blob: e8504b65176c47a0f86eb3f439791dfd1562f0a2 [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{
Nick Piggin72ed3d02007-02-10 01:46:22 -080081 smp_mb__before_clear_bit();
Linus Torvalds1da177e2005-04-16 15:20:36 -070082 clear_buffer_locked(bh);
83 smp_mb__after_clear_bit();
84 wake_up_bit(&bh->b_state, BH_Lock);
85}
86
87/*
88 * Block until a buffer comes unlocked. This doesn't stop it
89 * from becoming locked again - you have to lock it yourself
90 * if you want to preserve its state.
91 */
92void __wait_on_buffer(struct buffer_head * bh)
93{
94 wait_on_bit(&bh->b_state, BH_Lock, sync_buffer, TASK_UNINTERRUPTIBLE);
95}
96
97static void
98__clear_page_buffers(struct page *page)
99{
100 ClearPagePrivate(page);
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700101 set_page_private(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700102 page_cache_release(page);
103}
104
105static void buffer_io_error(struct buffer_head *bh)
106{
107 char b[BDEVNAME_SIZE];
108
109 printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
110 bdevname(bh->b_bdev, b),
111 (unsigned long long)bh->b_blocknr);
112}
113
114/*
115 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
116 * unlock the buffer. This is what ll_rw_block uses too.
117 */
118void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
119{
120 if (uptodate) {
121 set_buffer_uptodate(bh);
122 } else {
123 /* This happens, due to failed READA attempts. */
124 clear_buffer_uptodate(bh);
125 }
126 unlock_buffer(bh);
127 put_bh(bh);
128}
129
130void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
131{
132 char b[BDEVNAME_SIZE];
133
134 if (uptodate) {
135 set_buffer_uptodate(bh);
136 } else {
137 if (!buffer_eopnotsupp(bh) && printk_ratelimit()) {
138 buffer_io_error(bh);
139 printk(KERN_WARNING "lost page write due to "
140 "I/O error on %s\n",
141 bdevname(bh->b_bdev, b));
142 }
143 set_buffer_write_io_error(bh);
144 clear_buffer_uptodate(bh);
145 }
146 unlock_buffer(bh);
147 put_bh(bh);
148}
149
150/*
151 * Write out and wait upon all the dirty data associated with a block
152 * device via its mapping. Does not take the superblock lock.
153 */
154int sync_blockdev(struct block_device *bdev)
155{
156 int ret = 0;
157
OGAWA Hirofumi28fd1292006-01-08 01:02:14 -0800158 if (bdev)
159 ret = filemap_write_and_wait(bdev->bd_inode->i_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700160 return ret;
161}
162EXPORT_SYMBOL(sync_blockdev);
163
Linus Torvalds1da177e2005-04-16 15:20:36 -0700164/*
165 * Write out and wait upon all dirty data associated with this
166 * device. Filesystem data as well as the underlying block
167 * device. Takes the superblock lock.
168 */
169int fsync_bdev(struct block_device *bdev)
170{
171 struct super_block *sb = get_super(bdev);
172 if (sb) {
173 int res = fsync_super(sb);
174 drop_super(sb);
175 return res;
176 }
177 return sync_blockdev(bdev);
178}
179
180/**
181 * freeze_bdev -- lock a filesystem and force it into a consistent state
182 * @bdev: blockdevice to lock
183 *
David Chinnerf73ca1b2007-01-10 23:15:41 -0800184 * This takes the block device bd_mount_sem to make sure no new mounts
Linus Torvalds1da177e2005-04-16 15:20:36 -0700185 * happen on bdev until thaw_bdev() is called.
186 * If a superblock is found on this device, we take the s_umount semaphore
187 * on it to make sure nobody unmounts until the snapshot creation is done.
188 */
189struct super_block *freeze_bdev(struct block_device *bdev)
190{
191 struct super_block *sb;
192
David Chinnerf73ca1b2007-01-10 23:15:41 -0800193 down(&bdev->bd_mount_sem);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700194 sb = get_super(bdev);
195 if (sb && !(sb->s_flags & MS_RDONLY)) {
196 sb->s_frozen = SB_FREEZE_WRITE;
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700197 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700198
OGAWA Hirofumid25b9a12006-03-25 03:07:44 -0800199 __fsync_super(sb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700200
201 sb->s_frozen = SB_FREEZE_TRANS;
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700202 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700203
204 sync_blockdev(sb->s_bdev);
205
206 if (sb->s_op->write_super_lockfs)
207 sb->s_op->write_super_lockfs(sb);
208 }
209
210 sync_blockdev(bdev);
211 return sb; /* thaw_bdev releases s->s_umount and bd_mount_sem */
212}
213EXPORT_SYMBOL(freeze_bdev);
214
215/**
216 * thaw_bdev -- unlock filesystem
217 * @bdev: blockdevice to unlock
218 * @sb: associated superblock
219 *
220 * Unlocks the filesystem and marks it writeable again after freeze_bdev().
221 */
222void thaw_bdev(struct block_device *bdev, struct super_block *sb)
223{
224 if (sb) {
225 BUG_ON(sb->s_bdev != bdev);
226
227 if (sb->s_op->unlockfs)
228 sb->s_op->unlockfs(sb);
229 sb->s_frozen = SB_UNFROZEN;
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700230 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700231 wake_up(&sb->s_wait_unfrozen);
232 drop_super(sb);
233 }
234
David Chinnerf73ca1b2007-01-10 23:15:41 -0800235 up(&bdev->bd_mount_sem);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700236}
237EXPORT_SYMBOL(thaw_bdev);
238
239/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700240 * Various filesystems appear to want __find_get_block to be non-blocking.
241 * But it's the page lock which protects the buffers. To get around this,
242 * we get exclusion from try_to_free_buffers with the blockdev mapping's
243 * private_lock.
244 *
245 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
246 * may be quite high. This code could TryLock the page, and if that
247 * succeeds, there is no need to take private_lock. (But if
248 * private_lock is contended then so is mapping->tree_lock).
249 */
250static struct buffer_head *
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -0800251__find_get_block_slow(struct block_device *bdev, sector_t block)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700252{
253 struct inode *bd_inode = bdev->bd_inode;
254 struct address_space *bd_mapping = bd_inode->i_mapping;
255 struct buffer_head *ret = NULL;
256 pgoff_t index;
257 struct buffer_head *bh;
258 struct buffer_head *head;
259 struct page *page;
260 int all_mapped = 1;
261
262 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
263 page = find_get_page(bd_mapping, index);
264 if (!page)
265 goto out;
266
267 spin_lock(&bd_mapping->private_lock);
268 if (!page_has_buffers(page))
269 goto out_unlock;
270 head = page_buffers(page);
271 bh = head;
272 do {
273 if (bh->b_blocknr == block) {
274 ret = bh;
275 get_bh(bh);
276 goto out_unlock;
277 }
278 if (!buffer_mapped(bh))
279 all_mapped = 0;
280 bh = bh->b_this_page;
281 } while (bh != head);
282
283 /* we might be here because some of the buffers on this page are
284 * not mapped. This is due to various races between
285 * file io on the block device and getblk. It gets dealt with
286 * elsewhere, don't buffer_error if we had some unmapped buffers
287 */
288 if (all_mapped) {
289 printk("__find_get_block_slow() failed. "
290 "block=%llu, b_blocknr=%llu\n",
Badari Pulavarty205f87f2006-03-26 01:38:00 -0800291 (unsigned long long)block,
292 (unsigned long long)bh->b_blocknr);
293 printk("b_state=0x%08lx, b_size=%zu\n",
294 bh->b_state, bh->b_size);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700295 printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits);
296 }
297out_unlock:
298 spin_unlock(&bd_mapping->private_lock);
299 page_cache_release(page);
300out:
301 return ret;
302}
303
304/* If invalidate_buffers() will trash dirty buffers, it means some kind
305 of fs corruption is going on. Trashing dirty data always imply losing
306 information that was supposed to be just stored on the physical layer
307 by the user.
308
309 Thus invalidate_buffers in general usage is not allwowed to trash
310 dirty buffers. For example ioctl(FLSBLKBUF) expects dirty data to
311 be preserved. These buffers are simply skipped.
312
313 We also skip buffers which are still in use. For example this can
314 happen if a userspace program is reading the block device.
315
316 NOTE: In the case where the user removed a removable-media-disk even if
317 there's still dirty data not synced on disk (due a bug in the device driver
318 or due an error of the user), by not destroying the dirty buffers we could
319 generate corruption also on the next media inserted, thus a parameter is
320 necessary to handle this case in the most safe way possible (trying
321 to not corrupt also the new disk inserted with the data belonging to
322 the old now corrupted disk). Also for the ramdisk the natural thing
323 to do in order to release the ramdisk memory is to destroy dirty buffers.
324
325 These are two special cases. Normal usage imply the device driver
326 to issue a sync on the device (without waiting I/O completion) and
327 then an invalidate_buffers call that doesn't trash dirty buffers.
328
329 For handling cache coherency with the blkdev pagecache the 'update' case
330 is been introduced. It is needed to re-read from disk any pinned
331 buffer. NOTE: re-reading from disk is destructive so we can do it only
332 when we assume nobody is changing the buffercache under our I/O and when
333 we think the disk contains more recent information than the buffercache.
334 The update == 1 pass marks the buffers we need to update, the update == 2
335 pass does the actual I/O. */
336void invalidate_bdev(struct block_device *bdev, int destroy_dirty_buffers)
337{
Andrew Morton0e1dfc62006-07-30 03:03:28 -0700338 struct address_space *mapping = bdev->bd_inode->i_mapping;
339
340 if (mapping->nrpages == 0)
341 return;
342
Linus Torvalds1da177e2005-04-16 15:20:36 -0700343 invalidate_bh_lrus();
344 /*
345 * FIXME: what about destroy_dirty_buffers?
346 * We really want to use invalidate_inode_pages2() for
347 * that, but not until that's cleaned up.
348 */
Andrew Mortonfc0ecff2007-02-10 01:45:39 -0800349 invalidate_mapping_pages(mapping, 0, -1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700350}
351
352/*
353 * Kick pdflush then try to free up some ZONE_NORMAL memory.
354 */
355static void free_more_memory(void)
356{
357 struct zone **zones;
358 pg_data_t *pgdat;
359
Pekka J Enberg687a21c2005-06-28 20:44:55 -0700360 wakeup_pdflush(1024);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700361 yield();
362
KAMEZAWA Hiroyukiec936fc2006-03-27 01:15:59 -0800363 for_each_online_pgdat(pgdat) {
Al Viroaf4ca452005-10-21 02:55:38 -0400364 zones = pgdat->node_zonelists[gfp_zone(GFP_NOFS)].zones;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700365 if (*zones)
Darren Hart1ad539b2005-06-21 17:14:53 -0700366 try_to_free_pages(zones, GFP_NOFS);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700367 }
368}
369
370/*
371 * I/O completion handler for block_read_full_page() - pages
372 * which come unlocked at the end of I/O.
373 */
374static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
375{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700376 unsigned long flags;
Nick Piggina3972202005-07-07 17:56:56 -0700377 struct buffer_head *first;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700378 struct buffer_head *tmp;
379 struct page *page;
380 int page_uptodate = 1;
381
382 BUG_ON(!buffer_async_read(bh));
383
384 page = bh->b_page;
385 if (uptodate) {
386 set_buffer_uptodate(bh);
387 } else {
388 clear_buffer_uptodate(bh);
389 if (printk_ratelimit())
390 buffer_io_error(bh);
391 SetPageError(page);
392 }
393
394 /*
395 * Be _very_ careful from here on. Bad things can happen if
396 * two buffer heads end IO at almost the same time and both
397 * decide that the page is now completely done.
398 */
Nick Piggina3972202005-07-07 17:56:56 -0700399 first = page_buffers(page);
400 local_irq_save(flags);
401 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700402 clear_buffer_async_read(bh);
403 unlock_buffer(bh);
404 tmp = bh;
405 do {
406 if (!buffer_uptodate(tmp))
407 page_uptodate = 0;
408 if (buffer_async_read(tmp)) {
409 BUG_ON(!buffer_locked(tmp));
410 goto still_busy;
411 }
412 tmp = tmp->b_this_page;
413 } while (tmp != bh);
Nick Piggina3972202005-07-07 17:56:56 -0700414 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
415 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700416
417 /*
418 * If none of the buffers had errors and they are all
419 * uptodate then we can set the page uptodate.
420 */
421 if (page_uptodate && !PageError(page))
422 SetPageUptodate(page);
423 unlock_page(page);
424 return;
425
426still_busy:
Nick Piggina3972202005-07-07 17:56:56 -0700427 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
428 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700429 return;
430}
431
432/*
433 * Completion handler for block_write_full_page() - pages which are unlocked
434 * during I/O, and which have PageWriteback cleared upon I/O completion.
435 */
Adrian Bunkb6cd0b72006-06-27 02:53:54 -0700436static void end_buffer_async_write(struct buffer_head *bh, int uptodate)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700437{
438 char b[BDEVNAME_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700439 unsigned long flags;
Nick Piggina3972202005-07-07 17:56:56 -0700440 struct buffer_head *first;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700441 struct buffer_head *tmp;
442 struct page *page;
443
444 BUG_ON(!buffer_async_write(bh));
445
446 page = bh->b_page;
447 if (uptodate) {
448 set_buffer_uptodate(bh);
449 } else {
450 if (printk_ratelimit()) {
451 buffer_io_error(bh);
452 printk(KERN_WARNING "lost page write due to "
453 "I/O error on %s\n",
454 bdevname(bh->b_bdev, b));
455 }
456 set_bit(AS_EIO, &page->mapping->flags);
Jan Kara58ff4072006-10-17 00:10:19 -0700457 set_buffer_write_io_error(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700458 clear_buffer_uptodate(bh);
459 SetPageError(page);
460 }
461
Nick Piggina3972202005-07-07 17:56:56 -0700462 first = page_buffers(page);
463 local_irq_save(flags);
464 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
465
Linus Torvalds1da177e2005-04-16 15:20:36 -0700466 clear_buffer_async_write(bh);
467 unlock_buffer(bh);
468 tmp = bh->b_this_page;
469 while (tmp != bh) {
470 if (buffer_async_write(tmp)) {
471 BUG_ON(!buffer_locked(tmp));
472 goto still_busy;
473 }
474 tmp = tmp->b_this_page;
475 }
Nick Piggina3972202005-07-07 17:56:56 -0700476 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
477 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700478 end_page_writeback(page);
479 return;
480
481still_busy:
Nick Piggina3972202005-07-07 17:56:56 -0700482 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
483 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700484 return;
485}
486
487/*
488 * If a page's buffers are under async readin (end_buffer_async_read
489 * completion) then there is a possibility that another thread of
490 * control could lock one of the buffers after it has completed
491 * but while some of the other buffers have not completed. This
492 * locked buffer would confuse end_buffer_async_read() into not unlocking
493 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
494 * that this buffer is not under async I/O.
495 *
496 * The page comes unlocked when it has no locked buffer_async buffers
497 * left.
498 *
499 * PageLocked prevents anyone starting new async I/O reads any of
500 * the buffers.
501 *
502 * PageWriteback is used to prevent simultaneous writeout of the same
503 * page.
504 *
505 * PageLocked prevents anyone from starting writeback of a page which is
506 * under read I/O (PageWriteback is only ever set against a locked page).
507 */
508static void mark_buffer_async_read(struct buffer_head *bh)
509{
510 bh->b_end_io = end_buffer_async_read;
511 set_buffer_async_read(bh);
512}
513
514void mark_buffer_async_write(struct buffer_head *bh)
515{
516 bh->b_end_io = end_buffer_async_write;
517 set_buffer_async_write(bh);
518}
519EXPORT_SYMBOL(mark_buffer_async_write);
520
521
522/*
523 * fs/buffer.c contains helper functions for buffer-backed address space's
524 * fsync functions. A common requirement for buffer-based filesystems is
525 * that certain data from the backing blockdev needs to be written out for
526 * a successful fsync(). For example, ext2 indirect blocks need to be
527 * written back and waited upon before fsync() returns.
528 *
529 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
530 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
531 * management of a list of dependent buffers at ->i_mapping->private_list.
532 *
533 * Locking is a little subtle: try_to_free_buffers() will remove buffers
534 * from their controlling inode's queue when they are being freed. But
535 * try_to_free_buffers() will be operating against the *blockdev* mapping
536 * at the time, not against the S_ISREG file which depends on those buffers.
537 * So the locking for private_list is via the private_lock in the address_space
538 * which backs the buffers. Which is different from the address_space
539 * against which the buffers are listed. So for a particular address_space,
540 * mapping->private_lock does *not* protect mapping->private_list! In fact,
541 * mapping->private_list will always be protected by the backing blockdev's
542 * ->private_lock.
543 *
544 * Which introduces a requirement: all buffers on an address_space's
545 * ->private_list must be from the same address_space: the blockdev's.
546 *
547 * address_spaces which do not place buffers at ->private_list via these
548 * utility functions are free to use private_lock and private_list for
549 * whatever they want. The only requirement is that list_empty(private_list)
550 * be true at clear_inode() time.
551 *
552 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
553 * filesystems should do that. invalidate_inode_buffers() should just go
554 * BUG_ON(!list_empty).
555 *
556 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
557 * take an address_space, not an inode. And it should be called
558 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
559 * queued up.
560 *
561 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
562 * list if it is already on a list. Because if the buffer is on a list,
563 * it *must* already be on the right one. If not, the filesystem is being
564 * silly. This will save a ton of locking. But first we have to ensure
565 * that buffers are taken *off* the old inode's list when they are freed
566 * (presumably in truncate). That requires careful auditing of all
567 * filesystems (do it inside bforget()). It could also be done by bringing
568 * b_inode back.
569 */
570
571/*
572 * The buffer's backing address_space's private_lock must be held
573 */
574static inline void __remove_assoc_queue(struct buffer_head *bh)
575{
576 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -0700577 WARN_ON(!bh->b_assoc_map);
578 if (buffer_write_io_error(bh))
579 set_bit(AS_EIO, &bh->b_assoc_map->flags);
580 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700581}
582
583int inode_has_buffers(struct inode *inode)
584{
585 return !list_empty(&inode->i_data.private_list);
586}
587
588/*
589 * osync is designed to support O_SYNC io. It waits synchronously for
590 * all already-submitted IO to complete, but does not queue any new
591 * writes to the disk.
592 *
593 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
594 * you dirty the buffers, and then use osync_inode_buffers to wait for
595 * completion. Any other dirty buffers which are not yet queued for
596 * write will not be flushed to disk by the osync.
597 */
598static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
599{
600 struct buffer_head *bh;
601 struct list_head *p;
602 int err = 0;
603
604 spin_lock(lock);
605repeat:
606 list_for_each_prev(p, list) {
607 bh = BH_ENTRY(p);
608 if (buffer_locked(bh)) {
609 get_bh(bh);
610 spin_unlock(lock);
611 wait_on_buffer(bh);
612 if (!buffer_uptodate(bh))
613 err = -EIO;
614 brelse(bh);
615 spin_lock(lock);
616 goto repeat;
617 }
618 }
619 spin_unlock(lock);
620 return err;
621}
622
623/**
624 * sync_mapping_buffers - write out and wait upon a mapping's "associated"
625 * buffers
Martin Waitz67be2dd2005-05-01 08:59:26 -0700626 * @mapping: the mapping which wants those buffers written
Linus Torvalds1da177e2005-04-16 15:20:36 -0700627 *
628 * Starts I/O against the buffers at mapping->private_list, and waits upon
629 * that I/O.
630 *
Martin Waitz67be2dd2005-05-01 08:59:26 -0700631 * Basically, this is a convenience function for fsync().
632 * @mapping is a file or directory which needs those buffers to be written for
633 * a successful fsync().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700634 */
635int sync_mapping_buffers(struct address_space *mapping)
636{
637 struct address_space *buffer_mapping = mapping->assoc_mapping;
638
639 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
640 return 0;
641
642 return fsync_buffers_list(&buffer_mapping->private_lock,
643 &mapping->private_list);
644}
645EXPORT_SYMBOL(sync_mapping_buffers);
646
647/*
648 * Called when we've recently written block `bblock', and it is known that
649 * `bblock' was for a buffer_boundary() buffer. This means that the block at
650 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
651 * dirty, schedule it for IO. So that indirects merge nicely with their data.
652 */
653void write_boundary_block(struct block_device *bdev,
654 sector_t bblock, unsigned blocksize)
655{
656 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
657 if (bh) {
658 if (buffer_dirty(bh))
659 ll_rw_block(WRITE, 1, &bh);
660 put_bh(bh);
661 }
662}
663
664void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
665{
666 struct address_space *mapping = inode->i_mapping;
667 struct address_space *buffer_mapping = bh->b_page->mapping;
668
669 mark_buffer_dirty(bh);
670 if (!mapping->assoc_mapping) {
671 mapping->assoc_mapping = buffer_mapping;
672 } else {
Eric Sesterhenne827f922006-03-26 18:24:46 +0200673 BUG_ON(mapping->assoc_mapping != buffer_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700674 }
675 if (list_empty(&bh->b_assoc_buffers)) {
676 spin_lock(&buffer_mapping->private_lock);
677 list_move_tail(&bh->b_assoc_buffers,
678 &mapping->private_list);
Jan Kara58ff4072006-10-17 00:10:19 -0700679 bh->b_assoc_map = mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700680 spin_unlock(&buffer_mapping->private_lock);
681 }
682}
683EXPORT_SYMBOL(mark_buffer_dirty_inode);
684
685/*
686 * Add a page to the dirty page list.
687 *
688 * It is a sad fact of life that this function is called from several places
689 * deeply under spinlocking. It may not sleep.
690 *
691 * If the page has buffers, the uptodate buffers are set dirty, to preserve
692 * dirty-state coherency between the page and the buffers. It the page does
693 * not have buffers then when they are later attached they will all be set
694 * dirty.
695 *
696 * The buffers are dirtied before the page is dirtied. There's a small race
697 * window in which a writepage caller may see the page cleanness but not the
698 * buffer dirtiness. That's fine. If this code were to set the page dirty
699 * before the buffers, a concurrent writepage caller could clear the page dirty
700 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
701 * page on the dirty page list.
702 *
703 * We use private_lock to lock against try_to_free_buffers while using the
704 * page's buffer list. Also use this to protect against clean buffers being
705 * added to the page after it was set dirty.
706 *
707 * FIXME: may need to call ->reservepage here as well. That's rather up to the
708 * address_space though.
709 */
710int __set_page_dirty_buffers(struct page *page)
711{
Nick Pigginebf7a222006-10-10 04:36:54 +0200712 struct address_space * const mapping = page_mapping(page);
713
714 if (unlikely(!mapping))
715 return !TestSetPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700716
717 spin_lock(&mapping->private_lock);
718 if (page_has_buffers(page)) {
719 struct buffer_head *head = page_buffers(page);
720 struct buffer_head *bh = head;
721
722 do {
723 set_buffer_dirty(bh);
724 bh = bh->b_this_page;
725 } while (bh != head);
726 }
727 spin_unlock(&mapping->private_lock);
728
Andrew Morton8c085402006-12-10 02:19:24 -0800729 if (TestSetPageDirty(page))
730 return 0;
731
732 write_lock_irq(&mapping->tree_lock);
733 if (page->mapping) { /* Race with truncate? */
Andrew Morton55e829a2006-12-10 02:19:27 -0800734 if (mapping_cap_account_dirty(mapping)) {
Andrew Morton8c085402006-12-10 02:19:24 -0800735 __inc_zone_page_state(page, NR_FILE_DIRTY);
Andrew Morton55e829a2006-12-10 02:19:27 -0800736 task_io_account_write(PAGE_CACHE_SIZE);
737 }
Andrew Morton8c085402006-12-10 02:19:24 -0800738 radix_tree_tag_set(&mapping->page_tree,
739 page_index(page), PAGECACHE_TAG_DIRTY);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700740 }
Andrew Morton8c085402006-12-10 02:19:24 -0800741 write_unlock_irq(&mapping->tree_lock);
742 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
743 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700744}
745EXPORT_SYMBOL(__set_page_dirty_buffers);
746
747/*
748 * Write out and wait upon a list of buffers.
749 *
750 * We have conflicting pressures: we want to make sure that all
751 * initially dirty buffers get waited on, but that any subsequently
752 * dirtied buffers don't. After all, we don't want fsync to last
753 * forever if somebody is actively writing to the file.
754 *
755 * Do this in two main stages: first we copy dirty buffers to a
756 * temporary inode list, queueing the writes as we go. Then we clean
757 * up, waiting for those writes to complete.
758 *
759 * During this second stage, any subsequent updates to the file may end
760 * up refiling the buffer on the original inode's dirty list again, so
761 * there is a chance we will end up with a buffer queued for write but
762 * not yet completed on that list. So, as a final cleanup we go through
763 * the osync code to catch these locked, dirty buffers without requeuing
764 * any newly dirty buffers for write.
765 */
766static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
767{
768 struct buffer_head *bh;
769 struct list_head tmp;
770 int err = 0, err2;
771
772 INIT_LIST_HEAD(&tmp);
773
774 spin_lock(lock);
775 while (!list_empty(list)) {
776 bh = BH_ENTRY(list->next);
Jan Kara58ff4072006-10-17 00:10:19 -0700777 __remove_assoc_queue(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700778 if (buffer_dirty(bh) || buffer_locked(bh)) {
779 list_add(&bh->b_assoc_buffers, &tmp);
780 if (buffer_dirty(bh)) {
781 get_bh(bh);
782 spin_unlock(lock);
783 /*
784 * Ensure any pending I/O completes so that
785 * ll_rw_block() actually writes the current
786 * contents - it is a noop if I/O is still in
787 * flight on potentially older contents.
788 */
Jan Karaa7662232005-09-06 15:19:10 -0700789 ll_rw_block(SWRITE, 1, &bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700790 brelse(bh);
791 spin_lock(lock);
792 }
793 }
794 }
795
796 while (!list_empty(&tmp)) {
797 bh = BH_ENTRY(tmp.prev);
Jan Kara58ff4072006-10-17 00:10:19 -0700798 list_del_init(&bh->b_assoc_buffers);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700799 get_bh(bh);
800 spin_unlock(lock);
801 wait_on_buffer(bh);
802 if (!buffer_uptodate(bh))
803 err = -EIO;
804 brelse(bh);
805 spin_lock(lock);
806 }
807
808 spin_unlock(lock);
809 err2 = osync_buffers_list(lock, list);
810 if (err)
811 return err;
812 else
813 return err2;
814}
815
816/*
817 * Invalidate any and all dirty buffers on a given inode. We are
818 * probably unmounting the fs, but that doesn't mean we have already
819 * done a sync(). Just drop the buffers from the inode list.
820 *
821 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
822 * assumes that all the buffers are against the blockdev. Not true
823 * for reiserfs.
824 */
825void invalidate_inode_buffers(struct inode *inode)
826{
827 if (inode_has_buffers(inode)) {
828 struct address_space *mapping = &inode->i_data;
829 struct list_head *list = &mapping->private_list;
830 struct address_space *buffer_mapping = mapping->assoc_mapping;
831
832 spin_lock(&buffer_mapping->private_lock);
833 while (!list_empty(list))
834 __remove_assoc_queue(BH_ENTRY(list->next));
835 spin_unlock(&buffer_mapping->private_lock);
836 }
837}
838
839/*
840 * Remove any clean buffers from the inode's buffer list. This is called
841 * when we're trying to free the inode itself. Those buffers can pin it.
842 *
843 * Returns true if all buffers were removed.
844 */
845int remove_inode_buffers(struct inode *inode)
846{
847 int ret = 1;
848
849 if (inode_has_buffers(inode)) {
850 struct address_space *mapping = &inode->i_data;
851 struct list_head *list = &mapping->private_list;
852 struct address_space *buffer_mapping = mapping->assoc_mapping;
853
854 spin_lock(&buffer_mapping->private_lock);
855 while (!list_empty(list)) {
856 struct buffer_head *bh = BH_ENTRY(list->next);
857 if (buffer_dirty(bh)) {
858 ret = 0;
859 break;
860 }
861 __remove_assoc_queue(bh);
862 }
863 spin_unlock(&buffer_mapping->private_lock);
864 }
865 return ret;
866}
867
868/*
869 * Create the appropriate buffers when given a page for data area and
870 * the size of each buffer.. Use the bh->b_this_page linked list to
871 * follow the buffers created. Return NULL if unable to create more
872 * buffers.
873 *
874 * The retry flag is used to differentiate async IO (paging, swapping)
875 * which may not fail from ordinary buffer allocations.
876 */
877struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
878 int retry)
879{
880 struct buffer_head *bh, *head;
881 long offset;
882
883try_again:
884 head = NULL;
885 offset = PAGE_SIZE;
886 while ((offset -= size) >= 0) {
887 bh = alloc_buffer_head(GFP_NOFS);
888 if (!bh)
889 goto no_grow;
890
891 bh->b_bdev = NULL;
892 bh->b_this_page = head;
893 bh->b_blocknr = -1;
894 head = bh;
895
896 bh->b_state = 0;
897 atomic_set(&bh->b_count, 0);
Chris Masonfc5cd582006-02-01 03:06:48 -0800898 bh->b_private = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700899 bh->b_size = size;
900
901 /* Link the buffer to its page */
902 set_bh_page(bh, page, offset);
903
Nathan Scott01ffe332006-01-17 09:02:07 +1100904 init_buffer(bh, NULL, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700905 }
906 return head;
907/*
908 * In case anything failed, we just free everything we got.
909 */
910no_grow:
911 if (head) {
912 do {
913 bh = head;
914 head = head->b_this_page;
915 free_buffer_head(bh);
916 } while (head);
917 }
918
919 /*
920 * Return failure for non-async IO requests. Async IO requests
921 * are not allowed to fail, so we have to wait until buffer heads
922 * become available. But we don't want tasks sleeping with
923 * partially complete buffers, so all were released above.
924 */
925 if (!retry)
926 return NULL;
927
928 /* We're _really_ low on memory. Now we just
929 * wait for old buffer heads to become free due to
930 * finishing IO. Since this is an async request and
931 * the reserve list is empty, we're sure there are
932 * async buffer heads in use.
933 */
934 free_more_memory();
935 goto try_again;
936}
937EXPORT_SYMBOL_GPL(alloc_page_buffers);
938
939static inline void
940link_dev_buffers(struct page *page, struct buffer_head *head)
941{
942 struct buffer_head *bh, *tail;
943
944 bh = head;
945 do {
946 tail = bh;
947 bh = bh->b_this_page;
948 } while (bh);
949 tail->b_this_page = head;
950 attach_page_buffers(page, head);
951}
952
953/*
954 * Initialise the state of a blockdev page's buffers.
955 */
956static void
957init_page_buffers(struct page *page, struct block_device *bdev,
958 sector_t block, int size)
959{
960 struct buffer_head *head = page_buffers(page);
961 struct buffer_head *bh = head;
962 int uptodate = PageUptodate(page);
963
964 do {
965 if (!buffer_mapped(bh)) {
966 init_buffer(bh, NULL, NULL);
967 bh->b_bdev = bdev;
968 bh->b_blocknr = block;
969 if (uptodate)
970 set_buffer_uptodate(bh);
971 set_buffer_mapped(bh);
972 }
973 block++;
974 bh = bh->b_this_page;
975 } while (bh != head);
976}
977
978/*
979 * Create the page-cache page that contains the requested block.
980 *
981 * This is user purely for blockdev mappings.
982 */
983static struct page *
984grow_dev_page(struct block_device *bdev, sector_t block,
985 pgoff_t index, int size)
986{
987 struct inode *inode = bdev->bd_inode;
988 struct page *page;
989 struct buffer_head *bh;
990
991 page = find_or_create_page(inode->i_mapping, index, GFP_NOFS);
992 if (!page)
993 return NULL;
994
Eric Sesterhenne827f922006-03-26 18:24:46 +0200995 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700996
997 if (page_has_buffers(page)) {
998 bh = page_buffers(page);
999 if (bh->b_size == size) {
1000 init_page_buffers(page, bdev, block, size);
1001 return page;
1002 }
1003 if (!try_to_free_buffers(page))
1004 goto failed;
1005 }
1006
1007 /*
1008 * Allocate some buffers for this page
1009 */
1010 bh = alloc_page_buffers(page, size, 0);
1011 if (!bh)
1012 goto failed;
1013
1014 /*
1015 * Link the page to the buffers and initialise them. Take the
1016 * lock to be atomic wrt __find_get_block(), which does not
1017 * run under the page lock.
1018 */
1019 spin_lock(&inode->i_mapping->private_lock);
1020 link_dev_buffers(page, bh);
1021 init_page_buffers(page, bdev, block, size);
1022 spin_unlock(&inode->i_mapping->private_lock);
1023 return page;
1024
1025failed:
1026 BUG();
1027 unlock_page(page);
1028 page_cache_release(page);
1029 return NULL;
1030}
1031
1032/*
1033 * Create buffers for the specified block device block's page. If
1034 * that page was dirty, the buffers are set dirty also.
1035 *
1036 * Except that's a bug. Attaching dirty buffers to a dirty
1037 * blockdev's page can result in filesystem corruption, because
1038 * some of those buffers may be aliases of filesystem data.
1039 * grow_dev_page() will go BUG() if this happens.
1040 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001041static int
Linus Torvalds1da177e2005-04-16 15:20:36 -07001042grow_buffers(struct block_device *bdev, sector_t block, int size)
1043{
1044 struct page *page;
1045 pgoff_t index;
1046 int sizebits;
1047
1048 sizebits = -1;
1049 do {
1050 sizebits++;
1051 } while ((size << sizebits) < PAGE_SIZE);
1052
1053 index = block >> sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001054
Andrew Mortone5657932006-10-11 01:21:46 -07001055 /*
1056 * Check for a block which wants to lie outside our maximum possible
1057 * pagecache index. (this comparison is done using sector_t types).
1058 */
1059 if (unlikely(index != block >> sizebits)) {
1060 char b[BDEVNAME_SIZE];
1061
1062 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1063 "device %s\n",
1064 __FUNCTION__, (unsigned long long)block,
1065 bdevname(bdev, b));
1066 return -EIO;
1067 }
1068 block = index << sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001069 /* Create a page with the proper size buffers.. */
1070 page = grow_dev_page(bdev, block, index, size);
1071 if (!page)
1072 return 0;
1073 unlock_page(page);
1074 page_cache_release(page);
1075 return 1;
1076}
1077
Adrian Bunk75c96f82005-05-05 16:16:09 -07001078static struct buffer_head *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001079__getblk_slow(struct block_device *bdev, sector_t block, int size)
1080{
1081 /* Size must be multiple of hard sectorsize */
1082 if (unlikely(size & (bdev_hardsect_size(bdev)-1) ||
1083 (size < 512 || size > PAGE_SIZE))) {
1084 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1085 size);
1086 printk(KERN_ERR "hardsect size: %d\n",
1087 bdev_hardsect_size(bdev));
1088
1089 dump_stack();
1090 return NULL;
1091 }
1092
1093 for (;;) {
1094 struct buffer_head * bh;
Andrew Mortone5657932006-10-11 01:21:46 -07001095 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001096
1097 bh = __find_get_block(bdev, block, size);
1098 if (bh)
1099 return bh;
1100
Andrew Mortone5657932006-10-11 01:21:46 -07001101 ret = grow_buffers(bdev, block, size);
1102 if (ret < 0)
1103 return NULL;
1104 if (ret == 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001105 free_more_memory();
1106 }
1107}
1108
1109/*
1110 * The relationship between dirty buffers and dirty pages:
1111 *
1112 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1113 * the page is tagged dirty in its radix tree.
1114 *
1115 * At all times, the dirtiness of the buffers represents the dirtiness of
1116 * subsections of the page. If the page has buffers, the page dirty bit is
1117 * merely a hint about the true dirty state.
1118 *
1119 * When a page is set dirty in its entirety, all its buffers are marked dirty
1120 * (if the page has buffers).
1121 *
1122 * When a buffer is marked dirty, its page is dirtied, but the page's other
1123 * buffers are not.
1124 *
1125 * Also. When blockdev buffers are explicitly read with bread(), they
1126 * individually become uptodate. But their backing page remains not
1127 * uptodate - even if all of its buffers are uptodate. A subsequent
1128 * block_read_full_page() against that page will discover all the uptodate
1129 * buffers, will set the page uptodate and will perform no I/O.
1130 */
1131
1132/**
1133 * mark_buffer_dirty - mark a buffer_head as needing writeout
Martin Waitz67be2dd2005-05-01 08:59:26 -07001134 * @bh: the buffer_head to mark dirty
Linus Torvalds1da177e2005-04-16 15:20:36 -07001135 *
1136 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1137 * backing page dirty, then tag the page as dirty in its address_space's radix
1138 * tree and then attach the address_space's inode to its superblock's dirty
1139 * inode list.
1140 *
1141 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1142 * mapping->tree_lock and the global inode_lock.
1143 */
1144void fastcall mark_buffer_dirty(struct buffer_head *bh)
1145{
1146 if (!buffer_dirty(bh) && !test_set_buffer_dirty(bh))
1147 __set_page_dirty_nobuffers(bh->b_page);
1148}
1149
1150/*
1151 * Decrement a buffer_head's reference count. If all buffers against a page
1152 * have zero reference count, are clean and unlocked, and if the page is clean
1153 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1154 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1155 * a page but it ends up not being freed, and buffers may later be reattached).
1156 */
1157void __brelse(struct buffer_head * buf)
1158{
1159 if (atomic_read(&buf->b_count)) {
1160 put_bh(buf);
1161 return;
1162 }
1163 printk(KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1164 WARN_ON(1);
1165}
1166
1167/*
1168 * bforget() is like brelse(), except it discards any
1169 * potentially dirty data.
1170 */
1171void __bforget(struct buffer_head *bh)
1172{
1173 clear_buffer_dirty(bh);
1174 if (!list_empty(&bh->b_assoc_buffers)) {
1175 struct address_space *buffer_mapping = bh->b_page->mapping;
1176
1177 spin_lock(&buffer_mapping->private_lock);
1178 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -07001179 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001180 spin_unlock(&buffer_mapping->private_lock);
1181 }
1182 __brelse(bh);
1183}
1184
1185static struct buffer_head *__bread_slow(struct buffer_head *bh)
1186{
1187 lock_buffer(bh);
1188 if (buffer_uptodate(bh)) {
1189 unlock_buffer(bh);
1190 return bh;
1191 } else {
1192 get_bh(bh);
1193 bh->b_end_io = end_buffer_read_sync;
1194 submit_bh(READ, bh);
1195 wait_on_buffer(bh);
1196 if (buffer_uptodate(bh))
1197 return bh;
1198 }
1199 brelse(bh);
1200 return NULL;
1201}
1202
1203/*
1204 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1205 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1206 * refcount elevated by one when they're in an LRU. A buffer can only appear
1207 * once in a particular CPU's LRU. A single buffer can be present in multiple
1208 * CPU's LRUs at the same time.
1209 *
1210 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1211 * sb_find_get_block().
1212 *
1213 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1214 * a local interrupt disable for that.
1215 */
1216
1217#define BH_LRU_SIZE 8
1218
1219struct bh_lru {
1220 struct buffer_head *bhs[BH_LRU_SIZE];
1221};
1222
1223static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1224
1225#ifdef CONFIG_SMP
1226#define bh_lru_lock() local_irq_disable()
1227#define bh_lru_unlock() local_irq_enable()
1228#else
1229#define bh_lru_lock() preempt_disable()
1230#define bh_lru_unlock() preempt_enable()
1231#endif
1232
1233static inline void check_irqs_on(void)
1234{
1235#ifdef irqs_disabled
1236 BUG_ON(irqs_disabled());
1237#endif
1238}
1239
1240/*
1241 * The LRU management algorithm is dopey-but-simple. Sorry.
1242 */
1243static void bh_lru_install(struct buffer_head *bh)
1244{
1245 struct buffer_head *evictee = NULL;
1246 struct bh_lru *lru;
1247
1248 check_irqs_on();
1249 bh_lru_lock();
1250 lru = &__get_cpu_var(bh_lrus);
1251 if (lru->bhs[0] != bh) {
1252 struct buffer_head *bhs[BH_LRU_SIZE];
1253 int in;
1254 int out = 0;
1255
1256 get_bh(bh);
1257 bhs[out++] = bh;
1258 for (in = 0; in < BH_LRU_SIZE; in++) {
1259 struct buffer_head *bh2 = lru->bhs[in];
1260
1261 if (bh2 == bh) {
1262 __brelse(bh2);
1263 } else {
1264 if (out >= BH_LRU_SIZE) {
1265 BUG_ON(evictee != NULL);
1266 evictee = bh2;
1267 } else {
1268 bhs[out++] = bh2;
1269 }
1270 }
1271 }
1272 while (out < BH_LRU_SIZE)
1273 bhs[out++] = NULL;
1274 memcpy(lru->bhs, bhs, sizeof(bhs));
1275 }
1276 bh_lru_unlock();
1277
1278 if (evictee)
1279 __brelse(evictee);
1280}
1281
1282/*
1283 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1284 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001285static struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001286lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001287{
1288 struct buffer_head *ret = NULL;
1289 struct bh_lru *lru;
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001290 unsigned int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001291
1292 check_irqs_on();
1293 bh_lru_lock();
1294 lru = &__get_cpu_var(bh_lrus);
1295 for (i = 0; i < BH_LRU_SIZE; i++) {
1296 struct buffer_head *bh = lru->bhs[i];
1297
1298 if (bh && bh->b_bdev == bdev &&
1299 bh->b_blocknr == block && bh->b_size == size) {
1300 if (i) {
1301 while (i) {
1302 lru->bhs[i] = lru->bhs[i - 1];
1303 i--;
1304 }
1305 lru->bhs[0] = bh;
1306 }
1307 get_bh(bh);
1308 ret = bh;
1309 break;
1310 }
1311 }
1312 bh_lru_unlock();
1313 return ret;
1314}
1315
1316/*
1317 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1318 * it in the LRU and mark it as accessed. If it is not present then return
1319 * NULL
1320 */
1321struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001322__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001323{
1324 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1325
1326 if (bh == NULL) {
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001327 bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001328 if (bh)
1329 bh_lru_install(bh);
1330 }
1331 if (bh)
1332 touch_buffer(bh);
1333 return bh;
1334}
1335EXPORT_SYMBOL(__find_get_block);
1336
1337/*
1338 * __getblk will locate (and, if necessary, create) the buffer_head
1339 * which corresponds to the passed block_device, block and size. The
1340 * returned buffer has its reference count incremented.
1341 *
1342 * __getblk() cannot fail - it just keeps trying. If you pass it an
1343 * illegal block number, __getblk() will happily return a buffer_head
1344 * which represents the non-existent block. Very weird.
1345 *
1346 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1347 * attempt is failing. FIXME, perhaps?
1348 */
1349struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001350__getblk(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001351{
1352 struct buffer_head *bh = __find_get_block(bdev, block, size);
1353
1354 might_sleep();
1355 if (bh == NULL)
1356 bh = __getblk_slow(bdev, block, size);
1357 return bh;
1358}
1359EXPORT_SYMBOL(__getblk);
1360
1361/*
1362 * Do async read-ahead on a buffer..
1363 */
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001364void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001365{
1366 struct buffer_head *bh = __getblk(bdev, block, size);
Andrew Mortona3e713b2005-10-30 15:03:15 -08001367 if (likely(bh)) {
1368 ll_rw_block(READA, 1, &bh);
1369 brelse(bh);
1370 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001371}
1372EXPORT_SYMBOL(__breadahead);
1373
1374/**
1375 * __bread() - reads a specified block and returns the bh
Martin Waitz67be2dd2005-05-01 08:59:26 -07001376 * @bdev: the block_device to read from
Linus Torvalds1da177e2005-04-16 15:20:36 -07001377 * @block: number of block
1378 * @size: size (in bytes) to read
1379 *
1380 * Reads a specified block, and returns buffer head that contains it.
1381 * It returns NULL if the block was unreadable.
1382 */
1383struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001384__bread(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001385{
1386 struct buffer_head *bh = __getblk(bdev, block, size);
1387
Andrew Mortona3e713b2005-10-30 15:03:15 -08001388 if (likely(bh) && !buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001389 bh = __bread_slow(bh);
1390 return bh;
1391}
1392EXPORT_SYMBOL(__bread);
1393
1394/*
1395 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1396 * This doesn't race because it runs in each cpu either in irq
1397 * or with preempt disabled.
1398 */
1399static void invalidate_bh_lru(void *arg)
1400{
1401 struct bh_lru *b = &get_cpu_var(bh_lrus);
1402 int i;
1403
1404 for (i = 0; i < BH_LRU_SIZE; i++) {
1405 brelse(b->bhs[i]);
1406 b->bhs[i] = NULL;
1407 }
1408 put_cpu_var(bh_lrus);
1409}
1410
1411static void invalidate_bh_lrus(void)
1412{
1413 on_each_cpu(invalidate_bh_lru, NULL, 1, 1);
1414}
1415
1416void set_bh_page(struct buffer_head *bh,
1417 struct page *page, unsigned long offset)
1418{
1419 bh->b_page = page;
Eric Sesterhenne827f922006-03-26 18:24:46 +02001420 BUG_ON(offset >= PAGE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001421 if (PageHighMem(page))
1422 /*
1423 * This catches illegal uses and preserves the offset:
1424 */
1425 bh->b_data = (char *)(0 + offset);
1426 else
1427 bh->b_data = page_address(page) + offset;
1428}
1429EXPORT_SYMBOL(set_bh_page);
1430
1431/*
1432 * Called when truncating a buffer on a page completely.
1433 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001434static void discard_buffer(struct buffer_head * bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001435{
1436 lock_buffer(bh);
1437 clear_buffer_dirty(bh);
1438 bh->b_bdev = NULL;
1439 clear_buffer_mapped(bh);
1440 clear_buffer_req(bh);
1441 clear_buffer_new(bh);
1442 clear_buffer_delay(bh);
David Chinner33a266d2007-02-12 00:51:41 -08001443 clear_buffer_unwritten(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001444 unlock_buffer(bh);
1445}
1446
1447/**
Linus Torvalds1da177e2005-04-16 15:20:36 -07001448 * block_invalidatepage - invalidate part of all of a buffer-backed page
1449 *
1450 * @page: the page which is affected
1451 * @offset: the index of the truncation point
1452 *
1453 * block_invalidatepage() is called when all or part of the page has become
1454 * invalidatedby a truncate operation.
1455 *
1456 * block_invalidatepage() does not have to release all buffers, but it must
1457 * ensure that no dirty buffer is left outside @offset and that no I/O
1458 * is underway against any of the blocks which are outside the truncation
1459 * point. Because the caller is about to free (and possibly reuse) those
1460 * blocks on-disk.
1461 */
NeilBrown2ff28e22006-03-26 01:37:18 -08001462void block_invalidatepage(struct page *page, unsigned long offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001463{
1464 struct buffer_head *head, *bh, *next;
1465 unsigned int curr_off = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001466
1467 BUG_ON(!PageLocked(page));
1468 if (!page_has_buffers(page))
1469 goto out;
1470
1471 head = page_buffers(page);
1472 bh = head;
1473 do {
1474 unsigned int next_off = curr_off + bh->b_size;
1475 next = bh->b_this_page;
1476
1477 /*
1478 * is this block fully invalidated?
1479 */
1480 if (offset <= curr_off)
1481 discard_buffer(bh);
1482 curr_off = next_off;
1483 bh = next;
1484 } while (bh != head);
1485
1486 /*
1487 * We release buffers only if the entire page is being invalidated.
1488 * The get_block cached value has been unconditionally invalidated,
1489 * so real IO is not possible anymore.
1490 */
1491 if (offset == 0)
NeilBrown2ff28e22006-03-26 01:37:18 -08001492 try_to_release_page(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001493out:
NeilBrown2ff28e22006-03-26 01:37:18 -08001494 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001495}
1496EXPORT_SYMBOL(block_invalidatepage);
1497
1498/*
1499 * We attach and possibly dirty the buffers atomically wrt
1500 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1501 * is already excluded via the page lock.
1502 */
1503void create_empty_buffers(struct page *page,
1504 unsigned long blocksize, unsigned long b_state)
1505{
1506 struct buffer_head *bh, *head, *tail;
1507
1508 head = alloc_page_buffers(page, blocksize, 1);
1509 bh = head;
1510 do {
1511 bh->b_state |= b_state;
1512 tail = bh;
1513 bh = bh->b_this_page;
1514 } while (bh);
1515 tail->b_this_page = head;
1516
1517 spin_lock(&page->mapping->private_lock);
1518 if (PageUptodate(page) || PageDirty(page)) {
1519 bh = head;
1520 do {
1521 if (PageDirty(page))
1522 set_buffer_dirty(bh);
1523 if (PageUptodate(page))
1524 set_buffer_uptodate(bh);
1525 bh = bh->b_this_page;
1526 } while (bh != head);
1527 }
1528 attach_page_buffers(page, head);
1529 spin_unlock(&page->mapping->private_lock);
1530}
1531EXPORT_SYMBOL(create_empty_buffers);
1532
1533/*
1534 * We are taking a block for data and we don't want any output from any
1535 * buffer-cache aliases starting from return from that function and
1536 * until the moment when something will explicitly mark the buffer
1537 * dirty (hopefully that will not happen until we will free that block ;-)
1538 * We don't even need to mark it not-uptodate - nobody can expect
1539 * anything from a newly allocated buffer anyway. We used to used
1540 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1541 * don't want to mark the alias unmapped, for example - it would confuse
1542 * anyone who might pick it with bread() afterwards...
1543 *
1544 * Also.. Note that bforget() doesn't lock the buffer. So there can
1545 * be writeout I/O going on against recently-freed buffers. We don't
1546 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1547 * only if we really need to. That happens here.
1548 */
1549void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1550{
1551 struct buffer_head *old_bh;
1552
1553 might_sleep();
1554
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001555 old_bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001556 if (old_bh) {
1557 clear_buffer_dirty(old_bh);
1558 wait_on_buffer(old_bh);
1559 clear_buffer_req(old_bh);
1560 __brelse(old_bh);
1561 }
1562}
1563EXPORT_SYMBOL(unmap_underlying_metadata);
1564
1565/*
1566 * NOTE! All mapped/uptodate combinations are valid:
1567 *
1568 * Mapped Uptodate Meaning
1569 *
1570 * No No "unknown" - must do get_block()
1571 * No Yes "hole" - zero-filled
1572 * Yes No "allocated" - allocated on disk, not read in
1573 * Yes Yes "valid" - allocated and up-to-date in memory.
1574 *
1575 * "Dirty" is valid only with the last case (mapped+uptodate).
1576 */
1577
1578/*
1579 * While block_write_full_page is writing back the dirty buffers under
1580 * the page lock, whoever dirtied the buffers may decide to clean them
1581 * again at any time. We handle that by only looking at the buffer
1582 * state inside lock_buffer().
1583 *
1584 * If block_write_full_page() is called for regular writeback
1585 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1586 * locked buffer. This only can happen if someone has written the buffer
1587 * directly, with submit_bh(). At the address_space level PageWriteback
1588 * prevents this contention from occurring.
1589 */
1590static int __block_write_full_page(struct inode *inode, struct page *page,
1591 get_block_t *get_block, struct writeback_control *wbc)
1592{
1593 int err;
1594 sector_t block;
1595 sector_t last_block;
Andrew Mortonf0fbd5f2005-05-05 16:15:48 -07001596 struct buffer_head *bh, *head;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001597 const unsigned blocksize = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001598 int nr_underway = 0;
1599
1600 BUG_ON(!PageLocked(page));
1601
1602 last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
1603
1604 if (!page_has_buffers(page)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001605 create_empty_buffers(page, blocksize,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001606 (1 << BH_Dirty)|(1 << BH_Uptodate));
1607 }
1608
1609 /*
1610 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1611 * here, and the (potentially unmapped) buffers may become dirty at
1612 * any time. If a buffer becomes dirty here after we've inspected it
1613 * then we just miss that fact, and the page stays dirty.
1614 *
1615 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1616 * handle that here by just cleaning them.
1617 */
1618
Andrew Morton54b21a72006-01-08 01:03:05 -08001619 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001620 head = page_buffers(page);
1621 bh = head;
1622
1623 /*
1624 * Get all the dirty buffers mapped to disk addresses and
1625 * handle any aliases from the underlying blockdev's mapping.
1626 */
1627 do {
1628 if (block > last_block) {
1629 /*
1630 * mapped buffers outside i_size will occur, because
1631 * this page can be outside i_size when there is a
1632 * truncate in progress.
1633 */
1634 /*
1635 * The buffer was zeroed by block_write_full_page()
1636 */
1637 clear_buffer_dirty(bh);
1638 set_buffer_uptodate(bh);
1639 } else if (!buffer_mapped(bh) && buffer_dirty(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001640 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001641 err = get_block(inode, block, bh, 1);
1642 if (err)
1643 goto recover;
1644 if (buffer_new(bh)) {
1645 /* blockdev mappings never come here */
1646 clear_buffer_new(bh);
1647 unmap_underlying_metadata(bh->b_bdev,
1648 bh->b_blocknr);
1649 }
1650 }
1651 bh = bh->b_this_page;
1652 block++;
1653 } while (bh != head);
1654
1655 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001656 if (!buffer_mapped(bh))
1657 continue;
1658 /*
1659 * If it's a fully non-blocking write attempt and we cannot
1660 * lock the buffer then redirty the page. Note that this can
1661 * potentially cause a busy-wait loop from pdflush and kswapd
1662 * activity, but those code paths have their own higher-level
1663 * throttling.
1664 */
1665 if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
1666 lock_buffer(bh);
1667 } else if (test_set_buffer_locked(bh)) {
1668 redirty_page_for_writepage(wbc, page);
1669 continue;
1670 }
1671 if (test_clear_buffer_dirty(bh)) {
1672 mark_buffer_async_write(bh);
1673 } else {
1674 unlock_buffer(bh);
1675 }
1676 } while ((bh = bh->b_this_page) != head);
1677
1678 /*
1679 * The page and its buffers are protected by PageWriteback(), so we can
1680 * drop the bh refcounts early.
1681 */
1682 BUG_ON(PageWriteback(page));
1683 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001684
1685 do {
1686 struct buffer_head *next = bh->b_this_page;
1687 if (buffer_async_write(bh)) {
1688 submit_bh(WRITE, bh);
1689 nr_underway++;
1690 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001691 bh = next;
1692 } while (bh != head);
Andrew Morton05937ba2005-05-05 16:15:47 -07001693 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001694
1695 err = 0;
1696done:
1697 if (nr_underway == 0) {
1698 /*
1699 * The page was marked dirty, but the buffers were
1700 * clean. Someone wrote them back by hand with
1701 * ll_rw_block/submit_bh. A rare case.
1702 */
1703 int uptodate = 1;
1704 do {
1705 if (!buffer_uptodate(bh)) {
1706 uptodate = 0;
1707 break;
1708 }
1709 bh = bh->b_this_page;
1710 } while (bh != head);
1711 if (uptodate)
1712 SetPageUptodate(page);
1713 end_page_writeback(page);
1714 /*
1715 * The page and buffer_heads can be released at any time from
1716 * here on.
1717 */
1718 wbc->pages_skipped++; /* We didn't write this page */
1719 }
1720 return err;
1721
1722recover:
1723 /*
1724 * ENOSPC, or some other error. We may already have added some
1725 * blocks to the file, so we need to write these out to avoid
1726 * exposing stale data.
1727 * The page is currently locked and not marked for writeback
1728 */
1729 bh = head;
1730 /* Recovery: lock and submit the mapped buffers */
1731 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001732 if (buffer_mapped(bh) && buffer_dirty(bh)) {
1733 lock_buffer(bh);
1734 mark_buffer_async_write(bh);
1735 } else {
1736 /*
1737 * The buffer may have been set dirty during
1738 * attachment to a dirty page.
1739 */
1740 clear_buffer_dirty(bh);
1741 }
1742 } while ((bh = bh->b_this_page) != head);
1743 SetPageError(page);
1744 BUG_ON(PageWriteback(page));
1745 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001746 do {
1747 struct buffer_head *next = bh->b_this_page;
1748 if (buffer_async_write(bh)) {
1749 clear_buffer_dirty(bh);
1750 submit_bh(WRITE, bh);
1751 nr_underway++;
1752 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001753 bh = next;
1754 } while (bh != head);
Nick Pigginffda9d32007-02-20 13:57:54 -08001755 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001756 goto done;
1757}
1758
1759static int __block_prepare_write(struct inode *inode, struct page *page,
1760 unsigned from, unsigned to, get_block_t *get_block)
1761{
1762 unsigned block_start, block_end;
1763 sector_t block;
1764 int err = 0;
1765 unsigned blocksize, bbits;
1766 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1767
1768 BUG_ON(!PageLocked(page));
1769 BUG_ON(from > PAGE_CACHE_SIZE);
1770 BUG_ON(to > PAGE_CACHE_SIZE);
1771 BUG_ON(from > to);
1772
1773 blocksize = 1 << inode->i_blkbits;
1774 if (!page_has_buffers(page))
1775 create_empty_buffers(page, blocksize, 0);
1776 head = page_buffers(page);
1777
1778 bbits = inode->i_blkbits;
1779 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1780
1781 for(bh = head, block_start = 0; bh != head || !block_start;
1782 block++, block_start=block_end, bh = bh->b_this_page) {
1783 block_end = block_start + blocksize;
1784 if (block_end <= from || block_start >= to) {
1785 if (PageUptodate(page)) {
1786 if (!buffer_uptodate(bh))
1787 set_buffer_uptodate(bh);
1788 }
1789 continue;
1790 }
1791 if (buffer_new(bh))
1792 clear_buffer_new(bh);
1793 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001794 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001795 err = get_block(inode, block, bh, 1);
1796 if (err)
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001797 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001798 if (buffer_new(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001799 unmap_underlying_metadata(bh->b_bdev,
1800 bh->b_blocknr);
1801 if (PageUptodate(page)) {
1802 set_buffer_uptodate(bh);
1803 continue;
1804 }
1805 if (block_end > to || block_start < from) {
1806 void *kaddr;
1807
1808 kaddr = kmap_atomic(page, KM_USER0);
1809 if (block_end > to)
1810 memset(kaddr+to, 0,
1811 block_end-to);
1812 if (block_start < from)
1813 memset(kaddr+block_start,
1814 0, from-block_start);
1815 flush_dcache_page(page);
1816 kunmap_atomic(kaddr, KM_USER0);
1817 }
1818 continue;
1819 }
1820 }
1821 if (PageUptodate(page)) {
1822 if (!buffer_uptodate(bh))
1823 set_buffer_uptodate(bh);
1824 continue;
1825 }
1826 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
David Chinner33a266d2007-02-12 00:51:41 -08001827 !buffer_unwritten(bh) &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001828 (block_start < from || block_end > to)) {
1829 ll_rw_block(READ, 1, &bh);
1830 *wait_bh++=bh;
1831 }
1832 }
1833 /*
1834 * If we issued read requests - let them complete.
1835 */
1836 while(wait_bh > wait) {
1837 wait_on_buffer(*--wait_bh);
1838 if (!buffer_uptodate(*wait_bh))
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001839 err = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001840 }
Anton Altaparmakov152becd2005-06-23 00:10:21 -07001841 if (!err) {
1842 bh = head;
1843 do {
1844 if (buffer_new(bh))
1845 clear_buffer_new(bh);
1846 } while ((bh = bh->b_this_page) != head);
1847 return 0;
1848 }
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001849 /* Error case: */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001850 /*
1851 * Zero out any newly allocated blocks to avoid exposing stale
1852 * data. If BH_New is set, we know that the block was newly
1853 * allocated in the above loop.
1854 */
1855 bh = head;
1856 block_start = 0;
1857 do {
1858 block_end = block_start+blocksize;
1859 if (block_end <= from)
1860 goto next_bh;
1861 if (block_start >= to)
1862 break;
1863 if (buffer_new(bh)) {
1864 void *kaddr;
1865
1866 clear_buffer_new(bh);
1867 kaddr = kmap_atomic(page, KM_USER0);
1868 memset(kaddr+block_start, 0, bh->b_size);
Monakhov Dmitriy8c581652006-10-11 01:22:00 -07001869 flush_dcache_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001870 kunmap_atomic(kaddr, KM_USER0);
1871 set_buffer_uptodate(bh);
1872 mark_buffer_dirty(bh);
1873 }
1874next_bh:
1875 block_start = block_end;
1876 bh = bh->b_this_page;
1877 } while (bh != head);
1878 return err;
1879}
1880
1881static int __block_commit_write(struct inode *inode, struct page *page,
1882 unsigned from, unsigned to)
1883{
1884 unsigned block_start, block_end;
1885 int partial = 0;
1886 unsigned blocksize;
1887 struct buffer_head *bh, *head;
1888
1889 blocksize = 1 << inode->i_blkbits;
1890
1891 for(bh = head = page_buffers(page), block_start = 0;
1892 bh != head || !block_start;
1893 block_start=block_end, bh = bh->b_this_page) {
1894 block_end = block_start + blocksize;
1895 if (block_end <= from || block_start >= to) {
1896 if (!buffer_uptodate(bh))
1897 partial = 1;
1898 } else {
1899 set_buffer_uptodate(bh);
1900 mark_buffer_dirty(bh);
1901 }
1902 }
1903
1904 /*
1905 * If this is a partial write which happened to make all buffers
1906 * uptodate then we can optimize away a bogus readpage() for
1907 * the next read(). Here we 'discover' whether the page went
1908 * uptodate as a result of this (potentially partial) write.
1909 */
1910 if (!partial)
1911 SetPageUptodate(page);
1912 return 0;
1913}
1914
1915/*
1916 * Generic "read page" function for block devices that have the normal
1917 * get_block functionality. This is most of the block device filesystems.
1918 * Reads the page asynchronously --- the unlock_buffer() and
1919 * set/clear_buffer_uptodate() functions propagate buffer state into the
1920 * page struct once IO has completed.
1921 */
1922int block_read_full_page(struct page *page, get_block_t *get_block)
1923{
1924 struct inode *inode = page->mapping->host;
1925 sector_t iblock, lblock;
1926 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
1927 unsigned int blocksize;
1928 int nr, i;
1929 int fully_mapped = 1;
1930
Matt Mackallcd7619d2005-05-01 08:59:01 -07001931 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001932 blocksize = 1 << inode->i_blkbits;
1933 if (!page_has_buffers(page))
1934 create_empty_buffers(page, blocksize, 0);
1935 head = page_buffers(page);
1936
1937 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
1938 lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
1939 bh = head;
1940 nr = 0;
1941 i = 0;
1942
1943 do {
1944 if (buffer_uptodate(bh))
1945 continue;
1946
1947 if (!buffer_mapped(bh)) {
Andrew Mortonc64610b2005-05-16 21:53:49 -07001948 int err = 0;
1949
Linus Torvalds1da177e2005-04-16 15:20:36 -07001950 fully_mapped = 0;
1951 if (iblock < lblock) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001952 WARN_ON(bh->b_size != blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07001953 err = get_block(inode, iblock, bh, 0);
1954 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001955 SetPageError(page);
1956 }
1957 if (!buffer_mapped(bh)) {
1958 void *kaddr = kmap_atomic(page, KM_USER0);
1959 memset(kaddr + i * blocksize, 0, blocksize);
1960 flush_dcache_page(page);
1961 kunmap_atomic(kaddr, KM_USER0);
Andrew Mortonc64610b2005-05-16 21:53:49 -07001962 if (!err)
1963 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001964 continue;
1965 }
1966 /*
1967 * get_block() might have updated the buffer
1968 * synchronously
1969 */
1970 if (buffer_uptodate(bh))
1971 continue;
1972 }
1973 arr[nr++] = bh;
1974 } while (i++, iblock++, (bh = bh->b_this_page) != head);
1975
1976 if (fully_mapped)
1977 SetPageMappedToDisk(page);
1978
1979 if (!nr) {
1980 /*
1981 * All buffers are uptodate - we can set the page uptodate
1982 * as well. But not if get_block() returned an error.
1983 */
1984 if (!PageError(page))
1985 SetPageUptodate(page);
1986 unlock_page(page);
1987 return 0;
1988 }
1989
1990 /* Stage two: lock the buffers */
1991 for (i = 0; i < nr; i++) {
1992 bh = arr[i];
1993 lock_buffer(bh);
1994 mark_buffer_async_read(bh);
1995 }
1996
1997 /*
1998 * Stage 3: start the IO. Check for uptodateness
1999 * inside the buffer lock in case another process reading
2000 * the underlying blockdev brought it uptodate (the sct fix).
2001 */
2002 for (i = 0; i < nr; i++) {
2003 bh = arr[i];
2004 if (buffer_uptodate(bh))
2005 end_buffer_async_read(bh, 1);
2006 else
2007 submit_bh(READ, bh);
2008 }
2009 return 0;
2010}
2011
2012/* utility function for filesystems that need to do work on expanding
2013 * truncates. Uses prepare/commit_write to allow the filesystem to
2014 * deal with the hole.
2015 */
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002016static int __generic_cont_expand(struct inode *inode, loff_t size,
2017 pgoff_t index, unsigned int offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002018{
2019 struct address_space *mapping = inode->i_mapping;
2020 struct page *page;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002021 unsigned long limit;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002022 int err;
2023
2024 err = -EFBIG;
2025 limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
2026 if (limit != RLIM_INFINITY && size > (loff_t)limit) {
2027 send_sig(SIGXFSZ, current, 0);
2028 goto out;
2029 }
2030 if (size > inode->i_sb->s_maxbytes)
2031 goto out;
2032
Linus Torvalds1da177e2005-04-16 15:20:36 -07002033 err = -ENOMEM;
2034 page = grab_cache_page(mapping, index);
2035 if (!page)
2036 goto out;
2037 err = mapping->a_ops->prepare_write(NULL, page, offset, offset);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002038 if (err) {
2039 /*
2040 * ->prepare_write() may have instantiated a few blocks
2041 * outside i_size. Trim these off again.
2042 */
2043 unlock_page(page);
2044 page_cache_release(page);
2045 vmtruncate(inode, inode->i_size);
2046 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002047 }
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002048
2049 err = mapping->a_ops->commit_write(NULL, page, offset, offset);
2050
Linus Torvalds1da177e2005-04-16 15:20:36 -07002051 unlock_page(page);
2052 page_cache_release(page);
2053 if (err > 0)
2054 err = 0;
2055out:
2056 return err;
2057}
2058
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002059int generic_cont_expand(struct inode *inode, loff_t size)
2060{
2061 pgoff_t index;
2062 unsigned int offset;
2063
2064 offset = (size & (PAGE_CACHE_SIZE - 1)); /* Within page */
2065
2066 /* ugh. in prepare/commit_write, if from==to==start of block, we
2067 ** skip the prepare. make sure we never send an offset for the start
2068 ** of a block
2069 */
2070 if ((offset & (inode->i_sb->s_blocksize - 1)) == 0) {
2071 /* caller must handle this extra byte. */
2072 offset++;
2073 }
2074 index = size >> PAGE_CACHE_SHIFT;
2075
2076 return __generic_cont_expand(inode, size, index, offset);
2077}
2078
2079int generic_cont_expand_simple(struct inode *inode, loff_t size)
2080{
2081 loff_t pos = size - 1;
2082 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
2083 unsigned int offset = (pos & (PAGE_CACHE_SIZE - 1)) + 1;
2084
2085 /* prepare/commit_write can handle even if from==to==start of block. */
2086 return __generic_cont_expand(inode, size, index, offset);
2087}
2088
Linus Torvalds1da177e2005-04-16 15:20:36 -07002089/*
2090 * For moronic filesystems that do not allow holes in file.
2091 * We may have to extend the file.
2092 */
2093
2094int cont_prepare_write(struct page *page, unsigned offset,
2095 unsigned to, get_block_t *get_block, loff_t *bytes)
2096{
2097 struct address_space *mapping = page->mapping;
2098 struct inode *inode = mapping->host;
2099 struct page *new_page;
2100 pgoff_t pgpos;
2101 long status;
2102 unsigned zerofrom;
2103 unsigned blocksize = 1 << inode->i_blkbits;
2104 void *kaddr;
2105
2106 while(page->index > (pgpos = *bytes>>PAGE_CACHE_SHIFT)) {
2107 status = -ENOMEM;
2108 new_page = grab_cache_page(mapping, pgpos);
2109 if (!new_page)
2110 goto out;
2111 /* we might sleep */
2112 if (*bytes>>PAGE_CACHE_SHIFT != pgpos) {
2113 unlock_page(new_page);
2114 page_cache_release(new_page);
2115 continue;
2116 }
2117 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2118 if (zerofrom & (blocksize-1)) {
2119 *bytes |= (blocksize-1);
2120 (*bytes)++;
2121 }
2122 status = __block_prepare_write(inode, new_page, zerofrom,
2123 PAGE_CACHE_SIZE, get_block);
2124 if (status)
2125 goto out_unmap;
2126 kaddr = kmap_atomic(new_page, KM_USER0);
2127 memset(kaddr+zerofrom, 0, PAGE_CACHE_SIZE-zerofrom);
2128 flush_dcache_page(new_page);
2129 kunmap_atomic(kaddr, KM_USER0);
2130 generic_commit_write(NULL, new_page, zerofrom, PAGE_CACHE_SIZE);
2131 unlock_page(new_page);
2132 page_cache_release(new_page);
2133 }
2134
2135 if (page->index < pgpos) {
2136 /* completely inside the area */
2137 zerofrom = offset;
2138 } else {
2139 /* page covers the boundary, find the boundary offset */
2140 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2141
2142 /* if we will expand the thing last block will be filled */
2143 if (to > zerofrom && (zerofrom & (blocksize-1))) {
2144 *bytes |= (blocksize-1);
2145 (*bytes)++;
2146 }
2147
2148 /* starting below the boundary? Nothing to zero out */
2149 if (offset <= zerofrom)
2150 zerofrom = offset;
2151 }
2152 status = __block_prepare_write(inode, page, zerofrom, to, get_block);
2153 if (status)
2154 goto out1;
2155 if (zerofrom < offset) {
2156 kaddr = kmap_atomic(page, KM_USER0);
2157 memset(kaddr+zerofrom, 0, offset-zerofrom);
2158 flush_dcache_page(page);
2159 kunmap_atomic(kaddr, KM_USER0);
2160 __block_commit_write(inode, page, zerofrom, offset);
2161 }
2162 return 0;
2163out1:
2164 ClearPageUptodate(page);
2165 return status;
2166
2167out_unmap:
2168 ClearPageUptodate(new_page);
2169 unlock_page(new_page);
2170 page_cache_release(new_page);
2171out:
2172 return status;
2173}
2174
2175int block_prepare_write(struct page *page, unsigned from, unsigned to,
2176 get_block_t *get_block)
2177{
2178 struct inode *inode = page->mapping->host;
2179 int err = __block_prepare_write(inode, page, from, to, get_block);
2180 if (err)
2181 ClearPageUptodate(page);
2182 return err;
2183}
2184
2185int block_commit_write(struct page *page, unsigned from, unsigned to)
2186{
2187 struct inode *inode = page->mapping->host;
2188 __block_commit_write(inode,page,from,to);
2189 return 0;
2190}
2191
2192int generic_commit_write(struct file *file, struct page *page,
2193 unsigned from, unsigned to)
2194{
2195 struct inode *inode = page->mapping->host;
2196 loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
2197 __block_commit_write(inode,page,from,to);
2198 /*
2199 * No need to use i_size_read() here, the i_size
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08002200 * cannot change under us because we hold i_mutex.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002201 */
2202 if (pos > inode->i_size) {
2203 i_size_write(inode, pos);
2204 mark_inode_dirty(inode);
2205 }
2206 return 0;
2207}
2208
2209
2210/*
2211 * nobh_prepare_write()'s prereads are special: the buffer_heads are freed
2212 * immediately, while under the page lock. So it needs a special end_io
2213 * handler which does not touch the bh after unlocking it.
2214 *
2215 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
2216 * a race there is benign: unlock_buffer() only use the bh's address for
2217 * hashing after unlocking the buffer, so it doesn't actually touch the bh
2218 * itself.
2219 */
2220static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2221{
2222 if (uptodate) {
2223 set_buffer_uptodate(bh);
2224 } else {
2225 /* This happens, due to failed READA attempts. */
2226 clear_buffer_uptodate(bh);
2227 }
2228 unlock_buffer(bh);
2229}
2230
2231/*
2232 * On entry, the page is fully not uptodate.
2233 * On exit the page is fully uptodate in the areas outside (from,to)
2234 */
2235int nobh_prepare_write(struct page *page, unsigned from, unsigned to,
2236 get_block_t *get_block)
2237{
2238 struct inode *inode = page->mapping->host;
2239 const unsigned blkbits = inode->i_blkbits;
2240 const unsigned blocksize = 1 << blkbits;
2241 struct buffer_head map_bh;
2242 struct buffer_head *read_bh[MAX_BUF_PER_PAGE];
2243 unsigned block_in_page;
2244 unsigned block_start;
2245 sector_t block_in_file;
2246 char *kaddr;
2247 int nr_reads = 0;
2248 int i;
2249 int ret = 0;
2250 int is_mapped_to_disk = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002251
2252 if (PageMappedToDisk(page))
2253 return 0;
2254
2255 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
2256 map_bh.b_page = page;
2257
2258 /*
2259 * We loop across all blocks in the page, whether or not they are
2260 * part of the affected region. This is so we can discover if the
2261 * page is fully mapped-to-disk.
2262 */
2263 for (block_start = 0, block_in_page = 0;
2264 block_start < PAGE_CACHE_SIZE;
2265 block_in_page++, block_start += blocksize) {
2266 unsigned block_end = block_start + blocksize;
2267 int create;
2268
2269 map_bh.b_state = 0;
2270 create = 1;
2271 if (block_start >= to)
2272 create = 0;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002273 map_bh.b_size = blocksize;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002274 ret = get_block(inode, block_in_file + block_in_page,
2275 &map_bh, create);
2276 if (ret)
2277 goto failed;
2278 if (!buffer_mapped(&map_bh))
2279 is_mapped_to_disk = 0;
2280 if (buffer_new(&map_bh))
2281 unmap_underlying_metadata(map_bh.b_bdev,
2282 map_bh.b_blocknr);
2283 if (PageUptodate(page))
2284 continue;
2285 if (buffer_new(&map_bh) || !buffer_mapped(&map_bh)) {
2286 kaddr = kmap_atomic(page, KM_USER0);
Nick Piggin22c8ca72007-02-20 13:58:09 -08002287 if (block_start < from)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002288 memset(kaddr+block_start, 0, from-block_start);
Nick Piggin22c8ca72007-02-20 13:58:09 -08002289 if (block_end > to)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002290 memset(kaddr + to, 0, block_end - to);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002291 flush_dcache_page(page);
2292 kunmap_atomic(kaddr, KM_USER0);
2293 continue;
2294 }
2295 if (buffer_uptodate(&map_bh))
2296 continue; /* reiserfs does this */
2297 if (block_start < from || block_end > to) {
2298 struct buffer_head *bh = alloc_buffer_head(GFP_NOFS);
2299
2300 if (!bh) {
2301 ret = -ENOMEM;
2302 goto failed;
2303 }
2304 bh->b_state = map_bh.b_state;
2305 atomic_set(&bh->b_count, 0);
2306 bh->b_this_page = NULL;
2307 bh->b_page = page;
2308 bh->b_blocknr = map_bh.b_blocknr;
2309 bh->b_size = blocksize;
2310 bh->b_data = (char *)(long)block_start;
2311 bh->b_bdev = map_bh.b_bdev;
2312 bh->b_private = NULL;
2313 read_bh[nr_reads++] = bh;
2314 }
2315 }
2316
2317 if (nr_reads) {
2318 struct buffer_head *bh;
2319
2320 /*
2321 * The page is locked, so these buffers are protected from
2322 * any VM or truncate activity. Hence we don't need to care
2323 * for the buffer_head refcounts.
2324 */
2325 for (i = 0; i < nr_reads; i++) {
2326 bh = read_bh[i];
2327 lock_buffer(bh);
2328 bh->b_end_io = end_buffer_read_nobh;
2329 submit_bh(READ, bh);
2330 }
2331 for (i = 0; i < nr_reads; i++) {
2332 bh = read_bh[i];
2333 wait_on_buffer(bh);
2334 if (!buffer_uptodate(bh))
2335 ret = -EIO;
2336 free_buffer_head(bh);
2337 read_bh[i] = NULL;
2338 }
2339 if (ret)
2340 goto failed;
2341 }
2342
2343 if (is_mapped_to_disk)
2344 SetPageMappedToDisk(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002345
2346 return 0;
2347
2348failed:
2349 for (i = 0; i < nr_reads; i++) {
2350 if (read_bh[i])
2351 free_buffer_head(read_bh[i]);
2352 }
2353
2354 /*
2355 * Error recovery is pretty slack. Clear the page and mark it dirty
2356 * so we'll later zero out any blocks which _were_ allocated.
2357 */
2358 kaddr = kmap_atomic(page, KM_USER0);
2359 memset(kaddr, 0, PAGE_CACHE_SIZE);
Monakhov Dmitriy8c581652006-10-11 01:22:00 -07002360 flush_dcache_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002361 kunmap_atomic(kaddr, KM_USER0);
2362 SetPageUptodate(page);
2363 set_page_dirty(page);
2364 return ret;
2365}
2366EXPORT_SYMBOL(nobh_prepare_write);
2367
2368int nobh_commit_write(struct file *file, struct page *page,
2369 unsigned from, unsigned to)
2370{
2371 struct inode *inode = page->mapping->host;
2372 loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
2373
Nick Piggin22c8ca72007-02-20 13:58:09 -08002374 SetPageUptodate(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002375 set_page_dirty(page);
2376 if (pos > inode->i_size) {
2377 i_size_write(inode, pos);
2378 mark_inode_dirty(inode);
2379 }
2380 return 0;
2381}
2382EXPORT_SYMBOL(nobh_commit_write);
2383
2384/*
2385 * nobh_writepage() - based on block_full_write_page() except
2386 * that it tries to operate without attaching bufferheads to
2387 * the page.
2388 */
2389int nobh_writepage(struct page *page, get_block_t *get_block,
2390 struct writeback_control *wbc)
2391{
2392 struct inode * const inode = page->mapping->host;
2393 loff_t i_size = i_size_read(inode);
2394 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2395 unsigned offset;
2396 void *kaddr;
2397 int ret;
2398
2399 /* Is the page fully inside i_size? */
2400 if (page->index < end_index)
2401 goto out;
2402
2403 /* Is the page fully outside i_size? (truncate in progress) */
2404 offset = i_size & (PAGE_CACHE_SIZE-1);
2405 if (page->index >= end_index+1 || !offset) {
2406 /*
2407 * The page may have dirty, unmapped buffers. For example,
2408 * they may have been added in ext3_writepage(). Make them
2409 * freeable here, so the page does not leak.
2410 */
2411#if 0
2412 /* Not really sure about this - do we need this ? */
2413 if (page->mapping->a_ops->invalidatepage)
2414 page->mapping->a_ops->invalidatepage(page, offset);
2415#endif
2416 unlock_page(page);
2417 return 0; /* don't care */
2418 }
2419
2420 /*
2421 * The page straddles i_size. It must be zeroed out on each and every
2422 * writepage invocation because it may be mmapped. "A file is mapped
2423 * in multiples of the page size. For a file that is not a multiple of
2424 * the page size, the remaining memory is zeroed when mapped, and
2425 * writes to that region are not written out to the file."
2426 */
2427 kaddr = kmap_atomic(page, KM_USER0);
2428 memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
2429 flush_dcache_page(page);
2430 kunmap_atomic(kaddr, KM_USER0);
2431out:
2432 ret = mpage_writepage(page, get_block, wbc);
2433 if (ret == -EAGAIN)
2434 ret = __block_write_full_page(inode, page, get_block, wbc);
2435 return ret;
2436}
2437EXPORT_SYMBOL(nobh_writepage);
2438
2439/*
2440 * This function assumes that ->prepare_write() uses nobh_prepare_write().
2441 */
2442int nobh_truncate_page(struct address_space *mapping, loff_t from)
2443{
2444 struct inode *inode = mapping->host;
2445 unsigned blocksize = 1 << inode->i_blkbits;
2446 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2447 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2448 unsigned to;
2449 struct page *page;
Christoph Hellwigf5e54d62006-06-28 04:26:44 -07002450 const struct address_space_operations *a_ops = mapping->a_ops;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002451 char *kaddr;
2452 int ret = 0;
2453
2454 if ((offset & (blocksize - 1)) == 0)
2455 goto out;
2456
2457 ret = -ENOMEM;
2458 page = grab_cache_page(mapping, index);
2459 if (!page)
2460 goto out;
2461
2462 to = (offset + blocksize) & ~(blocksize - 1);
2463 ret = a_ops->prepare_write(NULL, page, offset, to);
2464 if (ret == 0) {
2465 kaddr = kmap_atomic(page, KM_USER0);
2466 memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
2467 flush_dcache_page(page);
2468 kunmap_atomic(kaddr, KM_USER0);
2469 set_page_dirty(page);
2470 }
2471 unlock_page(page);
2472 page_cache_release(page);
2473out:
2474 return ret;
2475}
2476EXPORT_SYMBOL(nobh_truncate_page);
2477
2478int block_truncate_page(struct address_space *mapping,
2479 loff_t from, get_block_t *get_block)
2480{
2481 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2482 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2483 unsigned blocksize;
Andrew Morton54b21a72006-01-08 01:03:05 -08002484 sector_t iblock;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002485 unsigned length, pos;
2486 struct inode *inode = mapping->host;
2487 struct page *page;
2488 struct buffer_head *bh;
2489 void *kaddr;
2490 int err;
2491
2492 blocksize = 1 << inode->i_blkbits;
2493 length = offset & (blocksize - 1);
2494
2495 /* Block boundary? Nothing to do */
2496 if (!length)
2497 return 0;
2498
2499 length = blocksize - length;
Andrew Morton54b21a72006-01-08 01:03:05 -08002500 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002501
2502 page = grab_cache_page(mapping, index);
2503 err = -ENOMEM;
2504 if (!page)
2505 goto out;
2506
2507 if (!page_has_buffers(page))
2508 create_empty_buffers(page, blocksize, 0);
2509
2510 /* Find the buffer that contains "offset" */
2511 bh = page_buffers(page);
2512 pos = blocksize;
2513 while (offset >= pos) {
2514 bh = bh->b_this_page;
2515 iblock++;
2516 pos += blocksize;
2517 }
2518
2519 err = 0;
2520 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002521 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002522 err = get_block(inode, iblock, bh, 0);
2523 if (err)
2524 goto unlock;
2525 /* unmapped? It's a hole - nothing to do */
2526 if (!buffer_mapped(bh))
2527 goto unlock;
2528 }
2529
2530 /* Ok, it's mapped. Make sure it's up-to-date */
2531 if (PageUptodate(page))
2532 set_buffer_uptodate(bh);
2533
David Chinner33a266d2007-02-12 00:51:41 -08002534 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002535 err = -EIO;
2536 ll_rw_block(READ, 1, &bh);
2537 wait_on_buffer(bh);
2538 /* Uhhuh. Read error. Complain and punt. */
2539 if (!buffer_uptodate(bh))
2540 goto unlock;
2541 }
2542
2543 kaddr = kmap_atomic(page, KM_USER0);
2544 memset(kaddr + offset, 0, length);
2545 flush_dcache_page(page);
2546 kunmap_atomic(kaddr, KM_USER0);
2547
2548 mark_buffer_dirty(bh);
2549 err = 0;
2550
2551unlock:
2552 unlock_page(page);
2553 page_cache_release(page);
2554out:
2555 return err;
2556}
2557
2558/*
2559 * The generic ->writepage function for buffer-backed address_spaces
2560 */
2561int block_write_full_page(struct page *page, get_block_t *get_block,
2562 struct writeback_control *wbc)
2563{
2564 struct inode * const inode = page->mapping->host;
2565 loff_t i_size = i_size_read(inode);
2566 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2567 unsigned offset;
2568 void *kaddr;
2569
2570 /* Is the page fully inside i_size? */
2571 if (page->index < end_index)
2572 return __block_write_full_page(inode, page, get_block, wbc);
2573
2574 /* Is the page fully outside i_size? (truncate in progress) */
2575 offset = i_size & (PAGE_CACHE_SIZE-1);
2576 if (page->index >= end_index+1 || !offset) {
2577 /*
2578 * The page may have dirty, unmapped buffers. For example,
2579 * they may have been added in ext3_writepage(). Make them
2580 * freeable here, so the page does not leak.
2581 */
Jan Karaaaa40592005-10-30 15:00:16 -08002582 do_invalidatepage(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002583 unlock_page(page);
2584 return 0; /* don't care */
2585 }
2586
2587 /*
2588 * The page straddles i_size. It must be zeroed out on each and every
2589 * writepage invokation because it may be mmapped. "A file is mapped
2590 * in multiples of the page size. For a file that is not a multiple of
2591 * the page size, the remaining memory is zeroed when mapped, and
2592 * writes to that region are not written out to the file."
2593 */
2594 kaddr = kmap_atomic(page, KM_USER0);
2595 memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
2596 flush_dcache_page(page);
2597 kunmap_atomic(kaddr, KM_USER0);
2598 return __block_write_full_page(inode, page, get_block, wbc);
2599}
2600
2601sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2602 get_block_t *get_block)
2603{
2604 struct buffer_head tmp;
2605 struct inode *inode = mapping->host;
2606 tmp.b_state = 0;
2607 tmp.b_blocknr = 0;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002608 tmp.b_size = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002609 get_block(inode, block, &tmp, 0);
2610 return tmp.b_blocknr;
2611}
2612
2613static int end_bio_bh_io_sync(struct bio *bio, unsigned int bytes_done, int err)
2614{
2615 struct buffer_head *bh = bio->bi_private;
2616
2617 if (bio->bi_size)
2618 return 1;
2619
2620 if (err == -EOPNOTSUPP) {
2621 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
2622 set_bit(BH_Eopnotsupp, &bh->b_state);
2623 }
2624
2625 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2626 bio_put(bio);
2627 return 0;
2628}
2629
2630int submit_bh(int rw, struct buffer_head * bh)
2631{
2632 struct bio *bio;
2633 int ret = 0;
2634
2635 BUG_ON(!buffer_locked(bh));
2636 BUG_ON(!buffer_mapped(bh));
2637 BUG_ON(!bh->b_end_io);
2638
2639 if (buffer_ordered(bh) && (rw == WRITE))
2640 rw = WRITE_BARRIER;
2641
2642 /*
2643 * Only clear out a write error when rewriting, should this
2644 * include WRITE_SYNC as well?
2645 */
2646 if (test_set_buffer_req(bh) && (rw == WRITE || rw == WRITE_BARRIER))
2647 clear_buffer_write_io_error(bh);
2648
2649 /*
2650 * from here on down, it's all bio -- do the initial mapping,
2651 * submit_bio -> generic_make_request may further map this bio around
2652 */
2653 bio = bio_alloc(GFP_NOIO, 1);
2654
2655 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2656 bio->bi_bdev = bh->b_bdev;
2657 bio->bi_io_vec[0].bv_page = bh->b_page;
2658 bio->bi_io_vec[0].bv_len = bh->b_size;
2659 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
2660
2661 bio->bi_vcnt = 1;
2662 bio->bi_idx = 0;
2663 bio->bi_size = bh->b_size;
2664
2665 bio->bi_end_io = end_bio_bh_io_sync;
2666 bio->bi_private = bh;
2667
2668 bio_get(bio);
2669 submit_bio(rw, bio);
2670
2671 if (bio_flagged(bio, BIO_EOPNOTSUPP))
2672 ret = -EOPNOTSUPP;
2673
2674 bio_put(bio);
2675 return ret;
2676}
2677
2678/**
2679 * ll_rw_block: low-level access to block devices (DEPRECATED)
Jan Karaa7662232005-09-06 15:19:10 -07002680 * @rw: whether to %READ or %WRITE or %SWRITE or maybe %READA (readahead)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002681 * @nr: number of &struct buffer_heads in the array
2682 * @bhs: array of pointers to &struct buffer_head
2683 *
Jan Karaa7662232005-09-06 15:19:10 -07002684 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
2685 * requests an I/O operation on them, either a %READ or a %WRITE. The third
2686 * %SWRITE is like %WRITE only we make sure that the *current* data in buffers
2687 * are sent to disk. The fourth %READA option is described in the documentation
2688 * for generic_make_request() which ll_rw_block() calls.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002689 *
2690 * This function drops any buffer that it cannot get a lock on (with the
Jan Karaa7662232005-09-06 15:19:10 -07002691 * BH_Lock state bit) unless SWRITE is required, any buffer that appears to be
2692 * clean when doing a write request, and any buffer that appears to be
2693 * up-to-date when doing read request. Further it marks as clean buffers that
2694 * are processed for writing (the buffer cache won't assume that they are
2695 * actually clean until the buffer gets unlocked).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002696 *
2697 * ll_rw_block sets b_end_io to simple completion handler that marks
2698 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
2699 * any waiters.
2700 *
2701 * All of the buffers must be for the same device, and must also be a
2702 * multiple of the current approved size for the device.
2703 */
2704void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
2705{
2706 int i;
2707
2708 for (i = 0; i < nr; i++) {
2709 struct buffer_head *bh = bhs[i];
2710
Jan Karaa7662232005-09-06 15:19:10 -07002711 if (rw == SWRITE)
2712 lock_buffer(bh);
2713 else if (test_set_buffer_locked(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002714 continue;
2715
Jan Karaa7662232005-09-06 15:19:10 -07002716 if (rw == WRITE || rw == SWRITE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002717 if (test_clear_buffer_dirty(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07002718 bh->b_end_io = end_buffer_write_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08002719 get_bh(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002720 submit_bh(WRITE, bh);
2721 continue;
2722 }
2723 } else {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002724 if (!buffer_uptodate(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07002725 bh->b_end_io = end_buffer_read_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08002726 get_bh(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002727 submit_bh(rw, bh);
2728 continue;
2729 }
2730 }
2731 unlock_buffer(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002732 }
2733}
2734
2735/*
2736 * For a data-integrity writeout, we need to wait upon any in-progress I/O
2737 * and then start new I/O and then wait upon it. The caller must have a ref on
2738 * the buffer_head.
2739 */
2740int sync_dirty_buffer(struct buffer_head *bh)
2741{
2742 int ret = 0;
2743
2744 WARN_ON(atomic_read(&bh->b_count) < 1);
2745 lock_buffer(bh);
2746 if (test_clear_buffer_dirty(bh)) {
2747 get_bh(bh);
2748 bh->b_end_io = end_buffer_write_sync;
2749 ret = submit_bh(WRITE, bh);
2750 wait_on_buffer(bh);
2751 if (buffer_eopnotsupp(bh)) {
2752 clear_buffer_eopnotsupp(bh);
2753 ret = -EOPNOTSUPP;
2754 }
2755 if (!ret && !buffer_uptodate(bh))
2756 ret = -EIO;
2757 } else {
2758 unlock_buffer(bh);
2759 }
2760 return ret;
2761}
2762
2763/*
2764 * try_to_free_buffers() checks if all the buffers on this particular page
2765 * are unused, and releases them if so.
2766 *
2767 * Exclusion against try_to_free_buffers may be obtained by either
2768 * locking the page or by holding its mapping's private_lock.
2769 *
2770 * If the page is dirty but all the buffers are clean then we need to
2771 * be sure to mark the page clean as well. This is because the page
2772 * may be against a block device, and a later reattachment of buffers
2773 * to a dirty page will set *all* buffers dirty. Which would corrupt
2774 * filesystem data on the same device.
2775 *
2776 * The same applies to regular filesystem pages: if all the buffers are
2777 * clean then we set the page clean and proceed. To do that, we require
2778 * total exclusion from __set_page_dirty_buffers(). That is obtained with
2779 * private_lock.
2780 *
2781 * try_to_free_buffers() is non-blocking.
2782 */
2783static inline int buffer_busy(struct buffer_head *bh)
2784{
2785 return atomic_read(&bh->b_count) |
2786 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
2787}
2788
2789static int
2790drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
2791{
2792 struct buffer_head *head = page_buffers(page);
2793 struct buffer_head *bh;
2794
2795 bh = head;
2796 do {
akpm@osdl.orgde7d5a32005-05-01 08:58:39 -07002797 if (buffer_write_io_error(bh) && page->mapping)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002798 set_bit(AS_EIO, &page->mapping->flags);
2799 if (buffer_busy(bh))
2800 goto failed;
2801 bh = bh->b_this_page;
2802 } while (bh != head);
2803
2804 do {
2805 struct buffer_head *next = bh->b_this_page;
2806
2807 if (!list_empty(&bh->b_assoc_buffers))
2808 __remove_assoc_queue(bh);
2809 bh = next;
2810 } while (bh != head);
2811 *buffers_to_free = head;
2812 __clear_page_buffers(page);
2813 return 1;
2814failed:
2815 return 0;
2816}
2817
2818int try_to_free_buffers(struct page *page)
2819{
2820 struct address_space * const mapping = page->mapping;
2821 struct buffer_head *buffers_to_free = NULL;
2822 int ret = 0;
2823
2824 BUG_ON(!PageLocked(page));
Linus Torvaldsecdfc972007-01-26 12:47:06 -08002825 if (PageWriteback(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002826 return 0;
2827
2828 if (mapping == NULL) { /* can this still happen? */
2829 ret = drop_buffers(page, &buffers_to_free);
2830 goto out;
2831 }
2832
2833 spin_lock(&mapping->private_lock);
2834 ret = drop_buffers(page, &buffers_to_free);
Linus Torvaldsecdfc972007-01-26 12:47:06 -08002835
2836 /*
2837 * If the filesystem writes its buffers by hand (eg ext3)
2838 * then we can have clean buffers against a dirty page. We
2839 * clean the page here; otherwise the VM will never notice
2840 * that the filesystem did any IO at all.
2841 *
2842 * Also, during truncate, discard_buffer will have marked all
2843 * the page's buffers clean. We discover that here and clean
2844 * the page also.
Nick Piggin87df7242007-01-30 14:36:27 +11002845 *
2846 * private_lock must be held over this entire operation in order
2847 * to synchronise against __set_page_dirty_buffers and prevent the
2848 * dirty bit from being lost.
Linus Torvaldsecdfc972007-01-26 12:47:06 -08002849 */
2850 if (ret)
2851 cancel_dirty_page(page, PAGE_CACHE_SIZE);
Nick Piggin87df7242007-01-30 14:36:27 +11002852 spin_unlock(&mapping->private_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002853out:
2854 if (buffers_to_free) {
2855 struct buffer_head *bh = buffers_to_free;
2856
2857 do {
2858 struct buffer_head *next = bh->b_this_page;
2859 free_buffer_head(bh);
2860 bh = next;
2861 } while (bh != buffers_to_free);
2862 }
2863 return ret;
2864}
2865EXPORT_SYMBOL(try_to_free_buffers);
2866
NeilBrown3978d712006-03-26 01:37:17 -08002867void block_sync_page(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002868{
2869 struct address_space *mapping;
2870
2871 smp_mb();
2872 mapping = page_mapping(page);
2873 if (mapping)
2874 blk_run_backing_dev(mapping->backing_dev_info, page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002875}
2876
2877/*
2878 * There are no bdflush tunables left. But distributions are
2879 * still running obsolete flush daemons, so we terminate them here.
2880 *
2881 * Use of bdflush() is deprecated and will be removed in a future kernel.
2882 * The `pdflush' kernel threads fully replace bdflush daemons and this call.
2883 */
2884asmlinkage long sys_bdflush(int func, long data)
2885{
2886 static int msg_count;
2887
2888 if (!capable(CAP_SYS_ADMIN))
2889 return -EPERM;
2890
2891 if (msg_count < 5) {
2892 msg_count++;
2893 printk(KERN_INFO
2894 "warning: process `%s' used the obsolete bdflush"
2895 " system call\n", current->comm);
2896 printk(KERN_INFO "Fix your initscripts?\n");
2897 }
2898
2899 if (func == 1)
2900 do_exit(0);
2901 return 0;
2902}
2903
2904/*
2905 * Buffer-head allocation
2906 */
Christoph Lametere18b8902006-12-06 20:33:20 -08002907static struct kmem_cache *bh_cachep;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002908
2909/*
2910 * Once the number of bh's in the machine exceeds this level, we start
2911 * stripping them in writeback.
2912 */
2913static int max_buffer_heads;
2914
2915int buffer_heads_over_limit;
2916
2917struct bh_accounting {
2918 int nr; /* Number of live bh's */
2919 int ratelimit; /* Limit cacheline bouncing */
2920};
2921
2922static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
2923
2924static void recalc_bh_state(void)
2925{
2926 int i;
2927 int tot = 0;
2928
2929 if (__get_cpu_var(bh_accounting).ratelimit++ < 4096)
2930 return;
2931 __get_cpu_var(bh_accounting).ratelimit = 0;
Eric Dumazet8a143422006-03-24 03:18:10 -08002932 for_each_online_cpu(i)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002933 tot += per_cpu(bh_accounting, i).nr;
2934 buffer_heads_over_limit = (tot > max_buffer_heads);
2935}
2936
Al Virodd0fc662005-10-07 07:46:04 +01002937struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002938{
2939 struct buffer_head *ret = kmem_cache_alloc(bh_cachep, gfp_flags);
2940 if (ret) {
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07002941 get_cpu_var(bh_accounting).nr++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002942 recalc_bh_state();
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07002943 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002944 }
2945 return ret;
2946}
2947EXPORT_SYMBOL(alloc_buffer_head);
2948
2949void free_buffer_head(struct buffer_head *bh)
2950{
2951 BUG_ON(!list_empty(&bh->b_assoc_buffers));
2952 kmem_cache_free(bh_cachep, bh);
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}
2957EXPORT_SYMBOL(free_buffer_head);
2958
2959static void
Christoph Lametere18b8902006-12-06 20:33:20 -08002960init_buffer_head(void *data, struct kmem_cache *cachep, unsigned long flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002961{
2962 if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
2963 SLAB_CTOR_CONSTRUCTOR) {
2964 struct buffer_head * bh = (struct buffer_head *)data;
2965
2966 memset(bh, 0, sizeof(*bh));
2967 INIT_LIST_HEAD(&bh->b_assoc_buffers);
2968 }
2969}
2970
Linus Torvalds1da177e2005-04-16 15:20:36 -07002971static void buffer_exit_cpu(int cpu)
2972{
2973 int i;
2974 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
2975
2976 for (i = 0; i < BH_LRU_SIZE; i++) {
2977 brelse(b->bhs[i]);
2978 b->bhs[i] = NULL;
2979 }
Eric Dumazet8a143422006-03-24 03:18:10 -08002980 get_cpu_var(bh_accounting).nr += per_cpu(bh_accounting, cpu).nr;
2981 per_cpu(bh_accounting, cpu).nr = 0;
2982 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002983}
2984
2985static int buffer_cpu_notify(struct notifier_block *self,
2986 unsigned long action, void *hcpu)
2987{
2988 if (action == CPU_DEAD)
2989 buffer_exit_cpu((unsigned long)hcpu);
2990 return NOTIFY_OK;
2991}
Linus Torvalds1da177e2005-04-16 15:20:36 -07002992
2993void __init buffer_init(void)
2994{
2995 int nrpages;
2996
2997 bh_cachep = kmem_cache_create("buffer_head",
Paul Jacksonb0196002006-03-24 03:16:09 -08002998 sizeof(struct buffer_head), 0,
2999 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3000 SLAB_MEM_SPREAD),
3001 init_buffer_head,
3002 NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003003
3004 /*
3005 * Limit the bh occupancy to 10% of ZONE_NORMAL
3006 */
3007 nrpages = (nr_free_buffer_pages() * 10) / 100;
3008 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3009 hotcpu_notifier(buffer_cpu_notify, 0);
3010}
3011
3012EXPORT_SYMBOL(__bforget);
3013EXPORT_SYMBOL(__brelse);
3014EXPORT_SYMBOL(__wait_on_buffer);
3015EXPORT_SYMBOL(block_commit_write);
3016EXPORT_SYMBOL(block_prepare_write);
3017EXPORT_SYMBOL(block_read_full_page);
3018EXPORT_SYMBOL(block_sync_page);
3019EXPORT_SYMBOL(block_truncate_page);
3020EXPORT_SYMBOL(block_write_full_page);
3021EXPORT_SYMBOL(cont_prepare_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003022EXPORT_SYMBOL(end_buffer_read_sync);
3023EXPORT_SYMBOL(end_buffer_write_sync);
3024EXPORT_SYMBOL(file_fsync);
3025EXPORT_SYMBOL(fsync_bdev);
3026EXPORT_SYMBOL(generic_block_bmap);
3027EXPORT_SYMBOL(generic_commit_write);
3028EXPORT_SYMBOL(generic_cont_expand);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08003029EXPORT_SYMBOL(generic_cont_expand_simple);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003030EXPORT_SYMBOL(init_buffer);
3031EXPORT_SYMBOL(invalidate_bdev);
3032EXPORT_SYMBOL(ll_rw_block);
3033EXPORT_SYMBOL(mark_buffer_dirty);
3034EXPORT_SYMBOL(submit_bh);
3035EXPORT_SYMBOL(sync_dirty_buffer);
3036EXPORT_SYMBOL(unlock_buffer);