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[cor_2_6_31.git] / fs / buffer.c
bloba3ef091a45bd4664e5ba5e683f9329bda3d1d3df
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 clear_bit_unlock(BH_Lock, &bh->b_state);
80 smp_mb__after_clear_bit();
81 wake_up_bit(&bh->b_state, BH_Lock);
85 * Block until a buffer comes unlocked. This doesn't stop it
86 * from becoming locked again - you have to lock it yourself
87 * if you want to preserve its state.
89 void __wait_on_buffer(struct buffer_head * bh)
91 wait_on_bit(&bh->b_state, BH_Lock, sync_buffer, TASK_UNINTERRUPTIBLE);
94 static void
95 __clear_page_buffers(struct page *page)
97 ClearPagePrivate(page);
98 set_page_private(page, 0);
99 page_cache_release(page);
103 static int quiet_error(struct buffer_head *bh)
105 if (!test_bit(BH_Quiet, &bh->b_state) && printk_ratelimit())
106 return 0;
107 return 1;
111 static void buffer_io_error(struct buffer_head *bh)
113 char b[BDEVNAME_SIZE];
114 printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
115 bdevname(bh->b_bdev, b),
116 (unsigned long long)bh->b_blocknr);
120 * End-of-IO handler helper function which does not touch the bh after
121 * unlocking it.
122 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
123 * a race there is benign: unlock_buffer() only use the bh's address for
124 * hashing after unlocking the buffer, so it doesn't actually touch the bh
125 * itself.
127 static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
129 if (uptodate) {
130 set_buffer_uptodate(bh);
131 } else {
132 /* This happens, due to failed READA attempts. */
133 clear_buffer_uptodate(bh);
135 unlock_buffer(bh);
139 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
140 * unlock the buffer. This is what ll_rw_block uses too.
142 void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
144 __end_buffer_read_notouch(bh, uptodate);
145 put_bh(bh);
148 void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
150 char b[BDEVNAME_SIZE];
152 if (uptodate) {
153 set_buffer_uptodate(bh);
154 } else {
155 if (!buffer_eopnotsupp(bh) && !quiet_error(bh)) {
156 buffer_io_error(bh);
157 printk(KERN_WARNING "lost page write due to "
158 "I/O error on %s\n",
159 bdevname(bh->b_bdev, b));
161 set_buffer_write_io_error(bh);
162 clear_buffer_uptodate(bh);
164 unlock_buffer(bh);
165 put_bh(bh);
169 * Various filesystems appear to want __find_get_block to be non-blocking.
170 * But it's the page lock which protects the buffers. To get around this,
171 * we get exclusion from try_to_free_buffers with the blockdev mapping's
172 * private_lock.
174 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
175 * may be quite high. This code could TryLock the page, and if that
176 * succeeds, there is no need to take private_lock. (But if
177 * private_lock is contended then so is mapping->tree_lock).
179 static struct buffer_head *
180 __find_get_block_slow(struct block_device *bdev, sector_t block)
182 struct inode *bd_inode = bdev->bd_inode;
183 struct address_space *bd_mapping = bd_inode->i_mapping;
184 struct buffer_head *ret = NULL;
185 pgoff_t index;
186 struct buffer_head *bh;
187 struct buffer_head *head;
188 struct page *page;
189 int all_mapped = 1;
191 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
192 page = find_get_page(bd_mapping, index);
193 if (!page)
194 goto out;
196 spin_lock(&bd_mapping->private_lock);
197 if (!page_has_buffers(page))
198 goto out_unlock;
199 head = page_buffers(page);
200 bh = head;
201 do {
202 if (!buffer_mapped(bh))
203 all_mapped = 0;
204 else if (bh->b_blocknr == block) {
205 ret = bh;
206 get_bh(bh);
207 goto out_unlock;
209 bh = bh->b_this_page;
210 } while (bh != head);
212 /* we might be here because some of the buffers on this page are
213 * not mapped. This is due to various races between
214 * file io on the block device and getblk. It gets dealt with
215 * elsewhere, don't buffer_error if we had some unmapped buffers
217 if (all_mapped) {
218 printk("__find_get_block_slow() failed. "
219 "block=%llu, b_blocknr=%llu\n",
220 (unsigned long long)block,
221 (unsigned long long)bh->b_blocknr);
222 printk("b_state=0x%08lx, b_size=%zu\n",
223 bh->b_state, bh->b_size);
224 printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits);
226 out_unlock:
227 spin_unlock(&bd_mapping->private_lock);
228 page_cache_release(page);
229 out:
230 return ret;
233 /* If invalidate_buffers() will trash dirty buffers, it means some kind
234 of fs corruption is going on. Trashing dirty data always imply losing
235 information that was supposed to be just stored on the physical layer
236 by the user.
238 Thus invalidate_buffers in general usage is not allwowed to trash
239 dirty buffers. For example ioctl(FLSBLKBUF) expects dirty data to
240 be preserved. These buffers are simply skipped.
242 We also skip buffers which are still in use. For example this can
243 happen if a userspace program is reading the block device.
245 NOTE: In the case where the user removed a removable-media-disk even if
246 there's still dirty data not synced on disk (due a bug in the device driver
247 or due an error of the user), by not destroying the dirty buffers we could
248 generate corruption also on the next media inserted, thus a parameter is
249 necessary to handle this case in the most safe way possible (trying
250 to not corrupt also the new disk inserted with the data belonging to
251 the old now corrupted disk). Also for the ramdisk the natural thing
252 to do in order to release the ramdisk memory is to destroy dirty buffers.
254 These are two special cases. Normal usage imply the device driver
255 to issue a sync on the device (without waiting I/O completion) and
256 then an invalidate_buffers call that doesn't trash dirty buffers.
258 For handling cache coherency with the blkdev pagecache the 'update' case
259 is been introduced. It is needed to re-read from disk any pinned
260 buffer. NOTE: re-reading from disk is destructive so we can do it only
261 when we assume nobody is changing the buffercache under our I/O and when
262 we think the disk contains more recent information than the buffercache.
263 The update == 1 pass marks the buffers we need to update, the update == 2
264 pass does the actual I/O. */
265 void invalidate_bdev(struct block_device *bdev)
267 struct address_space *mapping = bdev->bd_inode->i_mapping;
269 if (mapping->nrpages == 0)
270 return;
272 invalidate_bh_lrus();
273 invalidate_mapping_pages(mapping, 0, -1);
277 * Kick pdflush then try to free up some ZONE_NORMAL memory.
279 static void free_more_memory(void)
281 struct zone *zone;
282 int nid;
284 wakeup_pdflush(1024);
285 yield();
287 for_each_online_node(nid) {
288 (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS),
289 gfp_zone(GFP_NOFS), NULL,
290 &zone);
291 if (zone)
292 try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0,
293 GFP_NOFS, NULL);
298 * I/O completion handler for block_read_full_page() - pages
299 * which come unlocked at the end of I/O.
301 static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
303 unsigned long flags;
304 struct buffer_head *first;
305 struct buffer_head *tmp;
306 struct page *page;
307 int page_uptodate = 1;
309 BUG_ON(!buffer_async_read(bh));
311 page = bh->b_page;
312 if (uptodate) {
313 set_buffer_uptodate(bh);
314 } else {
315 clear_buffer_uptodate(bh);
316 if (!quiet_error(bh))
317 buffer_io_error(bh);
318 SetPageError(page);
322 * Be _very_ careful from here on. Bad things can happen if
323 * two buffer heads end IO at almost the same time and both
324 * decide that the page is now completely done.
326 first = page_buffers(page);
327 local_irq_save(flags);
328 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
329 clear_buffer_async_read(bh);
330 unlock_buffer(bh);
331 tmp = bh;
332 do {
333 if (!buffer_uptodate(tmp))
334 page_uptodate = 0;
335 if (buffer_async_read(tmp)) {
336 BUG_ON(!buffer_locked(tmp));
337 goto still_busy;
339 tmp = tmp->b_this_page;
340 } while (tmp != bh);
341 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
342 local_irq_restore(flags);
345 * If none of the buffers had errors and they are all
346 * uptodate then we can set the page uptodate.
348 if (page_uptodate && !PageError(page))
349 SetPageUptodate(page);
350 unlock_page(page);
351 return;
353 still_busy:
354 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
355 local_irq_restore(flags);
356 return;
360 * Completion handler for block_write_full_page() - pages which are unlocked
361 * during I/O, and which have PageWriteback cleared upon I/O completion.
363 void end_buffer_async_write(struct buffer_head *bh, int uptodate)
365 char b[BDEVNAME_SIZE];
366 unsigned long flags;
367 struct buffer_head *first;
368 struct buffer_head *tmp;
369 struct page *page;
371 BUG_ON(!buffer_async_write(bh));
373 page = bh->b_page;
374 if (uptodate) {
375 set_buffer_uptodate(bh);
376 } else {
377 if (!quiet_error(bh)) {
378 buffer_io_error(bh);
379 printk(KERN_WARNING "lost page write due to "
380 "I/O error on %s\n",
381 bdevname(bh->b_bdev, b));
383 set_bit(AS_EIO, &page->mapping->flags);
384 set_buffer_write_io_error(bh);
385 clear_buffer_uptodate(bh);
386 SetPageError(page);
389 first = page_buffers(page);
390 local_irq_save(flags);
391 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
393 clear_buffer_async_write(bh);
394 unlock_buffer(bh);
395 tmp = bh->b_this_page;
396 while (tmp != bh) {
397 if (buffer_async_write(tmp)) {
398 BUG_ON(!buffer_locked(tmp));
399 goto still_busy;
401 tmp = tmp->b_this_page;
403 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
404 local_irq_restore(flags);
405 end_page_writeback(page);
406 return;
408 still_busy:
409 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
410 local_irq_restore(flags);
411 return;
415 * If a page's buffers are under async readin (end_buffer_async_read
416 * completion) then there is a possibility that another thread of
417 * control could lock one of the buffers after it has completed
418 * but while some of the other buffers have not completed. This
419 * locked buffer would confuse end_buffer_async_read() into not unlocking
420 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
421 * that this buffer is not under async I/O.
423 * The page comes unlocked when it has no locked buffer_async buffers
424 * left.
426 * PageLocked prevents anyone starting new async I/O reads any of
427 * the buffers.
429 * PageWriteback is used to prevent simultaneous writeout of the same
430 * page.
432 * PageLocked prevents anyone from starting writeback of a page which is
433 * under read I/O (PageWriteback is only ever set against a locked page).
435 static void mark_buffer_async_read(struct buffer_head *bh)
437 bh->b_end_io = end_buffer_async_read;
438 set_buffer_async_read(bh);
441 void mark_buffer_async_write_endio(struct buffer_head *bh,
442 bh_end_io_t *handler)
444 bh->b_end_io = handler;
445 set_buffer_async_write(bh);
448 void mark_buffer_async_write(struct buffer_head *bh)
450 mark_buffer_async_write_endio(bh, end_buffer_async_write);
452 EXPORT_SYMBOL(mark_buffer_async_write);
456 * fs/buffer.c contains helper functions for buffer-backed address space's
457 * fsync functions. A common requirement for buffer-based filesystems is
458 * that certain data from the backing blockdev needs to be written out for
459 * a successful fsync(). For example, ext2 indirect blocks need to be
460 * written back and waited upon before fsync() returns.
462 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
463 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
464 * management of a list of dependent buffers at ->i_mapping->private_list.
466 * Locking is a little subtle: try_to_free_buffers() will remove buffers
467 * from their controlling inode's queue when they are being freed. But
468 * try_to_free_buffers() will be operating against the *blockdev* mapping
469 * at the time, not against the S_ISREG file which depends on those buffers.
470 * So the locking for private_list is via the private_lock in the address_space
471 * which backs the buffers. Which is different from the address_space
472 * against which the buffers are listed. So for a particular address_space,
473 * mapping->private_lock does *not* protect mapping->private_list! In fact,
474 * mapping->private_list will always be protected by the backing blockdev's
475 * ->private_lock.
477 * Which introduces a requirement: all buffers on an address_space's
478 * ->private_list must be from the same address_space: the blockdev's.
480 * address_spaces which do not place buffers at ->private_list via these
481 * utility functions are free to use private_lock and private_list for
482 * whatever they want. The only requirement is that list_empty(private_list)
483 * be true at clear_inode() time.
485 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
486 * filesystems should do that. invalidate_inode_buffers() should just go
487 * BUG_ON(!list_empty).
489 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
490 * take an address_space, not an inode. And it should be called
491 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
492 * queued up.
494 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
495 * list if it is already on a list. Because if the buffer is on a list,
496 * it *must* already be on the right one. If not, the filesystem is being
497 * silly. This will save a ton of locking. But first we have to ensure
498 * that buffers are taken *off* the old inode's list when they are freed
499 * (presumably in truncate). That requires careful auditing of all
500 * filesystems (do it inside bforget()). It could also be done by bringing
501 * b_inode back.
505 * The buffer's backing address_space's private_lock must be held
507 static void __remove_assoc_queue(struct buffer_head *bh)
509 list_del_init(&bh->b_assoc_buffers);
510 WARN_ON(!bh->b_assoc_map);
511 if (buffer_write_io_error(bh))
512 set_bit(AS_EIO, &bh->b_assoc_map->flags);
513 bh->b_assoc_map = NULL;
516 int inode_has_buffers(struct inode *inode)
518 return !list_empty(&inode->i_data.private_list);
522 * osync is designed to support O_SYNC io. It waits synchronously for
523 * all already-submitted IO to complete, but does not queue any new
524 * writes to the disk.
526 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
527 * you dirty the buffers, and then use osync_inode_buffers to wait for
528 * completion. Any other dirty buffers which are not yet queued for
529 * write will not be flushed to disk by the osync.
531 static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
533 struct buffer_head *bh;
534 struct list_head *p;
535 int err = 0;
537 spin_lock(lock);
538 repeat:
539 list_for_each_prev(p, list) {
540 bh = BH_ENTRY(p);
541 if (buffer_locked(bh)) {
542 get_bh(bh);
543 spin_unlock(lock);
544 wait_on_buffer(bh);
545 if (!buffer_uptodate(bh))
546 err = -EIO;
547 brelse(bh);
548 spin_lock(lock);
549 goto repeat;
552 spin_unlock(lock);
553 return err;
556 void do_thaw_all(struct work_struct *work)
558 struct super_block *sb;
559 char b[BDEVNAME_SIZE];
561 spin_lock(&sb_lock);
562 restart:
563 list_for_each_entry(sb, &super_blocks, s_list) {
564 sb->s_count++;
565 spin_unlock(&sb_lock);
566 down_read(&sb->s_umount);
567 while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
568 printk(KERN_WARNING "Emergency Thaw on %s\n",
569 bdevname(sb->s_bdev, b));
570 up_read(&sb->s_umount);
571 spin_lock(&sb_lock);
572 if (__put_super_and_need_restart(sb))
573 goto restart;
575 spin_unlock(&sb_lock);
576 kfree(work);
577 printk(KERN_WARNING "Emergency Thaw complete\n");
581 * emergency_thaw_all -- forcibly thaw every frozen filesystem
583 * Used for emergency unfreeze of all filesystems via SysRq
585 void emergency_thaw_all(void)
587 struct work_struct *work;
589 work = kmalloc(sizeof(*work), GFP_ATOMIC);
590 if (work) {
591 INIT_WORK(work, do_thaw_all);
592 schedule_work(work);
597 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
598 * @mapping: the mapping which wants those buffers written
600 * Starts I/O against the buffers at mapping->private_list, and waits upon
601 * that I/O.
603 * Basically, this is a convenience function for fsync().
604 * @mapping is a file or directory which needs those buffers to be written for
605 * a successful fsync().
607 int sync_mapping_buffers(struct address_space *mapping)
609 struct address_space *buffer_mapping = mapping->assoc_mapping;
611 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
612 return 0;
614 return fsync_buffers_list(&buffer_mapping->private_lock,
615 &mapping->private_list);
617 EXPORT_SYMBOL(sync_mapping_buffers);
620 * Called when we've recently written block `bblock', and it is known that
621 * `bblock' was for a buffer_boundary() buffer. This means that the block at
622 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
623 * dirty, schedule it for IO. So that indirects merge nicely with their data.
625 void write_boundary_block(struct block_device *bdev,
626 sector_t bblock, unsigned blocksize)
628 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
629 if (bh) {
630 if (buffer_dirty(bh))
631 ll_rw_block(WRITE, 1, &bh);
632 put_bh(bh);
636 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
638 struct address_space *mapping = inode->i_mapping;
639 struct address_space *buffer_mapping = bh->b_page->mapping;
641 mark_buffer_dirty(bh);
642 if (!mapping->assoc_mapping) {
643 mapping->assoc_mapping = buffer_mapping;
644 } else {
645 BUG_ON(mapping->assoc_mapping != buffer_mapping);
647 if (!bh->b_assoc_map) {
648 spin_lock(&buffer_mapping->private_lock);
649 list_move_tail(&bh->b_assoc_buffers,
650 &mapping->private_list);
651 bh->b_assoc_map = mapping;
652 spin_unlock(&buffer_mapping->private_lock);
655 EXPORT_SYMBOL(mark_buffer_dirty_inode);
658 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
659 * dirty.
661 * If warn is true, then emit a warning if the page is not uptodate and has
662 * not been truncated.
664 static void __set_page_dirty(struct page *page,
665 struct address_space *mapping, int warn)
667 spin_lock_irq(&mapping->tree_lock);
668 if (page->mapping) { /* Race with truncate? */
669 WARN_ON_ONCE(warn && !PageUptodate(page));
670 account_page_dirtied(page, mapping);
671 radix_tree_tag_set(&mapping->page_tree,
672 page_index(page), PAGECACHE_TAG_DIRTY);
674 spin_unlock_irq(&mapping->tree_lock);
675 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
679 * Add a page to the dirty page list.
681 * It is a sad fact of life that this function is called from several places
682 * deeply under spinlocking. It may not sleep.
684 * If the page has buffers, the uptodate buffers are set dirty, to preserve
685 * dirty-state coherency between the page and the buffers. It the page does
686 * not have buffers then when they are later attached they will all be set
687 * dirty.
689 * The buffers are dirtied before the page is dirtied. There's a small race
690 * window in which a writepage caller may see the page cleanness but not the
691 * buffer dirtiness. That's fine. If this code were to set the page dirty
692 * before the buffers, a concurrent writepage caller could clear the page dirty
693 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
694 * page on the dirty page list.
696 * We use private_lock to lock against try_to_free_buffers while using the
697 * page's buffer list. Also use this to protect against clean buffers being
698 * added to the page after it was set dirty.
700 * FIXME: may need to call ->reservepage here as well. That's rather up to the
701 * address_space though.
703 int __set_page_dirty_buffers(struct page *page)
705 int newly_dirty;
706 struct address_space *mapping = page_mapping(page);
708 if (unlikely(!mapping))
709 return !TestSetPageDirty(page);
711 spin_lock(&mapping->private_lock);
712 if (page_has_buffers(page)) {
713 struct buffer_head *head = page_buffers(page);
714 struct buffer_head *bh = head;
716 do {
717 set_buffer_dirty(bh);
718 bh = bh->b_this_page;
719 } while (bh != head);
721 newly_dirty = !TestSetPageDirty(page);
722 spin_unlock(&mapping->private_lock);
724 if (newly_dirty)
725 __set_page_dirty(page, mapping, 1);
726 return newly_dirty;
728 EXPORT_SYMBOL(__set_page_dirty_buffers);
731 * Write out and wait upon a list of buffers.
733 * We have conflicting pressures: we want to make sure that all
734 * initially dirty buffers get waited on, but that any subsequently
735 * dirtied buffers don't. After all, we don't want fsync to last
736 * forever if somebody is actively writing to the file.
738 * Do this in two main stages: first we copy dirty buffers to a
739 * temporary inode list, queueing the writes as we go. Then we clean
740 * up, waiting for those writes to complete.
742 * During this second stage, any subsequent updates to the file may end
743 * up refiling the buffer on the original inode's dirty list again, so
744 * there is a chance we will end up with a buffer queued for write but
745 * not yet completed on that list. So, as a final cleanup we go through
746 * the osync code to catch these locked, dirty buffers without requeuing
747 * any newly dirty buffers for write.
749 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
751 struct buffer_head *bh;
752 struct list_head tmp;
753 struct address_space *mapping, *prev_mapping = NULL;
754 int err = 0, err2;
756 INIT_LIST_HEAD(&tmp);
758 spin_lock(lock);
759 while (!list_empty(list)) {
760 bh = BH_ENTRY(list->next);
761 mapping = bh->b_assoc_map;
762 __remove_assoc_queue(bh);
763 /* Avoid race with mark_buffer_dirty_inode() which does
764 * a lockless check and we rely on seeing the dirty bit */
765 smp_mb();
766 if (buffer_dirty(bh) || buffer_locked(bh)) {
767 list_add(&bh->b_assoc_buffers, &tmp);
768 bh->b_assoc_map = mapping;
769 if (buffer_dirty(bh)) {
770 get_bh(bh);
771 spin_unlock(lock);
773 * Ensure any pending I/O completes so that
774 * ll_rw_block() actually writes the current
775 * contents - it is a noop if I/O is still in
776 * flight on potentially older contents.
778 ll_rw_block(SWRITE_SYNC_PLUG, 1, &bh);
781 * Kick off IO for the previous mapping. Note
782 * that we will not run the very last mapping,
783 * wait_on_buffer() will do that for us
784 * through sync_buffer().
786 if (prev_mapping && prev_mapping != mapping)
787 blk_run_address_space(prev_mapping);
788 prev_mapping = mapping;
790 brelse(bh);
791 spin_lock(lock);
796 while (!list_empty(&tmp)) {
797 bh = BH_ENTRY(tmp.prev);
798 get_bh(bh);
799 mapping = bh->b_assoc_map;
800 __remove_assoc_queue(bh);
801 /* Avoid race with mark_buffer_dirty_inode() which does
802 * a lockless check and we rely on seeing the dirty bit */
803 smp_mb();
804 if (buffer_dirty(bh)) {
805 list_add(&bh->b_assoc_buffers,
806 &mapping->private_list);
807 bh->b_assoc_map = mapping;
809 spin_unlock(lock);
810 wait_on_buffer(bh);
811 if (!buffer_uptodate(bh))
812 err = -EIO;
813 brelse(bh);
814 spin_lock(lock);
817 spin_unlock(lock);
818 err2 = osync_buffers_list(lock, list);
819 if (err)
820 return err;
821 else
822 return err2;
826 * Invalidate any and all dirty buffers on a given inode. We are
827 * probably unmounting the fs, but that doesn't mean we have already
828 * done a sync(). Just drop the buffers from the inode list.
830 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
831 * assumes that all the buffers are against the blockdev. Not true
832 * for reiserfs.
834 void invalidate_inode_buffers(struct inode *inode)
836 if (inode_has_buffers(inode)) {
837 struct address_space *mapping = &inode->i_data;
838 struct list_head *list = &mapping->private_list;
839 struct address_space *buffer_mapping = mapping->assoc_mapping;
841 spin_lock(&buffer_mapping->private_lock);
842 while (!list_empty(list))
843 __remove_assoc_queue(BH_ENTRY(list->next));
844 spin_unlock(&buffer_mapping->private_lock);
847 EXPORT_SYMBOL(invalidate_inode_buffers);
850 * Remove any clean buffers from the inode's buffer list. This is called
851 * when we're trying to free the inode itself. Those buffers can pin it.
853 * Returns true if all buffers were removed.
855 int remove_inode_buffers(struct inode *inode)
857 int ret = 1;
859 if (inode_has_buffers(inode)) {
860 struct address_space *mapping = &inode->i_data;
861 struct list_head *list = &mapping->private_list;
862 struct address_space *buffer_mapping = mapping->assoc_mapping;
864 spin_lock(&buffer_mapping->private_lock);
865 while (!list_empty(list)) {
866 struct buffer_head *bh = BH_ENTRY(list->next);
867 if (buffer_dirty(bh)) {
868 ret = 0;
869 break;
871 __remove_assoc_queue(bh);
873 spin_unlock(&buffer_mapping->private_lock);
875 return ret;
879 * Create the appropriate buffers when given a page for data area and
880 * the size of each buffer.. Use the bh->b_this_page linked list to
881 * follow the buffers created. Return NULL if unable to create more
882 * buffers.
884 * The retry flag is used to differentiate async IO (paging, swapping)
885 * which may not fail from ordinary buffer allocations.
887 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
888 int retry)
890 struct buffer_head *bh, *head;
891 long offset;
893 try_again:
894 head = NULL;
895 offset = PAGE_SIZE;
896 while ((offset -= size) >= 0) {
897 bh = alloc_buffer_head(GFP_NOFS);
898 if (!bh)
899 goto no_grow;
901 bh->b_bdev = NULL;
902 bh->b_this_page = head;
903 bh->b_blocknr = -1;
904 head = bh;
906 bh->b_state = 0;
907 atomic_set(&bh->b_count, 0);
908 bh->b_private = NULL;
909 bh->b_size = size;
911 /* Link the buffer to its page */
912 set_bh_page(bh, page, offset);
914 init_buffer(bh, NULL, NULL);
916 return head;
918 * In case anything failed, we just free everything we got.
920 no_grow:
921 if (head) {
922 do {
923 bh = head;
924 head = head->b_this_page;
925 free_buffer_head(bh);
926 } while (head);
930 * Return failure for non-async IO requests. Async IO requests
931 * are not allowed to fail, so we have to wait until buffer heads
932 * become available. But we don't want tasks sleeping with
933 * partially complete buffers, so all were released above.
935 if (!retry)
936 return NULL;
938 /* We're _really_ low on memory. Now we just
939 * wait for old buffer heads to become free due to
940 * finishing IO. Since this is an async request and
941 * the reserve list is empty, we're sure there are
942 * async buffer heads in use.
944 free_more_memory();
945 goto try_again;
947 EXPORT_SYMBOL_GPL(alloc_page_buffers);
949 static inline void
950 link_dev_buffers(struct page *page, struct buffer_head *head)
952 struct buffer_head *bh, *tail;
954 bh = head;
955 do {
956 tail = bh;
957 bh = bh->b_this_page;
958 } while (bh);
959 tail->b_this_page = head;
960 attach_page_buffers(page, head);
964 * Initialise the state of a blockdev page's buffers.
966 static void
967 init_page_buffers(struct page *page, struct block_device *bdev,
968 sector_t block, int size)
970 struct buffer_head *head = page_buffers(page);
971 struct buffer_head *bh = head;
972 int uptodate = PageUptodate(page);
974 do {
975 if (!buffer_mapped(bh)) {
976 init_buffer(bh, NULL, NULL);
977 bh->b_bdev = bdev;
978 bh->b_blocknr = block;
979 if (uptodate)
980 set_buffer_uptodate(bh);
981 set_buffer_mapped(bh);
983 block++;
984 bh = bh->b_this_page;
985 } while (bh != head);
989 * Create the page-cache page that contains the requested block.
991 * This is user purely for blockdev mappings.
993 static struct page *
994 grow_dev_page(struct block_device *bdev, sector_t block,
995 pgoff_t index, int size)
997 struct inode *inode = bdev->bd_inode;
998 struct page *page;
999 struct buffer_head *bh;
1001 page = find_or_create_page(inode->i_mapping, index,
1002 (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE);
1003 if (!page)
1004 return NULL;
1006 BUG_ON(!PageLocked(page));
1008 if (page_has_buffers(page)) {
1009 bh = page_buffers(page);
1010 if (bh->b_size == size) {
1011 init_page_buffers(page, bdev, block, size);
1012 return page;
1014 if (!try_to_free_buffers(page))
1015 goto failed;
1019 * Allocate some buffers for this page
1021 bh = alloc_page_buffers(page, size, 0);
1022 if (!bh)
1023 goto failed;
1026 * Link the page to the buffers and initialise them. Take the
1027 * lock to be atomic wrt __find_get_block(), which does not
1028 * run under the page lock.
1030 spin_lock(&inode->i_mapping->private_lock);
1031 link_dev_buffers(page, bh);
1032 init_page_buffers(page, bdev, block, size);
1033 spin_unlock(&inode->i_mapping->private_lock);
1034 return page;
1036 failed:
1037 BUG();
1038 unlock_page(page);
1039 page_cache_release(page);
1040 return NULL;
1044 * Create buffers for the specified block device block's page. If
1045 * that page was dirty, the buffers are set dirty also.
1047 static int
1048 grow_buffers(struct block_device *bdev, sector_t block, int size)
1050 struct page *page;
1051 pgoff_t index;
1052 int sizebits;
1054 sizebits = -1;
1055 do {
1056 sizebits++;
1057 } while ((size << sizebits) < PAGE_SIZE);
1059 index = block >> sizebits;
1062 * Check for a block which wants to lie outside our maximum possible
1063 * pagecache index. (this comparison is done using sector_t types).
1065 if (unlikely(index != block >> sizebits)) {
1066 char b[BDEVNAME_SIZE];
1068 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1069 "device %s\n",
1070 __func__, (unsigned long long)block,
1071 bdevname(bdev, b));
1072 return -EIO;
1074 block = index << sizebits;
1075 /* Create a page with the proper size buffers.. */
1076 page = grow_dev_page(bdev, block, index, size);
1077 if (!page)
1078 return 0;
1079 unlock_page(page);
1080 page_cache_release(page);
1081 return 1;
1084 static struct buffer_head *
1085 __getblk_slow(struct block_device *bdev, sector_t block, int size)
1087 /* Size must be multiple of hard sectorsize */
1088 if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
1089 (size < 512 || size > PAGE_SIZE))) {
1090 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1091 size);
1092 printk(KERN_ERR "logical block size: %d\n",
1093 bdev_logical_block_size(bdev));
1095 dump_stack();
1096 return NULL;
1099 for (;;) {
1100 struct buffer_head * bh;
1101 int ret;
1103 bh = __find_get_block(bdev, block, size);
1104 if (bh)
1105 return bh;
1107 ret = grow_buffers(bdev, block, size);
1108 if (ret < 0)
1109 return NULL;
1110 if (ret == 0)
1111 free_more_memory();
1116 * The relationship between dirty buffers and dirty pages:
1118 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1119 * the page is tagged dirty in its radix tree.
1121 * At all times, the dirtiness of the buffers represents the dirtiness of
1122 * subsections of the page. If the page has buffers, the page dirty bit is
1123 * merely a hint about the true dirty state.
1125 * When a page is set dirty in its entirety, all its buffers are marked dirty
1126 * (if the page has buffers).
1128 * When a buffer is marked dirty, its page is dirtied, but the page's other
1129 * buffers are not.
1131 * Also. When blockdev buffers are explicitly read with bread(), they
1132 * individually become uptodate. But their backing page remains not
1133 * uptodate - even if all of its buffers are uptodate. A subsequent
1134 * block_read_full_page() against that page will discover all the uptodate
1135 * buffers, will set the page uptodate and will perform no I/O.
1139 * mark_buffer_dirty - mark a buffer_head as needing writeout
1140 * @bh: the buffer_head to mark dirty
1142 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1143 * backing page dirty, then tag the page as dirty in its address_space's radix
1144 * tree and then attach the address_space's inode to its superblock's dirty
1145 * inode list.
1147 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1148 * mapping->tree_lock and the global inode_lock.
1150 void mark_buffer_dirty(struct buffer_head *bh)
1152 WARN_ON_ONCE(!buffer_uptodate(bh));
1155 * Very *carefully* optimize the it-is-already-dirty case.
1157 * Don't let the final "is it dirty" escape to before we
1158 * perhaps modified the buffer.
1160 if (buffer_dirty(bh)) {
1161 smp_mb();
1162 if (buffer_dirty(bh))
1163 return;
1166 if (!test_set_buffer_dirty(bh)) {
1167 struct page *page = bh->b_page;
1168 if (!TestSetPageDirty(page))
1169 __set_page_dirty(page, page_mapping(page), 0);
1174 * Decrement a buffer_head's reference count. If all buffers against a page
1175 * have zero reference count, are clean and unlocked, and if the page is clean
1176 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1177 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1178 * a page but it ends up not being freed, and buffers may later be reattached).
1180 void __brelse(struct buffer_head * buf)
1182 if (atomic_read(&buf->b_count)) {
1183 put_bh(buf);
1184 return;
1186 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1190 * bforget() is like brelse(), except it discards any
1191 * potentially dirty data.
1193 void __bforget(struct buffer_head *bh)
1195 clear_buffer_dirty(bh);
1196 if (bh->b_assoc_map) {
1197 struct address_space *buffer_mapping = bh->b_page->mapping;
1199 spin_lock(&buffer_mapping->private_lock);
1200 list_del_init(&bh->b_assoc_buffers);
1201 bh->b_assoc_map = NULL;
1202 spin_unlock(&buffer_mapping->private_lock);
1204 __brelse(bh);
1207 static struct buffer_head *__bread_slow(struct buffer_head *bh)
1209 lock_buffer(bh);
1210 if (buffer_uptodate(bh)) {
1211 unlock_buffer(bh);
1212 return bh;
1213 } else {
1214 get_bh(bh);
1215 bh->b_end_io = end_buffer_read_sync;
1216 submit_bh(READ, bh);
1217 wait_on_buffer(bh);
1218 if (buffer_uptodate(bh))
1219 return bh;
1221 brelse(bh);
1222 return NULL;
1226 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1227 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1228 * refcount elevated by one when they're in an LRU. A buffer can only appear
1229 * once in a particular CPU's LRU. A single buffer can be present in multiple
1230 * CPU's LRUs at the same time.
1232 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1233 * sb_find_get_block().
1235 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1236 * a local interrupt disable for that.
1239 #define BH_LRU_SIZE 8
1241 struct bh_lru {
1242 struct buffer_head *bhs[BH_LRU_SIZE];
1245 static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1247 #ifdef CONFIG_SMP
1248 #define bh_lru_lock() local_irq_disable()
1249 #define bh_lru_unlock() local_irq_enable()
1250 #else
1251 #define bh_lru_lock() preempt_disable()
1252 #define bh_lru_unlock() preempt_enable()
1253 #endif
1255 static inline void check_irqs_on(void)
1257 #ifdef irqs_disabled
1258 BUG_ON(irqs_disabled());
1259 #endif
1263 * The LRU management algorithm is dopey-but-simple. Sorry.
1265 static void bh_lru_install(struct buffer_head *bh)
1267 struct buffer_head *evictee = NULL;
1268 struct bh_lru *lru;
1270 check_irqs_on();
1271 bh_lru_lock();
1272 lru = &__get_cpu_var(bh_lrus);
1273 if (lru->bhs[0] != bh) {
1274 struct buffer_head *bhs[BH_LRU_SIZE];
1275 int in;
1276 int out = 0;
1278 get_bh(bh);
1279 bhs[out++] = bh;
1280 for (in = 0; in < BH_LRU_SIZE; in++) {
1281 struct buffer_head *bh2 = lru->bhs[in];
1283 if (bh2 == bh) {
1284 __brelse(bh2);
1285 } else {
1286 if (out >= BH_LRU_SIZE) {
1287 BUG_ON(evictee != NULL);
1288 evictee = bh2;
1289 } else {
1290 bhs[out++] = bh2;
1294 while (out < BH_LRU_SIZE)
1295 bhs[out++] = NULL;
1296 memcpy(lru->bhs, bhs, sizeof(bhs));
1298 bh_lru_unlock();
1300 if (evictee)
1301 __brelse(evictee);
1305 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1307 static struct buffer_head *
1308 lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1310 struct buffer_head *ret = NULL;
1311 struct bh_lru *lru;
1312 unsigned int i;
1314 check_irqs_on();
1315 bh_lru_lock();
1316 lru = &__get_cpu_var(bh_lrus);
1317 for (i = 0; i < BH_LRU_SIZE; i++) {
1318 struct buffer_head *bh = lru->bhs[i];
1320 if (bh && bh->b_bdev == bdev &&
1321 bh->b_blocknr == block && bh->b_size == size) {
1322 if (i) {
1323 while (i) {
1324 lru->bhs[i] = lru->bhs[i - 1];
1325 i--;
1327 lru->bhs[0] = bh;
1329 get_bh(bh);
1330 ret = bh;
1331 break;
1334 bh_lru_unlock();
1335 return ret;
1339 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1340 * it in the LRU and mark it as accessed. If it is not present then return
1341 * NULL
1343 struct buffer_head *
1344 __find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1346 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1348 if (bh == NULL) {
1349 bh = __find_get_block_slow(bdev, block);
1350 if (bh)
1351 bh_lru_install(bh);
1353 if (bh)
1354 touch_buffer(bh);
1355 return bh;
1357 EXPORT_SYMBOL(__find_get_block);
1360 * __getblk will locate (and, if necessary, create) the buffer_head
1361 * which corresponds to the passed block_device, block and size. The
1362 * returned buffer has its reference count incremented.
1364 * __getblk() cannot fail - it just keeps trying. If you pass it an
1365 * illegal block number, __getblk() will happily return a buffer_head
1366 * which represents the non-existent block. Very weird.
1368 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1369 * attempt is failing. FIXME, perhaps?
1371 struct buffer_head *
1372 __getblk(struct block_device *bdev, sector_t block, unsigned size)
1374 struct buffer_head *bh = __find_get_block(bdev, block, size);
1376 might_sleep();
1377 if (bh == NULL)
1378 bh = __getblk_slow(bdev, block, size);
1379 return bh;
1381 EXPORT_SYMBOL(__getblk);
1384 * Do async read-ahead on a buffer..
1386 void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1388 struct buffer_head *bh = __getblk(bdev, block, size);
1389 if (likely(bh)) {
1390 ll_rw_block(READA, 1, &bh);
1391 brelse(bh);
1394 EXPORT_SYMBOL(__breadahead);
1397 * __bread() - reads a specified block and returns the bh
1398 * @bdev: the block_device to read from
1399 * @block: number of block
1400 * @size: size (in bytes) to read
1402 * Reads a specified block, and returns buffer head that contains it.
1403 * It returns NULL if the block was unreadable.
1405 struct buffer_head *
1406 __bread(struct block_device *bdev, sector_t block, unsigned size)
1408 struct buffer_head *bh = __getblk(bdev, block, size);
1410 if (likely(bh) && !buffer_uptodate(bh))
1411 bh = __bread_slow(bh);
1412 return bh;
1414 EXPORT_SYMBOL(__bread);
1417 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1418 * This doesn't race because it runs in each cpu either in irq
1419 * or with preempt disabled.
1421 static void invalidate_bh_lru(void *arg)
1423 struct bh_lru *b = &get_cpu_var(bh_lrus);
1424 int i;
1426 for (i = 0; i < BH_LRU_SIZE; i++) {
1427 brelse(b->bhs[i]);
1428 b->bhs[i] = NULL;
1430 put_cpu_var(bh_lrus);
1433 void invalidate_bh_lrus(void)
1435 on_each_cpu(invalidate_bh_lru, NULL, 1);
1437 EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1439 void set_bh_page(struct buffer_head *bh,
1440 struct page *page, unsigned long offset)
1442 bh->b_page = page;
1443 BUG_ON(offset >= PAGE_SIZE);
1444 if (PageHighMem(page))
1446 * This catches illegal uses and preserves the offset:
1448 bh->b_data = (char *)(0 + offset);
1449 else
1450 bh->b_data = page_address(page) + offset;
1452 EXPORT_SYMBOL(set_bh_page);
1455 * Called when truncating a buffer on a page completely.
1457 static void discard_buffer(struct buffer_head * bh)
1459 lock_buffer(bh);
1460 clear_buffer_dirty(bh);
1461 bh->b_bdev = NULL;
1462 clear_buffer_mapped(bh);
1463 clear_buffer_req(bh);
1464 clear_buffer_new(bh);
1465 clear_buffer_delay(bh);
1466 clear_buffer_unwritten(bh);
1467 unlock_buffer(bh);
1471 * block_invalidatepage - invalidate part of all of a buffer-backed page
1473 * @page: the page which is affected
1474 * @offset: the index of the truncation point
1476 * block_invalidatepage() is called when all or part of the page has become
1477 * invalidatedby a truncate operation.
1479 * block_invalidatepage() does not have to release all buffers, but it must
1480 * ensure that no dirty buffer is left outside @offset and that no I/O
1481 * is underway against any of the blocks which are outside the truncation
1482 * point. Because the caller is about to free (and possibly reuse) those
1483 * blocks on-disk.
1485 void block_invalidatepage(struct page *page, unsigned long offset)
1487 struct buffer_head *head, *bh, *next;
1488 unsigned int curr_off = 0;
1490 BUG_ON(!PageLocked(page));
1491 if (!page_has_buffers(page))
1492 goto out;
1494 head = page_buffers(page);
1495 bh = head;
1496 do {
1497 unsigned int next_off = curr_off + bh->b_size;
1498 next = bh->b_this_page;
1501 * is this block fully invalidated?
1503 if (offset <= curr_off)
1504 discard_buffer(bh);
1505 curr_off = next_off;
1506 bh = next;
1507 } while (bh != head);
1510 * We release buffers only if the entire page is being invalidated.
1511 * The get_block cached value has been unconditionally invalidated,
1512 * so real IO is not possible anymore.
1514 if (offset == 0)
1515 try_to_release_page(page, 0);
1516 out:
1517 return;
1519 EXPORT_SYMBOL(block_invalidatepage);
1522 * We attach and possibly dirty the buffers atomically wrt
1523 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1524 * is already excluded via the page lock.
1526 void create_empty_buffers(struct page *page,
1527 unsigned long blocksize, unsigned long b_state)
1529 struct buffer_head *bh, *head, *tail;
1531 head = alloc_page_buffers(page, blocksize, 1);
1532 bh = head;
1533 do {
1534 bh->b_state |= b_state;
1535 tail = bh;
1536 bh = bh->b_this_page;
1537 } while (bh);
1538 tail->b_this_page = head;
1540 spin_lock(&page->mapping->private_lock);
1541 if (PageUptodate(page) || PageDirty(page)) {
1542 bh = head;
1543 do {
1544 if (PageDirty(page))
1545 set_buffer_dirty(bh);
1546 if (PageUptodate(page))
1547 set_buffer_uptodate(bh);
1548 bh = bh->b_this_page;
1549 } while (bh != head);
1551 attach_page_buffers(page, head);
1552 spin_unlock(&page->mapping->private_lock);
1554 EXPORT_SYMBOL(create_empty_buffers);
1557 * We are taking a block for data and we don't want any output from any
1558 * buffer-cache aliases starting from return from that function and
1559 * until the moment when something will explicitly mark the buffer
1560 * dirty (hopefully that will not happen until we will free that block ;-)
1561 * We don't even need to mark it not-uptodate - nobody can expect
1562 * anything from a newly allocated buffer anyway. We used to used
1563 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1564 * don't want to mark the alias unmapped, for example - it would confuse
1565 * anyone who might pick it with bread() afterwards...
1567 * Also.. Note that bforget() doesn't lock the buffer. So there can
1568 * be writeout I/O going on against recently-freed buffers. We don't
1569 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1570 * only if we really need to. That happens here.
1572 void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1574 struct buffer_head *old_bh;
1576 might_sleep();
1578 old_bh = __find_get_block_slow(bdev, block);
1579 if (old_bh) {
1580 clear_buffer_dirty(old_bh);
1581 wait_on_buffer(old_bh);
1582 clear_buffer_req(old_bh);
1583 __brelse(old_bh);
1586 EXPORT_SYMBOL(unmap_underlying_metadata);
1589 * NOTE! All mapped/uptodate combinations are valid:
1591 * Mapped Uptodate Meaning
1593 * No No "unknown" - must do get_block()
1594 * No Yes "hole" - zero-filled
1595 * Yes No "allocated" - allocated on disk, not read in
1596 * Yes Yes "valid" - allocated and up-to-date in memory.
1598 * "Dirty" is valid only with the last case (mapped+uptodate).
1602 * While block_write_full_page is writing back the dirty buffers under
1603 * the page lock, whoever dirtied the buffers may decide to clean them
1604 * again at any time. We handle that by only looking at the buffer
1605 * state inside lock_buffer().
1607 * If block_write_full_page() is called for regular writeback
1608 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1609 * locked buffer. This only can happen if someone has written the buffer
1610 * directly, with submit_bh(). At the address_space level PageWriteback
1611 * prevents this contention from occurring.
1613 * If block_write_full_page() is called with wbc->sync_mode ==
1614 * WB_SYNC_ALL, the writes are posted using WRITE_SYNC_PLUG; this
1615 * causes the writes to be flagged as synchronous writes, but the
1616 * block device queue will NOT be unplugged, since usually many pages
1617 * will be pushed to the out before the higher-level caller actually
1618 * waits for the writes to be completed. The various wait functions,
1619 * such as wait_on_writeback_range() will ultimately call sync_page()
1620 * which will ultimately call blk_run_backing_dev(), which will end up
1621 * unplugging the device queue.
1623 static int __block_write_full_page(struct inode *inode, struct page *page,
1624 get_block_t *get_block, struct writeback_control *wbc,
1625 bh_end_io_t *handler)
1627 int err;
1628 sector_t block;
1629 sector_t last_block;
1630 struct buffer_head *bh, *head;
1631 const unsigned blocksize = 1 << inode->i_blkbits;
1632 int nr_underway = 0;
1633 int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
1634 WRITE_SYNC_PLUG : WRITE);
1636 BUG_ON(!PageLocked(page));
1638 last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
1640 if (!page_has_buffers(page)) {
1641 create_empty_buffers(page, blocksize,
1642 (1 << BH_Dirty)|(1 << BH_Uptodate));
1646 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1647 * here, and the (potentially unmapped) buffers may become dirty at
1648 * any time. If a buffer becomes dirty here after we've inspected it
1649 * then we just miss that fact, and the page stays dirty.
1651 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1652 * handle that here by just cleaning them.
1655 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
1656 head = page_buffers(page);
1657 bh = head;
1660 * Get all the dirty buffers mapped to disk addresses and
1661 * handle any aliases from the underlying blockdev's mapping.
1663 do {
1664 if (block > last_block) {
1666 * mapped buffers outside i_size will occur, because
1667 * this page can be outside i_size when there is a
1668 * truncate in progress.
1671 * The buffer was zeroed by block_write_full_page()
1673 clear_buffer_dirty(bh);
1674 set_buffer_uptodate(bh);
1675 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1676 buffer_dirty(bh)) {
1677 WARN_ON(bh->b_size != blocksize);
1678 err = get_block(inode, block, bh, 1);
1679 if (err)
1680 goto recover;
1681 clear_buffer_delay(bh);
1682 if (buffer_new(bh)) {
1683 /* blockdev mappings never come here */
1684 clear_buffer_new(bh);
1685 unmap_underlying_metadata(bh->b_bdev,
1686 bh->b_blocknr);
1689 bh = bh->b_this_page;
1690 block++;
1691 } while (bh != head);
1693 do {
1694 if (!buffer_mapped(bh))
1695 continue;
1697 * If it's a fully non-blocking write attempt and we cannot
1698 * lock the buffer then redirty the page. Note that this can
1699 * potentially cause a busy-wait loop from pdflush and kswapd
1700 * activity, but those code paths have their own higher-level
1701 * throttling.
1703 if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
1704 lock_buffer(bh);
1705 } else if (!trylock_buffer(bh)) {
1706 redirty_page_for_writepage(wbc, page);
1707 continue;
1709 if (test_clear_buffer_dirty(bh)) {
1710 mark_buffer_async_write_endio(bh, handler);
1711 } else {
1712 unlock_buffer(bh);
1714 } while ((bh = bh->b_this_page) != head);
1717 * The page and its buffers are protected by PageWriteback(), so we can
1718 * drop the bh refcounts early.
1720 BUG_ON(PageWriteback(page));
1721 set_page_writeback(page);
1723 do {
1724 struct buffer_head *next = bh->b_this_page;
1725 if (buffer_async_write(bh)) {
1726 submit_bh(write_op, bh);
1727 nr_underway++;
1729 bh = next;
1730 } while (bh != head);
1731 unlock_page(page);
1733 err = 0;
1734 done:
1735 if (nr_underway == 0) {
1737 * The page was marked dirty, but the buffers were
1738 * clean. Someone wrote them back by hand with
1739 * ll_rw_block/submit_bh. A rare case.
1741 end_page_writeback(page);
1744 * The page and buffer_heads can be released at any time from
1745 * here on.
1748 return err;
1750 recover:
1752 * ENOSPC, or some other error. We may already have added some
1753 * blocks to the file, so we need to write these out to avoid
1754 * exposing stale data.
1755 * The page is currently locked and not marked for writeback
1757 bh = head;
1758 /* Recovery: lock and submit the mapped buffers */
1759 do {
1760 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1761 !buffer_delay(bh)) {
1762 lock_buffer(bh);
1763 mark_buffer_async_write_endio(bh, handler);
1764 } else {
1766 * The buffer may have been set dirty during
1767 * attachment to a dirty page.
1769 clear_buffer_dirty(bh);
1771 } while ((bh = bh->b_this_page) != head);
1772 SetPageError(page);
1773 BUG_ON(PageWriteback(page));
1774 mapping_set_error(page->mapping, err);
1775 set_page_writeback(page);
1776 do {
1777 struct buffer_head *next = bh->b_this_page;
1778 if (buffer_async_write(bh)) {
1779 clear_buffer_dirty(bh);
1780 submit_bh(write_op, bh);
1781 nr_underway++;
1783 bh = next;
1784 } while (bh != head);
1785 unlock_page(page);
1786 goto done;
1790 * If a page has any new buffers, zero them out here, and mark them uptodate
1791 * and dirty so they'll be written out (in order to prevent uninitialised
1792 * block data from leaking). And clear the new bit.
1794 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1796 unsigned int block_start, block_end;
1797 struct buffer_head *head, *bh;
1799 BUG_ON(!PageLocked(page));
1800 if (!page_has_buffers(page))
1801 return;
1803 bh = head = page_buffers(page);
1804 block_start = 0;
1805 do {
1806 block_end = block_start + bh->b_size;
1808 if (buffer_new(bh)) {
1809 if (block_end > from && block_start < to) {
1810 if (!PageUptodate(page)) {
1811 unsigned start, size;
1813 start = max(from, block_start);
1814 size = min(to, block_end) - start;
1816 zero_user(page, start, size);
1817 set_buffer_uptodate(bh);
1820 clear_buffer_new(bh);
1821 mark_buffer_dirty(bh);
1825 block_start = block_end;
1826 bh = bh->b_this_page;
1827 } while (bh != head);
1829 EXPORT_SYMBOL(page_zero_new_buffers);
1831 static int __block_prepare_write(struct inode *inode, struct page *page,
1832 unsigned from, unsigned to, get_block_t *get_block)
1834 unsigned block_start, block_end;
1835 sector_t block;
1836 int err = 0;
1837 unsigned blocksize, bbits;
1838 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1840 BUG_ON(!PageLocked(page));
1841 BUG_ON(from > PAGE_CACHE_SIZE);
1842 BUG_ON(to > PAGE_CACHE_SIZE);
1843 BUG_ON(from > to);
1845 blocksize = 1 << inode->i_blkbits;
1846 if (!page_has_buffers(page))
1847 create_empty_buffers(page, blocksize, 0);
1848 head = page_buffers(page);
1850 bbits = inode->i_blkbits;
1851 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1853 for(bh = head, block_start = 0; bh != head || !block_start;
1854 block++, block_start=block_end, bh = bh->b_this_page) {
1855 block_end = block_start + blocksize;
1856 if (block_end <= from || block_start >= to) {
1857 if (PageUptodate(page)) {
1858 if (!buffer_uptodate(bh))
1859 set_buffer_uptodate(bh);
1861 continue;
1863 if (buffer_new(bh))
1864 clear_buffer_new(bh);
1865 if (!buffer_mapped(bh)) {
1866 WARN_ON(bh->b_size != blocksize);
1867 err = get_block(inode, block, bh, 1);
1868 if (err)
1869 break;
1870 if (buffer_new(bh)) {
1871 unmap_underlying_metadata(bh->b_bdev,
1872 bh->b_blocknr);
1873 if (PageUptodate(page)) {
1874 clear_buffer_new(bh);
1875 set_buffer_uptodate(bh);
1876 mark_buffer_dirty(bh);
1877 continue;
1879 if (block_end > to || block_start < from)
1880 zero_user_segments(page,
1881 to, block_end,
1882 block_start, from);
1883 continue;
1886 if (PageUptodate(page)) {
1887 if (!buffer_uptodate(bh))
1888 set_buffer_uptodate(bh);
1889 continue;
1891 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1892 !buffer_unwritten(bh) &&
1893 (block_start < from || block_end > to)) {
1894 ll_rw_block(READ, 1, &bh);
1895 *wait_bh++=bh;
1899 * If we issued read requests - let them complete.
1901 while(wait_bh > wait) {
1902 wait_on_buffer(*--wait_bh);
1903 if (!buffer_uptodate(*wait_bh))
1904 err = -EIO;
1906 if (unlikely(err))
1907 page_zero_new_buffers(page, from, to);
1908 return err;
1911 static int __block_commit_write(struct inode *inode, struct page *page,
1912 unsigned from, unsigned to)
1914 unsigned block_start, block_end;
1915 int partial = 0;
1916 unsigned blocksize;
1917 struct buffer_head *bh, *head;
1919 blocksize = 1 << inode->i_blkbits;
1921 for(bh = head = page_buffers(page), block_start = 0;
1922 bh != head || !block_start;
1923 block_start=block_end, bh = bh->b_this_page) {
1924 block_end = block_start + blocksize;
1925 if (block_end <= from || block_start >= to) {
1926 if (!buffer_uptodate(bh))
1927 partial = 1;
1928 } else {
1929 set_buffer_uptodate(bh);
1930 mark_buffer_dirty(bh);
1932 clear_buffer_new(bh);
1936 * If this is a partial write which happened to make all buffers
1937 * uptodate then we can optimize away a bogus readpage() for
1938 * the next read(). Here we 'discover' whether the page went
1939 * uptodate as a result of this (potentially partial) write.
1941 if (!partial)
1942 SetPageUptodate(page);
1943 return 0;
1947 * block_write_begin takes care of the basic task of block allocation and
1948 * bringing partial write blocks uptodate first.
1950 * If *pagep is not NULL, then block_write_begin uses the locked page
1951 * at *pagep rather than allocating its own. In this case, the page will
1952 * not be unlocked or deallocated on failure.
1954 int block_write_begin(struct file *file, struct address_space *mapping,
1955 loff_t pos, unsigned len, unsigned flags,
1956 struct page **pagep, void **fsdata,
1957 get_block_t *get_block)
1959 struct inode *inode = mapping->host;
1960 int status = 0;
1961 struct page *page;
1962 pgoff_t index;
1963 unsigned start, end;
1964 int ownpage = 0;
1966 index = pos >> PAGE_CACHE_SHIFT;
1967 start = pos & (PAGE_CACHE_SIZE - 1);
1968 end = start + len;
1970 page = *pagep;
1971 if (page == NULL) {
1972 ownpage = 1;
1973 page = grab_cache_page_write_begin(mapping, index, flags);
1974 if (!page) {
1975 status = -ENOMEM;
1976 goto out;
1978 *pagep = page;
1979 } else
1980 BUG_ON(!PageLocked(page));
1982 status = __block_prepare_write(inode, page, start, end, get_block);
1983 if (unlikely(status)) {
1984 ClearPageUptodate(page);
1986 if (ownpage) {
1987 unlock_page(page);
1988 page_cache_release(page);
1989 *pagep = NULL;
1992 * prepare_write() may have instantiated a few blocks
1993 * outside i_size. Trim these off again. Don't need
1994 * i_size_read because we hold i_mutex.
1996 if (pos + len > inode->i_size)
1997 vmtruncate(inode, inode->i_size);
2001 out:
2002 return status;
2004 EXPORT_SYMBOL(block_write_begin);
2006 int block_write_end(struct file *file, struct address_space *mapping,
2007 loff_t pos, unsigned len, unsigned copied,
2008 struct page *page, void *fsdata)
2010 struct inode *inode = mapping->host;
2011 unsigned start;
2013 start = pos & (PAGE_CACHE_SIZE - 1);
2015 if (unlikely(copied < len)) {
2017 * The buffers that were written will now be uptodate, so we
2018 * don't have to worry about a readpage reading them and
2019 * overwriting a partial write. However if we have encountered
2020 * a short write and only partially written into a buffer, it
2021 * will not be marked uptodate, so a readpage might come in and
2022 * destroy our partial write.
2024 * Do the simplest thing, and just treat any short write to a
2025 * non uptodate page as a zero-length write, and force the
2026 * caller to redo the whole thing.
2028 if (!PageUptodate(page))
2029 copied = 0;
2031 page_zero_new_buffers(page, start+copied, start+len);
2033 flush_dcache_page(page);
2035 /* This could be a short (even 0-length) commit */
2036 __block_commit_write(inode, page, start, start+copied);
2038 return copied;
2040 EXPORT_SYMBOL(block_write_end);
2042 int generic_write_end(struct file *file, struct address_space *mapping,
2043 loff_t pos, unsigned len, unsigned copied,
2044 struct page *page, void *fsdata)
2046 struct inode *inode = mapping->host;
2047 int i_size_changed = 0;
2049 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2052 * No need to use i_size_read() here, the i_size
2053 * cannot change under us because we hold i_mutex.
2055 * But it's important to update i_size while still holding page lock:
2056 * page writeout could otherwise come in and zero beyond i_size.
2058 if (pos+copied > inode->i_size) {
2059 i_size_write(inode, pos+copied);
2060 i_size_changed = 1;
2063 unlock_page(page);
2064 page_cache_release(page);
2067 * Don't mark the inode dirty under page lock. First, it unnecessarily
2068 * makes the holding time of page lock longer. Second, it forces lock
2069 * ordering of page lock and transaction start for journaling
2070 * filesystems.
2072 if (i_size_changed)
2073 mark_inode_dirty(inode);
2075 return copied;
2077 EXPORT_SYMBOL(generic_write_end);
2080 * block_is_partially_uptodate checks whether buffers within a page are
2081 * uptodate or not.
2083 * Returns true if all buffers which correspond to a file portion
2084 * we want to read are uptodate.
2086 int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
2087 unsigned long from)
2089 struct inode *inode = page->mapping->host;
2090 unsigned block_start, block_end, blocksize;
2091 unsigned to;
2092 struct buffer_head *bh, *head;
2093 int ret = 1;
2095 if (!page_has_buffers(page))
2096 return 0;
2098 blocksize = 1 << inode->i_blkbits;
2099 to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count);
2100 to = from + to;
2101 if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
2102 return 0;
2104 head = page_buffers(page);
2105 bh = head;
2106 block_start = 0;
2107 do {
2108 block_end = block_start + blocksize;
2109 if (block_end > from && block_start < to) {
2110 if (!buffer_uptodate(bh)) {
2111 ret = 0;
2112 break;
2114 if (block_end >= to)
2115 break;
2117 block_start = block_end;
2118 bh = bh->b_this_page;
2119 } while (bh != head);
2121 return ret;
2123 EXPORT_SYMBOL(block_is_partially_uptodate);
2126 * Generic "read page" function for block devices that have the normal
2127 * get_block functionality. This is most of the block device filesystems.
2128 * Reads the page asynchronously --- the unlock_buffer() and
2129 * set/clear_buffer_uptodate() functions propagate buffer state into the
2130 * page struct once IO has completed.
2132 int block_read_full_page(struct page *page, get_block_t *get_block)
2134 struct inode *inode = page->mapping->host;
2135 sector_t iblock, lblock;
2136 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2137 unsigned int blocksize;
2138 int nr, i;
2139 int fully_mapped = 1;
2141 BUG_ON(!PageLocked(page));
2142 blocksize = 1 << inode->i_blkbits;
2143 if (!page_has_buffers(page))
2144 create_empty_buffers(page, blocksize, 0);
2145 head = page_buffers(page);
2147 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2148 lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
2149 bh = head;
2150 nr = 0;
2151 i = 0;
2153 do {
2154 if (buffer_uptodate(bh))
2155 continue;
2157 if (!buffer_mapped(bh)) {
2158 int err = 0;
2160 fully_mapped = 0;
2161 if (iblock < lblock) {
2162 WARN_ON(bh->b_size != blocksize);
2163 err = get_block(inode, iblock, bh, 0);
2164 if (err)
2165 SetPageError(page);
2167 if (!buffer_mapped(bh)) {
2168 zero_user(page, i * blocksize, blocksize);
2169 if (!err)
2170 set_buffer_uptodate(bh);
2171 continue;
2174 * get_block() might have updated the buffer
2175 * synchronously
2177 if (buffer_uptodate(bh))
2178 continue;
2180 arr[nr++] = bh;
2181 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2183 if (fully_mapped)
2184 SetPageMappedToDisk(page);
2186 if (!nr) {
2188 * All buffers are uptodate - we can set the page uptodate
2189 * as well. But not if get_block() returned an error.
2191 if (!PageError(page))
2192 SetPageUptodate(page);
2193 unlock_page(page);
2194 return 0;
2197 /* Stage two: lock the buffers */
2198 for (i = 0; i < nr; i++) {
2199 bh = arr[i];
2200 lock_buffer(bh);
2201 mark_buffer_async_read(bh);
2205 * Stage 3: start the IO. Check for uptodateness
2206 * inside the buffer lock in case another process reading
2207 * the underlying blockdev brought it uptodate (the sct fix).
2209 for (i = 0; i < nr; i++) {
2210 bh = arr[i];
2211 if (buffer_uptodate(bh))
2212 end_buffer_async_read(bh, 1);
2213 else
2214 submit_bh(READ, bh);
2216 return 0;
2219 /* utility function for filesystems that need to do work on expanding
2220 * truncates. Uses filesystem pagecache writes to allow the filesystem to
2221 * deal with the hole.
2223 int generic_cont_expand_simple(struct inode *inode, loff_t size)
2225 struct address_space *mapping = inode->i_mapping;
2226 struct page *page;
2227 void *fsdata;
2228 unsigned long limit;
2229 int err;
2231 err = -EFBIG;
2232 limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
2233 if (limit != RLIM_INFINITY && size > (loff_t)limit) {
2234 send_sig(SIGXFSZ, current, 0);
2235 goto out;
2237 if (size > inode->i_sb->s_maxbytes)
2238 goto out;
2240 err = pagecache_write_begin(NULL, mapping, size, 0,
2241 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2242 &page, &fsdata);
2243 if (err)
2244 goto out;
2246 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2247 BUG_ON(err > 0);
2249 out:
2250 return err;
2253 static int cont_expand_zero(struct file *file, struct address_space *mapping,
2254 loff_t pos, loff_t *bytes)
2256 struct inode *inode = mapping->host;
2257 unsigned blocksize = 1 << inode->i_blkbits;
2258 struct page *page;
2259 void *fsdata;
2260 pgoff_t index, curidx;
2261 loff_t curpos;
2262 unsigned zerofrom, offset, len;
2263 int err = 0;
2265 index = pos >> PAGE_CACHE_SHIFT;
2266 offset = pos & ~PAGE_CACHE_MASK;
2268 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
2269 zerofrom = curpos & ~PAGE_CACHE_MASK;
2270 if (zerofrom & (blocksize-1)) {
2271 *bytes |= (blocksize-1);
2272 (*bytes)++;
2274 len = PAGE_CACHE_SIZE - zerofrom;
2276 err = pagecache_write_begin(file, mapping, curpos, len,
2277 AOP_FLAG_UNINTERRUPTIBLE,
2278 &page, &fsdata);
2279 if (err)
2280 goto out;
2281 zero_user(page, zerofrom, len);
2282 err = pagecache_write_end(file, mapping, curpos, len, len,
2283 page, fsdata);
2284 if (err < 0)
2285 goto out;
2286 BUG_ON(err != len);
2287 err = 0;
2289 balance_dirty_pages_ratelimited(mapping);
2292 /* page covers the boundary, find the boundary offset */
2293 if (index == curidx) {
2294 zerofrom = curpos & ~PAGE_CACHE_MASK;
2295 /* if we will expand the thing last block will be filled */
2296 if (offset <= zerofrom) {
2297 goto out;
2299 if (zerofrom & (blocksize-1)) {
2300 *bytes |= (blocksize-1);
2301 (*bytes)++;
2303 len = offset - zerofrom;
2305 err = pagecache_write_begin(file, mapping, curpos, len,
2306 AOP_FLAG_UNINTERRUPTIBLE,
2307 &page, &fsdata);
2308 if (err)
2309 goto out;
2310 zero_user(page, zerofrom, len);
2311 err = pagecache_write_end(file, mapping, curpos, len, len,
2312 page, fsdata);
2313 if (err < 0)
2314 goto out;
2315 BUG_ON(err != len);
2316 err = 0;
2318 out:
2319 return err;
2323 * For moronic filesystems that do not allow holes in file.
2324 * We may have to extend the file.
2326 int cont_write_begin(struct file *file, struct address_space *mapping,
2327 loff_t pos, unsigned len, unsigned flags,
2328 struct page **pagep, void **fsdata,
2329 get_block_t *get_block, loff_t *bytes)
2331 struct inode *inode = mapping->host;
2332 unsigned blocksize = 1 << inode->i_blkbits;
2333 unsigned zerofrom;
2334 int err;
2336 err = cont_expand_zero(file, mapping, pos, bytes);
2337 if (err)
2338 goto out;
2340 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2341 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2342 *bytes |= (blocksize-1);
2343 (*bytes)++;
2346 *pagep = NULL;
2347 err = block_write_begin(file, mapping, pos, len,
2348 flags, pagep, fsdata, get_block);
2349 out:
2350 return err;
2353 int block_prepare_write(struct page *page, unsigned from, unsigned to,
2354 get_block_t *get_block)
2356 struct inode *inode = page->mapping->host;
2357 int err = __block_prepare_write(inode, page, from, to, get_block);
2358 if (err)
2359 ClearPageUptodate(page);
2360 return err;
2363 int block_commit_write(struct page *page, unsigned from, unsigned to)
2365 struct inode *inode = page->mapping->host;
2366 __block_commit_write(inode,page,from,to);
2367 return 0;
2371 * block_page_mkwrite() is not allowed to change the file size as it gets
2372 * called from a page fault handler when a page is first dirtied. Hence we must
2373 * be careful to check for EOF conditions here. We set the page up correctly
2374 * for a written page which means we get ENOSPC checking when writing into
2375 * holes and correct delalloc and unwritten extent mapping on filesystems that
2376 * support these features.
2378 * We are not allowed to take the i_mutex here so we have to play games to
2379 * protect against truncate races as the page could now be beyond EOF. Because
2380 * vmtruncate() writes the inode size before removing pages, once we have the
2381 * page lock we can determine safely if the page is beyond EOF. If it is not
2382 * beyond EOF, then the page is guaranteed safe against truncation until we
2383 * unlock the page.
2386 block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2387 get_block_t get_block)
2389 struct page *page = vmf->page;
2390 struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
2391 unsigned long end;
2392 loff_t size;
2393 int ret = VM_FAULT_NOPAGE; /* make the VM retry the fault */
2395 lock_page(page);
2396 size = i_size_read(inode);
2397 if ((page->mapping != inode->i_mapping) ||
2398 (page_offset(page) > size)) {
2399 /* page got truncated out from underneath us */
2400 unlock_page(page);
2401 goto out;
2404 /* page is wholly or partially inside EOF */
2405 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
2406 end = size & ~PAGE_CACHE_MASK;
2407 else
2408 end = PAGE_CACHE_SIZE;
2410 ret = block_prepare_write(page, 0, end, get_block);
2411 if (!ret)
2412 ret = block_commit_write(page, 0, end);
2414 if (unlikely(ret)) {
2415 unlock_page(page);
2416 if (ret == -ENOMEM)
2417 ret = VM_FAULT_OOM;
2418 else /* -ENOSPC, -EIO, etc */
2419 ret = VM_FAULT_SIGBUS;
2420 } else
2421 ret = VM_FAULT_LOCKED;
2423 out:
2424 return ret;
2428 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
2429 * immediately, while under the page lock. So it needs a special end_io
2430 * handler which does not touch the bh after unlocking it.
2432 static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2434 __end_buffer_read_notouch(bh, uptodate);
2438 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2439 * the page (converting it to circular linked list and taking care of page
2440 * dirty races).
2442 static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2444 struct buffer_head *bh;
2446 BUG_ON(!PageLocked(page));
2448 spin_lock(&page->mapping->private_lock);
2449 bh = head;
2450 do {
2451 if (PageDirty(page))
2452 set_buffer_dirty(bh);
2453 if (!bh->b_this_page)
2454 bh->b_this_page = head;
2455 bh = bh->b_this_page;
2456 } while (bh != head);
2457 attach_page_buffers(page, head);
2458 spin_unlock(&page->mapping->private_lock);
2462 * On entry, the page is fully not uptodate.
2463 * On exit the page is fully uptodate in the areas outside (from,to)
2465 int nobh_write_begin(struct file *file, struct address_space *mapping,
2466 loff_t pos, unsigned len, unsigned flags,
2467 struct page **pagep, void **fsdata,
2468 get_block_t *get_block)
2470 struct inode *inode = mapping->host;
2471 const unsigned blkbits = inode->i_blkbits;
2472 const unsigned blocksize = 1 << blkbits;
2473 struct buffer_head *head, *bh;
2474 struct page *page;
2475 pgoff_t index;
2476 unsigned from, to;
2477 unsigned block_in_page;
2478 unsigned block_start, block_end;
2479 sector_t block_in_file;
2480 int nr_reads = 0;
2481 int ret = 0;
2482 int is_mapped_to_disk = 1;
2484 index = pos >> PAGE_CACHE_SHIFT;
2485 from = pos & (PAGE_CACHE_SIZE - 1);
2486 to = from + len;
2488 page = grab_cache_page_write_begin(mapping, index, flags);
2489 if (!page)
2490 return -ENOMEM;
2491 *pagep = page;
2492 *fsdata = NULL;
2494 if (page_has_buffers(page)) {
2495 unlock_page(page);
2496 page_cache_release(page);
2497 *pagep = NULL;
2498 return block_write_begin(file, mapping, pos, len, flags, pagep,
2499 fsdata, get_block);
2502 if (PageMappedToDisk(page))
2503 return 0;
2506 * Allocate buffers so that we can keep track of state, and potentially
2507 * attach them to the page if an error occurs. In the common case of
2508 * no error, they will just be freed again without ever being attached
2509 * to the page (which is all OK, because we're under the page lock).
2511 * Be careful: the buffer linked list is a NULL terminated one, rather
2512 * than the circular one we're used to.
2514 head = alloc_page_buffers(page, blocksize, 0);
2515 if (!head) {
2516 ret = -ENOMEM;
2517 goto out_release;
2520 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
2523 * We loop across all blocks in the page, whether or not they are
2524 * part of the affected region. This is so we can discover if the
2525 * page is fully mapped-to-disk.
2527 for (block_start = 0, block_in_page = 0, bh = head;
2528 block_start < PAGE_CACHE_SIZE;
2529 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
2530 int create;
2532 block_end = block_start + blocksize;
2533 bh->b_state = 0;
2534 create = 1;
2535 if (block_start >= to)
2536 create = 0;
2537 ret = get_block(inode, block_in_file + block_in_page,
2538 bh, create);
2539 if (ret)
2540 goto failed;
2541 if (!buffer_mapped(bh))
2542 is_mapped_to_disk = 0;
2543 if (buffer_new(bh))
2544 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
2545 if (PageUptodate(page)) {
2546 set_buffer_uptodate(bh);
2547 continue;
2549 if (buffer_new(bh) || !buffer_mapped(bh)) {
2550 zero_user_segments(page, block_start, from,
2551 to, block_end);
2552 continue;
2554 if (buffer_uptodate(bh))
2555 continue; /* reiserfs does this */
2556 if (block_start < from || block_end > to) {
2557 lock_buffer(bh);
2558 bh->b_end_io = end_buffer_read_nobh;
2559 submit_bh(READ, bh);
2560 nr_reads++;
2564 if (nr_reads) {
2566 * The page is locked, so these buffers are protected from
2567 * any VM or truncate activity. Hence we don't need to care
2568 * for the buffer_head refcounts.
2570 for (bh = head; bh; bh = bh->b_this_page) {
2571 wait_on_buffer(bh);
2572 if (!buffer_uptodate(bh))
2573 ret = -EIO;
2575 if (ret)
2576 goto failed;
2579 if (is_mapped_to_disk)
2580 SetPageMappedToDisk(page);
2582 *fsdata = head; /* to be released by nobh_write_end */
2584 return 0;
2586 failed:
2587 BUG_ON(!ret);
2589 * Error recovery is a bit difficult. We need to zero out blocks that
2590 * were newly allocated, and dirty them to ensure they get written out.
2591 * Buffers need to be attached to the page at this point, otherwise
2592 * the handling of potential IO errors during writeout would be hard
2593 * (could try doing synchronous writeout, but what if that fails too?)
2595 attach_nobh_buffers(page, head);
2596 page_zero_new_buffers(page, from, to);
2598 out_release:
2599 unlock_page(page);
2600 page_cache_release(page);
2601 *pagep = NULL;
2603 if (pos + len > inode->i_size)
2604 vmtruncate(inode, inode->i_size);
2606 return ret;
2608 EXPORT_SYMBOL(nobh_write_begin);
2610 int nobh_write_end(struct file *file, struct address_space *mapping,
2611 loff_t pos, unsigned len, unsigned copied,
2612 struct page *page, void *fsdata)
2614 struct inode *inode = page->mapping->host;
2615 struct buffer_head *head = fsdata;
2616 struct buffer_head *bh;
2617 BUG_ON(fsdata != NULL && page_has_buffers(page));
2619 if (unlikely(copied < len) && head)
2620 attach_nobh_buffers(page, head);
2621 if (page_has_buffers(page))
2622 return generic_write_end(file, mapping, pos, len,
2623 copied, page, fsdata);
2625 SetPageUptodate(page);
2626 set_page_dirty(page);
2627 if (pos+copied > inode->i_size) {
2628 i_size_write(inode, pos+copied);
2629 mark_inode_dirty(inode);
2632 unlock_page(page);
2633 page_cache_release(page);
2635 while (head) {
2636 bh = head;
2637 head = head->b_this_page;
2638 free_buffer_head(bh);
2641 return copied;
2643 EXPORT_SYMBOL(nobh_write_end);
2646 * nobh_writepage() - based on block_full_write_page() except
2647 * that it tries to operate without attaching bufferheads to
2648 * the page.
2650 int nobh_writepage(struct page *page, get_block_t *get_block,
2651 struct writeback_control *wbc)
2653 struct inode * const inode = page->mapping->host;
2654 loff_t i_size = i_size_read(inode);
2655 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2656 unsigned offset;
2657 int ret;
2659 /* Is the page fully inside i_size? */
2660 if (page->index < end_index)
2661 goto out;
2663 /* Is the page fully outside i_size? (truncate in progress) */
2664 offset = i_size & (PAGE_CACHE_SIZE-1);
2665 if (page->index >= end_index+1 || !offset) {
2667 * The page may have dirty, unmapped buffers. For example,
2668 * they may have been added in ext3_writepage(). Make them
2669 * freeable here, so the page does not leak.
2671 #if 0
2672 /* Not really sure about this - do we need this ? */
2673 if (page->mapping->a_ops->invalidatepage)
2674 page->mapping->a_ops->invalidatepage(page, offset);
2675 #endif
2676 unlock_page(page);
2677 return 0; /* don't care */
2681 * The page straddles i_size. It must be zeroed out on each and every
2682 * writepage invocation because it may be mmapped. "A file is mapped
2683 * in multiples of the page size. For a file that is not a multiple of
2684 * the page size, the remaining memory is zeroed when mapped, and
2685 * writes to that region are not written out to the file."
2687 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2688 out:
2689 ret = mpage_writepage(page, get_block, wbc);
2690 if (ret == -EAGAIN)
2691 ret = __block_write_full_page(inode, page, get_block, wbc,
2692 end_buffer_async_write);
2693 return ret;
2695 EXPORT_SYMBOL(nobh_writepage);
2697 int nobh_truncate_page(struct address_space *mapping,
2698 loff_t from, get_block_t *get_block)
2700 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2701 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2702 unsigned blocksize;
2703 sector_t iblock;
2704 unsigned length, pos;
2705 struct inode *inode = mapping->host;
2706 struct page *page;
2707 struct buffer_head map_bh;
2708 int err;
2710 blocksize = 1 << inode->i_blkbits;
2711 length = offset & (blocksize - 1);
2713 /* Block boundary? Nothing to do */
2714 if (!length)
2715 return 0;
2717 length = blocksize - length;
2718 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2720 page = grab_cache_page(mapping, index);
2721 err = -ENOMEM;
2722 if (!page)
2723 goto out;
2725 if (page_has_buffers(page)) {
2726 has_buffers:
2727 unlock_page(page);
2728 page_cache_release(page);
2729 return block_truncate_page(mapping, from, get_block);
2732 /* Find the buffer that contains "offset" */
2733 pos = blocksize;
2734 while (offset >= pos) {
2735 iblock++;
2736 pos += blocksize;
2739 map_bh.b_size = blocksize;
2740 map_bh.b_state = 0;
2741 err = get_block(inode, iblock, &map_bh, 0);
2742 if (err)
2743 goto unlock;
2744 /* unmapped? It's a hole - nothing to do */
2745 if (!buffer_mapped(&map_bh))
2746 goto unlock;
2748 /* Ok, it's mapped. Make sure it's up-to-date */
2749 if (!PageUptodate(page)) {
2750 err = mapping->a_ops->readpage(NULL, page);
2751 if (err) {
2752 page_cache_release(page);
2753 goto out;
2755 lock_page(page);
2756 if (!PageUptodate(page)) {
2757 err = -EIO;
2758 goto unlock;
2760 if (page_has_buffers(page))
2761 goto has_buffers;
2763 zero_user(page, offset, length);
2764 set_page_dirty(page);
2765 err = 0;
2767 unlock:
2768 unlock_page(page);
2769 page_cache_release(page);
2770 out:
2771 return err;
2773 EXPORT_SYMBOL(nobh_truncate_page);
2775 int block_truncate_page(struct address_space *mapping,
2776 loff_t from, get_block_t *get_block)
2778 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2779 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2780 unsigned blocksize;
2781 sector_t iblock;
2782 unsigned length, pos;
2783 struct inode *inode = mapping->host;
2784 struct page *page;
2785 struct buffer_head *bh;
2786 int err;
2788 blocksize = 1 << inode->i_blkbits;
2789 length = offset & (blocksize - 1);
2791 /* Block boundary? Nothing to do */
2792 if (!length)
2793 return 0;
2795 length = blocksize - length;
2796 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2798 page = grab_cache_page(mapping, index);
2799 err = -ENOMEM;
2800 if (!page)
2801 goto out;
2803 if (!page_has_buffers(page))
2804 create_empty_buffers(page, blocksize, 0);
2806 /* Find the buffer that contains "offset" */
2807 bh = page_buffers(page);
2808 pos = blocksize;
2809 while (offset >= pos) {
2810 bh = bh->b_this_page;
2811 iblock++;
2812 pos += blocksize;
2815 err = 0;
2816 if (!buffer_mapped(bh)) {
2817 WARN_ON(bh->b_size != blocksize);
2818 err = get_block(inode, iblock, bh, 0);
2819 if (err)
2820 goto unlock;
2821 /* unmapped? It's a hole - nothing to do */
2822 if (!buffer_mapped(bh))
2823 goto unlock;
2826 /* Ok, it's mapped. Make sure it's up-to-date */
2827 if (PageUptodate(page))
2828 set_buffer_uptodate(bh);
2830 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2831 err = -EIO;
2832 ll_rw_block(READ, 1, &bh);
2833 wait_on_buffer(bh);
2834 /* Uhhuh. Read error. Complain and punt. */
2835 if (!buffer_uptodate(bh))
2836 goto unlock;
2839 zero_user(page, offset, length);
2840 mark_buffer_dirty(bh);
2841 err = 0;
2843 unlock:
2844 unlock_page(page);
2845 page_cache_release(page);
2846 out:
2847 return err;
2851 * The generic ->writepage function for buffer-backed address_spaces
2852 * this form passes in the end_io handler used to finish the IO.
2854 int block_write_full_page_endio(struct page *page, get_block_t *get_block,
2855 struct writeback_control *wbc, bh_end_io_t *handler)
2857 struct inode * const inode = page->mapping->host;
2858 loff_t i_size = i_size_read(inode);
2859 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2860 unsigned offset;
2862 /* Is the page fully inside i_size? */
2863 if (page->index < end_index)
2864 return __block_write_full_page(inode, page, get_block, wbc,
2865 handler);
2867 /* Is the page fully outside i_size? (truncate in progress) */
2868 offset = i_size & (PAGE_CACHE_SIZE-1);
2869 if (page->index >= end_index+1 || !offset) {
2871 * The page may have dirty, unmapped buffers. For example,
2872 * they may have been added in ext3_writepage(). Make them
2873 * freeable here, so the page does not leak.
2875 do_invalidatepage(page, 0);
2876 unlock_page(page);
2877 return 0; /* don't care */
2881 * The page straddles i_size. It must be zeroed out on each and every
2882 * writepage invokation because it may be mmapped. "A file is mapped
2883 * in multiples of the page size. For a file that is not a multiple of
2884 * the page size, the remaining memory is zeroed when mapped, and
2885 * writes to that region are not written out to the file."
2887 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2888 return __block_write_full_page(inode, page, get_block, wbc, handler);
2892 * The generic ->writepage function for buffer-backed address_spaces
2894 int block_write_full_page(struct page *page, get_block_t *get_block,
2895 struct writeback_control *wbc)
2897 return block_write_full_page_endio(page, get_block, wbc,
2898 end_buffer_async_write);
2902 sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2903 get_block_t *get_block)
2905 struct buffer_head tmp;
2906 struct inode *inode = mapping->host;
2907 tmp.b_state = 0;
2908 tmp.b_blocknr = 0;
2909 tmp.b_size = 1 << inode->i_blkbits;
2910 get_block(inode, block, &tmp, 0);
2911 return tmp.b_blocknr;
2914 static void end_bio_bh_io_sync(struct bio *bio, int err)
2916 struct buffer_head *bh = bio->bi_private;
2918 if (err == -EOPNOTSUPP) {
2919 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
2920 set_bit(BH_Eopnotsupp, &bh->b_state);
2923 if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags)))
2924 set_bit(BH_Quiet, &bh->b_state);
2926 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2927 bio_put(bio);
2930 int submit_bh(int rw, struct buffer_head * bh)
2932 struct bio *bio;
2933 int ret = 0;
2935 BUG_ON(!buffer_locked(bh));
2936 BUG_ON(!buffer_mapped(bh));
2937 BUG_ON(!bh->b_end_io);
2938 BUG_ON(buffer_delay(bh));
2939 BUG_ON(buffer_unwritten(bh));
2942 * Mask in barrier bit for a write (could be either a WRITE or a
2943 * WRITE_SYNC
2945 if (buffer_ordered(bh) && (rw & WRITE))
2946 rw |= WRITE_BARRIER;
2949 * Only clear out a write error when rewriting
2951 if (test_set_buffer_req(bh) && (rw & WRITE))
2952 clear_buffer_write_io_error(bh);
2955 * from here on down, it's all bio -- do the initial mapping,
2956 * submit_bio -> generic_make_request may further map this bio around
2958 bio = bio_alloc(GFP_NOIO, 1);
2960 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2961 bio->bi_bdev = bh->b_bdev;
2962 bio->bi_io_vec[0].bv_page = bh->b_page;
2963 bio->bi_io_vec[0].bv_len = bh->b_size;
2964 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
2966 bio->bi_vcnt = 1;
2967 bio->bi_idx = 0;
2968 bio->bi_size = bh->b_size;
2970 bio->bi_end_io = end_bio_bh_io_sync;
2971 bio->bi_private = bh;
2973 bio_get(bio);
2974 submit_bio(rw, bio);
2976 if (bio_flagged(bio, BIO_EOPNOTSUPP))
2977 ret = -EOPNOTSUPP;
2979 bio_put(bio);
2980 return ret;
2984 * ll_rw_block: low-level access to block devices (DEPRECATED)
2985 * @rw: whether to %READ or %WRITE or %SWRITE or maybe %READA (readahead)
2986 * @nr: number of &struct buffer_heads in the array
2987 * @bhs: array of pointers to &struct buffer_head
2989 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
2990 * requests an I/O operation on them, either a %READ or a %WRITE. The third
2991 * %SWRITE is like %WRITE only we make sure that the *current* data in buffers
2992 * are sent to disk. The fourth %READA option is described in the documentation
2993 * for generic_make_request() which ll_rw_block() calls.
2995 * This function drops any buffer that it cannot get a lock on (with the
2996 * BH_Lock state bit) unless SWRITE is required, any buffer that appears to be
2997 * clean when doing a write request, and any buffer that appears to be
2998 * up-to-date when doing read request. Further it marks as clean buffers that
2999 * are processed for writing (the buffer cache won't assume that they are
3000 * actually clean until the buffer gets unlocked).
3002 * ll_rw_block sets b_end_io to simple completion handler that marks
3003 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
3004 * any waiters.
3006 * All of the buffers must be for the same device, and must also be a
3007 * multiple of the current approved size for the device.
3009 void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
3011 int i;
3013 for (i = 0; i < nr; i++) {
3014 struct buffer_head *bh = bhs[i];
3016 if (rw == SWRITE || rw == SWRITE_SYNC || rw == SWRITE_SYNC_PLUG)
3017 lock_buffer(bh);
3018 else if (!trylock_buffer(bh))
3019 continue;
3021 if (rw == WRITE || rw == SWRITE || rw == SWRITE_SYNC ||
3022 rw == SWRITE_SYNC_PLUG) {
3023 if (test_clear_buffer_dirty(bh)) {
3024 bh->b_end_io = end_buffer_write_sync;
3025 get_bh(bh);
3026 if (rw == SWRITE_SYNC)
3027 submit_bh(WRITE_SYNC, bh);
3028 else
3029 submit_bh(WRITE, bh);
3030 continue;
3032 } else {
3033 if (!buffer_uptodate(bh)) {
3034 bh->b_end_io = end_buffer_read_sync;
3035 get_bh(bh);
3036 submit_bh(rw, bh);
3037 continue;
3040 unlock_buffer(bh);
3045 * For a data-integrity writeout, we need to wait upon any in-progress I/O
3046 * and then start new I/O and then wait upon it. The caller must have a ref on
3047 * the buffer_head.
3049 int sync_dirty_buffer(struct buffer_head *bh)
3051 int ret = 0;
3053 WARN_ON(atomic_read(&bh->b_count) < 1);
3054 lock_buffer(bh);
3055 if (test_clear_buffer_dirty(bh)) {
3056 get_bh(bh);
3057 bh->b_end_io = end_buffer_write_sync;
3058 ret = submit_bh(WRITE_SYNC, bh);
3059 wait_on_buffer(bh);
3060 if (buffer_eopnotsupp(bh)) {
3061 clear_buffer_eopnotsupp(bh);
3062 ret = -EOPNOTSUPP;
3064 if (!ret && !buffer_uptodate(bh))
3065 ret = -EIO;
3066 } else {
3067 unlock_buffer(bh);
3069 return ret;
3073 * try_to_free_buffers() checks if all the buffers on this particular page
3074 * are unused, and releases them if so.
3076 * Exclusion against try_to_free_buffers may be obtained by either
3077 * locking the page or by holding its mapping's private_lock.
3079 * If the page is dirty but all the buffers are clean then we need to
3080 * be sure to mark the page clean as well. This is because the page
3081 * may be against a block device, and a later reattachment of buffers
3082 * to a dirty page will set *all* buffers dirty. Which would corrupt
3083 * filesystem data on the same device.
3085 * The same applies to regular filesystem pages: if all the buffers are
3086 * clean then we set the page clean and proceed. To do that, we require
3087 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3088 * private_lock.
3090 * try_to_free_buffers() is non-blocking.
3092 static inline int buffer_busy(struct buffer_head *bh)
3094 return atomic_read(&bh->b_count) |
3095 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3098 static int
3099 drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3101 struct buffer_head *head = page_buffers(page);
3102 struct buffer_head *bh;
3104 bh = head;
3105 do {
3106 if (buffer_write_io_error(bh) && page->mapping)
3107 set_bit(AS_EIO, &page->mapping->flags);
3108 if (buffer_busy(bh))
3109 goto failed;
3110 bh = bh->b_this_page;
3111 } while (bh != head);
3113 do {
3114 struct buffer_head *next = bh->b_this_page;
3116 if (bh->b_assoc_map)
3117 __remove_assoc_queue(bh);
3118 bh = next;
3119 } while (bh != head);
3120 *buffers_to_free = head;
3121 __clear_page_buffers(page);
3122 return 1;
3123 failed:
3124 return 0;
3127 int try_to_free_buffers(struct page *page)
3129 struct address_space * const mapping = page->mapping;
3130 struct buffer_head *buffers_to_free = NULL;
3131 int ret = 0;
3133 BUG_ON(!PageLocked(page));
3134 if (PageWriteback(page))
3135 return 0;
3137 if (mapping == NULL) { /* can this still happen? */
3138 ret = drop_buffers(page, &buffers_to_free);
3139 goto out;
3142 spin_lock(&mapping->private_lock);
3143 ret = drop_buffers(page, &buffers_to_free);
3146 * If the filesystem writes its buffers by hand (eg ext3)
3147 * then we can have clean buffers against a dirty page. We
3148 * clean the page here; otherwise the VM will never notice
3149 * that the filesystem did any IO at all.
3151 * Also, during truncate, discard_buffer will have marked all
3152 * the page's buffers clean. We discover that here and clean
3153 * the page also.
3155 * private_lock must be held over this entire operation in order
3156 * to synchronise against __set_page_dirty_buffers and prevent the
3157 * dirty bit from being lost.
3159 if (ret)
3160 cancel_dirty_page(page, PAGE_CACHE_SIZE);
3161 spin_unlock(&mapping->private_lock);
3162 out:
3163 if (buffers_to_free) {
3164 struct buffer_head *bh = buffers_to_free;
3166 do {
3167 struct buffer_head *next = bh->b_this_page;
3168 free_buffer_head(bh);
3169 bh = next;
3170 } while (bh != buffers_to_free);
3172 return ret;
3174 EXPORT_SYMBOL(try_to_free_buffers);
3176 void block_sync_page(struct page *page)
3178 struct address_space *mapping;
3180 smp_mb();
3181 mapping = page_mapping(page);
3182 if (mapping)
3183 blk_run_backing_dev(mapping->backing_dev_info, page);
3187 * There are no bdflush tunables left. But distributions are
3188 * still running obsolete flush daemons, so we terminate them here.
3190 * Use of bdflush() is deprecated and will be removed in a future kernel.
3191 * The `pdflush' kernel threads fully replace bdflush daemons and this call.
3193 SYSCALL_DEFINE2(bdflush, int, func, long, data)
3195 static int msg_count;
3197 if (!capable(CAP_SYS_ADMIN))
3198 return -EPERM;
3200 if (msg_count < 5) {
3201 msg_count++;
3202 printk(KERN_INFO
3203 "warning: process `%s' used the obsolete bdflush"
3204 " system call\n", current->comm);
3205 printk(KERN_INFO "Fix your initscripts?\n");
3208 if (func == 1)
3209 do_exit(0);
3210 return 0;
3214 * Buffer-head allocation
3216 static struct kmem_cache *bh_cachep;
3219 * Once the number of bh's in the machine exceeds this level, we start
3220 * stripping them in writeback.
3222 static int max_buffer_heads;
3224 int buffer_heads_over_limit;
3226 struct bh_accounting {
3227 int nr; /* Number of live bh's */
3228 int ratelimit; /* Limit cacheline bouncing */
3231 static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3233 static void recalc_bh_state(void)
3235 int i;
3236 int tot = 0;
3238 if (__get_cpu_var(bh_accounting).ratelimit++ < 4096)
3239 return;
3240 __get_cpu_var(bh_accounting).ratelimit = 0;
3241 for_each_online_cpu(i)
3242 tot += per_cpu(bh_accounting, i).nr;
3243 buffer_heads_over_limit = (tot > max_buffer_heads);
3246 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3248 struct buffer_head *ret = kmem_cache_alloc(bh_cachep, gfp_flags);
3249 if (ret) {
3250 INIT_LIST_HEAD(&ret->b_assoc_buffers);
3251 get_cpu_var(bh_accounting).nr++;
3252 recalc_bh_state();
3253 put_cpu_var(bh_accounting);
3255 return ret;
3257 EXPORT_SYMBOL(alloc_buffer_head);
3259 void free_buffer_head(struct buffer_head *bh)
3261 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3262 kmem_cache_free(bh_cachep, bh);
3263 get_cpu_var(bh_accounting).nr--;
3264 recalc_bh_state();
3265 put_cpu_var(bh_accounting);
3267 EXPORT_SYMBOL(free_buffer_head);
3269 static void buffer_exit_cpu(int cpu)
3271 int i;
3272 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3274 for (i = 0; i < BH_LRU_SIZE; i++) {
3275 brelse(b->bhs[i]);
3276 b->bhs[i] = NULL;
3278 get_cpu_var(bh_accounting).nr += per_cpu(bh_accounting, cpu).nr;
3279 per_cpu(bh_accounting, cpu).nr = 0;
3280 put_cpu_var(bh_accounting);
3283 static int buffer_cpu_notify(struct notifier_block *self,
3284 unsigned long action, void *hcpu)
3286 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
3287 buffer_exit_cpu((unsigned long)hcpu);
3288 return NOTIFY_OK;
3292 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3293 * @bh: struct buffer_head
3295 * Return true if the buffer is up-to-date and false,
3296 * with the buffer locked, if not.
3298 int bh_uptodate_or_lock(struct buffer_head *bh)
3300 if (!buffer_uptodate(bh)) {
3301 lock_buffer(bh);
3302 if (!buffer_uptodate(bh))
3303 return 0;
3304 unlock_buffer(bh);
3306 return 1;
3308 EXPORT_SYMBOL(bh_uptodate_or_lock);
3311 * bh_submit_read - Submit a locked buffer for reading
3312 * @bh: struct buffer_head
3314 * Returns zero on success and -EIO on error.
3316 int bh_submit_read(struct buffer_head *bh)
3318 BUG_ON(!buffer_locked(bh));
3320 if (buffer_uptodate(bh)) {
3321 unlock_buffer(bh);
3322 return 0;
3325 get_bh(bh);
3326 bh->b_end_io = end_buffer_read_sync;
3327 submit_bh(READ, bh);
3328 wait_on_buffer(bh);
3329 if (buffer_uptodate(bh))
3330 return 0;
3331 return -EIO;
3333 EXPORT_SYMBOL(bh_submit_read);
3335 static void
3336 init_buffer_head(void *data)
3338 struct buffer_head *bh = data;
3340 memset(bh, 0, sizeof(*bh));
3341 INIT_LIST_HEAD(&bh->b_assoc_buffers);
3344 void __init buffer_init(void)
3346 int nrpages;
3348 bh_cachep = kmem_cache_create("buffer_head",
3349 sizeof(struct buffer_head), 0,
3350 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3351 SLAB_MEM_SPREAD),
3352 init_buffer_head);
3355 * Limit the bh occupancy to 10% of ZONE_NORMAL
3357 nrpages = (nr_free_buffer_pages() * 10) / 100;
3358 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3359 hotcpu_notifier(buffer_cpu_notify, 0);
3362 EXPORT_SYMBOL(__bforget);
3363 EXPORT_SYMBOL(__brelse);
3364 EXPORT_SYMBOL(__wait_on_buffer);
3365 EXPORT_SYMBOL(block_commit_write);
3366 EXPORT_SYMBOL(block_prepare_write);
3367 EXPORT_SYMBOL(block_page_mkwrite);
3368 EXPORT_SYMBOL(block_read_full_page);
3369 EXPORT_SYMBOL(block_sync_page);
3370 EXPORT_SYMBOL(block_truncate_page);
3371 EXPORT_SYMBOL(block_write_full_page);
3372 EXPORT_SYMBOL(block_write_full_page_endio);
3373 EXPORT_SYMBOL(cont_write_begin);
3374 EXPORT_SYMBOL(end_buffer_read_sync);
3375 EXPORT_SYMBOL(end_buffer_write_sync);
3376 EXPORT_SYMBOL(end_buffer_async_write);
3377 EXPORT_SYMBOL(file_fsync);
3378 EXPORT_SYMBOL(generic_block_bmap);
3379 EXPORT_SYMBOL(generic_cont_expand_simple);
3380 EXPORT_SYMBOL(init_buffer);
3381 EXPORT_SYMBOL(invalidate_bdev);
3382 EXPORT_SYMBOL(ll_rw_block);
3383 EXPORT_SYMBOL(mark_buffer_dirty);
3384 EXPORT_SYMBOL(submit_bh);
3385 EXPORT_SYMBOL(sync_dirty_buffer);
3386 EXPORT_SYMBOL(unlock_buffer);