usbfs: fix race between open and unregister
[linux-2.6/mini2440.git] / fs / buffer.c
blobd48caee12e2a4adaae056451f7dcef71205ccfa5
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 *zone;
364 int nid;
366 wakeup_pdflush(1024);
367 yield();
369 for_each_online_node(nid) {
370 (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS),
371 gfp_zone(GFP_NOFS), NULL,
372 &zone);
373 if (zone)
374 try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0,
375 GFP_NOFS);
380 * I/O completion handler for block_read_full_page() - pages
381 * which come unlocked at the end of I/O.
383 static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
385 unsigned long flags;
386 struct buffer_head *first;
387 struct buffer_head *tmp;
388 struct page *page;
389 int page_uptodate = 1;
391 BUG_ON(!buffer_async_read(bh));
393 page = bh->b_page;
394 if (uptodate) {
395 set_buffer_uptodate(bh);
396 } else {
397 clear_buffer_uptodate(bh);
398 if (printk_ratelimit())
399 buffer_io_error(bh);
400 SetPageError(page);
404 * Be _very_ careful from here on. Bad things can happen if
405 * two buffer heads end IO at almost the same time and both
406 * decide that the page is now completely done.
408 first = page_buffers(page);
409 local_irq_save(flags);
410 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
411 clear_buffer_async_read(bh);
412 unlock_buffer(bh);
413 tmp = bh;
414 do {
415 if (!buffer_uptodate(tmp))
416 page_uptodate = 0;
417 if (buffer_async_read(tmp)) {
418 BUG_ON(!buffer_locked(tmp));
419 goto still_busy;
421 tmp = tmp->b_this_page;
422 } while (tmp != bh);
423 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
424 local_irq_restore(flags);
427 * If none of the buffers had errors and they are all
428 * uptodate then we can set the page uptodate.
430 if (page_uptodate && !PageError(page))
431 SetPageUptodate(page);
432 unlock_page(page);
433 return;
435 still_busy:
436 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
437 local_irq_restore(flags);
438 return;
442 * Completion handler for block_write_full_page() - pages which are unlocked
443 * during I/O, and which have PageWriteback cleared upon I/O completion.
445 static void end_buffer_async_write(struct buffer_head *bh, int uptodate)
447 char b[BDEVNAME_SIZE];
448 unsigned long flags;
449 struct buffer_head *first;
450 struct buffer_head *tmp;
451 struct page *page;
453 BUG_ON(!buffer_async_write(bh));
455 page = bh->b_page;
456 if (uptodate) {
457 set_buffer_uptodate(bh);
458 } else {
459 if (printk_ratelimit()) {
460 buffer_io_error(bh);
461 printk(KERN_WARNING "lost page write due to "
462 "I/O error on %s\n",
463 bdevname(bh->b_bdev, b));
465 set_bit(AS_EIO, &page->mapping->flags);
466 set_buffer_write_io_error(bh);
467 clear_buffer_uptodate(bh);
468 SetPageError(page);
471 first = page_buffers(page);
472 local_irq_save(flags);
473 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
475 clear_buffer_async_write(bh);
476 unlock_buffer(bh);
477 tmp = bh->b_this_page;
478 while (tmp != bh) {
479 if (buffer_async_write(tmp)) {
480 BUG_ON(!buffer_locked(tmp));
481 goto still_busy;
483 tmp = tmp->b_this_page;
485 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
486 local_irq_restore(flags);
487 end_page_writeback(page);
488 return;
490 still_busy:
491 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
492 local_irq_restore(flags);
493 return;
497 * If a page's buffers are under async readin (end_buffer_async_read
498 * completion) then there is a possibility that another thread of
499 * control could lock one of the buffers after it has completed
500 * but while some of the other buffers have not completed. This
501 * locked buffer would confuse end_buffer_async_read() into not unlocking
502 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
503 * that this buffer is not under async I/O.
505 * The page comes unlocked when it has no locked buffer_async buffers
506 * left.
508 * PageLocked prevents anyone starting new async I/O reads any of
509 * the buffers.
511 * PageWriteback is used to prevent simultaneous writeout of the same
512 * page.
514 * PageLocked prevents anyone from starting writeback of a page which is
515 * under read I/O (PageWriteback is only ever set against a locked page).
517 static void mark_buffer_async_read(struct buffer_head *bh)
519 bh->b_end_io = end_buffer_async_read;
520 set_buffer_async_read(bh);
523 void mark_buffer_async_write(struct buffer_head *bh)
525 bh->b_end_io = end_buffer_async_write;
526 set_buffer_async_write(bh);
528 EXPORT_SYMBOL(mark_buffer_async_write);
532 * fs/buffer.c contains helper functions for buffer-backed address space's
533 * fsync functions. A common requirement for buffer-based filesystems is
534 * that certain data from the backing blockdev needs to be written out for
535 * a successful fsync(). For example, ext2 indirect blocks need to be
536 * written back and waited upon before fsync() returns.
538 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
539 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
540 * management of a list of dependent buffers at ->i_mapping->private_list.
542 * Locking is a little subtle: try_to_free_buffers() will remove buffers
543 * from their controlling inode's queue when they are being freed. But
544 * try_to_free_buffers() will be operating against the *blockdev* mapping
545 * at the time, not against the S_ISREG file which depends on those buffers.
546 * So the locking for private_list is via the private_lock in the address_space
547 * which backs the buffers. Which is different from the address_space
548 * against which the buffers are listed. So for a particular address_space,
549 * mapping->private_lock does *not* protect mapping->private_list! In fact,
550 * mapping->private_list will always be protected by the backing blockdev's
551 * ->private_lock.
553 * Which introduces a requirement: all buffers on an address_space's
554 * ->private_list must be from the same address_space: the blockdev's.
556 * address_spaces which do not place buffers at ->private_list via these
557 * utility functions are free to use private_lock and private_list for
558 * whatever they want. The only requirement is that list_empty(private_list)
559 * be true at clear_inode() time.
561 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
562 * filesystems should do that. invalidate_inode_buffers() should just go
563 * BUG_ON(!list_empty).
565 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
566 * take an address_space, not an inode. And it should be called
567 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
568 * queued up.
570 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
571 * list if it is already on a list. Because if the buffer is on a list,
572 * it *must* already be on the right one. If not, the filesystem is being
573 * silly. This will save a ton of locking. But first we have to ensure
574 * that buffers are taken *off* the old inode's list when they are freed
575 * (presumably in truncate). That requires careful auditing of all
576 * filesystems (do it inside bforget()). It could also be done by bringing
577 * b_inode back.
581 * The buffer's backing address_space's private_lock must be held
583 static inline void __remove_assoc_queue(struct buffer_head *bh)
585 list_del_init(&bh->b_assoc_buffers);
586 WARN_ON(!bh->b_assoc_map);
587 if (buffer_write_io_error(bh))
588 set_bit(AS_EIO, &bh->b_assoc_map->flags);
589 bh->b_assoc_map = NULL;
592 int inode_has_buffers(struct inode *inode)
594 return !list_empty(&inode->i_data.private_list);
598 * osync is designed to support O_SYNC io. It waits synchronously for
599 * all already-submitted IO to complete, but does not queue any new
600 * writes to the disk.
602 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
603 * you dirty the buffers, and then use osync_inode_buffers to wait for
604 * completion. Any other dirty buffers which are not yet queued for
605 * write will not be flushed to disk by the osync.
607 static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
609 struct buffer_head *bh;
610 struct list_head *p;
611 int err = 0;
613 spin_lock(lock);
614 repeat:
615 list_for_each_prev(p, list) {
616 bh = BH_ENTRY(p);
617 if (buffer_locked(bh)) {
618 get_bh(bh);
619 spin_unlock(lock);
620 wait_on_buffer(bh);
621 if (!buffer_uptodate(bh))
622 err = -EIO;
623 brelse(bh);
624 spin_lock(lock);
625 goto repeat;
628 spin_unlock(lock);
629 return err;
633 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
634 * @mapping: the mapping which wants those buffers written
636 * Starts I/O against the buffers at mapping->private_list, and waits upon
637 * that I/O.
639 * Basically, this is a convenience function for fsync().
640 * @mapping is a file or directory which needs those buffers to be written for
641 * a successful fsync().
643 int sync_mapping_buffers(struct address_space *mapping)
645 struct address_space *buffer_mapping = mapping->assoc_mapping;
647 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
648 return 0;
650 return fsync_buffers_list(&buffer_mapping->private_lock,
651 &mapping->private_list);
653 EXPORT_SYMBOL(sync_mapping_buffers);
656 * Called when we've recently written block `bblock', and it is known that
657 * `bblock' was for a buffer_boundary() buffer. This means that the block at
658 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
659 * dirty, schedule it for IO. So that indirects merge nicely with their data.
661 void write_boundary_block(struct block_device *bdev,
662 sector_t bblock, unsigned blocksize)
664 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
665 if (bh) {
666 if (buffer_dirty(bh))
667 ll_rw_block(WRITE, 1, &bh);
668 put_bh(bh);
672 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
674 struct address_space *mapping = inode->i_mapping;
675 struct address_space *buffer_mapping = bh->b_page->mapping;
677 mark_buffer_dirty(bh);
678 if (!mapping->assoc_mapping) {
679 mapping->assoc_mapping = buffer_mapping;
680 } else {
681 BUG_ON(mapping->assoc_mapping != buffer_mapping);
683 if (!bh->b_assoc_map) {
684 spin_lock(&buffer_mapping->private_lock);
685 list_move_tail(&bh->b_assoc_buffers,
686 &mapping->private_list);
687 bh->b_assoc_map = mapping;
688 spin_unlock(&buffer_mapping->private_lock);
691 EXPORT_SYMBOL(mark_buffer_dirty_inode);
694 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
695 * dirty.
697 * If warn is true, then emit a warning if the page is not uptodate and has
698 * not been truncated.
700 static int __set_page_dirty(struct page *page,
701 struct address_space *mapping, int warn)
703 if (unlikely(!mapping))
704 return !TestSetPageDirty(page);
706 if (TestSetPageDirty(page))
707 return 0;
709 write_lock_irq(&mapping->tree_lock);
710 if (page->mapping) { /* Race with truncate? */
711 WARN_ON_ONCE(warn && !PageUptodate(page));
713 if (mapping_cap_account_dirty(mapping)) {
714 __inc_zone_page_state(page, NR_FILE_DIRTY);
715 __inc_bdi_stat(mapping->backing_dev_info,
716 BDI_RECLAIMABLE);
717 task_io_account_write(PAGE_CACHE_SIZE);
719 radix_tree_tag_set(&mapping->page_tree,
720 page_index(page), PAGECACHE_TAG_DIRTY);
722 write_unlock_irq(&mapping->tree_lock);
723 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
725 return 1;
729 * Add a page to the dirty page list.
731 * It is a sad fact of life that this function is called from several places
732 * deeply under spinlocking. It may not sleep.
734 * If the page has buffers, the uptodate buffers are set dirty, to preserve
735 * dirty-state coherency between the page and the buffers. It the page does
736 * not have buffers then when they are later attached they will all be set
737 * dirty.
739 * The buffers are dirtied before the page is dirtied. There's a small race
740 * window in which a writepage caller may see the page cleanness but not the
741 * buffer dirtiness. That's fine. If this code were to set the page dirty
742 * before the buffers, a concurrent writepage caller could clear the page dirty
743 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
744 * page on the dirty page list.
746 * We use private_lock to lock against try_to_free_buffers while using the
747 * page's buffer list. Also use this to protect against clean buffers being
748 * added to the page after it was set dirty.
750 * FIXME: may need to call ->reservepage here as well. That's rather up to the
751 * address_space though.
753 int __set_page_dirty_buffers(struct page *page)
755 struct address_space *mapping = page_mapping(page);
757 if (unlikely(!mapping))
758 return !TestSetPageDirty(page);
760 spin_lock(&mapping->private_lock);
761 if (page_has_buffers(page)) {
762 struct buffer_head *head = page_buffers(page);
763 struct buffer_head *bh = head;
765 do {
766 set_buffer_dirty(bh);
767 bh = bh->b_this_page;
768 } while (bh != head);
770 spin_unlock(&mapping->private_lock);
772 return __set_page_dirty(page, mapping, 1);
774 EXPORT_SYMBOL(__set_page_dirty_buffers);
777 * Write out and wait upon a list of buffers.
779 * We have conflicting pressures: we want to make sure that all
780 * initially dirty buffers get waited on, but that any subsequently
781 * dirtied buffers don't. After all, we don't want fsync to last
782 * forever if somebody is actively writing to the file.
784 * Do this in two main stages: first we copy dirty buffers to a
785 * temporary inode list, queueing the writes as we go. Then we clean
786 * up, waiting for those writes to complete.
788 * During this second stage, any subsequent updates to the file may end
789 * up refiling the buffer on the original inode's dirty list again, so
790 * there is a chance we will end up with a buffer queued for write but
791 * not yet completed on that list. So, as a final cleanup we go through
792 * the osync code to catch these locked, dirty buffers without requeuing
793 * any newly dirty buffers for write.
795 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
797 struct buffer_head *bh;
798 struct list_head tmp;
799 struct address_space *mapping;
800 int err = 0, err2;
802 INIT_LIST_HEAD(&tmp);
804 spin_lock(lock);
805 while (!list_empty(list)) {
806 bh = BH_ENTRY(list->next);
807 mapping = bh->b_assoc_map;
808 __remove_assoc_queue(bh);
809 /* Avoid race with mark_buffer_dirty_inode() which does
810 * a lockless check and we rely on seeing the dirty bit */
811 smp_mb();
812 if (buffer_dirty(bh) || buffer_locked(bh)) {
813 list_add(&bh->b_assoc_buffers, &tmp);
814 bh->b_assoc_map = mapping;
815 if (buffer_dirty(bh)) {
816 get_bh(bh);
817 spin_unlock(lock);
819 * Ensure any pending I/O completes so that
820 * ll_rw_block() actually writes the current
821 * contents - it is a noop if I/O is still in
822 * flight on potentially older contents.
824 ll_rw_block(SWRITE_SYNC, 1, &bh);
825 brelse(bh);
826 spin_lock(lock);
831 while (!list_empty(&tmp)) {
832 bh = BH_ENTRY(tmp.prev);
833 get_bh(bh);
834 mapping = bh->b_assoc_map;
835 __remove_assoc_queue(bh);
836 /* Avoid race with mark_buffer_dirty_inode() which does
837 * a lockless check and we rely on seeing the dirty bit */
838 smp_mb();
839 if (buffer_dirty(bh)) {
840 list_add(&bh->b_assoc_buffers,
841 &mapping->private_list);
842 bh->b_assoc_map = mapping;
844 spin_unlock(lock);
845 wait_on_buffer(bh);
846 if (!buffer_uptodate(bh))
847 err = -EIO;
848 brelse(bh);
849 spin_lock(lock);
852 spin_unlock(lock);
853 err2 = osync_buffers_list(lock, list);
854 if (err)
855 return err;
856 else
857 return err2;
861 * Invalidate any and all dirty buffers on a given inode. We are
862 * probably unmounting the fs, but that doesn't mean we have already
863 * done a sync(). Just drop the buffers from the inode list.
865 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
866 * assumes that all the buffers are against the blockdev. Not true
867 * for reiserfs.
869 void invalidate_inode_buffers(struct inode *inode)
871 if (inode_has_buffers(inode)) {
872 struct address_space *mapping = &inode->i_data;
873 struct list_head *list = &mapping->private_list;
874 struct address_space *buffer_mapping = mapping->assoc_mapping;
876 spin_lock(&buffer_mapping->private_lock);
877 while (!list_empty(list))
878 __remove_assoc_queue(BH_ENTRY(list->next));
879 spin_unlock(&buffer_mapping->private_lock);
884 * Remove any clean buffers from the inode's buffer list. This is called
885 * when we're trying to free the inode itself. Those buffers can pin it.
887 * Returns true if all buffers were removed.
889 int remove_inode_buffers(struct inode *inode)
891 int ret = 1;
893 if (inode_has_buffers(inode)) {
894 struct address_space *mapping = &inode->i_data;
895 struct list_head *list = &mapping->private_list;
896 struct address_space *buffer_mapping = mapping->assoc_mapping;
898 spin_lock(&buffer_mapping->private_lock);
899 while (!list_empty(list)) {
900 struct buffer_head *bh = BH_ENTRY(list->next);
901 if (buffer_dirty(bh)) {
902 ret = 0;
903 break;
905 __remove_assoc_queue(bh);
907 spin_unlock(&buffer_mapping->private_lock);
909 return ret;
913 * Create the appropriate buffers when given a page for data area and
914 * the size of each buffer.. Use the bh->b_this_page linked list to
915 * follow the buffers created. Return NULL if unable to create more
916 * buffers.
918 * The retry flag is used to differentiate async IO (paging, swapping)
919 * which may not fail from ordinary buffer allocations.
921 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
922 int retry)
924 struct buffer_head *bh, *head;
925 long offset;
927 try_again:
928 head = NULL;
929 offset = PAGE_SIZE;
930 while ((offset -= size) >= 0) {
931 bh = alloc_buffer_head(GFP_NOFS);
932 if (!bh)
933 goto no_grow;
935 bh->b_bdev = NULL;
936 bh->b_this_page = head;
937 bh->b_blocknr = -1;
938 head = bh;
940 bh->b_state = 0;
941 atomic_set(&bh->b_count, 0);
942 bh->b_private = NULL;
943 bh->b_size = size;
945 /* Link the buffer to its page */
946 set_bh_page(bh, page, offset);
948 init_buffer(bh, NULL, NULL);
950 return head;
952 * In case anything failed, we just free everything we got.
954 no_grow:
955 if (head) {
956 do {
957 bh = head;
958 head = head->b_this_page;
959 free_buffer_head(bh);
960 } while (head);
964 * Return failure for non-async IO requests. Async IO requests
965 * are not allowed to fail, so we have to wait until buffer heads
966 * become available. But we don't want tasks sleeping with
967 * partially complete buffers, so all were released above.
969 if (!retry)
970 return NULL;
972 /* We're _really_ low on memory. Now we just
973 * wait for old buffer heads to become free due to
974 * finishing IO. Since this is an async request and
975 * the reserve list is empty, we're sure there are
976 * async buffer heads in use.
978 free_more_memory();
979 goto try_again;
981 EXPORT_SYMBOL_GPL(alloc_page_buffers);
983 static inline void
984 link_dev_buffers(struct page *page, struct buffer_head *head)
986 struct buffer_head *bh, *tail;
988 bh = head;
989 do {
990 tail = bh;
991 bh = bh->b_this_page;
992 } while (bh);
993 tail->b_this_page = head;
994 attach_page_buffers(page, head);
998 * Initialise the state of a blockdev page's buffers.
1000 static void
1001 init_page_buffers(struct page *page, struct block_device *bdev,
1002 sector_t block, int size)
1004 struct buffer_head *head = page_buffers(page);
1005 struct buffer_head *bh = head;
1006 int uptodate = PageUptodate(page);
1008 do {
1009 if (!buffer_mapped(bh)) {
1010 init_buffer(bh, NULL, NULL);
1011 bh->b_bdev = bdev;
1012 bh->b_blocknr = block;
1013 if (uptodate)
1014 set_buffer_uptodate(bh);
1015 set_buffer_mapped(bh);
1017 block++;
1018 bh = bh->b_this_page;
1019 } while (bh != head);
1023 * Create the page-cache page that contains the requested block.
1025 * This is user purely for blockdev mappings.
1027 static struct page *
1028 grow_dev_page(struct block_device *bdev, sector_t block,
1029 pgoff_t index, int size)
1031 struct inode *inode = bdev->bd_inode;
1032 struct page *page;
1033 struct buffer_head *bh;
1035 page = find_or_create_page(inode->i_mapping, index,
1036 (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE);
1037 if (!page)
1038 return NULL;
1040 BUG_ON(!PageLocked(page));
1042 if (page_has_buffers(page)) {
1043 bh = page_buffers(page);
1044 if (bh->b_size == size) {
1045 init_page_buffers(page, bdev, block, size);
1046 return page;
1048 if (!try_to_free_buffers(page))
1049 goto failed;
1053 * Allocate some buffers for this page
1055 bh = alloc_page_buffers(page, size, 0);
1056 if (!bh)
1057 goto failed;
1060 * Link the page to the buffers and initialise them. Take the
1061 * lock to be atomic wrt __find_get_block(), which does not
1062 * run under the page lock.
1064 spin_lock(&inode->i_mapping->private_lock);
1065 link_dev_buffers(page, bh);
1066 init_page_buffers(page, bdev, block, size);
1067 spin_unlock(&inode->i_mapping->private_lock);
1068 return page;
1070 failed:
1071 BUG();
1072 unlock_page(page);
1073 page_cache_release(page);
1074 return NULL;
1078 * Create buffers for the specified block device block's page. If
1079 * that page was dirty, the buffers are set dirty also.
1081 static int
1082 grow_buffers(struct block_device *bdev, sector_t block, int size)
1084 struct page *page;
1085 pgoff_t index;
1086 int sizebits;
1088 sizebits = -1;
1089 do {
1090 sizebits++;
1091 } while ((size << sizebits) < PAGE_SIZE);
1093 index = block >> sizebits;
1096 * Check for a block which wants to lie outside our maximum possible
1097 * pagecache index. (this comparison is done using sector_t types).
1099 if (unlikely(index != block >> sizebits)) {
1100 char b[BDEVNAME_SIZE];
1102 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1103 "device %s\n",
1104 __func__, (unsigned long long)block,
1105 bdevname(bdev, b));
1106 return -EIO;
1108 block = index << sizebits;
1109 /* Create a page with the proper size buffers.. */
1110 page = grow_dev_page(bdev, block, index, size);
1111 if (!page)
1112 return 0;
1113 unlock_page(page);
1114 page_cache_release(page);
1115 return 1;
1118 static struct buffer_head *
1119 __getblk_slow(struct block_device *bdev, sector_t block, int size)
1121 /* Size must be multiple of hard sectorsize */
1122 if (unlikely(size & (bdev_hardsect_size(bdev)-1) ||
1123 (size < 512 || size > PAGE_SIZE))) {
1124 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1125 size);
1126 printk(KERN_ERR "hardsect size: %d\n",
1127 bdev_hardsect_size(bdev));
1129 dump_stack();
1130 return NULL;
1133 for (;;) {
1134 struct buffer_head * bh;
1135 int ret;
1137 bh = __find_get_block(bdev, block, size);
1138 if (bh)
1139 return bh;
1141 ret = grow_buffers(bdev, block, size);
1142 if (ret < 0)
1143 return NULL;
1144 if (ret == 0)
1145 free_more_memory();
1150 * The relationship between dirty buffers and dirty pages:
1152 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1153 * the page is tagged dirty in its radix tree.
1155 * At all times, the dirtiness of the buffers represents the dirtiness of
1156 * subsections of the page. If the page has buffers, the page dirty bit is
1157 * merely a hint about the true dirty state.
1159 * When a page is set dirty in its entirety, all its buffers are marked dirty
1160 * (if the page has buffers).
1162 * When a buffer is marked dirty, its page is dirtied, but the page's other
1163 * buffers are not.
1165 * Also. When blockdev buffers are explicitly read with bread(), they
1166 * individually become uptodate. But their backing page remains not
1167 * uptodate - even if all of its buffers are uptodate. A subsequent
1168 * block_read_full_page() against that page will discover all the uptodate
1169 * buffers, will set the page uptodate and will perform no I/O.
1173 * mark_buffer_dirty - mark a buffer_head as needing writeout
1174 * @bh: the buffer_head to mark dirty
1176 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1177 * backing page dirty, then tag the page as dirty in its address_space's radix
1178 * tree and then attach the address_space's inode to its superblock's dirty
1179 * inode list.
1181 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1182 * mapping->tree_lock and the global inode_lock.
1184 void mark_buffer_dirty(struct buffer_head *bh)
1186 WARN_ON_ONCE(!buffer_uptodate(bh));
1189 * Very *carefully* optimize the it-is-already-dirty case.
1191 * Don't let the final "is it dirty" escape to before we
1192 * perhaps modified the buffer.
1194 if (buffer_dirty(bh)) {
1195 smp_mb();
1196 if (buffer_dirty(bh))
1197 return;
1200 if (!test_set_buffer_dirty(bh))
1201 __set_page_dirty(bh->b_page, page_mapping(bh->b_page), 0);
1205 * Decrement a buffer_head's reference count. If all buffers against a page
1206 * have zero reference count, are clean and unlocked, and if the page is clean
1207 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1208 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1209 * a page but it ends up not being freed, and buffers may later be reattached).
1211 void __brelse(struct buffer_head * buf)
1213 if (atomic_read(&buf->b_count)) {
1214 put_bh(buf);
1215 return;
1217 printk(KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1218 WARN_ON(1);
1222 * bforget() is like brelse(), except it discards any
1223 * potentially dirty data.
1225 void __bforget(struct buffer_head *bh)
1227 clear_buffer_dirty(bh);
1228 if (bh->b_assoc_map) {
1229 struct address_space *buffer_mapping = bh->b_page->mapping;
1231 spin_lock(&buffer_mapping->private_lock);
1232 list_del_init(&bh->b_assoc_buffers);
1233 bh->b_assoc_map = NULL;
1234 spin_unlock(&buffer_mapping->private_lock);
1236 __brelse(bh);
1239 static struct buffer_head *__bread_slow(struct buffer_head *bh)
1241 lock_buffer(bh);
1242 if (buffer_uptodate(bh)) {
1243 unlock_buffer(bh);
1244 return bh;
1245 } else {
1246 get_bh(bh);
1247 bh->b_end_io = end_buffer_read_sync;
1248 submit_bh(READ, bh);
1249 wait_on_buffer(bh);
1250 if (buffer_uptodate(bh))
1251 return bh;
1253 brelse(bh);
1254 return NULL;
1258 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1259 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1260 * refcount elevated by one when they're in an LRU. A buffer can only appear
1261 * once in a particular CPU's LRU. A single buffer can be present in multiple
1262 * CPU's LRUs at the same time.
1264 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1265 * sb_find_get_block().
1267 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1268 * a local interrupt disable for that.
1271 #define BH_LRU_SIZE 8
1273 struct bh_lru {
1274 struct buffer_head *bhs[BH_LRU_SIZE];
1277 static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1279 #ifdef CONFIG_SMP
1280 #define bh_lru_lock() local_irq_disable()
1281 #define bh_lru_unlock() local_irq_enable()
1282 #else
1283 #define bh_lru_lock() preempt_disable()
1284 #define bh_lru_unlock() preempt_enable()
1285 #endif
1287 static inline void check_irqs_on(void)
1289 #ifdef irqs_disabled
1290 BUG_ON(irqs_disabled());
1291 #endif
1295 * The LRU management algorithm is dopey-but-simple. Sorry.
1297 static void bh_lru_install(struct buffer_head *bh)
1299 struct buffer_head *evictee = NULL;
1300 struct bh_lru *lru;
1302 check_irqs_on();
1303 bh_lru_lock();
1304 lru = &__get_cpu_var(bh_lrus);
1305 if (lru->bhs[0] != bh) {
1306 struct buffer_head *bhs[BH_LRU_SIZE];
1307 int in;
1308 int out = 0;
1310 get_bh(bh);
1311 bhs[out++] = bh;
1312 for (in = 0; in < BH_LRU_SIZE; in++) {
1313 struct buffer_head *bh2 = lru->bhs[in];
1315 if (bh2 == bh) {
1316 __brelse(bh2);
1317 } else {
1318 if (out >= BH_LRU_SIZE) {
1319 BUG_ON(evictee != NULL);
1320 evictee = bh2;
1321 } else {
1322 bhs[out++] = bh2;
1326 while (out < BH_LRU_SIZE)
1327 bhs[out++] = NULL;
1328 memcpy(lru->bhs, bhs, sizeof(bhs));
1330 bh_lru_unlock();
1332 if (evictee)
1333 __brelse(evictee);
1337 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1339 static struct buffer_head *
1340 lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1342 struct buffer_head *ret = NULL;
1343 struct bh_lru *lru;
1344 unsigned int i;
1346 check_irqs_on();
1347 bh_lru_lock();
1348 lru = &__get_cpu_var(bh_lrus);
1349 for (i = 0; i < BH_LRU_SIZE; i++) {
1350 struct buffer_head *bh = lru->bhs[i];
1352 if (bh && bh->b_bdev == bdev &&
1353 bh->b_blocknr == block && bh->b_size == size) {
1354 if (i) {
1355 while (i) {
1356 lru->bhs[i] = lru->bhs[i - 1];
1357 i--;
1359 lru->bhs[0] = bh;
1361 get_bh(bh);
1362 ret = bh;
1363 break;
1366 bh_lru_unlock();
1367 return ret;
1371 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1372 * it in the LRU and mark it as accessed. If it is not present then return
1373 * NULL
1375 struct buffer_head *
1376 __find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1378 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1380 if (bh == NULL) {
1381 bh = __find_get_block_slow(bdev, block);
1382 if (bh)
1383 bh_lru_install(bh);
1385 if (bh)
1386 touch_buffer(bh);
1387 return bh;
1389 EXPORT_SYMBOL(__find_get_block);
1392 * __getblk will locate (and, if necessary, create) the buffer_head
1393 * which corresponds to the passed block_device, block and size. The
1394 * returned buffer has its reference count incremented.
1396 * __getblk() cannot fail - it just keeps trying. If you pass it an
1397 * illegal block number, __getblk() will happily return a buffer_head
1398 * which represents the non-existent block. Very weird.
1400 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1401 * attempt is failing. FIXME, perhaps?
1403 struct buffer_head *
1404 __getblk(struct block_device *bdev, sector_t block, unsigned size)
1406 struct buffer_head *bh = __find_get_block(bdev, block, size);
1408 might_sleep();
1409 if (bh == NULL)
1410 bh = __getblk_slow(bdev, block, size);
1411 return bh;
1413 EXPORT_SYMBOL(__getblk);
1416 * Do async read-ahead on a buffer..
1418 void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1420 struct buffer_head *bh = __getblk(bdev, block, size);
1421 if (likely(bh)) {
1422 ll_rw_block(READA, 1, &bh);
1423 brelse(bh);
1426 EXPORT_SYMBOL(__breadahead);
1429 * __bread() - reads a specified block and returns the bh
1430 * @bdev: the block_device to read from
1431 * @block: number of block
1432 * @size: size (in bytes) to read
1434 * Reads a specified block, and returns buffer head that contains it.
1435 * It returns NULL if the block was unreadable.
1437 struct buffer_head *
1438 __bread(struct block_device *bdev, sector_t block, unsigned size)
1440 struct buffer_head *bh = __getblk(bdev, block, size);
1442 if (likely(bh) && !buffer_uptodate(bh))
1443 bh = __bread_slow(bh);
1444 return bh;
1446 EXPORT_SYMBOL(__bread);
1449 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1450 * This doesn't race because it runs in each cpu either in irq
1451 * or with preempt disabled.
1453 static void invalidate_bh_lru(void *arg)
1455 struct bh_lru *b = &get_cpu_var(bh_lrus);
1456 int i;
1458 for (i = 0; i < BH_LRU_SIZE; i++) {
1459 brelse(b->bhs[i]);
1460 b->bhs[i] = NULL;
1462 put_cpu_var(bh_lrus);
1465 void invalidate_bh_lrus(void)
1467 on_each_cpu(invalidate_bh_lru, NULL, 1);
1469 EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1471 void set_bh_page(struct buffer_head *bh,
1472 struct page *page, unsigned long offset)
1474 bh->b_page = page;
1475 BUG_ON(offset >= PAGE_SIZE);
1476 if (PageHighMem(page))
1478 * This catches illegal uses and preserves the offset:
1480 bh->b_data = (char *)(0 + offset);
1481 else
1482 bh->b_data = page_address(page) + offset;
1484 EXPORT_SYMBOL(set_bh_page);
1487 * Called when truncating a buffer on a page completely.
1489 static void discard_buffer(struct buffer_head * bh)
1491 lock_buffer(bh);
1492 clear_buffer_dirty(bh);
1493 bh->b_bdev = NULL;
1494 clear_buffer_mapped(bh);
1495 clear_buffer_req(bh);
1496 clear_buffer_new(bh);
1497 clear_buffer_delay(bh);
1498 clear_buffer_unwritten(bh);
1499 unlock_buffer(bh);
1503 * block_invalidatepage - invalidate part of all of a buffer-backed page
1505 * @page: the page which is affected
1506 * @offset: the index of the truncation point
1508 * block_invalidatepage() is called when all or part of the page has become
1509 * invalidatedby a truncate operation.
1511 * block_invalidatepage() does not have to release all buffers, but it must
1512 * ensure that no dirty buffer is left outside @offset and that no I/O
1513 * is underway against any of the blocks which are outside the truncation
1514 * point. Because the caller is about to free (and possibly reuse) those
1515 * blocks on-disk.
1517 void block_invalidatepage(struct page *page, unsigned long offset)
1519 struct buffer_head *head, *bh, *next;
1520 unsigned int curr_off = 0;
1522 BUG_ON(!PageLocked(page));
1523 if (!page_has_buffers(page))
1524 goto out;
1526 head = page_buffers(page);
1527 bh = head;
1528 do {
1529 unsigned int next_off = curr_off + bh->b_size;
1530 next = bh->b_this_page;
1533 * is this block fully invalidated?
1535 if (offset <= curr_off)
1536 discard_buffer(bh);
1537 curr_off = next_off;
1538 bh = next;
1539 } while (bh != head);
1542 * We release buffers only if the entire page is being invalidated.
1543 * The get_block cached value has been unconditionally invalidated,
1544 * so real IO is not possible anymore.
1546 if (offset == 0)
1547 try_to_release_page(page, 0);
1548 out:
1549 return;
1551 EXPORT_SYMBOL(block_invalidatepage);
1554 * We attach and possibly dirty the buffers atomically wrt
1555 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1556 * is already excluded via the page lock.
1558 void create_empty_buffers(struct page *page,
1559 unsigned long blocksize, unsigned long b_state)
1561 struct buffer_head *bh, *head, *tail;
1563 head = alloc_page_buffers(page, blocksize, 1);
1564 bh = head;
1565 do {
1566 bh->b_state |= b_state;
1567 tail = bh;
1568 bh = bh->b_this_page;
1569 } while (bh);
1570 tail->b_this_page = head;
1572 spin_lock(&page->mapping->private_lock);
1573 if (PageUptodate(page) || PageDirty(page)) {
1574 bh = head;
1575 do {
1576 if (PageDirty(page))
1577 set_buffer_dirty(bh);
1578 if (PageUptodate(page))
1579 set_buffer_uptodate(bh);
1580 bh = bh->b_this_page;
1581 } while (bh != head);
1583 attach_page_buffers(page, head);
1584 spin_unlock(&page->mapping->private_lock);
1586 EXPORT_SYMBOL(create_empty_buffers);
1589 * We are taking a block for data and we don't want any output from any
1590 * buffer-cache aliases starting from return from that function and
1591 * until the moment when something will explicitly mark the buffer
1592 * dirty (hopefully that will not happen until we will free that block ;-)
1593 * We don't even need to mark it not-uptodate - nobody can expect
1594 * anything from a newly allocated buffer anyway. We used to used
1595 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1596 * don't want to mark the alias unmapped, for example - it would confuse
1597 * anyone who might pick it with bread() afterwards...
1599 * Also.. Note that bforget() doesn't lock the buffer. So there can
1600 * be writeout I/O going on against recently-freed buffers. We don't
1601 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1602 * only if we really need to. That happens here.
1604 void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1606 struct buffer_head *old_bh;
1608 might_sleep();
1610 old_bh = __find_get_block_slow(bdev, block);
1611 if (old_bh) {
1612 clear_buffer_dirty(old_bh);
1613 wait_on_buffer(old_bh);
1614 clear_buffer_req(old_bh);
1615 __brelse(old_bh);
1618 EXPORT_SYMBOL(unmap_underlying_metadata);
1621 * NOTE! All mapped/uptodate combinations are valid:
1623 * Mapped Uptodate Meaning
1625 * No No "unknown" - must do get_block()
1626 * No Yes "hole" - zero-filled
1627 * Yes No "allocated" - allocated on disk, not read in
1628 * Yes Yes "valid" - allocated and up-to-date in memory.
1630 * "Dirty" is valid only with the last case (mapped+uptodate).
1634 * While block_write_full_page is writing back the dirty buffers under
1635 * the page lock, whoever dirtied the buffers may decide to clean them
1636 * again at any time. We handle that by only looking at the buffer
1637 * state inside lock_buffer().
1639 * If block_write_full_page() is called for regular writeback
1640 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1641 * locked buffer. This only can happen if someone has written the buffer
1642 * directly, with submit_bh(). At the address_space level PageWriteback
1643 * prevents this contention from occurring.
1645 static int __block_write_full_page(struct inode *inode, struct page *page,
1646 get_block_t *get_block, struct writeback_control *wbc)
1648 int err;
1649 sector_t block;
1650 sector_t last_block;
1651 struct buffer_head *bh, *head;
1652 const unsigned blocksize = 1 << inode->i_blkbits;
1653 int nr_underway = 0;
1655 BUG_ON(!PageLocked(page));
1657 last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
1659 if (!page_has_buffers(page)) {
1660 create_empty_buffers(page, blocksize,
1661 (1 << BH_Dirty)|(1 << BH_Uptodate));
1665 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1666 * here, and the (potentially unmapped) buffers may become dirty at
1667 * any time. If a buffer becomes dirty here after we've inspected it
1668 * then we just miss that fact, and the page stays dirty.
1670 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1671 * handle that here by just cleaning them.
1674 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
1675 head = page_buffers(page);
1676 bh = head;
1679 * Get all the dirty buffers mapped to disk addresses and
1680 * handle any aliases from the underlying blockdev's mapping.
1682 do {
1683 if (block > last_block) {
1685 * mapped buffers outside i_size will occur, because
1686 * this page can be outside i_size when there is a
1687 * truncate in progress.
1690 * The buffer was zeroed by block_write_full_page()
1692 clear_buffer_dirty(bh);
1693 set_buffer_uptodate(bh);
1694 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1695 buffer_dirty(bh)) {
1696 WARN_ON(bh->b_size != blocksize);
1697 err = get_block(inode, block, bh, 1);
1698 if (err)
1699 goto recover;
1700 clear_buffer_delay(bh);
1701 if (buffer_new(bh)) {
1702 /* blockdev mappings never come here */
1703 clear_buffer_new(bh);
1704 unmap_underlying_metadata(bh->b_bdev,
1705 bh->b_blocknr);
1708 bh = bh->b_this_page;
1709 block++;
1710 } while (bh != head);
1712 do {
1713 if (!buffer_mapped(bh))
1714 continue;
1716 * If it's a fully non-blocking write attempt and we cannot
1717 * lock the buffer then redirty the page. Note that this can
1718 * potentially cause a busy-wait loop from pdflush and kswapd
1719 * activity, but those code paths have their own higher-level
1720 * throttling.
1722 if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
1723 lock_buffer(bh);
1724 } else if (test_set_buffer_locked(bh)) {
1725 redirty_page_for_writepage(wbc, page);
1726 continue;
1728 if (test_clear_buffer_dirty(bh)) {
1729 mark_buffer_async_write(bh);
1730 } else {
1731 unlock_buffer(bh);
1733 } while ((bh = bh->b_this_page) != head);
1736 * The page and its buffers are protected by PageWriteback(), so we can
1737 * drop the bh refcounts early.
1739 BUG_ON(PageWriteback(page));
1740 set_page_writeback(page);
1742 do {
1743 struct buffer_head *next = bh->b_this_page;
1744 if (buffer_async_write(bh)) {
1745 submit_bh(WRITE, bh);
1746 nr_underway++;
1748 bh = next;
1749 } while (bh != head);
1750 unlock_page(page);
1752 err = 0;
1753 done:
1754 if (nr_underway == 0) {
1756 * The page was marked dirty, but the buffers were
1757 * clean. Someone wrote them back by hand with
1758 * ll_rw_block/submit_bh. A rare case.
1760 end_page_writeback(page);
1763 * The page and buffer_heads can be released at any time from
1764 * here on.
1767 return err;
1769 recover:
1771 * ENOSPC, or some other error. We may already have added some
1772 * blocks to the file, so we need to write these out to avoid
1773 * exposing stale data.
1774 * The page is currently locked and not marked for writeback
1776 bh = head;
1777 /* Recovery: lock and submit the mapped buffers */
1778 do {
1779 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1780 !buffer_delay(bh)) {
1781 lock_buffer(bh);
1782 mark_buffer_async_write(bh);
1783 } else {
1785 * The buffer may have been set dirty during
1786 * attachment to a dirty page.
1788 clear_buffer_dirty(bh);
1790 } while ((bh = bh->b_this_page) != head);
1791 SetPageError(page);
1792 BUG_ON(PageWriteback(page));
1793 mapping_set_error(page->mapping, err);
1794 set_page_writeback(page);
1795 do {
1796 struct buffer_head *next = bh->b_this_page;
1797 if (buffer_async_write(bh)) {
1798 clear_buffer_dirty(bh);
1799 submit_bh(WRITE, bh);
1800 nr_underway++;
1802 bh = next;
1803 } while (bh != head);
1804 unlock_page(page);
1805 goto done;
1809 * If a page has any new buffers, zero them out here, and mark them uptodate
1810 * and dirty so they'll be written out (in order to prevent uninitialised
1811 * block data from leaking). And clear the new bit.
1813 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1815 unsigned int block_start, block_end;
1816 struct buffer_head *head, *bh;
1818 BUG_ON(!PageLocked(page));
1819 if (!page_has_buffers(page))
1820 return;
1822 bh = head = page_buffers(page);
1823 block_start = 0;
1824 do {
1825 block_end = block_start + bh->b_size;
1827 if (buffer_new(bh)) {
1828 if (block_end > from && block_start < to) {
1829 if (!PageUptodate(page)) {
1830 unsigned start, size;
1832 start = max(from, block_start);
1833 size = min(to, block_end) - start;
1835 zero_user(page, start, size);
1836 set_buffer_uptodate(bh);
1839 clear_buffer_new(bh);
1840 mark_buffer_dirty(bh);
1844 block_start = block_end;
1845 bh = bh->b_this_page;
1846 } while (bh != head);
1848 EXPORT_SYMBOL(page_zero_new_buffers);
1850 static int __block_prepare_write(struct inode *inode, struct page *page,
1851 unsigned from, unsigned to, get_block_t *get_block)
1853 unsigned block_start, block_end;
1854 sector_t block;
1855 int err = 0;
1856 unsigned blocksize, bbits;
1857 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1859 BUG_ON(!PageLocked(page));
1860 BUG_ON(from > PAGE_CACHE_SIZE);
1861 BUG_ON(to > PAGE_CACHE_SIZE);
1862 BUG_ON(from > to);
1864 blocksize = 1 << inode->i_blkbits;
1865 if (!page_has_buffers(page))
1866 create_empty_buffers(page, blocksize, 0);
1867 head = page_buffers(page);
1869 bbits = inode->i_blkbits;
1870 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1872 for(bh = head, block_start = 0; bh != head || !block_start;
1873 block++, block_start=block_end, bh = bh->b_this_page) {
1874 block_end = block_start + blocksize;
1875 if (block_end <= from || block_start >= to) {
1876 if (PageUptodate(page)) {
1877 if (!buffer_uptodate(bh))
1878 set_buffer_uptodate(bh);
1880 continue;
1882 if (buffer_new(bh))
1883 clear_buffer_new(bh);
1884 if (!buffer_mapped(bh)) {
1885 WARN_ON(bh->b_size != blocksize);
1886 err = get_block(inode, block, bh, 1);
1887 if (err)
1888 break;
1889 if (buffer_new(bh)) {
1890 unmap_underlying_metadata(bh->b_bdev,
1891 bh->b_blocknr);
1892 if (PageUptodate(page)) {
1893 clear_buffer_new(bh);
1894 set_buffer_uptodate(bh);
1895 mark_buffer_dirty(bh);
1896 continue;
1898 if (block_end > to || block_start < from)
1899 zero_user_segments(page,
1900 to, block_end,
1901 block_start, from);
1902 continue;
1905 if (PageUptodate(page)) {
1906 if (!buffer_uptodate(bh))
1907 set_buffer_uptodate(bh);
1908 continue;
1910 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1911 !buffer_unwritten(bh) &&
1912 (block_start < from || block_end > to)) {
1913 ll_rw_block(READ, 1, &bh);
1914 *wait_bh++=bh;
1918 * If we issued read requests - let them complete.
1920 while(wait_bh > wait) {
1921 wait_on_buffer(*--wait_bh);
1922 if (!buffer_uptodate(*wait_bh))
1923 err = -EIO;
1925 if (unlikely(err))
1926 page_zero_new_buffers(page, from, to);
1927 return err;
1930 static int __block_commit_write(struct inode *inode, struct page *page,
1931 unsigned from, unsigned to)
1933 unsigned block_start, block_end;
1934 int partial = 0;
1935 unsigned blocksize;
1936 struct buffer_head *bh, *head;
1938 blocksize = 1 << inode->i_blkbits;
1940 for(bh = head = page_buffers(page), block_start = 0;
1941 bh != head || !block_start;
1942 block_start=block_end, bh = bh->b_this_page) {
1943 block_end = block_start + blocksize;
1944 if (block_end <= from || block_start >= to) {
1945 if (!buffer_uptodate(bh))
1946 partial = 1;
1947 } else {
1948 set_buffer_uptodate(bh);
1949 mark_buffer_dirty(bh);
1951 clear_buffer_new(bh);
1955 * If this is a partial write which happened to make all buffers
1956 * uptodate then we can optimize away a bogus readpage() for
1957 * the next read(). Here we 'discover' whether the page went
1958 * uptodate as a result of this (potentially partial) write.
1960 if (!partial)
1961 SetPageUptodate(page);
1962 return 0;
1966 * block_write_begin takes care of the basic task of block allocation and
1967 * bringing partial write blocks uptodate first.
1969 * If *pagep is not NULL, then block_write_begin uses the locked page
1970 * at *pagep rather than allocating its own. In this case, the page will
1971 * not be unlocked or deallocated on failure.
1973 int block_write_begin(struct file *file, struct address_space *mapping,
1974 loff_t pos, unsigned len, unsigned flags,
1975 struct page **pagep, void **fsdata,
1976 get_block_t *get_block)
1978 struct inode *inode = mapping->host;
1979 int status = 0;
1980 struct page *page;
1981 pgoff_t index;
1982 unsigned start, end;
1983 int ownpage = 0;
1985 index = pos >> PAGE_CACHE_SHIFT;
1986 start = pos & (PAGE_CACHE_SIZE - 1);
1987 end = start + len;
1989 page = *pagep;
1990 if (page == NULL) {
1991 ownpage = 1;
1992 page = __grab_cache_page(mapping, index);
1993 if (!page) {
1994 status = -ENOMEM;
1995 goto out;
1997 *pagep = page;
1998 } else
1999 BUG_ON(!PageLocked(page));
2001 status = __block_prepare_write(inode, page, start, end, get_block);
2002 if (unlikely(status)) {
2003 ClearPageUptodate(page);
2005 if (ownpage) {
2006 unlock_page(page);
2007 page_cache_release(page);
2008 *pagep = NULL;
2011 * prepare_write() may have instantiated a few blocks
2012 * outside i_size. Trim these off again. Don't need
2013 * i_size_read because we hold i_mutex.
2015 if (pos + len > inode->i_size)
2016 vmtruncate(inode, inode->i_size);
2018 goto out;
2021 out:
2022 return status;
2024 EXPORT_SYMBOL(block_write_begin);
2026 int block_write_end(struct file *file, struct address_space *mapping,
2027 loff_t pos, unsigned len, unsigned copied,
2028 struct page *page, void *fsdata)
2030 struct inode *inode = mapping->host;
2031 unsigned start;
2033 start = pos & (PAGE_CACHE_SIZE - 1);
2035 if (unlikely(copied < len)) {
2037 * The buffers that were written will now be uptodate, so we
2038 * don't have to worry about a readpage reading them and
2039 * overwriting a partial write. However if we have encountered
2040 * a short write and only partially written into a buffer, it
2041 * will not be marked uptodate, so a readpage might come in and
2042 * destroy our partial write.
2044 * Do the simplest thing, and just treat any short write to a
2045 * non uptodate page as a zero-length write, and force the
2046 * caller to redo the whole thing.
2048 if (!PageUptodate(page))
2049 copied = 0;
2051 page_zero_new_buffers(page, start+copied, start+len);
2053 flush_dcache_page(page);
2055 /* This could be a short (even 0-length) commit */
2056 __block_commit_write(inode, page, start, start+copied);
2058 return copied;
2060 EXPORT_SYMBOL(block_write_end);
2062 int generic_write_end(struct file *file, struct address_space *mapping,
2063 loff_t pos, unsigned len, unsigned copied,
2064 struct page *page, void *fsdata)
2066 struct inode *inode = mapping->host;
2067 int i_size_changed = 0;
2069 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2072 * No need to use i_size_read() here, the i_size
2073 * cannot change under us because we hold i_mutex.
2075 * But it's important to update i_size while still holding page lock:
2076 * page writeout could otherwise come in and zero beyond i_size.
2078 if (pos+copied > inode->i_size) {
2079 i_size_write(inode, pos+copied);
2080 i_size_changed = 1;
2083 unlock_page(page);
2084 page_cache_release(page);
2087 * Don't mark the inode dirty under page lock. First, it unnecessarily
2088 * makes the holding time of page lock longer. Second, it forces lock
2089 * ordering of page lock and transaction start for journaling
2090 * filesystems.
2092 if (i_size_changed)
2093 mark_inode_dirty(inode);
2095 return copied;
2097 EXPORT_SYMBOL(generic_write_end);
2100 * Generic "read page" function for block devices that have the normal
2101 * get_block functionality. This is most of the block device filesystems.
2102 * Reads the page asynchronously --- the unlock_buffer() and
2103 * set/clear_buffer_uptodate() functions propagate buffer state into the
2104 * page struct once IO has completed.
2106 int block_read_full_page(struct page *page, get_block_t *get_block)
2108 struct inode *inode = page->mapping->host;
2109 sector_t iblock, lblock;
2110 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2111 unsigned int blocksize;
2112 int nr, i;
2113 int fully_mapped = 1;
2115 BUG_ON(!PageLocked(page));
2116 blocksize = 1 << inode->i_blkbits;
2117 if (!page_has_buffers(page))
2118 create_empty_buffers(page, blocksize, 0);
2119 head = page_buffers(page);
2121 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2122 lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
2123 bh = head;
2124 nr = 0;
2125 i = 0;
2127 do {
2128 if (buffer_uptodate(bh))
2129 continue;
2131 if (!buffer_mapped(bh)) {
2132 int err = 0;
2134 fully_mapped = 0;
2135 if (iblock < lblock) {
2136 WARN_ON(bh->b_size != blocksize);
2137 err = get_block(inode, iblock, bh, 0);
2138 if (err)
2139 SetPageError(page);
2141 if (!buffer_mapped(bh)) {
2142 zero_user(page, i * blocksize, blocksize);
2143 if (!err)
2144 set_buffer_uptodate(bh);
2145 continue;
2148 * get_block() might have updated the buffer
2149 * synchronously
2151 if (buffer_uptodate(bh))
2152 continue;
2154 arr[nr++] = bh;
2155 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2157 if (fully_mapped)
2158 SetPageMappedToDisk(page);
2160 if (!nr) {
2162 * All buffers are uptodate - we can set the page uptodate
2163 * as well. But not if get_block() returned an error.
2165 if (!PageError(page))
2166 SetPageUptodate(page);
2167 unlock_page(page);
2168 return 0;
2171 /* Stage two: lock the buffers */
2172 for (i = 0; i < nr; i++) {
2173 bh = arr[i];
2174 lock_buffer(bh);
2175 mark_buffer_async_read(bh);
2179 * Stage 3: start the IO. Check for uptodateness
2180 * inside the buffer lock in case another process reading
2181 * the underlying blockdev brought it uptodate (the sct fix).
2183 for (i = 0; i < nr; i++) {
2184 bh = arr[i];
2185 if (buffer_uptodate(bh))
2186 end_buffer_async_read(bh, 1);
2187 else
2188 submit_bh(READ, bh);
2190 return 0;
2193 /* utility function for filesystems that need to do work on expanding
2194 * truncates. Uses filesystem pagecache writes to allow the filesystem to
2195 * deal with the hole.
2197 int generic_cont_expand_simple(struct inode *inode, loff_t size)
2199 struct address_space *mapping = inode->i_mapping;
2200 struct page *page;
2201 void *fsdata;
2202 unsigned long limit;
2203 int err;
2205 err = -EFBIG;
2206 limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
2207 if (limit != RLIM_INFINITY && size > (loff_t)limit) {
2208 send_sig(SIGXFSZ, current, 0);
2209 goto out;
2211 if (size > inode->i_sb->s_maxbytes)
2212 goto out;
2214 err = pagecache_write_begin(NULL, mapping, size, 0,
2215 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2216 &page, &fsdata);
2217 if (err)
2218 goto out;
2220 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2221 BUG_ON(err > 0);
2223 out:
2224 return err;
2227 static int cont_expand_zero(struct file *file, struct address_space *mapping,
2228 loff_t pos, loff_t *bytes)
2230 struct inode *inode = mapping->host;
2231 unsigned blocksize = 1 << inode->i_blkbits;
2232 struct page *page;
2233 void *fsdata;
2234 pgoff_t index, curidx;
2235 loff_t curpos;
2236 unsigned zerofrom, offset, len;
2237 int err = 0;
2239 index = pos >> PAGE_CACHE_SHIFT;
2240 offset = pos & ~PAGE_CACHE_MASK;
2242 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
2243 zerofrom = curpos & ~PAGE_CACHE_MASK;
2244 if (zerofrom & (blocksize-1)) {
2245 *bytes |= (blocksize-1);
2246 (*bytes)++;
2248 len = PAGE_CACHE_SIZE - zerofrom;
2250 err = pagecache_write_begin(file, mapping, curpos, len,
2251 AOP_FLAG_UNINTERRUPTIBLE,
2252 &page, &fsdata);
2253 if (err)
2254 goto out;
2255 zero_user(page, zerofrom, len);
2256 err = pagecache_write_end(file, mapping, curpos, len, len,
2257 page, fsdata);
2258 if (err < 0)
2259 goto out;
2260 BUG_ON(err != len);
2261 err = 0;
2263 balance_dirty_pages_ratelimited(mapping);
2266 /* page covers the boundary, find the boundary offset */
2267 if (index == curidx) {
2268 zerofrom = curpos & ~PAGE_CACHE_MASK;
2269 /* if we will expand the thing last block will be filled */
2270 if (offset <= zerofrom) {
2271 goto out;
2273 if (zerofrom & (blocksize-1)) {
2274 *bytes |= (blocksize-1);
2275 (*bytes)++;
2277 len = offset - zerofrom;
2279 err = pagecache_write_begin(file, mapping, curpos, len,
2280 AOP_FLAG_UNINTERRUPTIBLE,
2281 &page, &fsdata);
2282 if (err)
2283 goto out;
2284 zero_user(page, zerofrom, len);
2285 err = pagecache_write_end(file, mapping, curpos, len, len,
2286 page, fsdata);
2287 if (err < 0)
2288 goto out;
2289 BUG_ON(err != len);
2290 err = 0;
2292 out:
2293 return err;
2297 * For moronic filesystems that do not allow holes in file.
2298 * We may have to extend the file.
2300 int cont_write_begin(struct file *file, struct address_space *mapping,
2301 loff_t pos, unsigned len, unsigned flags,
2302 struct page **pagep, void **fsdata,
2303 get_block_t *get_block, loff_t *bytes)
2305 struct inode *inode = mapping->host;
2306 unsigned blocksize = 1 << inode->i_blkbits;
2307 unsigned zerofrom;
2308 int err;
2310 err = cont_expand_zero(file, mapping, pos, bytes);
2311 if (err)
2312 goto out;
2314 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2315 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2316 *bytes |= (blocksize-1);
2317 (*bytes)++;
2320 *pagep = NULL;
2321 err = block_write_begin(file, mapping, pos, len,
2322 flags, pagep, fsdata, get_block);
2323 out:
2324 return err;
2327 int block_prepare_write(struct page *page, unsigned from, unsigned to,
2328 get_block_t *get_block)
2330 struct inode *inode = page->mapping->host;
2331 int err = __block_prepare_write(inode, page, from, to, get_block);
2332 if (err)
2333 ClearPageUptodate(page);
2334 return err;
2337 int block_commit_write(struct page *page, unsigned from, unsigned to)
2339 struct inode *inode = page->mapping->host;
2340 __block_commit_write(inode,page,from,to);
2341 return 0;
2345 * block_page_mkwrite() is not allowed to change the file size as it gets
2346 * called from a page fault handler when a page is first dirtied. Hence we must
2347 * be careful to check for EOF conditions here. We set the page up correctly
2348 * for a written page which means we get ENOSPC checking when writing into
2349 * holes and correct delalloc and unwritten extent mapping on filesystems that
2350 * support these features.
2352 * We are not allowed to take the i_mutex here so we have to play games to
2353 * protect against truncate races as the page could now be beyond EOF. Because
2354 * vmtruncate() writes the inode size before removing pages, once we have the
2355 * page lock we can determine safely if the page is beyond EOF. If it is not
2356 * beyond EOF, then the page is guaranteed safe against truncation until we
2357 * unlock the page.
2360 block_page_mkwrite(struct vm_area_struct *vma, struct page *page,
2361 get_block_t get_block)
2363 struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
2364 unsigned long end;
2365 loff_t size;
2366 int ret = -EINVAL;
2368 lock_page(page);
2369 size = i_size_read(inode);
2370 if ((page->mapping != inode->i_mapping) ||
2371 (page_offset(page) > size)) {
2372 /* page got truncated out from underneath us */
2373 goto out_unlock;
2376 /* page is wholly or partially inside EOF */
2377 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
2378 end = size & ~PAGE_CACHE_MASK;
2379 else
2380 end = PAGE_CACHE_SIZE;
2382 ret = block_prepare_write(page, 0, end, get_block);
2383 if (!ret)
2384 ret = block_commit_write(page, 0, end);
2386 out_unlock:
2387 unlock_page(page);
2388 return ret;
2392 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
2393 * immediately, while under the page lock. So it needs a special end_io
2394 * handler which does not touch the bh after unlocking it.
2396 static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2398 __end_buffer_read_notouch(bh, uptodate);
2402 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2403 * the page (converting it to circular linked list and taking care of page
2404 * dirty races).
2406 static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2408 struct buffer_head *bh;
2410 BUG_ON(!PageLocked(page));
2412 spin_lock(&page->mapping->private_lock);
2413 bh = head;
2414 do {
2415 if (PageDirty(page))
2416 set_buffer_dirty(bh);
2417 if (!bh->b_this_page)
2418 bh->b_this_page = head;
2419 bh = bh->b_this_page;
2420 } while (bh != head);
2421 attach_page_buffers(page, head);
2422 spin_unlock(&page->mapping->private_lock);
2426 * On entry, the page is fully not uptodate.
2427 * On exit the page is fully uptodate in the areas outside (from,to)
2429 int nobh_write_begin(struct file *file, struct address_space *mapping,
2430 loff_t pos, unsigned len, unsigned flags,
2431 struct page **pagep, void **fsdata,
2432 get_block_t *get_block)
2434 struct inode *inode = mapping->host;
2435 const unsigned blkbits = inode->i_blkbits;
2436 const unsigned blocksize = 1 << blkbits;
2437 struct buffer_head *head, *bh;
2438 struct page *page;
2439 pgoff_t index;
2440 unsigned from, to;
2441 unsigned block_in_page;
2442 unsigned block_start, block_end;
2443 sector_t block_in_file;
2444 int nr_reads = 0;
2445 int ret = 0;
2446 int is_mapped_to_disk = 1;
2448 index = pos >> PAGE_CACHE_SHIFT;
2449 from = pos & (PAGE_CACHE_SIZE - 1);
2450 to = from + len;
2452 page = __grab_cache_page(mapping, index);
2453 if (!page)
2454 return -ENOMEM;
2455 *pagep = page;
2456 *fsdata = NULL;
2458 if (page_has_buffers(page)) {
2459 unlock_page(page);
2460 page_cache_release(page);
2461 *pagep = NULL;
2462 return block_write_begin(file, mapping, pos, len, flags, pagep,
2463 fsdata, get_block);
2466 if (PageMappedToDisk(page))
2467 return 0;
2470 * Allocate buffers so that we can keep track of state, and potentially
2471 * attach them to the page if an error occurs. In the common case of
2472 * no error, they will just be freed again without ever being attached
2473 * to the page (which is all OK, because we're under the page lock).
2475 * Be careful: the buffer linked list is a NULL terminated one, rather
2476 * than the circular one we're used to.
2478 head = alloc_page_buffers(page, blocksize, 0);
2479 if (!head) {
2480 ret = -ENOMEM;
2481 goto out_release;
2484 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
2487 * We loop across all blocks in the page, whether or not they are
2488 * part of the affected region. This is so we can discover if the
2489 * page is fully mapped-to-disk.
2491 for (block_start = 0, block_in_page = 0, bh = head;
2492 block_start < PAGE_CACHE_SIZE;
2493 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
2494 int create;
2496 block_end = block_start + blocksize;
2497 bh->b_state = 0;
2498 create = 1;
2499 if (block_start >= to)
2500 create = 0;
2501 ret = get_block(inode, block_in_file + block_in_page,
2502 bh, create);
2503 if (ret)
2504 goto failed;
2505 if (!buffer_mapped(bh))
2506 is_mapped_to_disk = 0;
2507 if (buffer_new(bh))
2508 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
2509 if (PageUptodate(page)) {
2510 set_buffer_uptodate(bh);
2511 continue;
2513 if (buffer_new(bh) || !buffer_mapped(bh)) {
2514 zero_user_segments(page, block_start, from,
2515 to, block_end);
2516 continue;
2518 if (buffer_uptodate(bh))
2519 continue; /* reiserfs does this */
2520 if (block_start < from || block_end > to) {
2521 lock_buffer(bh);
2522 bh->b_end_io = end_buffer_read_nobh;
2523 submit_bh(READ, bh);
2524 nr_reads++;
2528 if (nr_reads) {
2530 * The page is locked, so these buffers are protected from
2531 * any VM or truncate activity. Hence we don't need to care
2532 * for the buffer_head refcounts.
2534 for (bh = head; bh; bh = bh->b_this_page) {
2535 wait_on_buffer(bh);
2536 if (!buffer_uptodate(bh))
2537 ret = -EIO;
2539 if (ret)
2540 goto failed;
2543 if (is_mapped_to_disk)
2544 SetPageMappedToDisk(page);
2546 *fsdata = head; /* to be released by nobh_write_end */
2548 return 0;
2550 failed:
2551 BUG_ON(!ret);
2553 * Error recovery is a bit difficult. We need to zero out blocks that
2554 * were newly allocated, and dirty them to ensure they get written out.
2555 * Buffers need to be attached to the page at this point, otherwise
2556 * the handling of potential IO errors during writeout would be hard
2557 * (could try doing synchronous writeout, but what if that fails too?)
2559 attach_nobh_buffers(page, head);
2560 page_zero_new_buffers(page, from, to);
2562 out_release:
2563 unlock_page(page);
2564 page_cache_release(page);
2565 *pagep = NULL;
2567 if (pos + len > inode->i_size)
2568 vmtruncate(inode, inode->i_size);
2570 return ret;
2572 EXPORT_SYMBOL(nobh_write_begin);
2574 int nobh_write_end(struct file *file, struct address_space *mapping,
2575 loff_t pos, unsigned len, unsigned copied,
2576 struct page *page, void *fsdata)
2578 struct inode *inode = page->mapping->host;
2579 struct buffer_head *head = fsdata;
2580 struct buffer_head *bh;
2581 BUG_ON(fsdata != NULL && page_has_buffers(page));
2583 if (unlikely(copied < len) && !page_has_buffers(page))
2584 attach_nobh_buffers(page, head);
2585 if (page_has_buffers(page))
2586 return generic_write_end(file, mapping, pos, len,
2587 copied, page, fsdata);
2589 SetPageUptodate(page);
2590 set_page_dirty(page);
2591 if (pos+copied > inode->i_size) {
2592 i_size_write(inode, pos+copied);
2593 mark_inode_dirty(inode);
2596 unlock_page(page);
2597 page_cache_release(page);
2599 while (head) {
2600 bh = head;
2601 head = head->b_this_page;
2602 free_buffer_head(bh);
2605 return copied;
2607 EXPORT_SYMBOL(nobh_write_end);
2610 * nobh_writepage() - based on block_full_write_page() except
2611 * that it tries to operate without attaching bufferheads to
2612 * the page.
2614 int nobh_writepage(struct page *page, get_block_t *get_block,
2615 struct writeback_control *wbc)
2617 struct inode * const inode = page->mapping->host;
2618 loff_t i_size = i_size_read(inode);
2619 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2620 unsigned offset;
2621 int ret;
2623 /* Is the page fully inside i_size? */
2624 if (page->index < end_index)
2625 goto out;
2627 /* Is the page fully outside i_size? (truncate in progress) */
2628 offset = i_size & (PAGE_CACHE_SIZE-1);
2629 if (page->index >= end_index+1 || !offset) {
2631 * The page may have dirty, unmapped buffers. For example,
2632 * they may have been added in ext3_writepage(). Make them
2633 * freeable here, so the page does not leak.
2635 #if 0
2636 /* Not really sure about this - do we need this ? */
2637 if (page->mapping->a_ops->invalidatepage)
2638 page->mapping->a_ops->invalidatepage(page, offset);
2639 #endif
2640 unlock_page(page);
2641 return 0; /* don't care */
2645 * The page straddles i_size. It must be zeroed out on each and every
2646 * writepage invocation because it may be mmapped. "A file is mapped
2647 * in multiples of the page size. For a file that is not a multiple of
2648 * the page size, the remaining memory is zeroed when mapped, and
2649 * writes to that region are not written out to the file."
2651 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2652 out:
2653 ret = mpage_writepage(page, get_block, wbc);
2654 if (ret == -EAGAIN)
2655 ret = __block_write_full_page(inode, page, get_block, wbc);
2656 return ret;
2658 EXPORT_SYMBOL(nobh_writepage);
2660 int nobh_truncate_page(struct address_space *mapping,
2661 loff_t from, get_block_t *get_block)
2663 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2664 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2665 unsigned blocksize;
2666 sector_t iblock;
2667 unsigned length, pos;
2668 struct inode *inode = mapping->host;
2669 struct page *page;
2670 struct buffer_head map_bh;
2671 int err;
2673 blocksize = 1 << inode->i_blkbits;
2674 length = offset & (blocksize - 1);
2676 /* Block boundary? Nothing to do */
2677 if (!length)
2678 return 0;
2680 length = blocksize - length;
2681 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2683 page = grab_cache_page(mapping, index);
2684 err = -ENOMEM;
2685 if (!page)
2686 goto out;
2688 if (page_has_buffers(page)) {
2689 has_buffers:
2690 unlock_page(page);
2691 page_cache_release(page);
2692 return block_truncate_page(mapping, from, get_block);
2695 /* Find the buffer that contains "offset" */
2696 pos = blocksize;
2697 while (offset >= pos) {
2698 iblock++;
2699 pos += blocksize;
2702 err = get_block(inode, iblock, &map_bh, 0);
2703 if (err)
2704 goto unlock;
2705 /* unmapped? It's a hole - nothing to do */
2706 if (!buffer_mapped(&map_bh))
2707 goto unlock;
2709 /* Ok, it's mapped. Make sure it's up-to-date */
2710 if (!PageUptodate(page)) {
2711 err = mapping->a_ops->readpage(NULL, page);
2712 if (err) {
2713 page_cache_release(page);
2714 goto out;
2716 lock_page(page);
2717 if (!PageUptodate(page)) {
2718 err = -EIO;
2719 goto unlock;
2721 if (page_has_buffers(page))
2722 goto has_buffers;
2724 zero_user(page, offset, length);
2725 set_page_dirty(page);
2726 err = 0;
2728 unlock:
2729 unlock_page(page);
2730 page_cache_release(page);
2731 out:
2732 return err;
2734 EXPORT_SYMBOL(nobh_truncate_page);
2736 int block_truncate_page(struct address_space *mapping,
2737 loff_t from, get_block_t *get_block)
2739 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2740 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2741 unsigned blocksize;
2742 sector_t iblock;
2743 unsigned length, pos;
2744 struct inode *inode = mapping->host;
2745 struct page *page;
2746 struct buffer_head *bh;
2747 int err;
2749 blocksize = 1 << inode->i_blkbits;
2750 length = offset & (blocksize - 1);
2752 /* Block boundary? Nothing to do */
2753 if (!length)
2754 return 0;
2756 length = blocksize - length;
2757 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2759 page = grab_cache_page(mapping, index);
2760 err = -ENOMEM;
2761 if (!page)
2762 goto out;
2764 if (!page_has_buffers(page))
2765 create_empty_buffers(page, blocksize, 0);
2767 /* Find the buffer that contains "offset" */
2768 bh = page_buffers(page);
2769 pos = blocksize;
2770 while (offset >= pos) {
2771 bh = bh->b_this_page;
2772 iblock++;
2773 pos += blocksize;
2776 err = 0;
2777 if (!buffer_mapped(bh)) {
2778 WARN_ON(bh->b_size != blocksize);
2779 err = get_block(inode, iblock, bh, 0);
2780 if (err)
2781 goto unlock;
2782 /* unmapped? It's a hole - nothing to do */
2783 if (!buffer_mapped(bh))
2784 goto unlock;
2787 /* Ok, it's mapped. Make sure it's up-to-date */
2788 if (PageUptodate(page))
2789 set_buffer_uptodate(bh);
2791 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2792 err = -EIO;
2793 ll_rw_block(READ, 1, &bh);
2794 wait_on_buffer(bh);
2795 /* Uhhuh. Read error. Complain and punt. */
2796 if (!buffer_uptodate(bh))
2797 goto unlock;
2800 zero_user(page, offset, length);
2801 mark_buffer_dirty(bh);
2802 err = 0;
2804 unlock:
2805 unlock_page(page);
2806 page_cache_release(page);
2807 out:
2808 return err;
2812 * The generic ->writepage function for buffer-backed address_spaces
2814 int block_write_full_page(struct page *page, get_block_t *get_block,
2815 struct writeback_control *wbc)
2817 struct inode * const inode = page->mapping->host;
2818 loff_t i_size = i_size_read(inode);
2819 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2820 unsigned offset;
2822 /* Is the page fully inside i_size? */
2823 if (page->index < end_index)
2824 return __block_write_full_page(inode, page, get_block, wbc);
2826 /* Is the page fully outside i_size? (truncate in progress) */
2827 offset = i_size & (PAGE_CACHE_SIZE-1);
2828 if (page->index >= end_index+1 || !offset) {
2830 * The page may have dirty, unmapped buffers. For example,
2831 * they may have been added in ext3_writepage(). Make them
2832 * freeable here, so the page does not leak.
2834 do_invalidatepage(page, 0);
2835 unlock_page(page);
2836 return 0; /* don't care */
2840 * The page straddles i_size. It must be zeroed out on each and every
2841 * writepage invokation because it may be mmapped. "A file is mapped
2842 * in multiples of the page size. For a file that is not a multiple of
2843 * the page size, the remaining memory is zeroed when mapped, and
2844 * writes to that region are not written out to the file."
2846 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2847 return __block_write_full_page(inode, page, get_block, wbc);
2850 sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2851 get_block_t *get_block)
2853 struct buffer_head tmp;
2854 struct inode *inode = mapping->host;
2855 tmp.b_state = 0;
2856 tmp.b_blocknr = 0;
2857 tmp.b_size = 1 << inode->i_blkbits;
2858 get_block(inode, block, &tmp, 0);
2859 return tmp.b_blocknr;
2862 static void end_bio_bh_io_sync(struct bio *bio, int err)
2864 struct buffer_head *bh = bio->bi_private;
2866 if (err == -EOPNOTSUPP) {
2867 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
2868 set_bit(BH_Eopnotsupp, &bh->b_state);
2871 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2872 bio_put(bio);
2875 int submit_bh(int rw, struct buffer_head * bh)
2877 struct bio *bio;
2878 int ret = 0;
2880 BUG_ON(!buffer_locked(bh));
2881 BUG_ON(!buffer_mapped(bh));
2882 BUG_ON(!bh->b_end_io);
2884 if (buffer_ordered(bh) && (rw == WRITE))
2885 rw = WRITE_BARRIER;
2888 * Only clear out a write error when rewriting, should this
2889 * include WRITE_SYNC as well?
2891 if (test_set_buffer_req(bh) && (rw == WRITE || rw == WRITE_BARRIER))
2892 clear_buffer_write_io_error(bh);
2895 * from here on down, it's all bio -- do the initial mapping,
2896 * submit_bio -> generic_make_request may further map this bio around
2898 bio = bio_alloc(GFP_NOIO, 1);
2900 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2901 bio->bi_bdev = bh->b_bdev;
2902 bio->bi_io_vec[0].bv_page = bh->b_page;
2903 bio->bi_io_vec[0].bv_len = bh->b_size;
2904 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
2906 bio->bi_vcnt = 1;
2907 bio->bi_idx = 0;
2908 bio->bi_size = bh->b_size;
2910 bio->bi_end_io = end_bio_bh_io_sync;
2911 bio->bi_private = bh;
2913 bio_get(bio);
2914 submit_bio(rw, bio);
2916 if (bio_flagged(bio, BIO_EOPNOTSUPP))
2917 ret = -EOPNOTSUPP;
2919 bio_put(bio);
2920 return ret;
2924 * ll_rw_block: low-level access to block devices (DEPRECATED)
2925 * @rw: whether to %READ or %WRITE or %SWRITE or maybe %READA (readahead)
2926 * @nr: number of &struct buffer_heads in the array
2927 * @bhs: array of pointers to &struct buffer_head
2929 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
2930 * requests an I/O operation on them, either a %READ or a %WRITE. The third
2931 * %SWRITE is like %WRITE only we make sure that the *current* data in buffers
2932 * are sent to disk. The fourth %READA option is described in the documentation
2933 * for generic_make_request() which ll_rw_block() calls.
2935 * This function drops any buffer that it cannot get a lock on (with the
2936 * BH_Lock state bit) unless SWRITE is required, any buffer that appears to be
2937 * clean when doing a write request, and any buffer that appears to be
2938 * up-to-date when doing read request. Further it marks as clean buffers that
2939 * are processed for writing (the buffer cache won't assume that they are
2940 * actually clean until the buffer gets unlocked).
2942 * ll_rw_block sets b_end_io to simple completion handler that marks
2943 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
2944 * any waiters.
2946 * All of the buffers must be for the same device, and must also be a
2947 * multiple of the current approved size for the device.
2949 void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
2951 int i;
2953 for (i = 0; i < nr; i++) {
2954 struct buffer_head *bh = bhs[i];
2956 if (rw == SWRITE || rw == SWRITE_SYNC)
2957 lock_buffer(bh);
2958 else if (test_set_buffer_locked(bh))
2959 continue;
2961 if (rw == WRITE || rw == SWRITE || rw == SWRITE_SYNC) {
2962 if (test_clear_buffer_dirty(bh)) {
2963 bh->b_end_io = end_buffer_write_sync;
2964 get_bh(bh);
2965 if (rw == SWRITE_SYNC)
2966 submit_bh(WRITE_SYNC, bh);
2967 else
2968 submit_bh(WRITE, bh);
2969 continue;
2971 } else {
2972 if (!buffer_uptodate(bh)) {
2973 bh->b_end_io = end_buffer_read_sync;
2974 get_bh(bh);
2975 submit_bh(rw, bh);
2976 continue;
2979 unlock_buffer(bh);
2984 * For a data-integrity writeout, we need to wait upon any in-progress I/O
2985 * and then start new I/O and then wait upon it. The caller must have a ref on
2986 * the buffer_head.
2988 int sync_dirty_buffer(struct buffer_head *bh)
2990 int ret = 0;
2992 WARN_ON(atomic_read(&bh->b_count) < 1);
2993 lock_buffer(bh);
2994 if (test_clear_buffer_dirty(bh)) {
2995 get_bh(bh);
2996 bh->b_end_io = end_buffer_write_sync;
2997 ret = submit_bh(WRITE_SYNC, bh);
2998 wait_on_buffer(bh);
2999 if (buffer_eopnotsupp(bh)) {
3000 clear_buffer_eopnotsupp(bh);
3001 ret = -EOPNOTSUPP;
3003 if (!ret && !buffer_uptodate(bh))
3004 ret = -EIO;
3005 } else {
3006 unlock_buffer(bh);
3008 return ret;
3012 * try_to_free_buffers() checks if all the buffers on this particular page
3013 * are unused, and releases them if so.
3015 * Exclusion against try_to_free_buffers may be obtained by either
3016 * locking the page or by holding its mapping's private_lock.
3018 * If the page is dirty but all the buffers are clean then we need to
3019 * be sure to mark the page clean as well. This is because the page
3020 * may be against a block device, and a later reattachment of buffers
3021 * to a dirty page will set *all* buffers dirty. Which would corrupt
3022 * filesystem data on the same device.
3024 * The same applies to regular filesystem pages: if all the buffers are
3025 * clean then we set the page clean and proceed. To do that, we require
3026 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3027 * private_lock.
3029 * try_to_free_buffers() is non-blocking.
3031 static inline int buffer_busy(struct buffer_head *bh)
3033 return atomic_read(&bh->b_count) |
3034 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3037 static int
3038 drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3040 struct buffer_head *head = page_buffers(page);
3041 struct buffer_head *bh;
3043 bh = head;
3044 do {
3045 if (buffer_write_io_error(bh) && page->mapping)
3046 set_bit(AS_EIO, &page->mapping->flags);
3047 if (buffer_busy(bh))
3048 goto failed;
3049 bh = bh->b_this_page;
3050 } while (bh != head);
3052 do {
3053 struct buffer_head *next = bh->b_this_page;
3055 if (bh->b_assoc_map)
3056 __remove_assoc_queue(bh);
3057 bh = next;
3058 } while (bh != head);
3059 *buffers_to_free = head;
3060 __clear_page_buffers(page);
3061 return 1;
3062 failed:
3063 return 0;
3066 int try_to_free_buffers(struct page *page)
3068 struct address_space * const mapping = page->mapping;
3069 struct buffer_head *buffers_to_free = NULL;
3070 int ret = 0;
3072 BUG_ON(!PageLocked(page));
3073 if (PageWriteback(page))
3074 return 0;
3076 if (mapping == NULL) { /* can this still happen? */
3077 ret = drop_buffers(page, &buffers_to_free);
3078 goto out;
3081 spin_lock(&mapping->private_lock);
3082 ret = drop_buffers(page, &buffers_to_free);
3085 * If the filesystem writes its buffers by hand (eg ext3)
3086 * then we can have clean buffers against a dirty page. We
3087 * clean the page here; otherwise the VM will never notice
3088 * that the filesystem did any IO at all.
3090 * Also, during truncate, discard_buffer will have marked all
3091 * the page's buffers clean. We discover that here and clean
3092 * the page also.
3094 * private_lock must be held over this entire operation in order
3095 * to synchronise against __set_page_dirty_buffers and prevent the
3096 * dirty bit from being lost.
3098 if (ret)
3099 cancel_dirty_page(page, PAGE_CACHE_SIZE);
3100 spin_unlock(&mapping->private_lock);
3101 out:
3102 if (buffers_to_free) {
3103 struct buffer_head *bh = buffers_to_free;
3105 do {
3106 struct buffer_head *next = bh->b_this_page;
3107 free_buffer_head(bh);
3108 bh = next;
3109 } while (bh != buffers_to_free);
3111 return ret;
3113 EXPORT_SYMBOL(try_to_free_buffers);
3115 void block_sync_page(struct page *page)
3117 struct address_space *mapping;
3119 smp_mb();
3120 mapping = page_mapping(page);
3121 if (mapping)
3122 blk_run_backing_dev(mapping->backing_dev_info, page);
3126 * There are no bdflush tunables left. But distributions are
3127 * still running obsolete flush daemons, so we terminate them here.
3129 * Use of bdflush() is deprecated and will be removed in a future kernel.
3130 * The `pdflush' kernel threads fully replace bdflush daemons and this call.
3132 asmlinkage long sys_bdflush(int func, long data)
3134 static int msg_count;
3136 if (!capable(CAP_SYS_ADMIN))
3137 return -EPERM;
3139 if (msg_count < 5) {
3140 msg_count++;
3141 printk(KERN_INFO
3142 "warning: process `%s' used the obsolete bdflush"
3143 " system call\n", current->comm);
3144 printk(KERN_INFO "Fix your initscripts?\n");
3147 if (func == 1)
3148 do_exit(0);
3149 return 0;
3153 * Buffer-head allocation
3155 static struct kmem_cache *bh_cachep;
3158 * Once the number of bh's in the machine exceeds this level, we start
3159 * stripping them in writeback.
3161 static int max_buffer_heads;
3163 int buffer_heads_over_limit;
3165 struct bh_accounting {
3166 int nr; /* Number of live bh's */
3167 int ratelimit; /* Limit cacheline bouncing */
3170 static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3172 static void recalc_bh_state(void)
3174 int i;
3175 int tot = 0;
3177 if (__get_cpu_var(bh_accounting).ratelimit++ < 4096)
3178 return;
3179 __get_cpu_var(bh_accounting).ratelimit = 0;
3180 for_each_online_cpu(i)
3181 tot += per_cpu(bh_accounting, i).nr;
3182 buffer_heads_over_limit = (tot > max_buffer_heads);
3185 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3187 struct buffer_head *ret = kmem_cache_alloc(bh_cachep, gfp_flags);
3188 if (ret) {
3189 INIT_LIST_HEAD(&ret->b_assoc_buffers);
3190 get_cpu_var(bh_accounting).nr++;
3191 recalc_bh_state();
3192 put_cpu_var(bh_accounting);
3194 return ret;
3196 EXPORT_SYMBOL(alloc_buffer_head);
3198 void free_buffer_head(struct buffer_head *bh)
3200 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3201 kmem_cache_free(bh_cachep, bh);
3202 get_cpu_var(bh_accounting).nr--;
3203 recalc_bh_state();
3204 put_cpu_var(bh_accounting);
3206 EXPORT_SYMBOL(free_buffer_head);
3208 static void buffer_exit_cpu(int cpu)
3210 int i;
3211 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3213 for (i = 0; i < BH_LRU_SIZE; i++) {
3214 brelse(b->bhs[i]);
3215 b->bhs[i] = NULL;
3217 get_cpu_var(bh_accounting).nr += per_cpu(bh_accounting, cpu).nr;
3218 per_cpu(bh_accounting, cpu).nr = 0;
3219 put_cpu_var(bh_accounting);
3222 static int buffer_cpu_notify(struct notifier_block *self,
3223 unsigned long action, void *hcpu)
3225 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
3226 buffer_exit_cpu((unsigned long)hcpu);
3227 return NOTIFY_OK;
3231 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3232 * @bh: struct buffer_head
3234 * Return true if the buffer is up-to-date and false,
3235 * with the buffer locked, if not.
3237 int bh_uptodate_or_lock(struct buffer_head *bh)
3239 if (!buffer_uptodate(bh)) {
3240 lock_buffer(bh);
3241 if (!buffer_uptodate(bh))
3242 return 0;
3243 unlock_buffer(bh);
3245 return 1;
3247 EXPORT_SYMBOL(bh_uptodate_or_lock);
3250 * bh_submit_read - Submit a locked buffer for reading
3251 * @bh: struct buffer_head
3253 * Returns zero on success and -EIO on error.
3255 int bh_submit_read(struct buffer_head *bh)
3257 BUG_ON(!buffer_locked(bh));
3259 if (buffer_uptodate(bh)) {
3260 unlock_buffer(bh);
3261 return 0;
3264 get_bh(bh);
3265 bh->b_end_io = end_buffer_read_sync;
3266 submit_bh(READ, bh);
3267 wait_on_buffer(bh);
3268 if (buffer_uptodate(bh))
3269 return 0;
3270 return -EIO;
3272 EXPORT_SYMBOL(bh_submit_read);
3274 static void
3275 init_buffer_head(struct kmem_cache *cachep, void *data)
3277 struct buffer_head *bh = data;
3279 memset(bh, 0, sizeof(*bh));
3280 INIT_LIST_HEAD(&bh->b_assoc_buffers);
3283 void __init buffer_init(void)
3285 int nrpages;
3287 bh_cachep = kmem_cache_create("buffer_head",
3288 sizeof(struct buffer_head), 0,
3289 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3290 SLAB_MEM_SPREAD),
3291 init_buffer_head);
3294 * Limit the bh occupancy to 10% of ZONE_NORMAL
3296 nrpages = (nr_free_buffer_pages() * 10) / 100;
3297 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3298 hotcpu_notifier(buffer_cpu_notify, 0);
3301 EXPORT_SYMBOL(__bforget);
3302 EXPORT_SYMBOL(__brelse);
3303 EXPORT_SYMBOL(__wait_on_buffer);
3304 EXPORT_SYMBOL(block_commit_write);
3305 EXPORT_SYMBOL(block_prepare_write);
3306 EXPORT_SYMBOL(block_page_mkwrite);
3307 EXPORT_SYMBOL(block_read_full_page);
3308 EXPORT_SYMBOL(block_sync_page);
3309 EXPORT_SYMBOL(block_truncate_page);
3310 EXPORT_SYMBOL(block_write_full_page);
3311 EXPORT_SYMBOL(cont_write_begin);
3312 EXPORT_SYMBOL(end_buffer_read_sync);
3313 EXPORT_SYMBOL(end_buffer_write_sync);
3314 EXPORT_SYMBOL(file_fsync);
3315 EXPORT_SYMBOL(fsync_bdev);
3316 EXPORT_SYMBOL(generic_block_bmap);
3317 EXPORT_SYMBOL(generic_cont_expand_simple);
3318 EXPORT_SYMBOL(init_buffer);
3319 EXPORT_SYMBOL(invalidate_bdev);
3320 EXPORT_SYMBOL(ll_rw_block);
3321 EXPORT_SYMBOL(mark_buffer_dirty);
3322 EXPORT_SYMBOL(submit_bh);
3323 EXPORT_SYMBOL(sync_dirty_buffer);
3324 EXPORT_SYMBOL(unlock_buffer);