blob: ac78d4c19b3b3b27e812f13c0bd7669e962cea04 [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>
Randy Dunlap16f7e0f2006-01-11 12:17:46 -080027#include <linux/capability.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070028#include <linux/blkdev.h>
29#include <linux/file.h>
30#include <linux/quotaops.h>
31#include <linux/highmem.h>
32#include <linux/module.h>
33#include <linux/writeback.h>
34#include <linux/hash.h>
35#include <linux/suspend.h>
36#include <linux/buffer_head.h>
Andrew Morton55e829a2006-12-10 02:19:27 -080037#include <linux/task_io_accounting_ops.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070038#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);
Linus Torvalds1da177e2005-04-16 15:20:36 -070046
47#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
48
49inline void
50init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
51{
52 bh->b_end_io = handler;
53 bh->b_private = private;
54}
55
56static int sync_buffer(void *word)
57{
58 struct block_device *bd;
59 struct buffer_head *bh
60 = container_of(word, struct buffer_head, b_state);
61
62 smp_mb();
63 bd = bh->b_bdev;
64 if (bd)
65 blk_run_address_space(bd->bd_inode->i_mapping);
66 io_schedule();
67 return 0;
68}
69
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -080070void __lock_buffer(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -070071{
72 wait_on_bit_lock(&bh->b_state, BH_Lock, sync_buffer,
73 TASK_UNINTERRUPTIBLE);
74}
75EXPORT_SYMBOL(__lock_buffer);
76
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -080077void unlock_buffer(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -070078{
Nick Piggin72ed3d02007-02-10 01:46:22 -080079 smp_mb__before_clear_bit();
Linus Torvalds1da177e2005-04-16 15:20:36 -070080 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/*
Dmitry Monakhov68671f32007-10-16 01:24:47 -0700113 * End-of-IO handler helper function which does not touch the bh after
114 * unlocking it.
115 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
116 * a race there is benign: unlock_buffer() only use the bh's address for
117 * hashing after unlocking the buffer, so it doesn't actually touch the bh
118 * itself.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700119 */
Dmitry Monakhov68671f32007-10-16 01:24:47 -0700120static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700121{
122 if (uptodate) {
123 set_buffer_uptodate(bh);
124 } else {
125 /* This happens, due to failed READA attempts. */
126 clear_buffer_uptodate(bh);
127 }
128 unlock_buffer(bh);
Dmitry Monakhov68671f32007-10-16 01:24:47 -0700129}
130
131/*
132 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
133 * unlock the buffer. This is what ll_rw_block uses too.
134 */
135void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
136{
137 __end_buffer_read_notouch(bh, uptodate);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700138 put_bh(bh);
139}
140
141void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
142{
143 char b[BDEVNAME_SIZE];
144
145 if (uptodate) {
146 set_buffer_uptodate(bh);
147 } else {
148 if (!buffer_eopnotsupp(bh) && printk_ratelimit()) {
149 buffer_io_error(bh);
150 printk(KERN_WARNING "lost page write due to "
151 "I/O error on %s\n",
152 bdevname(bh->b_bdev, b));
153 }
154 set_buffer_write_io_error(bh);
155 clear_buffer_uptodate(bh);
156 }
157 unlock_buffer(bh);
158 put_bh(bh);
159}
160
161/*
162 * Write out and wait upon all the dirty data associated with a block
163 * device via its mapping. Does not take the superblock lock.
164 */
165int sync_blockdev(struct block_device *bdev)
166{
167 int ret = 0;
168
OGAWA Hirofumi28fd1292006-01-08 01:02:14 -0800169 if (bdev)
170 ret = filemap_write_and_wait(bdev->bd_inode->i_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700171 return ret;
172}
173EXPORT_SYMBOL(sync_blockdev);
174
Linus Torvalds1da177e2005-04-16 15:20:36 -0700175/*
176 * Write out and wait upon all dirty data associated with this
177 * device. Filesystem data as well as the underlying block
178 * device. Takes the superblock lock.
179 */
180int fsync_bdev(struct block_device *bdev)
181{
182 struct super_block *sb = get_super(bdev);
183 if (sb) {
184 int res = fsync_super(sb);
185 drop_super(sb);
186 return res;
187 }
188 return sync_blockdev(bdev);
189}
190
191/**
192 * freeze_bdev -- lock a filesystem and force it into a consistent state
193 * @bdev: blockdevice to lock
194 *
David Chinnerf73ca1b2007-01-10 23:15:41 -0800195 * This takes the block device bd_mount_sem to make sure no new mounts
Linus Torvalds1da177e2005-04-16 15:20:36 -0700196 * happen on bdev until thaw_bdev() is called.
197 * If a superblock is found on this device, we take the s_umount semaphore
198 * on it to make sure nobody unmounts until the snapshot creation is done.
199 */
200struct super_block *freeze_bdev(struct block_device *bdev)
201{
202 struct super_block *sb;
203
David Chinnerf73ca1b2007-01-10 23:15:41 -0800204 down(&bdev->bd_mount_sem);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700205 sb = get_super(bdev);
206 if (sb && !(sb->s_flags & MS_RDONLY)) {
207 sb->s_frozen = SB_FREEZE_WRITE;
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700208 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700209
OGAWA Hirofumid25b9a12006-03-25 03:07:44 -0800210 __fsync_super(sb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700211
212 sb->s_frozen = SB_FREEZE_TRANS;
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700213 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700214
215 sync_blockdev(sb->s_bdev);
216
217 if (sb->s_op->write_super_lockfs)
218 sb->s_op->write_super_lockfs(sb);
219 }
220
221 sync_blockdev(bdev);
222 return sb; /* thaw_bdev releases s->s_umount and bd_mount_sem */
223}
224EXPORT_SYMBOL(freeze_bdev);
225
226/**
227 * thaw_bdev -- unlock filesystem
228 * @bdev: blockdevice to unlock
229 * @sb: associated superblock
230 *
231 * Unlocks the filesystem and marks it writeable again after freeze_bdev().
232 */
233void thaw_bdev(struct block_device *bdev, struct super_block *sb)
234{
235 if (sb) {
236 BUG_ON(sb->s_bdev != bdev);
237
238 if (sb->s_op->unlockfs)
239 sb->s_op->unlockfs(sb);
240 sb->s_frozen = SB_UNFROZEN;
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700241 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700242 wake_up(&sb->s_wait_unfrozen);
243 drop_super(sb);
244 }
245
David Chinnerf73ca1b2007-01-10 23:15:41 -0800246 up(&bdev->bd_mount_sem);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700247}
248EXPORT_SYMBOL(thaw_bdev);
249
250/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700251 * Various filesystems appear to want __find_get_block to be non-blocking.
252 * But it's the page lock which protects the buffers. To get around this,
253 * we get exclusion from try_to_free_buffers with the blockdev mapping's
254 * private_lock.
255 *
256 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
257 * may be quite high. This code could TryLock the page, and if that
258 * succeeds, there is no need to take private_lock. (But if
259 * private_lock is contended then so is mapping->tree_lock).
260 */
261static struct buffer_head *
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -0800262__find_get_block_slow(struct block_device *bdev, sector_t block)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700263{
264 struct inode *bd_inode = bdev->bd_inode;
265 struct address_space *bd_mapping = bd_inode->i_mapping;
266 struct buffer_head *ret = NULL;
267 pgoff_t index;
268 struct buffer_head *bh;
269 struct buffer_head *head;
270 struct page *page;
271 int all_mapped = 1;
272
273 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
274 page = find_get_page(bd_mapping, index);
275 if (!page)
276 goto out;
277
278 spin_lock(&bd_mapping->private_lock);
279 if (!page_has_buffers(page))
280 goto out_unlock;
281 head = page_buffers(page);
282 bh = head;
283 do {
284 if (bh->b_blocknr == block) {
285 ret = bh;
286 get_bh(bh);
287 goto out_unlock;
288 }
289 if (!buffer_mapped(bh))
290 all_mapped = 0;
291 bh = bh->b_this_page;
292 } while (bh != head);
293
294 /* we might be here because some of the buffers on this page are
295 * not mapped. This is due to various races between
296 * file io on the block device and getblk. It gets dealt with
297 * elsewhere, don't buffer_error if we had some unmapped buffers
298 */
299 if (all_mapped) {
300 printk("__find_get_block_slow() failed. "
301 "block=%llu, b_blocknr=%llu\n",
Badari Pulavarty205f87f2006-03-26 01:38:00 -0800302 (unsigned long long)block,
303 (unsigned long long)bh->b_blocknr);
304 printk("b_state=0x%08lx, b_size=%zu\n",
305 bh->b_state, bh->b_size);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700306 printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits);
307 }
308out_unlock:
309 spin_unlock(&bd_mapping->private_lock);
310 page_cache_release(page);
311out:
312 return ret;
313}
314
315/* If invalidate_buffers() will trash dirty buffers, it means some kind
316 of fs corruption is going on. Trashing dirty data always imply losing
317 information that was supposed to be just stored on the physical layer
318 by the user.
319
320 Thus invalidate_buffers in general usage is not allwowed to trash
321 dirty buffers. For example ioctl(FLSBLKBUF) expects dirty data to
322 be preserved. These buffers are simply skipped.
323
324 We also skip buffers which are still in use. For example this can
325 happen if a userspace program is reading the block device.
326
327 NOTE: In the case where the user removed a removable-media-disk even if
328 there's still dirty data not synced on disk (due a bug in the device driver
329 or due an error of the user), by not destroying the dirty buffers we could
330 generate corruption also on the next media inserted, thus a parameter is
331 necessary to handle this case in the most safe way possible (trying
332 to not corrupt also the new disk inserted with the data belonging to
333 the old now corrupted disk). Also for the ramdisk the natural thing
334 to do in order to release the ramdisk memory is to destroy dirty buffers.
335
336 These are two special cases. Normal usage imply the device driver
337 to issue a sync on the device (without waiting I/O completion) and
338 then an invalidate_buffers call that doesn't trash dirty buffers.
339
340 For handling cache coherency with the blkdev pagecache the 'update' case
341 is been introduced. It is needed to re-read from disk any pinned
342 buffer. NOTE: re-reading from disk is destructive so we can do it only
343 when we assume nobody is changing the buffercache under our I/O and when
344 we think the disk contains more recent information than the buffercache.
345 The update == 1 pass marks the buffers we need to update, the update == 2
346 pass does the actual I/O. */
Peter Zijlstraf98393a2007-05-06 14:49:54 -0700347void invalidate_bdev(struct block_device *bdev)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700348{
Andrew Morton0e1dfc62006-07-30 03:03:28 -0700349 struct address_space *mapping = bdev->bd_inode->i_mapping;
350
351 if (mapping->nrpages == 0)
352 return;
353
Linus Torvalds1da177e2005-04-16 15:20:36 -0700354 invalidate_bh_lrus();
Andrew Mortonfc0ecff2007-02-10 01:45:39 -0800355 invalidate_mapping_pages(mapping, 0, -1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700356}
357
358/*
359 * Kick pdflush then try to free up some ZONE_NORMAL memory.
360 */
361static void free_more_memory(void)
362{
Mel Gorman19770b32008-04-28 02:12:18 -0700363 struct zone *zone;
Mel Gorman0e884602008-04-28 02:12:14 -0700364 int nid;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700365
Pekka J Enberg687a21c2005-06-28 20:44:55 -0700366 wakeup_pdflush(1024);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700367 yield();
368
Mel Gorman0e884602008-04-28 02:12:14 -0700369 for_each_online_node(nid) {
Mel Gorman19770b32008-04-28 02:12:18 -0700370 (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS),
371 gfp_zone(GFP_NOFS), NULL,
372 &zone);
373 if (zone)
Mel Gorman54a6eb52008-04-28 02:12:16 -0700374 try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0,
375 GFP_NOFS);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700376 }
377}
378
379/*
380 * I/O completion handler for block_read_full_page() - pages
381 * which come unlocked at the end of I/O.
382 */
383static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
384{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700385 unsigned long flags;
Nick Piggina3972202005-07-07 17:56:56 -0700386 struct buffer_head *first;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700387 struct buffer_head *tmp;
388 struct page *page;
389 int page_uptodate = 1;
390
391 BUG_ON(!buffer_async_read(bh));
392
393 page = bh->b_page;
394 if (uptodate) {
395 set_buffer_uptodate(bh);
396 } else {
397 clear_buffer_uptodate(bh);
398 if (printk_ratelimit())
399 buffer_io_error(bh);
400 SetPageError(page);
401 }
402
403 /*
404 * Be _very_ careful from here on. Bad things can happen if
405 * two buffer heads end IO at almost the same time and both
406 * decide that the page is now completely done.
407 */
Nick Piggina3972202005-07-07 17:56:56 -0700408 first = page_buffers(page);
409 local_irq_save(flags);
410 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700411 clear_buffer_async_read(bh);
412 unlock_buffer(bh);
413 tmp = bh;
414 do {
415 if (!buffer_uptodate(tmp))
416 page_uptodate = 0;
417 if (buffer_async_read(tmp)) {
418 BUG_ON(!buffer_locked(tmp));
419 goto still_busy;
420 }
421 tmp = tmp->b_this_page;
422 } while (tmp != bh);
Nick Piggina3972202005-07-07 17:56:56 -0700423 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
424 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700425
426 /*
427 * If none of the buffers had errors and they are all
428 * uptodate then we can set the page uptodate.
429 */
430 if (page_uptodate && !PageError(page))
431 SetPageUptodate(page);
432 unlock_page(page);
433 return;
434
435still_busy:
Nick Piggina3972202005-07-07 17:56:56 -0700436 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
437 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700438 return;
439}
440
441/*
442 * Completion handler for block_write_full_page() - pages which are unlocked
443 * during I/O, and which have PageWriteback cleared upon I/O completion.
444 */
Adrian Bunkb6cd0b72006-06-27 02:53:54 -0700445static void end_buffer_async_write(struct buffer_head *bh, int uptodate)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700446{
447 char b[BDEVNAME_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700448 unsigned long flags;
Nick Piggina3972202005-07-07 17:56:56 -0700449 struct buffer_head *first;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700450 struct buffer_head *tmp;
451 struct page *page;
452
453 BUG_ON(!buffer_async_write(bh));
454
455 page = bh->b_page;
456 if (uptodate) {
457 set_buffer_uptodate(bh);
458 } else {
459 if (printk_ratelimit()) {
460 buffer_io_error(bh);
461 printk(KERN_WARNING "lost page write due to "
462 "I/O error on %s\n",
463 bdevname(bh->b_bdev, b));
464 }
465 set_bit(AS_EIO, &page->mapping->flags);
Jan Kara58ff4072006-10-17 00:10:19 -0700466 set_buffer_write_io_error(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700467 clear_buffer_uptodate(bh);
468 SetPageError(page);
469 }
470
Nick Piggina3972202005-07-07 17:56:56 -0700471 first = page_buffers(page);
472 local_irq_save(flags);
473 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
474
Linus Torvalds1da177e2005-04-16 15:20:36 -0700475 clear_buffer_async_write(bh);
476 unlock_buffer(bh);
477 tmp = bh->b_this_page;
478 while (tmp != bh) {
479 if (buffer_async_write(tmp)) {
480 BUG_ON(!buffer_locked(tmp));
481 goto still_busy;
482 }
483 tmp = tmp->b_this_page;
484 }
Nick Piggina3972202005-07-07 17:56:56 -0700485 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
486 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700487 end_page_writeback(page);
488 return;
489
490still_busy:
Nick Piggina3972202005-07-07 17:56:56 -0700491 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
492 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700493 return;
494}
495
496/*
497 * If a page's buffers are under async readin (end_buffer_async_read
498 * completion) then there is a possibility that another thread of
499 * control could lock one of the buffers after it has completed
500 * but while some of the other buffers have not completed. This
501 * locked buffer would confuse end_buffer_async_read() into not unlocking
502 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
503 * that this buffer is not under async I/O.
504 *
505 * The page comes unlocked when it has no locked buffer_async buffers
506 * left.
507 *
508 * PageLocked prevents anyone starting new async I/O reads any of
509 * the buffers.
510 *
511 * PageWriteback is used to prevent simultaneous writeout of the same
512 * page.
513 *
514 * PageLocked prevents anyone from starting writeback of a page which is
515 * under read I/O (PageWriteback is only ever set against a locked page).
516 */
517static void mark_buffer_async_read(struct buffer_head *bh)
518{
519 bh->b_end_io = end_buffer_async_read;
520 set_buffer_async_read(bh);
521}
522
523void mark_buffer_async_write(struct buffer_head *bh)
524{
525 bh->b_end_io = end_buffer_async_write;
526 set_buffer_async_write(bh);
527}
528EXPORT_SYMBOL(mark_buffer_async_write);
529
530
531/*
532 * fs/buffer.c contains helper functions for buffer-backed address space's
533 * fsync functions. A common requirement for buffer-based filesystems is
534 * that certain data from the backing blockdev needs to be written out for
535 * a successful fsync(). For example, ext2 indirect blocks need to be
536 * written back and waited upon before fsync() returns.
537 *
538 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
539 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
540 * management of a list of dependent buffers at ->i_mapping->private_list.
541 *
542 * Locking is a little subtle: try_to_free_buffers() will remove buffers
543 * from their controlling inode's queue when they are being freed. But
544 * try_to_free_buffers() will be operating against the *blockdev* mapping
545 * at the time, not against the S_ISREG file which depends on those buffers.
546 * So the locking for private_list is via the private_lock in the address_space
547 * which backs the buffers. Which is different from the address_space
548 * against which the buffers are listed. So for a particular address_space,
549 * mapping->private_lock does *not* protect mapping->private_list! In fact,
550 * mapping->private_list will always be protected by the backing blockdev's
551 * ->private_lock.
552 *
553 * Which introduces a requirement: all buffers on an address_space's
554 * ->private_list must be from the same address_space: the blockdev's.
555 *
556 * address_spaces which do not place buffers at ->private_list via these
557 * utility functions are free to use private_lock and private_list for
558 * whatever they want. The only requirement is that list_empty(private_list)
559 * be true at clear_inode() time.
560 *
561 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
562 * filesystems should do that. invalidate_inode_buffers() should just go
563 * BUG_ON(!list_empty).
564 *
565 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
566 * take an address_space, not an inode. And it should be called
567 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
568 * queued up.
569 *
570 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
571 * list if it is already on a list. Because if the buffer is on a list,
572 * it *must* already be on the right one. If not, the filesystem is being
573 * silly. This will save a ton of locking. But first we have to ensure
574 * that buffers are taken *off* the old inode's list when they are freed
575 * (presumably in truncate). That requires careful auditing of all
576 * filesystems (do it inside bforget()). It could also be done by bringing
577 * b_inode back.
578 */
579
580/*
581 * The buffer's backing address_space's private_lock must be held
582 */
Thomas Petazzonidbacefc2008-07-29 22:33:47 -0700583static void __remove_assoc_queue(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700584{
585 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -0700586 WARN_ON(!bh->b_assoc_map);
587 if (buffer_write_io_error(bh))
588 set_bit(AS_EIO, &bh->b_assoc_map->flags);
589 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700590}
591
592int inode_has_buffers(struct inode *inode)
593{
594 return !list_empty(&inode->i_data.private_list);
595}
596
597/*
598 * osync is designed to support O_SYNC io. It waits synchronously for
599 * all already-submitted IO to complete, but does not queue any new
600 * writes to the disk.
601 *
602 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
603 * you dirty the buffers, and then use osync_inode_buffers to wait for
604 * completion. Any other dirty buffers which are not yet queued for
605 * write will not be flushed to disk by the osync.
606 */
607static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
608{
609 struct buffer_head *bh;
610 struct list_head *p;
611 int err = 0;
612
613 spin_lock(lock);
614repeat:
615 list_for_each_prev(p, list) {
616 bh = BH_ENTRY(p);
617 if (buffer_locked(bh)) {
618 get_bh(bh);
619 spin_unlock(lock);
620 wait_on_buffer(bh);
621 if (!buffer_uptodate(bh))
622 err = -EIO;
623 brelse(bh);
624 spin_lock(lock);
625 goto repeat;
626 }
627 }
628 spin_unlock(lock);
629 return err;
630}
631
632/**
Randy Dunlap78a4a502008-02-29 22:02:31 -0800633 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
Martin Waitz67be2dd2005-05-01 08:59:26 -0700634 * @mapping: the mapping which wants those buffers written
Linus Torvalds1da177e2005-04-16 15:20:36 -0700635 *
636 * Starts I/O against the buffers at mapping->private_list, and waits upon
637 * that I/O.
638 *
Martin Waitz67be2dd2005-05-01 08:59:26 -0700639 * Basically, this is a convenience function for fsync().
640 * @mapping is a file or directory which needs those buffers to be written for
641 * a successful fsync().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700642 */
643int sync_mapping_buffers(struct address_space *mapping)
644{
645 struct address_space *buffer_mapping = mapping->assoc_mapping;
646
647 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
648 return 0;
649
650 return fsync_buffers_list(&buffer_mapping->private_lock,
651 &mapping->private_list);
652}
653EXPORT_SYMBOL(sync_mapping_buffers);
654
655/*
656 * Called when we've recently written block `bblock', and it is known that
657 * `bblock' was for a buffer_boundary() buffer. This means that the block at
658 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
659 * dirty, schedule it for IO. So that indirects merge nicely with their data.
660 */
661void write_boundary_block(struct block_device *bdev,
662 sector_t bblock, unsigned blocksize)
663{
664 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
665 if (bh) {
666 if (buffer_dirty(bh))
667 ll_rw_block(WRITE, 1, &bh);
668 put_bh(bh);
669 }
670}
671
672void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
673{
674 struct address_space *mapping = inode->i_mapping;
675 struct address_space *buffer_mapping = bh->b_page->mapping;
676
677 mark_buffer_dirty(bh);
678 if (!mapping->assoc_mapping) {
679 mapping->assoc_mapping = buffer_mapping;
680 } else {
Eric Sesterhenne827f922006-03-26 18:24:46 +0200681 BUG_ON(mapping->assoc_mapping != buffer_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700682 }
Jan Kara535ee2f2008-02-08 04:21:59 -0800683 if (!bh->b_assoc_map) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700684 spin_lock(&buffer_mapping->private_lock);
685 list_move_tail(&bh->b_assoc_buffers,
686 &mapping->private_list);
Jan Kara58ff4072006-10-17 00:10:19 -0700687 bh->b_assoc_map = mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700688 spin_unlock(&buffer_mapping->private_lock);
689 }
690}
691EXPORT_SYMBOL(mark_buffer_dirty_inode);
692
693/*
Nick Piggin787d2212007-07-17 04:03:34 -0700694 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
695 * dirty.
696 *
697 * If warn is true, then emit a warning if the page is not uptodate and has
698 * not been truncated.
699 */
700static int __set_page_dirty(struct page *page,
701 struct address_space *mapping, int warn)
702{
703 if (unlikely(!mapping))
704 return !TestSetPageDirty(page);
705
706 if (TestSetPageDirty(page))
707 return 0;
708
Nick Piggin19fd6232008-07-25 19:45:32 -0700709 spin_lock_irq(&mapping->tree_lock);
Nick Piggin787d2212007-07-17 04:03:34 -0700710 if (page->mapping) { /* Race with truncate? */
711 WARN_ON_ONCE(warn && !PageUptodate(page));
712
713 if (mapping_cap_account_dirty(mapping)) {
714 __inc_zone_page_state(page, NR_FILE_DIRTY);
Peter Zijlstrac9e51e42007-10-16 23:25:47 -0700715 __inc_bdi_stat(mapping->backing_dev_info,
716 BDI_RECLAIMABLE);
Nick Piggin787d2212007-07-17 04:03:34 -0700717 task_io_account_write(PAGE_CACHE_SIZE);
718 }
719 radix_tree_tag_set(&mapping->page_tree,
720 page_index(page), PAGECACHE_TAG_DIRTY);
721 }
Nick Piggin19fd6232008-07-25 19:45:32 -0700722 spin_unlock_irq(&mapping->tree_lock);
Nick Piggin787d2212007-07-17 04:03:34 -0700723 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
724
725 return 1;
726}
727
728/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700729 * Add a page to the dirty page list.
730 *
731 * It is a sad fact of life that this function is called from several places
732 * deeply under spinlocking. It may not sleep.
733 *
734 * If the page has buffers, the uptodate buffers are set dirty, to preserve
735 * dirty-state coherency between the page and the buffers. It the page does
736 * not have buffers then when they are later attached they will all be set
737 * dirty.
738 *
739 * The buffers are dirtied before the page is dirtied. There's a small race
740 * window in which a writepage caller may see the page cleanness but not the
741 * buffer dirtiness. That's fine. If this code were to set the page dirty
742 * before the buffers, a concurrent writepage caller could clear the page dirty
743 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
744 * page on the dirty page list.
745 *
746 * We use private_lock to lock against try_to_free_buffers while using the
747 * page's buffer list. Also use this to protect against clean buffers being
748 * added to the page after it was set dirty.
749 *
750 * FIXME: may need to call ->reservepage here as well. That's rather up to the
751 * address_space though.
752 */
753int __set_page_dirty_buffers(struct page *page)
754{
Nick Piggin787d2212007-07-17 04:03:34 -0700755 struct address_space *mapping = page_mapping(page);
Nick Pigginebf7a222006-10-10 04:36:54 +0200756
757 if (unlikely(!mapping))
758 return !TestSetPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700759
760 spin_lock(&mapping->private_lock);
761 if (page_has_buffers(page)) {
762 struct buffer_head *head = page_buffers(page);
763 struct buffer_head *bh = head;
764
765 do {
766 set_buffer_dirty(bh);
767 bh = bh->b_this_page;
768 } while (bh != head);
769 }
770 spin_unlock(&mapping->private_lock);
771
Nick Piggin787d2212007-07-17 04:03:34 -0700772 return __set_page_dirty(page, mapping, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700773}
774EXPORT_SYMBOL(__set_page_dirty_buffers);
775
776/*
777 * Write out and wait upon a list of buffers.
778 *
779 * We have conflicting pressures: we want to make sure that all
780 * initially dirty buffers get waited on, but that any subsequently
781 * dirtied buffers don't. After all, we don't want fsync to last
782 * forever if somebody is actively writing to the file.
783 *
784 * Do this in two main stages: first we copy dirty buffers to a
785 * temporary inode list, queueing the writes as we go. Then we clean
786 * up, waiting for those writes to complete.
787 *
788 * During this second stage, any subsequent updates to the file may end
789 * up refiling the buffer on the original inode's dirty list again, so
790 * there is a chance we will end up with a buffer queued for write but
791 * not yet completed on that list. So, as a final cleanup we go through
792 * the osync code to catch these locked, dirty buffers without requeuing
793 * any newly dirty buffers for write.
794 */
795static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
796{
797 struct buffer_head *bh;
798 struct list_head tmp;
Jan Kara535ee2f2008-02-08 04:21:59 -0800799 struct address_space *mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700800 int err = 0, err2;
801
802 INIT_LIST_HEAD(&tmp);
803
804 spin_lock(lock);
805 while (!list_empty(list)) {
806 bh = BH_ENTRY(list->next);
Jan Kara535ee2f2008-02-08 04:21:59 -0800807 mapping = bh->b_assoc_map;
Jan Kara58ff4072006-10-17 00:10:19 -0700808 __remove_assoc_queue(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -0800809 /* Avoid race with mark_buffer_dirty_inode() which does
810 * a lockless check and we rely on seeing the dirty bit */
811 smp_mb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700812 if (buffer_dirty(bh) || buffer_locked(bh)) {
813 list_add(&bh->b_assoc_buffers, &tmp);
Jan Kara535ee2f2008-02-08 04:21:59 -0800814 bh->b_assoc_map = mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700815 if (buffer_dirty(bh)) {
816 get_bh(bh);
817 spin_unlock(lock);
818 /*
819 * Ensure any pending I/O completes so that
820 * ll_rw_block() actually writes the current
821 * contents - it is a noop if I/O is still in
822 * flight on potentially older contents.
823 */
Jens Axboe18ce3752008-07-01 09:07:34 +0200824 ll_rw_block(SWRITE_SYNC, 1, &bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700825 brelse(bh);
826 spin_lock(lock);
827 }
828 }
829 }
830
831 while (!list_empty(&tmp)) {
832 bh = BH_ENTRY(tmp.prev);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700833 get_bh(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -0800834 mapping = bh->b_assoc_map;
835 __remove_assoc_queue(bh);
836 /* Avoid race with mark_buffer_dirty_inode() which does
837 * a lockless check and we rely on seeing the dirty bit */
838 smp_mb();
839 if (buffer_dirty(bh)) {
840 list_add(&bh->b_assoc_buffers,
Jan Karae3892292008-03-04 14:28:33 -0800841 &mapping->private_list);
Jan Kara535ee2f2008-02-08 04:21:59 -0800842 bh->b_assoc_map = mapping;
843 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700844 spin_unlock(lock);
845 wait_on_buffer(bh);
846 if (!buffer_uptodate(bh))
847 err = -EIO;
848 brelse(bh);
849 spin_lock(lock);
850 }
851
852 spin_unlock(lock);
853 err2 = osync_buffers_list(lock, list);
854 if (err)
855 return err;
856 else
857 return err2;
858}
859
860/*
861 * Invalidate any and all dirty buffers on a given inode. We are
862 * probably unmounting the fs, but that doesn't mean we have already
863 * done a sync(). Just drop the buffers from the inode list.
864 *
865 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
866 * assumes that all the buffers are against the blockdev. Not true
867 * for reiserfs.
868 */
869void invalidate_inode_buffers(struct inode *inode)
870{
871 if (inode_has_buffers(inode)) {
872 struct address_space *mapping = &inode->i_data;
873 struct list_head *list = &mapping->private_list;
874 struct address_space *buffer_mapping = mapping->assoc_mapping;
875
876 spin_lock(&buffer_mapping->private_lock);
877 while (!list_empty(list))
878 __remove_assoc_queue(BH_ENTRY(list->next));
879 spin_unlock(&buffer_mapping->private_lock);
880 }
881}
882
883/*
884 * Remove any clean buffers from the inode's buffer list. This is called
885 * when we're trying to free the inode itself. Those buffers can pin it.
886 *
887 * Returns true if all buffers were removed.
888 */
889int remove_inode_buffers(struct inode *inode)
890{
891 int ret = 1;
892
893 if (inode_has_buffers(inode)) {
894 struct address_space *mapping = &inode->i_data;
895 struct list_head *list = &mapping->private_list;
896 struct address_space *buffer_mapping = mapping->assoc_mapping;
897
898 spin_lock(&buffer_mapping->private_lock);
899 while (!list_empty(list)) {
900 struct buffer_head *bh = BH_ENTRY(list->next);
901 if (buffer_dirty(bh)) {
902 ret = 0;
903 break;
904 }
905 __remove_assoc_queue(bh);
906 }
907 spin_unlock(&buffer_mapping->private_lock);
908 }
909 return ret;
910}
911
912/*
913 * Create the appropriate buffers when given a page for data area and
914 * the size of each buffer.. Use the bh->b_this_page linked list to
915 * follow the buffers created. Return NULL if unable to create more
916 * buffers.
917 *
918 * The retry flag is used to differentiate async IO (paging, swapping)
919 * which may not fail from ordinary buffer allocations.
920 */
921struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
922 int retry)
923{
924 struct buffer_head *bh, *head;
925 long offset;
926
927try_again:
928 head = NULL;
929 offset = PAGE_SIZE;
930 while ((offset -= size) >= 0) {
931 bh = alloc_buffer_head(GFP_NOFS);
932 if (!bh)
933 goto no_grow;
934
935 bh->b_bdev = NULL;
936 bh->b_this_page = head;
937 bh->b_blocknr = -1;
938 head = bh;
939
940 bh->b_state = 0;
941 atomic_set(&bh->b_count, 0);
Chris Masonfc5cd582006-02-01 03:06:48 -0800942 bh->b_private = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700943 bh->b_size = size;
944
945 /* Link the buffer to its page */
946 set_bh_page(bh, page, offset);
947
Nathan Scott01ffe332006-01-17 09:02:07 +1100948 init_buffer(bh, NULL, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700949 }
950 return head;
951/*
952 * In case anything failed, we just free everything we got.
953 */
954no_grow:
955 if (head) {
956 do {
957 bh = head;
958 head = head->b_this_page;
959 free_buffer_head(bh);
960 } while (head);
961 }
962
963 /*
964 * Return failure for non-async IO requests. Async IO requests
965 * are not allowed to fail, so we have to wait until buffer heads
966 * become available. But we don't want tasks sleeping with
967 * partially complete buffers, so all were released above.
968 */
969 if (!retry)
970 return NULL;
971
972 /* We're _really_ low on memory. Now we just
973 * wait for old buffer heads to become free due to
974 * finishing IO. Since this is an async request and
975 * the reserve list is empty, we're sure there are
976 * async buffer heads in use.
977 */
978 free_more_memory();
979 goto try_again;
980}
981EXPORT_SYMBOL_GPL(alloc_page_buffers);
982
983static inline void
984link_dev_buffers(struct page *page, struct buffer_head *head)
985{
986 struct buffer_head *bh, *tail;
987
988 bh = head;
989 do {
990 tail = bh;
991 bh = bh->b_this_page;
992 } while (bh);
993 tail->b_this_page = head;
994 attach_page_buffers(page, head);
995}
996
997/*
998 * Initialise the state of a blockdev page's buffers.
999 */
1000static void
1001init_page_buffers(struct page *page, struct block_device *bdev,
1002 sector_t block, int size)
1003{
1004 struct buffer_head *head = page_buffers(page);
1005 struct buffer_head *bh = head;
1006 int uptodate = PageUptodate(page);
1007
1008 do {
1009 if (!buffer_mapped(bh)) {
1010 init_buffer(bh, NULL, NULL);
1011 bh->b_bdev = bdev;
1012 bh->b_blocknr = block;
1013 if (uptodate)
1014 set_buffer_uptodate(bh);
1015 set_buffer_mapped(bh);
1016 }
1017 block++;
1018 bh = bh->b_this_page;
1019 } while (bh != head);
1020}
1021
1022/*
1023 * Create the page-cache page that contains the requested block.
1024 *
1025 * This is user purely for blockdev mappings.
1026 */
1027static struct page *
1028grow_dev_page(struct block_device *bdev, sector_t block,
1029 pgoff_t index, int size)
1030{
1031 struct inode *inode = bdev->bd_inode;
1032 struct page *page;
1033 struct buffer_head *bh;
1034
Christoph Lameterea125892007-05-16 22:11:21 -07001035 page = find_or_create_page(inode->i_mapping, index,
Mel Gorman769848c2007-07-17 04:03:05 -07001036 (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001037 if (!page)
1038 return NULL;
1039
Eric Sesterhenne827f922006-03-26 18:24:46 +02001040 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001041
1042 if (page_has_buffers(page)) {
1043 bh = page_buffers(page);
1044 if (bh->b_size == size) {
1045 init_page_buffers(page, bdev, block, size);
1046 return page;
1047 }
1048 if (!try_to_free_buffers(page))
1049 goto failed;
1050 }
1051
1052 /*
1053 * Allocate some buffers for this page
1054 */
1055 bh = alloc_page_buffers(page, size, 0);
1056 if (!bh)
1057 goto failed;
1058
1059 /*
1060 * Link the page to the buffers and initialise them. Take the
1061 * lock to be atomic wrt __find_get_block(), which does not
1062 * run under the page lock.
1063 */
1064 spin_lock(&inode->i_mapping->private_lock);
1065 link_dev_buffers(page, bh);
1066 init_page_buffers(page, bdev, block, size);
1067 spin_unlock(&inode->i_mapping->private_lock);
1068 return page;
1069
1070failed:
1071 BUG();
1072 unlock_page(page);
1073 page_cache_release(page);
1074 return NULL;
1075}
1076
1077/*
1078 * Create buffers for the specified block device block's page. If
1079 * that page was dirty, the buffers are set dirty also.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001080 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001081static int
Linus Torvalds1da177e2005-04-16 15:20:36 -07001082grow_buffers(struct block_device *bdev, sector_t block, int size)
1083{
1084 struct page *page;
1085 pgoff_t index;
1086 int sizebits;
1087
1088 sizebits = -1;
1089 do {
1090 sizebits++;
1091 } while ((size << sizebits) < PAGE_SIZE);
1092
1093 index = block >> sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001094
Andrew Mortone5657932006-10-11 01:21:46 -07001095 /*
1096 * Check for a block which wants to lie outside our maximum possible
1097 * pagecache index. (this comparison is done using sector_t types).
1098 */
1099 if (unlikely(index != block >> sizebits)) {
1100 char b[BDEVNAME_SIZE];
1101
1102 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1103 "device %s\n",
Harvey Harrison8e24eea2008-04-30 00:55:09 -07001104 __func__, (unsigned long long)block,
Andrew Mortone5657932006-10-11 01:21:46 -07001105 bdevname(bdev, b));
1106 return -EIO;
1107 }
1108 block = index << sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001109 /* Create a page with the proper size buffers.. */
1110 page = grow_dev_page(bdev, block, index, size);
1111 if (!page)
1112 return 0;
1113 unlock_page(page);
1114 page_cache_release(page);
1115 return 1;
1116}
1117
Adrian Bunk75c96f82005-05-05 16:16:09 -07001118static struct buffer_head *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001119__getblk_slow(struct block_device *bdev, sector_t block, int size)
1120{
1121 /* Size must be multiple of hard sectorsize */
1122 if (unlikely(size & (bdev_hardsect_size(bdev)-1) ||
1123 (size < 512 || size > PAGE_SIZE))) {
1124 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1125 size);
1126 printk(KERN_ERR "hardsect size: %d\n",
1127 bdev_hardsect_size(bdev));
1128
1129 dump_stack();
1130 return NULL;
1131 }
1132
1133 for (;;) {
1134 struct buffer_head * bh;
Andrew Mortone5657932006-10-11 01:21:46 -07001135 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001136
1137 bh = __find_get_block(bdev, block, size);
1138 if (bh)
1139 return bh;
1140
Andrew Mortone5657932006-10-11 01:21:46 -07001141 ret = grow_buffers(bdev, block, size);
1142 if (ret < 0)
1143 return NULL;
1144 if (ret == 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001145 free_more_memory();
1146 }
1147}
1148
1149/*
1150 * The relationship between dirty buffers and dirty pages:
1151 *
1152 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1153 * the page is tagged dirty in its radix tree.
1154 *
1155 * At all times, the dirtiness of the buffers represents the dirtiness of
1156 * subsections of the page. If the page has buffers, the page dirty bit is
1157 * merely a hint about the true dirty state.
1158 *
1159 * When a page is set dirty in its entirety, all its buffers are marked dirty
1160 * (if the page has buffers).
1161 *
1162 * When a buffer is marked dirty, its page is dirtied, but the page's other
1163 * buffers are not.
1164 *
1165 * Also. When blockdev buffers are explicitly read with bread(), they
1166 * individually become uptodate. But their backing page remains not
1167 * uptodate - even if all of its buffers are uptodate. A subsequent
1168 * block_read_full_page() against that page will discover all the uptodate
1169 * buffers, will set the page uptodate and will perform no I/O.
1170 */
1171
1172/**
1173 * mark_buffer_dirty - mark a buffer_head as needing writeout
Martin Waitz67be2dd2005-05-01 08:59:26 -07001174 * @bh: the buffer_head to mark dirty
Linus Torvalds1da177e2005-04-16 15:20:36 -07001175 *
1176 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1177 * backing page dirty, then tag the page as dirty in its address_space's radix
1178 * tree and then attach the address_space's inode to its superblock's dirty
1179 * inode list.
1180 *
1181 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1182 * mapping->tree_lock and the global inode_lock.
1183 */
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -08001184void mark_buffer_dirty(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001185{
Nick Piggin787d2212007-07-17 04:03:34 -07001186 WARN_ON_ONCE(!buffer_uptodate(bh));
Linus Torvalds1be62dc2008-04-04 14:38:17 -07001187
1188 /*
1189 * Very *carefully* optimize the it-is-already-dirty case.
1190 *
1191 * Don't let the final "is it dirty" escape to before we
1192 * perhaps modified the buffer.
1193 */
1194 if (buffer_dirty(bh)) {
1195 smp_mb();
1196 if (buffer_dirty(bh))
1197 return;
1198 }
1199
1200 if (!test_set_buffer_dirty(bh))
Nick Piggin787d2212007-07-17 04:03:34 -07001201 __set_page_dirty(bh->b_page, page_mapping(bh->b_page), 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001202}
1203
1204/*
1205 * Decrement a buffer_head's reference count. If all buffers against a page
1206 * have zero reference count, are clean and unlocked, and if the page is clean
1207 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1208 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1209 * a page but it ends up not being freed, and buffers may later be reattached).
1210 */
1211void __brelse(struct buffer_head * buf)
1212{
1213 if (atomic_read(&buf->b_count)) {
1214 put_bh(buf);
1215 return;
1216 }
Arjan van de Ven5c752ad2008-07-25 19:45:40 -07001217 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
Linus Torvalds1da177e2005-04-16 15:20:36 -07001218}
1219
1220/*
1221 * bforget() is like brelse(), except it discards any
1222 * potentially dirty data.
1223 */
1224void __bforget(struct buffer_head *bh)
1225{
1226 clear_buffer_dirty(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -08001227 if (bh->b_assoc_map) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001228 struct address_space *buffer_mapping = bh->b_page->mapping;
1229
1230 spin_lock(&buffer_mapping->private_lock);
1231 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -07001232 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001233 spin_unlock(&buffer_mapping->private_lock);
1234 }
1235 __brelse(bh);
1236}
1237
1238static struct buffer_head *__bread_slow(struct buffer_head *bh)
1239{
1240 lock_buffer(bh);
1241 if (buffer_uptodate(bh)) {
1242 unlock_buffer(bh);
1243 return bh;
1244 } else {
1245 get_bh(bh);
1246 bh->b_end_io = end_buffer_read_sync;
1247 submit_bh(READ, bh);
1248 wait_on_buffer(bh);
1249 if (buffer_uptodate(bh))
1250 return bh;
1251 }
1252 brelse(bh);
1253 return NULL;
1254}
1255
1256/*
1257 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1258 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1259 * refcount elevated by one when they're in an LRU. A buffer can only appear
1260 * once in a particular CPU's LRU. A single buffer can be present in multiple
1261 * CPU's LRUs at the same time.
1262 *
1263 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1264 * sb_find_get_block().
1265 *
1266 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1267 * a local interrupt disable for that.
1268 */
1269
1270#define BH_LRU_SIZE 8
1271
1272struct bh_lru {
1273 struct buffer_head *bhs[BH_LRU_SIZE];
1274};
1275
1276static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1277
1278#ifdef CONFIG_SMP
1279#define bh_lru_lock() local_irq_disable()
1280#define bh_lru_unlock() local_irq_enable()
1281#else
1282#define bh_lru_lock() preempt_disable()
1283#define bh_lru_unlock() preempt_enable()
1284#endif
1285
1286static inline void check_irqs_on(void)
1287{
1288#ifdef irqs_disabled
1289 BUG_ON(irqs_disabled());
1290#endif
1291}
1292
1293/*
1294 * The LRU management algorithm is dopey-but-simple. Sorry.
1295 */
1296static void bh_lru_install(struct buffer_head *bh)
1297{
1298 struct buffer_head *evictee = NULL;
1299 struct bh_lru *lru;
1300
1301 check_irqs_on();
1302 bh_lru_lock();
1303 lru = &__get_cpu_var(bh_lrus);
1304 if (lru->bhs[0] != bh) {
1305 struct buffer_head *bhs[BH_LRU_SIZE];
1306 int in;
1307 int out = 0;
1308
1309 get_bh(bh);
1310 bhs[out++] = bh;
1311 for (in = 0; in < BH_LRU_SIZE; in++) {
1312 struct buffer_head *bh2 = lru->bhs[in];
1313
1314 if (bh2 == bh) {
1315 __brelse(bh2);
1316 } else {
1317 if (out >= BH_LRU_SIZE) {
1318 BUG_ON(evictee != NULL);
1319 evictee = bh2;
1320 } else {
1321 bhs[out++] = bh2;
1322 }
1323 }
1324 }
1325 while (out < BH_LRU_SIZE)
1326 bhs[out++] = NULL;
1327 memcpy(lru->bhs, bhs, sizeof(bhs));
1328 }
1329 bh_lru_unlock();
1330
1331 if (evictee)
1332 __brelse(evictee);
1333}
1334
1335/*
1336 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1337 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001338static struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001339lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001340{
1341 struct buffer_head *ret = NULL;
1342 struct bh_lru *lru;
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001343 unsigned int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001344
1345 check_irqs_on();
1346 bh_lru_lock();
1347 lru = &__get_cpu_var(bh_lrus);
1348 for (i = 0; i < BH_LRU_SIZE; i++) {
1349 struct buffer_head *bh = lru->bhs[i];
1350
1351 if (bh && bh->b_bdev == bdev &&
1352 bh->b_blocknr == block && bh->b_size == size) {
1353 if (i) {
1354 while (i) {
1355 lru->bhs[i] = lru->bhs[i - 1];
1356 i--;
1357 }
1358 lru->bhs[0] = bh;
1359 }
1360 get_bh(bh);
1361 ret = bh;
1362 break;
1363 }
1364 }
1365 bh_lru_unlock();
1366 return ret;
1367}
1368
1369/*
1370 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1371 * it in the LRU and mark it as accessed. If it is not present then return
1372 * NULL
1373 */
1374struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001375__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001376{
1377 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1378
1379 if (bh == NULL) {
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001380 bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001381 if (bh)
1382 bh_lru_install(bh);
1383 }
1384 if (bh)
1385 touch_buffer(bh);
1386 return bh;
1387}
1388EXPORT_SYMBOL(__find_get_block);
1389
1390/*
1391 * __getblk will locate (and, if necessary, create) the buffer_head
1392 * which corresponds to the passed block_device, block and size. The
1393 * returned buffer has its reference count incremented.
1394 *
1395 * __getblk() cannot fail - it just keeps trying. If you pass it an
1396 * illegal block number, __getblk() will happily return a buffer_head
1397 * which represents the non-existent block. Very weird.
1398 *
1399 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1400 * attempt is failing. FIXME, perhaps?
1401 */
1402struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001403__getblk(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001404{
1405 struct buffer_head *bh = __find_get_block(bdev, block, size);
1406
1407 might_sleep();
1408 if (bh == NULL)
1409 bh = __getblk_slow(bdev, block, size);
1410 return bh;
1411}
1412EXPORT_SYMBOL(__getblk);
1413
1414/*
1415 * Do async read-ahead on a buffer..
1416 */
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001417void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001418{
1419 struct buffer_head *bh = __getblk(bdev, block, size);
Andrew Mortona3e713b2005-10-30 15:03:15 -08001420 if (likely(bh)) {
1421 ll_rw_block(READA, 1, &bh);
1422 brelse(bh);
1423 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001424}
1425EXPORT_SYMBOL(__breadahead);
1426
1427/**
1428 * __bread() - reads a specified block and returns the bh
Martin Waitz67be2dd2005-05-01 08:59:26 -07001429 * @bdev: the block_device to read from
Linus Torvalds1da177e2005-04-16 15:20:36 -07001430 * @block: number of block
1431 * @size: size (in bytes) to read
1432 *
1433 * Reads a specified block, and returns buffer head that contains it.
1434 * It returns NULL if the block was unreadable.
1435 */
1436struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001437__bread(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001438{
1439 struct buffer_head *bh = __getblk(bdev, block, size);
1440
Andrew Mortona3e713b2005-10-30 15:03:15 -08001441 if (likely(bh) && !buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001442 bh = __bread_slow(bh);
1443 return bh;
1444}
1445EXPORT_SYMBOL(__bread);
1446
1447/*
1448 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1449 * This doesn't race because it runs in each cpu either in irq
1450 * or with preempt disabled.
1451 */
1452static void invalidate_bh_lru(void *arg)
1453{
1454 struct bh_lru *b = &get_cpu_var(bh_lrus);
1455 int i;
1456
1457 for (i = 0; i < BH_LRU_SIZE; i++) {
1458 brelse(b->bhs[i]);
1459 b->bhs[i] = NULL;
1460 }
1461 put_cpu_var(bh_lrus);
1462}
1463
Peter Zijlstraf9a14392007-05-06 14:49:55 -07001464void invalidate_bh_lrus(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001465{
Jens Axboe15c8b6c2008-05-09 09:39:44 +02001466 on_each_cpu(invalidate_bh_lru, NULL, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001467}
Nick Piggin9db55792008-02-08 04:19:49 -08001468EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001469
1470void set_bh_page(struct buffer_head *bh,
1471 struct page *page, unsigned long offset)
1472{
1473 bh->b_page = page;
Eric Sesterhenne827f922006-03-26 18:24:46 +02001474 BUG_ON(offset >= PAGE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001475 if (PageHighMem(page))
1476 /*
1477 * This catches illegal uses and preserves the offset:
1478 */
1479 bh->b_data = (char *)(0 + offset);
1480 else
1481 bh->b_data = page_address(page) + offset;
1482}
1483EXPORT_SYMBOL(set_bh_page);
1484
1485/*
1486 * Called when truncating a buffer on a page completely.
1487 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001488static void discard_buffer(struct buffer_head * bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001489{
1490 lock_buffer(bh);
1491 clear_buffer_dirty(bh);
1492 bh->b_bdev = NULL;
1493 clear_buffer_mapped(bh);
1494 clear_buffer_req(bh);
1495 clear_buffer_new(bh);
1496 clear_buffer_delay(bh);
David Chinner33a266d2007-02-12 00:51:41 -08001497 clear_buffer_unwritten(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001498 unlock_buffer(bh);
1499}
1500
1501/**
Linus Torvalds1da177e2005-04-16 15:20:36 -07001502 * block_invalidatepage - invalidate part of all of a buffer-backed page
1503 *
1504 * @page: the page which is affected
1505 * @offset: the index of the truncation point
1506 *
1507 * block_invalidatepage() is called when all or part of the page has become
1508 * invalidatedby a truncate operation.
1509 *
1510 * block_invalidatepage() does not have to release all buffers, but it must
1511 * ensure that no dirty buffer is left outside @offset and that no I/O
1512 * is underway against any of the blocks which are outside the truncation
1513 * point. Because the caller is about to free (and possibly reuse) those
1514 * blocks on-disk.
1515 */
NeilBrown2ff28e22006-03-26 01:37:18 -08001516void block_invalidatepage(struct page *page, unsigned long offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001517{
1518 struct buffer_head *head, *bh, *next;
1519 unsigned int curr_off = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001520
1521 BUG_ON(!PageLocked(page));
1522 if (!page_has_buffers(page))
1523 goto out;
1524
1525 head = page_buffers(page);
1526 bh = head;
1527 do {
1528 unsigned int next_off = curr_off + bh->b_size;
1529 next = bh->b_this_page;
1530
1531 /*
1532 * is this block fully invalidated?
1533 */
1534 if (offset <= curr_off)
1535 discard_buffer(bh);
1536 curr_off = next_off;
1537 bh = next;
1538 } while (bh != head);
1539
1540 /*
1541 * We release buffers only if the entire page is being invalidated.
1542 * The get_block cached value has been unconditionally invalidated,
1543 * so real IO is not possible anymore.
1544 */
1545 if (offset == 0)
NeilBrown2ff28e22006-03-26 01:37:18 -08001546 try_to_release_page(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001547out:
NeilBrown2ff28e22006-03-26 01:37:18 -08001548 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001549}
1550EXPORT_SYMBOL(block_invalidatepage);
1551
1552/*
1553 * We attach and possibly dirty the buffers atomically wrt
1554 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1555 * is already excluded via the page lock.
1556 */
1557void create_empty_buffers(struct page *page,
1558 unsigned long blocksize, unsigned long b_state)
1559{
1560 struct buffer_head *bh, *head, *tail;
1561
1562 head = alloc_page_buffers(page, blocksize, 1);
1563 bh = head;
1564 do {
1565 bh->b_state |= b_state;
1566 tail = bh;
1567 bh = bh->b_this_page;
1568 } while (bh);
1569 tail->b_this_page = head;
1570
1571 spin_lock(&page->mapping->private_lock);
1572 if (PageUptodate(page) || PageDirty(page)) {
1573 bh = head;
1574 do {
1575 if (PageDirty(page))
1576 set_buffer_dirty(bh);
1577 if (PageUptodate(page))
1578 set_buffer_uptodate(bh);
1579 bh = bh->b_this_page;
1580 } while (bh != head);
1581 }
1582 attach_page_buffers(page, head);
1583 spin_unlock(&page->mapping->private_lock);
1584}
1585EXPORT_SYMBOL(create_empty_buffers);
1586
1587/*
1588 * We are taking a block for data and we don't want any output from any
1589 * buffer-cache aliases starting from return from that function and
1590 * until the moment when something will explicitly mark the buffer
1591 * dirty (hopefully that will not happen until we will free that block ;-)
1592 * We don't even need to mark it not-uptodate - nobody can expect
1593 * anything from a newly allocated buffer anyway. We used to used
1594 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1595 * don't want to mark the alias unmapped, for example - it would confuse
1596 * anyone who might pick it with bread() afterwards...
1597 *
1598 * Also.. Note that bforget() doesn't lock the buffer. So there can
1599 * be writeout I/O going on against recently-freed buffers. We don't
1600 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1601 * only if we really need to. That happens here.
1602 */
1603void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1604{
1605 struct buffer_head *old_bh;
1606
1607 might_sleep();
1608
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001609 old_bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001610 if (old_bh) {
1611 clear_buffer_dirty(old_bh);
1612 wait_on_buffer(old_bh);
1613 clear_buffer_req(old_bh);
1614 __brelse(old_bh);
1615 }
1616}
1617EXPORT_SYMBOL(unmap_underlying_metadata);
1618
1619/*
1620 * NOTE! All mapped/uptodate combinations are valid:
1621 *
1622 * Mapped Uptodate Meaning
1623 *
1624 * No No "unknown" - must do get_block()
1625 * No Yes "hole" - zero-filled
1626 * Yes No "allocated" - allocated on disk, not read in
1627 * Yes Yes "valid" - allocated and up-to-date in memory.
1628 *
1629 * "Dirty" is valid only with the last case (mapped+uptodate).
1630 */
1631
1632/*
1633 * While block_write_full_page is writing back the dirty buffers under
1634 * the page lock, whoever dirtied the buffers may decide to clean them
1635 * again at any time. We handle that by only looking at the buffer
1636 * state inside lock_buffer().
1637 *
1638 * If block_write_full_page() is called for regular writeback
1639 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1640 * locked buffer. This only can happen if someone has written the buffer
1641 * directly, with submit_bh(). At the address_space level PageWriteback
1642 * prevents this contention from occurring.
1643 */
1644static int __block_write_full_page(struct inode *inode, struct page *page,
1645 get_block_t *get_block, struct writeback_control *wbc)
1646{
1647 int err;
1648 sector_t block;
1649 sector_t last_block;
Andrew Mortonf0fbd5f2005-05-05 16:15:48 -07001650 struct buffer_head *bh, *head;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001651 const unsigned blocksize = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001652 int nr_underway = 0;
1653
1654 BUG_ON(!PageLocked(page));
1655
1656 last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
1657
1658 if (!page_has_buffers(page)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001659 create_empty_buffers(page, blocksize,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001660 (1 << BH_Dirty)|(1 << BH_Uptodate));
1661 }
1662
1663 /*
1664 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1665 * here, and the (potentially unmapped) buffers may become dirty at
1666 * any time. If a buffer becomes dirty here after we've inspected it
1667 * then we just miss that fact, and the page stays dirty.
1668 *
1669 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1670 * handle that here by just cleaning them.
1671 */
1672
Andrew Morton54b21a72006-01-08 01:03:05 -08001673 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001674 head = page_buffers(page);
1675 bh = head;
1676
1677 /*
1678 * Get all the dirty buffers mapped to disk addresses and
1679 * handle any aliases from the underlying blockdev's mapping.
1680 */
1681 do {
1682 if (block > last_block) {
1683 /*
1684 * mapped buffers outside i_size will occur, because
1685 * this page can be outside i_size when there is a
1686 * truncate in progress.
1687 */
1688 /*
1689 * The buffer was zeroed by block_write_full_page()
1690 */
1691 clear_buffer_dirty(bh);
1692 set_buffer_uptodate(bh);
Alex Tomas29a814d2008-07-11 19:27:31 -04001693 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1694 buffer_dirty(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001695 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001696 err = get_block(inode, block, bh, 1);
1697 if (err)
1698 goto recover;
Alex Tomas29a814d2008-07-11 19:27:31 -04001699 clear_buffer_delay(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001700 if (buffer_new(bh)) {
1701 /* blockdev mappings never come here */
1702 clear_buffer_new(bh);
1703 unmap_underlying_metadata(bh->b_bdev,
1704 bh->b_blocknr);
1705 }
1706 }
1707 bh = bh->b_this_page;
1708 block++;
1709 } while (bh != head);
1710
1711 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001712 if (!buffer_mapped(bh))
1713 continue;
1714 /*
1715 * If it's a fully non-blocking write attempt and we cannot
1716 * lock the buffer then redirty the page. Note that this can
1717 * potentially cause a busy-wait loop from pdflush and kswapd
1718 * activity, but those code paths have their own higher-level
1719 * throttling.
1720 */
1721 if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
1722 lock_buffer(bh);
Nick Pigginca5de402008-08-02 12:02:13 +02001723 } else if (!trylock_buffer(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001724 redirty_page_for_writepage(wbc, page);
1725 continue;
1726 }
1727 if (test_clear_buffer_dirty(bh)) {
1728 mark_buffer_async_write(bh);
1729 } else {
1730 unlock_buffer(bh);
1731 }
1732 } while ((bh = bh->b_this_page) != head);
1733
1734 /*
1735 * The page and its buffers are protected by PageWriteback(), so we can
1736 * drop the bh refcounts early.
1737 */
1738 BUG_ON(PageWriteback(page));
1739 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001740
1741 do {
1742 struct buffer_head *next = bh->b_this_page;
1743 if (buffer_async_write(bh)) {
1744 submit_bh(WRITE, bh);
1745 nr_underway++;
1746 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001747 bh = next;
1748 } while (bh != head);
Andrew Morton05937ba2005-05-05 16:15:47 -07001749 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001750
1751 err = 0;
1752done:
1753 if (nr_underway == 0) {
1754 /*
1755 * The page was marked dirty, but the buffers were
1756 * clean. Someone wrote them back by hand with
1757 * ll_rw_block/submit_bh. A rare case.
1758 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001759 end_page_writeback(page);
Nick Piggin3d67f2d2007-05-06 14:49:05 -07001760
Linus Torvalds1da177e2005-04-16 15:20:36 -07001761 /*
1762 * The page and buffer_heads can be released at any time from
1763 * here on.
1764 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001765 }
1766 return err;
1767
1768recover:
1769 /*
1770 * ENOSPC, or some other error. We may already have added some
1771 * blocks to the file, so we need to write these out to avoid
1772 * exposing stale data.
1773 * The page is currently locked and not marked for writeback
1774 */
1775 bh = head;
1776 /* Recovery: lock and submit the mapped buffers */
1777 do {
Alex Tomas29a814d2008-07-11 19:27:31 -04001778 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1779 !buffer_delay(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001780 lock_buffer(bh);
1781 mark_buffer_async_write(bh);
1782 } else {
1783 /*
1784 * The buffer may have been set dirty during
1785 * attachment to a dirty page.
1786 */
1787 clear_buffer_dirty(bh);
1788 }
1789 } while ((bh = bh->b_this_page) != head);
1790 SetPageError(page);
1791 BUG_ON(PageWriteback(page));
Andrew Morton7e4c3692007-05-08 00:23:27 -07001792 mapping_set_error(page->mapping, err);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001793 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001794 do {
1795 struct buffer_head *next = bh->b_this_page;
1796 if (buffer_async_write(bh)) {
1797 clear_buffer_dirty(bh);
1798 submit_bh(WRITE, bh);
1799 nr_underway++;
1800 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001801 bh = next;
1802 } while (bh != head);
Nick Pigginffda9d32007-02-20 13:57:54 -08001803 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001804 goto done;
1805}
1806
Nick Pigginafddba42007-10-16 01:25:01 -07001807/*
1808 * If a page has any new buffers, zero them out here, and mark them uptodate
1809 * and dirty so they'll be written out (in order to prevent uninitialised
1810 * block data from leaking). And clear the new bit.
1811 */
1812void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1813{
1814 unsigned int block_start, block_end;
1815 struct buffer_head *head, *bh;
1816
1817 BUG_ON(!PageLocked(page));
1818 if (!page_has_buffers(page))
1819 return;
1820
1821 bh = head = page_buffers(page);
1822 block_start = 0;
1823 do {
1824 block_end = block_start + bh->b_size;
1825
1826 if (buffer_new(bh)) {
1827 if (block_end > from && block_start < to) {
1828 if (!PageUptodate(page)) {
1829 unsigned start, size;
1830
1831 start = max(from, block_start);
1832 size = min(to, block_end) - start;
1833
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001834 zero_user(page, start, size);
Nick Pigginafddba42007-10-16 01:25:01 -07001835 set_buffer_uptodate(bh);
1836 }
1837
1838 clear_buffer_new(bh);
1839 mark_buffer_dirty(bh);
1840 }
1841 }
1842
1843 block_start = block_end;
1844 bh = bh->b_this_page;
1845 } while (bh != head);
1846}
1847EXPORT_SYMBOL(page_zero_new_buffers);
1848
Linus Torvalds1da177e2005-04-16 15:20:36 -07001849static int __block_prepare_write(struct inode *inode, struct page *page,
1850 unsigned from, unsigned to, get_block_t *get_block)
1851{
1852 unsigned block_start, block_end;
1853 sector_t block;
1854 int err = 0;
1855 unsigned blocksize, bbits;
1856 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1857
1858 BUG_ON(!PageLocked(page));
1859 BUG_ON(from > PAGE_CACHE_SIZE);
1860 BUG_ON(to > PAGE_CACHE_SIZE);
1861 BUG_ON(from > to);
1862
1863 blocksize = 1 << inode->i_blkbits;
1864 if (!page_has_buffers(page))
1865 create_empty_buffers(page, blocksize, 0);
1866 head = page_buffers(page);
1867
1868 bbits = inode->i_blkbits;
1869 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1870
1871 for(bh = head, block_start = 0; bh != head || !block_start;
1872 block++, block_start=block_end, bh = bh->b_this_page) {
1873 block_end = block_start + blocksize;
1874 if (block_end <= from || block_start >= to) {
1875 if (PageUptodate(page)) {
1876 if (!buffer_uptodate(bh))
1877 set_buffer_uptodate(bh);
1878 }
1879 continue;
1880 }
1881 if (buffer_new(bh))
1882 clear_buffer_new(bh);
1883 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001884 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001885 err = get_block(inode, block, bh, 1);
1886 if (err)
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001887 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001888 if (buffer_new(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001889 unmap_underlying_metadata(bh->b_bdev,
1890 bh->b_blocknr);
1891 if (PageUptodate(page)) {
Nick Piggin637aff42007-10-16 01:25:00 -07001892 clear_buffer_new(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001893 set_buffer_uptodate(bh);
Nick Piggin637aff42007-10-16 01:25:00 -07001894 mark_buffer_dirty(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001895 continue;
1896 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001897 if (block_end > to || block_start < from)
1898 zero_user_segments(page,
1899 to, block_end,
1900 block_start, from);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001901 continue;
1902 }
1903 }
1904 if (PageUptodate(page)) {
1905 if (!buffer_uptodate(bh))
1906 set_buffer_uptodate(bh);
1907 continue;
1908 }
1909 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
David Chinner33a266d2007-02-12 00:51:41 -08001910 !buffer_unwritten(bh) &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001911 (block_start < from || block_end > to)) {
1912 ll_rw_block(READ, 1, &bh);
1913 *wait_bh++=bh;
1914 }
1915 }
1916 /*
1917 * If we issued read requests - let them complete.
1918 */
1919 while(wait_bh > wait) {
1920 wait_on_buffer(*--wait_bh);
1921 if (!buffer_uptodate(*wait_bh))
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001922 err = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001923 }
Nick Pigginafddba42007-10-16 01:25:01 -07001924 if (unlikely(err))
1925 page_zero_new_buffers(page, from, to);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001926 return err;
1927}
1928
1929static int __block_commit_write(struct inode *inode, struct page *page,
1930 unsigned from, unsigned to)
1931{
1932 unsigned block_start, block_end;
1933 int partial = 0;
1934 unsigned blocksize;
1935 struct buffer_head *bh, *head;
1936
1937 blocksize = 1 << inode->i_blkbits;
1938
1939 for(bh = head = page_buffers(page), block_start = 0;
1940 bh != head || !block_start;
1941 block_start=block_end, bh = bh->b_this_page) {
1942 block_end = block_start + blocksize;
1943 if (block_end <= from || block_start >= to) {
1944 if (!buffer_uptodate(bh))
1945 partial = 1;
1946 } else {
1947 set_buffer_uptodate(bh);
1948 mark_buffer_dirty(bh);
1949 }
Nick Pigginafddba42007-10-16 01:25:01 -07001950 clear_buffer_new(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001951 }
1952
1953 /*
1954 * If this is a partial write which happened to make all buffers
1955 * uptodate then we can optimize away a bogus readpage() for
1956 * the next read(). Here we 'discover' whether the page went
1957 * uptodate as a result of this (potentially partial) write.
1958 */
1959 if (!partial)
1960 SetPageUptodate(page);
1961 return 0;
1962}
1963
1964/*
Nick Pigginafddba42007-10-16 01:25:01 -07001965 * block_write_begin takes care of the basic task of block allocation and
1966 * bringing partial write blocks uptodate first.
1967 *
1968 * If *pagep is not NULL, then block_write_begin uses the locked page
1969 * at *pagep rather than allocating its own. In this case, the page will
1970 * not be unlocked or deallocated on failure.
1971 */
1972int block_write_begin(struct file *file, struct address_space *mapping,
1973 loff_t pos, unsigned len, unsigned flags,
1974 struct page **pagep, void **fsdata,
1975 get_block_t *get_block)
1976{
1977 struct inode *inode = mapping->host;
1978 int status = 0;
1979 struct page *page;
1980 pgoff_t index;
1981 unsigned start, end;
1982 int ownpage = 0;
1983
1984 index = pos >> PAGE_CACHE_SHIFT;
1985 start = pos & (PAGE_CACHE_SIZE - 1);
1986 end = start + len;
1987
1988 page = *pagep;
1989 if (page == NULL) {
1990 ownpage = 1;
1991 page = __grab_cache_page(mapping, index);
1992 if (!page) {
1993 status = -ENOMEM;
1994 goto out;
1995 }
1996 *pagep = page;
1997 } else
1998 BUG_ON(!PageLocked(page));
1999
2000 status = __block_prepare_write(inode, page, start, end, get_block);
2001 if (unlikely(status)) {
2002 ClearPageUptodate(page);
2003
2004 if (ownpage) {
2005 unlock_page(page);
2006 page_cache_release(page);
2007 *pagep = NULL;
2008
2009 /*
2010 * prepare_write() may have instantiated a few blocks
2011 * outside i_size. Trim these off again. Don't need
2012 * i_size_read because we hold i_mutex.
2013 */
2014 if (pos + len > inode->i_size)
2015 vmtruncate(inode, inode->i_size);
2016 }
2017 goto out;
2018 }
2019
2020out:
2021 return status;
2022}
2023EXPORT_SYMBOL(block_write_begin);
2024
2025int block_write_end(struct file *file, struct address_space *mapping,
2026 loff_t pos, unsigned len, unsigned copied,
2027 struct page *page, void *fsdata)
2028{
2029 struct inode *inode = mapping->host;
2030 unsigned start;
2031
2032 start = pos & (PAGE_CACHE_SIZE - 1);
2033
2034 if (unlikely(copied < len)) {
2035 /*
2036 * The buffers that were written will now be uptodate, so we
2037 * don't have to worry about a readpage reading them and
2038 * overwriting a partial write. However if we have encountered
2039 * a short write and only partially written into a buffer, it
2040 * will not be marked uptodate, so a readpage might come in and
2041 * destroy our partial write.
2042 *
2043 * Do the simplest thing, and just treat any short write to a
2044 * non uptodate page as a zero-length write, and force the
2045 * caller to redo the whole thing.
2046 */
2047 if (!PageUptodate(page))
2048 copied = 0;
2049
2050 page_zero_new_buffers(page, start+copied, start+len);
2051 }
2052 flush_dcache_page(page);
2053
2054 /* This could be a short (even 0-length) commit */
2055 __block_commit_write(inode, page, start, start+copied);
2056
2057 return copied;
2058}
2059EXPORT_SYMBOL(block_write_end);
2060
2061int generic_write_end(struct file *file, struct address_space *mapping,
2062 loff_t pos, unsigned len, unsigned copied,
2063 struct page *page, void *fsdata)
2064{
2065 struct inode *inode = mapping->host;
Jan Karac7d206b2008-07-11 19:27:31 -04002066 int i_size_changed = 0;
Nick Pigginafddba42007-10-16 01:25:01 -07002067
2068 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2069
2070 /*
2071 * No need to use i_size_read() here, the i_size
2072 * cannot change under us because we hold i_mutex.
2073 *
2074 * But it's important to update i_size while still holding page lock:
2075 * page writeout could otherwise come in and zero beyond i_size.
2076 */
2077 if (pos+copied > inode->i_size) {
2078 i_size_write(inode, pos+copied);
Jan Karac7d206b2008-07-11 19:27:31 -04002079 i_size_changed = 1;
Nick Pigginafddba42007-10-16 01:25:01 -07002080 }
2081
2082 unlock_page(page);
2083 page_cache_release(page);
2084
Jan Karac7d206b2008-07-11 19:27:31 -04002085 /*
2086 * Don't mark the inode dirty under page lock. First, it unnecessarily
2087 * makes the holding time of page lock longer. Second, it forces lock
2088 * ordering of page lock and transaction start for journaling
2089 * filesystems.
2090 */
2091 if (i_size_changed)
2092 mark_inode_dirty(inode);
2093
Nick Pigginafddba42007-10-16 01:25:01 -07002094 return copied;
2095}
2096EXPORT_SYMBOL(generic_write_end);
2097
2098/*
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07002099 * block_is_partially_uptodate checks whether buffers within a page are
2100 * uptodate or not.
2101 *
2102 * Returns true if all buffers which correspond to a file portion
2103 * we want to read are uptodate.
2104 */
2105int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
2106 unsigned long from)
2107{
2108 struct inode *inode = page->mapping->host;
2109 unsigned block_start, block_end, blocksize;
2110 unsigned to;
2111 struct buffer_head *bh, *head;
2112 int ret = 1;
2113
2114 if (!page_has_buffers(page))
2115 return 0;
2116
2117 blocksize = 1 << inode->i_blkbits;
2118 to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count);
2119 to = from + to;
2120 if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
2121 return 0;
2122
2123 head = page_buffers(page);
2124 bh = head;
2125 block_start = 0;
2126 do {
2127 block_end = block_start + blocksize;
2128 if (block_end > from && block_start < to) {
2129 if (!buffer_uptodate(bh)) {
2130 ret = 0;
2131 break;
2132 }
2133 if (block_end >= to)
2134 break;
2135 }
2136 block_start = block_end;
2137 bh = bh->b_this_page;
2138 } while (bh != head);
2139
2140 return ret;
2141}
2142EXPORT_SYMBOL(block_is_partially_uptodate);
2143
2144/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002145 * Generic "read page" function for block devices that have the normal
2146 * get_block functionality. This is most of the block device filesystems.
2147 * Reads the page asynchronously --- the unlock_buffer() and
2148 * set/clear_buffer_uptodate() functions propagate buffer state into the
2149 * page struct once IO has completed.
2150 */
2151int block_read_full_page(struct page *page, get_block_t *get_block)
2152{
2153 struct inode *inode = page->mapping->host;
2154 sector_t iblock, lblock;
2155 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2156 unsigned int blocksize;
2157 int nr, i;
2158 int fully_mapped = 1;
2159
Matt Mackallcd7619d2005-05-01 08:59:01 -07002160 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002161 blocksize = 1 << inode->i_blkbits;
2162 if (!page_has_buffers(page))
2163 create_empty_buffers(page, blocksize, 0);
2164 head = page_buffers(page);
2165
2166 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2167 lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
2168 bh = head;
2169 nr = 0;
2170 i = 0;
2171
2172 do {
2173 if (buffer_uptodate(bh))
2174 continue;
2175
2176 if (!buffer_mapped(bh)) {
Andrew Mortonc64610b2005-05-16 21:53:49 -07002177 int err = 0;
2178
Linus Torvalds1da177e2005-04-16 15:20:36 -07002179 fully_mapped = 0;
2180 if (iblock < lblock) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002181 WARN_ON(bh->b_size != blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002182 err = get_block(inode, iblock, bh, 0);
2183 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002184 SetPageError(page);
2185 }
2186 if (!buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002187 zero_user(page, i * blocksize, blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002188 if (!err)
2189 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002190 continue;
2191 }
2192 /*
2193 * get_block() might have updated the buffer
2194 * synchronously
2195 */
2196 if (buffer_uptodate(bh))
2197 continue;
2198 }
2199 arr[nr++] = bh;
2200 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2201
2202 if (fully_mapped)
2203 SetPageMappedToDisk(page);
2204
2205 if (!nr) {
2206 /*
2207 * All buffers are uptodate - we can set the page uptodate
2208 * as well. But not if get_block() returned an error.
2209 */
2210 if (!PageError(page))
2211 SetPageUptodate(page);
2212 unlock_page(page);
2213 return 0;
2214 }
2215
2216 /* Stage two: lock the buffers */
2217 for (i = 0; i < nr; i++) {
2218 bh = arr[i];
2219 lock_buffer(bh);
2220 mark_buffer_async_read(bh);
2221 }
2222
2223 /*
2224 * Stage 3: start the IO. Check for uptodateness
2225 * inside the buffer lock in case another process reading
2226 * the underlying blockdev brought it uptodate (the sct fix).
2227 */
2228 for (i = 0; i < nr; i++) {
2229 bh = arr[i];
2230 if (buffer_uptodate(bh))
2231 end_buffer_async_read(bh, 1);
2232 else
2233 submit_bh(READ, bh);
2234 }
2235 return 0;
2236}
2237
2238/* utility function for filesystems that need to do work on expanding
Nick Piggin89e10782007-10-16 01:25:07 -07002239 * truncates. Uses filesystem pagecache writes to allow the filesystem to
Linus Torvalds1da177e2005-04-16 15:20:36 -07002240 * deal with the hole.
2241 */
Nick Piggin89e10782007-10-16 01:25:07 -07002242int generic_cont_expand_simple(struct inode *inode, loff_t size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002243{
2244 struct address_space *mapping = inode->i_mapping;
2245 struct page *page;
Nick Piggin89e10782007-10-16 01:25:07 -07002246 void *fsdata;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002247 unsigned long limit;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002248 int err;
2249
2250 err = -EFBIG;
2251 limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
2252 if (limit != RLIM_INFINITY && size > (loff_t)limit) {
2253 send_sig(SIGXFSZ, current, 0);
2254 goto out;
2255 }
2256 if (size > inode->i_sb->s_maxbytes)
2257 goto out;
2258
Nick Piggin89e10782007-10-16 01:25:07 -07002259 err = pagecache_write_begin(NULL, mapping, size, 0,
2260 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2261 &page, &fsdata);
2262 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002263 goto out;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002264
Nick Piggin89e10782007-10-16 01:25:07 -07002265 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2266 BUG_ON(err > 0);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002267
Linus Torvalds1da177e2005-04-16 15:20:36 -07002268out:
2269 return err;
2270}
2271
Adrian Bunkf1e3af72008-04-29 00:59:01 -07002272static int cont_expand_zero(struct file *file, struct address_space *mapping,
2273 loff_t pos, loff_t *bytes)
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002274{
Nick Piggin89e10782007-10-16 01:25:07 -07002275 struct inode *inode = mapping->host;
2276 unsigned blocksize = 1 << inode->i_blkbits;
2277 struct page *page;
2278 void *fsdata;
2279 pgoff_t index, curidx;
2280 loff_t curpos;
2281 unsigned zerofrom, offset, len;
2282 int err = 0;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002283
Nick Piggin89e10782007-10-16 01:25:07 -07002284 index = pos >> PAGE_CACHE_SHIFT;
2285 offset = pos & ~PAGE_CACHE_MASK;
2286
2287 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
2288 zerofrom = curpos & ~PAGE_CACHE_MASK;
2289 if (zerofrom & (blocksize-1)) {
2290 *bytes |= (blocksize-1);
2291 (*bytes)++;
2292 }
2293 len = PAGE_CACHE_SIZE - zerofrom;
2294
2295 err = pagecache_write_begin(file, mapping, curpos, len,
2296 AOP_FLAG_UNINTERRUPTIBLE,
2297 &page, &fsdata);
2298 if (err)
2299 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002300 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002301 err = pagecache_write_end(file, mapping, curpos, len, len,
2302 page, fsdata);
2303 if (err < 0)
2304 goto out;
2305 BUG_ON(err != len);
2306 err = 0;
OGAWA Hirofumi061e9742008-04-28 02:16:28 -07002307
2308 balance_dirty_pages_ratelimited(mapping);
Nick Piggin89e10782007-10-16 01:25:07 -07002309 }
2310
2311 /* page covers the boundary, find the boundary offset */
2312 if (index == curidx) {
2313 zerofrom = curpos & ~PAGE_CACHE_MASK;
2314 /* if we will expand the thing last block will be filled */
2315 if (offset <= zerofrom) {
2316 goto out;
2317 }
2318 if (zerofrom & (blocksize-1)) {
2319 *bytes |= (blocksize-1);
2320 (*bytes)++;
2321 }
2322 len = offset - zerofrom;
2323
2324 err = pagecache_write_begin(file, mapping, curpos, len,
2325 AOP_FLAG_UNINTERRUPTIBLE,
2326 &page, &fsdata);
2327 if (err)
2328 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002329 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002330 err = pagecache_write_end(file, mapping, curpos, len, len,
2331 page, fsdata);
2332 if (err < 0)
2333 goto out;
2334 BUG_ON(err != len);
2335 err = 0;
2336 }
2337out:
2338 return err;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002339}
2340
Linus Torvalds1da177e2005-04-16 15:20:36 -07002341/*
2342 * For moronic filesystems that do not allow holes in file.
2343 * We may have to extend the file.
2344 */
Nick Piggin89e10782007-10-16 01:25:07 -07002345int cont_write_begin(struct file *file, struct address_space *mapping,
2346 loff_t pos, unsigned len, unsigned flags,
2347 struct page **pagep, void **fsdata,
2348 get_block_t *get_block, loff_t *bytes)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002349{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002350 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002351 unsigned blocksize = 1 << inode->i_blkbits;
Nick Piggin89e10782007-10-16 01:25:07 -07002352 unsigned zerofrom;
2353 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002354
Nick Piggin89e10782007-10-16 01:25:07 -07002355 err = cont_expand_zero(file, mapping, pos, bytes);
2356 if (err)
2357 goto out;
2358
2359 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2360 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2361 *bytes |= (blocksize-1);
2362 (*bytes)++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002363 }
2364
Nick Piggin89e10782007-10-16 01:25:07 -07002365 *pagep = NULL;
2366 err = block_write_begin(file, mapping, pos, len,
2367 flags, pagep, fsdata, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002368out:
Nick Piggin89e10782007-10-16 01:25:07 -07002369 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002370}
2371
2372int block_prepare_write(struct page *page, unsigned from, unsigned to,
2373 get_block_t *get_block)
2374{
2375 struct inode *inode = page->mapping->host;
2376 int err = __block_prepare_write(inode, page, from, to, get_block);
2377 if (err)
2378 ClearPageUptodate(page);
2379 return err;
2380}
2381
2382int block_commit_write(struct page *page, unsigned from, unsigned to)
2383{
2384 struct inode *inode = page->mapping->host;
2385 __block_commit_write(inode,page,from,to);
2386 return 0;
2387}
2388
David Chinner54171692007-07-19 17:39:55 +10002389/*
2390 * block_page_mkwrite() is not allowed to change the file size as it gets
2391 * called from a page fault handler when a page is first dirtied. Hence we must
2392 * be careful to check for EOF conditions here. We set the page up correctly
2393 * for a written page which means we get ENOSPC checking when writing into
2394 * holes and correct delalloc and unwritten extent mapping on filesystems that
2395 * support these features.
2396 *
2397 * We are not allowed to take the i_mutex here so we have to play games to
2398 * protect against truncate races as the page could now be beyond EOF. Because
2399 * vmtruncate() writes the inode size before removing pages, once we have the
2400 * page lock we can determine safely if the page is beyond EOF. If it is not
2401 * beyond EOF, then the page is guaranteed safe against truncation until we
2402 * unlock the page.
2403 */
2404int
2405block_page_mkwrite(struct vm_area_struct *vma, struct page *page,
2406 get_block_t get_block)
2407{
2408 struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
2409 unsigned long end;
2410 loff_t size;
2411 int ret = -EINVAL;
2412
2413 lock_page(page);
2414 size = i_size_read(inode);
2415 if ((page->mapping != inode->i_mapping) ||
Nick Piggin18336332007-07-20 00:31:45 -07002416 (page_offset(page) > size)) {
David Chinner54171692007-07-19 17:39:55 +10002417 /* page got truncated out from underneath us */
2418 goto out_unlock;
2419 }
2420
2421 /* page is wholly or partially inside EOF */
2422 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
2423 end = size & ~PAGE_CACHE_MASK;
2424 else
2425 end = PAGE_CACHE_SIZE;
2426
2427 ret = block_prepare_write(page, 0, end, get_block);
2428 if (!ret)
2429 ret = block_commit_write(page, 0, end);
2430
2431out_unlock:
2432 unlock_page(page);
2433 return ret;
2434}
Linus Torvalds1da177e2005-04-16 15:20:36 -07002435
2436/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002437 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
Linus Torvalds1da177e2005-04-16 15:20:36 -07002438 * immediately, while under the page lock. So it needs a special end_io
2439 * handler which does not touch the bh after unlocking it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002440 */
2441static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2442{
Dmitry Monakhov68671f32007-10-16 01:24:47 -07002443 __end_buffer_read_notouch(bh, uptodate);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002444}
2445
2446/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002447 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2448 * the page (converting it to circular linked list and taking care of page
2449 * dirty races).
2450 */
2451static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2452{
2453 struct buffer_head *bh;
2454
2455 BUG_ON(!PageLocked(page));
2456
2457 spin_lock(&page->mapping->private_lock);
2458 bh = head;
2459 do {
2460 if (PageDirty(page))
2461 set_buffer_dirty(bh);
2462 if (!bh->b_this_page)
2463 bh->b_this_page = head;
2464 bh = bh->b_this_page;
2465 } while (bh != head);
2466 attach_page_buffers(page, head);
2467 spin_unlock(&page->mapping->private_lock);
2468}
2469
2470/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002471 * On entry, the page is fully not uptodate.
2472 * On exit the page is fully uptodate in the areas outside (from,to)
2473 */
Nick Piggin03158cd2007-10-16 01:25:25 -07002474int nobh_write_begin(struct file *file, struct address_space *mapping,
2475 loff_t pos, unsigned len, unsigned flags,
2476 struct page **pagep, void **fsdata,
Linus Torvalds1da177e2005-04-16 15:20:36 -07002477 get_block_t *get_block)
2478{
Nick Piggin03158cd2007-10-16 01:25:25 -07002479 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002480 const unsigned blkbits = inode->i_blkbits;
2481 const unsigned blocksize = 1 << blkbits;
Nick Piggina4b06722007-10-16 01:24:48 -07002482 struct buffer_head *head, *bh;
Nick Piggin03158cd2007-10-16 01:25:25 -07002483 struct page *page;
2484 pgoff_t index;
2485 unsigned from, to;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002486 unsigned block_in_page;
Nick Piggina4b06722007-10-16 01:24:48 -07002487 unsigned block_start, block_end;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002488 sector_t block_in_file;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002489 int nr_reads = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002490 int ret = 0;
2491 int is_mapped_to_disk = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002492
Nick Piggin03158cd2007-10-16 01:25:25 -07002493 index = pos >> PAGE_CACHE_SHIFT;
2494 from = pos & (PAGE_CACHE_SIZE - 1);
2495 to = from + len;
2496
2497 page = __grab_cache_page(mapping, index);
2498 if (!page)
2499 return -ENOMEM;
2500 *pagep = page;
2501 *fsdata = NULL;
2502
2503 if (page_has_buffers(page)) {
2504 unlock_page(page);
2505 page_cache_release(page);
2506 *pagep = NULL;
2507 return block_write_begin(file, mapping, pos, len, flags, pagep,
2508 fsdata, get_block);
2509 }
Nick Piggina4b06722007-10-16 01:24:48 -07002510
Linus Torvalds1da177e2005-04-16 15:20:36 -07002511 if (PageMappedToDisk(page))
2512 return 0;
2513
Nick Piggina4b06722007-10-16 01:24:48 -07002514 /*
2515 * Allocate buffers so that we can keep track of state, and potentially
2516 * attach them to the page if an error occurs. In the common case of
2517 * no error, they will just be freed again without ever being attached
2518 * to the page (which is all OK, because we're under the page lock).
2519 *
2520 * Be careful: the buffer linked list is a NULL terminated one, rather
2521 * than the circular one we're used to.
2522 */
2523 head = alloc_page_buffers(page, blocksize, 0);
Nick Piggin03158cd2007-10-16 01:25:25 -07002524 if (!head) {
2525 ret = -ENOMEM;
2526 goto out_release;
2527 }
Nick Piggina4b06722007-10-16 01:24:48 -07002528
Linus Torvalds1da177e2005-04-16 15:20:36 -07002529 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002530
2531 /*
2532 * We loop across all blocks in the page, whether or not they are
2533 * part of the affected region. This is so we can discover if the
2534 * page is fully mapped-to-disk.
2535 */
Nick Piggina4b06722007-10-16 01:24:48 -07002536 for (block_start = 0, block_in_page = 0, bh = head;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002537 block_start < PAGE_CACHE_SIZE;
Nick Piggina4b06722007-10-16 01:24:48 -07002538 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002539 int create;
2540
Nick Piggina4b06722007-10-16 01:24:48 -07002541 block_end = block_start + blocksize;
2542 bh->b_state = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002543 create = 1;
2544 if (block_start >= to)
2545 create = 0;
2546 ret = get_block(inode, block_in_file + block_in_page,
Nick Piggina4b06722007-10-16 01:24:48 -07002547 bh, create);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002548 if (ret)
2549 goto failed;
Nick Piggina4b06722007-10-16 01:24:48 -07002550 if (!buffer_mapped(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002551 is_mapped_to_disk = 0;
Nick Piggina4b06722007-10-16 01:24:48 -07002552 if (buffer_new(bh))
2553 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
2554 if (PageUptodate(page)) {
2555 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002556 continue;
Nick Piggina4b06722007-10-16 01:24:48 -07002557 }
2558 if (buffer_new(bh) || !buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002559 zero_user_segments(page, block_start, from,
2560 to, block_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002561 continue;
2562 }
Nick Piggina4b06722007-10-16 01:24:48 -07002563 if (buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002564 continue; /* reiserfs does this */
2565 if (block_start < from || block_end > to) {
Nick Piggina4b06722007-10-16 01:24:48 -07002566 lock_buffer(bh);
2567 bh->b_end_io = end_buffer_read_nobh;
2568 submit_bh(READ, bh);
2569 nr_reads++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002570 }
2571 }
2572
2573 if (nr_reads) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002574 /*
2575 * The page is locked, so these buffers are protected from
2576 * any VM or truncate activity. Hence we don't need to care
2577 * for the buffer_head refcounts.
2578 */
Nick Piggina4b06722007-10-16 01:24:48 -07002579 for (bh = head; bh; bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002580 wait_on_buffer(bh);
2581 if (!buffer_uptodate(bh))
2582 ret = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002583 }
2584 if (ret)
2585 goto failed;
2586 }
2587
2588 if (is_mapped_to_disk)
2589 SetPageMappedToDisk(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002590
Nick Piggin03158cd2007-10-16 01:25:25 -07002591 *fsdata = head; /* to be released by nobh_write_end */
Nick Piggina4b06722007-10-16 01:24:48 -07002592
Linus Torvalds1da177e2005-04-16 15:20:36 -07002593 return 0;
2594
2595failed:
Nick Piggin03158cd2007-10-16 01:25:25 -07002596 BUG_ON(!ret);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002597 /*
Nick Piggina4b06722007-10-16 01:24:48 -07002598 * Error recovery is a bit difficult. We need to zero out blocks that
2599 * were newly allocated, and dirty them to ensure they get written out.
2600 * Buffers need to be attached to the page at this point, otherwise
2601 * the handling of potential IO errors during writeout would be hard
2602 * (could try doing synchronous writeout, but what if that fails too?)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002603 */
Nick Piggin03158cd2007-10-16 01:25:25 -07002604 attach_nobh_buffers(page, head);
2605 page_zero_new_buffers(page, from, to);
Nick Piggina4b06722007-10-16 01:24:48 -07002606
Nick Piggin03158cd2007-10-16 01:25:25 -07002607out_release:
2608 unlock_page(page);
2609 page_cache_release(page);
2610 *pagep = NULL;
Nick Piggina4b06722007-10-16 01:24:48 -07002611
Nick Piggin03158cd2007-10-16 01:25:25 -07002612 if (pos + len > inode->i_size)
2613 vmtruncate(inode, inode->i_size);
Nick Piggina4b06722007-10-16 01:24:48 -07002614
Linus Torvalds1da177e2005-04-16 15:20:36 -07002615 return ret;
2616}
Nick Piggin03158cd2007-10-16 01:25:25 -07002617EXPORT_SYMBOL(nobh_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002618
Nick Piggin03158cd2007-10-16 01:25:25 -07002619int nobh_write_end(struct file *file, struct address_space *mapping,
2620 loff_t pos, unsigned len, unsigned copied,
2621 struct page *page, void *fsdata)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002622{
2623 struct inode *inode = page->mapping->host;
Nick Pigginefdc3132007-10-21 06:57:41 +02002624 struct buffer_head *head = fsdata;
Nick Piggin03158cd2007-10-16 01:25:25 -07002625 struct buffer_head *bh;
Dmitri Monakhov5b41e742008-03-28 14:15:52 -07002626 BUG_ON(fsdata != NULL && page_has_buffers(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002627
Dmitri Monakhov5b41e742008-03-28 14:15:52 -07002628 if (unlikely(copied < len) && !page_has_buffers(page))
2629 attach_nobh_buffers(page, head);
2630 if (page_has_buffers(page))
2631 return generic_write_end(file, mapping, pos, len,
2632 copied, page, fsdata);
Nick Piggina4b06722007-10-16 01:24:48 -07002633
Nick Piggin22c8ca72007-02-20 13:58:09 -08002634 SetPageUptodate(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002635 set_page_dirty(page);
Nick Piggin03158cd2007-10-16 01:25:25 -07002636 if (pos+copied > inode->i_size) {
2637 i_size_write(inode, pos+copied);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002638 mark_inode_dirty(inode);
2639 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002640
2641 unlock_page(page);
2642 page_cache_release(page);
2643
Nick Piggin03158cd2007-10-16 01:25:25 -07002644 while (head) {
2645 bh = head;
2646 head = head->b_this_page;
2647 free_buffer_head(bh);
2648 }
2649
2650 return copied;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002651}
Nick Piggin03158cd2007-10-16 01:25:25 -07002652EXPORT_SYMBOL(nobh_write_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002653
2654/*
2655 * nobh_writepage() - based on block_full_write_page() except
2656 * that it tries to operate without attaching bufferheads to
2657 * the page.
2658 */
2659int nobh_writepage(struct page *page, get_block_t *get_block,
2660 struct writeback_control *wbc)
2661{
2662 struct inode * const inode = page->mapping->host;
2663 loff_t i_size = i_size_read(inode);
2664 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2665 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002666 int ret;
2667
2668 /* Is the page fully inside i_size? */
2669 if (page->index < end_index)
2670 goto out;
2671
2672 /* Is the page fully outside i_size? (truncate in progress) */
2673 offset = i_size & (PAGE_CACHE_SIZE-1);
2674 if (page->index >= end_index+1 || !offset) {
2675 /*
2676 * The page may have dirty, unmapped buffers. For example,
2677 * they may have been added in ext3_writepage(). Make them
2678 * freeable here, so the page does not leak.
2679 */
2680#if 0
2681 /* Not really sure about this - do we need this ? */
2682 if (page->mapping->a_ops->invalidatepage)
2683 page->mapping->a_ops->invalidatepage(page, offset);
2684#endif
2685 unlock_page(page);
2686 return 0; /* don't care */
2687 }
2688
2689 /*
2690 * The page straddles i_size. It must be zeroed out on each and every
2691 * writepage invocation because it may be mmapped. "A file is mapped
2692 * in multiples of the page size. For a file that is not a multiple of
2693 * the page size, the remaining memory is zeroed when mapped, and
2694 * writes to that region are not written out to the file."
2695 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002696 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002697out:
2698 ret = mpage_writepage(page, get_block, wbc);
2699 if (ret == -EAGAIN)
2700 ret = __block_write_full_page(inode, page, get_block, wbc);
2701 return ret;
2702}
2703EXPORT_SYMBOL(nobh_writepage);
2704
Nick Piggin03158cd2007-10-16 01:25:25 -07002705int nobh_truncate_page(struct address_space *mapping,
2706 loff_t from, get_block_t *get_block)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002707{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002708 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2709 unsigned offset = from & (PAGE_CACHE_SIZE-1);
Nick Piggin03158cd2007-10-16 01:25:25 -07002710 unsigned blocksize;
2711 sector_t iblock;
2712 unsigned length, pos;
2713 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002714 struct page *page;
Nick Piggin03158cd2007-10-16 01:25:25 -07002715 struct buffer_head map_bh;
2716 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002717
Nick Piggin03158cd2007-10-16 01:25:25 -07002718 blocksize = 1 << inode->i_blkbits;
2719 length = offset & (blocksize - 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002720
Nick Piggin03158cd2007-10-16 01:25:25 -07002721 /* Block boundary? Nothing to do */
2722 if (!length)
2723 return 0;
2724
2725 length = blocksize - length;
2726 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2727
Linus Torvalds1da177e2005-04-16 15:20:36 -07002728 page = grab_cache_page(mapping, index);
Nick Piggin03158cd2007-10-16 01:25:25 -07002729 err = -ENOMEM;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002730 if (!page)
2731 goto out;
2732
Nick Piggin03158cd2007-10-16 01:25:25 -07002733 if (page_has_buffers(page)) {
2734has_buffers:
2735 unlock_page(page);
2736 page_cache_release(page);
2737 return block_truncate_page(mapping, from, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002738 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002739
2740 /* Find the buffer that contains "offset" */
2741 pos = blocksize;
2742 while (offset >= pos) {
2743 iblock++;
2744 pos += blocksize;
2745 }
2746
2747 err = get_block(inode, iblock, &map_bh, 0);
2748 if (err)
2749 goto unlock;
2750 /* unmapped? It's a hole - nothing to do */
2751 if (!buffer_mapped(&map_bh))
2752 goto unlock;
2753
2754 /* Ok, it's mapped. Make sure it's up-to-date */
2755 if (!PageUptodate(page)) {
2756 err = mapping->a_ops->readpage(NULL, page);
2757 if (err) {
2758 page_cache_release(page);
2759 goto out;
2760 }
2761 lock_page(page);
2762 if (!PageUptodate(page)) {
2763 err = -EIO;
2764 goto unlock;
2765 }
2766 if (page_has_buffers(page))
2767 goto has_buffers;
2768 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002769 zero_user(page, offset, length);
Nick Piggin03158cd2007-10-16 01:25:25 -07002770 set_page_dirty(page);
2771 err = 0;
2772
2773unlock:
Linus Torvalds1da177e2005-04-16 15:20:36 -07002774 unlock_page(page);
2775 page_cache_release(page);
2776out:
Nick Piggin03158cd2007-10-16 01:25:25 -07002777 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002778}
2779EXPORT_SYMBOL(nobh_truncate_page);
2780
2781int block_truncate_page(struct address_space *mapping,
2782 loff_t from, get_block_t *get_block)
2783{
2784 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2785 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2786 unsigned blocksize;
Andrew Morton54b21a72006-01-08 01:03:05 -08002787 sector_t iblock;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002788 unsigned length, pos;
2789 struct inode *inode = mapping->host;
2790 struct page *page;
2791 struct buffer_head *bh;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002792 int err;
2793
2794 blocksize = 1 << inode->i_blkbits;
2795 length = offset & (blocksize - 1);
2796
2797 /* Block boundary? Nothing to do */
2798 if (!length)
2799 return 0;
2800
2801 length = blocksize - length;
Andrew Morton54b21a72006-01-08 01:03:05 -08002802 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002803
2804 page = grab_cache_page(mapping, index);
2805 err = -ENOMEM;
2806 if (!page)
2807 goto out;
2808
2809 if (!page_has_buffers(page))
2810 create_empty_buffers(page, blocksize, 0);
2811
2812 /* Find the buffer that contains "offset" */
2813 bh = page_buffers(page);
2814 pos = blocksize;
2815 while (offset >= pos) {
2816 bh = bh->b_this_page;
2817 iblock++;
2818 pos += blocksize;
2819 }
2820
2821 err = 0;
2822 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002823 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002824 err = get_block(inode, iblock, bh, 0);
2825 if (err)
2826 goto unlock;
2827 /* unmapped? It's a hole - nothing to do */
2828 if (!buffer_mapped(bh))
2829 goto unlock;
2830 }
2831
2832 /* Ok, it's mapped. Make sure it's up-to-date */
2833 if (PageUptodate(page))
2834 set_buffer_uptodate(bh);
2835
David Chinner33a266d2007-02-12 00:51:41 -08002836 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002837 err = -EIO;
2838 ll_rw_block(READ, 1, &bh);
2839 wait_on_buffer(bh);
2840 /* Uhhuh. Read error. Complain and punt. */
2841 if (!buffer_uptodate(bh))
2842 goto unlock;
2843 }
2844
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002845 zero_user(page, offset, length);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002846 mark_buffer_dirty(bh);
2847 err = 0;
2848
2849unlock:
2850 unlock_page(page);
2851 page_cache_release(page);
2852out:
2853 return err;
2854}
2855
2856/*
2857 * The generic ->writepage function for buffer-backed address_spaces
2858 */
2859int block_write_full_page(struct page *page, get_block_t *get_block,
2860 struct writeback_control *wbc)
2861{
2862 struct inode * const inode = page->mapping->host;
2863 loff_t i_size = i_size_read(inode);
2864 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2865 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002866
2867 /* Is the page fully inside i_size? */
2868 if (page->index < end_index)
2869 return __block_write_full_page(inode, page, get_block, wbc);
2870
2871 /* Is the page fully outside i_size? (truncate in progress) */
2872 offset = i_size & (PAGE_CACHE_SIZE-1);
2873 if (page->index >= end_index+1 || !offset) {
2874 /*
2875 * The page may have dirty, unmapped buffers. For example,
2876 * they may have been added in ext3_writepage(). Make them
2877 * freeable here, so the page does not leak.
2878 */
Jan Karaaaa40592005-10-30 15:00:16 -08002879 do_invalidatepage(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002880 unlock_page(page);
2881 return 0; /* don't care */
2882 }
2883
2884 /*
2885 * The page straddles i_size. It must be zeroed out on each and every
2886 * writepage invokation because it may be mmapped. "A file is mapped
2887 * in multiples of the page size. For a file that is not a multiple of
2888 * the page size, the remaining memory is zeroed when mapped, and
2889 * writes to that region are not written out to the file."
2890 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002891 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002892 return __block_write_full_page(inode, page, get_block, wbc);
2893}
2894
2895sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2896 get_block_t *get_block)
2897{
2898 struct buffer_head tmp;
2899 struct inode *inode = mapping->host;
2900 tmp.b_state = 0;
2901 tmp.b_blocknr = 0;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002902 tmp.b_size = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002903 get_block(inode, block, &tmp, 0);
2904 return tmp.b_blocknr;
2905}
2906
NeilBrown6712ecf2007-09-27 12:47:43 +02002907static void end_bio_bh_io_sync(struct bio *bio, int err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002908{
2909 struct buffer_head *bh = bio->bi_private;
2910
Linus Torvalds1da177e2005-04-16 15:20:36 -07002911 if (err == -EOPNOTSUPP) {
2912 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
2913 set_bit(BH_Eopnotsupp, &bh->b_state);
2914 }
2915
2916 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2917 bio_put(bio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002918}
2919
2920int submit_bh(int rw, struct buffer_head * bh)
2921{
2922 struct bio *bio;
2923 int ret = 0;
2924
2925 BUG_ON(!buffer_locked(bh));
2926 BUG_ON(!buffer_mapped(bh));
2927 BUG_ON(!bh->b_end_io);
2928
Jens Axboe48fd4f92008-08-22 10:00:36 +02002929 /*
2930 * Mask in barrier bit for a write (could be either a WRITE or a
2931 * WRITE_SYNC
2932 */
2933 if (buffer_ordered(bh) && (rw & WRITE))
2934 rw |= WRITE_BARRIER;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002935
2936 /*
Jens Axboe48fd4f92008-08-22 10:00:36 +02002937 * Only clear out a write error when rewriting
Linus Torvalds1da177e2005-04-16 15:20:36 -07002938 */
Jens Axboe48fd4f92008-08-22 10:00:36 +02002939 if (test_set_buffer_req(bh) && (rw & WRITE))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002940 clear_buffer_write_io_error(bh);
2941
2942 /*
2943 * from here on down, it's all bio -- do the initial mapping,
2944 * submit_bio -> generic_make_request may further map this bio around
2945 */
2946 bio = bio_alloc(GFP_NOIO, 1);
2947
2948 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2949 bio->bi_bdev = bh->b_bdev;
2950 bio->bi_io_vec[0].bv_page = bh->b_page;
2951 bio->bi_io_vec[0].bv_len = bh->b_size;
2952 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
2953
2954 bio->bi_vcnt = 1;
2955 bio->bi_idx = 0;
2956 bio->bi_size = bh->b_size;
2957
2958 bio->bi_end_io = end_bio_bh_io_sync;
2959 bio->bi_private = bh;
2960
2961 bio_get(bio);
2962 submit_bio(rw, bio);
2963
2964 if (bio_flagged(bio, BIO_EOPNOTSUPP))
2965 ret = -EOPNOTSUPP;
2966
2967 bio_put(bio);
2968 return ret;
2969}
2970
2971/**
2972 * ll_rw_block: low-level access to block devices (DEPRECATED)
Jan Karaa7662232005-09-06 15:19:10 -07002973 * @rw: whether to %READ or %WRITE or %SWRITE or maybe %READA (readahead)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002974 * @nr: number of &struct buffer_heads in the array
2975 * @bhs: array of pointers to &struct buffer_head
2976 *
Jan Karaa7662232005-09-06 15:19:10 -07002977 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
2978 * requests an I/O operation on them, either a %READ or a %WRITE. The third
2979 * %SWRITE is like %WRITE only we make sure that the *current* data in buffers
2980 * are sent to disk. The fourth %READA option is described in the documentation
2981 * for generic_make_request() which ll_rw_block() calls.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002982 *
2983 * This function drops any buffer that it cannot get a lock on (with the
Jan Karaa7662232005-09-06 15:19:10 -07002984 * BH_Lock state bit) unless SWRITE is required, any buffer that appears to be
2985 * clean when doing a write request, and any buffer that appears to be
2986 * up-to-date when doing read request. Further it marks as clean buffers that
2987 * are processed for writing (the buffer cache won't assume that they are
2988 * actually clean until the buffer gets unlocked).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002989 *
2990 * ll_rw_block sets b_end_io to simple completion handler that marks
2991 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
2992 * any waiters.
2993 *
2994 * All of the buffers must be for the same device, and must also be a
2995 * multiple of the current approved size for the device.
2996 */
2997void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
2998{
2999 int i;
3000
3001 for (i = 0; i < nr; i++) {
3002 struct buffer_head *bh = bhs[i];
3003
Jens Axboe18ce3752008-07-01 09:07:34 +02003004 if (rw == SWRITE || rw == SWRITE_SYNC)
Jan Karaa7662232005-09-06 15:19:10 -07003005 lock_buffer(bh);
Nick Pigginca5de402008-08-02 12:02:13 +02003006 else if (!trylock_buffer(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003007 continue;
3008
Jens Axboe18ce3752008-07-01 09:07:34 +02003009 if (rw == WRITE || rw == SWRITE || rw == SWRITE_SYNC) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003010 if (test_clear_buffer_dirty(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07003011 bh->b_end_io = end_buffer_write_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08003012 get_bh(bh);
Jens Axboe18ce3752008-07-01 09:07:34 +02003013 if (rw == SWRITE_SYNC)
3014 submit_bh(WRITE_SYNC, bh);
3015 else
3016 submit_bh(WRITE, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003017 continue;
3018 }
3019 } else {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003020 if (!buffer_uptodate(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07003021 bh->b_end_io = end_buffer_read_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08003022 get_bh(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003023 submit_bh(rw, bh);
3024 continue;
3025 }
3026 }
3027 unlock_buffer(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003028 }
3029}
3030
3031/*
3032 * For a data-integrity writeout, we need to wait upon any in-progress I/O
3033 * and then start new I/O and then wait upon it. The caller must have a ref on
3034 * the buffer_head.
3035 */
3036int sync_dirty_buffer(struct buffer_head *bh)
3037{
3038 int ret = 0;
3039
3040 WARN_ON(atomic_read(&bh->b_count) < 1);
3041 lock_buffer(bh);
3042 if (test_clear_buffer_dirty(bh)) {
3043 get_bh(bh);
3044 bh->b_end_io = end_buffer_write_sync;
Jens Axboe18ce3752008-07-01 09:07:34 +02003045 ret = submit_bh(WRITE_SYNC, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003046 wait_on_buffer(bh);
3047 if (buffer_eopnotsupp(bh)) {
3048 clear_buffer_eopnotsupp(bh);
3049 ret = -EOPNOTSUPP;
3050 }
3051 if (!ret && !buffer_uptodate(bh))
3052 ret = -EIO;
3053 } else {
3054 unlock_buffer(bh);
3055 }
3056 return ret;
3057}
3058
3059/*
3060 * try_to_free_buffers() checks if all the buffers on this particular page
3061 * are unused, and releases them if so.
3062 *
3063 * Exclusion against try_to_free_buffers may be obtained by either
3064 * locking the page or by holding its mapping's private_lock.
3065 *
3066 * If the page is dirty but all the buffers are clean then we need to
3067 * be sure to mark the page clean as well. This is because the page
3068 * may be against a block device, and a later reattachment of buffers
3069 * to a dirty page will set *all* buffers dirty. Which would corrupt
3070 * filesystem data on the same device.
3071 *
3072 * The same applies to regular filesystem pages: if all the buffers are
3073 * clean then we set the page clean and proceed. To do that, we require
3074 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3075 * private_lock.
3076 *
3077 * try_to_free_buffers() is non-blocking.
3078 */
3079static inline int buffer_busy(struct buffer_head *bh)
3080{
3081 return atomic_read(&bh->b_count) |
3082 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3083}
3084
3085static int
3086drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3087{
3088 struct buffer_head *head = page_buffers(page);
3089 struct buffer_head *bh;
3090
3091 bh = head;
3092 do {
akpm@osdl.orgde7d5a32005-05-01 08:58:39 -07003093 if (buffer_write_io_error(bh) && page->mapping)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003094 set_bit(AS_EIO, &page->mapping->flags);
3095 if (buffer_busy(bh))
3096 goto failed;
3097 bh = bh->b_this_page;
3098 } while (bh != head);
3099
3100 do {
3101 struct buffer_head *next = bh->b_this_page;
3102
Jan Kara535ee2f2008-02-08 04:21:59 -08003103 if (bh->b_assoc_map)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003104 __remove_assoc_queue(bh);
3105 bh = next;
3106 } while (bh != head);
3107 *buffers_to_free = head;
3108 __clear_page_buffers(page);
3109 return 1;
3110failed:
3111 return 0;
3112}
3113
3114int try_to_free_buffers(struct page *page)
3115{
3116 struct address_space * const mapping = page->mapping;
3117 struct buffer_head *buffers_to_free = NULL;
3118 int ret = 0;
3119
3120 BUG_ON(!PageLocked(page));
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003121 if (PageWriteback(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003122 return 0;
3123
3124 if (mapping == NULL) { /* can this still happen? */
3125 ret = drop_buffers(page, &buffers_to_free);
3126 goto out;
3127 }
3128
3129 spin_lock(&mapping->private_lock);
3130 ret = drop_buffers(page, &buffers_to_free);
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003131
3132 /*
3133 * If the filesystem writes its buffers by hand (eg ext3)
3134 * then we can have clean buffers against a dirty page. We
3135 * clean the page here; otherwise the VM will never notice
3136 * that the filesystem did any IO at all.
3137 *
3138 * Also, during truncate, discard_buffer will have marked all
3139 * the page's buffers clean. We discover that here and clean
3140 * the page also.
Nick Piggin87df7242007-01-30 14:36:27 +11003141 *
3142 * private_lock must be held over this entire operation in order
3143 * to synchronise against __set_page_dirty_buffers and prevent the
3144 * dirty bit from being lost.
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003145 */
3146 if (ret)
3147 cancel_dirty_page(page, PAGE_CACHE_SIZE);
Nick Piggin87df7242007-01-30 14:36:27 +11003148 spin_unlock(&mapping->private_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003149out:
3150 if (buffers_to_free) {
3151 struct buffer_head *bh = buffers_to_free;
3152
3153 do {
3154 struct buffer_head *next = bh->b_this_page;
3155 free_buffer_head(bh);
3156 bh = next;
3157 } while (bh != buffers_to_free);
3158 }
3159 return ret;
3160}
3161EXPORT_SYMBOL(try_to_free_buffers);
3162
NeilBrown3978d7172006-03-26 01:37:17 -08003163void block_sync_page(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003164{
3165 struct address_space *mapping;
3166
3167 smp_mb();
3168 mapping = page_mapping(page);
3169 if (mapping)
3170 blk_run_backing_dev(mapping->backing_dev_info, page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003171}
3172
3173/*
3174 * There are no bdflush tunables left. But distributions are
3175 * still running obsolete flush daemons, so we terminate them here.
3176 *
3177 * Use of bdflush() is deprecated and will be removed in a future kernel.
3178 * The `pdflush' kernel threads fully replace bdflush daemons and this call.
3179 */
3180asmlinkage long sys_bdflush(int func, long data)
3181{
3182 static int msg_count;
3183
3184 if (!capable(CAP_SYS_ADMIN))
3185 return -EPERM;
3186
3187 if (msg_count < 5) {
3188 msg_count++;
3189 printk(KERN_INFO
3190 "warning: process `%s' used the obsolete bdflush"
3191 " system call\n", current->comm);
3192 printk(KERN_INFO "Fix your initscripts?\n");
3193 }
3194
3195 if (func == 1)
3196 do_exit(0);
3197 return 0;
3198}
3199
3200/*
3201 * Buffer-head allocation
3202 */
Christoph Lametere18b8902006-12-06 20:33:20 -08003203static struct kmem_cache *bh_cachep;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003204
3205/*
3206 * Once the number of bh's in the machine exceeds this level, we start
3207 * stripping them in writeback.
3208 */
3209static int max_buffer_heads;
3210
3211int buffer_heads_over_limit;
3212
3213struct bh_accounting {
3214 int nr; /* Number of live bh's */
3215 int ratelimit; /* Limit cacheline bouncing */
3216};
3217
3218static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3219
3220static void recalc_bh_state(void)
3221{
3222 int i;
3223 int tot = 0;
3224
3225 if (__get_cpu_var(bh_accounting).ratelimit++ < 4096)
3226 return;
3227 __get_cpu_var(bh_accounting).ratelimit = 0;
Eric Dumazet8a143422006-03-24 03:18:10 -08003228 for_each_online_cpu(i)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003229 tot += per_cpu(bh_accounting, i).nr;
3230 buffer_heads_over_limit = (tot > max_buffer_heads);
3231}
3232
Al Virodd0fc662005-10-07 07:46:04 +01003233struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003234{
Christoph Lameter488514d2008-04-28 02:12:05 -07003235 struct buffer_head *ret = kmem_cache_alloc(bh_cachep, gfp_flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003236 if (ret) {
Christoph Lametera35afb82007-05-16 22:10:57 -07003237 INIT_LIST_HEAD(&ret->b_assoc_buffers);
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07003238 get_cpu_var(bh_accounting).nr++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003239 recalc_bh_state();
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07003240 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003241 }
3242 return ret;
3243}
3244EXPORT_SYMBOL(alloc_buffer_head);
3245
3246void free_buffer_head(struct buffer_head *bh)
3247{
3248 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3249 kmem_cache_free(bh_cachep, bh);
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07003250 get_cpu_var(bh_accounting).nr--;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003251 recalc_bh_state();
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07003252 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003253}
3254EXPORT_SYMBOL(free_buffer_head);
3255
Linus Torvalds1da177e2005-04-16 15:20:36 -07003256static void buffer_exit_cpu(int cpu)
3257{
3258 int i;
3259 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3260
3261 for (i = 0; i < BH_LRU_SIZE; i++) {
3262 brelse(b->bhs[i]);
3263 b->bhs[i] = NULL;
3264 }
Eric Dumazet8a143422006-03-24 03:18:10 -08003265 get_cpu_var(bh_accounting).nr += per_cpu(bh_accounting, cpu).nr;
3266 per_cpu(bh_accounting, cpu).nr = 0;
3267 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003268}
3269
3270static int buffer_cpu_notify(struct notifier_block *self,
3271 unsigned long action, void *hcpu)
3272{
Rafael J. Wysocki8bb78442007-05-09 02:35:10 -07003273 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003274 buffer_exit_cpu((unsigned long)hcpu);
3275 return NOTIFY_OK;
3276}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003277
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003278/**
Randy Dunlapa6b91912008-03-19 17:01:00 -07003279 * bh_uptodate_or_lock - Test whether the buffer is uptodate
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003280 * @bh: struct buffer_head
3281 *
3282 * Return true if the buffer is up-to-date and false,
3283 * with the buffer locked, if not.
3284 */
3285int bh_uptodate_or_lock(struct buffer_head *bh)
3286{
3287 if (!buffer_uptodate(bh)) {
3288 lock_buffer(bh);
3289 if (!buffer_uptodate(bh))
3290 return 0;
3291 unlock_buffer(bh);
3292 }
3293 return 1;
3294}
3295EXPORT_SYMBOL(bh_uptodate_or_lock);
3296
3297/**
Randy Dunlapa6b91912008-03-19 17:01:00 -07003298 * bh_submit_read - Submit a locked buffer for reading
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003299 * @bh: struct buffer_head
3300 *
3301 * Returns zero on success and -EIO on error.
3302 */
3303int bh_submit_read(struct buffer_head *bh)
3304{
3305 BUG_ON(!buffer_locked(bh));
3306
3307 if (buffer_uptodate(bh)) {
3308 unlock_buffer(bh);
3309 return 0;
3310 }
3311
3312 get_bh(bh);
3313 bh->b_end_io = end_buffer_read_sync;
3314 submit_bh(READ, bh);
3315 wait_on_buffer(bh);
3316 if (buffer_uptodate(bh))
3317 return 0;
3318 return -EIO;
3319}
3320EXPORT_SYMBOL(bh_submit_read);
3321
Christoph Lameterb98938c2008-02-04 22:28:36 -08003322static void
Alexey Dobriyan51cc5062008-07-25 19:45:34 -07003323init_buffer_head(void *data)
Christoph Lameterb98938c2008-02-04 22:28:36 -08003324{
3325 struct buffer_head *bh = data;
3326
3327 memset(bh, 0, sizeof(*bh));
3328 INIT_LIST_HEAD(&bh->b_assoc_buffers);
3329}
3330
Linus Torvalds1da177e2005-04-16 15:20:36 -07003331void __init buffer_init(void)
3332{
3333 int nrpages;
3334
Christoph Lameterb98938c2008-02-04 22:28:36 -08003335 bh_cachep = kmem_cache_create("buffer_head",
3336 sizeof(struct buffer_head), 0,
3337 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3338 SLAB_MEM_SPREAD),
3339 init_buffer_head);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003340
3341 /*
3342 * Limit the bh occupancy to 10% of ZONE_NORMAL
3343 */
3344 nrpages = (nr_free_buffer_pages() * 10) / 100;
3345 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3346 hotcpu_notifier(buffer_cpu_notify, 0);
3347}
3348
3349EXPORT_SYMBOL(__bforget);
3350EXPORT_SYMBOL(__brelse);
3351EXPORT_SYMBOL(__wait_on_buffer);
3352EXPORT_SYMBOL(block_commit_write);
3353EXPORT_SYMBOL(block_prepare_write);
David Chinner54171692007-07-19 17:39:55 +10003354EXPORT_SYMBOL(block_page_mkwrite);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003355EXPORT_SYMBOL(block_read_full_page);
3356EXPORT_SYMBOL(block_sync_page);
3357EXPORT_SYMBOL(block_truncate_page);
3358EXPORT_SYMBOL(block_write_full_page);
Nick Piggin89e10782007-10-16 01:25:07 -07003359EXPORT_SYMBOL(cont_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003360EXPORT_SYMBOL(end_buffer_read_sync);
3361EXPORT_SYMBOL(end_buffer_write_sync);
3362EXPORT_SYMBOL(file_fsync);
3363EXPORT_SYMBOL(fsync_bdev);
3364EXPORT_SYMBOL(generic_block_bmap);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08003365EXPORT_SYMBOL(generic_cont_expand_simple);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003366EXPORT_SYMBOL(init_buffer);
3367EXPORT_SYMBOL(invalidate_bdev);
3368EXPORT_SYMBOL(ll_rw_block);
3369EXPORT_SYMBOL(mark_buffer_dirty);
3370EXPORT_SYMBOL(submit_bh);
3371EXPORT_SYMBOL(sync_dirty_buffer);
3372EXPORT_SYMBOL(unlock_buffer);