4 * Copyright (C) 1991, 1992, 2002 Linus Torvalds
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>
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)
50 init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
52 bh->b_end_io = handler;
53 bh->b_private = private;
55 EXPORT_SYMBOL(init_buffer);
57 static int sleep_on_buffer(void *word)
63 void __lock_buffer(struct buffer_head *bh)
65 wait_on_bit_lock(&bh->b_state, BH_Lock, sleep_on_buffer,
66 TASK_UNINTERRUPTIBLE);
68 EXPORT_SYMBOL(__lock_buffer);
70 void unlock_buffer(struct buffer_head *bh)
72 clear_bit_unlock(BH_Lock, &bh->b_state);
73 smp_mb__after_clear_bit();
74 wake_up_bit(&bh->b_state, BH_Lock);
76 EXPORT_SYMBOL(unlock_buffer);
79 * Block until a buffer comes unlocked. This doesn't stop it
80 * from becoming locked again - you have to lock it yourself
81 * if you want to preserve its state.
83 void __wait_on_buffer(struct buffer_head * bh)
85 wait_on_bit(&bh->b_state, BH_Lock, sleep_on_buffer, TASK_UNINTERRUPTIBLE);
87 EXPORT_SYMBOL(__wait_on_buffer);
90 __clear_page_buffers(struct page *page)
92 ClearPagePrivate(page);
93 set_page_private(page, 0);
94 page_cache_release(page);
98 static int quiet_error(struct buffer_head *bh)
100 if (!test_bit(BH_Quiet, &bh->b_state) && printk_ratelimit())
106 static void buffer_io_error(struct buffer_head *bh)
108 char b[BDEVNAME_SIZE];
109 printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
110 bdevname(bh->b_bdev, b),
111 (unsigned long long)bh->b_blocknr);
115 * End-of-IO handler helper function which does not touch the bh after
117 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
118 * a race there is benign: unlock_buffer() only use the bh's address for
119 * hashing after unlocking the buffer, so it doesn't actually touch the bh
122 static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
125 set_buffer_uptodate(bh);
127 /* This happens, due to failed READA attempts. */
128 clear_buffer_uptodate(bh);
134 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
135 * unlock the buffer. This is what ll_rw_block uses too.
137 void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
139 __end_buffer_read_notouch(bh, uptodate);
142 EXPORT_SYMBOL(end_buffer_read_sync);
144 void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
146 char b[BDEVNAME_SIZE];
149 set_buffer_uptodate(bh);
151 if (!quiet_error(bh)) {
153 printk(KERN_WARNING "lost page write due to "
155 bdevname(bh->b_bdev, b));
157 set_buffer_write_io_error(bh);
158 clear_buffer_uptodate(bh);
163 EXPORT_SYMBOL(end_buffer_write_sync);
166 * Various filesystems appear to want __find_get_block to be non-blocking.
167 * But it's the page lock which protects the buffers. To get around this,
168 * we get exclusion from try_to_free_buffers with the blockdev mapping's
171 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
172 * may be quite high. This code could TryLock the page, and if that
173 * succeeds, there is no need to take private_lock. (But if
174 * private_lock is contended then so is mapping->tree_lock).
176 static struct buffer_head *
177 __find_get_block_slow(struct block_device *bdev, sector_t block)
179 struct inode *bd_inode = bdev->bd_inode;
180 struct address_space *bd_mapping = bd_inode->i_mapping;
181 struct buffer_head *ret = NULL;
183 struct buffer_head *bh;
184 struct buffer_head *head;
188 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
189 page = find_get_page(bd_mapping, index);
193 spin_lock(&bd_mapping->private_lock);
194 if (!page_has_buffers(page))
196 head = page_buffers(page);
199 if (!buffer_mapped(bh))
201 else if (bh->b_blocknr == block) {
206 bh = bh->b_this_page;
207 } while (bh != head);
209 /* we might be here because some of the buffers on this page are
210 * not mapped. This is due to various races between
211 * file io on the block device and getblk. It gets dealt with
212 * elsewhere, don't buffer_error if we had some unmapped buffers
215 char b[BDEVNAME_SIZE];
217 printk("__find_get_block_slow() failed. "
218 "block=%llu, b_blocknr=%llu\n",
219 (unsigned long long)block,
220 (unsigned long long)bh->b_blocknr);
221 printk("b_state=0x%08lx, b_size=%zu\n",
222 bh->b_state, bh->b_size);
223 printk("device %s blocksize: %d\n", bdevname(bdev, b),
224 1 << bd_inode->i_blkbits);
227 spin_unlock(&bd_mapping->private_lock);
228 page_cache_release(page);
234 * Kick the writeback threads then try to free up some ZONE_NORMAL memory.
236 static void free_more_memory(void)
241 wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM);
244 for_each_online_node(nid) {
245 (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS),
246 gfp_zone(GFP_NOFS), NULL,
249 try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0,
255 * I/O completion handler for block_read_full_page() - pages
256 * which come unlocked at the end of I/O.
258 static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
261 struct buffer_head *first;
262 struct buffer_head *tmp;
264 int page_uptodate = 1;
266 BUG_ON(!buffer_async_read(bh));
270 set_buffer_uptodate(bh);
272 clear_buffer_uptodate(bh);
273 if (!quiet_error(bh))
279 * Be _very_ careful from here on. Bad things can happen if
280 * two buffer heads end IO at almost the same time and both
281 * decide that the page is now completely done.
283 first = page_buffers(page);
284 local_irq_save(flags);
285 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
286 clear_buffer_async_read(bh);
290 if (!buffer_uptodate(tmp))
292 if (buffer_async_read(tmp)) {
293 BUG_ON(!buffer_locked(tmp));
296 tmp = tmp->b_this_page;
298 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
299 local_irq_restore(flags);
302 * If none of the buffers had errors and they are all
303 * uptodate then we can set the page uptodate.
305 if (page_uptodate && !PageError(page))
306 SetPageUptodate(page);
311 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
312 local_irq_restore(flags);
317 * Completion handler for block_write_full_page() - pages which are unlocked
318 * during I/O, and which have PageWriteback cleared upon I/O completion.
320 void end_buffer_async_write(struct buffer_head *bh, int uptodate)
322 char b[BDEVNAME_SIZE];
324 struct buffer_head *first;
325 struct buffer_head *tmp;
328 BUG_ON(!buffer_async_write(bh));
332 set_buffer_uptodate(bh);
334 if (!quiet_error(bh)) {
336 printk(KERN_WARNING "lost page write due to "
338 bdevname(bh->b_bdev, b));
340 set_bit(AS_EIO, &page->mapping->flags);
341 set_buffer_write_io_error(bh);
342 clear_buffer_uptodate(bh);
346 first = page_buffers(page);
347 local_irq_save(flags);
348 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
350 clear_buffer_async_write(bh);
352 tmp = bh->b_this_page;
354 if (buffer_async_write(tmp)) {
355 BUG_ON(!buffer_locked(tmp));
358 tmp = tmp->b_this_page;
360 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
361 local_irq_restore(flags);
362 end_page_writeback(page);
366 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
367 local_irq_restore(flags);
370 EXPORT_SYMBOL(end_buffer_async_write);
373 * If a page's buffers are under async readin (end_buffer_async_read
374 * completion) then there is a possibility that another thread of
375 * control could lock one of the buffers after it has completed
376 * but while some of the other buffers have not completed. This
377 * locked buffer would confuse end_buffer_async_read() into not unlocking
378 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
379 * that this buffer is not under async I/O.
381 * The page comes unlocked when it has no locked buffer_async buffers
384 * PageLocked prevents anyone starting new async I/O reads any of
387 * PageWriteback is used to prevent simultaneous writeout of the same
390 * PageLocked prevents anyone from starting writeback of a page which is
391 * under read I/O (PageWriteback is only ever set against a locked page).
393 static void mark_buffer_async_read(struct buffer_head *bh)
395 bh->b_end_io = end_buffer_async_read;
396 set_buffer_async_read(bh);
399 static void mark_buffer_async_write_endio(struct buffer_head *bh,
400 bh_end_io_t *handler)
402 bh->b_end_io = handler;
403 set_buffer_async_write(bh);
406 void mark_buffer_async_write(struct buffer_head *bh)
408 mark_buffer_async_write_endio(bh, end_buffer_async_write);
410 EXPORT_SYMBOL(mark_buffer_async_write);
414 * fs/buffer.c contains helper functions for buffer-backed address space's
415 * fsync functions. A common requirement for buffer-based filesystems is
416 * that certain data from the backing blockdev needs to be written out for
417 * a successful fsync(). For example, ext2 indirect blocks need to be
418 * written back and waited upon before fsync() returns.
420 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
421 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
422 * management of a list of dependent buffers at ->i_mapping->private_list.
424 * Locking is a little subtle: try_to_free_buffers() will remove buffers
425 * from their controlling inode's queue when they are being freed. But
426 * try_to_free_buffers() will be operating against the *blockdev* mapping
427 * at the time, not against the S_ISREG file which depends on those buffers.
428 * So the locking for private_list is via the private_lock in the address_space
429 * which backs the buffers. Which is different from the address_space
430 * against which the buffers are listed. So for a particular address_space,
431 * mapping->private_lock does *not* protect mapping->private_list! In fact,
432 * mapping->private_list will always be protected by the backing blockdev's
435 * Which introduces a requirement: all buffers on an address_space's
436 * ->private_list must be from the same address_space: the blockdev's.
438 * address_spaces which do not place buffers at ->private_list via these
439 * utility functions are free to use private_lock and private_list for
440 * whatever they want. The only requirement is that list_empty(private_list)
441 * be true at clear_inode() time.
443 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
444 * filesystems should do that. invalidate_inode_buffers() should just go
445 * BUG_ON(!list_empty).
447 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
448 * take an address_space, not an inode. And it should be called
449 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
452 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
453 * list if it is already on a list. Because if the buffer is on a list,
454 * it *must* already be on the right one. If not, the filesystem is being
455 * silly. This will save a ton of locking. But first we have to ensure
456 * that buffers are taken *off* the old inode's list when they are freed
457 * (presumably in truncate). That requires careful auditing of all
458 * filesystems (do it inside bforget()). It could also be done by bringing
463 * The buffer's backing address_space's private_lock must be held
465 static void __remove_assoc_queue(struct buffer_head *bh)
467 list_del_init(&bh->b_assoc_buffers);
468 WARN_ON(!bh->b_assoc_map);
469 if (buffer_write_io_error(bh))
470 set_bit(AS_EIO, &bh->b_assoc_map->flags);
471 bh->b_assoc_map = NULL;
474 int inode_has_buffers(struct inode *inode)
476 return !list_empty(&inode->i_data.private_list);
480 * osync is designed to support O_SYNC io. It waits synchronously for
481 * all already-submitted IO to complete, but does not queue any new
482 * writes to the disk.
484 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
485 * you dirty the buffers, and then use osync_inode_buffers to wait for
486 * completion. Any other dirty buffers which are not yet queued for
487 * write will not be flushed to disk by the osync.
489 static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
491 struct buffer_head *bh;
497 list_for_each_prev(p, list) {
499 if (buffer_locked(bh)) {
503 if (!buffer_uptodate(bh))
514 static void do_thaw_one(struct super_block *sb, void *unused)
516 char b[BDEVNAME_SIZE];
517 while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
518 printk(KERN_WARNING "Emergency Thaw on %s\n",
519 bdevname(sb->s_bdev, b));
522 static void do_thaw_all(struct work_struct *work)
524 iterate_supers(do_thaw_one, NULL);
526 printk(KERN_WARNING "Emergency Thaw complete\n");
530 * emergency_thaw_all -- forcibly thaw every frozen filesystem
532 * Used for emergency unfreeze of all filesystems via SysRq
534 void emergency_thaw_all(void)
536 struct work_struct *work;
538 work = kmalloc(sizeof(*work), GFP_ATOMIC);
540 INIT_WORK(work, do_thaw_all);
546 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
547 * @mapping: the mapping which wants those buffers written
549 * Starts I/O against the buffers at mapping->private_list, and waits upon
552 * Basically, this is a convenience function for fsync().
553 * @mapping is a file or directory which needs those buffers to be written for
554 * a successful fsync().
556 int sync_mapping_buffers(struct address_space *mapping)
558 struct address_space *buffer_mapping = mapping->assoc_mapping;
560 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
563 return fsync_buffers_list(&buffer_mapping->private_lock,
564 &mapping->private_list);
566 EXPORT_SYMBOL(sync_mapping_buffers);
569 * Called when we've recently written block `bblock', and it is known that
570 * `bblock' was for a buffer_boundary() buffer. This means that the block at
571 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
572 * dirty, schedule it for IO. So that indirects merge nicely with their data.
574 void write_boundary_block(struct block_device *bdev,
575 sector_t bblock, unsigned blocksize)
577 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
579 if (buffer_dirty(bh))
580 ll_rw_block(WRITE, 1, &bh);
585 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
587 struct address_space *mapping = inode->i_mapping;
588 struct address_space *buffer_mapping = bh->b_page->mapping;
590 mark_buffer_dirty(bh);
591 if (!mapping->assoc_mapping) {
592 mapping->assoc_mapping = buffer_mapping;
594 BUG_ON(mapping->assoc_mapping != buffer_mapping);
596 if (!bh->b_assoc_map) {
597 spin_lock(&buffer_mapping->private_lock);
598 list_move_tail(&bh->b_assoc_buffers,
599 &mapping->private_list);
600 bh->b_assoc_map = mapping;
601 spin_unlock(&buffer_mapping->private_lock);
604 EXPORT_SYMBOL(mark_buffer_dirty_inode);
607 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
610 * If warn is true, then emit a warning if the page is not uptodate and has
611 * not been truncated.
613 static void __set_page_dirty(struct page *page,
614 struct address_space *mapping, int warn)
616 spin_lock_irq(&mapping->tree_lock);
617 if (page->mapping) { /* Race with truncate? */
618 WARN_ON_ONCE(warn && !PageUptodate(page));
619 account_page_dirtied(page, mapping);
620 radix_tree_tag_set(&mapping->page_tree,
621 page_index(page), PAGECACHE_TAG_DIRTY);
623 spin_unlock_irq(&mapping->tree_lock);
624 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
628 * Add a page to the dirty page list.
630 * It is a sad fact of life that this function is called from several places
631 * deeply under spinlocking. It may not sleep.
633 * If the page has buffers, the uptodate buffers are set dirty, to preserve
634 * dirty-state coherency between the page and the buffers. It the page does
635 * not have buffers then when they are later attached they will all be set
638 * The buffers are dirtied before the page is dirtied. There's a small race
639 * window in which a writepage caller may see the page cleanness but not the
640 * buffer dirtiness. That's fine. If this code were to set the page dirty
641 * before the buffers, a concurrent writepage caller could clear the page dirty
642 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
643 * page on the dirty page list.
645 * We use private_lock to lock against try_to_free_buffers while using the
646 * page's buffer list. Also use this to protect against clean buffers being
647 * added to the page after it was set dirty.
649 * FIXME: may need to call ->reservepage here as well. That's rather up to the
650 * address_space though.
652 int __set_page_dirty_buffers(struct page *page)
655 struct address_space *mapping = page_mapping(page);
657 if (unlikely(!mapping))
658 return !TestSetPageDirty(page);
660 spin_lock(&mapping->private_lock);
661 if (page_has_buffers(page)) {
662 struct buffer_head *head = page_buffers(page);
663 struct buffer_head *bh = head;
666 set_buffer_dirty(bh);
667 bh = bh->b_this_page;
668 } while (bh != head);
670 newly_dirty = !TestSetPageDirty(page);
671 spin_unlock(&mapping->private_lock);
674 __set_page_dirty(page, mapping, 1);
677 EXPORT_SYMBOL(__set_page_dirty_buffers);
680 * Write out and wait upon a list of buffers.
682 * We have conflicting pressures: we want to make sure that all
683 * initially dirty buffers get waited on, but that any subsequently
684 * dirtied buffers don't. After all, we don't want fsync to last
685 * forever if somebody is actively writing to the file.
687 * Do this in two main stages: first we copy dirty buffers to a
688 * temporary inode list, queueing the writes as we go. Then we clean
689 * up, waiting for those writes to complete.
691 * During this second stage, any subsequent updates to the file may end
692 * up refiling the buffer on the original inode's dirty list again, so
693 * there is a chance we will end up with a buffer queued for write but
694 * not yet completed on that list. So, as a final cleanup we go through
695 * the osync code to catch these locked, dirty buffers without requeuing
696 * any newly dirty buffers for write.
698 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
700 struct buffer_head *bh;
701 struct list_head tmp;
702 struct address_space *mapping;
704 struct blk_plug plug;
706 INIT_LIST_HEAD(&tmp);
707 blk_start_plug(&plug);
710 while (!list_empty(list)) {
711 bh = BH_ENTRY(list->next);
712 mapping = bh->b_assoc_map;
713 __remove_assoc_queue(bh);
714 /* Avoid race with mark_buffer_dirty_inode() which does
715 * a lockless check and we rely on seeing the dirty bit */
717 if (buffer_dirty(bh) || buffer_locked(bh)) {
718 list_add(&bh->b_assoc_buffers, &tmp);
719 bh->b_assoc_map = mapping;
720 if (buffer_dirty(bh)) {
724 * Ensure any pending I/O completes so that
725 * write_dirty_buffer() actually writes the
726 * current contents - it is a noop if I/O is
727 * still in flight on potentially older
730 write_dirty_buffer(bh, WRITE_SYNC);
733 * Kick off IO for the previous mapping. Note
734 * that we will not run the very last mapping,
735 * wait_on_buffer() will do that for us
736 * through sync_buffer().
745 blk_finish_plug(&plug);
748 while (!list_empty(&tmp)) {
749 bh = BH_ENTRY(tmp.prev);
751 mapping = bh->b_assoc_map;
752 __remove_assoc_queue(bh);
753 /* Avoid race with mark_buffer_dirty_inode() which does
754 * a lockless check and we rely on seeing the dirty bit */
756 if (buffer_dirty(bh)) {
757 list_add(&bh->b_assoc_buffers,
758 &mapping->private_list);
759 bh->b_assoc_map = mapping;
763 if (!buffer_uptodate(bh))
770 err2 = osync_buffers_list(lock, list);
778 * Invalidate any and all dirty buffers on a given inode. We are
779 * probably unmounting the fs, but that doesn't mean we have already
780 * done a sync(). Just drop the buffers from the inode list.
782 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
783 * assumes that all the buffers are against the blockdev. Not true
786 void invalidate_inode_buffers(struct inode *inode)
788 if (inode_has_buffers(inode)) {
789 struct address_space *mapping = &inode->i_data;
790 struct list_head *list = &mapping->private_list;
791 struct address_space *buffer_mapping = mapping->assoc_mapping;
793 spin_lock(&buffer_mapping->private_lock);
794 while (!list_empty(list))
795 __remove_assoc_queue(BH_ENTRY(list->next));
796 spin_unlock(&buffer_mapping->private_lock);
799 EXPORT_SYMBOL(invalidate_inode_buffers);
802 * Remove any clean buffers from the inode's buffer list. This is called
803 * when we're trying to free the inode itself. Those buffers can pin it.
805 * Returns true if all buffers were removed.
807 int remove_inode_buffers(struct inode *inode)
811 if (inode_has_buffers(inode)) {
812 struct address_space *mapping = &inode->i_data;
813 struct list_head *list = &mapping->private_list;
814 struct address_space *buffer_mapping = mapping->assoc_mapping;
816 spin_lock(&buffer_mapping->private_lock);
817 while (!list_empty(list)) {
818 struct buffer_head *bh = BH_ENTRY(list->next);
819 if (buffer_dirty(bh)) {
823 __remove_assoc_queue(bh);
825 spin_unlock(&buffer_mapping->private_lock);
831 * Create the appropriate buffers when given a page for data area and
832 * the size of each buffer.. Use the bh->b_this_page linked list to
833 * follow the buffers created. Return NULL if unable to create more
836 * The retry flag is used to differentiate async IO (paging, swapping)
837 * which may not fail from ordinary buffer allocations.
839 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
842 struct buffer_head *bh, *head;
848 while ((offset -= size) >= 0) {
849 bh = alloc_buffer_head(GFP_NOFS);
854 bh->b_this_page = head;
859 atomic_set(&bh->b_count, 0);
862 /* Link the buffer to its page */
863 set_bh_page(bh, page, offset);
865 init_buffer(bh, NULL, NULL);
869 * In case anything failed, we just free everything we got.
875 head = head->b_this_page;
876 free_buffer_head(bh);
881 * Return failure for non-async IO requests. Async IO requests
882 * are not allowed to fail, so we have to wait until buffer heads
883 * become available. But we don't want tasks sleeping with
884 * partially complete buffers, so all were released above.
889 /* We're _really_ low on memory. Now we just
890 * wait for old buffer heads to become free due to
891 * finishing IO. Since this is an async request and
892 * the reserve list is empty, we're sure there are
893 * async buffer heads in use.
898 EXPORT_SYMBOL_GPL(alloc_page_buffers);
901 link_dev_buffers(struct page *page, struct buffer_head *head)
903 struct buffer_head *bh, *tail;
908 bh = bh->b_this_page;
910 tail->b_this_page = head;
911 attach_page_buffers(page, head);
915 * Initialise the state of a blockdev page's buffers.
918 init_page_buffers(struct page *page, struct block_device *bdev,
919 sector_t block, int size)
921 struct buffer_head *head = page_buffers(page);
922 struct buffer_head *bh = head;
923 int uptodate = PageUptodate(page);
924 sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode));
927 if (!buffer_mapped(bh)) {
928 init_buffer(bh, NULL, NULL);
930 bh->b_blocknr = block;
932 set_buffer_uptodate(bh);
933 if (block < end_block)
934 set_buffer_mapped(bh);
937 bh = bh->b_this_page;
938 } while (bh != head);
942 * Create the page-cache page that contains the requested block.
944 * This is user purely for blockdev mappings.
947 grow_dev_page(struct block_device *bdev, sector_t block,
948 pgoff_t index, int size)
950 struct inode *inode = bdev->bd_inode;
952 struct buffer_head *bh;
954 page = find_or_create_page(inode->i_mapping, index,
955 (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE);
959 BUG_ON(!PageLocked(page));
961 if (page_has_buffers(page)) {
962 bh = page_buffers(page);
963 if (bh->b_size == size) {
964 init_page_buffers(page, bdev, block, size);
967 if (!try_to_free_buffers(page))
972 * Allocate some buffers for this page
974 bh = alloc_page_buffers(page, size, 0);
979 * Link the page to the buffers and initialise them. Take the
980 * lock to be atomic wrt __find_get_block(), which does not
981 * run under the page lock.
983 spin_lock(&inode->i_mapping->private_lock);
984 link_dev_buffers(page, bh);
985 init_page_buffers(page, bdev, block, size);
986 spin_unlock(&inode->i_mapping->private_lock);
991 page_cache_release(page);
996 * Create buffers for the specified block device block's page. If
997 * that page was dirty, the buffers are set dirty also.
1000 grow_buffers(struct block_device *bdev, sector_t block, int size)
1009 } while ((size << sizebits) < PAGE_SIZE);
1011 index = block >> sizebits;
1014 * Check for a block which wants to lie outside our maximum possible
1015 * pagecache index. (this comparison is done using sector_t types).
1017 if (unlikely(index != block >> sizebits)) {
1018 char b[BDEVNAME_SIZE];
1020 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1022 __func__, (unsigned long long)block,
1026 block = index << sizebits;
1027 /* Create a page with the proper size buffers.. */
1028 page = grow_dev_page(bdev, block, index, size);
1032 page_cache_release(page);
1036 static struct buffer_head *
1037 __getblk_slow(struct block_device *bdev, sector_t block, int size)
1040 struct buffer_head *bh;
1042 /* Size must be multiple of hard sectorsize */
1043 if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
1044 (size < 512 || size > PAGE_SIZE))) {
1045 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1047 printk(KERN_ERR "logical block size: %d\n",
1048 bdev_logical_block_size(bdev));
1055 bh = __find_get_block(bdev, block, size);
1059 ret = grow_buffers(bdev, block, size);
1063 } else if (ret > 0) {
1064 bh = __find_get_block(bdev, block, size);
1072 * The relationship between dirty buffers and dirty pages:
1074 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1075 * the page is tagged dirty in its radix tree.
1077 * At all times, the dirtiness of the buffers represents the dirtiness of
1078 * subsections of the page. If the page has buffers, the page dirty bit is
1079 * merely a hint about the true dirty state.
1081 * When a page is set dirty in its entirety, all its buffers are marked dirty
1082 * (if the page has buffers).
1084 * When a buffer is marked dirty, its page is dirtied, but the page's other
1087 * Also. When blockdev buffers are explicitly read with bread(), they
1088 * individually become uptodate. But their backing page remains not
1089 * uptodate - even if all of its buffers are uptodate. A subsequent
1090 * block_read_full_page() against that page will discover all the uptodate
1091 * buffers, will set the page uptodate and will perform no I/O.
1095 * mark_buffer_dirty - mark a buffer_head as needing writeout
1096 * @bh: the buffer_head to mark dirty
1098 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1099 * backing page dirty, then tag the page as dirty in its address_space's radix
1100 * tree and then attach the address_space's inode to its superblock's dirty
1103 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1104 * mapping->tree_lock and mapping->host->i_lock.
1106 void mark_buffer_dirty(struct buffer_head *bh)
1108 WARN_ON_ONCE(!buffer_uptodate(bh));
1111 * Very *carefully* optimize the it-is-already-dirty case.
1113 * Don't let the final "is it dirty" escape to before we
1114 * perhaps modified the buffer.
1116 if (buffer_dirty(bh)) {
1118 if (buffer_dirty(bh))
1122 if (!test_set_buffer_dirty(bh)) {
1123 struct page *page = bh->b_page;
1124 if (!TestSetPageDirty(page)) {
1125 struct address_space *mapping = page_mapping(page);
1127 __set_page_dirty(page, mapping, 0);
1131 EXPORT_SYMBOL(mark_buffer_dirty);
1134 * Decrement a buffer_head's reference count. If all buffers against a page
1135 * have zero reference count, are clean and unlocked, and if the page is clean
1136 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1137 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1138 * a page but it ends up not being freed, and buffers may later be reattached).
1140 void __brelse(struct buffer_head * buf)
1142 if (atomic_read(&buf->b_count)) {
1146 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1148 EXPORT_SYMBOL(__brelse);
1151 * bforget() is like brelse(), except it discards any
1152 * potentially dirty data.
1154 void __bforget(struct buffer_head *bh)
1156 clear_buffer_dirty(bh);
1157 if (bh->b_assoc_map) {
1158 struct address_space *buffer_mapping = bh->b_page->mapping;
1160 spin_lock(&buffer_mapping->private_lock);
1161 list_del_init(&bh->b_assoc_buffers);
1162 bh->b_assoc_map = NULL;
1163 spin_unlock(&buffer_mapping->private_lock);
1167 EXPORT_SYMBOL(__bforget);
1169 static struct buffer_head *__bread_slow(struct buffer_head *bh)
1172 if (buffer_uptodate(bh)) {
1177 bh->b_end_io = end_buffer_read_sync;
1178 submit_bh(READ, bh);
1180 if (buffer_uptodate(bh))
1188 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1189 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1190 * refcount elevated by one when they're in an LRU. A buffer can only appear
1191 * once in a particular CPU's LRU. A single buffer can be present in multiple
1192 * CPU's LRUs at the same time.
1194 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1195 * sb_find_get_block().
1197 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1198 * a local interrupt disable for that.
1201 #define BH_LRU_SIZE 8
1204 struct buffer_head *bhs[BH_LRU_SIZE];
1207 static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1210 #define bh_lru_lock() local_irq_disable()
1211 #define bh_lru_unlock() local_irq_enable()
1213 #define bh_lru_lock() preempt_disable()
1214 #define bh_lru_unlock() preempt_enable()
1217 static inline void check_irqs_on(void)
1219 #ifdef irqs_disabled
1220 BUG_ON(irqs_disabled());
1225 * The LRU management algorithm is dopey-but-simple. Sorry.
1227 static void bh_lru_install(struct buffer_head *bh)
1229 struct buffer_head *evictee = NULL;
1233 if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
1234 struct buffer_head *bhs[BH_LRU_SIZE];
1240 for (in = 0; in < BH_LRU_SIZE; in++) {
1241 struct buffer_head *bh2 =
1242 __this_cpu_read(bh_lrus.bhs[in]);
1247 if (out >= BH_LRU_SIZE) {
1248 BUG_ON(evictee != NULL);
1255 while (out < BH_LRU_SIZE)
1257 memcpy(__this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
1266 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1268 static struct buffer_head *
1269 lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1271 struct buffer_head *ret = NULL;
1276 for (i = 0; i < BH_LRU_SIZE; i++) {
1277 struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
1279 if (bh && bh->b_bdev == bdev &&
1280 bh->b_blocknr == block && bh->b_size == size) {
1283 __this_cpu_write(bh_lrus.bhs[i],
1284 __this_cpu_read(bh_lrus.bhs[i - 1]));
1287 __this_cpu_write(bh_lrus.bhs[0], bh);
1299 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1300 * it in the LRU and mark it as accessed. If it is not present then return
1303 struct buffer_head *
1304 __find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1306 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1309 bh = __find_get_block_slow(bdev, block);
1317 EXPORT_SYMBOL(__find_get_block);
1320 * __getblk will locate (and, if necessary, create) the buffer_head
1321 * which corresponds to the passed block_device, block and size. The
1322 * returned buffer has its reference count incremented.
1324 * __getblk() cannot fail - it just keeps trying. If you pass it an
1325 * illegal block number, __getblk() will happily return a buffer_head
1326 * which represents the non-existent block. Very weird.
1328 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1329 * attempt is failing. FIXME, perhaps?
1331 struct buffer_head *
1332 __getblk(struct block_device *bdev, sector_t block, unsigned size)
1334 struct buffer_head *bh = __find_get_block(bdev, block, size);
1338 bh = __getblk_slow(bdev, block, size);
1341 EXPORT_SYMBOL(__getblk);
1344 * Do async read-ahead on a buffer..
1346 void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1348 struct buffer_head *bh = __getblk(bdev, block, size);
1350 ll_rw_block(READA, 1, &bh);
1354 EXPORT_SYMBOL(__breadahead);
1357 * __bread() - reads a specified block and returns the bh
1358 * @bdev: the block_device to read from
1359 * @block: number of block
1360 * @size: size (in bytes) to read
1362 * Reads a specified block, and returns buffer head that contains it.
1363 * It returns NULL if the block was unreadable.
1365 struct buffer_head *
1366 __bread(struct block_device *bdev, sector_t block, unsigned size)
1368 struct buffer_head *bh = __getblk(bdev, block, size);
1370 if (likely(bh) && !buffer_uptodate(bh))
1371 bh = __bread_slow(bh);
1374 EXPORT_SYMBOL(__bread);
1377 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1378 * This doesn't race because it runs in each cpu either in irq
1379 * or with preempt disabled.
1381 static void invalidate_bh_lru(void *arg)
1383 struct bh_lru *b = &get_cpu_var(bh_lrus);
1386 for (i = 0; i < BH_LRU_SIZE; i++) {
1390 put_cpu_var(bh_lrus);
1393 static bool has_bh_in_lru(int cpu, void *dummy)
1395 struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1398 for (i = 0; i < BH_LRU_SIZE; i++) {
1406 void invalidate_bh_lrus(void)
1408 on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL);
1410 EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1412 void set_bh_page(struct buffer_head *bh,
1413 struct page *page, unsigned long offset)
1416 BUG_ON(offset >= PAGE_SIZE);
1417 if (PageHighMem(page))
1419 * This catches illegal uses and preserves the offset:
1421 bh->b_data = (char *)(0 + offset);
1423 bh->b_data = page_address(page) + offset;
1425 EXPORT_SYMBOL(set_bh_page);
1428 * Called when truncating a buffer on a page completely.
1430 static void discard_buffer(struct buffer_head * bh)
1433 clear_buffer_dirty(bh);
1435 clear_buffer_mapped(bh);
1436 clear_buffer_req(bh);
1437 clear_buffer_new(bh);
1438 clear_buffer_delay(bh);
1439 clear_buffer_unwritten(bh);
1444 * block_invalidatepage - invalidate part or all of a buffer-backed page
1446 * @page: the page which is affected
1447 * @offset: the index of the truncation point
1449 * block_invalidatepage() is called when all or part of the page has become
1450 * invalidated by a truncate operation.
1452 * block_invalidatepage() does not have to release all buffers, but it must
1453 * ensure that no dirty buffer is left outside @offset and that no I/O
1454 * is underway against any of the blocks which are outside the truncation
1455 * point. Because the caller is about to free (and possibly reuse) those
1458 void block_invalidatepage(struct page *page, unsigned long offset)
1460 struct buffer_head *head, *bh, *next;
1461 unsigned int curr_off = 0;
1463 BUG_ON(!PageLocked(page));
1464 if (!page_has_buffers(page))
1467 head = page_buffers(page);
1470 unsigned int next_off = curr_off + bh->b_size;
1471 next = bh->b_this_page;
1474 * is this block fully invalidated?
1476 if (offset <= curr_off)
1478 curr_off = next_off;
1480 } while (bh != head);
1483 * We release buffers only if the entire page is being invalidated.
1484 * The get_block cached value has been unconditionally invalidated,
1485 * so real IO is not possible anymore.
1488 try_to_release_page(page, 0);
1492 EXPORT_SYMBOL(block_invalidatepage);
1495 * We attach and possibly dirty the buffers atomically wrt
1496 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1497 * is already excluded via the page lock.
1499 void create_empty_buffers(struct page *page,
1500 unsigned long blocksize, unsigned long b_state)
1502 struct buffer_head *bh, *head, *tail;
1504 head = alloc_page_buffers(page, blocksize, 1);
1507 bh->b_state |= b_state;
1509 bh = bh->b_this_page;
1511 tail->b_this_page = head;
1513 spin_lock(&page->mapping->private_lock);
1514 if (PageUptodate(page) || PageDirty(page)) {
1517 if (PageDirty(page))
1518 set_buffer_dirty(bh);
1519 if (PageUptodate(page))
1520 set_buffer_uptodate(bh);
1521 bh = bh->b_this_page;
1522 } while (bh != head);
1524 attach_page_buffers(page, head);
1525 spin_unlock(&page->mapping->private_lock);
1527 EXPORT_SYMBOL(create_empty_buffers);
1530 * We are taking a block for data and we don't want any output from any
1531 * buffer-cache aliases starting from return from that function and
1532 * until the moment when something will explicitly mark the buffer
1533 * dirty (hopefully that will not happen until we will free that block ;-)
1534 * We don't even need to mark it not-uptodate - nobody can expect
1535 * anything from a newly allocated buffer anyway. We used to used
1536 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1537 * don't want to mark the alias unmapped, for example - it would confuse
1538 * anyone who might pick it with bread() afterwards...
1540 * Also.. Note that bforget() doesn't lock the buffer. So there can
1541 * be writeout I/O going on against recently-freed buffers. We don't
1542 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1543 * only if we really need to. That happens here.
1545 void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1547 struct buffer_head *old_bh;
1551 old_bh = __find_get_block_slow(bdev, block);
1553 clear_buffer_dirty(old_bh);
1554 wait_on_buffer(old_bh);
1555 clear_buffer_req(old_bh);
1559 EXPORT_SYMBOL(unmap_underlying_metadata);
1562 * NOTE! All mapped/uptodate combinations are valid:
1564 * Mapped Uptodate Meaning
1566 * No No "unknown" - must do get_block()
1567 * No Yes "hole" - zero-filled
1568 * Yes No "allocated" - allocated on disk, not read in
1569 * Yes Yes "valid" - allocated and up-to-date in memory.
1571 * "Dirty" is valid only with the last case (mapped+uptodate).
1575 * While block_write_full_page is writing back the dirty buffers under
1576 * the page lock, whoever dirtied the buffers may decide to clean them
1577 * again at any time. We handle that by only looking at the buffer
1578 * state inside lock_buffer().
1580 * If block_write_full_page() is called for regular writeback
1581 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1582 * locked buffer. This only can happen if someone has written the buffer
1583 * directly, with submit_bh(). At the address_space level PageWriteback
1584 * prevents this contention from occurring.
1586 * If block_write_full_page() is called with wbc->sync_mode ==
1587 * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this
1588 * causes the writes to be flagged as synchronous writes.
1590 static int __block_write_full_page(struct inode *inode, struct page *page,
1591 get_block_t *get_block, struct writeback_control *wbc,
1592 bh_end_io_t *handler)
1596 sector_t last_block;
1597 struct buffer_head *bh, *head;
1598 const unsigned blocksize = 1 << inode->i_blkbits;
1599 int nr_underway = 0;
1600 int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
1601 WRITE_SYNC : WRITE);
1603 BUG_ON(!PageLocked(page));
1605 last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
1607 if (!page_has_buffers(page)) {
1608 create_empty_buffers(page, blocksize,
1609 (1 << BH_Dirty)|(1 << BH_Uptodate));
1613 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1614 * here, and the (potentially unmapped) buffers may become dirty at
1615 * any time. If a buffer becomes dirty here after we've inspected it
1616 * then we just miss that fact, and the page stays dirty.
1618 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1619 * handle that here by just cleaning them.
1622 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
1623 head = page_buffers(page);
1627 * Get all the dirty buffers mapped to disk addresses and
1628 * handle any aliases from the underlying blockdev's mapping.
1631 if (block > last_block) {
1633 * mapped buffers outside i_size will occur, because
1634 * this page can be outside i_size when there is a
1635 * truncate in progress.
1638 * The buffer was zeroed by block_write_full_page()
1640 clear_buffer_dirty(bh);
1641 set_buffer_uptodate(bh);
1642 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1644 WARN_ON(bh->b_size != blocksize);
1645 err = get_block(inode, block, bh, 1);
1648 clear_buffer_delay(bh);
1649 if (buffer_new(bh)) {
1650 /* blockdev mappings never come here */
1651 clear_buffer_new(bh);
1652 unmap_underlying_metadata(bh->b_bdev,
1656 bh = bh->b_this_page;
1658 } while (bh != head);
1661 if (!buffer_mapped(bh))
1664 * If it's a fully non-blocking write attempt and we cannot
1665 * lock the buffer then redirty the page. Note that this can
1666 * potentially cause a busy-wait loop from writeback threads
1667 * and kswapd activity, but those code paths have their own
1668 * higher-level throttling.
1670 if (wbc->sync_mode != WB_SYNC_NONE) {
1672 } else if (!trylock_buffer(bh)) {
1673 redirty_page_for_writepage(wbc, page);
1676 if (test_clear_buffer_dirty(bh)) {
1677 mark_buffer_async_write_endio(bh, handler);
1681 } while ((bh = bh->b_this_page) != head);
1684 * The page and its buffers are protected by PageWriteback(), so we can
1685 * drop the bh refcounts early.
1687 BUG_ON(PageWriteback(page));
1688 set_page_writeback(page);
1691 struct buffer_head *next = bh->b_this_page;
1692 if (buffer_async_write(bh)) {
1693 submit_bh(write_op, bh);
1697 } while (bh != head);
1702 if (nr_underway == 0) {
1704 * The page was marked dirty, but the buffers were
1705 * clean. Someone wrote them back by hand with
1706 * ll_rw_block/submit_bh. A rare case.
1708 end_page_writeback(page);
1711 * The page and buffer_heads can be released at any time from
1719 * ENOSPC, or some other error. We may already have added some
1720 * blocks to the file, so we need to write these out to avoid
1721 * exposing stale data.
1722 * The page is currently locked and not marked for writeback
1725 /* Recovery: lock and submit the mapped buffers */
1727 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1728 !buffer_delay(bh)) {
1730 mark_buffer_async_write_endio(bh, handler);
1733 * The buffer may have been set dirty during
1734 * attachment to a dirty page.
1736 clear_buffer_dirty(bh);
1738 } while ((bh = bh->b_this_page) != head);
1740 BUG_ON(PageWriteback(page));
1741 mapping_set_error(page->mapping, err);
1742 set_page_writeback(page);
1744 struct buffer_head *next = bh->b_this_page;
1745 if (buffer_async_write(bh)) {
1746 clear_buffer_dirty(bh);
1747 submit_bh(write_op, bh);
1751 } while (bh != head);
1757 * If a page has any new buffers, zero them out here, and mark them uptodate
1758 * and dirty so they'll be written out (in order to prevent uninitialised
1759 * block data from leaking). And clear the new bit.
1761 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1763 unsigned int block_start, block_end;
1764 struct buffer_head *head, *bh;
1766 BUG_ON(!PageLocked(page));
1767 if (!page_has_buffers(page))
1770 bh = head = page_buffers(page);
1773 block_end = block_start + bh->b_size;
1775 if (buffer_new(bh)) {
1776 if (block_end > from && block_start < to) {
1777 if (!PageUptodate(page)) {
1778 unsigned start, size;
1780 start = max(from, block_start);
1781 size = min(to, block_end) - start;
1783 zero_user(page, start, size);
1784 set_buffer_uptodate(bh);
1787 clear_buffer_new(bh);
1788 mark_buffer_dirty(bh);
1792 block_start = block_end;
1793 bh = bh->b_this_page;
1794 } while (bh != head);
1796 EXPORT_SYMBOL(page_zero_new_buffers);
1798 int __block_write_begin(struct page *page, loff_t pos, unsigned len,
1799 get_block_t *get_block)
1801 unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1802 unsigned to = from + len;
1803 struct inode *inode = page->mapping->host;
1804 unsigned block_start, block_end;
1807 unsigned blocksize, bbits;
1808 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1810 BUG_ON(!PageLocked(page));
1811 BUG_ON(from > PAGE_CACHE_SIZE);
1812 BUG_ON(to > PAGE_CACHE_SIZE);
1815 blocksize = 1 << inode->i_blkbits;
1816 if (!page_has_buffers(page))
1817 create_empty_buffers(page, blocksize, 0);
1818 head = page_buffers(page);
1820 bbits = inode->i_blkbits;
1821 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1823 for(bh = head, block_start = 0; bh != head || !block_start;
1824 block++, block_start=block_end, bh = bh->b_this_page) {
1825 block_end = block_start + blocksize;
1826 if (block_end <= from || block_start >= to) {
1827 if (PageUptodate(page)) {
1828 if (!buffer_uptodate(bh))
1829 set_buffer_uptodate(bh);
1834 clear_buffer_new(bh);
1835 if (!buffer_mapped(bh)) {
1836 WARN_ON(bh->b_size != blocksize);
1837 err = get_block(inode, block, bh, 1);
1840 if (buffer_new(bh)) {
1841 unmap_underlying_metadata(bh->b_bdev,
1843 if (PageUptodate(page)) {
1844 clear_buffer_new(bh);
1845 set_buffer_uptodate(bh);
1846 mark_buffer_dirty(bh);
1849 if (block_end > to || block_start < from)
1850 zero_user_segments(page,
1856 if (PageUptodate(page)) {
1857 if (!buffer_uptodate(bh))
1858 set_buffer_uptodate(bh);
1861 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1862 !buffer_unwritten(bh) &&
1863 (block_start < from || block_end > to)) {
1864 ll_rw_block(READ, 1, &bh);
1869 * If we issued read requests - let them complete.
1871 while(wait_bh > wait) {
1872 wait_on_buffer(*--wait_bh);
1873 if (!buffer_uptodate(*wait_bh))
1877 page_zero_new_buffers(page, from, to);
1880 EXPORT_SYMBOL(__block_write_begin);
1882 static int __block_commit_write(struct inode *inode, struct page *page,
1883 unsigned from, unsigned to)
1885 unsigned block_start, block_end;
1888 struct buffer_head *bh, *head;
1890 blocksize = 1 << inode->i_blkbits;
1892 for(bh = head = page_buffers(page), block_start = 0;
1893 bh != head || !block_start;
1894 block_start=block_end, bh = bh->b_this_page) {
1895 block_end = block_start + blocksize;
1896 if (block_end <= from || block_start >= to) {
1897 if (!buffer_uptodate(bh))
1900 set_buffer_uptodate(bh);
1901 mark_buffer_dirty(bh);
1903 clear_buffer_new(bh);
1907 * If this is a partial write which happened to make all buffers
1908 * uptodate then we can optimize away a bogus readpage() for
1909 * the next read(). Here we 'discover' whether the page went
1910 * uptodate as a result of this (potentially partial) write.
1913 SetPageUptodate(page);
1918 * block_write_begin takes care of the basic task of block allocation and
1919 * bringing partial write blocks uptodate first.
1921 * The filesystem needs to handle block truncation upon failure.
1923 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
1924 unsigned flags, struct page **pagep, get_block_t *get_block)
1926 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1930 page = grab_cache_page_write_begin(mapping, index, flags);
1934 status = __block_write_begin(page, pos, len, get_block);
1935 if (unlikely(status)) {
1937 page_cache_release(page);
1944 EXPORT_SYMBOL(block_write_begin);
1946 int block_write_end(struct file *file, struct address_space *mapping,
1947 loff_t pos, unsigned len, unsigned copied,
1948 struct page *page, void *fsdata)
1950 struct inode *inode = mapping->host;
1953 start = pos & (PAGE_CACHE_SIZE - 1);
1955 if (unlikely(copied < len)) {
1957 * The buffers that were written will now be uptodate, so we
1958 * don't have to worry about a readpage reading them and
1959 * overwriting a partial write. However if we have encountered
1960 * a short write and only partially written into a buffer, it
1961 * will not be marked uptodate, so a readpage might come in and
1962 * destroy our partial write.
1964 * Do the simplest thing, and just treat any short write to a
1965 * non uptodate page as a zero-length write, and force the
1966 * caller to redo the whole thing.
1968 if (!PageUptodate(page))
1971 page_zero_new_buffers(page, start+copied, start+len);
1973 flush_dcache_page(page);
1975 /* This could be a short (even 0-length) commit */
1976 __block_commit_write(inode, page, start, start+copied);
1980 EXPORT_SYMBOL(block_write_end);
1982 int generic_write_end(struct file *file, struct address_space *mapping,
1983 loff_t pos, unsigned len, unsigned copied,
1984 struct page *page, void *fsdata)
1986 struct inode *inode = mapping->host;
1987 int i_size_changed = 0;
1989 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
1992 * No need to use i_size_read() here, the i_size
1993 * cannot change under us because we hold i_mutex.
1995 * But it's important to update i_size while still holding page lock:
1996 * page writeout could otherwise come in and zero beyond i_size.
1998 if (pos+copied > inode->i_size) {
1999 i_size_write(inode, pos+copied);
2004 page_cache_release(page);
2007 * Don't mark the inode dirty under page lock. First, it unnecessarily
2008 * makes the holding time of page lock longer. Second, it forces lock
2009 * ordering of page lock and transaction start for journaling
2013 mark_inode_dirty(inode);
2017 EXPORT_SYMBOL(generic_write_end);
2020 * block_is_partially_uptodate checks whether buffers within a page are
2023 * Returns true if all buffers which correspond to a file portion
2024 * we want to read are uptodate.
2026 int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
2029 struct inode *inode = page->mapping->host;
2030 unsigned block_start, block_end, blocksize;
2032 struct buffer_head *bh, *head;
2035 if (!page_has_buffers(page))
2038 blocksize = 1 << inode->i_blkbits;
2039 to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count);
2041 if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
2044 head = page_buffers(page);
2048 block_end = block_start + blocksize;
2049 if (block_end > from && block_start < to) {
2050 if (!buffer_uptodate(bh)) {
2054 if (block_end >= to)
2057 block_start = block_end;
2058 bh = bh->b_this_page;
2059 } while (bh != head);
2063 EXPORT_SYMBOL(block_is_partially_uptodate);
2066 * Generic "read page" function for block devices that have the normal
2067 * get_block functionality. This is most of the block device filesystems.
2068 * Reads the page asynchronously --- the unlock_buffer() and
2069 * set/clear_buffer_uptodate() functions propagate buffer state into the
2070 * page struct once IO has completed.
2072 int block_read_full_page(struct page *page, get_block_t *get_block)
2074 struct inode *inode = page->mapping->host;
2075 sector_t iblock, lblock;
2076 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2077 unsigned int blocksize;
2079 int fully_mapped = 1;
2081 BUG_ON(!PageLocked(page));
2082 blocksize = 1 << inode->i_blkbits;
2083 if (!page_has_buffers(page))
2084 create_empty_buffers(page, blocksize, 0);
2085 head = page_buffers(page);
2087 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2088 lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
2094 if (buffer_uptodate(bh))
2097 if (!buffer_mapped(bh)) {
2101 if (iblock < lblock) {
2102 WARN_ON(bh->b_size != blocksize);
2103 err = get_block(inode, iblock, bh, 0);
2107 if (!buffer_mapped(bh)) {
2108 zero_user(page, i * blocksize, blocksize);
2110 set_buffer_uptodate(bh);
2114 * get_block() might have updated the buffer
2117 if (buffer_uptodate(bh))
2121 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2124 SetPageMappedToDisk(page);
2128 * All buffers are uptodate - we can set the page uptodate
2129 * as well. But not if get_block() returned an error.
2131 if (!PageError(page))
2132 SetPageUptodate(page);
2137 /* Stage two: lock the buffers */
2138 for (i = 0; i < nr; i++) {
2141 mark_buffer_async_read(bh);
2145 * Stage 3: start the IO. Check for uptodateness
2146 * inside the buffer lock in case another process reading
2147 * the underlying blockdev brought it uptodate (the sct fix).
2149 for (i = 0; i < nr; i++) {
2151 if (buffer_uptodate(bh))
2152 end_buffer_async_read(bh, 1);
2154 submit_bh(READ, bh);
2158 EXPORT_SYMBOL(block_read_full_page);
2160 /* utility function for filesystems that need to do work on expanding
2161 * truncates. Uses filesystem pagecache writes to allow the filesystem to
2162 * deal with the hole.
2164 int generic_cont_expand_simple(struct inode *inode, loff_t size)
2166 struct address_space *mapping = inode->i_mapping;
2171 err = inode_newsize_ok(inode, size);
2175 err = pagecache_write_begin(NULL, mapping, size, 0,
2176 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2181 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2187 EXPORT_SYMBOL(generic_cont_expand_simple);
2189 static int cont_expand_zero(struct file *file, struct address_space *mapping,
2190 loff_t pos, loff_t *bytes)
2192 struct inode *inode = mapping->host;
2193 unsigned blocksize = 1 << inode->i_blkbits;
2196 pgoff_t index, curidx;
2198 unsigned zerofrom, offset, len;
2201 index = pos >> PAGE_CACHE_SHIFT;
2202 offset = pos & ~PAGE_CACHE_MASK;
2204 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
2205 zerofrom = curpos & ~PAGE_CACHE_MASK;
2206 if (zerofrom & (blocksize-1)) {
2207 *bytes |= (blocksize-1);
2210 len = PAGE_CACHE_SIZE - zerofrom;
2212 err = pagecache_write_begin(file, mapping, curpos, len,
2213 AOP_FLAG_UNINTERRUPTIBLE,
2217 zero_user(page, zerofrom, len);
2218 err = pagecache_write_end(file, mapping, curpos, len, len,
2225 balance_dirty_pages_ratelimited(mapping);
2228 /* page covers the boundary, find the boundary offset */
2229 if (index == curidx) {
2230 zerofrom = curpos & ~PAGE_CACHE_MASK;
2231 /* if we will expand the thing last block will be filled */
2232 if (offset <= zerofrom) {
2235 if (zerofrom & (blocksize-1)) {
2236 *bytes |= (blocksize-1);
2239 len = offset - zerofrom;
2241 err = pagecache_write_begin(file, mapping, curpos, len,
2242 AOP_FLAG_UNINTERRUPTIBLE,
2246 zero_user(page, zerofrom, len);
2247 err = pagecache_write_end(file, mapping, curpos, len, len,
2259 * For moronic filesystems that do not allow holes in file.
2260 * We may have to extend the file.
2262 int cont_write_begin(struct file *file, struct address_space *mapping,
2263 loff_t pos, unsigned len, unsigned flags,
2264 struct page **pagep, void **fsdata,
2265 get_block_t *get_block, loff_t *bytes)
2267 struct inode *inode = mapping->host;
2268 unsigned blocksize = 1 << inode->i_blkbits;
2272 err = cont_expand_zero(file, mapping, pos, bytes);
2276 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2277 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2278 *bytes |= (blocksize-1);
2282 return block_write_begin(mapping, pos, len, flags, pagep, get_block);
2284 EXPORT_SYMBOL(cont_write_begin);
2286 int block_commit_write(struct page *page, unsigned from, unsigned to)
2288 struct inode *inode = page->mapping->host;
2289 __block_commit_write(inode,page,from,to);
2292 EXPORT_SYMBOL(block_commit_write);
2295 * block_page_mkwrite() is not allowed to change the file size as it gets
2296 * called from a page fault handler when a page is first dirtied. Hence we must
2297 * be careful to check for EOF conditions here. We set the page up correctly
2298 * for a written page which means we get ENOSPC checking when writing into
2299 * holes and correct delalloc and unwritten extent mapping on filesystems that
2300 * support these features.
2302 * We are not allowed to take the i_mutex here so we have to play games to
2303 * protect against truncate races as the page could now be beyond EOF. Because
2304 * truncate writes the inode size before removing pages, once we have the
2305 * page lock we can determine safely if the page is beyond EOF. If it is not
2306 * beyond EOF, then the page is guaranteed safe against truncation until we
2309 * Direct callers of this function should call vfs_check_frozen() so that page
2310 * fault does not busyloop until the fs is thawed.
2312 int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2313 get_block_t get_block)
2315 struct page *page = vmf->page;
2316 struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
2322 size = i_size_read(inode);
2323 if ((page->mapping != inode->i_mapping) ||
2324 (page_offset(page) > size)) {
2325 /* We overload EFAULT to mean page got truncated */
2330 /* page is wholly or partially inside EOF */
2331 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
2332 end = size & ~PAGE_CACHE_MASK;
2334 end = PAGE_CACHE_SIZE;
2336 ret = __block_write_begin(page, 0, end, get_block);
2338 ret = block_commit_write(page, 0, end);
2340 if (unlikely(ret < 0))
2343 * Freezing in progress? We check after the page is marked dirty and
2344 * with page lock held so if the test here fails, we are sure freezing
2345 * code will wait during syncing until the page fault is done - at that
2346 * point page will be dirty and unlocked so freezing code will write it
2347 * and writeprotect it again.
2349 set_page_dirty(page);
2350 if (inode->i_sb->s_frozen != SB_UNFROZEN) {
2354 wait_on_page_writeback(page);
2360 EXPORT_SYMBOL(__block_page_mkwrite);
2362 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2363 get_block_t get_block)
2366 struct super_block *sb = vma->vm_file->f_path.dentry->d_inode->i_sb;
2369 * This check is racy but catches the common case. The check in
2370 * __block_page_mkwrite() is reliable.
2372 vfs_check_frozen(sb, SB_FREEZE_WRITE);
2373 ret = __block_page_mkwrite(vma, vmf, get_block);
2374 return block_page_mkwrite_return(ret);
2376 EXPORT_SYMBOL(block_page_mkwrite);
2379 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
2380 * immediately, while under the page lock. So it needs a special end_io
2381 * handler which does not touch the bh after unlocking it.
2383 static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2385 __end_buffer_read_notouch(bh, uptodate);
2389 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2390 * the page (converting it to circular linked list and taking care of page
2393 static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2395 struct buffer_head *bh;
2397 BUG_ON(!PageLocked(page));
2399 spin_lock(&page->mapping->private_lock);
2402 if (PageDirty(page))
2403 set_buffer_dirty(bh);
2404 if (!bh->b_this_page)
2405 bh->b_this_page = head;
2406 bh = bh->b_this_page;
2407 } while (bh != head);
2408 attach_page_buffers(page, head);
2409 spin_unlock(&page->mapping->private_lock);
2413 * On entry, the page is fully not uptodate.
2414 * On exit the page is fully uptodate in the areas outside (from,to)
2415 * The filesystem needs to handle block truncation upon failure.
2417 int nobh_write_begin(struct address_space *mapping,
2418 loff_t pos, unsigned len, unsigned flags,
2419 struct page **pagep, void **fsdata,
2420 get_block_t *get_block)
2422 struct inode *inode = mapping->host;
2423 const unsigned blkbits = inode->i_blkbits;
2424 const unsigned blocksize = 1 << blkbits;
2425 struct buffer_head *head, *bh;
2429 unsigned block_in_page;
2430 unsigned block_start, block_end;
2431 sector_t block_in_file;
2434 int is_mapped_to_disk = 1;
2436 index = pos >> PAGE_CACHE_SHIFT;
2437 from = pos & (PAGE_CACHE_SIZE - 1);
2440 page = grab_cache_page_write_begin(mapping, index, flags);
2446 if (page_has_buffers(page)) {
2447 ret = __block_write_begin(page, pos, len, get_block);
2453 if (PageMappedToDisk(page))
2457 * Allocate buffers so that we can keep track of state, and potentially
2458 * attach them to the page if an error occurs. In the common case of
2459 * no error, they will just be freed again without ever being attached
2460 * to the page (which is all OK, because we're under the page lock).
2462 * Be careful: the buffer linked list is a NULL terminated one, rather
2463 * than the circular one we're used to.
2465 head = alloc_page_buffers(page, blocksize, 0);
2471 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
2474 * We loop across all blocks in the page, whether or not they are
2475 * part of the affected region. This is so we can discover if the
2476 * page is fully mapped-to-disk.
2478 for (block_start = 0, block_in_page = 0, bh = head;
2479 block_start < PAGE_CACHE_SIZE;
2480 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
2483 block_end = block_start + blocksize;
2486 if (block_start >= to)
2488 ret = get_block(inode, block_in_file + block_in_page,
2492 if (!buffer_mapped(bh))
2493 is_mapped_to_disk = 0;
2495 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
2496 if (PageUptodate(page)) {
2497 set_buffer_uptodate(bh);
2500 if (buffer_new(bh) || !buffer_mapped(bh)) {
2501 zero_user_segments(page, block_start, from,
2505 if (buffer_uptodate(bh))
2506 continue; /* reiserfs does this */
2507 if (block_start < from || block_end > to) {
2509 bh->b_end_io = end_buffer_read_nobh;
2510 submit_bh(READ, bh);
2517 * The page is locked, so these buffers are protected from
2518 * any VM or truncate activity. Hence we don't need to care
2519 * for the buffer_head refcounts.
2521 for (bh = head; bh; bh = bh->b_this_page) {
2523 if (!buffer_uptodate(bh))
2530 if (is_mapped_to_disk)
2531 SetPageMappedToDisk(page);
2533 *fsdata = head; /* to be released by nobh_write_end */
2540 * Error recovery is a bit difficult. We need to zero out blocks that
2541 * were newly allocated, and dirty them to ensure they get written out.
2542 * Buffers need to be attached to the page at this point, otherwise
2543 * the handling of potential IO errors during writeout would be hard
2544 * (could try doing synchronous writeout, but what if that fails too?)
2546 attach_nobh_buffers(page, head);
2547 page_zero_new_buffers(page, from, to);
2551 page_cache_release(page);
2556 EXPORT_SYMBOL(nobh_write_begin);
2558 int nobh_write_end(struct file *file, struct address_space *mapping,
2559 loff_t pos, unsigned len, unsigned copied,
2560 struct page *page, void *fsdata)
2562 struct inode *inode = page->mapping->host;
2563 struct buffer_head *head = fsdata;
2564 struct buffer_head *bh;
2565 BUG_ON(fsdata != NULL && page_has_buffers(page));
2567 if (unlikely(copied < len) && head)
2568 attach_nobh_buffers(page, head);
2569 if (page_has_buffers(page))
2570 return generic_write_end(file, mapping, pos, len,
2571 copied, page, fsdata);
2573 SetPageUptodate(page);
2574 set_page_dirty(page);
2575 if (pos+copied > inode->i_size) {
2576 i_size_write(inode, pos+copied);
2577 mark_inode_dirty(inode);
2581 page_cache_release(page);
2585 head = head->b_this_page;
2586 free_buffer_head(bh);
2591 EXPORT_SYMBOL(nobh_write_end);
2594 * nobh_writepage() - based on block_full_write_page() except
2595 * that it tries to operate without attaching bufferheads to
2598 int nobh_writepage(struct page *page, get_block_t *get_block,
2599 struct writeback_control *wbc)
2601 struct inode * const inode = page->mapping->host;
2602 loff_t i_size = i_size_read(inode);
2603 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2607 /* Is the page fully inside i_size? */
2608 if (page->index < end_index)
2611 /* Is the page fully outside i_size? (truncate in progress) */
2612 offset = i_size & (PAGE_CACHE_SIZE-1);
2613 if (page->index >= end_index+1 || !offset) {
2615 * The page may have dirty, unmapped buffers. For example,
2616 * they may have been added in ext3_writepage(). Make them
2617 * freeable here, so the page does not leak.
2620 /* Not really sure about this - do we need this ? */
2621 if (page->mapping->a_ops->invalidatepage)
2622 page->mapping->a_ops->invalidatepage(page, offset);
2625 return 0; /* don't care */
2629 * The page straddles i_size. It must be zeroed out on each and every
2630 * writepage invocation because it may be mmapped. "A file is mapped
2631 * in multiples of the page size. For a file that is not a multiple of
2632 * the page size, the remaining memory is zeroed when mapped, and
2633 * writes to that region are not written out to the file."
2635 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2637 ret = mpage_writepage(page, get_block, wbc);
2639 ret = __block_write_full_page(inode, page, get_block, wbc,
2640 end_buffer_async_write);
2643 EXPORT_SYMBOL(nobh_writepage);
2645 int nobh_truncate_page(struct address_space *mapping,
2646 loff_t from, get_block_t *get_block)
2648 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2649 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2652 unsigned length, pos;
2653 struct inode *inode = mapping->host;
2655 struct buffer_head map_bh;
2658 blocksize = 1 << inode->i_blkbits;
2659 length = offset & (blocksize - 1);
2661 /* Block boundary? Nothing to do */
2665 length = blocksize - length;
2666 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2668 page = grab_cache_page(mapping, index);
2673 if (page_has_buffers(page)) {
2676 page_cache_release(page);
2677 return block_truncate_page(mapping, from, get_block);
2680 /* Find the buffer that contains "offset" */
2682 while (offset >= pos) {
2687 map_bh.b_size = blocksize;
2689 err = get_block(inode, iblock, &map_bh, 0);
2692 /* unmapped? It's a hole - nothing to do */
2693 if (!buffer_mapped(&map_bh))
2696 /* Ok, it's mapped. Make sure it's up-to-date */
2697 if (!PageUptodate(page)) {
2698 err = mapping->a_ops->readpage(NULL, page);
2700 page_cache_release(page);
2704 if (!PageUptodate(page)) {
2708 if (page_has_buffers(page))
2711 zero_user(page, offset, length);
2712 set_page_dirty(page);
2717 page_cache_release(page);
2721 EXPORT_SYMBOL(nobh_truncate_page);
2723 int block_truncate_page(struct address_space *mapping,
2724 loff_t from, get_block_t *get_block)
2726 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2727 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2730 unsigned length, pos;
2731 struct inode *inode = mapping->host;
2733 struct buffer_head *bh;
2736 blocksize = 1 << inode->i_blkbits;
2737 length = offset & (blocksize - 1);
2739 /* Block boundary? Nothing to do */
2743 length = blocksize - length;
2744 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2746 page = grab_cache_page(mapping, index);
2751 if (!page_has_buffers(page))
2752 create_empty_buffers(page, blocksize, 0);
2754 /* Find the buffer that contains "offset" */
2755 bh = page_buffers(page);
2757 while (offset >= pos) {
2758 bh = bh->b_this_page;
2764 if (!buffer_mapped(bh)) {
2765 WARN_ON(bh->b_size != blocksize);
2766 err = get_block(inode, iblock, bh, 0);
2769 /* unmapped? It's a hole - nothing to do */
2770 if (!buffer_mapped(bh))
2774 /* Ok, it's mapped. Make sure it's up-to-date */
2775 if (PageUptodate(page))
2776 set_buffer_uptodate(bh);
2778 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2780 ll_rw_block(READ, 1, &bh);
2782 /* Uhhuh. Read error. Complain and punt. */
2783 if (!buffer_uptodate(bh))
2787 zero_user(page, offset, length);
2788 mark_buffer_dirty(bh);
2793 page_cache_release(page);
2797 EXPORT_SYMBOL(block_truncate_page);
2800 * The generic ->writepage function for buffer-backed address_spaces
2801 * this form passes in the end_io handler used to finish the IO.
2803 int block_write_full_page_endio(struct page *page, get_block_t *get_block,
2804 struct writeback_control *wbc, bh_end_io_t *handler)
2806 struct inode * const inode = page->mapping->host;
2807 loff_t i_size = i_size_read(inode);
2808 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2811 /* Is the page fully inside i_size? */
2812 if (page->index < end_index)
2813 return __block_write_full_page(inode, page, get_block, wbc,
2816 /* Is the page fully outside i_size? (truncate in progress) */
2817 offset = i_size & (PAGE_CACHE_SIZE-1);
2818 if (page->index >= end_index+1 || !offset) {
2820 * The page may have dirty, unmapped buffers. For example,
2821 * they may have been added in ext3_writepage(). Make them
2822 * freeable here, so the page does not leak.
2824 do_invalidatepage(page, 0);
2826 return 0; /* don't care */
2830 * The page straddles i_size. It must be zeroed out on each and every
2831 * writepage invocation because it may be mmapped. "A file is mapped
2832 * in multiples of the page size. For a file that is not a multiple of
2833 * the page size, the remaining memory is zeroed when mapped, and
2834 * writes to that region are not written out to the file."
2836 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2837 return __block_write_full_page(inode, page, get_block, wbc, handler);
2839 EXPORT_SYMBOL(block_write_full_page_endio);
2842 * The generic ->writepage function for buffer-backed address_spaces
2844 int block_write_full_page(struct page *page, get_block_t *get_block,
2845 struct writeback_control *wbc)
2847 return block_write_full_page_endio(page, get_block, wbc,
2848 end_buffer_async_write);
2850 EXPORT_SYMBOL(block_write_full_page);
2852 sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2853 get_block_t *get_block)
2855 struct buffer_head tmp;
2856 struct inode *inode = mapping->host;
2859 tmp.b_size = 1 << inode->i_blkbits;
2860 get_block(inode, block, &tmp, 0);
2861 return tmp.b_blocknr;
2863 EXPORT_SYMBOL(generic_block_bmap);
2865 static void end_bio_bh_io_sync(struct bio *bio, int err)
2867 struct buffer_head *bh = bio->bi_private;
2869 if (err == -EOPNOTSUPP) {
2870 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
2873 if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags)))
2874 set_bit(BH_Quiet, &bh->b_state);
2876 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2880 int submit_bh(int rw, struct buffer_head * bh)
2885 BUG_ON(!buffer_locked(bh));
2886 BUG_ON(!buffer_mapped(bh));
2887 BUG_ON(!bh->b_end_io);
2888 BUG_ON(buffer_delay(bh));
2889 BUG_ON(buffer_unwritten(bh));
2892 * Only clear out a write error when rewriting
2894 if (test_set_buffer_req(bh) && (rw & WRITE))
2895 clear_buffer_write_io_error(bh);
2898 * from here on down, it's all bio -- do the initial mapping,
2899 * submit_bio -> generic_make_request may further map this bio around
2901 bio = bio_alloc(GFP_NOIO, 1);
2903 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2904 bio->bi_bdev = bh->b_bdev;
2905 bio->bi_io_vec[0].bv_page = bh->b_page;
2906 bio->bi_io_vec[0].bv_len = bh->b_size;
2907 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
2911 bio->bi_size = bh->b_size;
2913 bio->bi_end_io = end_bio_bh_io_sync;
2914 bio->bi_private = bh;
2917 submit_bio(rw, bio);
2919 if (bio_flagged(bio, BIO_EOPNOTSUPP))
2925 EXPORT_SYMBOL(submit_bh);
2928 * ll_rw_block: low-level access to block devices (DEPRECATED)
2929 * @rw: whether to %READ or %WRITE or maybe %READA (readahead)
2930 * @nr: number of &struct buffer_heads in the array
2931 * @bhs: array of pointers to &struct buffer_head
2933 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
2934 * requests an I/O operation on them, either a %READ or a %WRITE. The third
2935 * %READA option is described in the documentation for generic_make_request()
2936 * which ll_rw_block() calls.
2938 * This function drops any buffer that it cannot get a lock on (with the
2939 * BH_Lock state bit), any buffer that appears to be clean when doing a write
2940 * request, and any buffer that appears to be up-to-date when doing read
2941 * request. Further it marks as clean buffers that are processed for
2942 * writing (the buffer cache won't assume that they are actually clean
2943 * until the buffer gets unlocked).
2945 * ll_rw_block sets b_end_io to simple completion handler that marks
2946 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
2949 * All of the buffers must be for the same device, and must also be a
2950 * multiple of the current approved size for the device.
2952 void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
2956 for (i = 0; i < nr; i++) {
2957 struct buffer_head *bh = bhs[i];
2959 if (!trylock_buffer(bh))
2962 if (test_clear_buffer_dirty(bh)) {
2963 bh->b_end_io = end_buffer_write_sync;
2965 submit_bh(WRITE, bh);
2969 if (!buffer_uptodate(bh)) {
2970 bh->b_end_io = end_buffer_read_sync;
2979 EXPORT_SYMBOL(ll_rw_block);
2981 void write_dirty_buffer(struct buffer_head *bh, int rw)
2984 if (!test_clear_buffer_dirty(bh)) {
2988 bh->b_end_io = end_buffer_write_sync;
2992 EXPORT_SYMBOL(write_dirty_buffer);
2995 * For a data-integrity writeout, we need to wait upon any in-progress I/O
2996 * and then start new I/O and then wait upon it. The caller must have a ref on
2999 int __sync_dirty_buffer(struct buffer_head *bh, int rw)
3003 WARN_ON(atomic_read(&bh->b_count) < 1);
3005 if (test_clear_buffer_dirty(bh)) {
3007 bh->b_end_io = end_buffer_write_sync;
3008 ret = submit_bh(rw, bh);
3010 if (!ret && !buffer_uptodate(bh))
3017 EXPORT_SYMBOL(__sync_dirty_buffer);
3019 int sync_dirty_buffer(struct buffer_head *bh)
3021 return __sync_dirty_buffer(bh, WRITE_SYNC);
3023 EXPORT_SYMBOL(sync_dirty_buffer);
3026 * try_to_free_buffers() checks if all the buffers on this particular page
3027 * are unused, and releases them if so.
3029 * Exclusion against try_to_free_buffers may be obtained by either
3030 * locking the page or by holding its mapping's private_lock.
3032 * If the page is dirty but all the buffers are clean then we need to
3033 * be sure to mark the page clean as well. This is because the page
3034 * may be against a block device, and a later reattachment of buffers
3035 * to a dirty page will set *all* buffers dirty. Which would corrupt
3036 * filesystem data on the same device.
3038 * The same applies to regular filesystem pages: if all the buffers are
3039 * clean then we set the page clean and proceed. To do that, we require
3040 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3043 * try_to_free_buffers() is non-blocking.
3045 static inline int buffer_busy(struct buffer_head *bh)
3047 return atomic_read(&bh->b_count) |
3048 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3052 drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3054 struct buffer_head *head = page_buffers(page);
3055 struct buffer_head *bh;
3059 if (buffer_write_io_error(bh) && page->mapping)
3060 set_bit(AS_EIO, &page->mapping->flags);
3061 if (buffer_busy(bh))
3063 bh = bh->b_this_page;
3064 } while (bh != head);
3067 struct buffer_head *next = bh->b_this_page;
3069 if (bh->b_assoc_map)
3070 __remove_assoc_queue(bh);
3072 } while (bh != head);
3073 *buffers_to_free = head;
3074 __clear_page_buffers(page);
3080 int try_to_free_buffers(struct page *page)
3082 struct address_space * const mapping = page->mapping;
3083 struct buffer_head *buffers_to_free = NULL;
3086 BUG_ON(!PageLocked(page));
3087 if (PageWriteback(page))
3090 if (mapping == NULL) { /* can this still happen? */
3091 ret = drop_buffers(page, &buffers_to_free);
3095 spin_lock(&mapping->private_lock);
3096 ret = drop_buffers(page, &buffers_to_free);
3099 * If the filesystem writes its buffers by hand (eg ext3)
3100 * then we can have clean buffers against a dirty page. We
3101 * clean the page here; otherwise the VM will never notice
3102 * that the filesystem did any IO at all.
3104 * Also, during truncate, discard_buffer will have marked all
3105 * the page's buffers clean. We discover that here and clean
3108 * private_lock must be held over this entire operation in order
3109 * to synchronise against __set_page_dirty_buffers and prevent the
3110 * dirty bit from being lost.
3113 cancel_dirty_page(page, PAGE_CACHE_SIZE);
3114 spin_unlock(&mapping->private_lock);
3116 if (buffers_to_free) {
3117 struct buffer_head *bh = buffers_to_free;
3120 struct buffer_head *next = bh->b_this_page;
3121 free_buffer_head(bh);
3123 } while (bh != buffers_to_free);
3127 EXPORT_SYMBOL(try_to_free_buffers);
3130 * There are no bdflush tunables left. But distributions are
3131 * still running obsolete flush daemons, so we terminate them here.
3133 * Use of bdflush() is deprecated and will be removed in a future kernel.
3134 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
3136 SYSCALL_DEFINE2(bdflush, int, func, long, data)
3138 static int msg_count;
3140 if (!capable(CAP_SYS_ADMIN))
3143 if (msg_count < 5) {
3146 "warning: process `%s' used the obsolete bdflush"
3147 " system call\n", current->comm);
3148 printk(KERN_INFO "Fix your initscripts?\n");
3157 * Buffer-head allocation
3159 static struct kmem_cache *bh_cachep __read_mostly;
3162 * Once the number of bh's in the machine exceeds this level, we start
3163 * stripping them in writeback.
3165 static int max_buffer_heads;
3167 int buffer_heads_over_limit;
3169 struct bh_accounting {
3170 int nr; /* Number of live bh's */
3171 int ratelimit; /* Limit cacheline bouncing */
3174 static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3176 static void recalc_bh_state(void)
3181 if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
3183 __this_cpu_write(bh_accounting.ratelimit, 0);
3184 for_each_online_cpu(i)
3185 tot += per_cpu(bh_accounting, i).nr;
3186 buffer_heads_over_limit = (tot > max_buffer_heads);
3189 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3191 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
3193 INIT_LIST_HEAD(&ret->b_assoc_buffers);
3195 __this_cpu_inc(bh_accounting.nr);
3201 EXPORT_SYMBOL(alloc_buffer_head);
3203 void free_buffer_head(struct buffer_head *bh)
3205 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3206 kmem_cache_free(bh_cachep, bh);
3208 __this_cpu_dec(bh_accounting.nr);
3212 EXPORT_SYMBOL(free_buffer_head);
3214 static void buffer_exit_cpu(int cpu)
3217 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3219 for (i = 0; i < BH_LRU_SIZE; i++) {
3223 this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3224 per_cpu(bh_accounting, cpu).nr = 0;
3227 static int buffer_cpu_notify(struct notifier_block *self,
3228 unsigned long action, void *hcpu)
3230 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
3231 buffer_exit_cpu((unsigned long)hcpu);
3236 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3237 * @bh: struct buffer_head
3239 * Return true if the buffer is up-to-date and false,
3240 * with the buffer locked, if not.
3242 int bh_uptodate_or_lock(struct buffer_head *bh)
3244 if (!buffer_uptodate(bh)) {
3246 if (!buffer_uptodate(bh))
3252 EXPORT_SYMBOL(bh_uptodate_or_lock);
3255 * bh_submit_read - Submit a locked buffer for reading
3256 * @bh: struct buffer_head
3258 * Returns zero on success and -EIO on error.
3260 int bh_submit_read(struct buffer_head *bh)
3262 BUG_ON(!buffer_locked(bh));
3264 if (buffer_uptodate(bh)) {
3270 bh->b_end_io = end_buffer_read_sync;
3271 submit_bh(READ, bh);
3273 if (buffer_uptodate(bh))
3277 EXPORT_SYMBOL(bh_submit_read);
3279 void __init buffer_init(void)
3283 bh_cachep = kmem_cache_create("buffer_head",
3284 sizeof(struct buffer_head), 0,
3285 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3290 * Limit the bh occupancy to 10% of ZONE_NORMAL
3292 nrpages = (nr_free_buffer_pages() * 10) / 100;
3293 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3294 hotcpu_notifier(buffer_cpu_notify, 0);