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