc_map;
725 __remove_assoc_queue(bh);
726 /* Avoid race with mark_buffer_dirty_inode() which does
727 * a lockless check and we rely on seeing the dirty bit */
728 smp_mb();
729 if (buffer_dirty(bh)) {
730 list_add(&bh->b_assoc_buffers,
731 &mapping->private_list);
732 bh->b_assoc_map = mapping;
733 }
734 spin_unlock(lock);
735 wait_on_buffer(bh);
736 if (!buffer_uptodate(bh))
737 err = -EIO;
738 brelse(bh);
739 spin_lock(lock);
740 }
741
742 spin_unlock(lock);
743 err2 = osync_buffers_list(lock, list);
744 if (err)
745 return err;
746 else
747 return err2;
748}
749
750/*
751 * Invalidate any and all dirty buffers on a given inode. We are
752 * probably unmounting the fs, but that doesn't mean we have already
753 * done a sync(). Just drop the buffers from the inode list.
754 *
755 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
756 * assumes that all the buffers are against the blockdev. Not true
757 * for reiserfs.
758 */
759void invalidate_inode_buffers(struct inode *inode)
760{
761 if (inode_has_buffers(inode)) {
762 struct address_space *mapping = &inode->i_data;
763 struct list_head *list = &mapping->private_list;
764 struct address_space *buffer_mapping = mapping->private_data;
765
766 spin_lock(&buffer_mapping->private_lock);
767 while (!list_empty(list))
768 __remove_assoc_queue(BH_ENTRY(list->next));
769 spin_unlock(&buffer_mapping->private_lock);
770 }
771}
772EXPORT_SYMBOL(invalidate_inode_buffers);
773
774/*
775 * Remove any clean buffers from the inode's buffer list. This is called
776 * when we're trying to free the inode itself. Those buffers can pin it.
777 *
778 * Returns true if all buffers were removed.
779 */
780int remove_inode_buffers(struct inode *inode)
781{
782 int ret = 1;
783
784 if (inode_has_buffers(inode)) {
785 struct address_space *mapping = &inode->i_data;
786 struct list_head *list = &mapping->private_list;
787 struct address_space *buffer_mapping = mapping->private_data;
788
789 spin_lock(&buffer_mapping->private_lock);
790 while (!list_empty(list)) {
791 struct buffer_head *bh = BH_ENTRY(list->next);
792 if (buffer_dirty(bh)) {
793 ret = 0;
794 break;
795 }
796 __remove_assoc_queue(bh);
797 }
798 spin_unlock(&buffer_mapping->private_lock);
799 }
800 return ret;
801}
802
803/*
804 * Create the appropriate buffers when given a page for data area and
805 * the size of each buffer.. Use the bh->b_this_page linked list to
806 * follow the buffers created. Return NULL if unable to create more
807 * buffers.
808 *
809 * The retry flag is used to differentiate async IO (paging, swapping)
810 * which may not fail from ordinary buffer allocations.
811 */
812struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
813 bool retry)
814{
815 struct buffer_head *bh, *head;
816 gfp_t gfp = GFP_NOFS;
817 long offset;
818
819 if (retry)
820 gfp |= __GFP_NOFAIL;
821
822 head = NULL;
823 offset = PAGE_SIZE;
824 while ((offset -= size) >= 0) {
825 bh = alloc_buffer_head(gfp);
826 if (!bh)
827 goto no_grow;
828
829 bh->b_this_page = head;
830 bh->b_blocknr = -1;
831 head = bh;
832
833 bh->b_size = size;
834
835 /* Link the buffer to its page */
836 set_bh_page(bh, page, offset);
837 }
838 return head;
839/*
840 * In case anything failed, we just free everything we got.
841 */
842no_grow:
843 if (head) {
844 do {
845 bh = head;
846 head = head->b_this_page;
847 free_buffer_head(bh);
848 } while (head);
849 }
850
851 return NULL;
852}
853EXPORT_SYMBOL_GPL(alloc_page_buffers);
854
855static inline void
856link_dev_buffers(struct page *page, struct buffer_head *head)
857{
858 struct buffer_head *bh, *tail;
859
860 bh = head;
861 do {
862 tail = bh;
863 bh = bh->b_this_page;
864 } while (bh);
865 tail->b_this_page = head;
866 attach_page_buffers(page, head);
867}
868
869static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
870{
871 sector_t retval = ~((sector_t)0);
872 loff_t sz = i_size_read(bdev->bd_inode);
873
874 if (sz) {
875 unsigned int sizebits = blksize_bits(size);
876 retval = (sz >> sizebits);
877 }
878 return retval;
879}
880
881/*
882 * Initialise the state of a blockdev page's buffers.
883 */
884static sector_t
885init_page_buffers(struct page *page, struct block_device *bdev,
886 sector_t block, int size)
887{
888 struct buffer_head *head = page_buffers(page);
889 struct buffer_head *bh = head;
890 int uptodate = PageUptodate(page);
891 sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode), size);
892
893 do {
894 if (!buffer_mapped(bh)) {
895 bh->b_end_io = NULL;
896 bh->b_private = NULL;
897 bh->b_bdev = bdev;
898 bh->b_blocknr = block;
899 if (uptodate)
900 set_buffer_uptodate(bh);
901 if (block < end_block)
902 set_buffer_mapped(bh);
903 }
904 block++;
905 bh = bh->b_this_page;
906 } while (bh != head);
907
908 /*
909 * Caller needs to validate requested block against end of device.
910 */
911 return end_block;
912}
913
914/*
915 * Create the page-cache page that contains the requested block.
916 *
917 * This is used purely for blockdev mappings.
918 */
919static int
920grow_dev_page(struct block_device *bdev, sector_t block,
921 pgoff_t index, int size, int sizebits, gfp_t gfp)
922{
923 struct inode *inode = bdev->bd_inode;
924 struct page *page;
925 struct buffer_head *bh;
926 sector_t end_block;
927 int ret = 0; /* Will call free_more_memory() */
928 gfp_t gfp_mask;
929
930 gfp_mask = mapping_gfp_constraint(inode->i_mapping, ~__GFP_FS) | gfp;
931
932 /*
933 * XXX: __getblk_slow() can not really deal with failure and
934 * will endlessly loop on improvised global reclaim. Prefer
935 * looping in the allocator rather than here, at least that
936 * code knows what it's doing.
937 */
938 gfp_mask |= __GFP_NOFAIL;
939
940 page = find_or_create_page(inode->i_mapping, index, gfp_mask);
941
942 BUG_ON(!PageLocked(page));
943
944 if (page_has_buffers(page)) {
945 bh = page_buffers(page);
946 if (bh->b_size == size) {
947 end_block = init_page_buffers(page, bdev,
948 (sector_t)index << sizebits,
949 size);
950 goto done;
951 }
952 if (!try_to_free_buffers(page))
953 goto failed;
954 }
955
956 /*
957 * Allocate some buffers for this page
958 */
959 bh = alloc_page_buffers(page, size, true);
960
961 /*
962 * Link the page to the buffers and initialise them. Take the
963 * lock to be atomic wrt __find_get_block(), which does not
964 * run under the page lock.
965 */
966 spin_lock(&inode->i_mapping->private_lock);
967 link_dev_buffers(page, bh);
968 end_block = init_page_buffers(page, bdev, (sector_t)index << sizebits,
969 size);
970 spin_unlock(&inode->i_mapping->private_lock);
971done:
972 ret = (block < end_block) ? 1 : -ENXIO;
973failed:
974 unlock_page(page);
975 put_page(page);
976 return ret;
977}
978
979/*
980 * Create buffers for the specified block device block's page. If
981 * that page was dirty, the buffers are set dirty also.
982 */
983static int
984grow_buffers(struct block_device *bdev, sector_t block, int size, gfp_t gfp)
985{
986 pgoff_t index;
987 int sizebits;
988
989 sizebits = -1;
990 do {
991 sizebits++;
992 } while ((size << sizebits) < PAGE_SIZE);
993
994 index = block >> sizebits;
995
996 /*
997 * Check for a block which wants to lie outside our maximum possible
998 * pagecache index. (this comparison is done using sector_t types).
999 */
1000 if (unlikely(index != block >> sizebits)) {
1001 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1002 "device %pg\n",
1003 __func__, (unsigned long long)block,
1004 bdev);
1005 return -EIO;
1006 }
1007
1008 /* Create a page with the proper size buffers.. */
1009 return grow_dev_page(bdev, block, index, size, sizebits, gfp);
1010}
1011
1012static struct buffer_head *
1013__getblk_slow(struct block_device *bdev, sector_t block,
1014 unsigned size, gfp_t gfp)
1015{
1016 /* Size must be multiple of hard sectorsize */
1017 if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
1018 (size < 512 || size > PAGE_SIZE))) {
1019 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1020 size);
1021 printk(KERN_ERR "logical block size: %d\n",
1022 bdev_logical_block_size(bdev));
1023
1024 dump_stack();
1025 return NULL;
1026 }
1027
1028 for (;;) {
1029 struct buffer_head *bh;
1030 int ret;
1031
1032 bh = __find_get_block(bdev, block, size);
1033 if (bh)
1034 return bh;
1035
1036 ret = grow_buffers(bdev, block, size, gfp);
1037 if (ret < 0)
1038 return NULL;
1039 }
1040}
1041
1042/*
1043 * The relationship between dirty buffers and dirty pages:
1044 *
1045 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1046 * the page is tagged dirty in its radix tree.
1047 *
1048 * At all times, the dirtiness of the buffers represents the dirtiness of
1049 * subsections of the page. If the page has buffers, the page dirty bit is
1050 * merely a hint about the true dirty state.
1051 *
1052 * When a page is set dirty in its entirety, all its buffers are marked dirty
1053 * (if the page has buffers).
1054 *
1055 * When a buffer is marked dirty, its page is dirtied, but the page's other
1056 * buffers are not.
1057 *
1058 * Also. When blockdev buffers are explicitly read with bread(), they
1059 * individually become uptodate. But their backing page remains not
1060 * uptodate - even if all of its buffers are uptodate. A subsequent
1061 * block_read_full_page() against that page will discover all the uptodate
1062 * buffers, will set the page uptodate and will perform no I/O.
1063 */
1064
1065/**
1066 * mark_buffer_dirty - mark a buffer_head as needing writeout
1067 * @bh: the buffer_head to mark dirty
1068 *
1069 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1070 * backing page dirty, then tag the page as dirty in its address_space's radix
1071 * tree and then attach the address_space's inode to its superblock's dirty
1072 * inode list.
1073 *
1074 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1075 * i_pages lock and mapping->host->i_lock.
1076 */
1077void mark_buffer_dirty(struct buffer_head *bh)
1078{
1079 WARN_ON_ONCE(!buffer_uptodate(bh));
1080
1081 trace_block_dirty_buffer(bh);
1082
1083 /*
1084 * Very *carefully* optimize the it-is-already-dirty case.
1085 *
1086 * Don't let the final "is it dirty" escape to before we
1087 * perhaps modified the buffer.
1088 */
1089 if (buffer_dirty(bh)) {
1090 smp_mb();
1091 if (buffer_dirty(bh))
1092 return;
1093 }
1094
1095 if (!test_set_buffer_dirty(bh)) {
1096 struct page *page = bh->b_page;
1097 struct address_space *mapping = NULL;
1098
1099 lock_page_memcg(page);
1100 if (!TestSetPageDirty(page)) {
1101 mapping = page_mapping(page);
1102 if (mapping)
1103 __set_page_dirty(page, mapping, 0);
1104 }
1105 unlock_page_memcg(page);
1106 if (mapping)
1107 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
1108 }
1109}
1110EXPORT_SYMBOL(mark_buffer_dirty);
1111
1112void mark_buffer_write_io_error(struct buffer_head *bh)
1113{
1114 set_buffer_write_io_error(bh);
1115 /* FIXME: do we need to set this in both places? */
1116 if (bh->b_page && bh->b_page->mapping)
1117 mapping_set_error(bh->b_page->mapping, -EIO);
1118 if (bh->b_assoc_map)
1119 mapping_set_error(bh->b_assoc_map, -EIO);
1120}
1121EXPORT_SYMBOL(mark_buffer_write_io_error);
1122
1123/*
1124 * Decrement a buffer_head's reference count. If all buffers against a page
1125 * have zero reference count, are clean and unlocked, and if the page is clean
1126 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1127 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1128 * a page but it ends up not being freed, and buffers may later be reattached).
1129 */
1130void __brelse(struct buffer_head * buf)
1131{
1132 if (atomic_read(&buf->b_count)) {
1133 put_bh(buf);
1134 return;
1135 }
1136 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1137}
1138EXPORT_SYMBOL(__brelse);
1139
1140/*
1141 * bforget() is like brelse(), except it discards any
1142 * potentially dirty data.
1143 */
1144void __bforget(struct buffer_head *bh)
1145{
1146 clear_buffer_dirty(bh);
1147 if (bh->b_assoc_map) {
1148 struct address_space *buffer_mapping = bh->b_page->mapping;
1149
1150 spin_lock(&buffer_mapping->private_lock);
1151 list_del_init(&bh->b_assoc_buffers);
1152 bh->b_assoc_map = NULL;
1153 spin_unlock(&buffer_mapping->private_lock);
1154 }
1155 __brelse(bh);
1156}
1157EXPORT_SYMBOL(__bforget);
1158
1159static struct buffer_head *__bread_slow(struct buffer_head *bh)
1160{
1161 lock_buffer(bh);
1162 if (buffer_uptodate(bh)) {
1163 unlock_buffer(bh);
1164 return bh;
1165 } else {
1166 get_bh(bh);
1167 bh->b_end_io = end_buffer_read_sync;
1168 submit_bh(REQ_OP_READ, 0, bh);
1169 wait_on_buffer(bh);
1170 if (buffer_uptodate(bh))
1171 return bh;
1172 }
1173 brelse(bh);
1174 return NULL;
1175}
1176
1177/*
1178 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1179 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1180 * refcount elevated by one when they're in an LRU. A buffer can only appear
1181 * once in a particular CPU's LRU. A single buffer can be present in multiple
1182 * CPU's LRUs at the same time.
1183 *
1184 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1185 * sb_find_get_block().
1186 *
1187 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1188 * a local interrupt disable for that.
1189 */
1190
1191#define BH_LRU_SIZE 16
1192
1193struct bh_lru {
1194 struct buffer_head *bhs[BH_LRU_SIZE];
1195};
1196
1197static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1198
1199#ifdef CONFIG_SMP
1200#define bh_lru_lock() local_irq_disable()
1201#define bh_lru_unlock() local_irq_enable()
1202#else
1203#define bh_lru_lock() preempt_disable()
1204#define bh_lru_unlock() preempt_enable()
1205#endif
1206
1207static inline void check_irqs_on(void)
1208{
1209#ifdef irqs_disabled
1210 BUG_ON(irqs_disabled());
1211#endif
1212}
1213
1214/*
1215 * Install a buffer_head into this cpu's LRU. If not already in the LRU, it is
1216 * inserted at the front, and the buffer_head at the back if any is evicted.
1217 * Or, if already in the LRU it is moved to the front.
1218 */
1219static void bh_lru_install(struct buffer_head *bh)
1220{
1221 struct buffer_head *evictee = bh;
1222 struct bh_lru *b;
1223 int i;
1224
1225 check_irqs_on();
1226 bh_lru_lock();
1227
1228 b = this_cpu_ptr(&bh_lrus);
1229 for (i = 0; i < BH_LRU_SIZE; i++) {
1230 swap(evictee, b->bhs[i]);
1231 if (evictee == bh) {
1232 bh_lru_unlock();
1233 return;
1234 }
1235 }
1236
1237 get_bh(bh);
1238 bh_lru_unlock();
1239 brelse(evictee);
1240}
1241
1242/*
1243 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1244 */
1245static struct buffer_head *
1246lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1247{
1248 struct buffer_head *ret = NULL;
1249 unsigned int i;
1250
1251 check_irqs_on();
1252 bh_lru_lock();
1253 for (i = 0; i < BH_LRU_SIZE; i++) {
1254 struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
1255
1256 if (bh && bh->b_blocknr == block && bh->b_bdev == bdev &&
1257 bh->b_size == size) {
1258 if (i) {
1259 while (i) {
1260 __this_cpu_write(bh_lrus.bhs[i],
1261 __this_cpu_read(bh_lrus.bhs[i - 1]));
1262 i--;
1263 }
1264 __this_cpu_write(bh_lrus.bhs[0], bh);
1265 }
1266 get_bh(bh);
1267 ret = bh;
1268 break;
1269 }
1270 }
1271 bh_lru_unlock();
1272 return ret;
1273}
1274
1275/*
1276 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1277 * it in the LRU and mark it as accessed. If it is not present then return
1278 * NULL
1279 */
1280struct buffer_head *
1281__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1282{
1283 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1284
1285 if (bh == NULL) {
1286 /* __find_get_block_slow will mark the page accessed */
1287 bh = __find_get_block_slow(bdev, block);
1288 if (bh)
1289 bh_lru_install(bh);
1290 } else
1291 touch_buffer(bh);
1292
1293 return bh;
1294}
1295EXPORT_SYMBOL(__find_get_block);
1296
1297/*
1298 * __getblk_gfp() will locate (and, if necessary, create) the buffer_head
1299 * which corresponds to the passed block_device, block and size. The
1300 * returned buffer has its reference count incremented.
1301 *
1302 * __getblk_gfp() will lock up the machine if grow_dev_page's
1303 * try_to_free_buffers() attempt is failing. FIXME, perhaps?
1304 */
1305struct buffer_head *
1306__getblk_gfp(struct block_device *bdev, sector_t block,
1307 unsigned size, gfp_t gfp)
1308{
1309 struct buffer_head *bh = __find_get_block(bdev, block, size);
1310
1311 might_sleep();
1312 if (bh == NULL)
1313 bh = __getblk_slow(bdev, block, size, gfp);
1314 return bh;
1315}
1316EXPORT_SYMBOL(__getblk_gfp);
1317
1318/*
1319 * Do async read-ahead on a buffer..
1320 */
1321void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1322{
1323 struct buffer_head *bh = __getblk(bdev, block, size);
1324 if (likely(bh)) {
1325 ll_rw_block(REQ_OP_READ, REQ_RAHEAD, 1, &bh);
1326 brelse(bh);
1327 }
1328}
1329EXPORT_SYMBOL(__breadahead);
1330
1331/**
1332 * __bread_gfp() - reads a specified block and returns the bh
1333 * @bdev: the block_device to read from
1334 * @block: number of block
1335 * @size: size (in bytes) to read
1336 * @gfp: page allocation flag
1337 *
1338 * Reads a specified block, and returns buffer head that contains it.
1339 * The page cache can be allocated from non-movable area
1340 * not to prevent page migration if you set gfp to zero.
1341 * It returns NULL if the block was unreadable.
1342 */
1343struct buffer_head *
1344__bread_gfp(struct block_device *bdev, sector_t block,
1345 unsigned size, gfp_t gfp)
1346{
1347 struct buffer_head *bh = __getblk_gfp(bdev, block, size, gfp);
1348
1349 if (likely(bh) && !buffer_uptodate(bh))
1350 bh = __bread_slow(bh);
1351 return bh;
1352}
1353EXPORT_SYMBOL(__bread_gfp);
1354
1355/*
1356 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1357 * This doesn't race because it runs in each cpu either in irq
1358 * or with preempt disabled.
1359 */
1360static void invalidate_bh_lru(void *arg)
1361{
1362 struct bh_lru *b = &get_cpu_var(bh_lrus);
1363 int i;
1364
1365 for (i = 0; i < BH_LRU_SIZE; i++) {
1366 brelse(b->bhs[i]);
1367 b->bhs[i] = NULL;
1368 }
1369 put_cpu_var(bh_lrus);
1370}
1371
1372static bool has_bh_in_lru(int cpu, void *dummy)
1373{
1374 struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1375 int i;
1376
1377 for (i = 0; i < BH_LRU_SIZE; i++) {
1378 if (b->bhs[i])
1379 return 1;
1380 }
1381
1382 return 0;
1383}
1384
1385void invalidate_bh_lrus(void)
1386{
1387 on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL);
1388}
1389EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1390
1391void set_bh_page(struct buffer_head *bh,
1392 struct page *page, unsigned long offset)
1393{
1394 bh->b_page = page;
1395 BUG_ON(offset >= PAGE_SIZE);
1396 if (PageHighMem(page))
1397 /*
1398 * This catches illegal uses and preserves the offset:
1399 */
1400 bh->b_data = (char *)(0 + offset);
1401 else
1402 bh->b_data = page_address(page) + offset;
1403}
1404EXPORT_SYMBOL(set_bh_page);
1405
1406/*
1407 * Called when truncating a buffer on a page completely.
1408 */
1409
1410/* Bits that are cleared during an invalidate */
1411#define BUFFER_FLAGS_DISCARD \
1412 (1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \
1413 1 << BH_Delay | 1 << BH_Unwritten)
1414
1415static void discard_buffer(struct buffer_head * bh)
1416{
1417 unsigned long b_state, b_state_old;
1418
1419 lock_buffer(bh);
1420 clear_buffer_dirty(bh);
1421 bh->b_bdev = NULL;
1422 b_state = bh->b_state;
1423 for (;;) {
1424 b_state_old = cmpxchg(&bh->b_state, b_state,
1425 (b_state & ~BUFFER_FLAGS_DISCARD));
1426 if (b_state_old == b_state)
1427 break;
1428 b_state = b_state_old;
1429 }
1430 unlock_buffer(bh);
1431}
1432
1433/**
1434 * block_invalidatepage - invalidate part or all of a buffer-backed page
1435 *
1436 * @page: the page which is affected
1437 * @offset: start of the range to invalidate
1438 * @length: length of the range to invalidate
1439 *
1440 * block_invalidatepage() is called when all or part of the page has become
1441 * invalidated by a truncate operation.
1442 *
1443 * block_invalidatepage() does not have to release all buffers, but it must
1444 * ensure that no dirty buffer is left outside @offset and that no I/O
1445 * is underway against any of the blocks which are outside the truncation
1446 * point. Because the caller is about to free (and possibly reuse) those
1447 * blocks on-disk.
1448 */
1449void block_invalidatepage(struct page *page, unsigned int offset,
1450 unsigned int length)
1451{
1452 struct buffer_head *head, *bh, *next;
1453 unsigned int curr_off = 0;
1454 unsigned int stop = length + offset;
1455
1456 BUG_ON(!PageLocked(page));
1457 if (!page_has_buffers(page))
1458 goto out;
1459
1460 /*
1461 * Check for overflow
1462 */
1463 BUG_ON(stop > PAGE_SIZE || stop < length);
1464
1465 head = page_buffers(page);
1466 bh = head;
1467 do {
1468 unsigned int next_off = curr_off + bh->b_size;
1469 next = bh->b_this_page;
1470
1471 /*
1472 * Are we still fully in range ?
1473 */
1474 if (next_off > stop)
1475 goto out;
1476
1477 /*
1478 * is this block fully invalidated?
1479 */
1480 if (offset <= curr_off)
1481 discard_buffer(bh);
1482 curr_off = next_off;
1483 bh = next;
1484 } while (bh != head);
1485
1486 /*
1487 * We release buffers only if the entire page is being invalidated.
1488 * The get_block cached value has been unconditionally invalidated,
1489 * so real IO is not possible anymore.
1490 */
1491 if (length == PAGE_SIZE)
1492 try_to_release_page(page, 0);
1493out:
1494 return;
1495}
1496EXPORT_SYMBOL(block_invalidatepage);
1497
1498
1499/*
1500 * We attach and possibly dirty the buffers atomically wrt
1501 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1502 * is already excluded via the page lock.
1503 */
1504void create_empty_buffers(struct page *page,
1505 unsigned long blocksize, unsigned long b_state)
1506{
1507 struct buffer_head *bh, *head, *tail;
1508
1509 head = alloc_page_buffers(page, blocksize, true);
1510 bh = head;
1511 do {
1512 bh->b_state |= b_state;
1513 tail = bh;
1514 bh = bh->b_this_page;
1515 } while (bh);
1516 tail->b_this_page = head;
1517
1518 spin_lock(&page->mapping->private_lock);
1519 if (PageUptodate(page) || PageDirty(page)) {
1520 bh = head;
1521 do {
1522 if (PageDirty(page))
1523 set_buffer_dirty(bh);
1524 if (PageUptodate(page))
1525 set_buffer_uptodate(bh);
1526 bh = bh->b_this_page;
1527 } while (bh != head);
1528 }
1529 attach_page_buffers(page, head);
1530 spin_unlock(&page->mapping->private_lock);
1531}
1532EXPORT_SYMBOL(create_empty_buffers);
1533
1534/**
1535 * clean_bdev_aliases: clean a range of buffers in block device
1536 * @bdev: Block device to clean buffers in
1537 * @block: Start of a range of blocks to clean
1538 * @len: Number of blocks to clean
1539 *
1540 * We are taking a range of blocks for data and we don't want writeback of any
1541 * buffer-cache aliases starting from return from this function and until the
1542 * moment when something will explicitly mark the buffer dirty (hopefully that
1543 * will not happen until we will free that block ;-) We don't even need to mark
1544 * it not-uptodate - nobody can expect anything from a newly allocated buffer
1545 * anyway. We used to use unmap_buffer() for such invalidation, but that was
1546 * wrong. We definitely don't want to mark the alias unmapped, for example - it
1547 * would confuse anyone who might pick it with bread() afterwards...
1548 *
1549 * Also.. Note that bforget() doesn't lock the buffer. So there can be
1550 * writeout I/O going on against recently-freed buffers. We don't wait on that
1551 * I/O in bforget() - it's more efficient to wait on the I/O only if we really
1552 * need to. That happens here.
1553 */
1554void clean_bdev_aliases(struct block_device *bdev, sector_t block, sector_t len)
1555{
1556 struct inode *bd_inode = bdev->bd_inode;
1557 struct address_space *bd_mapping = bd_inode->i_mapping;
1558 struct pagevec pvec;
1559 pgoff_t index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
1560 pgoff_t end;
1561 int i, count;
1562 struct buffer_head *bh;
1563 struct buffer_head *head;
1564
1565 end = (block + len - 1) >> (PAGE_SHIFT - bd_inode->i_blkbits);
1566 pagevec_init(&pvec);
1567 while (pagevec_lookup_range(&pvec, bd_mapping, &index, end)) {
1568 count = pagevec_count(&pvec);
1569 for (i = 0; i < count; i++) {
1570 struct page *page = pvec.pages[i];
1571
1572 if (!page_has_buffers(page))
1573 continue;
1574 /*
1575 * We use page lock instead of bd_mapping->private_lock
1576 * to pin buffers here since we can afford to sleep and
1577 * it scales better than a global spinlock lock.
1578 */
1579 lock_page(page);
1580 /* Recheck when the page is locked which pins bhs */
1581 if (!page_has_buffers(page))
1582 goto unlock_page;
1583 head = page_buffers(page);
1584 bh = head;
1585 do {
1586 if (!buffer_mapped(bh) || (bh->b_blocknr < block))
1587 goto next;
1588 if (bh->b_blocknr >= block + len)
1589 break;
1590 clear_buffer_dirty(bh);
1591 wait_on_buffer(bh);
1592 clear_buffer_req(bh);
1593next:
1594 bh = bh->b_this_page;
1595 } while (bh != head);
1596unlock_page:
1597 unlock_page(page);
1598 }
1599 pagevec_release(&pvec);
1600 cond_resched();
1601 /* End of range already reached? */
1602 if (index > end || !index)
1603 break;
1604 }
1605}
1606EXPORT_SYMBOL(clean_bdev_aliases);
1607
1608/*
1609 * Size is a power-of-two in the range 512..PAGE_SIZE,
1610 * and the case we care about most is PAGE_SIZE.
1611 *
1612 * So this *could* possibly be written with those
1613 * constraints in mind (relevant mostly if some
1614 * architecture has a slow bit-scan instruction)
1615 */
1616static inline int block_size_bits(unsigned int blocksize)
1617{
1618 return ilog2(blocksize);
1619}
1620
1621static struct buffer_head *create_page_buffers(struct page *page, struct inode *inode, unsigned int b_state)
1622{
1623 BUG_ON(!PageLocked(page));
1624
1625 if (!page_has_buffers(page))
1626 create_empty_buffers(page, 1 << READ_ONCE(inode->i_blkbits),
1627 b_state);
1628 return page_buffers(page);
1629}
1630
1631/*
1632 * NOTE! All mapped/uptodate combinations are valid:
1633 *
1634 * Mapped Uptodate Meaning
1635 *
1636 * No No "unknown" - must do get_block()
1637 * No Yes "hole" - zero-filled
1638 * Yes No "allocated" - allocated on disk, not read in
1639 * Yes Yes "valid" - allocated and up-to-date in memory.
1640 *
1641 * "Dirty" is valid only with the last case (mapped+uptodate).
1642 */
1643
1644/*
1645 * While block_write_full_page is writing back the dirty buffers under
1646 * the page lock, whoever dirtied the buffers may decide to clean them
1647 * again at any time. We handle that by only looking at the buffer
1648 * state inside lock_buffer().
1649 *
1650 * If block_write_full_page() is called for regular writeback
1651 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1652 * locked buffer. This only can happen if someone has written the buffer
1653 * directly, with submit_bh(). At the address_space level PageWriteback
1654 * prevents this contention from occurring.
1655 *
1656 * If block_write_full_page() is called with wbc->sync_mode ==
1657 * WB_SYNC_ALL, the writes are posted using REQ_SYNC; this
1658 * causes the writes to be flagged as synchronous writes.
1659 */
1660int __block_write_full_page(struct inode *inode, struct page *page,
1661 get_block_t *get_block, struct writeback_control *wbc,
1662 bh_end_io_t *handler)
1663{
1664 int err;
1665 sector_t block;
1666 sector_t last_block;
1667 struct buffer_head *bh, *head;
1668 unsigned int blocksize, bbits;
1669 int nr_underway = 0;
1670 int write_flags = wbc_to_write_flags(wbc);
1671
1672 head = create_page_buffers(page, inode,
1673 (1 << BH_Dirty)|(1 << BH_Uptodate));
1674
1675 /*
1676 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1677 * here, and the (potentially unmapped) buffers may become dirty at
1678 * any time. If a buffer becomes dirty here after we've inspected it
1679 * then we just miss that fact, and the page stays dirty.
1680 *
1681 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1682 * handle that here by just cleaning them.
1683 */
1684
1685 bh = head;
1686 blocksize = bh->b_size;
1687 bbits = block_size_bits(blocksize);
1688
1689 block = (sector_t)page->index << (PAGE_SHIFT - bbits);
1690 last_block = (i_size_read(inode) - 1) >> bbits;
1691
1692 /*
1693 * Get all the dirty buffers mapped to disk addresses and
1694 * handle any aliases from the underlying blockdev's mapping.
1695 */
1696 do {
1697 if (block > last_block) {
1698 /*
1699 * mapped buffers outside i_size will occur, because
1700 * this page can be outside i_size when there is a
1701 * truncate in progress.
1702 */
1703 /*
1704 * The buffer was zeroed by block_write_full_page()
1705 */
1706 clear_buffer_dirty(bh);
1707 set_buffer_uptodate(bh);
1708 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1709 buffer_dirty(bh)) {
1710 WARN_ON(bh->b_size != blocksize);
1711 err = get_block(inode, block, bh, 1);
1712 if (err)
1713 goto recover;
1714 clear_buffer_delay(bh);
1715 if (buffer_new(bh)) {
1716 /* blockdev mappings never come here */
1717 clear_buffer_new(bh);
1718 clean_bdev_bh_alias(bh);
1719 }
1720 }
1721 bh = bh->b_this_page;
1722 block++;
1723 } while (bh != head);
1724
1725 do {
1726 if (!buffer_mapped(bh))
1727 continue;
1728 /*
1729 * If it's a fully non-blocking write attempt and we cannot
1730 * lock the buffer then redirty the page. Note that this can
1731 * potentially cause a busy-wait loop from writeback threads
1732 * and kswapd activity, but those code paths have their own
1733 * higher-level throttling.
1734 */
1735 if (wbc->sync_mode != WB_SYNC_NONE) {
1736 lock_buffer(bh);
1737 } else if (!trylock_buffer(bh)) {
1738 redirty_page_for_writepage(wbc, page);
1739 continue;
1740 }
1741 if (test_clear_buffer_dirty(bh)) {
1742 mark_buffer_async_write_endio(bh, handler);
1743 } else {
1744 unlock_buffer(bh);
1745 }
1746 } while ((bh = bh->b_this_page) != head);
1747
1748 /*
1749 * The page and its buffers are protected by PageWriteback(), so we can
1750 * drop the bh refcounts early.
1751 */
1752 BUG_ON(PageWriteback(page));
1753 set_page_writeback(page);
1754
1755 do {
1756 struct buffer_head *next = bh->b_this_page;
1757 if (buffer_async_write(bh)) {
1758 submit_bh_wbc(REQ_OP_WRITE, write_flags, bh,
1759 inode->i_write_hint, wbc);
1760 nr_underway++;
1761 }
1762 bh = next;
1763 } while (bh != head);
1764 unlock_page(page);
1765
1766 err = 0;
1767done:
1768 if (nr_underway == 0) {
1769 /*
1770 * The page was marked dirty, but the buffers were
1771 * clean. Someone wrote them back by hand with
1772 * ll_rw_block/submit_bh. A rare case.
1773 */
1774 end_page_writeback(page);
1775
1776 /*
1777 * The page and buffer_heads can be released at any time from
1778 * here on.
1779 */
1780 }
1781 return err;
1782
1783recover:
1784 /*
1785 * ENOSPC, or some other error. We may already have added some
1786 * blocks to the file, so we need to write these out to avoid
1787 * exposing stale data.
1788 * The page is currently locked and not marked for writeback
1789 */
1790 bh = head;
1791 /* Recovery: lock and submit the mapped buffers */
1792 do {
1793 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1794 !buffer_delay(bh)) {
1795 lock_buffer(bh);
1796 mark_buffer_async_write_endio(bh, handler);
1797 } else {
1798 /*
1799 * The buffer may have been set dirty during
1800 * attachment to a dirty page.
1801 */
1802 clear_buffer_dirty(bh);
1803 }
1804 } while ((bh = bh->b_this_page) != head);
1805 SetPageError(page);
1806 BUG_ON(PageWriteback(page));
1807 mapping_set_error(page->mapping, err);
1808 set_page_writeback(page);
1809 do {
1810 struct buffer_head *next = bh->b_this_page;
1811 if (buffer_async_write(bh)) {
1812 clear_buffer_dirty(bh);
1813 submit_bh_wbc(REQ_OP_WRITE, write_flags, bh,
1814 inode->i_write_hint, wbc);
1815 nr_underway++;
1816 }
1817 bh = next;
1818 } while (bh != head);
1819 unlock_page(page);
1820 goto done;
1821}
1822EXPORT_SYMBOL(__block_write_full_page);
1823
1824/*
1825 * If a page has any new buffers, zero them out here, and mark them uptodate
1826 * and dirty so they'll be written out (in order to prevent uninitialised
1827 * block data from leaking). And clear the new bit.
1828 */
1829void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1830{
1831 unsigned int block_start, block_end;
1832 struct buffer_head *head, *bh;
1833
1834 BUG_ON(!PageLocked(page));
1835 if (!page_has_buffers(page))
1836 return;
1837
1838 bh = head = page_buffers(page);
1839 block_start = 0;
1840 do {
1841 block_end = block_start + bh->b_size;
1842
1843 if (buffer_new(bh)) {
1844 if (block_end > from && block_start < to) {
1845 if (!PageUptodate(page)) {
1846 unsigned start, size;
1847
1848 start = max(from, block_start);
1849 size = min(to, block_end) - start;
1850
1851 zero_user(page, start, size);
1852 set_buffer_uptodate(bh);
1853 }
1854
1855 clear_buffer_new(bh);
1856 mark_buffer_dirty(bh);
1857 }
1858 }
1859
1860 block_start = block_end;
1861 bh = bh->b_this_page;
1862 } while (bh != head);
1863}
1864EXPORT_SYMBOL(page_zero_new_buffers);
1865
1866static void
1867iomap_to_bh(struct inode *inode, sector_t block, struct buffer_head *bh,
1868 struct iomap *iomap)
1869{
1870 loff_t offset = block << inode->i_blkbits;
1871
1872 bh->b_bdev = iomap->bdev;
1873
1874 /*
1875 * Block points to offset in file we need to map, iomap contains
1876 * the offset at which the map starts. If the map ends before the
1877 * current block, then do not map the buffer and let the caller
1878 * handle it.
1879 */
1880 BUG_ON(offset >= iomap->offset + iomap->length);
1881
1882 switch (iomap->type) {
1883 case IOMAP_HOLE:
1884 /*
1885 * If the buffer is not up to date or beyond the current EOF,
1886 * we need to mark it as new to ensure sub-block zeroing is
1887 * executed if necessary.
1888 */
1889 if (!buffer_uptodate(bh) ||
1890 (offset >= i_size_read(inode)))
1891 set_buffer_new(bh);
1892 break;
1893 case IOMAP_DELALLOC:
1894 if (!buffer_uptodate(bh) ||
1895 (offset >= i_size_read(inode)))
1896 set_buffer_new(bh);
1897 set_buffer_uptodate(bh);
1898 set_buffer_mapped(bh);
1899 set_buffer_delay(bh);
1900 break;
1901 case IOMAP_UNWRITTEN:
1902 /*
1903 * For unwritten regions, we always need to ensure that
1904 * sub-block writes cause the regions in the block we are not
1905 * writing to are zeroed. Set the buffer as new to ensure this.
1906 */
1907 set_buffer_new(bh);
1908 set_buffer_unwritten(bh);
1909 /* FALLTHRU */
1910 case IOMAP_MAPPED:
1911 if (offset >= i_size_read(inode))
1912 set_buffer_new(bh);
1913 bh->b_blocknr = (iomap->addr + offset - iomap->offset) >>
1914 inode->i_blkbits;
1915 set_buffer_mapped(bh);
1916 break;
1917 }
1918}
1919
1920int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
1921 get_block_t *get_block, struct iomap *iomap)
1922{
1923 unsigned from = pos & (PAGE_SIZE - 1);
1924 unsigned to = from + len;
1925 struct inode *inode = page->mapping->host;
1926 unsigned block_start, block_end;
1927 sector_t block;
1928 int err = 0;
1929 unsigned blocksize, bbits;
1930 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1931
1932 BUG_ON(!PageLocked(page));
1933 BUG_ON(from > PAGE_SIZE);
1934 BUG_ON(to > PAGE_SIZE);
1935 BUG_ON(from > to);
1936
1937 head = create_page_buffers(page, inode, 0);
1938 blocksize = head->b_size;
1939 bbits = block_size_bits(blocksize);
1940
1941 block = (sector_t)page->index << (PAGE_SHIFT - bbits);
1942
1943 for(bh = head, block_start = 0; bh != head || !block_start;
1944 block++, block_start=block_end, bh = bh->b_this_page) {
1945 block_end = block_start + blocksize;
1946 if (block_end <= from || block_start >= to) {
1947 if (PageUptodate(page)) {
1948 if (!buffer_uptodate(bh))
1949 set_buffer_uptodate(bh);
1950 }
1951 continue;
1952 }
1953 if (buffer_new(bh))
1954 clear_buffer_new(bh);
1955 if (!buffer_mapped(bh)) {
1956 WARN_ON(bh->b_size != blocksize);
1957 if (get_block) {
1958 err = get_block(inode, block, bh, 1);
1959 if (err)
1960 break;
1961 } else {
1962 iomap_to_bh(inode, block, bh, iomap);
1963 }
1964
1965 if (buffer_new(bh)) {
1966 clean_bdev_bh_alias(bh);
1967 if (PageUptodate(page)) {
1968 clear_buffer_new(bh);
1969 set_buffer_uptodate(bh);
1970 mark_buffer_dirty(bh);
1971 continue;
1972 }
1973 if (block_end > to || block_start < from)
1974 zero_user_segments(page,
1975 to, block_end,
1976 block_start, from);
1977 continue;
1978 }
1979 }
1980 if (PageUptodate(page)) {
1981 if (!buffer_uptodate(bh))
1982 set_buffer_uptodate(bh);
1983 continue;
1984 }
1985 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1986 !buffer_unwritten(bh) &&
1987 (block_start < from || block_end > to)) {
1988 ll_rw_block(REQ_OP_READ, 0, 1, &bh);
1989 *wait_bh++=bh;
1990 }
1991 }
1992 /*
1993 * If we issued read requests - let them complete.
1994 */
1995 while(wait_bh > wait) {
1996 wait_on_buffer(*--wait_bh);
1997 if (!buffer_uptodate(*wait_bh))
1998 err = -EIO;
1999 }
2000 if (unlikely(err))
2001 page_zero_new_buffers(page, from, to);
2002 return err;
2003}
2004
2005int __block_write_begin(struct page *page, loff_t pos, unsigned len,
2006 get_block_t *get_block)
2007{
2008 return __block_write_begin_int(page, pos, len, get_block, NULL);
2009}
2010EXPORT_SYMBOL(__block_write_begin);
2011
2012static int __block_commit_write(struct inode *inode, struct page *page,
2013 unsigned from, unsigned to)
2014{
2015 unsigned block_start, block_end;
2016 int partial = 0;
2017 unsigned blocksize;
2018 struct buffer_head *bh, *head;
2019
2020 bh = head = page_buffers(page);
2021 blocksize = bh->b_size;
2022
2023 block_start = 0;
2024 do {
2025 block_end = block_start + blocksize;
2026 if (block_end <= from || block_start >= to) {
2027 if (!buffer_uptodate(bh))
2028 partial = 1;
2029 } else {
2030 set_buffer_uptodate(bh);
2031 mark_buffer_dirty(bh);
2032 }
2033 clear_buffer_new(bh);
2034
2035 block_start = block_end;
2036 bh = bh->b_this_page;
2037 } while (bh != head);
2038
2039 /*
2040 * If this is a partial write which happened to make all buffers
2041 * uptodate then we can optimize away a bogus readpage() for
2042 * the next read(). Here we 'discover' whether the page went
2043 * uptodate as a result of this (potentially partial) write.
2044 */
2045 if (!partial)
2046 SetPageUptodate(page);
2047 return 0;
2048}
2049
2050/*
2051 * block_write_begin takes care of the basic task of block allocation and
2052 * bringing partial write blocks uptodate first.
2053 *
2054 * The filesystem needs to handle block truncation upon failure.
2055 */
2056int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
2057 unsigned flags, struct page **pagep, get_block_t *get_block)
2058{
2059 pgoff_t index = pos >> PAGE_SHIFT;
2060 struct page *page;
2061 int status;
2062
2063 page = grab_cache_page_write_begin(mapping, index, flags);
2064 if (!page)
2065 return -ENOMEM;
2066
2067 status = __block_write_begin(page, pos, len, get_block);
2068 if (unlikely(status)) {
2069 unlock_page(page);
2070 put_page(page);
2071 page = NULL;
2072 }
2073
2074 *pagep = page;
2075 return status;
2076}
2077EXPORT_SYMBOL(block_write_begin);
2078
2079int block_write_end(struct file *file, struct address_space *mapping,
2080 loff_t pos, unsigned len, unsigned copied,
2081 struct page *page, void *fsdata)
2082{
2083 struct inode *inode = mapping->host;
2084 unsigned start;
2085
2086 start = pos & (PAGE_SIZE - 1);
2087
2088 if (unlikely(copied < len)) {
2089 /*
2090 * The buffers that were written will now be uptodate, so we
2091 * don't have to worry about a readpage reading them and
2092 * overwriting a partial write. However if we have encountered
2093 * a short write and only partially written into a buffer, it
2094 * will not be marked uptodate, so a readpage might come in and
2095 * destroy our partial write.
2096 *
2097 * Do the simplest thing, and just treat any short write to a
2098 * non uptodate page as a zero-length write, and force the
2099 * caller to redo the whole thing.
2100 */
2101 if (!PageUptodate(page))
2102 copied = 0;
2103
2104 page_zero_new_buffers(page, start+copied, start+len);
2105 }
2106 flush_dcache_page(page);
2107
2108 /* This could be a short (even 0-length) commit */
2109 __block_commit_write(inode, page, start, start+copied);
2110
2111 return copied;
2112}
2113EXPORT_SYMBOL(block_write_end);
2114
2115int generic_write_end(struct file *file, struct address_space *mapping,
2116 loff_t pos, unsigned len, unsigned copied,
2117 struct page *page, void *fsdata)
2118{
2119 struct inode *inode = mapping->host;
2120 loff_t old_size = inode->i_size;
2121 int i_size_changed = 0;
2122
2123 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2124
2125 /*
2126 * No need to use i_size_read() here, the i_size
2127 * cannot change under us because we hold i_mutex.
2128 *
2129 * But it's important to update i_size while still holding page lock:
2130 * page writeout could otherwise come in and zero beyond i_size.
2131 */
2132 if (pos+copied > inode->i_size) {
2133 i_size_write(inode, pos+copied);
2134 i_size_changed = 1;
2135 }
2136
2137 unlock_page(page);
2138 put_page(page);
2139
2140 if (old_size < pos)
2141 pagecache_isize_extended(inode, old_size, pos);
2142 /*
2143 * Don't mark the inode dirty under page lock. First, it unnecessarily
2144 * makes the holding time of page lock longer. Second, it forces lock
2145 * ordering of page lock and transaction start for journaling
2146 * filesystems.
2147 */
2148 if (i_size_changed)
2149 mark_inode_dirty(inode);
2150
2151 return copied;
2152}
2153EXPORT_SYMBOL(generic_write_end);
2154
2155/*
2156 * block_is_partially_uptodate checks whether buffers within a page are
2157 * uptodate or not.
2158 *
2159 * Returns true if all buffers which correspond to a file portion
2160 * we want to read are uptodate.
2161 */
2162int block_is_partially_uptodate(struct page *page, unsigned long from,
2163 unsigned long count)
2164{
2165 unsigned block_start, block_end, blocksize;
2166 unsigned to;
2167 struct buffer_head *bh, *head;
2168 int ret = 1;
2169
2170 if (!page_has_buffers(page))
2171 return 0;
2172
2173 head = page_buffers(page);
2174 blocksize = head->b_size;
2175 to = min_t(unsigned, PAGE_SIZE - from, count);
2176 to = from + to;
2177 if (from < blocksize && to > PAGE_SIZE - blocksize)
2178 return 0;
2179
2180 bh = head;
2181 block_start = 0;
2182 do {
2183 block_end = block_start + blocksize;
2184 if (block_end > from && block_start < to) {
2185 if (!buffer_uptodate(bh)) {
2186 ret = 0;
2187 break;
2188 }
2189 if (block_end >= to)
2190 break;
2191 }
2192 block_start = block_end;
2193 bh = bh->b_this_page;
2194 } while (bh != head);
2195
2196 return ret;
2197}
2198EXPORT_SYMBOL(block_is_partially_uptodate);
2199
2200/*
2201 * Generic "read page" function for block devices that have the normal
2202 * get_block functionality. This is most of the block device filesystems.
2203 * Reads the page asynchronously --- the unlock_buffer() and
2204 * set/clear_buffer_uptodate() functions propagate buffer state into the
2205 * page struct once IO has completed.
2206 */
2207int block_read_full_page(struct page *page, get_block_t *get_block)
2208{
2209 struct inode *inode = page->mapping->host;
2210 sector_t iblock, lblock;
2211 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2212 unsigned int blocksize, bbits;
2213 int nr, i;
2214 int fully_mapped = 1;
2215
2216 head = create_page_buffers(page, inode, 0);
2217 blocksize = head->b_size;
2218 bbits = block_size_bits(blocksize);
2219
2220 iblock = (sector_t)page->index << (PAGE_SHIFT - bbits);
2221 lblock = (i_size_read(inode)+blocksize-1) >> bbits;
2222 bh = head;
2223 nr = 0;
2224 i = 0;
2225
2226 do {
2227 if (buffer_uptodate(bh))
2228 continue;
2229
2230 if (!buffer_mapped(bh)) {
2231 int err = 0;
2232
2233 fully_mapped = 0;
2234 if (iblock < lblock) {
2235 WARN_ON(bh->b_size != blocksize);
2236 err = get_block(inode, iblock, bh, 0);
2237 if (err)
2238 SetPageError(page);
2239 }
2240 if (!buffer_mapped(bh)) {
2241 zero_user(page, i * blocksize, blocksize);
2242 if (!err)
2243 set_buffer_uptodate(bh);
2244 continue;
2245 }
2246 /*
2247 * get_block() might have updated the buffer
2248 * synchronously
2249 */
2250 if (buffer_uptodate(bh))
2251 continue;
2252 }
2253 arr[nr++] = bh;
2254 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2255
2256 if (fully_mapped)
2257 SetPageMappedToDisk(page);
2258
2259 if (!nr) {
2260 /*
2261 * All buffers are uptodate - we can set the page uptodate
2262 * as well. But not if get_block() returned an error.
2263 */
2264 if (!PageError(page))
2265 SetPageUptodate(page);
2266 unlock_page(page);
2267 return 0;
2268 }
2269
2270 /* Stage two: lock the buffers */
2271 for (i = 0; i < nr; i++) {
2272 bh = arr[i];
2273 lock_buffer(bh);
2274 mark_buffer_async_read(bh);
2275 }
2276
2277 /*
2278 * Stage 3: start the IO. Check for uptodateness
2279 * inside the buffer lock in case another process reading
2280 * the underlying blockdev brought it uptodate (the sct fix).
2281 */
2282 for (i = 0; i < nr; i++) {
2283 bh = arr[i];
2284 if (buffer_uptodate(bh))
2285 end_buffer_async_read(bh, 1);
2286 else
2287 submit_bh(REQ_OP_READ, 0, bh);
2288 }
2289 return 0;
2290}
2291EXPORT_SYMBOL(block_read_full_page);
2292
2293/* utility function for filesystems that need to do work on expanding
2294 * truncates. Uses filesystem pagecache writes to allow the filesystem to
2295 * deal with the hole.
2296 */
2297int generic_cont_expand_simple(struct inode *inode, loff_t size)
2298{
2299 struct address_space *mapping = inode->i_mapping;
2300 struct page *page;
2301 void *fsdata;
2302 int err;
2303
2304 err = inode_newsize_ok(inode, size);
2305 if (err)
2306 goto out;
2307
2308 err = pagecache_write_begin(NULL, mapping, size, 0,
2309 AOP_FLAG_CONT_EXPAND, &page, &fsdata);
2310 if (err)
2311 goto out;
2312
2313 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2314 BUG_ON(err > 0);
2315
2316out:
2317 return err;
2318}
2319EXPORT_SYMBOL(generic_cont_expand_simple);
2320
2321static int cont_expand_zero(struct file *file, struct address_space *mapping,
2322 loff_t pos, loff_t *bytes)
2323{
2324 struct inode *inode = mapping->host;
2325 unsigned int blocksize = i_blocksize(inode);
2326 struct page *page;
2327 void *fsdata;
2328 pgoff_t index, curidx;
2329 loff_t curpos;
2330 unsigned zerofrom, offset, len;
2331 int err = 0;
2332
2333 index = pos >> PAGE_SHIFT;
2334 offset = pos & ~PAGE_MASK;
2335
2336 while (index > (curidx = (curpos = *bytes)>>PAGE_SHIFT)) {
2337 zerofrom = curpos & ~PAGE_MASK;
2338 if (zerofrom & (blocksize-1)) {
2339 *bytes |= (blocksize-1);
2340 (*bytes)++;
2341 }
2342 len = PAGE_SIZE - zerofrom;
2343
2344 err = pagecache_write_begin(file, mapping, curpos, len, 0,
2345 &page, &fsdata);
2346 if (err)
2347 goto out;
2348 zero_user(page, zerofrom, len);
2349 err = pagecache_write_end(file, mapping, curpos, len, len,
2350 page, fsdata);
2351 if (err < 0)
2352 goto out;
2353 BUG_ON(err != len);
2354 err = 0;
2355
2356 balance_dirty_pages_ratelimited(mapping);
2357
2358 if (unlikely(fatal_signal_pending(current))) {
2359 err = -EINTR;
2360 goto out;
2361 }
2362 }
2363
2364 /* page covers the boundary, find the boundary offset */
2365 if (index == curidx) {
2366 zerofrom = curpos & ~PAGE_MASK;
2367 /* if we will expand the thing last block will be filled */
2368 if (offset <= zerofrom) {
2369 goto out;
2370 }
2371 if (zerofrom & (blocksize-1)) {
2372 *bytes |= (blocksize-1);
2373 (*bytes)++;
2374 }
2375 len = offset - zerofrom;
2376
2377 err = pagecache_write_begin(file, mapping, curpos, len, 0,
2378 &page, &fsdata);
2379 if (err)
2380 goto out;
2381 zero_user(page, zerofrom, len);
2382 err = pagecache_write_end(file, mapping, curpos, len, len,
2383 page, fsdata);
2384 if (err < 0)
2385 goto out;
2386 BUG_ON(err != len);
2387 err = 0;
2388 }
2389out:
2390 return err;
2391}
2392
2393/*
2394 * For moronic filesystems that do not allow holes in file.
2395 * We may have to extend the file.
2396 */
2397int cont_write_begin(struct file *file, struct address_space *mapping,
2398 loff_t pos, unsigned len, unsigned flags,
2399 struct page **pagep, void **fsdata,
2400 get_block_t *get_block, loff_t *bytes)
2401{
2402 struct inode *inode = mapping->host;
2403 unsigned int blocksize = i_blocksize(inode);
2404 unsigned int zerofrom;
2405 int err;
2406
2407 err = cont_expand_zero(file, mapping, pos, bytes);
2408 if (err)
2409 return err;
2410
2411 zerofrom = *bytes & ~PAGE_MASK;
2412 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2413 *bytes |= (blocksize-1);
2414 (*bytes)++;
2415 }
2416
2417 return block_write_begin(mapping, pos, len, flags, pagep, get_block);
2418}
2419EXPORT_SYMBOL(cont_write_begin);
2420
2421int block_commit_write(struct page *page, unsigned from, unsigned to)
2422{
2423 struct inode *inode = page->mapping->host;
2424 __block_commit_write(inode,page,from,to);
2425 return 0;
2426}
2427EXPORT_SYMBOL(block_commit_write);
2428
2429/*
2430 * block_page_mkwrite() is not allowed to change the file size as it gets
2431 * called from a page fault handler when a page is first dirtied. Hence we must
2432 * be careful to check for EOF conditions here. We set the page up correctly
2433 * for a written page which means we get ENOSPC checking when writing into
2434 * holes and correct delalloc and unwritten extent mapping on filesystems that
2435 * support these features.
2436 *
2437 * We are not allowed to take the i_mutex here so we have to play games to
2438 * protect against truncate races as the page could now be beyond EOF. Because
2439 * truncate writes the inode size before removing pages, once we have the
2440 * page lock we can determine safely if the page is beyond EOF. If it is not
2441 * beyond EOF, then the page is guaranteed safe against truncation until we
2442 * unlock the page.
2443 *
2444 * Direct callers of this function should protect against filesystem freezing
2445 * using sb_start_pagefault() - sb_end_pagefault() functions.
2446 */
2447int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2448 get_block_t get_block)
2449{
2450 struct page *page = vmf->page;
2451 struct inode *inode = file_inode(vma->vm_file);
2452 unsigned long end;
2453 loff_t size;
2454 int ret;
2455
2456 lock_page(page);
2457 size = i_size_read(inode);
2458 if ((page->mapping != inode->i_mapping) ||
2459 (page_offset(page) > size)) {
2460 /* We overload EFAULT to mean page got truncated */
2461 ret = -EFAULT;
2462 goto out_unlock;
2463 }
2464
2465 /* page is wholly or partially inside EOF */
2466 if (((page->index + 1) << PAGE_SHIFT) > size)
2467 end = size & ~PAGE_MASK;
2468 else
2469 end = PAGE_SIZE;
2470
2471 ret = __block_write_begin(page, 0, end, get_block);
2472 if (!ret)
2473 ret = block_commit_write(page, 0, end);
2474
2475 if (unlikely(ret < 0))
2476 goto out_unlock;
2477 set_page_dirty(page);
2478 wait_for_stable_page(page);
2479 return 0;
2480out_unlock:
2481 unlock_page(page);
2482 return ret;
2483}
2484EXPORT_SYMBOL(block_page_mkwrite);
2485
2486/*
2487 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
2488 * immediately, while under the page lock. So it needs a special end_io
2489 * handler which does not touch the bh after unlocking it.
2490 */
2491static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2492{
2493 __end_buffer_read_notouch(bh, uptodate);
2494}
2495
2496/*
2497 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2498 * the page (converting it to circular linked list and taking care of page
2499 * dirty races).
2500 */
2501static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2502{
2503 struct buffer_head *bh;
2504
2505 BUG_ON(!PageLocked(page));
2506
2507 spin_lock(&page->mapping->private_lock);
2508 bh = head;
2509 do {
2510 if (PageDirty(page))
2511 set_buffer_dirty(bh);
2512 if (!bh->b_this_page)
2513 bh->b_this_page = head;
2514 bh = bh->b_this_page;
2515 } while (bh != head);
2516 attach_page_buffers(page, head);
2517 spin_unlock(&page->mapping->private_lock);
2518}
2519
2520/*
2521 * On entry, the page is fully not uptodate.
2522 * On exit the page is fully uptodate in the areas outside (from,to)
2523 * The filesystem needs to handle block truncation upon failure.
2524 */
2525int nobh_write_begin(struct address_space *mapping,
2526 loff_t pos, unsigned len, unsigned flags,
2527 struct page **pagep, void **fsdata,
2528 get_block_t *get_block)
2529{
2530 struct inode *inode = mapping->host;
2531 const unsigned blkbits = inode->i_blkbits;
2532 const unsigned blocksize = 1 << blkbits;
2533 struct buffer_head *head, *bh;
2534 struct page *page;
2535 pgoff_t index;
2536 unsigned from, to;
2537 unsigned block_in_page;
2538 unsigned block_start, block_end;
2539 sector_t block_in_file;
2540 int nr_reads = 0;
2541 int ret = 0;
2542 int is_mapped_to_disk = 1;
2543
2544 index = pos >> PAGE_SHIFT;
2545 from = pos & (PAGE_SIZE - 1);
2546 to = from + len;
2547
2548 page = grab_cache_page_write_begin(mapping, index, flags);
2549 if (!page)
2550 return -ENOMEM;
2551 *pagep = page;
2552 *fsdata = NULL;
2553
2554 if (page_has_buffers(page)) {
2555 ret = __block_write_begin(page, pos, len, get_block);
2556 if (unlikely(ret))
2557 goto out_release;
2558 return ret;
2559 }
2560
2561 if (PageMappedToDisk(page))
2562 return 0;
2563
2564 /*
2565 * Allocate buffers so that we can keep track of state, and potentially
2566 * attach them to the page if an error occurs. In the common case of
2567 * no error, they will just be freed again without ever being attached
2568 * to the page (which is all OK, because we're under the page lock).
2569 *
2570 * Be careful: the buffer linked list is a NULL terminated one, rather
2571 * than the circular one we're used to.
2572 */
2573 head = alloc_page_buffers(page, blocksize, false);
2574 if (!head) {
2575 ret = -ENOMEM;
2576 goto out_release;
2577 }
2578
2579 block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
2580
2581 /*
2582 * We loop across all blocks in the page, whether or not they are
2583 * part of the affected region. This is so we can discover if the
2584 * page is fully mapped-to-disk.
2585 */
2586 for (block_start = 0, block_in_page = 0, bh = head;
2587 block_start < PAGE_SIZE;
2588 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
2589 int create;
2590
2591 block_end = block_start + blocksize;
2592 bh->b_state = 0;
2593 create = 1;
2594 if (block_start >= to)
2595 create = 0;
2596 ret = get_block(inode, block_in_file + block_in_page,
2597 bh, create);
2598 if (ret)
2599 goto failed;
2600 if (!buffer_mapped(bh))
2601 is_mapped_to_disk = 0;
2602 if (buffer_new(bh))
2603 clean_bdev_bh_alias(bh);
2604 if (PageUptodate(page)) {
2605 set_buffer_uptodate(bh);
2606 continue;
2607 }
2608 if (buffer_new(bh) || !buffer_mapped(bh)) {
2609 zero_user_segments(page, block_start, from,
2610 to, block_end);
2611 continue;
2612 }
2613 if (buffer_uptodate(bh))
2614 continue; /* reiserfs does this */
2615 if (block_start < from || block_end > to) {
2616 lock_buffer(bh);
2617 bh->b_end_io = end_buffer_read_nobh;
2618 submit_bh(REQ_OP_READ, 0, bh);
2619 nr_reads++;
2620 }
2621 }
2622
2623 if (nr_reads) {
2624 /*
2625 * The page is locked, so these buffers are protected from
2626 * any VM or truncate activity. Hence we don't need to care
2627 * for the buffer_head refcounts.
2628 */
2629 for (bh = head; bh; bh = bh->b_this_page) {
2630 wait_on_buffer(bh);
2631 if (!buffer_uptodate(bh))
2632 ret = -EIO;
2633 }
2634 if (ret)
2635 goto failed;
2636 }
2637
2638 if (is_mapped_to_disk)
2639 SetPageMappedToDisk(page);
2640
2641 *fsdata = head; /* to be released by nobh_write_end */
2642
2643 return 0;
2644
2645failed:
2646 BUG_ON(!ret);
2647 /*
2648 * Error recovery is a bit difficult. We need to zero out blocks that
2649 * were newly allocated, and dirty them to ensure they get written out.
2650 * Buffers need to be attached to the page at this point, otherwise
2651 * the handling of potential IO errors during writeout would be hard
2652 * (could try doing synchronous writeout, but what if that fails too?)
2653 */
2654 attach_nobh_buffers(page, head);
2655 page_zero_new_buffers(page, from, to);
2656
2657out_release:
2658 unlock_page(page);
2659 put_page(page);
2660 *pagep = NULL;
2661
2662 return ret;
2663}
2664EXPORT_SYMBOL(nobh_write_begin);
2665
2666int nobh_write_end(struct file *file, struct address_space *mapping,
2667 loff_t pos, unsigned len, unsigned copied,
2668 struct page *page, void *fsdata)
2669{
2670 struct inode *inode = page->mapping->host;
2671 struct buffer_head *head = fsdata;
2672 struct buffer_head *bh;
2673 BUG_ON(fsdata != NULL && page_has_buffers(page));
2674
2675 if (unlikely(copied < len) && head)
2676 attach_nobh_buffers(page, head);
2677 if (page_has_buffers(page))
2678 return generic_write_end(file, mapping, pos, len,
2679 copied, page, fsdata);
2680
2681 SetPageUptodate(page);
2682 set_page_dirty(page);
2683 if (pos+copied > inode->i_size) {
2684 i_size_write(inode, pos+copied);
2685 mark_inode_dirty(inode);
2686 }
2687
2688 unlock_page(page);
2689 put_page(page);
2690
2691 while (head) {
2692 bh = head;
2693 head = head->b_this_page;
2694 free_buffer_head(bh);
2695 }
2696
2697 return copied;
2698}
2699EXPORT_SYMBOL(nobh_write_end);
2700
2701/*
2702 * nobh_writepage() - based on block_full_write_page() except
2703 * that it tries to operate without attaching bufferheads to
2704 * the page.
2705 */
2706int nobh_writepage(struct page *page, get_block_t *get_block,
2707 struct writeback_control *wbc)
2708{
2709 struct inode * const inode = page->mapping->host;
2710 loff_t i_size = i_size_read(inode);
2711 const pgoff_t end_index = i_size >> PAGE_SHIFT;
2712 unsigned offset;
2713 int ret;
2714
2715 /* Is the page fully inside i_size? */
2716 if (page->index < end_index)
2717 goto out;
2718
2719 /* Is the page fully outside i_size? (truncate in progress) */
2720 offset = i_size & (PAGE_SIZE-1);
2721 if (page->index >= end_index+1 || !offset) {
2722 /*
2723 * The page may have dirty, unmapped buffers. For example,
2724 * they may have been added in ext3_writepage(). Make them
2725 * freeable here, so the page does not leak.
2726 */
2727#if 0
2728 /* Not really sure about this - do we need this ? */
2729 if (page->mapping->a_ops->invalidatepage)
2730 page->mapping->a_ops->invalidatepage(page, offset);
2731#endif
2732 unlock_page(page);
2733 return 0; /* don't care */
2734 }
2735
2736 /*
2737 * The page straddles i_size. It must be zeroed out on each and every
2738 * writepage invocation because it may be mmapped. "A file is mapped
2739 * in multiples of the page size. For a file that is not a multiple of
2740 * the page size, the remaining memory is zeroed when mapped, and
2741 * writes to that region are not written out to the file."
2742 */
2743 zero_user_segment(page, offset, PAGE_SIZE);
2744out:
2745 ret = mpage_writepage(page, get_block, wbc);
2746 if (ret == -EAGAIN)
2747 ret = __block_write_full_page(inode, page, get_block, wbc,
2748 end_buffer_async_write);
2749 return ret;
2750}
2751EXPORT_SYMBOL(nobh_writepage);
2752
2753int nobh_truncate_page(struct address_space *mapping,
2754 loff_t from, get_block_t *get_block)
2755{
2756 pgoff_t index = from >> PAGE_SHIFT;
2757 unsigned offset = from & (PAGE_SIZE-1);
2758 unsigned blocksize;
2759 sector_t iblock;
2760 unsigned length, pos;
2761 struct inode *inode = mapping->host;
2762 struct page *page;
2763 struct buffer_head map_bh;
2764 int err;
2765
2766 blocksize = i_blocksize(inode);
2767 length = offset & (blocksize - 1);
2768
2769 /* Block boundary? Nothing to do */
2770 if (!length)
2771 return 0;
2772
2773 length = blocksize - length;
2774 iblock = (sector_t)index << (PAGE_SHIFT - inode->i_blkbits);
2775
2776 page = grab_cache_page(mapping, index);
2777 err = -ENOMEM;
2778 if (!page)
2779 goto out;
2780
2781 if (page_has_buffers(page)) {
2782has_buffers:
2783 unlock_page(page);
2784 put_page(page);
2785 return block_truncate_page(mapping, from, get_block);
2786 }
2787
2788 /* Find the buffer that contains "offset" */
2789 pos = blocksize;
2790 while (offset >= pos) {
2791 iblock++;
2792 pos += blocksize;
2793 }
2794
2795 map_bh.b_size = blocksize;
2796 map_bh.b_state = 0;
2797 err = get_block(inode, iblock, &map_bh, 0);
2798 if (err)
2799 goto unlock;
2800 /* unmapped? It's a hole - nothing to do */
2801 if (!buffer_mapped(&map_bh))
2802 goto unlock;
2803
2804 /* Ok, it's mapped. Make sure it's up-to-date */
2805 if (!PageUptodate(page)) {
2806 err = mapping->a_ops->readpage(NULL, page);
2807 if (err) {
2808 put_page(page);
2809 goto out;
2810 }
2811 lock_page(page);
2812 if (!PageUptodate(page)) {
2813 err = -EIO;
2814 goto unlock;
2815 }
2816 if (page_has_buffers(page))
2817 goto has_buffers;
2818 }
2819 zero_user(page, offset, length);
2820 set_page_dirty(page);
2821 err = 0;
2822
2823unlock:
2824 unlock_page(page);
2825 put_page(page);
2826out:
2827 return err;
2828}
2829EXPORT_SYMBOL(nobh_truncate_page);
2830
2831int block_truncate_page(struct address_space *mapping,
2832 loff_t from, get_block_t *get_block)
2833{
2834 pgoff_t index = from >> PAGE_SHIFT;
2835 unsigned offset = from & (PAGE_SIZE-1);
2836 unsigned blocksize;
2837 sector_t iblock;
2838 unsigned length, pos;
2839 struct inode *inode = mapping->host;
2840 struct page *page;
2841 struct buffer_head *bh;
2842 int err;
2843
2844 blocksize = i_blocksize(inode);
2845 length = offset & (blocksize - 1);
2846
2847 /* Block boundary? Nothing to do */
2848 if (!length)
2849 return 0;
2850
2851 length = blocksize - length;
2852 iblock = (sector_t)index << (PAGE_SHIFT - inode->i_blkbits);
2853
2854 page = grab_cache_page(mapping, index);
2855 err = -ENOMEM;
2856 if (!page)
2857 goto out;
2858
2859 if (!page_has_buffers(page))
2860 create_empty_buffers(page, blocksize, 0);
2861
2862 /* Find the buffer that contains "offset" */
2863 bh = page_buffers(page);
2864 pos = blocksize;
2865 while (offset >= pos) {
2866 bh = bh->b_this_page;
2867 iblock++;
2868 pos += blocksize;
2869 }
2870
2871 err = 0;
2872 if (!buffer_mapped(bh)) {
2873 WARN_ON(bh->b_size != blocksize);
2874 err = get_block(inode, iblock, bh, 0);
2875 if (err)
2876 goto unlock;
2877 /* unmapped? It's a hole - nothing to do */
2878 if (!buffer_mapped(bh))
2879 goto unlock;
2880 }
2881
2882 /* Ok, it's mapped. Make sure it's up-to-date */
2883 if (PageUptodate(page))
2884 set_buffer_uptodate(bh);
2885
2886 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2887 err = -EIO;
2888 ll_rw_block(REQ_OP_READ, 0, 1, &bh);
2889 wait_on_buffer(bh);
2890 /* Uhhuh. Read error. Complain and punt. */
2891 if (!buffer_uptodate(bh))
2892 goto unlock;
2893 }
2894
2895 zero_user(page, offset, length);
2896 mark_buffer_dirty(bh);
2897 err = 0;
2898
2899unlock:
2900 unlock_page(page);
2901 put_page(page);
2902out:
2903 return err;
2904}
2905EXPORT_SYMBOL(block_truncate_page);
2906
2907/*
2908 * The generic ->writepage function for buffer-backed address_spaces
2909 */
2910int block_write_full_page(struct page *page, get_block_t *get_block,
2911 struct writeback_control *wbc)
2912{
2913 struct inode * const inode = page->mapping->host;
2914 loff_t i_size = i_size_read(inode);
2915 const pgoff_t end_index = i_size >> PAGE_SHIFT;
2916 unsigned offset;
2917
2918 /* Is the page fully inside i_size? */
2919 if (page->index < end_index)
2920 return __block_write_full_page(inode, page, get_block, wbc,
2921 end_buffer_async_write);
2922
2923 /* Is the page fully outside i_size? (truncate in progress) */
2924 offset = i_size & (PAGE_SIZE-1);
2925 if (page->index >= end_index+1 || !offset) {
2926 /*
2927 * The page may have dirty, unmapped buffers. For example,
2928 * they may have been added in ext3_writepage(). Make them
2929 * freeable here, so the page does not leak.
2930 */
2931 do_invalidatepage(page, 0, PAGE_SIZE);
2932 unlock_page(page);
2933 return 0; /* don't care */
2934 }
2935
2936 /*
2937 * The page straddles i_size. It must be zeroed out on each and every
2938 * writepage invocation because it may be mmapped. "A file is mapped
2939 * in multiples of the page size. For a file that is not a multiple of
2940 * the page size, the remaining memory is zeroed when mapped, and
2941 * writes to that region are not written out to the file."
2942 */
2943 zero_user_segment(page, offset, PAGE_SIZE);
2944 return __block_write_full_page(inode, page, get_block, wbc,
2945 end_buffer_async_write);
2946}
2947EXPORT_SYMBOL(block_write_full_page);
2948
2949sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2950 get_block_t *get_block)
2951{
2952 struct inode *inode = mapping->host;
2953 struct buffer_head tmp = {
2954 .b_size = i_blocksize(inode),
2955 };
2956
2957 get_block(inode, block, &tmp, 0);
2958 return tmp.b_blocknr;
2959}
2960EXPORT_SYMBOL(generic_block_bmap);
2961
2962static void end_bio_bh_io_sync(struct bio *bio)
2963{
2964 struct buffer_head *bh = bio->bi_private;
2965
2966 if (unlikely(bio_flagged(bio, BIO_QUIET)))
2967 set_bit(BH_Quiet, &bh->b_state);
2968
2969 bh->b_end_io(bh, !bio->bi_status);
2970 bio_put(bio);
2971}
2972
2973/*
2974 * This allows us to do IO even on the odd last sectors
2975 * of a device, even if the block size is some multiple
2976 * of the physical sector size.
2977 *
2978 * We'll just truncate the bio to the size of the device,
2979 * and clear the end of the buffer head manually.
2980 *
2981 * Truly out-of-range accesses will turn into actual IO
2982 * errors, this only handles the "we need to be able to
2983 * do IO at the final sector" case.
2984 */
2985void guard_bio_eod(int op, struct bio *bio)
2986{
2987 sector_t maxsector;
2988 struct bio_vec *bvec = bio_last_bvec_all(bio);
2989 unsigned truncated_bytes;
2990 struct hd_struct *part;
2991
2992 rcu_read_lock();
2993 part = __disk_get_part(bio->bi_disk, bio->bi_partno);
2994 if (part)
2995 maxsector = part_nr_sects_read(part);
2996 else
2997 maxsector = get_capacity(bio->bi_disk);
2998 rcu_read_unlock();
2999
3000 if (!maxsector)
3001 return;
3002
3003 /*
3004 * If the *whole* IO is past the end of the device,
3005 * let it through, and the IO layer will turn it into
3006 * an EIO.
3007 */
3008 if (unlikely(bio->bi_iter.bi_sector >= maxsector))
3009 return;
3010
3011 maxsector -= bio->bi_iter.bi_sector;
3012 if (likely((bio->bi_iter.bi_size >> 9) <= maxsector))
3013 return;
3014
3015 /* Uhhuh. We've got a bio that straddles the device size! */
3016 truncated_bytes = bio->bi_iter.bi_size - (maxsector << 9);
3017
3018 /* Truncate the bio.. */
3019 bio->bi_iter.bi_size -= truncated_bytes;
3020 bvec->bv_len -= truncated_bytes;
3021
3022 /* ..and clear the end of the buffer for reads */
3023 if (op == REQ_OP_READ) {
3024 zero_user(bvec->bv_page, bvec->bv_offset + bvec->bv_len,
3025 truncated_bytes);
3026 }
3027}
3028
3029static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
3030 enum rw_hint write_hint, struct writeback_control *wbc)
3031{
3032 struct bio *bio;
3033
3034 BUG_ON(!buffer_locked(bh));
3035 BUG_ON(!buffer_mapped(bh));
3036 BUG_ON(!bh->b_end_io);
3037 BUG_ON(buffer_delay(bh));
3038 BUG_ON(buffer_unwritten(bh));
3039
3040 /*
3041 * Only clear out a write error when rewriting
3042 */
3043 if (test_set_buffer_req(bh) && (op == REQ_OP_WRITE))
3044 clear_buffer_write_io_error(bh);
3045
3046 /*
3047 * from here on down, it's all bio -- do the initial mapping,
3048 * submit_bio -> generic_make_request may further map this bio around
3049 */
3050 bio = bio_alloc(GFP_NOIO, 1);
3051
3052 if (wbc) {
3053 wbc_init_bio(wbc, bio);
3054 wbc_account_io(wbc, bh->b_page, bh->b_size);
3055 }
3056
3057 bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
3058 bio_set_dev(bio, bh->b_bdev);
3059 bio->bi_write_hint = write_hint;
3060
3061 bio_add_page(bio, bh->b_page, bh->b_size, bh_offset(bh));
3062 BUG_ON(bio->bi_iter.bi_size != bh->b_size);
3063
3064 bio->bi_end_io = end_bio_bh_io_sync;
3065 bio->bi_private = bh;
3066
3067 /* Take care of bh's that straddle the end of the device */
3068 guard_bio_eod(op, bio);
3069
3070 if (buffer_meta(bh))
3071 op_flags |= REQ_META;
3072 if (buffer_prio(bh))
3073 op_flags |= REQ_PRIO;
3074 bio_set_op_attrs(bio, op, op_flags);
3075
3076 submit_bio(bio);
3077 return 0;
3078}
3079
3080int submit_bh(int op, int op_flags, struct buffer_head *bh)
3081{
3082 return submit_bh_wbc(op, op_flags, bh, 0, NULL);
3083}
3084EXPORT_SYMBOL(submit_bh);
3085
3086/**
3087 * ll_rw_block: low-level access to block devices (DEPRECATED)
3088 * @op: whether to %READ or %WRITE
3089 * @op_flags: req_flag_bits
3090 * @nr: number of &struct buffer_heads in the array
3091 * @bhs: array of pointers to &struct buffer_head
3092 *
3093 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
3094 * requests an I/O operation on them, either a %REQ_OP_READ or a %REQ_OP_WRITE.
3095 * @op_flags contains flags modifying the detailed I/O behavior, most notably
3096 * %REQ_RAHEAD.
3097 *
3098 * This function drops any buffer that it cannot get a lock on (with the
3099 * BH_Lock state bit), any buffer that appears to be clean when doing a write
3100 * request, and any buffer that appears to be up-to-date when doing read
3101 * request. Further it marks as clean buffers that are processed for
3102 * writing (the buffer cache won't assume that they are actually clean
3103 * until the buffer gets unlocked).
3104 *
3105 * ll_rw_block sets b_end_io to simple completion handler that marks
3106 * the buffer up-to-date (if appropriate), unlocks the buffer and wakes
3107 * any waiters.
3108 *
3109 * All of the buffers must be for the same device, and must also be a
3110 * multiple of the current approved size for the device.
3111 */
3112void ll_rw_block(int op, int op_flags, int nr, struct buffer_head *bhs[])
3113{
3114 int i;
3115
3116 for (i = 0; i < nr; i++) {
3117 struct buffer_head *bh = bhs[i];
3118
3119 if (!trylock_buffer(bh))
3120 continue;
3121 if (op == WRITE) {
3122 if (test_clear_buffer_dirty(bh)) {
3123 bh->b_end_io = end_buffer_write_sync;
3124 get_bh(bh);
3125 submit_bh(op, op_flags, bh);
3126 continue;
3127 }
3128 } else {
3129 if (!buffer_uptodate(bh)) {
3130 bh->b_end_io = end_buffer_read_sync;
3131 get_bh(bh);
3132 submit_bh(op, op_flags, bh);
3133 continue;
3134 }
3135 }
3136 unlock_buffer(bh);
3137 }
3138}
3139EXPORT_SYMBOL(ll_rw_block);
3140
3141void write_dirty_buffer(struct buffer_head *bh, int op_flags)
3142{
3143 lock_buffer(bh);
3144 if (!test_clear_buffer_dirty(bh)) {
3145 unlock_buffer(bh);
3146 return;
3147 }
3148 bh->b_end_io = end_buffer_write_sync;
3149 get_bh(bh);
3150 submit_bh(REQ_OP_WRITE, op_flags, bh);
3151}
3152EXPORT_SYMBOL(write_dirty_buffer);
3153
3154/*
3155 * For a data-integrity writeout, we need to wait upon any in-progress I/O
3156 * and then start new I/O and then wait upon it. The caller must have a ref on
3157 * the buffer_head.
3158 */
3159int __sync_dirty_buffer(struct buffer_head *bh, int op_flags)
3160{
3161 int ret = 0;
3162
3163 WARN_ON(atomic_read(&bh->b_count) < 1);
3164 lock_buffer(bh);
3165 if (test_clear_buffer_dirty(bh)) {
3166 get_bh(bh);
3167 bh->b_end_io = end_buffer_write_sync;
3168 ret = submit_bh(REQ_OP_WRITE, op_flags, bh);
3169 wait_on_buffer(bh);
3170 if (!ret && !buffer_uptodate(bh))
3171 ret = -EIO;
3172 } else {
3173 unlock_buffer(bh);
3174 }
3175 return ret;
3176}
3177EXPORT_SYMBOL(__sync_dirty_buffer);
3178
3179int sync_dirty_buffer(struct buffer_head *bh)
3180{
3181 return __sync_dirty_buffer(bh, REQ_SYNC);
3182}
3183EXPORT_SYMBOL(sync_dirty_buffer);
3184
3185/*
3186 * try_to_free_buffers() checks if all the buffers on this particular page
3187 * are unused, and releases them if so.
3188 *
3189 * Exclusion against try_to_free_buffers may be obtained by either
3190 * locking the page or by holding its mapping's private_lock.
3191 *
3192 * If the page is dirty but all the buffers are clean then we need to
3193 * be sure to mark the page clean as well. This is because the page
3194 * may be against a block device, and a later reattachment of buffers
3195 * to a dirty page will set *all* buffers dirty. Which would corrupt
3196 * filesystem data on the same device.
3197 *
3198 * The same applies to regular filesystem pages: if all the buffers are
3199 * clean then we set the page clean and proceed. To do that, we require
3200 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3201 * private_lock.
3202 *
3203 * try_to_free_buffers() is non-blocking.
3204 */
3205static inline int buffer_busy(struct buffer_head *bh)
3206{
3207 return atomic_read(&bh->b_count) |
3208 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3209}
3210
3211static int
3212drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3213{
3214 struct buffer_head *head = page_buffers(page);
3215 struct buffer_head *bh;
3216
3217 bh = head;
3218 do {
3219 if (buffer_busy(bh))
3220 goto failed;
3221 bh = bh->b_this_page;
3222 } while (bh != head);
3223
3224 do {
3225 struct buffer_head *next = bh->b_this_page;
3226
3227 if (bh->b_assoc_map)
3228 __remove_assoc_queue(bh);
3229 bh = next;
3230 } while (bh != head);
3231 *buffers_to_free = head;
3232 __clear_page_buffers(page);
3233 return 1;
3234failed:
3235 return 0;
3236}
3237
3238int try_to_free_buffers(struct page *page)
3239{
3240 struct address_space * const mapping = page->mapping;
3241 struct buffer_head *buffers_to_free = NULL;
3242 int ret = 0;
3243
3244 BUG_ON(!PageLocked(page));
3245 if (PageWriteback(page))
3246 return 0;
3247
3248 if (mapping == NULL) { /* can this still happen? */
3249 ret = drop_buffers(page, &buffers_to_free);
3250 goto out;
3251 }
3252
3253 spin_lock(&mapping->private_lock);
3254 ret = drop_buffers(page, &buffers_to_free);
3255
3256 /*
3257 * If the filesystem writes its buffers by hand (eg ext3)
3258 * then we can have clean buffers against a dirty page. We
3259 * clean the page here; otherwise the VM will never notice
3260 * that the filesystem did any IO at all.
3261 *
3262 * Also, during truncate, discard_buffer will have marked all
3263 * the page's buffers clean. We discover that here and clean
3264 * the page also.
3265 *
3266 * private_lock must be held over this entire operation in order
3267 * to synchronise against __set_page_dirty_buffers and prevent the
3268 * dirty bit from being lost.
3269 */
3270 if (ret)
3271 cancel_dirty_page(page);
3272 spin_unlock(&mapping->private_lock);
3273out:
3274 if (buffers_to_free) {
3275 struct buffer_head *bh = buffers_to_free;
3276
3277 do {
3278 struct buffer_head *next = bh->b_this_page;
3279 free_buffer_head(bh);
3280 bh = next;
3281 } while (bh != buffers_to_free);
3282 }
3283 return ret;
3284}
3285EXPORT_SYMBOL(try_to_free_buffers);
3286
3287/*
3288 * There are no bdflush tunables left. But distributions are
3289 * still running obsolete flush daemons, so we terminate them here.
3290 *
3291 * Use of bdflush() is deprecated and will be removed in a future kernel.
3292 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
3293 */
3294SYSCALL_DEFINE2(bdflush, int, func, long, data)
3295{
3296 static int msg_count;
3297
3298 if (!capable(CAP_SYS_ADMIN))
3299 return -EPERM;
3300
3301 if (msg_count < 5) {
3302 msg_count++;
3303 printk(KERN_INFO
3304 "warning: process `%s' used the obsolete bdflush"
3305 " system call\n", current->comm);
3306 printk(KERN_INFO "Fix your initscripts?\n");
3307 }
3308
3309 if (func == 1)
3310 do_exit(0);
3311 return 0;
3312}
3313
3314/*
3315 * Buffer-head allocation
3316 */
3317static struct kmem_cache *bh_cachep __read_mostly;
3318
3319/*
3320 * Once the number of bh's in the machine exceeds this level, we start
3321 * stripping them in writeback.
3322 */
3323static unsigned long max_buffer_heads;
3324
3325int buffer_heads_over_limit;
3326
3327struct bh_accounting {
3328 int nr; /* Number of live bh's */
3329 int ratelimit; /* Limit cacheline bouncing */
3330};
3331
3332static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3333
3334static void recalc_bh_state(void)
3335{
3336 int i;
3337 int tot = 0;
3338
3339 if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
3340 return;
3341 __this_cpu_write(bh_accounting.ratelimit, 0);
3342 for_each_online_cpu(i)
3343 tot += per_cpu(bh_accounting, i).nr;
3344 buffer_heads_over_limit = (tot > max_buffer_heads);
3345}
3346
3347struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3348{
3349 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
3350 if (ret) {
3351 INIT_LIST_HEAD(&ret->b_assoc_buffers);
3352 preempt_disable();
3353 __this_cpu_inc(bh_accounting.nr);
3354 recalc_bh_state();
3355 preempt_enable();
3356 }
3357 return ret;
3358}
3359EXPORT_SYMBOL(alloc_buffer_head);
3360
3361void free_buffer_head(struct buffer_head *bh)
3362{
3363 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3364 kmem_cache_free(bh_cachep, bh);
3365 preempt_disable();
3366 __this_cpu_dec(bh_accounting.nr);
3367 recalc_bh_state();
3368 preempt_enable();
3369}
3370EXPORT_SYMBOL(free_buffer_head);
3371
3372static int buffer_exit_cpu_dead(unsigned int cpu)
3373{
3374 int i;
3375 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3376
3377 for (i = 0; i < BH_LRU_SIZE; i++) {
3378 brelse(b->bhs[i]);
3379 b->bhs[i] = NULL;
3380 }
3381 this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3382 per_cpu(bh_accounting, cpu).nr = 0;
3383 return 0;
3384}
3385
3386/**
3387 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3388 * @bh: struct buffer_head
3389 *
3390 * Return true if the buffer is up-to-date and false,
3391 * with the buffer locked, if not.
3392 */
3393int bh_uptodate_or_lock(struct buffer_head *bh)
3394{
3395 if (!buffer_uptodate(bh)) {
3396 lock_buffer(bh);
3397 if (!buffer_uptodate(bh))
3398 return 0;
3399 unlock_buffer(bh);
3400 }
3401 return 1;
3402}
3403EXPORT_SYMBOL(bh_uptodate_or_lock);
3404
3405/**
3406 * bh_submit_read - Submit a locked buffer for reading
3407 * @bh: struct buffer_head
3408 *
3409 * Returns zero on success and -EIO on error.
3410 */
3411int bh_submit_read(struct buffer_head *bh)
3412{
3413 BUG_ON(!buffer_locked(bh));
3414
3415 if (buffer_uptodate(bh)) {
3416 unlock_buffer(bh);
3417 return 0;
3418 }
3419
3420 get_bh(bh);
3421 bh->b_end_io = end_buffer_read_sync;
3422 submit_bh(REQ_OP_READ, 0, bh);
3423 wait_on_buffer(bh);
3424 if (buffer_uptodate(bh))
3425 return 0;
3426 return -EIO;
3427}
3428EXPORT_SYMBOL(bh_submit_read);
3429
3430/*
3431 * Seek for SEEK_DATA / SEEK_HOLE within @page, starting at @lastoff.
3432 *
3433 * Returns the offset within the file on success, and -ENOENT otherwise.
3434 */
3435static loff_t
3436page_seek_hole_data(struct page *page, loff_t lastoff, int whence)
3437{
3438 loff_t offset = page_offset(page);
3439 struct buffer_head *bh, *head;
3440 bool seek_data = whence == SEEK_DATA;
3441
3442 if (lastoff < offset)
3443 lastoff = offset;
3444
3445 bh = head = page_buffers(page);
3446 do {
3447 offset += bh->b_size;
3448 if (lastoff >= offset)
3449 continue;
3450
3451 /*
3452 * Unwritten extents that have data in the page cache covering
3453 * them can be identified by the BH_Unwritten state flag.
3454 * Pages with multiple buffers might have a mix of holes, data
3455 * and unwritten extents - any buffer with valid data in it
3456 * should have BH_Uptodate flag set on it.
3457 */
3458
3459 if ((buffer_unwritten(bh) || buffer_uptodate(bh)) == seek_data)
3460 return lastoff;
3461
3462 lastoff = offset;
3463 } while ((bh = bh->b_this_page) != head);
3464 return -ENOENT;
3465}
3466
3467/*
3468 * Seek for SEEK_DATA / SEEK_HOLE in the page cache.
3469 *
3470 * Within unwritten extents, the page cache determines which parts are holes
3471 * and which are data: unwritten and uptodate buffer heads count as data;
3472 * everything else counts as a hole.
3473 *
3474 * Returns the resulting offset on successs, and -ENOENT otherwise.
3475 */
3476loff_t
3477page_cache_seek_hole_data(struct inode *inode, loff_t offset, loff_t length,
3478 int whence)
3479{
3480 pgoff_t index = offset >> PAGE_SHIFT;
3481 pgoff_t end = DIV_ROUND_UP(offset + length, PAGE_SIZE);
3482 loff_t lastoff = offset;
3483 struct pagevec pvec;
3484
3485 if (length <= 0)
3486 return -ENOENT;
3487
3488 pagevec_init(&pvec);
3489
3490 do {
3491 unsigned nr_pages, i;
3492
3493 nr_pages = pagevec_lookup_range(&pvec, inode->i_mapping, &index,
3494 end - 1);
3495 if (nr_pages == 0)
3496 break;
3497
3498 for (i = 0; i < nr_pages; i++) {
3499 struct page *page = pvec.pages[i];
3500
3501 /*
3502 * At this point, the page may be truncated or
3503 * invalidated (changing page->mapping to NULL), or
3504 * even swizzled back from swapper_space to tmpfs file
3505 * mapping. However, page->index will not change
3506 * because we have a reference on the page.
3507 *
3508 * If current page offset is beyond where we've ended,
3509 * we've found a hole.
3510 */
3511 if (whence == SEEK_HOLE &&
3512 lastoff < page_offset(page))
3513 goto check_range;
3514
3515 lock_page(page);
3516 if (likely(page->mapping == inode->i_mapping) &&
3517 page_has_buffers(page)) {
3518 lastoff = page_seek_hole_data(page, lastoff, whence);
3519 if (lastoff >= 0) {
3520 unlock_page(page);
3521 goto check_range;
3522 }
3523 }
3524 unlock_page(page);
3525 lastoff = page_offset(page) + PAGE_SIZE;
3526 }
3527 pagevec_release(&pvec);
3528 } while (index < end);
3529
3530 /* When no page at lastoff and we are not done, we found a hole. */
3531 if (whence != SEEK_HOLE)
3532 goto not_found;
3533
3534check_range:
3535 if (lastoff < offset + length)
3536 goto out;
3537not_found:
3538 lastoff = -ENOENT;
3539out:
3540 pagevec_release(&pvec);
3541 return lastoff;
3542}
3543
3544void __init buffer_init(void)
3545{
3546 unsigned long nrpages;
3547 int ret;
3548
3549 bh_cachep = kmem_cache_create("buffer_head",
3550 sizeof(struct buffer_head), 0,
3551 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3552 SLAB_MEM_SPREAD),
3553 NULL);
3554
3555 /*
3556 * Limit the bh occupancy to 10% of ZONE_NORMAL
3557 */
3558 nrpages = (nr_free_buffer_pages() * 10) / 100;
3559 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3560 ret = cpuhp_setup_state_nocalls(CPUHP_FS_BUFF_DEAD, "fs/buffer:dead",
3561 NULL, buffer_exit_cpu_dead);
3562 WARN_ON(ret < 0);
3563}