blob: 826baf4f04bc738fdfea27f6652bc3c0bfe9969d [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
70void fastcall __lock_buffer(struct buffer_head *bh)
71{
72 wait_on_bit_lock(&bh->b_state, BH_Lock, sync_buffer,
73 TASK_UNINTERRUPTIBLE);
74}
75EXPORT_SYMBOL(__lock_buffer);
76
77void fastcall unlock_buffer(struct buffer_head *bh)
78{
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{
363 struct zone **zones;
364 pg_data_t *pgdat;
365
Pekka J Enberg687a21c2005-06-28 20:44:55 -0700366 wakeup_pdflush(1024);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700367 yield();
368
KAMEZAWA Hiroyukiec936fc2006-03-27 01:15:59 -0800369 for_each_online_pgdat(pgdat) {
Al Viroaf4ca452005-10-21 02:55:38 -0400370 zones = pgdat->node_zonelists[gfp_zone(GFP_NOFS)].zones;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700371 if (*zones)
Andy Whitcroft5ad333e2007-07-17 04:03:16 -0700372 try_to_free_pages(zones, 0, GFP_NOFS);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700373 }
374}
375
376/*
377 * I/O completion handler for block_read_full_page() - pages
378 * which come unlocked at the end of I/O.
379 */
380static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
381{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700382 unsigned long flags;
Nick Piggina3972202005-07-07 17:56:56 -0700383 struct buffer_head *first;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700384 struct buffer_head *tmp;
385 struct page *page;
386 int page_uptodate = 1;
387
388 BUG_ON(!buffer_async_read(bh));
389
390 page = bh->b_page;
391 if (uptodate) {
392 set_buffer_uptodate(bh);
393 } else {
394 clear_buffer_uptodate(bh);
395 if (printk_ratelimit())
396 buffer_io_error(bh);
397 SetPageError(page);
398 }
399
400 /*
401 * Be _very_ careful from here on. Bad things can happen if
402 * two buffer heads end IO at almost the same time and both
403 * decide that the page is now completely done.
404 */
Nick Piggina3972202005-07-07 17:56:56 -0700405 first = page_buffers(page);
406 local_irq_save(flags);
407 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700408 clear_buffer_async_read(bh);
409 unlock_buffer(bh);
410 tmp = bh;
411 do {
412 if (!buffer_uptodate(tmp))
413 page_uptodate = 0;
414 if (buffer_async_read(tmp)) {
415 BUG_ON(!buffer_locked(tmp));
416 goto still_busy;
417 }
418 tmp = tmp->b_this_page;
419 } while (tmp != bh);
Nick Piggina3972202005-07-07 17:56:56 -0700420 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
421 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700422
423 /*
424 * If none of the buffers had errors and they are all
425 * uptodate then we can set the page uptodate.
426 */
427 if (page_uptodate && !PageError(page))
428 SetPageUptodate(page);
429 unlock_page(page);
430 return;
431
432still_busy:
Nick Piggina3972202005-07-07 17:56:56 -0700433 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
434 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700435 return;
436}
437
438/*
439 * Completion handler for block_write_full_page() - pages which are unlocked
440 * during I/O, and which have PageWriteback cleared upon I/O completion.
441 */
Adrian Bunkb6cd0b72006-06-27 02:53:54 -0700442static void end_buffer_async_write(struct buffer_head *bh, int uptodate)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700443{
444 char b[BDEVNAME_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700445 unsigned long flags;
Nick Piggina3972202005-07-07 17:56:56 -0700446 struct buffer_head *first;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700447 struct buffer_head *tmp;
448 struct page *page;
449
450 BUG_ON(!buffer_async_write(bh));
451
452 page = bh->b_page;
453 if (uptodate) {
454 set_buffer_uptodate(bh);
455 } else {
456 if (printk_ratelimit()) {
457 buffer_io_error(bh);
458 printk(KERN_WARNING "lost page write due to "
459 "I/O error on %s\n",
460 bdevname(bh->b_bdev, b));
461 }
462 set_bit(AS_EIO, &page->mapping->flags);
Jan Kara58ff4072006-10-17 00:10:19 -0700463 set_buffer_write_io_error(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700464 clear_buffer_uptodate(bh);
465 SetPageError(page);
466 }
467
Nick Piggina3972202005-07-07 17:56:56 -0700468 first = page_buffers(page);
469 local_irq_save(flags);
470 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
471
Linus Torvalds1da177e2005-04-16 15:20:36 -0700472 clear_buffer_async_write(bh);
473 unlock_buffer(bh);
474 tmp = bh->b_this_page;
475 while (tmp != bh) {
476 if (buffer_async_write(tmp)) {
477 BUG_ON(!buffer_locked(tmp));
478 goto still_busy;
479 }
480 tmp = tmp->b_this_page;
481 }
Nick Piggina3972202005-07-07 17:56:56 -0700482 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
483 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700484 end_page_writeback(page);
485 return;
486
487still_busy:
Nick Piggina3972202005-07-07 17:56:56 -0700488 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
489 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700490 return;
491}
492
493/*
494 * If a page's buffers are under async readin (end_buffer_async_read
495 * completion) then there is a possibility that another thread of
496 * control could lock one of the buffers after it has completed
497 * but while some of the other buffers have not completed. This
498 * locked buffer would confuse end_buffer_async_read() into not unlocking
499 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
500 * that this buffer is not under async I/O.
501 *
502 * The page comes unlocked when it has no locked buffer_async buffers
503 * left.
504 *
505 * PageLocked prevents anyone starting new async I/O reads any of
506 * the buffers.
507 *
508 * PageWriteback is used to prevent simultaneous writeout of the same
509 * page.
510 *
511 * PageLocked prevents anyone from starting writeback of a page which is
512 * under read I/O (PageWriteback is only ever set against a locked page).
513 */
514static void mark_buffer_async_read(struct buffer_head *bh)
515{
516 bh->b_end_io = end_buffer_async_read;
517 set_buffer_async_read(bh);
518}
519
520void mark_buffer_async_write(struct buffer_head *bh)
521{
522 bh->b_end_io = end_buffer_async_write;
523 set_buffer_async_write(bh);
524}
525EXPORT_SYMBOL(mark_buffer_async_write);
526
527
528/*
529 * fs/buffer.c contains helper functions for buffer-backed address space's
530 * fsync functions. A common requirement for buffer-based filesystems is
531 * that certain data from the backing blockdev needs to be written out for
532 * a successful fsync(). For example, ext2 indirect blocks need to be
533 * written back and waited upon before fsync() returns.
534 *
535 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
536 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
537 * management of a list of dependent buffers at ->i_mapping->private_list.
538 *
539 * Locking is a little subtle: try_to_free_buffers() will remove buffers
540 * from their controlling inode's queue when they are being freed. But
541 * try_to_free_buffers() will be operating against the *blockdev* mapping
542 * at the time, not against the S_ISREG file which depends on those buffers.
543 * So the locking for private_list is via the private_lock in the address_space
544 * which backs the buffers. Which is different from the address_space
545 * against which the buffers are listed. So for a particular address_space,
546 * mapping->private_lock does *not* protect mapping->private_list! In fact,
547 * mapping->private_list will always be protected by the backing blockdev's
548 * ->private_lock.
549 *
550 * Which introduces a requirement: all buffers on an address_space's
551 * ->private_list must be from the same address_space: the blockdev's.
552 *
553 * address_spaces which do not place buffers at ->private_list via these
554 * utility functions are free to use private_lock and private_list for
555 * whatever they want. The only requirement is that list_empty(private_list)
556 * be true at clear_inode() time.
557 *
558 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
559 * filesystems should do that. invalidate_inode_buffers() should just go
560 * BUG_ON(!list_empty).
561 *
562 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
563 * take an address_space, not an inode. And it should be called
564 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
565 * queued up.
566 *
567 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
568 * list if it is already on a list. Because if the buffer is on a list,
569 * it *must* already be on the right one. If not, the filesystem is being
570 * silly. This will save a ton of locking. But first we have to ensure
571 * that buffers are taken *off* the old inode's list when they are freed
572 * (presumably in truncate). That requires careful auditing of all
573 * filesystems (do it inside bforget()). It could also be done by bringing
574 * b_inode back.
575 */
576
577/*
578 * The buffer's backing address_space's private_lock must be held
579 */
580static inline void __remove_assoc_queue(struct buffer_head *bh)
581{
582 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -0700583 WARN_ON(!bh->b_assoc_map);
584 if (buffer_write_io_error(bh))
585 set_bit(AS_EIO, &bh->b_assoc_map->flags);
586 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700587}
588
589int inode_has_buffers(struct inode *inode)
590{
591 return !list_empty(&inode->i_data.private_list);
592}
593
594/*
595 * osync is designed to support O_SYNC io. It waits synchronously for
596 * all already-submitted IO to complete, but does not queue any new
597 * writes to the disk.
598 *
599 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
600 * you dirty the buffers, and then use osync_inode_buffers to wait for
601 * completion. Any other dirty buffers which are not yet queued for
602 * write will not be flushed to disk by the osync.
603 */
604static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
605{
606 struct buffer_head *bh;
607 struct list_head *p;
608 int err = 0;
609
610 spin_lock(lock);
611repeat:
612 list_for_each_prev(p, list) {
613 bh = BH_ENTRY(p);
614 if (buffer_locked(bh)) {
615 get_bh(bh);
616 spin_unlock(lock);
617 wait_on_buffer(bh);
618 if (!buffer_uptodate(bh))
619 err = -EIO;
620 brelse(bh);
621 spin_lock(lock);
622 goto repeat;
623 }
624 }
625 spin_unlock(lock);
626 return err;
627}
628
629/**
630 * sync_mapping_buffers - write out and wait upon a mapping's "associated"
631 * buffers
Martin Waitz67be2dd2005-05-01 08:59:26 -0700632 * @mapping: the mapping which wants those buffers written
Linus Torvalds1da177e2005-04-16 15:20:36 -0700633 *
634 * Starts I/O against the buffers at mapping->private_list, and waits upon
635 * that I/O.
636 *
Martin Waitz67be2dd2005-05-01 08:59:26 -0700637 * Basically, this is a convenience function for fsync().
638 * @mapping is a file or directory which needs those buffers to be written for
639 * a successful fsync().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700640 */
641int sync_mapping_buffers(struct address_space *mapping)
642{
643 struct address_space *buffer_mapping = mapping->assoc_mapping;
644
645 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
646 return 0;
647
648 return fsync_buffers_list(&buffer_mapping->private_lock,
649 &mapping->private_list);
650}
651EXPORT_SYMBOL(sync_mapping_buffers);
652
653/*
654 * Called when we've recently written block `bblock', and it is known that
655 * `bblock' was for a buffer_boundary() buffer. This means that the block at
656 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
657 * dirty, schedule it for IO. So that indirects merge nicely with their data.
658 */
659void write_boundary_block(struct block_device *bdev,
660 sector_t bblock, unsigned blocksize)
661{
662 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
663 if (bh) {
664 if (buffer_dirty(bh))
665 ll_rw_block(WRITE, 1, &bh);
666 put_bh(bh);
667 }
668}
669
670void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
671{
672 struct address_space *mapping = inode->i_mapping;
673 struct address_space *buffer_mapping = bh->b_page->mapping;
674
675 mark_buffer_dirty(bh);
676 if (!mapping->assoc_mapping) {
677 mapping->assoc_mapping = buffer_mapping;
678 } else {
Eric Sesterhenne827f922006-03-26 18:24:46 +0200679 BUG_ON(mapping->assoc_mapping != buffer_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700680 }
681 if (list_empty(&bh->b_assoc_buffers)) {
682 spin_lock(&buffer_mapping->private_lock);
683 list_move_tail(&bh->b_assoc_buffers,
684 &mapping->private_list);
Jan Kara58ff4072006-10-17 00:10:19 -0700685 bh->b_assoc_map = mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700686 spin_unlock(&buffer_mapping->private_lock);
687 }
688}
689EXPORT_SYMBOL(mark_buffer_dirty_inode);
690
691/*
Nick Piggin787d2212007-07-17 04:03:34 -0700692 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
693 * dirty.
694 *
695 * If warn is true, then emit a warning if the page is not uptodate and has
696 * not been truncated.
697 */
698static int __set_page_dirty(struct page *page,
699 struct address_space *mapping, int warn)
700{
701 if (unlikely(!mapping))
702 return !TestSetPageDirty(page);
703
704 if (TestSetPageDirty(page))
705 return 0;
706
707 write_lock_irq(&mapping->tree_lock);
708 if (page->mapping) { /* Race with truncate? */
709 WARN_ON_ONCE(warn && !PageUptodate(page));
710
711 if (mapping_cap_account_dirty(mapping)) {
712 __inc_zone_page_state(page, NR_FILE_DIRTY);
Peter Zijlstrac9e51e42007-10-16 23:25:47 -0700713 __inc_bdi_stat(mapping->backing_dev_info,
714 BDI_RECLAIMABLE);
Nick Piggin787d2212007-07-17 04:03:34 -0700715 task_io_account_write(PAGE_CACHE_SIZE);
716 }
717 radix_tree_tag_set(&mapping->page_tree,
718 page_index(page), PAGECACHE_TAG_DIRTY);
719 }
720 write_unlock_irq(&mapping->tree_lock);
721 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
722
723 return 1;
724}
725
726/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700727 * Add a page to the dirty page list.
728 *
729 * It is a sad fact of life that this function is called from several places
730 * deeply under spinlocking. It may not sleep.
731 *
732 * If the page has buffers, the uptodate buffers are set dirty, to preserve
733 * dirty-state coherency between the page and the buffers. It the page does
734 * not have buffers then when they are later attached they will all be set
735 * dirty.
736 *
737 * The buffers are dirtied before the page is dirtied. There's a small race
738 * window in which a writepage caller may see the page cleanness but not the
739 * buffer dirtiness. That's fine. If this code were to set the page dirty
740 * before the buffers, a concurrent writepage caller could clear the page dirty
741 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
742 * page on the dirty page list.
743 *
744 * We use private_lock to lock against try_to_free_buffers while using the
745 * page's buffer list. Also use this to protect against clean buffers being
746 * added to the page after it was set dirty.
747 *
748 * FIXME: may need to call ->reservepage here as well. That's rather up to the
749 * address_space though.
750 */
751int __set_page_dirty_buffers(struct page *page)
752{
Nick Piggin787d2212007-07-17 04:03:34 -0700753 struct address_space *mapping = page_mapping(page);
Nick Pigginebf7a222006-10-10 04:36:54 +0200754
755 if (unlikely(!mapping))
756 return !TestSetPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700757
758 spin_lock(&mapping->private_lock);
759 if (page_has_buffers(page)) {
760 struct buffer_head *head = page_buffers(page);
761 struct buffer_head *bh = head;
762
763 do {
764 set_buffer_dirty(bh);
765 bh = bh->b_this_page;
766 } while (bh != head);
767 }
768 spin_unlock(&mapping->private_lock);
769
Nick Piggin787d2212007-07-17 04:03:34 -0700770 return __set_page_dirty(page, mapping, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700771}
772EXPORT_SYMBOL(__set_page_dirty_buffers);
773
774/*
775 * Write out and wait upon a list of buffers.
776 *
777 * We have conflicting pressures: we want to make sure that all
778 * initially dirty buffers get waited on, but that any subsequently
779 * dirtied buffers don't. After all, we don't want fsync to last
780 * forever if somebody is actively writing to the file.
781 *
782 * Do this in two main stages: first we copy dirty buffers to a
783 * temporary inode list, queueing the writes as we go. Then we clean
784 * up, waiting for those writes to complete.
785 *
786 * During this second stage, any subsequent updates to the file may end
787 * up refiling the buffer on the original inode's dirty list again, so
788 * there is a chance we will end up with a buffer queued for write but
789 * not yet completed on that list. So, as a final cleanup we go through
790 * the osync code to catch these locked, dirty buffers without requeuing
791 * any newly dirty buffers for write.
792 */
793static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
794{
795 struct buffer_head *bh;
796 struct list_head tmp;
797 int err = 0, err2;
798
799 INIT_LIST_HEAD(&tmp);
800
801 spin_lock(lock);
802 while (!list_empty(list)) {
803 bh = BH_ENTRY(list->next);
Jan Kara58ff4072006-10-17 00:10:19 -0700804 __remove_assoc_queue(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700805 if (buffer_dirty(bh) || buffer_locked(bh)) {
806 list_add(&bh->b_assoc_buffers, &tmp);
807 if (buffer_dirty(bh)) {
808 get_bh(bh);
809 spin_unlock(lock);
810 /*
811 * Ensure any pending I/O completes so that
812 * ll_rw_block() actually writes the current
813 * contents - it is a noop if I/O is still in
814 * flight on potentially older contents.
815 */
Jan Karaa7662232005-09-06 15:19:10 -0700816 ll_rw_block(SWRITE, 1, &bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700817 brelse(bh);
818 spin_lock(lock);
819 }
820 }
821 }
822
823 while (!list_empty(&tmp)) {
824 bh = BH_ENTRY(tmp.prev);
Jan Kara58ff4072006-10-17 00:10:19 -0700825 list_del_init(&bh->b_assoc_buffers);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700826 get_bh(bh);
827 spin_unlock(lock);
828 wait_on_buffer(bh);
829 if (!buffer_uptodate(bh))
830 err = -EIO;
831 brelse(bh);
832 spin_lock(lock);
833 }
834
835 spin_unlock(lock);
836 err2 = osync_buffers_list(lock, list);
837 if (err)
838 return err;
839 else
840 return err2;
841}
842
843/*
844 * Invalidate any and all dirty buffers on a given inode. We are
845 * probably unmounting the fs, but that doesn't mean we have already
846 * done a sync(). Just drop the buffers from the inode list.
847 *
848 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
849 * assumes that all the buffers are against the blockdev. Not true
850 * for reiserfs.
851 */
852void invalidate_inode_buffers(struct inode *inode)
853{
854 if (inode_has_buffers(inode)) {
855 struct address_space *mapping = &inode->i_data;
856 struct list_head *list = &mapping->private_list;
857 struct address_space *buffer_mapping = mapping->assoc_mapping;
858
859 spin_lock(&buffer_mapping->private_lock);
860 while (!list_empty(list))
861 __remove_assoc_queue(BH_ENTRY(list->next));
862 spin_unlock(&buffer_mapping->private_lock);
863 }
864}
865
866/*
867 * Remove any clean buffers from the inode's buffer list. This is called
868 * when we're trying to free the inode itself. Those buffers can pin it.
869 *
870 * Returns true if all buffers were removed.
871 */
872int remove_inode_buffers(struct inode *inode)
873{
874 int ret = 1;
875
876 if (inode_has_buffers(inode)) {
877 struct address_space *mapping = &inode->i_data;
878 struct list_head *list = &mapping->private_list;
879 struct address_space *buffer_mapping = mapping->assoc_mapping;
880
881 spin_lock(&buffer_mapping->private_lock);
882 while (!list_empty(list)) {
883 struct buffer_head *bh = BH_ENTRY(list->next);
884 if (buffer_dirty(bh)) {
885 ret = 0;
886 break;
887 }
888 __remove_assoc_queue(bh);
889 }
890 spin_unlock(&buffer_mapping->private_lock);
891 }
892 return ret;
893}
894
895/*
896 * Create the appropriate buffers when given a page for data area and
897 * the size of each buffer.. Use the bh->b_this_page linked list to
898 * follow the buffers created. Return NULL if unable to create more
899 * buffers.
900 *
901 * The retry flag is used to differentiate async IO (paging, swapping)
902 * which may not fail from ordinary buffer allocations.
903 */
904struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
905 int retry)
906{
907 struct buffer_head *bh, *head;
908 long offset;
909
910try_again:
911 head = NULL;
912 offset = PAGE_SIZE;
913 while ((offset -= size) >= 0) {
914 bh = alloc_buffer_head(GFP_NOFS);
915 if (!bh)
916 goto no_grow;
917
918 bh->b_bdev = NULL;
919 bh->b_this_page = head;
920 bh->b_blocknr = -1;
921 head = bh;
922
923 bh->b_state = 0;
924 atomic_set(&bh->b_count, 0);
Chris Masonfc5cd582006-02-01 03:06:48 -0800925 bh->b_private = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700926 bh->b_size = size;
927
928 /* Link the buffer to its page */
929 set_bh_page(bh, page, offset);
930
Nathan Scott01ffe332006-01-17 09:02:07 +1100931 init_buffer(bh, NULL, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700932 }
933 return head;
934/*
935 * In case anything failed, we just free everything we got.
936 */
937no_grow:
938 if (head) {
939 do {
940 bh = head;
941 head = head->b_this_page;
942 free_buffer_head(bh);
943 } while (head);
944 }
945
946 /*
947 * Return failure for non-async IO requests. Async IO requests
948 * are not allowed to fail, so we have to wait until buffer heads
949 * become available. But we don't want tasks sleeping with
950 * partially complete buffers, so all were released above.
951 */
952 if (!retry)
953 return NULL;
954
955 /* We're _really_ low on memory. Now we just
956 * wait for old buffer heads to become free due to
957 * finishing IO. Since this is an async request and
958 * the reserve list is empty, we're sure there are
959 * async buffer heads in use.
960 */
961 free_more_memory();
962 goto try_again;
963}
964EXPORT_SYMBOL_GPL(alloc_page_buffers);
965
966static inline void
967link_dev_buffers(struct page *page, struct buffer_head *head)
968{
969 struct buffer_head *bh, *tail;
970
971 bh = head;
972 do {
973 tail = bh;
974 bh = bh->b_this_page;
975 } while (bh);
976 tail->b_this_page = head;
977 attach_page_buffers(page, head);
978}
979
980/*
981 * Initialise the state of a blockdev page's buffers.
982 */
983static void
984init_page_buffers(struct page *page, struct block_device *bdev,
985 sector_t block, int size)
986{
987 struct buffer_head *head = page_buffers(page);
988 struct buffer_head *bh = head;
989 int uptodate = PageUptodate(page);
990
991 do {
992 if (!buffer_mapped(bh)) {
993 init_buffer(bh, NULL, NULL);
994 bh->b_bdev = bdev;
995 bh->b_blocknr = block;
996 if (uptodate)
997 set_buffer_uptodate(bh);
998 set_buffer_mapped(bh);
999 }
1000 block++;
1001 bh = bh->b_this_page;
1002 } while (bh != head);
1003}
1004
1005/*
1006 * Create the page-cache page that contains the requested block.
1007 *
1008 * This is user purely for blockdev mappings.
1009 */
1010static struct page *
1011grow_dev_page(struct block_device *bdev, sector_t block,
1012 pgoff_t index, int size)
1013{
1014 struct inode *inode = bdev->bd_inode;
1015 struct page *page;
1016 struct buffer_head *bh;
1017
Christoph Lameterea125892007-05-16 22:11:21 -07001018 page = find_or_create_page(inode->i_mapping, index,
Mel Gorman769848c2007-07-17 04:03:05 -07001019 (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001020 if (!page)
1021 return NULL;
1022
Eric Sesterhenne827f922006-03-26 18:24:46 +02001023 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001024
1025 if (page_has_buffers(page)) {
1026 bh = page_buffers(page);
1027 if (bh->b_size == size) {
1028 init_page_buffers(page, bdev, block, size);
1029 return page;
1030 }
1031 if (!try_to_free_buffers(page))
1032 goto failed;
1033 }
1034
1035 /*
1036 * Allocate some buffers for this page
1037 */
1038 bh = alloc_page_buffers(page, size, 0);
1039 if (!bh)
1040 goto failed;
1041
1042 /*
1043 * Link the page to the buffers and initialise them. Take the
1044 * lock to be atomic wrt __find_get_block(), which does not
1045 * run under the page lock.
1046 */
1047 spin_lock(&inode->i_mapping->private_lock);
1048 link_dev_buffers(page, bh);
1049 init_page_buffers(page, bdev, block, size);
1050 spin_unlock(&inode->i_mapping->private_lock);
1051 return page;
1052
1053failed:
1054 BUG();
1055 unlock_page(page);
1056 page_cache_release(page);
1057 return NULL;
1058}
1059
1060/*
1061 * Create buffers for the specified block device block's page. If
1062 * that page was dirty, the buffers are set dirty also.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001063 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001064static int
Linus Torvalds1da177e2005-04-16 15:20:36 -07001065grow_buffers(struct block_device *bdev, sector_t block, int size)
1066{
1067 struct page *page;
1068 pgoff_t index;
1069 int sizebits;
1070
1071 sizebits = -1;
1072 do {
1073 sizebits++;
1074 } while ((size << sizebits) < PAGE_SIZE);
1075
1076 index = block >> sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001077
Andrew Mortone5657932006-10-11 01:21:46 -07001078 /*
1079 * Check for a block which wants to lie outside our maximum possible
1080 * pagecache index. (this comparison is done using sector_t types).
1081 */
1082 if (unlikely(index != block >> sizebits)) {
1083 char b[BDEVNAME_SIZE];
1084
1085 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1086 "device %s\n",
1087 __FUNCTION__, (unsigned long long)block,
1088 bdevname(bdev, b));
1089 return -EIO;
1090 }
1091 block = index << sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001092 /* Create a page with the proper size buffers.. */
1093 page = grow_dev_page(bdev, block, index, size);
1094 if (!page)
1095 return 0;
1096 unlock_page(page);
1097 page_cache_release(page);
1098 return 1;
1099}
1100
Adrian Bunk75c96f82005-05-05 16:16:09 -07001101static struct buffer_head *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001102__getblk_slow(struct block_device *bdev, sector_t block, int size)
1103{
1104 /* Size must be multiple of hard sectorsize */
1105 if (unlikely(size & (bdev_hardsect_size(bdev)-1) ||
1106 (size < 512 || size > PAGE_SIZE))) {
1107 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1108 size);
1109 printk(KERN_ERR "hardsect size: %d\n",
1110 bdev_hardsect_size(bdev));
1111
1112 dump_stack();
1113 return NULL;
1114 }
1115
1116 for (;;) {
1117 struct buffer_head * bh;
Andrew Mortone5657932006-10-11 01:21:46 -07001118 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001119
1120 bh = __find_get_block(bdev, block, size);
1121 if (bh)
1122 return bh;
1123
Andrew Mortone5657932006-10-11 01:21:46 -07001124 ret = grow_buffers(bdev, block, size);
1125 if (ret < 0)
1126 return NULL;
1127 if (ret == 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001128 free_more_memory();
1129 }
1130}
1131
1132/*
1133 * The relationship between dirty buffers and dirty pages:
1134 *
1135 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1136 * the page is tagged dirty in its radix tree.
1137 *
1138 * At all times, the dirtiness of the buffers represents the dirtiness of
1139 * subsections of the page. If the page has buffers, the page dirty bit is
1140 * merely a hint about the true dirty state.
1141 *
1142 * When a page is set dirty in its entirety, all its buffers are marked dirty
1143 * (if the page has buffers).
1144 *
1145 * When a buffer is marked dirty, its page is dirtied, but the page's other
1146 * buffers are not.
1147 *
1148 * Also. When blockdev buffers are explicitly read with bread(), they
1149 * individually become uptodate. But their backing page remains not
1150 * uptodate - even if all of its buffers are uptodate. A subsequent
1151 * block_read_full_page() against that page will discover all the uptodate
1152 * buffers, will set the page uptodate and will perform no I/O.
1153 */
1154
1155/**
1156 * mark_buffer_dirty - mark a buffer_head as needing writeout
Martin Waitz67be2dd2005-05-01 08:59:26 -07001157 * @bh: the buffer_head to mark dirty
Linus Torvalds1da177e2005-04-16 15:20:36 -07001158 *
1159 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1160 * backing page dirty, then tag the page as dirty in its address_space's radix
1161 * tree and then attach the address_space's inode to its superblock's dirty
1162 * inode list.
1163 *
1164 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1165 * mapping->tree_lock and the global inode_lock.
1166 */
1167void fastcall mark_buffer_dirty(struct buffer_head *bh)
1168{
Nick Piggin787d2212007-07-17 04:03:34 -07001169 WARN_ON_ONCE(!buffer_uptodate(bh));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001170 if (!buffer_dirty(bh) && !test_set_buffer_dirty(bh))
Nick Piggin787d2212007-07-17 04:03:34 -07001171 __set_page_dirty(bh->b_page, page_mapping(bh->b_page), 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001172}
1173
1174/*
1175 * Decrement a buffer_head's reference count. If all buffers against a page
1176 * have zero reference count, are clean and unlocked, and if the page is clean
1177 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1178 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1179 * a page but it ends up not being freed, and buffers may later be reattached).
1180 */
1181void __brelse(struct buffer_head * buf)
1182{
1183 if (atomic_read(&buf->b_count)) {
1184 put_bh(buf);
1185 return;
1186 }
1187 printk(KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1188 WARN_ON(1);
1189}
1190
1191/*
1192 * bforget() is like brelse(), except it discards any
1193 * potentially dirty data.
1194 */
1195void __bforget(struct buffer_head *bh)
1196{
1197 clear_buffer_dirty(bh);
1198 if (!list_empty(&bh->b_assoc_buffers)) {
1199 struct address_space *buffer_mapping = bh->b_page->mapping;
1200
1201 spin_lock(&buffer_mapping->private_lock);
1202 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -07001203 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001204 spin_unlock(&buffer_mapping->private_lock);
1205 }
1206 __brelse(bh);
1207}
1208
1209static struct buffer_head *__bread_slow(struct buffer_head *bh)
1210{
1211 lock_buffer(bh);
1212 if (buffer_uptodate(bh)) {
1213 unlock_buffer(bh);
1214 return bh;
1215 } else {
1216 get_bh(bh);
1217 bh->b_end_io = end_buffer_read_sync;
1218 submit_bh(READ, bh);
1219 wait_on_buffer(bh);
1220 if (buffer_uptodate(bh))
1221 return bh;
1222 }
1223 brelse(bh);
1224 return NULL;
1225}
1226
1227/*
1228 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1229 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1230 * refcount elevated by one when they're in an LRU. A buffer can only appear
1231 * once in a particular CPU's LRU. A single buffer can be present in multiple
1232 * CPU's LRUs at the same time.
1233 *
1234 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1235 * sb_find_get_block().
1236 *
1237 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1238 * a local interrupt disable for that.
1239 */
1240
1241#define BH_LRU_SIZE 8
1242
1243struct bh_lru {
1244 struct buffer_head *bhs[BH_LRU_SIZE];
1245};
1246
1247static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1248
1249#ifdef CONFIG_SMP
1250#define bh_lru_lock() local_irq_disable()
1251#define bh_lru_unlock() local_irq_enable()
1252#else
1253#define bh_lru_lock() preempt_disable()
1254#define bh_lru_unlock() preempt_enable()
1255#endif
1256
1257static inline void check_irqs_on(void)
1258{
1259#ifdef irqs_disabled
1260 BUG_ON(irqs_disabled());
1261#endif
1262}
1263
1264/*
1265 * The LRU management algorithm is dopey-but-simple. Sorry.
1266 */
1267static void bh_lru_install(struct buffer_head *bh)
1268{
1269 struct buffer_head *evictee = NULL;
1270 struct bh_lru *lru;
1271
1272 check_irqs_on();
1273 bh_lru_lock();
1274 lru = &__get_cpu_var(bh_lrus);
1275 if (lru->bhs[0] != bh) {
1276 struct buffer_head *bhs[BH_LRU_SIZE];
1277 int in;
1278 int out = 0;
1279
1280 get_bh(bh);
1281 bhs[out++] = bh;
1282 for (in = 0; in < BH_LRU_SIZE; in++) {
1283 struct buffer_head *bh2 = lru->bhs[in];
1284
1285 if (bh2 == bh) {
1286 __brelse(bh2);
1287 } else {
1288 if (out >= BH_LRU_SIZE) {
1289 BUG_ON(evictee != NULL);
1290 evictee = bh2;
1291 } else {
1292 bhs[out++] = bh2;
1293 }
1294 }
1295 }
1296 while (out < BH_LRU_SIZE)
1297 bhs[out++] = NULL;
1298 memcpy(lru->bhs, bhs, sizeof(bhs));
1299 }
1300 bh_lru_unlock();
1301
1302 if (evictee)
1303 __brelse(evictee);
1304}
1305
1306/*
1307 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1308 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001309static struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001310lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001311{
1312 struct buffer_head *ret = NULL;
1313 struct bh_lru *lru;
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001314 unsigned int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001315
1316 check_irqs_on();
1317 bh_lru_lock();
1318 lru = &__get_cpu_var(bh_lrus);
1319 for (i = 0; i < BH_LRU_SIZE; i++) {
1320 struct buffer_head *bh = lru->bhs[i];
1321
1322 if (bh && bh->b_bdev == bdev &&
1323 bh->b_blocknr == block && bh->b_size == size) {
1324 if (i) {
1325 while (i) {
1326 lru->bhs[i] = lru->bhs[i - 1];
1327 i--;
1328 }
1329 lru->bhs[0] = bh;
1330 }
1331 get_bh(bh);
1332 ret = bh;
1333 break;
1334 }
1335 }
1336 bh_lru_unlock();
1337 return ret;
1338}
1339
1340/*
1341 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1342 * it in the LRU and mark it as accessed. If it is not present then return
1343 * NULL
1344 */
1345struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001346__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001347{
1348 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1349
1350 if (bh == NULL) {
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001351 bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001352 if (bh)
1353 bh_lru_install(bh);
1354 }
1355 if (bh)
1356 touch_buffer(bh);
1357 return bh;
1358}
1359EXPORT_SYMBOL(__find_get_block);
1360
1361/*
1362 * __getblk will locate (and, if necessary, create) the buffer_head
1363 * which corresponds to the passed block_device, block and size. The
1364 * returned buffer has its reference count incremented.
1365 *
1366 * __getblk() cannot fail - it just keeps trying. If you pass it an
1367 * illegal block number, __getblk() will happily return a buffer_head
1368 * which represents the non-existent block. Very weird.
1369 *
1370 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1371 * attempt is failing. FIXME, perhaps?
1372 */
1373struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001374__getblk(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001375{
1376 struct buffer_head *bh = __find_get_block(bdev, block, size);
1377
1378 might_sleep();
1379 if (bh == NULL)
1380 bh = __getblk_slow(bdev, block, size);
1381 return bh;
1382}
1383EXPORT_SYMBOL(__getblk);
1384
1385/*
1386 * Do async read-ahead on a buffer..
1387 */
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001388void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001389{
1390 struct buffer_head *bh = __getblk(bdev, block, size);
Andrew Mortona3e713b2005-10-30 15:03:15 -08001391 if (likely(bh)) {
1392 ll_rw_block(READA, 1, &bh);
1393 brelse(bh);
1394 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001395}
1396EXPORT_SYMBOL(__breadahead);
1397
1398/**
1399 * __bread() - reads a specified block and returns the bh
Martin Waitz67be2dd2005-05-01 08:59:26 -07001400 * @bdev: the block_device to read from
Linus Torvalds1da177e2005-04-16 15:20:36 -07001401 * @block: number of block
1402 * @size: size (in bytes) to read
1403 *
1404 * Reads a specified block, and returns buffer head that contains it.
1405 * It returns NULL if the block was unreadable.
1406 */
1407struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001408__bread(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001409{
1410 struct buffer_head *bh = __getblk(bdev, block, size);
1411
Andrew Mortona3e713b2005-10-30 15:03:15 -08001412 if (likely(bh) && !buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001413 bh = __bread_slow(bh);
1414 return bh;
1415}
1416EXPORT_SYMBOL(__bread);
1417
1418/*
1419 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1420 * This doesn't race because it runs in each cpu either in irq
1421 * or with preempt disabled.
1422 */
1423static void invalidate_bh_lru(void *arg)
1424{
1425 struct bh_lru *b = &get_cpu_var(bh_lrus);
1426 int i;
1427
1428 for (i = 0; i < BH_LRU_SIZE; i++) {
1429 brelse(b->bhs[i]);
1430 b->bhs[i] = NULL;
1431 }
1432 put_cpu_var(bh_lrus);
1433}
1434
Peter Zijlstraf9a14392007-05-06 14:49:55 -07001435void invalidate_bh_lrus(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001436{
1437 on_each_cpu(invalidate_bh_lru, NULL, 1, 1);
1438}
1439
1440void set_bh_page(struct buffer_head *bh,
1441 struct page *page, unsigned long offset)
1442{
1443 bh->b_page = page;
Eric Sesterhenne827f922006-03-26 18:24:46 +02001444 BUG_ON(offset >= PAGE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001445 if (PageHighMem(page))
1446 /*
1447 * This catches illegal uses and preserves the offset:
1448 */
1449 bh->b_data = (char *)(0 + offset);
1450 else
1451 bh->b_data = page_address(page) + offset;
1452}
1453EXPORT_SYMBOL(set_bh_page);
1454
1455/*
1456 * Called when truncating a buffer on a page completely.
1457 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001458static void discard_buffer(struct buffer_head * bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001459{
1460 lock_buffer(bh);
1461 clear_buffer_dirty(bh);
1462 bh->b_bdev = NULL;
1463 clear_buffer_mapped(bh);
1464 clear_buffer_req(bh);
1465 clear_buffer_new(bh);
1466 clear_buffer_delay(bh);
David Chinner33a266d2007-02-12 00:51:41 -08001467 clear_buffer_unwritten(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001468 unlock_buffer(bh);
1469}
1470
1471/**
Linus Torvalds1da177e2005-04-16 15:20:36 -07001472 * block_invalidatepage - invalidate part of all of a buffer-backed page
1473 *
1474 * @page: the page which is affected
1475 * @offset: the index of the truncation point
1476 *
1477 * block_invalidatepage() is called when all or part of the page has become
1478 * invalidatedby a truncate operation.
1479 *
1480 * block_invalidatepage() does not have to release all buffers, but it must
1481 * ensure that no dirty buffer is left outside @offset and that no I/O
1482 * is underway against any of the blocks which are outside the truncation
1483 * point. Because the caller is about to free (and possibly reuse) those
1484 * blocks on-disk.
1485 */
NeilBrown2ff28e22006-03-26 01:37:18 -08001486void block_invalidatepage(struct page *page, unsigned long offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001487{
1488 struct buffer_head *head, *bh, *next;
1489 unsigned int curr_off = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001490
1491 BUG_ON(!PageLocked(page));
1492 if (!page_has_buffers(page))
1493 goto out;
1494
1495 head = page_buffers(page);
1496 bh = head;
1497 do {
1498 unsigned int next_off = curr_off + bh->b_size;
1499 next = bh->b_this_page;
1500
1501 /*
1502 * is this block fully invalidated?
1503 */
1504 if (offset <= curr_off)
1505 discard_buffer(bh);
1506 curr_off = next_off;
1507 bh = next;
1508 } while (bh != head);
1509
1510 /*
1511 * We release buffers only if the entire page is being invalidated.
1512 * The get_block cached value has been unconditionally invalidated,
1513 * so real IO is not possible anymore.
1514 */
1515 if (offset == 0)
NeilBrown2ff28e22006-03-26 01:37:18 -08001516 try_to_release_page(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001517out:
NeilBrown2ff28e22006-03-26 01:37:18 -08001518 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001519}
1520EXPORT_SYMBOL(block_invalidatepage);
1521
1522/*
1523 * We attach and possibly dirty the buffers atomically wrt
1524 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1525 * is already excluded via the page lock.
1526 */
1527void create_empty_buffers(struct page *page,
1528 unsigned long blocksize, unsigned long b_state)
1529{
1530 struct buffer_head *bh, *head, *tail;
1531
1532 head = alloc_page_buffers(page, blocksize, 1);
1533 bh = head;
1534 do {
1535 bh->b_state |= b_state;
1536 tail = bh;
1537 bh = bh->b_this_page;
1538 } while (bh);
1539 tail->b_this_page = head;
1540
1541 spin_lock(&page->mapping->private_lock);
1542 if (PageUptodate(page) || PageDirty(page)) {
1543 bh = head;
1544 do {
1545 if (PageDirty(page))
1546 set_buffer_dirty(bh);
1547 if (PageUptodate(page))
1548 set_buffer_uptodate(bh);
1549 bh = bh->b_this_page;
1550 } while (bh != head);
1551 }
1552 attach_page_buffers(page, head);
1553 spin_unlock(&page->mapping->private_lock);
1554}
1555EXPORT_SYMBOL(create_empty_buffers);
1556
1557/*
1558 * We are taking a block for data and we don't want any output from any
1559 * buffer-cache aliases starting from return from that function and
1560 * until the moment when something will explicitly mark the buffer
1561 * dirty (hopefully that will not happen until we will free that block ;-)
1562 * We don't even need to mark it not-uptodate - nobody can expect
1563 * anything from a newly allocated buffer anyway. We used to used
1564 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1565 * don't want to mark the alias unmapped, for example - it would confuse
1566 * anyone who might pick it with bread() afterwards...
1567 *
1568 * Also.. Note that bforget() doesn't lock the buffer. So there can
1569 * be writeout I/O going on against recently-freed buffers. We don't
1570 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1571 * only if we really need to. That happens here.
1572 */
1573void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1574{
1575 struct buffer_head *old_bh;
1576
1577 might_sleep();
1578
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001579 old_bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001580 if (old_bh) {
1581 clear_buffer_dirty(old_bh);
1582 wait_on_buffer(old_bh);
1583 clear_buffer_req(old_bh);
1584 __brelse(old_bh);
1585 }
1586}
1587EXPORT_SYMBOL(unmap_underlying_metadata);
1588
1589/*
1590 * NOTE! All mapped/uptodate combinations are valid:
1591 *
1592 * Mapped Uptodate Meaning
1593 *
1594 * No No "unknown" - must do get_block()
1595 * No Yes "hole" - zero-filled
1596 * Yes No "allocated" - allocated on disk, not read in
1597 * Yes Yes "valid" - allocated and up-to-date in memory.
1598 *
1599 * "Dirty" is valid only with the last case (mapped+uptodate).
1600 */
1601
1602/*
1603 * While block_write_full_page is writing back the dirty buffers under
1604 * the page lock, whoever dirtied the buffers may decide to clean them
1605 * again at any time. We handle that by only looking at the buffer
1606 * state inside lock_buffer().
1607 *
1608 * If block_write_full_page() is called for regular writeback
1609 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1610 * locked buffer. This only can happen if someone has written the buffer
1611 * directly, with submit_bh(). At the address_space level PageWriteback
1612 * prevents this contention from occurring.
1613 */
1614static int __block_write_full_page(struct inode *inode, struct page *page,
1615 get_block_t *get_block, struct writeback_control *wbc)
1616{
1617 int err;
1618 sector_t block;
1619 sector_t last_block;
Andrew Mortonf0fbd5f2005-05-05 16:15:48 -07001620 struct buffer_head *bh, *head;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001621 const unsigned blocksize = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001622 int nr_underway = 0;
1623
1624 BUG_ON(!PageLocked(page));
1625
1626 last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
1627
1628 if (!page_has_buffers(page)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001629 create_empty_buffers(page, blocksize,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001630 (1 << BH_Dirty)|(1 << BH_Uptodate));
1631 }
1632
1633 /*
1634 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1635 * here, and the (potentially unmapped) buffers may become dirty at
1636 * any time. If a buffer becomes dirty here after we've inspected it
1637 * then we just miss that fact, and the page stays dirty.
1638 *
1639 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1640 * handle that here by just cleaning them.
1641 */
1642
Andrew Morton54b21a72006-01-08 01:03:05 -08001643 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001644 head = page_buffers(page);
1645 bh = head;
1646
1647 /*
1648 * Get all the dirty buffers mapped to disk addresses and
1649 * handle any aliases from the underlying blockdev's mapping.
1650 */
1651 do {
1652 if (block > last_block) {
1653 /*
1654 * mapped buffers outside i_size will occur, because
1655 * this page can be outside i_size when there is a
1656 * truncate in progress.
1657 */
1658 /*
1659 * The buffer was zeroed by block_write_full_page()
1660 */
1661 clear_buffer_dirty(bh);
1662 set_buffer_uptodate(bh);
1663 } else if (!buffer_mapped(bh) && buffer_dirty(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001664 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001665 err = get_block(inode, block, bh, 1);
1666 if (err)
1667 goto recover;
1668 if (buffer_new(bh)) {
1669 /* blockdev mappings never come here */
1670 clear_buffer_new(bh);
1671 unmap_underlying_metadata(bh->b_bdev,
1672 bh->b_blocknr);
1673 }
1674 }
1675 bh = bh->b_this_page;
1676 block++;
1677 } while (bh != head);
1678
1679 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001680 if (!buffer_mapped(bh))
1681 continue;
1682 /*
1683 * If it's a fully non-blocking write attempt and we cannot
1684 * lock the buffer then redirty the page. Note that this can
1685 * potentially cause a busy-wait loop from pdflush and kswapd
1686 * activity, but those code paths have their own higher-level
1687 * throttling.
1688 */
1689 if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
1690 lock_buffer(bh);
1691 } else if (test_set_buffer_locked(bh)) {
1692 redirty_page_for_writepage(wbc, page);
1693 continue;
1694 }
1695 if (test_clear_buffer_dirty(bh)) {
1696 mark_buffer_async_write(bh);
1697 } else {
1698 unlock_buffer(bh);
1699 }
1700 } while ((bh = bh->b_this_page) != head);
1701
1702 /*
1703 * The page and its buffers are protected by PageWriteback(), so we can
1704 * drop the bh refcounts early.
1705 */
1706 BUG_ON(PageWriteback(page));
1707 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001708
1709 do {
1710 struct buffer_head *next = bh->b_this_page;
1711 if (buffer_async_write(bh)) {
1712 submit_bh(WRITE, bh);
1713 nr_underway++;
1714 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001715 bh = next;
1716 } while (bh != head);
Andrew Morton05937ba2005-05-05 16:15:47 -07001717 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001718
1719 err = 0;
1720done:
1721 if (nr_underway == 0) {
1722 /*
1723 * The page was marked dirty, but the buffers were
1724 * clean. Someone wrote them back by hand with
1725 * ll_rw_block/submit_bh. A rare case.
1726 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001727 end_page_writeback(page);
Nick Piggin3d67f2d2007-05-06 14:49:05 -07001728
Linus Torvalds1da177e2005-04-16 15:20:36 -07001729 /*
1730 * The page and buffer_heads can be released at any time from
1731 * here on.
1732 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001733 }
1734 return err;
1735
1736recover:
1737 /*
1738 * ENOSPC, or some other error. We may already have added some
1739 * blocks to the file, so we need to write these out to avoid
1740 * exposing stale data.
1741 * The page is currently locked and not marked for writeback
1742 */
1743 bh = head;
1744 /* Recovery: lock and submit the mapped buffers */
1745 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001746 if (buffer_mapped(bh) && buffer_dirty(bh)) {
1747 lock_buffer(bh);
1748 mark_buffer_async_write(bh);
1749 } else {
1750 /*
1751 * The buffer may have been set dirty during
1752 * attachment to a dirty page.
1753 */
1754 clear_buffer_dirty(bh);
1755 }
1756 } while ((bh = bh->b_this_page) != head);
1757 SetPageError(page);
1758 BUG_ON(PageWriteback(page));
Andrew Morton7e4c3692007-05-08 00:23:27 -07001759 mapping_set_error(page->mapping, err);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001760 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001761 do {
1762 struct buffer_head *next = bh->b_this_page;
1763 if (buffer_async_write(bh)) {
1764 clear_buffer_dirty(bh);
1765 submit_bh(WRITE, bh);
1766 nr_underway++;
1767 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001768 bh = next;
1769 } while (bh != head);
Nick Pigginffda9d32007-02-20 13:57:54 -08001770 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001771 goto done;
1772}
1773
Nick Pigginafddba42007-10-16 01:25:01 -07001774/*
1775 * If a page has any new buffers, zero them out here, and mark them uptodate
1776 * and dirty so they'll be written out (in order to prevent uninitialised
1777 * block data from leaking). And clear the new bit.
1778 */
1779void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1780{
1781 unsigned int block_start, block_end;
1782 struct buffer_head *head, *bh;
1783
1784 BUG_ON(!PageLocked(page));
1785 if (!page_has_buffers(page))
1786 return;
1787
1788 bh = head = page_buffers(page);
1789 block_start = 0;
1790 do {
1791 block_end = block_start + bh->b_size;
1792
1793 if (buffer_new(bh)) {
1794 if (block_end > from && block_start < to) {
1795 if (!PageUptodate(page)) {
1796 unsigned start, size;
1797
1798 start = max(from, block_start);
1799 size = min(to, block_end) - start;
1800
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001801 zero_user(page, start, size);
Nick Pigginafddba42007-10-16 01:25:01 -07001802 set_buffer_uptodate(bh);
1803 }
1804
1805 clear_buffer_new(bh);
1806 mark_buffer_dirty(bh);
1807 }
1808 }
1809
1810 block_start = block_end;
1811 bh = bh->b_this_page;
1812 } while (bh != head);
1813}
1814EXPORT_SYMBOL(page_zero_new_buffers);
1815
Linus Torvalds1da177e2005-04-16 15:20:36 -07001816static int __block_prepare_write(struct inode *inode, struct page *page,
1817 unsigned from, unsigned to, get_block_t *get_block)
1818{
1819 unsigned block_start, block_end;
1820 sector_t block;
1821 int err = 0;
1822 unsigned blocksize, bbits;
1823 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1824
1825 BUG_ON(!PageLocked(page));
1826 BUG_ON(from > PAGE_CACHE_SIZE);
1827 BUG_ON(to > PAGE_CACHE_SIZE);
1828 BUG_ON(from > to);
1829
1830 blocksize = 1 << inode->i_blkbits;
1831 if (!page_has_buffers(page))
1832 create_empty_buffers(page, blocksize, 0);
1833 head = page_buffers(page);
1834
1835 bbits = inode->i_blkbits;
1836 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1837
1838 for(bh = head, block_start = 0; bh != head || !block_start;
1839 block++, block_start=block_end, bh = bh->b_this_page) {
1840 block_end = block_start + blocksize;
1841 if (block_end <= from || block_start >= to) {
1842 if (PageUptodate(page)) {
1843 if (!buffer_uptodate(bh))
1844 set_buffer_uptodate(bh);
1845 }
1846 continue;
1847 }
1848 if (buffer_new(bh))
1849 clear_buffer_new(bh);
1850 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001851 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001852 err = get_block(inode, block, bh, 1);
1853 if (err)
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001854 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001855 if (buffer_new(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001856 unmap_underlying_metadata(bh->b_bdev,
1857 bh->b_blocknr);
1858 if (PageUptodate(page)) {
Nick Piggin637aff42007-10-16 01:25:00 -07001859 clear_buffer_new(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001860 set_buffer_uptodate(bh);
Nick Piggin637aff42007-10-16 01:25:00 -07001861 mark_buffer_dirty(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001862 continue;
1863 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001864 if (block_end > to || block_start < from)
1865 zero_user_segments(page,
1866 to, block_end,
1867 block_start, from);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001868 continue;
1869 }
1870 }
1871 if (PageUptodate(page)) {
1872 if (!buffer_uptodate(bh))
1873 set_buffer_uptodate(bh);
1874 continue;
1875 }
1876 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
David Chinner33a266d2007-02-12 00:51:41 -08001877 !buffer_unwritten(bh) &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001878 (block_start < from || block_end > to)) {
1879 ll_rw_block(READ, 1, &bh);
1880 *wait_bh++=bh;
1881 }
1882 }
1883 /*
1884 * If we issued read requests - let them complete.
1885 */
1886 while(wait_bh > wait) {
1887 wait_on_buffer(*--wait_bh);
1888 if (!buffer_uptodate(*wait_bh))
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001889 err = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001890 }
Nick Pigginafddba42007-10-16 01:25:01 -07001891 if (unlikely(err))
1892 page_zero_new_buffers(page, from, to);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001893 return err;
1894}
1895
1896static int __block_commit_write(struct inode *inode, struct page *page,
1897 unsigned from, unsigned to)
1898{
1899 unsigned block_start, block_end;
1900 int partial = 0;
1901 unsigned blocksize;
1902 struct buffer_head *bh, *head;
1903
1904 blocksize = 1 << inode->i_blkbits;
1905
1906 for(bh = head = page_buffers(page), block_start = 0;
1907 bh != head || !block_start;
1908 block_start=block_end, bh = bh->b_this_page) {
1909 block_end = block_start + blocksize;
1910 if (block_end <= from || block_start >= to) {
1911 if (!buffer_uptodate(bh))
1912 partial = 1;
1913 } else {
1914 set_buffer_uptodate(bh);
1915 mark_buffer_dirty(bh);
1916 }
Nick Pigginafddba42007-10-16 01:25:01 -07001917 clear_buffer_new(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001918 }
1919
1920 /*
1921 * If this is a partial write which happened to make all buffers
1922 * uptodate then we can optimize away a bogus readpage() for
1923 * the next read(). Here we 'discover' whether the page went
1924 * uptodate as a result of this (potentially partial) write.
1925 */
1926 if (!partial)
1927 SetPageUptodate(page);
1928 return 0;
1929}
1930
1931/*
Nick Pigginafddba42007-10-16 01:25:01 -07001932 * block_write_begin takes care of the basic task of block allocation and
1933 * bringing partial write blocks uptodate first.
1934 *
1935 * If *pagep is not NULL, then block_write_begin uses the locked page
1936 * at *pagep rather than allocating its own. In this case, the page will
1937 * not be unlocked or deallocated on failure.
1938 */
1939int block_write_begin(struct file *file, struct address_space *mapping,
1940 loff_t pos, unsigned len, unsigned flags,
1941 struct page **pagep, void **fsdata,
1942 get_block_t *get_block)
1943{
1944 struct inode *inode = mapping->host;
1945 int status = 0;
1946 struct page *page;
1947 pgoff_t index;
1948 unsigned start, end;
1949 int ownpage = 0;
1950
1951 index = pos >> PAGE_CACHE_SHIFT;
1952 start = pos & (PAGE_CACHE_SIZE - 1);
1953 end = start + len;
1954
1955 page = *pagep;
1956 if (page == NULL) {
1957 ownpage = 1;
1958 page = __grab_cache_page(mapping, index);
1959 if (!page) {
1960 status = -ENOMEM;
1961 goto out;
1962 }
1963 *pagep = page;
1964 } else
1965 BUG_ON(!PageLocked(page));
1966
1967 status = __block_prepare_write(inode, page, start, end, get_block);
1968 if (unlikely(status)) {
1969 ClearPageUptodate(page);
1970
1971 if (ownpage) {
1972 unlock_page(page);
1973 page_cache_release(page);
1974 *pagep = NULL;
1975
1976 /*
1977 * prepare_write() may have instantiated a few blocks
1978 * outside i_size. Trim these off again. Don't need
1979 * i_size_read because we hold i_mutex.
1980 */
1981 if (pos + len > inode->i_size)
1982 vmtruncate(inode, inode->i_size);
1983 }
1984 goto out;
1985 }
1986
1987out:
1988 return status;
1989}
1990EXPORT_SYMBOL(block_write_begin);
1991
1992int block_write_end(struct file *file, struct address_space *mapping,
1993 loff_t pos, unsigned len, unsigned copied,
1994 struct page *page, void *fsdata)
1995{
1996 struct inode *inode = mapping->host;
1997 unsigned start;
1998
1999 start = pos & (PAGE_CACHE_SIZE - 1);
2000
2001 if (unlikely(copied < len)) {
2002 /*
2003 * The buffers that were written will now be uptodate, so we
2004 * don't have to worry about a readpage reading them and
2005 * overwriting a partial write. However if we have encountered
2006 * a short write and only partially written into a buffer, it
2007 * will not be marked uptodate, so a readpage might come in and
2008 * destroy our partial write.
2009 *
2010 * Do the simplest thing, and just treat any short write to a
2011 * non uptodate page as a zero-length write, and force the
2012 * caller to redo the whole thing.
2013 */
2014 if (!PageUptodate(page))
2015 copied = 0;
2016
2017 page_zero_new_buffers(page, start+copied, start+len);
2018 }
2019 flush_dcache_page(page);
2020
2021 /* This could be a short (even 0-length) commit */
2022 __block_commit_write(inode, page, start, start+copied);
2023
2024 return copied;
2025}
2026EXPORT_SYMBOL(block_write_end);
2027
2028int generic_write_end(struct file *file, struct address_space *mapping,
2029 loff_t pos, unsigned len, unsigned copied,
2030 struct page *page, void *fsdata)
2031{
2032 struct inode *inode = mapping->host;
2033
2034 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2035
2036 /*
2037 * No need to use i_size_read() here, the i_size
2038 * cannot change under us because we hold i_mutex.
2039 *
2040 * But it's important to update i_size while still holding page lock:
2041 * page writeout could otherwise come in and zero beyond i_size.
2042 */
2043 if (pos+copied > inode->i_size) {
2044 i_size_write(inode, pos+copied);
2045 mark_inode_dirty(inode);
2046 }
2047
2048 unlock_page(page);
2049 page_cache_release(page);
2050
2051 return copied;
2052}
2053EXPORT_SYMBOL(generic_write_end);
2054
2055/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002056 * Generic "read page" function for block devices that have the normal
2057 * get_block functionality. This is most of the block device filesystems.
2058 * Reads the page asynchronously --- the unlock_buffer() and
2059 * set/clear_buffer_uptodate() functions propagate buffer state into the
2060 * page struct once IO has completed.
2061 */
2062int block_read_full_page(struct page *page, get_block_t *get_block)
2063{
2064 struct inode *inode = page->mapping->host;
2065 sector_t iblock, lblock;
2066 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2067 unsigned int blocksize;
2068 int nr, i;
2069 int fully_mapped = 1;
2070
Matt Mackallcd7619d2005-05-01 08:59:01 -07002071 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002072 blocksize = 1 << inode->i_blkbits;
2073 if (!page_has_buffers(page))
2074 create_empty_buffers(page, blocksize, 0);
2075 head = page_buffers(page);
2076
2077 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2078 lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
2079 bh = head;
2080 nr = 0;
2081 i = 0;
2082
2083 do {
2084 if (buffer_uptodate(bh))
2085 continue;
2086
2087 if (!buffer_mapped(bh)) {
Andrew Mortonc64610b2005-05-16 21:53:49 -07002088 int err = 0;
2089
Linus Torvalds1da177e2005-04-16 15:20:36 -07002090 fully_mapped = 0;
2091 if (iblock < lblock) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002092 WARN_ON(bh->b_size != blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002093 err = get_block(inode, iblock, bh, 0);
2094 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002095 SetPageError(page);
2096 }
2097 if (!buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002098 zero_user(page, i * blocksize, blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002099 if (!err)
2100 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002101 continue;
2102 }
2103 /*
2104 * get_block() might have updated the buffer
2105 * synchronously
2106 */
2107 if (buffer_uptodate(bh))
2108 continue;
2109 }
2110 arr[nr++] = bh;
2111 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2112
2113 if (fully_mapped)
2114 SetPageMappedToDisk(page);
2115
2116 if (!nr) {
2117 /*
2118 * All buffers are uptodate - we can set the page uptodate
2119 * as well. But not if get_block() returned an error.
2120 */
2121 if (!PageError(page))
2122 SetPageUptodate(page);
2123 unlock_page(page);
2124 return 0;
2125 }
2126
2127 /* Stage two: lock the buffers */
2128 for (i = 0; i < nr; i++) {
2129 bh = arr[i];
2130 lock_buffer(bh);
2131 mark_buffer_async_read(bh);
2132 }
2133
2134 /*
2135 * Stage 3: start the IO. Check for uptodateness
2136 * inside the buffer lock in case another process reading
2137 * the underlying blockdev brought it uptodate (the sct fix).
2138 */
2139 for (i = 0; i < nr; i++) {
2140 bh = arr[i];
2141 if (buffer_uptodate(bh))
2142 end_buffer_async_read(bh, 1);
2143 else
2144 submit_bh(READ, bh);
2145 }
2146 return 0;
2147}
2148
2149/* utility function for filesystems that need to do work on expanding
Nick Piggin89e10782007-10-16 01:25:07 -07002150 * truncates. Uses filesystem pagecache writes to allow the filesystem to
Linus Torvalds1da177e2005-04-16 15:20:36 -07002151 * deal with the hole.
2152 */
Nick Piggin89e10782007-10-16 01:25:07 -07002153int generic_cont_expand_simple(struct inode *inode, loff_t size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002154{
2155 struct address_space *mapping = inode->i_mapping;
2156 struct page *page;
Nick Piggin89e10782007-10-16 01:25:07 -07002157 void *fsdata;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002158 unsigned long limit;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002159 int err;
2160
2161 err = -EFBIG;
2162 limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
2163 if (limit != RLIM_INFINITY && size > (loff_t)limit) {
2164 send_sig(SIGXFSZ, current, 0);
2165 goto out;
2166 }
2167 if (size > inode->i_sb->s_maxbytes)
2168 goto out;
2169
Nick Piggin89e10782007-10-16 01:25:07 -07002170 err = pagecache_write_begin(NULL, mapping, size, 0,
2171 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2172 &page, &fsdata);
2173 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002174 goto out;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002175
Nick Piggin89e10782007-10-16 01:25:07 -07002176 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2177 BUG_ON(err > 0);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002178
Linus Torvalds1da177e2005-04-16 15:20:36 -07002179out:
2180 return err;
2181}
2182
Nick Piggin89e10782007-10-16 01:25:07 -07002183int cont_expand_zero(struct file *file, struct address_space *mapping,
2184 loff_t pos, loff_t *bytes)
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002185{
Nick Piggin89e10782007-10-16 01:25:07 -07002186 struct inode *inode = mapping->host;
2187 unsigned blocksize = 1 << inode->i_blkbits;
2188 struct page *page;
2189 void *fsdata;
2190 pgoff_t index, curidx;
2191 loff_t curpos;
2192 unsigned zerofrom, offset, len;
2193 int err = 0;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002194
Nick Piggin89e10782007-10-16 01:25:07 -07002195 index = pos >> PAGE_CACHE_SHIFT;
2196 offset = pos & ~PAGE_CACHE_MASK;
2197
2198 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
2199 zerofrom = curpos & ~PAGE_CACHE_MASK;
2200 if (zerofrom & (blocksize-1)) {
2201 *bytes |= (blocksize-1);
2202 (*bytes)++;
2203 }
2204 len = PAGE_CACHE_SIZE - zerofrom;
2205
2206 err = pagecache_write_begin(file, mapping, curpos, len,
2207 AOP_FLAG_UNINTERRUPTIBLE,
2208 &page, &fsdata);
2209 if (err)
2210 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002211 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002212 err = pagecache_write_end(file, mapping, curpos, len, len,
2213 page, fsdata);
2214 if (err < 0)
2215 goto out;
2216 BUG_ON(err != len);
2217 err = 0;
2218 }
2219
2220 /* page covers the boundary, find the boundary offset */
2221 if (index == curidx) {
2222 zerofrom = curpos & ~PAGE_CACHE_MASK;
2223 /* if we will expand the thing last block will be filled */
2224 if (offset <= zerofrom) {
2225 goto out;
2226 }
2227 if (zerofrom & (blocksize-1)) {
2228 *bytes |= (blocksize-1);
2229 (*bytes)++;
2230 }
2231 len = offset - zerofrom;
2232
2233 err = pagecache_write_begin(file, mapping, curpos, len,
2234 AOP_FLAG_UNINTERRUPTIBLE,
2235 &page, &fsdata);
2236 if (err)
2237 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002238 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002239 err = pagecache_write_end(file, mapping, curpos, len, len,
2240 page, fsdata);
2241 if (err < 0)
2242 goto out;
2243 BUG_ON(err != len);
2244 err = 0;
2245 }
2246out:
2247 return err;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002248}
2249
Linus Torvalds1da177e2005-04-16 15:20:36 -07002250/*
2251 * For moronic filesystems that do not allow holes in file.
2252 * We may have to extend the file.
2253 */
Nick Piggin89e10782007-10-16 01:25:07 -07002254int cont_write_begin(struct file *file, struct address_space *mapping,
2255 loff_t pos, unsigned len, unsigned flags,
2256 struct page **pagep, void **fsdata,
2257 get_block_t *get_block, loff_t *bytes)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002258{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002259 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002260 unsigned blocksize = 1 << inode->i_blkbits;
Nick Piggin89e10782007-10-16 01:25:07 -07002261 unsigned zerofrom;
2262 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002263
Nick Piggin89e10782007-10-16 01:25:07 -07002264 err = cont_expand_zero(file, mapping, pos, bytes);
2265 if (err)
2266 goto out;
2267
2268 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2269 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2270 *bytes |= (blocksize-1);
2271 (*bytes)++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002272 }
2273
Nick Piggin89e10782007-10-16 01:25:07 -07002274 *pagep = NULL;
2275 err = block_write_begin(file, mapping, pos, len,
2276 flags, pagep, fsdata, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002277out:
Nick Piggin89e10782007-10-16 01:25:07 -07002278 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002279}
2280
2281int block_prepare_write(struct page *page, unsigned from, unsigned to,
2282 get_block_t *get_block)
2283{
2284 struct inode *inode = page->mapping->host;
2285 int err = __block_prepare_write(inode, page, from, to, get_block);
2286 if (err)
2287 ClearPageUptodate(page);
2288 return err;
2289}
2290
2291int block_commit_write(struct page *page, unsigned from, unsigned to)
2292{
2293 struct inode *inode = page->mapping->host;
2294 __block_commit_write(inode,page,from,to);
2295 return 0;
2296}
2297
2298int generic_commit_write(struct file *file, struct page *page,
2299 unsigned from, unsigned to)
2300{
2301 struct inode *inode = page->mapping->host;
2302 loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
2303 __block_commit_write(inode,page,from,to);
2304 /*
2305 * No need to use i_size_read() here, the i_size
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08002306 * cannot change under us because we hold i_mutex.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002307 */
2308 if (pos > inode->i_size) {
2309 i_size_write(inode, pos);
2310 mark_inode_dirty(inode);
2311 }
2312 return 0;
2313}
2314
David Chinner54171692007-07-19 17:39:55 +10002315/*
2316 * block_page_mkwrite() is not allowed to change the file size as it gets
2317 * called from a page fault handler when a page is first dirtied. Hence we must
2318 * be careful to check for EOF conditions here. We set the page up correctly
2319 * for a written page which means we get ENOSPC checking when writing into
2320 * holes and correct delalloc and unwritten extent mapping on filesystems that
2321 * support these features.
2322 *
2323 * We are not allowed to take the i_mutex here so we have to play games to
2324 * protect against truncate races as the page could now be beyond EOF. Because
2325 * vmtruncate() writes the inode size before removing pages, once we have the
2326 * page lock we can determine safely if the page is beyond EOF. If it is not
2327 * beyond EOF, then the page is guaranteed safe against truncation until we
2328 * unlock the page.
2329 */
2330int
2331block_page_mkwrite(struct vm_area_struct *vma, struct page *page,
2332 get_block_t get_block)
2333{
2334 struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
2335 unsigned long end;
2336 loff_t size;
2337 int ret = -EINVAL;
2338
2339 lock_page(page);
2340 size = i_size_read(inode);
2341 if ((page->mapping != inode->i_mapping) ||
Nick Piggin18336332007-07-20 00:31:45 -07002342 (page_offset(page) > size)) {
David Chinner54171692007-07-19 17:39:55 +10002343 /* page got truncated out from underneath us */
2344 goto out_unlock;
2345 }
2346
2347 /* page is wholly or partially inside EOF */
2348 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
2349 end = size & ~PAGE_CACHE_MASK;
2350 else
2351 end = PAGE_CACHE_SIZE;
2352
2353 ret = block_prepare_write(page, 0, end, get_block);
2354 if (!ret)
2355 ret = block_commit_write(page, 0, end);
2356
2357out_unlock:
2358 unlock_page(page);
2359 return ret;
2360}
Linus Torvalds1da177e2005-04-16 15:20:36 -07002361
2362/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002363 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
Linus Torvalds1da177e2005-04-16 15:20:36 -07002364 * immediately, while under the page lock. So it needs a special end_io
2365 * handler which does not touch the bh after unlocking it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002366 */
2367static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2368{
Dmitry Monakhov68671f32007-10-16 01:24:47 -07002369 __end_buffer_read_notouch(bh, uptodate);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002370}
2371
2372/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002373 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2374 * the page (converting it to circular linked list and taking care of page
2375 * dirty races).
2376 */
2377static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2378{
2379 struct buffer_head *bh;
2380
2381 BUG_ON(!PageLocked(page));
2382
2383 spin_lock(&page->mapping->private_lock);
2384 bh = head;
2385 do {
2386 if (PageDirty(page))
2387 set_buffer_dirty(bh);
2388 if (!bh->b_this_page)
2389 bh->b_this_page = head;
2390 bh = bh->b_this_page;
2391 } while (bh != head);
2392 attach_page_buffers(page, head);
2393 spin_unlock(&page->mapping->private_lock);
2394}
2395
2396/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002397 * On entry, the page is fully not uptodate.
2398 * On exit the page is fully uptodate in the areas outside (from,to)
2399 */
Nick Piggin03158cd2007-10-16 01:25:25 -07002400int nobh_write_begin(struct file *file, struct address_space *mapping,
2401 loff_t pos, unsigned len, unsigned flags,
2402 struct page **pagep, void **fsdata,
Linus Torvalds1da177e2005-04-16 15:20:36 -07002403 get_block_t *get_block)
2404{
Nick Piggin03158cd2007-10-16 01:25:25 -07002405 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002406 const unsigned blkbits = inode->i_blkbits;
2407 const unsigned blocksize = 1 << blkbits;
Nick Piggina4b06722007-10-16 01:24:48 -07002408 struct buffer_head *head, *bh;
Nick Piggin03158cd2007-10-16 01:25:25 -07002409 struct page *page;
2410 pgoff_t index;
2411 unsigned from, to;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002412 unsigned block_in_page;
Nick Piggina4b06722007-10-16 01:24:48 -07002413 unsigned block_start, block_end;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002414 sector_t block_in_file;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002415 int nr_reads = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002416 int ret = 0;
2417 int is_mapped_to_disk = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002418
Nick Piggin03158cd2007-10-16 01:25:25 -07002419 index = pos >> PAGE_CACHE_SHIFT;
2420 from = pos & (PAGE_CACHE_SIZE - 1);
2421 to = from + len;
2422
2423 page = __grab_cache_page(mapping, index);
2424 if (!page)
2425 return -ENOMEM;
2426 *pagep = page;
2427 *fsdata = NULL;
2428
2429 if (page_has_buffers(page)) {
2430 unlock_page(page);
2431 page_cache_release(page);
2432 *pagep = NULL;
2433 return block_write_begin(file, mapping, pos, len, flags, pagep,
2434 fsdata, get_block);
2435 }
Nick Piggina4b06722007-10-16 01:24:48 -07002436
Linus Torvalds1da177e2005-04-16 15:20:36 -07002437 if (PageMappedToDisk(page))
2438 return 0;
2439
Nick Piggina4b06722007-10-16 01:24:48 -07002440 /*
2441 * Allocate buffers so that we can keep track of state, and potentially
2442 * attach them to the page if an error occurs. In the common case of
2443 * no error, they will just be freed again without ever being attached
2444 * to the page (which is all OK, because we're under the page lock).
2445 *
2446 * Be careful: the buffer linked list is a NULL terminated one, rather
2447 * than the circular one we're used to.
2448 */
2449 head = alloc_page_buffers(page, blocksize, 0);
Nick Piggin03158cd2007-10-16 01:25:25 -07002450 if (!head) {
2451 ret = -ENOMEM;
2452 goto out_release;
2453 }
Nick Piggina4b06722007-10-16 01:24:48 -07002454
Linus Torvalds1da177e2005-04-16 15:20:36 -07002455 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002456
2457 /*
2458 * We loop across all blocks in the page, whether or not they are
2459 * part of the affected region. This is so we can discover if the
2460 * page is fully mapped-to-disk.
2461 */
Nick Piggina4b06722007-10-16 01:24:48 -07002462 for (block_start = 0, block_in_page = 0, bh = head;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002463 block_start < PAGE_CACHE_SIZE;
Nick Piggina4b06722007-10-16 01:24:48 -07002464 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002465 int create;
2466
Nick Piggina4b06722007-10-16 01:24:48 -07002467 block_end = block_start + blocksize;
2468 bh->b_state = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002469 create = 1;
2470 if (block_start >= to)
2471 create = 0;
2472 ret = get_block(inode, block_in_file + block_in_page,
Nick Piggina4b06722007-10-16 01:24:48 -07002473 bh, create);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002474 if (ret)
2475 goto failed;
Nick Piggina4b06722007-10-16 01:24:48 -07002476 if (!buffer_mapped(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002477 is_mapped_to_disk = 0;
Nick Piggina4b06722007-10-16 01:24:48 -07002478 if (buffer_new(bh))
2479 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
2480 if (PageUptodate(page)) {
2481 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002482 continue;
Nick Piggina4b06722007-10-16 01:24:48 -07002483 }
2484 if (buffer_new(bh) || !buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002485 zero_user_segments(page, block_start, from,
2486 to, block_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002487 continue;
2488 }
Nick Piggina4b06722007-10-16 01:24:48 -07002489 if (buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002490 continue; /* reiserfs does this */
2491 if (block_start < from || block_end > to) {
Nick Piggina4b06722007-10-16 01:24:48 -07002492 lock_buffer(bh);
2493 bh->b_end_io = end_buffer_read_nobh;
2494 submit_bh(READ, bh);
2495 nr_reads++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002496 }
2497 }
2498
2499 if (nr_reads) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002500 /*
2501 * The page is locked, so these buffers are protected from
2502 * any VM or truncate activity. Hence we don't need to care
2503 * for the buffer_head refcounts.
2504 */
Nick Piggina4b06722007-10-16 01:24:48 -07002505 for (bh = head; bh; bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002506 wait_on_buffer(bh);
2507 if (!buffer_uptodate(bh))
2508 ret = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002509 }
2510 if (ret)
2511 goto failed;
2512 }
2513
2514 if (is_mapped_to_disk)
2515 SetPageMappedToDisk(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002516
Nick Piggin03158cd2007-10-16 01:25:25 -07002517 *fsdata = head; /* to be released by nobh_write_end */
Nick Piggina4b06722007-10-16 01:24:48 -07002518
Linus Torvalds1da177e2005-04-16 15:20:36 -07002519 return 0;
2520
2521failed:
Nick Piggin03158cd2007-10-16 01:25:25 -07002522 BUG_ON(!ret);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002523 /*
Nick Piggina4b06722007-10-16 01:24:48 -07002524 * Error recovery is a bit difficult. We need to zero out blocks that
2525 * were newly allocated, and dirty them to ensure they get written out.
2526 * Buffers need to be attached to the page at this point, otherwise
2527 * the handling of potential IO errors during writeout would be hard
2528 * (could try doing synchronous writeout, but what if that fails too?)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002529 */
Nick Piggin03158cd2007-10-16 01:25:25 -07002530 attach_nobh_buffers(page, head);
2531 page_zero_new_buffers(page, from, to);
Nick Piggina4b06722007-10-16 01:24:48 -07002532
Nick Piggin03158cd2007-10-16 01:25:25 -07002533out_release:
2534 unlock_page(page);
2535 page_cache_release(page);
2536 *pagep = NULL;
Nick Piggina4b06722007-10-16 01:24:48 -07002537
Nick Piggin03158cd2007-10-16 01:25:25 -07002538 if (pos + len > inode->i_size)
2539 vmtruncate(inode, inode->i_size);
Nick Piggina4b06722007-10-16 01:24:48 -07002540
Linus Torvalds1da177e2005-04-16 15:20:36 -07002541 return ret;
2542}
Nick Piggin03158cd2007-10-16 01:25:25 -07002543EXPORT_SYMBOL(nobh_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002544
Nick Piggin03158cd2007-10-16 01:25:25 -07002545int nobh_write_end(struct file *file, struct address_space *mapping,
2546 loff_t pos, unsigned len, unsigned copied,
2547 struct page *page, void *fsdata)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002548{
2549 struct inode *inode = page->mapping->host;
Nick Pigginefdc3132007-10-21 06:57:41 +02002550 struct buffer_head *head = fsdata;
Nick Piggin03158cd2007-10-16 01:25:25 -07002551 struct buffer_head *bh;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002552
Nick Piggin03158cd2007-10-16 01:25:25 -07002553 if (!PageMappedToDisk(page)) {
2554 if (unlikely(copied < len) && !page_has_buffers(page))
2555 attach_nobh_buffers(page, head);
2556 if (page_has_buffers(page))
2557 return generic_write_end(file, mapping, pos, len,
2558 copied, page, fsdata);
2559 }
Nick Piggina4b06722007-10-16 01:24:48 -07002560
Nick Piggin22c8ca72007-02-20 13:58:09 -08002561 SetPageUptodate(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002562 set_page_dirty(page);
Nick Piggin03158cd2007-10-16 01:25:25 -07002563 if (pos+copied > inode->i_size) {
2564 i_size_write(inode, pos+copied);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002565 mark_inode_dirty(inode);
2566 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002567
2568 unlock_page(page);
2569 page_cache_release(page);
2570
Nick Piggin03158cd2007-10-16 01:25:25 -07002571 while (head) {
2572 bh = head;
2573 head = head->b_this_page;
2574 free_buffer_head(bh);
2575 }
2576
2577 return copied;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002578}
Nick Piggin03158cd2007-10-16 01:25:25 -07002579EXPORT_SYMBOL(nobh_write_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002580
2581/*
2582 * nobh_writepage() - based on block_full_write_page() except
2583 * that it tries to operate without attaching bufferheads to
2584 * the page.
2585 */
2586int nobh_writepage(struct page *page, get_block_t *get_block,
2587 struct writeback_control *wbc)
2588{
2589 struct inode * const inode = page->mapping->host;
2590 loff_t i_size = i_size_read(inode);
2591 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2592 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002593 int ret;
2594
2595 /* Is the page fully inside i_size? */
2596 if (page->index < end_index)
2597 goto out;
2598
2599 /* Is the page fully outside i_size? (truncate in progress) */
2600 offset = i_size & (PAGE_CACHE_SIZE-1);
2601 if (page->index >= end_index+1 || !offset) {
2602 /*
2603 * The page may have dirty, unmapped buffers. For example,
2604 * they may have been added in ext3_writepage(). Make them
2605 * freeable here, so the page does not leak.
2606 */
2607#if 0
2608 /* Not really sure about this - do we need this ? */
2609 if (page->mapping->a_ops->invalidatepage)
2610 page->mapping->a_ops->invalidatepage(page, offset);
2611#endif
2612 unlock_page(page);
2613 return 0; /* don't care */
2614 }
2615
2616 /*
2617 * The page straddles i_size. It must be zeroed out on each and every
2618 * writepage invocation because it may be mmapped. "A file is mapped
2619 * in multiples of the page size. For a file that is not a multiple of
2620 * the page size, the remaining memory is zeroed when mapped, and
2621 * writes to that region are not written out to the file."
2622 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002623 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002624out:
2625 ret = mpage_writepage(page, get_block, wbc);
2626 if (ret == -EAGAIN)
2627 ret = __block_write_full_page(inode, page, get_block, wbc);
2628 return ret;
2629}
2630EXPORT_SYMBOL(nobh_writepage);
2631
Nick Piggin03158cd2007-10-16 01:25:25 -07002632int nobh_truncate_page(struct address_space *mapping,
2633 loff_t from, get_block_t *get_block)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002634{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002635 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2636 unsigned offset = from & (PAGE_CACHE_SIZE-1);
Nick Piggin03158cd2007-10-16 01:25:25 -07002637 unsigned blocksize;
2638 sector_t iblock;
2639 unsigned length, pos;
2640 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002641 struct page *page;
Nick Piggin03158cd2007-10-16 01:25:25 -07002642 struct buffer_head map_bh;
2643 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002644
Nick Piggin03158cd2007-10-16 01:25:25 -07002645 blocksize = 1 << inode->i_blkbits;
2646 length = offset & (blocksize - 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002647
Nick Piggin03158cd2007-10-16 01:25:25 -07002648 /* Block boundary? Nothing to do */
2649 if (!length)
2650 return 0;
2651
2652 length = blocksize - length;
2653 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2654
Linus Torvalds1da177e2005-04-16 15:20:36 -07002655 page = grab_cache_page(mapping, index);
Nick Piggin03158cd2007-10-16 01:25:25 -07002656 err = -ENOMEM;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002657 if (!page)
2658 goto out;
2659
Nick Piggin03158cd2007-10-16 01:25:25 -07002660 if (page_has_buffers(page)) {
2661has_buffers:
2662 unlock_page(page);
2663 page_cache_release(page);
2664 return block_truncate_page(mapping, from, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002665 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002666
2667 /* Find the buffer that contains "offset" */
2668 pos = blocksize;
2669 while (offset >= pos) {
2670 iblock++;
2671 pos += blocksize;
2672 }
2673
2674 err = get_block(inode, iblock, &map_bh, 0);
2675 if (err)
2676 goto unlock;
2677 /* unmapped? It's a hole - nothing to do */
2678 if (!buffer_mapped(&map_bh))
2679 goto unlock;
2680
2681 /* Ok, it's mapped. Make sure it's up-to-date */
2682 if (!PageUptodate(page)) {
2683 err = mapping->a_ops->readpage(NULL, page);
2684 if (err) {
2685 page_cache_release(page);
2686 goto out;
2687 }
2688 lock_page(page);
2689 if (!PageUptodate(page)) {
2690 err = -EIO;
2691 goto unlock;
2692 }
2693 if (page_has_buffers(page))
2694 goto has_buffers;
2695 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002696 zero_user(page, offset, length);
Nick Piggin03158cd2007-10-16 01:25:25 -07002697 set_page_dirty(page);
2698 err = 0;
2699
2700unlock:
Linus Torvalds1da177e2005-04-16 15:20:36 -07002701 unlock_page(page);
2702 page_cache_release(page);
2703out:
Nick Piggin03158cd2007-10-16 01:25:25 -07002704 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002705}
2706EXPORT_SYMBOL(nobh_truncate_page);
2707
2708int block_truncate_page(struct address_space *mapping,
2709 loff_t from, get_block_t *get_block)
2710{
2711 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2712 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2713 unsigned blocksize;
Andrew Morton54b21a72006-01-08 01:03:05 -08002714 sector_t iblock;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002715 unsigned length, pos;
2716 struct inode *inode = mapping->host;
2717 struct page *page;
2718 struct buffer_head *bh;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002719 int err;
2720
2721 blocksize = 1 << inode->i_blkbits;
2722 length = offset & (blocksize - 1);
2723
2724 /* Block boundary? Nothing to do */
2725 if (!length)
2726 return 0;
2727
2728 length = blocksize - length;
Andrew Morton54b21a72006-01-08 01:03:05 -08002729 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002730
2731 page = grab_cache_page(mapping, index);
2732 err = -ENOMEM;
2733 if (!page)
2734 goto out;
2735
2736 if (!page_has_buffers(page))
2737 create_empty_buffers(page, blocksize, 0);
2738
2739 /* Find the buffer that contains "offset" */
2740 bh = page_buffers(page);
2741 pos = blocksize;
2742 while (offset >= pos) {
2743 bh = bh->b_this_page;
2744 iblock++;
2745 pos += blocksize;
2746 }
2747
2748 err = 0;
2749 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002750 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002751 err = get_block(inode, iblock, bh, 0);
2752 if (err)
2753 goto unlock;
2754 /* unmapped? It's a hole - nothing to do */
2755 if (!buffer_mapped(bh))
2756 goto unlock;
2757 }
2758
2759 /* Ok, it's mapped. Make sure it's up-to-date */
2760 if (PageUptodate(page))
2761 set_buffer_uptodate(bh);
2762
David Chinner33a266d2007-02-12 00:51:41 -08002763 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002764 err = -EIO;
2765 ll_rw_block(READ, 1, &bh);
2766 wait_on_buffer(bh);
2767 /* Uhhuh. Read error. Complain and punt. */
2768 if (!buffer_uptodate(bh))
2769 goto unlock;
2770 }
2771
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002772 zero_user(page, offset, length);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002773 mark_buffer_dirty(bh);
2774 err = 0;
2775
2776unlock:
2777 unlock_page(page);
2778 page_cache_release(page);
2779out:
2780 return err;
2781}
2782
2783/*
2784 * The generic ->writepage function for buffer-backed address_spaces
2785 */
2786int block_write_full_page(struct page *page, get_block_t *get_block,
2787 struct writeback_control *wbc)
2788{
2789 struct inode * const inode = page->mapping->host;
2790 loff_t i_size = i_size_read(inode);
2791 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2792 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002793
2794 /* Is the page fully inside i_size? */
2795 if (page->index < end_index)
2796 return __block_write_full_page(inode, page, get_block, wbc);
2797
2798 /* Is the page fully outside i_size? (truncate in progress) */
2799 offset = i_size & (PAGE_CACHE_SIZE-1);
2800 if (page->index >= end_index+1 || !offset) {
2801 /*
2802 * The page may have dirty, unmapped buffers. For example,
2803 * they may have been added in ext3_writepage(). Make them
2804 * freeable here, so the page does not leak.
2805 */
Jan Karaaaa40592005-10-30 15:00:16 -08002806 do_invalidatepage(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002807 unlock_page(page);
2808 return 0; /* don't care */
2809 }
2810
2811 /*
2812 * The page straddles i_size. It must be zeroed out on each and every
2813 * writepage invokation because it may be mmapped. "A file is mapped
2814 * in multiples of the page size. For a file that is not a multiple of
2815 * the page size, the remaining memory is zeroed when mapped, and
2816 * writes to that region are not written out to the file."
2817 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002818 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002819 return __block_write_full_page(inode, page, get_block, wbc);
2820}
2821
2822sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2823 get_block_t *get_block)
2824{
2825 struct buffer_head tmp;
2826 struct inode *inode = mapping->host;
2827 tmp.b_state = 0;
2828 tmp.b_blocknr = 0;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002829 tmp.b_size = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002830 get_block(inode, block, &tmp, 0);
2831 return tmp.b_blocknr;
2832}
2833
NeilBrown6712ecf2007-09-27 12:47:43 +02002834static void end_bio_bh_io_sync(struct bio *bio, int err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002835{
2836 struct buffer_head *bh = bio->bi_private;
2837
Linus Torvalds1da177e2005-04-16 15:20:36 -07002838 if (err == -EOPNOTSUPP) {
2839 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
2840 set_bit(BH_Eopnotsupp, &bh->b_state);
2841 }
2842
2843 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2844 bio_put(bio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002845}
2846
2847int submit_bh(int rw, struct buffer_head * bh)
2848{
2849 struct bio *bio;
2850 int ret = 0;
2851
2852 BUG_ON(!buffer_locked(bh));
2853 BUG_ON(!buffer_mapped(bh));
2854 BUG_ON(!bh->b_end_io);
2855
2856 if (buffer_ordered(bh) && (rw == WRITE))
2857 rw = WRITE_BARRIER;
2858
2859 /*
2860 * Only clear out a write error when rewriting, should this
2861 * include WRITE_SYNC as well?
2862 */
2863 if (test_set_buffer_req(bh) && (rw == WRITE || rw == WRITE_BARRIER))
2864 clear_buffer_write_io_error(bh);
2865
2866 /*
2867 * from here on down, it's all bio -- do the initial mapping,
2868 * submit_bio -> generic_make_request may further map this bio around
2869 */
2870 bio = bio_alloc(GFP_NOIO, 1);
2871
2872 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2873 bio->bi_bdev = bh->b_bdev;
2874 bio->bi_io_vec[0].bv_page = bh->b_page;
2875 bio->bi_io_vec[0].bv_len = bh->b_size;
2876 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
2877
2878 bio->bi_vcnt = 1;
2879 bio->bi_idx = 0;
2880 bio->bi_size = bh->b_size;
2881
2882 bio->bi_end_io = end_bio_bh_io_sync;
2883 bio->bi_private = bh;
2884
2885 bio_get(bio);
2886 submit_bio(rw, bio);
2887
2888 if (bio_flagged(bio, BIO_EOPNOTSUPP))
2889 ret = -EOPNOTSUPP;
2890
2891 bio_put(bio);
2892 return ret;
2893}
2894
2895/**
2896 * ll_rw_block: low-level access to block devices (DEPRECATED)
Jan Karaa7662232005-09-06 15:19:10 -07002897 * @rw: whether to %READ or %WRITE or %SWRITE or maybe %READA (readahead)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002898 * @nr: number of &struct buffer_heads in the array
2899 * @bhs: array of pointers to &struct buffer_head
2900 *
Jan Karaa7662232005-09-06 15:19:10 -07002901 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
2902 * requests an I/O operation on them, either a %READ or a %WRITE. The third
2903 * %SWRITE is like %WRITE only we make sure that the *current* data in buffers
2904 * are sent to disk. The fourth %READA option is described in the documentation
2905 * for generic_make_request() which ll_rw_block() calls.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002906 *
2907 * This function drops any buffer that it cannot get a lock on (with the
Jan Karaa7662232005-09-06 15:19:10 -07002908 * BH_Lock state bit) unless SWRITE is required, any buffer that appears to be
2909 * clean when doing a write request, and any buffer that appears to be
2910 * up-to-date when doing read request. Further it marks as clean buffers that
2911 * are processed for writing (the buffer cache won't assume that they are
2912 * actually clean until the buffer gets unlocked).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002913 *
2914 * ll_rw_block sets b_end_io to simple completion handler that marks
2915 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
2916 * any waiters.
2917 *
2918 * All of the buffers must be for the same device, and must also be a
2919 * multiple of the current approved size for the device.
2920 */
2921void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
2922{
2923 int i;
2924
2925 for (i = 0; i < nr; i++) {
2926 struct buffer_head *bh = bhs[i];
2927
Jan Karaa7662232005-09-06 15:19:10 -07002928 if (rw == SWRITE)
2929 lock_buffer(bh);
2930 else if (test_set_buffer_locked(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002931 continue;
2932
Jan Karaa7662232005-09-06 15:19:10 -07002933 if (rw == WRITE || rw == SWRITE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002934 if (test_clear_buffer_dirty(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07002935 bh->b_end_io = end_buffer_write_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08002936 get_bh(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002937 submit_bh(WRITE, bh);
2938 continue;
2939 }
2940 } else {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002941 if (!buffer_uptodate(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07002942 bh->b_end_io = end_buffer_read_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08002943 get_bh(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002944 submit_bh(rw, bh);
2945 continue;
2946 }
2947 }
2948 unlock_buffer(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002949 }
2950}
2951
2952/*
2953 * For a data-integrity writeout, we need to wait upon any in-progress I/O
2954 * and then start new I/O and then wait upon it. The caller must have a ref on
2955 * the buffer_head.
2956 */
2957int sync_dirty_buffer(struct buffer_head *bh)
2958{
2959 int ret = 0;
2960
2961 WARN_ON(atomic_read(&bh->b_count) < 1);
2962 lock_buffer(bh);
2963 if (test_clear_buffer_dirty(bh)) {
2964 get_bh(bh);
2965 bh->b_end_io = end_buffer_write_sync;
2966 ret = submit_bh(WRITE, bh);
2967 wait_on_buffer(bh);
2968 if (buffer_eopnotsupp(bh)) {
2969 clear_buffer_eopnotsupp(bh);
2970 ret = -EOPNOTSUPP;
2971 }
2972 if (!ret && !buffer_uptodate(bh))
2973 ret = -EIO;
2974 } else {
2975 unlock_buffer(bh);
2976 }
2977 return ret;
2978}
2979
2980/*
2981 * try_to_free_buffers() checks if all the buffers on this particular page
2982 * are unused, and releases them if so.
2983 *
2984 * Exclusion against try_to_free_buffers may be obtained by either
2985 * locking the page or by holding its mapping's private_lock.
2986 *
2987 * If the page is dirty but all the buffers are clean then we need to
2988 * be sure to mark the page clean as well. This is because the page
2989 * may be against a block device, and a later reattachment of buffers
2990 * to a dirty page will set *all* buffers dirty. Which would corrupt
2991 * filesystem data on the same device.
2992 *
2993 * The same applies to regular filesystem pages: if all the buffers are
2994 * clean then we set the page clean and proceed. To do that, we require
2995 * total exclusion from __set_page_dirty_buffers(). That is obtained with
2996 * private_lock.
2997 *
2998 * try_to_free_buffers() is non-blocking.
2999 */
3000static inline int buffer_busy(struct buffer_head *bh)
3001{
3002 return atomic_read(&bh->b_count) |
3003 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3004}
3005
3006static int
3007drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3008{
3009 struct buffer_head *head = page_buffers(page);
3010 struct buffer_head *bh;
3011
3012 bh = head;
3013 do {
akpm@osdl.orgde7d5a32005-05-01 08:58:39 -07003014 if (buffer_write_io_error(bh) && page->mapping)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003015 set_bit(AS_EIO, &page->mapping->flags);
3016 if (buffer_busy(bh))
3017 goto failed;
3018 bh = bh->b_this_page;
3019 } while (bh != head);
3020
3021 do {
3022 struct buffer_head *next = bh->b_this_page;
3023
3024 if (!list_empty(&bh->b_assoc_buffers))
3025 __remove_assoc_queue(bh);
3026 bh = next;
3027 } while (bh != head);
3028 *buffers_to_free = head;
3029 __clear_page_buffers(page);
3030 return 1;
3031failed:
3032 return 0;
3033}
3034
3035int try_to_free_buffers(struct page *page)
3036{
3037 struct address_space * const mapping = page->mapping;
3038 struct buffer_head *buffers_to_free = NULL;
3039 int ret = 0;
3040
3041 BUG_ON(!PageLocked(page));
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003042 if (PageWriteback(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003043 return 0;
3044
3045 if (mapping == NULL) { /* can this still happen? */
3046 ret = drop_buffers(page, &buffers_to_free);
3047 goto out;
3048 }
3049
3050 spin_lock(&mapping->private_lock);
3051 ret = drop_buffers(page, &buffers_to_free);
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003052
3053 /*
3054 * If the filesystem writes its buffers by hand (eg ext3)
3055 * then we can have clean buffers against a dirty page. We
3056 * clean the page here; otherwise the VM will never notice
3057 * that the filesystem did any IO at all.
3058 *
3059 * Also, during truncate, discard_buffer will have marked all
3060 * the page's buffers clean. We discover that here and clean
3061 * the page also.
Nick Piggin87df7242007-01-30 14:36:27 +11003062 *
3063 * private_lock must be held over this entire operation in order
3064 * to synchronise against __set_page_dirty_buffers and prevent the
3065 * dirty bit from being lost.
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003066 */
3067 if (ret)
3068 cancel_dirty_page(page, PAGE_CACHE_SIZE);
Nick Piggin87df7242007-01-30 14:36:27 +11003069 spin_unlock(&mapping->private_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003070out:
3071 if (buffers_to_free) {
3072 struct buffer_head *bh = buffers_to_free;
3073
3074 do {
3075 struct buffer_head *next = bh->b_this_page;
3076 free_buffer_head(bh);
3077 bh = next;
3078 } while (bh != buffers_to_free);
3079 }
3080 return ret;
3081}
3082EXPORT_SYMBOL(try_to_free_buffers);
3083
NeilBrown3978d712006-03-26 01:37:17 -08003084void block_sync_page(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003085{
3086 struct address_space *mapping;
3087
3088 smp_mb();
3089 mapping = page_mapping(page);
3090 if (mapping)
3091 blk_run_backing_dev(mapping->backing_dev_info, page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003092}
3093
3094/*
3095 * There are no bdflush tunables left. But distributions are
3096 * still running obsolete flush daemons, so we terminate them here.
3097 *
3098 * Use of bdflush() is deprecated and will be removed in a future kernel.
3099 * The `pdflush' kernel threads fully replace bdflush daemons and this call.
3100 */
3101asmlinkage long sys_bdflush(int func, long data)
3102{
3103 static int msg_count;
3104
3105 if (!capable(CAP_SYS_ADMIN))
3106 return -EPERM;
3107
3108 if (msg_count < 5) {
3109 msg_count++;
3110 printk(KERN_INFO
3111 "warning: process `%s' used the obsolete bdflush"
3112 " system call\n", current->comm);
3113 printk(KERN_INFO "Fix your initscripts?\n");
3114 }
3115
3116 if (func == 1)
3117 do_exit(0);
3118 return 0;
3119}
3120
3121/*
3122 * Buffer-head allocation
3123 */
Christoph Lametere18b8902006-12-06 20:33:20 -08003124static struct kmem_cache *bh_cachep;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003125
3126/*
3127 * Once the number of bh's in the machine exceeds this level, we start
3128 * stripping them in writeback.
3129 */
3130static int max_buffer_heads;
3131
3132int buffer_heads_over_limit;
3133
3134struct bh_accounting {
3135 int nr; /* Number of live bh's */
3136 int ratelimit; /* Limit cacheline bouncing */
3137};
3138
3139static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3140
3141static void recalc_bh_state(void)
3142{
3143 int i;
3144 int tot = 0;
3145
3146 if (__get_cpu_var(bh_accounting).ratelimit++ < 4096)
3147 return;
3148 __get_cpu_var(bh_accounting).ratelimit = 0;
Eric Dumazet8a143422006-03-24 03:18:10 -08003149 for_each_online_cpu(i)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003150 tot += per_cpu(bh_accounting, i).nr;
3151 buffer_heads_over_limit = (tot > max_buffer_heads);
3152}
3153
Al Virodd0fc662005-10-07 07:46:04 +01003154struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003155{
Christoph Lameterb98938c2008-02-04 22:28:36 -08003156 struct buffer_head *ret = kmem_cache_alloc(bh_cachep,
Mel Gormane12ba742007-10-16 01:25:52 -07003157 set_migrateflags(gfp_flags, __GFP_RECLAIMABLE));
Linus Torvalds1da177e2005-04-16 15:20:36 -07003158 if (ret) {
Christoph Lametera35afb82007-05-16 22:10:57 -07003159 INIT_LIST_HEAD(&ret->b_assoc_buffers);
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07003160 get_cpu_var(bh_accounting).nr++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003161 recalc_bh_state();
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07003162 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003163 }
3164 return ret;
3165}
3166EXPORT_SYMBOL(alloc_buffer_head);
3167
3168void free_buffer_head(struct buffer_head *bh)
3169{
3170 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3171 kmem_cache_free(bh_cachep, bh);
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07003172 get_cpu_var(bh_accounting).nr--;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003173 recalc_bh_state();
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07003174 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003175}
3176EXPORT_SYMBOL(free_buffer_head);
3177
Linus Torvalds1da177e2005-04-16 15:20:36 -07003178static void buffer_exit_cpu(int cpu)
3179{
3180 int i;
3181 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3182
3183 for (i = 0; i < BH_LRU_SIZE; i++) {
3184 brelse(b->bhs[i]);
3185 b->bhs[i] = NULL;
3186 }
Eric Dumazet8a143422006-03-24 03:18:10 -08003187 get_cpu_var(bh_accounting).nr += per_cpu(bh_accounting, cpu).nr;
3188 per_cpu(bh_accounting, cpu).nr = 0;
3189 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003190}
3191
3192static int buffer_cpu_notify(struct notifier_block *self,
3193 unsigned long action, void *hcpu)
3194{
Rafael J. Wysocki8bb78442007-05-09 02:35:10 -07003195 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003196 buffer_exit_cpu((unsigned long)hcpu);
3197 return NOTIFY_OK;
3198}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003199
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003200/**
3201 * bh_uptodate_or_lock: Test whether the buffer is uptodate
3202 * @bh: struct buffer_head
3203 *
3204 * Return true if the buffer is up-to-date and false,
3205 * with the buffer locked, if not.
3206 */
3207int bh_uptodate_or_lock(struct buffer_head *bh)
3208{
3209 if (!buffer_uptodate(bh)) {
3210 lock_buffer(bh);
3211 if (!buffer_uptodate(bh))
3212 return 0;
3213 unlock_buffer(bh);
3214 }
3215 return 1;
3216}
3217EXPORT_SYMBOL(bh_uptodate_or_lock);
3218
3219/**
3220 * bh_submit_read: Submit a locked buffer for reading
3221 * @bh: struct buffer_head
3222 *
3223 * Returns zero on success and -EIO on error.
3224 */
3225int bh_submit_read(struct buffer_head *bh)
3226{
3227 BUG_ON(!buffer_locked(bh));
3228
3229 if (buffer_uptodate(bh)) {
3230 unlock_buffer(bh);
3231 return 0;
3232 }
3233
3234 get_bh(bh);
3235 bh->b_end_io = end_buffer_read_sync;
3236 submit_bh(READ, bh);
3237 wait_on_buffer(bh);
3238 if (buffer_uptodate(bh))
3239 return 0;
3240 return -EIO;
3241}
3242EXPORT_SYMBOL(bh_submit_read);
3243
Christoph Lameterb98938c2008-02-04 22:28:36 -08003244static void
3245init_buffer_head(struct kmem_cache *cachep, void *data)
3246{
3247 struct buffer_head *bh = data;
3248
3249 memset(bh, 0, sizeof(*bh));
3250 INIT_LIST_HEAD(&bh->b_assoc_buffers);
3251}
3252
Linus Torvalds1da177e2005-04-16 15:20:36 -07003253void __init buffer_init(void)
3254{
3255 int nrpages;
3256
Christoph Lameterb98938c2008-02-04 22:28:36 -08003257 bh_cachep = kmem_cache_create("buffer_head",
3258 sizeof(struct buffer_head), 0,
3259 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3260 SLAB_MEM_SPREAD),
3261 init_buffer_head);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003262
3263 /*
3264 * Limit the bh occupancy to 10% of ZONE_NORMAL
3265 */
3266 nrpages = (nr_free_buffer_pages() * 10) / 100;
3267 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3268 hotcpu_notifier(buffer_cpu_notify, 0);
3269}
3270
3271EXPORT_SYMBOL(__bforget);
3272EXPORT_SYMBOL(__brelse);
3273EXPORT_SYMBOL(__wait_on_buffer);
3274EXPORT_SYMBOL(block_commit_write);
3275EXPORT_SYMBOL(block_prepare_write);
David Chinner54171692007-07-19 17:39:55 +10003276EXPORT_SYMBOL(block_page_mkwrite);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003277EXPORT_SYMBOL(block_read_full_page);
3278EXPORT_SYMBOL(block_sync_page);
3279EXPORT_SYMBOL(block_truncate_page);
3280EXPORT_SYMBOL(block_write_full_page);
Nick Piggin89e10782007-10-16 01:25:07 -07003281EXPORT_SYMBOL(cont_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003282EXPORT_SYMBOL(end_buffer_read_sync);
3283EXPORT_SYMBOL(end_buffer_write_sync);
3284EXPORT_SYMBOL(file_fsync);
3285EXPORT_SYMBOL(fsync_bdev);
3286EXPORT_SYMBOL(generic_block_bmap);
3287EXPORT_SYMBOL(generic_commit_write);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08003288EXPORT_SYMBOL(generic_cont_expand_simple);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003289EXPORT_SYMBOL(init_buffer);
3290EXPORT_SYMBOL(invalidate_bdev);
3291EXPORT_SYMBOL(ll_rw_block);
3292EXPORT_SYMBOL(mark_buffer_dirty);
3293EXPORT_SYMBOL(submit_bh);
3294EXPORT_SYMBOL(sync_dirty_buffer);
3295EXPORT_SYMBOL(unlock_buffer);