blob: 891e1c78e4f1cdf2fef0a5737983f245901371a3 [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 Piggin51b07fc2008-10-18 20:27:00 -070079 clear_bit_unlock(BH_Lock, &bh->b_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -070080 smp_mb__after_clear_bit();
81 wake_up_bit(&bh->b_state, BH_Lock);
82}
83
84/*
85 * Block until a buffer comes unlocked. This doesn't stop it
86 * from becoming locked again - you have to lock it yourself
87 * if you want to preserve its state.
88 */
89void __wait_on_buffer(struct buffer_head * bh)
90{
91 wait_on_bit(&bh->b_state, BH_Lock, sync_buffer, TASK_UNINTERRUPTIBLE);
92}
93
94static void
95__clear_page_buffers(struct page *page)
96{
97 ClearPagePrivate(page);
Hugh Dickins4c21e2f2005-10-29 18:16:40 -070098 set_page_private(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -070099 page_cache_release(page);
100}
101
Keith Mannthey08bafc02008-11-25 10:24:35 +0100102
103static int quiet_error(struct buffer_head *bh)
104{
105 if (!test_bit(BH_Quiet, &bh->b_state) && printk_ratelimit())
106 return 0;
107 return 1;
108}
109
110
Linus Torvalds1da177e2005-04-16 15:20:36 -0700111static void buffer_io_error(struct buffer_head *bh)
112{
113 char b[BDEVNAME_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700114 printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
115 bdevname(bh->b_bdev, b),
116 (unsigned long long)bh->b_blocknr);
117}
118
119/*
Dmitry Monakhov68671f32007-10-16 01:24:47 -0700120 * End-of-IO handler helper function which does not touch the bh after
121 * unlocking it.
122 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
123 * a race there is benign: unlock_buffer() only use the bh's address for
124 * hashing after unlocking the buffer, so it doesn't actually touch the bh
125 * itself.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700126 */
Dmitry Monakhov68671f32007-10-16 01:24:47 -0700127static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700128{
129 if (uptodate) {
130 set_buffer_uptodate(bh);
131 } else {
132 /* This happens, due to failed READA attempts. */
133 clear_buffer_uptodate(bh);
134 }
135 unlock_buffer(bh);
Dmitry Monakhov68671f32007-10-16 01:24:47 -0700136}
137
138/*
139 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
140 * unlock the buffer. This is what ll_rw_block uses too.
141 */
142void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
143{
144 __end_buffer_read_notouch(bh, uptodate);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700145 put_bh(bh);
146}
147
148void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
149{
150 char b[BDEVNAME_SIZE];
151
152 if (uptodate) {
153 set_buffer_uptodate(bh);
154 } else {
Keith Mannthey08bafc02008-11-25 10:24:35 +0100155 if (!buffer_eopnotsupp(bh) && !quiet_error(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700156 buffer_io_error(bh);
157 printk(KERN_WARNING "lost page write due to "
158 "I/O error on %s\n",
159 bdevname(bh->b_bdev, b));
160 }
161 set_buffer_write_io_error(bh);
162 clear_buffer_uptodate(bh);
163 }
164 unlock_buffer(bh);
165 put_bh(bh);
166}
167
168/*
169 * Write out and wait upon all the dirty data associated with a block
170 * device via its mapping. Does not take the superblock lock.
171 */
172int sync_blockdev(struct block_device *bdev)
173{
174 int ret = 0;
175
OGAWA Hirofumi28fd1292006-01-08 01:02:14 -0800176 if (bdev)
177 ret = filemap_write_and_wait(bdev->bd_inode->i_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700178 return ret;
179}
180EXPORT_SYMBOL(sync_blockdev);
181
Linus Torvalds1da177e2005-04-16 15:20:36 -0700182/*
183 * Write out and wait upon all dirty data associated with this
184 * device. Filesystem data as well as the underlying block
185 * device. Takes the superblock lock.
186 */
187int fsync_bdev(struct block_device *bdev)
188{
189 struct super_block *sb = get_super(bdev);
190 if (sb) {
191 int res = fsync_super(sb);
192 drop_super(sb);
193 return res;
194 }
195 return sync_blockdev(bdev);
196}
197
198/**
199 * freeze_bdev -- lock a filesystem and force it into a consistent state
200 * @bdev: blockdevice to lock
201 *
David Chinnerf73ca1b2007-01-10 23:15:41 -0800202 * This takes the block device bd_mount_sem to make sure no new mounts
Linus Torvalds1da177e2005-04-16 15:20:36 -0700203 * happen on bdev until thaw_bdev() is called.
204 * If a superblock is found on this device, we take the s_umount semaphore
205 * on it to make sure nobody unmounts until the snapshot creation is done.
Takashi Satofcccf502009-01-09 16:40:59 -0800206 * The reference counter (bd_fsfreeze_count) guarantees that only the last
207 * unfreeze process can unfreeze the frozen filesystem actually when multiple
208 * freeze requests arrive simultaneously. It counts up in freeze_bdev() and
209 * count down in thaw_bdev(). When it becomes 0, thaw_bdev() will unfreeze
210 * actually.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700211 */
212struct super_block *freeze_bdev(struct block_device *bdev)
213{
214 struct super_block *sb;
Takashi Satofcccf502009-01-09 16:40:59 -0800215 int error = 0;
216
217 mutex_lock(&bdev->bd_fsfreeze_mutex);
218 if (bdev->bd_fsfreeze_count > 0) {
219 bdev->bd_fsfreeze_count++;
220 sb = get_super(bdev);
221 mutex_unlock(&bdev->bd_fsfreeze_mutex);
222 return sb;
223 }
224 bdev->bd_fsfreeze_count++;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700225
David Chinnerf73ca1b2007-01-10 23:15:41 -0800226 down(&bdev->bd_mount_sem);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700227 sb = get_super(bdev);
228 if (sb && !(sb->s_flags & MS_RDONLY)) {
229 sb->s_frozen = SB_FREEZE_WRITE;
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700230 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700231
OGAWA Hirofumid25b9a12006-03-25 03:07:44 -0800232 __fsync_super(sb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700233
234 sb->s_frozen = SB_FREEZE_TRANS;
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700235 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700236
237 sync_blockdev(sb->s_bdev);
238
Takashi Satofcccf502009-01-09 16:40:59 -0800239 if (sb->s_op->freeze_fs) {
240 error = sb->s_op->freeze_fs(sb);
241 if (error) {
242 printk(KERN_ERR
243 "VFS:Filesystem freeze failed\n");
244 sb->s_frozen = SB_UNFROZEN;
245 drop_super(sb);
246 up(&bdev->bd_mount_sem);
247 bdev->bd_fsfreeze_count--;
248 mutex_unlock(&bdev->bd_fsfreeze_mutex);
249 return ERR_PTR(error);
250 }
251 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700252 }
253
254 sync_blockdev(bdev);
Takashi Satofcccf502009-01-09 16:40:59 -0800255 mutex_unlock(&bdev->bd_fsfreeze_mutex);
256
Linus Torvalds1da177e2005-04-16 15:20:36 -0700257 return sb; /* thaw_bdev releases s->s_umount and bd_mount_sem */
258}
259EXPORT_SYMBOL(freeze_bdev);
260
261/**
262 * thaw_bdev -- unlock filesystem
263 * @bdev: blockdevice to unlock
264 * @sb: associated superblock
265 *
266 * Unlocks the filesystem and marks it writeable again after freeze_bdev().
267 */
Takashi Satofcccf502009-01-09 16:40:59 -0800268int thaw_bdev(struct block_device *bdev, struct super_block *sb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700269{
Takashi Satofcccf502009-01-09 16:40:59 -0800270 int error = 0;
271
272 mutex_lock(&bdev->bd_fsfreeze_mutex);
273 if (!bdev->bd_fsfreeze_count) {
274 mutex_unlock(&bdev->bd_fsfreeze_mutex);
275 return -EINVAL;
276 }
277
278 bdev->bd_fsfreeze_count--;
279 if (bdev->bd_fsfreeze_count > 0) {
280 if (sb)
281 drop_super(sb);
282 mutex_unlock(&bdev->bd_fsfreeze_mutex);
283 return 0;
284 }
285
Linus Torvalds1da177e2005-04-16 15:20:36 -0700286 if (sb) {
287 BUG_ON(sb->s_bdev != bdev);
Takashi Satofcccf502009-01-09 16:40:59 -0800288 if (!(sb->s_flags & MS_RDONLY)) {
289 if (sb->s_op->unfreeze_fs) {
290 error = sb->s_op->unfreeze_fs(sb);
291 if (error) {
292 printk(KERN_ERR
293 "VFS:Filesystem thaw failed\n");
294 sb->s_frozen = SB_FREEZE_TRANS;
295 bdev->bd_fsfreeze_count++;
296 mutex_unlock(&bdev->bd_fsfreeze_mutex);
297 return error;
298 }
299 }
300 sb->s_frozen = SB_UNFROZEN;
301 smp_wmb();
302 wake_up(&sb->s_wait_unfrozen);
303 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700304 drop_super(sb);
305 }
306
David Chinnerf73ca1b2007-01-10 23:15:41 -0800307 up(&bdev->bd_mount_sem);
Takashi Satofcccf502009-01-09 16:40:59 -0800308 mutex_unlock(&bdev->bd_fsfreeze_mutex);
309 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700310}
311EXPORT_SYMBOL(thaw_bdev);
312
313/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700314 * Various filesystems appear to want __find_get_block to be non-blocking.
315 * But it's the page lock which protects the buffers. To get around this,
316 * we get exclusion from try_to_free_buffers with the blockdev mapping's
317 * private_lock.
318 *
319 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
320 * may be quite high. This code could TryLock the page, and if that
321 * succeeds, there is no need to take private_lock. (But if
322 * private_lock is contended then so is mapping->tree_lock).
323 */
324static struct buffer_head *
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -0800325__find_get_block_slow(struct block_device *bdev, sector_t block)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700326{
327 struct inode *bd_inode = bdev->bd_inode;
328 struct address_space *bd_mapping = bd_inode->i_mapping;
329 struct buffer_head *ret = NULL;
330 pgoff_t index;
331 struct buffer_head *bh;
332 struct buffer_head *head;
333 struct page *page;
334 int all_mapped = 1;
335
336 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
337 page = find_get_page(bd_mapping, index);
338 if (!page)
339 goto out;
340
341 spin_lock(&bd_mapping->private_lock);
342 if (!page_has_buffers(page))
343 goto out_unlock;
344 head = page_buffers(page);
345 bh = head;
346 do {
347 if (bh->b_blocknr == block) {
348 ret = bh;
349 get_bh(bh);
350 goto out_unlock;
351 }
352 if (!buffer_mapped(bh))
353 all_mapped = 0;
354 bh = bh->b_this_page;
355 } while (bh != head);
356
357 /* we might be here because some of the buffers on this page are
358 * not mapped. This is due to various races between
359 * file io on the block device and getblk. It gets dealt with
360 * elsewhere, don't buffer_error if we had some unmapped buffers
361 */
362 if (all_mapped) {
363 printk("__find_get_block_slow() failed. "
364 "block=%llu, b_blocknr=%llu\n",
Badari Pulavarty205f87f2006-03-26 01:38:00 -0800365 (unsigned long long)block,
366 (unsigned long long)bh->b_blocknr);
367 printk("b_state=0x%08lx, b_size=%zu\n",
368 bh->b_state, bh->b_size);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700369 printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits);
370 }
371out_unlock:
372 spin_unlock(&bd_mapping->private_lock);
373 page_cache_release(page);
374out:
375 return ret;
376}
377
378/* If invalidate_buffers() will trash dirty buffers, it means some kind
379 of fs corruption is going on. Trashing dirty data always imply losing
380 information that was supposed to be just stored on the physical layer
381 by the user.
382
383 Thus invalidate_buffers in general usage is not allwowed to trash
384 dirty buffers. For example ioctl(FLSBLKBUF) expects dirty data to
385 be preserved. These buffers are simply skipped.
386
387 We also skip buffers which are still in use. For example this can
388 happen if a userspace program is reading the block device.
389
390 NOTE: In the case where the user removed a removable-media-disk even if
391 there's still dirty data not synced on disk (due a bug in the device driver
392 or due an error of the user), by not destroying the dirty buffers we could
393 generate corruption also on the next media inserted, thus a parameter is
394 necessary to handle this case in the most safe way possible (trying
395 to not corrupt also the new disk inserted with the data belonging to
396 the old now corrupted disk). Also for the ramdisk the natural thing
397 to do in order to release the ramdisk memory is to destroy dirty buffers.
398
399 These are two special cases. Normal usage imply the device driver
400 to issue a sync on the device (without waiting I/O completion) and
401 then an invalidate_buffers call that doesn't trash dirty buffers.
402
403 For handling cache coherency with the blkdev pagecache the 'update' case
404 is been introduced. It is needed to re-read from disk any pinned
405 buffer. NOTE: re-reading from disk is destructive so we can do it only
406 when we assume nobody is changing the buffercache under our I/O and when
407 we think the disk contains more recent information than the buffercache.
408 The update == 1 pass marks the buffers we need to update, the update == 2
409 pass does the actual I/O. */
Peter Zijlstraf98393a2007-05-06 14:49:54 -0700410void invalidate_bdev(struct block_device *bdev)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700411{
Andrew Morton0e1dfc62006-07-30 03:03:28 -0700412 struct address_space *mapping = bdev->bd_inode->i_mapping;
413
414 if (mapping->nrpages == 0)
415 return;
416
Linus Torvalds1da177e2005-04-16 15:20:36 -0700417 invalidate_bh_lrus();
Andrew Mortonfc0ecff2007-02-10 01:45:39 -0800418 invalidate_mapping_pages(mapping, 0, -1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700419}
420
421/*
422 * Kick pdflush then try to free up some ZONE_NORMAL memory.
423 */
424static void free_more_memory(void)
425{
Mel Gorman19770b32008-04-28 02:12:18 -0700426 struct zone *zone;
Mel Gorman0e884602008-04-28 02:12:14 -0700427 int nid;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700428
Pekka J Enberg687a21c2005-06-28 20:44:55 -0700429 wakeup_pdflush(1024);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700430 yield();
431
Mel Gorman0e884602008-04-28 02:12:14 -0700432 for_each_online_node(nid) {
Mel Gorman19770b32008-04-28 02:12:18 -0700433 (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS),
434 gfp_zone(GFP_NOFS), NULL,
435 &zone);
436 if (zone)
Mel Gorman54a6eb52008-04-28 02:12:16 -0700437 try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0,
438 GFP_NOFS);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700439 }
440}
441
442/*
443 * I/O completion handler for block_read_full_page() - pages
444 * which come unlocked at the end of I/O.
445 */
446static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
447{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700448 unsigned long flags;
Nick Piggina3972202005-07-07 17:56:56 -0700449 struct buffer_head *first;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700450 struct buffer_head *tmp;
451 struct page *page;
452 int page_uptodate = 1;
453
454 BUG_ON(!buffer_async_read(bh));
455
456 page = bh->b_page;
457 if (uptodate) {
458 set_buffer_uptodate(bh);
459 } else {
460 clear_buffer_uptodate(bh);
Keith Mannthey08bafc02008-11-25 10:24:35 +0100461 if (!quiet_error(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700462 buffer_io_error(bh);
463 SetPageError(page);
464 }
465
466 /*
467 * Be _very_ careful from here on. Bad things can happen if
468 * two buffer heads end IO at almost the same time and both
469 * decide that the page is now completely done.
470 */
Nick Piggina3972202005-07-07 17:56:56 -0700471 first = page_buffers(page);
472 local_irq_save(flags);
473 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700474 clear_buffer_async_read(bh);
475 unlock_buffer(bh);
476 tmp = bh;
477 do {
478 if (!buffer_uptodate(tmp))
479 page_uptodate = 0;
480 if (buffer_async_read(tmp)) {
481 BUG_ON(!buffer_locked(tmp));
482 goto still_busy;
483 }
484 tmp = tmp->b_this_page;
485 } while (tmp != bh);
Nick Piggina3972202005-07-07 17:56:56 -0700486 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
487 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700488
489 /*
490 * If none of the buffers had errors and they are all
491 * uptodate then we can set the page uptodate.
492 */
493 if (page_uptodate && !PageError(page))
494 SetPageUptodate(page);
495 unlock_page(page);
496 return;
497
498still_busy:
Nick Piggina3972202005-07-07 17:56:56 -0700499 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
500 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700501 return;
502}
503
504/*
505 * Completion handler for block_write_full_page() - pages which are unlocked
506 * during I/O, and which have PageWriteback cleared upon I/O completion.
507 */
Adrian Bunkb6cd0b72006-06-27 02:53:54 -0700508static void end_buffer_async_write(struct buffer_head *bh, int uptodate)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700509{
510 char b[BDEVNAME_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700511 unsigned long flags;
Nick Piggina3972202005-07-07 17:56:56 -0700512 struct buffer_head *first;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700513 struct buffer_head *tmp;
514 struct page *page;
515
516 BUG_ON(!buffer_async_write(bh));
517
518 page = bh->b_page;
519 if (uptodate) {
520 set_buffer_uptodate(bh);
521 } else {
Keith Mannthey08bafc02008-11-25 10:24:35 +0100522 if (!quiet_error(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700523 buffer_io_error(bh);
524 printk(KERN_WARNING "lost page write due to "
525 "I/O error on %s\n",
526 bdevname(bh->b_bdev, b));
527 }
528 set_bit(AS_EIO, &page->mapping->flags);
Jan Kara58ff4072006-10-17 00:10:19 -0700529 set_buffer_write_io_error(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700530 clear_buffer_uptodate(bh);
531 SetPageError(page);
532 }
533
Nick Piggina3972202005-07-07 17:56:56 -0700534 first = page_buffers(page);
535 local_irq_save(flags);
536 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
537
Linus Torvalds1da177e2005-04-16 15:20:36 -0700538 clear_buffer_async_write(bh);
539 unlock_buffer(bh);
540 tmp = bh->b_this_page;
541 while (tmp != bh) {
542 if (buffer_async_write(tmp)) {
543 BUG_ON(!buffer_locked(tmp));
544 goto still_busy;
545 }
546 tmp = tmp->b_this_page;
547 }
Nick Piggina3972202005-07-07 17:56:56 -0700548 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
549 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700550 end_page_writeback(page);
551 return;
552
553still_busy:
Nick Piggina3972202005-07-07 17:56:56 -0700554 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
555 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700556 return;
557}
558
559/*
560 * If a page's buffers are under async readin (end_buffer_async_read
561 * completion) then there is a possibility that another thread of
562 * control could lock one of the buffers after it has completed
563 * but while some of the other buffers have not completed. This
564 * locked buffer would confuse end_buffer_async_read() into not unlocking
565 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
566 * that this buffer is not under async I/O.
567 *
568 * The page comes unlocked when it has no locked buffer_async buffers
569 * left.
570 *
571 * PageLocked prevents anyone starting new async I/O reads any of
572 * the buffers.
573 *
574 * PageWriteback is used to prevent simultaneous writeout of the same
575 * page.
576 *
577 * PageLocked prevents anyone from starting writeback of a page which is
578 * under read I/O (PageWriteback is only ever set against a locked page).
579 */
580static void mark_buffer_async_read(struct buffer_head *bh)
581{
582 bh->b_end_io = end_buffer_async_read;
583 set_buffer_async_read(bh);
584}
585
586void mark_buffer_async_write(struct buffer_head *bh)
587{
588 bh->b_end_io = end_buffer_async_write;
589 set_buffer_async_write(bh);
590}
591EXPORT_SYMBOL(mark_buffer_async_write);
592
593
594/*
595 * fs/buffer.c contains helper functions for buffer-backed address space's
596 * fsync functions. A common requirement for buffer-based filesystems is
597 * that certain data from the backing blockdev needs to be written out for
598 * a successful fsync(). For example, ext2 indirect blocks need to be
599 * written back and waited upon before fsync() returns.
600 *
601 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
602 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
603 * management of a list of dependent buffers at ->i_mapping->private_list.
604 *
605 * Locking is a little subtle: try_to_free_buffers() will remove buffers
606 * from their controlling inode's queue when they are being freed. But
607 * try_to_free_buffers() will be operating against the *blockdev* mapping
608 * at the time, not against the S_ISREG file which depends on those buffers.
609 * So the locking for private_list is via the private_lock in the address_space
610 * which backs the buffers. Which is different from the address_space
611 * against which the buffers are listed. So for a particular address_space,
612 * mapping->private_lock does *not* protect mapping->private_list! In fact,
613 * mapping->private_list will always be protected by the backing blockdev's
614 * ->private_lock.
615 *
616 * Which introduces a requirement: all buffers on an address_space's
617 * ->private_list must be from the same address_space: the blockdev's.
618 *
619 * address_spaces which do not place buffers at ->private_list via these
620 * utility functions are free to use private_lock and private_list for
621 * whatever they want. The only requirement is that list_empty(private_list)
622 * be true at clear_inode() time.
623 *
624 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
625 * filesystems should do that. invalidate_inode_buffers() should just go
626 * BUG_ON(!list_empty).
627 *
628 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
629 * take an address_space, not an inode. And it should be called
630 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
631 * queued up.
632 *
633 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
634 * list if it is already on a list. Because if the buffer is on a list,
635 * it *must* already be on the right one. If not, the filesystem is being
636 * silly. This will save a ton of locking. But first we have to ensure
637 * that buffers are taken *off* the old inode's list when they are freed
638 * (presumably in truncate). That requires careful auditing of all
639 * filesystems (do it inside bforget()). It could also be done by bringing
640 * b_inode back.
641 */
642
643/*
644 * The buffer's backing address_space's private_lock must be held
645 */
Thomas Petazzonidbacefc2008-07-29 22:33:47 -0700646static void __remove_assoc_queue(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700647{
648 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -0700649 WARN_ON(!bh->b_assoc_map);
650 if (buffer_write_io_error(bh))
651 set_bit(AS_EIO, &bh->b_assoc_map->flags);
652 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700653}
654
655int inode_has_buffers(struct inode *inode)
656{
657 return !list_empty(&inode->i_data.private_list);
658}
659
660/*
661 * osync is designed to support O_SYNC io. It waits synchronously for
662 * all already-submitted IO to complete, but does not queue any new
663 * writes to the disk.
664 *
665 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
666 * you dirty the buffers, and then use osync_inode_buffers to wait for
667 * completion. Any other dirty buffers which are not yet queued for
668 * write will not be flushed to disk by the osync.
669 */
670static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
671{
672 struct buffer_head *bh;
673 struct list_head *p;
674 int err = 0;
675
676 spin_lock(lock);
677repeat:
678 list_for_each_prev(p, list) {
679 bh = BH_ENTRY(p);
680 if (buffer_locked(bh)) {
681 get_bh(bh);
682 spin_unlock(lock);
683 wait_on_buffer(bh);
684 if (!buffer_uptodate(bh))
685 err = -EIO;
686 brelse(bh);
687 spin_lock(lock);
688 goto repeat;
689 }
690 }
691 spin_unlock(lock);
692 return err;
693}
694
695/**
Randy Dunlap78a4a502008-02-29 22:02:31 -0800696 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
Martin Waitz67be2dd2005-05-01 08:59:26 -0700697 * @mapping: the mapping which wants those buffers written
Linus Torvalds1da177e2005-04-16 15:20:36 -0700698 *
699 * Starts I/O against the buffers at mapping->private_list, and waits upon
700 * that I/O.
701 *
Martin Waitz67be2dd2005-05-01 08:59:26 -0700702 * Basically, this is a convenience function for fsync().
703 * @mapping is a file or directory which needs those buffers to be written for
704 * a successful fsync().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700705 */
706int sync_mapping_buffers(struct address_space *mapping)
707{
708 struct address_space *buffer_mapping = mapping->assoc_mapping;
709
710 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
711 return 0;
712
713 return fsync_buffers_list(&buffer_mapping->private_lock,
714 &mapping->private_list);
715}
716EXPORT_SYMBOL(sync_mapping_buffers);
717
718/*
719 * Called when we've recently written block `bblock', and it is known that
720 * `bblock' was for a buffer_boundary() buffer. This means that the block at
721 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
722 * dirty, schedule it for IO. So that indirects merge nicely with their data.
723 */
724void write_boundary_block(struct block_device *bdev,
725 sector_t bblock, unsigned blocksize)
726{
727 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
728 if (bh) {
729 if (buffer_dirty(bh))
730 ll_rw_block(WRITE, 1, &bh);
731 put_bh(bh);
732 }
733}
734
735void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
736{
737 struct address_space *mapping = inode->i_mapping;
738 struct address_space *buffer_mapping = bh->b_page->mapping;
739
740 mark_buffer_dirty(bh);
741 if (!mapping->assoc_mapping) {
742 mapping->assoc_mapping = buffer_mapping;
743 } else {
Eric Sesterhenne827f922006-03-26 18:24:46 +0200744 BUG_ON(mapping->assoc_mapping != buffer_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700745 }
Jan Kara535ee2f2008-02-08 04:21:59 -0800746 if (!bh->b_assoc_map) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700747 spin_lock(&buffer_mapping->private_lock);
748 list_move_tail(&bh->b_assoc_buffers,
749 &mapping->private_list);
Jan Kara58ff4072006-10-17 00:10:19 -0700750 bh->b_assoc_map = mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700751 spin_unlock(&buffer_mapping->private_lock);
752 }
753}
754EXPORT_SYMBOL(mark_buffer_dirty_inode);
755
756/*
Nick Piggin787d2212007-07-17 04:03:34 -0700757 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
758 * dirty.
759 *
760 * If warn is true, then emit a warning if the page is not uptodate and has
761 * not been truncated.
762 */
Linus Torvaldsa8e7d492009-03-19 11:32:05 -0700763static void __set_page_dirty(struct page *page,
Nick Piggin787d2212007-07-17 04:03:34 -0700764 struct address_space *mapping, int warn)
765{
Nick Piggin19fd6232008-07-25 19:45:32 -0700766 spin_lock_irq(&mapping->tree_lock);
Nick Piggin787d2212007-07-17 04:03:34 -0700767 if (page->mapping) { /* Race with truncate? */
768 WARN_ON_ONCE(warn && !PageUptodate(page));
769
770 if (mapping_cap_account_dirty(mapping)) {
771 __inc_zone_page_state(page, NR_FILE_DIRTY);
Peter Zijlstrac9e51e42007-10-16 23:25:47 -0700772 __inc_bdi_stat(mapping->backing_dev_info,
773 BDI_RECLAIMABLE);
Nick Piggin1cf6e7d2009-02-18 14:48:18 -0800774 task_dirty_inc(current);
Nick Piggin787d2212007-07-17 04:03:34 -0700775 task_io_account_write(PAGE_CACHE_SIZE);
776 }
777 radix_tree_tag_set(&mapping->page_tree,
778 page_index(page), PAGECACHE_TAG_DIRTY);
779 }
Nick Piggin19fd6232008-07-25 19:45:32 -0700780 spin_unlock_irq(&mapping->tree_lock);
Nick Piggin787d2212007-07-17 04:03:34 -0700781 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
Nick Piggin787d2212007-07-17 04:03:34 -0700782}
783
784/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700785 * Add a page to the dirty page list.
786 *
787 * It is a sad fact of life that this function is called from several places
788 * deeply under spinlocking. It may not sleep.
789 *
790 * If the page has buffers, the uptodate buffers are set dirty, to preserve
791 * dirty-state coherency between the page and the buffers. It the page does
792 * not have buffers then when they are later attached they will all be set
793 * dirty.
794 *
795 * The buffers are dirtied before the page is dirtied. There's a small race
796 * window in which a writepage caller may see the page cleanness but not the
797 * buffer dirtiness. That's fine. If this code were to set the page dirty
798 * before the buffers, a concurrent writepage caller could clear the page dirty
799 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
800 * page on the dirty page list.
801 *
802 * We use private_lock to lock against try_to_free_buffers while using the
803 * page's buffer list. Also use this to protect against clean buffers being
804 * added to the page after it was set dirty.
805 *
806 * FIXME: may need to call ->reservepage here as well. That's rather up to the
807 * address_space though.
808 */
809int __set_page_dirty_buffers(struct page *page)
810{
Linus Torvaldsa8e7d492009-03-19 11:32:05 -0700811 int newly_dirty;
Nick Piggin787d2212007-07-17 04:03:34 -0700812 struct address_space *mapping = page_mapping(page);
Nick Pigginebf7a222006-10-10 04:36:54 +0200813
814 if (unlikely(!mapping))
815 return !TestSetPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700816
817 spin_lock(&mapping->private_lock);
818 if (page_has_buffers(page)) {
819 struct buffer_head *head = page_buffers(page);
820 struct buffer_head *bh = head;
821
822 do {
823 set_buffer_dirty(bh);
824 bh = bh->b_this_page;
825 } while (bh != head);
826 }
Linus Torvaldsa8e7d492009-03-19 11:32:05 -0700827 newly_dirty = !TestSetPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700828 spin_unlock(&mapping->private_lock);
829
Linus Torvaldsa8e7d492009-03-19 11:32:05 -0700830 if (newly_dirty)
831 __set_page_dirty(page, mapping, 1);
832 return newly_dirty;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700833}
834EXPORT_SYMBOL(__set_page_dirty_buffers);
835
836/*
837 * Write out and wait upon a list of buffers.
838 *
839 * We have conflicting pressures: we want to make sure that all
840 * initially dirty buffers get waited on, but that any subsequently
841 * dirtied buffers don't. After all, we don't want fsync to last
842 * forever if somebody is actively writing to the file.
843 *
844 * Do this in two main stages: first we copy dirty buffers to a
845 * temporary inode list, queueing the writes as we go. Then we clean
846 * up, waiting for those writes to complete.
847 *
848 * During this second stage, any subsequent updates to the file may end
849 * up refiling the buffer on the original inode's dirty list again, so
850 * there is a chance we will end up with a buffer queued for write but
851 * not yet completed on that list. So, as a final cleanup we go through
852 * the osync code to catch these locked, dirty buffers without requeuing
853 * any newly dirty buffers for write.
854 */
855static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
856{
857 struct buffer_head *bh;
858 struct list_head tmp;
Jan Kara535ee2f2008-02-08 04:21:59 -0800859 struct address_space *mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700860 int err = 0, err2;
861
862 INIT_LIST_HEAD(&tmp);
863
864 spin_lock(lock);
865 while (!list_empty(list)) {
866 bh = BH_ENTRY(list->next);
Jan Kara535ee2f2008-02-08 04:21:59 -0800867 mapping = bh->b_assoc_map;
Jan Kara58ff4072006-10-17 00:10:19 -0700868 __remove_assoc_queue(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -0800869 /* Avoid race with mark_buffer_dirty_inode() which does
870 * a lockless check and we rely on seeing the dirty bit */
871 smp_mb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700872 if (buffer_dirty(bh) || buffer_locked(bh)) {
873 list_add(&bh->b_assoc_buffers, &tmp);
Jan Kara535ee2f2008-02-08 04:21:59 -0800874 bh->b_assoc_map = mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700875 if (buffer_dirty(bh)) {
876 get_bh(bh);
877 spin_unlock(lock);
878 /*
879 * Ensure any pending I/O completes so that
880 * ll_rw_block() actually writes the current
881 * contents - it is a noop if I/O is still in
882 * flight on potentially older contents.
883 */
Jens Axboe18ce3752008-07-01 09:07:34 +0200884 ll_rw_block(SWRITE_SYNC, 1, &bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700885 brelse(bh);
886 spin_lock(lock);
887 }
888 }
889 }
890
891 while (!list_empty(&tmp)) {
892 bh = BH_ENTRY(tmp.prev);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700893 get_bh(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -0800894 mapping = bh->b_assoc_map;
895 __remove_assoc_queue(bh);
896 /* Avoid race with mark_buffer_dirty_inode() which does
897 * a lockless check and we rely on seeing the dirty bit */
898 smp_mb();
899 if (buffer_dirty(bh)) {
900 list_add(&bh->b_assoc_buffers,
Jan Karae3892292008-03-04 14:28:33 -0800901 &mapping->private_list);
Jan Kara535ee2f2008-02-08 04:21:59 -0800902 bh->b_assoc_map = mapping;
903 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700904 spin_unlock(lock);
905 wait_on_buffer(bh);
906 if (!buffer_uptodate(bh))
907 err = -EIO;
908 brelse(bh);
909 spin_lock(lock);
910 }
911
912 spin_unlock(lock);
913 err2 = osync_buffers_list(lock, list);
914 if (err)
915 return err;
916 else
917 return err2;
918}
919
920/*
921 * Invalidate any and all dirty buffers on a given inode. We are
922 * probably unmounting the fs, but that doesn't mean we have already
923 * done a sync(). Just drop the buffers from the inode list.
924 *
925 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
926 * assumes that all the buffers are against the blockdev. Not true
927 * for reiserfs.
928 */
929void invalidate_inode_buffers(struct inode *inode)
930{
931 if (inode_has_buffers(inode)) {
932 struct address_space *mapping = &inode->i_data;
933 struct list_head *list = &mapping->private_list;
934 struct address_space *buffer_mapping = mapping->assoc_mapping;
935
936 spin_lock(&buffer_mapping->private_lock);
937 while (!list_empty(list))
938 __remove_assoc_queue(BH_ENTRY(list->next));
939 spin_unlock(&buffer_mapping->private_lock);
940 }
941}
Jan Kara52b19ac2008-09-23 18:24:08 +0200942EXPORT_SYMBOL(invalidate_inode_buffers);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700943
944/*
945 * Remove any clean buffers from the inode's buffer list. This is called
946 * when we're trying to free the inode itself. Those buffers can pin it.
947 *
948 * Returns true if all buffers were removed.
949 */
950int remove_inode_buffers(struct inode *inode)
951{
952 int ret = 1;
953
954 if (inode_has_buffers(inode)) {
955 struct address_space *mapping = &inode->i_data;
956 struct list_head *list = &mapping->private_list;
957 struct address_space *buffer_mapping = mapping->assoc_mapping;
958
959 spin_lock(&buffer_mapping->private_lock);
960 while (!list_empty(list)) {
961 struct buffer_head *bh = BH_ENTRY(list->next);
962 if (buffer_dirty(bh)) {
963 ret = 0;
964 break;
965 }
966 __remove_assoc_queue(bh);
967 }
968 spin_unlock(&buffer_mapping->private_lock);
969 }
970 return ret;
971}
972
973/*
974 * Create the appropriate buffers when given a page for data area and
975 * the size of each buffer.. Use the bh->b_this_page linked list to
976 * follow the buffers created. Return NULL if unable to create more
977 * buffers.
978 *
979 * The retry flag is used to differentiate async IO (paging, swapping)
980 * which may not fail from ordinary buffer allocations.
981 */
982struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
983 int retry)
984{
985 struct buffer_head *bh, *head;
986 long offset;
987
988try_again:
989 head = NULL;
990 offset = PAGE_SIZE;
991 while ((offset -= size) >= 0) {
992 bh = alloc_buffer_head(GFP_NOFS);
993 if (!bh)
994 goto no_grow;
995
996 bh->b_bdev = NULL;
997 bh->b_this_page = head;
998 bh->b_blocknr = -1;
999 head = bh;
1000
1001 bh->b_state = 0;
1002 atomic_set(&bh->b_count, 0);
Chris Masonfc5cd582006-02-01 03:06:48 -08001003 bh->b_private = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001004 bh->b_size = size;
1005
1006 /* Link the buffer to its page */
1007 set_bh_page(bh, page, offset);
1008
Nathan Scott01ffe332006-01-17 09:02:07 +11001009 init_buffer(bh, NULL, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001010 }
1011 return head;
1012/*
1013 * In case anything failed, we just free everything we got.
1014 */
1015no_grow:
1016 if (head) {
1017 do {
1018 bh = head;
1019 head = head->b_this_page;
1020 free_buffer_head(bh);
1021 } while (head);
1022 }
1023
1024 /*
1025 * Return failure for non-async IO requests. Async IO requests
1026 * are not allowed to fail, so we have to wait until buffer heads
1027 * become available. But we don't want tasks sleeping with
1028 * partially complete buffers, so all were released above.
1029 */
1030 if (!retry)
1031 return NULL;
1032
1033 /* We're _really_ low on memory. Now we just
1034 * wait for old buffer heads to become free due to
1035 * finishing IO. Since this is an async request and
1036 * the reserve list is empty, we're sure there are
1037 * async buffer heads in use.
1038 */
1039 free_more_memory();
1040 goto try_again;
1041}
1042EXPORT_SYMBOL_GPL(alloc_page_buffers);
1043
1044static inline void
1045link_dev_buffers(struct page *page, struct buffer_head *head)
1046{
1047 struct buffer_head *bh, *tail;
1048
1049 bh = head;
1050 do {
1051 tail = bh;
1052 bh = bh->b_this_page;
1053 } while (bh);
1054 tail->b_this_page = head;
1055 attach_page_buffers(page, head);
1056}
1057
1058/*
1059 * Initialise the state of a blockdev page's buffers.
1060 */
1061static void
1062init_page_buffers(struct page *page, struct block_device *bdev,
1063 sector_t block, int size)
1064{
1065 struct buffer_head *head = page_buffers(page);
1066 struct buffer_head *bh = head;
1067 int uptodate = PageUptodate(page);
1068
1069 do {
1070 if (!buffer_mapped(bh)) {
1071 init_buffer(bh, NULL, NULL);
1072 bh->b_bdev = bdev;
1073 bh->b_blocknr = block;
1074 if (uptodate)
1075 set_buffer_uptodate(bh);
1076 set_buffer_mapped(bh);
1077 }
1078 block++;
1079 bh = bh->b_this_page;
1080 } while (bh != head);
1081}
1082
1083/*
1084 * Create the page-cache page that contains the requested block.
1085 *
1086 * This is user purely for blockdev mappings.
1087 */
1088static struct page *
1089grow_dev_page(struct block_device *bdev, sector_t block,
1090 pgoff_t index, int size)
1091{
1092 struct inode *inode = bdev->bd_inode;
1093 struct page *page;
1094 struct buffer_head *bh;
1095
Christoph Lameterea125892007-05-16 22:11:21 -07001096 page = find_or_create_page(inode->i_mapping, index,
Mel Gorman769848c2007-07-17 04:03:05 -07001097 (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001098 if (!page)
1099 return NULL;
1100
Eric Sesterhenne827f922006-03-26 18:24:46 +02001101 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001102
1103 if (page_has_buffers(page)) {
1104 bh = page_buffers(page);
1105 if (bh->b_size == size) {
1106 init_page_buffers(page, bdev, block, size);
1107 return page;
1108 }
1109 if (!try_to_free_buffers(page))
1110 goto failed;
1111 }
1112
1113 /*
1114 * Allocate some buffers for this page
1115 */
1116 bh = alloc_page_buffers(page, size, 0);
1117 if (!bh)
1118 goto failed;
1119
1120 /*
1121 * Link the page to the buffers and initialise them. Take the
1122 * lock to be atomic wrt __find_get_block(), which does not
1123 * run under the page lock.
1124 */
1125 spin_lock(&inode->i_mapping->private_lock);
1126 link_dev_buffers(page, bh);
1127 init_page_buffers(page, bdev, block, size);
1128 spin_unlock(&inode->i_mapping->private_lock);
1129 return page;
1130
1131failed:
1132 BUG();
1133 unlock_page(page);
1134 page_cache_release(page);
1135 return NULL;
1136}
1137
1138/*
1139 * Create buffers for the specified block device block's page. If
1140 * that page was dirty, the buffers are set dirty also.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001141 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001142static int
Linus Torvalds1da177e2005-04-16 15:20:36 -07001143grow_buffers(struct block_device *bdev, sector_t block, int size)
1144{
1145 struct page *page;
1146 pgoff_t index;
1147 int sizebits;
1148
1149 sizebits = -1;
1150 do {
1151 sizebits++;
1152 } while ((size << sizebits) < PAGE_SIZE);
1153
1154 index = block >> sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001155
Andrew Mortone5657932006-10-11 01:21:46 -07001156 /*
1157 * Check for a block which wants to lie outside our maximum possible
1158 * pagecache index. (this comparison is done using sector_t types).
1159 */
1160 if (unlikely(index != block >> sizebits)) {
1161 char b[BDEVNAME_SIZE];
1162
1163 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1164 "device %s\n",
Harvey Harrison8e24eea2008-04-30 00:55:09 -07001165 __func__, (unsigned long long)block,
Andrew Mortone5657932006-10-11 01:21:46 -07001166 bdevname(bdev, b));
1167 return -EIO;
1168 }
1169 block = index << sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001170 /* Create a page with the proper size buffers.. */
1171 page = grow_dev_page(bdev, block, index, size);
1172 if (!page)
1173 return 0;
1174 unlock_page(page);
1175 page_cache_release(page);
1176 return 1;
1177}
1178
Adrian Bunk75c96f82005-05-05 16:16:09 -07001179static struct buffer_head *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001180__getblk_slow(struct block_device *bdev, sector_t block, int size)
1181{
1182 /* Size must be multiple of hard sectorsize */
1183 if (unlikely(size & (bdev_hardsect_size(bdev)-1) ||
1184 (size < 512 || size > PAGE_SIZE))) {
1185 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1186 size);
1187 printk(KERN_ERR "hardsect size: %d\n",
1188 bdev_hardsect_size(bdev));
1189
1190 dump_stack();
1191 return NULL;
1192 }
1193
1194 for (;;) {
1195 struct buffer_head * bh;
Andrew Mortone5657932006-10-11 01:21:46 -07001196 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001197
1198 bh = __find_get_block(bdev, block, size);
1199 if (bh)
1200 return bh;
1201
Andrew Mortone5657932006-10-11 01:21:46 -07001202 ret = grow_buffers(bdev, block, size);
1203 if (ret < 0)
1204 return NULL;
1205 if (ret == 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001206 free_more_memory();
1207 }
1208}
1209
1210/*
1211 * The relationship between dirty buffers and dirty pages:
1212 *
1213 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1214 * the page is tagged dirty in its radix tree.
1215 *
1216 * At all times, the dirtiness of the buffers represents the dirtiness of
1217 * subsections of the page. If the page has buffers, the page dirty bit is
1218 * merely a hint about the true dirty state.
1219 *
1220 * When a page is set dirty in its entirety, all its buffers are marked dirty
1221 * (if the page has buffers).
1222 *
1223 * When a buffer is marked dirty, its page is dirtied, but the page's other
1224 * buffers are not.
1225 *
1226 * Also. When blockdev buffers are explicitly read with bread(), they
1227 * individually become uptodate. But their backing page remains not
1228 * uptodate - even if all of its buffers are uptodate. A subsequent
1229 * block_read_full_page() against that page will discover all the uptodate
1230 * buffers, will set the page uptodate and will perform no I/O.
1231 */
1232
1233/**
1234 * mark_buffer_dirty - mark a buffer_head as needing writeout
Martin Waitz67be2dd2005-05-01 08:59:26 -07001235 * @bh: the buffer_head to mark dirty
Linus Torvalds1da177e2005-04-16 15:20:36 -07001236 *
1237 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1238 * backing page dirty, then tag the page as dirty in its address_space's radix
1239 * tree and then attach the address_space's inode to its superblock's dirty
1240 * inode list.
1241 *
1242 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1243 * mapping->tree_lock and the global inode_lock.
1244 */
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -08001245void mark_buffer_dirty(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001246{
Nick Piggin787d2212007-07-17 04:03:34 -07001247 WARN_ON_ONCE(!buffer_uptodate(bh));
Linus Torvalds1be62dc2008-04-04 14:38:17 -07001248
1249 /*
1250 * Very *carefully* optimize the it-is-already-dirty case.
1251 *
1252 * Don't let the final "is it dirty" escape to before we
1253 * perhaps modified the buffer.
1254 */
1255 if (buffer_dirty(bh)) {
1256 smp_mb();
1257 if (buffer_dirty(bh))
1258 return;
1259 }
1260
Linus Torvaldsa8e7d492009-03-19 11:32:05 -07001261 if (!test_set_buffer_dirty(bh)) {
1262 struct page *page = bh->b_page;
1263 if (!TestSetPageDirty(page))
1264 __set_page_dirty(page, page_mapping(page), 0);
1265 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001266}
1267
1268/*
1269 * Decrement a buffer_head's reference count. If all buffers against a page
1270 * have zero reference count, are clean and unlocked, and if the page is clean
1271 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1272 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1273 * a page but it ends up not being freed, and buffers may later be reattached).
1274 */
1275void __brelse(struct buffer_head * buf)
1276{
1277 if (atomic_read(&buf->b_count)) {
1278 put_bh(buf);
1279 return;
1280 }
Arjan van de Ven5c752ad2008-07-25 19:45:40 -07001281 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
Linus Torvalds1da177e2005-04-16 15:20:36 -07001282}
1283
1284/*
1285 * bforget() is like brelse(), except it discards any
1286 * potentially dirty data.
1287 */
1288void __bforget(struct buffer_head *bh)
1289{
1290 clear_buffer_dirty(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -08001291 if (bh->b_assoc_map) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001292 struct address_space *buffer_mapping = bh->b_page->mapping;
1293
1294 spin_lock(&buffer_mapping->private_lock);
1295 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -07001296 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001297 spin_unlock(&buffer_mapping->private_lock);
1298 }
1299 __brelse(bh);
1300}
1301
1302static struct buffer_head *__bread_slow(struct buffer_head *bh)
1303{
1304 lock_buffer(bh);
1305 if (buffer_uptodate(bh)) {
1306 unlock_buffer(bh);
1307 return bh;
1308 } else {
1309 get_bh(bh);
1310 bh->b_end_io = end_buffer_read_sync;
1311 submit_bh(READ, bh);
1312 wait_on_buffer(bh);
1313 if (buffer_uptodate(bh))
1314 return bh;
1315 }
1316 brelse(bh);
1317 return NULL;
1318}
1319
1320/*
1321 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1322 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1323 * refcount elevated by one when they're in an LRU. A buffer can only appear
1324 * once in a particular CPU's LRU. A single buffer can be present in multiple
1325 * CPU's LRUs at the same time.
1326 *
1327 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1328 * sb_find_get_block().
1329 *
1330 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1331 * a local interrupt disable for that.
1332 */
1333
1334#define BH_LRU_SIZE 8
1335
1336struct bh_lru {
1337 struct buffer_head *bhs[BH_LRU_SIZE];
1338};
1339
1340static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1341
1342#ifdef CONFIG_SMP
1343#define bh_lru_lock() local_irq_disable()
1344#define bh_lru_unlock() local_irq_enable()
1345#else
1346#define bh_lru_lock() preempt_disable()
1347#define bh_lru_unlock() preempt_enable()
1348#endif
1349
1350static inline void check_irqs_on(void)
1351{
1352#ifdef irqs_disabled
1353 BUG_ON(irqs_disabled());
1354#endif
1355}
1356
1357/*
1358 * The LRU management algorithm is dopey-but-simple. Sorry.
1359 */
1360static void bh_lru_install(struct buffer_head *bh)
1361{
1362 struct buffer_head *evictee = NULL;
1363 struct bh_lru *lru;
1364
1365 check_irqs_on();
1366 bh_lru_lock();
1367 lru = &__get_cpu_var(bh_lrus);
1368 if (lru->bhs[0] != bh) {
1369 struct buffer_head *bhs[BH_LRU_SIZE];
1370 int in;
1371 int out = 0;
1372
1373 get_bh(bh);
1374 bhs[out++] = bh;
1375 for (in = 0; in < BH_LRU_SIZE; in++) {
1376 struct buffer_head *bh2 = lru->bhs[in];
1377
1378 if (bh2 == bh) {
1379 __brelse(bh2);
1380 } else {
1381 if (out >= BH_LRU_SIZE) {
1382 BUG_ON(evictee != NULL);
1383 evictee = bh2;
1384 } else {
1385 bhs[out++] = bh2;
1386 }
1387 }
1388 }
1389 while (out < BH_LRU_SIZE)
1390 bhs[out++] = NULL;
1391 memcpy(lru->bhs, bhs, sizeof(bhs));
1392 }
1393 bh_lru_unlock();
1394
1395 if (evictee)
1396 __brelse(evictee);
1397}
1398
1399/*
1400 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1401 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001402static struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001403lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001404{
1405 struct buffer_head *ret = NULL;
1406 struct bh_lru *lru;
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001407 unsigned int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001408
1409 check_irqs_on();
1410 bh_lru_lock();
1411 lru = &__get_cpu_var(bh_lrus);
1412 for (i = 0; i < BH_LRU_SIZE; i++) {
1413 struct buffer_head *bh = lru->bhs[i];
1414
1415 if (bh && bh->b_bdev == bdev &&
1416 bh->b_blocknr == block && bh->b_size == size) {
1417 if (i) {
1418 while (i) {
1419 lru->bhs[i] = lru->bhs[i - 1];
1420 i--;
1421 }
1422 lru->bhs[0] = bh;
1423 }
1424 get_bh(bh);
1425 ret = bh;
1426 break;
1427 }
1428 }
1429 bh_lru_unlock();
1430 return ret;
1431}
1432
1433/*
1434 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1435 * it in the LRU and mark it as accessed. If it is not present then return
1436 * NULL
1437 */
1438struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001439__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001440{
1441 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1442
1443 if (bh == NULL) {
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001444 bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001445 if (bh)
1446 bh_lru_install(bh);
1447 }
1448 if (bh)
1449 touch_buffer(bh);
1450 return bh;
1451}
1452EXPORT_SYMBOL(__find_get_block);
1453
1454/*
1455 * __getblk will locate (and, if necessary, create) the buffer_head
1456 * which corresponds to the passed block_device, block and size. The
1457 * returned buffer has its reference count incremented.
1458 *
1459 * __getblk() cannot fail - it just keeps trying. If you pass it an
1460 * illegal block number, __getblk() will happily return a buffer_head
1461 * which represents the non-existent block. Very weird.
1462 *
1463 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1464 * attempt is failing. FIXME, perhaps?
1465 */
1466struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001467__getblk(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001468{
1469 struct buffer_head *bh = __find_get_block(bdev, block, size);
1470
1471 might_sleep();
1472 if (bh == NULL)
1473 bh = __getblk_slow(bdev, block, size);
1474 return bh;
1475}
1476EXPORT_SYMBOL(__getblk);
1477
1478/*
1479 * Do async read-ahead on a buffer..
1480 */
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001481void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001482{
1483 struct buffer_head *bh = __getblk(bdev, block, size);
Andrew Mortona3e713b2005-10-30 15:03:15 -08001484 if (likely(bh)) {
1485 ll_rw_block(READA, 1, &bh);
1486 brelse(bh);
1487 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001488}
1489EXPORT_SYMBOL(__breadahead);
1490
1491/**
1492 * __bread() - reads a specified block and returns the bh
Martin Waitz67be2dd2005-05-01 08:59:26 -07001493 * @bdev: the block_device to read from
Linus Torvalds1da177e2005-04-16 15:20:36 -07001494 * @block: number of block
1495 * @size: size (in bytes) to read
1496 *
1497 * Reads a specified block, and returns buffer head that contains it.
1498 * It returns NULL if the block was unreadable.
1499 */
1500struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001501__bread(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001502{
1503 struct buffer_head *bh = __getblk(bdev, block, size);
1504
Andrew Mortona3e713b2005-10-30 15:03:15 -08001505 if (likely(bh) && !buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001506 bh = __bread_slow(bh);
1507 return bh;
1508}
1509EXPORT_SYMBOL(__bread);
1510
1511/*
1512 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1513 * This doesn't race because it runs in each cpu either in irq
1514 * or with preempt disabled.
1515 */
1516static void invalidate_bh_lru(void *arg)
1517{
1518 struct bh_lru *b = &get_cpu_var(bh_lrus);
1519 int i;
1520
1521 for (i = 0; i < BH_LRU_SIZE; i++) {
1522 brelse(b->bhs[i]);
1523 b->bhs[i] = NULL;
1524 }
1525 put_cpu_var(bh_lrus);
1526}
1527
Peter Zijlstraf9a14392007-05-06 14:49:55 -07001528void invalidate_bh_lrus(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001529{
Jens Axboe15c8b6c2008-05-09 09:39:44 +02001530 on_each_cpu(invalidate_bh_lru, NULL, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001531}
Nick Piggin9db55792008-02-08 04:19:49 -08001532EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001533
1534void set_bh_page(struct buffer_head *bh,
1535 struct page *page, unsigned long offset)
1536{
1537 bh->b_page = page;
Eric Sesterhenne827f922006-03-26 18:24:46 +02001538 BUG_ON(offset >= PAGE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001539 if (PageHighMem(page))
1540 /*
1541 * This catches illegal uses and preserves the offset:
1542 */
1543 bh->b_data = (char *)(0 + offset);
1544 else
1545 bh->b_data = page_address(page) + offset;
1546}
1547EXPORT_SYMBOL(set_bh_page);
1548
1549/*
1550 * Called when truncating a buffer on a page completely.
1551 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001552static void discard_buffer(struct buffer_head * bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001553{
1554 lock_buffer(bh);
1555 clear_buffer_dirty(bh);
1556 bh->b_bdev = NULL;
1557 clear_buffer_mapped(bh);
1558 clear_buffer_req(bh);
1559 clear_buffer_new(bh);
1560 clear_buffer_delay(bh);
David Chinner33a266d2007-02-12 00:51:41 -08001561 clear_buffer_unwritten(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001562 unlock_buffer(bh);
1563}
1564
1565/**
Linus Torvalds1da177e2005-04-16 15:20:36 -07001566 * block_invalidatepage - invalidate part of all of a buffer-backed page
1567 *
1568 * @page: the page which is affected
1569 * @offset: the index of the truncation point
1570 *
1571 * block_invalidatepage() is called when all or part of the page has become
1572 * invalidatedby a truncate operation.
1573 *
1574 * block_invalidatepage() does not have to release all buffers, but it must
1575 * ensure that no dirty buffer is left outside @offset and that no I/O
1576 * is underway against any of the blocks which are outside the truncation
1577 * point. Because the caller is about to free (and possibly reuse) those
1578 * blocks on-disk.
1579 */
NeilBrown2ff28e22006-03-26 01:37:18 -08001580void block_invalidatepage(struct page *page, unsigned long offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001581{
1582 struct buffer_head *head, *bh, *next;
1583 unsigned int curr_off = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001584
1585 BUG_ON(!PageLocked(page));
1586 if (!page_has_buffers(page))
1587 goto out;
1588
1589 head = page_buffers(page);
1590 bh = head;
1591 do {
1592 unsigned int next_off = curr_off + bh->b_size;
1593 next = bh->b_this_page;
1594
1595 /*
1596 * is this block fully invalidated?
1597 */
1598 if (offset <= curr_off)
1599 discard_buffer(bh);
1600 curr_off = next_off;
1601 bh = next;
1602 } while (bh != head);
1603
1604 /*
1605 * We release buffers only if the entire page is being invalidated.
1606 * The get_block cached value has been unconditionally invalidated,
1607 * so real IO is not possible anymore.
1608 */
1609 if (offset == 0)
NeilBrown2ff28e22006-03-26 01:37:18 -08001610 try_to_release_page(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001611out:
NeilBrown2ff28e22006-03-26 01:37:18 -08001612 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001613}
1614EXPORT_SYMBOL(block_invalidatepage);
1615
1616/*
1617 * We attach and possibly dirty the buffers atomically wrt
1618 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1619 * is already excluded via the page lock.
1620 */
1621void create_empty_buffers(struct page *page,
1622 unsigned long blocksize, unsigned long b_state)
1623{
1624 struct buffer_head *bh, *head, *tail;
1625
1626 head = alloc_page_buffers(page, blocksize, 1);
1627 bh = head;
1628 do {
1629 bh->b_state |= b_state;
1630 tail = bh;
1631 bh = bh->b_this_page;
1632 } while (bh);
1633 tail->b_this_page = head;
1634
1635 spin_lock(&page->mapping->private_lock);
1636 if (PageUptodate(page) || PageDirty(page)) {
1637 bh = head;
1638 do {
1639 if (PageDirty(page))
1640 set_buffer_dirty(bh);
1641 if (PageUptodate(page))
1642 set_buffer_uptodate(bh);
1643 bh = bh->b_this_page;
1644 } while (bh != head);
1645 }
1646 attach_page_buffers(page, head);
1647 spin_unlock(&page->mapping->private_lock);
1648}
1649EXPORT_SYMBOL(create_empty_buffers);
1650
1651/*
1652 * We are taking a block for data and we don't want any output from any
1653 * buffer-cache aliases starting from return from that function and
1654 * until the moment when something will explicitly mark the buffer
1655 * dirty (hopefully that will not happen until we will free that block ;-)
1656 * We don't even need to mark it not-uptodate - nobody can expect
1657 * anything from a newly allocated buffer anyway. We used to used
1658 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1659 * don't want to mark the alias unmapped, for example - it would confuse
1660 * anyone who might pick it with bread() afterwards...
1661 *
1662 * Also.. Note that bforget() doesn't lock the buffer. So there can
1663 * be writeout I/O going on against recently-freed buffers. We don't
1664 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1665 * only if we really need to. That happens here.
1666 */
1667void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1668{
1669 struct buffer_head *old_bh;
1670
1671 might_sleep();
1672
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001673 old_bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001674 if (old_bh) {
1675 clear_buffer_dirty(old_bh);
1676 wait_on_buffer(old_bh);
1677 clear_buffer_req(old_bh);
1678 __brelse(old_bh);
1679 }
1680}
1681EXPORT_SYMBOL(unmap_underlying_metadata);
1682
1683/*
1684 * NOTE! All mapped/uptodate combinations are valid:
1685 *
1686 * Mapped Uptodate Meaning
1687 *
1688 * No No "unknown" - must do get_block()
1689 * No Yes "hole" - zero-filled
1690 * Yes No "allocated" - allocated on disk, not read in
1691 * Yes Yes "valid" - allocated and up-to-date in memory.
1692 *
1693 * "Dirty" is valid only with the last case (mapped+uptodate).
1694 */
1695
1696/*
1697 * While block_write_full_page is writing back the dirty buffers under
1698 * the page lock, whoever dirtied the buffers may decide to clean them
1699 * again at any time. We handle that by only looking at the buffer
1700 * state inside lock_buffer().
1701 *
1702 * If block_write_full_page() is called for regular writeback
1703 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1704 * locked buffer. This only can happen if someone has written the buffer
1705 * directly, with submit_bh(). At the address_space level PageWriteback
1706 * prevents this contention from occurring.
1707 */
1708static int __block_write_full_page(struct inode *inode, struct page *page,
1709 get_block_t *get_block, struct writeback_control *wbc)
1710{
1711 int err;
1712 sector_t block;
1713 sector_t last_block;
Andrew Mortonf0fbd5f2005-05-05 16:15:48 -07001714 struct buffer_head *bh, *head;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001715 const unsigned blocksize = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001716 int nr_underway = 0;
1717
1718 BUG_ON(!PageLocked(page));
1719
1720 last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
1721
1722 if (!page_has_buffers(page)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001723 create_empty_buffers(page, blocksize,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001724 (1 << BH_Dirty)|(1 << BH_Uptodate));
1725 }
1726
1727 /*
1728 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1729 * here, and the (potentially unmapped) buffers may become dirty at
1730 * any time. If a buffer becomes dirty here after we've inspected it
1731 * then we just miss that fact, and the page stays dirty.
1732 *
1733 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1734 * handle that here by just cleaning them.
1735 */
1736
Andrew Morton54b21a72006-01-08 01:03:05 -08001737 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001738 head = page_buffers(page);
1739 bh = head;
1740
1741 /*
1742 * Get all the dirty buffers mapped to disk addresses and
1743 * handle any aliases from the underlying blockdev's mapping.
1744 */
1745 do {
1746 if (block > last_block) {
1747 /*
1748 * mapped buffers outside i_size will occur, because
1749 * this page can be outside i_size when there is a
1750 * truncate in progress.
1751 */
1752 /*
1753 * The buffer was zeroed by block_write_full_page()
1754 */
1755 clear_buffer_dirty(bh);
1756 set_buffer_uptodate(bh);
Alex Tomas29a814d2008-07-11 19:27:31 -04001757 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1758 buffer_dirty(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001759 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001760 err = get_block(inode, block, bh, 1);
1761 if (err)
1762 goto recover;
Alex Tomas29a814d2008-07-11 19:27:31 -04001763 clear_buffer_delay(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001764 if (buffer_new(bh)) {
1765 /* blockdev mappings never come here */
1766 clear_buffer_new(bh);
1767 unmap_underlying_metadata(bh->b_bdev,
1768 bh->b_blocknr);
1769 }
1770 }
1771 bh = bh->b_this_page;
1772 block++;
1773 } while (bh != head);
1774
1775 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001776 if (!buffer_mapped(bh))
1777 continue;
1778 /*
1779 * If it's a fully non-blocking write attempt and we cannot
1780 * lock the buffer then redirty the page. Note that this can
1781 * potentially cause a busy-wait loop from pdflush and kswapd
1782 * activity, but those code paths have their own higher-level
1783 * throttling.
1784 */
1785 if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
1786 lock_buffer(bh);
Nick Pigginca5de402008-08-02 12:02:13 +02001787 } else if (!trylock_buffer(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001788 redirty_page_for_writepage(wbc, page);
1789 continue;
1790 }
1791 if (test_clear_buffer_dirty(bh)) {
1792 mark_buffer_async_write(bh);
1793 } else {
1794 unlock_buffer(bh);
1795 }
1796 } while ((bh = bh->b_this_page) != head);
1797
1798 /*
1799 * The page and its buffers are protected by PageWriteback(), so we can
1800 * drop the bh refcounts early.
1801 */
1802 BUG_ON(PageWriteback(page));
1803 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001804
1805 do {
1806 struct buffer_head *next = bh->b_this_page;
1807 if (buffer_async_write(bh)) {
1808 submit_bh(WRITE, bh);
1809 nr_underway++;
1810 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001811 bh = next;
1812 } while (bh != head);
Andrew Morton05937ba2005-05-05 16:15:47 -07001813 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001814
1815 err = 0;
1816done:
1817 if (nr_underway == 0) {
1818 /*
1819 * The page was marked dirty, but the buffers were
1820 * clean. Someone wrote them back by hand with
1821 * ll_rw_block/submit_bh. A rare case.
1822 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001823 end_page_writeback(page);
Nick Piggin3d67f2d2007-05-06 14:49:05 -07001824
Linus Torvalds1da177e2005-04-16 15:20:36 -07001825 /*
1826 * The page and buffer_heads can be released at any time from
1827 * here on.
1828 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001829 }
1830 return err;
1831
1832recover:
1833 /*
1834 * ENOSPC, or some other error. We may already have added some
1835 * blocks to the file, so we need to write these out to avoid
1836 * exposing stale data.
1837 * The page is currently locked and not marked for writeback
1838 */
1839 bh = head;
1840 /* Recovery: lock and submit the mapped buffers */
1841 do {
Alex Tomas29a814d2008-07-11 19:27:31 -04001842 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1843 !buffer_delay(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001844 lock_buffer(bh);
1845 mark_buffer_async_write(bh);
1846 } else {
1847 /*
1848 * The buffer may have been set dirty during
1849 * attachment to a dirty page.
1850 */
1851 clear_buffer_dirty(bh);
1852 }
1853 } while ((bh = bh->b_this_page) != head);
1854 SetPageError(page);
1855 BUG_ON(PageWriteback(page));
Andrew Morton7e4c3692007-05-08 00:23:27 -07001856 mapping_set_error(page->mapping, err);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001857 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001858 do {
1859 struct buffer_head *next = bh->b_this_page;
1860 if (buffer_async_write(bh)) {
1861 clear_buffer_dirty(bh);
1862 submit_bh(WRITE, bh);
1863 nr_underway++;
1864 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001865 bh = next;
1866 } while (bh != head);
Nick Pigginffda9d32007-02-20 13:57:54 -08001867 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001868 goto done;
1869}
1870
Nick Pigginafddba42007-10-16 01:25:01 -07001871/*
1872 * If a page has any new buffers, zero them out here, and mark them uptodate
1873 * and dirty so they'll be written out (in order to prevent uninitialised
1874 * block data from leaking). And clear the new bit.
1875 */
1876void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1877{
1878 unsigned int block_start, block_end;
1879 struct buffer_head *head, *bh;
1880
1881 BUG_ON(!PageLocked(page));
1882 if (!page_has_buffers(page))
1883 return;
1884
1885 bh = head = page_buffers(page);
1886 block_start = 0;
1887 do {
1888 block_end = block_start + bh->b_size;
1889
1890 if (buffer_new(bh)) {
1891 if (block_end > from && block_start < to) {
1892 if (!PageUptodate(page)) {
1893 unsigned start, size;
1894
1895 start = max(from, block_start);
1896 size = min(to, block_end) - start;
1897
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001898 zero_user(page, start, size);
Nick Pigginafddba42007-10-16 01:25:01 -07001899 set_buffer_uptodate(bh);
1900 }
1901
1902 clear_buffer_new(bh);
1903 mark_buffer_dirty(bh);
1904 }
1905 }
1906
1907 block_start = block_end;
1908 bh = bh->b_this_page;
1909 } while (bh != head);
1910}
1911EXPORT_SYMBOL(page_zero_new_buffers);
1912
Linus Torvalds1da177e2005-04-16 15:20:36 -07001913static int __block_prepare_write(struct inode *inode, struct page *page,
1914 unsigned from, unsigned to, get_block_t *get_block)
1915{
1916 unsigned block_start, block_end;
1917 sector_t block;
1918 int err = 0;
1919 unsigned blocksize, bbits;
1920 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1921
1922 BUG_ON(!PageLocked(page));
1923 BUG_ON(from > PAGE_CACHE_SIZE);
1924 BUG_ON(to > PAGE_CACHE_SIZE);
1925 BUG_ON(from > to);
1926
1927 blocksize = 1 << inode->i_blkbits;
1928 if (!page_has_buffers(page))
1929 create_empty_buffers(page, blocksize, 0);
1930 head = page_buffers(page);
1931
1932 bbits = inode->i_blkbits;
1933 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1934
1935 for(bh = head, block_start = 0; bh != head || !block_start;
1936 block++, 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 (PageUptodate(page)) {
1940 if (!buffer_uptodate(bh))
1941 set_buffer_uptodate(bh);
1942 }
1943 continue;
1944 }
1945 if (buffer_new(bh))
1946 clear_buffer_new(bh);
1947 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001948 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001949 err = get_block(inode, block, bh, 1);
1950 if (err)
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001951 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001952 if (buffer_new(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001953 unmap_underlying_metadata(bh->b_bdev,
1954 bh->b_blocknr);
1955 if (PageUptodate(page)) {
Nick Piggin637aff42007-10-16 01:25:00 -07001956 clear_buffer_new(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001957 set_buffer_uptodate(bh);
Nick Piggin637aff42007-10-16 01:25:00 -07001958 mark_buffer_dirty(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001959 continue;
1960 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001961 if (block_end > to || block_start < from)
1962 zero_user_segments(page,
1963 to, block_end,
1964 block_start, from);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001965 continue;
1966 }
1967 }
1968 if (PageUptodate(page)) {
1969 if (!buffer_uptodate(bh))
1970 set_buffer_uptodate(bh);
1971 continue;
1972 }
1973 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
David Chinner33a266d2007-02-12 00:51:41 -08001974 !buffer_unwritten(bh) &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001975 (block_start < from || block_end > to)) {
1976 ll_rw_block(READ, 1, &bh);
1977 *wait_bh++=bh;
1978 }
1979 }
1980 /*
1981 * If we issued read requests - let them complete.
1982 */
1983 while(wait_bh > wait) {
1984 wait_on_buffer(*--wait_bh);
1985 if (!buffer_uptodate(*wait_bh))
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001986 err = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001987 }
Nick Pigginafddba42007-10-16 01:25:01 -07001988 if (unlikely(err))
1989 page_zero_new_buffers(page, from, to);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001990 return err;
1991}
1992
1993static int __block_commit_write(struct inode *inode, struct page *page,
1994 unsigned from, unsigned to)
1995{
1996 unsigned block_start, block_end;
1997 int partial = 0;
1998 unsigned blocksize;
1999 struct buffer_head *bh, *head;
2000
2001 blocksize = 1 << inode->i_blkbits;
2002
2003 for(bh = head = page_buffers(page), block_start = 0;
2004 bh != head || !block_start;
2005 block_start=block_end, bh = bh->b_this_page) {
2006 block_end = block_start + blocksize;
2007 if (block_end <= from || block_start >= to) {
2008 if (!buffer_uptodate(bh))
2009 partial = 1;
2010 } else {
2011 set_buffer_uptodate(bh);
2012 mark_buffer_dirty(bh);
2013 }
Nick Pigginafddba42007-10-16 01:25:01 -07002014 clear_buffer_new(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002015 }
2016
2017 /*
2018 * If this is a partial write which happened to make all buffers
2019 * uptodate then we can optimize away a bogus readpage() for
2020 * the next read(). Here we 'discover' whether the page went
2021 * uptodate as a result of this (potentially partial) write.
2022 */
2023 if (!partial)
2024 SetPageUptodate(page);
2025 return 0;
2026}
2027
2028/*
Nick Pigginafddba42007-10-16 01:25:01 -07002029 * block_write_begin takes care of the basic task of block allocation and
2030 * bringing partial write blocks uptodate first.
2031 *
2032 * If *pagep is not NULL, then block_write_begin uses the locked page
2033 * at *pagep rather than allocating its own. In this case, the page will
2034 * not be unlocked or deallocated on failure.
2035 */
2036int block_write_begin(struct file *file, struct address_space *mapping,
2037 loff_t pos, unsigned len, unsigned flags,
2038 struct page **pagep, void **fsdata,
2039 get_block_t *get_block)
2040{
2041 struct inode *inode = mapping->host;
2042 int status = 0;
2043 struct page *page;
2044 pgoff_t index;
2045 unsigned start, end;
2046 int ownpage = 0;
2047
2048 index = pos >> PAGE_CACHE_SHIFT;
2049 start = pos & (PAGE_CACHE_SIZE - 1);
2050 end = start + len;
2051
2052 page = *pagep;
2053 if (page == NULL) {
2054 ownpage = 1;
Nick Piggin54566b22009-01-04 12:00:53 -08002055 page = grab_cache_page_write_begin(mapping, index, flags);
Nick Pigginafddba42007-10-16 01:25:01 -07002056 if (!page) {
2057 status = -ENOMEM;
2058 goto out;
2059 }
2060 *pagep = page;
2061 } else
2062 BUG_ON(!PageLocked(page));
2063
2064 status = __block_prepare_write(inode, page, start, end, get_block);
2065 if (unlikely(status)) {
2066 ClearPageUptodate(page);
2067
2068 if (ownpage) {
2069 unlock_page(page);
2070 page_cache_release(page);
2071 *pagep = NULL;
2072
2073 /*
2074 * prepare_write() may have instantiated a few blocks
2075 * outside i_size. Trim these off again. Don't need
2076 * i_size_read because we hold i_mutex.
2077 */
2078 if (pos + len > inode->i_size)
2079 vmtruncate(inode, inode->i_size);
2080 }
Nick Pigginafddba42007-10-16 01:25:01 -07002081 }
2082
2083out:
2084 return status;
2085}
2086EXPORT_SYMBOL(block_write_begin);
2087
2088int block_write_end(struct file *file, struct address_space *mapping,
2089 loff_t pos, unsigned len, unsigned copied,
2090 struct page *page, void *fsdata)
2091{
2092 struct inode *inode = mapping->host;
2093 unsigned start;
2094
2095 start = pos & (PAGE_CACHE_SIZE - 1);
2096
2097 if (unlikely(copied < len)) {
2098 /*
2099 * The buffers that were written will now be uptodate, so we
2100 * don't have to worry about a readpage reading them and
2101 * overwriting a partial write. However if we have encountered
2102 * a short write and only partially written into a buffer, it
2103 * will not be marked uptodate, so a readpage might come in and
2104 * destroy our partial write.
2105 *
2106 * Do the simplest thing, and just treat any short write to a
2107 * non uptodate page as a zero-length write, and force the
2108 * caller to redo the whole thing.
2109 */
2110 if (!PageUptodate(page))
2111 copied = 0;
2112
2113 page_zero_new_buffers(page, start+copied, start+len);
2114 }
2115 flush_dcache_page(page);
2116
2117 /* This could be a short (even 0-length) commit */
2118 __block_commit_write(inode, page, start, start+copied);
2119
2120 return copied;
2121}
2122EXPORT_SYMBOL(block_write_end);
2123
2124int generic_write_end(struct file *file, struct address_space *mapping,
2125 loff_t pos, unsigned len, unsigned copied,
2126 struct page *page, void *fsdata)
2127{
2128 struct inode *inode = mapping->host;
Jan Karac7d206b2008-07-11 19:27:31 -04002129 int i_size_changed = 0;
Nick Pigginafddba42007-10-16 01:25:01 -07002130
2131 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2132
2133 /*
2134 * No need to use i_size_read() here, the i_size
2135 * cannot change under us because we hold i_mutex.
2136 *
2137 * But it's important to update i_size while still holding page lock:
2138 * page writeout could otherwise come in and zero beyond i_size.
2139 */
2140 if (pos+copied > inode->i_size) {
2141 i_size_write(inode, pos+copied);
Jan Karac7d206b2008-07-11 19:27:31 -04002142 i_size_changed = 1;
Nick Pigginafddba42007-10-16 01:25:01 -07002143 }
2144
2145 unlock_page(page);
2146 page_cache_release(page);
2147
Jan Karac7d206b2008-07-11 19:27:31 -04002148 /*
2149 * Don't mark the inode dirty under page lock. First, it unnecessarily
2150 * makes the holding time of page lock longer. Second, it forces lock
2151 * ordering of page lock and transaction start for journaling
2152 * filesystems.
2153 */
2154 if (i_size_changed)
2155 mark_inode_dirty(inode);
2156
Nick Pigginafddba42007-10-16 01:25:01 -07002157 return copied;
2158}
2159EXPORT_SYMBOL(generic_write_end);
2160
2161/*
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07002162 * block_is_partially_uptodate checks whether buffers within a page are
2163 * uptodate or not.
2164 *
2165 * Returns true if all buffers which correspond to a file portion
2166 * we want to read are uptodate.
2167 */
2168int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
2169 unsigned long from)
2170{
2171 struct inode *inode = page->mapping->host;
2172 unsigned block_start, block_end, blocksize;
2173 unsigned to;
2174 struct buffer_head *bh, *head;
2175 int ret = 1;
2176
2177 if (!page_has_buffers(page))
2178 return 0;
2179
2180 blocksize = 1 << inode->i_blkbits;
2181 to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count);
2182 to = from + to;
2183 if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
2184 return 0;
2185
2186 head = page_buffers(page);
2187 bh = head;
2188 block_start = 0;
2189 do {
2190 block_end = block_start + blocksize;
2191 if (block_end > from && block_start < to) {
2192 if (!buffer_uptodate(bh)) {
2193 ret = 0;
2194 break;
2195 }
2196 if (block_end >= to)
2197 break;
2198 }
2199 block_start = block_end;
2200 bh = bh->b_this_page;
2201 } while (bh != head);
2202
2203 return ret;
2204}
2205EXPORT_SYMBOL(block_is_partially_uptodate);
2206
2207/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002208 * Generic "read page" function for block devices that have the normal
2209 * get_block functionality. This is most of the block device filesystems.
2210 * Reads the page asynchronously --- the unlock_buffer() and
2211 * set/clear_buffer_uptodate() functions propagate buffer state into the
2212 * page struct once IO has completed.
2213 */
2214int block_read_full_page(struct page *page, get_block_t *get_block)
2215{
2216 struct inode *inode = page->mapping->host;
2217 sector_t iblock, lblock;
2218 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2219 unsigned int blocksize;
2220 int nr, i;
2221 int fully_mapped = 1;
2222
Matt Mackallcd7619d2005-05-01 08:59:01 -07002223 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002224 blocksize = 1 << inode->i_blkbits;
2225 if (!page_has_buffers(page))
2226 create_empty_buffers(page, blocksize, 0);
2227 head = page_buffers(page);
2228
2229 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2230 lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
2231 bh = head;
2232 nr = 0;
2233 i = 0;
2234
2235 do {
2236 if (buffer_uptodate(bh))
2237 continue;
2238
2239 if (!buffer_mapped(bh)) {
Andrew Mortonc64610b2005-05-16 21:53:49 -07002240 int err = 0;
2241
Linus Torvalds1da177e2005-04-16 15:20:36 -07002242 fully_mapped = 0;
2243 if (iblock < lblock) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002244 WARN_ON(bh->b_size != blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002245 err = get_block(inode, iblock, bh, 0);
2246 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002247 SetPageError(page);
2248 }
2249 if (!buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002250 zero_user(page, i * blocksize, blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002251 if (!err)
2252 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002253 continue;
2254 }
2255 /*
2256 * get_block() might have updated the buffer
2257 * synchronously
2258 */
2259 if (buffer_uptodate(bh))
2260 continue;
2261 }
2262 arr[nr++] = bh;
2263 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2264
2265 if (fully_mapped)
2266 SetPageMappedToDisk(page);
2267
2268 if (!nr) {
2269 /*
2270 * All buffers are uptodate - we can set the page uptodate
2271 * as well. But not if get_block() returned an error.
2272 */
2273 if (!PageError(page))
2274 SetPageUptodate(page);
2275 unlock_page(page);
2276 return 0;
2277 }
2278
2279 /* Stage two: lock the buffers */
2280 for (i = 0; i < nr; i++) {
2281 bh = arr[i];
2282 lock_buffer(bh);
2283 mark_buffer_async_read(bh);
2284 }
2285
2286 /*
2287 * Stage 3: start the IO. Check for uptodateness
2288 * inside the buffer lock in case another process reading
2289 * the underlying blockdev brought it uptodate (the sct fix).
2290 */
2291 for (i = 0; i < nr; i++) {
2292 bh = arr[i];
2293 if (buffer_uptodate(bh))
2294 end_buffer_async_read(bh, 1);
2295 else
2296 submit_bh(READ, bh);
2297 }
2298 return 0;
2299}
2300
2301/* utility function for filesystems that need to do work on expanding
Nick Piggin89e10782007-10-16 01:25:07 -07002302 * truncates. Uses filesystem pagecache writes to allow the filesystem to
Linus Torvalds1da177e2005-04-16 15:20:36 -07002303 * deal with the hole.
2304 */
Nick Piggin89e10782007-10-16 01:25:07 -07002305int generic_cont_expand_simple(struct inode *inode, loff_t size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002306{
2307 struct address_space *mapping = inode->i_mapping;
2308 struct page *page;
Nick Piggin89e10782007-10-16 01:25:07 -07002309 void *fsdata;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002310 unsigned long limit;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002311 int err;
2312
2313 err = -EFBIG;
2314 limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
2315 if (limit != RLIM_INFINITY && size > (loff_t)limit) {
2316 send_sig(SIGXFSZ, current, 0);
2317 goto out;
2318 }
2319 if (size > inode->i_sb->s_maxbytes)
2320 goto out;
2321
Nick Piggin89e10782007-10-16 01:25:07 -07002322 err = pagecache_write_begin(NULL, mapping, size, 0,
2323 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2324 &page, &fsdata);
2325 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002326 goto out;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002327
Nick Piggin89e10782007-10-16 01:25:07 -07002328 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2329 BUG_ON(err > 0);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002330
Linus Torvalds1da177e2005-04-16 15:20:36 -07002331out:
2332 return err;
2333}
2334
Adrian Bunkf1e3af72008-04-29 00:59:01 -07002335static int cont_expand_zero(struct file *file, struct address_space *mapping,
2336 loff_t pos, loff_t *bytes)
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002337{
Nick Piggin89e10782007-10-16 01:25:07 -07002338 struct inode *inode = mapping->host;
2339 unsigned blocksize = 1 << inode->i_blkbits;
2340 struct page *page;
2341 void *fsdata;
2342 pgoff_t index, curidx;
2343 loff_t curpos;
2344 unsigned zerofrom, offset, len;
2345 int err = 0;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002346
Nick Piggin89e10782007-10-16 01:25:07 -07002347 index = pos >> PAGE_CACHE_SHIFT;
2348 offset = pos & ~PAGE_CACHE_MASK;
2349
2350 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
2351 zerofrom = curpos & ~PAGE_CACHE_MASK;
2352 if (zerofrom & (blocksize-1)) {
2353 *bytes |= (blocksize-1);
2354 (*bytes)++;
2355 }
2356 len = PAGE_CACHE_SIZE - zerofrom;
2357
2358 err = pagecache_write_begin(file, mapping, curpos, len,
2359 AOP_FLAG_UNINTERRUPTIBLE,
2360 &page, &fsdata);
2361 if (err)
2362 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002363 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002364 err = pagecache_write_end(file, mapping, curpos, len, len,
2365 page, fsdata);
2366 if (err < 0)
2367 goto out;
2368 BUG_ON(err != len);
2369 err = 0;
OGAWA Hirofumi061e9742008-04-28 02:16:28 -07002370
2371 balance_dirty_pages_ratelimited(mapping);
Nick Piggin89e10782007-10-16 01:25:07 -07002372 }
2373
2374 /* page covers the boundary, find the boundary offset */
2375 if (index == curidx) {
2376 zerofrom = curpos & ~PAGE_CACHE_MASK;
2377 /* if we will expand the thing last block will be filled */
2378 if (offset <= zerofrom) {
2379 goto out;
2380 }
2381 if (zerofrom & (blocksize-1)) {
2382 *bytes |= (blocksize-1);
2383 (*bytes)++;
2384 }
2385 len = offset - zerofrom;
2386
2387 err = pagecache_write_begin(file, mapping, curpos, len,
2388 AOP_FLAG_UNINTERRUPTIBLE,
2389 &page, &fsdata);
2390 if (err)
2391 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002392 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002393 err = pagecache_write_end(file, mapping, curpos, len, len,
2394 page, fsdata);
2395 if (err < 0)
2396 goto out;
2397 BUG_ON(err != len);
2398 err = 0;
2399 }
2400out:
2401 return err;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002402}
2403
Linus Torvalds1da177e2005-04-16 15:20:36 -07002404/*
2405 * For moronic filesystems that do not allow holes in file.
2406 * We may have to extend the file.
2407 */
Nick Piggin89e10782007-10-16 01:25:07 -07002408int cont_write_begin(struct file *file, struct address_space *mapping,
2409 loff_t pos, unsigned len, unsigned flags,
2410 struct page **pagep, void **fsdata,
2411 get_block_t *get_block, loff_t *bytes)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002412{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002413 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002414 unsigned blocksize = 1 << inode->i_blkbits;
Nick Piggin89e10782007-10-16 01:25:07 -07002415 unsigned zerofrom;
2416 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002417
Nick Piggin89e10782007-10-16 01:25:07 -07002418 err = cont_expand_zero(file, mapping, pos, bytes);
2419 if (err)
2420 goto out;
2421
2422 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2423 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2424 *bytes |= (blocksize-1);
2425 (*bytes)++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002426 }
2427
Nick Piggin89e10782007-10-16 01:25:07 -07002428 *pagep = NULL;
2429 err = block_write_begin(file, mapping, pos, len,
2430 flags, pagep, fsdata, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002431out:
Nick Piggin89e10782007-10-16 01:25:07 -07002432 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002433}
2434
2435int block_prepare_write(struct page *page, unsigned from, unsigned to,
2436 get_block_t *get_block)
2437{
2438 struct inode *inode = page->mapping->host;
2439 int err = __block_prepare_write(inode, page, from, to, get_block);
2440 if (err)
2441 ClearPageUptodate(page);
2442 return err;
2443}
2444
2445int block_commit_write(struct page *page, unsigned from, unsigned to)
2446{
2447 struct inode *inode = page->mapping->host;
2448 __block_commit_write(inode,page,from,to);
2449 return 0;
2450}
2451
David Chinner54171692007-07-19 17:39:55 +10002452/*
2453 * block_page_mkwrite() is not allowed to change the file size as it gets
2454 * called from a page fault handler when a page is first dirtied. Hence we must
2455 * be careful to check for EOF conditions here. We set the page up correctly
2456 * for a written page which means we get ENOSPC checking when writing into
2457 * holes and correct delalloc and unwritten extent mapping on filesystems that
2458 * support these features.
2459 *
2460 * We are not allowed to take the i_mutex here so we have to play games to
2461 * protect against truncate races as the page could now be beyond EOF. Because
2462 * vmtruncate() writes the inode size before removing pages, once we have the
2463 * page lock we can determine safely if the page is beyond EOF. If it is not
2464 * beyond EOF, then the page is guaranteed safe against truncation until we
2465 * unlock the page.
2466 */
2467int
2468block_page_mkwrite(struct vm_area_struct *vma, struct page *page,
2469 get_block_t get_block)
2470{
2471 struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
2472 unsigned long end;
2473 loff_t size;
2474 int ret = -EINVAL;
2475
2476 lock_page(page);
2477 size = i_size_read(inode);
2478 if ((page->mapping != inode->i_mapping) ||
Nick Piggin18336332007-07-20 00:31:45 -07002479 (page_offset(page) > size)) {
David Chinner54171692007-07-19 17:39:55 +10002480 /* page got truncated out from underneath us */
2481 goto out_unlock;
2482 }
2483
2484 /* page is wholly or partially inside EOF */
2485 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
2486 end = size & ~PAGE_CACHE_MASK;
2487 else
2488 end = PAGE_CACHE_SIZE;
2489
2490 ret = block_prepare_write(page, 0, end, get_block);
2491 if (!ret)
2492 ret = block_commit_write(page, 0, end);
2493
2494out_unlock:
2495 unlock_page(page);
2496 return ret;
2497}
Linus Torvalds1da177e2005-04-16 15:20:36 -07002498
2499/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002500 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
Linus Torvalds1da177e2005-04-16 15:20:36 -07002501 * immediately, while under the page lock. So it needs a special end_io
2502 * handler which does not touch the bh after unlocking it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002503 */
2504static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2505{
Dmitry Monakhov68671f32007-10-16 01:24:47 -07002506 __end_buffer_read_notouch(bh, uptodate);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002507}
2508
2509/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002510 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2511 * the page (converting it to circular linked list and taking care of page
2512 * dirty races).
2513 */
2514static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2515{
2516 struct buffer_head *bh;
2517
2518 BUG_ON(!PageLocked(page));
2519
2520 spin_lock(&page->mapping->private_lock);
2521 bh = head;
2522 do {
2523 if (PageDirty(page))
2524 set_buffer_dirty(bh);
2525 if (!bh->b_this_page)
2526 bh->b_this_page = head;
2527 bh = bh->b_this_page;
2528 } while (bh != head);
2529 attach_page_buffers(page, head);
2530 spin_unlock(&page->mapping->private_lock);
2531}
2532
2533/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002534 * On entry, the page is fully not uptodate.
2535 * On exit the page is fully uptodate in the areas outside (from,to)
2536 */
Nick Piggin03158cd2007-10-16 01:25:25 -07002537int nobh_write_begin(struct file *file, struct address_space *mapping,
2538 loff_t pos, unsigned len, unsigned flags,
2539 struct page **pagep, void **fsdata,
Linus Torvalds1da177e2005-04-16 15:20:36 -07002540 get_block_t *get_block)
2541{
Nick Piggin03158cd2007-10-16 01:25:25 -07002542 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002543 const unsigned blkbits = inode->i_blkbits;
2544 const unsigned blocksize = 1 << blkbits;
Nick Piggina4b06722007-10-16 01:24:48 -07002545 struct buffer_head *head, *bh;
Nick Piggin03158cd2007-10-16 01:25:25 -07002546 struct page *page;
2547 pgoff_t index;
2548 unsigned from, to;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002549 unsigned block_in_page;
Nick Piggina4b06722007-10-16 01:24:48 -07002550 unsigned block_start, block_end;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002551 sector_t block_in_file;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002552 int nr_reads = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002553 int ret = 0;
2554 int is_mapped_to_disk = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002555
Nick Piggin03158cd2007-10-16 01:25:25 -07002556 index = pos >> PAGE_CACHE_SHIFT;
2557 from = pos & (PAGE_CACHE_SIZE - 1);
2558 to = from + len;
2559
Nick Piggin54566b22009-01-04 12:00:53 -08002560 page = grab_cache_page_write_begin(mapping, index, flags);
Nick Piggin03158cd2007-10-16 01:25:25 -07002561 if (!page)
2562 return -ENOMEM;
2563 *pagep = page;
2564 *fsdata = NULL;
2565
2566 if (page_has_buffers(page)) {
2567 unlock_page(page);
2568 page_cache_release(page);
2569 *pagep = NULL;
2570 return block_write_begin(file, mapping, pos, len, flags, pagep,
2571 fsdata, get_block);
2572 }
Nick Piggina4b06722007-10-16 01:24:48 -07002573
Linus Torvalds1da177e2005-04-16 15:20:36 -07002574 if (PageMappedToDisk(page))
2575 return 0;
2576
Nick Piggina4b06722007-10-16 01:24:48 -07002577 /*
2578 * Allocate buffers so that we can keep track of state, and potentially
2579 * attach them to the page if an error occurs. In the common case of
2580 * no error, they will just be freed again without ever being attached
2581 * to the page (which is all OK, because we're under the page lock).
2582 *
2583 * Be careful: the buffer linked list is a NULL terminated one, rather
2584 * than the circular one we're used to.
2585 */
2586 head = alloc_page_buffers(page, blocksize, 0);
Nick Piggin03158cd2007-10-16 01:25:25 -07002587 if (!head) {
2588 ret = -ENOMEM;
2589 goto out_release;
2590 }
Nick Piggina4b06722007-10-16 01:24:48 -07002591
Linus Torvalds1da177e2005-04-16 15:20:36 -07002592 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002593
2594 /*
2595 * We loop across all blocks in the page, whether or not they are
2596 * part of the affected region. This is so we can discover if the
2597 * page is fully mapped-to-disk.
2598 */
Nick Piggina4b06722007-10-16 01:24:48 -07002599 for (block_start = 0, block_in_page = 0, bh = head;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002600 block_start < PAGE_CACHE_SIZE;
Nick Piggina4b06722007-10-16 01:24:48 -07002601 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002602 int create;
2603
Nick Piggina4b06722007-10-16 01:24:48 -07002604 block_end = block_start + blocksize;
2605 bh->b_state = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002606 create = 1;
2607 if (block_start >= to)
2608 create = 0;
2609 ret = get_block(inode, block_in_file + block_in_page,
Nick Piggina4b06722007-10-16 01:24:48 -07002610 bh, create);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002611 if (ret)
2612 goto failed;
Nick Piggina4b06722007-10-16 01:24:48 -07002613 if (!buffer_mapped(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002614 is_mapped_to_disk = 0;
Nick Piggina4b06722007-10-16 01:24:48 -07002615 if (buffer_new(bh))
2616 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
2617 if (PageUptodate(page)) {
2618 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002619 continue;
Nick Piggina4b06722007-10-16 01:24:48 -07002620 }
2621 if (buffer_new(bh) || !buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002622 zero_user_segments(page, block_start, from,
2623 to, block_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002624 continue;
2625 }
Nick Piggina4b06722007-10-16 01:24:48 -07002626 if (buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002627 continue; /* reiserfs does this */
2628 if (block_start < from || block_end > to) {
Nick Piggina4b06722007-10-16 01:24:48 -07002629 lock_buffer(bh);
2630 bh->b_end_io = end_buffer_read_nobh;
2631 submit_bh(READ, bh);
2632 nr_reads++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002633 }
2634 }
2635
2636 if (nr_reads) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002637 /*
2638 * The page is locked, so these buffers are protected from
2639 * any VM or truncate activity. Hence we don't need to care
2640 * for the buffer_head refcounts.
2641 */
Nick Piggina4b06722007-10-16 01:24:48 -07002642 for (bh = head; bh; bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002643 wait_on_buffer(bh);
2644 if (!buffer_uptodate(bh))
2645 ret = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002646 }
2647 if (ret)
2648 goto failed;
2649 }
2650
2651 if (is_mapped_to_disk)
2652 SetPageMappedToDisk(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002653
Nick Piggin03158cd2007-10-16 01:25:25 -07002654 *fsdata = head; /* to be released by nobh_write_end */
Nick Piggina4b06722007-10-16 01:24:48 -07002655
Linus Torvalds1da177e2005-04-16 15:20:36 -07002656 return 0;
2657
2658failed:
Nick Piggin03158cd2007-10-16 01:25:25 -07002659 BUG_ON(!ret);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002660 /*
Nick Piggina4b06722007-10-16 01:24:48 -07002661 * Error recovery is a bit difficult. We need to zero out blocks that
2662 * were newly allocated, and dirty them to ensure they get written out.
2663 * Buffers need to be attached to the page at this point, otherwise
2664 * the handling of potential IO errors during writeout would be hard
2665 * (could try doing synchronous writeout, but what if that fails too?)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002666 */
Nick Piggin03158cd2007-10-16 01:25:25 -07002667 attach_nobh_buffers(page, head);
2668 page_zero_new_buffers(page, from, to);
Nick Piggina4b06722007-10-16 01:24:48 -07002669
Nick Piggin03158cd2007-10-16 01:25:25 -07002670out_release:
2671 unlock_page(page);
2672 page_cache_release(page);
2673 *pagep = NULL;
Nick Piggina4b06722007-10-16 01:24:48 -07002674
Nick Piggin03158cd2007-10-16 01:25:25 -07002675 if (pos + len > inode->i_size)
2676 vmtruncate(inode, inode->i_size);
Nick Piggina4b06722007-10-16 01:24:48 -07002677
Linus Torvalds1da177e2005-04-16 15:20:36 -07002678 return ret;
2679}
Nick Piggin03158cd2007-10-16 01:25:25 -07002680EXPORT_SYMBOL(nobh_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002681
Nick Piggin03158cd2007-10-16 01:25:25 -07002682int nobh_write_end(struct file *file, struct address_space *mapping,
2683 loff_t pos, unsigned len, unsigned copied,
2684 struct page *page, void *fsdata)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002685{
2686 struct inode *inode = page->mapping->host;
Nick Pigginefdc3132007-10-21 06:57:41 +02002687 struct buffer_head *head = fsdata;
Nick Piggin03158cd2007-10-16 01:25:25 -07002688 struct buffer_head *bh;
Dmitri Monakhov5b41e742008-03-28 14:15:52 -07002689 BUG_ON(fsdata != NULL && page_has_buffers(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002690
Dave Kleikampd4cf1092009-02-06 14:59:26 -06002691 if (unlikely(copied < len) && head)
Dmitri Monakhov5b41e742008-03-28 14:15:52 -07002692 attach_nobh_buffers(page, head);
2693 if (page_has_buffers(page))
2694 return generic_write_end(file, mapping, pos, len,
2695 copied, page, fsdata);
Nick Piggina4b06722007-10-16 01:24:48 -07002696
Nick Piggin22c8ca72007-02-20 13:58:09 -08002697 SetPageUptodate(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002698 set_page_dirty(page);
Nick Piggin03158cd2007-10-16 01:25:25 -07002699 if (pos+copied > inode->i_size) {
2700 i_size_write(inode, pos+copied);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002701 mark_inode_dirty(inode);
2702 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002703
2704 unlock_page(page);
2705 page_cache_release(page);
2706
Nick Piggin03158cd2007-10-16 01:25:25 -07002707 while (head) {
2708 bh = head;
2709 head = head->b_this_page;
2710 free_buffer_head(bh);
2711 }
2712
2713 return copied;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002714}
Nick Piggin03158cd2007-10-16 01:25:25 -07002715EXPORT_SYMBOL(nobh_write_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002716
2717/*
2718 * nobh_writepage() - based on block_full_write_page() except
2719 * that it tries to operate without attaching bufferheads to
2720 * the page.
2721 */
2722int nobh_writepage(struct page *page, get_block_t *get_block,
2723 struct writeback_control *wbc)
2724{
2725 struct inode * const inode = page->mapping->host;
2726 loff_t i_size = i_size_read(inode);
2727 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2728 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002729 int ret;
2730
2731 /* Is the page fully inside i_size? */
2732 if (page->index < end_index)
2733 goto out;
2734
2735 /* Is the page fully outside i_size? (truncate in progress) */
2736 offset = i_size & (PAGE_CACHE_SIZE-1);
2737 if (page->index >= end_index+1 || !offset) {
2738 /*
2739 * The page may have dirty, unmapped buffers. For example,
2740 * they may have been added in ext3_writepage(). Make them
2741 * freeable here, so the page does not leak.
2742 */
2743#if 0
2744 /* Not really sure about this - do we need this ? */
2745 if (page->mapping->a_ops->invalidatepage)
2746 page->mapping->a_ops->invalidatepage(page, offset);
2747#endif
2748 unlock_page(page);
2749 return 0; /* don't care */
2750 }
2751
2752 /*
2753 * The page straddles i_size. It must be zeroed out on each and every
2754 * writepage invocation because it may be mmapped. "A file is mapped
2755 * in multiples of the page size. For a file that is not a multiple of
2756 * the page size, the remaining memory is zeroed when mapped, and
2757 * writes to that region are not written out to the file."
2758 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002759 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002760out:
2761 ret = mpage_writepage(page, get_block, wbc);
2762 if (ret == -EAGAIN)
2763 ret = __block_write_full_page(inode, page, get_block, wbc);
2764 return ret;
2765}
2766EXPORT_SYMBOL(nobh_writepage);
2767
Nick Piggin03158cd2007-10-16 01:25:25 -07002768int nobh_truncate_page(struct address_space *mapping,
2769 loff_t from, get_block_t *get_block)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002770{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002771 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2772 unsigned offset = from & (PAGE_CACHE_SIZE-1);
Nick Piggin03158cd2007-10-16 01:25:25 -07002773 unsigned blocksize;
2774 sector_t iblock;
2775 unsigned length, pos;
2776 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002777 struct page *page;
Nick Piggin03158cd2007-10-16 01:25:25 -07002778 struct buffer_head map_bh;
2779 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002780
Nick Piggin03158cd2007-10-16 01:25:25 -07002781 blocksize = 1 << inode->i_blkbits;
2782 length = offset & (blocksize - 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002783
Nick Piggin03158cd2007-10-16 01:25:25 -07002784 /* Block boundary? Nothing to do */
2785 if (!length)
2786 return 0;
2787
2788 length = blocksize - length;
2789 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2790
Linus Torvalds1da177e2005-04-16 15:20:36 -07002791 page = grab_cache_page(mapping, index);
Nick Piggin03158cd2007-10-16 01:25:25 -07002792 err = -ENOMEM;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002793 if (!page)
2794 goto out;
2795
Nick Piggin03158cd2007-10-16 01:25:25 -07002796 if (page_has_buffers(page)) {
2797has_buffers:
2798 unlock_page(page);
2799 page_cache_release(page);
2800 return block_truncate_page(mapping, from, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002801 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002802
2803 /* Find the buffer that contains "offset" */
2804 pos = blocksize;
2805 while (offset >= pos) {
2806 iblock++;
2807 pos += blocksize;
2808 }
2809
2810 err = get_block(inode, iblock, &map_bh, 0);
2811 if (err)
2812 goto unlock;
2813 /* unmapped? It's a hole - nothing to do */
2814 if (!buffer_mapped(&map_bh))
2815 goto unlock;
2816
2817 /* Ok, it's mapped. Make sure it's up-to-date */
2818 if (!PageUptodate(page)) {
2819 err = mapping->a_ops->readpage(NULL, page);
2820 if (err) {
2821 page_cache_release(page);
2822 goto out;
2823 }
2824 lock_page(page);
2825 if (!PageUptodate(page)) {
2826 err = -EIO;
2827 goto unlock;
2828 }
2829 if (page_has_buffers(page))
2830 goto has_buffers;
2831 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002832 zero_user(page, offset, length);
Nick Piggin03158cd2007-10-16 01:25:25 -07002833 set_page_dirty(page);
2834 err = 0;
2835
2836unlock:
Linus Torvalds1da177e2005-04-16 15:20:36 -07002837 unlock_page(page);
2838 page_cache_release(page);
2839out:
Nick Piggin03158cd2007-10-16 01:25:25 -07002840 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002841}
2842EXPORT_SYMBOL(nobh_truncate_page);
2843
2844int block_truncate_page(struct address_space *mapping,
2845 loff_t from, get_block_t *get_block)
2846{
2847 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2848 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2849 unsigned blocksize;
Andrew Morton54b21a72006-01-08 01:03:05 -08002850 sector_t iblock;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002851 unsigned length, pos;
2852 struct inode *inode = mapping->host;
2853 struct page *page;
2854 struct buffer_head *bh;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002855 int err;
2856
2857 blocksize = 1 << inode->i_blkbits;
2858 length = offset & (blocksize - 1);
2859
2860 /* Block boundary? Nothing to do */
2861 if (!length)
2862 return 0;
2863
2864 length = blocksize - length;
Andrew Morton54b21a72006-01-08 01:03:05 -08002865 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002866
2867 page = grab_cache_page(mapping, index);
2868 err = -ENOMEM;
2869 if (!page)
2870 goto out;
2871
2872 if (!page_has_buffers(page))
2873 create_empty_buffers(page, blocksize, 0);
2874
2875 /* Find the buffer that contains "offset" */
2876 bh = page_buffers(page);
2877 pos = blocksize;
2878 while (offset >= pos) {
2879 bh = bh->b_this_page;
2880 iblock++;
2881 pos += blocksize;
2882 }
2883
2884 err = 0;
2885 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002886 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002887 err = get_block(inode, iblock, bh, 0);
2888 if (err)
2889 goto unlock;
2890 /* unmapped? It's a hole - nothing to do */
2891 if (!buffer_mapped(bh))
2892 goto unlock;
2893 }
2894
2895 /* Ok, it's mapped. Make sure it's up-to-date */
2896 if (PageUptodate(page))
2897 set_buffer_uptodate(bh);
2898
David Chinner33a266d2007-02-12 00:51:41 -08002899 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002900 err = -EIO;
2901 ll_rw_block(READ, 1, &bh);
2902 wait_on_buffer(bh);
2903 /* Uhhuh. Read error. Complain and punt. */
2904 if (!buffer_uptodate(bh))
2905 goto unlock;
2906 }
2907
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002908 zero_user(page, offset, length);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002909 mark_buffer_dirty(bh);
2910 err = 0;
2911
2912unlock:
2913 unlock_page(page);
2914 page_cache_release(page);
2915out:
2916 return err;
2917}
2918
2919/*
2920 * The generic ->writepage function for buffer-backed address_spaces
2921 */
2922int block_write_full_page(struct page *page, get_block_t *get_block,
2923 struct writeback_control *wbc)
2924{
2925 struct inode * const inode = page->mapping->host;
2926 loff_t i_size = i_size_read(inode);
2927 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2928 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002929
2930 /* Is the page fully inside i_size? */
2931 if (page->index < end_index)
2932 return __block_write_full_page(inode, page, get_block, wbc);
2933
2934 /* Is the page fully outside i_size? (truncate in progress) */
2935 offset = i_size & (PAGE_CACHE_SIZE-1);
2936 if (page->index >= end_index+1 || !offset) {
2937 /*
2938 * The page may have dirty, unmapped buffers. For example,
2939 * they may have been added in ext3_writepage(). Make them
2940 * freeable here, so the page does not leak.
2941 */
Jan Karaaaa40592005-10-30 15:00:16 -08002942 do_invalidatepage(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002943 unlock_page(page);
2944 return 0; /* don't care */
2945 }
2946
2947 /*
2948 * The page straddles i_size. It must be zeroed out on each and every
2949 * writepage invokation because it may be mmapped. "A file is mapped
2950 * in multiples of the page size. For a file that is not a multiple of
2951 * the page size, the remaining memory is zeroed when mapped, and
2952 * writes to that region are not written out to the file."
2953 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002954 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002955 return __block_write_full_page(inode, page, get_block, wbc);
2956}
2957
2958sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2959 get_block_t *get_block)
2960{
2961 struct buffer_head tmp;
2962 struct inode *inode = mapping->host;
2963 tmp.b_state = 0;
2964 tmp.b_blocknr = 0;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002965 tmp.b_size = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002966 get_block(inode, block, &tmp, 0);
2967 return tmp.b_blocknr;
2968}
2969
NeilBrown6712ecf2007-09-27 12:47:43 +02002970static void end_bio_bh_io_sync(struct bio *bio, int err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002971{
2972 struct buffer_head *bh = bio->bi_private;
2973
Linus Torvalds1da177e2005-04-16 15:20:36 -07002974 if (err == -EOPNOTSUPP) {
2975 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
2976 set_bit(BH_Eopnotsupp, &bh->b_state);
2977 }
2978
Keith Mannthey08bafc02008-11-25 10:24:35 +01002979 if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags)))
2980 set_bit(BH_Quiet, &bh->b_state);
2981
Linus Torvalds1da177e2005-04-16 15:20:36 -07002982 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2983 bio_put(bio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002984}
2985
2986int submit_bh(int rw, struct buffer_head * bh)
2987{
2988 struct bio *bio;
2989 int ret = 0;
2990
2991 BUG_ON(!buffer_locked(bh));
2992 BUG_ON(!buffer_mapped(bh));
2993 BUG_ON(!bh->b_end_io);
2994
Jens Axboe48fd4f92008-08-22 10:00:36 +02002995 /*
2996 * Mask in barrier bit for a write (could be either a WRITE or a
2997 * WRITE_SYNC
2998 */
2999 if (buffer_ordered(bh) && (rw & WRITE))
3000 rw |= WRITE_BARRIER;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003001
3002 /*
Jens Axboe48fd4f92008-08-22 10:00:36 +02003003 * Only clear out a write error when rewriting
Linus Torvalds1da177e2005-04-16 15:20:36 -07003004 */
Jens Axboe48fd4f92008-08-22 10:00:36 +02003005 if (test_set_buffer_req(bh) && (rw & WRITE))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003006 clear_buffer_write_io_error(bh);
3007
3008 /*
3009 * from here on down, it's all bio -- do the initial mapping,
3010 * submit_bio -> generic_make_request may further map this bio around
3011 */
3012 bio = bio_alloc(GFP_NOIO, 1);
3013
3014 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
3015 bio->bi_bdev = bh->b_bdev;
3016 bio->bi_io_vec[0].bv_page = bh->b_page;
3017 bio->bi_io_vec[0].bv_len = bh->b_size;
3018 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
3019
3020 bio->bi_vcnt = 1;
3021 bio->bi_idx = 0;
3022 bio->bi_size = bh->b_size;
3023
3024 bio->bi_end_io = end_bio_bh_io_sync;
3025 bio->bi_private = bh;
3026
3027 bio_get(bio);
3028 submit_bio(rw, bio);
3029
3030 if (bio_flagged(bio, BIO_EOPNOTSUPP))
3031 ret = -EOPNOTSUPP;
3032
3033 bio_put(bio);
3034 return ret;
3035}
3036
3037/**
3038 * ll_rw_block: low-level access to block devices (DEPRECATED)
Jan Karaa7662232005-09-06 15:19:10 -07003039 * @rw: whether to %READ or %WRITE or %SWRITE or maybe %READA (readahead)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003040 * @nr: number of &struct buffer_heads in the array
3041 * @bhs: array of pointers to &struct buffer_head
3042 *
Jan Karaa7662232005-09-06 15:19:10 -07003043 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
3044 * requests an I/O operation on them, either a %READ or a %WRITE. The third
3045 * %SWRITE is like %WRITE only we make sure that the *current* data in buffers
3046 * are sent to disk. The fourth %READA option is described in the documentation
3047 * for generic_make_request() which ll_rw_block() calls.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003048 *
3049 * This function drops any buffer that it cannot get a lock on (with the
Jan Karaa7662232005-09-06 15:19:10 -07003050 * BH_Lock state bit) unless SWRITE is required, any buffer that appears to be
3051 * clean when doing a write request, and any buffer that appears to be
3052 * up-to-date when doing read request. Further it marks as clean buffers that
3053 * are processed for writing (the buffer cache won't assume that they are
3054 * actually clean until the buffer gets unlocked).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003055 *
3056 * ll_rw_block sets b_end_io to simple completion handler that marks
3057 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
3058 * any waiters.
3059 *
3060 * All of the buffers must be for the same device, and must also be a
3061 * multiple of the current approved size for the device.
3062 */
3063void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
3064{
3065 int i;
3066
3067 for (i = 0; i < nr; i++) {
3068 struct buffer_head *bh = bhs[i];
3069
Jens Axboe18ce3752008-07-01 09:07:34 +02003070 if (rw == SWRITE || rw == SWRITE_SYNC)
Jan Karaa7662232005-09-06 15:19:10 -07003071 lock_buffer(bh);
Nick Pigginca5de402008-08-02 12:02:13 +02003072 else if (!trylock_buffer(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003073 continue;
3074
Jens Axboe18ce3752008-07-01 09:07:34 +02003075 if (rw == WRITE || rw == SWRITE || rw == SWRITE_SYNC) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003076 if (test_clear_buffer_dirty(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07003077 bh->b_end_io = end_buffer_write_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08003078 get_bh(bh);
Jens Axboe18ce3752008-07-01 09:07:34 +02003079 if (rw == SWRITE_SYNC)
3080 submit_bh(WRITE_SYNC, bh);
3081 else
3082 submit_bh(WRITE, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003083 continue;
3084 }
3085 } else {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003086 if (!buffer_uptodate(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07003087 bh->b_end_io = end_buffer_read_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08003088 get_bh(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003089 submit_bh(rw, bh);
3090 continue;
3091 }
3092 }
3093 unlock_buffer(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003094 }
3095}
3096
3097/*
3098 * For a data-integrity writeout, we need to wait upon any in-progress I/O
3099 * and then start new I/O and then wait upon it. The caller must have a ref on
3100 * the buffer_head.
3101 */
3102int sync_dirty_buffer(struct buffer_head *bh)
3103{
3104 int ret = 0;
3105
3106 WARN_ON(atomic_read(&bh->b_count) < 1);
3107 lock_buffer(bh);
3108 if (test_clear_buffer_dirty(bh)) {
3109 get_bh(bh);
3110 bh->b_end_io = end_buffer_write_sync;
Jens Axboe78f707b2009-02-17 13:59:08 +01003111 ret = submit_bh(WRITE, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003112 wait_on_buffer(bh);
3113 if (buffer_eopnotsupp(bh)) {
3114 clear_buffer_eopnotsupp(bh);
3115 ret = -EOPNOTSUPP;
3116 }
3117 if (!ret && !buffer_uptodate(bh))
3118 ret = -EIO;
3119 } else {
3120 unlock_buffer(bh);
3121 }
3122 return ret;
3123}
3124
3125/*
3126 * try_to_free_buffers() checks if all the buffers on this particular page
3127 * are unused, and releases them if so.
3128 *
3129 * Exclusion against try_to_free_buffers may be obtained by either
3130 * locking the page or by holding its mapping's private_lock.
3131 *
3132 * If the page is dirty but all the buffers are clean then we need to
3133 * be sure to mark the page clean as well. This is because the page
3134 * may be against a block device, and a later reattachment of buffers
3135 * to a dirty page will set *all* buffers dirty. Which would corrupt
3136 * filesystem data on the same device.
3137 *
3138 * The same applies to regular filesystem pages: if all the buffers are
3139 * clean then we set the page clean and proceed. To do that, we require
3140 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3141 * private_lock.
3142 *
3143 * try_to_free_buffers() is non-blocking.
3144 */
3145static inline int buffer_busy(struct buffer_head *bh)
3146{
3147 return atomic_read(&bh->b_count) |
3148 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3149}
3150
3151static int
3152drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3153{
3154 struct buffer_head *head = page_buffers(page);
3155 struct buffer_head *bh;
3156
3157 bh = head;
3158 do {
akpm@osdl.orgde7d5a32005-05-01 08:58:39 -07003159 if (buffer_write_io_error(bh) && page->mapping)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003160 set_bit(AS_EIO, &page->mapping->flags);
3161 if (buffer_busy(bh))
3162 goto failed;
3163 bh = bh->b_this_page;
3164 } while (bh != head);
3165
3166 do {
3167 struct buffer_head *next = bh->b_this_page;
3168
Jan Kara535ee2f2008-02-08 04:21:59 -08003169 if (bh->b_assoc_map)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003170 __remove_assoc_queue(bh);
3171 bh = next;
3172 } while (bh != head);
3173 *buffers_to_free = head;
3174 __clear_page_buffers(page);
3175 return 1;
3176failed:
3177 return 0;
3178}
3179
3180int try_to_free_buffers(struct page *page)
3181{
3182 struct address_space * const mapping = page->mapping;
3183 struct buffer_head *buffers_to_free = NULL;
3184 int ret = 0;
3185
3186 BUG_ON(!PageLocked(page));
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003187 if (PageWriteback(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003188 return 0;
3189
3190 if (mapping == NULL) { /* can this still happen? */
3191 ret = drop_buffers(page, &buffers_to_free);
3192 goto out;
3193 }
3194
3195 spin_lock(&mapping->private_lock);
3196 ret = drop_buffers(page, &buffers_to_free);
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003197
3198 /*
3199 * If the filesystem writes its buffers by hand (eg ext3)
3200 * then we can have clean buffers against a dirty page. We
3201 * clean the page here; otherwise the VM will never notice
3202 * that the filesystem did any IO at all.
3203 *
3204 * Also, during truncate, discard_buffer will have marked all
3205 * the page's buffers clean. We discover that here and clean
3206 * the page also.
Nick Piggin87df7242007-01-30 14:36:27 +11003207 *
3208 * private_lock must be held over this entire operation in order
3209 * to synchronise against __set_page_dirty_buffers and prevent the
3210 * dirty bit from being lost.
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003211 */
3212 if (ret)
3213 cancel_dirty_page(page, PAGE_CACHE_SIZE);
Nick Piggin87df7242007-01-30 14:36:27 +11003214 spin_unlock(&mapping->private_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003215out:
3216 if (buffers_to_free) {
3217 struct buffer_head *bh = buffers_to_free;
3218
3219 do {
3220 struct buffer_head *next = bh->b_this_page;
3221 free_buffer_head(bh);
3222 bh = next;
3223 } while (bh != buffers_to_free);
3224 }
3225 return ret;
3226}
3227EXPORT_SYMBOL(try_to_free_buffers);
3228
NeilBrown3978d712006-03-26 01:37:17 -08003229void block_sync_page(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003230{
3231 struct address_space *mapping;
3232
3233 smp_mb();
3234 mapping = page_mapping(page);
3235 if (mapping)
3236 blk_run_backing_dev(mapping->backing_dev_info, page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003237}
3238
3239/*
3240 * There are no bdflush tunables left. But distributions are
3241 * still running obsolete flush daemons, so we terminate them here.
3242 *
3243 * Use of bdflush() is deprecated and will be removed in a future kernel.
3244 * The `pdflush' kernel threads fully replace bdflush daemons and this call.
3245 */
Heiko Carstensbdc480e2009-01-14 14:14:12 +01003246SYSCALL_DEFINE2(bdflush, int, func, long, data)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003247{
3248 static int msg_count;
3249
3250 if (!capable(CAP_SYS_ADMIN))
3251 return -EPERM;
3252
3253 if (msg_count < 5) {
3254 msg_count++;
3255 printk(KERN_INFO
3256 "warning: process `%s' used the obsolete bdflush"
3257 " system call\n", current->comm);
3258 printk(KERN_INFO "Fix your initscripts?\n");
3259 }
3260
3261 if (func == 1)
3262 do_exit(0);
3263 return 0;
3264}
3265
3266/*
3267 * Buffer-head allocation
3268 */
Christoph Lametere18b8902006-12-06 20:33:20 -08003269static struct kmem_cache *bh_cachep;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003270
3271/*
3272 * Once the number of bh's in the machine exceeds this level, we start
3273 * stripping them in writeback.
3274 */
3275static int max_buffer_heads;
3276
3277int buffer_heads_over_limit;
3278
3279struct bh_accounting {
3280 int nr; /* Number of live bh's */
3281 int ratelimit; /* Limit cacheline bouncing */
3282};
3283
3284static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3285
3286static void recalc_bh_state(void)
3287{
3288 int i;
3289 int tot = 0;
3290
3291 if (__get_cpu_var(bh_accounting).ratelimit++ < 4096)
3292 return;
3293 __get_cpu_var(bh_accounting).ratelimit = 0;
Eric Dumazet8a143422006-03-24 03:18:10 -08003294 for_each_online_cpu(i)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003295 tot += per_cpu(bh_accounting, i).nr;
3296 buffer_heads_over_limit = (tot > max_buffer_heads);
3297}
3298
Al Virodd0fc662005-10-07 07:46:04 +01003299struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003300{
Christoph Lameter488514d2008-04-28 02:12:05 -07003301 struct buffer_head *ret = kmem_cache_alloc(bh_cachep, gfp_flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003302 if (ret) {
Christoph Lametera35afb82007-05-16 22:10:57 -07003303 INIT_LIST_HEAD(&ret->b_assoc_buffers);
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07003304 get_cpu_var(bh_accounting).nr++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003305 recalc_bh_state();
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07003306 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003307 }
3308 return ret;
3309}
3310EXPORT_SYMBOL(alloc_buffer_head);
3311
3312void free_buffer_head(struct buffer_head *bh)
3313{
3314 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3315 kmem_cache_free(bh_cachep, bh);
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07003316 get_cpu_var(bh_accounting).nr--;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003317 recalc_bh_state();
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07003318 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003319}
3320EXPORT_SYMBOL(free_buffer_head);
3321
Linus Torvalds1da177e2005-04-16 15:20:36 -07003322static void buffer_exit_cpu(int cpu)
3323{
3324 int i;
3325 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3326
3327 for (i = 0; i < BH_LRU_SIZE; i++) {
3328 brelse(b->bhs[i]);
3329 b->bhs[i] = NULL;
3330 }
Eric Dumazet8a143422006-03-24 03:18:10 -08003331 get_cpu_var(bh_accounting).nr += per_cpu(bh_accounting, cpu).nr;
3332 per_cpu(bh_accounting, cpu).nr = 0;
3333 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003334}
3335
3336static int buffer_cpu_notify(struct notifier_block *self,
3337 unsigned long action, void *hcpu)
3338{
Rafael J. Wysocki8bb78442007-05-09 02:35:10 -07003339 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003340 buffer_exit_cpu((unsigned long)hcpu);
3341 return NOTIFY_OK;
3342}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003343
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003344/**
Randy Dunlapa6b91912008-03-19 17:01:00 -07003345 * bh_uptodate_or_lock - Test whether the buffer is uptodate
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003346 * @bh: struct buffer_head
3347 *
3348 * Return true if the buffer is up-to-date and false,
3349 * with the buffer locked, if not.
3350 */
3351int bh_uptodate_or_lock(struct buffer_head *bh)
3352{
3353 if (!buffer_uptodate(bh)) {
3354 lock_buffer(bh);
3355 if (!buffer_uptodate(bh))
3356 return 0;
3357 unlock_buffer(bh);
3358 }
3359 return 1;
3360}
3361EXPORT_SYMBOL(bh_uptodate_or_lock);
3362
3363/**
Randy Dunlapa6b91912008-03-19 17:01:00 -07003364 * bh_submit_read - Submit a locked buffer for reading
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003365 * @bh: struct buffer_head
3366 *
3367 * Returns zero on success and -EIO on error.
3368 */
3369int bh_submit_read(struct buffer_head *bh)
3370{
3371 BUG_ON(!buffer_locked(bh));
3372
3373 if (buffer_uptodate(bh)) {
3374 unlock_buffer(bh);
3375 return 0;
3376 }
3377
3378 get_bh(bh);
3379 bh->b_end_io = end_buffer_read_sync;
3380 submit_bh(READ, bh);
3381 wait_on_buffer(bh);
3382 if (buffer_uptodate(bh))
3383 return 0;
3384 return -EIO;
3385}
3386EXPORT_SYMBOL(bh_submit_read);
3387
Christoph Lameterb98938c2008-02-04 22:28:36 -08003388static void
Alexey Dobriyan51cc5062008-07-25 19:45:34 -07003389init_buffer_head(void *data)
Christoph Lameterb98938c2008-02-04 22:28:36 -08003390{
3391 struct buffer_head *bh = data;
3392
3393 memset(bh, 0, sizeof(*bh));
3394 INIT_LIST_HEAD(&bh->b_assoc_buffers);
3395}
3396
Linus Torvalds1da177e2005-04-16 15:20:36 -07003397void __init buffer_init(void)
3398{
3399 int nrpages;
3400
Christoph Lameterb98938c2008-02-04 22:28:36 -08003401 bh_cachep = kmem_cache_create("buffer_head",
3402 sizeof(struct buffer_head), 0,
3403 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3404 SLAB_MEM_SPREAD),
3405 init_buffer_head);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003406
3407 /*
3408 * Limit the bh occupancy to 10% of ZONE_NORMAL
3409 */
3410 nrpages = (nr_free_buffer_pages() * 10) / 100;
3411 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3412 hotcpu_notifier(buffer_cpu_notify, 0);
3413}
3414
3415EXPORT_SYMBOL(__bforget);
3416EXPORT_SYMBOL(__brelse);
3417EXPORT_SYMBOL(__wait_on_buffer);
3418EXPORT_SYMBOL(block_commit_write);
3419EXPORT_SYMBOL(block_prepare_write);
David Chinner54171692007-07-19 17:39:55 +10003420EXPORT_SYMBOL(block_page_mkwrite);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003421EXPORT_SYMBOL(block_read_full_page);
3422EXPORT_SYMBOL(block_sync_page);
3423EXPORT_SYMBOL(block_truncate_page);
3424EXPORT_SYMBOL(block_write_full_page);
Nick Piggin89e10782007-10-16 01:25:07 -07003425EXPORT_SYMBOL(cont_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003426EXPORT_SYMBOL(end_buffer_read_sync);
3427EXPORT_SYMBOL(end_buffer_write_sync);
3428EXPORT_SYMBOL(file_fsync);
3429EXPORT_SYMBOL(fsync_bdev);
3430EXPORT_SYMBOL(generic_block_bmap);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08003431EXPORT_SYMBOL(generic_cont_expand_simple);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003432EXPORT_SYMBOL(init_buffer);
3433EXPORT_SYMBOL(invalidate_bdev);
3434EXPORT_SYMBOL(ll_rw_block);
3435EXPORT_SYMBOL(mark_buffer_dirty);
3436EXPORT_SYMBOL(submit_bh);
3437EXPORT_SYMBOL(sync_dirty_buffer);
3438EXPORT_SYMBOL(unlock_buffer);