file capabilities: remove cap_task_kill()
[pv_ops_mirror.git] / fs / buffer.c
blob7ba58386beee459779da2056d662572496ff2096
1 /*
2 * linux/fs/buffer.c
4 * Copyright (C) 1991, 1992, 2002 Linus Torvalds
5 */
7 /*
8 * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95
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
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
16 * Added 32k buffer block sizes - these are required older ARM systems. - RMK
18 * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de>
21 #include <linux/kernel.h>
22 #include <linux/syscalls.h>
23 #include <linux/fs.h>
24 #include <linux/mm.h>
25 #include <linux/percpu.h>
26 #include <linux/slab.h>
27 #include <linux/capability.h>
28 #include <linux/blkdev.h>
29 #include <linux/file.h>
30 #include <linux/quotaops.h>
31 #include <linux/highmem.h>
32 #include <linux/module.h>
33 #include <linux/writeback.h>
34 #include <linux/hash.h>
35 #include <linux/suspend.h>
36 #include <linux/buffer_head.h>
37 #include <linux/task_io_accounting_ops.h>
38 #include <linux/bio.h>
39 #include <linux/notifier.h>
40 #include <linux/cpu.h>
41 #include <linux/bitops.h>
42 #include <linux/mpage.h>
43 #include <linux/bit_spinlock.h>
45 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
47 #define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
49 inline void
50 init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
52 bh->b_end_io = handler;
53 bh->b_private = private;
56 static int sync_buffer(void *word)
58 struct block_device *bd;
59 struct buffer_head *bh
60 = container_of(word, struct buffer_head, b_state);
62 smp_mb();
63 bd = bh->b_bdev;
64 if (bd)
65 blk_run_address_space(bd->bd_inode->i_mapping);
66 io_schedule();
67 return 0;
70 void __lock_buffer(struct buffer_head *bh)
72 wait_on_bit_lock(&bh->b_state, BH_Lock, sync_buffer,
73 TASK_UNINTERRUPTIBLE);
75 EXPORT_SYMBOL(__lock_buffer);
77 void unlock_buffer(struct buffer_head *bh)
79 smp_mb__before_clear_bit();
80 clear_buffer_locked(bh);
81 smp_mb__after_clear_bit();
82 wake_up_bit(&bh->b_state, BH_Lock);
86 * Block until a buffer comes unlocked. This doesn't stop it
87 * from becoming locked again - you have to lock it yourself
88 * if you want to preserve its state.
90 void __wait_on_buffer(struct buffer_head * bh)
92 wait_on_bit(&bh->b_state, BH_Lock, sync_buffer, TASK_UNINTERRUPTIBLE);
95 static void
96 __clear_page_buffers(struct page *page)
98 ClearPagePrivate(page);
99 set_page_private(page, 0);
100 page_cache_release(page);
103 static void buffer_io_error(struct buffer_head *bh)
105 char b[BDEVNAME_SIZE];
107 printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
108 bdevname(bh->b_bdev, b),
109 (unsigned long long)bh->b_blocknr);
113 * End-of-IO handler helper function which does not touch the bh after
114 * unlocking it.
115 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
116 * a race there is benign: unlock_buffer() only use the bh's address for
117 * hashing after unlocking the buffer, so it doesn't actually touch the bh
118 * itself.
120 static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
122 if (uptodate) {
123 set_buffer_uptodate(bh);
124 } else {
125 /* This happens, due to failed READA attempts. */
126 clear_buffer_uptodate(bh);
128 unlock_buffer(bh);
132 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
133 * unlock the buffer. This is what ll_rw_block uses too.
135 void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
137 __end_buffer_read_notouch(bh, uptodate);
138 put_bh(bh);
141 void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
143 char b[BDEVNAME_SIZE];
145 if (uptodate) {
146 set_buffer_uptodate(bh);
147 } else {
148 if (!buffer_eopnotsupp(bh) && printk_ratelimit()) {
149 buffer_io_error(bh);
150 printk(KERN_WARNING "lost page write due to "
151 "I/O error on %s\n",
152 bdevname(bh->b_bdev, b));
154 set_buffer_write_io_error(bh);
155 clear_buffer_uptodate(bh);
157 unlock_buffer(bh);
158 put_bh(bh);
162 * Write out and wait upon all the dirty data associated with a block
163 * device via its mapping. Does not take the superblock lock.
165 int sync_blockdev(struct block_device *bdev)
167 int ret = 0;
169 if (bdev)
170 ret = filemap_write_and_wait(bdev->bd_inode->i_mapping);
171 return ret;
173 EXPORT_SYMBOL(sync_blockdev);
176 * Write out and wait upon all dirty data associated with this
177 * device. Filesystem data as well as the underlying block
178 * device. Takes the superblock lock.
180 int fsync_bdev(struct block_device *bdev)
182 struct super_block *sb = get_super(bdev);
183 if (sb) {
184 int res = fsync_super(sb);
185 drop_super(sb);
186 return res;
188 return sync_blockdev(bdev);
192 * freeze_bdev -- lock a filesystem and force it into a consistent state
193 * @bdev: blockdevice to lock
195 * This takes the block device bd_mount_sem to make sure no new mounts
196 * happen on bdev until thaw_bdev() is called.
197 * If a superblock is found on this device, we take the s_umount semaphore
198 * on it to make sure nobody unmounts until the snapshot creation is done.
200 struct super_block *freeze_bdev(struct block_device *bdev)
202 struct super_block *sb;
204 down(&bdev->bd_mount_sem);
205 sb = get_super(bdev);
206 if (sb && !(sb->s_flags & MS_RDONLY)) {
207 sb->s_frozen = SB_FREEZE_WRITE;
208 smp_wmb();
210 __fsync_super(sb);
212 sb->s_frozen = SB_FREEZE_TRANS;
213 smp_wmb();
215 sync_blockdev(sb->s_bdev);
217 if (sb->s_op->write_super_lockfs)
218 sb->s_op->write_super_lockfs(sb);
221 sync_blockdev(bdev);
222 return sb; /* thaw_bdev releases s->s_umount and bd_mount_sem */
224 EXPORT_SYMBOL(freeze_bdev);
227 * thaw_bdev -- unlock filesystem
228 * @bdev: blockdevice to unlock
229 * @sb: associated superblock
231 * Unlocks the filesystem and marks it writeable again after freeze_bdev().
233 void thaw_bdev(struct block_device *bdev, struct super_block *sb)
235 if (sb) {
236 BUG_ON(sb->s_bdev != bdev);
238 if (sb->s_op->unlockfs)
239 sb->s_op->unlockfs(sb);
240 sb->s_frozen = SB_UNFROZEN;
241 smp_wmb();
242 wake_up(&sb->s_wait_unfrozen);
243 drop_super(sb);
246 up(&bdev->bd_mount_sem);
248 EXPORT_SYMBOL(thaw_bdev);
251 * Various filesystems appear to want __find_get_block to be non-blocking.
252 * But it's the page lock which protects the buffers. To get around this,
253 * we get exclusion from try_to_free_buffers with the blockdev mapping's
254 * private_lock.
256 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
257 * may be quite high. This code could TryLock the page, and if that
258 * succeeds, there is no need to take private_lock. (But if
259 * private_lock is contended then so is mapping->tree_lock).
261 static struct buffer_head *
262 __find_get_block_slow(struct block_device *bdev, sector_t block)
264 struct inode *bd_inode = bdev->bd_inode;
265 struct address_space *bd_mapping = bd_inode->i_mapping;
266 struct buffer_head *ret = NULL;
267 pgoff_t index;
268 struct buffer_head *bh;
269 struct buffer_head *head;
270 struct page *page;
271 int all_mapped = 1;
273 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
274 page = find_get_page(bd_mapping, index);
275 if (!page)
276 goto out;
278 spin_lock(&bd_mapping->private_lock);
279 if (!page_has_buffers(page))
280 goto out_unlock;
281 head = page_buffers(page);
282 bh = head;
283 do {
284 if (bh->b_blocknr == block) {
285 ret = bh;
286 get_bh(bh);
287 goto out_unlock;
289 if (!buffer_mapped(bh))
290 all_mapped = 0;
291 bh = bh->b_this_page;
292 } while (bh != head);
294 /* we might be here because some of the buffers on this page are
295 * not mapped. This is due to various races between
296 * file io on the block device and getblk. It gets dealt with
297 * elsewhere, don't buffer_error if we had some unmapped buffers
299 if (all_mapped) {
300 printk("__find_get_block_slow() failed. "
301 "block=%llu, b_blocknr=%llu\n",
302 (unsigned long long)block,
303 (unsigned long long)bh->b_blocknr);
304 printk("b_state=0x%08lx, b_size=%zu\n",
305 bh->b_state, bh->b_size);
306 printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits);
308 out_unlock:
309 spin_unlock(&bd_mapping->private_lock);
310 page_cache_release(page);
311 out:
312 return ret;
315 /* If invalidate_buffers() will trash dirty buffers, it means some kind
316 of fs corruption is going on. Trashing dirty data always imply losing
317 information that was supposed to be just stored on the physical layer
318 by the user.
320 Thus invalidate_buffers in general usage is not allwowed to trash
321 dirty buffers. For example ioctl(FLSBLKBUF) expects dirty data to
322 be preserved. These buffers are simply skipped.
324 We also skip buffers which are still in use. For example this can
325 happen if a userspace program is reading the block device.
327 NOTE: In the case where the user removed a removable-media-disk even if
328 there's still dirty data not synced on disk (due a bug in the device driver
329 or due an error of the user), by not destroying the dirty buffers we could
330 generate corruption also on the next media inserted, thus a parameter is
331 necessary to handle this case in the most safe way possible (trying
332 to not corrupt also the new disk inserted with the data belonging to
333 the old now corrupted disk). Also for the ramdisk the natural thing
334 to do in order to release the ramdisk memory is to destroy dirty buffers.
336 These are two special cases. Normal usage imply the device driver
337 to issue a sync on the device (without waiting I/O completion) and
338 then an invalidate_buffers call that doesn't trash dirty buffers.
340 For handling cache coherency with the blkdev pagecache the 'update' case
341 is been introduced. It is needed to re-read from disk any pinned
342 buffer. NOTE: re-reading from disk is destructive so we can do it only
343 when we assume nobody is changing the buffercache under our I/O and when
344 we think the disk contains more recent information than the buffercache.
345 The update == 1 pass marks the buffers we need to update, the update == 2
346 pass does the actual I/O. */
347 void invalidate_bdev(struct block_device *bdev)
349 struct address_space *mapping = bdev->bd_inode->i_mapping;
351 if (mapping->nrpages == 0)
352 return;
354 invalidate_bh_lrus();
355 invalidate_mapping_pages(mapping, 0, -1);
359 * Kick pdflush then try to free up some ZONE_NORMAL memory.
361 static void free_more_memory(void)
363 struct zone **zones;
364 pg_data_t *pgdat;
366 wakeup_pdflush(1024);
367 yield();
369 for_each_online_pgdat(pgdat) {
370 zones = pgdat->node_zonelists[gfp_zone(GFP_NOFS)].zones;
371 if (*zones)
372 try_to_free_pages(zones, 0, GFP_NOFS);
377 * I/O completion handler for block_read_full_page() - pages
378 * which come unlocked at the end of I/O.
380 static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
382 unsigned long flags;
383 struct buffer_head *first;
384 struct buffer_head *tmp;
385 struct page *page;
386 int page_uptodate = 1;
388 BUG_ON(!buffer_async_read(bh));
390 page = bh->b_page;
391 if (uptodate) {
392 set_buffer_uptodate(bh);
393 } else {
394 clear_buffer_uptodate(bh);
395 if (printk_ratelimit())
396 buffer_io_error(bh);
397 SetPageError(page);
401 * Be _very_ careful from here on. Bad things can happen if
402 * two buffer heads end IO at almost the same time and both
403 * decide that the page is now completely done.
405 first = page_buffers(page);
406 local_irq_save(flags);
407 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
408 clear_buffer_async_read(bh);
409 unlock_buffer(bh);
410 tmp = bh;
411 do {
412 if (!buffer_uptodate(tmp))
413 page_uptodate = 0;
414 if (buffer_async_read(tmp)) {
415 BUG_ON(!buffer_locked(tmp));
416 goto still_busy;
418 tmp = tmp->b_this_page;
419 } while (tmp != bh);
420 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
421 local_irq_restore(flags);
424 * If none of the buffers had errors and they are all
425 * uptodate then we can set the page uptodate.
427 if (page_uptodate && !PageError(page))
428 SetPageUptodate(page);
429 unlock_page(page);
430 return;
432 still_busy:
433 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
434 local_irq_restore(flags);
435 return;
439 * Completion handler for block_write_full_page() - pages which are unlocked
440 * during I/O, and which have PageWriteback cleared upon I/O completion.
442 static void end_buffer_async_write(struct buffer_head *bh, int uptodate)
444 char b[BDEVNAME_SIZE];
445 unsigned long flags;
446 struct buffer_head *first;
447 struct buffer_head *tmp;
448 struct page *page;
450 BUG_ON(!buffer_async_write(bh));
452 page = bh->b_page;
453 if (uptodate) {
454 set_buffer_uptodate(bh);
455 } else {
456 if (printk_ratelimit()) {
457 buffer_io_error(bh);
458 printk(KERN_WARNING "lost page write due to "
459 "I/O error on %s\n",
460 bdevname(bh->b_bdev, b));
462 set_bit(AS_EIO, &page->mapping->flags);
463 set_buffer_write_io_error(bh);
464 clear_buffer_uptodate(bh);
465 SetPageError(page);
468 first = page_buffers(page);
469 local_irq_save(flags);
470 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
472 clear_buffer_async_write(bh);
473 unlock_buffer(bh);
474 tmp = bh->b_this_page;
475 while (tmp != bh) {
476 if (buffer_async_write(tmp)) {
477 BUG_ON(!buffer_locked(tmp));
478 goto still_busy;
480 tmp = tmp->b_this_page;
482 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
483 local_irq_restore(flags);
484 end_page_writeback(page);
485 return;
487 still_busy:
488 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
489 local_irq_restore(flags);
490 return;
494 * If a page's buffers are under async readin (end_buffer_async_read
495 * completion) then there is a possibility that another thread of
496 * control could lock one of the buffers after it has completed
497 * but while some of the other buffers have not completed. This
498 * locked buffer would confuse end_buffer_async_read() into not unlocking
499 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
500 * that this buffer is not under async I/O.
502 * The page comes unlocked when it has no locked buffer_async buffers
503 * left.
505 * PageLocked prevents anyone starting new async I/O reads any of
506 * the buffers.
508 * PageWriteback is used to prevent simultaneous writeout of the same
509 * page.
511 * PageLocked prevents anyone from starting writeback of a page which is
512 * under read I/O (PageWriteback is only ever set against a locked page).
514 static void mark_buffer_async_read(struct buffer_head *bh)
516 bh->b_end_io = end_buffer_async_read;
517 set_buffer_async_read(bh);
520 void mark_buffer_async_write(struct buffer_head *bh)
522 bh->b_end_io = end_buffer_async_write;
523 set_buffer_async_write(bh);
525 EXPORT_SYMBOL(mark_buffer_async_write);
529 * fs/buffer.c contains helper functions for buffer-backed address space's
530 * fsync functions. A common requirement for buffer-based filesystems is
531 * that certain data from the backing blockdev needs to be written out for
532 * a successful fsync(). For example, ext2 indirect blocks need to be
533 * written back and waited upon before fsync() returns.
535 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
536 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
537 * management of a list of dependent buffers at ->i_mapping->private_list.
539 * Locking is a little subtle: try_to_free_buffers() will remove buffers
540 * from their controlling inode's queue when they are being freed. But
541 * try_to_free_buffers() will be operating against the *blockdev* mapping
542 * at the time, not against the S_ISREG file which depends on those buffers.
543 * So the locking for private_list is via the private_lock in the address_space
544 * which backs the buffers. Which is different from the address_space
545 * against which the buffers are listed. So for a particular address_space,
546 * mapping->private_lock does *not* protect mapping->private_list! In fact,
547 * mapping->private_list will always be protected by the backing blockdev's
548 * ->private_lock.
550 * Which introduces a requirement: all buffers on an address_space's
551 * ->private_list must be from the same address_space: the blockdev's.
553 * address_spaces which do not place buffers at ->private_list via these
554 * utility functions are free to use private_lock and private_list for
555 * whatever they want. The only requirement is that list_empty(private_list)
556 * be true at clear_inode() time.
558 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
559 * filesystems should do that. invalidate_inode_buffers() should just go
560 * BUG_ON(!list_empty).
562 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
563 * take an address_space, not an inode. And it should be called
564 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
565 * queued up.
567 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
568 * list if it is already on a list. Because if the buffer is on a list,
569 * it *must* already be on the right one. If not, the filesystem is being
570 * silly. This will save a ton of locking. But first we have to ensure
571 * that buffers are taken *off* the old inode's list when they are freed
572 * (presumably in truncate). That requires careful auditing of all
573 * filesystems (do it inside bforget()). It could also be done by bringing
574 * b_inode back.
578 * The buffer's backing address_space's private_lock must be held
580 static inline void __remove_assoc_queue(struct buffer_head *bh)
582 list_del_init(&bh->b_assoc_buffers);
583 WARN_ON(!bh->b_assoc_map);
584 if (buffer_write_io_error(bh))
585 set_bit(AS_EIO, &bh->b_assoc_map->flags);
586 bh->b_assoc_map = NULL;
589 int inode_has_buffers(struct inode *inode)
591 return !list_empty(&inode->i_data.private_list);
595 * osync is designed to support O_SYNC io. It waits synchronously for
596 * all already-submitted IO to complete, but does not queue any new
597 * writes to the disk.
599 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
600 * you dirty the buffers, and then use osync_inode_buffers to wait for
601 * completion. Any other dirty buffers which are not yet queued for
602 * write will not be flushed to disk by the osync.
604 static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
606 struct buffer_head *bh;
607 struct list_head *p;
608 int err = 0;
610 spin_lock(lock);
611 repeat:
612 list_for_each_prev(p, list) {
613 bh = BH_ENTRY(p);
614 if (buffer_locked(bh)) {
615 get_bh(bh);
616 spin_unlock(lock);
617 wait_on_buffer(bh);
618 if (!buffer_uptodate(bh))
619 err = -EIO;
620 brelse(bh);
621 spin_lock(lock);
622 goto repeat;
625 spin_unlock(lock);
626 return err;
630 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
631 * @mapping: the mapping which wants those buffers written
633 * Starts I/O against the buffers at mapping->private_list, and waits upon
634 * that I/O.
636 * Basically, this is a convenience function for fsync().
637 * @mapping is a file or directory which needs those buffers to be written for
638 * a successful fsync().
640 int sync_mapping_buffers(struct address_space *mapping)
642 struct address_space *buffer_mapping = mapping->assoc_mapping;
644 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
645 return 0;
647 return fsync_buffers_list(&buffer_mapping->private_lock,
648 &mapping->private_list);
650 EXPORT_SYMBOL(sync_mapping_buffers);
653 * Called when we've recently written block `bblock', and it is known that
654 * `bblock' was for a buffer_boundary() buffer. This means that the block at
655 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
656 * dirty, schedule it for IO. So that indirects merge nicely with their data.
658 void write_boundary_block(struct block_device *bdev,
659 sector_t bblock, unsigned blocksize)
661 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
662 if (bh) {
663 if (buffer_dirty(bh))
664 ll_rw_block(WRITE, 1, &bh);
665 put_bh(bh);
669 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
671 struct address_space *mapping = inode->i_mapping;
672 struct address_space *buffer_mapping = bh->b_page->mapping;
674 mark_buffer_dirty(bh);
675 if (!mapping->assoc_mapping) {
676 mapping->assoc_mapping = buffer_mapping;
677 } else {
678 BUG_ON(mapping->assoc_mapping != buffer_mapping);
680 if (!bh->b_assoc_map) {
681 spin_lock(&buffer_mapping->private_lock);
682 list_move_tail(&bh->b_assoc_buffers,
683 &mapping->private_list);
684 bh->b_assoc_map = mapping;
685 spin_unlock(&buffer_mapping->private_lock);
688 EXPORT_SYMBOL(mark_buffer_dirty_inode);
691 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
692 * dirty.
694 * If warn is true, then emit a warning if the page is not uptodate and has
695 * not been truncated.
697 static int __set_page_dirty(struct page *page,
698 struct address_space *mapping, int warn)
700 if (unlikely(!mapping))
701 return !TestSetPageDirty(page);
703 if (TestSetPageDirty(page))
704 return 0;
706 write_lock_irq(&mapping->tree_lock);
707 if (page->mapping) { /* Race with truncate? */
708 WARN_ON_ONCE(warn && !PageUptodate(page));
710 if (mapping_cap_account_dirty(mapping)) {
711 __inc_zone_page_state(page, NR_FILE_DIRTY);
712 __inc_bdi_stat(mapping->backing_dev_info,
713 BDI_RECLAIMABLE);
714 task_io_account_write(PAGE_CACHE_SIZE);
716 radix_tree_tag_set(&mapping->page_tree,
717 page_index(page), PAGECACHE_TAG_DIRTY);
719 write_unlock_irq(&mapping->tree_lock);
720 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
722 return 1;
726 * Add a page to the dirty page list.
728 * It is a sad fact of life that this function is called from several places
729 * deeply under spinlocking. It may not sleep.
731 * If the page has buffers, the uptodate buffers are set dirty, to preserve
732 * dirty-state coherency between the page and the buffers. It the page does
733 * not have buffers then when they are later attached they will all be set
734 * dirty.
736 * The buffers are dirtied before the page is dirtied. There's a small race
737 * window in which a writepage caller may see the page cleanness but not the
738 * buffer dirtiness. That's fine. If this code were to set the page dirty
739 * before the buffers, a concurrent writepage caller could clear the page dirty
740 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
741 * page on the dirty page list.
743 * We use private_lock to lock against try_to_free_buffers while using the
744 * page's buffer list. Also use this to protect against clean buffers being
745 * added to the page after it was set dirty.
747 * FIXME: may need to call ->reservepage here as well. That's rather up to the
748 * address_space though.
750 int __set_page_dirty_buffers(struct page *page)
752 struct address_space *mapping = page_mapping(page);
754 if (unlikely(!mapping))
755 return !TestSetPageDirty(page);
757 spin_lock(&mapping->private_lock);
758 if (page_has_buffers(page)) {
759 struct buffer_head *head = page_buffers(page);
760 struct buffer_head *bh = head;
762 do {
763 set_buffer_dirty(bh);
764 bh = bh->b_this_page;
765 } while (bh != head);
767 spin_unlock(&mapping->private_lock);
769 return __set_page_dirty(page, mapping, 1);
771 EXPORT_SYMBOL(__set_page_dirty_buffers);
774 * Write out and wait upon a list of buffers.
776 * We have conflicting pressures: we want to make sure that all
777 * initially dirty buffers get waited on, but that any subsequently
778 * dirtied buffers don't. After all, we don't want fsync to last
779 * forever if somebody is actively writing to the file.
781 * Do this in two main stages: first we copy dirty buffers to a
782 * temporary inode list, queueing the writes as we go. Then we clean
783 * up, waiting for those writes to complete.
785 * During this second stage, any subsequent updates to the file may end
786 * up refiling the buffer on the original inode's dirty list again, so
787 * there is a chance we will end up with a buffer queued for write but
788 * not yet completed on that list. So, as a final cleanup we go through
789 * the osync code to catch these locked, dirty buffers without requeuing
790 * any newly dirty buffers for write.
792 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
794 struct buffer_head *bh;
795 struct list_head tmp;
796 struct address_space *mapping;
797 int err = 0, err2;
799 INIT_LIST_HEAD(&tmp);
801 spin_lock(lock);
802 while (!list_empty(list)) {
803 bh = BH_ENTRY(list->next);
804 mapping = bh->b_assoc_map;
805 __remove_assoc_queue(bh);
806 /* Avoid race with mark_buffer_dirty_inode() which does
807 * a lockless check and we rely on seeing the dirty bit */
808 smp_mb();
809 if (buffer_dirty(bh) || buffer_locked(bh)) {
810 list_add(&bh->b_assoc_buffers, &tmp);
811 bh->b_assoc_map = mapping;
812 if (buffer_dirty(bh)) {
813 get_bh(bh);
814 spin_unlock(lock);
816 * Ensure any pending I/O completes so that
817 * ll_rw_block() actually writes the current
818 * contents - it is a noop if I/O is still in
819 * flight on potentially older contents.
821 ll_rw_block(SWRITE, 1, &bh);
822 brelse(bh);
823 spin_lock(lock);
828 while (!list_empty(&tmp)) {
829 bh = BH_ENTRY(tmp.prev);
830 get_bh(bh);
831 mapping = bh->b_assoc_map;
832 __remove_assoc_queue(bh);
833 /* Avoid race with mark_buffer_dirty_inode() which does
834 * a lockless check and we rely on seeing the dirty bit */
835 smp_mb();
836 if (buffer_dirty(bh)) {
837 list_add(&bh->b_assoc_buffers,
838 &mapping->private_list);
839 bh->b_assoc_map = mapping;
841 spin_unlock(lock);
842 wait_on_buffer(bh);
843 if (!buffer_uptodate(bh))
844 err = -EIO;
845 brelse(bh);
846 spin_lock(lock);
849 spin_unlock(lock);
850 err2 = osync_buffers_list(lock, list);
851 if (err)
852 return err;
853 else
854 return err2;
858 * Invalidate any and all dirty buffers on a given inode. We are
859 * probably unmounting the fs, but that doesn't mean we have already
860 * done a sync(). Just drop the buffers from the inode list.
862 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
863 * assumes that all the buffers are against the blockdev. Not true
864 * for reiserfs.
866 void invalidate_inode_buffers(struct inode *inode)
868 if (inode_has_buffers(inode)) {
869 struct address_space *mapping = &inode->i_data;
870 struct list_head *list = &mapping->private_list;
871 struct address_space *buffer_mapping = mapping->assoc_mapping;
873 spin_lock(&buffer_mapping->private_lock);
874 while (!list_empty(list))
875 __remove_assoc_queue(BH_ENTRY(list->next));
876 spin_unlock(&buffer_mapping->private_lock);
881 * Remove any clean buffers from the inode's buffer list. This is called
882 * when we're trying to free the inode itself. Those buffers can pin it.
884 * Returns true if all buffers were removed.
886 int remove_inode_buffers(struct inode *inode)
888 int ret = 1;
890 if (inode_has_buffers(inode)) {
891 struct address_space *mapping = &inode->i_data;
892 struct list_head *list = &mapping->private_list;
893 struct address_space *buffer_mapping = mapping->assoc_mapping;
895 spin_lock(&buffer_mapping->private_lock);
896 while (!list_empty(list)) {
897 struct buffer_head *bh = BH_ENTRY(list->next);
898 if (buffer_dirty(bh)) {
899 ret = 0;
900 break;
902 __remove_assoc_queue(bh);
904 spin_unlock(&buffer_mapping->private_lock);
906 return ret;
910 * Create the appropriate buffers when given a page for data area and
911 * the size of each buffer.. Use the bh->b_this_page linked list to
912 * follow the buffers created. Return NULL if unable to create more
913 * buffers.
915 * The retry flag is used to differentiate async IO (paging, swapping)
916 * which may not fail from ordinary buffer allocations.
918 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
919 int retry)
921 struct buffer_head *bh, *head;
922 long offset;
924 try_again:
925 head = NULL;
926 offset = PAGE_SIZE;
927 while ((offset -= size) >= 0) {
928 bh = alloc_buffer_head(GFP_NOFS);
929 if (!bh)
930 goto no_grow;
932 bh->b_bdev = NULL;
933 bh->b_this_page = head;
934 bh->b_blocknr = -1;
935 head = bh;
937 bh->b_state = 0;
938 atomic_set(&bh->b_count, 0);
939 bh->b_private = NULL;
940 bh->b_size = size;
942 /* Link the buffer to its page */
943 set_bh_page(bh, page, offset);
945 init_buffer(bh, NULL, NULL);
947 return head;
949 * In case anything failed, we just free everything we got.
951 no_grow:
952 if (head) {
953 do {
954 bh = head;
955 head = head->b_this_page;
956 free_buffer_head(bh);
957 } while (head);
961 * Return failure for non-async IO requests. Async IO requests
962 * are not allowed to fail, so we have to wait until buffer heads
963 * become available. But we don't want tasks sleeping with
964 * partially complete buffers, so all were released above.
966 if (!retry)
967 return NULL;
969 /* We're _really_ low on memory. Now we just
970 * wait for old buffer heads to become free due to
971 * finishing IO. Since this is an async request and
972 * the reserve list is empty, we're sure there are
973 * async buffer heads in use.
975 free_more_memory();
976 goto try_again;
978 EXPORT_SYMBOL_GPL(alloc_page_buffers);
980 static inline void
981 link_dev_buffers(struct page *page, struct buffer_head *head)
983 struct buffer_head *bh, *tail;
985 bh = head;
986 do {
987 tail = bh;
988 bh = bh->b_this_page;
989 } while (bh);
990 tail->b_this_page = head;
991 attach_page_buffers(page, head);
995 * Initialise the state of a blockdev page's buffers.
997 static void
998 init_page_buffers(struct page *page, struct block_device *bdev,
999 sector_t block, int size)
1001 struct buffer_head *head = page_buffers(page);
1002 struct buffer_head *bh = head;
1003 int uptodate = PageUptodate(page);
1005 do {
1006 if (!buffer_mapped(bh)) {
1007 init_buffer(bh, NULL, NULL);
1008 bh->b_bdev = bdev;
1009 bh->b_blocknr = block;
1010 if (uptodate)
1011 set_buffer_uptodate(bh);
1012 set_buffer_mapped(bh);
1014 block++;
1015 bh = bh->b_this_page;
1016 } while (bh != head);
1020 * Create the page-cache page that contains the requested block.
1022 * This is user purely for blockdev mappings.
1024 static struct page *
1025 grow_dev_page(struct block_device *bdev, sector_t block,
1026 pgoff_t index, int size)
1028 struct inode *inode = bdev->bd_inode;
1029 struct page *page;
1030 struct buffer_head *bh;
1032 page = find_or_create_page(inode->i_mapping, index,
1033 (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE);
1034 if (!page)
1035 return NULL;
1037 BUG_ON(!PageLocked(page));
1039 if (page_has_buffers(page)) {
1040 bh = page_buffers(page);
1041 if (bh->b_size == size) {
1042 init_page_buffers(page, bdev, block, size);
1043 return page;
1045 if (!try_to_free_buffers(page))
1046 goto failed;
1050 * Allocate some buffers for this page
1052 bh = alloc_page_buffers(page, size, 0);
1053 if (!bh)
1054 goto failed;
1057 * Link the page to the buffers and initialise them. Take the
1058 * lock to be atomic wrt __find_get_block(), which does not
1059 * run under the page lock.
1061 spin_lock(&inode->i_mapping->private_lock);
1062 link_dev_buffers(page, bh);
1063 init_page_buffers(page, bdev, block, size);
1064 spin_unlock(&inode->i_mapping->private_lock);
1065 return page;
1067 failed:
1068 BUG();
1069 unlock_page(page);
1070 page_cache_release(page);
1071 return NULL;
1075 * Create buffers for the specified block device block's page. If
1076 * that page was dirty, the buffers are set dirty also.
1078 static int
1079 grow_buffers(struct block_device *bdev, sector_t block, int size)
1081 struct page *page;
1082 pgoff_t index;
1083 int sizebits;
1085 sizebits = -1;
1086 do {
1087 sizebits++;
1088 } while ((size << sizebits) < PAGE_SIZE);
1090 index = block >> sizebits;
1093 * Check for a block which wants to lie outside our maximum possible
1094 * pagecache index. (this comparison is done using sector_t types).
1096 if (unlikely(index != block >> sizebits)) {
1097 char b[BDEVNAME_SIZE];
1099 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1100 "device %s\n",
1101 __FUNCTION__, (unsigned long long)block,
1102 bdevname(bdev, b));
1103 return -EIO;
1105 block = index << sizebits;
1106 /* Create a page with the proper size buffers.. */
1107 page = grow_dev_page(bdev, block, index, size);
1108 if (!page)
1109 return 0;
1110 unlock_page(page);
1111 page_cache_release(page);
1112 return 1;
1115 static struct buffer_head *
1116 __getblk_slow(struct block_device *bdev, sector_t block, int size)
1118 /* Size must be multiple of hard sectorsize */
1119 if (unlikely(size & (bdev_hardsect_size(bdev)-1) ||
1120 (size < 512 || size > PAGE_SIZE))) {
1121 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1122 size);
1123 printk(KERN_ERR "hardsect size: %d\n",
1124 bdev_hardsect_size(bdev));
1126 dump_stack();
1127 return NULL;
1130 for (;;) {
1131 struct buffer_head * bh;
1132 int ret;
1134 bh = __find_get_block(bdev, block, size);
1135 if (bh)
1136 return bh;
1138 ret = grow_buffers(bdev, block, size);
1139 if (ret < 0)
1140 return NULL;
1141 if (ret == 0)
1142 free_more_memory();
1147 * The relationship between dirty buffers and dirty pages:
1149 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1150 * the page is tagged dirty in its radix tree.
1152 * At all times, the dirtiness of the buffers represents the dirtiness of
1153 * subsections of the page. If the page has buffers, the page dirty bit is
1154 * merely a hint about the true dirty state.
1156 * When a page is set dirty in its entirety, all its buffers are marked dirty
1157 * (if the page has buffers).
1159 * When a buffer is marked dirty, its page is dirtied, but the page's other
1160 * buffers are not.
1162 * Also. When blockdev buffers are explicitly read with bread(), they
1163 * individually become uptodate. But their backing page remains not
1164 * uptodate - even if all of its buffers are uptodate. A subsequent
1165 * block_read_full_page() against that page will discover all the uptodate
1166 * buffers, will set the page uptodate and will perform no I/O.
1170 * mark_buffer_dirty - mark a buffer_head as needing writeout
1171 * @bh: the buffer_head to mark dirty
1173 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1174 * backing page dirty, then tag the page as dirty in its address_space's radix
1175 * tree and then attach the address_space's inode to its superblock's dirty
1176 * inode list.
1178 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1179 * mapping->tree_lock and the global inode_lock.
1181 void mark_buffer_dirty(struct buffer_head *bh)
1183 WARN_ON_ONCE(!buffer_uptodate(bh));
1184 if (!buffer_dirty(bh) && !test_set_buffer_dirty(bh))
1185 __set_page_dirty(bh->b_page, page_mapping(bh->b_page), 0);
1189 * Decrement a buffer_head's reference count. If all buffers against a page
1190 * have zero reference count, are clean and unlocked, and if the page is clean
1191 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1192 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1193 * a page but it ends up not being freed, and buffers may later be reattached).
1195 void __brelse(struct buffer_head * buf)
1197 if (atomic_read(&buf->b_count)) {
1198 put_bh(buf);
1199 return;
1201 printk(KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1202 WARN_ON(1);
1206 * bforget() is like brelse(), except it discards any
1207 * potentially dirty data.
1209 void __bforget(struct buffer_head *bh)
1211 clear_buffer_dirty(bh);
1212 if (bh->b_assoc_map) {
1213 struct address_space *buffer_mapping = bh->b_page->mapping;
1215 spin_lock(&buffer_mapping->private_lock);
1216 list_del_init(&bh->b_assoc_buffers);
1217 bh->b_assoc_map = NULL;
1218 spin_unlock(&buffer_mapping->private_lock);
1220 __brelse(bh);
1223 static struct buffer_head *__bread_slow(struct buffer_head *bh)
1225 lock_buffer(bh);
1226 if (buffer_uptodate(bh)) {
1227 unlock_buffer(bh);
1228 return bh;
1229 } else {
1230 get_bh(bh);
1231 bh->b_end_io = end_buffer_read_sync;
1232 submit_bh(READ, bh);
1233 wait_on_buffer(bh);
1234 if (buffer_uptodate(bh))
1235 return bh;
1237 brelse(bh);
1238 return NULL;
1242 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1243 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1244 * refcount elevated by one when they're in an LRU. A buffer can only appear
1245 * once in a particular CPU's LRU. A single buffer can be present in multiple
1246 * CPU's LRUs at the same time.
1248 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1249 * sb_find_get_block().
1251 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1252 * a local interrupt disable for that.
1255 #define BH_LRU_SIZE 8
1257 struct bh_lru {
1258 struct buffer_head *bhs[BH_LRU_SIZE];
1261 static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1263 #ifdef CONFIG_SMP
1264 #define bh_lru_lock() local_irq_disable()
1265 #define bh_lru_unlock() local_irq_enable()
1266 #else
1267 #define bh_lru_lock() preempt_disable()
1268 #define bh_lru_unlock() preempt_enable()
1269 #endif
1271 static inline void check_irqs_on(void)
1273 #ifdef irqs_disabled
1274 BUG_ON(irqs_disabled());
1275 #endif
1279 * The LRU management algorithm is dopey-but-simple. Sorry.
1281 static void bh_lru_install(struct buffer_head *bh)
1283 struct buffer_head *evictee = NULL;
1284 struct bh_lru *lru;
1286 check_irqs_on();
1287 bh_lru_lock();
1288 lru = &__get_cpu_var(bh_lrus);
1289 if (lru->bhs[0] != bh) {
1290 struct buffer_head *bhs[BH_LRU_SIZE];
1291 int in;
1292 int out = 0;
1294 get_bh(bh);
1295 bhs[out++] = bh;
1296 for (in = 0; in < BH_LRU_SIZE; in++) {
1297 struct buffer_head *bh2 = lru->bhs[in];
1299 if (bh2 == bh) {
1300 __brelse(bh2);
1301 } else {
1302 if (out >= BH_LRU_SIZE) {
1303 BUG_ON(evictee != NULL);
1304 evictee = bh2;
1305 } else {
1306 bhs[out++] = bh2;
1310 while (out < BH_LRU_SIZE)
1311 bhs[out++] = NULL;
1312 memcpy(lru->bhs, bhs, sizeof(bhs));
1314 bh_lru_unlock();
1316 if (evictee)
1317 __brelse(evictee);
1321 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1323 static struct buffer_head *
1324 lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1326 struct buffer_head *ret = NULL;
1327 struct bh_lru *lru;
1328 unsigned int i;
1330 check_irqs_on();
1331 bh_lru_lock();
1332 lru = &__get_cpu_var(bh_lrus);
1333 for (i = 0; i < BH_LRU_SIZE; i++) {
1334 struct buffer_head *bh = lru->bhs[i];
1336 if (bh && bh->b_bdev == bdev &&
1337 bh->b_blocknr == block && bh->b_size == size) {
1338 if (i) {
1339 while (i) {
1340 lru->bhs[i] = lru->bhs[i - 1];
1341 i--;
1343 lru->bhs[0] = bh;
1345 get_bh(bh);
1346 ret = bh;
1347 break;
1350 bh_lru_unlock();
1351 return ret;
1355 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1356 * it in the LRU and mark it as accessed. If it is not present then return
1357 * NULL
1359 struct buffer_head *
1360 __find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1362 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1364 if (bh == NULL) {
1365 bh = __find_get_block_slow(bdev, block);
1366 if (bh)
1367 bh_lru_install(bh);
1369 if (bh)
1370 touch_buffer(bh);
1371 return bh;
1373 EXPORT_SYMBOL(__find_get_block);
1376 * __getblk will locate (and, if necessary, create) the buffer_head
1377 * which corresponds to the passed block_device, block and size. The
1378 * returned buffer has its reference count incremented.
1380 * __getblk() cannot fail - it just keeps trying. If you pass it an
1381 * illegal block number, __getblk() will happily return a buffer_head
1382 * which represents the non-existent block. Very weird.
1384 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1385 * attempt is failing. FIXME, perhaps?
1387 struct buffer_head *
1388 __getblk(struct block_device *bdev, sector_t block, unsigned size)
1390 struct buffer_head *bh = __find_get_block(bdev, block, size);
1392 might_sleep();
1393 if (bh == NULL)
1394 bh = __getblk_slow(bdev, block, size);
1395 return bh;
1397 EXPORT_SYMBOL(__getblk);
1400 * Do async read-ahead on a buffer..
1402 void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1404 struct buffer_head *bh = __getblk(bdev, block, size);
1405 if (likely(bh)) {
1406 ll_rw_block(READA, 1, &bh);
1407 brelse(bh);
1410 EXPORT_SYMBOL(__breadahead);
1413 * __bread() - reads a specified block and returns the bh
1414 * @bdev: the block_device to read from
1415 * @block: number of block
1416 * @size: size (in bytes) to read
1418 * Reads a specified block, and returns buffer head that contains it.
1419 * It returns NULL if the block was unreadable.
1421 struct buffer_head *
1422 __bread(struct block_device *bdev, sector_t block, unsigned size)
1424 struct buffer_head *bh = __getblk(bdev, block, size);
1426 if (likely(bh) && !buffer_uptodate(bh))
1427 bh = __bread_slow(bh);
1428 return bh;
1430 EXPORT_SYMBOL(__bread);
1433 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1434 * This doesn't race because it runs in each cpu either in irq
1435 * or with preempt disabled.
1437 static void invalidate_bh_lru(void *arg)
1439 struct bh_lru *b = &get_cpu_var(bh_lrus);
1440 int i;
1442 for (i = 0; i < BH_LRU_SIZE; i++) {
1443 brelse(b->bhs[i]);
1444 b->bhs[i] = NULL;
1446 put_cpu_var(bh_lrus);
1449 void invalidate_bh_lrus(void)
1451 on_each_cpu(invalidate_bh_lru, NULL, 1, 1);
1453 EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1455 void set_bh_page(struct buffer_head *bh,
1456 struct page *page, unsigned long offset)
1458 bh->b_page = page;
1459 BUG_ON(offset >= PAGE_SIZE);
1460 if (PageHighMem(page))
1462 * This catches illegal uses and preserves the offset:
1464 bh->b_data = (char *)(0 + offset);
1465 else
1466 bh->b_data = page_address(page) + offset;
1468 EXPORT_SYMBOL(set_bh_page);
1471 * Called when truncating a buffer on a page completely.
1473 static void discard_buffer(struct buffer_head * bh)
1475 lock_buffer(bh);
1476 clear_buffer_dirty(bh);
1477 bh->b_bdev = NULL;
1478 clear_buffer_mapped(bh);
1479 clear_buffer_req(bh);
1480 clear_buffer_new(bh);
1481 clear_buffer_delay(bh);
1482 clear_buffer_unwritten(bh);
1483 unlock_buffer(bh);
1487 * block_invalidatepage - invalidate part of all of a buffer-backed page
1489 * @page: the page which is affected
1490 * @offset: the index of the truncation point
1492 * block_invalidatepage() is called when all or part of the page has become
1493 * invalidatedby a truncate operation.
1495 * block_invalidatepage() does not have to release all buffers, but it must
1496 * ensure that no dirty buffer is left outside @offset and that no I/O
1497 * is underway against any of the blocks which are outside the truncation
1498 * point. Because the caller is about to free (and possibly reuse) those
1499 * blocks on-disk.
1501 void block_invalidatepage(struct page *page, unsigned long offset)
1503 struct buffer_head *head, *bh, *next;
1504 unsigned int curr_off = 0;
1506 BUG_ON(!PageLocked(page));
1507 if (!page_has_buffers(page))
1508 goto out;
1510 head = page_buffers(page);
1511 bh = head;
1512 do {
1513 unsigned int next_off = curr_off + bh->b_size;
1514 next = bh->b_this_page;
1517 * is this block fully invalidated?
1519 if (offset <= curr_off)
1520 discard_buffer(bh);
1521 curr_off = next_off;
1522 bh = next;
1523 } while (bh != head);
1526 * We release buffers only if the entire page is being invalidated.
1527 * The get_block cached value has been unconditionally invalidated,
1528 * so real IO is not possible anymore.
1530 if (offset == 0)
1531 try_to_release_page(page, 0);
1532 out:
1533 return;
1535 EXPORT_SYMBOL(block_invalidatepage);
1538 * We attach and possibly dirty the buffers atomically wrt
1539 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1540 * is already excluded via the page lock.
1542 void create_empty_buffers(struct page *page,
1543 unsigned long blocksize, unsigned long b_state)
1545 struct buffer_head *bh, *head, *tail;
1547 head = alloc_page_buffers(page, blocksize, 1);
1548 bh = head;
1549 do {
1550 bh->b_state |= b_state;
1551 tail = bh;
1552 bh = bh->b_this_page;
1553 } while (bh);
1554 tail->b_this_page = head;
1556 spin_lock(&page->mapping->private_lock);
1557 if (PageUptodate(page) || PageDirty(page)) {
1558 bh = head;
1559 do {
1560 if (PageDirty(page))
1561 set_buffer_dirty(bh);
1562 if (PageUptodate(page))
1563 set_buffer_uptodate(bh);
1564 bh = bh->b_this_page;
1565 } while (bh != head);
1567 attach_page_buffers(page, head);
1568 spin_unlock(&page->mapping->private_lock);
1570 EXPORT_SYMBOL(create_empty_buffers);
1573 * We are taking a block for data and we don't want any output from any
1574 * buffer-cache aliases starting from return from that function and
1575 * until the moment when something will explicitly mark the buffer
1576 * dirty (hopefully that will not happen until we will free that block ;-)
1577 * We don't even need to mark it not-uptodate - nobody can expect
1578 * anything from a newly allocated buffer anyway. We used to used
1579 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1580 * don't want to mark the alias unmapped, for example - it would confuse
1581 * anyone who might pick it with bread() afterwards...
1583 * Also.. Note that bforget() doesn't lock the buffer. So there can
1584 * be writeout I/O going on against recently-freed buffers. We don't
1585 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1586 * only if we really need to. That happens here.
1588 void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1590 struct buffer_head *old_bh;
1592 might_sleep();
1594 old_bh = __find_get_block_slow(bdev, block);
1595 if (old_bh) {
1596 clear_buffer_dirty(old_bh);
1597 wait_on_buffer(old_bh);
1598 clear_buffer_req(old_bh);
1599 __brelse(old_bh);
1602 EXPORT_SYMBOL(unmap_underlying_metadata);
1605 * NOTE! All mapped/uptodate combinations are valid:
1607 * Mapped Uptodate Meaning
1609 * No No "unknown" - must do get_block()
1610 * No Yes "hole" - zero-filled
1611 * Yes No "allocated" - allocated on disk, not read in
1612 * Yes Yes "valid" - allocated and up-to-date in memory.
1614 * "Dirty" is valid only with the last case (mapped+uptodate).
1618 * While block_write_full_page is writing back the dirty buffers under
1619 * the page lock, whoever dirtied the buffers may decide to clean them
1620 * again at any time. We handle that by only looking at the buffer
1621 * state inside lock_buffer().
1623 * If block_write_full_page() is called for regular writeback
1624 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1625 * locked buffer. This only can happen if someone has written the buffer
1626 * directly, with submit_bh(). At the address_space level PageWriteback
1627 * prevents this contention from occurring.
1629 static int __block_write_full_page(struct inode *inode, struct page *page,
1630 get_block_t *get_block, struct writeback_control *wbc)
1632 int err;
1633 sector_t block;
1634 sector_t last_block;
1635 struct buffer_head *bh, *head;
1636 const unsigned blocksize = 1 << inode->i_blkbits;
1637 int nr_underway = 0;
1639 BUG_ON(!PageLocked(page));
1641 last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
1643 if (!page_has_buffers(page)) {
1644 create_empty_buffers(page, blocksize,
1645 (1 << BH_Dirty)|(1 << BH_Uptodate));
1649 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1650 * here, and the (potentially unmapped) buffers may become dirty at
1651 * any time. If a buffer becomes dirty here after we've inspected it
1652 * then we just miss that fact, and the page stays dirty.
1654 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1655 * handle that here by just cleaning them.
1658 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
1659 head = page_buffers(page);
1660 bh = head;
1663 * Get all the dirty buffers mapped to disk addresses and
1664 * handle any aliases from the underlying blockdev's mapping.
1666 do {
1667 if (block > last_block) {
1669 * mapped buffers outside i_size will occur, because
1670 * this page can be outside i_size when there is a
1671 * truncate in progress.
1674 * The buffer was zeroed by block_write_full_page()
1676 clear_buffer_dirty(bh);
1677 set_buffer_uptodate(bh);
1678 } else if (!buffer_mapped(bh) && buffer_dirty(bh)) {
1679 WARN_ON(bh->b_size != blocksize);
1680 err = get_block(inode, block, bh, 1);
1681 if (err)
1682 goto recover;
1683 if (buffer_new(bh)) {
1684 /* blockdev mappings never come here */
1685 clear_buffer_new(bh);
1686 unmap_underlying_metadata(bh->b_bdev,
1687 bh->b_blocknr);
1690 bh = bh->b_this_page;
1691 block++;
1692 } while (bh != head);
1694 do {
1695 if (!buffer_mapped(bh))
1696 continue;
1698 * If it's a fully non-blocking write attempt and we cannot
1699 * lock the buffer then redirty the page. Note that this can
1700 * potentially cause a busy-wait loop from pdflush and kswapd
1701 * activity, but those code paths have their own higher-level
1702 * throttling.
1704 if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
1705 lock_buffer(bh);
1706 } else if (test_set_buffer_locked(bh)) {
1707 redirty_page_for_writepage(wbc, page);
1708 continue;
1710 if (test_clear_buffer_dirty(bh)) {
1711 mark_buffer_async_write(bh);
1712 } else {
1713 unlock_buffer(bh);
1715 } while ((bh = bh->b_this_page) != head);
1718 * The page and its buffers are protected by PageWriteback(), so we can
1719 * drop the bh refcounts early.
1721 BUG_ON(PageWriteback(page));
1722 set_page_writeback(page);
1724 do {
1725 struct buffer_head *next = bh->b_this_page;
1726 if (buffer_async_write(bh)) {
1727 submit_bh(WRITE, bh);
1728 nr_underway++;
1730 bh = next;
1731 } while (bh != head);
1732 unlock_page(page);
1734 err = 0;
1735 done:
1736 if (nr_underway == 0) {
1738 * The page was marked dirty, but the buffers were
1739 * clean. Someone wrote them back by hand with
1740 * ll_rw_block/submit_bh. A rare case.
1742 end_page_writeback(page);
1745 * The page and buffer_heads can be released at any time from
1746 * here on.
1749 return err;
1751 recover:
1753 * ENOSPC, or some other error. We may already have added some
1754 * blocks to the file, so we need to write these out to avoid
1755 * exposing stale data.
1756 * The page is currently locked and not marked for writeback
1758 bh = head;
1759 /* Recovery: lock and submit the mapped buffers */
1760 do {
1761 if (buffer_mapped(bh) && buffer_dirty(bh)) {
1762 lock_buffer(bh);
1763 mark_buffer_async_write(bh);
1764 } else {
1766 * The buffer may have been set dirty during
1767 * attachment to a dirty page.
1769 clear_buffer_dirty(bh);
1771 } while ((bh = bh->b_this_page) != head);
1772 SetPageError(page);
1773 BUG_ON(PageWriteback(page));
1774 mapping_set_error(page->mapping, err);
1775 set_page_writeback(page);
1776 do {
1777 struct buffer_head *next = bh->b_this_page;
1778 if (buffer_async_write(bh)) {
1779 clear_buffer_dirty(bh);
1780 submit_bh(WRITE, bh);
1781 nr_underway++;
1783 bh = next;
1784 } while (bh != head);
1785 unlock_page(page);
1786 goto done;
1790 * If a page has any new buffers, zero them out here, and mark them uptodate
1791 * and dirty so they'll be written out (in order to prevent uninitialised
1792 * block data from leaking). And clear the new bit.
1794 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1796 unsigned int block_start, block_end;
1797 struct buffer_head *head, *bh;
1799 BUG_ON(!PageLocked(page));
1800 if (!page_has_buffers(page))
1801 return;
1803 bh = head = page_buffers(page);
1804 block_start = 0;
1805 do {
1806 block_end = block_start + bh->b_size;
1808 if (buffer_new(bh)) {
1809 if (block_end > from && block_start < to) {
1810 if (!PageUptodate(page)) {
1811 unsigned start, size;
1813 start = max(from, block_start);
1814 size = min(to, block_end) - start;
1816 zero_user(page, start, size);
1817 set_buffer_uptodate(bh);
1820 clear_buffer_new(bh);
1821 mark_buffer_dirty(bh);
1825 block_start = block_end;
1826 bh = bh->b_this_page;
1827 } while (bh != head);
1829 EXPORT_SYMBOL(page_zero_new_buffers);
1831 static int __block_prepare_write(struct inode *inode, struct page *page,
1832 unsigned from, unsigned to, get_block_t *get_block)
1834 unsigned block_start, block_end;
1835 sector_t block;
1836 int err = 0;
1837 unsigned blocksize, bbits;
1838 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1840 BUG_ON(!PageLocked(page));
1841 BUG_ON(from > PAGE_CACHE_SIZE);
1842 BUG_ON(to > PAGE_CACHE_SIZE);
1843 BUG_ON(from > to);
1845 blocksize = 1 << inode->i_blkbits;
1846 if (!page_has_buffers(page))
1847 create_empty_buffers(page, blocksize, 0);
1848 head = page_buffers(page);
1850 bbits = inode->i_blkbits;
1851 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1853 for(bh = head, block_start = 0; bh != head || !block_start;
1854 block++, block_start=block_end, bh = bh->b_this_page) {
1855 block_end = block_start + blocksize;
1856 if (block_end <= from || block_start >= to) {
1857 if (PageUptodate(page)) {
1858 if (!buffer_uptodate(bh))
1859 set_buffer_uptodate(bh);
1861 continue;
1863 if (buffer_new(bh))
1864 clear_buffer_new(bh);
1865 if (!buffer_mapped(bh)) {
1866 WARN_ON(bh->b_size != blocksize);
1867 err = get_block(inode, block, bh, 1);
1868 if (err)
1869 break;
1870 if (buffer_new(bh)) {
1871 unmap_underlying_metadata(bh->b_bdev,
1872 bh->b_blocknr);
1873 if (PageUptodate(page)) {
1874 clear_buffer_new(bh);
1875 set_buffer_uptodate(bh);
1876 mark_buffer_dirty(bh);
1877 continue;
1879 if (block_end > to || block_start < from)
1880 zero_user_segments(page,
1881 to, block_end,
1882 block_start, from);
1883 continue;
1886 if (PageUptodate(page)) {
1887 if (!buffer_uptodate(bh))
1888 set_buffer_uptodate(bh);
1889 continue;
1891 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1892 !buffer_unwritten(bh) &&
1893 (block_start < from || block_end > to)) {
1894 ll_rw_block(READ, 1, &bh);
1895 *wait_bh++=bh;
1899 * If we issued read requests - let them complete.
1901 while(wait_bh > wait) {
1902 wait_on_buffer(*--wait_bh);
1903 if (!buffer_uptodate(*wait_bh))
1904 err = -EIO;
1906 if (unlikely(err))
1907 page_zero_new_buffers(page, from, to);
1908 return err;
1911 static int __block_commit_write(struct inode *inode, struct page *page,
1912 unsigned from, unsigned to)
1914 unsigned block_start, block_end;
1915 int partial = 0;
1916 unsigned blocksize;
1917 struct buffer_head *bh, *head;
1919 blocksize = 1 << inode->i_blkbits;
1921 for(bh = head = page_buffers(page), block_start = 0;
1922 bh != head || !block_start;
1923 block_start=block_end, bh = bh->b_this_page) {
1924 block_end = block_start + blocksize;
1925 if (block_end <= from || block_start >= to) {
1926 if (!buffer_uptodate(bh))
1927 partial = 1;
1928 } else {
1929 set_buffer_uptodate(bh);
1930 mark_buffer_dirty(bh);
1932 clear_buffer_new(bh);
1936 * If this is a partial write which happened to make all buffers
1937 * uptodate then we can optimize away a bogus readpage() for
1938 * the next read(). Here we 'discover' whether the page went
1939 * uptodate as a result of this (potentially partial) write.
1941 if (!partial)
1942 SetPageUptodate(page);
1943 return 0;
1947 * block_write_begin takes care of the basic task of block allocation and
1948 * bringing partial write blocks uptodate first.
1950 * If *pagep is not NULL, then block_write_begin uses the locked page
1951 * at *pagep rather than allocating its own. In this case, the page will
1952 * not be unlocked or deallocated on failure.
1954 int block_write_begin(struct file *file, struct address_space *mapping,
1955 loff_t pos, unsigned len, unsigned flags,
1956 struct page **pagep, void **fsdata,
1957 get_block_t *get_block)
1959 struct inode *inode = mapping->host;
1960 int status = 0;
1961 struct page *page;
1962 pgoff_t index;
1963 unsigned start, end;
1964 int ownpage = 0;
1966 index = pos >> PAGE_CACHE_SHIFT;
1967 start = pos & (PAGE_CACHE_SIZE - 1);
1968 end = start + len;
1970 page = *pagep;
1971 if (page == NULL) {
1972 ownpage = 1;
1973 page = __grab_cache_page(mapping, index);
1974 if (!page) {
1975 status = -ENOMEM;
1976 goto out;
1978 *pagep = page;
1979 } else
1980 BUG_ON(!PageLocked(page));
1982 status = __block_prepare_write(inode, page, start, end, get_block);
1983 if (unlikely(status)) {
1984 ClearPageUptodate(page);
1986 if (ownpage) {
1987 unlock_page(page);
1988 page_cache_release(page);
1989 *pagep = NULL;
1992 * prepare_write() may have instantiated a few blocks
1993 * outside i_size. Trim these off again. Don't need
1994 * i_size_read because we hold i_mutex.
1996 if (pos + len > inode->i_size)
1997 vmtruncate(inode, inode->i_size);
1999 goto out;
2002 out:
2003 return status;
2005 EXPORT_SYMBOL(block_write_begin);
2007 int block_write_end(struct file *file, struct address_space *mapping,
2008 loff_t pos, unsigned len, unsigned copied,
2009 struct page *page, void *fsdata)
2011 struct inode *inode = mapping->host;
2012 unsigned start;
2014 start = pos & (PAGE_CACHE_SIZE - 1);
2016 if (unlikely(copied < len)) {
2018 * The buffers that were written will now be uptodate, so we
2019 * don't have to worry about a readpage reading them and
2020 * overwriting a partial write. However if we have encountered
2021 * a short write and only partially written into a buffer, it
2022 * will not be marked uptodate, so a readpage might come in and
2023 * destroy our partial write.
2025 * Do the simplest thing, and just treat any short write to a
2026 * non uptodate page as a zero-length write, and force the
2027 * caller to redo the whole thing.
2029 if (!PageUptodate(page))
2030 copied = 0;
2032 page_zero_new_buffers(page, start+copied, start+len);
2034 flush_dcache_page(page);
2036 /* This could be a short (even 0-length) commit */
2037 __block_commit_write(inode, page, start, start+copied);
2039 return copied;
2041 EXPORT_SYMBOL(block_write_end);
2043 int generic_write_end(struct file *file, struct address_space *mapping,
2044 loff_t pos, unsigned len, unsigned copied,
2045 struct page *page, void *fsdata)
2047 struct inode *inode = mapping->host;
2049 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2052 * No need to use i_size_read() here, the i_size
2053 * cannot change under us because we hold i_mutex.
2055 * But it's important to update i_size while still holding page lock:
2056 * page writeout could otherwise come in and zero beyond i_size.
2058 if (pos+copied > inode->i_size) {
2059 i_size_write(inode, pos+copied);
2060 mark_inode_dirty(inode);
2063 unlock_page(page);
2064 page_cache_release(page);
2066 return copied;
2068 EXPORT_SYMBOL(generic_write_end);
2071 * Generic "read page" function for block devices that have the normal
2072 * get_block functionality. This is most of the block device filesystems.
2073 * Reads the page asynchronously --- the unlock_buffer() and
2074 * set/clear_buffer_uptodate() functions propagate buffer state into the
2075 * page struct once IO has completed.
2077 int block_read_full_page(struct page *page, get_block_t *get_block)
2079 struct inode *inode = page->mapping->host;
2080 sector_t iblock, lblock;
2081 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2082 unsigned int blocksize;
2083 int nr, i;
2084 int fully_mapped = 1;
2086 BUG_ON(!PageLocked(page));
2087 blocksize = 1 << inode->i_blkbits;
2088 if (!page_has_buffers(page))
2089 create_empty_buffers(page, blocksize, 0);
2090 head = page_buffers(page);
2092 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2093 lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
2094 bh = head;
2095 nr = 0;
2096 i = 0;
2098 do {
2099 if (buffer_uptodate(bh))
2100 continue;
2102 if (!buffer_mapped(bh)) {
2103 int err = 0;
2105 fully_mapped = 0;
2106 if (iblock < lblock) {
2107 WARN_ON(bh->b_size != blocksize);
2108 err = get_block(inode, iblock, bh, 0);
2109 if (err)
2110 SetPageError(page);
2112 if (!buffer_mapped(bh)) {
2113 zero_user(page, i * blocksize, blocksize);
2114 if (!err)
2115 set_buffer_uptodate(bh);
2116 continue;
2119 * get_block() might have updated the buffer
2120 * synchronously
2122 if (buffer_uptodate(bh))
2123 continue;
2125 arr[nr++] = bh;
2126 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2128 if (fully_mapped)
2129 SetPageMappedToDisk(page);
2131 if (!nr) {
2133 * All buffers are uptodate - we can set the page uptodate
2134 * as well. But not if get_block() returned an error.
2136 if (!PageError(page))
2137 SetPageUptodate(page);
2138 unlock_page(page);
2139 return 0;
2142 /* Stage two: lock the buffers */
2143 for (i = 0; i < nr; i++) {
2144 bh = arr[i];
2145 lock_buffer(bh);
2146 mark_buffer_async_read(bh);
2150 * Stage 3: start the IO. Check for uptodateness
2151 * inside the buffer lock in case another process reading
2152 * the underlying blockdev brought it uptodate (the sct fix).
2154 for (i = 0; i < nr; i++) {
2155 bh = arr[i];
2156 if (buffer_uptodate(bh))
2157 end_buffer_async_read(bh, 1);
2158 else
2159 submit_bh(READ, bh);
2161 return 0;
2164 /* utility function for filesystems that need to do work on expanding
2165 * truncates. Uses filesystem pagecache writes to allow the filesystem to
2166 * deal with the hole.
2168 int generic_cont_expand_simple(struct inode *inode, loff_t size)
2170 struct address_space *mapping = inode->i_mapping;
2171 struct page *page;
2172 void *fsdata;
2173 unsigned long limit;
2174 int err;
2176 err = -EFBIG;
2177 limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
2178 if (limit != RLIM_INFINITY && size > (loff_t)limit) {
2179 send_sig(SIGXFSZ, current, 0);
2180 goto out;
2182 if (size > inode->i_sb->s_maxbytes)
2183 goto out;
2185 err = pagecache_write_begin(NULL, mapping, size, 0,
2186 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2187 &page, &fsdata);
2188 if (err)
2189 goto out;
2191 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2192 BUG_ON(err > 0);
2194 out:
2195 return err;
2198 int cont_expand_zero(struct file *file, struct address_space *mapping,
2199 loff_t pos, loff_t *bytes)
2201 struct inode *inode = mapping->host;
2202 unsigned blocksize = 1 << inode->i_blkbits;
2203 struct page *page;
2204 void *fsdata;
2205 pgoff_t index, curidx;
2206 loff_t curpos;
2207 unsigned zerofrom, offset, len;
2208 int err = 0;
2210 index = pos >> PAGE_CACHE_SHIFT;
2211 offset = pos & ~PAGE_CACHE_MASK;
2213 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
2214 zerofrom = curpos & ~PAGE_CACHE_MASK;
2215 if (zerofrom & (blocksize-1)) {
2216 *bytes |= (blocksize-1);
2217 (*bytes)++;
2219 len = PAGE_CACHE_SIZE - zerofrom;
2221 err = pagecache_write_begin(file, mapping, curpos, len,
2222 AOP_FLAG_UNINTERRUPTIBLE,
2223 &page, &fsdata);
2224 if (err)
2225 goto out;
2226 zero_user(page, zerofrom, len);
2227 err = pagecache_write_end(file, mapping, curpos, len, len,
2228 page, fsdata);
2229 if (err < 0)
2230 goto out;
2231 BUG_ON(err != len);
2232 err = 0;
2235 /* page covers the boundary, find the boundary offset */
2236 if (index == curidx) {
2237 zerofrom = curpos & ~PAGE_CACHE_MASK;
2238 /* if we will expand the thing last block will be filled */
2239 if (offset <= zerofrom) {
2240 goto out;
2242 if (zerofrom & (blocksize-1)) {
2243 *bytes |= (blocksize-1);
2244 (*bytes)++;
2246 len = offset - zerofrom;
2248 err = pagecache_write_begin(file, mapping, curpos, len,
2249 AOP_FLAG_UNINTERRUPTIBLE,
2250 &page, &fsdata);
2251 if (err)
2252 goto out;
2253 zero_user(page, zerofrom, len);
2254 err = pagecache_write_end(file, mapping, curpos, len, len,
2255 page, fsdata);
2256 if (err < 0)
2257 goto out;
2258 BUG_ON(err != len);
2259 err = 0;
2261 out:
2262 return err;
2266 * For moronic filesystems that do not allow holes in file.
2267 * We may have to extend the file.
2269 int cont_write_begin(struct file *file, struct address_space *mapping,
2270 loff_t pos, unsigned len, unsigned flags,
2271 struct page **pagep, void **fsdata,
2272 get_block_t *get_block, loff_t *bytes)
2274 struct inode *inode = mapping->host;
2275 unsigned blocksize = 1 << inode->i_blkbits;
2276 unsigned zerofrom;
2277 int err;
2279 err = cont_expand_zero(file, mapping, pos, bytes);
2280 if (err)
2281 goto out;
2283 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2284 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2285 *bytes |= (blocksize-1);
2286 (*bytes)++;
2289 *pagep = NULL;
2290 err = block_write_begin(file, mapping, pos, len,
2291 flags, pagep, fsdata, get_block);
2292 out:
2293 return err;
2296 int block_prepare_write(struct page *page, unsigned from, unsigned to,
2297 get_block_t *get_block)
2299 struct inode *inode = page->mapping->host;
2300 int err = __block_prepare_write(inode, page, from, to, get_block);
2301 if (err)
2302 ClearPageUptodate(page);
2303 return err;
2306 int block_commit_write(struct page *page, unsigned from, unsigned to)
2308 struct inode *inode = page->mapping->host;
2309 __block_commit_write(inode,page,from,to);
2310 return 0;
2313 int generic_commit_write(struct file *file, struct page *page,
2314 unsigned from, unsigned to)
2316 struct inode *inode = page->mapping->host;
2317 loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
2318 __block_commit_write(inode,page,from,to);
2320 * No need to use i_size_read() here, the i_size
2321 * cannot change under us because we hold i_mutex.
2323 if (pos > inode->i_size) {
2324 i_size_write(inode, pos);
2325 mark_inode_dirty(inode);
2327 return 0;
2331 * block_page_mkwrite() is not allowed to change the file size as it gets
2332 * called from a page fault handler when a page is first dirtied. Hence we must
2333 * be careful to check for EOF conditions here. We set the page up correctly
2334 * for a written page which means we get ENOSPC checking when writing into
2335 * holes and correct delalloc and unwritten extent mapping on filesystems that
2336 * support these features.
2338 * We are not allowed to take the i_mutex here so we have to play games to
2339 * protect against truncate races as the page could now be beyond EOF. Because
2340 * vmtruncate() writes the inode size before removing pages, once we have the
2341 * page lock we can determine safely if the page is beyond EOF. If it is not
2342 * beyond EOF, then the page is guaranteed safe against truncation until we
2343 * unlock the page.
2346 block_page_mkwrite(struct vm_area_struct *vma, struct page *page,
2347 get_block_t get_block)
2349 struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
2350 unsigned long end;
2351 loff_t size;
2352 int ret = -EINVAL;
2354 lock_page(page);
2355 size = i_size_read(inode);
2356 if ((page->mapping != inode->i_mapping) ||
2357 (page_offset(page) > size)) {
2358 /* page got truncated out from underneath us */
2359 goto out_unlock;
2362 /* page is wholly or partially inside EOF */
2363 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
2364 end = size & ~PAGE_CACHE_MASK;
2365 else
2366 end = PAGE_CACHE_SIZE;
2368 ret = block_prepare_write(page, 0, end, get_block);
2369 if (!ret)
2370 ret = block_commit_write(page, 0, end);
2372 out_unlock:
2373 unlock_page(page);
2374 return ret;
2378 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
2379 * immediately, while under the page lock. So it needs a special end_io
2380 * handler which does not touch the bh after unlocking it.
2382 static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2384 __end_buffer_read_notouch(bh, uptodate);
2388 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2389 * the page (converting it to circular linked list and taking care of page
2390 * dirty races).
2392 static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2394 struct buffer_head *bh;
2396 BUG_ON(!PageLocked(page));
2398 spin_lock(&page->mapping->private_lock);
2399 bh = head;
2400 do {
2401 if (PageDirty(page))
2402 set_buffer_dirty(bh);
2403 if (!bh->b_this_page)
2404 bh->b_this_page = head;
2405 bh = bh->b_this_page;
2406 } while (bh != head);
2407 attach_page_buffers(page, head);
2408 spin_unlock(&page->mapping->private_lock);
2412 * On entry, the page is fully not uptodate.
2413 * On exit the page is fully uptodate in the areas outside (from,to)
2415 int nobh_write_begin(struct file *file, struct address_space *mapping,
2416 loff_t pos, unsigned len, unsigned flags,
2417 struct page **pagep, void **fsdata,
2418 get_block_t *get_block)
2420 struct inode *inode = mapping->host;
2421 const unsigned blkbits = inode->i_blkbits;
2422 const unsigned blocksize = 1 << blkbits;
2423 struct buffer_head *head, *bh;
2424 struct page *page;
2425 pgoff_t index;
2426 unsigned from, to;
2427 unsigned block_in_page;
2428 unsigned block_start, block_end;
2429 sector_t block_in_file;
2430 int nr_reads = 0;
2431 int ret = 0;
2432 int is_mapped_to_disk = 1;
2434 index = pos >> PAGE_CACHE_SHIFT;
2435 from = pos & (PAGE_CACHE_SIZE - 1);
2436 to = from + len;
2438 page = __grab_cache_page(mapping, index);
2439 if (!page)
2440 return -ENOMEM;
2441 *pagep = page;
2442 *fsdata = NULL;
2444 if (page_has_buffers(page)) {
2445 unlock_page(page);
2446 page_cache_release(page);
2447 *pagep = NULL;
2448 return block_write_begin(file, mapping, pos, len, flags, pagep,
2449 fsdata, get_block);
2452 if (PageMappedToDisk(page))
2453 return 0;
2456 * Allocate buffers so that we can keep track of state, and potentially
2457 * attach them to the page if an error occurs. In the common case of
2458 * no error, they will just be freed again without ever being attached
2459 * to the page (which is all OK, because we're under the page lock).
2461 * Be careful: the buffer linked list is a NULL terminated one, rather
2462 * than the circular one we're used to.
2464 head = alloc_page_buffers(page, blocksize, 0);
2465 if (!head) {
2466 ret = -ENOMEM;
2467 goto out_release;
2470 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
2473 * We loop across all blocks in the page, whether or not they are
2474 * part of the affected region. This is so we can discover if the
2475 * page is fully mapped-to-disk.
2477 for (block_start = 0, block_in_page = 0, bh = head;
2478 block_start < PAGE_CACHE_SIZE;
2479 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
2480 int create;
2482 block_end = block_start + blocksize;
2483 bh->b_state = 0;
2484 create = 1;
2485 if (block_start >= to)
2486 create = 0;
2487 ret = get_block(inode, block_in_file + block_in_page,
2488 bh, create);
2489 if (ret)
2490 goto failed;
2491 if (!buffer_mapped(bh))
2492 is_mapped_to_disk = 0;
2493 if (buffer_new(bh))
2494 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
2495 if (PageUptodate(page)) {
2496 set_buffer_uptodate(bh);
2497 continue;
2499 if (buffer_new(bh) || !buffer_mapped(bh)) {
2500 zero_user_segments(page, block_start, from,
2501 to, block_end);
2502 continue;
2504 if (buffer_uptodate(bh))
2505 continue; /* reiserfs does this */
2506 if (block_start < from || block_end > to) {
2507 lock_buffer(bh);
2508 bh->b_end_io = end_buffer_read_nobh;
2509 submit_bh(READ, bh);
2510 nr_reads++;
2514 if (nr_reads) {
2516 * The page is locked, so these buffers are protected from
2517 * any VM or truncate activity. Hence we don't need to care
2518 * for the buffer_head refcounts.
2520 for (bh = head; bh; bh = bh->b_this_page) {
2521 wait_on_buffer(bh);
2522 if (!buffer_uptodate(bh))
2523 ret = -EIO;
2525 if (ret)
2526 goto failed;
2529 if (is_mapped_to_disk)
2530 SetPageMappedToDisk(page);
2532 *fsdata = head; /* to be released by nobh_write_end */
2534 return 0;
2536 failed:
2537 BUG_ON(!ret);
2539 * Error recovery is a bit difficult. We need to zero out blocks that
2540 * were newly allocated, and dirty them to ensure they get written out.
2541 * Buffers need to be attached to the page at this point, otherwise
2542 * the handling of potential IO errors during writeout would be hard
2543 * (could try doing synchronous writeout, but what if that fails too?)
2545 attach_nobh_buffers(page, head);
2546 page_zero_new_buffers(page, from, to);
2548 out_release:
2549 unlock_page(page);
2550 page_cache_release(page);
2551 *pagep = NULL;
2553 if (pos + len > inode->i_size)
2554 vmtruncate(inode, inode->i_size);
2556 return ret;
2558 EXPORT_SYMBOL(nobh_write_begin);
2560 int nobh_write_end(struct file *file, struct address_space *mapping,
2561 loff_t pos, unsigned len, unsigned copied,
2562 struct page *page, void *fsdata)
2564 struct inode *inode = page->mapping->host;
2565 struct buffer_head *head = fsdata;
2566 struct buffer_head *bh;
2568 if (!PageMappedToDisk(page)) {
2569 if (unlikely(copied < len) && !page_has_buffers(page))
2570 attach_nobh_buffers(page, head);
2571 if (page_has_buffers(page))
2572 return generic_write_end(file, mapping, pos, len,
2573 copied, page, fsdata);
2576 SetPageUptodate(page);
2577 set_page_dirty(page);
2578 if (pos+copied > inode->i_size) {
2579 i_size_write(inode, pos+copied);
2580 mark_inode_dirty(inode);
2583 unlock_page(page);
2584 page_cache_release(page);
2586 while (head) {
2587 bh = head;
2588 head = head->b_this_page;
2589 free_buffer_head(bh);
2592 return copied;
2594 EXPORT_SYMBOL(nobh_write_end);
2597 * nobh_writepage() - based on block_full_write_page() except
2598 * that it tries to operate without attaching bufferheads to
2599 * the page.
2601 int nobh_writepage(struct page *page, get_block_t *get_block,
2602 struct writeback_control *wbc)
2604 struct inode * const inode = page->mapping->host;
2605 loff_t i_size = i_size_read(inode);
2606 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2607 unsigned offset;
2608 int ret;
2610 /* Is the page fully inside i_size? */
2611 if (page->index < end_index)
2612 goto out;
2614 /* Is the page fully outside i_size? (truncate in progress) */
2615 offset = i_size & (PAGE_CACHE_SIZE-1);
2616 if (page->index >= end_index+1 || !offset) {
2618 * The page may have dirty, unmapped buffers. For example,
2619 * they may have been added in ext3_writepage(). Make them
2620 * freeable here, so the page does not leak.
2622 #if 0
2623 /* Not really sure about this - do we need this ? */
2624 if (page->mapping->a_ops->invalidatepage)
2625 page->mapping->a_ops->invalidatepage(page, offset);
2626 #endif
2627 unlock_page(page);
2628 return 0; /* don't care */
2632 * The page straddles i_size. It must be zeroed out on each and every
2633 * writepage invocation because it may be mmapped. "A file is mapped
2634 * in multiples of the page size. For a file that is not a multiple of
2635 * the page size, the remaining memory is zeroed when mapped, and
2636 * writes to that region are not written out to the file."
2638 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2639 out:
2640 ret = mpage_writepage(page, get_block, wbc);
2641 if (ret == -EAGAIN)
2642 ret = __block_write_full_page(inode, page, get_block, wbc);
2643 return ret;
2645 EXPORT_SYMBOL(nobh_writepage);
2647 int nobh_truncate_page(struct address_space *mapping,
2648 loff_t from, get_block_t *get_block)
2650 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2651 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2652 unsigned blocksize;
2653 sector_t iblock;
2654 unsigned length, pos;
2655 struct inode *inode = mapping->host;
2656 struct page *page;
2657 struct buffer_head map_bh;
2658 int err;
2660 blocksize = 1 << inode->i_blkbits;
2661 length = offset & (blocksize - 1);
2663 /* Block boundary? Nothing to do */
2664 if (!length)
2665 return 0;
2667 length = blocksize - length;
2668 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2670 page = grab_cache_page(mapping, index);
2671 err = -ENOMEM;
2672 if (!page)
2673 goto out;
2675 if (page_has_buffers(page)) {
2676 has_buffers:
2677 unlock_page(page);
2678 page_cache_release(page);
2679 return block_truncate_page(mapping, from, get_block);
2682 /* Find the buffer that contains "offset" */
2683 pos = blocksize;
2684 while (offset >= pos) {
2685 iblock++;
2686 pos += blocksize;
2689 err = get_block(inode, iblock, &map_bh, 0);
2690 if (err)
2691 goto unlock;
2692 /* unmapped? It's a hole - nothing to do */
2693 if (!buffer_mapped(&map_bh))
2694 goto unlock;
2696 /* Ok, it's mapped. Make sure it's up-to-date */
2697 if (!PageUptodate(page)) {
2698 err = mapping->a_ops->readpage(NULL, page);
2699 if (err) {
2700 page_cache_release(page);
2701 goto out;
2703 lock_page(page);
2704 if (!PageUptodate(page)) {
2705 err = -EIO;
2706 goto unlock;
2708 if (page_has_buffers(page))
2709 goto has_buffers;
2711 zero_user(page, offset, length);
2712 set_page_dirty(page);
2713 err = 0;
2715 unlock:
2716 unlock_page(page);
2717 page_cache_release(page);
2718 out:
2719 return err;
2721 EXPORT_SYMBOL(nobh_truncate_page);
2723 int block_truncate_page(struct address_space *mapping,
2724 loff_t from, get_block_t *get_block)
2726 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2727 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2728 unsigned blocksize;
2729 sector_t iblock;
2730 unsigned length, pos;
2731 struct inode *inode = mapping->host;
2732 struct page *page;
2733 struct buffer_head *bh;
2734 int err;
2736 blocksize = 1 << inode->i_blkbits;
2737 length = offset & (blocksize - 1);
2739 /* Block boundary? Nothing to do */
2740 if (!length)
2741 return 0;
2743 length = blocksize - length;
2744 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2746 page = grab_cache_page(mapping, index);
2747 err = -ENOMEM;
2748 if (!page)
2749 goto out;
2751 if (!page_has_buffers(page))
2752 create_empty_buffers(page, blocksize, 0);
2754 /* Find the buffer that contains "offset" */
2755 bh = page_buffers(page);
2756 pos = blocksize;
2757 while (offset >= pos) {
2758 bh = bh->b_this_page;
2759 iblock++;
2760 pos += blocksize;
2763 err = 0;
2764 if (!buffer_mapped(bh)) {
2765 WARN_ON(bh->b_size != blocksize);
2766 err = get_block(inode, iblock, bh, 0);
2767 if (err)
2768 goto unlock;
2769 /* unmapped? It's a hole - nothing to do */
2770 if (!buffer_mapped(bh))
2771 goto unlock;
2774 /* Ok, it's mapped. Make sure it's up-to-date */
2775 if (PageUptodate(page))
2776 set_buffer_uptodate(bh);
2778 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2779 err = -EIO;
2780 ll_rw_block(READ, 1, &bh);
2781 wait_on_buffer(bh);
2782 /* Uhhuh. Read error. Complain and punt. */
2783 if (!buffer_uptodate(bh))
2784 goto unlock;
2787 zero_user(page, offset, length);
2788 mark_buffer_dirty(bh);
2789 err = 0;
2791 unlock:
2792 unlock_page(page);
2793 page_cache_release(page);
2794 out:
2795 return err;
2799 * The generic ->writepage function for buffer-backed address_spaces
2801 int block_write_full_page(struct page *page, get_block_t *get_block,
2802 struct writeback_control *wbc)
2804 struct inode * const inode = page->mapping->host;
2805 loff_t i_size = i_size_read(inode);
2806 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2807 unsigned offset;
2809 /* Is the page fully inside i_size? */
2810 if (page->index < end_index)
2811 return __block_write_full_page(inode, page, get_block, wbc);
2813 /* Is the page fully outside i_size? (truncate in progress) */
2814 offset = i_size & (PAGE_CACHE_SIZE-1);
2815 if (page->index >= end_index+1 || !offset) {
2817 * The page may have dirty, unmapped buffers. For example,
2818 * they may have been added in ext3_writepage(). Make them
2819 * freeable here, so the page does not leak.
2821 do_invalidatepage(page, 0);
2822 unlock_page(page);
2823 return 0; /* don't care */
2827 * The page straddles i_size. It must be zeroed out on each and every
2828 * writepage invokation because it may be mmapped. "A file is mapped
2829 * in multiples of the page size. For a file that is not a multiple of
2830 * the page size, the remaining memory is zeroed when mapped, and
2831 * writes to that region are not written out to the file."
2833 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2834 return __block_write_full_page(inode, page, get_block, wbc);
2837 sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2838 get_block_t *get_block)
2840 struct buffer_head tmp;
2841 struct inode *inode = mapping->host;
2842 tmp.b_state = 0;
2843 tmp.b_blocknr = 0;
2844 tmp.b_size = 1 << inode->i_blkbits;
2845 get_block(inode, block, &tmp, 0);
2846 return tmp.b_blocknr;
2849 static void end_bio_bh_io_sync(struct bio *bio, int err)
2851 struct buffer_head *bh = bio->bi_private;
2853 if (err == -EOPNOTSUPP) {
2854 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
2855 set_bit(BH_Eopnotsupp, &bh->b_state);
2858 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2859 bio_put(bio);
2862 int submit_bh(int rw, struct buffer_head * bh)
2864 struct bio *bio;
2865 int ret = 0;
2867 BUG_ON(!buffer_locked(bh));
2868 BUG_ON(!buffer_mapped(bh));
2869 BUG_ON(!bh->b_end_io);
2871 if (buffer_ordered(bh) && (rw == WRITE))
2872 rw = WRITE_BARRIER;
2875 * Only clear out a write error when rewriting, should this
2876 * include WRITE_SYNC as well?
2878 if (test_set_buffer_req(bh) && (rw == WRITE || rw == WRITE_BARRIER))
2879 clear_buffer_write_io_error(bh);
2882 * from here on down, it's all bio -- do the initial mapping,
2883 * submit_bio -> generic_make_request may further map this bio around
2885 bio = bio_alloc(GFP_NOIO, 1);
2887 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2888 bio->bi_bdev = bh->b_bdev;
2889 bio->bi_io_vec[0].bv_page = bh->b_page;
2890 bio->bi_io_vec[0].bv_len = bh->b_size;
2891 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
2893 bio->bi_vcnt = 1;
2894 bio->bi_idx = 0;
2895 bio->bi_size = bh->b_size;
2897 bio->bi_end_io = end_bio_bh_io_sync;
2898 bio->bi_private = bh;
2900 bio_get(bio);
2901 submit_bio(rw, bio);
2903 if (bio_flagged(bio, BIO_EOPNOTSUPP))
2904 ret = -EOPNOTSUPP;
2906 bio_put(bio);
2907 return ret;
2911 * ll_rw_block: low-level access to block devices (DEPRECATED)
2912 * @rw: whether to %READ or %WRITE or %SWRITE or maybe %READA (readahead)
2913 * @nr: number of &struct buffer_heads in the array
2914 * @bhs: array of pointers to &struct buffer_head
2916 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
2917 * requests an I/O operation on them, either a %READ or a %WRITE. The third
2918 * %SWRITE is like %WRITE only we make sure that the *current* data in buffers
2919 * are sent to disk. The fourth %READA option is described in the documentation
2920 * for generic_make_request() which ll_rw_block() calls.
2922 * This function drops any buffer that it cannot get a lock on (with the
2923 * BH_Lock state bit) unless SWRITE is required, any buffer that appears to be
2924 * clean when doing a write request, and any buffer that appears to be
2925 * up-to-date when doing read request. Further it marks as clean buffers that
2926 * are processed for writing (the buffer cache won't assume that they are
2927 * actually clean until the buffer gets unlocked).
2929 * ll_rw_block sets b_end_io to simple completion handler that marks
2930 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
2931 * any waiters.
2933 * All of the buffers must be for the same device, and must also be a
2934 * multiple of the current approved size for the device.
2936 void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
2938 int i;
2940 for (i = 0; i < nr; i++) {
2941 struct buffer_head *bh = bhs[i];
2943 if (rw == SWRITE)
2944 lock_buffer(bh);
2945 else if (test_set_buffer_locked(bh))
2946 continue;
2948 if (rw == WRITE || rw == SWRITE) {
2949 if (test_clear_buffer_dirty(bh)) {
2950 bh->b_end_io = end_buffer_write_sync;
2951 get_bh(bh);
2952 submit_bh(WRITE, bh);
2953 continue;
2955 } else {
2956 if (!buffer_uptodate(bh)) {
2957 bh->b_end_io = end_buffer_read_sync;
2958 get_bh(bh);
2959 submit_bh(rw, bh);
2960 continue;
2963 unlock_buffer(bh);
2968 * For a data-integrity writeout, we need to wait upon any in-progress I/O
2969 * and then start new I/O and then wait upon it. The caller must have a ref on
2970 * the buffer_head.
2972 int sync_dirty_buffer(struct buffer_head *bh)
2974 int ret = 0;
2976 WARN_ON(atomic_read(&bh->b_count) < 1);
2977 lock_buffer(bh);
2978 if (test_clear_buffer_dirty(bh)) {
2979 get_bh(bh);
2980 bh->b_end_io = end_buffer_write_sync;
2981 ret = submit_bh(WRITE, bh);
2982 wait_on_buffer(bh);
2983 if (buffer_eopnotsupp(bh)) {
2984 clear_buffer_eopnotsupp(bh);
2985 ret = -EOPNOTSUPP;
2987 if (!ret && !buffer_uptodate(bh))
2988 ret = -EIO;
2989 } else {
2990 unlock_buffer(bh);
2992 return ret;
2996 * try_to_free_buffers() checks if all the buffers on this particular page
2997 * are unused, and releases them if so.
2999 * Exclusion against try_to_free_buffers may be obtained by either
3000 * locking the page or by holding its mapping's private_lock.
3002 * If the page is dirty but all the buffers are clean then we need to
3003 * be sure to mark the page clean as well. This is because the page
3004 * may be against a block device, and a later reattachment of buffers
3005 * to a dirty page will set *all* buffers dirty. Which would corrupt
3006 * filesystem data on the same device.
3008 * The same applies to regular filesystem pages: if all the buffers are
3009 * clean then we set the page clean and proceed. To do that, we require
3010 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3011 * private_lock.
3013 * try_to_free_buffers() is non-blocking.
3015 static inline int buffer_busy(struct buffer_head *bh)
3017 return atomic_read(&bh->b_count) |
3018 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3021 static int
3022 drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3024 struct buffer_head *head = page_buffers(page);
3025 struct buffer_head *bh;
3027 bh = head;
3028 do {
3029 if (buffer_write_io_error(bh) && page->mapping)
3030 set_bit(AS_EIO, &page->mapping->flags);
3031 if (buffer_busy(bh))
3032 goto failed;
3033 bh = bh->b_this_page;
3034 } while (bh != head);
3036 do {
3037 struct buffer_head *next = bh->b_this_page;
3039 if (bh->b_assoc_map)
3040 __remove_assoc_queue(bh);
3041 bh = next;
3042 } while (bh != head);
3043 *buffers_to_free = head;
3044 __clear_page_buffers(page);
3045 return 1;
3046 failed:
3047 return 0;
3050 int try_to_free_buffers(struct page *page)
3052 struct address_space * const mapping = page->mapping;
3053 struct buffer_head *buffers_to_free = NULL;
3054 int ret = 0;
3056 BUG_ON(!PageLocked(page));
3057 if (PageWriteback(page))
3058 return 0;
3060 if (mapping == NULL) { /* can this still happen? */
3061 ret = drop_buffers(page, &buffers_to_free);
3062 goto out;
3065 spin_lock(&mapping->private_lock);
3066 ret = drop_buffers(page, &buffers_to_free);
3069 * If the filesystem writes its buffers by hand (eg ext3)
3070 * then we can have clean buffers against a dirty page. We
3071 * clean the page here; otherwise the VM will never notice
3072 * that the filesystem did any IO at all.
3074 * Also, during truncate, discard_buffer will have marked all
3075 * the page's buffers clean. We discover that here and clean
3076 * the page also.
3078 * private_lock must be held over this entire operation in order
3079 * to synchronise against __set_page_dirty_buffers and prevent the
3080 * dirty bit from being lost.
3082 if (ret)
3083 cancel_dirty_page(page, PAGE_CACHE_SIZE);
3084 spin_unlock(&mapping->private_lock);
3085 out:
3086 if (buffers_to_free) {
3087 struct buffer_head *bh = buffers_to_free;
3089 do {
3090 struct buffer_head *next = bh->b_this_page;
3091 free_buffer_head(bh);
3092 bh = next;
3093 } while (bh != buffers_to_free);
3095 return ret;
3097 EXPORT_SYMBOL(try_to_free_buffers);
3099 void block_sync_page(struct page *page)
3101 struct address_space *mapping;
3103 smp_mb();
3104 mapping = page_mapping(page);
3105 if (mapping)
3106 blk_run_backing_dev(mapping->backing_dev_info, page);
3110 * There are no bdflush tunables left. But distributions are
3111 * still running obsolete flush daemons, so we terminate them here.
3113 * Use of bdflush() is deprecated and will be removed in a future kernel.
3114 * The `pdflush' kernel threads fully replace bdflush daemons and this call.
3116 asmlinkage long sys_bdflush(int func, long data)
3118 static int msg_count;
3120 if (!capable(CAP_SYS_ADMIN))
3121 return -EPERM;
3123 if (msg_count < 5) {
3124 msg_count++;
3125 printk(KERN_INFO
3126 "warning: process `%s' used the obsolete bdflush"
3127 " system call\n", current->comm);
3128 printk(KERN_INFO "Fix your initscripts?\n");
3131 if (func == 1)
3132 do_exit(0);
3133 return 0;
3137 * Buffer-head allocation
3139 static struct kmem_cache *bh_cachep;
3142 * Once the number of bh's in the machine exceeds this level, we start
3143 * stripping them in writeback.
3145 static int max_buffer_heads;
3147 int buffer_heads_over_limit;
3149 struct bh_accounting {
3150 int nr; /* Number of live bh's */
3151 int ratelimit; /* Limit cacheline bouncing */
3154 static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3156 static void recalc_bh_state(void)
3158 int i;
3159 int tot = 0;
3161 if (__get_cpu_var(bh_accounting).ratelimit++ < 4096)
3162 return;
3163 __get_cpu_var(bh_accounting).ratelimit = 0;
3164 for_each_online_cpu(i)
3165 tot += per_cpu(bh_accounting, i).nr;
3166 buffer_heads_over_limit = (tot > max_buffer_heads);
3169 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3171 struct buffer_head *ret = kmem_cache_alloc(bh_cachep,
3172 set_migrateflags(gfp_flags, __GFP_RECLAIMABLE));
3173 if (ret) {
3174 INIT_LIST_HEAD(&ret->b_assoc_buffers);
3175 get_cpu_var(bh_accounting).nr++;
3176 recalc_bh_state();
3177 put_cpu_var(bh_accounting);
3179 return ret;
3181 EXPORT_SYMBOL(alloc_buffer_head);
3183 void free_buffer_head(struct buffer_head *bh)
3185 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3186 kmem_cache_free(bh_cachep, bh);
3187 get_cpu_var(bh_accounting).nr--;
3188 recalc_bh_state();
3189 put_cpu_var(bh_accounting);
3191 EXPORT_SYMBOL(free_buffer_head);
3193 static void buffer_exit_cpu(int cpu)
3195 int i;
3196 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3198 for (i = 0; i < BH_LRU_SIZE; i++) {
3199 brelse(b->bhs[i]);
3200 b->bhs[i] = NULL;
3202 get_cpu_var(bh_accounting).nr += per_cpu(bh_accounting, cpu).nr;
3203 per_cpu(bh_accounting, cpu).nr = 0;
3204 put_cpu_var(bh_accounting);
3207 static int buffer_cpu_notify(struct notifier_block *self,
3208 unsigned long action, void *hcpu)
3210 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
3211 buffer_exit_cpu((unsigned long)hcpu);
3212 return NOTIFY_OK;
3216 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3217 * @bh: struct buffer_head
3219 * Return true if the buffer is up-to-date and false,
3220 * with the buffer locked, if not.
3222 int bh_uptodate_or_lock(struct buffer_head *bh)
3224 if (!buffer_uptodate(bh)) {
3225 lock_buffer(bh);
3226 if (!buffer_uptodate(bh))
3227 return 0;
3228 unlock_buffer(bh);
3230 return 1;
3232 EXPORT_SYMBOL(bh_uptodate_or_lock);
3235 * bh_submit_read - Submit a locked buffer for reading
3236 * @bh: struct buffer_head
3238 * Returns zero on success and -EIO on error.
3240 int bh_submit_read(struct buffer_head *bh)
3242 BUG_ON(!buffer_locked(bh));
3244 if (buffer_uptodate(bh)) {
3245 unlock_buffer(bh);
3246 return 0;
3249 get_bh(bh);
3250 bh->b_end_io = end_buffer_read_sync;
3251 submit_bh(READ, bh);
3252 wait_on_buffer(bh);
3253 if (buffer_uptodate(bh))
3254 return 0;
3255 return -EIO;
3257 EXPORT_SYMBOL(bh_submit_read);
3259 static void
3260 init_buffer_head(struct kmem_cache *cachep, void *data)
3262 struct buffer_head *bh = data;
3264 memset(bh, 0, sizeof(*bh));
3265 INIT_LIST_HEAD(&bh->b_assoc_buffers);
3268 void __init buffer_init(void)
3270 int nrpages;
3272 bh_cachep = kmem_cache_create("buffer_head",
3273 sizeof(struct buffer_head), 0,
3274 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3275 SLAB_MEM_SPREAD),
3276 init_buffer_head);
3279 * Limit the bh occupancy to 10% of ZONE_NORMAL
3281 nrpages = (nr_free_buffer_pages() * 10) / 100;
3282 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3283 hotcpu_notifier(buffer_cpu_notify, 0);
3286 EXPORT_SYMBOL(__bforget);
3287 EXPORT_SYMBOL(__brelse);
3288 EXPORT_SYMBOL(__wait_on_buffer);
3289 EXPORT_SYMBOL(block_commit_write);
3290 EXPORT_SYMBOL(block_prepare_write);
3291 EXPORT_SYMBOL(block_page_mkwrite);
3292 EXPORT_SYMBOL(block_read_full_page);
3293 EXPORT_SYMBOL(block_sync_page);
3294 EXPORT_SYMBOL(block_truncate_page);
3295 EXPORT_SYMBOL(block_write_full_page);
3296 EXPORT_SYMBOL(cont_write_begin);
3297 EXPORT_SYMBOL(end_buffer_read_sync);
3298 EXPORT_SYMBOL(end_buffer_write_sync);
3299 EXPORT_SYMBOL(file_fsync);
3300 EXPORT_SYMBOL(fsync_bdev);
3301 EXPORT_SYMBOL(generic_block_bmap);
3302 EXPORT_SYMBOL(generic_commit_write);
3303 EXPORT_SYMBOL(generic_cont_expand_simple);
3304 EXPORT_SYMBOL(init_buffer);
3305 EXPORT_SYMBOL(invalidate_bdev);
3306 EXPORT_SYMBOL(ll_rw_block);
3307 EXPORT_SYMBOL(mark_buffer_dirty);
3308 EXPORT_SYMBOL(submit_bh);
3309 EXPORT_SYMBOL(sync_dirty_buffer);
3310 EXPORT_SYMBOL(unlock_buffer);