blob: f65ef8821c7364a718b64948166340a2fc418bdd [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>
38#include <linux/bio.h>
39#include <linux/notifier.h>
40#include <linux/cpu.h>
41#include <linux/bitops.h>
42#include <linux/mpage.h>
Ingo Molnarfb1c8f92005-09-10 00:25:56 -070043#include <linux/bit_spinlock.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070044
45static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
46static void invalidate_bh_lrus(void);
47
48#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
49
50inline void
51init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
52{
53 bh->b_end_io = handler;
54 bh->b_private = private;
55}
56
57static int sync_buffer(void *word)
58{
59 struct block_device *bd;
60 struct buffer_head *bh
61 = container_of(word, struct buffer_head, b_state);
62
63 smp_mb();
64 bd = bh->b_bdev;
65 if (bd)
66 blk_run_address_space(bd->bd_inode->i_mapping);
67 io_schedule();
68 return 0;
69}
70
71void fastcall __lock_buffer(struct buffer_head *bh)
72{
73 wait_on_bit_lock(&bh->b_state, BH_Lock, sync_buffer,
74 TASK_UNINTERRUPTIBLE);
75}
76EXPORT_SYMBOL(__lock_buffer);
77
78void fastcall unlock_buffer(struct buffer_head *bh)
79{
80 clear_buffer_locked(bh);
81 smp_mb__after_clear_bit();
82 wake_up_bit(&bh->b_state, BH_Lock);
83}
84
85/*
86 * Block until a buffer comes unlocked. This doesn't stop it
87 * from becoming locked again - you have to lock it yourself
88 * if you want to preserve its state.
89 */
90void __wait_on_buffer(struct buffer_head * bh)
91{
92 wait_on_bit(&bh->b_state, BH_Lock, sync_buffer, TASK_UNINTERRUPTIBLE);
93}
94
95static void
96__clear_page_buffers(struct page *page)
97{
98 ClearPagePrivate(page);
Hugh Dickins4c21e2f2005-10-29 18:16:40 -070099 set_page_private(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700100 page_cache_release(page);
101}
102
103static void buffer_io_error(struct buffer_head *bh)
104{
105 char b[BDEVNAME_SIZE];
106
107 printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
108 bdevname(bh->b_bdev, b),
109 (unsigned long long)bh->b_blocknr);
110}
111
112/*
113 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
114 * unlock the buffer. This is what ll_rw_block uses too.
115 */
116void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
117{
118 if (uptodate) {
119 set_buffer_uptodate(bh);
120 } else {
121 /* This happens, due to failed READA attempts. */
122 clear_buffer_uptodate(bh);
123 }
124 unlock_buffer(bh);
125 put_bh(bh);
126}
127
128void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
129{
130 char b[BDEVNAME_SIZE];
131
132 if (uptodate) {
133 set_buffer_uptodate(bh);
134 } else {
135 if (!buffer_eopnotsupp(bh) && printk_ratelimit()) {
136 buffer_io_error(bh);
137 printk(KERN_WARNING "lost page write due to "
138 "I/O error on %s\n",
139 bdevname(bh->b_bdev, b));
140 }
141 set_buffer_write_io_error(bh);
142 clear_buffer_uptodate(bh);
143 }
144 unlock_buffer(bh);
145 put_bh(bh);
146}
147
148/*
149 * Write out and wait upon all the dirty data associated with a block
150 * device via its mapping. Does not take the superblock lock.
151 */
152int sync_blockdev(struct block_device *bdev)
153{
154 int ret = 0;
155
OGAWA Hirofumi28fd1292006-01-08 01:02:14 -0800156 if (bdev)
157 ret = filemap_write_and_wait(bdev->bd_inode->i_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700158 return ret;
159}
160EXPORT_SYMBOL(sync_blockdev);
161
Linus Torvalds1da177e2005-04-16 15:20:36 -0700162/*
163 * Write out and wait upon all dirty data associated with this
164 * device. Filesystem data as well as the underlying block
165 * device. Takes the superblock lock.
166 */
167int fsync_bdev(struct block_device *bdev)
168{
169 struct super_block *sb = get_super(bdev);
170 if (sb) {
171 int res = fsync_super(sb);
172 drop_super(sb);
173 return res;
174 }
175 return sync_blockdev(bdev);
176}
177
178/**
179 * freeze_bdev -- lock a filesystem and force it into a consistent state
180 * @bdev: blockdevice to lock
181 *
Arjan van de Venc039e312006-03-23 03:00:28 -0800182 * This takes the block device bd_mount_mutex to make sure no new mounts
Linus Torvalds1da177e2005-04-16 15:20:36 -0700183 * happen on bdev until thaw_bdev() is called.
184 * If a superblock is found on this device, we take the s_umount semaphore
185 * on it to make sure nobody unmounts until the snapshot creation is done.
186 */
187struct super_block *freeze_bdev(struct block_device *bdev)
188{
189 struct super_block *sb;
190
Arjan van de Venc039e312006-03-23 03:00:28 -0800191 mutex_lock(&bdev->bd_mount_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700192 sb = get_super(bdev);
193 if (sb && !(sb->s_flags & MS_RDONLY)) {
194 sb->s_frozen = SB_FREEZE_WRITE;
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700195 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700196
OGAWA Hirofumid25b9a12006-03-25 03:07:44 -0800197 __fsync_super(sb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700198
199 sb->s_frozen = SB_FREEZE_TRANS;
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700200 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700201
202 sync_blockdev(sb->s_bdev);
203
204 if (sb->s_op->write_super_lockfs)
205 sb->s_op->write_super_lockfs(sb);
206 }
207
208 sync_blockdev(bdev);
209 return sb; /* thaw_bdev releases s->s_umount and bd_mount_sem */
210}
211EXPORT_SYMBOL(freeze_bdev);
212
213/**
214 * thaw_bdev -- unlock filesystem
215 * @bdev: blockdevice to unlock
216 * @sb: associated superblock
217 *
218 * Unlocks the filesystem and marks it writeable again after freeze_bdev().
219 */
220void thaw_bdev(struct block_device *bdev, struct super_block *sb)
221{
222 if (sb) {
223 BUG_ON(sb->s_bdev != bdev);
224
225 if (sb->s_op->unlockfs)
226 sb->s_op->unlockfs(sb);
227 sb->s_frozen = SB_UNFROZEN;
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700228 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700229 wake_up(&sb->s_wait_unfrozen);
230 drop_super(sb);
231 }
232
Arjan van de Venc039e312006-03-23 03:00:28 -0800233 mutex_unlock(&bdev->bd_mount_mutex);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700234}
235EXPORT_SYMBOL(thaw_bdev);
236
237/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700238 * Various filesystems appear to want __find_get_block to be non-blocking.
239 * But it's the page lock which protects the buffers. To get around this,
240 * we get exclusion from try_to_free_buffers with the blockdev mapping's
241 * private_lock.
242 *
243 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
244 * may be quite high. This code could TryLock the page, and if that
245 * succeeds, there is no need to take private_lock. (But if
246 * private_lock is contended then so is mapping->tree_lock).
247 */
248static struct buffer_head *
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -0800249__find_get_block_slow(struct block_device *bdev, sector_t block)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700250{
251 struct inode *bd_inode = bdev->bd_inode;
252 struct address_space *bd_mapping = bd_inode->i_mapping;
253 struct buffer_head *ret = NULL;
254 pgoff_t index;
255 struct buffer_head *bh;
256 struct buffer_head *head;
257 struct page *page;
258 int all_mapped = 1;
259
260 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
261 page = find_get_page(bd_mapping, index);
262 if (!page)
263 goto out;
264
265 spin_lock(&bd_mapping->private_lock);
266 if (!page_has_buffers(page))
267 goto out_unlock;
268 head = page_buffers(page);
269 bh = head;
270 do {
271 if (bh->b_blocknr == block) {
272 ret = bh;
273 get_bh(bh);
274 goto out_unlock;
275 }
276 if (!buffer_mapped(bh))
277 all_mapped = 0;
278 bh = bh->b_this_page;
279 } while (bh != head);
280
281 /* we might be here because some of the buffers on this page are
282 * not mapped. This is due to various races between
283 * file io on the block device and getblk. It gets dealt with
284 * elsewhere, don't buffer_error if we had some unmapped buffers
285 */
286 if (all_mapped) {
287 printk("__find_get_block_slow() failed. "
288 "block=%llu, b_blocknr=%llu\n",
Badari Pulavarty205f87f2006-03-26 01:38:00 -0800289 (unsigned long long)block,
290 (unsigned long long)bh->b_blocknr);
291 printk("b_state=0x%08lx, b_size=%zu\n",
292 bh->b_state, bh->b_size);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700293 printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits);
294 }
295out_unlock:
296 spin_unlock(&bd_mapping->private_lock);
297 page_cache_release(page);
298out:
299 return ret;
300}
301
302/* If invalidate_buffers() will trash dirty buffers, it means some kind
303 of fs corruption is going on. Trashing dirty data always imply losing
304 information that was supposed to be just stored on the physical layer
305 by the user.
306
307 Thus invalidate_buffers in general usage is not allwowed to trash
308 dirty buffers. For example ioctl(FLSBLKBUF) expects dirty data to
309 be preserved. These buffers are simply skipped.
310
311 We also skip buffers which are still in use. For example this can
312 happen if a userspace program is reading the block device.
313
314 NOTE: In the case where the user removed a removable-media-disk even if
315 there's still dirty data not synced on disk (due a bug in the device driver
316 or due an error of the user), by not destroying the dirty buffers we could
317 generate corruption also on the next media inserted, thus a parameter is
318 necessary to handle this case in the most safe way possible (trying
319 to not corrupt also the new disk inserted with the data belonging to
320 the old now corrupted disk). Also for the ramdisk the natural thing
321 to do in order to release the ramdisk memory is to destroy dirty buffers.
322
323 These are two special cases. Normal usage imply the device driver
324 to issue a sync on the device (without waiting I/O completion) and
325 then an invalidate_buffers call that doesn't trash dirty buffers.
326
327 For handling cache coherency with the blkdev pagecache the 'update' case
328 is been introduced. It is needed to re-read from disk any pinned
329 buffer. NOTE: re-reading from disk is destructive so we can do it only
330 when we assume nobody is changing the buffercache under our I/O and when
331 we think the disk contains more recent information than the buffercache.
332 The update == 1 pass marks the buffers we need to update, the update == 2
333 pass does the actual I/O. */
334void invalidate_bdev(struct block_device *bdev, int destroy_dirty_buffers)
335{
Andrew Morton0e1dfc62006-07-30 03:03:28 -0700336 struct address_space *mapping = bdev->bd_inode->i_mapping;
337
338 if (mapping->nrpages == 0)
339 return;
340
Linus Torvalds1da177e2005-04-16 15:20:36 -0700341 invalidate_bh_lrus();
342 /*
343 * FIXME: what about destroy_dirty_buffers?
344 * We really want to use invalidate_inode_pages2() for
345 * that, but not until that's cleaned up.
346 */
Andrew Morton0e1dfc62006-07-30 03:03:28 -0700347 invalidate_inode_pages(mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700348}
349
350/*
351 * Kick pdflush then try to free up some ZONE_NORMAL memory.
352 */
353static void free_more_memory(void)
354{
355 struct zone **zones;
356 pg_data_t *pgdat;
357
Pekka J Enberg687a21c2005-06-28 20:44:55 -0700358 wakeup_pdflush(1024);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700359 yield();
360
KAMEZAWA Hiroyukiec936fc2006-03-27 01:15:59 -0800361 for_each_online_pgdat(pgdat) {
Al Viroaf4ca452005-10-21 02:55:38 -0400362 zones = pgdat->node_zonelists[gfp_zone(GFP_NOFS)].zones;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700363 if (*zones)
Darren Hart1ad539b2005-06-21 17:14:53 -0700364 try_to_free_pages(zones, GFP_NOFS);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700365 }
366}
367
368/*
369 * I/O completion handler for block_read_full_page() - pages
370 * which come unlocked at the end of I/O.
371 */
372static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
373{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700374 unsigned long flags;
Nick Piggina3972202005-07-07 17:56:56 -0700375 struct buffer_head *first;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700376 struct buffer_head *tmp;
377 struct page *page;
378 int page_uptodate = 1;
379
380 BUG_ON(!buffer_async_read(bh));
381
382 page = bh->b_page;
383 if (uptodate) {
384 set_buffer_uptodate(bh);
385 } else {
386 clear_buffer_uptodate(bh);
387 if (printk_ratelimit())
388 buffer_io_error(bh);
389 SetPageError(page);
390 }
391
392 /*
393 * Be _very_ careful from here on. Bad things can happen if
394 * two buffer heads end IO at almost the same time and both
395 * decide that the page is now completely done.
396 */
Nick Piggina3972202005-07-07 17:56:56 -0700397 first = page_buffers(page);
398 local_irq_save(flags);
399 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700400 clear_buffer_async_read(bh);
401 unlock_buffer(bh);
402 tmp = bh;
403 do {
404 if (!buffer_uptodate(tmp))
405 page_uptodate = 0;
406 if (buffer_async_read(tmp)) {
407 BUG_ON(!buffer_locked(tmp));
408 goto still_busy;
409 }
410 tmp = tmp->b_this_page;
411 } while (tmp != bh);
Nick Piggina3972202005-07-07 17:56:56 -0700412 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
413 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700414
415 /*
416 * If none of the buffers had errors and they are all
417 * uptodate then we can set the page uptodate.
418 */
419 if (page_uptodate && !PageError(page))
420 SetPageUptodate(page);
421 unlock_page(page);
422 return;
423
424still_busy:
Nick Piggina3972202005-07-07 17:56:56 -0700425 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
426 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700427 return;
428}
429
430/*
431 * Completion handler for block_write_full_page() - pages which are unlocked
432 * during I/O, and which have PageWriteback cleared upon I/O completion.
433 */
Adrian Bunkb6cd0b72006-06-27 02:53:54 -0700434static void end_buffer_async_write(struct buffer_head *bh, int uptodate)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700435{
436 char b[BDEVNAME_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700437 unsigned long flags;
Nick Piggina3972202005-07-07 17:56:56 -0700438 struct buffer_head *first;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700439 struct buffer_head *tmp;
440 struct page *page;
441
442 BUG_ON(!buffer_async_write(bh));
443
444 page = bh->b_page;
445 if (uptodate) {
446 set_buffer_uptodate(bh);
447 } else {
448 if (printk_ratelimit()) {
449 buffer_io_error(bh);
450 printk(KERN_WARNING "lost page write due to "
451 "I/O error on %s\n",
452 bdevname(bh->b_bdev, b));
453 }
454 set_bit(AS_EIO, &page->mapping->flags);
455 clear_buffer_uptodate(bh);
456 SetPageError(page);
457 }
458
Nick Piggina3972202005-07-07 17:56:56 -0700459 first = page_buffers(page);
460 local_irq_save(flags);
461 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
462
Linus Torvalds1da177e2005-04-16 15:20:36 -0700463 clear_buffer_async_write(bh);
464 unlock_buffer(bh);
465 tmp = bh->b_this_page;
466 while (tmp != bh) {
467 if (buffer_async_write(tmp)) {
468 BUG_ON(!buffer_locked(tmp));
469 goto still_busy;
470 }
471 tmp = tmp->b_this_page;
472 }
Nick Piggina3972202005-07-07 17:56:56 -0700473 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
474 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700475 end_page_writeback(page);
476 return;
477
478still_busy:
Nick Piggina3972202005-07-07 17:56:56 -0700479 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
480 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700481 return;
482}
483
484/*
485 * If a page's buffers are under async readin (end_buffer_async_read
486 * completion) then there is a possibility that another thread of
487 * control could lock one of the buffers after it has completed
488 * but while some of the other buffers have not completed. This
489 * locked buffer would confuse end_buffer_async_read() into not unlocking
490 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
491 * that this buffer is not under async I/O.
492 *
493 * The page comes unlocked when it has no locked buffer_async buffers
494 * left.
495 *
496 * PageLocked prevents anyone starting new async I/O reads any of
497 * the buffers.
498 *
499 * PageWriteback is used to prevent simultaneous writeout of the same
500 * page.
501 *
502 * PageLocked prevents anyone from starting writeback of a page which is
503 * under read I/O (PageWriteback is only ever set against a locked page).
504 */
505static void mark_buffer_async_read(struct buffer_head *bh)
506{
507 bh->b_end_io = end_buffer_async_read;
508 set_buffer_async_read(bh);
509}
510
511void mark_buffer_async_write(struct buffer_head *bh)
512{
513 bh->b_end_io = end_buffer_async_write;
514 set_buffer_async_write(bh);
515}
516EXPORT_SYMBOL(mark_buffer_async_write);
517
518
519/*
520 * fs/buffer.c contains helper functions for buffer-backed address space's
521 * fsync functions. A common requirement for buffer-based filesystems is
522 * that certain data from the backing blockdev needs to be written out for
523 * a successful fsync(). For example, ext2 indirect blocks need to be
524 * written back and waited upon before fsync() returns.
525 *
526 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
527 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
528 * management of a list of dependent buffers at ->i_mapping->private_list.
529 *
530 * Locking is a little subtle: try_to_free_buffers() will remove buffers
531 * from their controlling inode's queue when they are being freed. But
532 * try_to_free_buffers() will be operating against the *blockdev* mapping
533 * at the time, not against the S_ISREG file which depends on those buffers.
534 * So the locking for private_list is via the private_lock in the address_space
535 * which backs the buffers. Which is different from the address_space
536 * against which the buffers are listed. So for a particular address_space,
537 * mapping->private_lock does *not* protect mapping->private_list! In fact,
538 * mapping->private_list will always be protected by the backing blockdev's
539 * ->private_lock.
540 *
541 * Which introduces a requirement: all buffers on an address_space's
542 * ->private_list must be from the same address_space: the blockdev's.
543 *
544 * address_spaces which do not place buffers at ->private_list via these
545 * utility functions are free to use private_lock and private_list for
546 * whatever they want. The only requirement is that list_empty(private_list)
547 * be true at clear_inode() time.
548 *
549 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
550 * filesystems should do that. invalidate_inode_buffers() should just go
551 * BUG_ON(!list_empty).
552 *
553 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
554 * take an address_space, not an inode. And it should be called
555 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
556 * queued up.
557 *
558 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
559 * list if it is already on a list. Because if the buffer is on a list,
560 * it *must* already be on the right one. If not, the filesystem is being
561 * silly. This will save a ton of locking. But first we have to ensure
562 * that buffers are taken *off* the old inode's list when they are freed
563 * (presumably in truncate). That requires careful auditing of all
564 * filesystems (do it inside bforget()). It could also be done by bringing
565 * b_inode back.
566 */
567
568/*
569 * The buffer's backing address_space's private_lock must be held
570 */
571static inline void __remove_assoc_queue(struct buffer_head *bh)
572{
573 list_del_init(&bh->b_assoc_buffers);
574}
575
576int inode_has_buffers(struct inode *inode)
577{
578 return !list_empty(&inode->i_data.private_list);
579}
580
581/*
582 * osync is designed to support O_SYNC io. It waits synchronously for
583 * all already-submitted IO to complete, but does not queue any new
584 * writes to the disk.
585 *
586 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
587 * you dirty the buffers, and then use osync_inode_buffers to wait for
588 * completion. Any other dirty buffers which are not yet queued for
589 * write will not be flushed to disk by the osync.
590 */
591static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
592{
593 struct buffer_head *bh;
594 struct list_head *p;
595 int err = 0;
596
597 spin_lock(lock);
598repeat:
599 list_for_each_prev(p, list) {
600 bh = BH_ENTRY(p);
601 if (buffer_locked(bh)) {
602 get_bh(bh);
603 spin_unlock(lock);
604 wait_on_buffer(bh);
605 if (!buffer_uptodate(bh))
606 err = -EIO;
607 brelse(bh);
608 spin_lock(lock);
609 goto repeat;
610 }
611 }
612 spin_unlock(lock);
613 return err;
614}
615
616/**
617 * sync_mapping_buffers - write out and wait upon a mapping's "associated"
618 * buffers
Martin Waitz67be2dd2005-05-01 08:59:26 -0700619 * @mapping: the mapping which wants those buffers written
Linus Torvalds1da177e2005-04-16 15:20:36 -0700620 *
621 * Starts I/O against the buffers at mapping->private_list, and waits upon
622 * that I/O.
623 *
Martin Waitz67be2dd2005-05-01 08:59:26 -0700624 * Basically, this is a convenience function for fsync().
625 * @mapping is a file or directory which needs those buffers to be written for
626 * a successful fsync().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700627 */
628int sync_mapping_buffers(struct address_space *mapping)
629{
630 struct address_space *buffer_mapping = mapping->assoc_mapping;
631
632 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
633 return 0;
634
635 return fsync_buffers_list(&buffer_mapping->private_lock,
636 &mapping->private_list);
637}
638EXPORT_SYMBOL(sync_mapping_buffers);
639
640/*
641 * Called when we've recently written block `bblock', and it is known that
642 * `bblock' was for a buffer_boundary() buffer. This means that the block at
643 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
644 * dirty, schedule it for IO. So that indirects merge nicely with their data.
645 */
646void write_boundary_block(struct block_device *bdev,
647 sector_t bblock, unsigned blocksize)
648{
649 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
650 if (bh) {
651 if (buffer_dirty(bh))
652 ll_rw_block(WRITE, 1, &bh);
653 put_bh(bh);
654 }
655}
656
657void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
658{
659 struct address_space *mapping = inode->i_mapping;
660 struct address_space *buffer_mapping = bh->b_page->mapping;
661
662 mark_buffer_dirty(bh);
663 if (!mapping->assoc_mapping) {
664 mapping->assoc_mapping = buffer_mapping;
665 } else {
Eric Sesterhenne827f922006-03-26 18:24:46 +0200666 BUG_ON(mapping->assoc_mapping != buffer_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700667 }
668 if (list_empty(&bh->b_assoc_buffers)) {
669 spin_lock(&buffer_mapping->private_lock);
670 list_move_tail(&bh->b_assoc_buffers,
671 &mapping->private_list);
672 spin_unlock(&buffer_mapping->private_lock);
673 }
674}
675EXPORT_SYMBOL(mark_buffer_dirty_inode);
676
677/*
678 * Add a page to the dirty page list.
679 *
680 * It is a sad fact of life that this function is called from several places
681 * deeply under spinlocking. It may not sleep.
682 *
683 * If the page has buffers, the uptodate buffers are set dirty, to preserve
684 * dirty-state coherency between the page and the buffers. It the page does
685 * not have buffers then when they are later attached they will all be set
686 * dirty.
687 *
688 * The buffers are dirtied before the page is dirtied. There's a small race
689 * window in which a writepage caller may see the page cleanness but not the
690 * buffer dirtiness. That's fine. If this code were to set the page dirty
691 * before the buffers, a concurrent writepage caller could clear the page dirty
692 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
693 * page on the dirty page list.
694 *
695 * We use private_lock to lock against try_to_free_buffers while using the
696 * page's buffer list. Also use this to protect against clean buffers being
697 * added to the page after it was set dirty.
698 *
699 * FIXME: may need to call ->reservepage here as well. That's rather up to the
700 * address_space though.
701 */
702int __set_page_dirty_buffers(struct page *page)
703{
Nick Pigginebf7a222006-10-10 04:36:54 +0200704 struct address_space * const mapping = page_mapping(page);
705
706 if (unlikely(!mapping))
707 return !TestSetPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700708
709 spin_lock(&mapping->private_lock);
710 if (page_has_buffers(page)) {
711 struct buffer_head *head = page_buffers(page);
712 struct buffer_head *bh = head;
713
714 do {
715 set_buffer_dirty(bh);
716 bh = bh->b_this_page;
717 } while (bh != head);
718 }
719 spin_unlock(&mapping->private_lock);
720
721 if (!TestSetPageDirty(page)) {
722 write_lock_irq(&mapping->tree_lock);
723 if (page->mapping) { /* Race with truncate? */
724 if (mapping_cap_account_dirty(mapping))
Christoph Lameterb1e7a8f2006-06-30 01:55:39 -0700725 __inc_zone_page_state(page, NR_FILE_DIRTY);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700726 radix_tree_tag_set(&mapping->page_tree,
727 page_index(page),
728 PAGECACHE_TAG_DIRTY);
729 }
730 write_unlock_irq(&mapping->tree_lock);
731 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
Andrew Morton4741c9f2006-03-24 03:18:11 -0800732 return 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700733 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700734 return 0;
735}
736EXPORT_SYMBOL(__set_page_dirty_buffers);
737
738/*
739 * Write out and wait upon a list of buffers.
740 *
741 * We have conflicting pressures: we want to make sure that all
742 * initially dirty buffers get waited on, but that any subsequently
743 * dirtied buffers don't. After all, we don't want fsync to last
744 * forever if somebody is actively writing to the file.
745 *
746 * Do this in two main stages: first we copy dirty buffers to a
747 * temporary inode list, queueing the writes as we go. Then we clean
748 * up, waiting for those writes to complete.
749 *
750 * During this second stage, any subsequent updates to the file may end
751 * up refiling the buffer on the original inode's dirty list again, so
752 * there is a chance we will end up with a buffer queued for write but
753 * not yet completed on that list. So, as a final cleanup we go through
754 * the osync code to catch these locked, dirty buffers without requeuing
755 * any newly dirty buffers for write.
756 */
757static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
758{
759 struct buffer_head *bh;
760 struct list_head tmp;
761 int err = 0, err2;
762
763 INIT_LIST_HEAD(&tmp);
764
765 spin_lock(lock);
766 while (!list_empty(list)) {
767 bh = BH_ENTRY(list->next);
768 list_del_init(&bh->b_assoc_buffers);
769 if (buffer_dirty(bh) || buffer_locked(bh)) {
770 list_add(&bh->b_assoc_buffers, &tmp);
771 if (buffer_dirty(bh)) {
772 get_bh(bh);
773 spin_unlock(lock);
774 /*
775 * Ensure any pending I/O completes so that
776 * ll_rw_block() actually writes the current
777 * contents - it is a noop if I/O is still in
778 * flight on potentially older contents.
779 */
Jan Karaa7662232005-09-06 15:19:10 -0700780 ll_rw_block(SWRITE, 1, &bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700781 brelse(bh);
782 spin_lock(lock);
783 }
784 }
785 }
786
787 while (!list_empty(&tmp)) {
788 bh = BH_ENTRY(tmp.prev);
789 __remove_assoc_queue(bh);
790 get_bh(bh);
791 spin_unlock(lock);
792 wait_on_buffer(bh);
793 if (!buffer_uptodate(bh))
794 err = -EIO;
795 brelse(bh);
796 spin_lock(lock);
797 }
798
799 spin_unlock(lock);
800 err2 = osync_buffers_list(lock, list);
801 if (err)
802 return err;
803 else
804 return err2;
805}
806
807/*
808 * Invalidate any and all dirty buffers on a given inode. We are
809 * probably unmounting the fs, but that doesn't mean we have already
810 * done a sync(). Just drop the buffers from the inode list.
811 *
812 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
813 * assumes that all the buffers are against the blockdev. Not true
814 * for reiserfs.
815 */
816void invalidate_inode_buffers(struct inode *inode)
817{
818 if (inode_has_buffers(inode)) {
819 struct address_space *mapping = &inode->i_data;
820 struct list_head *list = &mapping->private_list;
821 struct address_space *buffer_mapping = mapping->assoc_mapping;
822
823 spin_lock(&buffer_mapping->private_lock);
824 while (!list_empty(list))
825 __remove_assoc_queue(BH_ENTRY(list->next));
826 spin_unlock(&buffer_mapping->private_lock);
827 }
828}
829
830/*
831 * Remove any clean buffers from the inode's buffer list. This is called
832 * when we're trying to free the inode itself. Those buffers can pin it.
833 *
834 * Returns true if all buffers were removed.
835 */
836int remove_inode_buffers(struct inode *inode)
837{
838 int ret = 1;
839
840 if (inode_has_buffers(inode)) {
841 struct address_space *mapping = &inode->i_data;
842 struct list_head *list = &mapping->private_list;
843 struct address_space *buffer_mapping = mapping->assoc_mapping;
844
845 spin_lock(&buffer_mapping->private_lock);
846 while (!list_empty(list)) {
847 struct buffer_head *bh = BH_ENTRY(list->next);
848 if (buffer_dirty(bh)) {
849 ret = 0;
850 break;
851 }
852 __remove_assoc_queue(bh);
853 }
854 spin_unlock(&buffer_mapping->private_lock);
855 }
856 return ret;
857}
858
859/*
860 * Create the appropriate buffers when given a page for data area and
861 * the size of each buffer.. Use the bh->b_this_page linked list to
862 * follow the buffers created. Return NULL if unable to create more
863 * buffers.
864 *
865 * The retry flag is used to differentiate async IO (paging, swapping)
866 * which may not fail from ordinary buffer allocations.
867 */
868struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
869 int retry)
870{
871 struct buffer_head *bh, *head;
872 long offset;
873
874try_again:
875 head = NULL;
876 offset = PAGE_SIZE;
877 while ((offset -= size) >= 0) {
878 bh = alloc_buffer_head(GFP_NOFS);
879 if (!bh)
880 goto no_grow;
881
882 bh->b_bdev = NULL;
883 bh->b_this_page = head;
884 bh->b_blocknr = -1;
885 head = bh;
886
887 bh->b_state = 0;
888 atomic_set(&bh->b_count, 0);
Chris Masonfc5cd582006-02-01 03:06:48 -0800889 bh->b_private = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700890 bh->b_size = size;
891
892 /* Link the buffer to its page */
893 set_bh_page(bh, page, offset);
894
Nathan Scott01ffe332006-01-17 09:02:07 +1100895 init_buffer(bh, NULL, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700896 }
897 return head;
898/*
899 * In case anything failed, we just free everything we got.
900 */
901no_grow:
902 if (head) {
903 do {
904 bh = head;
905 head = head->b_this_page;
906 free_buffer_head(bh);
907 } while (head);
908 }
909
910 /*
911 * Return failure for non-async IO requests. Async IO requests
912 * are not allowed to fail, so we have to wait until buffer heads
913 * become available. But we don't want tasks sleeping with
914 * partially complete buffers, so all were released above.
915 */
916 if (!retry)
917 return NULL;
918
919 /* We're _really_ low on memory. Now we just
920 * wait for old buffer heads to become free due to
921 * finishing IO. Since this is an async request and
922 * the reserve list is empty, we're sure there are
923 * async buffer heads in use.
924 */
925 free_more_memory();
926 goto try_again;
927}
928EXPORT_SYMBOL_GPL(alloc_page_buffers);
929
930static inline void
931link_dev_buffers(struct page *page, struct buffer_head *head)
932{
933 struct buffer_head *bh, *tail;
934
935 bh = head;
936 do {
937 tail = bh;
938 bh = bh->b_this_page;
939 } while (bh);
940 tail->b_this_page = head;
941 attach_page_buffers(page, head);
942}
943
944/*
945 * Initialise the state of a blockdev page's buffers.
946 */
947static void
948init_page_buffers(struct page *page, struct block_device *bdev,
949 sector_t block, int size)
950{
951 struct buffer_head *head = page_buffers(page);
952 struct buffer_head *bh = head;
953 int uptodate = PageUptodate(page);
954
955 do {
956 if (!buffer_mapped(bh)) {
957 init_buffer(bh, NULL, NULL);
958 bh->b_bdev = bdev;
959 bh->b_blocknr = block;
960 if (uptodate)
961 set_buffer_uptodate(bh);
962 set_buffer_mapped(bh);
963 }
964 block++;
965 bh = bh->b_this_page;
966 } while (bh != head);
967}
968
969/*
970 * Create the page-cache page that contains the requested block.
971 *
972 * This is user purely for blockdev mappings.
973 */
974static struct page *
975grow_dev_page(struct block_device *bdev, sector_t block,
976 pgoff_t index, int size)
977{
978 struct inode *inode = bdev->bd_inode;
979 struct page *page;
980 struct buffer_head *bh;
981
982 page = find_or_create_page(inode->i_mapping, index, GFP_NOFS);
983 if (!page)
984 return NULL;
985
Eric Sesterhenne827f922006-03-26 18:24:46 +0200986 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700987
988 if (page_has_buffers(page)) {
989 bh = page_buffers(page);
990 if (bh->b_size == size) {
991 init_page_buffers(page, bdev, block, size);
992 return page;
993 }
994 if (!try_to_free_buffers(page))
995 goto failed;
996 }
997
998 /*
999 * Allocate some buffers for this page
1000 */
1001 bh = alloc_page_buffers(page, size, 0);
1002 if (!bh)
1003 goto failed;
1004
1005 /*
1006 * Link the page to the buffers and initialise them. Take the
1007 * lock to be atomic wrt __find_get_block(), which does not
1008 * run under the page lock.
1009 */
1010 spin_lock(&inode->i_mapping->private_lock);
1011 link_dev_buffers(page, bh);
1012 init_page_buffers(page, bdev, block, size);
1013 spin_unlock(&inode->i_mapping->private_lock);
1014 return page;
1015
1016failed:
1017 BUG();
1018 unlock_page(page);
1019 page_cache_release(page);
1020 return NULL;
1021}
1022
1023/*
1024 * Create buffers for the specified block device block's page. If
1025 * that page was dirty, the buffers are set dirty also.
1026 *
1027 * Except that's a bug. Attaching dirty buffers to a dirty
1028 * blockdev's page can result in filesystem corruption, because
1029 * some of those buffers may be aliases of filesystem data.
1030 * grow_dev_page() will go BUG() if this happens.
1031 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001032static int
Linus Torvalds1da177e2005-04-16 15:20:36 -07001033grow_buffers(struct block_device *bdev, sector_t block, int size)
1034{
1035 struct page *page;
1036 pgoff_t index;
1037 int sizebits;
1038
1039 sizebits = -1;
1040 do {
1041 sizebits++;
1042 } while ((size << sizebits) < PAGE_SIZE);
1043
1044 index = block >> sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001045
Andrew Mortone5657932006-10-11 01:21:46 -07001046 /*
1047 * Check for a block which wants to lie outside our maximum possible
1048 * pagecache index. (this comparison is done using sector_t types).
1049 */
1050 if (unlikely(index != block >> sizebits)) {
1051 char b[BDEVNAME_SIZE];
1052
1053 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1054 "device %s\n",
1055 __FUNCTION__, (unsigned long long)block,
1056 bdevname(bdev, b));
1057 return -EIO;
1058 }
1059 block = index << sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001060 /* Create a page with the proper size buffers.. */
1061 page = grow_dev_page(bdev, block, index, size);
1062 if (!page)
1063 return 0;
1064 unlock_page(page);
1065 page_cache_release(page);
1066 return 1;
1067}
1068
Adrian Bunk75c96f82005-05-05 16:16:09 -07001069static struct buffer_head *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001070__getblk_slow(struct block_device *bdev, sector_t block, int size)
1071{
1072 /* Size must be multiple of hard sectorsize */
1073 if (unlikely(size & (bdev_hardsect_size(bdev)-1) ||
1074 (size < 512 || size > PAGE_SIZE))) {
1075 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1076 size);
1077 printk(KERN_ERR "hardsect size: %d\n",
1078 bdev_hardsect_size(bdev));
1079
1080 dump_stack();
1081 return NULL;
1082 }
1083
1084 for (;;) {
1085 struct buffer_head * bh;
Andrew Mortone5657932006-10-11 01:21:46 -07001086 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001087
1088 bh = __find_get_block(bdev, block, size);
1089 if (bh)
1090 return bh;
1091
Andrew Mortone5657932006-10-11 01:21:46 -07001092 ret = grow_buffers(bdev, block, size);
1093 if (ret < 0)
1094 return NULL;
1095 if (ret == 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001096 free_more_memory();
1097 }
1098}
1099
1100/*
1101 * The relationship between dirty buffers and dirty pages:
1102 *
1103 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1104 * the page is tagged dirty in its radix tree.
1105 *
1106 * At all times, the dirtiness of the buffers represents the dirtiness of
1107 * subsections of the page. If the page has buffers, the page dirty bit is
1108 * merely a hint about the true dirty state.
1109 *
1110 * When a page is set dirty in its entirety, all its buffers are marked dirty
1111 * (if the page has buffers).
1112 *
1113 * When a buffer is marked dirty, its page is dirtied, but the page's other
1114 * buffers are not.
1115 *
1116 * Also. When blockdev buffers are explicitly read with bread(), they
1117 * individually become uptodate. But their backing page remains not
1118 * uptodate - even if all of its buffers are uptodate. A subsequent
1119 * block_read_full_page() against that page will discover all the uptodate
1120 * buffers, will set the page uptodate and will perform no I/O.
1121 */
1122
1123/**
1124 * mark_buffer_dirty - mark a buffer_head as needing writeout
Martin Waitz67be2dd2005-05-01 08:59:26 -07001125 * @bh: the buffer_head to mark dirty
Linus Torvalds1da177e2005-04-16 15:20:36 -07001126 *
1127 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1128 * backing page dirty, then tag the page as dirty in its address_space's radix
1129 * tree and then attach the address_space's inode to its superblock's dirty
1130 * inode list.
1131 *
1132 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1133 * mapping->tree_lock and the global inode_lock.
1134 */
1135void fastcall mark_buffer_dirty(struct buffer_head *bh)
1136{
1137 if (!buffer_dirty(bh) && !test_set_buffer_dirty(bh))
1138 __set_page_dirty_nobuffers(bh->b_page);
1139}
1140
1141/*
1142 * Decrement a buffer_head's reference count. If all buffers against a page
1143 * have zero reference count, are clean and unlocked, and if the page is clean
1144 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1145 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1146 * a page but it ends up not being freed, and buffers may later be reattached).
1147 */
1148void __brelse(struct buffer_head * buf)
1149{
1150 if (atomic_read(&buf->b_count)) {
1151 put_bh(buf);
1152 return;
1153 }
1154 printk(KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1155 WARN_ON(1);
1156}
1157
1158/*
1159 * bforget() is like brelse(), except it discards any
1160 * potentially dirty data.
1161 */
1162void __bforget(struct buffer_head *bh)
1163{
1164 clear_buffer_dirty(bh);
1165 if (!list_empty(&bh->b_assoc_buffers)) {
1166 struct address_space *buffer_mapping = bh->b_page->mapping;
1167
1168 spin_lock(&buffer_mapping->private_lock);
1169 list_del_init(&bh->b_assoc_buffers);
1170 spin_unlock(&buffer_mapping->private_lock);
1171 }
1172 __brelse(bh);
1173}
1174
1175static struct buffer_head *__bread_slow(struct buffer_head *bh)
1176{
1177 lock_buffer(bh);
1178 if (buffer_uptodate(bh)) {
1179 unlock_buffer(bh);
1180 return bh;
1181 } else {
1182 get_bh(bh);
1183 bh->b_end_io = end_buffer_read_sync;
1184 submit_bh(READ, bh);
1185 wait_on_buffer(bh);
1186 if (buffer_uptodate(bh))
1187 return bh;
1188 }
1189 brelse(bh);
1190 return NULL;
1191}
1192
1193/*
1194 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1195 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1196 * refcount elevated by one when they're in an LRU. A buffer can only appear
1197 * once in a particular CPU's LRU. A single buffer can be present in multiple
1198 * CPU's LRUs at the same time.
1199 *
1200 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1201 * sb_find_get_block().
1202 *
1203 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1204 * a local interrupt disable for that.
1205 */
1206
1207#define BH_LRU_SIZE 8
1208
1209struct bh_lru {
1210 struct buffer_head *bhs[BH_LRU_SIZE];
1211};
1212
1213static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1214
1215#ifdef CONFIG_SMP
1216#define bh_lru_lock() local_irq_disable()
1217#define bh_lru_unlock() local_irq_enable()
1218#else
1219#define bh_lru_lock() preempt_disable()
1220#define bh_lru_unlock() preempt_enable()
1221#endif
1222
1223static inline void check_irqs_on(void)
1224{
1225#ifdef irqs_disabled
1226 BUG_ON(irqs_disabled());
1227#endif
1228}
1229
1230/*
1231 * The LRU management algorithm is dopey-but-simple. Sorry.
1232 */
1233static void bh_lru_install(struct buffer_head *bh)
1234{
1235 struct buffer_head *evictee = NULL;
1236 struct bh_lru *lru;
1237
1238 check_irqs_on();
1239 bh_lru_lock();
1240 lru = &__get_cpu_var(bh_lrus);
1241 if (lru->bhs[0] != bh) {
1242 struct buffer_head *bhs[BH_LRU_SIZE];
1243 int in;
1244 int out = 0;
1245
1246 get_bh(bh);
1247 bhs[out++] = bh;
1248 for (in = 0; in < BH_LRU_SIZE; in++) {
1249 struct buffer_head *bh2 = lru->bhs[in];
1250
1251 if (bh2 == bh) {
1252 __brelse(bh2);
1253 } else {
1254 if (out >= BH_LRU_SIZE) {
1255 BUG_ON(evictee != NULL);
1256 evictee = bh2;
1257 } else {
1258 bhs[out++] = bh2;
1259 }
1260 }
1261 }
1262 while (out < BH_LRU_SIZE)
1263 bhs[out++] = NULL;
1264 memcpy(lru->bhs, bhs, sizeof(bhs));
1265 }
1266 bh_lru_unlock();
1267
1268 if (evictee)
1269 __brelse(evictee);
1270}
1271
1272/*
1273 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1274 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001275static struct buffer_head *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001276lookup_bh_lru(struct block_device *bdev, sector_t block, int size)
1277{
1278 struct buffer_head *ret = NULL;
1279 struct bh_lru *lru;
1280 int i;
1281
1282 check_irqs_on();
1283 bh_lru_lock();
1284 lru = &__get_cpu_var(bh_lrus);
1285 for (i = 0; i < BH_LRU_SIZE; i++) {
1286 struct buffer_head *bh = lru->bhs[i];
1287
1288 if (bh && bh->b_bdev == bdev &&
1289 bh->b_blocknr == block && bh->b_size == size) {
1290 if (i) {
1291 while (i) {
1292 lru->bhs[i] = lru->bhs[i - 1];
1293 i--;
1294 }
1295 lru->bhs[0] = bh;
1296 }
1297 get_bh(bh);
1298 ret = bh;
1299 break;
1300 }
1301 }
1302 bh_lru_unlock();
1303 return ret;
1304}
1305
1306/*
1307 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1308 * it in the LRU and mark it as accessed. If it is not present then return
1309 * NULL
1310 */
1311struct buffer_head *
1312__find_get_block(struct block_device *bdev, sector_t block, int size)
1313{
1314 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1315
1316 if (bh == NULL) {
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001317 bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001318 if (bh)
1319 bh_lru_install(bh);
1320 }
1321 if (bh)
1322 touch_buffer(bh);
1323 return bh;
1324}
1325EXPORT_SYMBOL(__find_get_block);
1326
1327/*
1328 * __getblk will locate (and, if necessary, create) the buffer_head
1329 * which corresponds to the passed block_device, block and size. The
1330 * returned buffer has its reference count incremented.
1331 *
1332 * __getblk() cannot fail - it just keeps trying. If you pass it an
1333 * illegal block number, __getblk() will happily return a buffer_head
1334 * which represents the non-existent block. Very weird.
1335 *
1336 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1337 * attempt is failing. FIXME, perhaps?
1338 */
1339struct buffer_head *
1340__getblk(struct block_device *bdev, sector_t block, int size)
1341{
1342 struct buffer_head *bh = __find_get_block(bdev, block, size);
1343
1344 might_sleep();
1345 if (bh == NULL)
1346 bh = __getblk_slow(bdev, block, size);
1347 return bh;
1348}
1349EXPORT_SYMBOL(__getblk);
1350
1351/*
1352 * Do async read-ahead on a buffer..
1353 */
1354void __breadahead(struct block_device *bdev, sector_t block, int size)
1355{
1356 struct buffer_head *bh = __getblk(bdev, block, size);
Andrew Mortona3e713b2005-10-30 15:03:15 -08001357 if (likely(bh)) {
1358 ll_rw_block(READA, 1, &bh);
1359 brelse(bh);
1360 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001361}
1362EXPORT_SYMBOL(__breadahead);
1363
1364/**
1365 * __bread() - reads a specified block and returns the bh
Martin Waitz67be2dd2005-05-01 08:59:26 -07001366 * @bdev: the block_device to read from
Linus Torvalds1da177e2005-04-16 15:20:36 -07001367 * @block: number of block
1368 * @size: size (in bytes) to read
1369 *
1370 * Reads a specified block, and returns buffer head that contains it.
1371 * It returns NULL if the block was unreadable.
1372 */
1373struct buffer_head *
1374__bread(struct block_device *bdev, sector_t block, int size)
1375{
1376 struct buffer_head *bh = __getblk(bdev, block, size);
1377
Andrew Mortona3e713b2005-10-30 15:03:15 -08001378 if (likely(bh) && !buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001379 bh = __bread_slow(bh);
1380 return bh;
1381}
1382EXPORT_SYMBOL(__bread);
1383
1384/*
1385 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1386 * This doesn't race because it runs in each cpu either in irq
1387 * or with preempt disabled.
1388 */
1389static void invalidate_bh_lru(void *arg)
1390{
1391 struct bh_lru *b = &get_cpu_var(bh_lrus);
1392 int i;
1393
1394 for (i = 0; i < BH_LRU_SIZE; i++) {
1395 brelse(b->bhs[i]);
1396 b->bhs[i] = NULL;
1397 }
1398 put_cpu_var(bh_lrus);
1399}
1400
1401static void invalidate_bh_lrus(void)
1402{
1403 on_each_cpu(invalidate_bh_lru, NULL, 1, 1);
1404}
1405
1406void set_bh_page(struct buffer_head *bh,
1407 struct page *page, unsigned long offset)
1408{
1409 bh->b_page = page;
Eric Sesterhenne827f922006-03-26 18:24:46 +02001410 BUG_ON(offset >= PAGE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001411 if (PageHighMem(page))
1412 /*
1413 * This catches illegal uses and preserves the offset:
1414 */
1415 bh->b_data = (char *)(0 + offset);
1416 else
1417 bh->b_data = page_address(page) + offset;
1418}
1419EXPORT_SYMBOL(set_bh_page);
1420
1421/*
1422 * Called when truncating a buffer on a page completely.
1423 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001424static void discard_buffer(struct buffer_head * bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001425{
1426 lock_buffer(bh);
1427 clear_buffer_dirty(bh);
1428 bh->b_bdev = NULL;
1429 clear_buffer_mapped(bh);
1430 clear_buffer_req(bh);
1431 clear_buffer_new(bh);
1432 clear_buffer_delay(bh);
1433 unlock_buffer(bh);
1434}
1435
1436/**
Linus Torvalds1da177e2005-04-16 15:20:36 -07001437 * block_invalidatepage - invalidate part of all of a buffer-backed page
1438 *
1439 * @page: the page which is affected
1440 * @offset: the index of the truncation point
1441 *
1442 * block_invalidatepage() is called when all or part of the page has become
1443 * invalidatedby a truncate operation.
1444 *
1445 * block_invalidatepage() does not have to release all buffers, but it must
1446 * ensure that no dirty buffer is left outside @offset and that no I/O
1447 * is underway against any of the blocks which are outside the truncation
1448 * point. Because the caller is about to free (and possibly reuse) those
1449 * blocks on-disk.
1450 */
NeilBrown2ff28e22006-03-26 01:37:18 -08001451void block_invalidatepage(struct page *page, unsigned long offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001452{
1453 struct buffer_head *head, *bh, *next;
1454 unsigned int curr_off = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001455
1456 BUG_ON(!PageLocked(page));
1457 if (!page_has_buffers(page))
1458 goto out;
1459
1460 head = page_buffers(page);
1461 bh = head;
1462 do {
1463 unsigned int next_off = curr_off + bh->b_size;
1464 next = bh->b_this_page;
1465
1466 /*
1467 * is this block fully invalidated?
1468 */
1469 if (offset <= curr_off)
1470 discard_buffer(bh);
1471 curr_off = next_off;
1472 bh = next;
1473 } while (bh != head);
1474
1475 /*
1476 * We release buffers only if the entire page is being invalidated.
1477 * The get_block cached value has been unconditionally invalidated,
1478 * so real IO is not possible anymore.
1479 */
1480 if (offset == 0)
NeilBrown2ff28e22006-03-26 01:37:18 -08001481 try_to_release_page(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001482out:
NeilBrown2ff28e22006-03-26 01:37:18 -08001483 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001484}
1485EXPORT_SYMBOL(block_invalidatepage);
1486
1487/*
1488 * We attach and possibly dirty the buffers atomically wrt
1489 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1490 * is already excluded via the page lock.
1491 */
1492void create_empty_buffers(struct page *page,
1493 unsigned long blocksize, unsigned long b_state)
1494{
1495 struct buffer_head *bh, *head, *tail;
1496
1497 head = alloc_page_buffers(page, blocksize, 1);
1498 bh = head;
1499 do {
1500 bh->b_state |= b_state;
1501 tail = bh;
1502 bh = bh->b_this_page;
1503 } while (bh);
1504 tail->b_this_page = head;
1505
1506 spin_lock(&page->mapping->private_lock);
1507 if (PageUptodate(page) || PageDirty(page)) {
1508 bh = head;
1509 do {
1510 if (PageDirty(page))
1511 set_buffer_dirty(bh);
1512 if (PageUptodate(page))
1513 set_buffer_uptodate(bh);
1514 bh = bh->b_this_page;
1515 } while (bh != head);
1516 }
1517 attach_page_buffers(page, head);
1518 spin_unlock(&page->mapping->private_lock);
1519}
1520EXPORT_SYMBOL(create_empty_buffers);
1521
1522/*
1523 * We are taking a block for data and we don't want any output from any
1524 * buffer-cache aliases starting from return from that function and
1525 * until the moment when something will explicitly mark the buffer
1526 * dirty (hopefully that will not happen until we will free that block ;-)
1527 * We don't even need to mark it not-uptodate - nobody can expect
1528 * anything from a newly allocated buffer anyway. We used to used
1529 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1530 * don't want to mark the alias unmapped, for example - it would confuse
1531 * anyone who might pick it with bread() afterwards...
1532 *
1533 * Also.. Note that bforget() doesn't lock the buffer. So there can
1534 * be writeout I/O going on against recently-freed buffers. We don't
1535 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1536 * only if we really need to. That happens here.
1537 */
1538void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1539{
1540 struct buffer_head *old_bh;
1541
1542 might_sleep();
1543
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001544 old_bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001545 if (old_bh) {
1546 clear_buffer_dirty(old_bh);
1547 wait_on_buffer(old_bh);
1548 clear_buffer_req(old_bh);
1549 __brelse(old_bh);
1550 }
1551}
1552EXPORT_SYMBOL(unmap_underlying_metadata);
1553
1554/*
1555 * NOTE! All mapped/uptodate combinations are valid:
1556 *
1557 * Mapped Uptodate Meaning
1558 *
1559 * No No "unknown" - must do get_block()
1560 * No Yes "hole" - zero-filled
1561 * Yes No "allocated" - allocated on disk, not read in
1562 * Yes Yes "valid" - allocated and up-to-date in memory.
1563 *
1564 * "Dirty" is valid only with the last case (mapped+uptodate).
1565 */
1566
1567/*
1568 * While block_write_full_page is writing back the dirty buffers under
1569 * the page lock, whoever dirtied the buffers may decide to clean them
1570 * again at any time. We handle that by only looking at the buffer
1571 * state inside lock_buffer().
1572 *
1573 * If block_write_full_page() is called for regular writeback
1574 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1575 * locked buffer. This only can happen if someone has written the buffer
1576 * directly, with submit_bh(). At the address_space level PageWriteback
1577 * prevents this contention from occurring.
1578 */
1579static int __block_write_full_page(struct inode *inode, struct page *page,
1580 get_block_t *get_block, struct writeback_control *wbc)
1581{
1582 int err;
1583 sector_t block;
1584 sector_t last_block;
Andrew Mortonf0fbd5f2005-05-05 16:15:48 -07001585 struct buffer_head *bh, *head;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001586 const unsigned blocksize = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001587 int nr_underway = 0;
1588
1589 BUG_ON(!PageLocked(page));
1590
1591 last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
1592
1593 if (!page_has_buffers(page)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001594 create_empty_buffers(page, blocksize,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001595 (1 << BH_Dirty)|(1 << BH_Uptodate));
1596 }
1597
1598 /*
1599 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1600 * here, and the (potentially unmapped) buffers may become dirty at
1601 * any time. If a buffer becomes dirty here after we've inspected it
1602 * then we just miss that fact, and the page stays dirty.
1603 *
1604 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1605 * handle that here by just cleaning them.
1606 */
1607
Andrew Morton54b21a72006-01-08 01:03:05 -08001608 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001609 head = page_buffers(page);
1610 bh = head;
1611
1612 /*
1613 * Get all the dirty buffers mapped to disk addresses and
1614 * handle any aliases from the underlying blockdev's mapping.
1615 */
1616 do {
1617 if (block > last_block) {
1618 /*
1619 * mapped buffers outside i_size will occur, because
1620 * this page can be outside i_size when there is a
1621 * truncate in progress.
1622 */
1623 /*
1624 * The buffer was zeroed by block_write_full_page()
1625 */
1626 clear_buffer_dirty(bh);
1627 set_buffer_uptodate(bh);
1628 } else if (!buffer_mapped(bh) && buffer_dirty(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001629 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001630 err = get_block(inode, block, bh, 1);
1631 if (err)
1632 goto recover;
1633 if (buffer_new(bh)) {
1634 /* blockdev mappings never come here */
1635 clear_buffer_new(bh);
1636 unmap_underlying_metadata(bh->b_bdev,
1637 bh->b_blocknr);
1638 }
1639 }
1640 bh = bh->b_this_page;
1641 block++;
1642 } while (bh != head);
1643
1644 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001645 if (!buffer_mapped(bh))
1646 continue;
1647 /*
1648 * If it's a fully non-blocking write attempt and we cannot
1649 * lock the buffer then redirty the page. Note that this can
1650 * potentially cause a busy-wait loop from pdflush and kswapd
1651 * activity, but those code paths have their own higher-level
1652 * throttling.
1653 */
1654 if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
1655 lock_buffer(bh);
1656 } else if (test_set_buffer_locked(bh)) {
1657 redirty_page_for_writepage(wbc, page);
1658 continue;
1659 }
1660 if (test_clear_buffer_dirty(bh)) {
1661 mark_buffer_async_write(bh);
1662 } else {
1663 unlock_buffer(bh);
1664 }
1665 } while ((bh = bh->b_this_page) != head);
1666
1667 /*
1668 * The page and its buffers are protected by PageWriteback(), so we can
1669 * drop the bh refcounts early.
1670 */
1671 BUG_ON(PageWriteback(page));
1672 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001673
1674 do {
1675 struct buffer_head *next = bh->b_this_page;
1676 if (buffer_async_write(bh)) {
1677 submit_bh(WRITE, bh);
1678 nr_underway++;
1679 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001680 bh = next;
1681 } while (bh != head);
Andrew Morton05937ba2005-05-05 16:15:47 -07001682 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001683
1684 err = 0;
1685done:
1686 if (nr_underway == 0) {
1687 /*
1688 * The page was marked dirty, but the buffers were
1689 * clean. Someone wrote them back by hand with
1690 * ll_rw_block/submit_bh. A rare case.
1691 */
1692 int uptodate = 1;
1693 do {
1694 if (!buffer_uptodate(bh)) {
1695 uptodate = 0;
1696 break;
1697 }
1698 bh = bh->b_this_page;
1699 } while (bh != head);
1700 if (uptodate)
1701 SetPageUptodate(page);
1702 end_page_writeback(page);
1703 /*
1704 * The page and buffer_heads can be released at any time from
1705 * here on.
1706 */
1707 wbc->pages_skipped++; /* We didn't write this page */
1708 }
1709 return err;
1710
1711recover:
1712 /*
1713 * ENOSPC, or some other error. We may already have added some
1714 * blocks to the file, so we need to write these out to avoid
1715 * exposing stale data.
1716 * The page is currently locked and not marked for writeback
1717 */
1718 bh = head;
1719 /* Recovery: lock and submit the mapped buffers */
1720 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001721 if (buffer_mapped(bh) && buffer_dirty(bh)) {
1722 lock_buffer(bh);
1723 mark_buffer_async_write(bh);
1724 } else {
1725 /*
1726 * The buffer may have been set dirty during
1727 * attachment to a dirty page.
1728 */
1729 clear_buffer_dirty(bh);
1730 }
1731 } while ((bh = bh->b_this_page) != head);
1732 SetPageError(page);
1733 BUG_ON(PageWriteback(page));
1734 set_page_writeback(page);
1735 unlock_page(page);
1736 do {
1737 struct buffer_head *next = bh->b_this_page;
1738 if (buffer_async_write(bh)) {
1739 clear_buffer_dirty(bh);
1740 submit_bh(WRITE, bh);
1741 nr_underway++;
1742 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001743 bh = next;
1744 } while (bh != head);
1745 goto done;
1746}
1747
1748static int __block_prepare_write(struct inode *inode, struct page *page,
1749 unsigned from, unsigned to, get_block_t *get_block)
1750{
1751 unsigned block_start, block_end;
1752 sector_t block;
1753 int err = 0;
1754 unsigned blocksize, bbits;
1755 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1756
1757 BUG_ON(!PageLocked(page));
1758 BUG_ON(from > PAGE_CACHE_SIZE);
1759 BUG_ON(to > PAGE_CACHE_SIZE);
1760 BUG_ON(from > to);
1761
1762 blocksize = 1 << inode->i_blkbits;
1763 if (!page_has_buffers(page))
1764 create_empty_buffers(page, blocksize, 0);
1765 head = page_buffers(page);
1766
1767 bbits = inode->i_blkbits;
1768 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1769
1770 for(bh = head, block_start = 0; bh != head || !block_start;
1771 block++, block_start=block_end, bh = bh->b_this_page) {
1772 block_end = block_start + blocksize;
1773 if (block_end <= from || block_start >= to) {
1774 if (PageUptodate(page)) {
1775 if (!buffer_uptodate(bh))
1776 set_buffer_uptodate(bh);
1777 }
1778 continue;
1779 }
1780 if (buffer_new(bh))
1781 clear_buffer_new(bh);
1782 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001783 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001784 err = get_block(inode, block, bh, 1);
1785 if (err)
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001786 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001787 if (buffer_new(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001788 unmap_underlying_metadata(bh->b_bdev,
1789 bh->b_blocknr);
1790 if (PageUptodate(page)) {
1791 set_buffer_uptodate(bh);
1792 continue;
1793 }
1794 if (block_end > to || block_start < from) {
1795 void *kaddr;
1796
1797 kaddr = kmap_atomic(page, KM_USER0);
1798 if (block_end > to)
1799 memset(kaddr+to, 0,
1800 block_end-to);
1801 if (block_start < from)
1802 memset(kaddr+block_start,
1803 0, from-block_start);
1804 flush_dcache_page(page);
1805 kunmap_atomic(kaddr, KM_USER0);
1806 }
1807 continue;
1808 }
1809 }
1810 if (PageUptodate(page)) {
1811 if (!buffer_uptodate(bh))
1812 set_buffer_uptodate(bh);
1813 continue;
1814 }
1815 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1816 (block_start < from || block_end > to)) {
1817 ll_rw_block(READ, 1, &bh);
1818 *wait_bh++=bh;
1819 }
1820 }
1821 /*
1822 * If we issued read requests - let them complete.
1823 */
1824 while(wait_bh > wait) {
1825 wait_on_buffer(*--wait_bh);
1826 if (!buffer_uptodate(*wait_bh))
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001827 err = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001828 }
Anton Altaparmakov152becd2005-06-23 00:10:21 -07001829 if (!err) {
1830 bh = head;
1831 do {
1832 if (buffer_new(bh))
1833 clear_buffer_new(bh);
1834 } while ((bh = bh->b_this_page) != head);
1835 return 0;
1836 }
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001837 /* Error case: */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001838 /*
1839 * Zero out any newly allocated blocks to avoid exposing stale
1840 * data. If BH_New is set, we know that the block was newly
1841 * allocated in the above loop.
1842 */
1843 bh = head;
1844 block_start = 0;
1845 do {
1846 block_end = block_start+blocksize;
1847 if (block_end <= from)
1848 goto next_bh;
1849 if (block_start >= to)
1850 break;
1851 if (buffer_new(bh)) {
1852 void *kaddr;
1853
1854 clear_buffer_new(bh);
1855 kaddr = kmap_atomic(page, KM_USER0);
1856 memset(kaddr+block_start, 0, bh->b_size);
Monakhov Dmitriy8c581652006-10-11 01:22:00 -07001857 flush_dcache_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001858 kunmap_atomic(kaddr, KM_USER0);
1859 set_buffer_uptodate(bh);
1860 mark_buffer_dirty(bh);
1861 }
1862next_bh:
1863 block_start = block_end;
1864 bh = bh->b_this_page;
1865 } while (bh != head);
1866 return err;
1867}
1868
1869static int __block_commit_write(struct inode *inode, struct page *page,
1870 unsigned from, unsigned to)
1871{
1872 unsigned block_start, block_end;
1873 int partial = 0;
1874 unsigned blocksize;
1875 struct buffer_head *bh, *head;
1876
1877 blocksize = 1 << inode->i_blkbits;
1878
1879 for(bh = head = page_buffers(page), block_start = 0;
1880 bh != head || !block_start;
1881 block_start=block_end, bh = bh->b_this_page) {
1882 block_end = block_start + blocksize;
1883 if (block_end <= from || block_start >= to) {
1884 if (!buffer_uptodate(bh))
1885 partial = 1;
1886 } else {
1887 set_buffer_uptodate(bh);
1888 mark_buffer_dirty(bh);
1889 }
1890 }
1891
1892 /*
1893 * If this is a partial write which happened to make all buffers
1894 * uptodate then we can optimize away a bogus readpage() for
1895 * the next read(). Here we 'discover' whether the page went
1896 * uptodate as a result of this (potentially partial) write.
1897 */
1898 if (!partial)
1899 SetPageUptodate(page);
1900 return 0;
1901}
1902
1903/*
1904 * Generic "read page" function for block devices that have the normal
1905 * get_block functionality. This is most of the block device filesystems.
1906 * Reads the page asynchronously --- the unlock_buffer() and
1907 * set/clear_buffer_uptodate() functions propagate buffer state into the
1908 * page struct once IO has completed.
1909 */
1910int block_read_full_page(struct page *page, get_block_t *get_block)
1911{
1912 struct inode *inode = page->mapping->host;
1913 sector_t iblock, lblock;
1914 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
1915 unsigned int blocksize;
1916 int nr, i;
1917 int fully_mapped = 1;
1918
Matt Mackallcd7619d2005-05-01 08:59:01 -07001919 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001920 blocksize = 1 << inode->i_blkbits;
1921 if (!page_has_buffers(page))
1922 create_empty_buffers(page, blocksize, 0);
1923 head = page_buffers(page);
1924
1925 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
1926 lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
1927 bh = head;
1928 nr = 0;
1929 i = 0;
1930
1931 do {
1932 if (buffer_uptodate(bh))
1933 continue;
1934
1935 if (!buffer_mapped(bh)) {
Andrew Mortonc64610b2005-05-16 21:53:49 -07001936 int err = 0;
1937
Linus Torvalds1da177e2005-04-16 15:20:36 -07001938 fully_mapped = 0;
1939 if (iblock < lblock) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001940 WARN_ON(bh->b_size != blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07001941 err = get_block(inode, iblock, bh, 0);
1942 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001943 SetPageError(page);
1944 }
1945 if (!buffer_mapped(bh)) {
1946 void *kaddr = kmap_atomic(page, KM_USER0);
1947 memset(kaddr + i * blocksize, 0, blocksize);
1948 flush_dcache_page(page);
1949 kunmap_atomic(kaddr, KM_USER0);
Andrew Mortonc64610b2005-05-16 21:53:49 -07001950 if (!err)
1951 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001952 continue;
1953 }
1954 /*
1955 * get_block() might have updated the buffer
1956 * synchronously
1957 */
1958 if (buffer_uptodate(bh))
1959 continue;
1960 }
1961 arr[nr++] = bh;
1962 } while (i++, iblock++, (bh = bh->b_this_page) != head);
1963
1964 if (fully_mapped)
1965 SetPageMappedToDisk(page);
1966
1967 if (!nr) {
1968 /*
1969 * All buffers are uptodate - we can set the page uptodate
1970 * as well. But not if get_block() returned an error.
1971 */
1972 if (!PageError(page))
1973 SetPageUptodate(page);
1974 unlock_page(page);
1975 return 0;
1976 }
1977
1978 /* Stage two: lock the buffers */
1979 for (i = 0; i < nr; i++) {
1980 bh = arr[i];
1981 lock_buffer(bh);
1982 mark_buffer_async_read(bh);
1983 }
1984
1985 /*
1986 * Stage 3: start the IO. Check for uptodateness
1987 * inside the buffer lock in case another process reading
1988 * the underlying blockdev brought it uptodate (the sct fix).
1989 */
1990 for (i = 0; i < nr; i++) {
1991 bh = arr[i];
1992 if (buffer_uptodate(bh))
1993 end_buffer_async_read(bh, 1);
1994 else
1995 submit_bh(READ, bh);
1996 }
1997 return 0;
1998}
1999
2000/* utility function for filesystems that need to do work on expanding
2001 * truncates. Uses prepare/commit_write to allow the filesystem to
2002 * deal with the hole.
2003 */
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002004static int __generic_cont_expand(struct inode *inode, loff_t size,
2005 pgoff_t index, unsigned int offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002006{
2007 struct address_space *mapping = inode->i_mapping;
2008 struct page *page;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002009 unsigned long limit;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002010 int err;
2011
2012 err = -EFBIG;
2013 limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
2014 if (limit != RLIM_INFINITY && size > (loff_t)limit) {
2015 send_sig(SIGXFSZ, current, 0);
2016 goto out;
2017 }
2018 if (size > inode->i_sb->s_maxbytes)
2019 goto out;
2020
Linus Torvalds1da177e2005-04-16 15:20:36 -07002021 err = -ENOMEM;
2022 page = grab_cache_page(mapping, index);
2023 if (!page)
2024 goto out;
2025 err = mapping->a_ops->prepare_write(NULL, page, offset, offset);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002026 if (err) {
2027 /*
2028 * ->prepare_write() may have instantiated a few blocks
2029 * outside i_size. Trim these off again.
2030 */
2031 unlock_page(page);
2032 page_cache_release(page);
2033 vmtruncate(inode, inode->i_size);
2034 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002035 }
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002036
2037 err = mapping->a_ops->commit_write(NULL, page, offset, offset);
2038
Linus Torvalds1da177e2005-04-16 15:20:36 -07002039 unlock_page(page);
2040 page_cache_release(page);
2041 if (err > 0)
2042 err = 0;
2043out:
2044 return err;
2045}
2046
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002047int generic_cont_expand(struct inode *inode, loff_t size)
2048{
2049 pgoff_t index;
2050 unsigned int offset;
2051
2052 offset = (size & (PAGE_CACHE_SIZE - 1)); /* Within page */
2053
2054 /* ugh. in prepare/commit_write, if from==to==start of block, we
2055 ** skip the prepare. make sure we never send an offset for the start
2056 ** of a block
2057 */
2058 if ((offset & (inode->i_sb->s_blocksize - 1)) == 0) {
2059 /* caller must handle this extra byte. */
2060 offset++;
2061 }
2062 index = size >> PAGE_CACHE_SHIFT;
2063
2064 return __generic_cont_expand(inode, size, index, offset);
2065}
2066
2067int generic_cont_expand_simple(struct inode *inode, loff_t size)
2068{
2069 loff_t pos = size - 1;
2070 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
2071 unsigned int offset = (pos & (PAGE_CACHE_SIZE - 1)) + 1;
2072
2073 /* prepare/commit_write can handle even if from==to==start of block. */
2074 return __generic_cont_expand(inode, size, index, offset);
2075}
2076
Linus Torvalds1da177e2005-04-16 15:20:36 -07002077/*
2078 * For moronic filesystems that do not allow holes in file.
2079 * We may have to extend the file.
2080 */
2081
2082int cont_prepare_write(struct page *page, unsigned offset,
2083 unsigned to, get_block_t *get_block, loff_t *bytes)
2084{
2085 struct address_space *mapping = page->mapping;
2086 struct inode *inode = mapping->host;
2087 struct page *new_page;
2088 pgoff_t pgpos;
2089 long status;
2090 unsigned zerofrom;
2091 unsigned blocksize = 1 << inode->i_blkbits;
2092 void *kaddr;
2093
2094 while(page->index > (pgpos = *bytes>>PAGE_CACHE_SHIFT)) {
2095 status = -ENOMEM;
2096 new_page = grab_cache_page(mapping, pgpos);
2097 if (!new_page)
2098 goto out;
2099 /* we might sleep */
2100 if (*bytes>>PAGE_CACHE_SHIFT != pgpos) {
2101 unlock_page(new_page);
2102 page_cache_release(new_page);
2103 continue;
2104 }
2105 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2106 if (zerofrom & (blocksize-1)) {
2107 *bytes |= (blocksize-1);
2108 (*bytes)++;
2109 }
2110 status = __block_prepare_write(inode, new_page, zerofrom,
2111 PAGE_CACHE_SIZE, get_block);
2112 if (status)
2113 goto out_unmap;
2114 kaddr = kmap_atomic(new_page, KM_USER0);
2115 memset(kaddr+zerofrom, 0, PAGE_CACHE_SIZE-zerofrom);
2116 flush_dcache_page(new_page);
2117 kunmap_atomic(kaddr, KM_USER0);
2118 generic_commit_write(NULL, new_page, zerofrom, PAGE_CACHE_SIZE);
2119 unlock_page(new_page);
2120 page_cache_release(new_page);
2121 }
2122
2123 if (page->index < pgpos) {
2124 /* completely inside the area */
2125 zerofrom = offset;
2126 } else {
2127 /* page covers the boundary, find the boundary offset */
2128 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2129
2130 /* if we will expand the thing last block will be filled */
2131 if (to > zerofrom && (zerofrom & (blocksize-1))) {
2132 *bytes |= (blocksize-1);
2133 (*bytes)++;
2134 }
2135
2136 /* starting below the boundary? Nothing to zero out */
2137 if (offset <= zerofrom)
2138 zerofrom = offset;
2139 }
2140 status = __block_prepare_write(inode, page, zerofrom, to, get_block);
2141 if (status)
2142 goto out1;
2143 if (zerofrom < offset) {
2144 kaddr = kmap_atomic(page, KM_USER0);
2145 memset(kaddr+zerofrom, 0, offset-zerofrom);
2146 flush_dcache_page(page);
2147 kunmap_atomic(kaddr, KM_USER0);
2148 __block_commit_write(inode, page, zerofrom, offset);
2149 }
2150 return 0;
2151out1:
2152 ClearPageUptodate(page);
2153 return status;
2154
2155out_unmap:
2156 ClearPageUptodate(new_page);
2157 unlock_page(new_page);
2158 page_cache_release(new_page);
2159out:
2160 return status;
2161}
2162
2163int block_prepare_write(struct page *page, unsigned from, unsigned to,
2164 get_block_t *get_block)
2165{
2166 struct inode *inode = page->mapping->host;
2167 int err = __block_prepare_write(inode, page, from, to, get_block);
2168 if (err)
2169 ClearPageUptodate(page);
2170 return err;
2171}
2172
2173int block_commit_write(struct page *page, unsigned from, unsigned to)
2174{
2175 struct inode *inode = page->mapping->host;
2176 __block_commit_write(inode,page,from,to);
2177 return 0;
2178}
2179
2180int generic_commit_write(struct file *file, struct page *page,
2181 unsigned from, unsigned to)
2182{
2183 struct inode *inode = page->mapping->host;
2184 loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
2185 __block_commit_write(inode,page,from,to);
2186 /*
2187 * No need to use i_size_read() here, the i_size
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08002188 * cannot change under us because we hold i_mutex.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002189 */
2190 if (pos > inode->i_size) {
2191 i_size_write(inode, pos);
2192 mark_inode_dirty(inode);
2193 }
2194 return 0;
2195}
2196
2197
2198/*
2199 * nobh_prepare_write()'s prereads are special: the buffer_heads are freed
2200 * immediately, while under the page lock. So it needs a special end_io
2201 * handler which does not touch the bh after unlocking it.
2202 *
2203 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
2204 * a race there is benign: unlock_buffer() only use the bh's address for
2205 * hashing after unlocking the buffer, so it doesn't actually touch the bh
2206 * itself.
2207 */
2208static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2209{
2210 if (uptodate) {
2211 set_buffer_uptodate(bh);
2212 } else {
2213 /* This happens, due to failed READA attempts. */
2214 clear_buffer_uptodate(bh);
2215 }
2216 unlock_buffer(bh);
2217}
2218
2219/*
2220 * On entry, the page is fully not uptodate.
2221 * On exit the page is fully uptodate in the areas outside (from,to)
2222 */
2223int nobh_prepare_write(struct page *page, unsigned from, unsigned to,
2224 get_block_t *get_block)
2225{
2226 struct inode *inode = page->mapping->host;
2227 const unsigned blkbits = inode->i_blkbits;
2228 const unsigned blocksize = 1 << blkbits;
2229 struct buffer_head map_bh;
2230 struct buffer_head *read_bh[MAX_BUF_PER_PAGE];
2231 unsigned block_in_page;
2232 unsigned block_start;
2233 sector_t block_in_file;
2234 char *kaddr;
2235 int nr_reads = 0;
2236 int i;
2237 int ret = 0;
2238 int is_mapped_to_disk = 1;
2239 int dirtied_it = 0;
2240
2241 if (PageMappedToDisk(page))
2242 return 0;
2243
2244 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
2245 map_bh.b_page = page;
2246
2247 /*
2248 * We loop across all blocks in the page, whether or not they are
2249 * part of the affected region. This is so we can discover if the
2250 * page is fully mapped-to-disk.
2251 */
2252 for (block_start = 0, block_in_page = 0;
2253 block_start < PAGE_CACHE_SIZE;
2254 block_in_page++, block_start += blocksize) {
2255 unsigned block_end = block_start + blocksize;
2256 int create;
2257
2258 map_bh.b_state = 0;
2259 create = 1;
2260 if (block_start >= to)
2261 create = 0;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002262 map_bh.b_size = blocksize;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002263 ret = get_block(inode, block_in_file + block_in_page,
2264 &map_bh, create);
2265 if (ret)
2266 goto failed;
2267 if (!buffer_mapped(&map_bh))
2268 is_mapped_to_disk = 0;
2269 if (buffer_new(&map_bh))
2270 unmap_underlying_metadata(map_bh.b_bdev,
2271 map_bh.b_blocknr);
2272 if (PageUptodate(page))
2273 continue;
2274 if (buffer_new(&map_bh) || !buffer_mapped(&map_bh)) {
2275 kaddr = kmap_atomic(page, KM_USER0);
2276 if (block_start < from) {
2277 memset(kaddr+block_start, 0, from-block_start);
2278 dirtied_it = 1;
2279 }
2280 if (block_end > to) {
2281 memset(kaddr + to, 0, block_end - to);
2282 dirtied_it = 1;
2283 }
2284 flush_dcache_page(page);
2285 kunmap_atomic(kaddr, KM_USER0);
2286 continue;
2287 }
2288 if (buffer_uptodate(&map_bh))
2289 continue; /* reiserfs does this */
2290 if (block_start < from || block_end > to) {
2291 struct buffer_head *bh = alloc_buffer_head(GFP_NOFS);
2292
2293 if (!bh) {
2294 ret = -ENOMEM;
2295 goto failed;
2296 }
2297 bh->b_state = map_bh.b_state;
2298 atomic_set(&bh->b_count, 0);
2299 bh->b_this_page = NULL;
2300 bh->b_page = page;
2301 bh->b_blocknr = map_bh.b_blocknr;
2302 bh->b_size = blocksize;
2303 bh->b_data = (char *)(long)block_start;
2304 bh->b_bdev = map_bh.b_bdev;
2305 bh->b_private = NULL;
2306 read_bh[nr_reads++] = bh;
2307 }
2308 }
2309
2310 if (nr_reads) {
2311 struct buffer_head *bh;
2312
2313 /*
2314 * The page is locked, so these buffers are protected from
2315 * any VM or truncate activity. Hence we don't need to care
2316 * for the buffer_head refcounts.
2317 */
2318 for (i = 0; i < nr_reads; i++) {
2319 bh = read_bh[i];
2320 lock_buffer(bh);
2321 bh->b_end_io = end_buffer_read_nobh;
2322 submit_bh(READ, bh);
2323 }
2324 for (i = 0; i < nr_reads; i++) {
2325 bh = read_bh[i];
2326 wait_on_buffer(bh);
2327 if (!buffer_uptodate(bh))
2328 ret = -EIO;
2329 free_buffer_head(bh);
2330 read_bh[i] = NULL;
2331 }
2332 if (ret)
2333 goto failed;
2334 }
2335
2336 if (is_mapped_to_disk)
2337 SetPageMappedToDisk(page);
2338 SetPageUptodate(page);
2339
2340 /*
2341 * Setting the page dirty here isn't necessary for the prepare_write
2342 * function - commit_write will do that. But if/when this function is
2343 * used within the pagefault handler to ensure that all mmapped pages
2344 * have backing space in the filesystem, we will need to dirty the page
2345 * if its contents were altered.
2346 */
2347 if (dirtied_it)
2348 set_page_dirty(page);
2349
2350 return 0;
2351
2352failed:
2353 for (i = 0; i < nr_reads; i++) {
2354 if (read_bh[i])
2355 free_buffer_head(read_bh[i]);
2356 }
2357
2358 /*
2359 * Error recovery is pretty slack. Clear the page and mark it dirty
2360 * so we'll later zero out any blocks which _were_ allocated.
2361 */
2362 kaddr = kmap_atomic(page, KM_USER0);
2363 memset(kaddr, 0, PAGE_CACHE_SIZE);
Monakhov Dmitriy8c581652006-10-11 01:22:00 -07002364 flush_dcache_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002365 kunmap_atomic(kaddr, KM_USER0);
2366 SetPageUptodate(page);
2367 set_page_dirty(page);
2368 return ret;
2369}
2370EXPORT_SYMBOL(nobh_prepare_write);
2371
2372int nobh_commit_write(struct file *file, struct page *page,
2373 unsigned from, unsigned to)
2374{
2375 struct inode *inode = page->mapping->host;
2376 loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
2377
2378 set_page_dirty(page);
2379 if (pos > inode->i_size) {
2380 i_size_write(inode, pos);
2381 mark_inode_dirty(inode);
2382 }
2383 return 0;
2384}
2385EXPORT_SYMBOL(nobh_commit_write);
2386
2387/*
2388 * nobh_writepage() - based on block_full_write_page() except
2389 * that it tries to operate without attaching bufferheads to
2390 * the page.
2391 */
2392int nobh_writepage(struct page *page, get_block_t *get_block,
2393 struct writeback_control *wbc)
2394{
2395 struct inode * const inode = page->mapping->host;
2396 loff_t i_size = i_size_read(inode);
2397 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2398 unsigned offset;
2399 void *kaddr;
2400 int ret;
2401
2402 /* Is the page fully inside i_size? */
2403 if (page->index < end_index)
2404 goto out;
2405
2406 /* Is the page fully outside i_size? (truncate in progress) */
2407 offset = i_size & (PAGE_CACHE_SIZE-1);
2408 if (page->index >= end_index+1 || !offset) {
2409 /*
2410 * The page may have dirty, unmapped buffers. For example,
2411 * they may have been added in ext3_writepage(). Make them
2412 * freeable here, so the page does not leak.
2413 */
2414#if 0
2415 /* Not really sure about this - do we need this ? */
2416 if (page->mapping->a_ops->invalidatepage)
2417 page->mapping->a_ops->invalidatepage(page, offset);
2418#endif
2419 unlock_page(page);
2420 return 0; /* don't care */
2421 }
2422
2423 /*
2424 * The page straddles i_size. It must be zeroed out on each and every
2425 * writepage invocation because it may be mmapped. "A file is mapped
2426 * in multiples of the page size. For a file that is not a multiple of
2427 * the page size, the remaining memory is zeroed when mapped, and
2428 * writes to that region are not written out to the file."
2429 */
2430 kaddr = kmap_atomic(page, KM_USER0);
2431 memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
2432 flush_dcache_page(page);
2433 kunmap_atomic(kaddr, KM_USER0);
2434out:
2435 ret = mpage_writepage(page, get_block, wbc);
2436 if (ret == -EAGAIN)
2437 ret = __block_write_full_page(inode, page, get_block, wbc);
2438 return ret;
2439}
2440EXPORT_SYMBOL(nobh_writepage);
2441
2442/*
2443 * This function assumes that ->prepare_write() uses nobh_prepare_write().
2444 */
2445int nobh_truncate_page(struct address_space *mapping, loff_t from)
2446{
2447 struct inode *inode = mapping->host;
2448 unsigned blocksize = 1 << inode->i_blkbits;
2449 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2450 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2451 unsigned to;
2452 struct page *page;
Christoph Hellwigf5e54d62006-06-28 04:26:44 -07002453 const struct address_space_operations *a_ops = mapping->a_ops;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002454 char *kaddr;
2455 int ret = 0;
2456
2457 if ((offset & (blocksize - 1)) == 0)
2458 goto out;
2459
2460 ret = -ENOMEM;
2461 page = grab_cache_page(mapping, index);
2462 if (!page)
2463 goto out;
2464
2465 to = (offset + blocksize) & ~(blocksize - 1);
2466 ret = a_ops->prepare_write(NULL, page, offset, to);
2467 if (ret == 0) {
2468 kaddr = kmap_atomic(page, KM_USER0);
2469 memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
2470 flush_dcache_page(page);
2471 kunmap_atomic(kaddr, KM_USER0);
2472 set_page_dirty(page);
2473 }
2474 unlock_page(page);
2475 page_cache_release(page);
2476out:
2477 return ret;
2478}
2479EXPORT_SYMBOL(nobh_truncate_page);
2480
2481int block_truncate_page(struct address_space *mapping,
2482 loff_t from, get_block_t *get_block)
2483{
2484 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2485 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2486 unsigned blocksize;
Andrew Morton54b21a72006-01-08 01:03:05 -08002487 sector_t iblock;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002488 unsigned length, pos;
2489 struct inode *inode = mapping->host;
2490 struct page *page;
2491 struct buffer_head *bh;
2492 void *kaddr;
2493 int err;
2494
2495 blocksize = 1 << inode->i_blkbits;
2496 length = offset & (blocksize - 1);
2497
2498 /* Block boundary? Nothing to do */
2499 if (!length)
2500 return 0;
2501
2502 length = blocksize - length;
Andrew Morton54b21a72006-01-08 01:03:05 -08002503 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002504
2505 page = grab_cache_page(mapping, index);
2506 err = -ENOMEM;
2507 if (!page)
2508 goto out;
2509
2510 if (!page_has_buffers(page))
2511 create_empty_buffers(page, blocksize, 0);
2512
2513 /* Find the buffer that contains "offset" */
2514 bh = page_buffers(page);
2515 pos = blocksize;
2516 while (offset >= pos) {
2517 bh = bh->b_this_page;
2518 iblock++;
2519 pos += blocksize;
2520 }
2521
2522 err = 0;
2523 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002524 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002525 err = get_block(inode, iblock, bh, 0);
2526 if (err)
2527 goto unlock;
2528 /* unmapped? It's a hole - nothing to do */
2529 if (!buffer_mapped(bh))
2530 goto unlock;
2531 }
2532
2533 /* Ok, it's mapped. Make sure it's up-to-date */
2534 if (PageUptodate(page))
2535 set_buffer_uptodate(bh);
2536
2537 if (!buffer_uptodate(bh) && !buffer_delay(bh)) {
2538 err = -EIO;
2539 ll_rw_block(READ, 1, &bh);
2540 wait_on_buffer(bh);
2541 /* Uhhuh. Read error. Complain and punt. */
2542 if (!buffer_uptodate(bh))
2543 goto unlock;
2544 }
2545
2546 kaddr = kmap_atomic(page, KM_USER0);
2547 memset(kaddr + offset, 0, length);
2548 flush_dcache_page(page);
2549 kunmap_atomic(kaddr, KM_USER0);
2550
2551 mark_buffer_dirty(bh);
2552 err = 0;
2553
2554unlock:
2555 unlock_page(page);
2556 page_cache_release(page);
2557out:
2558 return err;
2559}
2560
2561/*
2562 * The generic ->writepage function for buffer-backed address_spaces
2563 */
2564int block_write_full_page(struct page *page, get_block_t *get_block,
2565 struct writeback_control *wbc)
2566{
2567 struct inode * const inode = page->mapping->host;
2568 loff_t i_size = i_size_read(inode);
2569 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2570 unsigned offset;
2571 void *kaddr;
2572
2573 /* Is the page fully inside i_size? */
2574 if (page->index < end_index)
2575 return __block_write_full_page(inode, page, get_block, wbc);
2576
2577 /* Is the page fully outside i_size? (truncate in progress) */
2578 offset = i_size & (PAGE_CACHE_SIZE-1);
2579 if (page->index >= end_index+1 || !offset) {
2580 /*
2581 * The page may have dirty, unmapped buffers. For example,
2582 * they may have been added in ext3_writepage(). Make them
2583 * freeable here, so the page does not leak.
2584 */
Jan Karaaaa40592005-10-30 15:00:16 -08002585 do_invalidatepage(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002586 unlock_page(page);
2587 return 0; /* don't care */
2588 }
2589
2590 /*
2591 * The page straddles i_size. It must be zeroed out on each and every
2592 * writepage invokation because it may be mmapped. "A file is mapped
2593 * in multiples of the page size. For a file that is not a multiple of
2594 * the page size, the remaining memory is zeroed when mapped, and
2595 * writes to that region are not written out to the file."
2596 */
2597 kaddr = kmap_atomic(page, KM_USER0);
2598 memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
2599 flush_dcache_page(page);
2600 kunmap_atomic(kaddr, KM_USER0);
2601 return __block_write_full_page(inode, page, get_block, wbc);
2602}
2603
2604sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2605 get_block_t *get_block)
2606{
2607 struct buffer_head tmp;
2608 struct inode *inode = mapping->host;
2609 tmp.b_state = 0;
2610 tmp.b_blocknr = 0;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002611 tmp.b_size = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002612 get_block(inode, block, &tmp, 0);
2613 return tmp.b_blocknr;
2614}
2615
2616static int end_bio_bh_io_sync(struct bio *bio, unsigned int bytes_done, int err)
2617{
2618 struct buffer_head *bh = bio->bi_private;
2619
2620 if (bio->bi_size)
2621 return 1;
2622
2623 if (err == -EOPNOTSUPP) {
2624 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
2625 set_bit(BH_Eopnotsupp, &bh->b_state);
2626 }
2627
2628 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2629 bio_put(bio);
2630 return 0;
2631}
2632
2633int submit_bh(int rw, struct buffer_head * bh)
2634{
2635 struct bio *bio;
2636 int ret = 0;
2637
2638 BUG_ON(!buffer_locked(bh));
2639 BUG_ON(!buffer_mapped(bh));
2640 BUG_ON(!bh->b_end_io);
2641
2642 if (buffer_ordered(bh) && (rw == WRITE))
2643 rw = WRITE_BARRIER;
2644
2645 /*
2646 * Only clear out a write error when rewriting, should this
2647 * include WRITE_SYNC as well?
2648 */
2649 if (test_set_buffer_req(bh) && (rw == WRITE || rw == WRITE_BARRIER))
2650 clear_buffer_write_io_error(bh);
2651
2652 /*
2653 * from here on down, it's all bio -- do the initial mapping,
2654 * submit_bio -> generic_make_request may further map this bio around
2655 */
2656 bio = bio_alloc(GFP_NOIO, 1);
2657
2658 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2659 bio->bi_bdev = bh->b_bdev;
2660 bio->bi_io_vec[0].bv_page = bh->b_page;
2661 bio->bi_io_vec[0].bv_len = bh->b_size;
2662 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
2663
2664 bio->bi_vcnt = 1;
2665 bio->bi_idx = 0;
2666 bio->bi_size = bh->b_size;
2667
2668 bio->bi_end_io = end_bio_bh_io_sync;
2669 bio->bi_private = bh;
2670
2671 bio_get(bio);
2672 submit_bio(rw, bio);
2673
2674 if (bio_flagged(bio, BIO_EOPNOTSUPP))
2675 ret = -EOPNOTSUPP;
2676
2677 bio_put(bio);
2678 return ret;
2679}
2680
2681/**
2682 * ll_rw_block: low-level access to block devices (DEPRECATED)
Jan Karaa7662232005-09-06 15:19:10 -07002683 * @rw: whether to %READ or %WRITE or %SWRITE or maybe %READA (readahead)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002684 * @nr: number of &struct buffer_heads in the array
2685 * @bhs: array of pointers to &struct buffer_head
2686 *
Jan Karaa7662232005-09-06 15:19:10 -07002687 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
2688 * requests an I/O operation on them, either a %READ or a %WRITE. The third
2689 * %SWRITE is like %WRITE only we make sure that the *current* data in buffers
2690 * are sent to disk. The fourth %READA option is described in the documentation
2691 * for generic_make_request() which ll_rw_block() calls.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002692 *
2693 * This function drops any buffer that it cannot get a lock on (with the
Jan Karaa7662232005-09-06 15:19:10 -07002694 * BH_Lock state bit) unless SWRITE is required, any buffer that appears to be
2695 * clean when doing a write request, and any buffer that appears to be
2696 * up-to-date when doing read request. Further it marks as clean buffers that
2697 * are processed for writing (the buffer cache won't assume that they are
2698 * actually clean until the buffer gets unlocked).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002699 *
2700 * ll_rw_block sets b_end_io to simple completion handler that marks
2701 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
2702 * any waiters.
2703 *
2704 * All of the buffers must be for the same device, and must also be a
2705 * multiple of the current approved size for the device.
2706 */
2707void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
2708{
2709 int i;
2710
2711 for (i = 0; i < nr; i++) {
2712 struct buffer_head *bh = bhs[i];
2713
Jan Karaa7662232005-09-06 15:19:10 -07002714 if (rw == SWRITE)
2715 lock_buffer(bh);
2716 else if (test_set_buffer_locked(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002717 continue;
2718
Jan Karaa7662232005-09-06 15:19:10 -07002719 if (rw == WRITE || rw == SWRITE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002720 if (test_clear_buffer_dirty(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07002721 bh->b_end_io = end_buffer_write_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08002722 get_bh(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002723 submit_bh(WRITE, bh);
2724 continue;
2725 }
2726 } else {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002727 if (!buffer_uptodate(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07002728 bh->b_end_io = end_buffer_read_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08002729 get_bh(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002730 submit_bh(rw, bh);
2731 continue;
2732 }
2733 }
2734 unlock_buffer(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002735 }
2736}
2737
2738/*
2739 * For a data-integrity writeout, we need to wait upon any in-progress I/O
2740 * and then start new I/O and then wait upon it. The caller must have a ref on
2741 * the buffer_head.
2742 */
2743int sync_dirty_buffer(struct buffer_head *bh)
2744{
2745 int ret = 0;
2746
2747 WARN_ON(atomic_read(&bh->b_count) < 1);
2748 lock_buffer(bh);
2749 if (test_clear_buffer_dirty(bh)) {
2750 get_bh(bh);
2751 bh->b_end_io = end_buffer_write_sync;
2752 ret = submit_bh(WRITE, bh);
2753 wait_on_buffer(bh);
2754 if (buffer_eopnotsupp(bh)) {
2755 clear_buffer_eopnotsupp(bh);
2756 ret = -EOPNOTSUPP;
2757 }
2758 if (!ret && !buffer_uptodate(bh))
2759 ret = -EIO;
2760 } else {
2761 unlock_buffer(bh);
2762 }
2763 return ret;
2764}
2765
2766/*
2767 * try_to_free_buffers() checks if all the buffers on this particular page
2768 * are unused, and releases them if so.
2769 *
2770 * Exclusion against try_to_free_buffers may be obtained by either
2771 * locking the page or by holding its mapping's private_lock.
2772 *
2773 * If the page is dirty but all the buffers are clean then we need to
2774 * be sure to mark the page clean as well. This is because the page
2775 * may be against a block device, and a later reattachment of buffers
2776 * to a dirty page will set *all* buffers dirty. Which would corrupt
2777 * filesystem data on the same device.
2778 *
2779 * The same applies to regular filesystem pages: if all the buffers are
2780 * clean then we set the page clean and proceed. To do that, we require
2781 * total exclusion from __set_page_dirty_buffers(). That is obtained with
2782 * private_lock.
2783 *
2784 * try_to_free_buffers() is non-blocking.
2785 */
2786static inline int buffer_busy(struct buffer_head *bh)
2787{
2788 return atomic_read(&bh->b_count) |
2789 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
2790}
2791
2792static int
2793drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
2794{
2795 struct buffer_head *head = page_buffers(page);
2796 struct buffer_head *bh;
2797
2798 bh = head;
2799 do {
akpm@osdl.orgde7d5a32005-05-01 08:58:39 -07002800 if (buffer_write_io_error(bh) && page->mapping)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002801 set_bit(AS_EIO, &page->mapping->flags);
2802 if (buffer_busy(bh))
2803 goto failed;
2804 bh = bh->b_this_page;
2805 } while (bh != head);
2806
2807 do {
2808 struct buffer_head *next = bh->b_this_page;
2809
2810 if (!list_empty(&bh->b_assoc_buffers))
2811 __remove_assoc_queue(bh);
2812 bh = next;
2813 } while (bh != head);
2814 *buffers_to_free = head;
2815 __clear_page_buffers(page);
2816 return 1;
2817failed:
2818 return 0;
2819}
2820
2821int try_to_free_buffers(struct page *page)
2822{
2823 struct address_space * const mapping = page->mapping;
2824 struct buffer_head *buffers_to_free = NULL;
2825 int ret = 0;
2826
2827 BUG_ON(!PageLocked(page));
2828 if (PageWriteback(page))
2829 return 0;
2830
2831 if (mapping == NULL) { /* can this still happen? */
2832 ret = drop_buffers(page, &buffers_to_free);
2833 goto out;
2834 }
2835
2836 spin_lock(&mapping->private_lock);
2837 ret = drop_buffers(page, &buffers_to_free);
Peter Zijlstrad08b3852006-09-25 23:30:57 -07002838 spin_unlock(&mapping->private_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002839 if (ret) {
2840 /*
2841 * If the filesystem writes its buffers by hand (eg ext3)
2842 * then we can have clean buffers against a dirty page. We
2843 * clean the page here; otherwise later reattachment of buffers
2844 * could encounter a non-uptodate page, which is unresolvable.
2845 * This only applies in the rare case where try_to_free_buffers
2846 * succeeds but the page is not freed.
2847 */
2848 clear_page_dirty(page);
2849 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07002850out:
2851 if (buffers_to_free) {
2852 struct buffer_head *bh = buffers_to_free;
2853
2854 do {
2855 struct buffer_head *next = bh->b_this_page;
2856 free_buffer_head(bh);
2857 bh = next;
2858 } while (bh != buffers_to_free);
2859 }
2860 return ret;
2861}
2862EXPORT_SYMBOL(try_to_free_buffers);
2863
NeilBrown3978d712006-03-26 01:37:17 -08002864void block_sync_page(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002865{
2866 struct address_space *mapping;
2867
2868 smp_mb();
2869 mapping = page_mapping(page);
2870 if (mapping)
2871 blk_run_backing_dev(mapping->backing_dev_info, page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002872}
2873
2874/*
2875 * There are no bdflush tunables left. But distributions are
2876 * still running obsolete flush daemons, so we terminate them here.
2877 *
2878 * Use of bdflush() is deprecated and will be removed in a future kernel.
2879 * The `pdflush' kernel threads fully replace bdflush daemons and this call.
2880 */
2881asmlinkage long sys_bdflush(int func, long data)
2882{
2883 static int msg_count;
2884
2885 if (!capable(CAP_SYS_ADMIN))
2886 return -EPERM;
2887
2888 if (msg_count < 5) {
2889 msg_count++;
2890 printk(KERN_INFO
2891 "warning: process `%s' used the obsolete bdflush"
2892 " system call\n", current->comm);
2893 printk(KERN_INFO "Fix your initscripts?\n");
2894 }
2895
2896 if (func == 1)
2897 do_exit(0);
2898 return 0;
2899}
2900
2901/*
2902 * Buffer-head allocation
2903 */
2904static kmem_cache_t *bh_cachep;
2905
2906/*
2907 * Once the number of bh's in the machine exceeds this level, we start
2908 * stripping them in writeback.
2909 */
2910static int max_buffer_heads;
2911
2912int buffer_heads_over_limit;
2913
2914struct bh_accounting {
2915 int nr; /* Number of live bh's */
2916 int ratelimit; /* Limit cacheline bouncing */
2917};
2918
2919static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
2920
2921static void recalc_bh_state(void)
2922{
2923 int i;
2924 int tot = 0;
2925
2926 if (__get_cpu_var(bh_accounting).ratelimit++ < 4096)
2927 return;
2928 __get_cpu_var(bh_accounting).ratelimit = 0;
Eric Dumazet8a143422006-03-24 03:18:10 -08002929 for_each_online_cpu(i)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002930 tot += per_cpu(bh_accounting, i).nr;
2931 buffer_heads_over_limit = (tot > max_buffer_heads);
2932}
2933
Al Virodd0fc662005-10-07 07:46:04 +01002934struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002935{
2936 struct buffer_head *ret = kmem_cache_alloc(bh_cachep, gfp_flags);
2937 if (ret) {
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07002938 get_cpu_var(bh_accounting).nr++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002939 recalc_bh_state();
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07002940 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002941 }
2942 return ret;
2943}
2944EXPORT_SYMBOL(alloc_buffer_head);
2945
2946void free_buffer_head(struct buffer_head *bh)
2947{
2948 BUG_ON(!list_empty(&bh->b_assoc_buffers));
2949 kmem_cache_free(bh_cachep, bh);
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07002950 get_cpu_var(bh_accounting).nr--;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002951 recalc_bh_state();
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07002952 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002953}
2954EXPORT_SYMBOL(free_buffer_head);
2955
2956static void
2957init_buffer_head(void *data, kmem_cache_t *cachep, unsigned long flags)
2958{
2959 if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
2960 SLAB_CTOR_CONSTRUCTOR) {
2961 struct buffer_head * bh = (struct buffer_head *)data;
2962
2963 memset(bh, 0, sizeof(*bh));
2964 INIT_LIST_HEAD(&bh->b_assoc_buffers);
2965 }
2966}
2967
2968#ifdef CONFIG_HOTPLUG_CPU
2969static void buffer_exit_cpu(int cpu)
2970{
2971 int i;
2972 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
2973
2974 for (i = 0; i < BH_LRU_SIZE; i++) {
2975 brelse(b->bhs[i]);
2976 b->bhs[i] = NULL;
2977 }
Eric Dumazet8a143422006-03-24 03:18:10 -08002978 get_cpu_var(bh_accounting).nr += per_cpu(bh_accounting, cpu).nr;
2979 per_cpu(bh_accounting, cpu).nr = 0;
2980 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002981}
2982
2983static int buffer_cpu_notify(struct notifier_block *self,
2984 unsigned long action, void *hcpu)
2985{
2986 if (action == CPU_DEAD)
2987 buffer_exit_cpu((unsigned long)hcpu);
2988 return NOTIFY_OK;
2989}
2990#endif /* CONFIG_HOTPLUG_CPU */
2991
2992void __init buffer_init(void)
2993{
2994 int nrpages;
2995
2996 bh_cachep = kmem_cache_create("buffer_head",
Paul Jacksonb0196002006-03-24 03:16:09 -08002997 sizeof(struct buffer_head), 0,
2998 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
2999 SLAB_MEM_SPREAD),
3000 init_buffer_head,
3001 NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003002
3003 /*
3004 * Limit the bh occupancy to 10% of ZONE_NORMAL
3005 */
3006 nrpages = (nr_free_buffer_pages() * 10) / 100;
3007 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3008 hotcpu_notifier(buffer_cpu_notify, 0);
3009}
3010
3011EXPORT_SYMBOL(__bforget);
3012EXPORT_SYMBOL(__brelse);
3013EXPORT_SYMBOL(__wait_on_buffer);
3014EXPORT_SYMBOL(block_commit_write);
3015EXPORT_SYMBOL(block_prepare_write);
3016EXPORT_SYMBOL(block_read_full_page);
3017EXPORT_SYMBOL(block_sync_page);
3018EXPORT_SYMBOL(block_truncate_page);
3019EXPORT_SYMBOL(block_write_full_page);
3020EXPORT_SYMBOL(cont_prepare_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003021EXPORT_SYMBOL(end_buffer_read_sync);
3022EXPORT_SYMBOL(end_buffer_write_sync);
3023EXPORT_SYMBOL(file_fsync);
3024EXPORT_SYMBOL(fsync_bdev);
3025EXPORT_SYMBOL(generic_block_bmap);
3026EXPORT_SYMBOL(generic_commit_write);
3027EXPORT_SYMBOL(generic_cont_expand);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08003028EXPORT_SYMBOL(generic_cont_expand_simple);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003029EXPORT_SYMBOL(init_buffer);
3030EXPORT_SYMBOL(invalidate_bdev);
3031EXPORT_SYMBOL(ll_rw_block);
3032EXPORT_SYMBOL(mark_buffer_dirty);
3033EXPORT_SYMBOL(submit_bh);
3034EXPORT_SYMBOL(sync_dirty_buffer);
3035EXPORT_SYMBOL(unlock_buffer);