blob: 9f697419ed8e34ec041c92d8f6794c8b4b06ab33 [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 */
763static int __set_page_dirty(struct page *page,
764 struct address_space *mapping, int warn)
765{
766 if (unlikely(!mapping))
767 return !TestSetPageDirty(page);
768
769 if (TestSetPageDirty(page))
770 return 0;
771
Nick Piggin19fd6232008-07-25 19:45:32 -0700772 spin_lock_irq(&mapping->tree_lock);
Nick Piggin787d2212007-07-17 04:03:34 -0700773 if (page->mapping) { /* Race with truncate? */
774 WARN_ON_ONCE(warn && !PageUptodate(page));
775
776 if (mapping_cap_account_dirty(mapping)) {
777 __inc_zone_page_state(page, NR_FILE_DIRTY);
Peter Zijlstrac9e51e42007-10-16 23:25:47 -0700778 __inc_bdi_stat(mapping->backing_dev_info,
779 BDI_RECLAIMABLE);
Nick Piggin1cf6e7d2009-02-18 14:48:18 -0800780 task_dirty_inc(current);
Nick Piggin787d2212007-07-17 04:03:34 -0700781 task_io_account_write(PAGE_CACHE_SIZE);
782 }
783 radix_tree_tag_set(&mapping->page_tree,
784 page_index(page), PAGECACHE_TAG_DIRTY);
785 }
Nick Piggin19fd6232008-07-25 19:45:32 -0700786 spin_unlock_irq(&mapping->tree_lock);
Nick Piggin787d2212007-07-17 04:03:34 -0700787 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
788
789 return 1;
790}
791
792/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700793 * Add a page to the dirty page list.
794 *
795 * It is a sad fact of life that this function is called from several places
796 * deeply under spinlocking. It may not sleep.
797 *
798 * If the page has buffers, the uptodate buffers are set dirty, to preserve
799 * dirty-state coherency between the page and the buffers. It the page does
800 * not have buffers then when they are later attached they will all be set
801 * dirty.
802 *
803 * The buffers are dirtied before the page is dirtied. There's a small race
804 * window in which a writepage caller may see the page cleanness but not the
805 * buffer dirtiness. That's fine. If this code were to set the page dirty
806 * before the buffers, a concurrent writepage caller could clear the page dirty
807 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
808 * page on the dirty page list.
809 *
810 * We use private_lock to lock against try_to_free_buffers while using the
811 * page's buffer list. Also use this to protect against clean buffers being
812 * added to the page after it was set dirty.
813 *
814 * FIXME: may need to call ->reservepage here as well. That's rather up to the
815 * address_space though.
816 */
817int __set_page_dirty_buffers(struct page *page)
818{
Nick Piggin787d2212007-07-17 04:03:34 -0700819 struct address_space *mapping = page_mapping(page);
Nick Pigginebf7a222006-10-10 04:36:54 +0200820
821 if (unlikely(!mapping))
822 return !TestSetPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700823
824 spin_lock(&mapping->private_lock);
825 if (page_has_buffers(page)) {
826 struct buffer_head *head = page_buffers(page);
827 struct buffer_head *bh = head;
828
829 do {
830 set_buffer_dirty(bh);
831 bh = bh->b_this_page;
832 } while (bh != head);
833 }
834 spin_unlock(&mapping->private_lock);
835
Nick Piggin787d2212007-07-17 04:03:34 -0700836 return __set_page_dirty(page, mapping, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700837}
838EXPORT_SYMBOL(__set_page_dirty_buffers);
839
840/*
841 * Write out and wait upon a list of buffers.
842 *
843 * We have conflicting pressures: we want to make sure that all
844 * initially dirty buffers get waited on, but that any subsequently
845 * dirtied buffers don't. After all, we don't want fsync to last
846 * forever if somebody is actively writing to the file.
847 *
848 * Do this in two main stages: first we copy dirty buffers to a
849 * temporary inode list, queueing the writes as we go. Then we clean
850 * up, waiting for those writes to complete.
851 *
852 * During this second stage, any subsequent updates to the file may end
853 * up refiling the buffer on the original inode's dirty list again, so
854 * there is a chance we will end up with a buffer queued for write but
855 * not yet completed on that list. So, as a final cleanup we go through
856 * the osync code to catch these locked, dirty buffers without requeuing
857 * any newly dirty buffers for write.
858 */
859static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
860{
861 struct buffer_head *bh;
862 struct list_head tmp;
Jan Kara535ee2f2008-02-08 04:21:59 -0800863 struct address_space *mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700864 int err = 0, err2;
865
866 INIT_LIST_HEAD(&tmp);
867
868 spin_lock(lock);
869 while (!list_empty(list)) {
870 bh = BH_ENTRY(list->next);
Jan Kara535ee2f2008-02-08 04:21:59 -0800871 mapping = bh->b_assoc_map;
Jan Kara58ff4072006-10-17 00:10:19 -0700872 __remove_assoc_queue(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -0800873 /* Avoid race with mark_buffer_dirty_inode() which does
874 * a lockless check and we rely on seeing the dirty bit */
875 smp_mb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700876 if (buffer_dirty(bh) || buffer_locked(bh)) {
877 list_add(&bh->b_assoc_buffers, &tmp);
Jan Kara535ee2f2008-02-08 04:21:59 -0800878 bh->b_assoc_map = mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700879 if (buffer_dirty(bh)) {
880 get_bh(bh);
881 spin_unlock(lock);
882 /*
883 * Ensure any pending I/O completes so that
884 * ll_rw_block() actually writes the current
885 * contents - it is a noop if I/O is still in
886 * flight on potentially older contents.
887 */
Jens Axboe18ce3752008-07-01 09:07:34 +0200888 ll_rw_block(SWRITE_SYNC, 1, &bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700889 brelse(bh);
890 spin_lock(lock);
891 }
892 }
893 }
894
895 while (!list_empty(&tmp)) {
896 bh = BH_ENTRY(tmp.prev);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700897 get_bh(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -0800898 mapping = bh->b_assoc_map;
899 __remove_assoc_queue(bh);
900 /* Avoid race with mark_buffer_dirty_inode() which does
901 * a lockless check and we rely on seeing the dirty bit */
902 smp_mb();
903 if (buffer_dirty(bh)) {
904 list_add(&bh->b_assoc_buffers,
Jan Karae3892292008-03-04 14:28:33 -0800905 &mapping->private_list);
Jan Kara535ee2f2008-02-08 04:21:59 -0800906 bh->b_assoc_map = mapping;
907 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700908 spin_unlock(lock);
909 wait_on_buffer(bh);
910 if (!buffer_uptodate(bh))
911 err = -EIO;
912 brelse(bh);
913 spin_lock(lock);
914 }
915
916 spin_unlock(lock);
917 err2 = osync_buffers_list(lock, list);
918 if (err)
919 return err;
920 else
921 return err2;
922}
923
924/*
925 * Invalidate any and all dirty buffers on a given inode. We are
926 * probably unmounting the fs, but that doesn't mean we have already
927 * done a sync(). Just drop the buffers from the inode list.
928 *
929 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
930 * assumes that all the buffers are against the blockdev. Not true
931 * for reiserfs.
932 */
933void invalidate_inode_buffers(struct inode *inode)
934{
935 if (inode_has_buffers(inode)) {
936 struct address_space *mapping = &inode->i_data;
937 struct list_head *list = &mapping->private_list;
938 struct address_space *buffer_mapping = mapping->assoc_mapping;
939
940 spin_lock(&buffer_mapping->private_lock);
941 while (!list_empty(list))
942 __remove_assoc_queue(BH_ENTRY(list->next));
943 spin_unlock(&buffer_mapping->private_lock);
944 }
945}
Jan Kara52b19ac2008-09-23 18:24:08 +0200946EXPORT_SYMBOL(invalidate_inode_buffers);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700947
948/*
949 * Remove any clean buffers from the inode's buffer list. This is called
950 * when we're trying to free the inode itself. Those buffers can pin it.
951 *
952 * Returns true if all buffers were removed.
953 */
954int remove_inode_buffers(struct inode *inode)
955{
956 int ret = 1;
957
958 if (inode_has_buffers(inode)) {
959 struct address_space *mapping = &inode->i_data;
960 struct list_head *list = &mapping->private_list;
961 struct address_space *buffer_mapping = mapping->assoc_mapping;
962
963 spin_lock(&buffer_mapping->private_lock);
964 while (!list_empty(list)) {
965 struct buffer_head *bh = BH_ENTRY(list->next);
966 if (buffer_dirty(bh)) {
967 ret = 0;
968 break;
969 }
970 __remove_assoc_queue(bh);
971 }
972 spin_unlock(&buffer_mapping->private_lock);
973 }
974 return ret;
975}
976
977/*
978 * Create the appropriate buffers when given a page for data area and
979 * the size of each buffer.. Use the bh->b_this_page linked list to
980 * follow the buffers created. Return NULL if unable to create more
981 * buffers.
982 *
983 * The retry flag is used to differentiate async IO (paging, swapping)
984 * which may not fail from ordinary buffer allocations.
985 */
986struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
987 int retry)
988{
989 struct buffer_head *bh, *head;
990 long offset;
991
992try_again:
993 head = NULL;
994 offset = PAGE_SIZE;
995 while ((offset -= size) >= 0) {
996 bh = alloc_buffer_head(GFP_NOFS);
997 if (!bh)
998 goto no_grow;
999
1000 bh->b_bdev = NULL;
1001 bh->b_this_page = head;
1002 bh->b_blocknr = -1;
1003 head = bh;
1004
1005 bh->b_state = 0;
1006 atomic_set(&bh->b_count, 0);
Chris Masonfc5cd582006-02-01 03:06:48 -08001007 bh->b_private = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001008 bh->b_size = size;
1009
1010 /* Link the buffer to its page */
1011 set_bh_page(bh, page, offset);
1012
Nathan Scott01ffe332006-01-17 09:02:07 +11001013 init_buffer(bh, NULL, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001014 }
1015 return head;
1016/*
1017 * In case anything failed, we just free everything we got.
1018 */
1019no_grow:
1020 if (head) {
1021 do {
1022 bh = head;
1023 head = head->b_this_page;
1024 free_buffer_head(bh);
1025 } while (head);
1026 }
1027
1028 /*
1029 * Return failure for non-async IO requests. Async IO requests
1030 * are not allowed to fail, so we have to wait until buffer heads
1031 * become available. But we don't want tasks sleeping with
1032 * partially complete buffers, so all were released above.
1033 */
1034 if (!retry)
1035 return NULL;
1036
1037 /* We're _really_ low on memory. Now we just
1038 * wait for old buffer heads to become free due to
1039 * finishing IO. Since this is an async request and
1040 * the reserve list is empty, we're sure there are
1041 * async buffer heads in use.
1042 */
1043 free_more_memory();
1044 goto try_again;
1045}
1046EXPORT_SYMBOL_GPL(alloc_page_buffers);
1047
1048static inline void
1049link_dev_buffers(struct page *page, struct buffer_head *head)
1050{
1051 struct buffer_head *bh, *tail;
1052
1053 bh = head;
1054 do {
1055 tail = bh;
1056 bh = bh->b_this_page;
1057 } while (bh);
1058 tail->b_this_page = head;
1059 attach_page_buffers(page, head);
1060}
1061
1062/*
1063 * Initialise the state of a blockdev page's buffers.
1064 */
1065static void
1066init_page_buffers(struct page *page, struct block_device *bdev,
1067 sector_t block, int size)
1068{
1069 struct buffer_head *head = page_buffers(page);
1070 struct buffer_head *bh = head;
1071 int uptodate = PageUptodate(page);
1072
1073 do {
1074 if (!buffer_mapped(bh)) {
1075 init_buffer(bh, NULL, NULL);
1076 bh->b_bdev = bdev;
1077 bh->b_blocknr = block;
1078 if (uptodate)
1079 set_buffer_uptodate(bh);
1080 set_buffer_mapped(bh);
1081 }
1082 block++;
1083 bh = bh->b_this_page;
1084 } while (bh != head);
1085}
1086
1087/*
1088 * Create the page-cache page that contains the requested block.
1089 *
1090 * This is user purely for blockdev mappings.
1091 */
1092static struct page *
1093grow_dev_page(struct block_device *bdev, sector_t block,
1094 pgoff_t index, int size)
1095{
1096 struct inode *inode = bdev->bd_inode;
1097 struct page *page;
1098 struct buffer_head *bh;
1099
Christoph Lameterea125892007-05-16 22:11:21 -07001100 page = find_or_create_page(inode->i_mapping, index,
Mel Gorman769848c2007-07-17 04:03:05 -07001101 (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001102 if (!page)
1103 return NULL;
1104
Eric Sesterhenne827f922006-03-26 18:24:46 +02001105 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001106
1107 if (page_has_buffers(page)) {
1108 bh = page_buffers(page);
1109 if (bh->b_size == size) {
1110 init_page_buffers(page, bdev, block, size);
1111 return page;
1112 }
1113 if (!try_to_free_buffers(page))
1114 goto failed;
1115 }
1116
1117 /*
1118 * Allocate some buffers for this page
1119 */
1120 bh = alloc_page_buffers(page, size, 0);
1121 if (!bh)
1122 goto failed;
1123
1124 /*
1125 * Link the page to the buffers and initialise them. Take the
1126 * lock to be atomic wrt __find_get_block(), which does not
1127 * run under the page lock.
1128 */
1129 spin_lock(&inode->i_mapping->private_lock);
1130 link_dev_buffers(page, bh);
1131 init_page_buffers(page, bdev, block, size);
1132 spin_unlock(&inode->i_mapping->private_lock);
1133 return page;
1134
1135failed:
1136 BUG();
1137 unlock_page(page);
1138 page_cache_release(page);
1139 return NULL;
1140}
1141
1142/*
1143 * Create buffers for the specified block device block's page. If
1144 * that page was dirty, the buffers are set dirty also.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001145 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001146static int
Linus Torvalds1da177e2005-04-16 15:20:36 -07001147grow_buffers(struct block_device *bdev, sector_t block, int size)
1148{
1149 struct page *page;
1150 pgoff_t index;
1151 int sizebits;
1152
1153 sizebits = -1;
1154 do {
1155 sizebits++;
1156 } while ((size << sizebits) < PAGE_SIZE);
1157
1158 index = block >> sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001159
Andrew Mortone5657932006-10-11 01:21:46 -07001160 /*
1161 * Check for a block which wants to lie outside our maximum possible
1162 * pagecache index. (this comparison is done using sector_t types).
1163 */
1164 if (unlikely(index != block >> sizebits)) {
1165 char b[BDEVNAME_SIZE];
1166
1167 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1168 "device %s\n",
Harvey Harrison8e24eea2008-04-30 00:55:09 -07001169 __func__, (unsigned long long)block,
Andrew Mortone5657932006-10-11 01:21:46 -07001170 bdevname(bdev, b));
1171 return -EIO;
1172 }
1173 block = index << sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001174 /* Create a page with the proper size buffers.. */
1175 page = grow_dev_page(bdev, block, index, size);
1176 if (!page)
1177 return 0;
1178 unlock_page(page);
1179 page_cache_release(page);
1180 return 1;
1181}
1182
Adrian Bunk75c96f82005-05-05 16:16:09 -07001183static struct buffer_head *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001184__getblk_slow(struct block_device *bdev, sector_t block, int size)
1185{
1186 /* Size must be multiple of hard sectorsize */
1187 if (unlikely(size & (bdev_hardsect_size(bdev)-1) ||
1188 (size < 512 || size > PAGE_SIZE))) {
1189 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1190 size);
1191 printk(KERN_ERR "hardsect size: %d\n",
1192 bdev_hardsect_size(bdev));
1193
1194 dump_stack();
1195 return NULL;
1196 }
1197
1198 for (;;) {
1199 struct buffer_head * bh;
Andrew Mortone5657932006-10-11 01:21:46 -07001200 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001201
1202 bh = __find_get_block(bdev, block, size);
1203 if (bh)
1204 return bh;
1205
Andrew Mortone5657932006-10-11 01:21:46 -07001206 ret = grow_buffers(bdev, block, size);
1207 if (ret < 0)
1208 return NULL;
1209 if (ret == 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001210 free_more_memory();
1211 }
1212}
1213
1214/*
1215 * The relationship between dirty buffers and dirty pages:
1216 *
1217 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1218 * the page is tagged dirty in its radix tree.
1219 *
1220 * At all times, the dirtiness of the buffers represents the dirtiness of
1221 * subsections of the page. If the page has buffers, the page dirty bit is
1222 * merely a hint about the true dirty state.
1223 *
1224 * When a page is set dirty in its entirety, all its buffers are marked dirty
1225 * (if the page has buffers).
1226 *
1227 * When a buffer is marked dirty, its page is dirtied, but the page's other
1228 * buffers are not.
1229 *
1230 * Also. When blockdev buffers are explicitly read with bread(), they
1231 * individually become uptodate. But their backing page remains not
1232 * uptodate - even if all of its buffers are uptodate. A subsequent
1233 * block_read_full_page() against that page will discover all the uptodate
1234 * buffers, will set the page uptodate and will perform no I/O.
1235 */
1236
1237/**
1238 * mark_buffer_dirty - mark a buffer_head as needing writeout
Martin Waitz67be2dd2005-05-01 08:59:26 -07001239 * @bh: the buffer_head to mark dirty
Linus Torvalds1da177e2005-04-16 15:20:36 -07001240 *
1241 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1242 * backing page dirty, then tag the page as dirty in its address_space's radix
1243 * tree and then attach the address_space's inode to its superblock's dirty
1244 * inode list.
1245 *
1246 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1247 * mapping->tree_lock and the global inode_lock.
1248 */
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -08001249void mark_buffer_dirty(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001250{
Nick Piggin787d2212007-07-17 04:03:34 -07001251 WARN_ON_ONCE(!buffer_uptodate(bh));
Linus Torvalds1be62dc2008-04-04 14:38:17 -07001252
1253 /*
1254 * Very *carefully* optimize the it-is-already-dirty case.
1255 *
1256 * Don't let the final "is it dirty" escape to before we
1257 * perhaps modified the buffer.
1258 */
1259 if (buffer_dirty(bh)) {
1260 smp_mb();
1261 if (buffer_dirty(bh))
1262 return;
1263 }
1264
1265 if (!test_set_buffer_dirty(bh))
Nick Piggin787d2212007-07-17 04:03:34 -07001266 __set_page_dirty(bh->b_page, page_mapping(bh->b_page), 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001267}
1268
1269/*
1270 * Decrement a buffer_head's reference count. If all buffers against a page
1271 * have zero reference count, are clean and unlocked, and if the page is clean
1272 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1273 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1274 * a page but it ends up not being freed, and buffers may later be reattached).
1275 */
1276void __brelse(struct buffer_head * buf)
1277{
1278 if (atomic_read(&buf->b_count)) {
1279 put_bh(buf);
1280 return;
1281 }
Arjan van de Ven5c752ad2008-07-25 19:45:40 -07001282 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
Linus Torvalds1da177e2005-04-16 15:20:36 -07001283}
1284
1285/*
1286 * bforget() is like brelse(), except it discards any
1287 * potentially dirty data.
1288 */
1289void __bforget(struct buffer_head *bh)
1290{
1291 clear_buffer_dirty(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -08001292 if (bh->b_assoc_map) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001293 struct address_space *buffer_mapping = bh->b_page->mapping;
1294
1295 spin_lock(&buffer_mapping->private_lock);
1296 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -07001297 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001298 spin_unlock(&buffer_mapping->private_lock);
1299 }
1300 __brelse(bh);
1301}
1302
1303static struct buffer_head *__bread_slow(struct buffer_head *bh)
1304{
1305 lock_buffer(bh);
1306 if (buffer_uptodate(bh)) {
1307 unlock_buffer(bh);
1308 return bh;
1309 } else {
1310 get_bh(bh);
1311 bh->b_end_io = end_buffer_read_sync;
1312 submit_bh(READ, bh);
1313 wait_on_buffer(bh);
1314 if (buffer_uptodate(bh))
1315 return bh;
1316 }
1317 brelse(bh);
1318 return NULL;
1319}
1320
1321/*
1322 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1323 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1324 * refcount elevated by one when they're in an LRU. A buffer can only appear
1325 * once in a particular CPU's LRU. A single buffer can be present in multiple
1326 * CPU's LRUs at the same time.
1327 *
1328 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1329 * sb_find_get_block().
1330 *
1331 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1332 * a local interrupt disable for that.
1333 */
1334
1335#define BH_LRU_SIZE 8
1336
1337struct bh_lru {
1338 struct buffer_head *bhs[BH_LRU_SIZE];
1339};
1340
1341static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1342
1343#ifdef CONFIG_SMP
1344#define bh_lru_lock() local_irq_disable()
1345#define bh_lru_unlock() local_irq_enable()
1346#else
1347#define bh_lru_lock() preempt_disable()
1348#define bh_lru_unlock() preempt_enable()
1349#endif
1350
1351static inline void check_irqs_on(void)
1352{
1353#ifdef irqs_disabled
1354 BUG_ON(irqs_disabled());
1355#endif
1356}
1357
1358/*
1359 * The LRU management algorithm is dopey-but-simple. Sorry.
1360 */
1361static void bh_lru_install(struct buffer_head *bh)
1362{
1363 struct buffer_head *evictee = NULL;
1364 struct bh_lru *lru;
1365
1366 check_irqs_on();
1367 bh_lru_lock();
1368 lru = &__get_cpu_var(bh_lrus);
1369 if (lru->bhs[0] != bh) {
1370 struct buffer_head *bhs[BH_LRU_SIZE];
1371 int in;
1372 int out = 0;
1373
1374 get_bh(bh);
1375 bhs[out++] = bh;
1376 for (in = 0; in < BH_LRU_SIZE; in++) {
1377 struct buffer_head *bh2 = lru->bhs[in];
1378
1379 if (bh2 == bh) {
1380 __brelse(bh2);
1381 } else {
1382 if (out >= BH_LRU_SIZE) {
1383 BUG_ON(evictee != NULL);
1384 evictee = bh2;
1385 } else {
1386 bhs[out++] = bh2;
1387 }
1388 }
1389 }
1390 while (out < BH_LRU_SIZE)
1391 bhs[out++] = NULL;
1392 memcpy(lru->bhs, bhs, sizeof(bhs));
1393 }
1394 bh_lru_unlock();
1395
1396 if (evictee)
1397 __brelse(evictee);
1398}
1399
1400/*
1401 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1402 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001403static struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001404lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001405{
1406 struct buffer_head *ret = NULL;
1407 struct bh_lru *lru;
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001408 unsigned int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001409
1410 check_irqs_on();
1411 bh_lru_lock();
1412 lru = &__get_cpu_var(bh_lrus);
1413 for (i = 0; i < BH_LRU_SIZE; i++) {
1414 struct buffer_head *bh = lru->bhs[i];
1415
1416 if (bh && bh->b_bdev == bdev &&
1417 bh->b_blocknr == block && bh->b_size == size) {
1418 if (i) {
1419 while (i) {
1420 lru->bhs[i] = lru->bhs[i - 1];
1421 i--;
1422 }
1423 lru->bhs[0] = bh;
1424 }
1425 get_bh(bh);
1426 ret = bh;
1427 break;
1428 }
1429 }
1430 bh_lru_unlock();
1431 return ret;
1432}
1433
1434/*
1435 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1436 * it in the LRU and mark it as accessed. If it is not present then return
1437 * NULL
1438 */
1439struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001440__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001441{
1442 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1443
1444 if (bh == NULL) {
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001445 bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001446 if (bh)
1447 bh_lru_install(bh);
1448 }
1449 if (bh)
1450 touch_buffer(bh);
1451 return bh;
1452}
1453EXPORT_SYMBOL(__find_get_block);
1454
1455/*
1456 * __getblk will locate (and, if necessary, create) the buffer_head
1457 * which corresponds to the passed block_device, block and size. The
1458 * returned buffer has its reference count incremented.
1459 *
1460 * __getblk() cannot fail - it just keeps trying. If you pass it an
1461 * illegal block number, __getblk() will happily return a buffer_head
1462 * which represents the non-existent block. Very weird.
1463 *
1464 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1465 * attempt is failing. FIXME, perhaps?
1466 */
1467struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001468__getblk(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001469{
1470 struct buffer_head *bh = __find_get_block(bdev, block, size);
1471
1472 might_sleep();
1473 if (bh == NULL)
1474 bh = __getblk_slow(bdev, block, size);
1475 return bh;
1476}
1477EXPORT_SYMBOL(__getblk);
1478
1479/*
1480 * Do async read-ahead on a buffer..
1481 */
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001482void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001483{
1484 struct buffer_head *bh = __getblk(bdev, block, size);
Andrew Mortona3e713b2005-10-30 15:03:15 -08001485 if (likely(bh)) {
1486 ll_rw_block(READA, 1, &bh);
1487 brelse(bh);
1488 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001489}
1490EXPORT_SYMBOL(__breadahead);
1491
1492/**
1493 * __bread() - reads a specified block and returns the bh
Martin Waitz67be2dd2005-05-01 08:59:26 -07001494 * @bdev: the block_device to read from
Linus Torvalds1da177e2005-04-16 15:20:36 -07001495 * @block: number of block
1496 * @size: size (in bytes) to read
1497 *
1498 * Reads a specified block, and returns buffer head that contains it.
1499 * It returns NULL if the block was unreadable.
1500 */
1501struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001502__bread(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001503{
1504 struct buffer_head *bh = __getblk(bdev, block, size);
1505
Andrew Mortona3e713b2005-10-30 15:03:15 -08001506 if (likely(bh) && !buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001507 bh = __bread_slow(bh);
1508 return bh;
1509}
1510EXPORT_SYMBOL(__bread);
1511
1512/*
1513 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1514 * This doesn't race because it runs in each cpu either in irq
1515 * or with preempt disabled.
1516 */
1517static void invalidate_bh_lru(void *arg)
1518{
1519 struct bh_lru *b = &get_cpu_var(bh_lrus);
1520 int i;
1521
1522 for (i = 0; i < BH_LRU_SIZE; i++) {
1523 brelse(b->bhs[i]);
1524 b->bhs[i] = NULL;
1525 }
1526 put_cpu_var(bh_lrus);
1527}
1528
Peter Zijlstraf9a14392007-05-06 14:49:55 -07001529void invalidate_bh_lrus(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001530{
Jens Axboe15c8b6c2008-05-09 09:39:44 +02001531 on_each_cpu(invalidate_bh_lru, NULL, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001532}
Nick Piggin9db55792008-02-08 04:19:49 -08001533EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001534
1535void set_bh_page(struct buffer_head *bh,
1536 struct page *page, unsigned long offset)
1537{
1538 bh->b_page = page;
Eric Sesterhenne827f922006-03-26 18:24:46 +02001539 BUG_ON(offset >= PAGE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001540 if (PageHighMem(page))
1541 /*
1542 * This catches illegal uses and preserves the offset:
1543 */
1544 bh->b_data = (char *)(0 + offset);
1545 else
1546 bh->b_data = page_address(page) + offset;
1547}
1548EXPORT_SYMBOL(set_bh_page);
1549
1550/*
1551 * Called when truncating a buffer on a page completely.
1552 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001553static void discard_buffer(struct buffer_head * bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001554{
1555 lock_buffer(bh);
1556 clear_buffer_dirty(bh);
1557 bh->b_bdev = NULL;
1558 clear_buffer_mapped(bh);
1559 clear_buffer_req(bh);
1560 clear_buffer_new(bh);
1561 clear_buffer_delay(bh);
David Chinner33a266d2007-02-12 00:51:41 -08001562 clear_buffer_unwritten(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001563 unlock_buffer(bh);
1564}
1565
1566/**
Linus Torvalds1da177e2005-04-16 15:20:36 -07001567 * block_invalidatepage - invalidate part of all of a buffer-backed page
1568 *
1569 * @page: the page which is affected
1570 * @offset: the index of the truncation point
1571 *
1572 * block_invalidatepage() is called when all or part of the page has become
1573 * invalidatedby a truncate operation.
1574 *
1575 * block_invalidatepage() does not have to release all buffers, but it must
1576 * ensure that no dirty buffer is left outside @offset and that no I/O
1577 * is underway against any of the blocks which are outside the truncation
1578 * point. Because the caller is about to free (and possibly reuse) those
1579 * blocks on-disk.
1580 */
NeilBrown2ff28e22006-03-26 01:37:18 -08001581void block_invalidatepage(struct page *page, unsigned long offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001582{
1583 struct buffer_head *head, *bh, *next;
1584 unsigned int curr_off = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001585
1586 BUG_ON(!PageLocked(page));
1587 if (!page_has_buffers(page))
1588 goto out;
1589
1590 head = page_buffers(page);
1591 bh = head;
1592 do {
1593 unsigned int next_off = curr_off + bh->b_size;
1594 next = bh->b_this_page;
1595
1596 /*
1597 * is this block fully invalidated?
1598 */
1599 if (offset <= curr_off)
1600 discard_buffer(bh);
1601 curr_off = next_off;
1602 bh = next;
1603 } while (bh != head);
1604
1605 /*
1606 * We release buffers only if the entire page is being invalidated.
1607 * The get_block cached value has been unconditionally invalidated,
1608 * so real IO is not possible anymore.
1609 */
1610 if (offset == 0)
NeilBrown2ff28e22006-03-26 01:37:18 -08001611 try_to_release_page(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001612out:
NeilBrown2ff28e22006-03-26 01:37:18 -08001613 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001614}
1615EXPORT_SYMBOL(block_invalidatepage);
1616
1617/*
1618 * We attach and possibly dirty the buffers atomically wrt
1619 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1620 * is already excluded via the page lock.
1621 */
1622void create_empty_buffers(struct page *page,
1623 unsigned long blocksize, unsigned long b_state)
1624{
1625 struct buffer_head *bh, *head, *tail;
1626
1627 head = alloc_page_buffers(page, blocksize, 1);
1628 bh = head;
1629 do {
1630 bh->b_state |= b_state;
1631 tail = bh;
1632 bh = bh->b_this_page;
1633 } while (bh);
1634 tail->b_this_page = head;
1635
1636 spin_lock(&page->mapping->private_lock);
1637 if (PageUptodate(page) || PageDirty(page)) {
1638 bh = head;
1639 do {
1640 if (PageDirty(page))
1641 set_buffer_dirty(bh);
1642 if (PageUptodate(page))
1643 set_buffer_uptodate(bh);
1644 bh = bh->b_this_page;
1645 } while (bh != head);
1646 }
1647 attach_page_buffers(page, head);
1648 spin_unlock(&page->mapping->private_lock);
1649}
1650EXPORT_SYMBOL(create_empty_buffers);
1651
1652/*
1653 * We are taking a block for data and we don't want any output from any
1654 * buffer-cache aliases starting from return from that function and
1655 * until the moment when something will explicitly mark the buffer
1656 * dirty (hopefully that will not happen until we will free that block ;-)
1657 * We don't even need to mark it not-uptodate - nobody can expect
1658 * anything from a newly allocated buffer anyway. We used to used
1659 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1660 * don't want to mark the alias unmapped, for example - it would confuse
1661 * anyone who might pick it with bread() afterwards...
1662 *
1663 * Also.. Note that bforget() doesn't lock the buffer. So there can
1664 * be writeout I/O going on against recently-freed buffers. We don't
1665 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1666 * only if we really need to. That happens here.
1667 */
1668void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1669{
1670 struct buffer_head *old_bh;
1671
1672 might_sleep();
1673
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001674 old_bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001675 if (old_bh) {
1676 clear_buffer_dirty(old_bh);
1677 wait_on_buffer(old_bh);
1678 clear_buffer_req(old_bh);
1679 __brelse(old_bh);
1680 }
1681}
1682EXPORT_SYMBOL(unmap_underlying_metadata);
1683
1684/*
1685 * NOTE! All mapped/uptodate combinations are valid:
1686 *
1687 * Mapped Uptodate Meaning
1688 *
1689 * No No "unknown" - must do get_block()
1690 * No Yes "hole" - zero-filled
1691 * Yes No "allocated" - allocated on disk, not read in
1692 * Yes Yes "valid" - allocated and up-to-date in memory.
1693 *
1694 * "Dirty" is valid only with the last case (mapped+uptodate).
1695 */
1696
1697/*
1698 * While block_write_full_page is writing back the dirty buffers under
1699 * the page lock, whoever dirtied the buffers may decide to clean them
1700 * again at any time. We handle that by only looking at the buffer
1701 * state inside lock_buffer().
1702 *
1703 * If block_write_full_page() is called for regular writeback
1704 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1705 * locked buffer. This only can happen if someone has written the buffer
1706 * directly, with submit_bh(). At the address_space level PageWriteback
1707 * prevents this contention from occurring.
1708 */
1709static int __block_write_full_page(struct inode *inode, struct page *page,
1710 get_block_t *get_block, struct writeback_control *wbc)
1711{
1712 int err;
1713 sector_t block;
1714 sector_t last_block;
Andrew Mortonf0fbd5f2005-05-05 16:15:48 -07001715 struct buffer_head *bh, *head;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001716 const unsigned blocksize = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001717 int nr_underway = 0;
1718
1719 BUG_ON(!PageLocked(page));
1720
1721 last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
1722
1723 if (!page_has_buffers(page)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001724 create_empty_buffers(page, blocksize,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001725 (1 << BH_Dirty)|(1 << BH_Uptodate));
1726 }
1727
1728 /*
1729 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1730 * here, and the (potentially unmapped) buffers may become dirty at
1731 * any time. If a buffer becomes dirty here after we've inspected it
1732 * then we just miss that fact, and the page stays dirty.
1733 *
1734 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1735 * handle that here by just cleaning them.
1736 */
1737
Andrew Morton54b21a72006-01-08 01:03:05 -08001738 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001739 head = page_buffers(page);
1740 bh = head;
1741
1742 /*
1743 * Get all the dirty buffers mapped to disk addresses and
1744 * handle any aliases from the underlying blockdev's mapping.
1745 */
1746 do {
1747 if (block > last_block) {
1748 /*
1749 * mapped buffers outside i_size will occur, because
1750 * this page can be outside i_size when there is a
1751 * truncate in progress.
1752 */
1753 /*
1754 * The buffer was zeroed by block_write_full_page()
1755 */
1756 clear_buffer_dirty(bh);
1757 set_buffer_uptodate(bh);
Alex Tomas29a814d2008-07-11 19:27:31 -04001758 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1759 buffer_dirty(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001760 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001761 err = get_block(inode, block, bh, 1);
1762 if (err)
1763 goto recover;
Alex Tomas29a814d2008-07-11 19:27:31 -04001764 clear_buffer_delay(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001765 if (buffer_new(bh)) {
1766 /* blockdev mappings never come here */
1767 clear_buffer_new(bh);
1768 unmap_underlying_metadata(bh->b_bdev,
1769 bh->b_blocknr);
1770 }
1771 }
1772 bh = bh->b_this_page;
1773 block++;
1774 } while (bh != head);
1775
1776 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001777 if (!buffer_mapped(bh))
1778 continue;
1779 /*
1780 * If it's a fully non-blocking write attempt and we cannot
1781 * lock the buffer then redirty the page. Note that this can
1782 * potentially cause a busy-wait loop from pdflush and kswapd
1783 * activity, but those code paths have their own higher-level
1784 * throttling.
1785 */
1786 if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
1787 lock_buffer(bh);
Nick Pigginca5de402008-08-02 12:02:13 +02001788 } else if (!trylock_buffer(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001789 redirty_page_for_writepage(wbc, page);
1790 continue;
1791 }
1792 if (test_clear_buffer_dirty(bh)) {
1793 mark_buffer_async_write(bh);
1794 } else {
1795 unlock_buffer(bh);
1796 }
1797 } while ((bh = bh->b_this_page) != head);
1798
1799 /*
1800 * The page and its buffers are protected by PageWriteback(), so we can
1801 * drop the bh refcounts early.
1802 */
1803 BUG_ON(PageWriteback(page));
1804 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001805
1806 do {
1807 struct buffer_head *next = bh->b_this_page;
1808 if (buffer_async_write(bh)) {
1809 submit_bh(WRITE, bh);
1810 nr_underway++;
1811 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001812 bh = next;
1813 } while (bh != head);
Andrew Morton05937ba2005-05-05 16:15:47 -07001814 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001815
1816 err = 0;
1817done:
1818 if (nr_underway == 0) {
1819 /*
1820 * The page was marked dirty, but the buffers were
1821 * clean. Someone wrote them back by hand with
1822 * ll_rw_block/submit_bh. A rare case.
1823 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001824 end_page_writeback(page);
Nick Piggin3d67f2d2007-05-06 14:49:05 -07001825
Linus Torvalds1da177e2005-04-16 15:20:36 -07001826 /*
1827 * The page and buffer_heads can be released at any time from
1828 * here on.
1829 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001830 }
1831 return err;
1832
1833recover:
1834 /*
1835 * ENOSPC, or some other error. We may already have added some
1836 * blocks to the file, so we need to write these out to avoid
1837 * exposing stale data.
1838 * The page is currently locked and not marked for writeback
1839 */
1840 bh = head;
1841 /* Recovery: lock and submit the mapped buffers */
1842 do {
Alex Tomas29a814d2008-07-11 19:27:31 -04001843 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1844 !buffer_delay(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001845 lock_buffer(bh);
1846 mark_buffer_async_write(bh);
1847 } else {
1848 /*
1849 * The buffer may have been set dirty during
1850 * attachment to a dirty page.
1851 */
1852 clear_buffer_dirty(bh);
1853 }
1854 } while ((bh = bh->b_this_page) != head);
1855 SetPageError(page);
1856 BUG_ON(PageWriteback(page));
Andrew Morton7e4c3692007-05-08 00:23:27 -07001857 mapping_set_error(page->mapping, err);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001858 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001859 do {
1860 struct buffer_head *next = bh->b_this_page;
1861 if (buffer_async_write(bh)) {
1862 clear_buffer_dirty(bh);
1863 submit_bh(WRITE, bh);
1864 nr_underway++;
1865 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001866 bh = next;
1867 } while (bh != head);
Nick Pigginffda9d32007-02-20 13:57:54 -08001868 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001869 goto done;
1870}
1871
Nick Pigginafddba42007-10-16 01:25:01 -07001872/*
1873 * If a page has any new buffers, zero them out here, and mark them uptodate
1874 * and dirty so they'll be written out (in order to prevent uninitialised
1875 * block data from leaking). And clear the new bit.
1876 */
1877void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1878{
1879 unsigned int block_start, block_end;
1880 struct buffer_head *head, *bh;
1881
1882 BUG_ON(!PageLocked(page));
1883 if (!page_has_buffers(page))
1884 return;
1885
1886 bh = head = page_buffers(page);
1887 block_start = 0;
1888 do {
1889 block_end = block_start + bh->b_size;
1890
1891 if (buffer_new(bh)) {
1892 if (block_end > from && block_start < to) {
1893 if (!PageUptodate(page)) {
1894 unsigned start, size;
1895
1896 start = max(from, block_start);
1897 size = min(to, block_end) - start;
1898
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001899 zero_user(page, start, size);
Nick Pigginafddba42007-10-16 01:25:01 -07001900 set_buffer_uptodate(bh);
1901 }
1902
1903 clear_buffer_new(bh);
1904 mark_buffer_dirty(bh);
1905 }
1906 }
1907
1908 block_start = block_end;
1909 bh = bh->b_this_page;
1910 } while (bh != head);
1911}
1912EXPORT_SYMBOL(page_zero_new_buffers);
1913
Linus Torvalds1da177e2005-04-16 15:20:36 -07001914static int __block_prepare_write(struct inode *inode, struct page *page,
1915 unsigned from, unsigned to, get_block_t *get_block)
1916{
1917 unsigned block_start, block_end;
1918 sector_t block;
1919 int err = 0;
1920 unsigned blocksize, bbits;
1921 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1922
1923 BUG_ON(!PageLocked(page));
1924 BUG_ON(from > PAGE_CACHE_SIZE);
1925 BUG_ON(to > PAGE_CACHE_SIZE);
1926 BUG_ON(from > to);
1927
1928 blocksize = 1 << inode->i_blkbits;
1929 if (!page_has_buffers(page))
1930 create_empty_buffers(page, blocksize, 0);
1931 head = page_buffers(page);
1932
1933 bbits = inode->i_blkbits;
1934 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1935
1936 for(bh = head, block_start = 0; bh != head || !block_start;
1937 block++, block_start=block_end, bh = bh->b_this_page) {
1938 block_end = block_start + blocksize;
1939 if (block_end <= from || block_start >= to) {
1940 if (PageUptodate(page)) {
1941 if (!buffer_uptodate(bh))
1942 set_buffer_uptodate(bh);
1943 }
1944 continue;
1945 }
1946 if (buffer_new(bh))
1947 clear_buffer_new(bh);
1948 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001949 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001950 err = get_block(inode, block, bh, 1);
1951 if (err)
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001952 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001953 if (buffer_new(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001954 unmap_underlying_metadata(bh->b_bdev,
1955 bh->b_blocknr);
1956 if (PageUptodate(page)) {
Nick Piggin637aff42007-10-16 01:25:00 -07001957 clear_buffer_new(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001958 set_buffer_uptodate(bh);
Nick Piggin637aff42007-10-16 01:25:00 -07001959 mark_buffer_dirty(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001960 continue;
1961 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001962 if (block_end > to || block_start < from)
1963 zero_user_segments(page,
1964 to, block_end,
1965 block_start, from);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001966 continue;
1967 }
1968 }
1969 if (PageUptodate(page)) {
1970 if (!buffer_uptodate(bh))
1971 set_buffer_uptodate(bh);
1972 continue;
1973 }
1974 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
David Chinner33a266d2007-02-12 00:51:41 -08001975 !buffer_unwritten(bh) &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001976 (block_start < from || block_end > to)) {
1977 ll_rw_block(READ, 1, &bh);
1978 *wait_bh++=bh;
1979 }
1980 }
1981 /*
1982 * If we issued read requests - let them complete.
1983 */
1984 while(wait_bh > wait) {
1985 wait_on_buffer(*--wait_bh);
1986 if (!buffer_uptodate(*wait_bh))
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001987 err = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001988 }
Nick Pigginafddba42007-10-16 01:25:01 -07001989 if (unlikely(err))
1990 page_zero_new_buffers(page, from, to);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001991 return err;
1992}
1993
1994static int __block_commit_write(struct inode *inode, struct page *page,
1995 unsigned from, unsigned to)
1996{
1997 unsigned block_start, block_end;
1998 int partial = 0;
1999 unsigned blocksize;
2000 struct buffer_head *bh, *head;
2001
2002 blocksize = 1 << inode->i_blkbits;
2003
2004 for(bh = head = page_buffers(page), block_start = 0;
2005 bh != head || !block_start;
2006 block_start=block_end, bh = bh->b_this_page) {
2007 block_end = block_start + blocksize;
2008 if (block_end <= from || block_start >= to) {
2009 if (!buffer_uptodate(bh))
2010 partial = 1;
2011 } else {
2012 set_buffer_uptodate(bh);
2013 mark_buffer_dirty(bh);
2014 }
Nick Pigginafddba42007-10-16 01:25:01 -07002015 clear_buffer_new(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002016 }
2017
2018 /*
2019 * If this is a partial write which happened to make all buffers
2020 * uptodate then we can optimize away a bogus readpage() for
2021 * the next read(). Here we 'discover' whether the page went
2022 * uptodate as a result of this (potentially partial) write.
2023 */
2024 if (!partial)
2025 SetPageUptodate(page);
2026 return 0;
2027}
2028
2029/*
Nick Pigginafddba42007-10-16 01:25:01 -07002030 * block_write_begin takes care of the basic task of block allocation and
2031 * bringing partial write blocks uptodate first.
2032 *
2033 * If *pagep is not NULL, then block_write_begin uses the locked page
2034 * at *pagep rather than allocating its own. In this case, the page will
2035 * not be unlocked or deallocated on failure.
2036 */
2037int block_write_begin(struct file *file, struct address_space *mapping,
2038 loff_t pos, unsigned len, unsigned flags,
2039 struct page **pagep, void **fsdata,
2040 get_block_t *get_block)
2041{
2042 struct inode *inode = mapping->host;
2043 int status = 0;
2044 struct page *page;
2045 pgoff_t index;
2046 unsigned start, end;
2047 int ownpage = 0;
2048
2049 index = pos >> PAGE_CACHE_SHIFT;
2050 start = pos & (PAGE_CACHE_SIZE - 1);
2051 end = start + len;
2052
2053 page = *pagep;
2054 if (page == NULL) {
2055 ownpage = 1;
Nick Piggin54566b22009-01-04 12:00:53 -08002056 page = grab_cache_page_write_begin(mapping, index, flags);
Nick Pigginafddba42007-10-16 01:25:01 -07002057 if (!page) {
2058 status = -ENOMEM;
2059 goto out;
2060 }
2061 *pagep = page;
2062 } else
2063 BUG_ON(!PageLocked(page));
2064
2065 status = __block_prepare_write(inode, page, start, end, get_block);
2066 if (unlikely(status)) {
2067 ClearPageUptodate(page);
2068
2069 if (ownpage) {
2070 unlock_page(page);
2071 page_cache_release(page);
2072 *pagep = NULL;
2073
2074 /*
2075 * prepare_write() may have instantiated a few blocks
2076 * outside i_size. Trim these off again. Don't need
2077 * i_size_read because we hold i_mutex.
2078 */
2079 if (pos + len > inode->i_size)
2080 vmtruncate(inode, inode->i_size);
2081 }
Nick Pigginafddba42007-10-16 01:25:01 -07002082 }
2083
2084out:
2085 return status;
2086}
2087EXPORT_SYMBOL(block_write_begin);
2088
2089int block_write_end(struct file *file, struct address_space *mapping,
2090 loff_t pos, unsigned len, unsigned copied,
2091 struct page *page, void *fsdata)
2092{
2093 struct inode *inode = mapping->host;
2094 unsigned start;
2095
2096 start = pos & (PAGE_CACHE_SIZE - 1);
2097
2098 if (unlikely(copied < len)) {
2099 /*
2100 * The buffers that were written will now be uptodate, so we
2101 * don't have to worry about a readpage reading them and
2102 * overwriting a partial write. However if we have encountered
2103 * a short write and only partially written into a buffer, it
2104 * will not be marked uptodate, so a readpage might come in and
2105 * destroy our partial write.
2106 *
2107 * Do the simplest thing, and just treat any short write to a
2108 * non uptodate page as a zero-length write, and force the
2109 * caller to redo the whole thing.
2110 */
2111 if (!PageUptodate(page))
2112 copied = 0;
2113
2114 page_zero_new_buffers(page, start+copied, start+len);
2115 }
2116 flush_dcache_page(page);
2117
2118 /* This could be a short (even 0-length) commit */
2119 __block_commit_write(inode, page, start, start+copied);
2120
2121 return copied;
2122}
2123EXPORT_SYMBOL(block_write_end);
2124
2125int generic_write_end(struct file *file, struct address_space *mapping,
2126 loff_t pos, unsigned len, unsigned copied,
2127 struct page *page, void *fsdata)
2128{
2129 struct inode *inode = mapping->host;
Jan Karac7d206b2008-07-11 19:27:31 -04002130 int i_size_changed = 0;
Nick Pigginafddba42007-10-16 01:25:01 -07002131
2132 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2133
2134 /*
2135 * No need to use i_size_read() here, the i_size
2136 * cannot change under us because we hold i_mutex.
2137 *
2138 * But it's important to update i_size while still holding page lock:
2139 * page writeout could otherwise come in and zero beyond i_size.
2140 */
2141 if (pos+copied > inode->i_size) {
2142 i_size_write(inode, pos+copied);
Jan Karac7d206b2008-07-11 19:27:31 -04002143 i_size_changed = 1;
Nick Pigginafddba42007-10-16 01:25:01 -07002144 }
2145
2146 unlock_page(page);
2147 page_cache_release(page);
2148
Jan Karac7d206b2008-07-11 19:27:31 -04002149 /*
2150 * Don't mark the inode dirty under page lock. First, it unnecessarily
2151 * makes the holding time of page lock longer. Second, it forces lock
2152 * ordering of page lock and transaction start for journaling
2153 * filesystems.
2154 */
2155 if (i_size_changed)
2156 mark_inode_dirty(inode);
2157
Nick Pigginafddba42007-10-16 01:25:01 -07002158 return copied;
2159}
2160EXPORT_SYMBOL(generic_write_end);
2161
2162/*
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07002163 * block_is_partially_uptodate checks whether buffers within a page are
2164 * uptodate or not.
2165 *
2166 * Returns true if all buffers which correspond to a file portion
2167 * we want to read are uptodate.
2168 */
2169int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
2170 unsigned long from)
2171{
2172 struct inode *inode = page->mapping->host;
2173 unsigned block_start, block_end, blocksize;
2174 unsigned to;
2175 struct buffer_head *bh, *head;
2176 int ret = 1;
2177
2178 if (!page_has_buffers(page))
2179 return 0;
2180
2181 blocksize = 1 << inode->i_blkbits;
2182 to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count);
2183 to = from + to;
2184 if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
2185 return 0;
2186
2187 head = page_buffers(page);
2188 bh = head;
2189 block_start = 0;
2190 do {
2191 block_end = block_start + blocksize;
2192 if (block_end > from && block_start < to) {
2193 if (!buffer_uptodate(bh)) {
2194 ret = 0;
2195 break;
2196 }
2197 if (block_end >= to)
2198 break;
2199 }
2200 block_start = block_end;
2201 bh = bh->b_this_page;
2202 } while (bh != head);
2203
2204 return ret;
2205}
2206EXPORT_SYMBOL(block_is_partially_uptodate);
2207
2208/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002209 * Generic "read page" function for block devices that have the normal
2210 * get_block functionality. This is most of the block device filesystems.
2211 * Reads the page asynchronously --- the unlock_buffer() and
2212 * set/clear_buffer_uptodate() functions propagate buffer state into the
2213 * page struct once IO has completed.
2214 */
2215int block_read_full_page(struct page *page, get_block_t *get_block)
2216{
2217 struct inode *inode = page->mapping->host;
2218 sector_t iblock, lblock;
2219 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2220 unsigned int blocksize;
2221 int nr, i;
2222 int fully_mapped = 1;
2223
Matt Mackallcd7619d2005-05-01 08:59:01 -07002224 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002225 blocksize = 1 << inode->i_blkbits;
2226 if (!page_has_buffers(page))
2227 create_empty_buffers(page, blocksize, 0);
2228 head = page_buffers(page);
2229
2230 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2231 lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
2232 bh = head;
2233 nr = 0;
2234 i = 0;
2235
2236 do {
2237 if (buffer_uptodate(bh))
2238 continue;
2239
2240 if (!buffer_mapped(bh)) {
Andrew Mortonc64610b2005-05-16 21:53:49 -07002241 int err = 0;
2242
Linus Torvalds1da177e2005-04-16 15:20:36 -07002243 fully_mapped = 0;
2244 if (iblock < lblock) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002245 WARN_ON(bh->b_size != blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002246 err = get_block(inode, iblock, bh, 0);
2247 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002248 SetPageError(page);
2249 }
2250 if (!buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002251 zero_user(page, i * blocksize, blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002252 if (!err)
2253 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002254 continue;
2255 }
2256 /*
2257 * get_block() might have updated the buffer
2258 * synchronously
2259 */
2260 if (buffer_uptodate(bh))
2261 continue;
2262 }
2263 arr[nr++] = bh;
2264 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2265
2266 if (fully_mapped)
2267 SetPageMappedToDisk(page);
2268
2269 if (!nr) {
2270 /*
2271 * All buffers are uptodate - we can set the page uptodate
2272 * as well. But not if get_block() returned an error.
2273 */
2274 if (!PageError(page))
2275 SetPageUptodate(page);
2276 unlock_page(page);
2277 return 0;
2278 }
2279
2280 /* Stage two: lock the buffers */
2281 for (i = 0; i < nr; i++) {
2282 bh = arr[i];
2283 lock_buffer(bh);
2284 mark_buffer_async_read(bh);
2285 }
2286
2287 /*
2288 * Stage 3: start the IO. Check for uptodateness
2289 * inside the buffer lock in case another process reading
2290 * the underlying blockdev brought it uptodate (the sct fix).
2291 */
2292 for (i = 0; i < nr; i++) {
2293 bh = arr[i];
2294 if (buffer_uptodate(bh))
2295 end_buffer_async_read(bh, 1);
2296 else
2297 submit_bh(READ, bh);
2298 }
2299 return 0;
2300}
2301
2302/* utility function for filesystems that need to do work on expanding
Nick Piggin89e10782007-10-16 01:25:07 -07002303 * truncates. Uses filesystem pagecache writes to allow the filesystem to
Linus Torvalds1da177e2005-04-16 15:20:36 -07002304 * deal with the hole.
2305 */
Nick Piggin89e10782007-10-16 01:25:07 -07002306int generic_cont_expand_simple(struct inode *inode, loff_t size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002307{
2308 struct address_space *mapping = inode->i_mapping;
2309 struct page *page;
Nick Piggin89e10782007-10-16 01:25:07 -07002310 void *fsdata;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002311 unsigned long limit;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002312 int err;
2313
2314 err = -EFBIG;
2315 limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
2316 if (limit != RLIM_INFINITY && size > (loff_t)limit) {
2317 send_sig(SIGXFSZ, current, 0);
2318 goto out;
2319 }
2320 if (size > inode->i_sb->s_maxbytes)
2321 goto out;
2322
Nick Piggin89e10782007-10-16 01:25:07 -07002323 err = pagecache_write_begin(NULL, mapping, size, 0,
2324 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2325 &page, &fsdata);
2326 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002327 goto out;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002328
Nick Piggin89e10782007-10-16 01:25:07 -07002329 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2330 BUG_ON(err > 0);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002331
Linus Torvalds1da177e2005-04-16 15:20:36 -07002332out:
2333 return err;
2334}
2335
Adrian Bunkf1e3af72008-04-29 00:59:01 -07002336static int cont_expand_zero(struct file *file, struct address_space *mapping,
2337 loff_t pos, loff_t *bytes)
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002338{
Nick Piggin89e10782007-10-16 01:25:07 -07002339 struct inode *inode = mapping->host;
2340 unsigned blocksize = 1 << inode->i_blkbits;
2341 struct page *page;
2342 void *fsdata;
2343 pgoff_t index, curidx;
2344 loff_t curpos;
2345 unsigned zerofrom, offset, len;
2346 int err = 0;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002347
Nick Piggin89e10782007-10-16 01:25:07 -07002348 index = pos >> PAGE_CACHE_SHIFT;
2349 offset = pos & ~PAGE_CACHE_MASK;
2350
2351 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
2352 zerofrom = curpos & ~PAGE_CACHE_MASK;
2353 if (zerofrom & (blocksize-1)) {
2354 *bytes |= (blocksize-1);
2355 (*bytes)++;
2356 }
2357 len = PAGE_CACHE_SIZE - zerofrom;
2358
2359 err = pagecache_write_begin(file, mapping, curpos, len,
2360 AOP_FLAG_UNINTERRUPTIBLE,
2361 &page, &fsdata);
2362 if (err)
2363 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002364 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002365 err = pagecache_write_end(file, mapping, curpos, len, len,
2366 page, fsdata);
2367 if (err < 0)
2368 goto out;
2369 BUG_ON(err != len);
2370 err = 0;
OGAWA Hirofumi061e9742008-04-28 02:16:28 -07002371
2372 balance_dirty_pages_ratelimited(mapping);
Nick Piggin89e10782007-10-16 01:25:07 -07002373 }
2374
2375 /* page covers the boundary, find the boundary offset */
2376 if (index == curidx) {
2377 zerofrom = curpos & ~PAGE_CACHE_MASK;
2378 /* if we will expand the thing last block will be filled */
2379 if (offset <= zerofrom) {
2380 goto out;
2381 }
2382 if (zerofrom & (blocksize-1)) {
2383 *bytes |= (blocksize-1);
2384 (*bytes)++;
2385 }
2386 len = offset - zerofrom;
2387
2388 err = pagecache_write_begin(file, mapping, curpos, len,
2389 AOP_FLAG_UNINTERRUPTIBLE,
2390 &page, &fsdata);
2391 if (err)
2392 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002393 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002394 err = pagecache_write_end(file, mapping, curpos, len, len,
2395 page, fsdata);
2396 if (err < 0)
2397 goto out;
2398 BUG_ON(err != len);
2399 err = 0;
2400 }
2401out:
2402 return err;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002403}
2404
Linus Torvalds1da177e2005-04-16 15:20:36 -07002405/*
2406 * For moronic filesystems that do not allow holes in file.
2407 * We may have to extend the file.
2408 */
Nick Piggin89e10782007-10-16 01:25:07 -07002409int cont_write_begin(struct file *file, struct address_space *mapping,
2410 loff_t pos, unsigned len, unsigned flags,
2411 struct page **pagep, void **fsdata,
2412 get_block_t *get_block, loff_t *bytes)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002413{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002414 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002415 unsigned blocksize = 1 << inode->i_blkbits;
Nick Piggin89e10782007-10-16 01:25:07 -07002416 unsigned zerofrom;
2417 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002418
Nick Piggin89e10782007-10-16 01:25:07 -07002419 err = cont_expand_zero(file, mapping, pos, bytes);
2420 if (err)
2421 goto out;
2422
2423 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2424 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2425 *bytes |= (blocksize-1);
2426 (*bytes)++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002427 }
2428
Nick Piggin89e10782007-10-16 01:25:07 -07002429 *pagep = NULL;
2430 err = block_write_begin(file, mapping, pos, len,
2431 flags, pagep, fsdata, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002432out:
Nick Piggin89e10782007-10-16 01:25:07 -07002433 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002434}
2435
2436int block_prepare_write(struct page *page, unsigned from, unsigned to,
2437 get_block_t *get_block)
2438{
2439 struct inode *inode = page->mapping->host;
2440 int err = __block_prepare_write(inode, page, from, to, get_block);
2441 if (err)
2442 ClearPageUptodate(page);
2443 return err;
2444}
2445
2446int block_commit_write(struct page *page, unsigned from, unsigned to)
2447{
2448 struct inode *inode = page->mapping->host;
2449 __block_commit_write(inode,page,from,to);
2450 return 0;
2451}
2452
David Chinner54171692007-07-19 17:39:55 +10002453/*
2454 * block_page_mkwrite() is not allowed to change the file size as it gets
2455 * called from a page fault handler when a page is first dirtied. Hence we must
2456 * be careful to check for EOF conditions here. We set the page up correctly
2457 * for a written page which means we get ENOSPC checking when writing into
2458 * holes and correct delalloc and unwritten extent mapping on filesystems that
2459 * support these features.
2460 *
2461 * We are not allowed to take the i_mutex here so we have to play games to
2462 * protect against truncate races as the page could now be beyond EOF. Because
2463 * vmtruncate() writes the inode size before removing pages, once we have the
2464 * page lock we can determine safely if the page is beyond EOF. If it is not
2465 * beyond EOF, then the page is guaranteed safe against truncation until we
2466 * unlock the page.
2467 */
2468int
2469block_page_mkwrite(struct vm_area_struct *vma, struct page *page,
2470 get_block_t get_block)
2471{
2472 struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
2473 unsigned long end;
2474 loff_t size;
2475 int ret = -EINVAL;
2476
2477 lock_page(page);
2478 size = i_size_read(inode);
2479 if ((page->mapping != inode->i_mapping) ||
Nick Piggin18336332007-07-20 00:31:45 -07002480 (page_offset(page) > size)) {
David Chinner54171692007-07-19 17:39:55 +10002481 /* page got truncated out from underneath us */
2482 goto out_unlock;
2483 }
2484
2485 /* page is wholly or partially inside EOF */
2486 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
2487 end = size & ~PAGE_CACHE_MASK;
2488 else
2489 end = PAGE_CACHE_SIZE;
2490
2491 ret = block_prepare_write(page, 0, end, get_block);
2492 if (!ret)
2493 ret = block_commit_write(page, 0, end);
2494
2495out_unlock:
2496 unlock_page(page);
2497 return ret;
2498}
Linus Torvalds1da177e2005-04-16 15:20:36 -07002499
2500/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002501 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
Linus Torvalds1da177e2005-04-16 15:20:36 -07002502 * immediately, while under the page lock. So it needs a special end_io
2503 * handler which does not touch the bh after unlocking it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002504 */
2505static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2506{
Dmitry Monakhov68671f32007-10-16 01:24:47 -07002507 __end_buffer_read_notouch(bh, uptodate);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002508}
2509
2510/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002511 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2512 * the page (converting it to circular linked list and taking care of page
2513 * dirty races).
2514 */
2515static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2516{
2517 struct buffer_head *bh;
2518
2519 BUG_ON(!PageLocked(page));
2520
2521 spin_lock(&page->mapping->private_lock);
2522 bh = head;
2523 do {
2524 if (PageDirty(page))
2525 set_buffer_dirty(bh);
2526 if (!bh->b_this_page)
2527 bh->b_this_page = head;
2528 bh = bh->b_this_page;
2529 } while (bh != head);
2530 attach_page_buffers(page, head);
2531 spin_unlock(&page->mapping->private_lock);
2532}
2533
2534/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002535 * On entry, the page is fully not uptodate.
2536 * On exit the page is fully uptodate in the areas outside (from,to)
2537 */
Nick Piggin03158cd2007-10-16 01:25:25 -07002538int nobh_write_begin(struct file *file, struct address_space *mapping,
2539 loff_t pos, unsigned len, unsigned flags,
2540 struct page **pagep, void **fsdata,
Linus Torvalds1da177e2005-04-16 15:20:36 -07002541 get_block_t *get_block)
2542{
Nick Piggin03158cd2007-10-16 01:25:25 -07002543 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002544 const unsigned blkbits = inode->i_blkbits;
2545 const unsigned blocksize = 1 << blkbits;
Nick Piggina4b06722007-10-16 01:24:48 -07002546 struct buffer_head *head, *bh;
Nick Piggin03158cd2007-10-16 01:25:25 -07002547 struct page *page;
2548 pgoff_t index;
2549 unsigned from, to;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002550 unsigned block_in_page;
Nick Piggina4b06722007-10-16 01:24:48 -07002551 unsigned block_start, block_end;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002552 sector_t block_in_file;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002553 int nr_reads = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002554 int ret = 0;
2555 int is_mapped_to_disk = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002556
Nick Piggin03158cd2007-10-16 01:25:25 -07002557 index = pos >> PAGE_CACHE_SHIFT;
2558 from = pos & (PAGE_CACHE_SIZE - 1);
2559 to = from + len;
2560
Nick Piggin54566b22009-01-04 12:00:53 -08002561 page = grab_cache_page_write_begin(mapping, index, flags);
Nick Piggin03158cd2007-10-16 01:25:25 -07002562 if (!page)
2563 return -ENOMEM;
2564 *pagep = page;
2565 *fsdata = NULL;
2566
2567 if (page_has_buffers(page)) {
2568 unlock_page(page);
2569 page_cache_release(page);
2570 *pagep = NULL;
2571 return block_write_begin(file, mapping, pos, len, flags, pagep,
2572 fsdata, get_block);
2573 }
Nick Piggina4b06722007-10-16 01:24:48 -07002574
Linus Torvalds1da177e2005-04-16 15:20:36 -07002575 if (PageMappedToDisk(page))
2576 return 0;
2577
Nick Piggina4b06722007-10-16 01:24:48 -07002578 /*
2579 * Allocate buffers so that we can keep track of state, and potentially
2580 * attach them to the page if an error occurs. In the common case of
2581 * no error, they will just be freed again without ever being attached
2582 * to the page (which is all OK, because we're under the page lock).
2583 *
2584 * Be careful: the buffer linked list is a NULL terminated one, rather
2585 * than the circular one we're used to.
2586 */
2587 head = alloc_page_buffers(page, blocksize, 0);
Nick Piggin03158cd2007-10-16 01:25:25 -07002588 if (!head) {
2589 ret = -ENOMEM;
2590 goto out_release;
2591 }
Nick Piggina4b06722007-10-16 01:24:48 -07002592
Linus Torvalds1da177e2005-04-16 15:20:36 -07002593 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002594
2595 /*
2596 * We loop across all blocks in the page, whether or not they are
2597 * part of the affected region. This is so we can discover if the
2598 * page is fully mapped-to-disk.
2599 */
Nick Piggina4b06722007-10-16 01:24:48 -07002600 for (block_start = 0, block_in_page = 0, bh = head;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002601 block_start < PAGE_CACHE_SIZE;
Nick Piggina4b06722007-10-16 01:24:48 -07002602 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002603 int create;
2604
Nick Piggina4b06722007-10-16 01:24:48 -07002605 block_end = block_start + blocksize;
2606 bh->b_state = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002607 create = 1;
2608 if (block_start >= to)
2609 create = 0;
2610 ret = get_block(inode, block_in_file + block_in_page,
Nick Piggina4b06722007-10-16 01:24:48 -07002611 bh, create);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002612 if (ret)
2613 goto failed;
Nick Piggina4b06722007-10-16 01:24:48 -07002614 if (!buffer_mapped(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002615 is_mapped_to_disk = 0;
Nick Piggina4b06722007-10-16 01:24:48 -07002616 if (buffer_new(bh))
2617 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
2618 if (PageUptodate(page)) {
2619 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002620 continue;
Nick Piggina4b06722007-10-16 01:24:48 -07002621 }
2622 if (buffer_new(bh) || !buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002623 zero_user_segments(page, block_start, from,
2624 to, block_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002625 continue;
2626 }
Nick Piggina4b06722007-10-16 01:24:48 -07002627 if (buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002628 continue; /* reiserfs does this */
2629 if (block_start < from || block_end > to) {
Nick Piggina4b06722007-10-16 01:24:48 -07002630 lock_buffer(bh);
2631 bh->b_end_io = end_buffer_read_nobh;
2632 submit_bh(READ, bh);
2633 nr_reads++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002634 }
2635 }
2636
2637 if (nr_reads) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002638 /*
2639 * The page is locked, so these buffers are protected from
2640 * any VM or truncate activity. Hence we don't need to care
2641 * for the buffer_head refcounts.
2642 */
Nick Piggina4b06722007-10-16 01:24:48 -07002643 for (bh = head; bh; bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002644 wait_on_buffer(bh);
2645 if (!buffer_uptodate(bh))
2646 ret = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002647 }
2648 if (ret)
2649 goto failed;
2650 }
2651
2652 if (is_mapped_to_disk)
2653 SetPageMappedToDisk(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002654
Nick Piggin03158cd2007-10-16 01:25:25 -07002655 *fsdata = head; /* to be released by nobh_write_end */
Nick Piggina4b06722007-10-16 01:24:48 -07002656
Linus Torvalds1da177e2005-04-16 15:20:36 -07002657 return 0;
2658
2659failed:
Nick Piggin03158cd2007-10-16 01:25:25 -07002660 BUG_ON(!ret);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002661 /*
Nick Piggina4b06722007-10-16 01:24:48 -07002662 * Error recovery is a bit difficult. We need to zero out blocks that
2663 * were newly allocated, and dirty them to ensure they get written out.
2664 * Buffers need to be attached to the page at this point, otherwise
2665 * the handling of potential IO errors during writeout would be hard
2666 * (could try doing synchronous writeout, but what if that fails too?)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002667 */
Nick Piggin03158cd2007-10-16 01:25:25 -07002668 attach_nobh_buffers(page, head);
2669 page_zero_new_buffers(page, from, to);
Nick Piggina4b06722007-10-16 01:24:48 -07002670
Nick Piggin03158cd2007-10-16 01:25:25 -07002671out_release:
2672 unlock_page(page);
2673 page_cache_release(page);
2674 *pagep = NULL;
Nick Piggina4b06722007-10-16 01:24:48 -07002675
Nick Piggin03158cd2007-10-16 01:25:25 -07002676 if (pos + len > inode->i_size)
2677 vmtruncate(inode, inode->i_size);
Nick Piggina4b06722007-10-16 01:24:48 -07002678
Linus Torvalds1da177e2005-04-16 15:20:36 -07002679 return ret;
2680}
Nick Piggin03158cd2007-10-16 01:25:25 -07002681EXPORT_SYMBOL(nobh_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002682
Nick Piggin03158cd2007-10-16 01:25:25 -07002683int nobh_write_end(struct file *file, struct address_space *mapping,
2684 loff_t pos, unsigned len, unsigned copied,
2685 struct page *page, void *fsdata)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002686{
2687 struct inode *inode = page->mapping->host;
Nick Pigginefdc3132007-10-21 06:57:41 +02002688 struct buffer_head *head = fsdata;
Nick Piggin03158cd2007-10-16 01:25:25 -07002689 struct buffer_head *bh;
Dmitri Monakhov5b41e742008-03-28 14:15:52 -07002690 BUG_ON(fsdata != NULL && page_has_buffers(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002691
Dave Kleikampd4cf1092009-02-06 14:59:26 -06002692 if (unlikely(copied < len) && head)
Dmitri Monakhov5b41e742008-03-28 14:15:52 -07002693 attach_nobh_buffers(page, head);
2694 if (page_has_buffers(page))
2695 return generic_write_end(file, mapping, pos, len,
2696 copied, page, fsdata);
Nick Piggina4b06722007-10-16 01:24:48 -07002697
Nick Piggin22c8ca72007-02-20 13:58:09 -08002698 SetPageUptodate(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002699 set_page_dirty(page);
Nick Piggin03158cd2007-10-16 01:25:25 -07002700 if (pos+copied > inode->i_size) {
2701 i_size_write(inode, pos+copied);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002702 mark_inode_dirty(inode);
2703 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002704
2705 unlock_page(page);
2706 page_cache_release(page);
2707
Nick Piggin03158cd2007-10-16 01:25:25 -07002708 while (head) {
2709 bh = head;
2710 head = head->b_this_page;
2711 free_buffer_head(bh);
2712 }
2713
2714 return copied;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002715}
Nick Piggin03158cd2007-10-16 01:25:25 -07002716EXPORT_SYMBOL(nobh_write_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002717
2718/*
2719 * nobh_writepage() - based on block_full_write_page() except
2720 * that it tries to operate without attaching bufferheads to
2721 * the page.
2722 */
2723int nobh_writepage(struct page *page, get_block_t *get_block,
2724 struct writeback_control *wbc)
2725{
2726 struct inode * const inode = page->mapping->host;
2727 loff_t i_size = i_size_read(inode);
2728 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2729 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002730 int ret;
2731
2732 /* Is the page fully inside i_size? */
2733 if (page->index < end_index)
2734 goto out;
2735
2736 /* Is the page fully outside i_size? (truncate in progress) */
2737 offset = i_size & (PAGE_CACHE_SIZE-1);
2738 if (page->index >= end_index+1 || !offset) {
2739 /*
2740 * The page may have dirty, unmapped buffers. For example,
2741 * they may have been added in ext3_writepage(). Make them
2742 * freeable here, so the page does not leak.
2743 */
2744#if 0
2745 /* Not really sure about this - do we need this ? */
2746 if (page->mapping->a_ops->invalidatepage)
2747 page->mapping->a_ops->invalidatepage(page, offset);
2748#endif
2749 unlock_page(page);
2750 return 0; /* don't care */
2751 }
2752
2753 /*
2754 * The page straddles i_size. It must be zeroed out on each and every
2755 * writepage invocation because it may be mmapped. "A file is mapped
2756 * in multiples of the page size. For a file that is not a multiple of
2757 * the page size, the remaining memory is zeroed when mapped, and
2758 * writes to that region are not written out to the file."
2759 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002760 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002761out:
2762 ret = mpage_writepage(page, get_block, wbc);
2763 if (ret == -EAGAIN)
2764 ret = __block_write_full_page(inode, page, get_block, wbc);
2765 return ret;
2766}
2767EXPORT_SYMBOL(nobh_writepage);
2768
Nick Piggin03158cd2007-10-16 01:25:25 -07002769int nobh_truncate_page(struct address_space *mapping,
2770 loff_t from, get_block_t *get_block)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002771{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002772 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2773 unsigned offset = from & (PAGE_CACHE_SIZE-1);
Nick Piggin03158cd2007-10-16 01:25:25 -07002774 unsigned blocksize;
2775 sector_t iblock;
2776 unsigned length, pos;
2777 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002778 struct page *page;
Nick Piggin03158cd2007-10-16 01:25:25 -07002779 struct buffer_head map_bh;
2780 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002781
Nick Piggin03158cd2007-10-16 01:25:25 -07002782 blocksize = 1 << inode->i_blkbits;
2783 length = offset & (blocksize - 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002784
Nick Piggin03158cd2007-10-16 01:25:25 -07002785 /* Block boundary? Nothing to do */
2786 if (!length)
2787 return 0;
2788
2789 length = blocksize - length;
2790 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2791
Linus Torvalds1da177e2005-04-16 15:20:36 -07002792 page = grab_cache_page(mapping, index);
Nick Piggin03158cd2007-10-16 01:25:25 -07002793 err = -ENOMEM;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002794 if (!page)
2795 goto out;
2796
Nick Piggin03158cd2007-10-16 01:25:25 -07002797 if (page_has_buffers(page)) {
2798has_buffers:
2799 unlock_page(page);
2800 page_cache_release(page);
2801 return block_truncate_page(mapping, from, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002802 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002803
2804 /* Find the buffer that contains "offset" */
2805 pos = blocksize;
2806 while (offset >= pos) {
2807 iblock++;
2808 pos += blocksize;
2809 }
2810
2811 err = get_block(inode, iblock, &map_bh, 0);
2812 if (err)
2813 goto unlock;
2814 /* unmapped? It's a hole - nothing to do */
2815 if (!buffer_mapped(&map_bh))
2816 goto unlock;
2817
2818 /* Ok, it's mapped. Make sure it's up-to-date */
2819 if (!PageUptodate(page)) {
2820 err = mapping->a_ops->readpage(NULL, page);
2821 if (err) {
2822 page_cache_release(page);
2823 goto out;
2824 }
2825 lock_page(page);
2826 if (!PageUptodate(page)) {
2827 err = -EIO;
2828 goto unlock;
2829 }
2830 if (page_has_buffers(page))
2831 goto has_buffers;
2832 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002833 zero_user(page, offset, length);
Nick Piggin03158cd2007-10-16 01:25:25 -07002834 set_page_dirty(page);
2835 err = 0;
2836
2837unlock:
Linus Torvalds1da177e2005-04-16 15:20:36 -07002838 unlock_page(page);
2839 page_cache_release(page);
2840out:
Nick Piggin03158cd2007-10-16 01:25:25 -07002841 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002842}
2843EXPORT_SYMBOL(nobh_truncate_page);
2844
2845int block_truncate_page(struct address_space *mapping,
2846 loff_t from, get_block_t *get_block)
2847{
2848 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2849 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2850 unsigned blocksize;
Andrew Morton54b21a72006-01-08 01:03:05 -08002851 sector_t iblock;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002852 unsigned length, pos;
2853 struct inode *inode = mapping->host;
2854 struct page *page;
2855 struct buffer_head *bh;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002856 int err;
2857
2858 blocksize = 1 << inode->i_blkbits;
2859 length = offset & (blocksize - 1);
2860
2861 /* Block boundary? Nothing to do */
2862 if (!length)
2863 return 0;
2864
2865 length = blocksize - length;
Andrew Morton54b21a72006-01-08 01:03:05 -08002866 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002867
2868 page = grab_cache_page(mapping, index);
2869 err = -ENOMEM;
2870 if (!page)
2871 goto out;
2872
2873 if (!page_has_buffers(page))
2874 create_empty_buffers(page, blocksize, 0);
2875
2876 /* Find the buffer that contains "offset" */
2877 bh = page_buffers(page);
2878 pos = blocksize;
2879 while (offset >= pos) {
2880 bh = bh->b_this_page;
2881 iblock++;
2882 pos += blocksize;
2883 }
2884
2885 err = 0;
2886 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002887 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002888 err = get_block(inode, iblock, bh, 0);
2889 if (err)
2890 goto unlock;
2891 /* unmapped? It's a hole - nothing to do */
2892 if (!buffer_mapped(bh))
2893 goto unlock;
2894 }
2895
2896 /* Ok, it's mapped. Make sure it's up-to-date */
2897 if (PageUptodate(page))
2898 set_buffer_uptodate(bh);
2899
David Chinner33a266d2007-02-12 00:51:41 -08002900 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002901 err = -EIO;
2902 ll_rw_block(READ, 1, &bh);
2903 wait_on_buffer(bh);
2904 /* Uhhuh. Read error. Complain and punt. */
2905 if (!buffer_uptodate(bh))
2906 goto unlock;
2907 }
2908
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002909 zero_user(page, offset, length);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002910 mark_buffer_dirty(bh);
2911 err = 0;
2912
2913unlock:
2914 unlock_page(page);
2915 page_cache_release(page);
2916out:
2917 return err;
2918}
2919
2920/*
2921 * The generic ->writepage function for buffer-backed address_spaces
2922 */
2923int block_write_full_page(struct page *page, get_block_t *get_block,
2924 struct writeback_control *wbc)
2925{
2926 struct inode * const inode = page->mapping->host;
2927 loff_t i_size = i_size_read(inode);
2928 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2929 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002930
2931 /* Is the page fully inside i_size? */
2932 if (page->index < end_index)
2933 return __block_write_full_page(inode, page, get_block, wbc);
2934
2935 /* Is the page fully outside i_size? (truncate in progress) */
2936 offset = i_size & (PAGE_CACHE_SIZE-1);
2937 if (page->index >= end_index+1 || !offset) {
2938 /*
2939 * The page may have dirty, unmapped buffers. For example,
2940 * they may have been added in ext3_writepage(). Make them
2941 * freeable here, so the page does not leak.
2942 */
Jan Karaaaa40592005-10-30 15:00:16 -08002943 do_invalidatepage(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002944 unlock_page(page);
2945 return 0; /* don't care */
2946 }
2947
2948 /*
2949 * The page straddles i_size. It must be zeroed out on each and every
2950 * writepage invokation because it may be mmapped. "A file is mapped
2951 * in multiples of the page size. For a file that is not a multiple of
2952 * the page size, the remaining memory is zeroed when mapped, and
2953 * writes to that region are not written out to the file."
2954 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002955 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002956 return __block_write_full_page(inode, page, get_block, wbc);
2957}
2958
2959sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2960 get_block_t *get_block)
2961{
2962 struct buffer_head tmp;
2963 struct inode *inode = mapping->host;
2964 tmp.b_state = 0;
2965 tmp.b_blocknr = 0;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002966 tmp.b_size = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002967 get_block(inode, block, &tmp, 0);
2968 return tmp.b_blocknr;
2969}
2970
NeilBrown6712ecf2007-09-27 12:47:43 +02002971static void end_bio_bh_io_sync(struct bio *bio, int err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002972{
2973 struct buffer_head *bh = bio->bi_private;
2974
Linus Torvalds1da177e2005-04-16 15:20:36 -07002975 if (err == -EOPNOTSUPP) {
2976 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
2977 set_bit(BH_Eopnotsupp, &bh->b_state);
2978 }
2979
Keith Mannthey08bafc02008-11-25 10:24:35 +01002980 if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags)))
2981 set_bit(BH_Quiet, &bh->b_state);
2982
Linus Torvalds1da177e2005-04-16 15:20:36 -07002983 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2984 bio_put(bio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002985}
2986
2987int submit_bh(int rw, struct buffer_head * bh)
2988{
2989 struct bio *bio;
2990 int ret = 0;
2991
2992 BUG_ON(!buffer_locked(bh));
2993 BUG_ON(!buffer_mapped(bh));
2994 BUG_ON(!bh->b_end_io);
2995
Jens Axboe48fd4f92008-08-22 10:00:36 +02002996 /*
2997 * Mask in barrier bit for a write (could be either a WRITE or a
2998 * WRITE_SYNC
2999 */
3000 if (buffer_ordered(bh) && (rw & WRITE))
3001 rw |= WRITE_BARRIER;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003002
3003 /*
Jens Axboe48fd4f92008-08-22 10:00:36 +02003004 * Only clear out a write error when rewriting
Linus Torvalds1da177e2005-04-16 15:20:36 -07003005 */
Jens Axboe48fd4f92008-08-22 10:00:36 +02003006 if (test_set_buffer_req(bh) && (rw & WRITE))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003007 clear_buffer_write_io_error(bh);
3008
3009 /*
3010 * from here on down, it's all bio -- do the initial mapping,
3011 * submit_bio -> generic_make_request may further map this bio around
3012 */
3013 bio = bio_alloc(GFP_NOIO, 1);
3014
3015 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
3016 bio->bi_bdev = bh->b_bdev;
3017 bio->bi_io_vec[0].bv_page = bh->b_page;
3018 bio->bi_io_vec[0].bv_len = bh->b_size;
3019 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
3020
3021 bio->bi_vcnt = 1;
3022 bio->bi_idx = 0;
3023 bio->bi_size = bh->b_size;
3024
3025 bio->bi_end_io = end_bio_bh_io_sync;
3026 bio->bi_private = bh;
3027
3028 bio_get(bio);
3029 submit_bio(rw, bio);
3030
3031 if (bio_flagged(bio, BIO_EOPNOTSUPP))
3032 ret = -EOPNOTSUPP;
3033
3034 bio_put(bio);
3035 return ret;
3036}
3037
3038/**
3039 * ll_rw_block: low-level access to block devices (DEPRECATED)
Jan Karaa7662232005-09-06 15:19:10 -07003040 * @rw: whether to %READ or %WRITE or %SWRITE or maybe %READA (readahead)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003041 * @nr: number of &struct buffer_heads in the array
3042 * @bhs: array of pointers to &struct buffer_head
3043 *
Jan Karaa7662232005-09-06 15:19:10 -07003044 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
3045 * requests an I/O operation on them, either a %READ or a %WRITE. The third
3046 * %SWRITE is like %WRITE only we make sure that the *current* data in buffers
3047 * are sent to disk. The fourth %READA option is described in the documentation
3048 * for generic_make_request() which ll_rw_block() calls.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003049 *
3050 * This function drops any buffer that it cannot get a lock on (with the
Jan Karaa7662232005-09-06 15:19:10 -07003051 * BH_Lock state bit) unless SWRITE is required, any buffer that appears to be
3052 * clean when doing a write request, and any buffer that appears to be
3053 * up-to-date when doing read request. Further it marks as clean buffers that
3054 * are processed for writing (the buffer cache won't assume that they are
3055 * actually clean until the buffer gets unlocked).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003056 *
3057 * ll_rw_block sets b_end_io to simple completion handler that marks
3058 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
3059 * any waiters.
3060 *
3061 * All of the buffers must be for the same device, and must also be a
3062 * multiple of the current approved size for the device.
3063 */
3064void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
3065{
3066 int i;
3067
3068 for (i = 0; i < nr; i++) {
3069 struct buffer_head *bh = bhs[i];
3070
Jens Axboe18ce3752008-07-01 09:07:34 +02003071 if (rw == SWRITE || rw == SWRITE_SYNC)
Jan Karaa7662232005-09-06 15:19:10 -07003072 lock_buffer(bh);
Nick Pigginca5de402008-08-02 12:02:13 +02003073 else if (!trylock_buffer(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003074 continue;
3075
Jens Axboe18ce3752008-07-01 09:07:34 +02003076 if (rw == WRITE || rw == SWRITE || rw == SWRITE_SYNC) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003077 if (test_clear_buffer_dirty(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07003078 bh->b_end_io = end_buffer_write_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08003079 get_bh(bh);
Jens Axboe18ce3752008-07-01 09:07:34 +02003080 if (rw == SWRITE_SYNC)
3081 submit_bh(WRITE_SYNC, bh);
3082 else
3083 submit_bh(WRITE, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003084 continue;
3085 }
3086 } else {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003087 if (!buffer_uptodate(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07003088 bh->b_end_io = end_buffer_read_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08003089 get_bh(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003090 submit_bh(rw, bh);
3091 continue;
3092 }
3093 }
3094 unlock_buffer(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003095 }
3096}
3097
3098/*
3099 * For a data-integrity writeout, we need to wait upon any in-progress I/O
3100 * and then start new I/O and then wait upon it. The caller must have a ref on
3101 * the buffer_head.
3102 */
3103int sync_dirty_buffer(struct buffer_head *bh)
3104{
3105 int ret = 0;
3106
3107 WARN_ON(atomic_read(&bh->b_count) < 1);
3108 lock_buffer(bh);
3109 if (test_clear_buffer_dirty(bh)) {
3110 get_bh(bh);
3111 bh->b_end_io = end_buffer_write_sync;
Jens Axboe78f707b2009-02-17 13:59:08 +01003112 ret = submit_bh(WRITE, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003113 wait_on_buffer(bh);
3114 if (buffer_eopnotsupp(bh)) {
3115 clear_buffer_eopnotsupp(bh);
3116 ret = -EOPNOTSUPP;
3117 }
3118 if (!ret && !buffer_uptodate(bh))
3119 ret = -EIO;
3120 } else {
3121 unlock_buffer(bh);
3122 }
3123 return ret;
3124}
3125
3126/*
3127 * try_to_free_buffers() checks if all the buffers on this particular page
3128 * are unused, and releases them if so.
3129 *
3130 * Exclusion against try_to_free_buffers may be obtained by either
3131 * locking the page or by holding its mapping's private_lock.
3132 *
3133 * If the page is dirty but all the buffers are clean then we need to
3134 * be sure to mark the page clean as well. This is because the page
3135 * may be against a block device, and a later reattachment of buffers
3136 * to a dirty page will set *all* buffers dirty. Which would corrupt
3137 * filesystem data on the same device.
3138 *
3139 * The same applies to regular filesystem pages: if all the buffers are
3140 * clean then we set the page clean and proceed. To do that, we require
3141 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3142 * private_lock.
3143 *
3144 * try_to_free_buffers() is non-blocking.
3145 */
3146static inline int buffer_busy(struct buffer_head *bh)
3147{
3148 return atomic_read(&bh->b_count) |
3149 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3150}
3151
3152static int
3153drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3154{
3155 struct buffer_head *head = page_buffers(page);
3156 struct buffer_head *bh;
3157
3158 bh = head;
3159 do {
akpm@osdl.orgde7d5a32005-05-01 08:58:39 -07003160 if (buffer_write_io_error(bh) && page->mapping)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003161 set_bit(AS_EIO, &page->mapping->flags);
3162 if (buffer_busy(bh))
3163 goto failed;
3164 bh = bh->b_this_page;
3165 } while (bh != head);
3166
3167 do {
3168 struct buffer_head *next = bh->b_this_page;
3169
Jan Kara535ee2f2008-02-08 04:21:59 -08003170 if (bh->b_assoc_map)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003171 __remove_assoc_queue(bh);
3172 bh = next;
3173 } while (bh != head);
3174 *buffers_to_free = head;
3175 __clear_page_buffers(page);
3176 return 1;
3177failed:
3178 return 0;
3179}
3180
3181int try_to_free_buffers(struct page *page)
3182{
3183 struct address_space * const mapping = page->mapping;
3184 struct buffer_head *buffers_to_free = NULL;
3185 int ret = 0;
3186
3187 BUG_ON(!PageLocked(page));
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003188 if (PageWriteback(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003189 return 0;
3190
3191 if (mapping == NULL) { /* can this still happen? */
3192 ret = drop_buffers(page, &buffers_to_free);
3193 goto out;
3194 }
3195
3196 spin_lock(&mapping->private_lock);
3197 ret = drop_buffers(page, &buffers_to_free);
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003198
3199 /*
3200 * If the filesystem writes its buffers by hand (eg ext3)
3201 * then we can have clean buffers against a dirty page. We
3202 * clean the page here; otherwise the VM will never notice
3203 * that the filesystem did any IO at all.
3204 *
3205 * Also, during truncate, discard_buffer will have marked all
3206 * the page's buffers clean. We discover that here and clean
3207 * the page also.
Nick Piggin87df7242007-01-30 14:36:27 +11003208 *
3209 * private_lock must be held over this entire operation in order
3210 * to synchronise against __set_page_dirty_buffers and prevent the
3211 * dirty bit from being lost.
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003212 */
3213 if (ret)
3214 cancel_dirty_page(page, PAGE_CACHE_SIZE);
Nick Piggin87df7242007-01-30 14:36:27 +11003215 spin_unlock(&mapping->private_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003216out:
3217 if (buffers_to_free) {
3218 struct buffer_head *bh = buffers_to_free;
3219
3220 do {
3221 struct buffer_head *next = bh->b_this_page;
3222 free_buffer_head(bh);
3223 bh = next;
3224 } while (bh != buffers_to_free);
3225 }
3226 return ret;
3227}
3228EXPORT_SYMBOL(try_to_free_buffers);
3229
NeilBrown3978d712006-03-26 01:37:17 -08003230void block_sync_page(struct page *page)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003231{
3232 struct address_space *mapping;
3233
3234 smp_mb();
3235 mapping = page_mapping(page);
3236 if (mapping)
3237 blk_run_backing_dev(mapping->backing_dev_info, page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003238}
3239
3240/*
3241 * There are no bdflush tunables left. But distributions are
3242 * still running obsolete flush daemons, so we terminate them here.
3243 *
3244 * Use of bdflush() is deprecated and will be removed in a future kernel.
3245 * The `pdflush' kernel threads fully replace bdflush daemons and this call.
3246 */
Heiko Carstensbdc480e2009-01-14 14:14:12 +01003247SYSCALL_DEFINE2(bdflush, int, func, long, data)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003248{
3249 static int msg_count;
3250
3251 if (!capable(CAP_SYS_ADMIN))
3252 return -EPERM;
3253
3254 if (msg_count < 5) {
3255 msg_count++;
3256 printk(KERN_INFO
3257 "warning: process `%s' used the obsolete bdflush"
3258 " system call\n", current->comm);
3259 printk(KERN_INFO "Fix your initscripts?\n");
3260 }
3261
3262 if (func == 1)
3263 do_exit(0);
3264 return 0;
3265}
3266
3267/*
3268 * Buffer-head allocation
3269 */
Christoph Lametere18b8902006-12-06 20:33:20 -08003270static struct kmem_cache *bh_cachep;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003271
3272/*
3273 * Once the number of bh's in the machine exceeds this level, we start
3274 * stripping them in writeback.
3275 */
3276static int max_buffer_heads;
3277
3278int buffer_heads_over_limit;
3279
3280struct bh_accounting {
3281 int nr; /* Number of live bh's */
3282 int ratelimit; /* Limit cacheline bouncing */
3283};
3284
3285static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3286
3287static void recalc_bh_state(void)
3288{
3289 int i;
3290 int tot = 0;
3291
3292 if (__get_cpu_var(bh_accounting).ratelimit++ < 4096)
3293 return;
3294 __get_cpu_var(bh_accounting).ratelimit = 0;
Eric Dumazet8a143422006-03-24 03:18:10 -08003295 for_each_online_cpu(i)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003296 tot += per_cpu(bh_accounting, i).nr;
3297 buffer_heads_over_limit = (tot > max_buffer_heads);
3298}
3299
Al Virodd0fc662005-10-07 07:46:04 +01003300struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003301{
Christoph Lameter488514d2008-04-28 02:12:05 -07003302 struct buffer_head *ret = kmem_cache_alloc(bh_cachep, gfp_flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003303 if (ret) {
Christoph Lametera35afb82007-05-16 22:10:57 -07003304 INIT_LIST_HEAD(&ret->b_assoc_buffers);
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07003305 get_cpu_var(bh_accounting).nr++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003306 recalc_bh_state();
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07003307 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003308 }
3309 return ret;
3310}
3311EXPORT_SYMBOL(alloc_buffer_head);
3312
3313void free_buffer_head(struct buffer_head *bh)
3314{
3315 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3316 kmem_cache_free(bh_cachep, bh);
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07003317 get_cpu_var(bh_accounting).nr--;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003318 recalc_bh_state();
Coywolf Qi Hunt736c7b82005-09-06 15:18:17 -07003319 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003320}
3321EXPORT_SYMBOL(free_buffer_head);
3322
Linus Torvalds1da177e2005-04-16 15:20:36 -07003323static void buffer_exit_cpu(int cpu)
3324{
3325 int i;
3326 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3327
3328 for (i = 0; i < BH_LRU_SIZE; i++) {
3329 brelse(b->bhs[i]);
3330 b->bhs[i] = NULL;
3331 }
Eric Dumazet8a143422006-03-24 03:18:10 -08003332 get_cpu_var(bh_accounting).nr += per_cpu(bh_accounting, cpu).nr;
3333 per_cpu(bh_accounting, cpu).nr = 0;
3334 put_cpu_var(bh_accounting);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003335}
3336
3337static int buffer_cpu_notify(struct notifier_block *self,
3338 unsigned long action, void *hcpu)
3339{
Rafael J. Wysocki8bb78442007-05-09 02:35:10 -07003340 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003341 buffer_exit_cpu((unsigned long)hcpu);
3342 return NOTIFY_OK;
3343}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003344
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003345/**
Randy Dunlapa6b91912008-03-19 17:01:00 -07003346 * bh_uptodate_or_lock - Test whether the buffer is uptodate
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003347 * @bh: struct buffer_head
3348 *
3349 * Return true if the buffer is up-to-date and false,
3350 * with the buffer locked, if not.
3351 */
3352int bh_uptodate_or_lock(struct buffer_head *bh)
3353{
3354 if (!buffer_uptodate(bh)) {
3355 lock_buffer(bh);
3356 if (!buffer_uptodate(bh))
3357 return 0;
3358 unlock_buffer(bh);
3359 }
3360 return 1;
3361}
3362EXPORT_SYMBOL(bh_uptodate_or_lock);
3363
3364/**
Randy Dunlapa6b91912008-03-19 17:01:00 -07003365 * bh_submit_read - Submit a locked buffer for reading
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003366 * @bh: struct buffer_head
3367 *
3368 * Returns zero on success and -EIO on error.
3369 */
3370int bh_submit_read(struct buffer_head *bh)
3371{
3372 BUG_ON(!buffer_locked(bh));
3373
3374 if (buffer_uptodate(bh)) {
3375 unlock_buffer(bh);
3376 return 0;
3377 }
3378
3379 get_bh(bh);
3380 bh->b_end_io = end_buffer_read_sync;
3381 submit_bh(READ, bh);
3382 wait_on_buffer(bh);
3383 if (buffer_uptodate(bh))
3384 return 0;
3385 return -EIO;
3386}
3387EXPORT_SYMBOL(bh_submit_read);
3388
Christoph Lameterb98938c2008-02-04 22:28:36 -08003389static void
Alexey Dobriyan51cc5062008-07-25 19:45:34 -07003390init_buffer_head(void *data)
Christoph Lameterb98938c2008-02-04 22:28:36 -08003391{
3392 struct buffer_head *bh = data;
3393
3394 memset(bh, 0, sizeof(*bh));
3395 INIT_LIST_HEAD(&bh->b_assoc_buffers);
3396}
3397
Linus Torvalds1da177e2005-04-16 15:20:36 -07003398void __init buffer_init(void)
3399{
3400 int nrpages;
3401
Christoph Lameterb98938c2008-02-04 22:28:36 -08003402 bh_cachep = kmem_cache_create("buffer_head",
3403 sizeof(struct buffer_head), 0,
3404 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3405 SLAB_MEM_SPREAD),
3406 init_buffer_head);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003407
3408 /*
3409 * Limit the bh occupancy to 10% of ZONE_NORMAL
3410 */
3411 nrpages = (nr_free_buffer_pages() * 10) / 100;
3412 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3413 hotcpu_notifier(buffer_cpu_notify, 0);
3414}
3415
3416EXPORT_SYMBOL(__bforget);
3417EXPORT_SYMBOL(__brelse);
3418EXPORT_SYMBOL(__wait_on_buffer);
3419EXPORT_SYMBOL(block_commit_write);
3420EXPORT_SYMBOL(block_prepare_write);
David Chinner54171692007-07-19 17:39:55 +10003421EXPORT_SYMBOL(block_page_mkwrite);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003422EXPORT_SYMBOL(block_read_full_page);
3423EXPORT_SYMBOL(block_sync_page);
3424EXPORT_SYMBOL(block_truncate_page);
3425EXPORT_SYMBOL(block_write_full_page);
Nick Piggin89e10782007-10-16 01:25:07 -07003426EXPORT_SYMBOL(cont_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003427EXPORT_SYMBOL(end_buffer_read_sync);
3428EXPORT_SYMBOL(end_buffer_write_sync);
3429EXPORT_SYMBOL(file_fsync);
3430EXPORT_SYMBOL(fsync_bdev);
3431EXPORT_SYMBOL(generic_block_bmap);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08003432EXPORT_SYMBOL(generic_cont_expand_simple);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003433EXPORT_SYMBOL(init_buffer);
3434EXPORT_SYMBOL(invalidate_bdev);
3435EXPORT_SYMBOL(ll_rw_block);
3436EXPORT_SYMBOL(mark_buffer_dirty);
3437EXPORT_SYMBOL(submit_bh);
3438EXPORT_SYMBOL(sync_dirty_buffer);
3439EXPORT_SYMBOL(unlock_buffer);