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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/mm.h>
25#include <linux/percpu.h>
26#include <linux/slab.h>
27#include <linux/capability.h>
28#include <linux/blkdev.h>
29#include <linux/file.h>
30#include <linux/quotaops.h>
31#include <linux/highmem.h>
32#include <linux/module.h>
33#include <linux/writeback.h>
34#include <linux/hash.h>
35#include <linux/suspend.h>
36#include <linux/buffer_head.h>
37#include <linux/task_io_accounting_ops.h>
38#include <linux/bio.h>
39#include <linux/notifier.h>
40#include <linux/cpu.h>
41#include <linux/bitops.h>
42#include <linux/mpage.h>
43#include <linux/bit_spinlock.h>
44#include <linux/cleancache.h>
45
46static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
47
48#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
49
50inline void
51init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
52{
53 bh->b_end_io = handler;
54 bh->b_private = private;
55}
56EXPORT_SYMBOL(init_buffer);
57
58static int sleep_on_buffer(void *word)
59{
60 io_schedule();
61 return 0;
62}
63
64void __lock_buffer(struct buffer_head *bh)
65{
66 wait_on_bit_lock(&bh->b_state, BH_Lock, sleep_on_buffer,
67 TASK_UNINTERRUPTIBLE);
68}
69EXPORT_SYMBOL(__lock_buffer);
70
71void unlock_buffer(struct buffer_head *bh)
72{
73 clear_bit_unlock(BH_Lock, &bh->b_state);
74 smp_mb__after_clear_bit();
75 wake_up_bit(&bh->b_state, BH_Lock);
76}
77EXPORT_SYMBOL(unlock_buffer);
78
79/*
80 * Block until a buffer comes unlocked. This doesn't stop it
81 * from becoming locked again - you have to lock it yourself
82 * if you want to preserve its state.
83 */
84void __wait_on_buffer(struct buffer_head * bh)
85{
86 wait_on_bit(&bh->b_state, BH_Lock, sleep_on_buffer, TASK_UNINTERRUPTIBLE);
87}
88EXPORT_SYMBOL(__wait_on_buffer);
89
90static void
91__clear_page_buffers(struct page *page)
92{
93 ClearPagePrivate(page);
94 set_page_private(page, 0);
95 page_cache_release(page);
96}
97
98
99static int quiet_error(struct buffer_head *bh)
100{
101 if (!test_bit(BH_Quiet, &bh->b_state) && printk_ratelimit())
102 return 0;
103 return 1;
104}
105
106
107static void buffer_io_error(struct buffer_head *bh)
108{
109 char b[BDEVNAME_SIZE];
110 printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
111 bdevname(bh->b_bdev, b),
112 (unsigned long long)bh->b_blocknr);
113}
114
115/*
116 * End-of-IO handler helper function which does not touch the bh after
117 * unlocking it.
118 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
119 * a race there is benign: unlock_buffer() only use the bh's address for
120 * hashing after unlocking the buffer, so it doesn't actually touch the bh
121 * itself.
122 */
123static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
124{
125 if (uptodate) {
126 set_buffer_uptodate(bh);
127 } else {
128 /* This happens, due to failed READA attempts. */
129 clear_buffer_uptodate(bh);
130 }
131 unlock_buffer(bh);
132}
133
134/*
135 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
136 * unlock the buffer. This is what ll_rw_block uses too.
137 */
138void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
139{
140 __end_buffer_read_notouch(bh, uptodate);
141 put_bh(bh);
142}
143EXPORT_SYMBOL(end_buffer_read_sync);
144
145void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
146{
147 char b[BDEVNAME_SIZE];
148
149 if (uptodate) {
150 set_buffer_uptodate(bh);
151 } else {
152 if (!quiet_error(bh)) {
153 buffer_io_error(bh);
154 printk(KERN_WARNING "lost page write due to "
155 "I/O error on %s\n",
156 bdevname(bh->b_bdev, b));
157 }
158 set_buffer_write_io_error(bh);
159 clear_buffer_uptodate(bh);
160 }
161 unlock_buffer(bh);
162 put_bh(bh);
163}
164EXPORT_SYMBOL(end_buffer_write_sync);
165
166/*
167 * Various filesystems appear to want __find_get_block to be non-blocking.
168 * But it's the page lock which protects the buffers. To get around this,
169 * we get exclusion from try_to_free_buffers with the blockdev mapping's
170 * private_lock.
171 *
172 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
173 * may be quite high. This code could TryLock the page, and if that
174 * succeeds, there is no need to take private_lock. (But if
175 * private_lock is contended then so is mapping->tree_lock).
176 */
177static struct buffer_head *
178__find_get_block_slow(struct block_device *bdev, sector_t block)
179{
180 struct inode *bd_inode = bdev->bd_inode;
181 struct address_space *bd_mapping = bd_inode->i_mapping;
182 struct buffer_head *ret = NULL;
183 pgoff_t index;
184 struct buffer_head *bh;
185 struct buffer_head *head;
186 struct page *page;
187 int all_mapped = 1;
188
189 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
190 page = find_get_page(bd_mapping, index);
191 if (!page)
192 goto out;
193
194 spin_lock(&bd_mapping->private_lock);
195 if (!page_has_buffers(page))
196 goto out_unlock;
197 head = page_buffers(page);
198 bh = head;
199 do {
200 if (!buffer_mapped(bh))
201 all_mapped = 0;
202 else if (bh->b_blocknr == block) {
203 ret = bh;
204 get_bh(bh);
205 goto out_unlock;
206 }
207 bh = bh->b_this_page;
208 } while (bh != head);
209
210 /* we might be here because some of the buffers on this page are
211 * not mapped. This is due to various races between
212 * file io on the block device and getblk. It gets dealt with
213 * elsewhere, don't buffer_error if we had some unmapped buffers
214 */
215 if (all_mapped) {
216 printk("__find_get_block_slow() failed. "
217 "block=%llu, b_blocknr=%llu\n",
218 (unsigned long long)block,
219 (unsigned long long)bh->b_blocknr);
220 printk("b_state=0x%08lx, b_size=%zu\n",
221 bh->b_state, bh->b_size);
222 printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits);
223 }
224out_unlock:
225 spin_unlock(&bd_mapping->private_lock);
226 page_cache_release(page);
227out:
228 return ret;
229}
230
231/* If invalidate_buffers() will trash dirty buffers, it means some kind
232 of fs corruption is going on. Trashing dirty data always imply losing
233 information that was supposed to be just stored on the physical layer
234 by the user.
235
236 Thus invalidate_buffers in general usage is not allwowed to trash
237 dirty buffers. For example ioctl(FLSBLKBUF) expects dirty data to
238 be preserved. These buffers are simply skipped.
239
240 We also skip buffers which are still in use. For example this can
241 happen if a userspace program is reading the block device.
242
243 NOTE: In the case where the user removed a removable-media-disk even if
244 there's still dirty data not synced on disk (due a bug in the device driver
245 or due an error of the user), by not destroying the dirty buffers we could
246 generate corruption also on the next media inserted, thus a parameter is
247 necessary to handle this case in the most safe way possible (trying
248 to not corrupt also the new disk inserted with the data belonging to
249 the old now corrupted disk). Also for the ramdisk the natural thing
250 to do in order to release the ramdisk memory is to destroy dirty buffers.
251
252 These are two special cases. Normal usage imply the device driver
253 to issue a sync on the device (without waiting I/O completion) and
254 then an invalidate_buffers call that doesn't trash dirty buffers.
255
256 For handling cache coherency with the blkdev pagecache the 'update' case
257 is been introduced. It is needed to re-read from disk any pinned
258 buffer. NOTE: re-reading from disk is destructive so we can do it only
259 when we assume nobody is changing the buffercache under our I/O and when
260 we think the disk contains more recent information than the buffercache.
261 The update == 1 pass marks the buffers we need to update, the update == 2
262 pass does the actual I/O. */
263void invalidate_bdev(struct block_device *bdev)
264{
265 struct address_space *mapping = bdev->bd_inode->i_mapping;
266
267 if (mapping->nrpages == 0)
268 return;
269
270 invalidate_bh_lrus();
271 lru_add_drain_all(); /* make sure all lru add caches are flushed */
272 invalidate_mapping_pages(mapping, 0, -1);
273 /* 99% of the time, we don't need to flush the cleancache on the bdev.
274 * But, for the strange corners, lets be cautious
275 */
276 cleancache_flush_inode(mapping);
277}
278EXPORT_SYMBOL(invalidate_bdev);
279
280/*
281 * Kick the writeback threads then try to free up some ZONE_NORMAL memory.
282 */
283static void free_more_memory(void)
284{
285 struct zone *zone;
286 int nid;
287
288 wakeup_flusher_threads(1024);
289 yield();
290
291 for_each_online_node(nid) {
292 (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS),
293 gfp_zone(GFP_NOFS), NULL,
294 &zone);
295 if (zone)
296 try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0,
297 GFP_NOFS, NULL);
298 }
299}
300
301/*
302 * I/O completion handler for block_read_full_page() - pages
303 * which come unlocked at the end of I/O.
304 */
305static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
306{
307 unsigned long flags;
308 struct buffer_head *first;
309 struct buffer_head *tmp;
310 struct page *page;
311 int page_uptodate = 1;
312
313 BUG_ON(!buffer_async_read(bh));
314
315 page = bh->b_page;
316 if (uptodate) {
317 set_buffer_uptodate(bh);
318 } else {
319 clear_buffer_uptodate(bh);
320 if (!quiet_error(bh))
321 buffer_io_error(bh);
322 SetPageError(page);
323 }
324
325 /*
326 * Be _very_ careful from here on. Bad things can happen if
327 * two buffer heads end IO at almost the same time and both
328 * decide that the page is now completely done.
329 */
330 first = page_buffers(page);
331 local_irq_save(flags);
332 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
333 clear_buffer_async_read(bh);
334 unlock_buffer(bh);
335 tmp = bh;
336 do {
337 if (!buffer_uptodate(tmp))
338 page_uptodate = 0;
339 if (buffer_async_read(tmp)) {
340 BUG_ON(!buffer_locked(tmp));
341 goto still_busy;
342 }
343 tmp = tmp->b_this_page;
344 } while (tmp != bh);
345 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
346 local_irq_restore(flags);
347
348 /*
349 * If none of the buffers had errors and they are all
350 * uptodate then we can set the page uptodate.
351 */
352 if (page_uptodate && !PageError(page))
353 SetPageUptodate(page);
354 unlock_page(page);
355 return;
356
357still_busy:
358 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
359 local_irq_restore(flags);
360 return;
361}
362
363/*
364 * Completion handler for block_write_full_page() - pages which are unlocked
365 * during I/O, and which have PageWriteback cleared upon I/O completion.
366 */
367void end_buffer_async_write(struct buffer_head *bh, int uptodate)
368{
369 char b[BDEVNAME_SIZE];
370 unsigned long flags;
371 struct buffer_head *first;
372 struct buffer_head *tmp;
373 struct page *page;
374
375 BUG_ON(!buffer_async_write(bh));
376
377 page = bh->b_page;
378 if (uptodate) {
379 set_buffer_uptodate(bh);
380 } else {
381 if (!quiet_error(bh)) {
382 buffer_io_error(bh);
383 printk(KERN_WARNING "lost page write due to "
384 "I/O error on %s\n",
385 bdevname(bh->b_bdev, b));
386 }
387 set_bit(AS_EIO, &page->mapping->flags);
388 set_buffer_write_io_error(bh);
389 clear_buffer_uptodate(bh);
390 SetPageError(page);
391 }
392
393 first = page_buffers(page);
394 local_irq_save(flags);
395 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
396
397 clear_buffer_async_write(bh);
398 unlock_buffer(bh);
399 tmp = bh->b_this_page;
400 while (tmp != bh) {
401 if (buffer_async_write(tmp)) {
402 BUG_ON(!buffer_locked(tmp));
403 goto still_busy;
404 }
405 tmp = tmp->b_this_page;
406 }
407 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
408 local_irq_restore(flags);
409 end_page_writeback(page);
410 return;
411
412still_busy:
413 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
414 local_irq_restore(flags);
415 return;
416}
417EXPORT_SYMBOL(end_buffer_async_write);
418
419/*
420 * If a page's buffers are under async readin (end_buffer_async_read
421 * completion) then there is a possibility that another thread of
422 * control could lock one of the buffers after it has completed
423 * but while some of the other buffers have not completed. This
424 * locked buffer would confuse end_buffer_async_read() into not unlocking
425 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
426 * that this buffer is not under async I/O.
427 *
428 * The page comes unlocked when it has no locked buffer_async buffers
429 * left.
430 *
431 * PageLocked prevents anyone starting new async I/O reads any of
432 * the buffers.
433 *
434 * PageWriteback is used to prevent simultaneous writeout of the same
435 * page.
436 *
437 * PageLocked prevents anyone from starting writeback of a page which is
438 * under read I/O (PageWriteback is only ever set against a locked page).
439 */
440static void mark_buffer_async_read(struct buffer_head *bh)
441{
442 bh->b_end_io = end_buffer_async_read;
443 set_buffer_async_read(bh);
444}
445
446static void mark_buffer_async_write_endio(struct buffer_head *bh,
447 bh_end_io_t *handler)
448{
449 bh->b_end_io = handler;
450 set_buffer_async_write(bh);
451}
452
453void mark_buffer_async_write(struct buffer_head *bh)
454{
455 mark_buffer_async_write_endio(bh, end_buffer_async_write);
456}
457EXPORT_SYMBOL(mark_buffer_async_write);
458
459
460/*
461 * fs/buffer.c contains helper functions for buffer-backed address space's
462 * fsync functions. A common requirement for buffer-based filesystems is
463 * that certain data from the backing blockdev needs to be written out for
464 * a successful fsync(). For example, ext2 indirect blocks need to be
465 * written back and waited upon before fsync() returns.
466 *
467 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
468 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
469 * management of a list of dependent buffers at ->i_mapping->private_list.
470 *
471 * Locking is a little subtle: try_to_free_buffers() will remove buffers
472 * from their controlling inode's queue when they are being freed. But
473 * try_to_free_buffers() will be operating against the *blockdev* mapping
474 * at the time, not against the S_ISREG file which depends on those buffers.
475 * So the locking for private_list is via the private_lock in the address_space
476 * which backs the buffers. Which is different from the address_space
477 * against which the buffers are listed. So for a particular address_space,
478 * mapping->private_lock does *not* protect mapping->private_list! In fact,
479 * mapping->private_list will always be protected by the backing blockdev's
480 * ->private_lock.
481 *
482 * Which introduces a requirement: all buffers on an address_space's
483 * ->private_list must be from the same address_space: the blockdev's.
484 *
485 * address_spaces which do not place buffers at ->private_list via these
486 * utility functions are free to use private_lock and private_list for
487 * whatever they want. The only requirement is that list_empty(private_list)
488 * be true at clear_inode() time.
489 *
490 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
491 * filesystems should do that. invalidate_inode_buffers() should just go
492 * BUG_ON(!list_empty).
493 *
494 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
495 * take an address_space, not an inode. And it should be called
496 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
497 * queued up.
498 *
499 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
500 * list if it is already on a list. Because if the buffer is on a list,
501 * it *must* already be on the right one. If not, the filesystem is being
502 * silly. This will save a ton of locking. But first we have to ensure
503 * that buffers are taken *off* the old inode's list when they are freed
504 * (presumably in truncate). That requires careful auditing of all
505 * filesystems (do it inside bforget()). It could also be done by bringing
506 * b_inode back.
507 */
508
509/*
510 * The buffer's backing address_space's private_lock must be held
511 */
512static void __remove_assoc_queue(struct buffer_head *bh)
513{
514 list_del_init(&bh->b_assoc_buffers);
515 WARN_ON(!bh->b_assoc_map);
516 if (buffer_write_io_error(bh))
517 set_bit(AS_EIO, &bh->b_assoc_map->flags);
518 bh->b_assoc_map = NULL;
519}
520
521int inode_has_buffers(struct inode *inode)
522{
523 return !list_empty(&inode->i_data.private_list);
524}
525
526/*
527 * osync is designed to support O_SYNC io. It waits synchronously for
528 * all already-submitted IO to complete, but does not queue any new
529 * writes to the disk.
530 *
531 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
532 * you dirty the buffers, and then use osync_inode_buffers to wait for
533 * completion. Any other dirty buffers which are not yet queued for
534 * write will not be flushed to disk by the osync.
535 */
536static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
537{
538 struct buffer_head *bh;
539 struct list_head *p;
540 int err = 0;
541
542 spin_lock(lock);
543repeat:
544 list_for_each_prev(p, list) {
545 bh = BH_ENTRY(p);
546 if (buffer_locked(bh)) {
547 get_bh(bh);
548 spin_unlock(lock);
549 wait_on_buffer(bh);
550 if (!buffer_uptodate(bh))
551 err = -EIO;
552 brelse(bh);
553 spin_lock(lock);
554 goto repeat;
555 }
556 }
557 spin_unlock(lock);
558 return err;
559}
560
561static void do_thaw_one(struct super_block *sb, void *unused)
562{
563 char b[BDEVNAME_SIZE];
564 while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
565 printk(KERN_WARNING "Emergency Thaw on %s\n",
566 bdevname(sb->s_bdev, b));
567}
568
569static void do_thaw_all(struct work_struct *work)
570{
571 iterate_supers(do_thaw_one, NULL);
572 kfree(work);
573 printk(KERN_WARNING "Emergency Thaw complete\n");
574}
575
576/**
577 * emergency_thaw_all -- forcibly thaw every frozen filesystem
578 *
579 * Used for emergency unfreeze of all filesystems via SysRq
580 */
581void emergency_thaw_all(void)
582{
583 struct work_struct *work;
584
585 work = kmalloc(sizeof(*work), GFP_ATOMIC);
586 if (work) {
587 INIT_WORK(work, do_thaw_all);
588 schedule_work(work);
589 }
590}
591
592/**
593 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
594 * @mapping: the mapping which wants those buffers written
595 *
596 * Starts I/O against the buffers at mapping->private_list, and waits upon
597 * that I/O.
598 *
599 * Basically, this is a convenience function for fsync().
600 * @mapping is a file or directory which needs those buffers to be written for
601 * a successful fsync().
602 */
603int sync_mapping_buffers(struct address_space *mapping)
604{
605 struct address_space *buffer_mapping = mapping->assoc_mapping;
606
607 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
608 return 0;
609
610 return fsync_buffers_list(&buffer_mapping->private_lock,
611 &mapping->private_list);
612}
613EXPORT_SYMBOL(sync_mapping_buffers);
614
615/*
616 * Called when we've recently written block `bblock', and it is known that
617 * `bblock' was for a buffer_boundary() buffer. This means that the block at
618 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
619 * dirty, schedule it for IO. So that indirects merge nicely with their data.
620 */
621void write_boundary_block(struct block_device *bdev,
622 sector_t bblock, unsigned blocksize)
623{
624 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
625 if (bh) {
626 if (buffer_dirty(bh))
627 ll_rw_block(WRITE, 1, &bh);
628 put_bh(bh);
629 }
630}
631
632void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
633{
634 struct address_space *mapping = inode->i_mapping;
635 struct address_space *buffer_mapping = bh->b_page->mapping;
636
637 mark_buffer_dirty(bh);
638 if (!mapping->assoc_mapping) {
639 mapping->assoc_mapping = buffer_mapping;
640 } else {
641 BUG_ON(mapping->assoc_mapping != buffer_mapping);
642 }
643 if (!bh->b_assoc_map) {
644 spin_lock(&buffer_mapping->private_lock);
645 list_move_tail(&bh->b_assoc_buffers,
646 &mapping->private_list);
647 bh->b_assoc_map = mapping;
648 spin_unlock(&buffer_mapping->private_lock);
649 }
650}
651EXPORT_SYMBOL(mark_buffer_dirty_inode);
652
653/*
654 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
655 * dirty.
656 *
657 * If warn is true, then emit a warning if the page is not uptodate and has
658 * not been truncated.
659 */
660static void __set_page_dirty(struct page *page,
661 struct address_space *mapping, int warn)
662{
663 spin_lock_irq(&mapping->tree_lock);
664 if (page->mapping) { /* Race with truncate? */
665 WARN_ON_ONCE(warn && !PageUptodate(page));
666 account_page_dirtied(page, mapping);
667 radix_tree_tag_set(&mapping->page_tree,
668 page_index(page), PAGECACHE_TAG_DIRTY);
669 }
670 spin_unlock_irq(&mapping->tree_lock);
671 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
672}
673
674/*
675 * Add a page to the dirty page list.
676 *
677 * It is a sad fact of life that this function is called from several places
678 * deeply under spinlocking. It may not sleep.
679 *
680 * If the page has buffers, the uptodate buffers are set dirty, to preserve
681 * dirty-state coherency between the page and the buffers. It the page does
682 * not have buffers then when they are later attached they will all be set
683 * dirty.
684 *
685 * The buffers are dirtied before the page is dirtied. There's a small race
686 * window in which a writepage caller may see the page cleanness but not the
687 * buffer dirtiness. That's fine. If this code were to set the page dirty
688 * before the buffers, a concurrent writepage caller could clear the page dirty
689 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
690 * page on the dirty page list.
691 *
692 * We use private_lock to lock against try_to_free_buffers while using the
693 * page's buffer list. Also use this to protect against clean buffers being
694 * added to the page after it was set dirty.
695 *
696 * FIXME: may need to call ->reservepage here as well. That's rather up to the
697 * address_space though.
698 */
699int __set_page_dirty_buffers(struct page *page)
700{
701 int newly_dirty;
702 struct address_space *mapping = page_mapping(page);
703
704 if (unlikely(!mapping))
705 return !TestSetPageDirty(page);
706
707 spin_lock(&mapping->private_lock);
708 if (page_has_buffers(page)) {
709 struct buffer_head *head = page_buffers(page);
710 struct buffer_head *bh = head;
711
712 do {
713 set_buffer_dirty(bh);
714 bh = bh->b_this_page;
715 } while (bh != head);
716 }
717 newly_dirty = !TestSetPageDirty(page);
718 spin_unlock(&mapping->private_lock);
719
720 if (newly_dirty)
721 __set_page_dirty(page, mapping, 1);
722 return newly_dirty;
723}
724EXPORT_SYMBOL(__set_page_dirty_buffers);
725
726/*
727 * Write out and wait upon a list of buffers.
728 *
729 * We have conflicting pressures: we want to make sure that all
730 * initially dirty buffers get waited on, but that any subsequently
731 * dirtied buffers don't. After all, we don't want fsync to last
732 * forever if somebody is actively writing to the file.
733 *
734 * Do this in two main stages: first we copy dirty buffers to a
735 * temporary inode list, queueing the writes as we go. Then we clean
736 * up, waiting for those writes to complete.
737 *
738 * During this second stage, any subsequent updates to the file may end
739 * up refiling the buffer on the original inode's dirty list again, so
740 * there is a chance we will end up with a buffer queued for write but
741 * not yet completed on that list. So, as a final cleanup we go through
742 * the osync code to catch these locked, dirty buffers without requeuing
743 * any newly dirty buffers for write.
744 */
745static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
746{
747 struct buffer_head *bh;
748 struct list_head tmp;
749 struct address_space *mapping;
750 int err = 0, err2;
751 struct blk_plug plug;
752
753 INIT_LIST_HEAD(&tmp);
754 blk_start_plug(&plug);
755
756 spin_lock(lock);
757 while (!list_empty(list)) {
758 bh = BH_ENTRY(list->next);
759 mapping = bh->b_assoc_map;
760 __remove_assoc_queue(bh);
761 /* Avoid race with mark_buffer_dirty_inode() which does
762 * a lockless check and we rely on seeing the dirty bit */
763 smp_mb();
764 if (buffer_dirty(bh) || buffer_locked(bh)) {
765 list_add(&bh->b_assoc_buffers, &tmp);
766 bh->b_assoc_map = mapping;
767 if (buffer_dirty(bh)) {
768 get_bh(bh);
769 spin_unlock(lock);
770 /*
771 * Ensure any pending I/O completes so that
772 * write_dirty_buffer() actually writes the
773 * current contents - it is a noop if I/O is
774 * still in flight on potentially older
775 * contents.
776 */
777 write_dirty_buffer(bh, WRITE_SYNC);
778
779 /*
780 * Kick off IO for the previous mapping. Note
781 * that we will not run the very last mapping,
782 * wait_on_buffer() will do that for us
783 * through sync_buffer().
784 */
785 brelse(bh);
786 spin_lock(lock);
787 }
788 }
789 }
790
791 spin_unlock(lock);
792 blk_finish_plug(&plug);
793 spin_lock(lock);
794
795 while (!list_empty(&tmp)) {
796 bh = BH_ENTRY(tmp.prev);
797 get_bh(bh);
798 mapping = bh->b_assoc_map;
799 __remove_assoc_queue(bh);
800 /* Avoid race with mark_buffer_dirty_inode() which does
801 * a lockless check and we rely on seeing the dirty bit */
802 smp_mb();
803 if (buffer_dirty(bh)) {
804 list_add(&bh->b_assoc_buffers,
805 &mapping->private_list);
806 bh->b_assoc_map = mapping;
807 }
808 spin_unlock(lock);
809 wait_on_buffer(bh);
810 if (!buffer_uptodate(bh))
811 err = -EIO;
812 brelse(bh);
813 spin_lock(lock);
814 }
815
816 spin_unlock(lock);
817 err2 = osync_buffers_list(lock, list);
818 if (err)
819 return err;
820 else
821 return err2;
822}
823
824/*
825 * Invalidate any and all dirty buffers on a given inode. We are
826 * probably unmounting the fs, but that doesn't mean we have already
827 * done a sync(). Just drop the buffers from the inode list.
828 *
829 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
830 * assumes that all the buffers are against the blockdev. Not true
831 * for reiserfs.
832 */
833void invalidate_inode_buffers(struct inode *inode)
834{
835 if (inode_has_buffers(inode)) {
836 struct address_space *mapping = &inode->i_data;
837 struct list_head *list = &mapping->private_list;
838 struct address_space *buffer_mapping = mapping->assoc_mapping;
839
840 spin_lock(&buffer_mapping->private_lock);
841 while (!list_empty(list))
842 __remove_assoc_queue(BH_ENTRY(list->next));
843 spin_unlock(&buffer_mapping->private_lock);
844 }
845}
846EXPORT_SYMBOL(invalidate_inode_buffers);
847
848/*
849 * Remove any clean buffers from the inode's buffer list. This is called
850 * when we're trying to free the inode itself. Those buffers can pin it.
851 *
852 * Returns true if all buffers were removed.
853 */
854int remove_inode_buffers(struct inode *inode)
855{
856 int ret = 1;
857
858 if (inode_has_buffers(inode)) {
859 struct address_space *mapping = &inode->i_data;
860 struct list_head *list = &mapping->private_list;
861 struct address_space *buffer_mapping = mapping->assoc_mapping;
862
863 spin_lock(&buffer_mapping->private_lock);
864 while (!list_empty(list)) {
865 struct buffer_head *bh = BH_ENTRY(list->next);
866 if (buffer_dirty(bh)) {
867 ret = 0;
868 break;
869 }
870 __remove_assoc_queue(bh);
871 }
872 spin_unlock(&buffer_mapping->private_lock);
873 }
874 return ret;
875}
876
877/*
878 * Create the appropriate buffers when given a page for data area and
879 * the size of each buffer.. Use the bh->b_this_page linked list to
880 * follow the buffers created. Return NULL if unable to create more
881 * buffers.
882 *
883 * The retry flag is used to differentiate async IO (paging, swapping)
884 * which may not fail from ordinary buffer allocations.
885 */
886struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
887 int retry)
888{
889 struct buffer_head *bh, *head;
890 long offset;
891
892try_again:
893 head = NULL;
894 offset = PAGE_SIZE;
895 while ((offset -= size) >= 0) {
896 bh = alloc_buffer_head(GFP_NOFS);
897 if (!bh)
898 goto no_grow;
899
900 bh->b_bdev = NULL;
901 bh->b_this_page = head;
902 bh->b_blocknr = -1;
903 head = bh;
904
905 bh->b_state = 0;
906 atomic_set(&bh->b_count, 0);
907 bh->b_size = size;
908
909 /* Link the buffer to its page */
910 set_bh_page(bh, page, offset);
911
912 init_buffer(bh, NULL, NULL);
913 }
914 return head;
915/*
916 * In case anything failed, we just free everything we got.
917 */
918no_grow:
919 if (head) {
920 do {
921 bh = head;
922 head = head->b_this_page;
923 free_buffer_head(bh);
924 } while (head);
925 }
926
927 /*
928 * Return failure for non-async IO requests. Async IO requests
929 * are not allowed to fail, so we have to wait until buffer heads
930 * become available. But we don't want tasks sleeping with
931 * partially complete buffers, so all were released above.
932 */
933 if (!retry)
934 return NULL;
935
936 /* We're _really_ low on memory. Now we just
937 * wait for old buffer heads to become free due to
938 * finishing IO. Since this is an async request and
939 * the reserve list is empty, we're sure there are
940 * async buffer heads in use.
941 */
942 free_more_memory();
943 goto try_again;
944}
945EXPORT_SYMBOL_GPL(alloc_page_buffers);
946
947static inline void
948link_dev_buffers(struct page *page, struct buffer_head *head)
949{
950 struct buffer_head *bh, *tail;
951
952 bh = head;
953 do {
954 tail = bh;
955 bh = bh->b_this_page;
956 } while (bh);
957 tail->b_this_page = head;
958 attach_page_buffers(page, head);
959}
960
961/*
962 * Initialise the state of a blockdev page's buffers.
963 */
964static void
965init_page_buffers(struct page *page, struct block_device *bdev,
966 sector_t block, int size)
967{
968 struct buffer_head *head = page_buffers(page);
969 struct buffer_head *bh = head;
970 int uptodate = PageUptodate(page);
971
972 do {
973 if (!buffer_mapped(bh)) {
974 init_buffer(bh, NULL, NULL);
975 bh->b_bdev = bdev;
976 bh->b_blocknr = block;
977 if (uptodate)
978 set_buffer_uptodate(bh);
979 set_buffer_mapped(bh);
980 }
981 block++;
982 bh = bh->b_this_page;
983 } while (bh != head);
984}
985
986/*
987 * Create the page-cache page that contains the requested block.
988 *
989 * This is user purely for blockdev mappings.
990 */
991static struct page *
992grow_dev_page(struct block_device *bdev, sector_t block,
993 pgoff_t index, int size)
994{
995 struct inode *inode = bdev->bd_inode;
996 struct page *page;
997 struct buffer_head *bh;
998
999 page = find_or_create_page(inode->i_mapping, index,
1000 (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE);
1001 if (!page)
1002 return NULL;
1003
1004 BUG_ON(!PageLocked(page));
1005
1006 if (page_has_buffers(page)) {
1007 bh = page_buffers(page);
1008 if (bh->b_size == size) {
1009 init_page_buffers(page, bdev, block, size);
1010 return page;
1011 }
1012 if (!try_to_free_buffers(page))
1013 goto failed;
1014 }
1015
1016 /*
1017 * Allocate some buffers for this page
1018 */
1019 bh = alloc_page_buffers(page, size, 0);
1020 if (!bh)
1021 goto failed;
1022
1023 /*
1024 * Link the page to the buffers and initialise them. Take the
1025 * lock to be atomic wrt __find_get_block(), which does not
1026 * run under the page lock.
1027 */
1028 spin_lock(&inode->i_mapping->private_lock);
1029 link_dev_buffers(page, bh);
1030 init_page_buffers(page, bdev, block, size);
1031 spin_unlock(&inode->i_mapping->private_lock);
1032 return page;
1033
1034failed:
1035 BUG();
1036 unlock_page(page);
1037 page_cache_release(page);
1038 return NULL;
1039}
1040
1041/*
1042 * Create buffers for the specified block device block's page. If
1043 * that page was dirty, the buffers are set dirty also.
1044 */
1045static int
1046grow_buffers(struct block_device *bdev, sector_t block, int size)
1047{
1048 struct page *page;
1049 pgoff_t index;
1050 int sizebits;
1051
1052 sizebits = -1;
1053 do {
1054 sizebits++;
1055 } while ((size << sizebits) < PAGE_SIZE);
1056
1057 index = block >> sizebits;
1058
1059 /*
1060 * Check for a block which wants to lie outside our maximum possible
1061 * pagecache index. (this comparison is done using sector_t types).
1062 */
1063 if (unlikely(index != block >> sizebits)) {
1064 char b[BDEVNAME_SIZE];
1065
1066 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1067 "device %s\n",
1068 __func__, (unsigned long long)block,
1069 bdevname(bdev, b));
1070 return -EIO;
1071 }
1072 block = index << sizebits;
1073 /* Create a page with the proper size buffers.. */
1074 page = grow_dev_page(bdev, block, index, size);
1075 if (!page)
1076 return 0;
1077 unlock_page(page);
1078 page_cache_release(page);
1079 return 1;
1080}
1081
1082static struct buffer_head *
1083__getblk_slow(struct block_device *bdev, sector_t block, int size)
1084{
1085 /* Size must be multiple of hard sectorsize */
1086 if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
1087 (size < 512 || size > PAGE_SIZE))) {
1088 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1089 size);
1090 printk(KERN_ERR "logical block size: %d\n",
1091 bdev_logical_block_size(bdev));
1092
1093 dump_stack();
1094 return NULL;
1095 }
1096
1097 for (;;) {
1098 struct buffer_head * bh;
1099 int ret;
1100
1101 bh = __find_get_block(bdev, block, size);
1102 if (bh)
1103 return bh;
1104
1105 ret = grow_buffers(bdev, block, size);
1106 if (ret < 0)
1107 return NULL;
1108 if (ret == 0)
1109 free_more_memory();
1110 }
1111}
1112
1113/*
1114 * The relationship between dirty buffers and dirty pages:
1115 *
1116 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1117 * the page is tagged dirty in its radix tree.
1118 *
1119 * At all times, the dirtiness of the buffers represents the dirtiness of
1120 * subsections of the page. If the page has buffers, the page dirty bit is
1121 * merely a hint about the true dirty state.
1122 *
1123 * When a page is set dirty in its entirety, all its buffers are marked dirty
1124 * (if the page has buffers).
1125 *
1126 * When a buffer is marked dirty, its page is dirtied, but the page's other
1127 * buffers are not.
1128 *
1129 * Also. When blockdev buffers are explicitly read with bread(), they
1130 * individually become uptodate. But their backing page remains not
1131 * uptodate - even if all of its buffers are uptodate. A subsequent
1132 * block_read_full_page() against that page will discover all the uptodate
1133 * buffers, will set the page uptodate and will perform no I/O.
1134 */
1135
1136/**
1137 * mark_buffer_dirty - mark a buffer_head as needing writeout
1138 * @bh: the buffer_head to mark dirty
1139 *
1140 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1141 * backing page dirty, then tag the page as dirty in its address_space's radix
1142 * tree and then attach the address_space's inode to its superblock's dirty
1143 * inode list.
1144 *
1145 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1146 * mapping->tree_lock and mapping->host->i_lock.
1147 */
1148void mark_buffer_dirty(struct buffer_head *bh)
1149{
1150 WARN_ON_ONCE(!buffer_uptodate(bh));
1151
1152 /*
1153 * Very *carefully* optimize the it-is-already-dirty case.
1154 *
1155 * Don't let the final "is it dirty" escape to before we
1156 * perhaps modified the buffer.
1157 */
1158 if (buffer_dirty(bh)) {
1159 smp_mb();
1160 if (buffer_dirty(bh))
1161 return;
1162 }
1163
1164 if (!test_set_buffer_dirty(bh)) {
1165 struct page *page = bh->b_page;
1166 if (!TestSetPageDirty(page)) {
1167 struct address_space *mapping = page_mapping(page);
1168 if (mapping)
1169 __set_page_dirty(page, mapping, 0);
1170 }
1171 }
1172}
1173EXPORT_SYMBOL(mark_buffer_dirty);
1174
1175/*
1176 * Decrement a buffer_head's reference count. If all buffers against a page
1177 * have zero reference count, are clean and unlocked, and if the page is clean
1178 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1179 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1180 * a page but it ends up not being freed, and buffers may later be reattached).
1181 */
1182void __brelse(struct buffer_head * buf)
1183{
1184 if (atomic_read(&buf->b_count)) {
1185 put_bh(buf);
1186 return;
1187 }
1188 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1189}
1190EXPORT_SYMBOL(__brelse);
1191
1192/*
1193 * bforget() is like brelse(), except it discards any
1194 * potentially dirty data.
1195 */
1196void __bforget(struct buffer_head *bh)
1197{
1198 clear_buffer_dirty(bh);
1199 if (bh->b_assoc_map) {
1200 struct address_space *buffer_mapping = bh->b_page->mapping;
1201
1202 spin_lock(&buffer_mapping->private_lock);
1203 list_del_init(&bh->b_assoc_buffers);
1204 bh->b_assoc_map = NULL;
1205 spin_unlock(&buffer_mapping->private_lock);
1206 }
1207 __brelse(bh);
1208}
1209EXPORT_SYMBOL(__bforget);
1210
1211static struct buffer_head *__bread_slow(struct buffer_head *bh)
1212{
1213 lock_buffer(bh);
1214 if (buffer_uptodate(bh)) {
1215 unlock_buffer(bh);
1216 return bh;
1217 } else {
1218 get_bh(bh);
1219 bh->b_end_io = end_buffer_read_sync;
1220 submit_bh(READ, bh);
1221 wait_on_buffer(bh);
1222 if (buffer_uptodate(bh))
1223 return bh;
1224 }
1225 brelse(bh);
1226 return NULL;
1227}
1228
1229/*
1230 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1231 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1232 * refcount elevated by one when they're in an LRU. A buffer can only appear
1233 * once in a particular CPU's LRU. A single buffer can be present in multiple
1234 * CPU's LRUs at the same time.
1235 *
1236 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1237 * sb_find_get_block().
1238 *
1239 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1240 * a local interrupt disable for that.
1241 */
1242
1243#define BH_LRU_SIZE 8
1244
1245struct bh_lru {
1246 struct buffer_head *bhs[BH_LRU_SIZE];
1247};
1248
1249static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1250
1251#ifdef CONFIG_SMP
1252#define bh_lru_lock() local_irq_disable()
1253#define bh_lru_unlock() local_irq_enable()
1254#else
1255#define bh_lru_lock() preempt_disable()
1256#define bh_lru_unlock() preempt_enable()
1257#endif
1258
1259static inline void check_irqs_on(void)
1260{
1261#ifdef irqs_disabled
1262 BUG_ON(irqs_disabled());
1263#endif
1264}
1265
1266/*
1267 * The LRU management algorithm is dopey-but-simple. Sorry.
1268 */
1269static void bh_lru_install(struct buffer_head *bh)
1270{
1271 struct buffer_head *evictee = NULL;
1272
1273 check_irqs_on();
1274 bh_lru_lock();
1275 if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
1276 struct buffer_head *bhs[BH_LRU_SIZE];
1277 int in;
1278 int out = 0;
1279
1280 get_bh(bh);
1281 bhs[out++] = bh;
1282 for (in = 0; in < BH_LRU_SIZE; in++) {
1283 struct buffer_head *bh2 =
1284 __this_cpu_read(bh_lrus.bhs[in]);
1285
1286 if (bh2 == bh) {
1287 __brelse(bh2);
1288 } else {
1289 if (out >= BH_LRU_SIZE) {
1290 BUG_ON(evictee != NULL);
1291 evictee = bh2;
1292 } else {
1293 bhs[out++] = bh2;
1294 }
1295 }
1296 }
1297 while (out < BH_LRU_SIZE)
1298 bhs[out++] = NULL;
1299 memcpy(__this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
1300 }
1301 bh_lru_unlock();
1302
1303 if (evictee)
1304 __brelse(evictee);
1305}
1306
1307/*
1308 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1309 */
1310static struct buffer_head *
1311lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1312{
1313 struct buffer_head *ret = NULL;
1314 unsigned int i;
1315
1316 check_irqs_on();
1317 bh_lru_lock();
1318 for (i = 0; i < BH_LRU_SIZE; i++) {
1319 struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
1320
1321 if (bh && bh->b_bdev == bdev &&
1322 bh->b_blocknr == block && bh->b_size == size) {
1323 if (i) {
1324 while (i) {
1325 __this_cpu_write(bh_lrus.bhs[i],
1326 __this_cpu_read(bh_lrus.bhs[i - 1]));
1327 i--;
1328 }
1329 __this_cpu_write(bh_lrus.bhs[0], bh);
1330 }
1331 get_bh(bh);
1332 ret = bh;
1333 break;
1334 }
1335 }
1336 bh_lru_unlock();
1337 return ret;
1338}
1339
1340/*
1341 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1342 * it in the LRU and mark it as accessed. If it is not present then return
1343 * NULL
1344 */
1345struct buffer_head *
1346__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1347{
1348 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1349
1350 if (bh == NULL) {
1351 bh = __find_get_block_slow(bdev, block);
1352 if (bh)
1353 bh_lru_install(bh);
1354 }
1355 if (bh)
1356 touch_buffer(bh);
1357 return bh;
1358}
1359EXPORT_SYMBOL(__find_get_block);
1360
1361/*
1362 * __getblk will locate (and, if necessary, create) the buffer_head
1363 * which corresponds to the passed block_device, block and size. The
1364 * returned buffer has its reference count incremented.
1365 *
1366 * __getblk() cannot fail - it just keeps trying. If you pass it an
1367 * illegal block number, __getblk() will happily return a buffer_head
1368 * which represents the non-existent block. Very weird.
1369 *
1370 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1371 * attempt is failing. FIXME, perhaps?
1372 */
1373struct buffer_head *
1374__getblk(struct block_device *bdev, sector_t block, unsigned size)
1375{
1376 struct buffer_head *bh = __find_get_block(bdev, block, size);
1377
1378 might_sleep();
1379 if (bh == NULL)
1380 bh = __getblk_slow(bdev, block, size);
1381 return bh;
1382}
1383EXPORT_SYMBOL(__getblk);
1384
1385/*
1386 * Do async read-ahead on a buffer..
1387 */
1388void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1389{
1390 struct buffer_head *bh = __getblk(bdev, block, size);
1391 if (likely(bh)) {
1392 ll_rw_block(READA, 1, &bh);
1393 brelse(bh);
1394 }
1395}
1396EXPORT_SYMBOL(__breadahead);
1397
1398/**
1399 * __bread() - reads a specified block and returns the bh
1400 * @bdev: the block_device to read from
1401 * @block: number of block
1402 * @size: size (in bytes) to read
1403 *
1404 * Reads a specified block, and returns buffer head that contains it.
1405 * It returns NULL if the block was unreadable.
1406 */
1407struct buffer_head *
1408__bread(struct block_device *bdev, sector_t block, unsigned size)
1409{
1410 struct buffer_head *bh = __getblk(bdev, block, size);
1411
1412 if (likely(bh) && !buffer_uptodate(bh))
1413 bh = __bread_slow(bh);
1414 return bh;
1415}
1416EXPORT_SYMBOL(__bread);
1417
1418/*
1419 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1420 * This doesn't race because it runs in each cpu either in irq
1421 * or with preempt disabled.
1422 */
1423static void invalidate_bh_lru(void *arg)
1424{
1425 struct bh_lru *b = &get_cpu_var(bh_lrus);
1426 int i;
1427
1428 for (i = 0; i < BH_LRU_SIZE; i++) {
1429 brelse(b->bhs[i]);
1430 b->bhs[i] = NULL;
1431 }
1432 put_cpu_var(bh_lrus);
1433}
1434
1435void invalidate_bh_lrus(void)
1436{
1437 on_each_cpu(invalidate_bh_lru, NULL, 1);
1438}
1439EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1440
1441void set_bh_page(struct buffer_head *bh,
1442 struct page *page, unsigned long offset)
1443{
1444 bh->b_page = page;
1445 BUG_ON(offset >= PAGE_SIZE);
1446 if (PageHighMem(page))
1447 /*
1448 * This catches illegal uses and preserves the offset:
1449 */
1450 bh->b_data = (char *)(0 + offset);
1451 else
1452 bh->b_data = page_address(page) + offset;
1453}
1454EXPORT_SYMBOL(set_bh_page);
1455
1456/*
1457 * Called when truncating a buffer on a page completely.
1458 */
1459static void discard_buffer(struct buffer_head * bh)
1460{
1461 lock_buffer(bh);
1462 clear_buffer_dirty(bh);
1463 bh->b_bdev = NULL;
1464 clear_buffer_mapped(bh);
1465 clear_buffer_req(bh);
1466 clear_buffer_new(bh);
1467 clear_buffer_delay(bh);
1468 clear_buffer_unwritten(bh);
1469 unlock_buffer(bh);
1470}
1471
1472/**
1473 * block_invalidatepage - invalidate part of all of a buffer-backed page
1474 *
1475 * @page: the page which is affected
1476 * @offset: the index of the truncation point
1477 *
1478 * block_invalidatepage() is called when all or part of the page has become
1479 * invalidatedby a truncate operation.
1480 *
1481 * block_invalidatepage() does not have to release all buffers, but it must
1482 * ensure that no dirty buffer is left outside @offset and that no I/O
1483 * is underway against any of the blocks which are outside the truncation
1484 * point. Because the caller is about to free (and possibly reuse) those
1485 * blocks on-disk.
1486 */
1487void block_invalidatepage(struct page *page, unsigned long offset)
1488{
1489 struct buffer_head *head, *bh, *next;
1490 unsigned int curr_off = 0;
1491
1492 BUG_ON(!PageLocked(page));
1493 if (!page_has_buffers(page))
1494 goto out;
1495
1496 head = page_buffers(page);
1497 bh = head;
1498 do {
1499 unsigned int next_off = curr_off + bh->b_size;
1500 next = bh->b_this_page;
1501
1502 /*
1503 * is this block fully invalidated?
1504 */
1505 if (offset <= curr_off)
1506 discard_buffer(bh);
1507 curr_off = next_off;
1508 bh = next;
1509 } while (bh != head);
1510
1511 /*
1512 * We release buffers only if the entire page is being invalidated.
1513 * The get_block cached value has been unconditionally invalidated,
1514 * so real IO is not possible anymore.
1515 */
1516 if (offset == 0)
1517 try_to_release_page(page, 0);
1518out:
1519 return;
1520}
1521EXPORT_SYMBOL(block_invalidatepage);
1522
1523/*
1524 * We attach and possibly dirty the buffers atomically wrt
1525 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1526 * is already excluded via the page lock.
1527 */
1528void create_empty_buffers(struct page *page,
1529 unsigned long blocksize, unsigned long b_state)
1530{
1531 struct buffer_head *bh, *head, *tail;
1532
1533 head = alloc_page_buffers(page, blocksize, 1);
1534 bh = head;
1535 do {
1536 bh->b_state |= b_state;
1537 tail = bh;
1538 bh = bh->b_this_page;
1539 } while (bh);
1540 tail->b_this_page = head;
1541
1542 spin_lock(&page->mapping->private_lock);
1543 if (PageUptodate(page) || PageDirty(page)) {
1544 bh = head;
1545 do {
1546 if (PageDirty(page))
1547 set_buffer_dirty(bh);
1548 if (PageUptodate(page))
1549 set_buffer_uptodate(bh);
1550 bh = bh->b_this_page;
1551 } while (bh != head);
1552 }
1553 attach_page_buffers(page, head);
1554 spin_unlock(&page->mapping->private_lock);
1555}
1556EXPORT_SYMBOL(create_empty_buffers);
1557
1558/*
1559 * We are taking a block for data and we don't want any output from any
1560 * buffer-cache aliases starting from return from that function and
1561 * until the moment when something will explicitly mark the buffer
1562 * dirty (hopefully that will not happen until we will free that block ;-)
1563 * We don't even need to mark it not-uptodate - nobody can expect
1564 * anything from a newly allocated buffer anyway. We used to used
1565 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1566 * don't want to mark the alias unmapped, for example - it would confuse
1567 * anyone who might pick it with bread() afterwards...
1568 *
1569 * Also.. Note that bforget() doesn't lock the buffer. So there can
1570 * be writeout I/O going on against recently-freed buffers. We don't
1571 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1572 * only if we really need to. That happens here.
1573 */
1574void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1575{
1576 struct buffer_head *old_bh;
1577
1578 might_sleep();
1579
1580 old_bh = __find_get_block_slow(bdev, block);
1581 if (old_bh) {
1582 clear_buffer_dirty(old_bh);
1583 wait_on_buffer(old_bh);
1584 clear_buffer_req(old_bh);
1585 __brelse(old_bh);
1586 }
1587}
1588EXPORT_SYMBOL(unmap_underlying_metadata);
1589
1590/*
1591 * NOTE! All mapped/uptodate combinations are valid:
1592 *
1593 * Mapped Uptodate Meaning
1594 *
1595 * No No "unknown" - must do get_block()
1596 * No Yes "hole" - zero-filled
1597 * Yes No "allocated" - allocated on disk, not read in
1598 * Yes Yes "valid" - allocated and up-to-date in memory.
1599 *
1600 * "Dirty" is valid only with the last case (mapped+uptodate).
1601 */
1602
1603/*
1604 * While block_write_full_page is writing back the dirty buffers under
1605 * the page lock, whoever dirtied the buffers may decide to clean them
1606 * again at any time. We handle that by only looking at the buffer
1607 * state inside lock_buffer().
1608 *
1609 * If block_write_full_page() is called for regular writeback
1610 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1611 * locked buffer. This only can happen if someone has written the buffer
1612 * directly, with submit_bh(). At the address_space level PageWriteback
1613 * prevents this contention from occurring.
1614 *
1615 * If block_write_full_page() is called with wbc->sync_mode ==
1616 * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this
1617 * causes the writes to be flagged as synchronous writes.
1618 */
1619static int __block_write_full_page(struct inode *inode, struct page *page,
1620 get_block_t *get_block, struct writeback_control *wbc,
1621 bh_end_io_t *handler)
1622{
1623 int err;
1624 sector_t block;
1625 sector_t last_block;
1626 struct buffer_head *bh, *head;
1627 const unsigned blocksize = 1 << inode->i_blkbits;
1628 int nr_underway = 0;
1629 int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
1630 WRITE_SYNC : WRITE);
1631
1632 BUG_ON(!PageLocked(page));
1633
1634 last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
1635
1636 if (!page_has_buffers(page)) {
1637 create_empty_buffers(page, blocksize,
1638 (1 << BH_Dirty)|(1 << BH_Uptodate));
1639 }
1640
1641 /*
1642 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1643 * here, and the (potentially unmapped) buffers may become dirty at
1644 * any time. If a buffer becomes dirty here after we've inspected it
1645 * then we just miss that fact, and the page stays dirty.
1646 *
1647 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1648 * handle that here by just cleaning them.
1649 */
1650
1651 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
1652 head = page_buffers(page);
1653 bh = head;
1654
1655 /*
1656 * Get all the dirty buffers mapped to disk addresses and
1657 * handle any aliases from the underlying blockdev's mapping.
1658 */
1659 do {
1660 if (block > last_block) {
1661 /*
1662 * mapped buffers outside i_size will occur, because
1663 * this page can be outside i_size when there is a
1664 * truncate in progress.
1665 */
1666 /*
1667 * The buffer was zeroed by block_write_full_page()
1668 */
1669 clear_buffer_dirty(bh);
1670 set_buffer_uptodate(bh);
1671 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1672 buffer_dirty(bh)) {
1673 WARN_ON(bh->b_size != blocksize);
1674 err = get_block(inode, block, bh, 1);
1675 if (err)
1676 goto recover;
1677 clear_buffer_delay(bh);
1678 if (buffer_new(bh)) {
1679 /* blockdev mappings never come here */
1680 clear_buffer_new(bh);
1681 unmap_underlying_metadata(bh->b_bdev,
1682 bh->b_blocknr);
1683 }
1684 }
1685 bh = bh->b_this_page;
1686 block++;
1687 } while (bh != head);
1688
1689 do {
1690 if (!buffer_mapped(bh))
1691 continue;
1692 /*
1693 * If it's a fully non-blocking write attempt and we cannot
1694 * lock the buffer then redirty the page. Note that this can
1695 * potentially cause a busy-wait loop from writeback threads
1696 * and kswapd activity, but those code paths have their own
1697 * higher-level throttling.
1698 */
1699 if (wbc->sync_mode != WB_SYNC_NONE) {
1700 lock_buffer(bh);
1701 } else if (!trylock_buffer(bh)) {
1702 redirty_page_for_writepage(wbc, page);
1703 continue;
1704 }
1705 if (test_clear_buffer_dirty(bh)) {
1706 mark_buffer_async_write_endio(bh, handler);
1707 } else {
1708 unlock_buffer(bh);
1709 }
1710 } while ((bh = bh->b_this_page) != head);
1711
1712 /*
1713 * The page and its buffers are protected by PageWriteback(), so we can
1714 * drop the bh refcounts early.
1715 */
1716 BUG_ON(PageWriteback(page));
1717 set_page_writeback(page);
1718
1719 do {
1720 struct buffer_head *next = bh->b_this_page;
1721 if (buffer_async_write(bh)) {
1722 submit_bh(write_op, bh);
1723 nr_underway++;
1724 }
1725 bh = next;
1726 } while (bh != head);
1727 unlock_page(page);
1728
1729 err = 0;
1730done:
1731 if (nr_underway == 0) {
1732 /*
1733 * The page was marked dirty, but the buffers were
1734 * clean. Someone wrote them back by hand with
1735 * ll_rw_block/submit_bh. A rare case.
1736 */
1737 end_page_writeback(page);
1738
1739 /*
1740 * The page and buffer_heads can be released at any time from
1741 * here on.
1742 */
1743 }
1744 return err;
1745
1746recover:
1747 /*
1748 * ENOSPC, or some other error. We may already have added some
1749 * blocks to the file, so we need to write these out to avoid
1750 * exposing stale data.
1751 * The page is currently locked and not marked for writeback
1752 */
1753 bh = head;
1754 /* Recovery: lock and submit the mapped buffers */
1755 do {
1756 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1757 !buffer_delay(bh)) {
1758 lock_buffer(bh);
1759 mark_buffer_async_write_endio(bh, handler);
1760 } else {
1761 /*
1762 * The buffer may have been set dirty during
1763 * attachment to a dirty page.
1764 */
1765 clear_buffer_dirty(bh);
1766 }
1767 } while ((bh = bh->b_this_page) != head);
1768 SetPageError(page);
1769 BUG_ON(PageWriteback(page));
1770 mapping_set_error(page->mapping, err);
1771 set_page_writeback(page);
1772 do {
1773 struct buffer_head *next = bh->b_this_page;
1774 if (buffer_async_write(bh)) {
1775 clear_buffer_dirty(bh);
1776 submit_bh(write_op, bh);
1777 nr_underway++;
1778 }
1779 bh = next;
1780 } while (bh != head);
1781 unlock_page(page);
1782 goto done;
1783}
1784
1785/*
1786 * If a page has any new buffers, zero them out here, and mark them uptodate
1787 * and dirty so they'll be written out (in order to prevent uninitialised
1788 * block data from leaking). And clear the new bit.
1789 */
1790void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1791{
1792 unsigned int block_start, block_end;
1793 struct buffer_head *head, *bh;
1794
1795 BUG_ON(!PageLocked(page));
1796 if (!page_has_buffers(page))
1797 return;
1798
1799 bh = head = page_buffers(page);
1800 block_start = 0;
1801 do {
1802 block_end = block_start + bh->b_size;
1803
1804 if (buffer_new(bh)) {
1805 if (block_end > from && block_start < to) {
1806 if (!PageUptodate(page)) {
1807 unsigned start, size;
1808
1809 start = max(from, block_start);
1810 size = min(to, block_end) - start;
1811
1812 zero_user(page, start, size);
1813 set_buffer_uptodate(bh);
1814 }
1815
1816 clear_buffer_new(bh);
1817 mark_buffer_dirty(bh);
1818 }
1819 }
1820
1821 block_start = block_end;
1822 bh = bh->b_this_page;
1823 } while (bh != head);
1824}
1825EXPORT_SYMBOL(page_zero_new_buffers);
1826
1827int __block_write_begin(struct page *page, loff_t pos, unsigned len,
1828 get_block_t *get_block)
1829{
1830 unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1831 unsigned to = from + len;
1832 struct inode *inode = page->mapping->host;
1833 unsigned block_start, block_end;
1834 sector_t block;
1835 int err = 0;
1836 unsigned blocksize, bbits;
1837 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1838
1839 BUG_ON(!PageLocked(page));
1840 BUG_ON(from > PAGE_CACHE_SIZE);
1841 BUG_ON(to > PAGE_CACHE_SIZE);
1842 BUG_ON(from > to);
1843
1844 blocksize = 1 << inode->i_blkbits;
1845 if (!page_has_buffers(page))
1846 create_empty_buffers(page, blocksize, 0);
1847 head = page_buffers(page);
1848
1849 bbits = inode->i_blkbits;
1850 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1851
1852 for(bh = head, block_start = 0; bh != head || !block_start;
1853 block++, block_start=block_end, bh = bh->b_this_page) {
1854 block_end = block_start + blocksize;
1855 if (block_end <= from || block_start >= to) {
1856 if (PageUptodate(page)) {
1857 if (!buffer_uptodate(bh))
1858 set_buffer_uptodate(bh);
1859 }
1860 continue;
1861 }
1862 if (buffer_new(bh))
1863 clear_buffer_new(bh);
1864 if (!buffer_mapped(bh)) {
1865 WARN_ON(bh->b_size != blocksize);
1866 err = get_block(inode, block, bh, 1);
1867 if (err)
1868 break;
1869 if (buffer_new(bh)) {
1870 unmap_underlying_metadata(bh->b_bdev,
1871 bh->b_blocknr);
1872 if (PageUptodate(page)) {
1873 clear_buffer_new(bh);
1874 set_buffer_uptodate(bh);
1875 mark_buffer_dirty(bh);
1876 continue;
1877 }
1878 if (block_end > to || block_start < from)
1879 zero_user_segments(page,
1880 to, block_end,
1881 block_start, from);
1882 continue;
1883 }
1884 }
1885 if (PageUptodate(page)) {
1886 if (!buffer_uptodate(bh))
1887 set_buffer_uptodate(bh);
1888 continue;
1889 }
1890 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1891 !buffer_unwritten(bh) &&
1892 (block_start < from || block_end > to)) {
1893 ll_rw_block(READ, 1, &bh);
1894 *wait_bh++=bh;
1895 }
1896 }
1897 /*
1898 * If we issued read requests - let them complete.
1899 */
1900 while(wait_bh > wait) {
1901 wait_on_buffer(*--wait_bh);
1902 if (!buffer_uptodate(*wait_bh))
1903 err = -EIO;
1904 }
1905 if (unlikely(err))
1906 page_zero_new_buffers(page, from, to);
1907 return err;
1908}
1909EXPORT_SYMBOL(__block_write_begin);
1910
1911static int __block_commit_write(struct inode *inode, struct page *page,
1912 unsigned from, unsigned to)
1913{
1914 unsigned block_start, block_end;
1915 int partial = 0;
1916 unsigned blocksize;
1917 struct buffer_head *bh, *head;
1918
1919 blocksize = 1 << inode->i_blkbits;
1920
1921 for(bh = head = page_buffers(page), block_start = 0;
1922 bh != head || !block_start;
1923 block_start=block_end, bh = bh->b_this_page) {
1924 block_end = block_start + blocksize;
1925 if (block_end <= from || block_start >= to) {
1926 if (!buffer_uptodate(bh))
1927 partial = 1;
1928 } else {
1929 set_buffer_uptodate(bh);
1930 mark_buffer_dirty(bh);
1931 }
1932 clear_buffer_new(bh);
1933 }
1934
1935 /*
1936 * If this is a partial write which happened to make all buffers
1937 * uptodate then we can optimize away a bogus readpage() for
1938 * the next read(). Here we 'discover' whether the page went
1939 * uptodate as a result of this (potentially partial) write.
1940 */
1941 if (!partial)
1942 SetPageUptodate(page);
1943 return 0;
1944}
1945
1946/*
1947 * block_write_begin takes care of the basic task of block allocation and
1948 * bringing partial write blocks uptodate first.
1949 *
1950 * The filesystem needs to handle block truncation upon failure.
1951 */
1952int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
1953 unsigned flags, struct page **pagep, get_block_t *get_block)
1954{
1955 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1956 struct page *page;
1957 int status;
1958
1959 page = grab_cache_page_write_begin(mapping, index, flags);
1960 if (!page)
1961 return -ENOMEM;
1962
1963 status = __block_write_begin(page, pos, len, get_block);
1964 if (unlikely(status)) {
1965 unlock_page(page);
1966 page_cache_release(page);
1967 page = NULL;
1968 }
1969
1970 *pagep = page;
1971 return status;
1972}
1973EXPORT_SYMBOL(block_write_begin);
1974
1975int block_write_end(struct file *file, struct address_space *mapping,
1976 loff_t pos, unsigned len, unsigned copied,
1977 struct page *page, void *fsdata)
1978{
1979 struct inode *inode = mapping->host;
1980 unsigned start;
1981
1982 start = pos & (PAGE_CACHE_SIZE - 1);
1983
1984 if (unlikely(copied < len)) {
1985 /*
1986 * The buffers that were written will now be uptodate, so we
1987 * don't have to worry about a readpage reading them and
1988 * overwriting a partial write. However if we have encountered
1989 * a short write and only partially written into a buffer, it
1990 * will not be marked uptodate, so a readpage might come in and
1991 * destroy our partial write.
1992 *
1993 * Do the simplest thing, and just treat any short write to a
1994 * non uptodate page as a zero-length write, and force the
1995 * caller to redo the whole thing.
1996 */
1997 if (!PageUptodate(page))
1998 copied = 0;
1999
2000 page_zero_new_buffers(page, start+copied, start+len);
2001 }
2002 flush_dcache_page(page);
2003
2004 /* This could be a short (even 0-length) commit */
2005 __block_commit_write(inode, page, start, start+copied);
2006
2007 return copied;
2008}
2009EXPORT_SYMBOL(block_write_end);
2010
2011int generic_write_end(struct file *file, struct address_space *mapping,
2012 loff_t pos, unsigned len, unsigned copied,
2013 struct page *page, void *fsdata)
2014{
2015 struct inode *inode = mapping->host;
2016 int i_size_changed = 0;
2017
2018 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2019
2020 /*
2021 * No need to use i_size_read() here, the i_size
2022 * cannot change under us because we hold i_mutex.
2023 *
2024 * But it's important to update i_size while still holding page lock:
2025 * page writeout could otherwise come in and zero beyond i_size.
2026 */
2027 if (pos+copied > inode->i_size) {
2028 i_size_write(inode, pos+copied);
2029 i_size_changed = 1;
2030 }
2031
2032 unlock_page(page);
2033 page_cache_release(page);
2034
2035 /*
2036 * Don't mark the inode dirty under page lock. First, it unnecessarily
2037 * makes the holding time of page lock longer. Second, it forces lock
2038 * ordering of page lock and transaction start for journaling
2039 * filesystems.
2040 */
2041 if (i_size_changed)
2042 mark_inode_dirty(inode);
2043
2044 return copied;
2045}
2046EXPORT_SYMBOL(generic_write_end);
2047
2048/*
2049 * block_is_partially_uptodate checks whether buffers within a page are
2050 * uptodate or not.
2051 *
2052 * Returns true if all buffers which correspond to a file portion
2053 * we want to read are uptodate.
2054 */
2055int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
2056 unsigned long from)
2057{
2058 struct inode *inode = page->mapping->host;
2059 unsigned block_start, block_end, blocksize;
2060 unsigned to;
2061 struct buffer_head *bh, *head;
2062 int ret = 1;
2063
2064 if (!page_has_buffers(page))
2065 return 0;
2066
2067 blocksize = 1 << inode->i_blkbits;
2068 to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count);
2069 to = from + to;
2070 if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
2071 return 0;
2072
2073 head = page_buffers(page);
2074 bh = head;
2075 block_start = 0;
2076 do {
2077 block_end = block_start + blocksize;
2078 if (block_end > from && block_start < to) {
2079 if (!buffer_uptodate(bh)) {
2080 ret = 0;
2081 break;
2082 }
2083 if (block_end >= to)
2084 break;
2085 }
2086 block_start = block_end;
2087 bh = bh->b_this_page;
2088 } while (bh != head);
2089
2090 return ret;
2091}
2092EXPORT_SYMBOL(block_is_partially_uptodate);
2093
2094/*
2095 * Generic "read page" function for block devices that have the normal
2096 * get_block functionality. This is most of the block device filesystems.
2097 * Reads the page asynchronously --- the unlock_buffer() and
2098 * set/clear_buffer_uptodate() functions propagate buffer state into the
2099 * page struct once IO has completed.
2100 */
2101int block_read_full_page(struct page *page, get_block_t *get_block)
2102{
2103 struct inode *inode = page->mapping->host;
2104 sector_t iblock, lblock;
2105 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2106 unsigned int blocksize;
2107 int nr, i;
2108 int fully_mapped = 1;
2109
2110 BUG_ON(!PageLocked(page));
2111 blocksize = 1 << inode->i_blkbits;
2112 if (!page_has_buffers(page))
2113 create_empty_buffers(page, blocksize, 0);
2114 head = page_buffers(page);
2115
2116 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2117 lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
2118 bh = head;
2119 nr = 0;
2120 i = 0;
2121
2122 do {
2123 if (buffer_uptodate(bh))
2124 continue;
2125
2126 if (!buffer_mapped(bh)) {
2127 int err = 0;
2128
2129 fully_mapped = 0;
2130 if (iblock < lblock) {
2131 WARN_ON(bh->b_size != blocksize);
2132 err = get_block(inode, iblock, bh, 0);
2133 if (err)
2134 SetPageError(page);
2135 }
2136 if (!buffer_mapped(bh)) {
2137 zero_user(page, i * blocksize, blocksize);
2138 if (!err)
2139 set_buffer_uptodate(bh);
2140 continue;
2141 }
2142 /*
2143 * get_block() might have updated the buffer
2144 * synchronously
2145 */
2146 if (buffer_uptodate(bh))
2147 continue;
2148 }
2149 arr[nr++] = bh;
2150 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2151
2152 if (fully_mapped)
2153 SetPageMappedToDisk(page);
2154
2155 if (!nr) {
2156 /*
2157 * All buffers are uptodate - we can set the page uptodate
2158 * as well. But not if get_block() returned an error.
2159 */
2160 if (!PageError(page))
2161 SetPageUptodate(page);
2162 unlock_page(page);
2163 return 0;
2164 }
2165
2166 /* Stage two: lock the buffers */
2167 for (i = 0; i < nr; i++) {
2168 bh = arr[i];
2169 lock_buffer(bh);
2170 mark_buffer_async_read(bh);
2171 }
2172
2173 /*
2174 * Stage 3: start the IO. Check for uptodateness
2175 * inside the buffer lock in case another process reading
2176 * the underlying blockdev brought it uptodate (the sct fix).
2177 */
2178 for (i = 0; i < nr; i++) {
2179 bh = arr[i];
2180 if (buffer_uptodate(bh))
2181 end_buffer_async_read(bh, 1);
2182 else
2183 submit_bh(READ, bh);
2184 }
2185 return 0;
2186}
2187EXPORT_SYMBOL(block_read_full_page);
2188
2189/* utility function for filesystems that need to do work on expanding
2190 * truncates. Uses filesystem pagecache writes to allow the filesystem to
2191 * deal with the hole.
2192 */
2193int generic_cont_expand_simple(struct inode *inode, loff_t size)
2194{
2195 struct address_space *mapping = inode->i_mapping;
2196 struct page *page;
2197 void *fsdata;
2198 int err;
2199
2200 err = inode_newsize_ok(inode, size);
2201 if (err)
2202 goto out;
2203
2204 err = pagecache_write_begin(NULL, mapping, size, 0,
2205 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2206 &page, &fsdata);
2207 if (err)
2208 goto out;
2209
2210 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2211 BUG_ON(err > 0);
2212
2213out:
2214 return err;
2215}
2216EXPORT_SYMBOL(generic_cont_expand_simple);
2217
2218static int cont_expand_zero(struct file *file, struct address_space *mapping,
2219 loff_t pos, loff_t *bytes)
2220{
2221 struct inode *inode = mapping->host;
2222 unsigned blocksize = 1 << inode->i_blkbits;
2223 struct page *page;
2224 void *fsdata;
2225 pgoff_t index, curidx;
2226 loff_t curpos;
2227 unsigned zerofrom, offset, len;
2228 int err = 0;
2229
2230 index = pos >> PAGE_CACHE_SHIFT;
2231 offset = pos & ~PAGE_CACHE_MASK;
2232
2233 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
2234 zerofrom = curpos & ~PAGE_CACHE_MASK;
2235 if (zerofrom & (blocksize-1)) {
2236 *bytes |= (blocksize-1);
2237 (*bytes)++;
2238 }
2239 len = PAGE_CACHE_SIZE - zerofrom;
2240
2241 err = pagecache_write_begin(file, mapping, curpos, len,
2242 AOP_FLAG_UNINTERRUPTIBLE,
2243 &page, &fsdata);
2244 if (err)
2245 goto out;
2246 zero_user(page, zerofrom, len);
2247 err = pagecache_write_end(file, mapping, curpos, len, len,
2248 page, fsdata);
2249 if (err < 0)
2250 goto out;
2251 BUG_ON(err != len);
2252 err = 0;
2253
2254 balance_dirty_pages_ratelimited(mapping);
2255 }
2256
2257 /* page covers the boundary, find the boundary offset */
2258 if (index == curidx) {
2259 zerofrom = curpos & ~PAGE_CACHE_MASK;
2260 /* if we will expand the thing last block will be filled */
2261 if (offset <= zerofrom) {
2262 goto out;
2263 }
2264 if (zerofrom & (blocksize-1)) {
2265 *bytes |= (blocksize-1);
2266 (*bytes)++;
2267 }
2268 len = offset - zerofrom;
2269
2270 err = pagecache_write_begin(file, mapping, curpos, len,
2271 AOP_FLAG_UNINTERRUPTIBLE,
2272 &page, &fsdata);
2273 if (err)
2274 goto out;
2275 zero_user(page, zerofrom, len);
2276 err = pagecache_write_end(file, mapping, curpos, len, len,
2277 page, fsdata);
2278 if (err < 0)
2279 goto out;
2280 BUG_ON(err != len);
2281 err = 0;
2282 }
2283out:
2284 return err;
2285}
2286
2287/*
2288 * For moronic filesystems that do not allow holes in file.
2289 * We may have to extend the file.
2290 */
2291int cont_write_begin(struct file *file, struct address_space *mapping,
2292 loff_t pos, unsigned len, unsigned flags,
2293 struct page **pagep, void **fsdata,
2294 get_block_t *get_block, loff_t *bytes)
2295{
2296 struct inode *inode = mapping->host;
2297 unsigned blocksize = 1 << inode->i_blkbits;
2298 unsigned zerofrom;
2299 int err;
2300
2301 err = cont_expand_zero(file, mapping, pos, bytes);
2302 if (err)
2303 return err;
2304
2305 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2306 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2307 *bytes |= (blocksize-1);
2308 (*bytes)++;
2309 }
2310
2311 return block_write_begin(mapping, pos, len, flags, pagep, get_block);
2312}
2313EXPORT_SYMBOL(cont_write_begin);
2314
2315int block_commit_write(struct page *page, unsigned from, unsigned to)
2316{
2317 struct inode *inode = page->mapping->host;
2318 __block_commit_write(inode,page,from,to);
2319 return 0;
2320}
2321EXPORT_SYMBOL(block_commit_write);
2322
2323/*
2324 * block_page_mkwrite() is not allowed to change the file size as it gets
2325 * called from a page fault handler when a page is first dirtied. Hence we must
2326 * be careful to check for EOF conditions here. We set the page up correctly
2327 * for a written page which means we get ENOSPC checking when writing into
2328 * holes and correct delalloc and unwritten extent mapping on filesystems that
2329 * support these features.
2330 *
2331 * We are not allowed to take the i_mutex here so we have to play games to
2332 * protect against truncate races as the page could now be beyond EOF. Because
2333 * truncate writes the inode size before removing pages, once we have the
2334 * page lock we can determine safely if the page is beyond EOF. If it is not
2335 * beyond EOF, then the page is guaranteed safe against truncation until we
2336 * unlock the page.
2337 *
2338 * Direct callers of this function should call vfs_check_frozen() so that page
2339 * fault does not busyloop until the fs is thawed.
2340 */
2341int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2342 get_block_t get_block)
2343{
2344 struct page *page = vmf->page;
2345 struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
2346 unsigned long end;
2347 loff_t size;
2348 int ret;
2349
2350 lock_page(page);
2351 size = i_size_read(inode);
2352 if ((page->mapping != inode->i_mapping) ||
2353 (page_offset(page) > size)) {
2354 /* We overload EFAULT to mean page got truncated */
2355 ret = -EFAULT;
2356 goto out_unlock;
2357 }
2358
2359 /* page is wholly or partially inside EOF */
2360 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
2361 end = size & ~PAGE_CACHE_MASK;
2362 else
2363 end = PAGE_CACHE_SIZE;
2364
2365 ret = __block_write_begin(page, 0, end, get_block);
2366 if (!ret)
2367 ret = block_commit_write(page, 0, end);
2368
2369 if (unlikely(ret < 0))
2370 goto out_unlock;
2371 /*
2372 * Freezing in progress? We check after the page is marked dirty and
2373 * with page lock held so if the test here fails, we are sure freezing
2374 * code will wait during syncing until the page fault is done - at that
2375 * point page will be dirty and unlocked so freezing code will write it
2376 * and writeprotect it again.
2377 */
2378 set_page_dirty(page);
2379 if (inode->i_sb->s_frozen != SB_UNFROZEN) {
2380 ret = -EAGAIN;
2381 goto out_unlock;
2382 }
2383 wait_on_page_writeback(page);
2384 return 0;
2385out_unlock:
2386 unlock_page(page);
2387 return ret;
2388}
2389EXPORT_SYMBOL(__block_page_mkwrite);
2390
2391int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2392 get_block_t get_block)
2393{
2394 int ret;
2395 struct super_block *sb = vma->vm_file->f_path.dentry->d_inode->i_sb;
2396
2397 /*
2398 * This check is racy but catches the common case. The check in
2399 * __block_page_mkwrite() is reliable.
2400 */
2401 vfs_check_frozen(sb, SB_FREEZE_WRITE);
2402 ret = __block_page_mkwrite(vma, vmf, get_block);
2403 return block_page_mkwrite_return(ret);
2404}
2405EXPORT_SYMBOL(block_page_mkwrite);
2406
2407/*
2408 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
2409 * immediately, while under the page lock. So it needs a special end_io
2410 * handler which does not touch the bh after unlocking it.
2411 */
2412static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2413{
2414 __end_buffer_read_notouch(bh, uptodate);
2415}
2416
2417/*
2418 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2419 * the page (converting it to circular linked list and taking care of page
2420 * dirty races).
2421 */
2422static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2423{
2424 struct buffer_head *bh;
2425
2426 BUG_ON(!PageLocked(page));
2427
2428 spin_lock(&page->mapping->private_lock);
2429 bh = head;
2430 do {
2431 if (PageDirty(page))
2432 set_buffer_dirty(bh);
2433 if (!bh->b_this_page)
2434 bh->b_this_page = head;
2435 bh = bh->b_this_page;
2436 } while (bh != head);
2437 attach_page_buffers(page, head);
2438 spin_unlock(&page->mapping->private_lock);
2439}
2440
2441/*
2442 * On entry, the page is fully not uptodate.
2443 * On exit the page is fully uptodate in the areas outside (from,to)
2444 * The filesystem needs to handle block truncation upon failure.
2445 */
2446int nobh_write_begin(struct address_space *mapping,
2447 loff_t pos, unsigned len, unsigned flags,
2448 struct page **pagep, void **fsdata,
2449 get_block_t *get_block)
2450{
2451 struct inode *inode = mapping->host;
2452 const unsigned blkbits = inode->i_blkbits;
2453 const unsigned blocksize = 1 << blkbits;
2454 struct buffer_head *head, *bh;
2455 struct page *page;
2456 pgoff_t index;
2457 unsigned from, to;
2458 unsigned block_in_page;
2459 unsigned block_start, block_end;
2460 sector_t block_in_file;
2461 int nr_reads = 0;
2462 int ret = 0;
2463 int is_mapped_to_disk = 1;
2464
2465 index = pos >> PAGE_CACHE_SHIFT;
2466 from = pos & (PAGE_CACHE_SIZE - 1);
2467 to = from + len;
2468
2469 page = grab_cache_page_write_begin(mapping, index, flags);
2470 if (!page)
2471 return -ENOMEM;
2472 *pagep = page;
2473 *fsdata = NULL;
2474
2475 if (page_has_buffers(page)) {
2476 ret = __block_write_begin(page, pos, len, get_block);
2477 if (unlikely(ret))
2478 goto out_release;
2479 return ret;
2480 }
2481
2482 if (PageMappedToDisk(page))
2483 return 0;
2484
2485 /*
2486 * Allocate buffers so that we can keep track of state, and potentially
2487 * attach them to the page if an error occurs. In the common case of
2488 * no error, they will just be freed again without ever being attached
2489 * to the page (which is all OK, because we're under the page lock).
2490 *
2491 * Be careful: the buffer linked list is a NULL terminated one, rather
2492 * than the circular one we're used to.
2493 */
2494 head = alloc_page_buffers(page, blocksize, 0);
2495 if (!head) {
2496 ret = -ENOMEM;
2497 goto out_release;
2498 }
2499
2500 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
2501
2502 /*
2503 * We loop across all blocks in the page, whether or not they are
2504 * part of the affected region. This is so we can discover if the
2505 * page is fully mapped-to-disk.
2506 */
2507 for (block_start = 0, block_in_page = 0, bh = head;
2508 block_start < PAGE_CACHE_SIZE;
2509 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
2510 int create;
2511
2512 block_end = block_start + blocksize;
2513 bh->b_state = 0;
2514 create = 1;
2515 if (block_start >= to)
2516 create = 0;
2517 ret = get_block(inode, block_in_file + block_in_page,
2518 bh, create);
2519 if (ret)
2520 goto failed;
2521 if (!buffer_mapped(bh))
2522 is_mapped_to_disk = 0;
2523 if (buffer_new(bh))
2524 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
2525 if (PageUptodate(page)) {
2526 set_buffer_uptodate(bh);
2527 continue;
2528 }
2529 if (buffer_new(bh) || !buffer_mapped(bh)) {
2530 zero_user_segments(page, block_start, from,
2531 to, block_end);
2532 continue;
2533 }
2534 if (buffer_uptodate(bh))
2535 continue; /* reiserfs does this */
2536 if (block_start < from || block_end > to) {
2537 lock_buffer(bh);
2538 bh->b_end_io = end_buffer_read_nobh;
2539 submit_bh(READ, bh);
2540 nr_reads++;
2541 }
2542 }
2543
2544 if (nr_reads) {
2545 /*
2546 * The page is locked, so these buffers are protected from
2547 * any VM or truncate activity. Hence we don't need to care
2548 * for the buffer_head refcounts.
2549 */
2550 for (bh = head; bh; bh = bh->b_this_page) {
2551 wait_on_buffer(bh);
2552 if (!buffer_uptodate(bh))
2553 ret = -EIO;
2554 }
2555 if (ret)
2556 goto failed;
2557 }
2558
2559 if (is_mapped_to_disk)
2560 SetPageMappedToDisk(page);
2561
2562 *fsdata = head; /* to be released by nobh_write_end */
2563
2564 return 0;
2565
2566failed:
2567 BUG_ON(!ret);
2568 /*
2569 * Error recovery is a bit difficult. We need to zero out blocks that
2570 * were newly allocated, and dirty them to ensure they get written out.
2571 * Buffers need to be attached to the page at this point, otherwise
2572 * the handling of potential IO errors during writeout would be hard
2573 * (could try doing synchronous writeout, but what if that fails too?)
2574 */
2575 attach_nobh_buffers(page, head);
2576 page_zero_new_buffers(page, from, to);
2577
2578out_release:
2579 unlock_page(page);
2580 page_cache_release(page);
2581 *pagep = NULL;
2582
2583 return ret;
2584}
2585EXPORT_SYMBOL(nobh_write_begin);
2586
2587int nobh_write_end(struct file *file, struct address_space *mapping,
2588 loff_t pos, unsigned len, unsigned copied,
2589 struct page *page, void *fsdata)
2590{
2591 struct inode *inode = page->mapping->host;
2592 struct buffer_head *head = fsdata;
2593 struct buffer_head *bh;
2594 BUG_ON(fsdata != NULL && page_has_buffers(page));
2595
2596 if (unlikely(copied < len) && head)
2597 attach_nobh_buffers(page, head);
2598 if (page_has_buffers(page))
2599 return generic_write_end(file, mapping, pos, len,
2600 copied, page, fsdata);
2601
2602 SetPageUptodate(page);
2603 set_page_dirty(page);
2604 if (pos+copied > inode->i_size) {
2605 i_size_write(inode, pos+copied);
2606 mark_inode_dirty(inode);
2607 }
2608
2609 unlock_page(page);
2610 page_cache_release(page);
2611
2612 while (head) {
2613 bh = head;
2614 head = head->b_this_page;
2615 free_buffer_head(bh);
2616 }
2617
2618 return copied;
2619}
2620EXPORT_SYMBOL(nobh_write_end);
2621
2622/*
2623 * nobh_writepage() - based on block_full_write_page() except
2624 * that it tries to operate without attaching bufferheads to
2625 * the page.
2626 */
2627int nobh_writepage(struct page *page, get_block_t *get_block,
2628 struct writeback_control *wbc)
2629{
2630 struct inode * const inode = page->mapping->host;
2631 loff_t i_size = i_size_read(inode);
2632 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2633 unsigned offset;
2634 int ret;
2635
2636 /* Is the page fully inside i_size? */
2637 if (page->index < end_index)
2638 goto out;
2639
2640 /* Is the page fully outside i_size? (truncate in progress) */
2641 offset = i_size & (PAGE_CACHE_SIZE-1);
2642 if (page->index >= end_index+1 || !offset) {
2643 /*
2644 * The page may have dirty, unmapped buffers. For example,
2645 * they may have been added in ext3_writepage(). Make them
2646 * freeable here, so the page does not leak.
2647 */
2648#if 0
2649 /* Not really sure about this - do we need this ? */
2650 if (page->mapping->a_ops->invalidatepage)
2651 page->mapping->a_ops->invalidatepage(page, offset);
2652#endif
2653 unlock_page(page);
2654 return 0; /* don't care */
2655 }
2656
2657 /*
2658 * The page straddles i_size. It must be zeroed out on each and every
2659 * writepage invocation because it may be mmapped. "A file is mapped
2660 * in multiples of the page size. For a file that is not a multiple of
2661 * the page size, the remaining memory is zeroed when mapped, and
2662 * writes to that region are not written out to the file."
2663 */
2664 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2665out:
2666 ret = mpage_writepage(page, get_block, wbc);
2667 if (ret == -EAGAIN)
2668 ret = __block_write_full_page(inode, page, get_block, wbc,
2669 end_buffer_async_write);
2670 return ret;
2671}
2672EXPORT_SYMBOL(nobh_writepage);
2673
2674int nobh_truncate_page(struct address_space *mapping,
2675 loff_t from, get_block_t *get_block)
2676{
2677 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2678 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2679 unsigned blocksize;
2680 sector_t iblock;
2681 unsigned length, pos;
2682 struct inode *inode = mapping->host;
2683 struct page *page;
2684 struct buffer_head map_bh;
2685 int err;
2686
2687 blocksize = 1 << inode->i_blkbits;
2688 length = offset & (blocksize - 1);
2689
2690 /* Block boundary? Nothing to do */
2691 if (!length)
2692 return 0;
2693
2694 length = blocksize - length;
2695 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2696
2697 page = grab_cache_page(mapping, index);
2698 err = -ENOMEM;
2699 if (!page)
2700 goto out;
2701
2702 if (page_has_buffers(page)) {
2703has_buffers:
2704 unlock_page(page);
2705 page_cache_release(page);
2706 return block_truncate_page(mapping, from, get_block);
2707 }
2708
2709 /* Find the buffer that contains "offset" */
2710 pos = blocksize;
2711 while (offset >= pos) {
2712 iblock++;
2713 pos += blocksize;
2714 }
2715
2716 map_bh.b_size = blocksize;
2717 map_bh.b_state = 0;
2718 err = get_block(inode, iblock, &map_bh, 0);
2719 if (err)
2720 goto unlock;
2721 /* unmapped? It's a hole - nothing to do */
2722 if (!buffer_mapped(&map_bh))
2723 goto unlock;
2724
2725 /* Ok, it's mapped. Make sure it's up-to-date */
2726 if (!PageUptodate(page)) {
2727 err = mapping->a_ops->readpage(NULL, page);
2728 if (err) {
2729 page_cache_release(page);
2730 goto out;
2731 }
2732 lock_page(page);
2733 if (!PageUptodate(page)) {
2734 err = -EIO;
2735 goto unlock;
2736 }
2737 if (page_has_buffers(page))
2738 goto has_buffers;
2739 }
2740 zero_user(page, offset, length);
2741 set_page_dirty(page);
2742 err = 0;
2743
2744unlock:
2745 unlock_page(page);
2746 page_cache_release(page);
2747out:
2748 return err;
2749}
2750EXPORT_SYMBOL(nobh_truncate_page);
2751
2752int block_truncate_page(struct address_space *mapping,
2753 loff_t from, get_block_t *get_block)
2754{
2755 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2756 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2757 unsigned blocksize;
2758 sector_t iblock;
2759 unsigned length, pos;
2760 struct inode *inode = mapping->host;
2761 struct page *page;
2762 struct buffer_head *bh;
2763 int err;
2764
2765 blocksize = 1 << inode->i_blkbits;
2766 length = offset & (blocksize - 1);
2767
2768 /* Block boundary? Nothing to do */
2769 if (!length)
2770 return 0;
2771
2772 length = blocksize - length;
2773 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2774
2775 page = grab_cache_page(mapping, index);
2776 err = -ENOMEM;
2777 if (!page)
2778 goto out;
2779
2780 if (!page_has_buffers(page))
2781 create_empty_buffers(page, blocksize, 0);
2782
2783 /* Find the buffer that contains "offset" */
2784 bh = page_buffers(page);
2785 pos = blocksize;
2786 while (offset >= pos) {
2787 bh = bh->b_this_page;
2788 iblock++;
2789 pos += blocksize;
2790 }
2791
2792 err = 0;
2793 if (!buffer_mapped(bh)) {
2794 WARN_ON(bh->b_size != blocksize);
2795 err = get_block(inode, iblock, bh, 0);
2796 if (err)
2797 goto unlock;
2798 /* unmapped? It's a hole - nothing to do */
2799 if (!buffer_mapped(bh))
2800 goto unlock;
2801 }
2802
2803 /* Ok, it's mapped. Make sure it's up-to-date */
2804 if (PageUptodate(page))
2805 set_buffer_uptodate(bh);
2806
2807 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2808 err = -EIO;
2809 ll_rw_block(READ, 1, &bh);
2810 wait_on_buffer(bh);
2811 /* Uhhuh. Read error. Complain and punt. */
2812 if (!buffer_uptodate(bh))
2813 goto unlock;
2814 }
2815
2816 zero_user(page, offset, length);
2817 mark_buffer_dirty(bh);
2818 err = 0;
2819
2820unlock:
2821 unlock_page(page);
2822 page_cache_release(page);
2823out:
2824 return err;
2825}
2826EXPORT_SYMBOL(block_truncate_page);
2827
2828/*
2829 * The generic ->writepage function for buffer-backed address_spaces
2830 * this form passes in the end_io handler used to finish the IO.
2831 */
2832int block_write_full_page_endio(struct page *page, get_block_t *get_block,
2833 struct writeback_control *wbc, bh_end_io_t *handler)
2834{
2835 struct inode * const inode = page->mapping->host;
2836 loff_t i_size = i_size_read(inode);
2837 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2838 unsigned offset;
2839
2840 /* Is the page fully inside i_size? */
2841 if (page->index < end_index)
2842 return __block_write_full_page(inode, page, get_block, wbc,
2843 handler);
2844
2845 /* Is the page fully outside i_size? (truncate in progress) */
2846 offset = i_size & (PAGE_CACHE_SIZE-1);
2847 if (page->index >= end_index+1 || !offset) {
2848 /*
2849 * The page may have dirty, unmapped buffers. For example,
2850 * they may have been added in ext3_writepage(). Make them
2851 * freeable here, so the page does not leak.
2852 */
2853 do_invalidatepage(page, 0);
2854 unlock_page(page);
2855 return 0; /* don't care */
2856 }
2857
2858 /*
2859 * The page straddles i_size. It must be zeroed out on each and every
2860 * writepage invocation because it may be mmapped. "A file is mapped
2861 * in multiples of the page size. For a file that is not a multiple of
2862 * the page size, the remaining memory is zeroed when mapped, and
2863 * writes to that region are not written out to the file."
2864 */
2865 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2866 return __block_write_full_page(inode, page, get_block, wbc, handler);
2867}
2868EXPORT_SYMBOL(block_write_full_page_endio);
2869
2870/*
2871 * The generic ->writepage function for buffer-backed address_spaces
2872 */
2873int block_write_full_page(struct page *page, get_block_t *get_block,
2874 struct writeback_control *wbc)
2875{
2876 return block_write_full_page_endio(page, get_block, wbc,
2877 end_buffer_async_write);
2878}
2879EXPORT_SYMBOL(block_write_full_page);
2880
2881sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2882 get_block_t *get_block)
2883{
2884 struct buffer_head tmp;
2885 struct inode *inode = mapping->host;
2886 tmp.b_state = 0;
2887 tmp.b_blocknr = 0;
2888 tmp.b_size = 1 << inode->i_blkbits;
2889 get_block(inode, block, &tmp, 0);
2890 return tmp.b_blocknr;
2891}
2892EXPORT_SYMBOL(generic_block_bmap);
2893
2894static void end_bio_bh_io_sync(struct bio *bio, int err)
2895{
2896 struct buffer_head *bh = bio->bi_private;
2897
2898 if (err == -EOPNOTSUPP) {
2899 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
2900 }
2901
2902 if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags)))
2903 set_bit(BH_Quiet, &bh->b_state);
2904
2905 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2906 bio_put(bio);
2907}
2908
2909int submit_bh(int rw, struct buffer_head * bh)
2910{
2911 struct bio *bio;
2912 int ret = 0;
2913
2914 BUG_ON(!buffer_locked(bh));
2915 BUG_ON(!buffer_mapped(bh));
2916 BUG_ON(!bh->b_end_io);
2917 BUG_ON(buffer_delay(bh));
2918 BUG_ON(buffer_unwritten(bh));
2919
2920 /*
2921 * Only clear out a write error when rewriting
2922 */
2923 if (test_set_buffer_req(bh) && (rw & WRITE))
2924 clear_buffer_write_io_error(bh);
2925
2926 /*
2927 * from here on down, it's all bio -- do the initial mapping,
2928 * submit_bio -> generic_make_request may further map this bio around
2929 */
2930 bio = bio_alloc(GFP_NOIO, 1);
2931
2932 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2933 bio->bi_bdev = bh->b_bdev;
2934 bio->bi_io_vec[0].bv_page = bh->b_page;
2935 bio->bi_io_vec[0].bv_len = bh->b_size;
2936 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
2937
2938 bio->bi_vcnt = 1;
2939 bio->bi_idx = 0;
2940 bio->bi_size = bh->b_size;
2941
2942 bio->bi_end_io = end_bio_bh_io_sync;
2943 bio->bi_private = bh;
2944
2945 bio_get(bio);
2946 submit_bio(rw, bio);
2947
2948 if (bio_flagged(bio, BIO_EOPNOTSUPP))
2949 ret = -EOPNOTSUPP;
2950
2951 bio_put(bio);
2952 return ret;
2953}
2954EXPORT_SYMBOL(submit_bh);
2955
2956/**
2957 * ll_rw_block: low-level access to block devices (DEPRECATED)
2958 * @rw: whether to %READ or %WRITE or maybe %READA (readahead)
2959 * @nr: number of &struct buffer_heads in the array
2960 * @bhs: array of pointers to &struct buffer_head
2961 *
2962 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
2963 * requests an I/O operation on them, either a %READ or a %WRITE. The third
2964 * %READA option is described in the documentation for generic_make_request()
2965 * which ll_rw_block() calls.
2966 *
2967 * This function drops any buffer that it cannot get a lock on (with the
2968 * BH_Lock state bit), any buffer that appears to be clean when doing a write
2969 * request, and any buffer that appears to be up-to-date when doing read
2970 * request. Further it marks as clean buffers that are processed for
2971 * writing (the buffer cache won't assume that they are actually clean
2972 * until the buffer gets unlocked).
2973 *
2974 * ll_rw_block sets b_end_io to simple completion handler that marks
2975 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
2976 * any waiters.
2977 *
2978 * All of the buffers must be for the same device, and must also be a
2979 * multiple of the current approved size for the device.
2980 */
2981void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
2982{
2983 int i;
2984
2985 for (i = 0; i < nr; i++) {
2986 struct buffer_head *bh = bhs[i];
2987
2988 if (!trylock_buffer(bh))
2989 continue;
2990 if (rw == WRITE) {
2991 if (test_clear_buffer_dirty(bh)) {
2992 bh->b_end_io = end_buffer_write_sync;
2993 get_bh(bh);
2994 submit_bh(WRITE, bh);
2995 continue;
2996 }
2997 } else {
2998 if (!buffer_uptodate(bh)) {
2999 bh->b_end_io = end_buffer_read_sync;
3000 get_bh(bh);
3001 submit_bh(rw, bh);
3002 continue;
3003 }
3004 }
3005 unlock_buffer(bh);
3006 }
3007}
3008EXPORT_SYMBOL(ll_rw_block);
3009
3010void write_dirty_buffer(struct buffer_head *bh, int rw)
3011{
3012 lock_buffer(bh);
3013 if (!test_clear_buffer_dirty(bh)) {
3014 unlock_buffer(bh);
3015 return;
3016 }
3017 bh->b_end_io = end_buffer_write_sync;
3018 get_bh(bh);
3019 submit_bh(rw, bh);
3020}
3021EXPORT_SYMBOL(write_dirty_buffer);
3022
3023/*
3024 * For a data-integrity writeout, we need to wait upon any in-progress I/O
3025 * and then start new I/O and then wait upon it. The caller must have a ref on
3026 * the buffer_head.
3027 */
3028int __sync_dirty_buffer(struct buffer_head *bh, int rw)
3029{
3030 int ret = 0;
3031
3032 WARN_ON(atomic_read(&bh->b_count) < 1);
3033 lock_buffer(bh);
3034 if (test_clear_buffer_dirty(bh)) {
3035 get_bh(bh);
3036 bh->b_end_io = end_buffer_write_sync;
3037 ret = submit_bh(rw, bh);
3038 wait_on_buffer(bh);
3039 if (!ret && !buffer_uptodate(bh))
3040 ret = -EIO;
3041 } else {
3042 unlock_buffer(bh);
3043 }
3044 return ret;
3045}
3046EXPORT_SYMBOL(__sync_dirty_buffer);
3047
3048int sync_dirty_buffer(struct buffer_head *bh)
3049{
3050 return __sync_dirty_buffer(bh, WRITE_SYNC);
3051}
3052EXPORT_SYMBOL(sync_dirty_buffer);
3053
3054/*
3055 * try_to_free_buffers() checks if all the buffers on this particular page
3056 * are unused, and releases them if so.
3057 *
3058 * Exclusion against try_to_free_buffers may be obtained by either
3059 * locking the page or by holding its mapping's private_lock.
3060 *
3061 * If the page is dirty but all the buffers are clean then we need to
3062 * be sure to mark the page clean as well. This is because the page
3063 * may be against a block device, and a later reattachment of buffers
3064 * to a dirty page will set *all* buffers dirty. Which would corrupt
3065 * filesystem data on the same device.
3066 *
3067 * The same applies to regular filesystem pages: if all the buffers are
3068 * clean then we set the page clean and proceed. To do that, we require
3069 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3070 * private_lock.
3071 *
3072 * try_to_free_buffers() is non-blocking.
3073 */
3074static inline int buffer_busy(struct buffer_head *bh)
3075{
3076 return atomic_read(&bh->b_count) |
3077 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3078}
3079
3080static int
3081drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3082{
3083 struct buffer_head *head = page_buffers(page);
3084 struct buffer_head *bh;
3085
3086 bh = head;
3087 do {
3088 if (buffer_write_io_error(bh) && page->mapping)
3089 set_bit(AS_EIO, &page->mapping->flags);
3090 if (buffer_busy(bh))
3091 goto failed;
3092 bh = bh->b_this_page;
3093 } while (bh != head);
3094
3095 do {
3096 struct buffer_head *next = bh->b_this_page;
3097
3098 if (bh->b_assoc_map)
3099 __remove_assoc_queue(bh);
3100 bh = next;
3101 } while (bh != head);
3102 *buffers_to_free = head;
3103 __clear_page_buffers(page);
3104 return 1;
3105failed:
3106 return 0;
3107}
3108
3109int try_to_free_buffers(struct page *page)
3110{
3111 struct address_space * const mapping = page->mapping;
3112 struct buffer_head *buffers_to_free = NULL;
3113 int ret = 0;
3114
3115 BUG_ON(!PageLocked(page));
3116 if (PageWriteback(page))
3117 return 0;
3118
3119 if (mapping == NULL) { /* can this still happen? */
3120 ret = drop_buffers(page, &buffers_to_free);
3121 goto out;
3122 }
3123
3124 spin_lock(&mapping->private_lock);
3125 ret = drop_buffers(page, &buffers_to_free);
3126
3127 /*
3128 * If the filesystem writes its buffers by hand (eg ext3)
3129 * then we can have clean buffers against a dirty page. We
3130 * clean the page here; otherwise the VM will never notice
3131 * that the filesystem did any IO at all.
3132 *
3133 * Also, during truncate, discard_buffer will have marked all
3134 * the page's buffers clean. We discover that here and clean
3135 * the page also.
3136 *
3137 * private_lock must be held over this entire operation in order
3138 * to synchronise against __set_page_dirty_buffers and prevent the
3139 * dirty bit from being lost.
3140 */
3141 if (ret)
3142 cancel_dirty_page(page, PAGE_CACHE_SIZE);
3143 spin_unlock(&mapping->private_lock);
3144out:
3145 if (buffers_to_free) {
3146 struct buffer_head *bh = buffers_to_free;
3147
3148 do {
3149 struct buffer_head *next = bh->b_this_page;
3150 free_buffer_head(bh);
3151 bh = next;
3152 } while (bh != buffers_to_free);
3153 }
3154 return ret;
3155}
3156EXPORT_SYMBOL(try_to_free_buffers);
3157
3158/*
3159 * There are no bdflush tunables left. But distributions are
3160 * still running obsolete flush daemons, so we terminate them here.
3161 *
3162 * Use of bdflush() is deprecated and will be removed in a future kernel.
3163 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
3164 */
3165SYSCALL_DEFINE2(bdflush, int, func, long, data)
3166{
3167 static int msg_count;
3168
3169 if (!capable(CAP_SYS_ADMIN))
3170 return -EPERM;
3171
3172 if (msg_count < 5) {
3173 msg_count++;
3174 printk(KERN_INFO
3175 "warning: process `%s' used the obsolete bdflush"
3176 " system call\n", current->comm);
3177 printk(KERN_INFO "Fix your initscripts?\n");
3178 }
3179
3180 if (func == 1)
3181 do_exit(0);
3182 return 0;
3183}
3184
3185/*
3186 * Buffer-head allocation
3187 */
3188static struct kmem_cache *bh_cachep;
3189
3190/*
3191 * Once the number of bh's in the machine exceeds this level, we start
3192 * stripping them in writeback.
3193 */
3194static int max_buffer_heads;
3195
3196int buffer_heads_over_limit;
3197
3198struct bh_accounting {
3199 int nr; /* Number of live bh's */
3200 int ratelimit; /* Limit cacheline bouncing */
3201};
3202
3203static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3204
3205static void recalc_bh_state(void)
3206{
3207 int i;
3208 int tot = 0;
3209
3210 if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
3211 return;
3212 __this_cpu_write(bh_accounting.ratelimit, 0);
3213 for_each_online_cpu(i)
3214 tot += per_cpu(bh_accounting, i).nr;
3215 buffer_heads_over_limit = (tot > max_buffer_heads);
3216}
3217
3218struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3219{
3220 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
3221 if (ret) {
3222 INIT_LIST_HEAD(&ret->b_assoc_buffers);
3223 preempt_disable();
3224 __this_cpu_inc(bh_accounting.nr);
3225 recalc_bh_state();
3226 preempt_enable();
3227 }
3228 return ret;
3229}
3230EXPORT_SYMBOL(alloc_buffer_head);
3231
3232void free_buffer_head(struct buffer_head *bh)
3233{
3234 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3235 kmem_cache_free(bh_cachep, bh);
3236 preempt_disable();
3237 __this_cpu_dec(bh_accounting.nr);
3238 recalc_bh_state();
3239 preempt_enable();
3240}
3241EXPORT_SYMBOL(free_buffer_head);
3242
3243static void buffer_exit_cpu(int cpu)
3244{
3245 int i;
3246 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3247
3248 for (i = 0; i < BH_LRU_SIZE; i++) {
3249 brelse(b->bhs[i]);
3250 b->bhs[i] = NULL;
3251 }
3252 this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3253 per_cpu(bh_accounting, cpu).nr = 0;
3254}
3255
3256static int buffer_cpu_notify(struct notifier_block *self,
3257 unsigned long action, void *hcpu)
3258{
3259 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
3260 buffer_exit_cpu((unsigned long)hcpu);
3261 return NOTIFY_OK;
3262}
3263
3264/**
3265 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3266 * @bh: struct buffer_head
3267 *
3268 * Return true if the buffer is up-to-date and false,
3269 * with the buffer locked, if not.
3270 */
3271int bh_uptodate_or_lock(struct buffer_head *bh)
3272{
3273 if (!buffer_uptodate(bh)) {
3274 lock_buffer(bh);
3275 if (!buffer_uptodate(bh))
3276 return 0;
3277 unlock_buffer(bh);
3278 }
3279 return 1;
3280}
3281EXPORT_SYMBOL(bh_uptodate_or_lock);
3282
3283/**
3284 * bh_submit_read - Submit a locked buffer for reading
3285 * @bh: struct buffer_head
3286 *
3287 * Returns zero on success and -EIO on error.
3288 */
3289int bh_submit_read(struct buffer_head *bh)
3290{
3291 BUG_ON(!buffer_locked(bh));
3292
3293 if (buffer_uptodate(bh)) {
3294 unlock_buffer(bh);
3295 return 0;
3296 }
3297
3298 get_bh(bh);
3299 bh->b_end_io = end_buffer_read_sync;
3300 submit_bh(READ, bh);
3301 wait_on_buffer(bh);
3302 if (buffer_uptodate(bh))
3303 return 0;
3304 return -EIO;
3305}
3306EXPORT_SYMBOL(bh_submit_read);
3307
3308void __init buffer_init(void)
3309{
3310 int nrpages;
3311
3312 bh_cachep = kmem_cache_create("buffer_head",
3313 sizeof(struct buffer_head), 0,
3314 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3315 SLAB_MEM_SPREAD),
3316 NULL);
3317
3318 /*
3319 * Limit the bh occupancy to 10% of ZONE_NORMAL
3320 */
3321 nrpages = (nr_free_buffer_pages() * 10) / 100;
3322 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3323 hotcpu_notifier(buffer_cpu_notify, 0);
3324}
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * linux/fs/buffer.c
4 *
5 * Copyright (C) 1991, 1992, 2002 Linus Torvalds
6 */
7
8/*
9 * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95
10 *
11 * Removed a lot of unnecessary code and simplified things now that
12 * the buffer cache isn't our primary cache - Andrew Tridgell 12/96
13 *
14 * Speed up hash, lru, and free list operations. Use gfp() for allocating
15 * hash table, use SLAB cache for buffer heads. SMP threading. -DaveM
16 *
17 * Added 32k buffer block sizes - these are required older ARM systems. - RMK
18 *
19 * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de>
20 */
21
22#include <linux/kernel.h>
23#include <linux/sched/signal.h>
24#include <linux/syscalls.h>
25#include <linux/fs.h>
26#include <linux/iomap.h>
27#include <linux/mm.h>
28#include <linux/percpu.h>
29#include <linux/slab.h>
30#include <linux/capability.h>
31#include <linux/blkdev.h>
32#include <linux/file.h>
33#include <linux/quotaops.h>
34#include <linux/highmem.h>
35#include <linux/export.h>
36#include <linux/backing-dev.h>
37#include <linux/writeback.h>
38#include <linux/hash.h>
39#include <linux/suspend.h>
40#include <linux/buffer_head.h>
41#include <linux/task_io_accounting_ops.h>
42#include <linux/bio.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 <linux/sched/mm.h>
49#include <trace/events/block.h>
50
51static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
52static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
53 enum rw_hint hint, struct writeback_control *wbc);
54
55#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
56
57inline void touch_buffer(struct buffer_head *bh)
58{
59 trace_block_touch_buffer(bh);
60 mark_page_accessed(bh->b_page);
61}
62EXPORT_SYMBOL(touch_buffer);
63
64void __lock_buffer(struct buffer_head *bh)
65{
66 wait_on_bit_lock_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
67}
68EXPORT_SYMBOL(__lock_buffer);
69
70void unlock_buffer(struct buffer_head *bh)
71{
72 clear_bit_unlock(BH_Lock, &bh->b_state);
73 smp_mb__after_atomic();
74 wake_up_bit(&bh->b_state, BH_Lock);
75}
76EXPORT_SYMBOL(unlock_buffer);
77
78/*
79 * Returns if the page has dirty or writeback buffers. If all the buffers
80 * are unlocked and clean then the PageDirty information is stale. If
81 * any of the pages are locked, it is assumed they are locked for IO.
82 */
83void buffer_check_dirty_writeback(struct page *page,
84 bool *dirty, bool *writeback)
85{
86 struct buffer_head *head, *bh;
87 *dirty = false;
88 *writeback = false;
89
90 BUG_ON(!PageLocked(page));
91
92 if (!page_has_buffers(page))
93 return;
94
95 if (PageWriteback(page))
96 *writeback = true;
97
98 head = page_buffers(page);
99 bh = head;
100 do {
101 if (buffer_locked(bh))
102 *writeback = true;
103
104 if (buffer_dirty(bh))
105 *dirty = true;
106
107 bh = bh->b_this_page;
108 } while (bh != head);
109}
110EXPORT_SYMBOL(buffer_check_dirty_writeback);
111
112/*
113 * Block until a buffer comes unlocked. This doesn't stop it
114 * from becoming locked again - you have to lock it yourself
115 * if you want to preserve its state.
116 */
117void __wait_on_buffer(struct buffer_head * bh)
118{
119 wait_on_bit_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
120}
121EXPORT_SYMBOL(__wait_on_buffer);
122
123static void
124__clear_page_buffers(struct page *page)
125{
126 ClearPagePrivate(page);
127 set_page_private(page, 0);
128 put_page(page);
129}
130
131static void buffer_io_error(struct buffer_head *bh, char *msg)
132{
133 if (!test_bit(BH_Quiet, &bh->b_state))
134 printk_ratelimited(KERN_ERR
135 "Buffer I/O error on dev %pg, logical block %llu%s\n",
136 bh->b_bdev, (unsigned long long)bh->b_blocknr, msg);
137}
138
139/*
140 * End-of-IO handler helper function which does not touch the bh after
141 * unlocking it.
142 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
143 * a race there is benign: unlock_buffer() only use the bh's address for
144 * hashing after unlocking the buffer, so it doesn't actually touch the bh
145 * itself.
146 */
147static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
148{
149 if (uptodate) {
150 set_buffer_uptodate(bh);
151 } else {
152 /* This happens, due to failed read-ahead attempts. */
153 clear_buffer_uptodate(bh);
154 }
155 unlock_buffer(bh);
156}
157
158/*
159 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
160 * unlock the buffer. This is what ll_rw_block uses too.
161 */
162void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
163{
164 __end_buffer_read_notouch(bh, uptodate);
165 put_bh(bh);
166}
167EXPORT_SYMBOL(end_buffer_read_sync);
168
169void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
170{
171 if (uptodate) {
172 set_buffer_uptodate(bh);
173 } else {
174 buffer_io_error(bh, ", lost sync page write");
175 mark_buffer_write_io_error(bh);
176 clear_buffer_uptodate(bh);
177 }
178 unlock_buffer(bh);
179 put_bh(bh);
180}
181EXPORT_SYMBOL(end_buffer_write_sync);
182
183/*
184 * Various filesystems appear to want __find_get_block to be non-blocking.
185 * But it's the page lock which protects the buffers. To get around this,
186 * we get exclusion from try_to_free_buffers with the blockdev mapping's
187 * private_lock.
188 *
189 * Hack idea: for the blockdev mapping, private_lock contention
190 * may be quite high. This code could TryLock the page, and if that
191 * succeeds, there is no need to take private_lock.
192 */
193static struct buffer_head *
194__find_get_block_slow(struct block_device *bdev, sector_t block)
195{
196 struct inode *bd_inode = bdev->bd_inode;
197 struct address_space *bd_mapping = bd_inode->i_mapping;
198 struct buffer_head *ret = NULL;
199 pgoff_t index;
200 struct buffer_head *bh;
201 struct buffer_head *head;
202 struct page *page;
203 int all_mapped = 1;
204 static DEFINE_RATELIMIT_STATE(last_warned, HZ, 1);
205
206 index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
207 page = find_get_page_flags(bd_mapping, index, FGP_ACCESSED);
208 if (!page)
209 goto out;
210
211 spin_lock(&bd_mapping->private_lock);
212 if (!page_has_buffers(page))
213 goto out_unlock;
214 head = page_buffers(page);
215 bh = head;
216 do {
217 if (!buffer_mapped(bh))
218 all_mapped = 0;
219 else if (bh->b_blocknr == block) {
220 ret = bh;
221 get_bh(bh);
222 goto out_unlock;
223 }
224 bh = bh->b_this_page;
225 } while (bh != head);
226
227 /* we might be here because some of the buffers on this page are
228 * not mapped. This is due to various races between
229 * file io on the block device and getblk. It gets dealt with
230 * elsewhere, don't buffer_error if we had some unmapped buffers
231 */
232 ratelimit_set_flags(&last_warned, RATELIMIT_MSG_ON_RELEASE);
233 if (all_mapped && __ratelimit(&last_warned)) {
234 printk("__find_get_block_slow() failed. block=%llu, "
235 "b_blocknr=%llu, b_state=0x%08lx, b_size=%zu, "
236 "device %pg blocksize: %d\n",
237 (unsigned long long)block,
238 (unsigned long long)bh->b_blocknr,
239 bh->b_state, bh->b_size, bdev,
240 1 << bd_inode->i_blkbits);
241 }
242out_unlock:
243 spin_unlock(&bd_mapping->private_lock);
244 put_page(page);
245out:
246 return ret;
247}
248
249/*
250 * I/O completion handler for block_read_full_page() - pages
251 * which come unlocked at the end of I/O.
252 */
253static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
254{
255 unsigned long flags;
256 struct buffer_head *first;
257 struct buffer_head *tmp;
258 struct page *page;
259 int page_uptodate = 1;
260
261 BUG_ON(!buffer_async_read(bh));
262
263 page = bh->b_page;
264 if (uptodate) {
265 set_buffer_uptodate(bh);
266 } else {
267 clear_buffer_uptodate(bh);
268 buffer_io_error(bh, ", async page read");
269 SetPageError(page);
270 }
271
272 /*
273 * Be _very_ careful from here on. Bad things can happen if
274 * two buffer heads end IO at almost the same time and both
275 * decide that the page is now completely done.
276 */
277 first = page_buffers(page);
278 local_irq_save(flags);
279 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
280 clear_buffer_async_read(bh);
281 unlock_buffer(bh);
282 tmp = bh;
283 do {
284 if (!buffer_uptodate(tmp))
285 page_uptodate = 0;
286 if (buffer_async_read(tmp)) {
287 BUG_ON(!buffer_locked(tmp));
288 goto still_busy;
289 }
290 tmp = tmp->b_this_page;
291 } while (tmp != bh);
292 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
293 local_irq_restore(flags);
294
295 /*
296 * If none of the buffers had errors and they are all
297 * uptodate then we can set the page uptodate.
298 */
299 if (page_uptodate && !PageError(page))
300 SetPageUptodate(page);
301 unlock_page(page);
302 return;
303
304still_busy:
305 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
306 local_irq_restore(flags);
307 return;
308}
309
310/*
311 * Completion handler for block_write_full_page() - pages which are unlocked
312 * during I/O, and which have PageWriteback cleared upon I/O completion.
313 */
314void end_buffer_async_write(struct buffer_head *bh, int uptodate)
315{
316 unsigned long flags;
317 struct buffer_head *first;
318 struct buffer_head *tmp;
319 struct page *page;
320
321 BUG_ON(!buffer_async_write(bh));
322
323 page = bh->b_page;
324 if (uptodate) {
325 set_buffer_uptodate(bh);
326 } else {
327 buffer_io_error(bh, ", lost async page write");
328 mark_buffer_write_io_error(bh);
329 clear_buffer_uptodate(bh);
330 SetPageError(page);
331 }
332
333 first = page_buffers(page);
334 local_irq_save(flags);
335 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
336
337 clear_buffer_async_write(bh);
338 unlock_buffer(bh);
339 tmp = bh->b_this_page;
340 while (tmp != bh) {
341 if (buffer_async_write(tmp)) {
342 BUG_ON(!buffer_locked(tmp));
343 goto still_busy;
344 }
345 tmp = tmp->b_this_page;
346 }
347 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
348 local_irq_restore(flags);
349 end_page_writeback(page);
350 return;
351
352still_busy:
353 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
354 local_irq_restore(flags);
355 return;
356}
357EXPORT_SYMBOL(end_buffer_async_write);
358
359/*
360 * If a page's buffers are under async readin (end_buffer_async_read
361 * completion) then there is a possibility that another thread of
362 * control could lock one of the buffers after it has completed
363 * but while some of the other buffers have not completed. This
364 * locked buffer would confuse end_buffer_async_read() into not unlocking
365 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
366 * that this buffer is not under async I/O.
367 *
368 * The page comes unlocked when it has no locked buffer_async buffers
369 * left.
370 *
371 * PageLocked prevents anyone starting new async I/O reads any of
372 * the buffers.
373 *
374 * PageWriteback is used to prevent simultaneous writeout of the same
375 * page.
376 *
377 * PageLocked prevents anyone from starting writeback of a page which is
378 * under read I/O (PageWriteback is only ever set against a locked page).
379 */
380static void mark_buffer_async_read(struct buffer_head *bh)
381{
382 bh->b_end_io = end_buffer_async_read;
383 set_buffer_async_read(bh);
384}
385
386static void mark_buffer_async_write_endio(struct buffer_head *bh,
387 bh_end_io_t *handler)
388{
389 bh->b_end_io = handler;
390 set_buffer_async_write(bh);
391}
392
393void mark_buffer_async_write(struct buffer_head *bh)
394{
395 mark_buffer_async_write_endio(bh, end_buffer_async_write);
396}
397EXPORT_SYMBOL(mark_buffer_async_write);
398
399
400/*
401 * fs/buffer.c contains helper functions for buffer-backed address space's
402 * fsync functions. A common requirement for buffer-based filesystems is
403 * that certain data from the backing blockdev needs to be written out for
404 * a successful fsync(). For example, ext2 indirect blocks need to be
405 * written back and waited upon before fsync() returns.
406 *
407 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
408 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
409 * management of a list of dependent buffers at ->i_mapping->private_list.
410 *
411 * Locking is a little subtle: try_to_free_buffers() will remove buffers
412 * from their controlling inode's queue when they are being freed. But
413 * try_to_free_buffers() will be operating against the *blockdev* mapping
414 * at the time, not against the S_ISREG file which depends on those buffers.
415 * So the locking for private_list is via the private_lock in the address_space
416 * which backs the buffers. Which is different from the address_space
417 * against which the buffers are listed. So for a particular address_space,
418 * mapping->private_lock does *not* protect mapping->private_list! In fact,
419 * mapping->private_list will always be protected by the backing blockdev's
420 * ->private_lock.
421 *
422 * Which introduces a requirement: all buffers on an address_space's
423 * ->private_list must be from the same address_space: the blockdev's.
424 *
425 * address_spaces which do not place buffers at ->private_list via these
426 * utility functions are free to use private_lock and private_list for
427 * whatever they want. The only requirement is that list_empty(private_list)
428 * be true at clear_inode() time.
429 *
430 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
431 * filesystems should do that. invalidate_inode_buffers() should just go
432 * BUG_ON(!list_empty).
433 *
434 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
435 * take an address_space, not an inode. And it should be called
436 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
437 * queued up.
438 *
439 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
440 * list if it is already on a list. Because if the buffer is on a list,
441 * it *must* already be on the right one. If not, the filesystem is being
442 * silly. This will save a ton of locking. But first we have to ensure
443 * that buffers are taken *off* the old inode's list when they are freed
444 * (presumably in truncate). That requires careful auditing of all
445 * filesystems (do it inside bforget()). It could also be done by bringing
446 * b_inode back.
447 */
448
449/*
450 * The buffer's backing address_space's private_lock must be held
451 */
452static void __remove_assoc_queue(struct buffer_head *bh)
453{
454 list_del_init(&bh->b_assoc_buffers);
455 WARN_ON(!bh->b_assoc_map);
456 bh->b_assoc_map = NULL;
457}
458
459int inode_has_buffers(struct inode *inode)
460{
461 return !list_empty(&inode->i_data.private_list);
462}
463
464/*
465 * osync is designed to support O_SYNC io. It waits synchronously for
466 * all already-submitted IO to complete, but does not queue any new
467 * writes to the disk.
468 *
469 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
470 * you dirty the buffers, and then use osync_inode_buffers to wait for
471 * completion. Any other dirty buffers which are not yet queued for
472 * write will not be flushed to disk by the osync.
473 */
474static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
475{
476 struct buffer_head *bh;
477 struct list_head *p;
478 int err = 0;
479
480 spin_lock(lock);
481repeat:
482 list_for_each_prev(p, list) {
483 bh = BH_ENTRY(p);
484 if (buffer_locked(bh)) {
485 get_bh(bh);
486 spin_unlock(lock);
487 wait_on_buffer(bh);
488 if (!buffer_uptodate(bh))
489 err = -EIO;
490 brelse(bh);
491 spin_lock(lock);
492 goto repeat;
493 }
494 }
495 spin_unlock(lock);
496 return err;
497}
498
499void emergency_thaw_bdev(struct super_block *sb)
500{
501 while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
502 printk(KERN_WARNING "Emergency Thaw on %pg\n", sb->s_bdev);
503}
504
505/**
506 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
507 * @mapping: the mapping which wants those buffers written
508 *
509 * Starts I/O against the buffers at mapping->private_list, and waits upon
510 * that I/O.
511 *
512 * Basically, this is a convenience function for fsync().
513 * @mapping is a file or directory which needs those buffers to be written for
514 * a successful fsync().
515 */
516int sync_mapping_buffers(struct address_space *mapping)
517{
518 struct address_space *buffer_mapping = mapping->private_data;
519
520 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
521 return 0;
522
523 return fsync_buffers_list(&buffer_mapping->private_lock,
524 &mapping->private_list);
525}
526EXPORT_SYMBOL(sync_mapping_buffers);
527
528/*
529 * Called when we've recently written block `bblock', and it is known that
530 * `bblock' was for a buffer_boundary() buffer. This means that the block at
531 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
532 * dirty, schedule it for IO. So that indirects merge nicely with their data.
533 */
534void write_boundary_block(struct block_device *bdev,
535 sector_t bblock, unsigned blocksize)
536{
537 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
538 if (bh) {
539 if (buffer_dirty(bh))
540 ll_rw_block(REQ_OP_WRITE, 0, 1, &bh);
541 put_bh(bh);
542 }
543}
544
545void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
546{
547 struct address_space *mapping = inode->i_mapping;
548 struct address_space *buffer_mapping = bh->b_page->mapping;
549
550 mark_buffer_dirty(bh);
551 if (!mapping->private_data) {
552 mapping->private_data = buffer_mapping;
553 } else {
554 BUG_ON(mapping->private_data != buffer_mapping);
555 }
556 if (!bh->b_assoc_map) {
557 spin_lock(&buffer_mapping->private_lock);
558 list_move_tail(&bh->b_assoc_buffers,
559 &mapping->private_list);
560 bh->b_assoc_map = mapping;
561 spin_unlock(&buffer_mapping->private_lock);
562 }
563}
564EXPORT_SYMBOL(mark_buffer_dirty_inode);
565
566/*
567 * Mark the page dirty, and set it dirty in the page cache, and mark the inode
568 * dirty.
569 *
570 * If warn is true, then emit a warning if the page is not uptodate and has
571 * not been truncated.
572 *
573 * The caller must hold lock_page_memcg().
574 */
575void __set_page_dirty(struct page *page, struct address_space *mapping,
576 int warn)
577{
578 unsigned long flags;
579
580 xa_lock_irqsave(&mapping->i_pages, flags);
581 if (page->mapping) { /* Race with truncate? */
582 WARN_ON_ONCE(warn && !PageUptodate(page));
583 account_page_dirtied(page, mapping);
584 __xa_set_mark(&mapping->i_pages, page_index(page),
585 PAGECACHE_TAG_DIRTY);
586 }
587 xa_unlock_irqrestore(&mapping->i_pages, flags);
588}
589EXPORT_SYMBOL_GPL(__set_page_dirty);
590
591/*
592 * Add a page to the dirty page list.
593 *
594 * It is a sad fact of life that this function is called from several places
595 * deeply under spinlocking. It may not sleep.
596 *
597 * If the page has buffers, the uptodate buffers are set dirty, to preserve
598 * dirty-state coherency between the page and the buffers. It the page does
599 * not have buffers then when they are later attached they will all be set
600 * dirty.
601 *
602 * The buffers are dirtied before the page is dirtied. There's a small race
603 * window in which a writepage caller may see the page cleanness but not the
604 * buffer dirtiness. That's fine. If this code were to set the page dirty
605 * before the buffers, a concurrent writepage caller could clear the page dirty
606 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
607 * page on the dirty page list.
608 *
609 * We use private_lock to lock against try_to_free_buffers while using the
610 * page's buffer list. Also use this to protect against clean buffers being
611 * added to the page after it was set dirty.
612 *
613 * FIXME: may need to call ->reservepage here as well. That's rather up to the
614 * address_space though.
615 */
616int __set_page_dirty_buffers(struct page *page)
617{
618 int newly_dirty;
619 struct address_space *mapping = page_mapping(page);
620
621 if (unlikely(!mapping))
622 return !TestSetPageDirty(page);
623
624 spin_lock(&mapping->private_lock);
625 if (page_has_buffers(page)) {
626 struct buffer_head *head = page_buffers(page);
627 struct buffer_head *bh = head;
628
629 do {
630 set_buffer_dirty(bh);
631 bh = bh->b_this_page;
632 } while (bh != head);
633 }
634 /*
635 * Lock out page->mem_cgroup migration to keep PageDirty
636 * synchronized with per-memcg dirty page counters.
637 */
638 lock_page_memcg(page);
639 newly_dirty = !TestSetPageDirty(page);
640 spin_unlock(&mapping->private_lock);
641
642 if (newly_dirty)
643 __set_page_dirty(page, mapping, 1);
644
645 unlock_page_memcg(page);
646
647 if (newly_dirty)
648 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
649
650 return newly_dirty;
651}
652EXPORT_SYMBOL(__set_page_dirty_buffers);
653
654/*
655 * Write out and wait upon a list of buffers.
656 *
657 * We have conflicting pressures: we want to make sure that all
658 * initially dirty buffers get waited on, but that any subsequently
659 * dirtied buffers don't. After all, we don't want fsync to last
660 * forever if somebody is actively writing to the file.
661 *
662 * Do this in two main stages: first we copy dirty buffers to a
663 * temporary inode list, queueing the writes as we go. Then we clean
664 * up, waiting for those writes to complete.
665 *
666 * During this second stage, any subsequent updates to the file may end
667 * up refiling the buffer on the original inode's dirty list again, so
668 * there is a chance we will end up with a buffer queued for write but
669 * not yet completed on that list. So, as a final cleanup we go through
670 * the osync code to catch these locked, dirty buffers without requeuing
671 * any newly dirty buffers for write.
672 */
673static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
674{
675 struct buffer_head *bh;
676 struct list_head tmp;
677 struct address_space *mapping;
678 int err = 0, err2;
679 struct blk_plug plug;
680
681 INIT_LIST_HEAD(&tmp);
682 blk_start_plug(&plug);
683
684 spin_lock(lock);
685 while (!list_empty(list)) {
686 bh = BH_ENTRY(list->next);
687 mapping = bh->b_assoc_map;
688 __remove_assoc_queue(bh);
689 /* Avoid race with mark_buffer_dirty_inode() which does
690 * a lockless check and we rely on seeing the dirty bit */
691 smp_mb();
692 if (buffer_dirty(bh) || buffer_locked(bh)) {
693 list_add(&bh->b_assoc_buffers, &tmp);
694 bh->b_assoc_map = mapping;
695 if (buffer_dirty(bh)) {
696 get_bh(bh);
697 spin_unlock(lock);
698 /*
699 * Ensure any pending I/O completes so that
700 * write_dirty_buffer() actually writes the
701 * current contents - it is a noop if I/O is
702 * still in flight on potentially older
703 * contents.
704 */
705 write_dirty_buffer(bh, REQ_SYNC);
706
707 /*
708 * Kick off IO for the previous mapping. Note
709 * that we will not run the very last mapping,
710 * wait_on_buffer() will do that for us
711 * through sync_buffer().
712 */
713 brelse(bh);
714 spin_lock(lock);
715 }
716 }
717 }
718
719 spin_unlock(lock);
720 blk_finish_plug(&plug);
721 spin_lock(lock);
722
723 while (!list_empty(&tmp)) {
724 bh = BH_ENTRY(tmp.prev);
725 get_bh(bh);
726 mapping = bh->b_assoc_map;
727 __remove_assoc_queue(bh);
728 /* Avoid race with mark_buffer_dirty_inode() which does
729 * a lockless check and we rely on seeing the dirty bit */
730 smp_mb();
731 if (buffer_dirty(bh)) {
732 list_add(&bh->b_assoc_buffers,
733 &mapping->private_list);
734 bh->b_assoc_map = mapping;
735 }
736 spin_unlock(lock);
737 wait_on_buffer(bh);
738 if (!buffer_uptodate(bh))
739 err = -EIO;
740 brelse(bh);
741 spin_lock(lock);
742 }
743
744 spin_unlock(lock);
745 err2 = osync_buffers_list(lock, list);
746 if (err)
747 return err;
748 else
749 return err2;
750}
751
752/*
753 * Invalidate any and all dirty buffers on a given inode. We are
754 * probably unmounting the fs, but that doesn't mean we have already
755 * done a sync(). Just drop the buffers from the inode list.
756 *
757 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
758 * assumes that all the buffers are against the blockdev. Not true
759 * for reiserfs.
760 */
761void invalidate_inode_buffers(struct inode *inode)
762{
763 if (inode_has_buffers(inode)) {
764 struct address_space *mapping = &inode->i_data;
765 struct list_head *list = &mapping->private_list;
766 struct address_space *buffer_mapping = mapping->private_data;
767
768 spin_lock(&buffer_mapping->private_lock);
769 while (!list_empty(list))
770 __remove_assoc_queue(BH_ENTRY(list->next));
771 spin_unlock(&buffer_mapping->private_lock);
772 }
773}
774EXPORT_SYMBOL(invalidate_inode_buffers);
775
776/*
777 * Remove any clean buffers from the inode's buffer list. This is called
778 * when we're trying to free the inode itself. Those buffers can pin it.
779 *
780 * Returns true if all buffers were removed.
781 */
782int remove_inode_buffers(struct inode *inode)
783{
784 int ret = 1;
785
786 if (inode_has_buffers(inode)) {
787 struct address_space *mapping = &inode->i_data;
788 struct list_head *list = &mapping->private_list;
789 struct address_space *buffer_mapping = mapping->private_data;
790
791 spin_lock(&buffer_mapping->private_lock);
792 while (!list_empty(list)) {
793 struct buffer_head *bh = BH_ENTRY(list->next);
794 if (buffer_dirty(bh)) {
795 ret = 0;
796 break;
797 }
798 __remove_assoc_queue(bh);
799 }
800 spin_unlock(&buffer_mapping->private_lock);
801 }
802 return ret;
803}
804
805/*
806 * Create the appropriate buffers when given a page for data area and
807 * the size of each buffer.. Use the bh->b_this_page linked list to
808 * follow the buffers created. Return NULL if unable to create more
809 * buffers.
810 *
811 * The retry flag is used to differentiate async IO (paging, swapping)
812 * which may not fail from ordinary buffer allocations.
813 */
814struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
815 bool retry)
816{
817 struct buffer_head *bh, *head;
818 gfp_t gfp = GFP_NOFS | __GFP_ACCOUNT;
819 long offset;
820 struct mem_cgroup *memcg;
821
822 if (retry)
823 gfp |= __GFP_NOFAIL;
824
825 memcg = get_mem_cgroup_from_page(page);
826 memalloc_use_memcg(memcg);
827
828 head = NULL;
829 offset = PAGE_SIZE;
830 while ((offset -= size) >= 0) {
831 bh = alloc_buffer_head(gfp);
832 if (!bh)
833 goto no_grow;
834
835 bh->b_this_page = head;
836 bh->b_blocknr = -1;
837 head = bh;
838
839 bh->b_size = size;
840
841 /* Link the buffer to its page */
842 set_bh_page(bh, page, offset);
843 }
844out:
845 memalloc_unuse_memcg();
846 mem_cgroup_put(memcg);
847 return head;
848/*
849 * In case anything failed, we just free everything we got.
850 */
851no_grow:
852 if (head) {
853 do {
854 bh = head;
855 head = head->b_this_page;
856 free_buffer_head(bh);
857 } while (head);
858 }
859
860 goto out;
861}
862EXPORT_SYMBOL_GPL(alloc_page_buffers);
863
864static inline void
865link_dev_buffers(struct page *page, struct buffer_head *head)
866{
867 struct buffer_head *bh, *tail;
868
869 bh = head;
870 do {
871 tail = bh;
872 bh = bh->b_this_page;
873 } while (bh);
874 tail->b_this_page = head;
875 attach_page_buffers(page, head);
876}
877
878static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
879{
880 sector_t retval = ~((sector_t)0);
881 loff_t sz = i_size_read(bdev->bd_inode);
882
883 if (sz) {
884 unsigned int sizebits = blksize_bits(size);
885 retval = (sz >> sizebits);
886 }
887 return retval;
888}
889
890/*
891 * Initialise the state of a blockdev page's buffers.
892 */
893static sector_t
894init_page_buffers(struct page *page, struct block_device *bdev,
895 sector_t block, int size)
896{
897 struct buffer_head *head = page_buffers(page);
898 struct buffer_head *bh = head;
899 int uptodate = PageUptodate(page);
900 sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode), size);
901
902 do {
903 if (!buffer_mapped(bh)) {
904 bh->b_end_io = NULL;
905 bh->b_private = NULL;
906 bh->b_bdev = bdev;
907 bh->b_blocknr = block;
908 if (uptodate)
909 set_buffer_uptodate(bh);
910 if (block < end_block)
911 set_buffer_mapped(bh);
912 }
913 block++;
914 bh = bh->b_this_page;
915 } while (bh != head);
916
917 /*
918 * Caller needs to validate requested block against end of device.
919 */
920 return end_block;
921}
922
923/*
924 * Create the page-cache page that contains the requested block.
925 *
926 * This is used purely for blockdev mappings.
927 */
928static int
929grow_dev_page(struct block_device *bdev, sector_t block,
930 pgoff_t index, int size, int sizebits, gfp_t gfp)
931{
932 struct inode *inode = bdev->bd_inode;
933 struct page *page;
934 struct buffer_head *bh;
935 sector_t end_block;
936 int ret = 0; /* Will call free_more_memory() */
937 gfp_t gfp_mask;
938
939 gfp_mask = mapping_gfp_constraint(inode->i_mapping, ~__GFP_FS) | gfp;
940
941 /*
942 * XXX: __getblk_slow() can not really deal with failure and
943 * will endlessly loop on improvised global reclaim. Prefer
944 * looping in the allocator rather than here, at least that
945 * code knows what it's doing.
946 */
947 gfp_mask |= __GFP_NOFAIL;
948
949 page = find_or_create_page(inode->i_mapping, index, gfp_mask);
950
951 BUG_ON(!PageLocked(page));
952
953 if (page_has_buffers(page)) {
954 bh = page_buffers(page);
955 if (bh->b_size == size) {
956 end_block = init_page_buffers(page, bdev,
957 (sector_t)index << sizebits,
958 size);
959 goto done;
960 }
961 if (!try_to_free_buffers(page))
962 goto failed;
963 }
964
965 /*
966 * Allocate some buffers for this page
967 */
968 bh = alloc_page_buffers(page, size, true);
969
970 /*
971 * Link the page to the buffers and initialise them. Take the
972 * lock to be atomic wrt __find_get_block(), which does not
973 * run under the page lock.
974 */
975 spin_lock(&inode->i_mapping->private_lock);
976 link_dev_buffers(page, bh);
977 end_block = init_page_buffers(page, bdev, (sector_t)index << sizebits,
978 size);
979 spin_unlock(&inode->i_mapping->private_lock);
980done:
981 ret = (block < end_block) ? 1 : -ENXIO;
982failed:
983 unlock_page(page);
984 put_page(page);
985 return ret;
986}
987
988/*
989 * Create buffers for the specified block device block's page. If
990 * that page was dirty, the buffers are set dirty also.
991 */
992static int
993grow_buffers(struct block_device *bdev, sector_t block, int size, gfp_t gfp)
994{
995 pgoff_t index;
996 int sizebits;
997
998 sizebits = -1;
999 do {
1000 sizebits++;
1001 } while ((size << sizebits) < PAGE_SIZE);
1002
1003 index = block >> sizebits;
1004
1005 /*
1006 * Check for a block which wants to lie outside our maximum possible
1007 * pagecache index. (this comparison is done using sector_t types).
1008 */
1009 if (unlikely(index != block >> sizebits)) {
1010 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1011 "device %pg\n",
1012 __func__, (unsigned long long)block,
1013 bdev);
1014 return -EIO;
1015 }
1016
1017 /* Create a page with the proper size buffers.. */
1018 return grow_dev_page(bdev, block, index, size, sizebits, gfp);
1019}
1020
1021static struct buffer_head *
1022__getblk_slow(struct block_device *bdev, sector_t block,
1023 unsigned size, gfp_t gfp)
1024{
1025 /* Size must be multiple of hard sectorsize */
1026 if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
1027 (size < 512 || size > PAGE_SIZE))) {
1028 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1029 size);
1030 printk(KERN_ERR "logical block size: %d\n",
1031 bdev_logical_block_size(bdev));
1032
1033 dump_stack();
1034 return NULL;
1035 }
1036
1037 for (;;) {
1038 struct buffer_head *bh;
1039 int ret;
1040
1041 bh = __find_get_block(bdev, block, size);
1042 if (bh)
1043 return bh;
1044
1045 ret = grow_buffers(bdev, block, size, gfp);
1046 if (ret < 0)
1047 return NULL;
1048 }
1049}
1050
1051/*
1052 * The relationship between dirty buffers and dirty pages:
1053 *
1054 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1055 * the page is tagged dirty in the page cache.
1056 *
1057 * At all times, the dirtiness of the buffers represents the dirtiness of
1058 * subsections of the page. If the page has buffers, the page dirty bit is
1059 * merely a hint about the true dirty state.
1060 *
1061 * When a page is set dirty in its entirety, all its buffers are marked dirty
1062 * (if the page has buffers).
1063 *
1064 * When a buffer is marked dirty, its page is dirtied, but the page's other
1065 * buffers are not.
1066 *
1067 * Also. When blockdev buffers are explicitly read with bread(), they
1068 * individually become uptodate. But their backing page remains not
1069 * uptodate - even if all of its buffers are uptodate. A subsequent
1070 * block_read_full_page() against that page will discover all the uptodate
1071 * buffers, will set the page uptodate and will perform no I/O.
1072 */
1073
1074/**
1075 * mark_buffer_dirty - mark a buffer_head as needing writeout
1076 * @bh: the buffer_head to mark dirty
1077 *
1078 * mark_buffer_dirty() will set the dirty bit against the buffer, then set
1079 * its backing page dirty, then tag the page as dirty in the page cache
1080 * and then attach the address_space's inode to its superblock's dirty
1081 * inode list.
1082 *
1083 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1084 * i_pages lock and mapping->host->i_lock.
1085 */
1086void mark_buffer_dirty(struct buffer_head *bh)
1087{
1088 WARN_ON_ONCE(!buffer_uptodate(bh));
1089
1090 trace_block_dirty_buffer(bh);
1091
1092 /*
1093 * Very *carefully* optimize the it-is-already-dirty case.
1094 *
1095 * Don't let the final "is it dirty" escape to before we
1096 * perhaps modified the buffer.
1097 */
1098 if (buffer_dirty(bh)) {
1099 smp_mb();
1100 if (buffer_dirty(bh))
1101 return;
1102 }
1103
1104 if (!test_set_buffer_dirty(bh)) {
1105 struct page *page = bh->b_page;
1106 struct address_space *mapping = NULL;
1107
1108 lock_page_memcg(page);
1109 if (!TestSetPageDirty(page)) {
1110 mapping = page_mapping(page);
1111 if (mapping)
1112 __set_page_dirty(page, mapping, 0);
1113 }
1114 unlock_page_memcg(page);
1115 if (mapping)
1116 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
1117 }
1118}
1119EXPORT_SYMBOL(mark_buffer_dirty);
1120
1121void mark_buffer_write_io_error(struct buffer_head *bh)
1122{
1123 set_buffer_write_io_error(bh);
1124 /* FIXME: do we need to set this in both places? */
1125 if (bh->b_page && bh->b_page->mapping)
1126 mapping_set_error(bh->b_page->mapping, -EIO);
1127 if (bh->b_assoc_map)
1128 mapping_set_error(bh->b_assoc_map, -EIO);
1129}
1130EXPORT_SYMBOL(mark_buffer_write_io_error);
1131
1132/*
1133 * Decrement a buffer_head's reference count. If all buffers against a page
1134 * have zero reference count, are clean and unlocked, and if the page is clean
1135 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1136 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1137 * a page but it ends up not being freed, and buffers may later be reattached).
1138 */
1139void __brelse(struct buffer_head * buf)
1140{
1141 if (atomic_read(&buf->b_count)) {
1142 put_bh(buf);
1143 return;
1144 }
1145 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1146}
1147EXPORT_SYMBOL(__brelse);
1148
1149/*
1150 * bforget() is like brelse(), except it discards any
1151 * potentially dirty data.
1152 */
1153void __bforget(struct buffer_head *bh)
1154{
1155 clear_buffer_dirty(bh);
1156 if (bh->b_assoc_map) {
1157 struct address_space *buffer_mapping = bh->b_page->mapping;
1158
1159 spin_lock(&buffer_mapping->private_lock);
1160 list_del_init(&bh->b_assoc_buffers);
1161 bh->b_assoc_map = NULL;
1162 spin_unlock(&buffer_mapping->private_lock);
1163 }
1164 __brelse(bh);
1165}
1166EXPORT_SYMBOL(__bforget);
1167
1168static struct buffer_head *__bread_slow(struct buffer_head *bh)
1169{
1170 lock_buffer(bh);
1171 if (buffer_uptodate(bh)) {
1172 unlock_buffer(bh);
1173 return bh;
1174 } else {
1175 get_bh(bh);
1176 bh->b_end_io = end_buffer_read_sync;
1177 submit_bh(REQ_OP_READ, 0, bh);
1178 wait_on_buffer(bh);
1179 if (buffer_uptodate(bh))
1180 return bh;
1181 }
1182 brelse(bh);
1183 return NULL;
1184}
1185
1186/*
1187 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1188 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1189 * refcount elevated by one when they're in an LRU. A buffer can only appear
1190 * once in a particular CPU's LRU. A single buffer can be present in multiple
1191 * CPU's LRUs at the same time.
1192 *
1193 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1194 * sb_find_get_block().
1195 *
1196 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1197 * a local interrupt disable for that.
1198 */
1199
1200#define BH_LRU_SIZE 16
1201
1202struct bh_lru {
1203 struct buffer_head *bhs[BH_LRU_SIZE];
1204};
1205
1206static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1207
1208#ifdef CONFIG_SMP
1209#define bh_lru_lock() local_irq_disable()
1210#define bh_lru_unlock() local_irq_enable()
1211#else
1212#define bh_lru_lock() preempt_disable()
1213#define bh_lru_unlock() preempt_enable()
1214#endif
1215
1216static inline void check_irqs_on(void)
1217{
1218#ifdef irqs_disabled
1219 BUG_ON(irqs_disabled());
1220#endif
1221}
1222
1223/*
1224 * Install a buffer_head into this cpu's LRU. If not already in the LRU, it is
1225 * inserted at the front, and the buffer_head at the back if any is evicted.
1226 * Or, if already in the LRU it is moved to the front.
1227 */
1228static void bh_lru_install(struct buffer_head *bh)
1229{
1230 struct buffer_head *evictee = bh;
1231 struct bh_lru *b;
1232 int i;
1233
1234 check_irqs_on();
1235 bh_lru_lock();
1236
1237 b = this_cpu_ptr(&bh_lrus);
1238 for (i = 0; i < BH_LRU_SIZE; i++) {
1239 swap(evictee, b->bhs[i]);
1240 if (evictee == bh) {
1241 bh_lru_unlock();
1242 return;
1243 }
1244 }
1245
1246 get_bh(bh);
1247 bh_lru_unlock();
1248 brelse(evictee);
1249}
1250
1251/*
1252 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1253 */
1254static struct buffer_head *
1255lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1256{
1257 struct buffer_head *ret = NULL;
1258 unsigned int i;
1259
1260 check_irqs_on();
1261 bh_lru_lock();
1262 for (i = 0; i < BH_LRU_SIZE; i++) {
1263 struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
1264
1265 if (bh && bh->b_blocknr == block && bh->b_bdev == bdev &&
1266 bh->b_size == size) {
1267 if (i) {
1268 while (i) {
1269 __this_cpu_write(bh_lrus.bhs[i],
1270 __this_cpu_read(bh_lrus.bhs[i - 1]));
1271 i--;
1272 }
1273 __this_cpu_write(bh_lrus.bhs[0], bh);
1274 }
1275 get_bh(bh);
1276 ret = bh;
1277 break;
1278 }
1279 }
1280 bh_lru_unlock();
1281 return ret;
1282}
1283
1284/*
1285 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1286 * it in the LRU and mark it as accessed. If it is not present then return
1287 * NULL
1288 */
1289struct buffer_head *
1290__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1291{
1292 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1293
1294 if (bh == NULL) {
1295 /* __find_get_block_slow will mark the page accessed */
1296 bh = __find_get_block_slow(bdev, block);
1297 if (bh)
1298 bh_lru_install(bh);
1299 } else
1300 touch_buffer(bh);
1301
1302 return bh;
1303}
1304EXPORT_SYMBOL(__find_get_block);
1305
1306/*
1307 * __getblk_gfp() will locate (and, if necessary, create) the buffer_head
1308 * which corresponds to the passed block_device, block and size. The
1309 * returned buffer has its reference count incremented.
1310 *
1311 * __getblk_gfp() will lock up the machine if grow_dev_page's
1312 * try_to_free_buffers() attempt is failing. FIXME, perhaps?
1313 */
1314struct buffer_head *
1315__getblk_gfp(struct block_device *bdev, sector_t block,
1316 unsigned size, gfp_t gfp)
1317{
1318 struct buffer_head *bh = __find_get_block(bdev, block, size);
1319
1320 might_sleep();
1321 if (bh == NULL)
1322 bh = __getblk_slow(bdev, block, size, gfp);
1323 return bh;
1324}
1325EXPORT_SYMBOL(__getblk_gfp);
1326
1327/*
1328 * Do async read-ahead on a buffer..
1329 */
1330void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1331{
1332 struct buffer_head *bh = __getblk(bdev, block, size);
1333 if (likely(bh)) {
1334 ll_rw_block(REQ_OP_READ, REQ_RAHEAD, 1, &bh);
1335 brelse(bh);
1336 }
1337}
1338EXPORT_SYMBOL(__breadahead);
1339
1340/**
1341 * __bread_gfp() - reads a specified block and returns the bh
1342 * @bdev: the block_device to read from
1343 * @block: number of block
1344 * @size: size (in bytes) to read
1345 * @gfp: page allocation flag
1346 *
1347 * Reads a specified block, and returns buffer head that contains it.
1348 * The page cache can be allocated from non-movable area
1349 * not to prevent page migration if you set gfp to zero.
1350 * It returns NULL if the block was unreadable.
1351 */
1352struct buffer_head *
1353__bread_gfp(struct block_device *bdev, sector_t block,
1354 unsigned size, gfp_t gfp)
1355{
1356 struct buffer_head *bh = __getblk_gfp(bdev, block, size, gfp);
1357
1358 if (likely(bh) && !buffer_uptodate(bh))
1359 bh = __bread_slow(bh);
1360 return bh;
1361}
1362EXPORT_SYMBOL(__bread_gfp);
1363
1364/*
1365 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1366 * This doesn't race because it runs in each cpu either in irq
1367 * or with preempt disabled.
1368 */
1369static void invalidate_bh_lru(void *arg)
1370{
1371 struct bh_lru *b = &get_cpu_var(bh_lrus);
1372 int i;
1373
1374 for (i = 0; i < BH_LRU_SIZE; i++) {
1375 brelse(b->bhs[i]);
1376 b->bhs[i] = NULL;
1377 }
1378 put_cpu_var(bh_lrus);
1379}
1380
1381static bool has_bh_in_lru(int cpu, void *dummy)
1382{
1383 struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1384 int i;
1385
1386 for (i = 0; i < BH_LRU_SIZE; i++) {
1387 if (b->bhs[i])
1388 return 1;
1389 }
1390
1391 return 0;
1392}
1393
1394void invalidate_bh_lrus(void)
1395{
1396 on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL);
1397}
1398EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1399
1400void set_bh_page(struct buffer_head *bh,
1401 struct page *page, unsigned long offset)
1402{
1403 bh->b_page = page;
1404 BUG_ON(offset >= PAGE_SIZE);
1405 if (PageHighMem(page))
1406 /*
1407 * This catches illegal uses and preserves the offset:
1408 */
1409 bh->b_data = (char *)(0 + offset);
1410 else
1411 bh->b_data = page_address(page) + offset;
1412}
1413EXPORT_SYMBOL(set_bh_page);
1414
1415/*
1416 * Called when truncating a buffer on a page completely.
1417 */
1418
1419/* Bits that are cleared during an invalidate */
1420#define BUFFER_FLAGS_DISCARD \
1421 (1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \
1422 1 << BH_Delay | 1 << BH_Unwritten)
1423
1424static void discard_buffer(struct buffer_head * bh)
1425{
1426 unsigned long b_state, b_state_old;
1427
1428 lock_buffer(bh);
1429 clear_buffer_dirty(bh);
1430 bh->b_bdev = NULL;
1431 b_state = bh->b_state;
1432 for (;;) {
1433 b_state_old = cmpxchg(&bh->b_state, b_state,
1434 (b_state & ~BUFFER_FLAGS_DISCARD));
1435 if (b_state_old == b_state)
1436 break;
1437 b_state = b_state_old;
1438 }
1439 unlock_buffer(bh);
1440}
1441
1442/**
1443 * block_invalidatepage - invalidate part or all of a buffer-backed page
1444 *
1445 * @page: the page which is affected
1446 * @offset: start of the range to invalidate
1447 * @length: length of the range to invalidate
1448 *
1449 * block_invalidatepage() is called when all or part of the page has become
1450 * invalidated by a truncate operation.
1451 *
1452 * block_invalidatepage() does not have to release all buffers, but it must
1453 * ensure that no dirty buffer is left outside @offset and that no I/O
1454 * is underway against any of the blocks which are outside the truncation
1455 * point. Because the caller is about to free (and possibly reuse) those
1456 * blocks on-disk.
1457 */
1458void block_invalidatepage(struct page *page, unsigned int offset,
1459 unsigned int length)
1460{
1461 struct buffer_head *head, *bh, *next;
1462 unsigned int curr_off = 0;
1463 unsigned int stop = length + offset;
1464
1465 BUG_ON(!PageLocked(page));
1466 if (!page_has_buffers(page))
1467 goto out;
1468
1469 /*
1470 * Check for overflow
1471 */
1472 BUG_ON(stop > PAGE_SIZE || stop < length);
1473
1474 head = page_buffers(page);
1475 bh = head;
1476 do {
1477 unsigned int next_off = curr_off + bh->b_size;
1478 next = bh->b_this_page;
1479
1480 /*
1481 * Are we still fully in range ?
1482 */
1483 if (next_off > stop)
1484 goto out;
1485
1486 /*
1487 * is this block fully invalidated?
1488 */
1489 if (offset <= curr_off)
1490 discard_buffer(bh);
1491 curr_off = next_off;
1492 bh = next;
1493 } while (bh != head);
1494
1495 /*
1496 * We release buffers only if the entire page is being invalidated.
1497 * The get_block cached value has been unconditionally invalidated,
1498 * so real IO is not possible anymore.
1499 */
1500 if (length == PAGE_SIZE)
1501 try_to_release_page(page, 0);
1502out:
1503 return;
1504}
1505EXPORT_SYMBOL(block_invalidatepage);
1506
1507
1508/*
1509 * We attach and possibly dirty the buffers atomically wrt
1510 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1511 * is already excluded via the page lock.
1512 */
1513void create_empty_buffers(struct page *page,
1514 unsigned long blocksize, unsigned long b_state)
1515{
1516 struct buffer_head *bh, *head, *tail;
1517
1518 head = alloc_page_buffers(page, blocksize, true);
1519 bh = head;
1520 do {
1521 bh->b_state |= b_state;
1522 tail = bh;
1523 bh = bh->b_this_page;
1524 } while (bh);
1525 tail->b_this_page = head;
1526
1527 spin_lock(&page->mapping->private_lock);
1528 if (PageUptodate(page) || PageDirty(page)) {
1529 bh = head;
1530 do {
1531 if (PageDirty(page))
1532 set_buffer_dirty(bh);
1533 if (PageUptodate(page))
1534 set_buffer_uptodate(bh);
1535 bh = bh->b_this_page;
1536 } while (bh != head);
1537 }
1538 attach_page_buffers(page, head);
1539 spin_unlock(&page->mapping->private_lock);
1540}
1541EXPORT_SYMBOL(create_empty_buffers);
1542
1543/**
1544 * clean_bdev_aliases: clean a range of buffers in block device
1545 * @bdev: Block device to clean buffers in
1546 * @block: Start of a range of blocks to clean
1547 * @len: Number of blocks to clean
1548 *
1549 * We are taking a range of blocks for data and we don't want writeback of any
1550 * buffer-cache aliases starting from return from this function and until the
1551 * moment when something will explicitly mark the buffer dirty (hopefully that
1552 * will not happen until we will free that block ;-) We don't even need to mark
1553 * it not-uptodate - nobody can expect anything from a newly allocated buffer
1554 * anyway. We used to use unmap_buffer() for such invalidation, but that was
1555 * wrong. We definitely don't want to mark the alias unmapped, for example - it
1556 * would confuse anyone who might pick it with bread() afterwards...
1557 *
1558 * Also.. Note that bforget() doesn't lock the buffer. So there can be
1559 * writeout I/O going on against recently-freed buffers. We don't wait on that
1560 * I/O in bforget() - it's more efficient to wait on the I/O only if we really
1561 * need to. That happens here.
1562 */
1563void clean_bdev_aliases(struct block_device *bdev, sector_t block, sector_t len)
1564{
1565 struct inode *bd_inode = bdev->bd_inode;
1566 struct address_space *bd_mapping = bd_inode->i_mapping;
1567 struct pagevec pvec;
1568 pgoff_t index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
1569 pgoff_t end;
1570 int i, count;
1571 struct buffer_head *bh;
1572 struct buffer_head *head;
1573
1574 end = (block + len - 1) >> (PAGE_SHIFT - bd_inode->i_blkbits);
1575 pagevec_init(&pvec);
1576 while (pagevec_lookup_range(&pvec, bd_mapping, &index, end)) {
1577 count = pagevec_count(&pvec);
1578 for (i = 0; i < count; i++) {
1579 struct page *page = pvec.pages[i];
1580
1581 if (!page_has_buffers(page))
1582 continue;
1583 /*
1584 * We use page lock instead of bd_mapping->private_lock
1585 * to pin buffers here since we can afford to sleep and
1586 * it scales better than a global spinlock lock.
1587 */
1588 lock_page(page);
1589 /* Recheck when the page is locked which pins bhs */
1590 if (!page_has_buffers(page))
1591 goto unlock_page;
1592 head = page_buffers(page);
1593 bh = head;
1594 do {
1595 if (!buffer_mapped(bh) || (bh->b_blocknr < block))
1596 goto next;
1597 if (bh->b_blocknr >= block + len)
1598 break;
1599 clear_buffer_dirty(bh);
1600 wait_on_buffer(bh);
1601 clear_buffer_req(bh);
1602next:
1603 bh = bh->b_this_page;
1604 } while (bh != head);
1605unlock_page:
1606 unlock_page(page);
1607 }
1608 pagevec_release(&pvec);
1609 cond_resched();
1610 /* End of range already reached? */
1611 if (index > end || !index)
1612 break;
1613 }
1614}
1615EXPORT_SYMBOL(clean_bdev_aliases);
1616
1617/*
1618 * Size is a power-of-two in the range 512..PAGE_SIZE,
1619 * and the case we care about most is PAGE_SIZE.
1620 *
1621 * So this *could* possibly be written with those
1622 * constraints in mind (relevant mostly if some
1623 * architecture has a slow bit-scan instruction)
1624 */
1625static inline int block_size_bits(unsigned int blocksize)
1626{
1627 return ilog2(blocksize);
1628}
1629
1630static struct buffer_head *create_page_buffers(struct page *page, struct inode *inode, unsigned int b_state)
1631{
1632 BUG_ON(!PageLocked(page));
1633
1634 if (!page_has_buffers(page))
1635 create_empty_buffers(page, 1 << READ_ONCE(inode->i_blkbits),
1636 b_state);
1637 return page_buffers(page);
1638}
1639
1640/*
1641 * NOTE! All mapped/uptodate combinations are valid:
1642 *
1643 * Mapped Uptodate Meaning
1644 *
1645 * No No "unknown" - must do get_block()
1646 * No Yes "hole" - zero-filled
1647 * Yes No "allocated" - allocated on disk, not read in
1648 * Yes Yes "valid" - allocated and up-to-date in memory.
1649 *
1650 * "Dirty" is valid only with the last case (mapped+uptodate).
1651 */
1652
1653/*
1654 * While block_write_full_page is writing back the dirty buffers under
1655 * the page lock, whoever dirtied the buffers may decide to clean them
1656 * again at any time. We handle that by only looking at the buffer
1657 * state inside lock_buffer().
1658 *
1659 * If block_write_full_page() is called for regular writeback
1660 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1661 * locked buffer. This only can happen if someone has written the buffer
1662 * directly, with submit_bh(). At the address_space level PageWriteback
1663 * prevents this contention from occurring.
1664 *
1665 * If block_write_full_page() is called with wbc->sync_mode ==
1666 * WB_SYNC_ALL, the writes are posted using REQ_SYNC; this
1667 * causes the writes to be flagged as synchronous writes.
1668 */
1669int __block_write_full_page(struct inode *inode, struct page *page,
1670 get_block_t *get_block, struct writeback_control *wbc,
1671 bh_end_io_t *handler)
1672{
1673 int err;
1674 sector_t block;
1675 sector_t last_block;
1676 struct buffer_head *bh, *head;
1677 unsigned int blocksize, bbits;
1678 int nr_underway = 0;
1679 int write_flags = wbc_to_write_flags(wbc);
1680
1681 head = create_page_buffers(page, inode,
1682 (1 << BH_Dirty)|(1 << BH_Uptodate));
1683
1684 /*
1685 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1686 * here, and the (potentially unmapped) buffers may become dirty at
1687 * any time. If a buffer becomes dirty here after we've inspected it
1688 * then we just miss that fact, and the page stays dirty.
1689 *
1690 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1691 * handle that here by just cleaning them.
1692 */
1693
1694 bh = head;
1695 blocksize = bh->b_size;
1696 bbits = block_size_bits(blocksize);
1697
1698 block = (sector_t)page->index << (PAGE_SHIFT - bbits);
1699 last_block = (i_size_read(inode) - 1) >> bbits;
1700
1701 /*
1702 * Get all the dirty buffers mapped to disk addresses and
1703 * handle any aliases from the underlying blockdev's mapping.
1704 */
1705 do {
1706 if (block > last_block) {
1707 /*
1708 * mapped buffers outside i_size will occur, because
1709 * this page can be outside i_size when there is a
1710 * truncate in progress.
1711 */
1712 /*
1713 * The buffer was zeroed by block_write_full_page()
1714 */
1715 clear_buffer_dirty(bh);
1716 set_buffer_uptodate(bh);
1717 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1718 buffer_dirty(bh)) {
1719 WARN_ON(bh->b_size != blocksize);
1720 err = get_block(inode, block, bh, 1);
1721 if (err)
1722 goto recover;
1723 clear_buffer_delay(bh);
1724 if (buffer_new(bh)) {
1725 /* blockdev mappings never come here */
1726 clear_buffer_new(bh);
1727 clean_bdev_bh_alias(bh);
1728 }
1729 }
1730 bh = bh->b_this_page;
1731 block++;
1732 } while (bh != head);
1733
1734 do {
1735 if (!buffer_mapped(bh))
1736 continue;
1737 /*
1738 * If it's a fully non-blocking write attempt and we cannot
1739 * lock the buffer then redirty the page. Note that this can
1740 * potentially cause a busy-wait loop from writeback threads
1741 * and kswapd activity, but those code paths have their own
1742 * higher-level throttling.
1743 */
1744 if (wbc->sync_mode != WB_SYNC_NONE) {
1745 lock_buffer(bh);
1746 } else if (!trylock_buffer(bh)) {
1747 redirty_page_for_writepage(wbc, page);
1748 continue;
1749 }
1750 if (test_clear_buffer_dirty(bh)) {
1751 mark_buffer_async_write_endio(bh, handler);
1752 } else {
1753 unlock_buffer(bh);
1754 }
1755 } while ((bh = bh->b_this_page) != head);
1756
1757 /*
1758 * The page and its buffers are protected by PageWriteback(), so we can
1759 * drop the bh refcounts early.
1760 */
1761 BUG_ON(PageWriteback(page));
1762 set_page_writeback(page);
1763
1764 do {
1765 struct buffer_head *next = bh->b_this_page;
1766 if (buffer_async_write(bh)) {
1767 submit_bh_wbc(REQ_OP_WRITE, write_flags, bh,
1768 inode->i_write_hint, wbc);
1769 nr_underway++;
1770 }
1771 bh = next;
1772 } while (bh != head);
1773 unlock_page(page);
1774
1775 err = 0;
1776done:
1777 if (nr_underway == 0) {
1778 /*
1779 * The page was marked dirty, but the buffers were
1780 * clean. Someone wrote them back by hand with
1781 * ll_rw_block/submit_bh. A rare case.
1782 */
1783 end_page_writeback(page);
1784
1785 /*
1786 * The page and buffer_heads can be released at any time from
1787 * here on.
1788 */
1789 }
1790 return err;
1791
1792recover:
1793 /*
1794 * ENOSPC, or some other error. We may already have added some
1795 * blocks to the file, so we need to write these out to avoid
1796 * exposing stale data.
1797 * The page is currently locked and not marked for writeback
1798 */
1799 bh = head;
1800 /* Recovery: lock and submit the mapped buffers */
1801 do {
1802 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1803 !buffer_delay(bh)) {
1804 lock_buffer(bh);
1805 mark_buffer_async_write_endio(bh, handler);
1806 } else {
1807 /*
1808 * The buffer may have been set dirty during
1809 * attachment to a dirty page.
1810 */
1811 clear_buffer_dirty(bh);
1812 }
1813 } while ((bh = bh->b_this_page) != head);
1814 SetPageError(page);
1815 BUG_ON(PageWriteback(page));
1816 mapping_set_error(page->mapping, err);
1817 set_page_writeback(page);
1818 do {
1819 struct buffer_head *next = bh->b_this_page;
1820 if (buffer_async_write(bh)) {
1821 clear_buffer_dirty(bh);
1822 submit_bh_wbc(REQ_OP_WRITE, write_flags, bh,
1823 inode->i_write_hint, wbc);
1824 nr_underway++;
1825 }
1826 bh = next;
1827 } while (bh != head);
1828 unlock_page(page);
1829 goto done;
1830}
1831EXPORT_SYMBOL(__block_write_full_page);
1832
1833/*
1834 * If a page has any new buffers, zero them out here, and mark them uptodate
1835 * and dirty so they'll be written out (in order to prevent uninitialised
1836 * block data from leaking). And clear the new bit.
1837 */
1838void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1839{
1840 unsigned int block_start, block_end;
1841 struct buffer_head *head, *bh;
1842
1843 BUG_ON(!PageLocked(page));
1844 if (!page_has_buffers(page))
1845 return;
1846
1847 bh = head = page_buffers(page);
1848 block_start = 0;
1849 do {
1850 block_end = block_start + bh->b_size;
1851
1852 if (buffer_new(bh)) {
1853 if (block_end > from && block_start < to) {
1854 if (!PageUptodate(page)) {
1855 unsigned start, size;
1856
1857 start = max(from, block_start);
1858 size = min(to, block_end) - start;
1859
1860 zero_user(page, start, size);
1861 set_buffer_uptodate(bh);
1862 }
1863
1864 clear_buffer_new(bh);
1865 mark_buffer_dirty(bh);
1866 }
1867 }
1868
1869 block_start = block_end;
1870 bh = bh->b_this_page;
1871 } while (bh != head);
1872}
1873EXPORT_SYMBOL(page_zero_new_buffers);
1874
1875static void
1876iomap_to_bh(struct inode *inode, sector_t block, struct buffer_head *bh,
1877 struct iomap *iomap)
1878{
1879 loff_t offset = block << inode->i_blkbits;
1880
1881 bh->b_bdev = iomap->bdev;
1882
1883 /*
1884 * Block points to offset in file we need to map, iomap contains
1885 * the offset at which the map starts. If the map ends before the
1886 * current block, then do not map the buffer and let the caller
1887 * handle it.
1888 */
1889 BUG_ON(offset >= iomap->offset + iomap->length);
1890
1891 switch (iomap->type) {
1892 case IOMAP_HOLE:
1893 /*
1894 * If the buffer is not up to date or beyond the current EOF,
1895 * we need to mark it as new to ensure sub-block zeroing is
1896 * executed if necessary.
1897 */
1898 if (!buffer_uptodate(bh) ||
1899 (offset >= i_size_read(inode)))
1900 set_buffer_new(bh);
1901 break;
1902 case IOMAP_DELALLOC:
1903 if (!buffer_uptodate(bh) ||
1904 (offset >= i_size_read(inode)))
1905 set_buffer_new(bh);
1906 set_buffer_uptodate(bh);
1907 set_buffer_mapped(bh);
1908 set_buffer_delay(bh);
1909 break;
1910 case IOMAP_UNWRITTEN:
1911 /*
1912 * For unwritten regions, we always need to ensure that regions
1913 * in the block we are not writing to are zeroed. Mark the
1914 * buffer as new to ensure this.
1915 */
1916 set_buffer_new(bh);
1917 set_buffer_unwritten(bh);
1918 /* FALLTHRU */
1919 case IOMAP_MAPPED:
1920 if ((iomap->flags & IOMAP_F_NEW) ||
1921 offset >= i_size_read(inode))
1922 set_buffer_new(bh);
1923 bh->b_blocknr = (iomap->addr + offset - iomap->offset) >>
1924 inode->i_blkbits;
1925 set_buffer_mapped(bh);
1926 break;
1927 }
1928}
1929
1930int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
1931 get_block_t *get_block, struct iomap *iomap)
1932{
1933 unsigned from = pos & (PAGE_SIZE - 1);
1934 unsigned to = from + len;
1935 struct inode *inode = page->mapping->host;
1936 unsigned block_start, block_end;
1937 sector_t block;
1938 int err = 0;
1939 unsigned blocksize, bbits;
1940 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1941
1942 BUG_ON(!PageLocked(page));
1943 BUG_ON(from > PAGE_SIZE);
1944 BUG_ON(to > PAGE_SIZE);
1945 BUG_ON(from > to);
1946
1947 head = create_page_buffers(page, inode, 0);
1948 blocksize = head->b_size;
1949 bbits = block_size_bits(blocksize);
1950
1951 block = (sector_t)page->index << (PAGE_SHIFT - bbits);
1952
1953 for(bh = head, block_start = 0; bh != head || !block_start;
1954 block++, block_start=block_end, bh = bh->b_this_page) {
1955 block_end = block_start + blocksize;
1956 if (block_end <= from || block_start >= to) {
1957 if (PageUptodate(page)) {
1958 if (!buffer_uptodate(bh))
1959 set_buffer_uptodate(bh);
1960 }
1961 continue;
1962 }
1963 if (buffer_new(bh))
1964 clear_buffer_new(bh);
1965 if (!buffer_mapped(bh)) {
1966 WARN_ON(bh->b_size != blocksize);
1967 if (get_block) {
1968 err = get_block(inode, block, bh, 1);
1969 if (err)
1970 break;
1971 } else {
1972 iomap_to_bh(inode, block, bh, iomap);
1973 }
1974
1975 if (buffer_new(bh)) {
1976 clean_bdev_bh_alias(bh);
1977 if (PageUptodate(page)) {
1978 clear_buffer_new(bh);
1979 set_buffer_uptodate(bh);
1980 mark_buffer_dirty(bh);
1981 continue;
1982 }
1983 if (block_end > to || block_start < from)
1984 zero_user_segments(page,
1985 to, block_end,
1986 block_start, from);
1987 continue;
1988 }
1989 }
1990 if (PageUptodate(page)) {
1991 if (!buffer_uptodate(bh))
1992 set_buffer_uptodate(bh);
1993 continue;
1994 }
1995 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1996 !buffer_unwritten(bh) &&
1997 (block_start < from || block_end > to)) {
1998 ll_rw_block(REQ_OP_READ, 0, 1, &bh);
1999 *wait_bh++=bh;
2000 }
2001 }
2002 /*
2003 * If we issued read requests - let them complete.
2004 */
2005 while(wait_bh > wait) {
2006 wait_on_buffer(*--wait_bh);
2007 if (!buffer_uptodate(*wait_bh))
2008 err = -EIO;
2009 }
2010 if (unlikely(err))
2011 page_zero_new_buffers(page, from, to);
2012 return err;
2013}
2014
2015int __block_write_begin(struct page *page, loff_t pos, unsigned len,
2016 get_block_t *get_block)
2017{
2018 return __block_write_begin_int(page, pos, len, get_block, NULL);
2019}
2020EXPORT_SYMBOL(__block_write_begin);
2021
2022static int __block_commit_write(struct inode *inode, struct page *page,
2023 unsigned from, unsigned to)
2024{
2025 unsigned block_start, block_end;
2026 int partial = 0;
2027 unsigned blocksize;
2028 struct buffer_head *bh, *head;
2029
2030 bh = head = page_buffers(page);
2031 blocksize = bh->b_size;
2032
2033 block_start = 0;
2034 do {
2035 block_end = block_start + blocksize;
2036 if (block_end <= from || block_start >= to) {
2037 if (!buffer_uptodate(bh))
2038 partial = 1;
2039 } else {
2040 set_buffer_uptodate(bh);
2041 mark_buffer_dirty(bh);
2042 }
2043 clear_buffer_new(bh);
2044
2045 block_start = block_end;
2046 bh = bh->b_this_page;
2047 } while (bh != head);
2048
2049 /*
2050 * If this is a partial write which happened to make all buffers
2051 * uptodate then we can optimize away a bogus readpage() for
2052 * the next read(). Here we 'discover' whether the page went
2053 * uptodate as a result of this (potentially partial) write.
2054 */
2055 if (!partial)
2056 SetPageUptodate(page);
2057 return 0;
2058}
2059
2060/*
2061 * block_write_begin takes care of the basic task of block allocation and
2062 * bringing partial write blocks uptodate first.
2063 *
2064 * The filesystem needs to handle block truncation upon failure.
2065 */
2066int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
2067 unsigned flags, struct page **pagep, get_block_t *get_block)
2068{
2069 pgoff_t index = pos >> PAGE_SHIFT;
2070 struct page *page;
2071 int status;
2072
2073 page = grab_cache_page_write_begin(mapping, index, flags);
2074 if (!page)
2075 return -ENOMEM;
2076
2077 status = __block_write_begin(page, pos, len, get_block);
2078 if (unlikely(status)) {
2079 unlock_page(page);
2080 put_page(page);
2081 page = NULL;
2082 }
2083
2084 *pagep = page;
2085 return status;
2086}
2087EXPORT_SYMBOL(block_write_begin);
2088
2089int block_write_end(struct file *file, struct address_space *mapping,
2090 loff_t pos, unsigned len, unsigned copied,
2091 struct page *page, void *fsdata)
2092{
2093 struct inode *inode = mapping->host;
2094 unsigned start;
2095
2096 start = pos & (PAGE_SIZE - 1);
2097
2098 if (unlikely(copied < len)) {
2099 /*
2100 * The buffers that were written will now be uptodate, so we
2101 * don't have to worry about a readpage reading them and
2102 * overwriting a partial write. However if we have encountered
2103 * a short write and only partially written into a buffer, it
2104 * will not be marked uptodate, so a readpage might come in and
2105 * destroy our partial write.
2106 *
2107 * Do the simplest thing, and just treat any short write to a
2108 * non uptodate page as a zero-length write, and force the
2109 * caller to redo the whole thing.
2110 */
2111 if (!PageUptodate(page))
2112 copied = 0;
2113
2114 page_zero_new_buffers(page, start+copied, start+len);
2115 }
2116 flush_dcache_page(page);
2117
2118 /* This could be a short (even 0-length) commit */
2119 __block_commit_write(inode, page, start, start+copied);
2120
2121 return copied;
2122}
2123EXPORT_SYMBOL(block_write_end);
2124
2125int generic_write_end(struct file *file, struct address_space *mapping,
2126 loff_t pos, unsigned len, unsigned copied,
2127 struct page *page, void *fsdata)
2128{
2129 struct inode *inode = mapping->host;
2130 loff_t old_size = inode->i_size;
2131 bool i_size_changed = false;
2132
2133 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2134
2135 /*
2136 * No need to use i_size_read() here, the i_size cannot change under us
2137 * because we hold i_rwsem.
2138 *
2139 * But it's important to update i_size while still holding page lock:
2140 * page writeout could otherwise come in and zero beyond i_size.
2141 */
2142 if (pos + copied > inode->i_size) {
2143 i_size_write(inode, pos + copied);
2144 i_size_changed = true;
2145 }
2146
2147 unlock_page(page);
2148 put_page(page);
2149
2150 if (old_size < pos)
2151 pagecache_isize_extended(inode, old_size, pos);
2152 /*
2153 * Don't mark the inode dirty under page lock. First, it unnecessarily
2154 * makes the holding time of page lock longer. Second, it forces lock
2155 * ordering of page lock and transaction start for journaling
2156 * filesystems.
2157 */
2158 if (i_size_changed)
2159 mark_inode_dirty(inode);
2160 return copied;
2161}
2162EXPORT_SYMBOL(generic_write_end);
2163
2164/*
2165 * block_is_partially_uptodate checks whether buffers within a page are
2166 * uptodate or not.
2167 *
2168 * Returns true if all buffers which correspond to a file portion
2169 * we want to read are uptodate.
2170 */
2171int block_is_partially_uptodate(struct page *page, unsigned long from,
2172 unsigned long count)
2173{
2174 unsigned block_start, block_end, blocksize;
2175 unsigned to;
2176 struct buffer_head *bh, *head;
2177 int ret = 1;
2178
2179 if (!page_has_buffers(page))
2180 return 0;
2181
2182 head = page_buffers(page);
2183 blocksize = head->b_size;
2184 to = min_t(unsigned, PAGE_SIZE - from, count);
2185 to = from + to;
2186 if (from < blocksize && to > PAGE_SIZE - blocksize)
2187 return 0;
2188
2189 bh = head;
2190 block_start = 0;
2191 do {
2192 block_end = block_start + blocksize;
2193 if (block_end > from && block_start < to) {
2194 if (!buffer_uptodate(bh)) {
2195 ret = 0;
2196 break;
2197 }
2198 if (block_end >= to)
2199 break;
2200 }
2201 block_start = block_end;
2202 bh = bh->b_this_page;
2203 } while (bh != head);
2204
2205 return ret;
2206}
2207EXPORT_SYMBOL(block_is_partially_uptodate);
2208
2209/*
2210 * Generic "read page" function for block devices that have the normal
2211 * get_block functionality. This is most of the block device filesystems.
2212 * Reads the page asynchronously --- the unlock_buffer() and
2213 * set/clear_buffer_uptodate() functions propagate buffer state into the
2214 * page struct once IO has completed.
2215 */
2216int block_read_full_page(struct page *page, get_block_t *get_block)
2217{
2218 struct inode *inode = page->mapping->host;
2219 sector_t iblock, lblock;
2220 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2221 unsigned int blocksize, bbits;
2222 int nr, i;
2223 int fully_mapped = 1;
2224
2225 head = create_page_buffers(page, inode, 0);
2226 blocksize = head->b_size;
2227 bbits = block_size_bits(blocksize);
2228
2229 iblock = (sector_t)page->index << (PAGE_SHIFT - bbits);
2230 lblock = (i_size_read(inode)+blocksize-1) >> bbits;
2231 bh = head;
2232 nr = 0;
2233 i = 0;
2234
2235 do {
2236 if (buffer_uptodate(bh))
2237 continue;
2238
2239 if (!buffer_mapped(bh)) {
2240 int err = 0;
2241
2242 fully_mapped = 0;
2243 if (iblock < lblock) {
2244 WARN_ON(bh->b_size != blocksize);
2245 err = get_block(inode, iblock, bh, 0);
2246 if (err)
2247 SetPageError(page);
2248 }
2249 if (!buffer_mapped(bh)) {
2250 zero_user(page, i * blocksize, blocksize);
2251 if (!err)
2252 set_buffer_uptodate(bh);
2253 continue;
2254 }
2255 /*
2256 * get_block() might have updated the buffer
2257 * synchronously
2258 */
2259 if (buffer_uptodate(bh))
2260 continue;
2261 }
2262 arr[nr++] = bh;
2263 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2264
2265 if (fully_mapped)
2266 SetPageMappedToDisk(page);
2267
2268 if (!nr) {
2269 /*
2270 * All buffers are uptodate - we can set the page uptodate
2271 * as well. But not if get_block() returned an error.
2272 */
2273 if (!PageError(page))
2274 SetPageUptodate(page);
2275 unlock_page(page);
2276 return 0;
2277 }
2278
2279 /* Stage two: lock the buffers */
2280 for (i = 0; i < nr; i++) {
2281 bh = arr[i];
2282 lock_buffer(bh);
2283 mark_buffer_async_read(bh);
2284 }
2285
2286 /*
2287 * Stage 3: start the IO. Check for uptodateness
2288 * inside the buffer lock in case another process reading
2289 * the underlying blockdev brought it uptodate (the sct fix).
2290 */
2291 for (i = 0; i < nr; i++) {
2292 bh = arr[i];
2293 if (buffer_uptodate(bh))
2294 end_buffer_async_read(bh, 1);
2295 else
2296 submit_bh(REQ_OP_READ, 0, bh);
2297 }
2298 return 0;
2299}
2300EXPORT_SYMBOL(block_read_full_page);
2301
2302/* utility function for filesystems that need to do work on expanding
2303 * truncates. Uses filesystem pagecache writes to allow the filesystem to
2304 * deal with the hole.
2305 */
2306int generic_cont_expand_simple(struct inode *inode, loff_t size)
2307{
2308 struct address_space *mapping = inode->i_mapping;
2309 struct page *page;
2310 void *fsdata;
2311 int err;
2312
2313 err = inode_newsize_ok(inode, size);
2314 if (err)
2315 goto out;
2316
2317 err = pagecache_write_begin(NULL, mapping, size, 0,
2318 AOP_FLAG_CONT_EXPAND, &page, &fsdata);
2319 if (err)
2320 goto out;
2321
2322 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2323 BUG_ON(err > 0);
2324
2325out:
2326 return err;
2327}
2328EXPORT_SYMBOL(generic_cont_expand_simple);
2329
2330static int cont_expand_zero(struct file *file, struct address_space *mapping,
2331 loff_t pos, loff_t *bytes)
2332{
2333 struct inode *inode = mapping->host;
2334 unsigned int blocksize = i_blocksize(inode);
2335 struct page *page;
2336 void *fsdata;
2337 pgoff_t index, curidx;
2338 loff_t curpos;
2339 unsigned zerofrom, offset, len;
2340 int err = 0;
2341
2342 index = pos >> PAGE_SHIFT;
2343 offset = pos & ~PAGE_MASK;
2344
2345 while (index > (curidx = (curpos = *bytes)>>PAGE_SHIFT)) {
2346 zerofrom = curpos & ~PAGE_MASK;
2347 if (zerofrom & (blocksize-1)) {
2348 *bytes |= (blocksize-1);
2349 (*bytes)++;
2350 }
2351 len = PAGE_SIZE - zerofrom;
2352
2353 err = pagecache_write_begin(file, mapping, curpos, len, 0,
2354 &page, &fsdata);
2355 if (err)
2356 goto out;
2357 zero_user(page, zerofrom, len);
2358 err = pagecache_write_end(file, mapping, curpos, len, len,
2359 page, fsdata);
2360 if (err < 0)
2361 goto out;
2362 BUG_ON(err != len);
2363 err = 0;
2364
2365 balance_dirty_pages_ratelimited(mapping);
2366
2367 if (fatal_signal_pending(current)) {
2368 err = -EINTR;
2369 goto out;
2370 }
2371 }
2372
2373 /* page covers the boundary, find the boundary offset */
2374 if (index == curidx) {
2375 zerofrom = curpos & ~PAGE_MASK;
2376 /* if we will expand the thing last block will be filled */
2377 if (offset <= zerofrom) {
2378 goto out;
2379 }
2380 if (zerofrom & (blocksize-1)) {
2381 *bytes |= (blocksize-1);
2382 (*bytes)++;
2383 }
2384 len = offset - zerofrom;
2385
2386 err = pagecache_write_begin(file, mapping, curpos, len, 0,
2387 &page, &fsdata);
2388 if (err)
2389 goto out;
2390 zero_user(page, zerofrom, len);
2391 err = pagecache_write_end(file, mapping, curpos, len, len,
2392 page, fsdata);
2393 if (err < 0)
2394 goto out;
2395 BUG_ON(err != len);
2396 err = 0;
2397 }
2398out:
2399 return err;
2400}
2401
2402/*
2403 * For moronic filesystems that do not allow holes in file.
2404 * We may have to extend the file.
2405 */
2406int cont_write_begin(struct file *file, struct address_space *mapping,
2407 loff_t pos, unsigned len, unsigned flags,
2408 struct page **pagep, void **fsdata,
2409 get_block_t *get_block, loff_t *bytes)
2410{
2411 struct inode *inode = mapping->host;
2412 unsigned int blocksize = i_blocksize(inode);
2413 unsigned int zerofrom;
2414 int err;
2415
2416 err = cont_expand_zero(file, mapping, pos, bytes);
2417 if (err)
2418 return err;
2419
2420 zerofrom = *bytes & ~PAGE_MASK;
2421 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2422 *bytes |= (blocksize-1);
2423 (*bytes)++;
2424 }
2425
2426 return block_write_begin(mapping, pos, len, flags, pagep, get_block);
2427}
2428EXPORT_SYMBOL(cont_write_begin);
2429
2430int block_commit_write(struct page *page, unsigned from, unsigned to)
2431{
2432 struct inode *inode = page->mapping->host;
2433 __block_commit_write(inode,page,from,to);
2434 return 0;
2435}
2436EXPORT_SYMBOL(block_commit_write);
2437
2438/*
2439 * block_page_mkwrite() is not allowed to change the file size as it gets
2440 * called from a page fault handler when a page is first dirtied. Hence we must
2441 * be careful to check for EOF conditions here. We set the page up correctly
2442 * for a written page which means we get ENOSPC checking when writing into
2443 * holes and correct delalloc and unwritten extent mapping on filesystems that
2444 * support these features.
2445 *
2446 * We are not allowed to take the i_mutex here so we have to play games to
2447 * protect against truncate races as the page could now be beyond EOF. Because
2448 * truncate writes the inode size before removing pages, once we have the
2449 * page lock we can determine safely if the page is beyond EOF. If it is not
2450 * beyond EOF, then the page is guaranteed safe against truncation until we
2451 * unlock the page.
2452 *
2453 * Direct callers of this function should protect against filesystem freezing
2454 * using sb_start_pagefault() - sb_end_pagefault() functions.
2455 */
2456int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2457 get_block_t get_block)
2458{
2459 struct page *page = vmf->page;
2460 struct inode *inode = file_inode(vma->vm_file);
2461 unsigned long end;
2462 loff_t size;
2463 int ret;
2464
2465 lock_page(page);
2466 size = i_size_read(inode);
2467 if ((page->mapping != inode->i_mapping) ||
2468 (page_offset(page) > size)) {
2469 /* We overload EFAULT to mean page got truncated */
2470 ret = -EFAULT;
2471 goto out_unlock;
2472 }
2473
2474 /* page is wholly or partially inside EOF */
2475 if (((page->index + 1) << PAGE_SHIFT) > size)
2476 end = size & ~PAGE_MASK;
2477 else
2478 end = PAGE_SIZE;
2479
2480 ret = __block_write_begin(page, 0, end, get_block);
2481 if (!ret)
2482 ret = block_commit_write(page, 0, end);
2483
2484 if (unlikely(ret < 0))
2485 goto out_unlock;
2486 set_page_dirty(page);
2487 wait_for_stable_page(page);
2488 return 0;
2489out_unlock:
2490 unlock_page(page);
2491 return ret;
2492}
2493EXPORT_SYMBOL(block_page_mkwrite);
2494
2495/*
2496 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
2497 * immediately, while under the page lock. So it needs a special end_io
2498 * handler which does not touch the bh after unlocking it.
2499 */
2500static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2501{
2502 __end_buffer_read_notouch(bh, uptodate);
2503}
2504
2505/*
2506 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2507 * the page (converting it to circular linked list and taking care of page
2508 * dirty races).
2509 */
2510static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2511{
2512 struct buffer_head *bh;
2513
2514 BUG_ON(!PageLocked(page));
2515
2516 spin_lock(&page->mapping->private_lock);
2517 bh = head;
2518 do {
2519 if (PageDirty(page))
2520 set_buffer_dirty(bh);
2521 if (!bh->b_this_page)
2522 bh->b_this_page = head;
2523 bh = bh->b_this_page;
2524 } while (bh != head);
2525 attach_page_buffers(page, head);
2526 spin_unlock(&page->mapping->private_lock);
2527}
2528
2529/*
2530 * On entry, the page is fully not uptodate.
2531 * On exit the page is fully uptodate in the areas outside (from,to)
2532 * The filesystem needs to handle block truncation upon failure.
2533 */
2534int nobh_write_begin(struct address_space *mapping,
2535 loff_t pos, unsigned len, unsigned flags,
2536 struct page **pagep, void **fsdata,
2537 get_block_t *get_block)
2538{
2539 struct inode *inode = mapping->host;
2540 const unsigned blkbits = inode->i_blkbits;
2541 const unsigned blocksize = 1 << blkbits;
2542 struct buffer_head *head, *bh;
2543 struct page *page;
2544 pgoff_t index;
2545 unsigned from, to;
2546 unsigned block_in_page;
2547 unsigned block_start, block_end;
2548 sector_t block_in_file;
2549 int nr_reads = 0;
2550 int ret = 0;
2551 int is_mapped_to_disk = 1;
2552
2553 index = pos >> PAGE_SHIFT;
2554 from = pos & (PAGE_SIZE - 1);
2555 to = from + len;
2556
2557 page = grab_cache_page_write_begin(mapping, index, flags);
2558 if (!page)
2559 return -ENOMEM;
2560 *pagep = page;
2561 *fsdata = NULL;
2562
2563 if (page_has_buffers(page)) {
2564 ret = __block_write_begin(page, pos, len, get_block);
2565 if (unlikely(ret))
2566 goto out_release;
2567 return ret;
2568 }
2569
2570 if (PageMappedToDisk(page))
2571 return 0;
2572
2573 /*
2574 * Allocate buffers so that we can keep track of state, and potentially
2575 * attach them to the page if an error occurs. In the common case of
2576 * no error, they will just be freed again without ever being attached
2577 * to the page (which is all OK, because we're under the page lock).
2578 *
2579 * Be careful: the buffer linked list is a NULL terminated one, rather
2580 * than the circular one we're used to.
2581 */
2582 head = alloc_page_buffers(page, blocksize, false);
2583 if (!head) {
2584 ret = -ENOMEM;
2585 goto out_release;
2586 }
2587
2588 block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
2589
2590 /*
2591 * We loop across all blocks in the page, whether or not they are
2592 * part of the affected region. This is so we can discover if the
2593 * page is fully mapped-to-disk.
2594 */
2595 for (block_start = 0, block_in_page = 0, bh = head;
2596 block_start < PAGE_SIZE;
2597 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
2598 int create;
2599
2600 block_end = block_start + blocksize;
2601 bh->b_state = 0;
2602 create = 1;
2603 if (block_start >= to)
2604 create = 0;
2605 ret = get_block(inode, block_in_file + block_in_page,
2606 bh, create);
2607 if (ret)
2608 goto failed;
2609 if (!buffer_mapped(bh))
2610 is_mapped_to_disk = 0;
2611 if (buffer_new(bh))
2612 clean_bdev_bh_alias(bh);
2613 if (PageUptodate(page)) {
2614 set_buffer_uptodate(bh);
2615 continue;
2616 }
2617 if (buffer_new(bh) || !buffer_mapped(bh)) {
2618 zero_user_segments(page, block_start, from,
2619 to, block_end);
2620 continue;
2621 }
2622 if (buffer_uptodate(bh))
2623 continue; /* reiserfs does this */
2624 if (block_start < from || block_end > to) {
2625 lock_buffer(bh);
2626 bh->b_end_io = end_buffer_read_nobh;
2627 submit_bh(REQ_OP_READ, 0, bh);
2628 nr_reads++;
2629 }
2630 }
2631
2632 if (nr_reads) {
2633 /*
2634 * The page is locked, so these buffers are protected from
2635 * any VM or truncate activity. Hence we don't need to care
2636 * for the buffer_head refcounts.
2637 */
2638 for (bh = head; bh; bh = bh->b_this_page) {
2639 wait_on_buffer(bh);
2640 if (!buffer_uptodate(bh))
2641 ret = -EIO;
2642 }
2643 if (ret)
2644 goto failed;
2645 }
2646
2647 if (is_mapped_to_disk)
2648 SetPageMappedToDisk(page);
2649
2650 *fsdata = head; /* to be released by nobh_write_end */
2651
2652 return 0;
2653
2654failed:
2655 BUG_ON(!ret);
2656 /*
2657 * Error recovery is a bit difficult. We need to zero out blocks that
2658 * were newly allocated, and dirty them to ensure they get written out.
2659 * Buffers need to be attached to the page at this point, otherwise
2660 * the handling of potential IO errors during writeout would be hard
2661 * (could try doing synchronous writeout, but what if that fails too?)
2662 */
2663 attach_nobh_buffers(page, head);
2664 page_zero_new_buffers(page, from, to);
2665
2666out_release:
2667 unlock_page(page);
2668 put_page(page);
2669 *pagep = NULL;
2670
2671 return ret;
2672}
2673EXPORT_SYMBOL(nobh_write_begin);
2674
2675int nobh_write_end(struct file *file, struct address_space *mapping,
2676 loff_t pos, unsigned len, unsigned copied,
2677 struct page *page, void *fsdata)
2678{
2679 struct inode *inode = page->mapping->host;
2680 struct buffer_head *head = fsdata;
2681 struct buffer_head *bh;
2682 BUG_ON(fsdata != NULL && page_has_buffers(page));
2683
2684 if (unlikely(copied < len) && head)
2685 attach_nobh_buffers(page, head);
2686 if (page_has_buffers(page))
2687 return generic_write_end(file, mapping, pos, len,
2688 copied, page, fsdata);
2689
2690 SetPageUptodate(page);
2691 set_page_dirty(page);
2692 if (pos+copied > inode->i_size) {
2693 i_size_write(inode, pos+copied);
2694 mark_inode_dirty(inode);
2695 }
2696
2697 unlock_page(page);
2698 put_page(page);
2699
2700 while (head) {
2701 bh = head;
2702 head = head->b_this_page;
2703 free_buffer_head(bh);
2704 }
2705
2706 return copied;
2707}
2708EXPORT_SYMBOL(nobh_write_end);
2709
2710/*
2711 * nobh_writepage() - based on block_full_write_page() except
2712 * that it tries to operate without attaching bufferheads to
2713 * the page.
2714 */
2715int nobh_writepage(struct page *page, get_block_t *get_block,
2716 struct writeback_control *wbc)
2717{
2718 struct inode * const inode = page->mapping->host;
2719 loff_t i_size = i_size_read(inode);
2720 const pgoff_t end_index = i_size >> PAGE_SHIFT;
2721 unsigned offset;
2722 int ret;
2723
2724 /* Is the page fully inside i_size? */
2725 if (page->index < end_index)
2726 goto out;
2727
2728 /* Is the page fully outside i_size? (truncate in progress) */
2729 offset = i_size & (PAGE_SIZE-1);
2730 if (page->index >= end_index+1 || !offset) {
2731 /*
2732 * The page may have dirty, unmapped buffers. For example,
2733 * they may have been added in ext3_writepage(). Make them
2734 * freeable here, so the page does not leak.
2735 */
2736#if 0
2737 /* Not really sure about this - do we need this ? */
2738 if (page->mapping->a_ops->invalidatepage)
2739 page->mapping->a_ops->invalidatepage(page, offset);
2740#endif
2741 unlock_page(page);
2742 return 0; /* don't care */
2743 }
2744
2745 /*
2746 * The page straddles i_size. It must be zeroed out on each and every
2747 * writepage invocation because it may be mmapped. "A file is mapped
2748 * in multiples of the page size. For a file that is not a multiple of
2749 * the page size, the remaining memory is zeroed when mapped, and
2750 * writes to that region are not written out to the file."
2751 */
2752 zero_user_segment(page, offset, PAGE_SIZE);
2753out:
2754 ret = mpage_writepage(page, get_block, wbc);
2755 if (ret == -EAGAIN)
2756 ret = __block_write_full_page(inode, page, get_block, wbc,
2757 end_buffer_async_write);
2758 return ret;
2759}
2760EXPORT_SYMBOL(nobh_writepage);
2761
2762int nobh_truncate_page(struct address_space *mapping,
2763 loff_t from, get_block_t *get_block)
2764{
2765 pgoff_t index = from >> PAGE_SHIFT;
2766 unsigned offset = from & (PAGE_SIZE-1);
2767 unsigned blocksize;
2768 sector_t iblock;
2769 unsigned length, pos;
2770 struct inode *inode = mapping->host;
2771 struct page *page;
2772 struct buffer_head map_bh;
2773 int err;
2774
2775 blocksize = i_blocksize(inode);
2776 length = offset & (blocksize - 1);
2777
2778 /* Block boundary? Nothing to do */
2779 if (!length)
2780 return 0;
2781
2782 length = blocksize - length;
2783 iblock = (sector_t)index << (PAGE_SHIFT - inode->i_blkbits);
2784
2785 page = grab_cache_page(mapping, index);
2786 err = -ENOMEM;
2787 if (!page)
2788 goto out;
2789
2790 if (page_has_buffers(page)) {
2791has_buffers:
2792 unlock_page(page);
2793 put_page(page);
2794 return block_truncate_page(mapping, from, get_block);
2795 }
2796
2797 /* Find the buffer that contains "offset" */
2798 pos = blocksize;
2799 while (offset >= pos) {
2800 iblock++;
2801 pos += blocksize;
2802 }
2803
2804 map_bh.b_size = blocksize;
2805 map_bh.b_state = 0;
2806 err = get_block(inode, iblock, &map_bh, 0);
2807 if (err)
2808 goto unlock;
2809 /* unmapped? It's a hole - nothing to do */
2810 if (!buffer_mapped(&map_bh))
2811 goto unlock;
2812
2813 /* Ok, it's mapped. Make sure it's up-to-date */
2814 if (!PageUptodate(page)) {
2815 err = mapping->a_ops->readpage(NULL, page);
2816 if (err) {
2817 put_page(page);
2818 goto out;
2819 }
2820 lock_page(page);
2821 if (!PageUptodate(page)) {
2822 err = -EIO;
2823 goto unlock;
2824 }
2825 if (page_has_buffers(page))
2826 goto has_buffers;
2827 }
2828 zero_user(page, offset, length);
2829 set_page_dirty(page);
2830 err = 0;
2831
2832unlock:
2833 unlock_page(page);
2834 put_page(page);
2835out:
2836 return err;
2837}
2838EXPORT_SYMBOL(nobh_truncate_page);
2839
2840int block_truncate_page(struct address_space *mapping,
2841 loff_t from, get_block_t *get_block)
2842{
2843 pgoff_t index = from >> PAGE_SHIFT;
2844 unsigned offset = from & (PAGE_SIZE-1);
2845 unsigned blocksize;
2846 sector_t iblock;
2847 unsigned length, pos;
2848 struct inode *inode = mapping->host;
2849 struct page *page;
2850 struct buffer_head *bh;
2851 int err;
2852
2853 blocksize = i_blocksize(inode);
2854 length = offset & (blocksize - 1);
2855
2856 /* Block boundary? Nothing to do */
2857 if (!length)
2858 return 0;
2859
2860 length = blocksize - length;
2861 iblock = (sector_t)index << (PAGE_SHIFT - inode->i_blkbits);
2862
2863 page = grab_cache_page(mapping, index);
2864 err = -ENOMEM;
2865 if (!page)
2866 goto out;
2867
2868 if (!page_has_buffers(page))
2869 create_empty_buffers(page, blocksize, 0);
2870
2871 /* Find the buffer that contains "offset" */
2872 bh = page_buffers(page);
2873 pos = blocksize;
2874 while (offset >= pos) {
2875 bh = bh->b_this_page;
2876 iblock++;
2877 pos += blocksize;
2878 }
2879
2880 err = 0;
2881 if (!buffer_mapped(bh)) {
2882 WARN_ON(bh->b_size != blocksize);
2883 err = get_block(inode, iblock, bh, 0);
2884 if (err)
2885 goto unlock;
2886 /* unmapped? It's a hole - nothing to do */
2887 if (!buffer_mapped(bh))
2888 goto unlock;
2889 }
2890
2891 /* Ok, it's mapped. Make sure it's up-to-date */
2892 if (PageUptodate(page))
2893 set_buffer_uptodate(bh);
2894
2895 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2896 err = -EIO;
2897 ll_rw_block(REQ_OP_READ, 0, 1, &bh);
2898 wait_on_buffer(bh);
2899 /* Uhhuh. Read error. Complain and punt. */
2900 if (!buffer_uptodate(bh))
2901 goto unlock;
2902 }
2903
2904 zero_user(page, offset, length);
2905 mark_buffer_dirty(bh);
2906 err = 0;
2907
2908unlock:
2909 unlock_page(page);
2910 put_page(page);
2911out:
2912 return err;
2913}
2914EXPORT_SYMBOL(block_truncate_page);
2915
2916/*
2917 * The generic ->writepage function for buffer-backed address_spaces
2918 */
2919int block_write_full_page(struct page *page, get_block_t *get_block,
2920 struct writeback_control *wbc)
2921{
2922 struct inode * const inode = page->mapping->host;
2923 loff_t i_size = i_size_read(inode);
2924 const pgoff_t end_index = i_size >> PAGE_SHIFT;
2925 unsigned offset;
2926
2927 /* Is the page fully inside i_size? */
2928 if (page->index < end_index)
2929 return __block_write_full_page(inode, page, get_block, wbc,
2930 end_buffer_async_write);
2931
2932 /* Is the page fully outside i_size? (truncate in progress) */
2933 offset = i_size & (PAGE_SIZE-1);
2934 if (page->index >= end_index+1 || !offset) {
2935 /*
2936 * The page may have dirty, unmapped buffers. For example,
2937 * they may have been added in ext3_writepage(). Make them
2938 * freeable here, so the page does not leak.
2939 */
2940 do_invalidatepage(page, 0, PAGE_SIZE);
2941 unlock_page(page);
2942 return 0; /* don't care */
2943 }
2944
2945 /*
2946 * The page straddles i_size. It must be zeroed out on each and every
2947 * writepage invocation because it may be mmapped. "A file is mapped
2948 * in multiples of the page size. For a file that is not a multiple of
2949 * the page size, the remaining memory is zeroed when mapped, and
2950 * writes to that region are not written out to the file."
2951 */
2952 zero_user_segment(page, offset, PAGE_SIZE);
2953 return __block_write_full_page(inode, page, get_block, wbc,
2954 end_buffer_async_write);
2955}
2956EXPORT_SYMBOL(block_write_full_page);
2957
2958sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2959 get_block_t *get_block)
2960{
2961 struct inode *inode = mapping->host;
2962 struct buffer_head tmp = {
2963 .b_size = i_blocksize(inode),
2964 };
2965
2966 get_block(inode, block, &tmp, 0);
2967 return tmp.b_blocknr;
2968}
2969EXPORT_SYMBOL(generic_block_bmap);
2970
2971static void end_bio_bh_io_sync(struct bio *bio)
2972{
2973 struct buffer_head *bh = bio->bi_private;
2974
2975 if (unlikely(bio_flagged(bio, BIO_QUIET)))
2976 set_bit(BH_Quiet, &bh->b_state);
2977
2978 bh->b_end_io(bh, !bio->bi_status);
2979 bio_put(bio);
2980}
2981
2982/*
2983 * This allows us to do IO even on the odd last sectors
2984 * of a device, even if the block size is some multiple
2985 * of the physical sector size.
2986 *
2987 * We'll just truncate the bio to the size of the device,
2988 * and clear the end of the buffer head manually.
2989 *
2990 * Truly out-of-range accesses will turn into actual IO
2991 * errors, this only handles the "we need to be able to
2992 * do IO at the final sector" case.
2993 */
2994void guard_bio_eod(int op, struct bio *bio)
2995{
2996 sector_t maxsector;
2997 struct bio_vec *bvec = bio_last_bvec_all(bio);
2998 unsigned truncated_bytes;
2999 struct hd_struct *part;
3000
3001 rcu_read_lock();
3002 part = __disk_get_part(bio->bi_disk, bio->bi_partno);
3003 if (part)
3004 maxsector = part_nr_sects_read(part);
3005 else
3006 maxsector = get_capacity(bio->bi_disk);
3007 rcu_read_unlock();
3008
3009 if (!maxsector)
3010 return;
3011
3012 /*
3013 * If the *whole* IO is past the end of the device,
3014 * let it through, and the IO layer will turn it into
3015 * an EIO.
3016 */
3017 if (unlikely(bio->bi_iter.bi_sector >= maxsector))
3018 return;
3019
3020 maxsector -= bio->bi_iter.bi_sector;
3021 if (likely((bio->bi_iter.bi_size >> 9) <= maxsector))
3022 return;
3023
3024 /* Uhhuh. We've got a bio that straddles the device size! */
3025 truncated_bytes = bio->bi_iter.bi_size - (maxsector << 9);
3026
3027 /*
3028 * The bio contains more than one segment which spans EOD, just return
3029 * and let IO layer turn it into an EIO
3030 */
3031 if (truncated_bytes > bvec->bv_len)
3032 return;
3033
3034 /* Truncate the bio.. */
3035 bio->bi_iter.bi_size -= truncated_bytes;
3036 bvec->bv_len -= truncated_bytes;
3037
3038 /* ..and clear the end of the buffer for reads */
3039 if (op == REQ_OP_READ) {
3040 struct bio_vec bv;
3041
3042 mp_bvec_last_segment(bvec, &bv);
3043 zero_user(bv.bv_page, bv.bv_offset + bv.bv_len,
3044 truncated_bytes);
3045 }
3046}
3047
3048static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
3049 enum rw_hint write_hint, struct writeback_control *wbc)
3050{
3051 struct bio *bio;
3052
3053 BUG_ON(!buffer_locked(bh));
3054 BUG_ON(!buffer_mapped(bh));
3055 BUG_ON(!bh->b_end_io);
3056 BUG_ON(buffer_delay(bh));
3057 BUG_ON(buffer_unwritten(bh));
3058
3059 /*
3060 * Only clear out a write error when rewriting
3061 */
3062 if (test_set_buffer_req(bh) && (op == REQ_OP_WRITE))
3063 clear_buffer_write_io_error(bh);
3064
3065 /*
3066 * from here on down, it's all bio -- do the initial mapping,
3067 * submit_bio -> generic_make_request may further map this bio around
3068 */
3069 bio = bio_alloc(GFP_NOIO, 1);
3070
3071 bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
3072 bio_set_dev(bio, bh->b_bdev);
3073 bio->bi_write_hint = write_hint;
3074
3075 bio_add_page(bio, bh->b_page, bh->b_size, bh_offset(bh));
3076 BUG_ON(bio->bi_iter.bi_size != bh->b_size);
3077
3078 bio->bi_end_io = end_bio_bh_io_sync;
3079 bio->bi_private = bh;
3080
3081 /* Take care of bh's that straddle the end of the device */
3082 guard_bio_eod(op, bio);
3083
3084 if (buffer_meta(bh))
3085 op_flags |= REQ_META;
3086 if (buffer_prio(bh))
3087 op_flags |= REQ_PRIO;
3088 bio_set_op_attrs(bio, op, op_flags);
3089
3090 if (wbc) {
3091 wbc_init_bio(wbc, bio);
3092 wbc_account_cgroup_owner(wbc, bh->b_page, bh->b_size);
3093 }
3094
3095 submit_bio(bio);
3096 return 0;
3097}
3098
3099int submit_bh(int op, int op_flags, struct buffer_head *bh)
3100{
3101 return submit_bh_wbc(op, op_flags, bh, 0, NULL);
3102}
3103EXPORT_SYMBOL(submit_bh);
3104
3105/**
3106 * ll_rw_block: low-level access to block devices (DEPRECATED)
3107 * @op: whether to %READ or %WRITE
3108 * @op_flags: req_flag_bits
3109 * @nr: number of &struct buffer_heads in the array
3110 * @bhs: array of pointers to &struct buffer_head
3111 *
3112 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
3113 * requests an I/O operation on them, either a %REQ_OP_READ or a %REQ_OP_WRITE.
3114 * @op_flags contains flags modifying the detailed I/O behavior, most notably
3115 * %REQ_RAHEAD.
3116 *
3117 * This function drops any buffer that it cannot get a lock on (with the
3118 * BH_Lock state bit), any buffer that appears to be clean when doing a write
3119 * request, and any buffer that appears to be up-to-date when doing read
3120 * request. Further it marks as clean buffers that are processed for
3121 * writing (the buffer cache won't assume that they are actually clean
3122 * until the buffer gets unlocked).
3123 *
3124 * ll_rw_block sets b_end_io to simple completion handler that marks
3125 * the buffer up-to-date (if appropriate), unlocks the buffer and wakes
3126 * any waiters.
3127 *
3128 * All of the buffers must be for the same device, and must also be a
3129 * multiple of the current approved size for the device.
3130 */
3131void ll_rw_block(int op, int op_flags, int nr, struct buffer_head *bhs[])
3132{
3133 int i;
3134
3135 for (i = 0; i < nr; i++) {
3136 struct buffer_head *bh = bhs[i];
3137
3138 if (!trylock_buffer(bh))
3139 continue;
3140 if (op == WRITE) {
3141 if (test_clear_buffer_dirty(bh)) {
3142 bh->b_end_io = end_buffer_write_sync;
3143 get_bh(bh);
3144 submit_bh(op, op_flags, bh);
3145 continue;
3146 }
3147 } else {
3148 if (!buffer_uptodate(bh)) {
3149 bh->b_end_io = end_buffer_read_sync;
3150 get_bh(bh);
3151 submit_bh(op, op_flags, bh);
3152 continue;
3153 }
3154 }
3155 unlock_buffer(bh);
3156 }
3157}
3158EXPORT_SYMBOL(ll_rw_block);
3159
3160void write_dirty_buffer(struct buffer_head *bh, int op_flags)
3161{
3162 lock_buffer(bh);
3163 if (!test_clear_buffer_dirty(bh)) {
3164 unlock_buffer(bh);
3165 return;
3166 }
3167 bh->b_end_io = end_buffer_write_sync;
3168 get_bh(bh);
3169 submit_bh(REQ_OP_WRITE, op_flags, bh);
3170}
3171EXPORT_SYMBOL(write_dirty_buffer);
3172
3173/*
3174 * For a data-integrity writeout, we need to wait upon any in-progress I/O
3175 * and then start new I/O and then wait upon it. The caller must have a ref on
3176 * the buffer_head.
3177 */
3178int __sync_dirty_buffer(struct buffer_head *bh, int op_flags)
3179{
3180 int ret = 0;
3181
3182 WARN_ON(atomic_read(&bh->b_count) < 1);
3183 lock_buffer(bh);
3184 if (test_clear_buffer_dirty(bh)) {
3185 get_bh(bh);
3186 bh->b_end_io = end_buffer_write_sync;
3187 ret = submit_bh(REQ_OP_WRITE, op_flags, bh);
3188 wait_on_buffer(bh);
3189 if (!ret && !buffer_uptodate(bh))
3190 ret = -EIO;
3191 } else {
3192 unlock_buffer(bh);
3193 }
3194 return ret;
3195}
3196EXPORT_SYMBOL(__sync_dirty_buffer);
3197
3198int sync_dirty_buffer(struct buffer_head *bh)
3199{
3200 return __sync_dirty_buffer(bh, REQ_SYNC);
3201}
3202EXPORT_SYMBOL(sync_dirty_buffer);
3203
3204/*
3205 * try_to_free_buffers() checks if all the buffers on this particular page
3206 * are unused, and releases them if so.
3207 *
3208 * Exclusion against try_to_free_buffers may be obtained by either
3209 * locking the page or by holding its mapping's private_lock.
3210 *
3211 * If the page is dirty but all the buffers are clean then we need to
3212 * be sure to mark the page clean as well. This is because the page
3213 * may be against a block device, and a later reattachment of buffers
3214 * to a dirty page will set *all* buffers dirty. Which would corrupt
3215 * filesystem data on the same device.
3216 *
3217 * The same applies to regular filesystem pages: if all the buffers are
3218 * clean then we set the page clean and proceed. To do that, we require
3219 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3220 * private_lock.
3221 *
3222 * try_to_free_buffers() is non-blocking.
3223 */
3224static inline int buffer_busy(struct buffer_head *bh)
3225{
3226 return atomic_read(&bh->b_count) |
3227 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3228}
3229
3230static int
3231drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3232{
3233 struct buffer_head *head = page_buffers(page);
3234 struct buffer_head *bh;
3235
3236 bh = head;
3237 do {
3238 if (buffer_busy(bh))
3239 goto failed;
3240 bh = bh->b_this_page;
3241 } while (bh != head);
3242
3243 do {
3244 struct buffer_head *next = bh->b_this_page;
3245
3246 if (bh->b_assoc_map)
3247 __remove_assoc_queue(bh);
3248 bh = next;
3249 } while (bh != head);
3250 *buffers_to_free = head;
3251 __clear_page_buffers(page);
3252 return 1;
3253failed:
3254 return 0;
3255}
3256
3257int try_to_free_buffers(struct page *page)
3258{
3259 struct address_space * const mapping = page->mapping;
3260 struct buffer_head *buffers_to_free = NULL;
3261 int ret = 0;
3262
3263 BUG_ON(!PageLocked(page));
3264 if (PageWriteback(page))
3265 return 0;
3266
3267 if (mapping == NULL) { /* can this still happen? */
3268 ret = drop_buffers(page, &buffers_to_free);
3269 goto out;
3270 }
3271
3272 spin_lock(&mapping->private_lock);
3273 ret = drop_buffers(page, &buffers_to_free);
3274
3275 /*
3276 * If the filesystem writes its buffers by hand (eg ext3)
3277 * then we can have clean buffers against a dirty page. We
3278 * clean the page here; otherwise the VM will never notice
3279 * that the filesystem did any IO at all.
3280 *
3281 * Also, during truncate, discard_buffer will have marked all
3282 * the page's buffers clean. We discover that here and clean
3283 * the page also.
3284 *
3285 * private_lock must be held over this entire operation in order
3286 * to synchronise against __set_page_dirty_buffers and prevent the
3287 * dirty bit from being lost.
3288 */
3289 if (ret)
3290 cancel_dirty_page(page);
3291 spin_unlock(&mapping->private_lock);
3292out:
3293 if (buffers_to_free) {
3294 struct buffer_head *bh = buffers_to_free;
3295
3296 do {
3297 struct buffer_head *next = bh->b_this_page;
3298 free_buffer_head(bh);
3299 bh = next;
3300 } while (bh != buffers_to_free);
3301 }
3302 return ret;
3303}
3304EXPORT_SYMBOL(try_to_free_buffers);
3305
3306/*
3307 * There are no bdflush tunables left. But distributions are
3308 * still running obsolete flush daemons, so we terminate them here.
3309 *
3310 * Use of bdflush() is deprecated and will be removed in a future kernel.
3311 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
3312 */
3313SYSCALL_DEFINE2(bdflush, int, func, long, data)
3314{
3315 static int msg_count;
3316
3317 if (!capable(CAP_SYS_ADMIN))
3318 return -EPERM;
3319
3320 if (msg_count < 5) {
3321 msg_count++;
3322 printk(KERN_INFO
3323 "warning: process `%s' used the obsolete bdflush"
3324 " system call\n", current->comm);
3325 printk(KERN_INFO "Fix your initscripts?\n");
3326 }
3327
3328 if (func == 1)
3329 do_exit(0);
3330 return 0;
3331}
3332
3333/*
3334 * Buffer-head allocation
3335 */
3336static struct kmem_cache *bh_cachep __read_mostly;
3337
3338/*
3339 * Once the number of bh's in the machine exceeds this level, we start
3340 * stripping them in writeback.
3341 */
3342static unsigned long max_buffer_heads;
3343
3344int buffer_heads_over_limit;
3345
3346struct bh_accounting {
3347 int nr; /* Number of live bh's */
3348 int ratelimit; /* Limit cacheline bouncing */
3349};
3350
3351static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3352
3353static void recalc_bh_state(void)
3354{
3355 int i;
3356 int tot = 0;
3357
3358 if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
3359 return;
3360 __this_cpu_write(bh_accounting.ratelimit, 0);
3361 for_each_online_cpu(i)
3362 tot += per_cpu(bh_accounting, i).nr;
3363 buffer_heads_over_limit = (tot > max_buffer_heads);
3364}
3365
3366struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3367{
3368 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
3369 if (ret) {
3370 INIT_LIST_HEAD(&ret->b_assoc_buffers);
3371 preempt_disable();
3372 __this_cpu_inc(bh_accounting.nr);
3373 recalc_bh_state();
3374 preempt_enable();
3375 }
3376 return ret;
3377}
3378EXPORT_SYMBOL(alloc_buffer_head);
3379
3380void free_buffer_head(struct buffer_head *bh)
3381{
3382 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3383 kmem_cache_free(bh_cachep, bh);
3384 preempt_disable();
3385 __this_cpu_dec(bh_accounting.nr);
3386 recalc_bh_state();
3387 preempt_enable();
3388}
3389EXPORT_SYMBOL(free_buffer_head);
3390
3391static int buffer_exit_cpu_dead(unsigned int cpu)
3392{
3393 int i;
3394 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3395
3396 for (i = 0; i < BH_LRU_SIZE; i++) {
3397 brelse(b->bhs[i]);
3398 b->bhs[i] = NULL;
3399 }
3400 this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3401 per_cpu(bh_accounting, cpu).nr = 0;
3402 return 0;
3403}
3404
3405/**
3406 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3407 * @bh: struct buffer_head
3408 *
3409 * Return true if the buffer is up-to-date and false,
3410 * with the buffer locked, if not.
3411 */
3412int bh_uptodate_or_lock(struct buffer_head *bh)
3413{
3414 if (!buffer_uptodate(bh)) {
3415 lock_buffer(bh);
3416 if (!buffer_uptodate(bh))
3417 return 0;
3418 unlock_buffer(bh);
3419 }
3420 return 1;
3421}
3422EXPORT_SYMBOL(bh_uptodate_or_lock);
3423
3424/**
3425 * bh_submit_read - Submit a locked buffer for reading
3426 * @bh: struct buffer_head
3427 *
3428 * Returns zero on success and -EIO on error.
3429 */
3430int bh_submit_read(struct buffer_head *bh)
3431{
3432 BUG_ON(!buffer_locked(bh));
3433
3434 if (buffer_uptodate(bh)) {
3435 unlock_buffer(bh);
3436 return 0;
3437 }
3438
3439 get_bh(bh);
3440 bh->b_end_io = end_buffer_read_sync;
3441 submit_bh(REQ_OP_READ, 0, bh);
3442 wait_on_buffer(bh);
3443 if (buffer_uptodate(bh))
3444 return 0;
3445 return -EIO;
3446}
3447EXPORT_SYMBOL(bh_submit_read);
3448
3449void __init buffer_init(void)
3450{
3451 unsigned long nrpages;
3452 int ret;
3453
3454 bh_cachep = kmem_cache_create("buffer_head",
3455 sizeof(struct buffer_head), 0,
3456 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3457 SLAB_MEM_SPREAD),
3458 NULL);
3459
3460 /*
3461 * Limit the bh occupancy to 10% of ZONE_NORMAL
3462 */
3463 nrpages = (nr_free_buffer_pages() * 10) / 100;
3464 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3465 ret = cpuhp_setup_state_nocalls(CPUHP_FS_BUFF_DEAD, "fs/buffer:dead",
3466 NULL, buffer_exit_cpu_dead);
3467 WARN_ON(ret < 0);
3468}