blob: 1ad674fd348c4bfe6f130bc9a958a3c38338619c [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/fs/buffer.c
3 *
4 * Copyright (C) 1991, 1992, 2002 Linus Torvalds
5 */
6
7/*
8 * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95
9 *
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
12 *
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
15 *
16 * Added 32k buffer block sizes - these are required older ARM systems. - RMK
17 *
18 * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de>
19 */
20
Linus Torvalds1da177e2005-04-16 15:20:36 -070021#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/smp_lock.h>
Randy Dunlap16f7e0f2006-01-11 12:17:46 -080028#include <linux/capability.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070029#include <linux/blkdev.h>
30#include <linux/file.h>
31#include <linux/quotaops.h>
32#include <linux/highmem.h>
33#include <linux/module.h>
34#include <linux/writeback.h>
35#include <linux/hash.h>
36#include <linux/suspend.h>
37#include <linux/buffer_head.h>
Andrew Morton55e829a2006-12-10 02:19:27 -080038#include <linux/task_io_accounting_ops.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070039#include <linux/bio.h>
40#include <linux/notifier.h>
41#include <linux/cpu.h>
42#include <linux/bitops.h>
43#include <linux/mpage.h>
Ingo Molnarfb1c8f92005-09-10 00:25:56 -070044#include <linux/bit_spinlock.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070045
46static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
47static void invalidate_bh_lrus(void);
48
49#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
50
51inline void
52init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
53{
54 bh->b_end_io = handler;
55 bh->b_private = private;
56}
57
58static int sync_buffer(void *word)
59{
60 struct block_device *bd;
61 struct buffer_head *bh
62 = container_of(word, struct buffer_head, b_state);
63
64 smp_mb();
65 bd = bh->b_bdev;
66 if (bd)
67 blk_run_address_space(bd->bd_inode->i_mapping);
68 io_schedule();
69 return 0;
70}
71
72void fastcall __lock_buffer(struct buffer_head *bh)
73{
74 wait_on_bit_lock(&bh->b_state, BH_Lock, sync_buffer,
75 TASK_UNINTERRUPTIBLE);
76}
77EXPORT_SYMBOL(__lock_buffer);
78
79void fastcall unlock_buffer(struct buffer_head *bh)
80{
81 clear_buffer_locked(bh);
82 smp_mb__after_clear_bit();
83 wake_up_bit(&bh->b_state, BH_Lock);
84}
85
86/*
87 * Block until a buffer comes unlocked. This doesn't stop it
88 * from becoming locked again - you have to lock it yourself
89 * if you want to preserve its state.
90 */
91void __wait_on_buffer(struct buffer_head * bh)
92{
93 wait_on_bit(&bh->b_state, BH_Lock, sync_buffer, TASK_UNINTERRUPTIBLE);
94}
95
96static void
97__clear_page_buffers(struct page *page)
98{
99 ClearPagePrivate(page);
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700100 set_page_private(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700101 page_cache_release(page);
102}
103
104static void buffer_io_error(struct buffer_head *bh)
105{
106 char b[BDEVNAME_SIZE];
107
108 printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
109 bdevname(bh->b_bdev, b),
110 (unsigned long long)bh->b_blocknr);
111}
112
113/*
114 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
115 * unlock the buffer. This is what ll_rw_block uses too.
116 */
117void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
118{
119 if (uptodate) {
120 set_buffer_uptodate(bh);
121 } else {
122 /* This happens, due to failed READA attempts. */
123 clear_buffer_uptodate(bh);
124 }
125 unlock_buffer(bh);
126 put_bh(bh);
127}
128
129void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
130{
131 char b[BDEVNAME_SIZE];
132
133 if (uptodate) {
134 set_buffer_uptodate(bh);
135 } else {
136 if (!buffer_eopnotsupp(bh) && printk_ratelimit()) {
137 buffer_io_error(bh);
138 printk(KERN_WARNING "lost page write due to "
139 "I/O error on %s\n",
140 bdevname(bh->b_bdev, b));
141 }
142 set_buffer_write_io_error(bh);
143 clear_buffer_uptodate(bh);
144 }
145 unlock_buffer(bh);
146 put_bh(bh);
147}
148
149/*
150 * Write out and wait upon all the dirty data associated with a block
151 * device via its mapping. Does not take the superblock lock.
152 */
153int sync_blockdev(struct block_device *bdev)
154{
155 int ret = 0;
156
OGAWA Hirofumi28fd1292006-01-08 01:02:14 -0800157 if (bdev)
158 ret = filemap_write_and_wait(bdev->bd_inode->i_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700159 return ret;
160}
161EXPORT_SYMBOL(sync_blockdev);
162
Linus Torvalds1da177e2005-04-16 15:20:36 -0700163/*
164 * Write out and wait upon all dirty data associated with this
165 * device. Filesystem data as well as the underlying block
166 * device. Takes the superblock lock.
167 */
168int fsync_bdev(struct block_device *bdev)
169{
170 struct super_block *sb = get_super(bdev);
171 if (sb) {
172 int res = fsync_super(sb);
173 drop_super(sb);
174 return res;
175 }
176 return sync_blockdev(bdev);
177}
178
179/**
180 * freeze_bdev -- lock a filesystem and force it into a consistent state
181 * @bdev: blockdevice to lock
182 *
David Chinnerf73ca1b2007-01-10 23:15:41 -0800183 * This takes the block device bd_mount_sem to make sure no new mounts
Linus Torvalds1da177e2005-04-16 15:20:36 -0700184 * happen on bdev until thaw_bdev() is called.
185 * If a superblock is found on this device, we take the s_umount semaphore
186 * on it to make sure nobody unmounts until the snapshot creation is done.
187 */
188struct super_block *freeze_bdev(struct block_device *bdev)
189{
190 struct super_block *sb;
191
David Chinnerf73ca1b2007-01-10 23:15:41 -0800192 down(&bdev->bd_mount_sem);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700193 sb = get_super(bdev);
194 if (sb && !(sb->s_flags & MS_RDONLY)) {
195 sb->s_frozen = SB_FREEZE_WRITE;
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700196 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700197
OGAWA Hirofumid25b9a12006-03-25 03:07:44 -0800198 __fsync_super(sb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700199
200 sb->s_frozen = SB_FREEZE_TRANS;
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700201 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700202
203 sync_blockdev(sb->s_bdev);
204
205 if (sb->s_op->write_super_lockfs)
206 sb->s_op->write_super_lockfs(sb);
207 }
208
209 sync_blockdev(bdev);
210 return sb; /* thaw_bdev releases s->s_umount and bd_mount_sem */
211}
212EXPORT_SYMBOL(freeze_bdev);
213
214/**
215 * thaw_bdev -- unlock filesystem
216 * @bdev: blockdevice to unlock
217 * @sb: associated superblock
218 *
219 * Unlocks the filesystem and marks it writeable again after freeze_bdev().
220 */
221void thaw_bdev(struct block_device *bdev, struct super_block *sb)
222{
223 if (sb) {
224 BUG_ON(sb->s_bdev != bdev);
225
226 if (sb->s_op->unlockfs)
227 sb->s_op->unlockfs(sb);
228 sb->s_frozen = SB_UNFROZEN;
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700229 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700230 wake_up(&sb->s_wait_unfrozen);
231 drop_super(sb);
232 }
233
David Chinnerf73ca1b2007-01-10 23:15:41 -0800234 up(&bdev->bd_mount_sem);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700235}
236EXPORT_SYMBOL(thaw_bdev);
237
238/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700239 * Various filesystems appear to want __find_get_block to be non-blocking.
240 * But it's the page lock which protects the buffers. To get around this,
241 * we get exclusion from try_to_free_buffers with the blockdev mapping's
242 * private_lock.
243 *
244 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
245 * may be quite high. This code could TryLock the page, and if that
246 * succeeds, there is no need to take private_lock. (But if
247 * private_lock is contended then so is mapping->tree_lock).
248 */
249static struct buffer_head *
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -0800250__find_get_block_slow(struct block_device *bdev, sector_t block)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700251{
252 struct inode *bd_inode = bdev->bd_inode;
253 struct address_space *bd_mapping = bd_inode->i_mapping;
254 struct buffer_head *ret = NULL;
255 pgoff_t index;
256 struct buffer_head *bh;
257 struct buffer_head *head;
258 struct page *page;
259 int all_mapped = 1;
260
261 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
262 page = find_get_page(bd_mapping, index);
263 if (!page)
264 goto out;
265
266 spin_lock(&bd_mapping->private_lock);
267 if (!page_has_buffers(page))
268 goto out_unlock;
269 head = page_buffers(page);
270 bh = head;
271 do {
272 if (bh->b_blocknr == block) {
273 ret = bh;
274 get_bh(bh);
275 goto out_unlock;
276 }
277 if (!buffer_mapped(bh))
278 all_mapped = 0;
279 bh = bh->b_this_page;
280 } while (bh != head);
281
282 /* we might be here because some of the buffers on this page are
283 * not mapped. This is due to various races between
284 * file io on the block device and getblk. It gets dealt with
285 * elsewhere, don't buffer_error if we had some unmapped buffers
286 */
287 if (all_mapped) {
288 printk("__find_get_block_slow() failed. "
289 "block=%llu, b_blocknr=%llu\n",
Badari Pulavarty205f87f2006-03-26 01:38:00 -0800290 (unsigned long long)block,
291 (unsigned long long)bh->b_blocknr);
292 printk("b_state=0x%08lx, b_size=%zu\n",
293 bh->b_state, bh->b_size);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700294 printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits);
295 }
296out_unlock:
297 spin_unlock(&bd_mapping->private_lock);
298 page_cache_release(page);
299out:
300 return ret;
301}
302
303/* If invalidate_buffers() will trash dirty buffers, it means some kind
304 of fs corruption is going on. Trashing dirty data always imply losing
305 information that was supposed to be just stored on the physical layer
306 by the user.
307
308 Thus invalidate_buffers in general usage is not allwowed to trash
309 dirty buffers. For example ioctl(FLSBLKBUF) expects dirty data to
310 be preserved. These buffers are simply skipped.
311
312 We also skip buffers which are still in use. For example this can
313 happen if a userspace program is reading the block device.
314
315 NOTE: In the case where the user removed a removable-media-disk even if
316 there's still dirty data not synced on disk (due a bug in the device driver
317 or due an error of the user), by not destroying the dirty buffers we could
318 generate corruption also on the next media inserted, thus a parameter is
319 necessary to handle this case in the most safe way possible (trying
320 to not corrupt also the new disk inserted with the data belonging to
321 the old now corrupted disk). Also for the ramdisk the natural thing
322 to do in order to release the ramdisk memory is to destroy dirty buffers.
323
324 These are two special cases. Normal usage imply the device driver
325 to issue a sync on the device (without waiting I/O completion) and
326 then an invalidate_buffers call that doesn't trash dirty buffers.
327
328 For handling cache coherency with the blkdev pagecache the 'update' case
329 is been introduced. It is needed to re-read from disk any pinned
330 buffer. NOTE: re-reading from disk is destructive so we can do it only
331 when we assume nobody is changing the buffercache under our I/O and when
332 we think the disk contains more recent information than the buffercache.
333 The update == 1 pass marks the buffers we need to update, the update == 2
334 pass does the actual I/O. */
335void invalidate_bdev(struct block_device *bdev, int destroy_dirty_buffers)
336{
Andrew Morton0e1dfc62006-07-30 03:03:28 -0700337 struct address_space *mapping = bdev->bd_inode->i_mapping;
338
339 if (mapping->nrpages == 0)
340 return;
341
Linus Torvalds1da177e2005-04-16 15:20:36 -0700342 invalidate_bh_lrus();
343 /*
344 * FIXME: what about destroy_dirty_buffers?
345 * We really want to use invalidate_inode_pages2() for
346 * that, but not until that's cleaned up.
347 */
Andrew Morton0e1dfc62006-07-30 03:03:28 -0700348 invalidate_inode_pages(mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700349}
350
351/*
352 * Kick pdflush then try to free up some ZONE_NORMAL memory.
353 */
354static void free_more_memory(void)
355{
356 struct zone **zones;
357 pg_data_t *pgdat;
358
Pekka J Enberg687a21c2005-06-28 20:44:55 -0700359 wakeup_pdflush(1024);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700360 yield();
361
KAMEZAWA Hiroyukiec936fc2006-03-27 01:15:59 -0800362 for_each_online_pgdat(pgdat) {
Al Viroaf4ca452005-10-21 02:55:38 -0400363 zones = pgdat->node_zonelists[gfp_zone(GFP_NOFS)].zones;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700364 if (*zones)
Darren Hart1ad539b2005-06-21 17:14:53 -0700365 try_to_free_pages(zones, GFP_NOFS);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700366 }
367}
368
369/*
370 * I/O completion handler for block_read_full_page() - pages
371 * which come unlocked at the end of I/O.
372 */
373static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
374{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700375 unsigned long flags;
Nick Piggina3972202005-07-07 17:56:56 -0700376 struct buffer_head *first;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700377 struct buffer_head *tmp;
378 struct page *page;
379 int page_uptodate = 1;
380
381 BUG_ON(!buffer_async_read(bh));
382
383 page = bh->b_page;
384 if (uptodate) {
385 set_buffer_uptodate(bh);
386 } else {
387 clear_buffer_uptodate(bh);
388 if (printk_ratelimit())
389 buffer_io_error(bh);
390 SetPageError(page);
391 }
392
393 /*
394 * Be _very_ careful from here on. Bad things can happen if
395 * two buffer heads end IO at almost the same time and both
396 * decide that the page is now completely done.
397 */
Nick Piggina3972202005-07-07 17:56:56 -0700398 first = page_buffers(page);
399 local_irq_save(flags);
400 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700401 clear_buffer_async_read(bh);
402 unlock_buffer(bh);
403 tmp = bh;
404 do {
405 if (!buffer_uptodate(tmp))
406 page_uptodate = 0;
407 if (buffer_async_read(tmp)) {
408 BUG_ON(!buffer_locked(tmp));
409 goto still_busy;
410 }
411 tmp = tmp->b_this_page;
412 } while (tmp != bh);
Nick Piggina3972202005-07-07 17:56:56 -0700413 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
414 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700415
416 /*
417 * If none of the buffers had errors and they are all
418 * uptodate then we can set the page uptodate.
419 */
420 if (page_uptodate && !PageError(page))
421 SetPageUptodate(page);
422 unlock_page(page);
423 return;
424
425still_busy:
Nick Piggina3972202005-07-07 17:56:56 -0700426 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
427 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700428 return;
429}
430
431/*
432 * Completion handler for block_write_full_page() - pages which are unlocked
433 * during I/O, and which have PageWriteback cleared upon I/O completion.
434 */
Adrian Bunkb6cd0b72006-06-27 02:53:54 -0700435static void end_buffer_async_write(struct buffer_head *bh, int uptodate)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700436{
437 char b[BDEVNAME_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700438 unsigned long flags;
Nick Piggina3972202005-07-07 17:56:56 -0700439 struct buffer_head *first;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700440 struct buffer_head *tmp;
441 struct page *page;
442
443 BUG_ON(!buffer_async_write(bh));
444
445 page = bh->b_page;
446 if (uptodate) {
447 set_buffer_uptodate(bh);
448 } else {
449 if (printk_ratelimit()) {
450 buffer_io_error(bh);
451 printk(KERN_WARNING "lost page write due to "
452 "I/O error on %s\n",
453 bdevname(bh->b_bdev, b));
454 }
455 set_bit(AS_EIO, &page->mapping->flags);
Jan Kara58ff4072006-10-17 00:10:19 -0700456 set_buffer_write_io_error(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700457 clear_buffer_uptodate(bh);
458 SetPageError(page);
459 }
460
Nick Piggina3972202005-07-07 17:56:56 -0700461 first = page_buffers(page);
462 local_irq_save(flags);
463 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
464
Linus Torvalds1da177e2005-04-16 15:20:36 -0700465 clear_buffer_async_write(bh);
466 unlock_buffer(bh);
467 tmp = bh->b_this_page;
468 while (tmp != bh) {
469 if (buffer_async_write(tmp)) {
470 BUG_ON(!buffer_locked(tmp));
471 goto still_busy;
472 }
473 tmp = tmp->b_this_page;
474 }
Nick Piggina3972202005-07-07 17:56:56 -0700475 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
476 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700477 end_page_writeback(page);
478 return;
479
480still_busy:
Nick Piggina3972202005-07-07 17:56:56 -0700481 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
482 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700483 return;
484}
485
486/*
487 * If a page's buffers are under async readin (end_buffer_async_read
488 * completion) then there is a possibility that another thread of
489 * control could lock one of the buffers after it has completed
490 * but while some of the other buffers have not completed. This
491 * locked buffer would confuse end_buffer_async_read() into not unlocking
492 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
493 * that this buffer is not under async I/O.
494 *
495 * The page comes unlocked when it has no locked buffer_async buffers
496 * left.
497 *
498 * PageLocked prevents anyone starting new async I/O reads any of
499 * the buffers.
500 *
501 * PageWriteback is used to prevent simultaneous writeout of the same
502 * page.
503 *
504 * PageLocked prevents anyone from starting writeback of a page which is
505 * under read I/O (PageWriteback is only ever set against a locked page).
506 */
507static void mark_buffer_async_read(struct buffer_head *bh)
508{
509 bh->b_end_io = end_buffer_async_read;
510 set_buffer_async_read(bh);
511}
512
513void mark_buffer_async_write(struct buffer_head *bh)
514{
515 bh->b_end_io = end_buffer_async_write;
516 set_buffer_async_write(bh);
517}
518EXPORT_SYMBOL(mark_buffer_async_write);
519
520
521/*
522 * fs/buffer.c contains helper functions for buffer-backed address space's
523 * fsync functions. A common requirement for buffer-based filesystems is
524 * that certain data from the backing blockdev needs to be written out for
525 * a successful fsync(). For example, ext2 indirect blocks need to be
526 * written back and waited upon before fsync() returns.
527 *
528 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
529 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
530 * management of a list of dependent buffers at ->i_mapping->private_list.
531 *
532 * Locking is a little subtle: try_to_free_buffers() will remove buffers
533 * from their controlling inode's queue when they are being freed. But
534 * try_to_free_buffers() will be operating against the *blockdev* mapping
535 * at the time, not against the S_ISREG file which depends on those buffers.
536 * So the locking for private_list is via the private_lock in the address_space
537 * which backs the buffers. Which is different from the address_space
538 * against which the buffers are listed. So for a particular address_space,
539 * mapping->private_lock does *not* protect mapping->private_list! In fact,
540 * mapping->private_list will always be protected by the backing blockdev's
541 * ->private_lock.
542 *
543 * Which introduces a requirement: all buffers on an address_space's
544 * ->private_list must be from the same address_space: the blockdev's.
545 *
546 * address_spaces which do not place buffers at ->private_list via these
547 * utility functions are free to use private_lock and private_list for
548 * whatever they want. The only requirement is that list_empty(private_list)
549 * be true at clear_inode() time.
550 *
551 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
552 * filesystems should do that. invalidate_inode_buffers() should just go
553 * BUG_ON(!list_empty).
554 *
555 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
556 * take an address_space, not an inode. And it should be called
557 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
558 * queued up.
559 *
560 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
561 * list if it is already on a list. Because if the buffer is on a list,
562 * it *must* already be on the right one. If not, the filesystem is being
563 * silly. This will save a ton of locking. But first we have to ensure
564 * that buffers are taken *off* the old inode's list when they are freed
565 * (presumably in truncate). That requires careful auditing of all
566 * filesystems (do it inside bforget()). It could also be done by bringing
567 * b_inode back.
568 */
569
570/*
571 * The buffer's backing address_space's private_lock must be held
572 */
573static inline void __remove_assoc_queue(struct buffer_head *bh)
574{
575 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -0700576 WARN_ON(!bh->b_assoc_map);
577 if (buffer_write_io_error(bh))
578 set_bit(AS_EIO, &bh->b_assoc_map->flags);
579 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700580}
581
582int inode_has_buffers(struct inode *inode)
583{
584 return !list_empty(&inode->i_data.private_list);
585}
586
587/*
588 * osync is designed to support O_SYNC io. It waits synchronously for
589 * all already-submitted IO to complete, but does not queue any new
590 * writes to the disk.
591 *
592 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
593 * you dirty the buffers, and then use osync_inode_buffers to wait for
594 * completion. Any other dirty buffers which are not yet queued for
595 * write will not be flushed to disk by the osync.
596 */
597static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
598{
599 struct buffer_head *bh;
600 struct list_head *p;
601 int err = 0;
602
603 spin_lock(lock);
604repeat:
605 list_for_each_prev(p, list) {
606 bh = BH_ENTRY(p);
607 if (buffer_locked(bh)) {
608 get_bh(bh);
609 spin_unlock(lock);
610 wait_on_buffer(bh);
611 if (!buffer_uptodate(bh))
612 err = -EIO;
613 brelse(bh);
614 spin_lock(lock);
615 goto repeat;
616 }
617 }
618 spin_unlock(lock);
619 return err;
620}
621
622/**
623 * sync_mapping_buffers - write out and wait upon a mapping's "associated"
624 * buffers
Martin Waitz67be2dd2005-05-01 08:59:26 -0700625 * @mapping: the mapping which wants those buffers written
Linus Torvalds1da177e2005-04-16 15:20:36 -0700626 *
627 * Starts I/O against the buffers at mapping->private_list, and waits upon
628 * that I/O.
629 *
Martin Waitz67be2dd2005-05-01 08:59:26 -0700630 * Basically, this is a convenience function for fsync().
631 * @mapping is a file or directory which needs those buffers to be written for
632 * a successful fsync().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700633 */
634int sync_mapping_buffers(struct address_space *mapping)
635{
636 struct address_space *buffer_mapping = mapping->assoc_mapping;
637
638 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
639 return 0;
640
641 return fsync_buffers_list(&buffer_mapping->private_lock,
642 &mapping->private_list);
643}
644EXPORT_SYMBOL(sync_mapping_buffers);
645
646/*
647 * Called when we've recently written block `bblock', and it is known that
648 * `bblock' was for a buffer_boundary() buffer. This means that the block at
649 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
650 * dirty, schedule it for IO. So that indirects merge nicely with their data.
651 */
652void write_boundary_block(struct block_device *bdev,
653 sector_t bblock, unsigned blocksize)
654{
655 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
656 if (bh) {
657 if (buffer_dirty(bh))
658 ll_rw_block(WRITE, 1, &bh);
659 put_bh(bh);
660 }
661}
662
663void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
664{
665 struct address_space *mapping = inode->i_mapping;
666 struct address_space *buffer_mapping = bh->b_page->mapping;
667
668 mark_buffer_dirty(bh);
669 if (!mapping->assoc_mapping) {
670 mapping->assoc_mapping = buffer_mapping;
671 } else {
Eric Sesterhenne827f922006-03-26 18:24:46 +0200672 BUG_ON(mapping->assoc_mapping != buffer_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700673 }
674 if (list_empty(&bh->b_assoc_buffers)) {
675 spin_lock(&buffer_mapping->private_lock);
676 list_move_tail(&bh->b_assoc_buffers,
677 &mapping->private_list);
Jan Kara58ff4072006-10-17 00:10:19 -0700678 bh->b_assoc_map = mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700679 spin_unlock(&buffer_mapping->private_lock);
680 }
681}
682EXPORT_SYMBOL(mark_buffer_dirty_inode);
683
684/*
685 * Add a page to the dirty page list.
686 *
687 * It is a sad fact of life that this function is called from several places
688 * deeply under spinlocking. It may not sleep.
689 *
690 * If the page has buffers, the uptodate buffers are set dirty, to preserve
691 * dirty-state coherency between the page and the buffers. It the page does
692 * not have buffers then when they are later attached they will all be set
693 * dirty.
694 *
695 * The buffers are dirtied before the page is dirtied. There's a small race
696 * window in which a writepage caller may see the page cleanness but not the
697 * buffer dirtiness. That's fine. If this code were to set the page dirty
698 * before the buffers, a concurrent writepage caller could clear the page dirty
699 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
700 * page on the dirty page list.
701 *
702 * We use private_lock to lock against try_to_free_buffers while using the
703 * page's buffer list. Also use this to protect against clean buffers being
704 * added to the page after it was set dirty.
705 *
706 * FIXME: may need to call ->reservepage here as well. That's rather up to the
707 * address_space though.
708 */
709int __set_page_dirty_buffers(struct page *page)
710{
Nick Pigginebf7a222006-10-10 04:36:54 +0200711 struct address_space * const mapping = page_mapping(page);
712
713 if (unlikely(!mapping))
714 return !TestSetPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700715
716 spin_lock(&mapping->private_lock);
717 if (page_has_buffers(page)) {
718 struct buffer_head *head = page_buffers(page);
719 struct buffer_head *bh = head;
720
721 do {
722 set_buffer_dirty(bh);
723 bh = bh->b_this_page;
724 } while (bh != head);
725 }
726 spin_unlock(&mapping->private_lock);
727
Andrew Morton8c085402006-12-10 02:19:24 -0800728 if (TestSetPageDirty(page))
729 return 0;
730
731 write_lock_irq(&mapping->tree_lock);
732 if (page->mapping) { /* Race with truncate? */
Andrew Morton55e829a2006-12-10 02:19:27 -0800733 if (mapping_cap_account_dirty(mapping)) {
Andrew Morton8c085402006-12-10 02:19:24 -0800734 __inc_zone_page_state(page, NR_FILE_DIRTY);
Andrew Morton55e829a2006-12-10 02:19:27 -0800735 task_io_account_write(PAGE_CACHE_SIZE);
736 }
Andrew Morton8c085402006-12-10 02:19:24 -0800737 radix_tree_tag_set(&mapping->page_tree,
738 page_index(page), PAGECACHE_TAG_DIRTY);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700739 }
Andrew Morton8c085402006-12-10 02:19:24 -0800740 write_unlock_irq(&mapping->tree_lock);
741 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
742 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700743}
744EXPORT_SYMBOL(__set_page_dirty_buffers);
745
746/*
747 * Write out and wait upon a list of buffers.
748 *
749 * We have conflicting pressures: we want to make sure that all
750 * initially dirty buffers get waited on, but that any subsequently
751 * dirtied buffers don't. After all, we don't want fsync to last
752 * forever if somebody is actively writing to the file.
753 *
754 * Do this in two main stages: first we copy dirty buffers to a
755 * temporary inode list, queueing the writes as we go. Then we clean
756 * up, waiting for those writes to complete.
757 *
758 * During this second stage, any subsequent updates to the file may end
759 * up refiling the buffer on the original inode's dirty list again, so
760 * there is a chance we will end up with a buffer queued for write but
761 * not yet completed on that list. So, as a final cleanup we go through
762 * the osync code to catch these locked, dirty buffers without requeuing
763 * any newly dirty buffers for write.
764 */
765static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
766{
767 struct buffer_head *bh;
768 struct list_head tmp;
769 int err = 0, err2;
770
771 INIT_LIST_HEAD(&tmp);
772
773 spin_lock(lock);
774 while (!list_empty(list)) {
775 bh = BH_ENTRY(list->next);
Jan Kara58ff4072006-10-17 00:10:19 -0700776 __remove_assoc_queue(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700777 if (buffer_dirty(bh) || buffer_locked(bh)) {
778 list_add(&bh->b_assoc_buffers, &tmp);
779 if (buffer_dirty(bh)) {
780 get_bh(bh);
781 spin_unlock(lock);
782 /*
783 * Ensure any pending I/O completes so that
784 * ll_rw_block() actually writes the current
785 * contents - it is a noop if I/O is still in
786 * flight on potentially older contents.
787 */
Jan Karaa7662232005-09-06 15:19:10 -0700788 ll_rw_block(SWRITE, 1, &bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700789 brelse(bh);
790 spin_lock(lock);
791 }
792 }
793 }
794
795 while (!list_empty(&tmp)) {
796 bh = BH_ENTRY(tmp.prev);
Jan Kara58ff4072006-10-17 00:10:19 -0700797 list_del_init(&bh->b_assoc_buffers);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700798 get_bh(bh);
799 spin_unlock(lock);
800 wait_on_buffer(bh);
801 if (!buffer_uptodate(bh))
802 err = -EIO;
803 brelse(bh);
804 spin_lock(lock);
805 }
806
807 spin_unlock(lock);
808 err2 = osync_buffers_list(lock, list);
809 if (err)
810 return err;
811 else
812 return err2;
813}
814
815/*
816 * Invalidate any and all dirty buffers on a given inode. We are
817 * probably unmounting the fs, but that doesn't mean we have already
818 * done a sync(). Just drop the buffers from the inode list.
819 *
820 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
821 * assumes that all the buffers are against the blockdev. Not true
822 * for reiserfs.
823 */
824void invalidate_inode_buffers(struct inode *inode)
825{
826 if (inode_has_buffers(inode)) {
827 struct address_space *mapping = &inode->i_data;
828 struct list_head *list = &mapping->private_list;
829 struct address_space *buffer_mapping = mapping->assoc_mapping;
830
831 spin_lock(&buffer_mapping->private_lock);
832 while (!list_empty(list))
833 __remove_assoc_queue(BH_ENTRY(list->next));
834 spin_unlock(&buffer_mapping->private_lock);
835 }
836}
837
838/*
839 * Remove any clean buffers from the inode's buffer list. This is called
840 * when we're trying to free the inode itself. Those buffers can pin it.
841 *
842 * Returns true if all buffers were removed.
843 */
844int remove_inode_buffers(struct inode *inode)
845{
846 int ret = 1;
847
848 if (inode_has_buffers(inode)) {
849 struct address_space *mapping = &inode->i_data;
850 struct list_head *list = &mapping->private_list;
851 struct address_space *buffer_mapping = mapping->assoc_mapping;
852
853 spin_lock(&buffer_mapping->private_lock);
854 while (!list_empty(list)) {
855 struct buffer_head *bh = BH_ENTRY(list->next);
856 if (buffer_dirty(bh)) {
857 ret = 0;
858 break;
859 }
860 __remove_assoc_queue(bh);
861 }
862 spin_unlock(&buffer_mapping->private_lock);
863 }
864 return ret;
865}
866
867/*
868 * Create the appropriate buffers when given a page for data area and
869 * the size of each buffer.. Use the bh->b_this_page linked list to
870 * follow the buffers created. Return NULL if unable to create more
871 * buffers.
872 *
873 * The retry flag is used to differentiate async IO (paging, swapping)
874 * which may not fail from ordinary buffer allocations.
875 */
876struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
877 int retry)
878{
879 struct buffer_head *bh, *head;
880 long offset;
881
882try_again:
883 head = NULL;
884 offset = PAGE_SIZE;
885 while ((offset -= size) >= 0) {
886 bh = alloc_buffer_head(GFP_NOFS);
887 if (!bh)
888 goto no_grow;
889
890 bh->b_bdev = NULL;
891 bh->b_this_page = head;
892 bh->b_blocknr = -1;
893 head = bh;
894
895 bh->b_state = 0;
896 atomic_set(&bh->b_count, 0);
Chris Masonfc5cd582006-02-01 03:06:48 -0800897 bh->b_private = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700898 bh->b_size = size;
899
900 /* Link the buffer to its page */
901 set_bh_page(bh, page, offset);
902
Nathan Scott01ffe332006-01-17 09:02:07 +1100903 init_buffer(bh, NULL, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700904 }
905 return head;
906/*
907 * In case anything failed, we just free everything we got.
908 */
909no_grow:
910 if (head) {
911 do {
912 bh = head;
913 head = head->b_this_page;
914 free_buffer_head(bh);
915 } while (head);
916 }
917
918 /*
919 * Return failure for non-async IO requests. Async IO requests
920 * are not allowed to fail, so we have to wait until buffer heads
921 * become available. But we don't want tasks sleeping with
922 * partially complete buffers, so all were released above.
923 */
924 if (!retry)
925 return NULL;
926
927 /* We're _really_ low on memory. Now we just
928 * wait for old buffer heads to become free due to
929 * finishing IO. Since this is an async request and
930 * the reserve list is empty, we're sure there are
931 * async buffer heads in use.
932 */
933 free_more_memory();
934 goto try_again;
935}
936EXPORT_SYMBOL_GPL(alloc_page_buffers);
937
938static inline void
939link_dev_buffers(struct page *page, struct buffer_head *head)
940{
941 struct buffer_head *bh, *tail;
942
943 bh = head;
944 do {
945 tail = bh;
946 bh = bh->b_this_page;
947 } while (bh);
948 tail->b_this_page = head;
949 attach_page_buffers(page, head);
950}
951
952/*
953 * Initialise the state of a blockdev page's buffers.
954 */
955static void
956init_page_buffers(struct page *page, struct block_device *bdev,
957 sector_t block, int size)
958{
959 struct buffer_head *head = page_buffers(page);
960 struct buffer_head *bh = head;
961 int uptodate = PageUptodate(page);
962
963 do {
964 if (!buffer_mapped(bh)) {
965 init_buffer(bh, NULL, NULL);
966 bh->b_bdev = bdev;
967 bh->b_blocknr = block;
968 if (uptodate)
969 set_buffer_uptodate(bh);
970 set_buffer_mapped(bh);
971 }
972 block++;
973 bh = bh->b_this_page;
974 } while (bh != head);
975}
976
977/*
978 * Create the page-cache page that contains the requested block.
979 *
980 * This is user purely for blockdev mappings.
981 */
982static struct page *
983grow_dev_page(struct block_device *bdev, sector_t block,
984 pgoff_t index, int size)
985{
986 struct inode *inode = bdev->bd_inode;
987 struct page *page;
988 struct buffer_head *bh;
989
990 page = find_or_create_page(inode->i_mapping, index, GFP_NOFS);
991 if (!page)
992 return NULL;
993
Eric Sesterhenne827f922006-03-26 18:24:46 +0200994 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700995
996 if (page_has_buffers(page)) {
997 bh = page_buffers(page);
998 if (bh->b_size == size) {
999 init_page_buffers(page, bdev, block, size);
1000 return page;
1001 }
1002 if (!try_to_free_buffers(page))
1003 goto failed;
1004 }
1005
1006 /*
1007 * Allocate some buffers for this page
1008 */
1009 bh = alloc_page_buffers(page, size, 0);
1010 if (!bh)
1011 goto failed;
1012
1013 /*
1014 * Link the page to the buffers and initialise them. Take the
1015 * lock to be atomic wrt __find_get_block(), which does not
1016 * run under the page lock.
1017 */
1018 spin_lock(&inode->i_mapping->private_lock);
1019 link_dev_buffers(page, bh);
1020 init_page_buffers(page, bdev, block, size);
1021 spin_unlock(&inode->i_mapping->private_lock);
1022 return page;
1023
1024failed:
1025 BUG();
1026 unlock_page(page);
1027 page_cache_release(page);
1028 return NULL;
1029}
1030
1031/*
1032 * Create buffers for the specified block device block's page. If
1033 * that page was dirty, the buffers are set dirty also.
1034 *
1035 * Except that's a bug. Attaching dirty buffers to a dirty
1036 * blockdev's page can result in filesystem corruption, because
1037 * some of those buffers may be aliases of filesystem data.
1038 * grow_dev_page() will go BUG() if this happens.
1039 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001040static int
Linus Torvalds1da177e2005-04-16 15:20:36 -07001041grow_buffers(struct block_device *bdev, sector_t block, int size)
1042{
1043 struct page *page;
1044 pgoff_t index;
1045 int sizebits;
1046
1047 sizebits = -1;
1048 do {
1049 sizebits++;
1050 } while ((size << sizebits) < PAGE_SIZE);
1051
1052 index = block >> sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001053
Andrew Mortone5657932006-10-11 01:21:46 -07001054 /*
1055 * Check for a block which wants to lie outside our maximum possible
1056 * pagecache index. (this comparison is done using sector_t types).
1057 */
1058 if (unlikely(index != block >> sizebits)) {
1059 char b[BDEVNAME_SIZE];
1060
1061 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1062 "device %s\n",
1063 __FUNCTION__, (unsigned long long)block,
1064 bdevname(bdev, b));
1065 return -EIO;
1066 }
1067 block = index << sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001068 /* Create a page with the proper size buffers.. */
1069 page = grow_dev_page(bdev, block, index, size);
1070 if (!page)
1071 return 0;
1072 unlock_page(page);
1073 page_cache_release(page);
1074 return 1;
1075}
1076
Adrian Bunk75c96f82005-05-05 16:16:09 -07001077static struct buffer_head *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001078__getblk_slow(struct block_device *bdev, sector_t block, int size)
1079{
1080 /* Size must be multiple of hard sectorsize */
1081 if (unlikely(size & (bdev_hardsect_size(bdev)-1) ||
1082 (size < 512 || size > PAGE_SIZE))) {
1083 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1084 size);
1085 printk(KERN_ERR "hardsect size: %d\n",
1086 bdev_hardsect_size(bdev));
1087
1088 dump_stack();
1089 return NULL;
1090 }
1091
1092 for (;;) {
1093 struct buffer_head * bh;
Andrew Mortone5657932006-10-11 01:21:46 -07001094 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001095
1096 bh = __find_get_block(bdev, block, size);
1097 if (bh)
1098 return bh;
1099
Andrew Mortone5657932006-10-11 01:21:46 -07001100 ret = grow_buffers(bdev, block, size);
1101 if (ret < 0)
1102 return NULL;
1103 if (ret == 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001104 free_more_memory();
1105 }
1106}
1107
1108/*
1109 * The relationship between dirty buffers and dirty pages:
1110 *
1111 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1112 * the page is tagged dirty in its radix tree.
1113 *
1114 * At all times, the dirtiness of the buffers represents the dirtiness of
1115 * subsections of the page. If the page has buffers, the page dirty bit is
1116 * merely a hint about the true dirty state.
1117 *
1118 * When a page is set dirty in its entirety, all its buffers are marked dirty
1119 * (if the page has buffers).
1120 *
1121 * When a buffer is marked dirty, its page is dirtied, but the page's other
1122 * buffers are not.
1123 *
1124 * Also. When blockdev buffers are explicitly read with bread(), they
1125 * individually become uptodate. But their backing page remains not
1126 * uptodate - even if all of its buffers are uptodate. A subsequent
1127 * block_read_full_page() against that page will discover all the uptodate
1128 * buffers, will set the page uptodate and will perform no I/O.
1129 */
1130
1131/**
1132 * mark_buffer_dirty - mark a buffer_head as needing writeout
Martin Waitz67be2dd2005-05-01 08:59:26 -07001133 * @bh: the buffer_head to mark dirty
Linus Torvalds1da177e2005-04-16 15:20:36 -07001134 *
1135 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1136 * backing page dirty, then tag the page as dirty in its address_space's radix
1137 * tree and then attach the address_space's inode to its superblock's dirty
1138 * inode list.
1139 *
1140 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1141 * mapping->tree_lock and the global inode_lock.
1142 */
1143void fastcall mark_buffer_dirty(struct buffer_head *bh)
1144{
1145 if (!buffer_dirty(bh) && !test_set_buffer_dirty(bh))
1146 __set_page_dirty_nobuffers(bh->b_page);
1147}
1148
1149/*
1150 * Decrement a buffer_head's reference count. If all buffers against a page
1151 * have zero reference count, are clean and unlocked, and if the page is clean
1152 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1153 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1154 * a page but it ends up not being freed, and buffers may later be reattached).
1155 */
1156void __brelse(struct buffer_head * buf)
1157{
1158 if (atomic_read(&buf->b_count)) {
1159 put_bh(buf);
1160 return;
1161 }
1162 printk(KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1163 WARN_ON(1);
1164}
1165
1166/*
1167 * bforget() is like brelse(), except it discards any
1168 * potentially dirty data.
1169 */
1170void __bforget(struct buffer_head *bh)
1171{
1172 clear_buffer_dirty(bh);
1173 if (!list_empty(&bh->b_assoc_buffers)) {
1174 struct address_space *buffer_mapping = bh->b_page->mapping;
1175
1176 spin_lock(&buffer_mapping->private_lock);
1177 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -07001178 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001179 spin_unlock(&buffer_mapping->private_lock);
1180 }
1181 __brelse(bh);
1182}
1183
1184static struct buffer_head *__bread_slow(struct buffer_head *bh)
1185{
1186 lock_buffer(bh);
1187 if (buffer_uptodate(bh)) {
1188 unlock_buffer(bh);
1189 return bh;
1190 } else {
1191 get_bh(bh);
1192 bh->b_end_io = end_buffer_read_sync;
1193 submit_bh(READ, bh);
1194 wait_on_buffer(bh);
1195 if (buffer_uptodate(bh))
1196 return bh;
1197 }
1198 brelse(bh);
1199 return NULL;
1200}
1201
1202/*
1203 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1204 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1205 * refcount elevated by one when they're in an LRU. A buffer can only appear
1206 * once in a particular CPU's LRU. A single buffer can be present in multiple
1207 * CPU's LRUs at the same time.
1208 *
1209 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1210 * sb_find_get_block().
1211 *
1212 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1213 * a local interrupt disable for that.
1214 */
1215
1216#define BH_LRU_SIZE 8
1217
1218struct bh_lru {
1219 struct buffer_head *bhs[BH_LRU_SIZE];
1220};
1221
1222static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1223
1224#ifdef CONFIG_SMP
1225#define bh_lru_lock() local_irq_disable()
1226#define bh_lru_unlock() local_irq_enable()
1227#else
1228#define bh_lru_lock() preempt_disable()
1229#define bh_lru_unlock() preempt_enable()
1230#endif
1231
1232static inline void check_irqs_on(void)
1233{
1234#ifdef irqs_disabled
1235 BUG_ON(irqs_disabled());
1236#endif
1237}
1238
1239/*
1240 * The LRU management algorithm is dopey-but-simple. Sorry.
1241 */
1242static void bh_lru_install(struct buffer_head *bh)
1243{
1244 struct buffer_head *evictee = NULL;
1245 struct bh_lru *lru;
1246
1247 check_irqs_on();
1248 bh_lru_lock();
1249 lru = &__get_cpu_var(bh_lrus);
1250 if (lru->bhs[0] != bh) {
1251 struct buffer_head *bhs[BH_LRU_SIZE];
1252 int in;
1253 int out = 0;
1254
1255 get_bh(bh);
1256 bhs[out++] = bh;
1257 for (in = 0; in < BH_LRU_SIZE; in++) {
1258 struct buffer_head *bh2 = lru->bhs[in];
1259
1260 if (bh2 == bh) {
1261 __brelse(bh2);
1262 } else {
1263 if (out >= BH_LRU_SIZE) {
1264 BUG_ON(evictee != NULL);
1265 evictee = bh2;
1266 } else {
1267 bhs[out++] = bh2;
1268 }
1269 }
1270 }
1271 while (out < BH_LRU_SIZE)
1272 bhs[out++] = NULL;
1273 memcpy(lru->bhs, bhs, sizeof(bhs));
1274 }
1275 bh_lru_unlock();
1276
1277 if (evictee)
1278 __brelse(evictee);
1279}
1280
1281/*
1282 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1283 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001284static struct buffer_head *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001285lookup_bh_lru(struct block_device *bdev, sector_t block, int size)
1286{
1287 struct buffer_head *ret = NULL;
1288 struct bh_lru *lru;
1289 int i;
1290
1291 check_irqs_on();
1292 bh_lru_lock();
1293 lru = &__get_cpu_var(bh_lrus);
1294 for (i = 0; i < BH_LRU_SIZE; i++) {
1295 struct buffer_head *bh = lru->bhs[i];
1296
1297 if (bh && bh->b_bdev == bdev &&
1298 bh->b_blocknr == block && bh->b_size == size) {
1299 if (i) {
1300 while (i) {
1301 lru->bhs[i] = lru->bhs[i - 1];
1302 i--;
1303 }
1304 lru->bhs[0] = bh;
1305 }
1306 get_bh(bh);
1307 ret = bh;
1308 break;
1309 }
1310 }
1311 bh_lru_unlock();
1312 return ret;
1313}
1314
1315/*
1316 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1317 * it in the LRU and mark it as accessed. If it is not present then return
1318 * NULL
1319 */
1320struct buffer_head *
1321__find_get_block(struct block_device *bdev, sector_t block, int size)
1322{
1323 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1324
1325 if (bh == NULL) {
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001326 bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001327 if (bh)
1328 bh_lru_install(bh);
1329 }
1330 if (bh)
1331 touch_buffer(bh);
1332 return bh;
1333}
1334EXPORT_SYMBOL(__find_get_block);
1335
1336/*
1337 * __getblk will locate (and, if necessary, create) the buffer_head
1338 * which corresponds to the passed block_device, block and size. The
1339 * returned buffer has its reference count incremented.
1340 *
1341 * __getblk() cannot fail - it just keeps trying. If you pass it an
1342 * illegal block number, __getblk() will happily return a buffer_head
1343 * which represents the non-existent block. Very weird.
1344 *
1345 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1346 * attempt is failing. FIXME, perhaps?
1347 */
1348struct buffer_head *
1349__getblk(struct block_device *bdev, sector_t block, int size)
1350{
1351 struct buffer_head *bh = __find_get_block(bdev, block, size);
1352
1353 might_sleep();
1354 if (bh == NULL)
1355 bh = __getblk_slow(bdev, block, size);
1356 return bh;
1357}
1358EXPORT_SYMBOL(__getblk);
1359
1360/*
1361 * Do async read-ahead on a buffer..
1362 */
1363void __breadahead(struct block_device *bdev, sector_t block, int size)
1364{
1365 struct buffer_head *bh = __getblk(bdev, block, size);
Andrew Mortona3e713b2005-10-30 15:03:15 -08001366 if (likely(bh)) {
1367 ll_rw_block(READA, 1, &bh);
1368 brelse(bh);
1369 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001370}
1371EXPORT_SYMBOL(__breadahead);
1372
1373/**
1374 * __bread() - reads a specified block and returns the bh
Martin Waitz67be2dd2005-05-01 08:59:26 -07001375 * @bdev: the block_device to read from
Linus Torvalds1da177e2005-04-16 15:20:36 -07001376 * @block: number of block
1377 * @size: size (in bytes) to read
1378 *
1379 * Reads a specified block, and returns buffer head that contains it.
1380 * It returns NULL if the block was unreadable.
1381 */
1382struct buffer_head *
1383__bread(struct block_device *bdev, sector_t block, int size)
1384{
1385 struct buffer_head *bh = __getblk(bdev, block, size);
1386
Andrew Mortona3e713b2005-10-30 15:03:15 -08001387 if (likely(bh) && !buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001388 bh = __bread_slow(bh);
1389 return bh;
1390}
1391EXPORT_SYMBOL(__bread);
1392
1393/*
1394 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1395 * This doesn't race because it runs in each cpu either in irq
1396 * or with preempt disabled.
1397 */
1398static void invalidate_bh_lru(void *arg)
1399{
1400 struct bh_lru *b = &get_cpu_var(bh_lrus);
1401 int i;
1402
1403 for (i = 0; i < BH_LRU_SIZE; i++) {
1404 brelse(b->bhs[i]);
1405 b->bhs[i] = NULL;
1406 }
1407 put_cpu_var(bh_lrus);
1408}
1409
1410static void invalidate_bh_lrus(void)
1411{
1412 on_each_cpu(invalidate_bh_lru, NULL, 1, 1);
1413}
1414
1415void set_bh_page(struct buffer_head *bh,
1416 struct page *page, unsigned long offset)
1417{
1418 bh->b_page = page;
Eric Sesterhenne827f922006-03-26 18:24:46 +02001419 BUG_ON(offset >= PAGE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001420 if (PageHighMem(page))
1421 /*
1422 * This catches illegal uses and preserves the offset:
1423 */
1424 bh->b_data = (char *)(0 + offset);
1425 else
1426 bh->b_data = page_address(page) + offset;
1427}
1428EXPORT_SYMBOL(set_bh_page);
1429
1430/*
1431 * Called when truncating a buffer on a page completely.
1432 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001433static void discard_buffer(struct buffer_head * bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001434{
1435 lock_buffer(bh);
1436 clear_buffer_dirty(bh);
1437 bh->b_bdev = NULL;
1438 clear_buffer_mapped(bh);
1439 clear_buffer_req(bh);
1440 clear_buffer_new(bh);
1441 clear_buffer_delay(bh);
1442 unlock_buffer(bh);
1443}
1444
1445/**
Linus Torvalds1da177e2005-04-16 15:20:36 -07001446 * block_invalidatepage - invalidate part of all of a buffer-backed page
1447 *
1448 * @page: the page which is affected
1449 * @offset: the index of the truncation point
1450 *
1451 * block_invalidatepage() is called when all or part of the page has become
1452 * invalidatedby a truncate operation.
1453 *
1454 * block_invalidatepage() does not have to release all buffers, but it must
1455 * ensure that no dirty buffer is left outside @offset and that no I/O
1456 * is underway against any of the blocks which are outside the truncation
1457 * point. Because the caller is about to free (and possibly reuse) those
1458 * blocks on-disk.
1459 */
NeilBrown2ff28e22006-03-26 01:37:18 -08001460void block_invalidatepage(struct page *page, unsigned long offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001461{
1462 struct buffer_head *head, *bh, *next;
1463 unsigned int curr_off = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001464
1465 BUG_ON(!PageLocked(page));
1466 if (!page_has_buffers(page))
1467 goto out;
1468
1469 head = page_buffers(page);
1470 bh = head;
1471 do {
1472 unsigned int next_off = curr_off + bh->b_size;
1473 next = bh->b_this_page;
1474
1475 /*
1476 * is this block fully invalidated?
1477 */
1478 if (offset <= curr_off)
1479 discard_buffer(bh);
1480 curr_off = next_off;
1481 bh = next;
1482 } while (bh != head);
1483
1484 /*
1485 * We release buffers only if the entire page is being invalidated.
1486 * The get_block cached value has been unconditionally invalidated,
1487 * so real IO is not possible anymore.
1488 */
1489 if (offset == 0)
NeilBrown2ff28e22006-03-26 01:37:18 -08001490 try_to_release_page(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001491out:
NeilBrown2ff28e22006-03-26 01:37:18 -08001492 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001493}
1494EXPORT_SYMBOL(block_invalidatepage);
1495
1496/*
1497 * We attach and possibly dirty the buffers atomically wrt
1498 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1499 * is already excluded via the page lock.
1500 */
1501void create_empty_buffers(struct page *page,
1502 unsigned long blocksize, unsigned long b_state)
1503{
1504 struct buffer_head *bh, *head, *tail;
1505
1506 head = alloc_page_buffers(page, blocksize, 1);
1507 bh = head;
1508 do {
1509 bh->b_state |= b_state;
1510 tail = bh;
1511 bh = bh->b_this_page;
1512 } while (bh);
1513 tail->b_this_page = head;
1514
1515 spin_lock(&page->mapping->private_lock);
1516 if (PageUptodate(page) || PageDirty(page)) {
1517 bh = head;
1518 do {
1519 if (PageDirty(page))
1520 set_buffer_dirty(bh);
1521 if (PageUptodate(page))
1522 set_buffer_uptodate(bh);
1523 bh = bh->b_this_page;
1524 } while (bh != head);
1525 }
1526 attach_page_buffers(page, head);
1527 spin_unlock(&page->mapping->private_lock);
1528}
1529EXPORT_SYMBOL(create_empty_buffers);
1530
1531/*
1532 * We are taking a block for data and we don't want any output from any
1533 * buffer-cache aliases starting from return from that function and
1534 * until the moment when something will explicitly mark the buffer
1535 * dirty (hopefully that will not happen until we will free that block ;-)
1536 * We don't even need to mark it not-uptodate - nobody can expect
1537 * anything from a newly allocated buffer anyway. We used to used
1538 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1539 * don't want to mark the alias unmapped, for example - it would confuse
1540 * anyone who might pick it with bread() afterwards...
1541 *
1542 * Also.. Note that bforget() doesn't lock the buffer. So there can
1543 * be writeout I/O going on against recently-freed buffers. We don't
1544 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1545 * only if we really need to. That happens here.
1546 */
1547void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1548{
1549 struct buffer_head *old_bh;
1550
1551 might_sleep();
1552
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001553 old_bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001554 if (old_bh) {
1555 clear_buffer_dirty(old_bh);
1556 wait_on_buffer(old_bh);
1557 clear_buffer_req(old_bh);
1558 __brelse(old_bh);
1559 }
1560}
1561EXPORT_SYMBOL(unmap_underlying_metadata);
1562
1563/*
1564 * NOTE! All mapped/uptodate combinations are valid:
1565 *
1566 * Mapped Uptodate Meaning
1567 *
1568 * No No "unknown" - must do get_block()
1569 * No Yes "hole" - zero-filled
1570 * Yes No "allocated" - allocated on disk, not read in
1571 * Yes Yes "valid" - allocated and up-to-date in memory.
1572 *
1573 * "Dirty" is valid only with the last case (mapped+uptodate).
1574 */
1575
1576/*
1577 * While block_write_full_page is writing back the dirty buffers under
1578 * the page lock, whoever dirtied the buffers may decide to clean them
1579 * again at any time. We handle that by only looking at the buffer
1580 * state inside lock_buffer().
1581 *
1582 * If block_write_full_page() is called for regular writeback
1583 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1584 * locked buffer. This only can happen if someone has written the buffer
1585 * directly, with submit_bh(). At the address_space level PageWriteback
1586 * prevents this contention from occurring.
1587 */
1588static int __block_write_full_page(struct inode *inode, struct page *page,
1589 get_block_t *get_block, struct writeback_control *wbc)
1590{
1591 int err;
1592 sector_t block;
1593 sector_t last_block;
Andrew Mortonf0fbd5f2005-05-05 16:15:48 -07001594 struct buffer_head *bh, *head;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001595 const unsigned blocksize = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001596 int nr_underway = 0;
1597
1598 BUG_ON(!PageLocked(page));
1599
1600 last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
1601
1602 if (!page_has_buffers(page)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001603 create_empty_buffers(page, blocksize,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001604 (1 << BH_Dirty)|(1 << BH_Uptodate));
1605 }
1606
1607 /*
1608 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1609 * here, and the (potentially unmapped) buffers may become dirty at
1610 * any time. If a buffer becomes dirty here after we've inspected it
1611 * then we just miss that fact, and the page stays dirty.
1612 *
1613 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1614 * handle that here by just cleaning them.
1615 */
1616
Andrew Morton54b21a72006-01-08 01:03:05 -08001617 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001618 head = page_buffers(page);
1619 bh = head;
1620
1621 /*
1622 * Get all the dirty buffers mapped to disk addresses and
1623 * handle any aliases from the underlying blockdev's mapping.
1624 */
1625 do {
1626 if (block > last_block) {
1627 /*
1628 * mapped buffers outside i_size will occur, because
1629 * this page can be outside i_size when there is a
1630 * truncate in progress.
1631 */
1632 /*
1633 * The buffer was zeroed by block_write_full_page()
1634 */
1635 clear_buffer_dirty(bh);
1636 set_buffer_uptodate(bh);
1637 } else if (!buffer_mapped(bh) && buffer_dirty(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001638 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001639 err = get_block(inode, block, bh, 1);
1640 if (err)
1641 goto recover;
1642 if (buffer_new(bh)) {
1643 /* blockdev mappings never come here */
1644 clear_buffer_new(bh);
1645 unmap_underlying_metadata(bh->b_bdev,
1646 bh->b_blocknr);
1647 }
1648 }
1649 bh = bh->b_this_page;
1650 block++;
1651 } while (bh != head);
1652
1653 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001654 if (!buffer_mapped(bh))
1655 continue;
1656 /*
1657 * If it's a fully non-blocking write attempt and we cannot
1658 * lock the buffer then redirty the page. Note that this can
1659 * potentially cause a busy-wait loop from pdflush and kswapd
1660 * activity, but those code paths have their own higher-level
1661 * throttling.
1662 */
1663 if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
1664 lock_buffer(bh);
1665 } else if (test_set_buffer_locked(bh)) {
1666 redirty_page_for_writepage(wbc, page);
1667 continue;
1668 }
1669 if (test_clear_buffer_dirty(bh)) {
1670 mark_buffer_async_write(bh);
1671 } else {
1672 unlock_buffer(bh);
1673 }
1674 } while ((bh = bh->b_this_page) != head);
1675
1676 /*
1677 * The page and its buffers are protected by PageWriteback(), so we can
1678 * drop the bh refcounts early.
1679 */
1680 BUG_ON(PageWriteback(page));
1681 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001682
1683 do {
1684 struct buffer_head *next = bh->b_this_page;
1685 if (buffer_async_write(bh)) {
1686 submit_bh(WRITE, bh);
1687 nr_underway++;
1688 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001689 bh = next;
1690 } while (bh != head);
Andrew Morton05937ba2005-05-05 16:15:47 -07001691 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001692
1693 err = 0;
1694done:
1695 if (nr_underway == 0) {
1696 /*
1697 * The page was marked dirty, but the buffers were
1698 * clean. Someone wrote them back by hand with
1699 * ll_rw_block/submit_bh. A rare case.
1700 */
1701 int uptodate = 1;
1702 do {
1703 if (!buffer_uptodate(bh)) {
1704 uptodate = 0;
1705 break;
1706 }
1707 bh = bh->b_this_page;
1708 } while (bh != head);
1709 if (uptodate)
1710 SetPageUptodate(page);
1711 end_page_writeback(page);
1712 /*
1713 * The page and buffer_heads can be released at any time from
1714 * here on.
1715 */
1716 wbc->pages_skipped++; /* We didn't write this page */
1717 }
1718 return err;
1719
1720recover:
1721 /*
1722 * ENOSPC, or some other error. We may already have added some
1723 * blocks to the file, so we need to write these out to avoid
1724 * exposing stale data.
1725 * The page is currently locked and not marked for writeback
1726 */
1727 bh = head;
1728 /* Recovery: lock and submit the mapped buffers */
1729 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001730 if (buffer_mapped(bh) && buffer_dirty(bh)) {
1731 lock_buffer(bh);
1732 mark_buffer_async_write(bh);
1733 } else {
1734 /*
1735 * The buffer may have been set dirty during
1736 * attachment to a dirty page.
1737 */
1738 clear_buffer_dirty(bh);
1739 }
1740 } while ((bh = bh->b_this_page) != head);
1741 SetPageError(page);
1742 BUG_ON(PageWriteback(page));
1743 set_page_writeback(page);
1744 unlock_page(page);
1745 do {
1746 struct buffer_head *next = bh->b_this_page;
1747 if (buffer_async_write(bh)) {
1748 clear_buffer_dirty(bh);
1749 submit_bh(WRITE, bh);
1750 nr_underway++;
1751 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001752 bh = next;
1753 } while (bh != head);
1754 goto done;
1755}
1756
1757static int __block_prepare_write(struct inode *inode, struct page *page,
1758 unsigned from, unsigned to, get_block_t *get_block)
1759{
1760 unsigned block_start, block_end;
1761 sector_t block;
1762 int err = 0;
1763 unsigned blocksize, bbits;
1764 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1765
1766 BUG_ON(!PageLocked(page));
1767 BUG_ON(from > PAGE_CACHE_SIZE);
1768 BUG_ON(to > PAGE_CACHE_SIZE);
1769 BUG_ON(from > to);
1770
1771 blocksize = 1 << inode->i_blkbits;
1772 if (!page_has_buffers(page))
1773 create_empty_buffers(page, blocksize, 0);
1774 head = page_buffers(page);
1775
1776 bbits = inode->i_blkbits;
1777 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1778
1779 for(bh = head, block_start = 0; bh != head || !block_start;
1780 block++, block_start=block_end, bh = bh->b_this_page) {
1781 block_end = block_start + blocksize;
1782 if (block_end <= from || block_start >= to) {
1783 if (PageUptodate(page)) {
1784 if (!buffer_uptodate(bh))
1785 set_buffer_uptodate(bh);
1786 }
1787 continue;
1788 }
1789 if (buffer_new(bh))
1790 clear_buffer_new(bh);
1791 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001792 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001793 err = get_block(inode, block, bh, 1);
1794 if (err)
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001795 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001796 if (buffer_new(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001797 unmap_underlying_metadata(bh->b_bdev,
1798 bh->b_blocknr);
1799 if (PageUptodate(page)) {
1800 set_buffer_uptodate(bh);
1801 continue;
1802 }
1803 if (block_end > to || block_start < from) {
1804 void *kaddr;
1805
1806 kaddr = kmap_atomic(page, KM_USER0);
1807 if (block_end > to)
1808 memset(kaddr+to, 0,
1809 block_end-to);
1810 if (block_start < from)
1811 memset(kaddr+block_start,
1812 0, from-block_start);
1813 flush_dcache_page(page);
1814 kunmap_atomic(kaddr, KM_USER0);
1815 }
1816 continue;
1817 }
1818 }
1819 if (PageUptodate(page)) {
1820 if (!buffer_uptodate(bh))
1821 set_buffer_uptodate(bh);
1822 continue;
1823 }
1824 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1825 (block_start < from || block_end > to)) {
1826 ll_rw_block(READ, 1, &bh);
1827 *wait_bh++=bh;
1828 }
1829 }
1830 /*
1831 * If we issued read requests - let them complete.
1832 */
1833 while(wait_bh > wait) {
1834 wait_on_buffer(*--wait_bh);
1835 if (!buffer_uptodate(*wait_bh))
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001836 err = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001837 }
Anton Altaparmakov152becd2005-06-23 00:10:21 -07001838 if (!err) {
1839 bh = head;
1840 do {
1841 if (buffer_new(bh))
1842 clear_buffer_new(bh);
1843 } while ((bh = bh->b_this_page) != head);
1844 return 0;
1845 }
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001846 /* Error case: */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001847 /*
1848 * Zero out any newly allocated blocks to avoid exposing stale
1849 * data. If BH_New is set, we know that the block was newly
1850 * allocated in the above loop.
1851 */
1852 bh = head;
1853 block_start = 0;
1854 do {
1855 block_end = block_start+blocksize;
1856 if (block_end <= from)
1857 goto next_bh;
1858 if (block_start >= to)
1859 break;
1860 if (buffer_new(bh)) {
1861 void *kaddr;
1862
1863 clear_buffer_new(bh);
1864 kaddr = kmap_atomic(page, KM_USER0);
1865 memset(kaddr+block_start, 0, bh->b_size);
Monakhov Dmitriy8c581652006-10-11 01:22:00 -07001866 flush_dcache_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001867 kunmap_atomic(kaddr, KM_USER0);
1868 set_buffer_uptodate(bh);
1869 mark_buffer_dirty(bh);
1870 }
1871next_bh:
1872 block_start = block_end;
1873 bh = bh->b_this_page;
1874 } while (bh != head);
1875 return err;
1876}
1877
1878static int __block_commit_write(struct inode *inode, struct page *page,
1879 unsigned from, unsigned to)
1880{
1881 unsigned block_start, block_end;
1882 int partial = 0;
1883 unsigned blocksize;
1884 struct buffer_head *bh, *head;
1885
1886 blocksize = 1 << inode->i_blkbits;
1887
1888 for(bh = head = page_buffers(page), block_start = 0;
1889 bh != head || !block_start;
1890 block_start=block_end, bh = bh->b_this_page) {
1891 block_end = block_start + blocksize;
1892 if (block_end <= from || block_start >= to) {
1893 if (!buffer_uptodate(bh))
1894 partial = 1;
1895 } else {
1896 set_buffer_uptodate(bh);
1897 mark_buffer_dirty(bh);
1898 }
1899 }
1900
1901 /*
1902 * If this is a partial write which happened to make all buffers
1903 * uptodate then we can optimize away a bogus readpage() for
1904 * the next read(). Here we 'discover' whether the page went
1905 * uptodate as a result of this (potentially partial) write.
1906 */
1907 if (!partial)
1908 SetPageUptodate(page);
1909 return 0;
1910}
1911
1912/*
1913 * Generic "read page" function for block devices that have the normal
1914 * get_block functionality. This is most of the block device filesystems.
1915 * Reads the page asynchronously --- the unlock_buffer() and
1916 * set/clear_buffer_uptodate() functions propagate buffer state into the
1917 * page struct once IO has completed.
1918 */
1919int block_read_full_page(struct page *page, get_block_t *get_block)
1920{
1921 struct inode *inode = page->mapping->host;
1922 sector_t iblock, lblock;
1923 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
1924 unsigned int blocksize;
1925 int nr, i;
1926 int fully_mapped = 1;
1927
Matt Mackallcd7619d2005-05-01 08:59:01 -07001928 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001929 blocksize = 1 << inode->i_blkbits;
1930 if (!page_has_buffers(page))
1931 create_empty_buffers(page, blocksize, 0);
1932 head = page_buffers(page);
1933
1934 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
1935 lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
1936 bh = head;
1937 nr = 0;
1938 i = 0;
1939
1940 do {
1941 if (buffer_uptodate(bh))
1942 continue;
1943
1944 if (!buffer_mapped(bh)) {
Andrew Mortonc64610b2005-05-16 21:53:49 -07001945 int err = 0;
1946
Linus Torvalds1da177e2005-04-16 15:20:36 -07001947 fully_mapped = 0;
1948 if (iblock < lblock) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001949 WARN_ON(bh->b_size != blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07001950 err = get_block(inode, iblock, bh, 0);
1951 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001952 SetPageError(page);
1953 }
1954 if (!buffer_mapped(bh)) {
1955 void *kaddr = kmap_atomic(page, KM_USER0);
1956 memset(kaddr + i * blocksize, 0, blocksize);
1957 flush_dcache_page(page);
1958 kunmap_atomic(kaddr, KM_USER0);
Andrew Mortonc64610b2005-05-16 21:53:49 -07001959 if (!err)
1960 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001961 continue;
1962 }
1963 /*
1964 * get_block() might have updated the buffer
1965 * synchronously
1966 */
1967 if (buffer_uptodate(bh))
1968 continue;
1969 }
1970 arr[nr++] = bh;
1971 } while (i++, iblock++, (bh = bh->b_this_page) != head);
1972
1973 if (fully_mapped)
1974 SetPageMappedToDisk(page);
1975
1976 if (!nr) {
1977 /*
1978 * All buffers are uptodate - we can set the page uptodate
1979 * as well. But not if get_block() returned an error.
1980 */
1981 if (!PageError(page))
1982 SetPageUptodate(page);
1983 unlock_page(page);
1984 return 0;
1985 }
1986
1987 /* Stage two: lock the buffers */
1988 for (i = 0; i < nr; i++) {
1989 bh = arr[i];
1990 lock_buffer(bh);
1991 mark_buffer_async_read(bh);
1992 }
1993
1994 /*
1995 * Stage 3: start the IO. Check for uptodateness
1996 * inside the buffer lock in case another process reading
1997 * the underlying blockdev brought it uptodate (the sct fix).
1998 */
1999 for (i = 0; i < nr; i++) {
2000 bh = arr[i];
2001 if (buffer_uptodate(bh))
2002 end_buffer_async_read(bh, 1);
2003 else
2004 submit_bh(READ, bh);
2005 }
2006 return 0;
2007}
2008
2009/* utility function for filesystems that need to do work on expanding
2010 * truncates. Uses prepare/commit_write to allow the filesystem to
2011 * deal with the hole.
2012 */
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002013static int __generic_cont_expand(struct inode *inode, loff_t size,
2014 pgoff_t index, unsigned int offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002015{
2016 struct address_space *mapping = inode->i_mapping;
2017 struct page *page;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002018 unsigned long limit;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002019 int err;
2020
2021 err = -EFBIG;
2022 limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
2023 if (limit != RLIM_INFINITY && size > (loff_t)limit) {
2024 send_sig(SIGXFSZ, current, 0);
2025 goto out;
2026 }
2027 if (size > inode->i_sb->s_maxbytes)
2028 goto out;
2029
Linus Torvalds1da177e2005-04-16 15:20:36 -07002030 err = -ENOMEM;
2031 page = grab_cache_page(mapping, index);
2032 if (!page)
2033 goto out;
2034 err = mapping->a_ops->prepare_write(NULL, page, offset, offset);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002035 if (err) {
2036 /*
2037 * ->prepare_write() may have instantiated a few blocks
2038 * outside i_size. Trim these off again.
2039 */
2040 unlock_page(page);
2041 page_cache_release(page);
2042 vmtruncate(inode, inode->i_size);
2043 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002044 }
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002045
2046 err = mapping->a_ops->commit_write(NULL, page, offset, offset);
2047
Linus Torvalds1da177e2005-04-16 15:20:36 -07002048 unlock_page(page);
2049 page_cache_release(page);
2050 if (err > 0)
2051 err = 0;
2052out:
2053 return err;
2054}
2055
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002056int generic_cont_expand(struct inode *inode, loff_t size)
2057{
2058 pgoff_t index;
2059 unsigned int offset;
2060
2061 offset = (size & (PAGE_CACHE_SIZE - 1)); /* Within page */
2062
2063 /* ugh. in prepare/commit_write, if from==to==start of block, we
2064 ** skip the prepare. make sure we never send an offset for the start
2065 ** of a block
2066 */
2067 if ((offset & (inode->i_sb->s_blocksize - 1)) == 0) {
2068 /* caller must handle this extra byte. */
2069 offset++;
2070 }
2071 index = size >> PAGE_CACHE_SHIFT;
2072
2073 return __generic_cont_expand(inode, size, index, offset);
2074}
2075
2076int generic_cont_expand_simple(struct inode *inode, loff_t size)
2077{
2078 loff_t pos = size - 1;
2079 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
2080 unsigned int offset = (pos & (PAGE_CACHE_SIZE - 1)) + 1;
2081
2082 /* prepare/commit_write can handle even if from==to==start of block. */
2083 return __generic_cont_expand(inode, size, index, offset);
2084}
2085
Linus Torvalds1da177e2005-04-16 15:20:36 -07002086/*
2087 * For moronic filesystems that do not allow holes in file.
2088 * We may have to extend the file.
2089 */
2090
2091int cont_prepare_write(struct page *page, unsigned offset,
2092 unsigned to, get_block_t *get_block, loff_t *bytes)
2093{
2094 struct address_space *mapping = page->mapping;
2095 struct inode *inode = mapping->host;
2096 struct page *new_page;
2097 pgoff_t pgpos;
2098 long status;
2099 unsigned zerofrom;
2100 unsigned blocksize = 1 << inode->i_blkbits;
2101 void *kaddr;
2102
2103 while(page->index > (pgpos = *bytes>>PAGE_CACHE_SHIFT)) {
2104 status = -ENOMEM;
2105 new_page = grab_cache_page(mapping, pgpos);
2106 if (!new_page)
2107 goto out;
2108 /* we might sleep */
2109 if (*bytes>>PAGE_CACHE_SHIFT != pgpos) {
2110 unlock_page(new_page);
2111 page_cache_release(new_page);
2112 continue;
2113 }
2114 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2115 if (zerofrom & (blocksize-1)) {
2116 *bytes |= (blocksize-1);
2117 (*bytes)++;
2118 }
2119 status = __block_prepare_write(inode, new_page, zerofrom,
2120 PAGE_CACHE_SIZE, get_block);
2121 if (status)
2122 goto out_unmap;
2123 kaddr = kmap_atomic(new_page, KM_USER0);
2124 memset(kaddr+zerofrom, 0, PAGE_CACHE_SIZE-zerofrom);
2125 flush_dcache_page(new_page);
2126 kunmap_atomic(kaddr, KM_USER0);
2127 generic_commit_write(NULL, new_page, zerofrom, PAGE_CACHE_SIZE);
2128 unlock_page(new_page);
2129 page_cache_release(new_page);
2130 }
2131
2132 if (page->index < pgpos) {
2133 /* completely inside the area */
2134 zerofrom = offset;
2135 } else {
2136 /* page covers the boundary, find the boundary offset */
2137 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2138
2139 /* if we will expand the thing last block will be filled */
2140 if (to > zerofrom && (zerofrom & (blocksize-1))) {
2141 *bytes |= (blocksize-1);
2142 (*bytes)++;
2143 }
2144
2145 /* starting below the boundary? Nothing to zero out */
2146 if (offset <= zerofrom)
2147 zerofrom = offset;
2148 }
2149 status = __block_prepare_write(inode, page, zerofrom, to, get_block);
2150 if (status)
2151 goto out1;
2152 if (zerofrom < offset) {
2153 kaddr = kmap_atomic(page, KM_USER0);
2154 memset(kaddr+zerofrom, 0, offset-zerofrom);
2155 flush_dcache_page(page);
2156 kunmap_atomic(kaddr, KM_USER0);
2157 __block_commit_write(inode, page, zerofrom, offset);
2158 }
2159 return 0;
2160out1:
2161 ClearPageUptodate(page);
2162 return status;
2163
2164out_unmap:
2165 ClearPageUptodate(new_page);
2166 unlock_page(new_page);
2167 page_cache_release(new_page);
2168out:
2169 return status;
2170}
2171
2172int block_prepare_write(struct page *page, unsigned from, unsigned to,
2173 get_block_t *get_block)
2174{
2175 struct inode *inode = page->mapping->host;
2176 int err = __block_prepare_write(inode, page, from, to, get_block);
2177 if (err)
2178 ClearPageUptodate(page);
2179 return err;
2180}
2181
2182int block_commit_write(struct page *page, unsigned from, unsigned to)
2183{
2184 struct inode *inode = page->mapping->host;
2185 __block_commit_write(inode,page,from,to);
2186 return 0;
2187}
2188
2189int generic_commit_write(struct file *file, struct page *page,
2190 unsigned from, unsigned to)
2191{
2192 struct inode *inode = page->mapping->host;
2193 loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
2194 __block_commit_write(inode,page,from,to);
2195 /*
2196 * No need to use i_size_read() here, the i_size
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08002197 * cannot change under us because we hold i_mutex.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002198 */
2199 if (pos > inode->i_size) {
2200 i_size_write(inode, pos);
2201 mark_inode_dirty(inode);
2202 }
2203 return 0;
2204}
2205
2206
2207/*
2208 * nobh_prepare_write()'s prereads are special: the buffer_heads are freed
2209 * immediately, while under the page lock. So it needs a special end_io
2210 * handler which does not touch the bh after unlocking it.
2211 *
2212 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
2213 * a race there is benign: unlock_buffer() only use the bh's address for
2214 * hashing after unlocking the buffer, so it doesn't actually touch the bh
2215 * itself.
2216 */
2217static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2218{
2219 if (uptodate) {
2220 set_buffer_uptodate(bh);
2221 } else {
2222 /* This happens, due to failed READA attempts. */
2223 clear_buffer_uptodate(bh);
2224 }
2225 unlock_buffer(bh);
2226}
2227
2228/*
2229 * On entry, the page is fully not uptodate.
2230 * On exit the page is fully uptodate in the areas outside (from,to)
2231 */
2232int nobh_prepare_write(struct page *page, unsigned from, unsigned to,
2233 get_block_t *get_block)
2234{
2235 struct inode *inode = page->mapping->host;
2236 const unsigned blkbits = inode->i_blkbits;
2237 const unsigned blocksize = 1 << blkbits;
2238 struct buffer_head map_bh;
2239 struct buffer_head *read_bh[MAX_BUF_PER_PAGE];
2240 unsigned block_in_page;
2241 unsigned block_start;
2242 sector_t block_in_file;
2243 char *kaddr;
2244 int nr_reads = 0;
2245 int i;
2246 int ret = 0;
2247 int is_mapped_to_disk = 1;
2248 int dirtied_it = 0;
2249
2250 if (PageMappedToDisk(page))
2251 return 0;
2252
2253 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
2254 map_bh.b_page = page;
2255
2256 /*
2257 * We loop across all blocks in the page, whether or not they are
2258 * part of the affected region. This is so we can discover if the
2259 * page is fully mapped-to-disk.
2260 */
2261 for (block_start = 0, block_in_page = 0;
2262 block_start < PAGE_CACHE_SIZE;
2263 block_in_page++, block_start += blocksize) {
2264 unsigned block_end = block_start + blocksize;
2265 int create;
2266
2267 map_bh.b_state = 0;
2268 create = 1;
2269 if (block_start >= to)
2270 create = 0;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002271 map_bh.b_size = blocksize;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002272 ret = get_block(inode, block_in_file + block_in_page,
2273 &map_bh, create);
2274 if (ret)
2275 goto failed;
2276 if (!buffer_mapped(&map_bh))
2277 is_mapped_to_disk = 0;
2278 if (buffer_new(&map_bh))
2279 unmap_underlying_metadata(map_bh.b_bdev,
2280 map_bh.b_blocknr);
2281 if (PageUptodate(page))
2282 continue;
2283 if (buffer_new(&map_bh) || !buffer_mapped(&map_bh)) {
2284 kaddr = kmap_atomic(page, KM_USER0);
2285 if (block_start < from) {
2286 memset(kaddr+block_start, 0, from-block_start);
2287 dirtied_it = 1;
2288 }
2289 if (block_end > to) {
2290 memset(kaddr + to, 0, block_end - to);
2291 dirtied_it = 1;
2292 }
2293 flush_dcache_page(page);
2294 kunmap_atomic(kaddr, KM_USER0);
2295 continue;
2296 }
2297 if (buffer_uptodate(&map_bh))
2298 continue; /* reiserfs does this */
2299 if (block_start < from || block_end > to) {
2300 struct buffer_head *bh = alloc_buffer_head(GFP_NOFS);
2301
2302 if (!bh) {
2303 ret = -ENOMEM;
2304 goto failed;
2305 }
2306 bh->b_state = map_bh.b_state;
2307 atomic_set(&bh->b_count, 0);
2308 bh->b_this_page = NULL;
2309 bh->b_page = page;
2310 bh->b_blocknr = map_bh.b_blocknr;
2311 bh->b_size = blocksize;
2312 bh->b_data = (char *)(long)block_start;
2313 bh->b_bdev = map_bh.b_bdev;
2314 bh->b_private = NULL;
2315 read_bh[nr_reads++] = bh;
2316 }
2317 }
2318
2319 if (nr_reads) {
2320 struct buffer_head *bh;
2321
2322 /*
2323 * The page is locked, so these buffers are protected from
2324 * any VM or truncate activity. Hence we don't need to care
2325 * for the buffer_head refcounts.
2326 */
2327 for (i = 0; i < nr_reads; i++) {
2328 bh = read_bh[i];
2329 lock_buffer(bh);
2330 bh->b_end_io = end_buffer_read_nobh;
2331 submit_bh(READ, bh);
2332 }
2333 for (i = 0; i < nr_reads; i++) {
2334 bh = read_bh[i];
2335 wait_on_buffer(bh);
2336 if (!buffer_uptodate(bh))
2337 ret = -EIO;
2338 free_buffer_head(bh);
2339 read_bh[i] = NULL;
2340 }
2341 if (ret)
2342 goto failed;
2343 }
2344
2345 if (is_mapped_to_disk)
2346 SetPageMappedToDisk(page);
2347 SetPageUptodate(page);
2348
2349 /*
2350 * Setting the page dirty here isn't necessary for the prepare_write
2351 * function - commit_write will do that. But if/when this function is
2352 * used within the pagefault handler to ensure that all mmapped pages
2353 * have backing space in the filesystem, we will need to dirty the page
2354 * if its contents were altered.
2355 */
2356 if (dirtied_it)
2357 set_page_dirty(page);
2358
2359 return 0;
2360
2361failed:
2362 for (i = 0; i < nr_reads; i++) {
2363 if (read_bh[i])
2364 free_buffer_head(read_bh[i]);
2365 }
2366
2367 /*
2368 * Error recovery is pretty slack. Clear the page and mark it dirty
2369 * so we'll later zero out any blocks which _were_ allocated.
2370 */
2371 kaddr = kmap_atomic(page, KM_USER0);
2372 memset(kaddr, 0, PAGE_CACHE_SIZE);
Monakhov Dmitriy8c581652006-10-11 01:22:00 -07002373 flush_dcache_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002374 kunmap_atomic(kaddr, KM_USER0);
2375 SetPageUptodate(page);
2376 set_page_dirty(page);
2377 return ret;
2378}
2379EXPORT_SYMBOL(nobh_prepare_write);
2380
2381int nobh_commit_write(struct file *file, struct page *page,
2382 unsigned from, unsigned to)
2383{
2384 struct inode *inode = page->mapping->host;
2385 loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
2386
2387 set_page_dirty(page);
2388 if (pos > inode->i_size) {
2389 i_size_write(inode, pos);
2390 mark_inode_dirty(inode);
2391 }
2392 return 0;
2393}
2394EXPORT_SYMBOL(nobh_commit_write);
2395
2396/*
2397 * nobh_writepage() - based on block_full_write_page() except
2398 * that it tries to operate without attaching bufferheads to
2399 * the page.
2400 */
2401int nobh_writepage(struct page *page, get_block_t *get_block,
2402 struct writeback_control *wbc)
2403{
2404 struct inode * const inode = page->mapping->host;
2405 loff_t i_size = i_size_read(inode);
2406 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2407 unsigned offset;
2408 void *kaddr;
2409 int ret;
2410
2411 /* Is the page fully inside i_size? */
2412 if (page->index < end_index)
2413 goto out;
2414
2415 /* Is the page fully outside i_size? (truncate in progress) */
2416 offset = i_size & (PAGE_CACHE_SIZE-1);
2417 if (page->index >= end_index+1 || !offset) {
2418 /*
2419 * The page may have dirty, unmapped buffers. For example,
2420 * they may have been added in ext3_writepage(). Make them
2421 * freeable here, so the page does not leak.
2422 */
2423#if 0
2424 /* Not really sure about this - do we need this ? */
2425 if (page->mapping->a_ops->invalidatepage)
2426 page->mapping->a_ops->invalidatepage(page, offset);
2427#endif
2428 unlock_page(page);
2429 return 0; /* don't care */
2430 }
2431
2432 /*
2433 * The page straddles i_size. It must be zeroed out on each and every
2434 * writepage invocation because it may be mmapped. "A file is mapped
2435 * in multiples of the page size. For a file that is not a multiple of
2436 * the page size, the remaining memory is zeroed when mapped, and
2437 * writes to that region are not written out to the file."
2438 */
2439 kaddr = kmap_atomic(page, KM_USER0);
2440 memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
2441 flush_dcache_page(page);
2442 kunmap_atomic(kaddr, KM_USER0);
2443out:
2444 ret = mpage_writepage(page, get_block, wbc);
2445 if (ret == -EAGAIN)
2446 ret = __block_write_full_page(inode, page, get_block, wbc);
2447 return ret;
2448}
2449EXPORT_SYMBOL(nobh_writepage);
2450
2451/*
2452 * This function assumes that ->prepare_write() uses nobh_prepare_write().
2453 */
2454int nobh_truncate_page(struct address_space *mapping, loff_t from)
2455{
2456 struct inode *inode = mapping->host;
2457 unsigned blocksize = 1 << inode->i_blkbits;
2458 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2459 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2460 unsigned to;
2461 struct page *page;
Christoph Hellwigf5e54d62006-06-28 04:26:44 -07002462 const struct address_space_operations *a_ops = mapping->a_ops;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002463 char *kaddr;
2464 int ret = 0;
2465
2466 if ((offset & (blocksize - 1)) == 0)
2467 goto out;
2468
2469 ret = -ENOMEM;
2470 page = grab_cache_page(mapping, index);
2471 if (!page)
2472 goto out;
2473
2474 to = (offset + blocksize) & ~(blocksize - 1);
2475 ret = a_ops->prepare_write(NULL, page, offset, to);
2476 if (ret == 0) {
2477 kaddr = kmap_atomic(page, KM_USER0);
2478 memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
2479 flush_dcache_page(page);
2480 kunmap_atomic(kaddr, KM_USER0);
2481 set_page_dirty(page);
2482 }
2483 unlock_page(page);
2484 page_cache_release(page);
2485out:
2486 return ret;
2487}
2488EXPORT_SYMBOL(nobh_truncate_page);
2489
2490int block_truncate_page(struct address_space *mapping,
2491 loff_t from, get_block_t *get_block)
2492{
2493 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2494 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2495 unsigned blocksize;
Andrew Morton54b21a72006-01-08 01:03:05 -08002496 sector_t iblock;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002497 unsigned length, pos;
2498 struct inode *inode = mapping->host;
2499 struct page *page;
2500 struct buffer_head *bh;
2501 void *kaddr;
2502 int err;
2503
2504 blocksize = 1 << inode->i_blkbits;
2505 length = offset & (blocksize - 1);
2506
2507 /* Block boundary? Nothing to do */
2508 if (!length)
2509 return 0;
2510
2511 length = blocksize - length;
Andrew Morton54b21a72006-01-08 01:03:05 -08002512 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002513
2514 page = grab_cache_page(mapping, index);
2515 err = -ENOMEM;
2516 if (!page)
2517 goto out;
2518
2519 if (!page_has_buffers(page))
2520 create_empty_buffers(page, blocksize, 0);
2521
2522 /* Find the buffer that contains "offset" */
2523 bh = page_buffers(page);
2524 pos = blocksize;
2525 while (offset >= pos) {
2526 bh = bh->b_this_page;
2527 iblock++;
2528 pos += blocksize;
2529 }
2530
2531 err = 0;
2532 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002533 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002534 err = get_block(inode, iblock, bh, 0);
2535 if (err)
2536 goto unlock;
2537 /* unmapped? It's a hole - nothing to do */
2538 if (!buffer_mapped(bh))
2539 goto unlock;
2540 }
2541
2542 /* Ok, it's mapped. Make sure it's up-to-date */
2543 if (PageUptodate(page))
2544 set_buffer_uptodate(bh);
2545
2546 if (!buffer_uptodate(bh) && !buffer_delay(bh)) {
2547 err = -EIO;
2548 ll_rw_block(READ, 1, &bh);
2549 wait_on_buffer(bh);
2550 /* Uhhuh. Read error. Complain and punt. */
2551 if (!buffer_uptodate(bh))
2552 goto unlock;
2553 }
2554
2555 kaddr = kmap_atomic(page, KM_USER0);
2556 memset(kaddr + offset, 0, length);
2557 flush_dcache_page(page);
2558 kunmap_atomic(kaddr, KM_USER0);
2559
2560 mark_buffer_dirty(bh);
2561 err = 0;
2562
2563unlock:
2564 unlock_page(page);
2565 page_cache_release(page);
2566out:
2567 return err;
2568}
2569
2570/*
2571 * The generic ->writepage function for buffer-backed address_spaces
2572 */
2573int block_write_full_page(struct page *page, get_block_t *get_block,
2574 struct writeback_control *wbc)
2575{
2576 struct inode * const inode = page->mapping->host;
2577 loff_t i_size = i_size_read(inode);
2578 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2579 unsigned offset;
2580 void *kaddr;
2581
2582 /* Is the page fully inside i_size? */
2583 if (page->index < end_index)
2584 return __block_write_full_page(inode, page, get_block, wbc);
2585
2586 /* Is the page fully outside i_size? (truncate in progress) */
2587 offset = i_size & (PAGE_CACHE_SIZE-1);
2588 if (page->index >= end_index+1 || !offset) {
2589 /*
2590 * The page may have dirty, unmapped buffers. For example,
2591 * they may have been added in ext3_writepage(). Make them
2592 * freeable here, so the page does not leak.
2593 */
Jan Karaaaa40592005-10-30 15:00:16 -08002594 do_invalidatepage(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002595 unlock_page(page);
2596 return 0; /* don't care */
2597 }
2598
2599 /*
2600 * The page straddles i_size. It must be zeroed out on each and every
2601 * writepage invokation because it may be mmapped. "A file is mapped
2602 * in multiples of the page size. For a file that is not a multiple of
2603 * the page size, the remaining memory is zeroed when mapped, and
2604 * writes to that region are not written out to the file."
2605 */
2606 kaddr = kmap_atomic(page, KM_USER0);
2607 memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
2608 flush_dcache_page(page);
2609 kunmap_atomic(kaddr, KM_USER0);
2610 return __block_write_full_page(inode, page, get_block, wbc);
2611}
2612
2613sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2614 get_block_t *get_block)
2615{
2616 struct buffer_head tmp;
2617 struct inode *inode = mapping->host;
2618 tmp.b_state = 0;
2619 tmp.b_blocknr = 0;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002620 tmp.b_size = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002621 get_block(inode, block, &tmp, 0);
2622 return tmp.b_blocknr;
2623}
2624
2625static int end_bio_bh_io_sync(struct bio *bio, unsigned int bytes_done, int err)
2626{
2627 struct buffer_head *bh = bio->bi_private;
2628
2629 if (bio->bi_size)
2630 return 1;
2631
2632 if (err == -EOPNOTSUPP) {
2633 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
2634 set_bit(BH_Eopnotsupp, &bh->b_state);
2635 }
2636
2637 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2638 bio_put(bio);
2639 return 0;
2640}
2641
2642int submit_bh(int rw, struct buffer_head * bh)
2643{
2644 struct bio *bio;
2645 int ret = 0;
2646
2647 BUG_ON(!buffer_locked(bh));
2648 BUG_ON(!buffer_mapped(bh));
2649 BUG_ON(!bh->b_end_io);
2650
2651 if (buffer_ordered(bh) && (rw == WRITE))
2652 rw = WRITE_BARRIER;
2653
2654 /*
2655 * Only clear out a write error when rewriting, should this
2656 * include WRITE_SYNC as well?
2657 */
2658 if (test_set_buffer_req(bh) && (rw == WRITE || rw == WRITE_BARRIER))
2659 clear_buffer_write_io_error(bh);
2660
2661 /*
2662 * from here on down, it's all bio -- do the initial mapping,
2663 * submit_bio -> generic_make_request may further map this bio around
2664 */
2665 bio = bio_alloc(GFP_NOIO, 1);
2666
2667 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2668 bio->bi_bdev = bh->b_bdev;
2669 bio->bi_io_vec[0].bv_page = bh->b_page;
2670 bio->bi_io_vec[0].bv_len = bh->b_size;
2671 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
2672
2673 bio->bi_vcnt = 1;
2674 bio->bi_idx = 0;
2675 bio->bi_size = bh->b_size;
2676
2677 bio->bi_end_io = end_bio_bh_io_sync;
2678 bio->bi_private = bh;
2679
2680 bio_get(bio);
2681 submit_bio(rw, bio);
2682
2683 if (bio_flagged(bio, BIO_EOPNOTSUPP))
2684 ret = -EOPNOTSUPP;
2685
2686 bio_put(bio);
2687 return ret;
2688}
2689
2690/**
2691 * ll_rw_block: low-level access to block devices (DEPRECATED)
Jan Karaa7662232005-09-06 15:19:10 -07002692 * @rw: whether to %READ or %WRITE or %SWRITE or maybe %READA (readahead)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002693 * @nr: number of &struct buffer_heads in the array
2694 * @bhs: array of pointers to &struct buffer_head
2695 *
Jan Karaa7662232005-09-06 15:19:10 -07002696 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
2697 * requests an I/O operation on them, either a %READ or a %WRITE. The third
2698 * %SWRITE is like %WRITE only we make sure that the *current* data in buffers
2699 * are sent to disk. The fourth %READA option is described in the documentation
2700 * for generic_make_request() which ll_rw_block() calls.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002701 *
2702 * This function drops any buffer that it cannot get a lock on (with the
Jan Karaa7662232005-09-06 15:19:10 -07002703 * BH_Lock state bit) unless SWRITE is required, any buffer that appears to be
2704 * clean when doing a write request, and any buffer that appears to be
2705 * up-to-date when doing read request. Further it marks as clean buffers that
2706 * are processed for writing (the buffer cache won't assume that they are
2707 * actually clean until the buffer gets unlocked).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002708 *
2709 * ll_rw_block sets b_end_io to simple completion handler that marks
2710 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
2711 * any waiters.
2712 *
2713 * All of the buffers must be for the same device, and must also be a
2714 * multiple of the current approved size for the device.
2715 */
2716void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
2717{
2718 int i;
2719
2720 for (i = 0; i < nr; i++) {
2721 struct buffer_head *bh = bhs[i];
2722
Jan Karaa7662232005-09-06 15:19:10 -07002723 if (rw == SWRITE)
2724 lock_buffer(bh);
2725 else if (test_set_buffer_locked(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002726 continue;
2727
Jan Karaa7662232005-09-06 15:19:10 -07002728 if (rw == WRITE || rw == SWRITE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002729 if (test_clear_buffer_dirty(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07002730 bh->b_end_io = end_buffer_write_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08002731 get_bh(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002732 submit_bh(WRITE, bh);
2733 continue;
2734 }
2735 } else {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002736 if (!buffer_uptodate(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07002737 bh->b_end_io = end_buffer_read_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08002738 get_bh(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002739 submit_bh(rw, bh);
2740 continue;
2741 }
2742 }
2743 unlock_buffer(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002744 }
2745}
2746
2747/*
2748 * For a data-integrity writeout, we need to wait upon any in-progress I/O
2749 * and then start new I/O and then wait upon it. The caller must have a ref on
2750 * the buffer_head.
2751 */
2752int sync_dirty_buffer(struct buffer_head *bh)
2753{
2754 int ret = 0;
2755
2756 WARN_ON(atomic_read(&bh->b_count) < 1);
2757 lock_buffer(bh);
2758 if (test_clear_buffer_dirty(bh)) {
2759 get_bh(bh);
2760 bh->b_end_io = end_buffer_write_sync;
2761 ret = submit_bh(WRITE, bh);
2762 wait_on_buffer(bh);
2763 if (buffer_eopnotsupp(bh)) {
2764 clear_buffer_eopnotsupp(bh);
2765 ret = -EOPNOTSUPP;
2766 }
2767 if (!ret && !buffer_uptodate(bh))
2768 ret = -EIO;
2769 } else {
2770 unlock_buffer(bh);
2771 }
2772 return ret;
2773}
2774
2775/*
2776 * try_to_free_buffers() checks if all the buffers on this particular page
2777 * are unused, and releases them if so.
2778 *
2779 * Exclusion against try_to_free_buffers may be obtained by either
2780 * locking the page or by holding its mapping's private_lock.
2781 *
2782 * If the page is dirty but all the buffers are clean then we need to
2783 * be sure to mark the page clean as well. This is because the page
2784 * may be against a block device, and a later reattachment of buffers
2785 * to a dirty page will set *all* buffers dirty. Which would corrupt
2786 * filesystem data on the same device.
2787 *
2788 * The same applies to regular filesystem pages: if all the buffers are
2789 * clean then we set the page clean and proceed. To do that, we require
2790 * total exclusion from __set_page_dirty_buffers(). That is obtained with
2791 * private_lock.
2792 *
2793 * try_to_free_buffers() is non-blocking.
2794 */
2795static inline int buffer_busy(struct buffer_head *bh)
2796{
2797 return atomic_read(&bh->b_count) |
2798 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
2799}
2800
2801static int
2802drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
2803{
2804 struct buffer_head *head = page_buffers(page);
2805 struct buffer_head *bh;
2806
2807 bh = head;
2808 do {
akpm@osdl.orgde7d5a32005-05-01 08:58:39 -07002809 if (buffer_write_io_error(bh) && page->mapping)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002810 set_bit(AS_EIO, &page->mapping->flags);
2811 if (buffer_busy(bh))
2812 goto failed;
2813 bh = bh->b_this_page;
2814 } while (bh != head);
2815
2816 do {
2817 struct buffer_head *next = bh->b_this_page;
2818
2819 if (!list_empty(&bh->b_assoc_buffers))
2820 __remove_assoc_queue(bh);
2821 bh = next;
2822 } while (bh != head);
2823 *buffers_to_free = head;
2824 __clear_page_buffers(page);
2825 return 1;
2826failed:
2827 return 0;
2828}
2829
2830int try_to_free_buffers(struct page *page)
2831{
2832 struct address_space * const mapping = page->mapping;
2833 struct buffer_head *buffers_to_free = NULL;
2834 int ret = 0;
2835
2836 BUG_ON(!PageLocked(page));
Linus Torvaldsecdfc972007-01-26 12:47:06 -08002837 if (PageWriteback(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002838 return 0;
2839
2840 if (mapping == NULL) { /* can this still happen? */
2841 ret = drop_buffers(page, &buffers_to_free);
2842 goto out;
2843 }
2844
2845 spin_lock(&mapping->private_lock);
2846 ret = drop_buffers(page, &buffers_to_free);
Linus Torvaldsecdfc972007-01-26 12:47:06 -08002847
2848 /*
2849 * If the filesystem writes its buffers by hand (eg ext3)
2850 * then we can have clean buffers against a dirty page. We
2851 * clean the page here; otherwise the VM will never notice
2852 * that the filesystem did any IO at all.
2853 *
2854 * Also, during truncate, discard_buffer will have marked all
2855 * the page's buffers clean. We discover that here and clean
2856 * the page also.
Nick Piggin87df7242007-01-30 14:36:27 +11002857 *
2858 * private_lock must be held over this entire operation in order
2859 * to synchronise against __set_page_dirty_buffers and prevent the
2860 * dirty bit from being lost.
Linus Torvaldsecdfc972007-01-26 12:47:06 -08002861 */
2862 if (ret)
2863 cancel_dirty_page(page, PAGE_CACHE_SIZE);
Nick Piggin87df7242007-01-30 14:36:27 +11002864 spin_unlock(&mapping->private_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002865out:
2866 if (buffers_to_free) {
2867 struct buffer_head *bh = buffers_to_free;
2868
2869 do {
2870 struct buffer_head *next = bh->b_this_page;
2871 free_buffer_head(bh);
2872 bh = next;
2873 } while (bh != buffers_to_free);
2874 }
2875 return ret;
2876}
2877EXPORT_SYMBOL(try_to_free_buffers);
2878
NeilBrown3978d712006-03-26 01:37:17 -08002879void block_sync_page(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002880{
2881 struct address_space *mapping;
2882
2883 smp_mb();
2884 mapping = page_mapping(page);
2885 if (mapping)
2886 blk_run_backing_dev(mapping->backing_dev_info, page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002887}
2888
2889/*
2890 * There are no bdflush tunables left. But distributions are
2891 * still running obsolete flush daemons, so we terminate them here.
2892 *
2893 * Use of bdflush() is deprecated and will be removed in a future kernel.
2894 * The `pdflush' kernel threads fully replace bdflush daemons and this call.
2895 */
2896asmlinkage long sys_bdflush(int func, long data)
2897{
2898 static int msg_count;
2899
2900 if (!capable(CAP_SYS_ADMIN))
2901 return -EPERM;
2902
2903 if (msg_count < 5) {
2904 msg_count++;
2905 printk(KERN_INFO
2906 "warning: process `%s' used the obsolete bdflush"
2907 " system call\n", current->comm);
2908 printk(KERN_INFO "Fix your initscripts?\n");
2909 }
2910
2911 if (func == 1)
2912 do_exit(0);
2913 return 0;
2914}
2915
2916/*
2917 * Buffer-head allocation
2918 */
Christoph Lametere18b8902006-12-06 20:33:20 -08002919static struct kmem_cache *bh_cachep;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002920
2921/*
2922 * Once the number of bh's in the machine exceeds this level, we start
2923 * stripping them in writeback.
2924 */
2925static int max_buffer_heads;
2926
2927int buffer_heads_over_limit;
2928
2929struct bh_accounting {
2930 int nr; /* Number of live bh's */
2931 int ratelimit; /* Limit cacheline bouncing */
2932};
2933
2934static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
2935
2936static void recalc_bh_state(void)
2937{
2938 int i;
2939 int tot = 0;
2940
2941 if (__get_cpu_var(bh_accounting).ratelimit++ < 4096)
2942 return;
2943 __get_cpu_var(bh_accounting).ratelimit = 0;
Eric Dumazet8a143422006-03-24 03:18:10 -08002944 for_each_online_cpu(i)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002945 tot += per_cpu(bh_accounting, i).nr;
2946 buffer_heads_over_limit = (tot > max_buffer_heads);
2947}
2948
Al Virodd0fc662005-10-07 07:46:04 +01002949struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002950{
2951 struct buffer_head *ret = kmem_cache_alloc(bh_cachep, gfp_flags);
2952 if (ret) {
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07002953 get_cpu_var(bh_accounting).nr++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002954 recalc_bh_state();
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07002955 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002956 }
2957 return ret;
2958}
2959EXPORT_SYMBOL(alloc_buffer_head);
2960
2961void free_buffer_head(struct buffer_head *bh)
2962{
2963 BUG_ON(!list_empty(&bh->b_assoc_buffers));
2964 kmem_cache_free(bh_cachep, bh);
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07002965 get_cpu_var(bh_accounting).nr--;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002966 recalc_bh_state();
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07002967 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002968}
2969EXPORT_SYMBOL(free_buffer_head);
2970
2971static void
Christoph Lametere18b8902006-12-06 20:33:20 -08002972init_buffer_head(void *data, struct kmem_cache *cachep, unsigned long flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002973{
2974 if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
2975 SLAB_CTOR_CONSTRUCTOR) {
2976 struct buffer_head * bh = (struct buffer_head *)data;
2977
2978 memset(bh, 0, sizeof(*bh));
2979 INIT_LIST_HEAD(&bh->b_assoc_buffers);
2980 }
2981}
2982
Linus Torvalds1da177e2005-04-16 15:20:36 -07002983static void buffer_exit_cpu(int cpu)
2984{
2985 int i;
2986 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
2987
2988 for (i = 0; i < BH_LRU_SIZE; i++) {
2989 brelse(b->bhs[i]);
2990 b->bhs[i] = NULL;
2991 }
Eric Dumazet8a143422006-03-24 03:18:10 -08002992 get_cpu_var(bh_accounting).nr += per_cpu(bh_accounting, cpu).nr;
2993 per_cpu(bh_accounting, cpu).nr = 0;
2994 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002995}
2996
2997static int buffer_cpu_notify(struct notifier_block *self,
2998 unsigned long action, void *hcpu)
2999{
3000 if (action == CPU_DEAD)
3001 buffer_exit_cpu((unsigned long)hcpu);
3002 return NOTIFY_OK;
3003}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003004
3005void __init buffer_init(void)
3006{
3007 int nrpages;
3008
3009 bh_cachep = kmem_cache_create("buffer_head",
Paul Jacksonb0196002006-03-24 03:16:09 -08003010 sizeof(struct buffer_head), 0,
3011 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3012 SLAB_MEM_SPREAD),
3013 init_buffer_head,
3014 NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003015
3016 /*
3017 * Limit the bh occupancy to 10% of ZONE_NORMAL
3018 */
3019 nrpages = (nr_free_buffer_pages() * 10) / 100;
3020 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3021 hotcpu_notifier(buffer_cpu_notify, 0);
3022}
3023
3024EXPORT_SYMBOL(__bforget);
3025EXPORT_SYMBOL(__brelse);
3026EXPORT_SYMBOL(__wait_on_buffer);
3027EXPORT_SYMBOL(block_commit_write);
3028EXPORT_SYMBOL(block_prepare_write);
3029EXPORT_SYMBOL(block_read_full_page);
3030EXPORT_SYMBOL(block_sync_page);
3031EXPORT_SYMBOL(block_truncate_page);
3032EXPORT_SYMBOL(block_write_full_page);
3033EXPORT_SYMBOL(cont_prepare_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003034EXPORT_SYMBOL(end_buffer_read_sync);
3035EXPORT_SYMBOL(end_buffer_write_sync);
3036EXPORT_SYMBOL(file_fsync);
3037EXPORT_SYMBOL(fsync_bdev);
3038EXPORT_SYMBOL(generic_block_bmap);
3039EXPORT_SYMBOL(generic_commit_write);
3040EXPORT_SYMBOL(generic_cont_expand);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08003041EXPORT_SYMBOL(generic_cont_expand_simple);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003042EXPORT_SYMBOL(init_buffer);
3043EXPORT_SYMBOL(invalidate_bdev);
3044EXPORT_SYMBOL(ll_rw_block);
3045EXPORT_SYMBOL(mark_buffer_dirty);
3046EXPORT_SYMBOL(submit_bh);
3047EXPORT_SYMBOL(sync_dirty_buffer);
3048EXPORT_SYMBOL(unlock_buffer);