ocfs2: fix locking for res->tracking and dlm->tracking_list
[linux/fpc-iii.git] / fs / buffer.c
blob6f7d519a093b2c69e51280483ac326cd1ec2cd5e
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/backing-dev.h>
34 #include <linux/writeback.h>
35 #include <linux/hash.h>
36 #include <linux/suspend.h>
37 #include <linux/buffer_head.h>
38 #include <linux/task_io_accounting_ops.h>
39 #include <linux/bio.h>
40 #include <linux/notifier.h>
41 #include <linux/cpu.h>
42 #include <linux/bitops.h>
43 #include <linux/mpage.h>
44 #include <linux/bit_spinlock.h>
45 #include <trace/events/block.h>
47 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
48 static int submit_bh_wbc(int rw, struct buffer_head *bh,
49 unsigned long bio_flags,
50 struct writeback_control *wbc);
52 #define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
54 void init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
56 bh->b_end_io = handler;
57 bh->b_private = private;
59 EXPORT_SYMBOL(init_buffer);
61 inline void touch_buffer(struct buffer_head *bh)
63 trace_block_touch_buffer(bh);
64 mark_page_accessed(bh->b_page);
66 EXPORT_SYMBOL(touch_buffer);
68 void __lock_buffer(struct buffer_head *bh)
70 wait_on_bit_lock_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
72 EXPORT_SYMBOL(__lock_buffer);
74 void unlock_buffer(struct buffer_head *bh)
76 clear_bit_unlock(BH_Lock, &bh->b_state);
77 smp_mb__after_atomic();
78 wake_up_bit(&bh->b_state, BH_Lock);
80 EXPORT_SYMBOL(unlock_buffer);
83 * Returns if the page has dirty or writeback buffers. If all the buffers
84 * are unlocked and clean then the PageDirty information is stale. If
85 * any of the pages are locked, it is assumed they are locked for IO.
87 void buffer_check_dirty_writeback(struct page *page,
88 bool *dirty, bool *writeback)
90 struct buffer_head *head, *bh;
91 *dirty = false;
92 *writeback = false;
94 BUG_ON(!PageLocked(page));
96 if (!page_has_buffers(page))
97 return;
99 if (PageWriteback(page))
100 *writeback = true;
102 head = page_buffers(page);
103 bh = head;
104 do {
105 if (buffer_locked(bh))
106 *writeback = true;
108 if (buffer_dirty(bh))
109 *dirty = true;
111 bh = bh->b_this_page;
112 } while (bh != head);
114 EXPORT_SYMBOL(buffer_check_dirty_writeback);
117 * Block until a buffer comes unlocked. This doesn't stop it
118 * from becoming locked again - you have to lock it yourself
119 * if you want to preserve its state.
121 void __wait_on_buffer(struct buffer_head * bh)
123 wait_on_bit_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
125 EXPORT_SYMBOL(__wait_on_buffer);
127 static void
128 __clear_page_buffers(struct page *page)
130 ClearPagePrivate(page);
131 set_page_private(page, 0);
132 page_cache_release(page);
135 static void buffer_io_error(struct buffer_head *bh, char *msg)
137 char b[BDEVNAME_SIZE];
139 if (!test_bit(BH_Quiet, &bh->b_state))
140 printk_ratelimited(KERN_ERR
141 "Buffer I/O error on dev %s, logical block %llu%s\n",
142 bdevname(bh->b_bdev, b),
143 (unsigned long long)bh->b_blocknr, msg);
147 * End-of-IO handler helper function which does not touch the bh after
148 * unlocking it.
149 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
150 * a race there is benign: unlock_buffer() only use the bh's address for
151 * hashing after unlocking the buffer, so it doesn't actually touch the bh
152 * itself.
154 static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
156 if (uptodate) {
157 set_buffer_uptodate(bh);
158 } else {
159 /* This happens, due to failed READA attempts. */
160 clear_buffer_uptodate(bh);
162 unlock_buffer(bh);
166 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
167 * unlock the buffer. This is what ll_rw_block uses too.
169 void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
171 __end_buffer_read_notouch(bh, uptodate);
172 put_bh(bh);
174 EXPORT_SYMBOL(end_buffer_read_sync);
176 void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
178 if (uptodate) {
179 set_buffer_uptodate(bh);
180 } else {
181 buffer_io_error(bh, ", lost sync page write");
182 set_buffer_write_io_error(bh);
183 clear_buffer_uptodate(bh);
185 unlock_buffer(bh);
186 put_bh(bh);
188 EXPORT_SYMBOL(end_buffer_write_sync);
191 * Various filesystems appear to want __find_get_block to be non-blocking.
192 * But it's the page lock which protects the buffers. To get around this,
193 * we get exclusion from try_to_free_buffers with the blockdev mapping's
194 * private_lock.
196 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
197 * may be quite high. This code could TryLock the page, and if that
198 * succeeds, there is no need to take private_lock. (But if
199 * private_lock is contended then so is mapping->tree_lock).
201 static struct buffer_head *
202 __find_get_block_slow(struct block_device *bdev, sector_t block)
204 struct inode *bd_inode = bdev->bd_inode;
205 struct address_space *bd_mapping = bd_inode->i_mapping;
206 struct buffer_head *ret = NULL;
207 pgoff_t index;
208 struct buffer_head *bh;
209 struct buffer_head *head;
210 struct page *page;
211 int all_mapped = 1;
213 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
214 page = find_get_page_flags(bd_mapping, index, FGP_ACCESSED);
215 if (!page)
216 goto out;
218 spin_lock(&bd_mapping->private_lock);
219 if (!page_has_buffers(page))
220 goto out_unlock;
221 head = page_buffers(page);
222 bh = head;
223 do {
224 if (!buffer_mapped(bh))
225 all_mapped = 0;
226 else if (bh->b_blocknr == block) {
227 ret = bh;
228 get_bh(bh);
229 goto out_unlock;
231 bh = bh->b_this_page;
232 } while (bh != head);
234 /* we might be here because some of the buffers on this page are
235 * not mapped. This is due to various races between
236 * file io on the block device and getblk. It gets dealt with
237 * elsewhere, don't buffer_error if we had some unmapped buffers
239 if (all_mapped) {
240 char b[BDEVNAME_SIZE];
242 printk("__find_get_block_slow() failed. "
243 "block=%llu, b_blocknr=%llu\n",
244 (unsigned long long)block,
245 (unsigned long long)bh->b_blocknr);
246 printk("b_state=0x%08lx, b_size=%zu\n",
247 bh->b_state, bh->b_size);
248 printk("device %s blocksize: %d\n", bdevname(bdev, b),
249 1 << bd_inode->i_blkbits);
251 out_unlock:
252 spin_unlock(&bd_mapping->private_lock);
253 page_cache_release(page);
254 out:
255 return ret;
259 * Kick the writeback threads then try to free up some ZONE_NORMAL memory.
261 static void free_more_memory(void)
263 struct zone *zone;
264 int nid;
266 wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM);
267 yield();
269 for_each_online_node(nid) {
270 (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS),
271 gfp_zone(GFP_NOFS), NULL,
272 &zone);
273 if (zone)
274 try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0,
275 GFP_NOFS, NULL);
280 * I/O completion handler for block_read_full_page() - pages
281 * which come unlocked at the end of I/O.
283 static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
285 unsigned long flags;
286 struct buffer_head *first;
287 struct buffer_head *tmp;
288 struct page *page;
289 int page_uptodate = 1;
291 BUG_ON(!buffer_async_read(bh));
293 page = bh->b_page;
294 if (uptodate) {
295 set_buffer_uptodate(bh);
296 } else {
297 clear_buffer_uptodate(bh);
298 buffer_io_error(bh, ", async page read");
299 SetPageError(page);
303 * Be _very_ careful from here on. Bad things can happen if
304 * two buffer heads end IO at almost the same time and both
305 * decide that the page is now completely done.
307 first = page_buffers(page);
308 local_irq_save(flags);
309 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
310 clear_buffer_async_read(bh);
311 unlock_buffer(bh);
312 tmp = bh;
313 do {
314 if (!buffer_uptodate(tmp))
315 page_uptodate = 0;
316 if (buffer_async_read(tmp)) {
317 BUG_ON(!buffer_locked(tmp));
318 goto still_busy;
320 tmp = tmp->b_this_page;
321 } while (tmp != bh);
322 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
323 local_irq_restore(flags);
326 * If none of the buffers had errors and they are all
327 * uptodate then we can set the page uptodate.
329 if (page_uptodate && !PageError(page))
330 SetPageUptodate(page);
331 unlock_page(page);
332 return;
334 still_busy:
335 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
336 local_irq_restore(flags);
337 return;
341 * Completion handler for block_write_full_page() - pages which are unlocked
342 * during I/O, and which have PageWriteback cleared upon I/O completion.
344 void end_buffer_async_write(struct buffer_head *bh, int uptodate)
346 unsigned long flags;
347 struct buffer_head *first;
348 struct buffer_head *tmp;
349 struct page *page;
351 BUG_ON(!buffer_async_write(bh));
353 page = bh->b_page;
354 if (uptodate) {
355 set_buffer_uptodate(bh);
356 } else {
357 buffer_io_error(bh, ", lost async page write");
358 set_bit(AS_EIO, &page->mapping->flags);
359 set_buffer_write_io_error(bh);
360 clear_buffer_uptodate(bh);
361 SetPageError(page);
364 first = page_buffers(page);
365 local_irq_save(flags);
366 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
368 clear_buffer_async_write(bh);
369 unlock_buffer(bh);
370 tmp = bh->b_this_page;
371 while (tmp != bh) {
372 if (buffer_async_write(tmp)) {
373 BUG_ON(!buffer_locked(tmp));
374 goto still_busy;
376 tmp = tmp->b_this_page;
378 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
379 local_irq_restore(flags);
380 end_page_writeback(page);
381 return;
383 still_busy:
384 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
385 local_irq_restore(flags);
386 return;
388 EXPORT_SYMBOL(end_buffer_async_write);
391 * If a page's buffers are under async readin (end_buffer_async_read
392 * completion) then there is a possibility that another thread of
393 * control could lock one of the buffers after it has completed
394 * but while some of the other buffers have not completed. This
395 * locked buffer would confuse end_buffer_async_read() into not unlocking
396 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
397 * that this buffer is not under async I/O.
399 * The page comes unlocked when it has no locked buffer_async buffers
400 * left.
402 * PageLocked prevents anyone starting new async I/O reads any of
403 * the buffers.
405 * PageWriteback is used to prevent simultaneous writeout of the same
406 * page.
408 * PageLocked prevents anyone from starting writeback of a page which is
409 * under read I/O (PageWriteback is only ever set against a locked page).
411 static void mark_buffer_async_read(struct buffer_head *bh)
413 bh->b_end_io = end_buffer_async_read;
414 set_buffer_async_read(bh);
417 static void mark_buffer_async_write_endio(struct buffer_head *bh,
418 bh_end_io_t *handler)
420 bh->b_end_io = handler;
421 set_buffer_async_write(bh);
424 void mark_buffer_async_write(struct buffer_head *bh)
426 mark_buffer_async_write_endio(bh, end_buffer_async_write);
428 EXPORT_SYMBOL(mark_buffer_async_write);
432 * fs/buffer.c contains helper functions for buffer-backed address space's
433 * fsync functions. A common requirement for buffer-based filesystems is
434 * that certain data from the backing blockdev needs to be written out for
435 * a successful fsync(). For example, ext2 indirect blocks need to be
436 * written back and waited upon before fsync() returns.
438 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
439 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
440 * management of a list of dependent buffers at ->i_mapping->private_list.
442 * Locking is a little subtle: try_to_free_buffers() will remove buffers
443 * from their controlling inode's queue when they are being freed. But
444 * try_to_free_buffers() will be operating against the *blockdev* mapping
445 * at the time, not against the S_ISREG file which depends on those buffers.
446 * So the locking for private_list is via the private_lock in the address_space
447 * which backs the buffers. Which is different from the address_space
448 * against which the buffers are listed. So for a particular address_space,
449 * mapping->private_lock does *not* protect mapping->private_list! In fact,
450 * mapping->private_list will always be protected by the backing blockdev's
451 * ->private_lock.
453 * Which introduces a requirement: all buffers on an address_space's
454 * ->private_list must be from the same address_space: the blockdev's.
456 * address_spaces which do not place buffers at ->private_list via these
457 * utility functions are free to use private_lock and private_list for
458 * whatever they want. The only requirement is that list_empty(private_list)
459 * be true at clear_inode() time.
461 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
462 * filesystems should do that. invalidate_inode_buffers() should just go
463 * BUG_ON(!list_empty).
465 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
466 * take an address_space, not an inode. And it should be called
467 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
468 * queued up.
470 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
471 * list if it is already on a list. Because if the buffer is on a list,
472 * it *must* already be on the right one. If not, the filesystem is being
473 * silly. This will save a ton of locking. But first we have to ensure
474 * that buffers are taken *off* the old inode's list when they are freed
475 * (presumably in truncate). That requires careful auditing of all
476 * filesystems (do it inside bforget()). It could also be done by bringing
477 * b_inode back.
481 * The buffer's backing address_space's private_lock must be held
483 static void __remove_assoc_queue(struct buffer_head *bh)
485 list_del_init(&bh->b_assoc_buffers);
486 WARN_ON(!bh->b_assoc_map);
487 if (buffer_write_io_error(bh))
488 set_bit(AS_EIO, &bh->b_assoc_map->flags);
489 bh->b_assoc_map = NULL;
492 int inode_has_buffers(struct inode *inode)
494 return !list_empty(&inode->i_data.private_list);
498 * osync is designed to support O_SYNC io. It waits synchronously for
499 * all already-submitted IO to complete, but does not queue any new
500 * writes to the disk.
502 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
503 * you dirty the buffers, and then use osync_inode_buffers to wait for
504 * completion. Any other dirty buffers which are not yet queued for
505 * write will not be flushed to disk by the osync.
507 static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
509 struct buffer_head *bh;
510 struct list_head *p;
511 int err = 0;
513 spin_lock(lock);
514 repeat:
515 list_for_each_prev(p, list) {
516 bh = BH_ENTRY(p);
517 if (buffer_locked(bh)) {
518 get_bh(bh);
519 spin_unlock(lock);
520 wait_on_buffer(bh);
521 if (!buffer_uptodate(bh))
522 err = -EIO;
523 brelse(bh);
524 spin_lock(lock);
525 goto repeat;
528 spin_unlock(lock);
529 return err;
532 static void do_thaw_one(struct super_block *sb, void *unused)
534 char b[BDEVNAME_SIZE];
535 while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
536 printk(KERN_WARNING "Emergency Thaw on %s\n",
537 bdevname(sb->s_bdev, b));
540 static void do_thaw_all(struct work_struct *work)
542 iterate_supers(do_thaw_one, NULL);
543 kfree(work);
544 printk(KERN_WARNING "Emergency Thaw complete\n");
548 * emergency_thaw_all -- forcibly thaw every frozen filesystem
550 * Used for emergency unfreeze of all filesystems via SysRq
552 void emergency_thaw_all(void)
554 struct work_struct *work;
556 work = kmalloc(sizeof(*work), GFP_ATOMIC);
557 if (work) {
558 INIT_WORK(work, do_thaw_all);
559 schedule_work(work);
564 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
565 * @mapping: the mapping which wants those buffers written
567 * Starts I/O against the buffers at mapping->private_list, and waits upon
568 * that I/O.
570 * Basically, this is a convenience function for fsync().
571 * @mapping is a file or directory which needs those buffers to be written for
572 * a successful fsync().
574 int sync_mapping_buffers(struct address_space *mapping)
576 struct address_space *buffer_mapping = mapping->private_data;
578 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
579 return 0;
581 return fsync_buffers_list(&buffer_mapping->private_lock,
582 &mapping->private_list);
584 EXPORT_SYMBOL(sync_mapping_buffers);
587 * Called when we've recently written block `bblock', and it is known that
588 * `bblock' was for a buffer_boundary() buffer. This means that the block at
589 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
590 * dirty, schedule it for IO. So that indirects merge nicely with their data.
592 void write_boundary_block(struct block_device *bdev,
593 sector_t bblock, unsigned blocksize)
595 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
596 if (bh) {
597 if (buffer_dirty(bh))
598 ll_rw_block(WRITE, 1, &bh);
599 put_bh(bh);
603 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
605 struct address_space *mapping = inode->i_mapping;
606 struct address_space *buffer_mapping = bh->b_page->mapping;
608 mark_buffer_dirty(bh);
609 if (!mapping->private_data) {
610 mapping->private_data = buffer_mapping;
611 } else {
612 BUG_ON(mapping->private_data != buffer_mapping);
614 if (!bh->b_assoc_map) {
615 spin_lock(&buffer_mapping->private_lock);
616 list_move_tail(&bh->b_assoc_buffers,
617 &mapping->private_list);
618 bh->b_assoc_map = mapping;
619 spin_unlock(&buffer_mapping->private_lock);
622 EXPORT_SYMBOL(mark_buffer_dirty_inode);
625 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
626 * dirty.
628 * If warn is true, then emit a warning if the page is not uptodate and has
629 * not been truncated.
631 * The caller must hold mem_cgroup_begin_page_stat() lock.
633 static void __set_page_dirty(struct page *page, struct address_space *mapping,
634 struct mem_cgroup *memcg, int warn)
636 unsigned long flags;
638 spin_lock_irqsave(&mapping->tree_lock, flags);
639 if (page->mapping) { /* Race with truncate? */
640 WARN_ON_ONCE(warn && !PageUptodate(page));
641 account_page_dirtied(page, mapping, memcg);
642 radix_tree_tag_set(&mapping->page_tree,
643 page_index(page), PAGECACHE_TAG_DIRTY);
645 spin_unlock_irqrestore(&mapping->tree_lock, flags);
649 * Add a page to the dirty page list.
651 * It is a sad fact of life that this function is called from several places
652 * deeply under spinlocking. It may not sleep.
654 * If the page has buffers, the uptodate buffers are set dirty, to preserve
655 * dirty-state coherency between the page and the buffers. It the page does
656 * not have buffers then when they are later attached they will all be set
657 * dirty.
659 * The buffers are dirtied before the page is dirtied. There's a small race
660 * window in which a writepage caller may see the page cleanness but not the
661 * buffer dirtiness. That's fine. If this code were to set the page dirty
662 * before the buffers, a concurrent writepage caller could clear the page dirty
663 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
664 * page on the dirty page list.
666 * We use private_lock to lock against try_to_free_buffers while using the
667 * page's buffer list. Also use this to protect against clean buffers being
668 * added to the page after it was set dirty.
670 * FIXME: may need to call ->reservepage here as well. That's rather up to the
671 * address_space though.
673 int __set_page_dirty_buffers(struct page *page)
675 int newly_dirty;
676 struct mem_cgroup *memcg;
677 struct address_space *mapping = page_mapping(page);
679 if (unlikely(!mapping))
680 return !TestSetPageDirty(page);
682 spin_lock(&mapping->private_lock);
683 if (page_has_buffers(page)) {
684 struct buffer_head *head = page_buffers(page);
685 struct buffer_head *bh = head;
687 do {
688 set_buffer_dirty(bh);
689 bh = bh->b_this_page;
690 } while (bh != head);
693 * Use mem_group_begin_page_stat() to keep PageDirty synchronized with
694 * per-memcg dirty page counters.
696 memcg = mem_cgroup_begin_page_stat(page);
697 newly_dirty = !TestSetPageDirty(page);
698 spin_unlock(&mapping->private_lock);
700 if (newly_dirty)
701 __set_page_dirty(page, mapping, memcg, 1);
703 mem_cgroup_end_page_stat(memcg);
705 if (newly_dirty)
706 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
708 return newly_dirty;
710 EXPORT_SYMBOL(__set_page_dirty_buffers);
713 * Write out and wait upon a list of buffers.
715 * We have conflicting pressures: we want to make sure that all
716 * initially dirty buffers get waited on, but that any subsequently
717 * dirtied buffers don't. After all, we don't want fsync to last
718 * forever if somebody is actively writing to the file.
720 * Do this in two main stages: first we copy dirty buffers to a
721 * temporary inode list, queueing the writes as we go. Then we clean
722 * up, waiting for those writes to complete.
724 * During this second stage, any subsequent updates to the file may end
725 * up refiling the buffer on the original inode's dirty list again, so
726 * there is a chance we will end up with a buffer queued for write but
727 * not yet completed on that list. So, as a final cleanup we go through
728 * the osync code to catch these locked, dirty buffers without requeuing
729 * any newly dirty buffers for write.
731 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
733 struct buffer_head *bh;
734 struct list_head tmp;
735 struct address_space *mapping;
736 int err = 0, err2;
737 struct blk_plug plug;
739 INIT_LIST_HEAD(&tmp);
740 blk_start_plug(&plug);
742 spin_lock(lock);
743 while (!list_empty(list)) {
744 bh = BH_ENTRY(list->next);
745 mapping = bh->b_assoc_map;
746 __remove_assoc_queue(bh);
747 /* Avoid race with mark_buffer_dirty_inode() which does
748 * a lockless check and we rely on seeing the dirty bit */
749 smp_mb();
750 if (buffer_dirty(bh) || buffer_locked(bh)) {
751 list_add(&bh->b_assoc_buffers, &tmp);
752 bh->b_assoc_map = mapping;
753 if (buffer_dirty(bh)) {
754 get_bh(bh);
755 spin_unlock(lock);
757 * Ensure any pending I/O completes so that
758 * write_dirty_buffer() actually writes the
759 * current contents - it is a noop if I/O is
760 * still in flight on potentially older
761 * contents.
763 write_dirty_buffer(bh, WRITE_SYNC);
766 * Kick off IO for the previous mapping. Note
767 * that we will not run the very last mapping,
768 * wait_on_buffer() will do that for us
769 * through sync_buffer().
771 brelse(bh);
772 spin_lock(lock);
777 spin_unlock(lock);
778 blk_finish_plug(&plug);
779 spin_lock(lock);
781 while (!list_empty(&tmp)) {
782 bh = BH_ENTRY(tmp.prev);
783 get_bh(bh);
784 mapping = bh->b_assoc_map;
785 __remove_assoc_queue(bh);
786 /* Avoid race with mark_buffer_dirty_inode() which does
787 * a lockless check and we rely on seeing the dirty bit */
788 smp_mb();
789 if (buffer_dirty(bh)) {
790 list_add(&bh->b_assoc_buffers,
791 &mapping->private_list);
792 bh->b_assoc_map = mapping;
794 spin_unlock(lock);
795 wait_on_buffer(bh);
796 if (!buffer_uptodate(bh))
797 err = -EIO;
798 brelse(bh);
799 spin_lock(lock);
802 spin_unlock(lock);
803 err2 = osync_buffers_list(lock, list);
804 if (err)
805 return err;
806 else
807 return err2;
811 * Invalidate any and all dirty buffers on a given inode. We are
812 * probably unmounting the fs, but that doesn't mean we have already
813 * done a sync(). Just drop the buffers from the inode list.
815 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
816 * assumes that all the buffers are against the blockdev. Not true
817 * for reiserfs.
819 void invalidate_inode_buffers(struct inode *inode)
821 if (inode_has_buffers(inode)) {
822 struct address_space *mapping = &inode->i_data;
823 struct list_head *list = &mapping->private_list;
824 struct address_space *buffer_mapping = mapping->private_data;
826 spin_lock(&buffer_mapping->private_lock);
827 while (!list_empty(list))
828 __remove_assoc_queue(BH_ENTRY(list->next));
829 spin_unlock(&buffer_mapping->private_lock);
832 EXPORT_SYMBOL(invalidate_inode_buffers);
835 * Remove any clean buffers from the inode's buffer list. This is called
836 * when we're trying to free the inode itself. Those buffers can pin it.
838 * Returns true if all buffers were removed.
840 int remove_inode_buffers(struct inode *inode)
842 int ret = 1;
844 if (inode_has_buffers(inode)) {
845 struct address_space *mapping = &inode->i_data;
846 struct list_head *list = &mapping->private_list;
847 struct address_space *buffer_mapping = mapping->private_data;
849 spin_lock(&buffer_mapping->private_lock);
850 while (!list_empty(list)) {
851 struct buffer_head *bh = BH_ENTRY(list->next);
852 if (buffer_dirty(bh)) {
853 ret = 0;
854 break;
856 __remove_assoc_queue(bh);
858 spin_unlock(&buffer_mapping->private_lock);
860 return ret;
864 * Create the appropriate buffers when given a page for data area and
865 * the size of each buffer.. Use the bh->b_this_page linked list to
866 * follow the buffers created. Return NULL if unable to create more
867 * buffers.
869 * The retry flag is used to differentiate async IO (paging, swapping)
870 * which may not fail from ordinary buffer allocations.
872 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
873 int retry)
875 struct buffer_head *bh, *head;
876 long offset;
878 try_again:
879 head = NULL;
880 offset = PAGE_SIZE;
881 while ((offset -= size) >= 0) {
882 bh = alloc_buffer_head(GFP_NOFS);
883 if (!bh)
884 goto no_grow;
886 bh->b_this_page = head;
887 bh->b_blocknr = -1;
888 head = bh;
890 bh->b_size = size;
892 /* Link the buffer to its page */
893 set_bh_page(bh, page, offset);
895 return head;
897 * In case anything failed, we just free everything we got.
899 no_grow:
900 if (head) {
901 do {
902 bh = head;
903 head = head->b_this_page;
904 free_buffer_head(bh);
905 } while (head);
909 * Return failure for non-async IO requests. Async IO requests
910 * are not allowed to fail, so we have to wait until buffer heads
911 * become available. But we don't want tasks sleeping with
912 * partially complete buffers, so all were released above.
914 if (!retry)
915 return NULL;
917 /* We're _really_ low on memory. Now we just
918 * wait for old buffer heads to become free due to
919 * finishing IO. Since this is an async request and
920 * the reserve list is empty, we're sure there are
921 * async buffer heads in use.
923 free_more_memory();
924 goto try_again;
926 EXPORT_SYMBOL_GPL(alloc_page_buffers);
928 static inline void
929 link_dev_buffers(struct page *page, struct buffer_head *head)
931 struct buffer_head *bh, *tail;
933 bh = head;
934 do {
935 tail = bh;
936 bh = bh->b_this_page;
937 } while (bh);
938 tail->b_this_page = head;
939 attach_page_buffers(page, head);
942 static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
944 sector_t retval = ~((sector_t)0);
945 loff_t sz = i_size_read(bdev->bd_inode);
947 if (sz) {
948 unsigned int sizebits = blksize_bits(size);
949 retval = (sz >> sizebits);
951 return retval;
955 * Initialise the state of a blockdev page's buffers.
957 static sector_t
958 init_page_buffers(struct page *page, struct block_device *bdev,
959 sector_t block, int size)
961 struct buffer_head *head = page_buffers(page);
962 struct buffer_head *bh = head;
963 int uptodate = PageUptodate(page);
964 sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode), size);
966 do {
967 if (!buffer_mapped(bh)) {
968 init_buffer(bh, NULL, NULL);
969 bh->b_bdev = bdev;
970 bh->b_blocknr = block;
971 if (uptodate)
972 set_buffer_uptodate(bh);
973 if (block < end_block)
974 set_buffer_mapped(bh);
976 block++;
977 bh = bh->b_this_page;
978 } while (bh != head);
981 * Caller needs to validate requested block against end of device.
983 return end_block;
987 * Create the page-cache page that contains the requested block.
989 * This is used purely for blockdev mappings.
991 static int
992 grow_dev_page(struct block_device *bdev, sector_t block,
993 pgoff_t index, int size, int sizebits, gfp_t gfp)
995 struct inode *inode = bdev->bd_inode;
996 struct page *page;
997 struct buffer_head *bh;
998 sector_t end_block;
999 int ret = 0; /* Will call free_more_memory() */
1000 gfp_t gfp_mask;
1002 gfp_mask = mapping_gfp_constraint(inode->i_mapping, ~__GFP_FS) | gfp;
1005 * XXX: __getblk_slow() can not really deal with failure and
1006 * will endlessly loop on improvised global reclaim. Prefer
1007 * looping in the allocator rather than here, at least that
1008 * code knows what it's doing.
1010 gfp_mask |= __GFP_NOFAIL;
1012 page = find_or_create_page(inode->i_mapping, index, gfp_mask);
1013 if (!page)
1014 return ret;
1016 BUG_ON(!PageLocked(page));
1018 if (page_has_buffers(page)) {
1019 bh = page_buffers(page);
1020 if (bh->b_size == size) {
1021 end_block = init_page_buffers(page, bdev,
1022 (sector_t)index << sizebits,
1023 size);
1024 goto done;
1026 if (!try_to_free_buffers(page))
1027 goto failed;
1031 * Allocate some buffers for this page
1033 bh = alloc_page_buffers(page, size, 0);
1034 if (!bh)
1035 goto failed;
1038 * Link the page to the buffers and initialise them. Take the
1039 * lock to be atomic wrt __find_get_block(), which does not
1040 * run under the page lock.
1042 spin_lock(&inode->i_mapping->private_lock);
1043 link_dev_buffers(page, bh);
1044 end_block = init_page_buffers(page, bdev, (sector_t)index << sizebits,
1045 size);
1046 spin_unlock(&inode->i_mapping->private_lock);
1047 done:
1048 ret = (block < end_block) ? 1 : -ENXIO;
1049 failed:
1050 unlock_page(page);
1051 page_cache_release(page);
1052 return ret;
1056 * Create buffers for the specified block device block's page. If
1057 * that page was dirty, the buffers are set dirty also.
1059 static int
1060 grow_buffers(struct block_device *bdev, sector_t block, int size, gfp_t gfp)
1062 pgoff_t index;
1063 int sizebits;
1065 sizebits = -1;
1066 do {
1067 sizebits++;
1068 } while ((size << sizebits) < PAGE_SIZE);
1070 index = block >> sizebits;
1073 * Check for a block which wants to lie outside our maximum possible
1074 * pagecache index. (this comparison is done using sector_t types).
1076 if (unlikely(index != block >> sizebits)) {
1077 char b[BDEVNAME_SIZE];
1079 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1080 "device %s\n",
1081 __func__, (unsigned long long)block,
1082 bdevname(bdev, b));
1083 return -EIO;
1086 /* Create a page with the proper size buffers.. */
1087 return grow_dev_page(bdev, block, index, size, sizebits, gfp);
1090 struct buffer_head *
1091 __getblk_slow(struct block_device *bdev, sector_t block,
1092 unsigned size, gfp_t gfp)
1094 /* Size must be multiple of hard sectorsize */
1095 if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
1096 (size < 512 || size > PAGE_SIZE))) {
1097 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1098 size);
1099 printk(KERN_ERR "logical block size: %d\n",
1100 bdev_logical_block_size(bdev));
1102 dump_stack();
1103 return NULL;
1106 for (;;) {
1107 struct buffer_head *bh;
1108 int ret;
1110 bh = __find_get_block(bdev, block, size);
1111 if (bh)
1112 return bh;
1114 ret = grow_buffers(bdev, block, size, gfp);
1115 if (ret < 0)
1116 return NULL;
1117 if (ret == 0)
1118 free_more_memory();
1121 EXPORT_SYMBOL(__getblk_slow);
1124 * The relationship between dirty buffers and dirty pages:
1126 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1127 * the page is tagged dirty in its radix tree.
1129 * At all times, the dirtiness of the buffers represents the dirtiness of
1130 * subsections of the page. If the page has buffers, the page dirty bit is
1131 * merely a hint about the true dirty state.
1133 * When a page is set dirty in its entirety, all its buffers are marked dirty
1134 * (if the page has buffers).
1136 * When a buffer is marked dirty, its page is dirtied, but the page's other
1137 * buffers are not.
1139 * Also. When blockdev buffers are explicitly read with bread(), they
1140 * individually become uptodate. But their backing page remains not
1141 * uptodate - even if all of its buffers are uptodate. A subsequent
1142 * block_read_full_page() against that page will discover all the uptodate
1143 * buffers, will set the page uptodate and will perform no I/O.
1147 * mark_buffer_dirty - mark a buffer_head as needing writeout
1148 * @bh: the buffer_head to mark dirty
1150 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1151 * backing page dirty, then tag the page as dirty in its address_space's radix
1152 * tree and then attach the address_space's inode to its superblock's dirty
1153 * inode list.
1155 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1156 * mapping->tree_lock and mapping->host->i_lock.
1158 void mark_buffer_dirty(struct buffer_head *bh)
1160 WARN_ON_ONCE(!buffer_uptodate(bh));
1162 trace_block_dirty_buffer(bh);
1165 * Very *carefully* optimize the it-is-already-dirty case.
1167 * Don't let the final "is it dirty" escape to before we
1168 * perhaps modified the buffer.
1170 if (buffer_dirty(bh)) {
1171 smp_mb();
1172 if (buffer_dirty(bh))
1173 return;
1176 if (!test_set_buffer_dirty(bh)) {
1177 struct page *page = bh->b_page;
1178 struct address_space *mapping = NULL;
1179 struct mem_cgroup *memcg;
1181 memcg = mem_cgroup_begin_page_stat(page);
1182 if (!TestSetPageDirty(page)) {
1183 mapping = page_mapping(page);
1184 if (mapping)
1185 __set_page_dirty(page, mapping, memcg, 0);
1187 mem_cgroup_end_page_stat(memcg);
1188 if (mapping)
1189 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
1192 EXPORT_SYMBOL(mark_buffer_dirty);
1195 * Decrement a buffer_head's reference count. If all buffers against a page
1196 * have zero reference count, are clean and unlocked, and if the page is clean
1197 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1198 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1199 * a page but it ends up not being freed, and buffers may later be reattached).
1201 void __brelse(struct buffer_head * buf)
1203 if (atomic_read(&buf->b_count)) {
1204 put_bh(buf);
1205 return;
1207 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1209 EXPORT_SYMBOL(__brelse);
1212 * bforget() is like brelse(), except it discards any
1213 * potentially dirty data.
1215 void __bforget(struct buffer_head *bh)
1217 clear_buffer_dirty(bh);
1218 if (bh->b_assoc_map) {
1219 struct address_space *buffer_mapping = bh->b_page->mapping;
1221 spin_lock(&buffer_mapping->private_lock);
1222 list_del_init(&bh->b_assoc_buffers);
1223 bh->b_assoc_map = NULL;
1224 spin_unlock(&buffer_mapping->private_lock);
1226 __brelse(bh);
1228 EXPORT_SYMBOL(__bforget);
1230 static struct buffer_head *__bread_slow(struct buffer_head *bh)
1232 lock_buffer(bh);
1233 if (buffer_uptodate(bh)) {
1234 unlock_buffer(bh);
1235 return bh;
1236 } else {
1237 get_bh(bh);
1238 bh->b_end_io = end_buffer_read_sync;
1239 submit_bh(READ, bh);
1240 wait_on_buffer(bh);
1241 if (buffer_uptodate(bh))
1242 return bh;
1244 brelse(bh);
1245 return NULL;
1249 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1250 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1251 * refcount elevated by one when they're in an LRU. A buffer can only appear
1252 * once in a particular CPU's LRU. A single buffer can be present in multiple
1253 * CPU's LRUs at the same time.
1255 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1256 * sb_find_get_block().
1258 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1259 * a local interrupt disable for that.
1262 #define BH_LRU_SIZE 16
1264 struct bh_lru {
1265 struct buffer_head *bhs[BH_LRU_SIZE];
1268 static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1270 #ifdef CONFIG_SMP
1271 #define bh_lru_lock() local_irq_disable()
1272 #define bh_lru_unlock() local_irq_enable()
1273 #else
1274 #define bh_lru_lock() preempt_disable()
1275 #define bh_lru_unlock() preempt_enable()
1276 #endif
1278 static inline void check_irqs_on(void)
1280 #ifdef irqs_disabled
1281 BUG_ON(irqs_disabled());
1282 #endif
1286 * The LRU management algorithm is dopey-but-simple. Sorry.
1288 static void bh_lru_install(struct buffer_head *bh)
1290 struct buffer_head *evictee = NULL;
1292 check_irqs_on();
1293 bh_lru_lock();
1294 if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
1295 struct buffer_head *bhs[BH_LRU_SIZE];
1296 int in;
1297 int out = 0;
1299 get_bh(bh);
1300 bhs[out++] = bh;
1301 for (in = 0; in < BH_LRU_SIZE; in++) {
1302 struct buffer_head *bh2 =
1303 __this_cpu_read(bh_lrus.bhs[in]);
1305 if (bh2 == bh) {
1306 __brelse(bh2);
1307 } else {
1308 if (out >= BH_LRU_SIZE) {
1309 BUG_ON(evictee != NULL);
1310 evictee = bh2;
1311 } else {
1312 bhs[out++] = bh2;
1316 while (out < BH_LRU_SIZE)
1317 bhs[out++] = NULL;
1318 memcpy(this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
1320 bh_lru_unlock();
1322 if (evictee)
1323 __brelse(evictee);
1327 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1329 static struct buffer_head *
1330 lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1332 struct buffer_head *ret = NULL;
1333 unsigned int i;
1335 check_irqs_on();
1336 bh_lru_lock();
1337 for (i = 0; i < BH_LRU_SIZE; i++) {
1338 struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
1340 if (bh && bh->b_blocknr == block && bh->b_bdev == bdev &&
1341 bh->b_size == size) {
1342 if (i) {
1343 while (i) {
1344 __this_cpu_write(bh_lrus.bhs[i],
1345 __this_cpu_read(bh_lrus.bhs[i - 1]));
1346 i--;
1348 __this_cpu_write(bh_lrus.bhs[0], bh);
1350 get_bh(bh);
1351 ret = bh;
1352 break;
1355 bh_lru_unlock();
1356 return ret;
1360 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1361 * it in the LRU and mark it as accessed. If it is not present then return
1362 * NULL
1364 struct buffer_head *
1365 __find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1367 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1369 if (bh == NULL) {
1370 /* __find_get_block_slow will mark the page accessed */
1371 bh = __find_get_block_slow(bdev, block);
1372 if (bh)
1373 bh_lru_install(bh);
1374 } else
1375 touch_buffer(bh);
1377 return bh;
1379 EXPORT_SYMBOL(__find_get_block);
1382 * __getblk_gfp() will locate (and, if necessary, create) the buffer_head
1383 * which corresponds to the passed block_device, block and size. The
1384 * returned buffer has its reference count incremented.
1386 * __getblk_gfp() will lock up the machine if grow_dev_page's
1387 * try_to_free_buffers() attempt is failing. FIXME, perhaps?
1389 struct buffer_head *
1390 __getblk_gfp(struct block_device *bdev, sector_t block,
1391 unsigned size, gfp_t gfp)
1393 struct buffer_head *bh = __find_get_block(bdev, block, size);
1395 might_sleep();
1396 if (bh == NULL)
1397 bh = __getblk_slow(bdev, block, size, gfp);
1398 return bh;
1400 EXPORT_SYMBOL(__getblk_gfp);
1403 * Do async read-ahead on a buffer..
1405 void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1407 struct buffer_head *bh = __getblk(bdev, block, size);
1408 if (likely(bh)) {
1409 ll_rw_block(READA, 1, &bh);
1410 brelse(bh);
1413 EXPORT_SYMBOL(__breadahead);
1416 * __bread_gfp() - reads a specified block and returns the bh
1417 * @bdev: the block_device to read from
1418 * @block: number of block
1419 * @size: size (in bytes) to read
1420 * @gfp: page allocation flag
1422 * Reads a specified block, and returns buffer head that contains it.
1423 * The page cache can be allocated from non-movable area
1424 * not to prevent page migration if you set gfp to zero.
1425 * It returns NULL if the block was unreadable.
1427 struct buffer_head *
1428 __bread_gfp(struct block_device *bdev, sector_t block,
1429 unsigned size, gfp_t gfp)
1431 struct buffer_head *bh = __getblk_gfp(bdev, block, size, gfp);
1433 if (likely(bh) && !buffer_uptodate(bh))
1434 bh = __bread_slow(bh);
1435 return bh;
1437 EXPORT_SYMBOL(__bread_gfp);
1440 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1441 * This doesn't race because it runs in each cpu either in irq
1442 * or with preempt disabled.
1444 static void invalidate_bh_lru(void *arg)
1446 struct bh_lru *b = &get_cpu_var(bh_lrus);
1447 int i;
1449 for (i = 0; i < BH_LRU_SIZE; i++) {
1450 brelse(b->bhs[i]);
1451 b->bhs[i] = NULL;
1453 put_cpu_var(bh_lrus);
1456 static bool has_bh_in_lru(int cpu, void *dummy)
1458 struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1459 int i;
1461 for (i = 0; i < BH_LRU_SIZE; i++) {
1462 if (b->bhs[i])
1463 return 1;
1466 return 0;
1469 void invalidate_bh_lrus(void)
1471 on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL);
1473 EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1475 void set_bh_page(struct buffer_head *bh,
1476 struct page *page, unsigned long offset)
1478 bh->b_page = page;
1479 BUG_ON(offset >= PAGE_SIZE);
1480 if (PageHighMem(page))
1482 * This catches illegal uses and preserves the offset:
1484 bh->b_data = (char *)(0 + offset);
1485 else
1486 bh->b_data = page_address(page) + offset;
1488 EXPORT_SYMBOL(set_bh_page);
1491 * Called when truncating a buffer on a page completely.
1494 /* Bits that are cleared during an invalidate */
1495 #define BUFFER_FLAGS_DISCARD \
1496 (1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \
1497 1 << BH_Delay | 1 << BH_Unwritten)
1499 static void discard_buffer(struct buffer_head * bh)
1501 unsigned long b_state, b_state_old;
1503 lock_buffer(bh);
1504 clear_buffer_dirty(bh);
1505 bh->b_bdev = NULL;
1506 b_state = bh->b_state;
1507 for (;;) {
1508 b_state_old = cmpxchg(&bh->b_state, b_state,
1509 (b_state & ~BUFFER_FLAGS_DISCARD));
1510 if (b_state_old == b_state)
1511 break;
1512 b_state = b_state_old;
1514 unlock_buffer(bh);
1518 * block_invalidatepage - invalidate part or all of a buffer-backed page
1520 * @page: the page which is affected
1521 * @offset: start of the range to invalidate
1522 * @length: length of the range to invalidate
1524 * block_invalidatepage() is called when all or part of the page has become
1525 * invalidated by a truncate operation.
1527 * block_invalidatepage() does not have to release all buffers, but it must
1528 * ensure that no dirty buffer is left outside @offset and that no I/O
1529 * is underway against any of the blocks which are outside the truncation
1530 * point. Because the caller is about to free (and possibly reuse) those
1531 * blocks on-disk.
1533 void block_invalidatepage(struct page *page, unsigned int offset,
1534 unsigned int length)
1536 struct buffer_head *head, *bh, *next;
1537 unsigned int curr_off = 0;
1538 unsigned int stop = length + offset;
1540 BUG_ON(!PageLocked(page));
1541 if (!page_has_buffers(page))
1542 goto out;
1545 * Check for overflow
1547 BUG_ON(stop > PAGE_CACHE_SIZE || stop < length);
1549 head = page_buffers(page);
1550 bh = head;
1551 do {
1552 unsigned int next_off = curr_off + bh->b_size;
1553 next = bh->b_this_page;
1556 * Are we still fully in range ?
1558 if (next_off > stop)
1559 goto out;
1562 * is this block fully invalidated?
1564 if (offset <= curr_off)
1565 discard_buffer(bh);
1566 curr_off = next_off;
1567 bh = next;
1568 } while (bh != head);
1571 * We release buffers only if the entire page is being invalidated.
1572 * The get_block cached value has been unconditionally invalidated,
1573 * so real IO is not possible anymore.
1575 if (offset == 0)
1576 try_to_release_page(page, 0);
1577 out:
1578 return;
1580 EXPORT_SYMBOL(block_invalidatepage);
1584 * We attach and possibly dirty the buffers atomically wrt
1585 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1586 * is already excluded via the page lock.
1588 void create_empty_buffers(struct page *page,
1589 unsigned long blocksize, unsigned long b_state)
1591 struct buffer_head *bh, *head, *tail;
1593 head = alloc_page_buffers(page, blocksize, 1);
1594 bh = head;
1595 do {
1596 bh->b_state |= b_state;
1597 tail = bh;
1598 bh = bh->b_this_page;
1599 } while (bh);
1600 tail->b_this_page = head;
1602 spin_lock(&page->mapping->private_lock);
1603 if (PageUptodate(page) || PageDirty(page)) {
1604 bh = head;
1605 do {
1606 if (PageDirty(page))
1607 set_buffer_dirty(bh);
1608 if (PageUptodate(page))
1609 set_buffer_uptodate(bh);
1610 bh = bh->b_this_page;
1611 } while (bh != head);
1613 attach_page_buffers(page, head);
1614 spin_unlock(&page->mapping->private_lock);
1616 EXPORT_SYMBOL(create_empty_buffers);
1619 * We are taking a block for data and we don't want any output from any
1620 * buffer-cache aliases starting from return from that function and
1621 * until the moment when something will explicitly mark the buffer
1622 * dirty (hopefully that will not happen until we will free that block ;-)
1623 * We don't even need to mark it not-uptodate - nobody can expect
1624 * anything from a newly allocated buffer anyway. We used to used
1625 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1626 * don't want to mark the alias unmapped, for example - it would confuse
1627 * anyone who might pick it with bread() afterwards...
1629 * Also.. Note that bforget() doesn't lock the buffer. So there can
1630 * be writeout I/O going on against recently-freed buffers. We don't
1631 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1632 * only if we really need to. That happens here.
1634 void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1636 struct buffer_head *old_bh;
1638 might_sleep();
1640 old_bh = __find_get_block_slow(bdev, block);
1641 if (old_bh) {
1642 clear_buffer_dirty(old_bh);
1643 wait_on_buffer(old_bh);
1644 clear_buffer_req(old_bh);
1645 __brelse(old_bh);
1648 EXPORT_SYMBOL(unmap_underlying_metadata);
1651 * Size is a power-of-two in the range 512..PAGE_SIZE,
1652 * and the case we care about most is PAGE_SIZE.
1654 * So this *could* possibly be written with those
1655 * constraints in mind (relevant mostly if some
1656 * architecture has a slow bit-scan instruction)
1658 static inline int block_size_bits(unsigned int blocksize)
1660 return ilog2(blocksize);
1663 static struct buffer_head *create_page_buffers(struct page *page, struct inode *inode, unsigned int b_state)
1665 BUG_ON(!PageLocked(page));
1667 if (!page_has_buffers(page))
1668 create_empty_buffers(page, 1 << ACCESS_ONCE(inode->i_blkbits), b_state);
1669 return page_buffers(page);
1673 * NOTE! All mapped/uptodate combinations are valid:
1675 * Mapped Uptodate Meaning
1677 * No No "unknown" - must do get_block()
1678 * No Yes "hole" - zero-filled
1679 * Yes No "allocated" - allocated on disk, not read in
1680 * Yes Yes "valid" - allocated and up-to-date in memory.
1682 * "Dirty" is valid only with the last case (mapped+uptodate).
1686 * While block_write_full_page is writing back the dirty buffers under
1687 * the page lock, whoever dirtied the buffers may decide to clean them
1688 * again at any time. We handle that by only looking at the buffer
1689 * state inside lock_buffer().
1691 * If block_write_full_page() is called for regular writeback
1692 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1693 * locked buffer. This only can happen if someone has written the buffer
1694 * directly, with submit_bh(). At the address_space level PageWriteback
1695 * prevents this contention from occurring.
1697 * If block_write_full_page() is called with wbc->sync_mode ==
1698 * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this
1699 * causes the writes to be flagged as synchronous writes.
1701 static int __block_write_full_page(struct inode *inode, struct page *page,
1702 get_block_t *get_block, struct writeback_control *wbc,
1703 bh_end_io_t *handler)
1705 int err;
1706 sector_t block;
1707 sector_t last_block;
1708 struct buffer_head *bh, *head;
1709 unsigned int blocksize, bbits;
1710 int nr_underway = 0;
1711 int write_op = (wbc->sync_mode == WB_SYNC_ALL ? WRITE_SYNC : WRITE);
1713 head = create_page_buffers(page, inode,
1714 (1 << BH_Dirty)|(1 << BH_Uptodate));
1717 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1718 * here, and the (potentially unmapped) buffers may become dirty at
1719 * any time. If a buffer becomes dirty here after we've inspected it
1720 * then we just miss that fact, and the page stays dirty.
1722 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1723 * handle that here by just cleaning them.
1726 bh = head;
1727 blocksize = bh->b_size;
1728 bbits = block_size_bits(blocksize);
1730 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1731 last_block = (i_size_read(inode) - 1) >> bbits;
1734 * Get all the dirty buffers mapped to disk addresses and
1735 * handle any aliases from the underlying blockdev's mapping.
1737 do {
1738 if (block > last_block) {
1740 * mapped buffers outside i_size will occur, because
1741 * this page can be outside i_size when there is a
1742 * truncate in progress.
1745 * The buffer was zeroed by block_write_full_page()
1747 clear_buffer_dirty(bh);
1748 set_buffer_uptodate(bh);
1749 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1750 buffer_dirty(bh)) {
1751 WARN_ON(bh->b_size != blocksize);
1752 err = get_block(inode, block, bh, 1);
1753 if (err)
1754 goto recover;
1755 clear_buffer_delay(bh);
1756 if (buffer_new(bh)) {
1757 /* blockdev mappings never come here */
1758 clear_buffer_new(bh);
1759 unmap_underlying_metadata(bh->b_bdev,
1760 bh->b_blocknr);
1763 bh = bh->b_this_page;
1764 block++;
1765 } while (bh != head);
1767 do {
1768 if (!buffer_mapped(bh))
1769 continue;
1771 * If it's a fully non-blocking write attempt and we cannot
1772 * lock the buffer then redirty the page. Note that this can
1773 * potentially cause a busy-wait loop from writeback threads
1774 * and kswapd activity, but those code paths have their own
1775 * higher-level throttling.
1777 if (wbc->sync_mode != WB_SYNC_NONE) {
1778 lock_buffer(bh);
1779 } else if (!trylock_buffer(bh)) {
1780 redirty_page_for_writepage(wbc, page);
1781 continue;
1783 if (test_clear_buffer_dirty(bh)) {
1784 mark_buffer_async_write_endio(bh, handler);
1785 } else {
1786 unlock_buffer(bh);
1788 } while ((bh = bh->b_this_page) != head);
1791 * The page and its buffers are protected by PageWriteback(), so we can
1792 * drop the bh refcounts early.
1794 BUG_ON(PageWriteback(page));
1795 set_page_writeback(page);
1797 do {
1798 struct buffer_head *next = bh->b_this_page;
1799 if (buffer_async_write(bh)) {
1800 submit_bh_wbc(write_op, bh, 0, wbc);
1801 nr_underway++;
1803 bh = next;
1804 } while (bh != head);
1805 unlock_page(page);
1807 err = 0;
1808 done:
1809 if (nr_underway == 0) {
1811 * The page was marked dirty, but the buffers were
1812 * clean. Someone wrote them back by hand with
1813 * ll_rw_block/submit_bh. A rare case.
1815 end_page_writeback(page);
1818 * The page and buffer_heads can be released at any time from
1819 * here on.
1822 return err;
1824 recover:
1826 * ENOSPC, or some other error. We may already have added some
1827 * blocks to the file, so we need to write these out to avoid
1828 * exposing stale data.
1829 * The page is currently locked and not marked for writeback
1831 bh = head;
1832 /* Recovery: lock and submit the mapped buffers */
1833 do {
1834 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1835 !buffer_delay(bh)) {
1836 lock_buffer(bh);
1837 mark_buffer_async_write_endio(bh, handler);
1838 } else {
1840 * The buffer may have been set dirty during
1841 * attachment to a dirty page.
1843 clear_buffer_dirty(bh);
1845 } while ((bh = bh->b_this_page) != head);
1846 SetPageError(page);
1847 BUG_ON(PageWriteback(page));
1848 mapping_set_error(page->mapping, err);
1849 set_page_writeback(page);
1850 do {
1851 struct buffer_head *next = bh->b_this_page;
1852 if (buffer_async_write(bh)) {
1853 clear_buffer_dirty(bh);
1854 submit_bh_wbc(write_op, bh, 0, wbc);
1855 nr_underway++;
1857 bh = next;
1858 } while (bh != head);
1859 unlock_page(page);
1860 goto done;
1864 * If a page has any new buffers, zero them out here, and mark them uptodate
1865 * and dirty so they'll be written out (in order to prevent uninitialised
1866 * block data from leaking). And clear the new bit.
1868 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1870 unsigned int block_start, block_end;
1871 struct buffer_head *head, *bh;
1873 BUG_ON(!PageLocked(page));
1874 if (!page_has_buffers(page))
1875 return;
1877 bh = head = page_buffers(page);
1878 block_start = 0;
1879 do {
1880 block_end = block_start + bh->b_size;
1882 if (buffer_new(bh)) {
1883 if (block_end > from && block_start < to) {
1884 if (!PageUptodate(page)) {
1885 unsigned start, size;
1887 start = max(from, block_start);
1888 size = min(to, block_end) - start;
1890 zero_user(page, start, size);
1891 set_buffer_uptodate(bh);
1894 clear_buffer_new(bh);
1895 mark_buffer_dirty(bh);
1899 block_start = block_end;
1900 bh = bh->b_this_page;
1901 } while (bh != head);
1903 EXPORT_SYMBOL(page_zero_new_buffers);
1905 int __block_write_begin(struct page *page, loff_t pos, unsigned len,
1906 get_block_t *get_block)
1908 unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1909 unsigned to = from + len;
1910 struct inode *inode = page->mapping->host;
1911 unsigned block_start, block_end;
1912 sector_t block;
1913 int err = 0;
1914 unsigned blocksize, bbits;
1915 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1917 BUG_ON(!PageLocked(page));
1918 BUG_ON(from > PAGE_CACHE_SIZE);
1919 BUG_ON(to > PAGE_CACHE_SIZE);
1920 BUG_ON(from > to);
1922 head = create_page_buffers(page, inode, 0);
1923 blocksize = head->b_size;
1924 bbits = block_size_bits(blocksize);
1926 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1928 for(bh = head, block_start = 0; bh != head || !block_start;
1929 block++, block_start=block_end, bh = bh->b_this_page) {
1930 block_end = block_start + blocksize;
1931 if (block_end <= from || block_start >= to) {
1932 if (PageUptodate(page)) {
1933 if (!buffer_uptodate(bh))
1934 set_buffer_uptodate(bh);
1936 continue;
1938 if (buffer_new(bh))
1939 clear_buffer_new(bh);
1940 if (!buffer_mapped(bh)) {
1941 WARN_ON(bh->b_size != blocksize);
1942 err = get_block(inode, block, bh, 1);
1943 if (err)
1944 break;
1945 if (buffer_new(bh)) {
1946 unmap_underlying_metadata(bh->b_bdev,
1947 bh->b_blocknr);
1948 if (PageUptodate(page)) {
1949 clear_buffer_new(bh);
1950 set_buffer_uptodate(bh);
1951 mark_buffer_dirty(bh);
1952 continue;
1954 if (block_end > to || block_start < from)
1955 zero_user_segments(page,
1956 to, block_end,
1957 block_start, from);
1958 continue;
1961 if (PageUptodate(page)) {
1962 if (!buffer_uptodate(bh))
1963 set_buffer_uptodate(bh);
1964 continue;
1966 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1967 !buffer_unwritten(bh) &&
1968 (block_start < from || block_end > to)) {
1969 ll_rw_block(READ, 1, &bh);
1970 *wait_bh++=bh;
1974 * If we issued read requests - let them complete.
1976 while(wait_bh > wait) {
1977 wait_on_buffer(*--wait_bh);
1978 if (!buffer_uptodate(*wait_bh))
1979 err = -EIO;
1981 if (unlikely(err))
1982 page_zero_new_buffers(page, from, to);
1983 return err;
1985 EXPORT_SYMBOL(__block_write_begin);
1987 static int __block_commit_write(struct inode *inode, struct page *page,
1988 unsigned from, unsigned to)
1990 unsigned block_start, block_end;
1991 int partial = 0;
1992 unsigned blocksize;
1993 struct buffer_head *bh, *head;
1995 bh = head = page_buffers(page);
1996 blocksize = bh->b_size;
1998 block_start = 0;
1999 do {
2000 block_end = block_start + blocksize;
2001 if (block_end <= from || block_start >= to) {
2002 if (!buffer_uptodate(bh))
2003 partial = 1;
2004 } else {
2005 set_buffer_uptodate(bh);
2006 mark_buffer_dirty(bh);
2008 clear_buffer_new(bh);
2010 block_start = block_end;
2011 bh = bh->b_this_page;
2012 } while (bh != head);
2015 * If this is a partial write which happened to make all buffers
2016 * uptodate then we can optimize away a bogus readpage() for
2017 * the next read(). Here we 'discover' whether the page went
2018 * uptodate as a result of this (potentially partial) write.
2020 if (!partial)
2021 SetPageUptodate(page);
2022 return 0;
2026 * block_write_begin takes care of the basic task of block allocation and
2027 * bringing partial write blocks uptodate first.
2029 * The filesystem needs to handle block truncation upon failure.
2031 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
2032 unsigned flags, struct page **pagep, get_block_t *get_block)
2034 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
2035 struct page *page;
2036 int status;
2038 page = grab_cache_page_write_begin(mapping, index, flags);
2039 if (!page)
2040 return -ENOMEM;
2042 status = __block_write_begin(page, pos, len, get_block);
2043 if (unlikely(status)) {
2044 unlock_page(page);
2045 page_cache_release(page);
2046 page = NULL;
2049 *pagep = page;
2050 return status;
2052 EXPORT_SYMBOL(block_write_begin);
2054 int block_write_end(struct file *file, struct address_space *mapping,
2055 loff_t pos, unsigned len, unsigned copied,
2056 struct page *page, void *fsdata)
2058 struct inode *inode = mapping->host;
2059 unsigned start;
2061 start = pos & (PAGE_CACHE_SIZE - 1);
2063 if (unlikely(copied < len)) {
2065 * The buffers that were written will now be uptodate, so we
2066 * don't have to worry about a readpage reading them and
2067 * overwriting a partial write. However if we have encountered
2068 * a short write and only partially written into a buffer, it
2069 * will not be marked uptodate, so a readpage might come in and
2070 * destroy our partial write.
2072 * Do the simplest thing, and just treat any short write to a
2073 * non uptodate page as a zero-length write, and force the
2074 * caller to redo the whole thing.
2076 if (!PageUptodate(page))
2077 copied = 0;
2079 page_zero_new_buffers(page, start+copied, start+len);
2081 flush_dcache_page(page);
2083 /* This could be a short (even 0-length) commit */
2084 __block_commit_write(inode, page, start, start+copied);
2086 return copied;
2088 EXPORT_SYMBOL(block_write_end);
2090 int generic_write_end(struct file *file, struct address_space *mapping,
2091 loff_t pos, unsigned len, unsigned copied,
2092 struct page *page, void *fsdata)
2094 struct inode *inode = mapping->host;
2095 loff_t old_size = inode->i_size;
2096 int i_size_changed = 0;
2098 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2101 * No need to use i_size_read() here, the i_size
2102 * cannot change under us because we hold i_mutex.
2104 * But it's important to update i_size while still holding page lock:
2105 * page writeout could otherwise come in and zero beyond i_size.
2107 if (pos+copied > inode->i_size) {
2108 i_size_write(inode, pos+copied);
2109 i_size_changed = 1;
2112 unlock_page(page);
2113 page_cache_release(page);
2115 if (old_size < pos)
2116 pagecache_isize_extended(inode, old_size, pos);
2118 * Don't mark the inode dirty under page lock. First, it unnecessarily
2119 * makes the holding time of page lock longer. Second, it forces lock
2120 * ordering of page lock and transaction start for journaling
2121 * filesystems.
2123 if (i_size_changed)
2124 mark_inode_dirty(inode);
2126 return copied;
2128 EXPORT_SYMBOL(generic_write_end);
2131 * block_is_partially_uptodate checks whether buffers within a page are
2132 * uptodate or not.
2134 * Returns true if all buffers which correspond to a file portion
2135 * we want to read are uptodate.
2137 int block_is_partially_uptodate(struct page *page, unsigned long from,
2138 unsigned long count)
2140 unsigned block_start, block_end, blocksize;
2141 unsigned to;
2142 struct buffer_head *bh, *head;
2143 int ret = 1;
2145 if (!page_has_buffers(page))
2146 return 0;
2148 head = page_buffers(page);
2149 blocksize = head->b_size;
2150 to = min_t(unsigned, PAGE_CACHE_SIZE - from, count);
2151 to = from + to;
2152 if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
2153 return 0;
2155 bh = head;
2156 block_start = 0;
2157 do {
2158 block_end = block_start + blocksize;
2159 if (block_end > from && block_start < to) {
2160 if (!buffer_uptodate(bh)) {
2161 ret = 0;
2162 break;
2164 if (block_end >= to)
2165 break;
2167 block_start = block_end;
2168 bh = bh->b_this_page;
2169 } while (bh != head);
2171 return ret;
2173 EXPORT_SYMBOL(block_is_partially_uptodate);
2176 * Generic "read page" function for block devices that have the normal
2177 * get_block functionality. This is most of the block device filesystems.
2178 * Reads the page asynchronously --- the unlock_buffer() and
2179 * set/clear_buffer_uptodate() functions propagate buffer state into the
2180 * page struct once IO has completed.
2182 int block_read_full_page(struct page *page, get_block_t *get_block)
2184 struct inode *inode = page->mapping->host;
2185 sector_t iblock, lblock;
2186 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2187 unsigned int blocksize, bbits;
2188 int nr, i;
2189 int fully_mapped = 1;
2191 head = create_page_buffers(page, inode, 0);
2192 blocksize = head->b_size;
2193 bbits = block_size_bits(blocksize);
2195 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
2196 lblock = (i_size_read(inode)+blocksize-1) >> bbits;
2197 bh = head;
2198 nr = 0;
2199 i = 0;
2201 do {
2202 if (buffer_uptodate(bh))
2203 continue;
2205 if (!buffer_mapped(bh)) {
2206 int err = 0;
2208 fully_mapped = 0;
2209 if (iblock < lblock) {
2210 WARN_ON(bh->b_size != blocksize);
2211 err = get_block(inode, iblock, bh, 0);
2212 if (err)
2213 SetPageError(page);
2215 if (!buffer_mapped(bh)) {
2216 zero_user(page, i * blocksize, blocksize);
2217 if (!err)
2218 set_buffer_uptodate(bh);
2219 continue;
2222 * get_block() might have updated the buffer
2223 * synchronously
2225 if (buffer_uptodate(bh))
2226 continue;
2228 arr[nr++] = bh;
2229 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2231 if (fully_mapped)
2232 SetPageMappedToDisk(page);
2234 if (!nr) {
2236 * All buffers are uptodate - we can set the page uptodate
2237 * as well. But not if get_block() returned an error.
2239 if (!PageError(page))
2240 SetPageUptodate(page);
2241 unlock_page(page);
2242 return 0;
2245 /* Stage two: lock the buffers */
2246 for (i = 0; i < nr; i++) {
2247 bh = arr[i];
2248 lock_buffer(bh);
2249 mark_buffer_async_read(bh);
2253 * Stage 3: start the IO. Check for uptodateness
2254 * inside the buffer lock in case another process reading
2255 * the underlying blockdev brought it uptodate (the sct fix).
2257 for (i = 0; i < nr; i++) {
2258 bh = arr[i];
2259 if (buffer_uptodate(bh))
2260 end_buffer_async_read(bh, 1);
2261 else
2262 submit_bh(READ, bh);
2264 return 0;
2266 EXPORT_SYMBOL(block_read_full_page);
2268 /* utility function for filesystems that need to do work on expanding
2269 * truncates. Uses filesystem pagecache writes to allow the filesystem to
2270 * deal with the hole.
2272 int generic_cont_expand_simple(struct inode *inode, loff_t size)
2274 struct address_space *mapping = inode->i_mapping;
2275 struct page *page;
2276 void *fsdata;
2277 int err;
2279 err = inode_newsize_ok(inode, size);
2280 if (err)
2281 goto out;
2283 err = pagecache_write_begin(NULL, mapping, size, 0,
2284 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2285 &page, &fsdata);
2286 if (err)
2287 goto out;
2289 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2290 BUG_ON(err > 0);
2292 out:
2293 return err;
2295 EXPORT_SYMBOL(generic_cont_expand_simple);
2297 static int cont_expand_zero(struct file *file, struct address_space *mapping,
2298 loff_t pos, loff_t *bytes)
2300 struct inode *inode = mapping->host;
2301 unsigned int blocksize = i_blocksize(inode);
2302 struct page *page;
2303 void *fsdata;
2304 pgoff_t index, curidx;
2305 loff_t curpos;
2306 unsigned zerofrom, offset, len;
2307 int err = 0;
2309 index = pos >> PAGE_CACHE_SHIFT;
2310 offset = pos & ~PAGE_CACHE_MASK;
2312 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
2313 zerofrom = curpos & ~PAGE_CACHE_MASK;
2314 if (zerofrom & (blocksize-1)) {
2315 *bytes |= (blocksize-1);
2316 (*bytes)++;
2318 len = PAGE_CACHE_SIZE - zerofrom;
2320 err = pagecache_write_begin(file, mapping, curpos, len,
2321 AOP_FLAG_UNINTERRUPTIBLE,
2322 &page, &fsdata);
2323 if (err)
2324 goto out;
2325 zero_user(page, zerofrom, len);
2326 err = pagecache_write_end(file, mapping, curpos, len, len,
2327 page, fsdata);
2328 if (err < 0)
2329 goto out;
2330 BUG_ON(err != len);
2331 err = 0;
2333 balance_dirty_pages_ratelimited(mapping);
2335 if (unlikely(fatal_signal_pending(current))) {
2336 err = -EINTR;
2337 goto out;
2341 /* page covers the boundary, find the boundary offset */
2342 if (index == curidx) {
2343 zerofrom = curpos & ~PAGE_CACHE_MASK;
2344 /* if we will expand the thing last block will be filled */
2345 if (offset <= zerofrom) {
2346 goto out;
2348 if (zerofrom & (blocksize-1)) {
2349 *bytes |= (blocksize-1);
2350 (*bytes)++;
2352 len = offset - zerofrom;
2354 err = pagecache_write_begin(file, mapping, curpos, len,
2355 AOP_FLAG_UNINTERRUPTIBLE,
2356 &page, &fsdata);
2357 if (err)
2358 goto out;
2359 zero_user(page, zerofrom, len);
2360 err = pagecache_write_end(file, mapping, curpos, len, len,
2361 page, fsdata);
2362 if (err < 0)
2363 goto out;
2364 BUG_ON(err != len);
2365 err = 0;
2367 out:
2368 return err;
2372 * For moronic filesystems that do not allow holes in file.
2373 * We may have to extend the file.
2375 int cont_write_begin(struct file *file, struct address_space *mapping,
2376 loff_t pos, unsigned len, unsigned flags,
2377 struct page **pagep, void **fsdata,
2378 get_block_t *get_block, loff_t *bytes)
2380 struct inode *inode = mapping->host;
2381 unsigned int blocksize = i_blocksize(inode);
2382 unsigned int zerofrom;
2383 int err;
2385 err = cont_expand_zero(file, mapping, pos, bytes);
2386 if (err)
2387 return err;
2389 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2390 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2391 *bytes |= (blocksize-1);
2392 (*bytes)++;
2395 return block_write_begin(mapping, pos, len, flags, pagep, get_block);
2397 EXPORT_SYMBOL(cont_write_begin);
2399 int block_commit_write(struct page *page, unsigned from, unsigned to)
2401 struct inode *inode = page->mapping->host;
2402 __block_commit_write(inode,page,from,to);
2403 return 0;
2405 EXPORT_SYMBOL(block_commit_write);
2408 * block_page_mkwrite() is not allowed to change the file size as it gets
2409 * called from a page fault handler when a page is first dirtied. Hence we must
2410 * be careful to check for EOF conditions here. We set the page up correctly
2411 * for a written page which means we get ENOSPC checking when writing into
2412 * holes and correct delalloc and unwritten extent mapping on filesystems that
2413 * support these features.
2415 * We are not allowed to take the i_mutex here so we have to play games to
2416 * protect against truncate races as the page could now be beyond EOF. Because
2417 * truncate writes the inode size before removing pages, once we have the
2418 * page lock we can determine safely if the page is beyond EOF. If it is not
2419 * beyond EOF, then the page is guaranteed safe against truncation until we
2420 * unlock the page.
2422 * Direct callers of this function should protect against filesystem freezing
2423 * using sb_start_pagefault() - sb_end_pagefault() functions.
2425 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2426 get_block_t get_block)
2428 struct page *page = vmf->page;
2429 struct inode *inode = file_inode(vma->vm_file);
2430 unsigned long end;
2431 loff_t size;
2432 int ret;
2434 lock_page(page);
2435 size = i_size_read(inode);
2436 if ((page->mapping != inode->i_mapping) ||
2437 (page_offset(page) > size)) {
2438 /* We overload EFAULT to mean page got truncated */
2439 ret = -EFAULT;
2440 goto out_unlock;
2443 /* page is wholly or partially inside EOF */
2444 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
2445 end = size & ~PAGE_CACHE_MASK;
2446 else
2447 end = PAGE_CACHE_SIZE;
2449 ret = __block_write_begin(page, 0, end, get_block);
2450 if (!ret)
2451 ret = block_commit_write(page, 0, end);
2453 if (unlikely(ret < 0))
2454 goto out_unlock;
2455 set_page_dirty(page);
2456 wait_for_stable_page(page);
2457 return 0;
2458 out_unlock:
2459 unlock_page(page);
2460 return ret;
2462 EXPORT_SYMBOL(block_page_mkwrite);
2465 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
2466 * immediately, while under the page lock. So it needs a special end_io
2467 * handler which does not touch the bh after unlocking it.
2469 static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2471 __end_buffer_read_notouch(bh, uptodate);
2475 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2476 * the page (converting it to circular linked list and taking care of page
2477 * dirty races).
2479 static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2481 struct buffer_head *bh;
2483 BUG_ON(!PageLocked(page));
2485 spin_lock(&page->mapping->private_lock);
2486 bh = head;
2487 do {
2488 if (PageDirty(page))
2489 set_buffer_dirty(bh);
2490 if (!bh->b_this_page)
2491 bh->b_this_page = head;
2492 bh = bh->b_this_page;
2493 } while (bh != head);
2494 attach_page_buffers(page, head);
2495 spin_unlock(&page->mapping->private_lock);
2499 * On entry, the page is fully not uptodate.
2500 * On exit the page is fully uptodate in the areas outside (from,to)
2501 * The filesystem needs to handle block truncation upon failure.
2503 int nobh_write_begin(struct address_space *mapping,
2504 loff_t pos, unsigned len, unsigned flags,
2505 struct page **pagep, void **fsdata,
2506 get_block_t *get_block)
2508 struct inode *inode = mapping->host;
2509 const unsigned blkbits = inode->i_blkbits;
2510 const unsigned blocksize = 1 << blkbits;
2511 struct buffer_head *head, *bh;
2512 struct page *page;
2513 pgoff_t index;
2514 unsigned from, to;
2515 unsigned block_in_page;
2516 unsigned block_start, block_end;
2517 sector_t block_in_file;
2518 int nr_reads = 0;
2519 int ret = 0;
2520 int is_mapped_to_disk = 1;
2522 index = pos >> PAGE_CACHE_SHIFT;
2523 from = pos & (PAGE_CACHE_SIZE - 1);
2524 to = from + len;
2526 page = grab_cache_page_write_begin(mapping, index, flags);
2527 if (!page)
2528 return -ENOMEM;
2529 *pagep = page;
2530 *fsdata = NULL;
2532 if (page_has_buffers(page)) {
2533 ret = __block_write_begin(page, pos, len, get_block);
2534 if (unlikely(ret))
2535 goto out_release;
2536 return ret;
2539 if (PageMappedToDisk(page))
2540 return 0;
2543 * Allocate buffers so that we can keep track of state, and potentially
2544 * attach them to the page if an error occurs. In the common case of
2545 * no error, they will just be freed again without ever being attached
2546 * to the page (which is all OK, because we're under the page lock).
2548 * Be careful: the buffer linked list is a NULL terminated one, rather
2549 * than the circular one we're used to.
2551 head = alloc_page_buffers(page, blocksize, 0);
2552 if (!head) {
2553 ret = -ENOMEM;
2554 goto out_release;
2557 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
2560 * We loop across all blocks in the page, whether or not they are
2561 * part of the affected region. This is so we can discover if the
2562 * page is fully mapped-to-disk.
2564 for (block_start = 0, block_in_page = 0, bh = head;
2565 block_start < PAGE_CACHE_SIZE;
2566 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
2567 int create;
2569 block_end = block_start + blocksize;
2570 bh->b_state = 0;
2571 create = 1;
2572 if (block_start >= to)
2573 create = 0;
2574 ret = get_block(inode, block_in_file + block_in_page,
2575 bh, create);
2576 if (ret)
2577 goto failed;
2578 if (!buffer_mapped(bh))
2579 is_mapped_to_disk = 0;
2580 if (buffer_new(bh))
2581 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
2582 if (PageUptodate(page)) {
2583 set_buffer_uptodate(bh);
2584 continue;
2586 if (buffer_new(bh) || !buffer_mapped(bh)) {
2587 zero_user_segments(page, block_start, from,
2588 to, block_end);
2589 continue;
2591 if (buffer_uptodate(bh))
2592 continue; /* reiserfs does this */
2593 if (block_start < from || block_end > to) {
2594 lock_buffer(bh);
2595 bh->b_end_io = end_buffer_read_nobh;
2596 submit_bh(READ, bh);
2597 nr_reads++;
2601 if (nr_reads) {
2603 * The page is locked, so these buffers are protected from
2604 * any VM or truncate activity. Hence we don't need to care
2605 * for the buffer_head refcounts.
2607 for (bh = head; bh; bh = bh->b_this_page) {
2608 wait_on_buffer(bh);
2609 if (!buffer_uptodate(bh))
2610 ret = -EIO;
2612 if (ret)
2613 goto failed;
2616 if (is_mapped_to_disk)
2617 SetPageMappedToDisk(page);
2619 *fsdata = head; /* to be released by nobh_write_end */
2621 return 0;
2623 failed:
2624 BUG_ON(!ret);
2626 * Error recovery is a bit difficult. We need to zero out blocks that
2627 * were newly allocated, and dirty them to ensure they get written out.
2628 * Buffers need to be attached to the page at this point, otherwise
2629 * the handling of potential IO errors during writeout would be hard
2630 * (could try doing synchronous writeout, but what if that fails too?)
2632 attach_nobh_buffers(page, head);
2633 page_zero_new_buffers(page, from, to);
2635 out_release:
2636 unlock_page(page);
2637 page_cache_release(page);
2638 *pagep = NULL;
2640 return ret;
2642 EXPORT_SYMBOL(nobh_write_begin);
2644 int nobh_write_end(struct file *file, struct address_space *mapping,
2645 loff_t pos, unsigned len, unsigned copied,
2646 struct page *page, void *fsdata)
2648 struct inode *inode = page->mapping->host;
2649 struct buffer_head *head = fsdata;
2650 struct buffer_head *bh;
2651 BUG_ON(fsdata != NULL && page_has_buffers(page));
2653 if (unlikely(copied < len) && head)
2654 attach_nobh_buffers(page, head);
2655 if (page_has_buffers(page))
2656 return generic_write_end(file, mapping, pos, len,
2657 copied, page, fsdata);
2659 SetPageUptodate(page);
2660 set_page_dirty(page);
2661 if (pos+copied > inode->i_size) {
2662 i_size_write(inode, pos+copied);
2663 mark_inode_dirty(inode);
2666 unlock_page(page);
2667 page_cache_release(page);
2669 while (head) {
2670 bh = head;
2671 head = head->b_this_page;
2672 free_buffer_head(bh);
2675 return copied;
2677 EXPORT_SYMBOL(nobh_write_end);
2680 * nobh_writepage() - based on block_full_write_page() except
2681 * that it tries to operate without attaching bufferheads to
2682 * the page.
2684 int nobh_writepage(struct page *page, get_block_t *get_block,
2685 struct writeback_control *wbc)
2687 struct inode * const inode = page->mapping->host;
2688 loff_t i_size = i_size_read(inode);
2689 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2690 unsigned offset;
2691 int ret;
2693 /* Is the page fully inside i_size? */
2694 if (page->index < end_index)
2695 goto out;
2697 /* Is the page fully outside i_size? (truncate in progress) */
2698 offset = i_size & (PAGE_CACHE_SIZE-1);
2699 if (page->index >= end_index+1 || !offset) {
2701 * The page may have dirty, unmapped buffers. For example,
2702 * they may have been added in ext3_writepage(). Make them
2703 * freeable here, so the page does not leak.
2705 #if 0
2706 /* Not really sure about this - do we need this ? */
2707 if (page->mapping->a_ops->invalidatepage)
2708 page->mapping->a_ops->invalidatepage(page, offset);
2709 #endif
2710 unlock_page(page);
2711 return 0; /* don't care */
2715 * The page straddles i_size. It must be zeroed out on each and every
2716 * writepage invocation because it may be mmapped. "A file is mapped
2717 * in multiples of the page size. For a file that is not a multiple of
2718 * the page size, the remaining memory is zeroed when mapped, and
2719 * writes to that region are not written out to the file."
2721 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2722 out:
2723 ret = mpage_writepage(page, get_block, wbc);
2724 if (ret == -EAGAIN)
2725 ret = __block_write_full_page(inode, page, get_block, wbc,
2726 end_buffer_async_write);
2727 return ret;
2729 EXPORT_SYMBOL(nobh_writepage);
2731 int nobh_truncate_page(struct address_space *mapping,
2732 loff_t from, get_block_t *get_block)
2734 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2735 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2736 unsigned blocksize;
2737 sector_t iblock;
2738 unsigned length, pos;
2739 struct inode *inode = mapping->host;
2740 struct page *page;
2741 struct buffer_head map_bh;
2742 int err;
2744 blocksize = i_blocksize(inode);
2745 length = offset & (blocksize - 1);
2747 /* Block boundary? Nothing to do */
2748 if (!length)
2749 return 0;
2751 length = blocksize - length;
2752 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2754 page = grab_cache_page(mapping, index);
2755 err = -ENOMEM;
2756 if (!page)
2757 goto out;
2759 if (page_has_buffers(page)) {
2760 has_buffers:
2761 unlock_page(page);
2762 page_cache_release(page);
2763 return block_truncate_page(mapping, from, get_block);
2766 /* Find the buffer that contains "offset" */
2767 pos = blocksize;
2768 while (offset >= pos) {
2769 iblock++;
2770 pos += blocksize;
2773 map_bh.b_size = blocksize;
2774 map_bh.b_state = 0;
2775 err = get_block(inode, iblock, &map_bh, 0);
2776 if (err)
2777 goto unlock;
2778 /* unmapped? It's a hole - nothing to do */
2779 if (!buffer_mapped(&map_bh))
2780 goto unlock;
2782 /* Ok, it's mapped. Make sure it's up-to-date */
2783 if (!PageUptodate(page)) {
2784 err = mapping->a_ops->readpage(NULL, page);
2785 if (err) {
2786 page_cache_release(page);
2787 goto out;
2789 lock_page(page);
2790 if (!PageUptodate(page)) {
2791 err = -EIO;
2792 goto unlock;
2794 if (page_has_buffers(page))
2795 goto has_buffers;
2797 zero_user(page, offset, length);
2798 set_page_dirty(page);
2799 err = 0;
2801 unlock:
2802 unlock_page(page);
2803 page_cache_release(page);
2804 out:
2805 return err;
2807 EXPORT_SYMBOL(nobh_truncate_page);
2809 int block_truncate_page(struct address_space *mapping,
2810 loff_t from, get_block_t *get_block)
2812 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2813 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2814 unsigned blocksize;
2815 sector_t iblock;
2816 unsigned length, pos;
2817 struct inode *inode = mapping->host;
2818 struct page *page;
2819 struct buffer_head *bh;
2820 int err;
2822 blocksize = i_blocksize(inode);
2823 length = offset & (blocksize - 1);
2825 /* Block boundary? Nothing to do */
2826 if (!length)
2827 return 0;
2829 length = blocksize - length;
2830 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2832 page = grab_cache_page(mapping, index);
2833 err = -ENOMEM;
2834 if (!page)
2835 goto out;
2837 if (!page_has_buffers(page))
2838 create_empty_buffers(page, blocksize, 0);
2840 /* Find the buffer that contains "offset" */
2841 bh = page_buffers(page);
2842 pos = blocksize;
2843 while (offset >= pos) {
2844 bh = bh->b_this_page;
2845 iblock++;
2846 pos += blocksize;
2849 err = 0;
2850 if (!buffer_mapped(bh)) {
2851 WARN_ON(bh->b_size != blocksize);
2852 err = get_block(inode, iblock, bh, 0);
2853 if (err)
2854 goto unlock;
2855 /* unmapped? It's a hole - nothing to do */
2856 if (!buffer_mapped(bh))
2857 goto unlock;
2860 /* Ok, it's mapped. Make sure it's up-to-date */
2861 if (PageUptodate(page))
2862 set_buffer_uptodate(bh);
2864 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2865 err = -EIO;
2866 ll_rw_block(READ, 1, &bh);
2867 wait_on_buffer(bh);
2868 /* Uhhuh. Read error. Complain and punt. */
2869 if (!buffer_uptodate(bh))
2870 goto unlock;
2873 zero_user(page, offset, length);
2874 mark_buffer_dirty(bh);
2875 err = 0;
2877 unlock:
2878 unlock_page(page);
2879 page_cache_release(page);
2880 out:
2881 return err;
2883 EXPORT_SYMBOL(block_truncate_page);
2886 * The generic ->writepage function for buffer-backed address_spaces
2888 int block_write_full_page(struct page *page, get_block_t *get_block,
2889 struct writeback_control *wbc)
2891 struct inode * const inode = page->mapping->host;
2892 loff_t i_size = i_size_read(inode);
2893 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2894 unsigned offset;
2896 /* Is the page fully inside i_size? */
2897 if (page->index < end_index)
2898 return __block_write_full_page(inode, page, get_block, wbc,
2899 end_buffer_async_write);
2901 /* Is the page fully outside i_size? (truncate in progress) */
2902 offset = i_size & (PAGE_CACHE_SIZE-1);
2903 if (page->index >= end_index+1 || !offset) {
2905 * The page may have dirty, unmapped buffers. For example,
2906 * they may have been added in ext3_writepage(). Make them
2907 * freeable here, so the page does not leak.
2909 do_invalidatepage(page, 0, PAGE_CACHE_SIZE);
2910 unlock_page(page);
2911 return 0; /* don't care */
2915 * The page straddles i_size. It must be zeroed out on each and every
2916 * writepage invocation because it may be mmapped. "A file is mapped
2917 * in multiples of the page size. For a file that is not a multiple of
2918 * the page size, the remaining memory is zeroed when mapped, and
2919 * writes to that region are not written out to the file."
2921 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2922 return __block_write_full_page(inode, page, get_block, wbc,
2923 end_buffer_async_write);
2925 EXPORT_SYMBOL(block_write_full_page);
2927 sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2928 get_block_t *get_block)
2930 struct buffer_head tmp;
2931 struct inode *inode = mapping->host;
2932 tmp.b_state = 0;
2933 tmp.b_blocknr = 0;
2934 tmp.b_size = i_blocksize(inode);
2935 get_block(inode, block, &tmp, 0);
2936 return tmp.b_blocknr;
2938 EXPORT_SYMBOL(generic_block_bmap);
2940 static void end_bio_bh_io_sync(struct bio *bio)
2942 struct buffer_head *bh = bio->bi_private;
2944 if (unlikely(bio_flagged(bio, BIO_QUIET)))
2945 set_bit(BH_Quiet, &bh->b_state);
2947 bh->b_end_io(bh, !bio->bi_error);
2948 bio_put(bio);
2952 * This allows us to do IO even on the odd last sectors
2953 * of a device, even if the block size is some multiple
2954 * of the physical sector size.
2956 * We'll just truncate the bio to the size of the device,
2957 * and clear the end of the buffer head manually.
2959 * Truly out-of-range accesses will turn into actual IO
2960 * errors, this only handles the "we need to be able to
2961 * do IO at the final sector" case.
2963 void guard_bio_eod(int rw, struct bio *bio)
2965 sector_t maxsector;
2966 struct bio_vec *bvec = &bio->bi_io_vec[bio->bi_vcnt - 1];
2967 unsigned truncated_bytes;
2969 maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
2970 if (!maxsector)
2971 return;
2974 * If the *whole* IO is past the end of the device,
2975 * let it through, and the IO layer will turn it into
2976 * an EIO.
2978 if (unlikely(bio->bi_iter.bi_sector >= maxsector))
2979 return;
2981 maxsector -= bio->bi_iter.bi_sector;
2982 if (likely((bio->bi_iter.bi_size >> 9) <= maxsector))
2983 return;
2985 /* Uhhuh. We've got a bio that straddles the device size! */
2986 truncated_bytes = bio->bi_iter.bi_size - (maxsector << 9);
2988 /* Truncate the bio.. */
2989 bio->bi_iter.bi_size -= truncated_bytes;
2990 bvec->bv_len -= truncated_bytes;
2992 /* ..and clear the end of the buffer for reads */
2993 if ((rw & RW_MASK) == READ) {
2994 zero_user(bvec->bv_page, bvec->bv_offset + bvec->bv_len,
2995 truncated_bytes);
2999 static int submit_bh_wbc(int rw, struct buffer_head *bh,
3000 unsigned long bio_flags, struct writeback_control *wbc)
3002 struct bio *bio;
3004 BUG_ON(!buffer_locked(bh));
3005 BUG_ON(!buffer_mapped(bh));
3006 BUG_ON(!bh->b_end_io);
3007 BUG_ON(buffer_delay(bh));
3008 BUG_ON(buffer_unwritten(bh));
3011 * Only clear out a write error when rewriting
3013 if (test_set_buffer_req(bh) && (rw & WRITE))
3014 clear_buffer_write_io_error(bh);
3017 * from here on down, it's all bio -- do the initial mapping,
3018 * submit_bio -> generic_make_request may further map this bio around
3020 bio = bio_alloc(GFP_NOIO, 1);
3022 if (wbc) {
3023 wbc_init_bio(wbc, bio);
3024 wbc_account_io(wbc, bh->b_page, bh->b_size);
3027 bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
3028 bio->bi_bdev = bh->b_bdev;
3030 bio_add_page(bio, bh->b_page, bh->b_size, bh_offset(bh));
3031 BUG_ON(bio->bi_iter.bi_size != bh->b_size);
3033 bio->bi_end_io = end_bio_bh_io_sync;
3034 bio->bi_private = bh;
3035 bio->bi_flags |= bio_flags;
3037 /* Take care of bh's that straddle the end of the device */
3038 guard_bio_eod(rw, bio);
3040 if (buffer_meta(bh))
3041 rw |= REQ_META;
3042 if (buffer_prio(bh))
3043 rw |= REQ_PRIO;
3045 submit_bio(rw, bio);
3046 return 0;
3049 int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags)
3051 return submit_bh_wbc(rw, bh, bio_flags, NULL);
3053 EXPORT_SYMBOL_GPL(_submit_bh);
3055 int submit_bh(int rw, struct buffer_head *bh)
3057 return submit_bh_wbc(rw, bh, 0, NULL);
3059 EXPORT_SYMBOL(submit_bh);
3062 * ll_rw_block: low-level access to block devices (DEPRECATED)
3063 * @rw: whether to %READ or %WRITE or maybe %READA (readahead)
3064 * @nr: number of &struct buffer_heads in the array
3065 * @bhs: array of pointers to &struct buffer_head
3067 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
3068 * requests an I/O operation on them, either a %READ or a %WRITE. The third
3069 * %READA option is described in the documentation for generic_make_request()
3070 * which ll_rw_block() calls.
3072 * This function drops any buffer that it cannot get a lock on (with the
3073 * BH_Lock state bit), any buffer that appears to be clean when doing a write
3074 * request, and any buffer that appears to be up-to-date when doing read
3075 * request. Further it marks as clean buffers that are processed for
3076 * writing (the buffer cache won't assume that they are actually clean
3077 * until the buffer gets unlocked).
3079 * ll_rw_block sets b_end_io to simple completion handler that marks
3080 * the buffer up-to-date (if appropriate), unlocks the buffer and wakes
3081 * any waiters.
3083 * All of the buffers must be for the same device, and must also be a
3084 * multiple of the current approved size for the device.
3086 void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
3088 int i;
3090 for (i = 0; i < nr; i++) {
3091 struct buffer_head *bh = bhs[i];
3093 if (!trylock_buffer(bh))
3094 continue;
3095 if (rw == WRITE) {
3096 if (test_clear_buffer_dirty(bh)) {
3097 bh->b_end_io = end_buffer_write_sync;
3098 get_bh(bh);
3099 submit_bh(WRITE, bh);
3100 continue;
3102 } else {
3103 if (!buffer_uptodate(bh)) {
3104 bh->b_end_io = end_buffer_read_sync;
3105 get_bh(bh);
3106 submit_bh(rw, bh);
3107 continue;
3110 unlock_buffer(bh);
3113 EXPORT_SYMBOL(ll_rw_block);
3115 void write_dirty_buffer(struct buffer_head *bh, int rw)
3117 lock_buffer(bh);
3118 if (!test_clear_buffer_dirty(bh)) {
3119 unlock_buffer(bh);
3120 return;
3122 bh->b_end_io = end_buffer_write_sync;
3123 get_bh(bh);
3124 submit_bh(rw, bh);
3126 EXPORT_SYMBOL(write_dirty_buffer);
3129 * For a data-integrity writeout, we need to wait upon any in-progress I/O
3130 * and then start new I/O and then wait upon it. The caller must have a ref on
3131 * the buffer_head.
3133 int __sync_dirty_buffer(struct buffer_head *bh, int rw)
3135 int ret = 0;
3137 WARN_ON(atomic_read(&bh->b_count) < 1);
3138 lock_buffer(bh);
3139 if (test_clear_buffer_dirty(bh)) {
3140 get_bh(bh);
3141 bh->b_end_io = end_buffer_write_sync;
3142 ret = submit_bh(rw, bh);
3143 wait_on_buffer(bh);
3144 if (!ret && !buffer_uptodate(bh))
3145 ret = -EIO;
3146 } else {
3147 unlock_buffer(bh);
3149 return ret;
3151 EXPORT_SYMBOL(__sync_dirty_buffer);
3153 int sync_dirty_buffer(struct buffer_head *bh)
3155 return __sync_dirty_buffer(bh, WRITE_SYNC);
3157 EXPORT_SYMBOL(sync_dirty_buffer);
3160 * try_to_free_buffers() checks if all the buffers on this particular page
3161 * are unused, and releases them if so.
3163 * Exclusion against try_to_free_buffers may be obtained by either
3164 * locking the page or by holding its mapping's private_lock.
3166 * If the page is dirty but all the buffers are clean then we need to
3167 * be sure to mark the page clean as well. This is because the page
3168 * may be against a block device, and a later reattachment of buffers
3169 * to a dirty page will set *all* buffers dirty. Which would corrupt
3170 * filesystem data on the same device.
3172 * The same applies to regular filesystem pages: if all the buffers are
3173 * clean then we set the page clean and proceed. To do that, we require
3174 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3175 * private_lock.
3177 * try_to_free_buffers() is non-blocking.
3179 static inline int buffer_busy(struct buffer_head *bh)
3181 return atomic_read(&bh->b_count) |
3182 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3185 static int
3186 drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3188 struct buffer_head *head = page_buffers(page);
3189 struct buffer_head *bh;
3191 bh = head;
3192 do {
3193 if (buffer_write_io_error(bh) && page->mapping)
3194 set_bit(AS_EIO, &page->mapping->flags);
3195 if (buffer_busy(bh))
3196 goto failed;
3197 bh = bh->b_this_page;
3198 } while (bh != head);
3200 do {
3201 struct buffer_head *next = bh->b_this_page;
3203 if (bh->b_assoc_map)
3204 __remove_assoc_queue(bh);
3205 bh = next;
3206 } while (bh != head);
3207 *buffers_to_free = head;
3208 __clear_page_buffers(page);
3209 return 1;
3210 failed:
3211 return 0;
3214 int try_to_free_buffers(struct page *page)
3216 struct address_space * const mapping = page->mapping;
3217 struct buffer_head *buffers_to_free = NULL;
3218 int ret = 0;
3220 BUG_ON(!PageLocked(page));
3221 if (PageWriteback(page))
3222 return 0;
3224 if (mapping == NULL) { /* can this still happen? */
3225 ret = drop_buffers(page, &buffers_to_free);
3226 goto out;
3229 spin_lock(&mapping->private_lock);
3230 ret = drop_buffers(page, &buffers_to_free);
3233 * If the filesystem writes its buffers by hand (eg ext3)
3234 * then we can have clean buffers against a dirty page. We
3235 * clean the page here; otherwise the VM will never notice
3236 * that the filesystem did any IO at all.
3238 * Also, during truncate, discard_buffer will have marked all
3239 * the page's buffers clean. We discover that here and clean
3240 * the page also.
3242 * private_lock must be held over this entire operation in order
3243 * to synchronise against __set_page_dirty_buffers and prevent the
3244 * dirty bit from being lost.
3246 if (ret)
3247 cancel_dirty_page(page);
3248 spin_unlock(&mapping->private_lock);
3249 out:
3250 if (buffers_to_free) {
3251 struct buffer_head *bh = buffers_to_free;
3253 do {
3254 struct buffer_head *next = bh->b_this_page;
3255 free_buffer_head(bh);
3256 bh = next;
3257 } while (bh != buffers_to_free);
3259 return ret;
3261 EXPORT_SYMBOL(try_to_free_buffers);
3264 * There are no bdflush tunables left. But distributions are
3265 * still running obsolete flush daemons, so we terminate them here.
3267 * Use of bdflush() is deprecated and will be removed in a future kernel.
3268 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
3270 SYSCALL_DEFINE2(bdflush, int, func, long, data)
3272 static int msg_count;
3274 if (!capable(CAP_SYS_ADMIN))
3275 return -EPERM;
3277 if (msg_count < 5) {
3278 msg_count++;
3279 printk(KERN_INFO
3280 "warning: process `%s' used the obsolete bdflush"
3281 " system call\n", current->comm);
3282 printk(KERN_INFO "Fix your initscripts?\n");
3285 if (func == 1)
3286 do_exit(0);
3287 return 0;
3291 * Buffer-head allocation
3293 static struct kmem_cache *bh_cachep __read_mostly;
3296 * Once the number of bh's in the machine exceeds this level, we start
3297 * stripping them in writeback.
3299 static unsigned long max_buffer_heads;
3301 int buffer_heads_over_limit;
3303 struct bh_accounting {
3304 int nr; /* Number of live bh's */
3305 int ratelimit; /* Limit cacheline bouncing */
3308 static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3310 static void recalc_bh_state(void)
3312 int i;
3313 int tot = 0;
3315 if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
3316 return;
3317 __this_cpu_write(bh_accounting.ratelimit, 0);
3318 for_each_online_cpu(i)
3319 tot += per_cpu(bh_accounting, i).nr;
3320 buffer_heads_over_limit = (tot > max_buffer_heads);
3323 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3325 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
3326 if (ret) {
3327 INIT_LIST_HEAD(&ret->b_assoc_buffers);
3328 preempt_disable();
3329 __this_cpu_inc(bh_accounting.nr);
3330 recalc_bh_state();
3331 preempt_enable();
3333 return ret;
3335 EXPORT_SYMBOL(alloc_buffer_head);
3337 void free_buffer_head(struct buffer_head *bh)
3339 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3340 kmem_cache_free(bh_cachep, bh);
3341 preempt_disable();
3342 __this_cpu_dec(bh_accounting.nr);
3343 recalc_bh_state();
3344 preempt_enable();
3346 EXPORT_SYMBOL(free_buffer_head);
3348 static void buffer_exit_cpu(int cpu)
3350 int i;
3351 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3353 for (i = 0; i < BH_LRU_SIZE; i++) {
3354 brelse(b->bhs[i]);
3355 b->bhs[i] = NULL;
3357 this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3358 per_cpu(bh_accounting, cpu).nr = 0;
3361 static int buffer_cpu_notify(struct notifier_block *self,
3362 unsigned long action, void *hcpu)
3364 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
3365 buffer_exit_cpu((unsigned long)hcpu);
3366 return NOTIFY_OK;
3370 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3371 * @bh: struct buffer_head
3373 * Return true if the buffer is up-to-date and false,
3374 * with the buffer locked, if not.
3376 int bh_uptodate_or_lock(struct buffer_head *bh)
3378 if (!buffer_uptodate(bh)) {
3379 lock_buffer(bh);
3380 if (!buffer_uptodate(bh))
3381 return 0;
3382 unlock_buffer(bh);
3384 return 1;
3386 EXPORT_SYMBOL(bh_uptodate_or_lock);
3389 * bh_submit_read - Submit a locked buffer for reading
3390 * @bh: struct buffer_head
3392 * Returns zero on success and -EIO on error.
3394 int bh_submit_read(struct buffer_head *bh)
3396 BUG_ON(!buffer_locked(bh));
3398 if (buffer_uptodate(bh)) {
3399 unlock_buffer(bh);
3400 return 0;
3403 get_bh(bh);
3404 bh->b_end_io = end_buffer_read_sync;
3405 submit_bh(READ, bh);
3406 wait_on_buffer(bh);
3407 if (buffer_uptodate(bh))
3408 return 0;
3409 return -EIO;
3411 EXPORT_SYMBOL(bh_submit_read);
3413 void __init buffer_init(void)
3415 unsigned long nrpages;
3417 bh_cachep = kmem_cache_create("buffer_head",
3418 sizeof(struct buffer_head), 0,
3419 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3420 SLAB_MEM_SPREAD),
3421 NULL);
3424 * Limit the bh occupancy to 10% of ZONE_NORMAL
3426 nrpages = (nr_free_buffer_pages() * 10) / 100;
3427 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3428 hotcpu_notifier(buffer_cpu_notify, 0);