Merge tag 'usb-3.8-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / fs / buffer.c
blobc017a2dfb9097e73837230d244ffb14f73dd0e1c
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/export.h>
33 #include <linux/writeback.h>
34 #include <linux/hash.h>
35 #include <linux/suspend.h>
36 #include <linux/buffer_head.h>
37 #include <linux/task_io_accounting_ops.h>
38 #include <linux/bio.h>
39 #include <linux/notifier.h>
40 #include <linux/cpu.h>
41 #include <linux/bitops.h>
42 #include <linux/mpage.h>
43 #include <linux/bit_spinlock.h>
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 void init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
51 bh->b_end_io = handler;
52 bh->b_private = private;
54 EXPORT_SYMBOL(init_buffer);
56 static int sleep_on_buffer(void *word)
58 io_schedule();
59 return 0;
62 void __lock_buffer(struct buffer_head *bh)
64 wait_on_bit_lock(&bh->b_state, BH_Lock, sleep_on_buffer,
65 TASK_UNINTERRUPTIBLE);
67 EXPORT_SYMBOL(__lock_buffer);
69 void unlock_buffer(struct buffer_head *bh)
71 clear_bit_unlock(BH_Lock, &bh->b_state);
72 smp_mb__after_clear_bit();
73 wake_up_bit(&bh->b_state, BH_Lock);
75 EXPORT_SYMBOL(unlock_buffer);
78 * Block until a buffer comes unlocked. This doesn't stop it
79 * from becoming locked again - you have to lock it yourself
80 * if you want to preserve its state.
82 void __wait_on_buffer(struct buffer_head * bh)
84 wait_on_bit(&bh->b_state, BH_Lock, sleep_on_buffer, TASK_UNINTERRUPTIBLE);
86 EXPORT_SYMBOL(__wait_on_buffer);
88 static void
89 __clear_page_buffers(struct page *page)
91 ClearPagePrivate(page);
92 set_page_private(page, 0);
93 page_cache_release(page);
97 static int quiet_error(struct buffer_head *bh)
99 if (!test_bit(BH_Quiet, &bh->b_state) && printk_ratelimit())
100 return 0;
101 return 1;
105 static void buffer_io_error(struct buffer_head *bh)
107 char b[BDEVNAME_SIZE];
108 printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
109 bdevname(bh->b_bdev, b),
110 (unsigned long long)bh->b_blocknr);
114 * End-of-IO handler helper function which does not touch the bh after
115 * unlocking it.
116 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
117 * a race there is benign: unlock_buffer() only use the bh's address for
118 * hashing after unlocking the buffer, so it doesn't actually touch the bh
119 * itself.
121 static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
123 if (uptodate) {
124 set_buffer_uptodate(bh);
125 } else {
126 /* This happens, due to failed READA attempts. */
127 clear_buffer_uptodate(bh);
129 unlock_buffer(bh);
133 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
134 * unlock the buffer. This is what ll_rw_block uses too.
136 void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
138 __end_buffer_read_notouch(bh, uptodate);
139 put_bh(bh);
141 EXPORT_SYMBOL(end_buffer_read_sync);
143 void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
145 char b[BDEVNAME_SIZE];
147 if (uptodate) {
148 set_buffer_uptodate(bh);
149 } else {
150 if (!quiet_error(bh)) {
151 buffer_io_error(bh);
152 printk(KERN_WARNING "lost page write due to "
153 "I/O error on %s\n",
154 bdevname(bh->b_bdev, b));
156 set_buffer_write_io_error(bh);
157 clear_buffer_uptodate(bh);
159 unlock_buffer(bh);
160 put_bh(bh);
162 EXPORT_SYMBOL(end_buffer_write_sync);
165 * Various filesystems appear to want __find_get_block to be non-blocking.
166 * But it's the page lock which protects the buffers. To get around this,
167 * we get exclusion from try_to_free_buffers with the blockdev mapping's
168 * private_lock.
170 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
171 * may be quite high. This code could TryLock the page, and if that
172 * succeeds, there is no need to take private_lock. (But if
173 * private_lock is contended then so is mapping->tree_lock).
175 static struct buffer_head *
176 __find_get_block_slow(struct block_device *bdev, sector_t block)
178 struct inode *bd_inode = bdev->bd_inode;
179 struct address_space *bd_mapping = bd_inode->i_mapping;
180 struct buffer_head *ret = NULL;
181 pgoff_t index;
182 struct buffer_head *bh;
183 struct buffer_head *head;
184 struct page *page;
185 int all_mapped = 1;
187 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
188 page = find_get_page(bd_mapping, index);
189 if (!page)
190 goto out;
192 spin_lock(&bd_mapping->private_lock);
193 if (!page_has_buffers(page))
194 goto out_unlock;
195 head = page_buffers(page);
196 bh = head;
197 do {
198 if (!buffer_mapped(bh))
199 all_mapped = 0;
200 else if (bh->b_blocknr == block) {
201 ret = bh;
202 get_bh(bh);
203 goto out_unlock;
205 bh = bh->b_this_page;
206 } while (bh != head);
208 /* we might be here because some of the buffers on this page are
209 * not mapped. This is due to various races between
210 * file io on the block device and getblk. It gets dealt with
211 * elsewhere, don't buffer_error if we had some unmapped buffers
213 if (all_mapped) {
214 char b[BDEVNAME_SIZE];
216 printk("__find_get_block_slow() failed. "
217 "block=%llu, b_blocknr=%llu\n",
218 (unsigned long long)block,
219 (unsigned long long)bh->b_blocknr);
220 printk("b_state=0x%08lx, b_size=%zu\n",
221 bh->b_state, bh->b_size);
222 printk("device %s blocksize: %d\n", bdevname(bdev, b),
223 1 << bd_inode->i_blkbits);
225 out_unlock:
226 spin_unlock(&bd_mapping->private_lock);
227 page_cache_release(page);
228 out:
229 return ret;
233 * Kick the writeback threads then try to free up some ZONE_NORMAL memory.
235 static void free_more_memory(void)
237 struct zone *zone;
238 int nid;
240 wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM);
241 yield();
243 for_each_online_node(nid) {
244 (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS),
245 gfp_zone(GFP_NOFS), NULL,
246 &zone);
247 if (zone)
248 try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0,
249 GFP_NOFS, NULL);
254 * I/O completion handler for block_read_full_page() - pages
255 * which come unlocked at the end of I/O.
257 static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
259 unsigned long flags;
260 struct buffer_head *first;
261 struct buffer_head *tmp;
262 struct page *page;
263 int page_uptodate = 1;
265 BUG_ON(!buffer_async_read(bh));
267 page = bh->b_page;
268 if (uptodate) {
269 set_buffer_uptodate(bh);
270 } else {
271 clear_buffer_uptodate(bh);
272 if (!quiet_error(bh))
273 buffer_io_error(bh);
274 SetPageError(page);
278 * Be _very_ careful from here on. Bad things can happen if
279 * two buffer heads end IO at almost the same time and both
280 * decide that the page is now completely done.
282 first = page_buffers(page);
283 local_irq_save(flags);
284 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
285 clear_buffer_async_read(bh);
286 unlock_buffer(bh);
287 tmp = bh;
288 do {
289 if (!buffer_uptodate(tmp))
290 page_uptodate = 0;
291 if (buffer_async_read(tmp)) {
292 BUG_ON(!buffer_locked(tmp));
293 goto still_busy;
295 tmp = tmp->b_this_page;
296 } while (tmp != bh);
297 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
298 local_irq_restore(flags);
301 * If none of the buffers had errors and they are all
302 * uptodate then we can set the page uptodate.
304 if (page_uptodate && !PageError(page))
305 SetPageUptodate(page);
306 unlock_page(page);
307 return;
309 still_busy:
310 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
311 local_irq_restore(flags);
312 return;
316 * Completion handler for block_write_full_page() - pages which are unlocked
317 * during I/O, and which have PageWriteback cleared upon I/O completion.
319 void end_buffer_async_write(struct buffer_head *bh, int uptodate)
321 char b[BDEVNAME_SIZE];
322 unsigned long flags;
323 struct buffer_head *first;
324 struct buffer_head *tmp;
325 struct page *page;
327 BUG_ON(!buffer_async_write(bh));
329 page = bh->b_page;
330 if (uptodate) {
331 set_buffer_uptodate(bh);
332 } else {
333 if (!quiet_error(bh)) {
334 buffer_io_error(bh);
335 printk(KERN_WARNING "lost page write due to "
336 "I/O error on %s\n",
337 bdevname(bh->b_bdev, b));
339 set_bit(AS_EIO, &page->mapping->flags);
340 set_buffer_write_io_error(bh);
341 clear_buffer_uptodate(bh);
342 SetPageError(page);
345 first = page_buffers(page);
346 local_irq_save(flags);
347 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
349 clear_buffer_async_write(bh);
350 unlock_buffer(bh);
351 tmp = bh->b_this_page;
352 while (tmp != bh) {
353 if (buffer_async_write(tmp)) {
354 BUG_ON(!buffer_locked(tmp));
355 goto still_busy;
357 tmp = tmp->b_this_page;
359 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
360 local_irq_restore(flags);
361 end_page_writeback(page);
362 return;
364 still_busy:
365 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
366 local_irq_restore(flags);
367 return;
369 EXPORT_SYMBOL(end_buffer_async_write);
372 * If a page's buffers are under async readin (end_buffer_async_read
373 * completion) then there is a possibility that another thread of
374 * control could lock one of the buffers after it has completed
375 * but while some of the other buffers have not completed. This
376 * locked buffer would confuse end_buffer_async_read() into not unlocking
377 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
378 * that this buffer is not under async I/O.
380 * The page comes unlocked when it has no locked buffer_async buffers
381 * left.
383 * PageLocked prevents anyone starting new async I/O reads any of
384 * the buffers.
386 * PageWriteback is used to prevent simultaneous writeout of the same
387 * page.
389 * PageLocked prevents anyone from starting writeback of a page which is
390 * under read I/O (PageWriteback is only ever set against a locked page).
392 static void mark_buffer_async_read(struct buffer_head *bh)
394 bh->b_end_io = end_buffer_async_read;
395 set_buffer_async_read(bh);
398 static void mark_buffer_async_write_endio(struct buffer_head *bh,
399 bh_end_io_t *handler)
401 bh->b_end_io = handler;
402 set_buffer_async_write(bh);
405 void mark_buffer_async_write(struct buffer_head *bh)
407 mark_buffer_async_write_endio(bh, end_buffer_async_write);
409 EXPORT_SYMBOL(mark_buffer_async_write);
413 * fs/buffer.c contains helper functions for buffer-backed address space's
414 * fsync functions. A common requirement for buffer-based filesystems is
415 * that certain data from the backing blockdev needs to be written out for
416 * a successful fsync(). For example, ext2 indirect blocks need to be
417 * written back and waited upon before fsync() returns.
419 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
420 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
421 * management of a list of dependent buffers at ->i_mapping->private_list.
423 * Locking is a little subtle: try_to_free_buffers() will remove buffers
424 * from their controlling inode's queue when they are being freed. But
425 * try_to_free_buffers() will be operating against the *blockdev* mapping
426 * at the time, not against the S_ISREG file which depends on those buffers.
427 * So the locking for private_list is via the private_lock in the address_space
428 * which backs the buffers. Which is different from the address_space
429 * against which the buffers are listed. So for a particular address_space,
430 * mapping->private_lock does *not* protect mapping->private_list! In fact,
431 * mapping->private_list will always be protected by the backing blockdev's
432 * ->private_lock.
434 * Which introduces a requirement: all buffers on an address_space's
435 * ->private_list must be from the same address_space: the blockdev's.
437 * address_spaces which do not place buffers at ->private_list via these
438 * utility functions are free to use private_lock and private_list for
439 * whatever they want. The only requirement is that list_empty(private_list)
440 * be true at clear_inode() time.
442 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
443 * filesystems should do that. invalidate_inode_buffers() should just go
444 * BUG_ON(!list_empty).
446 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
447 * take an address_space, not an inode. And it should be called
448 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
449 * queued up.
451 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
452 * list if it is already on a list. Because if the buffer is on a list,
453 * it *must* already be on the right one. If not, the filesystem is being
454 * silly. This will save a ton of locking. But first we have to ensure
455 * that buffers are taken *off* the old inode's list when they are freed
456 * (presumably in truncate). That requires careful auditing of all
457 * filesystems (do it inside bforget()). It could also be done by bringing
458 * b_inode back.
462 * The buffer's backing address_space's private_lock must be held
464 static void __remove_assoc_queue(struct buffer_head *bh)
466 list_del_init(&bh->b_assoc_buffers);
467 WARN_ON(!bh->b_assoc_map);
468 if (buffer_write_io_error(bh))
469 set_bit(AS_EIO, &bh->b_assoc_map->flags);
470 bh->b_assoc_map = NULL;
473 int inode_has_buffers(struct inode *inode)
475 return !list_empty(&inode->i_data.private_list);
479 * osync is designed to support O_SYNC io. It waits synchronously for
480 * all already-submitted IO to complete, but does not queue any new
481 * writes to the disk.
483 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
484 * you dirty the buffers, and then use osync_inode_buffers to wait for
485 * completion. Any other dirty buffers which are not yet queued for
486 * write will not be flushed to disk by the osync.
488 static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
490 struct buffer_head *bh;
491 struct list_head *p;
492 int err = 0;
494 spin_lock(lock);
495 repeat:
496 list_for_each_prev(p, list) {
497 bh = BH_ENTRY(p);
498 if (buffer_locked(bh)) {
499 get_bh(bh);
500 spin_unlock(lock);
501 wait_on_buffer(bh);
502 if (!buffer_uptodate(bh))
503 err = -EIO;
504 brelse(bh);
505 spin_lock(lock);
506 goto repeat;
509 spin_unlock(lock);
510 return err;
513 static void do_thaw_one(struct super_block *sb, void *unused)
515 char b[BDEVNAME_SIZE];
516 while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
517 printk(KERN_WARNING "Emergency Thaw on %s\n",
518 bdevname(sb->s_bdev, b));
521 static void do_thaw_all(struct work_struct *work)
523 iterate_supers(do_thaw_one, NULL);
524 kfree(work);
525 printk(KERN_WARNING "Emergency Thaw complete\n");
529 * emergency_thaw_all -- forcibly thaw every frozen filesystem
531 * Used for emergency unfreeze of all filesystems via SysRq
533 void emergency_thaw_all(void)
535 struct work_struct *work;
537 work = kmalloc(sizeof(*work), GFP_ATOMIC);
538 if (work) {
539 INIT_WORK(work, do_thaw_all);
540 schedule_work(work);
545 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
546 * @mapping: the mapping which wants those buffers written
548 * Starts I/O against the buffers at mapping->private_list, and waits upon
549 * that I/O.
551 * Basically, this is a convenience function for fsync().
552 * @mapping is a file or directory which needs those buffers to be written for
553 * a successful fsync().
555 int sync_mapping_buffers(struct address_space *mapping)
557 struct address_space *buffer_mapping = mapping->private_data;
559 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
560 return 0;
562 return fsync_buffers_list(&buffer_mapping->private_lock,
563 &mapping->private_list);
565 EXPORT_SYMBOL(sync_mapping_buffers);
568 * Called when we've recently written block `bblock', and it is known that
569 * `bblock' was for a buffer_boundary() buffer. This means that the block at
570 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
571 * dirty, schedule it for IO. So that indirects merge nicely with their data.
573 void write_boundary_block(struct block_device *bdev,
574 sector_t bblock, unsigned blocksize)
576 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
577 if (bh) {
578 if (buffer_dirty(bh))
579 ll_rw_block(WRITE, 1, &bh);
580 put_bh(bh);
584 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
586 struct address_space *mapping = inode->i_mapping;
587 struct address_space *buffer_mapping = bh->b_page->mapping;
589 mark_buffer_dirty(bh);
590 if (!mapping->private_data) {
591 mapping->private_data = buffer_mapping;
592 } else {
593 BUG_ON(mapping->private_data != buffer_mapping);
595 if (!bh->b_assoc_map) {
596 spin_lock(&buffer_mapping->private_lock);
597 list_move_tail(&bh->b_assoc_buffers,
598 &mapping->private_list);
599 bh->b_assoc_map = mapping;
600 spin_unlock(&buffer_mapping->private_lock);
603 EXPORT_SYMBOL(mark_buffer_dirty_inode);
606 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
607 * dirty.
609 * If warn is true, then emit a warning if the page is not uptodate and has
610 * not been truncated.
612 static void __set_page_dirty(struct page *page,
613 struct address_space *mapping, int warn)
615 spin_lock_irq(&mapping->tree_lock);
616 if (page->mapping) { /* Race with truncate? */
617 WARN_ON_ONCE(warn && !PageUptodate(page));
618 account_page_dirtied(page, mapping);
619 radix_tree_tag_set(&mapping->page_tree,
620 page_index(page), PAGECACHE_TAG_DIRTY);
622 spin_unlock_irq(&mapping->tree_lock);
623 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
627 * Add a page to the dirty page list.
629 * It is a sad fact of life that this function is called from several places
630 * deeply under spinlocking. It may not sleep.
632 * If the page has buffers, the uptodate buffers are set dirty, to preserve
633 * dirty-state coherency between the page and the buffers. It the page does
634 * not have buffers then when they are later attached they will all be set
635 * dirty.
637 * The buffers are dirtied before the page is dirtied. There's a small race
638 * window in which a writepage caller may see the page cleanness but not the
639 * buffer dirtiness. That's fine. If this code were to set the page dirty
640 * before the buffers, a concurrent writepage caller could clear the page dirty
641 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
642 * page on the dirty page list.
644 * We use private_lock to lock against try_to_free_buffers while using the
645 * page's buffer list. Also use this to protect against clean buffers being
646 * added to the page after it was set dirty.
648 * FIXME: may need to call ->reservepage here as well. That's rather up to the
649 * address_space though.
651 int __set_page_dirty_buffers(struct page *page)
653 int newly_dirty;
654 struct address_space *mapping = page_mapping(page);
656 if (unlikely(!mapping))
657 return !TestSetPageDirty(page);
659 spin_lock(&mapping->private_lock);
660 if (page_has_buffers(page)) {
661 struct buffer_head *head = page_buffers(page);
662 struct buffer_head *bh = head;
664 do {
665 set_buffer_dirty(bh);
666 bh = bh->b_this_page;
667 } while (bh != head);
669 newly_dirty = !TestSetPageDirty(page);
670 spin_unlock(&mapping->private_lock);
672 if (newly_dirty)
673 __set_page_dirty(page, mapping, 1);
674 return newly_dirty;
676 EXPORT_SYMBOL(__set_page_dirty_buffers);
679 * Write out and wait upon a list of buffers.
681 * We have conflicting pressures: we want to make sure that all
682 * initially dirty buffers get waited on, but that any subsequently
683 * dirtied buffers don't. After all, we don't want fsync to last
684 * forever if somebody is actively writing to the file.
686 * Do this in two main stages: first we copy dirty buffers to a
687 * temporary inode list, queueing the writes as we go. Then we clean
688 * up, waiting for those writes to complete.
690 * During this second stage, any subsequent updates to the file may end
691 * up refiling the buffer on the original inode's dirty list again, so
692 * there is a chance we will end up with a buffer queued for write but
693 * not yet completed on that list. So, as a final cleanup we go through
694 * the osync code to catch these locked, dirty buffers without requeuing
695 * any newly dirty buffers for write.
697 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
699 struct buffer_head *bh;
700 struct list_head tmp;
701 struct address_space *mapping;
702 int err = 0, err2;
703 struct blk_plug plug;
705 INIT_LIST_HEAD(&tmp);
706 blk_start_plug(&plug);
708 spin_lock(lock);
709 while (!list_empty(list)) {
710 bh = BH_ENTRY(list->next);
711 mapping = bh->b_assoc_map;
712 __remove_assoc_queue(bh);
713 /* Avoid race with mark_buffer_dirty_inode() which does
714 * a lockless check and we rely on seeing the dirty bit */
715 smp_mb();
716 if (buffer_dirty(bh) || buffer_locked(bh)) {
717 list_add(&bh->b_assoc_buffers, &tmp);
718 bh->b_assoc_map = mapping;
719 if (buffer_dirty(bh)) {
720 get_bh(bh);
721 spin_unlock(lock);
723 * Ensure any pending I/O completes so that
724 * write_dirty_buffer() actually writes the
725 * current contents - it is a noop if I/O is
726 * still in flight on potentially older
727 * contents.
729 write_dirty_buffer(bh, WRITE_SYNC);
732 * Kick off IO for the previous mapping. Note
733 * that we will not run the very last mapping,
734 * wait_on_buffer() will do that for us
735 * through sync_buffer().
737 brelse(bh);
738 spin_lock(lock);
743 spin_unlock(lock);
744 blk_finish_plug(&plug);
745 spin_lock(lock);
747 while (!list_empty(&tmp)) {
748 bh = BH_ENTRY(tmp.prev);
749 get_bh(bh);
750 mapping = bh->b_assoc_map;
751 __remove_assoc_queue(bh);
752 /* Avoid race with mark_buffer_dirty_inode() which does
753 * a lockless check and we rely on seeing the dirty bit */
754 smp_mb();
755 if (buffer_dirty(bh)) {
756 list_add(&bh->b_assoc_buffers,
757 &mapping->private_list);
758 bh->b_assoc_map = mapping;
760 spin_unlock(lock);
761 wait_on_buffer(bh);
762 if (!buffer_uptodate(bh))
763 err = -EIO;
764 brelse(bh);
765 spin_lock(lock);
768 spin_unlock(lock);
769 err2 = osync_buffers_list(lock, list);
770 if (err)
771 return err;
772 else
773 return err2;
777 * Invalidate any and all dirty buffers on a given inode. We are
778 * probably unmounting the fs, but that doesn't mean we have already
779 * done a sync(). Just drop the buffers from the inode list.
781 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
782 * assumes that all the buffers are against the blockdev. Not true
783 * for reiserfs.
785 void invalidate_inode_buffers(struct inode *inode)
787 if (inode_has_buffers(inode)) {
788 struct address_space *mapping = &inode->i_data;
789 struct list_head *list = &mapping->private_list;
790 struct address_space *buffer_mapping = mapping->private_data;
792 spin_lock(&buffer_mapping->private_lock);
793 while (!list_empty(list))
794 __remove_assoc_queue(BH_ENTRY(list->next));
795 spin_unlock(&buffer_mapping->private_lock);
798 EXPORT_SYMBOL(invalidate_inode_buffers);
801 * Remove any clean buffers from the inode's buffer list. This is called
802 * when we're trying to free the inode itself. Those buffers can pin it.
804 * Returns true if all buffers were removed.
806 int remove_inode_buffers(struct inode *inode)
808 int ret = 1;
810 if (inode_has_buffers(inode)) {
811 struct address_space *mapping = &inode->i_data;
812 struct list_head *list = &mapping->private_list;
813 struct address_space *buffer_mapping = mapping->private_data;
815 spin_lock(&buffer_mapping->private_lock);
816 while (!list_empty(list)) {
817 struct buffer_head *bh = BH_ENTRY(list->next);
818 if (buffer_dirty(bh)) {
819 ret = 0;
820 break;
822 __remove_assoc_queue(bh);
824 spin_unlock(&buffer_mapping->private_lock);
826 return ret;
830 * Create the appropriate buffers when given a page for data area and
831 * the size of each buffer.. Use the bh->b_this_page linked list to
832 * follow the buffers created. Return NULL if unable to create more
833 * buffers.
835 * The retry flag is used to differentiate async IO (paging, swapping)
836 * which may not fail from ordinary buffer allocations.
838 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
839 int retry)
841 struct buffer_head *bh, *head;
842 long offset;
844 try_again:
845 head = NULL;
846 offset = PAGE_SIZE;
847 while ((offset -= size) >= 0) {
848 bh = alloc_buffer_head(GFP_NOFS);
849 if (!bh)
850 goto no_grow;
852 bh->b_this_page = head;
853 bh->b_blocknr = -1;
854 head = bh;
856 bh->b_size = size;
858 /* Link the buffer to its page */
859 set_bh_page(bh, page, offset);
861 init_buffer(bh, NULL, NULL);
863 return head;
865 * In case anything failed, we just free everything we got.
867 no_grow:
868 if (head) {
869 do {
870 bh = head;
871 head = head->b_this_page;
872 free_buffer_head(bh);
873 } while (head);
877 * Return failure for non-async IO requests. Async IO requests
878 * are not allowed to fail, so we have to wait until buffer heads
879 * become available. But we don't want tasks sleeping with
880 * partially complete buffers, so all were released above.
882 if (!retry)
883 return NULL;
885 /* We're _really_ low on memory. Now we just
886 * wait for old buffer heads to become free due to
887 * finishing IO. Since this is an async request and
888 * the reserve list is empty, we're sure there are
889 * async buffer heads in use.
891 free_more_memory();
892 goto try_again;
894 EXPORT_SYMBOL_GPL(alloc_page_buffers);
896 static inline void
897 link_dev_buffers(struct page *page, struct buffer_head *head)
899 struct buffer_head *bh, *tail;
901 bh = head;
902 do {
903 tail = bh;
904 bh = bh->b_this_page;
905 } while (bh);
906 tail->b_this_page = head;
907 attach_page_buffers(page, head);
910 static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
912 sector_t retval = ~((sector_t)0);
913 loff_t sz = i_size_read(bdev->bd_inode);
915 if (sz) {
916 unsigned int sizebits = blksize_bits(size);
917 retval = (sz >> sizebits);
919 return retval;
923 * Initialise the state of a blockdev page's buffers.
925 static sector_t
926 init_page_buffers(struct page *page, struct block_device *bdev,
927 sector_t block, int size)
929 struct buffer_head *head = page_buffers(page);
930 struct buffer_head *bh = head;
931 int uptodate = PageUptodate(page);
932 sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode), size);
934 do {
935 if (!buffer_mapped(bh)) {
936 init_buffer(bh, NULL, NULL);
937 bh->b_bdev = bdev;
938 bh->b_blocknr = block;
939 if (uptodate)
940 set_buffer_uptodate(bh);
941 if (block < end_block)
942 set_buffer_mapped(bh);
944 block++;
945 bh = bh->b_this_page;
946 } while (bh != head);
949 * Caller needs to validate requested block against end of device.
951 return end_block;
955 * Create the page-cache page that contains the requested block.
957 * This is used purely for blockdev mappings.
959 static int
960 grow_dev_page(struct block_device *bdev, sector_t block,
961 pgoff_t index, int size, int sizebits)
963 struct inode *inode = bdev->bd_inode;
964 struct page *page;
965 struct buffer_head *bh;
966 sector_t end_block;
967 int ret = 0; /* Will call free_more_memory() */
969 page = find_or_create_page(inode->i_mapping, index,
970 (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE);
971 if (!page)
972 return ret;
974 BUG_ON(!PageLocked(page));
976 if (page_has_buffers(page)) {
977 bh = page_buffers(page);
978 if (bh->b_size == size) {
979 end_block = init_page_buffers(page, bdev,
980 index << sizebits, size);
981 goto done;
983 if (!try_to_free_buffers(page))
984 goto failed;
988 * Allocate some buffers for this page
990 bh = alloc_page_buffers(page, size, 0);
991 if (!bh)
992 goto failed;
995 * Link the page to the buffers and initialise them. Take the
996 * lock to be atomic wrt __find_get_block(), which does not
997 * run under the page lock.
999 spin_lock(&inode->i_mapping->private_lock);
1000 link_dev_buffers(page, bh);
1001 end_block = init_page_buffers(page, bdev, index << sizebits, size);
1002 spin_unlock(&inode->i_mapping->private_lock);
1003 done:
1004 ret = (block < end_block) ? 1 : -ENXIO;
1005 failed:
1006 unlock_page(page);
1007 page_cache_release(page);
1008 return ret;
1012 * Create buffers for the specified block device block's page. If
1013 * that page was dirty, the buffers are set dirty also.
1015 static int
1016 grow_buffers(struct block_device *bdev, sector_t block, int size)
1018 pgoff_t index;
1019 int sizebits;
1021 sizebits = -1;
1022 do {
1023 sizebits++;
1024 } while ((size << sizebits) < PAGE_SIZE);
1026 index = block >> sizebits;
1029 * Check for a block which wants to lie outside our maximum possible
1030 * pagecache index. (this comparison is done using sector_t types).
1032 if (unlikely(index != block >> sizebits)) {
1033 char b[BDEVNAME_SIZE];
1035 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1036 "device %s\n",
1037 __func__, (unsigned long long)block,
1038 bdevname(bdev, b));
1039 return -EIO;
1042 /* Create a page with the proper size buffers.. */
1043 return grow_dev_page(bdev, block, index, size, sizebits);
1046 static struct buffer_head *
1047 __getblk_slow(struct block_device *bdev, sector_t block, int size)
1049 /* Size must be multiple of hard sectorsize */
1050 if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
1051 (size < 512 || size > PAGE_SIZE))) {
1052 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1053 size);
1054 printk(KERN_ERR "logical block size: %d\n",
1055 bdev_logical_block_size(bdev));
1057 dump_stack();
1058 return NULL;
1061 for (;;) {
1062 struct buffer_head *bh;
1063 int ret;
1065 bh = __find_get_block(bdev, block, size);
1066 if (bh)
1067 return bh;
1069 ret = grow_buffers(bdev, block, size);
1070 if (ret < 0)
1071 return NULL;
1072 if (ret == 0)
1073 free_more_memory();
1078 * The relationship between dirty buffers and dirty pages:
1080 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1081 * the page is tagged dirty in its radix tree.
1083 * At all times, the dirtiness of the buffers represents the dirtiness of
1084 * subsections of the page. If the page has buffers, the page dirty bit is
1085 * merely a hint about the true dirty state.
1087 * When a page is set dirty in its entirety, all its buffers are marked dirty
1088 * (if the page has buffers).
1090 * When a buffer is marked dirty, its page is dirtied, but the page's other
1091 * buffers are not.
1093 * Also. When blockdev buffers are explicitly read with bread(), they
1094 * individually become uptodate. But their backing page remains not
1095 * uptodate - even if all of its buffers are uptodate. A subsequent
1096 * block_read_full_page() against that page will discover all the uptodate
1097 * buffers, will set the page uptodate and will perform no I/O.
1101 * mark_buffer_dirty - mark a buffer_head as needing writeout
1102 * @bh: the buffer_head to mark dirty
1104 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1105 * backing page dirty, then tag the page as dirty in its address_space's radix
1106 * tree and then attach the address_space's inode to its superblock's dirty
1107 * inode list.
1109 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1110 * mapping->tree_lock and mapping->host->i_lock.
1112 void mark_buffer_dirty(struct buffer_head *bh)
1114 WARN_ON_ONCE(!buffer_uptodate(bh));
1117 * Very *carefully* optimize the it-is-already-dirty case.
1119 * Don't let the final "is it dirty" escape to before we
1120 * perhaps modified the buffer.
1122 if (buffer_dirty(bh)) {
1123 smp_mb();
1124 if (buffer_dirty(bh))
1125 return;
1128 if (!test_set_buffer_dirty(bh)) {
1129 struct page *page = bh->b_page;
1130 if (!TestSetPageDirty(page)) {
1131 struct address_space *mapping = page_mapping(page);
1132 if (mapping)
1133 __set_page_dirty(page, mapping, 0);
1137 EXPORT_SYMBOL(mark_buffer_dirty);
1140 * Decrement a buffer_head's reference count. If all buffers against a page
1141 * have zero reference count, are clean and unlocked, and if the page is clean
1142 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1143 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1144 * a page but it ends up not being freed, and buffers may later be reattached).
1146 void __brelse(struct buffer_head * buf)
1148 if (atomic_read(&buf->b_count)) {
1149 put_bh(buf);
1150 return;
1152 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1154 EXPORT_SYMBOL(__brelse);
1157 * bforget() is like brelse(), except it discards any
1158 * potentially dirty data.
1160 void __bforget(struct buffer_head *bh)
1162 clear_buffer_dirty(bh);
1163 if (bh->b_assoc_map) {
1164 struct address_space *buffer_mapping = bh->b_page->mapping;
1166 spin_lock(&buffer_mapping->private_lock);
1167 list_del_init(&bh->b_assoc_buffers);
1168 bh->b_assoc_map = NULL;
1169 spin_unlock(&buffer_mapping->private_lock);
1171 __brelse(bh);
1173 EXPORT_SYMBOL(__bforget);
1175 static struct buffer_head *__bread_slow(struct buffer_head *bh)
1177 lock_buffer(bh);
1178 if (buffer_uptodate(bh)) {
1179 unlock_buffer(bh);
1180 return bh;
1181 } else {
1182 get_bh(bh);
1183 bh->b_end_io = end_buffer_read_sync;
1184 submit_bh(READ, bh);
1185 wait_on_buffer(bh);
1186 if (buffer_uptodate(bh))
1187 return bh;
1189 brelse(bh);
1190 return NULL;
1194 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1195 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1196 * refcount elevated by one when they're in an LRU. A buffer can only appear
1197 * once in a particular CPU's LRU. A single buffer can be present in multiple
1198 * CPU's LRUs at the same time.
1200 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1201 * sb_find_get_block().
1203 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1204 * a local interrupt disable for that.
1207 #define BH_LRU_SIZE 8
1209 struct bh_lru {
1210 struct buffer_head *bhs[BH_LRU_SIZE];
1213 static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1215 #ifdef CONFIG_SMP
1216 #define bh_lru_lock() local_irq_disable()
1217 #define bh_lru_unlock() local_irq_enable()
1218 #else
1219 #define bh_lru_lock() preempt_disable()
1220 #define bh_lru_unlock() preempt_enable()
1221 #endif
1223 static inline void check_irqs_on(void)
1225 #ifdef irqs_disabled
1226 BUG_ON(irqs_disabled());
1227 #endif
1231 * The LRU management algorithm is dopey-but-simple. Sorry.
1233 static void bh_lru_install(struct buffer_head *bh)
1235 struct buffer_head *evictee = NULL;
1237 check_irqs_on();
1238 bh_lru_lock();
1239 if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
1240 struct buffer_head *bhs[BH_LRU_SIZE];
1241 int in;
1242 int out = 0;
1244 get_bh(bh);
1245 bhs[out++] = bh;
1246 for (in = 0; in < BH_LRU_SIZE; in++) {
1247 struct buffer_head *bh2 =
1248 __this_cpu_read(bh_lrus.bhs[in]);
1250 if (bh2 == bh) {
1251 __brelse(bh2);
1252 } else {
1253 if (out >= BH_LRU_SIZE) {
1254 BUG_ON(evictee != NULL);
1255 evictee = bh2;
1256 } else {
1257 bhs[out++] = bh2;
1261 while (out < BH_LRU_SIZE)
1262 bhs[out++] = NULL;
1263 memcpy(__this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
1265 bh_lru_unlock();
1267 if (evictee)
1268 __brelse(evictee);
1272 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1274 static struct buffer_head *
1275 lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1277 struct buffer_head *ret = NULL;
1278 unsigned int i;
1280 check_irqs_on();
1281 bh_lru_lock();
1282 for (i = 0; i < BH_LRU_SIZE; i++) {
1283 struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
1285 if (bh && bh->b_bdev == bdev &&
1286 bh->b_blocknr == block && bh->b_size == size) {
1287 if (i) {
1288 while (i) {
1289 __this_cpu_write(bh_lrus.bhs[i],
1290 __this_cpu_read(bh_lrus.bhs[i - 1]));
1291 i--;
1293 __this_cpu_write(bh_lrus.bhs[0], bh);
1295 get_bh(bh);
1296 ret = bh;
1297 break;
1300 bh_lru_unlock();
1301 return ret;
1305 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1306 * it in the LRU and mark it as accessed. If it is not present then return
1307 * NULL
1309 struct buffer_head *
1310 __find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1312 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1314 if (bh == NULL) {
1315 bh = __find_get_block_slow(bdev, block);
1316 if (bh)
1317 bh_lru_install(bh);
1319 if (bh)
1320 touch_buffer(bh);
1321 return bh;
1323 EXPORT_SYMBOL(__find_get_block);
1326 * __getblk will locate (and, if necessary, create) the buffer_head
1327 * which corresponds to the passed block_device, block and size. The
1328 * returned buffer has its reference count incremented.
1330 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1331 * attempt is failing. FIXME, perhaps?
1333 struct buffer_head *
1334 __getblk(struct block_device *bdev, sector_t block, unsigned size)
1336 struct buffer_head *bh = __find_get_block(bdev, block, size);
1338 might_sleep();
1339 if (bh == NULL)
1340 bh = __getblk_slow(bdev, block, size);
1341 return bh;
1343 EXPORT_SYMBOL(__getblk);
1346 * Do async read-ahead on a buffer..
1348 void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1350 struct buffer_head *bh = __getblk(bdev, block, size);
1351 if (likely(bh)) {
1352 ll_rw_block(READA, 1, &bh);
1353 brelse(bh);
1356 EXPORT_SYMBOL(__breadahead);
1359 * __bread() - reads a specified block and returns the bh
1360 * @bdev: the block_device to read from
1361 * @block: number of block
1362 * @size: size (in bytes) to read
1364 * Reads a specified block, and returns buffer head that contains it.
1365 * It returns NULL if the block was unreadable.
1367 struct buffer_head *
1368 __bread(struct block_device *bdev, sector_t block, unsigned size)
1370 struct buffer_head *bh = __getblk(bdev, block, size);
1372 if (likely(bh) && !buffer_uptodate(bh))
1373 bh = __bread_slow(bh);
1374 return bh;
1376 EXPORT_SYMBOL(__bread);
1379 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1380 * This doesn't race because it runs in each cpu either in irq
1381 * or with preempt disabled.
1383 static void invalidate_bh_lru(void *arg)
1385 struct bh_lru *b = &get_cpu_var(bh_lrus);
1386 int i;
1388 for (i = 0; i < BH_LRU_SIZE; i++) {
1389 brelse(b->bhs[i]);
1390 b->bhs[i] = NULL;
1392 put_cpu_var(bh_lrus);
1395 static bool has_bh_in_lru(int cpu, void *dummy)
1397 struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1398 int i;
1400 for (i = 0; i < BH_LRU_SIZE; i++) {
1401 if (b->bhs[i])
1402 return 1;
1405 return 0;
1408 void invalidate_bh_lrus(void)
1410 on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL);
1412 EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1414 void set_bh_page(struct buffer_head *bh,
1415 struct page *page, unsigned long offset)
1417 bh->b_page = page;
1418 BUG_ON(offset >= PAGE_SIZE);
1419 if (PageHighMem(page))
1421 * This catches illegal uses and preserves the offset:
1423 bh->b_data = (char *)(0 + offset);
1424 else
1425 bh->b_data = page_address(page) + offset;
1427 EXPORT_SYMBOL(set_bh_page);
1430 * Called when truncating a buffer on a page completely.
1432 static void discard_buffer(struct buffer_head * bh)
1434 lock_buffer(bh);
1435 clear_buffer_dirty(bh);
1436 bh->b_bdev = NULL;
1437 clear_buffer_mapped(bh);
1438 clear_buffer_req(bh);
1439 clear_buffer_new(bh);
1440 clear_buffer_delay(bh);
1441 clear_buffer_unwritten(bh);
1442 unlock_buffer(bh);
1446 * block_invalidatepage - invalidate part or all of a buffer-backed page
1448 * @page: the page which is affected
1449 * @offset: the index of the truncation point
1451 * block_invalidatepage() is called when all or part of the page has become
1452 * invalidated by a truncate operation.
1454 * block_invalidatepage() does not have to release all buffers, but it must
1455 * ensure that no dirty buffer is left outside @offset and that no I/O
1456 * is underway against any of the blocks which are outside the truncation
1457 * point. Because the caller is about to free (and possibly reuse) those
1458 * blocks on-disk.
1460 void block_invalidatepage(struct page *page, unsigned long offset)
1462 struct buffer_head *head, *bh, *next;
1463 unsigned int curr_off = 0;
1465 BUG_ON(!PageLocked(page));
1466 if (!page_has_buffers(page))
1467 goto out;
1469 head = page_buffers(page);
1470 bh = head;
1471 do {
1472 unsigned int next_off = curr_off + bh->b_size;
1473 next = bh->b_this_page;
1476 * is this block fully invalidated?
1478 if (offset <= curr_off)
1479 discard_buffer(bh);
1480 curr_off = next_off;
1481 bh = next;
1482 } while (bh != head);
1485 * We release buffers only if the entire page is being invalidated.
1486 * The get_block cached value has been unconditionally invalidated,
1487 * so real IO is not possible anymore.
1489 if (offset == 0)
1490 try_to_release_page(page, 0);
1491 out:
1492 return;
1494 EXPORT_SYMBOL(block_invalidatepage);
1497 * We attach and possibly dirty the buffers atomically wrt
1498 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1499 * is already excluded via the page lock.
1501 void create_empty_buffers(struct page *page,
1502 unsigned long blocksize, unsigned long b_state)
1504 struct buffer_head *bh, *head, *tail;
1506 head = alloc_page_buffers(page, blocksize, 1);
1507 bh = head;
1508 do {
1509 bh->b_state |= b_state;
1510 tail = bh;
1511 bh = bh->b_this_page;
1512 } while (bh);
1513 tail->b_this_page = head;
1515 spin_lock(&page->mapping->private_lock);
1516 if (PageUptodate(page) || PageDirty(page)) {
1517 bh = head;
1518 do {
1519 if (PageDirty(page))
1520 set_buffer_dirty(bh);
1521 if (PageUptodate(page))
1522 set_buffer_uptodate(bh);
1523 bh = bh->b_this_page;
1524 } while (bh != head);
1526 attach_page_buffers(page, head);
1527 spin_unlock(&page->mapping->private_lock);
1529 EXPORT_SYMBOL(create_empty_buffers);
1532 * We are taking a block for data and we don't want any output from any
1533 * buffer-cache aliases starting from return from that function and
1534 * until the moment when something will explicitly mark the buffer
1535 * dirty (hopefully that will not happen until we will free that block ;-)
1536 * We don't even need to mark it not-uptodate - nobody can expect
1537 * anything from a newly allocated buffer anyway. We used to used
1538 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1539 * don't want to mark the alias unmapped, for example - it would confuse
1540 * anyone who might pick it with bread() afterwards...
1542 * Also.. Note that bforget() doesn't lock the buffer. So there can
1543 * be writeout I/O going on against recently-freed buffers. We don't
1544 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1545 * only if we really need to. That happens here.
1547 void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1549 struct buffer_head *old_bh;
1551 might_sleep();
1553 old_bh = __find_get_block_slow(bdev, block);
1554 if (old_bh) {
1555 clear_buffer_dirty(old_bh);
1556 wait_on_buffer(old_bh);
1557 clear_buffer_req(old_bh);
1558 __brelse(old_bh);
1561 EXPORT_SYMBOL(unmap_underlying_metadata);
1564 * Size is a power-of-two in the range 512..PAGE_SIZE,
1565 * and the case we care about most is PAGE_SIZE.
1567 * So this *could* possibly be written with those
1568 * constraints in mind (relevant mostly if some
1569 * architecture has a slow bit-scan instruction)
1571 static inline int block_size_bits(unsigned int blocksize)
1573 return ilog2(blocksize);
1576 static struct buffer_head *create_page_buffers(struct page *page, struct inode *inode, unsigned int b_state)
1578 BUG_ON(!PageLocked(page));
1580 if (!page_has_buffers(page))
1581 create_empty_buffers(page, 1 << ACCESS_ONCE(inode->i_blkbits), b_state);
1582 return page_buffers(page);
1586 * NOTE! All mapped/uptodate combinations are valid:
1588 * Mapped Uptodate Meaning
1590 * No No "unknown" - must do get_block()
1591 * No Yes "hole" - zero-filled
1592 * Yes No "allocated" - allocated on disk, not read in
1593 * Yes Yes "valid" - allocated and up-to-date in memory.
1595 * "Dirty" is valid only with the last case (mapped+uptodate).
1599 * While block_write_full_page is writing back the dirty buffers under
1600 * the page lock, whoever dirtied the buffers may decide to clean them
1601 * again at any time. We handle that by only looking at the buffer
1602 * state inside lock_buffer().
1604 * If block_write_full_page() is called for regular writeback
1605 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1606 * locked buffer. This only can happen if someone has written the buffer
1607 * directly, with submit_bh(). At the address_space level PageWriteback
1608 * prevents this contention from occurring.
1610 * If block_write_full_page() is called with wbc->sync_mode ==
1611 * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this
1612 * causes the writes to be flagged as synchronous writes.
1614 static int __block_write_full_page(struct inode *inode, struct page *page,
1615 get_block_t *get_block, struct writeback_control *wbc,
1616 bh_end_io_t *handler)
1618 int err;
1619 sector_t block;
1620 sector_t last_block;
1621 struct buffer_head *bh, *head;
1622 unsigned int blocksize, bbits;
1623 int nr_underway = 0;
1624 int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
1625 WRITE_SYNC : WRITE);
1627 head = create_page_buffers(page, inode,
1628 (1 << BH_Dirty)|(1 << BH_Uptodate));
1631 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1632 * here, and the (potentially unmapped) buffers may become dirty at
1633 * any time. If a buffer becomes dirty here after we've inspected it
1634 * then we just miss that fact, and the page stays dirty.
1636 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1637 * handle that here by just cleaning them.
1640 bh = head;
1641 blocksize = bh->b_size;
1642 bbits = block_size_bits(blocksize);
1644 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1645 last_block = (i_size_read(inode) - 1) >> bbits;
1648 * Get all the dirty buffers mapped to disk addresses and
1649 * handle any aliases from the underlying blockdev's mapping.
1651 do {
1652 if (block > last_block) {
1654 * mapped buffers outside i_size will occur, because
1655 * this page can be outside i_size when there is a
1656 * truncate in progress.
1659 * The buffer was zeroed by block_write_full_page()
1661 clear_buffer_dirty(bh);
1662 set_buffer_uptodate(bh);
1663 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1664 buffer_dirty(bh)) {
1665 WARN_ON(bh->b_size != blocksize);
1666 err = get_block(inode, block, bh, 1);
1667 if (err)
1668 goto recover;
1669 clear_buffer_delay(bh);
1670 if (buffer_new(bh)) {
1671 /* blockdev mappings never come here */
1672 clear_buffer_new(bh);
1673 unmap_underlying_metadata(bh->b_bdev,
1674 bh->b_blocknr);
1677 bh = bh->b_this_page;
1678 block++;
1679 } while (bh != head);
1681 do {
1682 if (!buffer_mapped(bh))
1683 continue;
1685 * If it's a fully non-blocking write attempt and we cannot
1686 * lock the buffer then redirty the page. Note that this can
1687 * potentially cause a busy-wait loop from writeback threads
1688 * and kswapd activity, but those code paths have their own
1689 * higher-level throttling.
1691 if (wbc->sync_mode != WB_SYNC_NONE) {
1692 lock_buffer(bh);
1693 } else if (!trylock_buffer(bh)) {
1694 redirty_page_for_writepage(wbc, page);
1695 continue;
1697 if (test_clear_buffer_dirty(bh)) {
1698 mark_buffer_async_write_endio(bh, handler);
1699 } else {
1700 unlock_buffer(bh);
1702 } while ((bh = bh->b_this_page) != head);
1705 * The page and its buffers are protected by PageWriteback(), so we can
1706 * drop the bh refcounts early.
1708 BUG_ON(PageWriteback(page));
1709 set_page_writeback(page);
1711 do {
1712 struct buffer_head *next = bh->b_this_page;
1713 if (buffer_async_write(bh)) {
1714 submit_bh(write_op, bh);
1715 nr_underway++;
1717 bh = next;
1718 } while (bh != head);
1719 unlock_page(page);
1721 err = 0;
1722 done:
1723 if (nr_underway == 0) {
1725 * The page was marked dirty, but the buffers were
1726 * clean. Someone wrote them back by hand with
1727 * ll_rw_block/submit_bh. A rare case.
1729 end_page_writeback(page);
1732 * The page and buffer_heads can be released at any time from
1733 * here on.
1736 return err;
1738 recover:
1740 * ENOSPC, or some other error. We may already have added some
1741 * blocks to the file, so we need to write these out to avoid
1742 * exposing stale data.
1743 * The page is currently locked and not marked for writeback
1745 bh = head;
1746 /* Recovery: lock and submit the mapped buffers */
1747 do {
1748 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1749 !buffer_delay(bh)) {
1750 lock_buffer(bh);
1751 mark_buffer_async_write_endio(bh, handler);
1752 } else {
1754 * The buffer may have been set dirty during
1755 * attachment to a dirty page.
1757 clear_buffer_dirty(bh);
1759 } while ((bh = bh->b_this_page) != head);
1760 SetPageError(page);
1761 BUG_ON(PageWriteback(page));
1762 mapping_set_error(page->mapping, err);
1763 set_page_writeback(page);
1764 do {
1765 struct buffer_head *next = bh->b_this_page;
1766 if (buffer_async_write(bh)) {
1767 clear_buffer_dirty(bh);
1768 submit_bh(write_op, bh);
1769 nr_underway++;
1771 bh = next;
1772 } while (bh != head);
1773 unlock_page(page);
1774 goto done;
1778 * If a page has any new buffers, zero them out here, and mark them uptodate
1779 * and dirty so they'll be written out (in order to prevent uninitialised
1780 * block data from leaking). And clear the new bit.
1782 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1784 unsigned int block_start, block_end;
1785 struct buffer_head *head, *bh;
1787 BUG_ON(!PageLocked(page));
1788 if (!page_has_buffers(page))
1789 return;
1791 bh = head = page_buffers(page);
1792 block_start = 0;
1793 do {
1794 block_end = block_start + bh->b_size;
1796 if (buffer_new(bh)) {
1797 if (block_end > from && block_start < to) {
1798 if (!PageUptodate(page)) {
1799 unsigned start, size;
1801 start = max(from, block_start);
1802 size = min(to, block_end) - start;
1804 zero_user(page, start, size);
1805 set_buffer_uptodate(bh);
1808 clear_buffer_new(bh);
1809 mark_buffer_dirty(bh);
1813 block_start = block_end;
1814 bh = bh->b_this_page;
1815 } while (bh != head);
1817 EXPORT_SYMBOL(page_zero_new_buffers);
1819 int __block_write_begin(struct page *page, loff_t pos, unsigned len,
1820 get_block_t *get_block)
1822 unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1823 unsigned to = from + len;
1824 struct inode *inode = page->mapping->host;
1825 unsigned block_start, block_end;
1826 sector_t block;
1827 int err = 0;
1828 unsigned blocksize, bbits;
1829 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1831 BUG_ON(!PageLocked(page));
1832 BUG_ON(from > PAGE_CACHE_SIZE);
1833 BUG_ON(to > PAGE_CACHE_SIZE);
1834 BUG_ON(from > to);
1836 head = create_page_buffers(page, inode, 0);
1837 blocksize = head->b_size;
1838 bbits = block_size_bits(blocksize);
1840 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1842 for(bh = head, block_start = 0; bh != head || !block_start;
1843 block++, block_start=block_end, bh = bh->b_this_page) {
1844 block_end = block_start + blocksize;
1845 if (block_end <= from || block_start >= to) {
1846 if (PageUptodate(page)) {
1847 if (!buffer_uptodate(bh))
1848 set_buffer_uptodate(bh);
1850 continue;
1852 if (buffer_new(bh))
1853 clear_buffer_new(bh);
1854 if (!buffer_mapped(bh)) {
1855 WARN_ON(bh->b_size != blocksize);
1856 err = get_block(inode, block, bh, 1);
1857 if (err)
1858 break;
1859 if (buffer_new(bh)) {
1860 unmap_underlying_metadata(bh->b_bdev,
1861 bh->b_blocknr);
1862 if (PageUptodate(page)) {
1863 clear_buffer_new(bh);
1864 set_buffer_uptodate(bh);
1865 mark_buffer_dirty(bh);
1866 continue;
1868 if (block_end > to || block_start < from)
1869 zero_user_segments(page,
1870 to, block_end,
1871 block_start, from);
1872 continue;
1875 if (PageUptodate(page)) {
1876 if (!buffer_uptodate(bh))
1877 set_buffer_uptodate(bh);
1878 continue;
1880 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1881 !buffer_unwritten(bh) &&
1882 (block_start < from || block_end > to)) {
1883 ll_rw_block(READ, 1, &bh);
1884 *wait_bh++=bh;
1888 * If we issued read requests - let them complete.
1890 while(wait_bh > wait) {
1891 wait_on_buffer(*--wait_bh);
1892 if (!buffer_uptodate(*wait_bh))
1893 err = -EIO;
1895 if (unlikely(err))
1896 page_zero_new_buffers(page, from, to);
1897 return err;
1899 EXPORT_SYMBOL(__block_write_begin);
1901 static int __block_commit_write(struct inode *inode, struct page *page,
1902 unsigned from, unsigned to)
1904 unsigned block_start, block_end;
1905 int partial = 0;
1906 unsigned blocksize;
1907 struct buffer_head *bh, *head;
1909 bh = head = page_buffers(page);
1910 blocksize = bh->b_size;
1912 block_start = 0;
1913 do {
1914 block_end = block_start + blocksize;
1915 if (block_end <= from || block_start >= to) {
1916 if (!buffer_uptodate(bh))
1917 partial = 1;
1918 } else {
1919 set_buffer_uptodate(bh);
1920 mark_buffer_dirty(bh);
1922 clear_buffer_new(bh);
1924 block_start = block_end;
1925 bh = bh->b_this_page;
1926 } while (bh != head);
1929 * If this is a partial write which happened to make all buffers
1930 * uptodate then we can optimize away a bogus readpage() for
1931 * the next read(). Here we 'discover' whether the page went
1932 * uptodate as a result of this (potentially partial) write.
1934 if (!partial)
1935 SetPageUptodate(page);
1936 return 0;
1940 * block_write_begin takes care of the basic task of block allocation and
1941 * bringing partial write blocks uptodate first.
1943 * The filesystem needs to handle block truncation upon failure.
1945 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
1946 unsigned flags, struct page **pagep, get_block_t *get_block)
1948 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1949 struct page *page;
1950 int status;
1952 page = grab_cache_page_write_begin(mapping, index, flags);
1953 if (!page)
1954 return -ENOMEM;
1956 status = __block_write_begin(page, pos, len, get_block);
1957 if (unlikely(status)) {
1958 unlock_page(page);
1959 page_cache_release(page);
1960 page = NULL;
1963 *pagep = page;
1964 return status;
1966 EXPORT_SYMBOL(block_write_begin);
1968 int block_write_end(struct file *file, struct address_space *mapping,
1969 loff_t pos, unsigned len, unsigned copied,
1970 struct page *page, void *fsdata)
1972 struct inode *inode = mapping->host;
1973 unsigned start;
1975 start = pos & (PAGE_CACHE_SIZE - 1);
1977 if (unlikely(copied < len)) {
1979 * The buffers that were written will now be uptodate, so we
1980 * don't have to worry about a readpage reading them and
1981 * overwriting a partial write. However if we have encountered
1982 * a short write and only partially written into a buffer, it
1983 * will not be marked uptodate, so a readpage might come in and
1984 * destroy our partial write.
1986 * Do the simplest thing, and just treat any short write to a
1987 * non uptodate page as a zero-length write, and force the
1988 * caller to redo the whole thing.
1990 if (!PageUptodate(page))
1991 copied = 0;
1993 page_zero_new_buffers(page, start+copied, start+len);
1995 flush_dcache_page(page);
1997 /* This could be a short (even 0-length) commit */
1998 __block_commit_write(inode, page, start, start+copied);
2000 return copied;
2002 EXPORT_SYMBOL(block_write_end);
2004 int generic_write_end(struct file *file, struct address_space *mapping,
2005 loff_t pos, unsigned len, unsigned copied,
2006 struct page *page, void *fsdata)
2008 struct inode *inode = mapping->host;
2009 int i_size_changed = 0;
2011 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2014 * No need to use i_size_read() here, the i_size
2015 * cannot change under us because we hold i_mutex.
2017 * But it's important to update i_size while still holding page lock:
2018 * page writeout could otherwise come in and zero beyond i_size.
2020 if (pos+copied > inode->i_size) {
2021 i_size_write(inode, pos+copied);
2022 i_size_changed = 1;
2025 unlock_page(page);
2026 page_cache_release(page);
2029 * Don't mark the inode dirty under page lock. First, it unnecessarily
2030 * makes the holding time of page lock longer. Second, it forces lock
2031 * ordering of page lock and transaction start for journaling
2032 * filesystems.
2034 if (i_size_changed)
2035 mark_inode_dirty(inode);
2037 return copied;
2039 EXPORT_SYMBOL(generic_write_end);
2042 * block_is_partially_uptodate checks whether buffers within a page are
2043 * uptodate or not.
2045 * Returns true if all buffers which correspond to a file portion
2046 * we want to read are uptodate.
2048 int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
2049 unsigned long from)
2051 unsigned block_start, block_end, blocksize;
2052 unsigned to;
2053 struct buffer_head *bh, *head;
2054 int ret = 1;
2056 if (!page_has_buffers(page))
2057 return 0;
2059 head = page_buffers(page);
2060 blocksize = head->b_size;
2061 to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count);
2062 to = from + to;
2063 if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
2064 return 0;
2066 bh = head;
2067 block_start = 0;
2068 do {
2069 block_end = block_start + blocksize;
2070 if (block_end > from && block_start < to) {
2071 if (!buffer_uptodate(bh)) {
2072 ret = 0;
2073 break;
2075 if (block_end >= to)
2076 break;
2078 block_start = block_end;
2079 bh = bh->b_this_page;
2080 } while (bh != head);
2082 return ret;
2084 EXPORT_SYMBOL(block_is_partially_uptodate);
2087 * Generic "read page" function for block devices that have the normal
2088 * get_block functionality. This is most of the block device filesystems.
2089 * Reads the page asynchronously --- the unlock_buffer() and
2090 * set/clear_buffer_uptodate() functions propagate buffer state into the
2091 * page struct once IO has completed.
2093 int block_read_full_page(struct page *page, get_block_t *get_block)
2095 struct inode *inode = page->mapping->host;
2096 sector_t iblock, lblock;
2097 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2098 unsigned int blocksize, bbits;
2099 int nr, i;
2100 int fully_mapped = 1;
2102 head = create_page_buffers(page, inode, 0);
2103 blocksize = head->b_size;
2104 bbits = block_size_bits(blocksize);
2106 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
2107 lblock = (i_size_read(inode)+blocksize-1) >> bbits;
2108 bh = head;
2109 nr = 0;
2110 i = 0;
2112 do {
2113 if (buffer_uptodate(bh))
2114 continue;
2116 if (!buffer_mapped(bh)) {
2117 int err = 0;
2119 fully_mapped = 0;
2120 if (iblock < lblock) {
2121 WARN_ON(bh->b_size != blocksize);
2122 err = get_block(inode, iblock, bh, 0);
2123 if (err)
2124 SetPageError(page);
2126 if (!buffer_mapped(bh)) {
2127 zero_user(page, i * blocksize, blocksize);
2128 if (!err)
2129 set_buffer_uptodate(bh);
2130 continue;
2133 * get_block() might have updated the buffer
2134 * synchronously
2136 if (buffer_uptodate(bh))
2137 continue;
2139 arr[nr++] = bh;
2140 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2142 if (fully_mapped)
2143 SetPageMappedToDisk(page);
2145 if (!nr) {
2147 * All buffers are uptodate - we can set the page uptodate
2148 * as well. But not if get_block() returned an error.
2150 if (!PageError(page))
2151 SetPageUptodate(page);
2152 unlock_page(page);
2153 return 0;
2156 /* Stage two: lock the buffers */
2157 for (i = 0; i < nr; i++) {
2158 bh = arr[i];
2159 lock_buffer(bh);
2160 mark_buffer_async_read(bh);
2164 * Stage 3: start the IO. Check for uptodateness
2165 * inside the buffer lock in case another process reading
2166 * the underlying blockdev brought it uptodate (the sct fix).
2168 for (i = 0; i < nr; i++) {
2169 bh = arr[i];
2170 if (buffer_uptodate(bh))
2171 end_buffer_async_read(bh, 1);
2172 else
2173 submit_bh(READ, bh);
2175 return 0;
2177 EXPORT_SYMBOL(block_read_full_page);
2179 /* utility function for filesystems that need to do work on expanding
2180 * truncates. Uses filesystem pagecache writes to allow the filesystem to
2181 * deal with the hole.
2183 int generic_cont_expand_simple(struct inode *inode, loff_t size)
2185 struct address_space *mapping = inode->i_mapping;
2186 struct page *page;
2187 void *fsdata;
2188 int err;
2190 err = inode_newsize_ok(inode, size);
2191 if (err)
2192 goto out;
2194 err = pagecache_write_begin(NULL, mapping, size, 0,
2195 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2196 &page, &fsdata);
2197 if (err)
2198 goto out;
2200 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2201 BUG_ON(err > 0);
2203 out:
2204 return err;
2206 EXPORT_SYMBOL(generic_cont_expand_simple);
2208 static int cont_expand_zero(struct file *file, struct address_space *mapping,
2209 loff_t pos, loff_t *bytes)
2211 struct inode *inode = mapping->host;
2212 unsigned blocksize = 1 << inode->i_blkbits;
2213 struct page *page;
2214 void *fsdata;
2215 pgoff_t index, curidx;
2216 loff_t curpos;
2217 unsigned zerofrom, offset, len;
2218 int err = 0;
2220 index = pos >> PAGE_CACHE_SHIFT;
2221 offset = pos & ~PAGE_CACHE_MASK;
2223 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
2224 zerofrom = curpos & ~PAGE_CACHE_MASK;
2225 if (zerofrom & (blocksize-1)) {
2226 *bytes |= (blocksize-1);
2227 (*bytes)++;
2229 len = PAGE_CACHE_SIZE - zerofrom;
2231 err = pagecache_write_begin(file, mapping, curpos, len,
2232 AOP_FLAG_UNINTERRUPTIBLE,
2233 &page, &fsdata);
2234 if (err)
2235 goto out;
2236 zero_user(page, zerofrom, len);
2237 err = pagecache_write_end(file, mapping, curpos, len, len,
2238 page, fsdata);
2239 if (err < 0)
2240 goto out;
2241 BUG_ON(err != len);
2242 err = 0;
2244 balance_dirty_pages_ratelimited(mapping);
2247 /* page covers the boundary, find the boundary offset */
2248 if (index == curidx) {
2249 zerofrom = curpos & ~PAGE_CACHE_MASK;
2250 /* if we will expand the thing last block will be filled */
2251 if (offset <= zerofrom) {
2252 goto out;
2254 if (zerofrom & (blocksize-1)) {
2255 *bytes |= (blocksize-1);
2256 (*bytes)++;
2258 len = offset - zerofrom;
2260 err = pagecache_write_begin(file, mapping, curpos, len,
2261 AOP_FLAG_UNINTERRUPTIBLE,
2262 &page, &fsdata);
2263 if (err)
2264 goto out;
2265 zero_user(page, zerofrom, len);
2266 err = pagecache_write_end(file, mapping, curpos, len, len,
2267 page, fsdata);
2268 if (err < 0)
2269 goto out;
2270 BUG_ON(err != len);
2271 err = 0;
2273 out:
2274 return err;
2278 * For moronic filesystems that do not allow holes in file.
2279 * We may have to extend the file.
2281 int cont_write_begin(struct file *file, struct address_space *mapping,
2282 loff_t pos, unsigned len, unsigned flags,
2283 struct page **pagep, void **fsdata,
2284 get_block_t *get_block, loff_t *bytes)
2286 struct inode *inode = mapping->host;
2287 unsigned blocksize = 1 << inode->i_blkbits;
2288 unsigned zerofrom;
2289 int err;
2291 err = cont_expand_zero(file, mapping, pos, bytes);
2292 if (err)
2293 return err;
2295 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2296 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2297 *bytes |= (blocksize-1);
2298 (*bytes)++;
2301 return block_write_begin(mapping, pos, len, flags, pagep, get_block);
2303 EXPORT_SYMBOL(cont_write_begin);
2305 int block_commit_write(struct page *page, unsigned from, unsigned to)
2307 struct inode *inode = page->mapping->host;
2308 __block_commit_write(inode,page,from,to);
2309 return 0;
2311 EXPORT_SYMBOL(block_commit_write);
2314 * block_page_mkwrite() is not allowed to change the file size as it gets
2315 * called from a page fault handler when a page is first dirtied. Hence we must
2316 * be careful to check for EOF conditions here. We set the page up correctly
2317 * for a written page which means we get ENOSPC checking when writing into
2318 * holes and correct delalloc and unwritten extent mapping on filesystems that
2319 * support these features.
2321 * We are not allowed to take the i_mutex here so we have to play games to
2322 * protect against truncate races as the page could now be beyond EOF. Because
2323 * truncate writes the inode size before removing pages, once we have the
2324 * page lock we can determine safely if the page is beyond EOF. If it is not
2325 * beyond EOF, then the page is guaranteed safe against truncation until we
2326 * unlock the page.
2328 * Direct callers of this function should protect against filesystem freezing
2329 * using sb_start_write() - sb_end_write() functions.
2331 int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2332 get_block_t get_block)
2334 struct page *page = vmf->page;
2335 struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
2336 unsigned long end;
2337 loff_t size;
2338 int ret;
2340 lock_page(page);
2341 size = i_size_read(inode);
2342 if ((page->mapping != inode->i_mapping) ||
2343 (page_offset(page) > size)) {
2344 /* We overload EFAULT to mean page got truncated */
2345 ret = -EFAULT;
2346 goto out_unlock;
2349 /* page is wholly or partially inside EOF */
2350 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
2351 end = size & ~PAGE_CACHE_MASK;
2352 else
2353 end = PAGE_CACHE_SIZE;
2355 ret = __block_write_begin(page, 0, end, get_block);
2356 if (!ret)
2357 ret = block_commit_write(page, 0, end);
2359 if (unlikely(ret < 0))
2360 goto out_unlock;
2361 set_page_dirty(page);
2362 wait_on_page_writeback(page);
2363 return 0;
2364 out_unlock:
2365 unlock_page(page);
2366 return ret;
2368 EXPORT_SYMBOL(__block_page_mkwrite);
2370 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2371 get_block_t get_block)
2373 int ret;
2374 struct super_block *sb = vma->vm_file->f_path.dentry->d_inode->i_sb;
2376 sb_start_pagefault(sb);
2379 * Update file times before taking page lock. We may end up failing the
2380 * fault so this update may be superfluous but who really cares...
2382 file_update_time(vma->vm_file);
2384 ret = __block_page_mkwrite(vma, vmf, get_block);
2385 sb_end_pagefault(sb);
2386 return block_page_mkwrite_return(ret);
2388 EXPORT_SYMBOL(block_page_mkwrite);
2391 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
2392 * immediately, while under the page lock. So it needs a special end_io
2393 * handler which does not touch the bh after unlocking it.
2395 static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2397 __end_buffer_read_notouch(bh, uptodate);
2401 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2402 * the page (converting it to circular linked list and taking care of page
2403 * dirty races).
2405 static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2407 struct buffer_head *bh;
2409 BUG_ON(!PageLocked(page));
2411 spin_lock(&page->mapping->private_lock);
2412 bh = head;
2413 do {
2414 if (PageDirty(page))
2415 set_buffer_dirty(bh);
2416 if (!bh->b_this_page)
2417 bh->b_this_page = head;
2418 bh = bh->b_this_page;
2419 } while (bh != head);
2420 attach_page_buffers(page, head);
2421 spin_unlock(&page->mapping->private_lock);
2425 * On entry, the page is fully not uptodate.
2426 * On exit the page is fully uptodate in the areas outside (from,to)
2427 * The filesystem needs to handle block truncation upon failure.
2429 int nobh_write_begin(struct address_space *mapping,
2430 loff_t pos, unsigned len, unsigned flags,
2431 struct page **pagep, void **fsdata,
2432 get_block_t *get_block)
2434 struct inode *inode = mapping->host;
2435 const unsigned blkbits = inode->i_blkbits;
2436 const unsigned blocksize = 1 << blkbits;
2437 struct buffer_head *head, *bh;
2438 struct page *page;
2439 pgoff_t index;
2440 unsigned from, to;
2441 unsigned block_in_page;
2442 unsigned block_start, block_end;
2443 sector_t block_in_file;
2444 int nr_reads = 0;
2445 int ret = 0;
2446 int is_mapped_to_disk = 1;
2448 index = pos >> PAGE_CACHE_SHIFT;
2449 from = pos & (PAGE_CACHE_SIZE - 1);
2450 to = from + len;
2452 page = grab_cache_page_write_begin(mapping, index, flags);
2453 if (!page)
2454 return -ENOMEM;
2455 *pagep = page;
2456 *fsdata = NULL;
2458 if (page_has_buffers(page)) {
2459 ret = __block_write_begin(page, pos, len, get_block);
2460 if (unlikely(ret))
2461 goto out_release;
2462 return ret;
2465 if (PageMappedToDisk(page))
2466 return 0;
2469 * Allocate buffers so that we can keep track of state, and potentially
2470 * attach them to the page if an error occurs. In the common case of
2471 * no error, they will just be freed again without ever being attached
2472 * to the page (which is all OK, because we're under the page lock).
2474 * Be careful: the buffer linked list is a NULL terminated one, rather
2475 * than the circular one we're used to.
2477 head = alloc_page_buffers(page, blocksize, 0);
2478 if (!head) {
2479 ret = -ENOMEM;
2480 goto out_release;
2483 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
2486 * We loop across all blocks in the page, whether or not they are
2487 * part of the affected region. This is so we can discover if the
2488 * page is fully mapped-to-disk.
2490 for (block_start = 0, block_in_page = 0, bh = head;
2491 block_start < PAGE_CACHE_SIZE;
2492 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
2493 int create;
2495 block_end = block_start + blocksize;
2496 bh->b_state = 0;
2497 create = 1;
2498 if (block_start >= to)
2499 create = 0;
2500 ret = get_block(inode, block_in_file + block_in_page,
2501 bh, create);
2502 if (ret)
2503 goto failed;
2504 if (!buffer_mapped(bh))
2505 is_mapped_to_disk = 0;
2506 if (buffer_new(bh))
2507 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
2508 if (PageUptodate(page)) {
2509 set_buffer_uptodate(bh);
2510 continue;
2512 if (buffer_new(bh) || !buffer_mapped(bh)) {
2513 zero_user_segments(page, block_start, from,
2514 to, block_end);
2515 continue;
2517 if (buffer_uptodate(bh))
2518 continue; /* reiserfs does this */
2519 if (block_start < from || block_end > to) {
2520 lock_buffer(bh);
2521 bh->b_end_io = end_buffer_read_nobh;
2522 submit_bh(READ, bh);
2523 nr_reads++;
2527 if (nr_reads) {
2529 * The page is locked, so these buffers are protected from
2530 * any VM or truncate activity. Hence we don't need to care
2531 * for the buffer_head refcounts.
2533 for (bh = head; bh; bh = bh->b_this_page) {
2534 wait_on_buffer(bh);
2535 if (!buffer_uptodate(bh))
2536 ret = -EIO;
2538 if (ret)
2539 goto failed;
2542 if (is_mapped_to_disk)
2543 SetPageMappedToDisk(page);
2545 *fsdata = head; /* to be released by nobh_write_end */
2547 return 0;
2549 failed:
2550 BUG_ON(!ret);
2552 * Error recovery is a bit difficult. We need to zero out blocks that
2553 * were newly allocated, and dirty them to ensure they get written out.
2554 * Buffers need to be attached to the page at this point, otherwise
2555 * the handling of potential IO errors during writeout would be hard
2556 * (could try doing synchronous writeout, but what if that fails too?)
2558 attach_nobh_buffers(page, head);
2559 page_zero_new_buffers(page, from, to);
2561 out_release:
2562 unlock_page(page);
2563 page_cache_release(page);
2564 *pagep = NULL;
2566 return ret;
2568 EXPORT_SYMBOL(nobh_write_begin);
2570 int nobh_write_end(struct file *file, struct address_space *mapping,
2571 loff_t pos, unsigned len, unsigned copied,
2572 struct page *page, void *fsdata)
2574 struct inode *inode = page->mapping->host;
2575 struct buffer_head *head = fsdata;
2576 struct buffer_head *bh;
2577 BUG_ON(fsdata != NULL && page_has_buffers(page));
2579 if (unlikely(copied < len) && head)
2580 attach_nobh_buffers(page, head);
2581 if (page_has_buffers(page))
2582 return generic_write_end(file, mapping, pos, len,
2583 copied, page, fsdata);
2585 SetPageUptodate(page);
2586 set_page_dirty(page);
2587 if (pos+copied > inode->i_size) {
2588 i_size_write(inode, pos+copied);
2589 mark_inode_dirty(inode);
2592 unlock_page(page);
2593 page_cache_release(page);
2595 while (head) {
2596 bh = head;
2597 head = head->b_this_page;
2598 free_buffer_head(bh);
2601 return copied;
2603 EXPORT_SYMBOL(nobh_write_end);
2606 * nobh_writepage() - based on block_full_write_page() except
2607 * that it tries to operate without attaching bufferheads to
2608 * the page.
2610 int nobh_writepage(struct page *page, get_block_t *get_block,
2611 struct writeback_control *wbc)
2613 struct inode * const inode = page->mapping->host;
2614 loff_t i_size = i_size_read(inode);
2615 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2616 unsigned offset;
2617 int ret;
2619 /* Is the page fully inside i_size? */
2620 if (page->index < end_index)
2621 goto out;
2623 /* Is the page fully outside i_size? (truncate in progress) */
2624 offset = i_size & (PAGE_CACHE_SIZE-1);
2625 if (page->index >= end_index+1 || !offset) {
2627 * The page may have dirty, unmapped buffers. For example,
2628 * they may have been added in ext3_writepage(). Make them
2629 * freeable here, so the page does not leak.
2631 #if 0
2632 /* Not really sure about this - do we need this ? */
2633 if (page->mapping->a_ops->invalidatepage)
2634 page->mapping->a_ops->invalidatepage(page, offset);
2635 #endif
2636 unlock_page(page);
2637 return 0; /* don't care */
2641 * The page straddles i_size. It must be zeroed out on each and every
2642 * writepage invocation because it may be mmapped. "A file is mapped
2643 * in multiples of the page size. For a file that is not a multiple of
2644 * the page size, the remaining memory is zeroed when mapped, and
2645 * writes to that region are not written out to the file."
2647 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2648 out:
2649 ret = mpage_writepage(page, get_block, wbc);
2650 if (ret == -EAGAIN)
2651 ret = __block_write_full_page(inode, page, get_block, wbc,
2652 end_buffer_async_write);
2653 return ret;
2655 EXPORT_SYMBOL(nobh_writepage);
2657 int nobh_truncate_page(struct address_space *mapping,
2658 loff_t from, get_block_t *get_block)
2660 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2661 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2662 unsigned blocksize;
2663 sector_t iblock;
2664 unsigned length, pos;
2665 struct inode *inode = mapping->host;
2666 struct page *page;
2667 struct buffer_head map_bh;
2668 int err;
2670 blocksize = 1 << inode->i_blkbits;
2671 length = offset & (blocksize - 1);
2673 /* Block boundary? Nothing to do */
2674 if (!length)
2675 return 0;
2677 length = blocksize - length;
2678 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2680 page = grab_cache_page(mapping, index);
2681 err = -ENOMEM;
2682 if (!page)
2683 goto out;
2685 if (page_has_buffers(page)) {
2686 has_buffers:
2687 unlock_page(page);
2688 page_cache_release(page);
2689 return block_truncate_page(mapping, from, get_block);
2692 /* Find the buffer that contains "offset" */
2693 pos = blocksize;
2694 while (offset >= pos) {
2695 iblock++;
2696 pos += blocksize;
2699 map_bh.b_size = blocksize;
2700 map_bh.b_state = 0;
2701 err = get_block(inode, iblock, &map_bh, 0);
2702 if (err)
2703 goto unlock;
2704 /* unmapped? It's a hole - nothing to do */
2705 if (!buffer_mapped(&map_bh))
2706 goto unlock;
2708 /* Ok, it's mapped. Make sure it's up-to-date */
2709 if (!PageUptodate(page)) {
2710 err = mapping->a_ops->readpage(NULL, page);
2711 if (err) {
2712 page_cache_release(page);
2713 goto out;
2715 lock_page(page);
2716 if (!PageUptodate(page)) {
2717 err = -EIO;
2718 goto unlock;
2720 if (page_has_buffers(page))
2721 goto has_buffers;
2723 zero_user(page, offset, length);
2724 set_page_dirty(page);
2725 err = 0;
2727 unlock:
2728 unlock_page(page);
2729 page_cache_release(page);
2730 out:
2731 return err;
2733 EXPORT_SYMBOL(nobh_truncate_page);
2735 int block_truncate_page(struct address_space *mapping,
2736 loff_t from, get_block_t *get_block)
2738 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2739 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2740 unsigned blocksize;
2741 sector_t iblock;
2742 unsigned length, pos;
2743 struct inode *inode = mapping->host;
2744 struct page *page;
2745 struct buffer_head *bh;
2746 int err;
2748 blocksize = 1 << inode->i_blkbits;
2749 length = offset & (blocksize - 1);
2751 /* Block boundary? Nothing to do */
2752 if (!length)
2753 return 0;
2755 length = blocksize - length;
2756 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2758 page = grab_cache_page(mapping, index);
2759 err = -ENOMEM;
2760 if (!page)
2761 goto out;
2763 if (!page_has_buffers(page))
2764 create_empty_buffers(page, blocksize, 0);
2766 /* Find the buffer that contains "offset" */
2767 bh = page_buffers(page);
2768 pos = blocksize;
2769 while (offset >= pos) {
2770 bh = bh->b_this_page;
2771 iblock++;
2772 pos += blocksize;
2775 err = 0;
2776 if (!buffer_mapped(bh)) {
2777 WARN_ON(bh->b_size != blocksize);
2778 err = get_block(inode, iblock, bh, 0);
2779 if (err)
2780 goto unlock;
2781 /* unmapped? It's a hole - nothing to do */
2782 if (!buffer_mapped(bh))
2783 goto unlock;
2786 /* Ok, it's mapped. Make sure it's up-to-date */
2787 if (PageUptodate(page))
2788 set_buffer_uptodate(bh);
2790 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2791 err = -EIO;
2792 ll_rw_block(READ, 1, &bh);
2793 wait_on_buffer(bh);
2794 /* Uhhuh. Read error. Complain and punt. */
2795 if (!buffer_uptodate(bh))
2796 goto unlock;
2799 zero_user(page, offset, length);
2800 mark_buffer_dirty(bh);
2801 err = 0;
2803 unlock:
2804 unlock_page(page);
2805 page_cache_release(page);
2806 out:
2807 return err;
2809 EXPORT_SYMBOL(block_truncate_page);
2812 * The generic ->writepage function for buffer-backed address_spaces
2813 * this form passes in the end_io handler used to finish the IO.
2815 int block_write_full_page_endio(struct page *page, get_block_t *get_block,
2816 struct writeback_control *wbc, bh_end_io_t *handler)
2818 struct inode * const inode = page->mapping->host;
2819 loff_t i_size = i_size_read(inode);
2820 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2821 unsigned offset;
2823 /* Is the page fully inside i_size? */
2824 if (page->index < end_index)
2825 return __block_write_full_page(inode, page, get_block, wbc,
2826 handler);
2828 /* Is the page fully outside i_size? (truncate in progress) */
2829 offset = i_size & (PAGE_CACHE_SIZE-1);
2830 if (page->index >= end_index+1 || !offset) {
2832 * The page may have dirty, unmapped buffers. For example,
2833 * they may have been added in ext3_writepage(). Make them
2834 * freeable here, so the page does not leak.
2836 do_invalidatepage(page, 0);
2837 unlock_page(page);
2838 return 0; /* don't care */
2842 * The page straddles i_size. It must be zeroed out on each and every
2843 * writepage invocation because it may be mmapped. "A file is mapped
2844 * in multiples of the page size. For a file that is not a multiple of
2845 * the page size, the remaining memory is zeroed when mapped, and
2846 * writes to that region are not written out to the file."
2848 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2849 return __block_write_full_page(inode, page, get_block, wbc, handler);
2851 EXPORT_SYMBOL(block_write_full_page_endio);
2854 * The generic ->writepage function for buffer-backed address_spaces
2856 int block_write_full_page(struct page *page, get_block_t *get_block,
2857 struct writeback_control *wbc)
2859 return block_write_full_page_endio(page, get_block, wbc,
2860 end_buffer_async_write);
2862 EXPORT_SYMBOL(block_write_full_page);
2864 sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2865 get_block_t *get_block)
2867 struct buffer_head tmp;
2868 struct inode *inode = mapping->host;
2869 tmp.b_state = 0;
2870 tmp.b_blocknr = 0;
2871 tmp.b_size = 1 << inode->i_blkbits;
2872 get_block(inode, block, &tmp, 0);
2873 return tmp.b_blocknr;
2875 EXPORT_SYMBOL(generic_block_bmap);
2877 static void end_bio_bh_io_sync(struct bio *bio, int err)
2879 struct buffer_head *bh = bio->bi_private;
2881 if (err == -EOPNOTSUPP) {
2882 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
2885 if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags)))
2886 set_bit(BH_Quiet, &bh->b_state);
2888 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2889 bio_put(bio);
2893 * This allows us to do IO even on the odd last sectors
2894 * of a device, even if the bh block size is some multiple
2895 * of the physical sector size.
2897 * We'll just truncate the bio to the size of the device,
2898 * and clear the end of the buffer head manually.
2900 * Truly out-of-range accesses will turn into actual IO
2901 * errors, this only handles the "we need to be able to
2902 * do IO at the final sector" case.
2904 static void guard_bh_eod(int rw, struct bio *bio, struct buffer_head *bh)
2906 sector_t maxsector;
2907 unsigned bytes;
2909 maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
2910 if (!maxsector)
2911 return;
2914 * If the *whole* IO is past the end of the device,
2915 * let it through, and the IO layer will turn it into
2916 * an EIO.
2918 if (unlikely(bio->bi_sector >= maxsector))
2919 return;
2921 maxsector -= bio->bi_sector;
2922 bytes = bio->bi_size;
2923 if (likely((bytes >> 9) <= maxsector))
2924 return;
2926 /* Uhhuh. We've got a bh that straddles the device size! */
2927 bytes = maxsector << 9;
2929 /* Truncate the bio.. */
2930 bio->bi_size = bytes;
2931 bio->bi_io_vec[0].bv_len = bytes;
2933 /* ..and clear the end of the buffer for reads */
2934 if ((rw & RW_MASK) == READ) {
2935 void *kaddr = kmap_atomic(bh->b_page);
2936 memset(kaddr + bh_offset(bh) + bytes, 0, bh->b_size - bytes);
2937 kunmap_atomic(kaddr);
2941 int submit_bh(int rw, struct buffer_head * bh)
2943 struct bio *bio;
2944 int ret = 0;
2946 BUG_ON(!buffer_locked(bh));
2947 BUG_ON(!buffer_mapped(bh));
2948 BUG_ON(!bh->b_end_io);
2949 BUG_ON(buffer_delay(bh));
2950 BUG_ON(buffer_unwritten(bh));
2953 * Only clear out a write error when rewriting
2955 if (test_set_buffer_req(bh) && (rw & WRITE))
2956 clear_buffer_write_io_error(bh);
2959 * from here on down, it's all bio -- do the initial mapping,
2960 * submit_bio -> generic_make_request may further map this bio around
2962 bio = bio_alloc(GFP_NOIO, 1);
2964 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2965 bio->bi_bdev = bh->b_bdev;
2966 bio->bi_io_vec[0].bv_page = bh->b_page;
2967 bio->bi_io_vec[0].bv_len = bh->b_size;
2968 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
2970 bio->bi_vcnt = 1;
2971 bio->bi_idx = 0;
2972 bio->bi_size = bh->b_size;
2974 bio->bi_end_io = end_bio_bh_io_sync;
2975 bio->bi_private = bh;
2977 /* Take care of bh's that straddle the end of the device */
2978 guard_bh_eod(rw, bio, bh);
2980 bio_get(bio);
2981 submit_bio(rw, bio);
2983 if (bio_flagged(bio, BIO_EOPNOTSUPP))
2984 ret = -EOPNOTSUPP;
2986 bio_put(bio);
2987 return ret;
2989 EXPORT_SYMBOL(submit_bh);
2992 * ll_rw_block: low-level access to block devices (DEPRECATED)
2993 * @rw: whether to %READ or %WRITE or maybe %READA (readahead)
2994 * @nr: number of &struct buffer_heads in the array
2995 * @bhs: array of pointers to &struct buffer_head
2997 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
2998 * requests an I/O operation on them, either a %READ or a %WRITE. The third
2999 * %READA option is described in the documentation for generic_make_request()
3000 * which ll_rw_block() calls.
3002 * This function drops any buffer that it cannot get a lock on (with the
3003 * BH_Lock state bit), any buffer that appears to be clean when doing a write
3004 * request, and any buffer that appears to be up-to-date when doing read
3005 * request. Further it marks as clean buffers that are processed for
3006 * writing (the buffer cache won't assume that they are actually clean
3007 * until the buffer gets unlocked).
3009 * ll_rw_block sets b_end_io to simple completion handler that marks
3010 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
3011 * any waiters.
3013 * All of the buffers must be for the same device, and must also be a
3014 * multiple of the current approved size for the device.
3016 void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
3018 int i;
3020 for (i = 0; i < nr; i++) {
3021 struct buffer_head *bh = bhs[i];
3023 if (!trylock_buffer(bh))
3024 continue;
3025 if (rw == WRITE) {
3026 if (test_clear_buffer_dirty(bh)) {
3027 bh->b_end_io = end_buffer_write_sync;
3028 get_bh(bh);
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);
3043 EXPORT_SYMBOL(ll_rw_block);
3045 void write_dirty_buffer(struct buffer_head *bh, int rw)
3047 lock_buffer(bh);
3048 if (!test_clear_buffer_dirty(bh)) {
3049 unlock_buffer(bh);
3050 return;
3052 bh->b_end_io = end_buffer_write_sync;
3053 get_bh(bh);
3054 submit_bh(rw, bh);
3056 EXPORT_SYMBOL(write_dirty_buffer);
3059 * For a data-integrity writeout, we need to wait upon any in-progress I/O
3060 * and then start new I/O and then wait upon it. The caller must have a ref on
3061 * the buffer_head.
3063 int __sync_dirty_buffer(struct buffer_head *bh, int rw)
3065 int ret = 0;
3067 WARN_ON(atomic_read(&bh->b_count) < 1);
3068 lock_buffer(bh);
3069 if (test_clear_buffer_dirty(bh)) {
3070 get_bh(bh);
3071 bh->b_end_io = end_buffer_write_sync;
3072 ret = submit_bh(rw, bh);
3073 wait_on_buffer(bh);
3074 if (!ret && !buffer_uptodate(bh))
3075 ret = -EIO;
3076 } else {
3077 unlock_buffer(bh);
3079 return ret;
3081 EXPORT_SYMBOL(__sync_dirty_buffer);
3083 int sync_dirty_buffer(struct buffer_head *bh)
3085 return __sync_dirty_buffer(bh, WRITE_SYNC);
3087 EXPORT_SYMBOL(sync_dirty_buffer);
3090 * try_to_free_buffers() checks if all the buffers on this particular page
3091 * are unused, and releases them if so.
3093 * Exclusion against try_to_free_buffers may be obtained by either
3094 * locking the page or by holding its mapping's private_lock.
3096 * If the page is dirty but all the buffers are clean then we need to
3097 * be sure to mark the page clean as well. This is because the page
3098 * may be against a block device, and a later reattachment of buffers
3099 * to a dirty page will set *all* buffers dirty. Which would corrupt
3100 * filesystem data on the same device.
3102 * The same applies to regular filesystem pages: if all the buffers are
3103 * clean then we set the page clean and proceed. To do that, we require
3104 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3105 * private_lock.
3107 * try_to_free_buffers() is non-blocking.
3109 static inline int buffer_busy(struct buffer_head *bh)
3111 return atomic_read(&bh->b_count) |
3112 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3115 static int
3116 drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3118 struct buffer_head *head = page_buffers(page);
3119 struct buffer_head *bh;
3121 bh = head;
3122 do {
3123 if (buffer_write_io_error(bh) && page->mapping)
3124 set_bit(AS_EIO, &page->mapping->flags);
3125 if (buffer_busy(bh))
3126 goto failed;
3127 bh = bh->b_this_page;
3128 } while (bh != head);
3130 do {
3131 struct buffer_head *next = bh->b_this_page;
3133 if (bh->b_assoc_map)
3134 __remove_assoc_queue(bh);
3135 bh = next;
3136 } while (bh != head);
3137 *buffers_to_free = head;
3138 __clear_page_buffers(page);
3139 return 1;
3140 failed:
3141 return 0;
3144 int try_to_free_buffers(struct page *page)
3146 struct address_space * const mapping = page->mapping;
3147 struct buffer_head *buffers_to_free = NULL;
3148 int ret = 0;
3150 BUG_ON(!PageLocked(page));
3151 if (PageWriteback(page))
3152 return 0;
3154 if (mapping == NULL) { /* can this still happen? */
3155 ret = drop_buffers(page, &buffers_to_free);
3156 goto out;
3159 spin_lock(&mapping->private_lock);
3160 ret = drop_buffers(page, &buffers_to_free);
3163 * If the filesystem writes its buffers by hand (eg ext3)
3164 * then we can have clean buffers against a dirty page. We
3165 * clean the page here; otherwise the VM will never notice
3166 * that the filesystem did any IO at all.
3168 * Also, during truncate, discard_buffer will have marked all
3169 * the page's buffers clean. We discover that here and clean
3170 * the page also.
3172 * private_lock must be held over this entire operation in order
3173 * to synchronise against __set_page_dirty_buffers and prevent the
3174 * dirty bit from being lost.
3176 if (ret)
3177 cancel_dirty_page(page, PAGE_CACHE_SIZE);
3178 spin_unlock(&mapping->private_lock);
3179 out:
3180 if (buffers_to_free) {
3181 struct buffer_head *bh = buffers_to_free;
3183 do {
3184 struct buffer_head *next = bh->b_this_page;
3185 free_buffer_head(bh);
3186 bh = next;
3187 } while (bh != buffers_to_free);
3189 return ret;
3191 EXPORT_SYMBOL(try_to_free_buffers);
3194 * There are no bdflush tunables left. But distributions are
3195 * still running obsolete flush daemons, so we terminate them here.
3197 * Use of bdflush() is deprecated and will be removed in a future kernel.
3198 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
3200 SYSCALL_DEFINE2(bdflush, int, func, long, data)
3202 static int msg_count;
3204 if (!capable(CAP_SYS_ADMIN))
3205 return -EPERM;
3207 if (msg_count < 5) {
3208 msg_count++;
3209 printk(KERN_INFO
3210 "warning: process `%s' used the obsolete bdflush"
3211 " system call\n", current->comm);
3212 printk(KERN_INFO "Fix your initscripts?\n");
3215 if (func == 1)
3216 do_exit(0);
3217 return 0;
3221 * Buffer-head allocation
3223 static struct kmem_cache *bh_cachep __read_mostly;
3226 * Once the number of bh's in the machine exceeds this level, we start
3227 * stripping them in writeback.
3229 static int max_buffer_heads;
3231 int buffer_heads_over_limit;
3233 struct bh_accounting {
3234 int nr; /* Number of live bh's */
3235 int ratelimit; /* Limit cacheline bouncing */
3238 static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3240 static void recalc_bh_state(void)
3242 int i;
3243 int tot = 0;
3245 if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
3246 return;
3247 __this_cpu_write(bh_accounting.ratelimit, 0);
3248 for_each_online_cpu(i)
3249 tot += per_cpu(bh_accounting, i).nr;
3250 buffer_heads_over_limit = (tot > max_buffer_heads);
3253 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3255 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
3256 if (ret) {
3257 INIT_LIST_HEAD(&ret->b_assoc_buffers);
3258 preempt_disable();
3259 __this_cpu_inc(bh_accounting.nr);
3260 recalc_bh_state();
3261 preempt_enable();
3263 return ret;
3265 EXPORT_SYMBOL(alloc_buffer_head);
3267 void free_buffer_head(struct buffer_head *bh)
3269 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3270 kmem_cache_free(bh_cachep, bh);
3271 preempt_disable();
3272 __this_cpu_dec(bh_accounting.nr);
3273 recalc_bh_state();
3274 preempt_enable();
3276 EXPORT_SYMBOL(free_buffer_head);
3278 static void buffer_exit_cpu(int cpu)
3280 int i;
3281 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3283 for (i = 0; i < BH_LRU_SIZE; i++) {
3284 brelse(b->bhs[i]);
3285 b->bhs[i] = NULL;
3287 this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3288 per_cpu(bh_accounting, cpu).nr = 0;
3291 static int buffer_cpu_notify(struct notifier_block *self,
3292 unsigned long action, void *hcpu)
3294 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
3295 buffer_exit_cpu((unsigned long)hcpu);
3296 return NOTIFY_OK;
3300 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3301 * @bh: struct buffer_head
3303 * Return true if the buffer is up-to-date and false,
3304 * with the buffer locked, if not.
3306 int bh_uptodate_or_lock(struct buffer_head *bh)
3308 if (!buffer_uptodate(bh)) {
3309 lock_buffer(bh);
3310 if (!buffer_uptodate(bh))
3311 return 0;
3312 unlock_buffer(bh);
3314 return 1;
3316 EXPORT_SYMBOL(bh_uptodate_or_lock);
3319 * bh_submit_read - Submit a locked buffer for reading
3320 * @bh: struct buffer_head
3322 * Returns zero on success and -EIO on error.
3324 int bh_submit_read(struct buffer_head *bh)
3326 BUG_ON(!buffer_locked(bh));
3328 if (buffer_uptodate(bh)) {
3329 unlock_buffer(bh);
3330 return 0;
3333 get_bh(bh);
3334 bh->b_end_io = end_buffer_read_sync;
3335 submit_bh(READ, bh);
3336 wait_on_buffer(bh);
3337 if (buffer_uptodate(bh))
3338 return 0;
3339 return -EIO;
3341 EXPORT_SYMBOL(bh_submit_read);
3343 void __init buffer_init(void)
3345 int nrpages;
3347 bh_cachep = kmem_cache_create("buffer_head",
3348 sizeof(struct buffer_head), 0,
3349 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3350 SLAB_MEM_SPREAD),
3351 NULL);
3354 * Limit the bh occupancy to 10% of ZONE_NORMAL
3356 nrpages = (nr_free_buffer_pages() * 10) / 100;
3357 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3358 hotcpu_notifier(buffer_cpu_notify, 0);