blob: 39ff14403d137be85dcd11161584abeabd9d7577 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/fs/buffer.c
3 *
4 * Copyright (C) 1991, 1992, 2002 Linus Torvalds
5 */
6
7/*
8 * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95
9 *
10 * Removed a lot of unnecessary code and simplified things now that
11 * the buffer cache isn't our primary cache - Andrew Tridgell 12/96
12 *
13 * Speed up hash, lru, and free list operations. Use gfp() for allocating
14 * hash table, use SLAB cache for buffer heads. SMP threading. -DaveM
15 *
16 * Added 32k buffer block sizes - these are required older ARM systems. - RMK
17 *
18 * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de>
19 */
20
Linus Torvalds1da177e2005-04-16 15:20:36 -070021#include <linux/kernel.h>
22#include <linux/syscalls.h>
23#include <linux/fs.h>
24#include <linux/mm.h>
25#include <linux/percpu.h>
26#include <linux/slab.h>
Randy Dunlap16f7e0f2006-01-11 12:17:46 -080027#include <linux/capability.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070028#include <linux/blkdev.h>
29#include <linux/file.h>
30#include <linux/quotaops.h>
31#include <linux/highmem.h>
32#include <linux/module.h>
33#include <linux/writeback.h>
34#include <linux/hash.h>
35#include <linux/suspend.h>
36#include <linux/buffer_head.h>
Andrew Morton55e829a2006-12-10 02:19:27 -080037#include <linux/task_io_accounting_ops.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070038#include <linux/bio.h>
39#include <linux/notifier.h>
40#include <linux/cpu.h>
41#include <linux/bitops.h>
42#include <linux/mpage.h>
Ingo Molnarfb1c8f92005-09-10 00:25:56 -070043#include <linux/bit_spinlock.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070044
45static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
Linus Torvalds1da177e2005-04-16 15:20:36 -070046
47#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
48
49inline void
50init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
51{
52 bh->b_end_io = handler;
53 bh->b_private = private;
54}
55
56static int sync_buffer(void *word)
57{
58 struct block_device *bd;
59 struct buffer_head *bh
60 = container_of(word, struct buffer_head, b_state);
61
62 smp_mb();
63 bd = bh->b_bdev;
64 if (bd)
65 blk_run_address_space(bd->bd_inode->i_mapping);
66 io_schedule();
67 return 0;
68}
69
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -080070void __lock_buffer(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -070071{
72 wait_on_bit_lock(&bh->b_state, BH_Lock, sync_buffer,
73 TASK_UNINTERRUPTIBLE);
74}
75EXPORT_SYMBOL(__lock_buffer);
76
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -080077void unlock_buffer(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -070078{
Nick Piggin72ed3d02007-02-10 01:46:22 -080079 smp_mb__before_clear_bit();
Linus Torvalds1da177e2005-04-16 15:20:36 -070080 clear_buffer_locked(bh);
81 smp_mb__after_clear_bit();
82 wake_up_bit(&bh->b_state, BH_Lock);
83}
84
85/*
86 * Block until a buffer comes unlocked. This doesn't stop it
87 * from becoming locked again - you have to lock it yourself
88 * if you want to preserve its state.
89 */
90void __wait_on_buffer(struct buffer_head * bh)
91{
92 wait_on_bit(&bh->b_state, BH_Lock, sync_buffer, TASK_UNINTERRUPTIBLE);
93}
94
95static void
96__clear_page_buffers(struct page *page)
97{
98 ClearPagePrivate(page);
Hugh Dickins4c21e2f2005-10-29 18:16:40 -070099 set_page_private(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700100 page_cache_release(page);
101}
102
103static void buffer_io_error(struct buffer_head *bh)
104{
105 char b[BDEVNAME_SIZE];
106
107 printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
108 bdevname(bh->b_bdev, b),
109 (unsigned long long)bh->b_blocknr);
110}
111
112/*
Dmitry Monakhov68671f32007-10-16 01:24:47 -0700113 * End-of-IO handler helper function which does not touch the bh after
114 * unlocking it.
115 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
116 * a race there is benign: unlock_buffer() only use the bh's address for
117 * hashing after unlocking the buffer, so it doesn't actually touch the bh
118 * itself.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700119 */
Dmitry Monakhov68671f32007-10-16 01:24:47 -0700120static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700121{
122 if (uptodate) {
123 set_buffer_uptodate(bh);
124 } else {
125 /* This happens, due to failed READA attempts. */
126 clear_buffer_uptodate(bh);
127 }
128 unlock_buffer(bh);
Dmitry Monakhov68671f32007-10-16 01:24:47 -0700129}
130
131/*
132 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
133 * unlock the buffer. This is what ll_rw_block uses too.
134 */
135void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
136{
137 __end_buffer_read_notouch(bh, uptodate);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700138 put_bh(bh);
139}
140
141void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
142{
143 char b[BDEVNAME_SIZE];
144
145 if (uptodate) {
146 set_buffer_uptodate(bh);
147 } else {
148 if (!buffer_eopnotsupp(bh) && printk_ratelimit()) {
149 buffer_io_error(bh);
150 printk(KERN_WARNING "lost page write due to "
151 "I/O error on %s\n",
152 bdevname(bh->b_bdev, b));
153 }
154 set_buffer_write_io_error(bh);
155 clear_buffer_uptodate(bh);
156 }
157 unlock_buffer(bh);
158 put_bh(bh);
159}
160
161/*
162 * Write out and wait upon all the dirty data associated with a block
163 * device via its mapping. Does not take the superblock lock.
164 */
165int sync_blockdev(struct block_device *bdev)
166{
167 int ret = 0;
168
OGAWA Hirofumi28fd1292006-01-08 01:02:14 -0800169 if (bdev)
170 ret = filemap_write_and_wait(bdev->bd_inode->i_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700171 return ret;
172}
173EXPORT_SYMBOL(sync_blockdev);
174
Linus Torvalds1da177e2005-04-16 15:20:36 -0700175/*
176 * Write out and wait upon all dirty data associated with this
177 * device. Filesystem data as well as the underlying block
178 * device. Takes the superblock lock.
179 */
180int fsync_bdev(struct block_device *bdev)
181{
182 struct super_block *sb = get_super(bdev);
183 if (sb) {
184 int res = fsync_super(sb);
185 drop_super(sb);
186 return res;
187 }
188 return sync_blockdev(bdev);
189}
190
191/**
192 * freeze_bdev -- lock a filesystem and force it into a consistent state
193 * @bdev: blockdevice to lock
194 *
David Chinnerf73ca1b2007-01-10 23:15:41 -0800195 * This takes the block device bd_mount_sem to make sure no new mounts
Linus Torvalds1da177e2005-04-16 15:20:36 -0700196 * happen on bdev until thaw_bdev() is called.
197 * If a superblock is found on this device, we take the s_umount semaphore
198 * on it to make sure nobody unmounts until the snapshot creation is done.
199 */
200struct super_block *freeze_bdev(struct block_device *bdev)
201{
202 struct super_block *sb;
203
David Chinnerf73ca1b2007-01-10 23:15:41 -0800204 down(&bdev->bd_mount_sem);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700205 sb = get_super(bdev);
206 if (sb && !(sb->s_flags & MS_RDONLY)) {
207 sb->s_frozen = SB_FREEZE_WRITE;
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700208 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700209
OGAWA Hirofumid25b9a12006-03-25 03:07:44 -0800210 __fsync_super(sb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700211
212 sb->s_frozen = SB_FREEZE_TRANS;
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700213 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700214
215 sync_blockdev(sb->s_bdev);
216
217 if (sb->s_op->write_super_lockfs)
218 sb->s_op->write_super_lockfs(sb);
219 }
220
221 sync_blockdev(bdev);
222 return sb; /* thaw_bdev releases s->s_umount and bd_mount_sem */
223}
224EXPORT_SYMBOL(freeze_bdev);
225
226/**
227 * thaw_bdev -- unlock filesystem
228 * @bdev: blockdevice to unlock
229 * @sb: associated superblock
230 *
231 * Unlocks the filesystem and marks it writeable again after freeze_bdev().
232 */
233void thaw_bdev(struct block_device *bdev, struct super_block *sb)
234{
235 if (sb) {
236 BUG_ON(sb->s_bdev != bdev);
237
238 if (sb->s_op->unlockfs)
239 sb->s_op->unlockfs(sb);
240 sb->s_frozen = SB_UNFROZEN;
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700241 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700242 wake_up(&sb->s_wait_unfrozen);
243 drop_super(sb);
244 }
245
David Chinnerf73ca1b2007-01-10 23:15:41 -0800246 up(&bdev->bd_mount_sem);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700247}
248EXPORT_SYMBOL(thaw_bdev);
249
250/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700251 * Various filesystems appear to want __find_get_block to be non-blocking.
252 * But it's the page lock which protects the buffers. To get around this,
253 * we get exclusion from try_to_free_buffers with the blockdev mapping's
254 * private_lock.
255 *
256 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
257 * may be quite high. This code could TryLock the page, and if that
258 * succeeds, there is no need to take private_lock. (But if
259 * private_lock is contended then so is mapping->tree_lock).
260 */
261static struct buffer_head *
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -0800262__find_get_block_slow(struct block_device *bdev, sector_t block)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700263{
264 struct inode *bd_inode = bdev->bd_inode;
265 struct address_space *bd_mapping = bd_inode->i_mapping;
266 struct buffer_head *ret = NULL;
267 pgoff_t index;
268 struct buffer_head *bh;
269 struct buffer_head *head;
270 struct page *page;
271 int all_mapped = 1;
272
273 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
274 page = find_get_page(bd_mapping, index);
275 if (!page)
276 goto out;
277
278 spin_lock(&bd_mapping->private_lock);
279 if (!page_has_buffers(page))
280 goto out_unlock;
281 head = page_buffers(page);
282 bh = head;
283 do {
284 if (bh->b_blocknr == block) {
285 ret = bh;
286 get_bh(bh);
287 goto out_unlock;
288 }
289 if (!buffer_mapped(bh))
290 all_mapped = 0;
291 bh = bh->b_this_page;
292 } while (bh != head);
293
294 /* we might be here because some of the buffers on this page are
295 * not mapped. This is due to various races between
296 * file io on the block device and getblk. It gets dealt with
297 * elsewhere, don't buffer_error if we had some unmapped buffers
298 */
299 if (all_mapped) {
300 printk("__find_get_block_slow() failed. "
301 "block=%llu, b_blocknr=%llu\n",
Badari Pulavarty205f87f2006-03-26 01:38:00 -0800302 (unsigned long long)block,
303 (unsigned long long)bh->b_blocknr);
304 printk("b_state=0x%08lx, b_size=%zu\n",
305 bh->b_state, bh->b_size);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700306 printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits);
307 }
308out_unlock:
309 spin_unlock(&bd_mapping->private_lock);
310 page_cache_release(page);
311out:
312 return ret;
313}
314
315/* If invalidate_buffers() will trash dirty buffers, it means some kind
316 of fs corruption is going on. Trashing dirty data always imply losing
317 information that was supposed to be just stored on the physical layer
318 by the user.
319
320 Thus invalidate_buffers in general usage is not allwowed to trash
321 dirty buffers. For example ioctl(FLSBLKBUF) expects dirty data to
322 be preserved. These buffers are simply skipped.
323
324 We also skip buffers which are still in use. For example this can
325 happen if a userspace program is reading the block device.
326
327 NOTE: In the case where the user removed a removable-media-disk even if
328 there's still dirty data not synced on disk (due a bug in the device driver
329 or due an error of the user), by not destroying the dirty buffers we could
330 generate corruption also on the next media inserted, thus a parameter is
331 necessary to handle this case in the most safe way possible (trying
332 to not corrupt also the new disk inserted with the data belonging to
333 the old now corrupted disk). Also for the ramdisk the natural thing
334 to do in order to release the ramdisk memory is to destroy dirty buffers.
335
336 These are two special cases. Normal usage imply the device driver
337 to issue a sync on the device (without waiting I/O completion) and
338 then an invalidate_buffers call that doesn't trash dirty buffers.
339
340 For handling cache coherency with the blkdev pagecache the 'update' case
341 is been introduced. It is needed to re-read from disk any pinned
342 buffer. NOTE: re-reading from disk is destructive so we can do it only
343 when we assume nobody is changing the buffercache under our I/O and when
344 we think the disk contains more recent information than the buffercache.
345 The update == 1 pass marks the buffers we need to update, the update == 2
346 pass does the actual I/O. */
Peter Zijlstraf98393a2007-05-06 14:49:54 -0700347void invalidate_bdev(struct block_device *bdev)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700348{
Andrew Morton0e1dfc62006-07-30 03:03:28 -0700349 struct address_space *mapping = bdev->bd_inode->i_mapping;
350
351 if (mapping->nrpages == 0)
352 return;
353
Linus Torvalds1da177e2005-04-16 15:20:36 -0700354 invalidate_bh_lrus();
Andrew Mortonfc0ecff2007-02-10 01:45:39 -0800355 invalidate_mapping_pages(mapping, 0, -1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700356}
357
358/*
359 * Kick pdflush then try to free up some ZONE_NORMAL memory.
360 */
361static void free_more_memory(void)
362{
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/**
Randy Dunlap78a4a502008-02-29 22:02:31 -0800630 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
Martin Waitz67be2dd2005-05-01 08:59:26 -0700631 * @mapping: the mapping which wants those buffers written
Linus Torvalds1da177e2005-04-16 15:20:36 -0700632 *
633 * Starts I/O against the buffers at mapping->private_list, and waits upon
634 * that I/O.
635 *
Martin Waitz67be2dd2005-05-01 08:59:26 -0700636 * Basically, this is a convenience function for fsync().
637 * @mapping is a file or directory which needs those buffers to be written for
638 * a successful fsync().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700639 */
640int sync_mapping_buffers(struct address_space *mapping)
641{
642 struct address_space *buffer_mapping = mapping->assoc_mapping;
643
644 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
645 return 0;
646
647 return fsync_buffers_list(&buffer_mapping->private_lock,
648 &mapping->private_list);
649}
650EXPORT_SYMBOL(sync_mapping_buffers);
651
652/*
653 * Called when we've recently written block `bblock', and it is known that
654 * `bblock' was for a buffer_boundary() buffer. This means that the block at
655 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
656 * dirty, schedule it for IO. So that indirects merge nicely with their data.
657 */
658void write_boundary_block(struct block_device *bdev,
659 sector_t bblock, unsigned blocksize)
660{
661 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
662 if (bh) {
663 if (buffer_dirty(bh))
664 ll_rw_block(WRITE, 1, &bh);
665 put_bh(bh);
666 }
667}
668
669void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
670{
671 struct address_space *mapping = inode->i_mapping;
672 struct address_space *buffer_mapping = bh->b_page->mapping;
673
674 mark_buffer_dirty(bh);
675 if (!mapping->assoc_mapping) {
676 mapping->assoc_mapping = buffer_mapping;
677 } else {
Eric Sesterhenne827f922006-03-26 18:24:46 +0200678 BUG_ON(mapping->assoc_mapping != buffer_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700679 }
Jan Kara535ee2f2008-02-08 04:21:59 -0800680 if (!bh->b_assoc_map) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700681 spin_lock(&buffer_mapping->private_lock);
682 list_move_tail(&bh->b_assoc_buffers,
683 &mapping->private_list);
Jan Kara58ff4072006-10-17 00:10:19 -0700684 bh->b_assoc_map = mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700685 spin_unlock(&buffer_mapping->private_lock);
686 }
687}
688EXPORT_SYMBOL(mark_buffer_dirty_inode);
689
690/*
Nick Piggin787d2212007-07-17 04:03:34 -0700691 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
692 * dirty.
693 *
694 * If warn is true, then emit a warning if the page is not uptodate and has
695 * not been truncated.
696 */
697static int __set_page_dirty(struct page *page,
698 struct address_space *mapping, int warn)
699{
700 if (unlikely(!mapping))
701 return !TestSetPageDirty(page);
702
703 if (TestSetPageDirty(page))
704 return 0;
705
706 write_lock_irq(&mapping->tree_lock);
707 if (page->mapping) { /* Race with truncate? */
708 WARN_ON_ONCE(warn && !PageUptodate(page));
709
710 if (mapping_cap_account_dirty(mapping)) {
711 __inc_zone_page_state(page, NR_FILE_DIRTY);
Peter Zijlstrac9e51e42007-10-16 23:25:47 -0700712 __inc_bdi_stat(mapping->backing_dev_info,
713 BDI_RECLAIMABLE);
Nick Piggin787d2212007-07-17 04:03:34 -0700714 task_io_account_write(PAGE_CACHE_SIZE);
715 }
716 radix_tree_tag_set(&mapping->page_tree,
717 page_index(page), PAGECACHE_TAG_DIRTY);
718 }
719 write_unlock_irq(&mapping->tree_lock);
720 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
721
722 return 1;
723}
724
725/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700726 * Add a page to the dirty page list.
727 *
728 * It is a sad fact of life that this function is called from several places
729 * deeply under spinlocking. It may not sleep.
730 *
731 * If the page has buffers, the uptodate buffers are set dirty, to preserve
732 * dirty-state coherency between the page and the buffers. It the page does
733 * not have buffers then when they are later attached they will all be set
734 * dirty.
735 *
736 * The buffers are dirtied before the page is dirtied. There's a small race
737 * window in which a writepage caller may see the page cleanness but not the
738 * buffer dirtiness. That's fine. If this code were to set the page dirty
739 * before the buffers, a concurrent writepage caller could clear the page dirty
740 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
741 * page on the dirty page list.
742 *
743 * We use private_lock to lock against try_to_free_buffers while using the
744 * page's buffer list. Also use this to protect against clean buffers being
745 * added to the page after it was set dirty.
746 *
747 * FIXME: may need to call ->reservepage here as well. That's rather up to the
748 * address_space though.
749 */
750int __set_page_dirty_buffers(struct page *page)
751{
Nick Piggin787d2212007-07-17 04:03:34 -0700752 struct address_space *mapping = page_mapping(page);
Nick Pigginebf7a222006-10-10 04:36:54 +0200753
754 if (unlikely(!mapping))
755 return !TestSetPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700756
757 spin_lock(&mapping->private_lock);
758 if (page_has_buffers(page)) {
759 struct buffer_head *head = page_buffers(page);
760 struct buffer_head *bh = head;
761
762 do {
763 set_buffer_dirty(bh);
764 bh = bh->b_this_page;
765 } while (bh != head);
766 }
767 spin_unlock(&mapping->private_lock);
768
Nick Piggin787d2212007-07-17 04:03:34 -0700769 return __set_page_dirty(page, mapping, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700770}
771EXPORT_SYMBOL(__set_page_dirty_buffers);
772
773/*
774 * Write out and wait upon a list of buffers.
775 *
776 * We have conflicting pressures: we want to make sure that all
777 * initially dirty buffers get waited on, but that any subsequently
778 * dirtied buffers don't. After all, we don't want fsync to last
779 * forever if somebody is actively writing to the file.
780 *
781 * Do this in two main stages: first we copy dirty buffers to a
782 * temporary inode list, queueing the writes as we go. Then we clean
783 * up, waiting for those writes to complete.
784 *
785 * During this second stage, any subsequent updates to the file may end
786 * up refiling the buffer on the original inode's dirty list again, so
787 * there is a chance we will end up with a buffer queued for write but
788 * not yet completed on that list. So, as a final cleanup we go through
789 * the osync code to catch these locked, dirty buffers without requeuing
790 * any newly dirty buffers for write.
791 */
792static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
793{
794 struct buffer_head *bh;
795 struct list_head tmp;
Jan Kara535ee2f2008-02-08 04:21:59 -0800796 struct address_space *mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700797 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 Kara535ee2f2008-02-08 04:21:59 -0800804 mapping = bh->b_assoc_map;
Jan Kara58ff4072006-10-17 00:10:19 -0700805 __remove_assoc_queue(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -0800806 /* Avoid race with mark_buffer_dirty_inode() which does
807 * a lockless check and we rely on seeing the dirty bit */
808 smp_mb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700809 if (buffer_dirty(bh) || buffer_locked(bh)) {
810 list_add(&bh->b_assoc_buffers, &tmp);
Jan Kara535ee2f2008-02-08 04:21:59 -0800811 bh->b_assoc_map = mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700812 if (buffer_dirty(bh)) {
813 get_bh(bh);
814 spin_unlock(lock);
815 /*
816 * Ensure any pending I/O completes so that
817 * ll_rw_block() actually writes the current
818 * contents - it is a noop if I/O is still in
819 * flight on potentially older contents.
820 */
Jan Karaa7662232005-09-06 15:19:10 -0700821 ll_rw_block(SWRITE, 1, &bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700822 brelse(bh);
823 spin_lock(lock);
824 }
825 }
826 }
827
828 while (!list_empty(&tmp)) {
829 bh = BH_ENTRY(tmp.prev);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700830 get_bh(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -0800831 mapping = bh->b_assoc_map;
832 __remove_assoc_queue(bh);
833 /* Avoid race with mark_buffer_dirty_inode() which does
834 * a lockless check and we rely on seeing the dirty bit */
835 smp_mb();
836 if (buffer_dirty(bh)) {
837 list_add(&bh->b_assoc_buffers,
Jan Karae3892292008-03-04 14:28:33 -0800838 &mapping->private_list);
Jan Kara535ee2f2008-02-08 04:21:59 -0800839 bh->b_assoc_map = mapping;
840 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700841 spin_unlock(lock);
842 wait_on_buffer(bh);
843 if (!buffer_uptodate(bh))
844 err = -EIO;
845 brelse(bh);
846 spin_lock(lock);
847 }
848
849 spin_unlock(lock);
850 err2 = osync_buffers_list(lock, list);
851 if (err)
852 return err;
853 else
854 return err2;
855}
856
857/*
858 * Invalidate any and all dirty buffers on a given inode. We are
859 * probably unmounting the fs, but that doesn't mean we have already
860 * done a sync(). Just drop the buffers from the inode list.
861 *
862 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
863 * assumes that all the buffers are against the blockdev. Not true
864 * for reiserfs.
865 */
866void invalidate_inode_buffers(struct inode *inode)
867{
868 if (inode_has_buffers(inode)) {
869 struct address_space *mapping = &inode->i_data;
870 struct list_head *list = &mapping->private_list;
871 struct address_space *buffer_mapping = mapping->assoc_mapping;
872
873 spin_lock(&buffer_mapping->private_lock);
874 while (!list_empty(list))
875 __remove_assoc_queue(BH_ENTRY(list->next));
876 spin_unlock(&buffer_mapping->private_lock);
877 }
878}
879
880/*
881 * Remove any clean buffers from the inode's buffer list. This is called
882 * when we're trying to free the inode itself. Those buffers can pin it.
883 *
884 * Returns true if all buffers were removed.
885 */
886int remove_inode_buffers(struct inode *inode)
887{
888 int ret = 1;
889
890 if (inode_has_buffers(inode)) {
891 struct address_space *mapping = &inode->i_data;
892 struct list_head *list = &mapping->private_list;
893 struct address_space *buffer_mapping = mapping->assoc_mapping;
894
895 spin_lock(&buffer_mapping->private_lock);
896 while (!list_empty(list)) {
897 struct buffer_head *bh = BH_ENTRY(list->next);
898 if (buffer_dirty(bh)) {
899 ret = 0;
900 break;
901 }
902 __remove_assoc_queue(bh);
903 }
904 spin_unlock(&buffer_mapping->private_lock);
905 }
906 return ret;
907}
908
909/*
910 * Create the appropriate buffers when given a page for data area and
911 * the size of each buffer.. Use the bh->b_this_page linked list to
912 * follow the buffers created. Return NULL if unable to create more
913 * buffers.
914 *
915 * The retry flag is used to differentiate async IO (paging, swapping)
916 * which may not fail from ordinary buffer allocations.
917 */
918struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
919 int retry)
920{
921 struct buffer_head *bh, *head;
922 long offset;
923
924try_again:
925 head = NULL;
926 offset = PAGE_SIZE;
927 while ((offset -= size) >= 0) {
928 bh = alloc_buffer_head(GFP_NOFS);
929 if (!bh)
930 goto no_grow;
931
932 bh->b_bdev = NULL;
933 bh->b_this_page = head;
934 bh->b_blocknr = -1;
935 head = bh;
936
937 bh->b_state = 0;
938 atomic_set(&bh->b_count, 0);
Chris Masonfc5cd582006-02-01 03:06:48 -0800939 bh->b_private = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700940 bh->b_size = size;
941
942 /* Link the buffer to its page */
943 set_bh_page(bh, page, offset);
944
Nathan Scott01ffe332006-01-17 09:02:07 +1100945 init_buffer(bh, NULL, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700946 }
947 return head;
948/*
949 * In case anything failed, we just free everything we got.
950 */
951no_grow:
952 if (head) {
953 do {
954 bh = head;
955 head = head->b_this_page;
956 free_buffer_head(bh);
957 } while (head);
958 }
959
960 /*
961 * Return failure for non-async IO requests. Async IO requests
962 * are not allowed to fail, so we have to wait until buffer heads
963 * become available. But we don't want tasks sleeping with
964 * partially complete buffers, so all were released above.
965 */
966 if (!retry)
967 return NULL;
968
969 /* We're _really_ low on memory. Now we just
970 * wait for old buffer heads to become free due to
971 * finishing IO. Since this is an async request and
972 * the reserve list is empty, we're sure there are
973 * async buffer heads in use.
974 */
975 free_more_memory();
976 goto try_again;
977}
978EXPORT_SYMBOL_GPL(alloc_page_buffers);
979
980static inline void
981link_dev_buffers(struct page *page, struct buffer_head *head)
982{
983 struct buffer_head *bh, *tail;
984
985 bh = head;
986 do {
987 tail = bh;
988 bh = bh->b_this_page;
989 } while (bh);
990 tail->b_this_page = head;
991 attach_page_buffers(page, head);
992}
993
994/*
995 * Initialise the state of a blockdev page's buffers.
996 */
997static void
998init_page_buffers(struct page *page, struct block_device *bdev,
999 sector_t block, int size)
1000{
1001 struct buffer_head *head = page_buffers(page);
1002 struct buffer_head *bh = head;
1003 int uptodate = PageUptodate(page);
1004
1005 do {
1006 if (!buffer_mapped(bh)) {
1007 init_buffer(bh, NULL, NULL);
1008 bh->b_bdev = bdev;
1009 bh->b_blocknr = block;
1010 if (uptodate)
1011 set_buffer_uptodate(bh);
1012 set_buffer_mapped(bh);
1013 }
1014 block++;
1015 bh = bh->b_this_page;
1016 } while (bh != head);
1017}
1018
1019/*
1020 * Create the page-cache page that contains the requested block.
1021 *
1022 * This is user purely for blockdev mappings.
1023 */
1024static struct page *
1025grow_dev_page(struct block_device *bdev, sector_t block,
1026 pgoff_t index, int size)
1027{
1028 struct inode *inode = bdev->bd_inode;
1029 struct page *page;
1030 struct buffer_head *bh;
1031
Christoph Lameterea125892007-05-16 22:11:21 -07001032 page = find_or_create_page(inode->i_mapping, index,
Mel Gorman769848c2007-07-17 04:03:05 -07001033 (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001034 if (!page)
1035 return NULL;
1036
Eric Sesterhenne827f922006-03-26 18:24:46 +02001037 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001038
1039 if (page_has_buffers(page)) {
1040 bh = page_buffers(page);
1041 if (bh->b_size == size) {
1042 init_page_buffers(page, bdev, block, size);
1043 return page;
1044 }
1045 if (!try_to_free_buffers(page))
1046 goto failed;
1047 }
1048
1049 /*
1050 * Allocate some buffers for this page
1051 */
1052 bh = alloc_page_buffers(page, size, 0);
1053 if (!bh)
1054 goto failed;
1055
1056 /*
1057 * Link the page to the buffers and initialise them. Take the
1058 * lock to be atomic wrt __find_get_block(), which does not
1059 * run under the page lock.
1060 */
1061 spin_lock(&inode->i_mapping->private_lock);
1062 link_dev_buffers(page, bh);
1063 init_page_buffers(page, bdev, block, size);
1064 spin_unlock(&inode->i_mapping->private_lock);
1065 return page;
1066
1067failed:
1068 BUG();
1069 unlock_page(page);
1070 page_cache_release(page);
1071 return NULL;
1072}
1073
1074/*
1075 * Create buffers for the specified block device block's page. If
1076 * that page was dirty, the buffers are set dirty also.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001077 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001078static int
Linus Torvalds1da177e2005-04-16 15:20:36 -07001079grow_buffers(struct block_device *bdev, sector_t block, int size)
1080{
1081 struct page *page;
1082 pgoff_t index;
1083 int sizebits;
1084
1085 sizebits = -1;
1086 do {
1087 sizebits++;
1088 } while ((size << sizebits) < PAGE_SIZE);
1089
1090 index = block >> sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001091
Andrew Mortone5657932006-10-11 01:21:46 -07001092 /*
1093 * Check for a block which wants to lie outside our maximum possible
1094 * pagecache index. (this comparison is done using sector_t types).
1095 */
1096 if (unlikely(index != block >> sizebits)) {
1097 char b[BDEVNAME_SIZE];
1098
1099 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1100 "device %s\n",
1101 __FUNCTION__, (unsigned long long)block,
1102 bdevname(bdev, b));
1103 return -EIO;
1104 }
1105 block = index << sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001106 /* Create a page with the proper size buffers.. */
1107 page = grow_dev_page(bdev, block, index, size);
1108 if (!page)
1109 return 0;
1110 unlock_page(page);
1111 page_cache_release(page);
1112 return 1;
1113}
1114
Adrian Bunk75c96f82005-05-05 16:16:09 -07001115static struct buffer_head *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001116__getblk_slow(struct block_device *bdev, sector_t block, int size)
1117{
1118 /* Size must be multiple of hard sectorsize */
1119 if (unlikely(size & (bdev_hardsect_size(bdev)-1) ||
1120 (size < 512 || size > PAGE_SIZE))) {
1121 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1122 size);
1123 printk(KERN_ERR "hardsect size: %d\n",
1124 bdev_hardsect_size(bdev));
1125
1126 dump_stack();
1127 return NULL;
1128 }
1129
1130 for (;;) {
1131 struct buffer_head * bh;
Andrew Mortone5657932006-10-11 01:21:46 -07001132 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001133
1134 bh = __find_get_block(bdev, block, size);
1135 if (bh)
1136 return bh;
1137
Andrew Mortone5657932006-10-11 01:21:46 -07001138 ret = grow_buffers(bdev, block, size);
1139 if (ret < 0)
1140 return NULL;
1141 if (ret == 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001142 free_more_memory();
1143 }
1144}
1145
1146/*
1147 * The relationship between dirty buffers and dirty pages:
1148 *
1149 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1150 * the page is tagged dirty in its radix tree.
1151 *
1152 * At all times, the dirtiness of the buffers represents the dirtiness of
1153 * subsections of the page. If the page has buffers, the page dirty bit is
1154 * merely a hint about the true dirty state.
1155 *
1156 * When a page is set dirty in its entirety, all its buffers are marked dirty
1157 * (if the page has buffers).
1158 *
1159 * When a buffer is marked dirty, its page is dirtied, but the page's other
1160 * buffers are not.
1161 *
1162 * Also. When blockdev buffers are explicitly read with bread(), they
1163 * individually become uptodate. But their backing page remains not
1164 * uptodate - even if all of its buffers are uptodate. A subsequent
1165 * block_read_full_page() against that page will discover all the uptodate
1166 * buffers, will set the page uptodate and will perform no I/O.
1167 */
1168
1169/**
1170 * mark_buffer_dirty - mark a buffer_head as needing writeout
Martin Waitz67be2dd2005-05-01 08:59:26 -07001171 * @bh: the buffer_head to mark dirty
Linus Torvalds1da177e2005-04-16 15:20:36 -07001172 *
1173 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1174 * backing page dirty, then tag the page as dirty in its address_space's radix
1175 * tree and then attach the address_space's inode to its superblock's dirty
1176 * inode list.
1177 *
1178 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1179 * mapping->tree_lock and the global inode_lock.
1180 */
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -08001181void mark_buffer_dirty(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001182{
Nick Piggin787d2212007-07-17 04:03:34 -07001183 WARN_ON_ONCE(!buffer_uptodate(bh));
Linus Torvalds1be62dc2008-04-04 14:38:17 -07001184
1185 /*
1186 * Very *carefully* optimize the it-is-already-dirty case.
1187 *
1188 * Don't let the final "is it dirty" escape to before we
1189 * perhaps modified the buffer.
1190 */
1191 if (buffer_dirty(bh)) {
1192 smp_mb();
1193 if (buffer_dirty(bh))
1194 return;
1195 }
1196
1197 if (!test_set_buffer_dirty(bh))
Nick Piggin787d2212007-07-17 04:03:34 -07001198 __set_page_dirty(bh->b_page, page_mapping(bh->b_page), 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001199}
1200
1201/*
1202 * Decrement a buffer_head's reference count. If all buffers against a page
1203 * have zero reference count, are clean and unlocked, and if the page is clean
1204 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1205 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1206 * a page but it ends up not being freed, and buffers may later be reattached).
1207 */
1208void __brelse(struct buffer_head * buf)
1209{
1210 if (atomic_read(&buf->b_count)) {
1211 put_bh(buf);
1212 return;
1213 }
1214 printk(KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1215 WARN_ON(1);
1216}
1217
1218/*
1219 * bforget() is like brelse(), except it discards any
1220 * potentially dirty data.
1221 */
1222void __bforget(struct buffer_head *bh)
1223{
1224 clear_buffer_dirty(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -08001225 if (bh->b_assoc_map) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001226 struct address_space *buffer_mapping = bh->b_page->mapping;
1227
1228 spin_lock(&buffer_mapping->private_lock);
1229 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -07001230 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001231 spin_unlock(&buffer_mapping->private_lock);
1232 }
1233 __brelse(bh);
1234}
1235
1236static struct buffer_head *__bread_slow(struct buffer_head *bh)
1237{
1238 lock_buffer(bh);
1239 if (buffer_uptodate(bh)) {
1240 unlock_buffer(bh);
1241 return bh;
1242 } else {
1243 get_bh(bh);
1244 bh->b_end_io = end_buffer_read_sync;
1245 submit_bh(READ, bh);
1246 wait_on_buffer(bh);
1247 if (buffer_uptodate(bh))
1248 return bh;
1249 }
1250 brelse(bh);
1251 return NULL;
1252}
1253
1254/*
1255 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1256 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1257 * refcount elevated by one when they're in an LRU. A buffer can only appear
1258 * once in a particular CPU's LRU. A single buffer can be present in multiple
1259 * CPU's LRUs at the same time.
1260 *
1261 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1262 * sb_find_get_block().
1263 *
1264 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1265 * a local interrupt disable for that.
1266 */
1267
1268#define BH_LRU_SIZE 8
1269
1270struct bh_lru {
1271 struct buffer_head *bhs[BH_LRU_SIZE];
1272};
1273
1274static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1275
1276#ifdef CONFIG_SMP
1277#define bh_lru_lock() local_irq_disable()
1278#define bh_lru_unlock() local_irq_enable()
1279#else
1280#define bh_lru_lock() preempt_disable()
1281#define bh_lru_unlock() preempt_enable()
1282#endif
1283
1284static inline void check_irqs_on(void)
1285{
1286#ifdef irqs_disabled
1287 BUG_ON(irqs_disabled());
1288#endif
1289}
1290
1291/*
1292 * The LRU management algorithm is dopey-but-simple. Sorry.
1293 */
1294static void bh_lru_install(struct buffer_head *bh)
1295{
1296 struct buffer_head *evictee = NULL;
1297 struct bh_lru *lru;
1298
1299 check_irqs_on();
1300 bh_lru_lock();
1301 lru = &__get_cpu_var(bh_lrus);
1302 if (lru->bhs[0] != bh) {
1303 struct buffer_head *bhs[BH_LRU_SIZE];
1304 int in;
1305 int out = 0;
1306
1307 get_bh(bh);
1308 bhs[out++] = bh;
1309 for (in = 0; in < BH_LRU_SIZE; in++) {
1310 struct buffer_head *bh2 = lru->bhs[in];
1311
1312 if (bh2 == bh) {
1313 __brelse(bh2);
1314 } else {
1315 if (out >= BH_LRU_SIZE) {
1316 BUG_ON(evictee != NULL);
1317 evictee = bh2;
1318 } else {
1319 bhs[out++] = bh2;
1320 }
1321 }
1322 }
1323 while (out < BH_LRU_SIZE)
1324 bhs[out++] = NULL;
1325 memcpy(lru->bhs, bhs, sizeof(bhs));
1326 }
1327 bh_lru_unlock();
1328
1329 if (evictee)
1330 __brelse(evictee);
1331}
1332
1333/*
1334 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1335 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001336static struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001337lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001338{
1339 struct buffer_head *ret = NULL;
1340 struct bh_lru *lru;
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001341 unsigned int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001342
1343 check_irqs_on();
1344 bh_lru_lock();
1345 lru = &__get_cpu_var(bh_lrus);
1346 for (i = 0; i < BH_LRU_SIZE; i++) {
1347 struct buffer_head *bh = lru->bhs[i];
1348
1349 if (bh && bh->b_bdev == bdev &&
1350 bh->b_blocknr == block && bh->b_size == size) {
1351 if (i) {
1352 while (i) {
1353 lru->bhs[i] = lru->bhs[i - 1];
1354 i--;
1355 }
1356 lru->bhs[0] = bh;
1357 }
1358 get_bh(bh);
1359 ret = bh;
1360 break;
1361 }
1362 }
1363 bh_lru_unlock();
1364 return ret;
1365}
1366
1367/*
1368 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1369 * it in the LRU and mark it as accessed. If it is not present then return
1370 * NULL
1371 */
1372struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001373__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001374{
1375 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1376
1377 if (bh == NULL) {
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001378 bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001379 if (bh)
1380 bh_lru_install(bh);
1381 }
1382 if (bh)
1383 touch_buffer(bh);
1384 return bh;
1385}
1386EXPORT_SYMBOL(__find_get_block);
1387
1388/*
1389 * __getblk will locate (and, if necessary, create) the buffer_head
1390 * which corresponds to the passed block_device, block and size. The
1391 * returned buffer has its reference count incremented.
1392 *
1393 * __getblk() cannot fail - it just keeps trying. If you pass it an
1394 * illegal block number, __getblk() will happily return a buffer_head
1395 * which represents the non-existent block. Very weird.
1396 *
1397 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1398 * attempt is failing. FIXME, perhaps?
1399 */
1400struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001401__getblk(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001402{
1403 struct buffer_head *bh = __find_get_block(bdev, block, size);
1404
1405 might_sleep();
1406 if (bh == NULL)
1407 bh = __getblk_slow(bdev, block, size);
1408 return bh;
1409}
1410EXPORT_SYMBOL(__getblk);
1411
1412/*
1413 * Do async read-ahead on a buffer..
1414 */
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001415void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001416{
1417 struct buffer_head *bh = __getblk(bdev, block, size);
Andrew Mortona3e713b2005-10-30 15:03:15 -08001418 if (likely(bh)) {
1419 ll_rw_block(READA, 1, &bh);
1420 brelse(bh);
1421 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001422}
1423EXPORT_SYMBOL(__breadahead);
1424
1425/**
1426 * __bread() - reads a specified block and returns the bh
Martin Waitz67be2dd2005-05-01 08:59:26 -07001427 * @bdev: the block_device to read from
Linus Torvalds1da177e2005-04-16 15:20:36 -07001428 * @block: number of block
1429 * @size: size (in bytes) to read
1430 *
1431 * Reads a specified block, and returns buffer head that contains it.
1432 * It returns NULL if the block was unreadable.
1433 */
1434struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001435__bread(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001436{
1437 struct buffer_head *bh = __getblk(bdev, block, size);
1438
Andrew Mortona3e713b2005-10-30 15:03:15 -08001439 if (likely(bh) && !buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001440 bh = __bread_slow(bh);
1441 return bh;
1442}
1443EXPORT_SYMBOL(__bread);
1444
1445/*
1446 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1447 * This doesn't race because it runs in each cpu either in irq
1448 * or with preempt disabled.
1449 */
1450static void invalidate_bh_lru(void *arg)
1451{
1452 struct bh_lru *b = &get_cpu_var(bh_lrus);
1453 int i;
1454
1455 for (i = 0; i < BH_LRU_SIZE; i++) {
1456 brelse(b->bhs[i]);
1457 b->bhs[i] = NULL;
1458 }
1459 put_cpu_var(bh_lrus);
1460}
1461
Peter Zijlstraf9a14392007-05-06 14:49:55 -07001462void invalidate_bh_lrus(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001463{
1464 on_each_cpu(invalidate_bh_lru, NULL, 1, 1);
1465}
Nick Piggin9db55792008-02-08 04:19:49 -08001466EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001467
1468void set_bh_page(struct buffer_head *bh,
1469 struct page *page, unsigned long offset)
1470{
1471 bh->b_page = page;
Eric Sesterhenne827f922006-03-26 18:24:46 +02001472 BUG_ON(offset >= PAGE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001473 if (PageHighMem(page))
1474 /*
1475 * This catches illegal uses and preserves the offset:
1476 */
1477 bh->b_data = (char *)(0 + offset);
1478 else
1479 bh->b_data = page_address(page) + offset;
1480}
1481EXPORT_SYMBOL(set_bh_page);
1482
1483/*
1484 * Called when truncating a buffer on a page completely.
1485 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001486static void discard_buffer(struct buffer_head * bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001487{
1488 lock_buffer(bh);
1489 clear_buffer_dirty(bh);
1490 bh->b_bdev = NULL;
1491 clear_buffer_mapped(bh);
1492 clear_buffer_req(bh);
1493 clear_buffer_new(bh);
1494 clear_buffer_delay(bh);
David Chinner33a266d2007-02-12 00:51:41 -08001495 clear_buffer_unwritten(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001496 unlock_buffer(bh);
1497}
1498
1499/**
Linus Torvalds1da177e2005-04-16 15:20:36 -07001500 * block_invalidatepage - invalidate part of all of a buffer-backed page
1501 *
1502 * @page: the page which is affected
1503 * @offset: the index of the truncation point
1504 *
1505 * block_invalidatepage() is called when all or part of the page has become
1506 * invalidatedby a truncate operation.
1507 *
1508 * block_invalidatepage() does not have to release all buffers, but it must
1509 * ensure that no dirty buffer is left outside @offset and that no I/O
1510 * is underway against any of the blocks which are outside the truncation
1511 * point. Because the caller is about to free (and possibly reuse) those
1512 * blocks on-disk.
1513 */
NeilBrown2ff28e22006-03-26 01:37:18 -08001514void block_invalidatepage(struct page *page, unsigned long offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001515{
1516 struct buffer_head *head, *bh, *next;
1517 unsigned int curr_off = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001518
1519 BUG_ON(!PageLocked(page));
1520 if (!page_has_buffers(page))
1521 goto out;
1522
1523 head = page_buffers(page);
1524 bh = head;
1525 do {
1526 unsigned int next_off = curr_off + bh->b_size;
1527 next = bh->b_this_page;
1528
1529 /*
1530 * is this block fully invalidated?
1531 */
1532 if (offset <= curr_off)
1533 discard_buffer(bh);
1534 curr_off = next_off;
1535 bh = next;
1536 } while (bh != head);
1537
1538 /*
1539 * We release buffers only if the entire page is being invalidated.
1540 * The get_block cached value has been unconditionally invalidated,
1541 * so real IO is not possible anymore.
1542 */
1543 if (offset == 0)
NeilBrown2ff28e22006-03-26 01:37:18 -08001544 try_to_release_page(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001545out:
NeilBrown2ff28e22006-03-26 01:37:18 -08001546 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001547}
1548EXPORT_SYMBOL(block_invalidatepage);
1549
1550/*
1551 * We attach and possibly dirty the buffers atomically wrt
1552 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1553 * is already excluded via the page lock.
1554 */
1555void create_empty_buffers(struct page *page,
1556 unsigned long blocksize, unsigned long b_state)
1557{
1558 struct buffer_head *bh, *head, *tail;
1559
1560 head = alloc_page_buffers(page, blocksize, 1);
1561 bh = head;
1562 do {
1563 bh->b_state |= b_state;
1564 tail = bh;
1565 bh = bh->b_this_page;
1566 } while (bh);
1567 tail->b_this_page = head;
1568
1569 spin_lock(&page->mapping->private_lock);
1570 if (PageUptodate(page) || PageDirty(page)) {
1571 bh = head;
1572 do {
1573 if (PageDirty(page))
1574 set_buffer_dirty(bh);
1575 if (PageUptodate(page))
1576 set_buffer_uptodate(bh);
1577 bh = bh->b_this_page;
1578 } while (bh != head);
1579 }
1580 attach_page_buffers(page, head);
1581 spin_unlock(&page->mapping->private_lock);
1582}
1583EXPORT_SYMBOL(create_empty_buffers);
1584
1585/*
1586 * We are taking a block for data and we don't want any output from any
1587 * buffer-cache aliases starting from return from that function and
1588 * until the moment when something will explicitly mark the buffer
1589 * dirty (hopefully that will not happen until we will free that block ;-)
1590 * We don't even need to mark it not-uptodate - nobody can expect
1591 * anything from a newly allocated buffer anyway. We used to used
1592 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1593 * don't want to mark the alias unmapped, for example - it would confuse
1594 * anyone who might pick it with bread() afterwards...
1595 *
1596 * Also.. Note that bforget() doesn't lock the buffer. So there can
1597 * be writeout I/O going on against recently-freed buffers. We don't
1598 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1599 * only if we really need to. That happens here.
1600 */
1601void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1602{
1603 struct buffer_head *old_bh;
1604
1605 might_sleep();
1606
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001607 old_bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001608 if (old_bh) {
1609 clear_buffer_dirty(old_bh);
1610 wait_on_buffer(old_bh);
1611 clear_buffer_req(old_bh);
1612 __brelse(old_bh);
1613 }
1614}
1615EXPORT_SYMBOL(unmap_underlying_metadata);
1616
1617/*
1618 * NOTE! All mapped/uptodate combinations are valid:
1619 *
1620 * Mapped Uptodate Meaning
1621 *
1622 * No No "unknown" - must do get_block()
1623 * No Yes "hole" - zero-filled
1624 * Yes No "allocated" - allocated on disk, not read in
1625 * Yes Yes "valid" - allocated and up-to-date in memory.
1626 *
1627 * "Dirty" is valid only with the last case (mapped+uptodate).
1628 */
1629
1630/*
1631 * While block_write_full_page is writing back the dirty buffers under
1632 * the page lock, whoever dirtied the buffers may decide to clean them
1633 * again at any time. We handle that by only looking at the buffer
1634 * state inside lock_buffer().
1635 *
1636 * If block_write_full_page() is called for regular writeback
1637 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1638 * locked buffer. This only can happen if someone has written the buffer
1639 * directly, with submit_bh(). At the address_space level PageWriteback
1640 * prevents this contention from occurring.
1641 */
1642static int __block_write_full_page(struct inode *inode, struct page *page,
1643 get_block_t *get_block, struct writeback_control *wbc)
1644{
1645 int err;
1646 sector_t block;
1647 sector_t last_block;
Andrew Mortonf0fbd5f2005-05-05 16:15:48 -07001648 struct buffer_head *bh, *head;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001649 const unsigned blocksize = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001650 int nr_underway = 0;
1651
1652 BUG_ON(!PageLocked(page));
1653
1654 last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
1655
1656 if (!page_has_buffers(page)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001657 create_empty_buffers(page, blocksize,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001658 (1 << BH_Dirty)|(1 << BH_Uptodate));
1659 }
1660
1661 /*
1662 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1663 * here, and the (potentially unmapped) buffers may become dirty at
1664 * any time. If a buffer becomes dirty here after we've inspected it
1665 * then we just miss that fact, and the page stays dirty.
1666 *
1667 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1668 * handle that here by just cleaning them.
1669 */
1670
Andrew Morton54b21a72006-01-08 01:03:05 -08001671 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001672 head = page_buffers(page);
1673 bh = head;
1674
1675 /*
1676 * Get all the dirty buffers mapped to disk addresses and
1677 * handle any aliases from the underlying blockdev's mapping.
1678 */
1679 do {
1680 if (block > last_block) {
1681 /*
1682 * mapped buffers outside i_size will occur, because
1683 * this page can be outside i_size when there is a
1684 * truncate in progress.
1685 */
1686 /*
1687 * The buffer was zeroed by block_write_full_page()
1688 */
1689 clear_buffer_dirty(bh);
1690 set_buffer_uptodate(bh);
1691 } else if (!buffer_mapped(bh) && buffer_dirty(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001692 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001693 err = get_block(inode, block, bh, 1);
1694 if (err)
1695 goto recover;
1696 if (buffer_new(bh)) {
1697 /* blockdev mappings never come here */
1698 clear_buffer_new(bh);
1699 unmap_underlying_metadata(bh->b_bdev,
1700 bh->b_blocknr);
1701 }
1702 }
1703 bh = bh->b_this_page;
1704 block++;
1705 } while (bh != head);
1706
1707 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001708 if (!buffer_mapped(bh))
1709 continue;
1710 /*
1711 * If it's a fully non-blocking write attempt and we cannot
1712 * lock the buffer then redirty the page. Note that this can
1713 * potentially cause a busy-wait loop from pdflush and kswapd
1714 * activity, but those code paths have their own higher-level
1715 * throttling.
1716 */
1717 if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
1718 lock_buffer(bh);
1719 } else if (test_set_buffer_locked(bh)) {
1720 redirty_page_for_writepage(wbc, page);
1721 continue;
1722 }
1723 if (test_clear_buffer_dirty(bh)) {
1724 mark_buffer_async_write(bh);
1725 } else {
1726 unlock_buffer(bh);
1727 }
1728 } while ((bh = bh->b_this_page) != head);
1729
1730 /*
1731 * The page and its buffers are protected by PageWriteback(), so we can
1732 * drop the bh refcounts early.
1733 */
1734 BUG_ON(PageWriteback(page));
1735 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001736
1737 do {
1738 struct buffer_head *next = bh->b_this_page;
1739 if (buffer_async_write(bh)) {
1740 submit_bh(WRITE, bh);
1741 nr_underway++;
1742 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001743 bh = next;
1744 } while (bh != head);
Andrew Morton05937ba2005-05-05 16:15:47 -07001745 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001746
1747 err = 0;
1748done:
1749 if (nr_underway == 0) {
1750 /*
1751 * The page was marked dirty, but the buffers were
1752 * clean. Someone wrote them back by hand with
1753 * ll_rw_block/submit_bh. A rare case.
1754 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001755 end_page_writeback(page);
Nick Piggin3d67f2d2007-05-06 14:49:05 -07001756
Linus Torvalds1da177e2005-04-16 15:20:36 -07001757 /*
1758 * The page and buffer_heads can be released at any time from
1759 * here on.
1760 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001761 }
1762 return err;
1763
1764recover:
1765 /*
1766 * ENOSPC, or some other error. We may already have added some
1767 * blocks to the file, so we need to write these out to avoid
1768 * exposing stale data.
1769 * The page is currently locked and not marked for writeback
1770 */
1771 bh = head;
1772 /* Recovery: lock and submit the mapped buffers */
1773 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001774 if (buffer_mapped(bh) && buffer_dirty(bh)) {
1775 lock_buffer(bh);
1776 mark_buffer_async_write(bh);
1777 } else {
1778 /*
1779 * The buffer may have been set dirty during
1780 * attachment to a dirty page.
1781 */
1782 clear_buffer_dirty(bh);
1783 }
1784 } while ((bh = bh->b_this_page) != head);
1785 SetPageError(page);
1786 BUG_ON(PageWriteback(page));
Andrew Morton7e4c3692007-05-08 00:23:27 -07001787 mapping_set_error(page->mapping, err);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001788 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001789 do {
1790 struct buffer_head *next = bh->b_this_page;
1791 if (buffer_async_write(bh)) {
1792 clear_buffer_dirty(bh);
1793 submit_bh(WRITE, bh);
1794 nr_underway++;
1795 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001796 bh = next;
1797 } while (bh != head);
Nick Pigginffda9d32007-02-20 13:57:54 -08001798 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001799 goto done;
1800}
1801
Nick Pigginafddba42007-10-16 01:25:01 -07001802/*
1803 * If a page has any new buffers, zero them out here, and mark them uptodate
1804 * and dirty so they'll be written out (in order to prevent uninitialised
1805 * block data from leaking). And clear the new bit.
1806 */
1807void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1808{
1809 unsigned int block_start, block_end;
1810 struct buffer_head *head, *bh;
1811
1812 BUG_ON(!PageLocked(page));
1813 if (!page_has_buffers(page))
1814 return;
1815
1816 bh = head = page_buffers(page);
1817 block_start = 0;
1818 do {
1819 block_end = block_start + bh->b_size;
1820
1821 if (buffer_new(bh)) {
1822 if (block_end > from && block_start < to) {
1823 if (!PageUptodate(page)) {
1824 unsigned start, size;
1825
1826 start = max(from, block_start);
1827 size = min(to, block_end) - start;
1828
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001829 zero_user(page, start, size);
Nick Pigginafddba42007-10-16 01:25:01 -07001830 set_buffer_uptodate(bh);
1831 }
1832
1833 clear_buffer_new(bh);
1834 mark_buffer_dirty(bh);
1835 }
1836 }
1837
1838 block_start = block_end;
1839 bh = bh->b_this_page;
1840 } while (bh != head);
1841}
1842EXPORT_SYMBOL(page_zero_new_buffers);
1843
Linus Torvalds1da177e2005-04-16 15:20:36 -07001844static int __block_prepare_write(struct inode *inode, struct page *page,
1845 unsigned from, unsigned to, get_block_t *get_block)
1846{
1847 unsigned block_start, block_end;
1848 sector_t block;
1849 int err = 0;
1850 unsigned blocksize, bbits;
1851 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1852
1853 BUG_ON(!PageLocked(page));
1854 BUG_ON(from > PAGE_CACHE_SIZE);
1855 BUG_ON(to > PAGE_CACHE_SIZE);
1856 BUG_ON(from > to);
1857
1858 blocksize = 1 << inode->i_blkbits;
1859 if (!page_has_buffers(page))
1860 create_empty_buffers(page, blocksize, 0);
1861 head = page_buffers(page);
1862
1863 bbits = inode->i_blkbits;
1864 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1865
1866 for(bh = head, block_start = 0; bh != head || !block_start;
1867 block++, block_start=block_end, bh = bh->b_this_page) {
1868 block_end = block_start + blocksize;
1869 if (block_end <= from || block_start >= to) {
1870 if (PageUptodate(page)) {
1871 if (!buffer_uptodate(bh))
1872 set_buffer_uptodate(bh);
1873 }
1874 continue;
1875 }
1876 if (buffer_new(bh))
1877 clear_buffer_new(bh);
1878 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001879 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001880 err = get_block(inode, block, bh, 1);
1881 if (err)
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001882 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001883 if (buffer_new(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001884 unmap_underlying_metadata(bh->b_bdev,
1885 bh->b_blocknr);
1886 if (PageUptodate(page)) {
Nick Piggin637aff42007-10-16 01:25:00 -07001887 clear_buffer_new(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001888 set_buffer_uptodate(bh);
Nick Piggin637aff42007-10-16 01:25:00 -07001889 mark_buffer_dirty(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001890 continue;
1891 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001892 if (block_end > to || block_start < from)
1893 zero_user_segments(page,
1894 to, block_end,
1895 block_start, from);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001896 continue;
1897 }
1898 }
1899 if (PageUptodate(page)) {
1900 if (!buffer_uptodate(bh))
1901 set_buffer_uptodate(bh);
1902 continue;
1903 }
1904 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
David Chinner33a266d2007-02-12 00:51:41 -08001905 !buffer_unwritten(bh) &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001906 (block_start < from || block_end > to)) {
1907 ll_rw_block(READ, 1, &bh);
1908 *wait_bh++=bh;
1909 }
1910 }
1911 /*
1912 * If we issued read requests - let them complete.
1913 */
1914 while(wait_bh > wait) {
1915 wait_on_buffer(*--wait_bh);
1916 if (!buffer_uptodate(*wait_bh))
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001917 err = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001918 }
Nick Pigginafddba42007-10-16 01:25:01 -07001919 if (unlikely(err))
1920 page_zero_new_buffers(page, from, to);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001921 return err;
1922}
1923
1924static int __block_commit_write(struct inode *inode, struct page *page,
1925 unsigned from, unsigned to)
1926{
1927 unsigned block_start, block_end;
1928 int partial = 0;
1929 unsigned blocksize;
1930 struct buffer_head *bh, *head;
1931
1932 blocksize = 1 << inode->i_blkbits;
1933
1934 for(bh = head = page_buffers(page), block_start = 0;
1935 bh != head || !block_start;
1936 block_start=block_end, bh = bh->b_this_page) {
1937 block_end = block_start + blocksize;
1938 if (block_end <= from || block_start >= to) {
1939 if (!buffer_uptodate(bh))
1940 partial = 1;
1941 } else {
1942 set_buffer_uptodate(bh);
1943 mark_buffer_dirty(bh);
1944 }
Nick Pigginafddba42007-10-16 01:25:01 -07001945 clear_buffer_new(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001946 }
1947
1948 /*
1949 * If this is a partial write which happened to make all buffers
1950 * uptodate then we can optimize away a bogus readpage() for
1951 * the next read(). Here we 'discover' whether the page went
1952 * uptodate as a result of this (potentially partial) write.
1953 */
1954 if (!partial)
1955 SetPageUptodate(page);
1956 return 0;
1957}
1958
1959/*
Nick Pigginafddba42007-10-16 01:25:01 -07001960 * block_write_begin takes care of the basic task of block allocation and
1961 * bringing partial write blocks uptodate first.
1962 *
1963 * If *pagep is not NULL, then block_write_begin uses the locked page
1964 * at *pagep rather than allocating its own. In this case, the page will
1965 * not be unlocked or deallocated on failure.
1966 */
1967int block_write_begin(struct file *file, struct address_space *mapping,
1968 loff_t pos, unsigned len, unsigned flags,
1969 struct page **pagep, void **fsdata,
1970 get_block_t *get_block)
1971{
1972 struct inode *inode = mapping->host;
1973 int status = 0;
1974 struct page *page;
1975 pgoff_t index;
1976 unsigned start, end;
1977 int ownpage = 0;
1978
1979 index = pos >> PAGE_CACHE_SHIFT;
1980 start = pos & (PAGE_CACHE_SIZE - 1);
1981 end = start + len;
1982
1983 page = *pagep;
1984 if (page == NULL) {
1985 ownpage = 1;
1986 page = __grab_cache_page(mapping, index);
1987 if (!page) {
1988 status = -ENOMEM;
1989 goto out;
1990 }
1991 *pagep = page;
1992 } else
1993 BUG_ON(!PageLocked(page));
1994
1995 status = __block_prepare_write(inode, page, start, end, get_block);
1996 if (unlikely(status)) {
1997 ClearPageUptodate(page);
1998
1999 if (ownpage) {
2000 unlock_page(page);
2001 page_cache_release(page);
2002 *pagep = NULL;
2003
2004 /*
2005 * prepare_write() may have instantiated a few blocks
2006 * outside i_size. Trim these off again. Don't need
2007 * i_size_read because we hold i_mutex.
2008 */
2009 if (pos + len > inode->i_size)
2010 vmtruncate(inode, inode->i_size);
2011 }
2012 goto out;
2013 }
2014
2015out:
2016 return status;
2017}
2018EXPORT_SYMBOL(block_write_begin);
2019
2020int block_write_end(struct file *file, struct address_space *mapping,
2021 loff_t pos, unsigned len, unsigned copied,
2022 struct page *page, void *fsdata)
2023{
2024 struct inode *inode = mapping->host;
2025 unsigned start;
2026
2027 start = pos & (PAGE_CACHE_SIZE - 1);
2028
2029 if (unlikely(copied < len)) {
2030 /*
2031 * The buffers that were written will now be uptodate, so we
2032 * don't have to worry about a readpage reading them and
2033 * overwriting a partial write. However if we have encountered
2034 * a short write and only partially written into a buffer, it
2035 * will not be marked uptodate, so a readpage might come in and
2036 * destroy our partial write.
2037 *
2038 * Do the simplest thing, and just treat any short write to a
2039 * non uptodate page as a zero-length write, and force the
2040 * caller to redo the whole thing.
2041 */
2042 if (!PageUptodate(page))
2043 copied = 0;
2044
2045 page_zero_new_buffers(page, start+copied, start+len);
2046 }
2047 flush_dcache_page(page);
2048
2049 /* This could be a short (even 0-length) commit */
2050 __block_commit_write(inode, page, start, start+copied);
2051
2052 return copied;
2053}
2054EXPORT_SYMBOL(block_write_end);
2055
2056int generic_write_end(struct file *file, struct address_space *mapping,
2057 loff_t pos, unsigned len, unsigned copied,
2058 struct page *page, void *fsdata)
2059{
2060 struct inode *inode = mapping->host;
2061
2062 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2063
2064 /*
2065 * No need to use i_size_read() here, the i_size
2066 * cannot change under us because we hold i_mutex.
2067 *
2068 * But it's important to update i_size while still holding page lock:
2069 * page writeout could otherwise come in and zero beyond i_size.
2070 */
2071 if (pos+copied > inode->i_size) {
2072 i_size_write(inode, pos+copied);
2073 mark_inode_dirty(inode);
2074 }
2075
2076 unlock_page(page);
2077 page_cache_release(page);
2078
2079 return copied;
2080}
2081EXPORT_SYMBOL(generic_write_end);
2082
2083/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002084 * Generic "read page" function for block devices that have the normal
2085 * get_block functionality. This is most of the block device filesystems.
2086 * Reads the page asynchronously --- the unlock_buffer() and
2087 * set/clear_buffer_uptodate() functions propagate buffer state into the
2088 * page struct once IO has completed.
2089 */
2090int block_read_full_page(struct page *page, get_block_t *get_block)
2091{
2092 struct inode *inode = page->mapping->host;
2093 sector_t iblock, lblock;
2094 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2095 unsigned int blocksize;
2096 int nr, i;
2097 int fully_mapped = 1;
2098
Matt Mackallcd7619d2005-05-01 08:59:01 -07002099 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002100 blocksize = 1 << inode->i_blkbits;
2101 if (!page_has_buffers(page))
2102 create_empty_buffers(page, blocksize, 0);
2103 head = page_buffers(page);
2104
2105 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2106 lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
2107 bh = head;
2108 nr = 0;
2109 i = 0;
2110
2111 do {
2112 if (buffer_uptodate(bh))
2113 continue;
2114
2115 if (!buffer_mapped(bh)) {
Andrew Mortonc64610b2005-05-16 21:53:49 -07002116 int err = 0;
2117
Linus Torvalds1da177e2005-04-16 15:20:36 -07002118 fully_mapped = 0;
2119 if (iblock < lblock) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002120 WARN_ON(bh->b_size != blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002121 err = get_block(inode, iblock, bh, 0);
2122 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002123 SetPageError(page);
2124 }
2125 if (!buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002126 zero_user(page, i * blocksize, blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002127 if (!err)
2128 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002129 continue;
2130 }
2131 /*
2132 * get_block() might have updated the buffer
2133 * synchronously
2134 */
2135 if (buffer_uptodate(bh))
2136 continue;
2137 }
2138 arr[nr++] = bh;
2139 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2140
2141 if (fully_mapped)
2142 SetPageMappedToDisk(page);
2143
2144 if (!nr) {
2145 /*
2146 * All buffers are uptodate - we can set the page uptodate
2147 * as well. But not if get_block() returned an error.
2148 */
2149 if (!PageError(page))
2150 SetPageUptodate(page);
2151 unlock_page(page);
2152 return 0;
2153 }
2154
2155 /* Stage two: lock the buffers */
2156 for (i = 0; i < nr; i++) {
2157 bh = arr[i];
2158 lock_buffer(bh);
2159 mark_buffer_async_read(bh);
2160 }
2161
2162 /*
2163 * Stage 3: start the IO. Check for uptodateness
2164 * inside the buffer lock in case another process reading
2165 * the underlying blockdev brought it uptodate (the sct fix).
2166 */
2167 for (i = 0; i < nr; i++) {
2168 bh = arr[i];
2169 if (buffer_uptodate(bh))
2170 end_buffer_async_read(bh, 1);
2171 else
2172 submit_bh(READ, bh);
2173 }
2174 return 0;
2175}
2176
2177/* utility function for filesystems that need to do work on expanding
Nick Piggin89e10782007-10-16 01:25:07 -07002178 * truncates. Uses filesystem pagecache writes to allow the filesystem to
Linus Torvalds1da177e2005-04-16 15:20:36 -07002179 * deal with the hole.
2180 */
Nick Piggin89e10782007-10-16 01:25:07 -07002181int generic_cont_expand_simple(struct inode *inode, loff_t size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002182{
2183 struct address_space *mapping = inode->i_mapping;
2184 struct page *page;
Nick Piggin89e10782007-10-16 01:25:07 -07002185 void *fsdata;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002186 unsigned long limit;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002187 int err;
2188
2189 err = -EFBIG;
2190 limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
2191 if (limit != RLIM_INFINITY && size > (loff_t)limit) {
2192 send_sig(SIGXFSZ, current, 0);
2193 goto out;
2194 }
2195 if (size > inode->i_sb->s_maxbytes)
2196 goto out;
2197
Nick Piggin89e10782007-10-16 01:25:07 -07002198 err = pagecache_write_begin(NULL, mapping, size, 0,
2199 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2200 &page, &fsdata);
2201 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002202 goto out;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002203
Nick Piggin89e10782007-10-16 01:25:07 -07002204 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2205 BUG_ON(err > 0);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002206
Linus Torvalds1da177e2005-04-16 15:20:36 -07002207out:
2208 return err;
2209}
2210
Nick Piggin89e10782007-10-16 01:25:07 -07002211int cont_expand_zero(struct file *file, struct address_space *mapping,
2212 loff_t pos, loff_t *bytes)
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002213{
Nick Piggin89e10782007-10-16 01:25:07 -07002214 struct inode *inode = mapping->host;
2215 unsigned blocksize = 1 << inode->i_blkbits;
2216 struct page *page;
2217 void *fsdata;
2218 pgoff_t index, curidx;
2219 loff_t curpos;
2220 unsigned zerofrom, offset, len;
2221 int err = 0;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002222
Nick Piggin89e10782007-10-16 01:25:07 -07002223 index = pos >> PAGE_CACHE_SHIFT;
2224 offset = pos & ~PAGE_CACHE_MASK;
2225
2226 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
2227 zerofrom = curpos & ~PAGE_CACHE_MASK;
2228 if (zerofrom & (blocksize-1)) {
2229 *bytes |= (blocksize-1);
2230 (*bytes)++;
2231 }
2232 len = PAGE_CACHE_SIZE - zerofrom;
2233
2234 err = pagecache_write_begin(file, mapping, curpos, len,
2235 AOP_FLAG_UNINTERRUPTIBLE,
2236 &page, &fsdata);
2237 if (err)
2238 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002239 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002240 err = pagecache_write_end(file, mapping, curpos, len, len,
2241 page, fsdata);
2242 if (err < 0)
2243 goto out;
2244 BUG_ON(err != len);
2245 err = 0;
2246 }
2247
2248 /* page covers the boundary, find the boundary offset */
2249 if (index == curidx) {
2250 zerofrom = curpos & ~PAGE_CACHE_MASK;
2251 /* if we will expand the thing last block will be filled */
2252 if (offset <= zerofrom) {
2253 goto out;
2254 }
2255 if (zerofrom & (blocksize-1)) {
2256 *bytes |= (blocksize-1);
2257 (*bytes)++;
2258 }
2259 len = offset - zerofrom;
2260
2261 err = pagecache_write_begin(file, mapping, curpos, len,
2262 AOP_FLAG_UNINTERRUPTIBLE,
2263 &page, &fsdata);
2264 if (err)
2265 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002266 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002267 err = pagecache_write_end(file, mapping, curpos, len, len,
2268 page, fsdata);
2269 if (err < 0)
2270 goto out;
2271 BUG_ON(err != len);
2272 err = 0;
2273 }
2274out:
2275 return err;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002276}
2277
Linus Torvalds1da177e2005-04-16 15:20:36 -07002278/*
2279 * For moronic filesystems that do not allow holes in file.
2280 * We may have to extend the file.
2281 */
Nick Piggin89e10782007-10-16 01:25:07 -07002282int cont_write_begin(struct file *file, struct address_space *mapping,
2283 loff_t pos, unsigned len, unsigned flags,
2284 struct page **pagep, void **fsdata,
2285 get_block_t *get_block, loff_t *bytes)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002286{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002287 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002288 unsigned blocksize = 1 << inode->i_blkbits;
Nick Piggin89e10782007-10-16 01:25:07 -07002289 unsigned zerofrom;
2290 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002291
Nick Piggin89e10782007-10-16 01:25:07 -07002292 err = cont_expand_zero(file, mapping, pos, bytes);
2293 if (err)
2294 goto out;
2295
2296 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2297 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2298 *bytes |= (blocksize-1);
2299 (*bytes)++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002300 }
2301
Nick Piggin89e10782007-10-16 01:25:07 -07002302 *pagep = NULL;
2303 err = block_write_begin(file, mapping, pos, len,
2304 flags, pagep, fsdata, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002305out:
Nick Piggin89e10782007-10-16 01:25:07 -07002306 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002307}
2308
2309int block_prepare_write(struct page *page, unsigned from, unsigned to,
2310 get_block_t *get_block)
2311{
2312 struct inode *inode = page->mapping->host;
2313 int err = __block_prepare_write(inode, page, from, to, get_block);
2314 if (err)
2315 ClearPageUptodate(page);
2316 return err;
2317}
2318
2319int block_commit_write(struct page *page, unsigned from, unsigned to)
2320{
2321 struct inode *inode = page->mapping->host;
2322 __block_commit_write(inode,page,from,to);
2323 return 0;
2324}
2325
2326int generic_commit_write(struct file *file, struct page *page,
2327 unsigned from, unsigned to)
2328{
2329 struct inode *inode = page->mapping->host;
2330 loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
2331 __block_commit_write(inode,page,from,to);
2332 /*
2333 * No need to use i_size_read() here, the i_size
Jes Sorensen1b1dcc12006-01-09 15:59:24 -08002334 * cannot change under us because we hold i_mutex.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002335 */
2336 if (pos > inode->i_size) {
2337 i_size_write(inode, pos);
2338 mark_inode_dirty(inode);
2339 }
2340 return 0;
2341}
2342
David Chinner54171692007-07-19 17:39:55 +10002343/*
2344 * block_page_mkwrite() is not allowed to change the file size as it gets
2345 * called from a page fault handler when a page is first dirtied. Hence we must
2346 * be careful to check for EOF conditions here. We set the page up correctly
2347 * for a written page which means we get ENOSPC checking when writing into
2348 * holes and correct delalloc and unwritten extent mapping on filesystems that
2349 * support these features.
2350 *
2351 * We are not allowed to take the i_mutex here so we have to play games to
2352 * protect against truncate races as the page could now be beyond EOF. Because
2353 * vmtruncate() writes the inode size before removing pages, once we have the
2354 * page lock we can determine safely if the page is beyond EOF. If it is not
2355 * beyond EOF, then the page is guaranteed safe against truncation until we
2356 * unlock the page.
2357 */
2358int
2359block_page_mkwrite(struct vm_area_struct *vma, struct page *page,
2360 get_block_t get_block)
2361{
2362 struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
2363 unsigned long end;
2364 loff_t size;
2365 int ret = -EINVAL;
2366
2367 lock_page(page);
2368 size = i_size_read(inode);
2369 if ((page->mapping != inode->i_mapping) ||
Nick Piggin18336332007-07-20 00:31:45 -07002370 (page_offset(page) > size)) {
David Chinner54171692007-07-19 17:39:55 +10002371 /* page got truncated out from underneath us */
2372 goto out_unlock;
2373 }
2374
2375 /* page is wholly or partially inside EOF */
2376 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
2377 end = size & ~PAGE_CACHE_MASK;
2378 else
2379 end = PAGE_CACHE_SIZE;
2380
2381 ret = block_prepare_write(page, 0, end, get_block);
2382 if (!ret)
2383 ret = block_commit_write(page, 0, end);
2384
2385out_unlock:
2386 unlock_page(page);
2387 return ret;
2388}
Linus Torvalds1da177e2005-04-16 15:20:36 -07002389
2390/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002391 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
Linus Torvalds1da177e2005-04-16 15:20:36 -07002392 * immediately, while under the page lock. So it needs a special end_io
2393 * handler which does not touch the bh after unlocking it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002394 */
2395static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2396{
Dmitry Monakhov68671f32007-10-16 01:24:47 -07002397 __end_buffer_read_notouch(bh, uptodate);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002398}
2399
2400/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002401 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2402 * the page (converting it to circular linked list and taking care of page
2403 * dirty races).
2404 */
2405static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2406{
2407 struct buffer_head *bh;
2408
2409 BUG_ON(!PageLocked(page));
2410
2411 spin_lock(&page->mapping->private_lock);
2412 bh = head;
2413 do {
2414 if (PageDirty(page))
2415 set_buffer_dirty(bh);
2416 if (!bh->b_this_page)
2417 bh->b_this_page = head;
2418 bh = bh->b_this_page;
2419 } while (bh != head);
2420 attach_page_buffers(page, head);
2421 spin_unlock(&page->mapping->private_lock);
2422}
2423
2424/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002425 * On entry, the page is fully not uptodate.
2426 * On exit the page is fully uptodate in the areas outside (from,to)
2427 */
Nick Piggin03158cd2007-10-16 01:25:25 -07002428int nobh_write_begin(struct file *file, struct address_space *mapping,
2429 loff_t pos, unsigned len, unsigned flags,
2430 struct page **pagep, void **fsdata,
Linus Torvalds1da177e2005-04-16 15:20:36 -07002431 get_block_t *get_block)
2432{
Nick Piggin03158cd2007-10-16 01:25:25 -07002433 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002434 const unsigned blkbits = inode->i_blkbits;
2435 const unsigned blocksize = 1 << blkbits;
Nick Piggina4b06722007-10-16 01:24:48 -07002436 struct buffer_head *head, *bh;
Nick Piggin03158cd2007-10-16 01:25:25 -07002437 struct page *page;
2438 pgoff_t index;
2439 unsigned from, to;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002440 unsigned block_in_page;
Nick Piggina4b06722007-10-16 01:24:48 -07002441 unsigned block_start, block_end;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002442 sector_t block_in_file;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002443 int nr_reads = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002444 int ret = 0;
2445 int is_mapped_to_disk = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002446
Nick Piggin03158cd2007-10-16 01:25:25 -07002447 index = pos >> PAGE_CACHE_SHIFT;
2448 from = pos & (PAGE_CACHE_SIZE - 1);
2449 to = from + len;
2450
2451 page = __grab_cache_page(mapping, index);
2452 if (!page)
2453 return -ENOMEM;
2454 *pagep = page;
2455 *fsdata = NULL;
2456
2457 if (page_has_buffers(page)) {
2458 unlock_page(page);
2459 page_cache_release(page);
2460 *pagep = NULL;
2461 return block_write_begin(file, mapping, pos, len, flags, pagep,
2462 fsdata, get_block);
2463 }
Nick Piggina4b06722007-10-16 01:24:48 -07002464
Linus Torvalds1da177e2005-04-16 15:20:36 -07002465 if (PageMappedToDisk(page))
2466 return 0;
2467
Nick Piggina4b06722007-10-16 01:24:48 -07002468 /*
2469 * Allocate buffers so that we can keep track of state, and potentially
2470 * attach them to the page if an error occurs. In the common case of
2471 * no error, they will just be freed again without ever being attached
2472 * to the page (which is all OK, because we're under the page lock).
2473 *
2474 * Be careful: the buffer linked list is a NULL terminated one, rather
2475 * than the circular one we're used to.
2476 */
2477 head = alloc_page_buffers(page, blocksize, 0);
Nick Piggin03158cd2007-10-16 01:25:25 -07002478 if (!head) {
2479 ret = -ENOMEM;
2480 goto out_release;
2481 }
Nick Piggina4b06722007-10-16 01:24:48 -07002482
Linus Torvalds1da177e2005-04-16 15:20:36 -07002483 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002484
2485 /*
2486 * We loop across all blocks in the page, whether or not they are
2487 * part of the affected region. This is so we can discover if the
2488 * page is fully mapped-to-disk.
2489 */
Nick Piggina4b06722007-10-16 01:24:48 -07002490 for (block_start = 0, block_in_page = 0, bh = head;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002491 block_start < PAGE_CACHE_SIZE;
Nick Piggina4b06722007-10-16 01:24:48 -07002492 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002493 int create;
2494
Nick Piggina4b06722007-10-16 01:24:48 -07002495 block_end = block_start + blocksize;
2496 bh->b_state = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002497 create = 1;
2498 if (block_start >= to)
2499 create = 0;
2500 ret = get_block(inode, block_in_file + block_in_page,
Nick Piggina4b06722007-10-16 01:24:48 -07002501 bh, create);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002502 if (ret)
2503 goto failed;
Nick Piggina4b06722007-10-16 01:24:48 -07002504 if (!buffer_mapped(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002505 is_mapped_to_disk = 0;
Nick Piggina4b06722007-10-16 01:24:48 -07002506 if (buffer_new(bh))
2507 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
2508 if (PageUptodate(page)) {
2509 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002510 continue;
Nick Piggina4b06722007-10-16 01:24:48 -07002511 }
2512 if (buffer_new(bh) || !buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002513 zero_user_segments(page, block_start, from,
2514 to, block_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002515 continue;
2516 }
Nick Piggina4b06722007-10-16 01:24:48 -07002517 if (buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002518 continue; /* reiserfs does this */
2519 if (block_start < from || block_end > to) {
Nick Piggina4b06722007-10-16 01:24:48 -07002520 lock_buffer(bh);
2521 bh->b_end_io = end_buffer_read_nobh;
2522 submit_bh(READ, bh);
2523 nr_reads++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002524 }
2525 }
2526
2527 if (nr_reads) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002528 /*
2529 * The page is locked, so these buffers are protected from
2530 * any VM or truncate activity. Hence we don't need to care
2531 * for the buffer_head refcounts.
2532 */
Nick Piggina4b06722007-10-16 01:24:48 -07002533 for (bh = head; bh; bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002534 wait_on_buffer(bh);
2535 if (!buffer_uptodate(bh))
2536 ret = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002537 }
2538 if (ret)
2539 goto failed;
2540 }
2541
2542 if (is_mapped_to_disk)
2543 SetPageMappedToDisk(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002544
Nick Piggin03158cd2007-10-16 01:25:25 -07002545 *fsdata = head; /* to be released by nobh_write_end */
Nick Piggina4b06722007-10-16 01:24:48 -07002546
Linus Torvalds1da177e2005-04-16 15:20:36 -07002547 return 0;
2548
2549failed:
Nick Piggin03158cd2007-10-16 01:25:25 -07002550 BUG_ON(!ret);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002551 /*
Nick Piggina4b06722007-10-16 01:24:48 -07002552 * Error recovery is a bit difficult. We need to zero out blocks that
2553 * were newly allocated, and dirty them to ensure they get written out.
2554 * Buffers need to be attached to the page at this point, otherwise
2555 * the handling of potential IO errors during writeout would be hard
2556 * (could try doing synchronous writeout, but what if that fails too?)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002557 */
Nick Piggin03158cd2007-10-16 01:25:25 -07002558 attach_nobh_buffers(page, head);
2559 page_zero_new_buffers(page, from, to);
Nick Piggina4b06722007-10-16 01:24:48 -07002560
Nick Piggin03158cd2007-10-16 01:25:25 -07002561out_release:
2562 unlock_page(page);
2563 page_cache_release(page);
2564 *pagep = NULL;
Nick Piggina4b06722007-10-16 01:24:48 -07002565
Nick Piggin03158cd2007-10-16 01:25:25 -07002566 if (pos + len > inode->i_size)
2567 vmtruncate(inode, inode->i_size);
Nick Piggina4b06722007-10-16 01:24:48 -07002568
Linus Torvalds1da177e2005-04-16 15:20:36 -07002569 return ret;
2570}
Nick Piggin03158cd2007-10-16 01:25:25 -07002571EXPORT_SYMBOL(nobh_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002572
Nick Piggin03158cd2007-10-16 01:25:25 -07002573int nobh_write_end(struct file *file, struct address_space *mapping,
2574 loff_t pos, unsigned len, unsigned copied,
2575 struct page *page, void *fsdata)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002576{
2577 struct inode *inode = page->mapping->host;
Nick Pigginefdc3132007-10-21 06:57:41 +02002578 struct buffer_head *head = fsdata;
Nick Piggin03158cd2007-10-16 01:25:25 -07002579 struct buffer_head *bh;
Dmitri Monakhov5b41e742008-03-28 14:15:52 -07002580 BUG_ON(fsdata != NULL && page_has_buffers(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002581
Dmitri Monakhov5b41e742008-03-28 14:15:52 -07002582 if (unlikely(copied < len) && !page_has_buffers(page))
2583 attach_nobh_buffers(page, head);
2584 if (page_has_buffers(page))
2585 return generic_write_end(file, mapping, pos, len,
2586 copied, page, fsdata);
Nick Piggina4b06722007-10-16 01:24:48 -07002587
Nick Piggin22c8ca72007-02-20 13:58:09 -08002588 SetPageUptodate(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002589 set_page_dirty(page);
Nick Piggin03158cd2007-10-16 01:25:25 -07002590 if (pos+copied > inode->i_size) {
2591 i_size_write(inode, pos+copied);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002592 mark_inode_dirty(inode);
2593 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002594
2595 unlock_page(page);
2596 page_cache_release(page);
2597
Nick Piggin03158cd2007-10-16 01:25:25 -07002598 while (head) {
2599 bh = head;
2600 head = head->b_this_page;
2601 free_buffer_head(bh);
2602 }
2603
2604 return copied;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002605}
Nick Piggin03158cd2007-10-16 01:25:25 -07002606EXPORT_SYMBOL(nobh_write_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002607
2608/*
2609 * nobh_writepage() - based on block_full_write_page() except
2610 * that it tries to operate without attaching bufferheads to
2611 * the page.
2612 */
2613int nobh_writepage(struct page *page, get_block_t *get_block,
2614 struct writeback_control *wbc)
2615{
2616 struct inode * const inode = page->mapping->host;
2617 loff_t i_size = i_size_read(inode);
2618 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2619 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002620 int ret;
2621
2622 /* Is the page fully inside i_size? */
2623 if (page->index < end_index)
2624 goto out;
2625
2626 /* Is the page fully outside i_size? (truncate in progress) */
2627 offset = i_size & (PAGE_CACHE_SIZE-1);
2628 if (page->index >= end_index+1 || !offset) {
2629 /*
2630 * The page may have dirty, unmapped buffers. For example,
2631 * they may have been added in ext3_writepage(). Make them
2632 * freeable here, so the page does not leak.
2633 */
2634#if 0
2635 /* Not really sure about this - do we need this ? */
2636 if (page->mapping->a_ops->invalidatepage)
2637 page->mapping->a_ops->invalidatepage(page, offset);
2638#endif
2639 unlock_page(page);
2640 return 0; /* don't care */
2641 }
2642
2643 /*
2644 * The page straddles i_size. It must be zeroed out on each and every
2645 * writepage invocation because it may be mmapped. "A file is mapped
2646 * in multiples of the page size. For a file that is not a multiple of
2647 * the page size, the remaining memory is zeroed when mapped, and
2648 * writes to that region are not written out to the file."
2649 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002650 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002651out:
2652 ret = mpage_writepage(page, get_block, wbc);
2653 if (ret == -EAGAIN)
2654 ret = __block_write_full_page(inode, page, get_block, wbc);
2655 return ret;
2656}
2657EXPORT_SYMBOL(nobh_writepage);
2658
Nick Piggin03158cd2007-10-16 01:25:25 -07002659int nobh_truncate_page(struct address_space *mapping,
2660 loff_t from, get_block_t *get_block)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002661{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002662 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2663 unsigned offset = from & (PAGE_CACHE_SIZE-1);
Nick Piggin03158cd2007-10-16 01:25:25 -07002664 unsigned blocksize;
2665 sector_t iblock;
2666 unsigned length, pos;
2667 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002668 struct page *page;
Nick Piggin03158cd2007-10-16 01:25:25 -07002669 struct buffer_head map_bh;
2670 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002671
Nick Piggin03158cd2007-10-16 01:25:25 -07002672 blocksize = 1 << inode->i_blkbits;
2673 length = offset & (blocksize - 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002674
Nick Piggin03158cd2007-10-16 01:25:25 -07002675 /* Block boundary? Nothing to do */
2676 if (!length)
2677 return 0;
2678
2679 length = blocksize - length;
2680 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2681
Linus Torvalds1da177e2005-04-16 15:20:36 -07002682 page = grab_cache_page(mapping, index);
Nick Piggin03158cd2007-10-16 01:25:25 -07002683 err = -ENOMEM;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002684 if (!page)
2685 goto out;
2686
Nick Piggin03158cd2007-10-16 01:25:25 -07002687 if (page_has_buffers(page)) {
2688has_buffers:
2689 unlock_page(page);
2690 page_cache_release(page);
2691 return block_truncate_page(mapping, from, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002692 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002693
2694 /* Find the buffer that contains "offset" */
2695 pos = blocksize;
2696 while (offset >= pos) {
2697 iblock++;
2698 pos += blocksize;
2699 }
2700
2701 err = get_block(inode, iblock, &map_bh, 0);
2702 if (err)
2703 goto unlock;
2704 /* unmapped? It's a hole - nothing to do */
2705 if (!buffer_mapped(&map_bh))
2706 goto unlock;
2707
2708 /* Ok, it's mapped. Make sure it's up-to-date */
2709 if (!PageUptodate(page)) {
2710 err = mapping->a_ops->readpage(NULL, page);
2711 if (err) {
2712 page_cache_release(page);
2713 goto out;
2714 }
2715 lock_page(page);
2716 if (!PageUptodate(page)) {
2717 err = -EIO;
2718 goto unlock;
2719 }
2720 if (page_has_buffers(page))
2721 goto has_buffers;
2722 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002723 zero_user(page, offset, length);
Nick Piggin03158cd2007-10-16 01:25:25 -07002724 set_page_dirty(page);
2725 err = 0;
2726
2727unlock:
Linus Torvalds1da177e2005-04-16 15:20:36 -07002728 unlock_page(page);
2729 page_cache_release(page);
2730out:
Nick Piggin03158cd2007-10-16 01:25:25 -07002731 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002732}
2733EXPORT_SYMBOL(nobh_truncate_page);
2734
2735int block_truncate_page(struct address_space *mapping,
2736 loff_t from, get_block_t *get_block)
2737{
2738 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2739 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2740 unsigned blocksize;
Andrew Morton54b21a72006-01-08 01:03:05 -08002741 sector_t iblock;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002742 unsigned length, pos;
2743 struct inode *inode = mapping->host;
2744 struct page *page;
2745 struct buffer_head *bh;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002746 int err;
2747
2748 blocksize = 1 << inode->i_blkbits;
2749 length = offset & (blocksize - 1);
2750
2751 /* Block boundary? Nothing to do */
2752 if (!length)
2753 return 0;
2754
2755 length = blocksize - length;
Andrew Morton54b21a72006-01-08 01:03:05 -08002756 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002757
2758 page = grab_cache_page(mapping, index);
2759 err = -ENOMEM;
2760 if (!page)
2761 goto out;
2762
2763 if (!page_has_buffers(page))
2764 create_empty_buffers(page, blocksize, 0);
2765
2766 /* Find the buffer that contains "offset" */
2767 bh = page_buffers(page);
2768 pos = blocksize;
2769 while (offset >= pos) {
2770 bh = bh->b_this_page;
2771 iblock++;
2772 pos += blocksize;
2773 }
2774
2775 err = 0;
2776 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002777 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002778 err = get_block(inode, iblock, bh, 0);
2779 if (err)
2780 goto unlock;
2781 /* unmapped? It's a hole - nothing to do */
2782 if (!buffer_mapped(bh))
2783 goto unlock;
2784 }
2785
2786 /* Ok, it's mapped. Make sure it's up-to-date */
2787 if (PageUptodate(page))
2788 set_buffer_uptodate(bh);
2789
David Chinner33a266d2007-02-12 00:51:41 -08002790 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002791 err = -EIO;
2792 ll_rw_block(READ, 1, &bh);
2793 wait_on_buffer(bh);
2794 /* Uhhuh. Read error. Complain and punt. */
2795 if (!buffer_uptodate(bh))
2796 goto unlock;
2797 }
2798
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002799 zero_user(page, offset, length);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002800 mark_buffer_dirty(bh);
2801 err = 0;
2802
2803unlock:
2804 unlock_page(page);
2805 page_cache_release(page);
2806out:
2807 return err;
2808}
2809
2810/*
2811 * The generic ->writepage function for buffer-backed address_spaces
2812 */
2813int block_write_full_page(struct page *page, get_block_t *get_block,
2814 struct writeback_control *wbc)
2815{
2816 struct inode * const inode = page->mapping->host;
2817 loff_t i_size = i_size_read(inode);
2818 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2819 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002820
2821 /* Is the page fully inside i_size? */
2822 if (page->index < end_index)
2823 return __block_write_full_page(inode, page, get_block, wbc);
2824
2825 /* Is the page fully outside i_size? (truncate in progress) */
2826 offset = i_size & (PAGE_CACHE_SIZE-1);
2827 if (page->index >= end_index+1 || !offset) {
2828 /*
2829 * The page may have dirty, unmapped buffers. For example,
2830 * they may have been added in ext3_writepage(). Make them
2831 * freeable here, so the page does not leak.
2832 */
Jan Karaaaa40592005-10-30 15:00:16 -08002833 do_invalidatepage(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002834 unlock_page(page);
2835 return 0; /* don't care */
2836 }
2837
2838 /*
2839 * The page straddles i_size. It must be zeroed out on each and every
2840 * writepage invokation because it may be mmapped. "A file is mapped
2841 * in multiples of the page size. For a file that is not a multiple of
2842 * the page size, the remaining memory is zeroed when mapped, and
2843 * writes to that region are not written out to the file."
2844 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002845 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002846 return __block_write_full_page(inode, page, get_block, wbc);
2847}
2848
2849sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2850 get_block_t *get_block)
2851{
2852 struct buffer_head tmp;
2853 struct inode *inode = mapping->host;
2854 tmp.b_state = 0;
2855 tmp.b_blocknr = 0;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002856 tmp.b_size = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002857 get_block(inode, block, &tmp, 0);
2858 return tmp.b_blocknr;
2859}
2860
NeilBrown6712ecf2007-09-27 12:47:43 +02002861static void end_bio_bh_io_sync(struct bio *bio, int err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002862{
2863 struct buffer_head *bh = bio->bi_private;
2864
Linus Torvalds1da177e2005-04-16 15:20:36 -07002865 if (err == -EOPNOTSUPP) {
2866 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
2867 set_bit(BH_Eopnotsupp, &bh->b_state);
2868 }
2869
2870 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2871 bio_put(bio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002872}
2873
2874int submit_bh(int rw, struct buffer_head * bh)
2875{
2876 struct bio *bio;
2877 int ret = 0;
2878
2879 BUG_ON(!buffer_locked(bh));
2880 BUG_ON(!buffer_mapped(bh));
2881 BUG_ON(!bh->b_end_io);
2882
2883 if (buffer_ordered(bh) && (rw == WRITE))
2884 rw = WRITE_BARRIER;
2885
2886 /*
2887 * Only clear out a write error when rewriting, should this
2888 * include WRITE_SYNC as well?
2889 */
2890 if (test_set_buffer_req(bh) && (rw == WRITE || rw == WRITE_BARRIER))
2891 clear_buffer_write_io_error(bh);
2892
2893 /*
2894 * from here on down, it's all bio -- do the initial mapping,
2895 * submit_bio -> generic_make_request may further map this bio around
2896 */
2897 bio = bio_alloc(GFP_NOIO, 1);
2898
2899 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2900 bio->bi_bdev = bh->b_bdev;
2901 bio->bi_io_vec[0].bv_page = bh->b_page;
2902 bio->bi_io_vec[0].bv_len = bh->b_size;
2903 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
2904
2905 bio->bi_vcnt = 1;
2906 bio->bi_idx = 0;
2907 bio->bi_size = bh->b_size;
2908
2909 bio->bi_end_io = end_bio_bh_io_sync;
2910 bio->bi_private = bh;
2911
2912 bio_get(bio);
2913 submit_bio(rw, bio);
2914
2915 if (bio_flagged(bio, BIO_EOPNOTSUPP))
2916 ret = -EOPNOTSUPP;
2917
2918 bio_put(bio);
2919 return ret;
2920}
2921
2922/**
2923 * ll_rw_block: low-level access to block devices (DEPRECATED)
Jan Karaa7662232005-09-06 15:19:10 -07002924 * @rw: whether to %READ or %WRITE or %SWRITE or maybe %READA (readahead)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002925 * @nr: number of &struct buffer_heads in the array
2926 * @bhs: array of pointers to &struct buffer_head
2927 *
Jan Karaa7662232005-09-06 15:19:10 -07002928 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
2929 * requests an I/O operation on them, either a %READ or a %WRITE. The third
2930 * %SWRITE is like %WRITE only we make sure that the *current* data in buffers
2931 * are sent to disk. The fourth %READA option is described in the documentation
2932 * for generic_make_request() which ll_rw_block() calls.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002933 *
2934 * This function drops any buffer that it cannot get a lock on (with the
Jan Karaa7662232005-09-06 15:19:10 -07002935 * BH_Lock state bit) unless SWRITE is required, any buffer that appears to be
2936 * clean when doing a write request, and any buffer that appears to be
2937 * up-to-date when doing read request. Further it marks as clean buffers that
2938 * are processed for writing (the buffer cache won't assume that they are
2939 * actually clean until the buffer gets unlocked).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002940 *
2941 * ll_rw_block sets b_end_io to simple completion handler that marks
2942 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
2943 * any waiters.
2944 *
2945 * All of the buffers must be for the same device, and must also be a
2946 * multiple of the current approved size for the device.
2947 */
2948void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
2949{
2950 int i;
2951
2952 for (i = 0; i < nr; i++) {
2953 struct buffer_head *bh = bhs[i];
2954
Jan Karaa7662232005-09-06 15:19:10 -07002955 if (rw == SWRITE)
2956 lock_buffer(bh);
2957 else if (test_set_buffer_locked(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002958 continue;
2959
Jan Karaa7662232005-09-06 15:19:10 -07002960 if (rw == WRITE || rw == SWRITE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002961 if (test_clear_buffer_dirty(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07002962 bh->b_end_io = end_buffer_write_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08002963 get_bh(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002964 submit_bh(WRITE, bh);
2965 continue;
2966 }
2967 } else {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002968 if (!buffer_uptodate(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07002969 bh->b_end_io = end_buffer_read_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08002970 get_bh(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002971 submit_bh(rw, bh);
2972 continue;
2973 }
2974 }
2975 unlock_buffer(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002976 }
2977}
2978
2979/*
2980 * For a data-integrity writeout, we need to wait upon any in-progress I/O
2981 * and then start new I/O and then wait upon it. The caller must have a ref on
2982 * the buffer_head.
2983 */
2984int sync_dirty_buffer(struct buffer_head *bh)
2985{
2986 int ret = 0;
2987
2988 WARN_ON(atomic_read(&bh->b_count) < 1);
2989 lock_buffer(bh);
2990 if (test_clear_buffer_dirty(bh)) {
2991 get_bh(bh);
2992 bh->b_end_io = end_buffer_write_sync;
2993 ret = submit_bh(WRITE, bh);
2994 wait_on_buffer(bh);
2995 if (buffer_eopnotsupp(bh)) {
2996 clear_buffer_eopnotsupp(bh);
2997 ret = -EOPNOTSUPP;
2998 }
2999 if (!ret && !buffer_uptodate(bh))
3000 ret = -EIO;
3001 } else {
3002 unlock_buffer(bh);
3003 }
3004 return ret;
3005}
3006
3007/*
3008 * try_to_free_buffers() checks if all the buffers on this particular page
3009 * are unused, and releases them if so.
3010 *
3011 * Exclusion against try_to_free_buffers may be obtained by either
3012 * locking the page or by holding its mapping's private_lock.
3013 *
3014 * If the page is dirty but all the buffers are clean then we need to
3015 * be sure to mark the page clean as well. This is because the page
3016 * may be against a block device, and a later reattachment of buffers
3017 * to a dirty page will set *all* buffers dirty. Which would corrupt
3018 * filesystem data on the same device.
3019 *
3020 * The same applies to regular filesystem pages: if all the buffers are
3021 * clean then we set the page clean and proceed. To do that, we require
3022 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3023 * private_lock.
3024 *
3025 * try_to_free_buffers() is non-blocking.
3026 */
3027static inline int buffer_busy(struct buffer_head *bh)
3028{
3029 return atomic_read(&bh->b_count) |
3030 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3031}
3032
3033static int
3034drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3035{
3036 struct buffer_head *head = page_buffers(page);
3037 struct buffer_head *bh;
3038
3039 bh = head;
3040 do {
akpm@osdl.orgde7d5a32005-05-01 08:58:39 -07003041 if (buffer_write_io_error(bh) && page->mapping)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003042 set_bit(AS_EIO, &page->mapping->flags);
3043 if (buffer_busy(bh))
3044 goto failed;
3045 bh = bh->b_this_page;
3046 } while (bh != head);
3047
3048 do {
3049 struct buffer_head *next = bh->b_this_page;
3050
Jan Kara535ee2f2008-02-08 04:21:59 -08003051 if (bh->b_assoc_map)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003052 __remove_assoc_queue(bh);
3053 bh = next;
3054 } while (bh != head);
3055 *buffers_to_free = head;
3056 __clear_page_buffers(page);
3057 return 1;
3058failed:
3059 return 0;
3060}
3061
3062int try_to_free_buffers(struct page *page)
3063{
3064 struct address_space * const mapping = page->mapping;
3065 struct buffer_head *buffers_to_free = NULL;
3066 int ret = 0;
3067
3068 BUG_ON(!PageLocked(page));
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003069 if (PageWriteback(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003070 return 0;
3071
3072 if (mapping == NULL) { /* can this still happen? */
3073 ret = drop_buffers(page, &buffers_to_free);
3074 goto out;
3075 }
3076
3077 spin_lock(&mapping->private_lock);
3078 ret = drop_buffers(page, &buffers_to_free);
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003079
3080 /*
3081 * If the filesystem writes its buffers by hand (eg ext3)
3082 * then we can have clean buffers against a dirty page. We
3083 * clean the page here; otherwise the VM will never notice
3084 * that the filesystem did any IO at all.
3085 *
3086 * Also, during truncate, discard_buffer will have marked all
3087 * the page's buffers clean. We discover that here and clean
3088 * the page also.
Nick Piggin87df7242007-01-30 14:36:27 +11003089 *
3090 * private_lock must be held over this entire operation in order
3091 * to synchronise against __set_page_dirty_buffers and prevent the
3092 * dirty bit from being lost.
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003093 */
3094 if (ret)
3095 cancel_dirty_page(page, PAGE_CACHE_SIZE);
Nick Piggin87df7242007-01-30 14:36:27 +11003096 spin_unlock(&mapping->private_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003097out:
3098 if (buffers_to_free) {
3099 struct buffer_head *bh = buffers_to_free;
3100
3101 do {
3102 struct buffer_head *next = bh->b_this_page;
3103 free_buffer_head(bh);
3104 bh = next;
3105 } while (bh != buffers_to_free);
3106 }
3107 return ret;
3108}
3109EXPORT_SYMBOL(try_to_free_buffers);
3110
NeilBrown3978d712006-03-26 01:37:17 -08003111void block_sync_page(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003112{
3113 struct address_space *mapping;
3114
3115 smp_mb();
3116 mapping = page_mapping(page);
3117 if (mapping)
3118 blk_run_backing_dev(mapping->backing_dev_info, page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003119}
3120
3121/*
3122 * There are no bdflush tunables left. But distributions are
3123 * still running obsolete flush daemons, so we terminate them here.
3124 *
3125 * Use of bdflush() is deprecated and will be removed in a future kernel.
3126 * The `pdflush' kernel threads fully replace bdflush daemons and this call.
3127 */
3128asmlinkage long sys_bdflush(int func, long data)
3129{
3130 static int msg_count;
3131
3132 if (!capable(CAP_SYS_ADMIN))
3133 return -EPERM;
3134
3135 if (msg_count < 5) {
3136 msg_count++;
3137 printk(KERN_INFO
3138 "warning: process `%s' used the obsolete bdflush"
3139 " system call\n", current->comm);
3140 printk(KERN_INFO "Fix your initscripts?\n");
3141 }
3142
3143 if (func == 1)
3144 do_exit(0);
3145 return 0;
3146}
3147
3148/*
3149 * Buffer-head allocation
3150 */
Christoph Lametere18b8902006-12-06 20:33:20 -08003151static struct kmem_cache *bh_cachep;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003152
3153/*
3154 * Once the number of bh's in the machine exceeds this level, we start
3155 * stripping them in writeback.
3156 */
3157static int max_buffer_heads;
3158
3159int buffer_heads_over_limit;
3160
3161struct bh_accounting {
3162 int nr; /* Number of live bh's */
3163 int ratelimit; /* Limit cacheline bouncing */
3164};
3165
3166static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3167
3168static void recalc_bh_state(void)
3169{
3170 int i;
3171 int tot = 0;
3172
3173 if (__get_cpu_var(bh_accounting).ratelimit++ < 4096)
3174 return;
3175 __get_cpu_var(bh_accounting).ratelimit = 0;
Eric Dumazet8a143422006-03-24 03:18:10 -08003176 for_each_online_cpu(i)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003177 tot += per_cpu(bh_accounting, i).nr;
3178 buffer_heads_over_limit = (tot > max_buffer_heads);
3179}
3180
Al Virodd0fc662005-10-07 07:46:04 +01003181struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003182{
Christoph Lameterb98938c2008-02-04 22:28:36 -08003183 struct buffer_head *ret = kmem_cache_alloc(bh_cachep,
Mel Gormane12ba742007-10-16 01:25:52 -07003184 set_migrateflags(gfp_flags, __GFP_RECLAIMABLE));
Linus Torvalds1da177e2005-04-16 15:20:36 -07003185 if (ret) {
Christoph Lametera35afb82007-05-16 22:10:57 -07003186 INIT_LIST_HEAD(&ret->b_assoc_buffers);
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07003187 get_cpu_var(bh_accounting).nr++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003188 recalc_bh_state();
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07003189 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003190 }
3191 return ret;
3192}
3193EXPORT_SYMBOL(alloc_buffer_head);
3194
3195void free_buffer_head(struct buffer_head *bh)
3196{
3197 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3198 kmem_cache_free(bh_cachep, bh);
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07003199 get_cpu_var(bh_accounting).nr--;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003200 recalc_bh_state();
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07003201 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003202}
3203EXPORT_SYMBOL(free_buffer_head);
3204
Linus Torvalds1da177e2005-04-16 15:20:36 -07003205static void buffer_exit_cpu(int cpu)
3206{
3207 int i;
3208 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3209
3210 for (i = 0; i < BH_LRU_SIZE; i++) {
3211 brelse(b->bhs[i]);
3212 b->bhs[i] = NULL;
3213 }
Eric Dumazet8a143422006-03-24 03:18:10 -08003214 get_cpu_var(bh_accounting).nr += per_cpu(bh_accounting, cpu).nr;
3215 per_cpu(bh_accounting, cpu).nr = 0;
3216 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003217}
3218
3219static int buffer_cpu_notify(struct notifier_block *self,
3220 unsigned long action, void *hcpu)
3221{
Rafael J. Wysocki8bb78442007-05-09 02:35:10 -07003222 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003223 buffer_exit_cpu((unsigned long)hcpu);
3224 return NOTIFY_OK;
3225}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003226
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003227/**
Randy Dunlapa6b91912008-03-19 17:01:00 -07003228 * bh_uptodate_or_lock - Test whether the buffer is uptodate
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003229 * @bh: struct buffer_head
3230 *
3231 * Return true if the buffer is up-to-date and false,
3232 * with the buffer locked, if not.
3233 */
3234int bh_uptodate_or_lock(struct buffer_head *bh)
3235{
3236 if (!buffer_uptodate(bh)) {
3237 lock_buffer(bh);
3238 if (!buffer_uptodate(bh))
3239 return 0;
3240 unlock_buffer(bh);
3241 }
3242 return 1;
3243}
3244EXPORT_SYMBOL(bh_uptodate_or_lock);
3245
3246/**
Randy Dunlapa6b91912008-03-19 17:01:00 -07003247 * bh_submit_read - Submit a locked buffer for reading
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003248 * @bh: struct buffer_head
3249 *
3250 * Returns zero on success and -EIO on error.
3251 */
3252int bh_submit_read(struct buffer_head *bh)
3253{
3254 BUG_ON(!buffer_locked(bh));
3255
3256 if (buffer_uptodate(bh)) {
3257 unlock_buffer(bh);
3258 return 0;
3259 }
3260
3261 get_bh(bh);
3262 bh->b_end_io = end_buffer_read_sync;
3263 submit_bh(READ, bh);
3264 wait_on_buffer(bh);
3265 if (buffer_uptodate(bh))
3266 return 0;
3267 return -EIO;
3268}
3269EXPORT_SYMBOL(bh_submit_read);
3270
Christoph Lameterb98938c2008-02-04 22:28:36 -08003271static void
3272init_buffer_head(struct kmem_cache *cachep, void *data)
3273{
3274 struct buffer_head *bh = data;
3275
3276 memset(bh, 0, sizeof(*bh));
3277 INIT_LIST_HEAD(&bh->b_assoc_buffers);
3278}
3279
Linus Torvalds1da177e2005-04-16 15:20:36 -07003280void __init buffer_init(void)
3281{
3282 int nrpages;
3283
Christoph Lameterb98938c2008-02-04 22:28:36 -08003284 bh_cachep = kmem_cache_create("buffer_head",
3285 sizeof(struct buffer_head), 0,
3286 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3287 SLAB_MEM_SPREAD),
3288 init_buffer_head);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003289
3290 /*
3291 * Limit the bh occupancy to 10% of ZONE_NORMAL
3292 */
3293 nrpages = (nr_free_buffer_pages() * 10) / 100;
3294 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3295 hotcpu_notifier(buffer_cpu_notify, 0);
3296}
3297
3298EXPORT_SYMBOL(__bforget);
3299EXPORT_SYMBOL(__brelse);
3300EXPORT_SYMBOL(__wait_on_buffer);
3301EXPORT_SYMBOL(block_commit_write);
3302EXPORT_SYMBOL(block_prepare_write);
David Chinner54171692007-07-19 17:39:55 +10003303EXPORT_SYMBOL(block_page_mkwrite);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003304EXPORT_SYMBOL(block_read_full_page);
3305EXPORT_SYMBOL(block_sync_page);
3306EXPORT_SYMBOL(block_truncate_page);
3307EXPORT_SYMBOL(block_write_full_page);
Nick Piggin89e10782007-10-16 01:25:07 -07003308EXPORT_SYMBOL(cont_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003309EXPORT_SYMBOL(end_buffer_read_sync);
3310EXPORT_SYMBOL(end_buffer_write_sync);
3311EXPORT_SYMBOL(file_fsync);
3312EXPORT_SYMBOL(fsync_bdev);
3313EXPORT_SYMBOL(generic_block_bmap);
3314EXPORT_SYMBOL(generic_commit_write);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08003315EXPORT_SYMBOL(generic_cont_expand_simple);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003316EXPORT_SYMBOL(init_buffer);
3317EXPORT_SYMBOL(invalidate_bdev);
3318EXPORT_SYMBOL(ll_rw_block);
3319EXPORT_SYMBOL(mark_buffer_dirty);
3320EXPORT_SYMBOL(submit_bh);
3321EXPORT_SYMBOL(sync_dirty_buffer);
3322EXPORT_SYMBOL(unlock_buffer);