blob: 5f525b3c6d9f04d520d117295f3d880d29e7e9ec [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
21#include <linux/config.h>
22#include <linux/kernel.h>
23#include <linux/syscalls.h>
24#include <linux/fs.h>
25#include <linux/mm.h>
26#include <linux/percpu.h>
27#include <linux/slab.h>
28#include <linux/smp_lock.h>
29#include <linux/blkdev.h>
30#include <linux/file.h>
31#include <linux/quotaops.h>
32#include <linux/highmem.h>
33#include <linux/module.h>
34#include <linux/writeback.h>
35#include <linux/hash.h>
36#include <linux/suspend.h>
37#include <linux/buffer_head.h>
38#include <linux/bio.h>
39#include <linux/notifier.h>
40#include <linux/cpu.h>
41#include <linux/bitops.h>
42#include <linux/mpage.h>
43
44static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
45static void invalidate_bh_lrus(void);
46
47#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
48
49inline void
50init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
51{
52 bh->b_end_io = handler;
53 bh->b_private = private;
54}
55
56static int sync_buffer(void *word)
57{
58 struct block_device *bd;
59 struct buffer_head *bh
60 = container_of(word, struct buffer_head, b_state);
61
62 smp_mb();
63 bd = bh->b_bdev;
64 if (bd)
65 blk_run_address_space(bd->bd_inode->i_mapping);
66 io_schedule();
67 return 0;
68}
69
70void fastcall __lock_buffer(struct buffer_head *bh)
71{
72 wait_on_bit_lock(&bh->b_state, BH_Lock, sync_buffer,
73 TASK_UNINTERRUPTIBLE);
74}
75EXPORT_SYMBOL(__lock_buffer);
76
77void fastcall unlock_buffer(struct buffer_head *bh)
78{
79 clear_buffer_locked(bh);
80 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);
98 page->private = 0;
99 page_cache_release(page);
100}
101
102static void buffer_io_error(struct buffer_head *bh)
103{
104 char b[BDEVNAME_SIZE];
105
106 printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
107 bdevname(bh->b_bdev, b),
108 (unsigned long long)bh->b_blocknr);
109}
110
111/*
112 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
113 * unlock the buffer. This is what ll_rw_block uses too.
114 */
115void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
116{
117 if (uptodate) {
118 set_buffer_uptodate(bh);
119 } else {
120 /* This happens, due to failed READA attempts. */
121 clear_buffer_uptodate(bh);
122 }
123 unlock_buffer(bh);
124 put_bh(bh);
125}
126
127void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
128{
129 char b[BDEVNAME_SIZE];
130
131 if (uptodate) {
132 set_buffer_uptodate(bh);
133 } else {
134 if (!buffer_eopnotsupp(bh) && printk_ratelimit()) {
135 buffer_io_error(bh);
136 printk(KERN_WARNING "lost page write due to "
137 "I/O error on %s\n",
138 bdevname(bh->b_bdev, b));
139 }
140 set_buffer_write_io_error(bh);
141 clear_buffer_uptodate(bh);
142 }
143 unlock_buffer(bh);
144 put_bh(bh);
145}
146
147/*
148 * Write out and wait upon all the dirty data associated with a block
149 * device via its mapping. Does not take the superblock lock.
150 */
151int sync_blockdev(struct block_device *bdev)
152{
153 int ret = 0;
154
155 if (bdev) {
156 int err;
157
158 ret = filemap_fdatawrite(bdev->bd_inode->i_mapping);
159 err = filemap_fdatawait(bdev->bd_inode->i_mapping);
160 if (!ret)
161 ret = err;
162 }
163 return ret;
164}
165EXPORT_SYMBOL(sync_blockdev);
166
167/*
168 * Write out and wait upon all dirty data associated with this
169 * superblock. Filesystem data as well as the underlying block
170 * device. Takes the superblock lock.
171 */
172int fsync_super(struct super_block *sb)
173{
174 sync_inodes_sb(sb, 0);
175 DQUOT_SYNC(sb);
176 lock_super(sb);
177 if (sb->s_dirt && sb->s_op->write_super)
178 sb->s_op->write_super(sb);
179 unlock_super(sb);
180 if (sb->s_op->sync_fs)
181 sb->s_op->sync_fs(sb, 1);
182 sync_blockdev(sb->s_bdev);
183 sync_inodes_sb(sb, 1);
184
185 return sync_blockdev(sb->s_bdev);
186}
187
188/*
189 * Write out and wait upon all dirty data associated with this
190 * device. Filesystem data as well as the underlying block
191 * device. Takes the superblock lock.
192 */
193int fsync_bdev(struct block_device *bdev)
194{
195 struct super_block *sb = get_super(bdev);
196 if (sb) {
197 int res = fsync_super(sb);
198 drop_super(sb);
199 return res;
200 }
201 return sync_blockdev(bdev);
202}
203
204/**
205 * freeze_bdev -- lock a filesystem and force it into a consistent state
206 * @bdev: blockdevice to lock
207 *
208 * This takes the block device bd_mount_sem to make sure no new mounts
209 * happen on bdev until thaw_bdev() is called.
210 * If a superblock is found on this device, we take the s_umount semaphore
211 * on it to make sure nobody unmounts until the snapshot creation is done.
212 */
213struct super_block *freeze_bdev(struct block_device *bdev)
214{
215 struct super_block *sb;
216
217 down(&bdev->bd_mount_sem);
218 sb = get_super(bdev);
219 if (sb && !(sb->s_flags & MS_RDONLY)) {
220 sb->s_frozen = SB_FREEZE_WRITE;
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700221 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700222
223 sync_inodes_sb(sb, 0);
224 DQUOT_SYNC(sb);
225
226 lock_super(sb);
227 if (sb->s_dirt && sb->s_op->write_super)
228 sb->s_op->write_super(sb);
229 unlock_super(sb);
230
231 if (sb->s_op->sync_fs)
232 sb->s_op->sync_fs(sb, 1);
233
234 sync_blockdev(sb->s_bdev);
235 sync_inodes_sb(sb, 1);
236
237 sb->s_frozen = SB_FREEZE_TRANS;
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700238 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700239
240 sync_blockdev(sb->s_bdev);
241
242 if (sb->s_op->write_super_lockfs)
243 sb->s_op->write_super_lockfs(sb);
244 }
245
246 sync_blockdev(bdev);
247 return sb; /* thaw_bdev releases s->s_umount and bd_mount_sem */
248}
249EXPORT_SYMBOL(freeze_bdev);
250
251/**
252 * thaw_bdev -- unlock filesystem
253 * @bdev: blockdevice to unlock
254 * @sb: associated superblock
255 *
256 * Unlocks the filesystem and marks it writeable again after freeze_bdev().
257 */
258void thaw_bdev(struct block_device *bdev, struct super_block *sb)
259{
260 if (sb) {
261 BUG_ON(sb->s_bdev != bdev);
262
263 if (sb->s_op->unlockfs)
264 sb->s_op->unlockfs(sb);
265 sb->s_frozen = SB_UNFROZEN;
akpm@osdl.orgd59dd462005-05-01 08:58:47 -0700266 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700267 wake_up(&sb->s_wait_unfrozen);
268 drop_super(sb);
269 }
270
271 up(&bdev->bd_mount_sem);
272}
273EXPORT_SYMBOL(thaw_bdev);
274
275/*
276 * sync everything. Start out by waking pdflush, because that writes back
277 * all queues in parallel.
278 */
279static void do_sync(unsigned long wait)
280{
281 wakeup_bdflush(0);
282 sync_inodes(0); /* All mappings, inodes and their blockdevs */
283 DQUOT_SYNC(NULL);
284 sync_supers(); /* Write the superblocks */
285 sync_filesystems(0); /* Start syncing the filesystems */
286 sync_filesystems(wait); /* Waitingly sync the filesystems */
287 sync_inodes(wait); /* Mappings, inodes and blockdevs, again. */
288 if (!wait)
289 printk("Emergency Sync complete\n");
290 if (unlikely(laptop_mode))
291 laptop_sync_completion();
292}
293
294asmlinkage long sys_sync(void)
295{
296 do_sync(1);
297 return 0;
298}
299
300void emergency_sync(void)
301{
302 pdflush_operation(do_sync, 0);
303}
304
305/*
306 * Generic function to fsync a file.
307 *
308 * filp may be NULL if called via the msync of a vma.
309 */
310
311int file_fsync(struct file *filp, struct dentry *dentry, int datasync)
312{
313 struct inode * inode = dentry->d_inode;
314 struct super_block * sb;
315 int ret, err;
316
317 /* sync the inode to buffers */
318 ret = write_inode_now(inode, 0);
319
320 /* sync the superblock to buffers */
321 sb = inode->i_sb;
322 lock_super(sb);
323 if (sb->s_op->write_super)
324 sb->s_op->write_super(sb);
325 unlock_super(sb);
326
327 /* .. finally sync the buffers to disk */
328 err = sync_blockdev(sb->s_bdev);
329 if (!ret)
330 ret = err;
331 return ret;
332}
333
334asmlinkage long sys_fsync(unsigned int fd)
335{
336 struct file * file;
337 struct address_space *mapping;
338 int ret, err;
339
340 ret = -EBADF;
341 file = fget(fd);
342 if (!file)
343 goto out;
344
345 mapping = file->f_mapping;
346
347 ret = -EINVAL;
348 if (!file->f_op || !file->f_op->fsync) {
349 /* Why? We can still call filemap_fdatawrite */
350 goto out_putf;
351 }
352
353 current->flags |= PF_SYNCWRITE;
354 ret = filemap_fdatawrite(mapping);
355
356 /*
357 * We need to protect against concurrent writers,
358 * which could cause livelocks in fsync_buffers_list
359 */
360 down(&mapping->host->i_sem);
361 err = file->f_op->fsync(file, file->f_dentry, 0);
362 if (!ret)
363 ret = err;
364 up(&mapping->host->i_sem);
365 err = filemap_fdatawait(mapping);
366 if (!ret)
367 ret = err;
368 current->flags &= ~PF_SYNCWRITE;
369
370out_putf:
371 fput(file);
372out:
373 return ret;
374}
375
376asmlinkage long sys_fdatasync(unsigned int fd)
377{
378 struct file * file;
379 struct address_space *mapping;
380 int ret, err;
381
382 ret = -EBADF;
383 file = fget(fd);
384 if (!file)
385 goto out;
386
387 ret = -EINVAL;
388 if (!file->f_op || !file->f_op->fsync)
389 goto out_putf;
390
391 mapping = file->f_mapping;
392
393 current->flags |= PF_SYNCWRITE;
394 ret = filemap_fdatawrite(mapping);
395 down(&mapping->host->i_sem);
396 err = file->f_op->fsync(file, file->f_dentry, 1);
397 if (!ret)
398 ret = err;
399 up(&mapping->host->i_sem);
400 err = filemap_fdatawait(mapping);
401 if (!ret)
402 ret = err;
403 current->flags &= ~PF_SYNCWRITE;
404
405out_putf:
406 fput(file);
407out:
408 return ret;
409}
410
411/*
412 * Various filesystems appear to want __find_get_block to be non-blocking.
413 * But it's the page lock which protects the buffers. To get around this,
414 * we get exclusion from try_to_free_buffers with the blockdev mapping's
415 * private_lock.
416 *
417 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
418 * may be quite high. This code could TryLock the page, and if that
419 * succeeds, there is no need to take private_lock. (But if
420 * private_lock is contended then so is mapping->tree_lock).
421 */
422static struct buffer_head *
423__find_get_block_slow(struct block_device *bdev, sector_t block, int unused)
424{
425 struct inode *bd_inode = bdev->bd_inode;
426 struct address_space *bd_mapping = bd_inode->i_mapping;
427 struct buffer_head *ret = NULL;
428 pgoff_t index;
429 struct buffer_head *bh;
430 struct buffer_head *head;
431 struct page *page;
432 int all_mapped = 1;
433
434 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
435 page = find_get_page(bd_mapping, index);
436 if (!page)
437 goto out;
438
439 spin_lock(&bd_mapping->private_lock);
440 if (!page_has_buffers(page))
441 goto out_unlock;
442 head = page_buffers(page);
443 bh = head;
444 do {
445 if (bh->b_blocknr == block) {
446 ret = bh;
447 get_bh(bh);
448 goto out_unlock;
449 }
450 if (!buffer_mapped(bh))
451 all_mapped = 0;
452 bh = bh->b_this_page;
453 } while (bh != head);
454
455 /* we might be here because some of the buffers on this page are
456 * not mapped. This is due to various races between
457 * file io on the block device and getblk. It gets dealt with
458 * elsewhere, don't buffer_error if we had some unmapped buffers
459 */
460 if (all_mapped) {
461 printk("__find_get_block_slow() failed. "
462 "block=%llu, b_blocknr=%llu\n",
463 (unsigned long long)block, (unsigned long long)bh->b_blocknr);
464 printk("b_state=0x%08lx, b_size=%u\n", bh->b_state, bh->b_size);
465 printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits);
466 }
467out_unlock:
468 spin_unlock(&bd_mapping->private_lock);
469 page_cache_release(page);
470out:
471 return ret;
472}
473
474/* If invalidate_buffers() will trash dirty buffers, it means some kind
475 of fs corruption is going on. Trashing dirty data always imply losing
476 information that was supposed to be just stored on the physical layer
477 by the user.
478
479 Thus invalidate_buffers in general usage is not allwowed to trash
480 dirty buffers. For example ioctl(FLSBLKBUF) expects dirty data to
481 be preserved. These buffers are simply skipped.
482
483 We also skip buffers which are still in use. For example this can
484 happen if a userspace program is reading the block device.
485
486 NOTE: In the case where the user removed a removable-media-disk even if
487 there's still dirty data not synced on disk (due a bug in the device driver
488 or due an error of the user), by not destroying the dirty buffers we could
489 generate corruption also on the next media inserted, thus a parameter is
490 necessary to handle this case in the most safe way possible (trying
491 to not corrupt also the new disk inserted with the data belonging to
492 the old now corrupted disk). Also for the ramdisk the natural thing
493 to do in order to release the ramdisk memory is to destroy dirty buffers.
494
495 These are two special cases. Normal usage imply the device driver
496 to issue a sync on the device (without waiting I/O completion) and
497 then an invalidate_buffers call that doesn't trash dirty buffers.
498
499 For handling cache coherency with the blkdev pagecache the 'update' case
500 is been introduced. It is needed to re-read from disk any pinned
501 buffer. NOTE: re-reading from disk is destructive so we can do it only
502 when we assume nobody is changing the buffercache under our I/O and when
503 we think the disk contains more recent information than the buffercache.
504 The update == 1 pass marks the buffers we need to update, the update == 2
505 pass does the actual I/O. */
506void invalidate_bdev(struct block_device *bdev, int destroy_dirty_buffers)
507{
508 invalidate_bh_lrus();
509 /*
510 * FIXME: what about destroy_dirty_buffers?
511 * We really want to use invalidate_inode_pages2() for
512 * that, but not until that's cleaned up.
513 */
514 invalidate_inode_pages(bdev->bd_inode->i_mapping);
515}
516
517/*
518 * Kick pdflush then try to free up some ZONE_NORMAL memory.
519 */
520static void free_more_memory(void)
521{
522 struct zone **zones;
523 pg_data_t *pgdat;
524
525 wakeup_bdflush(1024);
526 yield();
527
528 for_each_pgdat(pgdat) {
529 zones = pgdat->node_zonelists[GFP_NOFS&GFP_ZONEMASK].zones;
530 if (*zones)
531 try_to_free_pages(zones, GFP_NOFS, 0);
532 }
533}
534
535/*
536 * I/O completion handler for block_read_full_page() - pages
537 * which come unlocked at the end of I/O.
538 */
539static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
540{
541 static DEFINE_SPINLOCK(page_uptodate_lock);
542 unsigned long flags;
543 struct buffer_head *tmp;
544 struct page *page;
545 int page_uptodate = 1;
546
547 BUG_ON(!buffer_async_read(bh));
548
549 page = bh->b_page;
550 if (uptodate) {
551 set_buffer_uptodate(bh);
552 } else {
553 clear_buffer_uptodate(bh);
554 if (printk_ratelimit())
555 buffer_io_error(bh);
556 SetPageError(page);
557 }
558
559 /*
560 * Be _very_ careful from here on. Bad things can happen if
561 * two buffer heads end IO at almost the same time and both
562 * decide that the page is now completely done.
563 */
564 spin_lock_irqsave(&page_uptodate_lock, flags);
565 clear_buffer_async_read(bh);
566 unlock_buffer(bh);
567 tmp = bh;
568 do {
569 if (!buffer_uptodate(tmp))
570 page_uptodate = 0;
571 if (buffer_async_read(tmp)) {
572 BUG_ON(!buffer_locked(tmp));
573 goto still_busy;
574 }
575 tmp = tmp->b_this_page;
576 } while (tmp != bh);
577 spin_unlock_irqrestore(&page_uptodate_lock, flags);
578
579 /*
580 * If none of the buffers had errors and they are all
581 * uptodate then we can set the page uptodate.
582 */
583 if (page_uptodate && !PageError(page))
584 SetPageUptodate(page);
585 unlock_page(page);
586 return;
587
588still_busy:
589 spin_unlock_irqrestore(&page_uptodate_lock, flags);
590 return;
591}
592
593/*
594 * Completion handler for block_write_full_page() - pages which are unlocked
595 * during I/O, and which have PageWriteback cleared upon I/O completion.
596 */
597void end_buffer_async_write(struct buffer_head *bh, int uptodate)
598{
599 char b[BDEVNAME_SIZE];
600 static DEFINE_SPINLOCK(page_uptodate_lock);
601 unsigned long flags;
602 struct buffer_head *tmp;
603 struct page *page;
604
605 BUG_ON(!buffer_async_write(bh));
606
607 page = bh->b_page;
608 if (uptodate) {
609 set_buffer_uptodate(bh);
610 } else {
611 if (printk_ratelimit()) {
612 buffer_io_error(bh);
613 printk(KERN_WARNING "lost page write due to "
614 "I/O error on %s\n",
615 bdevname(bh->b_bdev, b));
616 }
617 set_bit(AS_EIO, &page->mapping->flags);
618 clear_buffer_uptodate(bh);
619 SetPageError(page);
620 }
621
622 spin_lock_irqsave(&page_uptodate_lock, flags);
623 clear_buffer_async_write(bh);
624 unlock_buffer(bh);
625 tmp = bh->b_this_page;
626 while (tmp != bh) {
627 if (buffer_async_write(tmp)) {
628 BUG_ON(!buffer_locked(tmp));
629 goto still_busy;
630 }
631 tmp = tmp->b_this_page;
632 }
633 spin_unlock_irqrestore(&page_uptodate_lock, flags);
634 end_page_writeback(page);
635 return;
636
637still_busy:
638 spin_unlock_irqrestore(&page_uptodate_lock, flags);
639 return;
640}
641
642/*
643 * If a page's buffers are under async readin (end_buffer_async_read
644 * completion) then there is a possibility that another thread of
645 * control could lock one of the buffers after it has completed
646 * but while some of the other buffers have not completed. This
647 * locked buffer would confuse end_buffer_async_read() into not unlocking
648 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
649 * that this buffer is not under async I/O.
650 *
651 * The page comes unlocked when it has no locked buffer_async buffers
652 * left.
653 *
654 * PageLocked prevents anyone starting new async I/O reads any of
655 * the buffers.
656 *
657 * PageWriteback is used to prevent simultaneous writeout of the same
658 * page.
659 *
660 * PageLocked prevents anyone from starting writeback of a page which is
661 * under read I/O (PageWriteback is only ever set against a locked page).
662 */
663static void mark_buffer_async_read(struct buffer_head *bh)
664{
665 bh->b_end_io = end_buffer_async_read;
666 set_buffer_async_read(bh);
667}
668
669void mark_buffer_async_write(struct buffer_head *bh)
670{
671 bh->b_end_io = end_buffer_async_write;
672 set_buffer_async_write(bh);
673}
674EXPORT_SYMBOL(mark_buffer_async_write);
675
676
677/*
678 * fs/buffer.c contains helper functions for buffer-backed address space's
679 * fsync functions. A common requirement for buffer-based filesystems is
680 * that certain data from the backing blockdev needs to be written out for
681 * a successful fsync(). For example, ext2 indirect blocks need to be
682 * written back and waited upon before fsync() returns.
683 *
684 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
685 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
686 * management of a list of dependent buffers at ->i_mapping->private_list.
687 *
688 * Locking is a little subtle: try_to_free_buffers() will remove buffers
689 * from their controlling inode's queue when they are being freed. But
690 * try_to_free_buffers() will be operating against the *blockdev* mapping
691 * at the time, not against the S_ISREG file which depends on those buffers.
692 * So the locking for private_list is via the private_lock in the address_space
693 * which backs the buffers. Which is different from the address_space
694 * against which the buffers are listed. So for a particular address_space,
695 * mapping->private_lock does *not* protect mapping->private_list! In fact,
696 * mapping->private_list will always be protected by the backing blockdev's
697 * ->private_lock.
698 *
699 * Which introduces a requirement: all buffers on an address_space's
700 * ->private_list must be from the same address_space: the blockdev's.
701 *
702 * address_spaces which do not place buffers at ->private_list via these
703 * utility functions are free to use private_lock and private_list for
704 * whatever they want. The only requirement is that list_empty(private_list)
705 * be true at clear_inode() time.
706 *
707 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
708 * filesystems should do that. invalidate_inode_buffers() should just go
709 * BUG_ON(!list_empty).
710 *
711 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
712 * take an address_space, not an inode. And it should be called
713 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
714 * queued up.
715 *
716 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
717 * list if it is already on a list. Because if the buffer is on a list,
718 * it *must* already be on the right one. If not, the filesystem is being
719 * silly. This will save a ton of locking. But first we have to ensure
720 * that buffers are taken *off* the old inode's list when they are freed
721 * (presumably in truncate). That requires careful auditing of all
722 * filesystems (do it inside bforget()). It could also be done by bringing
723 * b_inode back.
724 */
725
726/*
727 * The buffer's backing address_space's private_lock must be held
728 */
729static inline void __remove_assoc_queue(struct buffer_head *bh)
730{
731 list_del_init(&bh->b_assoc_buffers);
732}
733
734int inode_has_buffers(struct inode *inode)
735{
736 return !list_empty(&inode->i_data.private_list);
737}
738
739/*
740 * osync is designed to support O_SYNC io. It waits synchronously for
741 * all already-submitted IO to complete, but does not queue any new
742 * writes to the disk.
743 *
744 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
745 * you dirty the buffers, and then use osync_inode_buffers to wait for
746 * completion. Any other dirty buffers which are not yet queued for
747 * write will not be flushed to disk by the osync.
748 */
749static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
750{
751 struct buffer_head *bh;
752 struct list_head *p;
753 int err = 0;
754
755 spin_lock(lock);
756repeat:
757 list_for_each_prev(p, list) {
758 bh = BH_ENTRY(p);
759 if (buffer_locked(bh)) {
760 get_bh(bh);
761 spin_unlock(lock);
762 wait_on_buffer(bh);
763 if (!buffer_uptodate(bh))
764 err = -EIO;
765 brelse(bh);
766 spin_lock(lock);
767 goto repeat;
768 }
769 }
770 spin_unlock(lock);
771 return err;
772}
773
774/**
775 * sync_mapping_buffers - write out and wait upon a mapping's "associated"
776 * buffers
Martin Waitz67be2dd2005-05-01 08:59:26 -0700777 * @mapping: the mapping which wants those buffers written
Linus Torvalds1da177e2005-04-16 15:20:36 -0700778 *
779 * Starts I/O against the buffers at mapping->private_list, and waits upon
780 * that I/O.
781 *
Martin Waitz67be2dd2005-05-01 08:59:26 -0700782 * Basically, this is a convenience function for fsync().
783 * @mapping is a file or directory which needs those buffers to be written for
784 * a successful fsync().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700785 */
786int sync_mapping_buffers(struct address_space *mapping)
787{
788 struct address_space *buffer_mapping = mapping->assoc_mapping;
789
790 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
791 return 0;
792
793 return fsync_buffers_list(&buffer_mapping->private_lock,
794 &mapping->private_list);
795}
796EXPORT_SYMBOL(sync_mapping_buffers);
797
798/*
799 * Called when we've recently written block `bblock', and it is known that
800 * `bblock' was for a buffer_boundary() buffer. This means that the block at
801 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
802 * dirty, schedule it for IO. So that indirects merge nicely with their data.
803 */
804void write_boundary_block(struct block_device *bdev,
805 sector_t bblock, unsigned blocksize)
806{
807 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
808 if (bh) {
809 if (buffer_dirty(bh))
810 ll_rw_block(WRITE, 1, &bh);
811 put_bh(bh);
812 }
813}
814
815void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
816{
817 struct address_space *mapping = inode->i_mapping;
818 struct address_space *buffer_mapping = bh->b_page->mapping;
819
820 mark_buffer_dirty(bh);
821 if (!mapping->assoc_mapping) {
822 mapping->assoc_mapping = buffer_mapping;
823 } else {
824 if (mapping->assoc_mapping != buffer_mapping)
825 BUG();
826 }
827 if (list_empty(&bh->b_assoc_buffers)) {
828 spin_lock(&buffer_mapping->private_lock);
829 list_move_tail(&bh->b_assoc_buffers,
830 &mapping->private_list);
831 spin_unlock(&buffer_mapping->private_lock);
832 }
833}
834EXPORT_SYMBOL(mark_buffer_dirty_inode);
835
836/*
837 * Add a page to the dirty page list.
838 *
839 * It is a sad fact of life that this function is called from several places
840 * deeply under spinlocking. It may not sleep.
841 *
842 * If the page has buffers, the uptodate buffers are set dirty, to preserve
843 * dirty-state coherency between the page and the buffers. It the page does
844 * not have buffers then when they are later attached they will all be set
845 * dirty.
846 *
847 * The buffers are dirtied before the page is dirtied. There's a small race
848 * window in which a writepage caller may see the page cleanness but not the
849 * buffer dirtiness. That's fine. If this code were to set the page dirty
850 * before the buffers, a concurrent writepage caller could clear the page dirty
851 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
852 * page on the dirty page list.
853 *
854 * We use private_lock to lock against try_to_free_buffers while using the
855 * page's buffer list. Also use this to protect against clean buffers being
856 * added to the page after it was set dirty.
857 *
858 * FIXME: may need to call ->reservepage here as well. That's rather up to the
859 * address_space though.
860 */
861int __set_page_dirty_buffers(struct page *page)
862{
863 struct address_space * const mapping = page->mapping;
864
865 spin_lock(&mapping->private_lock);
866 if (page_has_buffers(page)) {
867 struct buffer_head *head = page_buffers(page);
868 struct buffer_head *bh = head;
869
870 do {
871 set_buffer_dirty(bh);
872 bh = bh->b_this_page;
873 } while (bh != head);
874 }
875 spin_unlock(&mapping->private_lock);
876
877 if (!TestSetPageDirty(page)) {
878 write_lock_irq(&mapping->tree_lock);
879 if (page->mapping) { /* Race with truncate? */
880 if (mapping_cap_account_dirty(mapping))
881 inc_page_state(nr_dirty);
882 radix_tree_tag_set(&mapping->page_tree,
883 page_index(page),
884 PAGECACHE_TAG_DIRTY);
885 }
886 write_unlock_irq(&mapping->tree_lock);
887 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
888 }
889
890 return 0;
891}
892EXPORT_SYMBOL(__set_page_dirty_buffers);
893
894/*
895 * Write out and wait upon a list of buffers.
896 *
897 * We have conflicting pressures: we want to make sure that all
898 * initially dirty buffers get waited on, but that any subsequently
899 * dirtied buffers don't. After all, we don't want fsync to last
900 * forever if somebody is actively writing to the file.
901 *
902 * Do this in two main stages: first we copy dirty buffers to a
903 * temporary inode list, queueing the writes as we go. Then we clean
904 * up, waiting for those writes to complete.
905 *
906 * During this second stage, any subsequent updates to the file may end
907 * up refiling the buffer on the original inode's dirty list again, so
908 * there is a chance we will end up with a buffer queued for write but
909 * not yet completed on that list. So, as a final cleanup we go through
910 * the osync code to catch these locked, dirty buffers without requeuing
911 * any newly dirty buffers for write.
912 */
913static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
914{
915 struct buffer_head *bh;
916 struct list_head tmp;
917 int err = 0, err2;
918
919 INIT_LIST_HEAD(&tmp);
920
921 spin_lock(lock);
922 while (!list_empty(list)) {
923 bh = BH_ENTRY(list->next);
924 list_del_init(&bh->b_assoc_buffers);
925 if (buffer_dirty(bh) || buffer_locked(bh)) {
926 list_add(&bh->b_assoc_buffers, &tmp);
927 if (buffer_dirty(bh)) {
928 get_bh(bh);
929 spin_unlock(lock);
930 /*
931 * Ensure any pending I/O completes so that
932 * ll_rw_block() actually writes the current
933 * contents - it is a noop if I/O is still in
934 * flight on potentially older contents.
935 */
936 wait_on_buffer(bh);
937 ll_rw_block(WRITE, 1, &bh);
938 brelse(bh);
939 spin_lock(lock);
940 }
941 }
942 }
943
944 while (!list_empty(&tmp)) {
945 bh = BH_ENTRY(tmp.prev);
946 __remove_assoc_queue(bh);
947 get_bh(bh);
948 spin_unlock(lock);
949 wait_on_buffer(bh);
950 if (!buffer_uptodate(bh))
951 err = -EIO;
952 brelse(bh);
953 spin_lock(lock);
954 }
955
956 spin_unlock(lock);
957 err2 = osync_buffers_list(lock, list);
958 if (err)
959 return err;
960 else
961 return err2;
962}
963
964/*
965 * Invalidate any and all dirty buffers on a given inode. We are
966 * probably unmounting the fs, but that doesn't mean we have already
967 * done a sync(). Just drop the buffers from the inode list.
968 *
969 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
970 * assumes that all the buffers are against the blockdev. Not true
971 * for reiserfs.
972 */
973void invalidate_inode_buffers(struct inode *inode)
974{
975 if (inode_has_buffers(inode)) {
976 struct address_space *mapping = &inode->i_data;
977 struct list_head *list = &mapping->private_list;
978 struct address_space *buffer_mapping = mapping->assoc_mapping;
979
980 spin_lock(&buffer_mapping->private_lock);
981 while (!list_empty(list))
982 __remove_assoc_queue(BH_ENTRY(list->next));
983 spin_unlock(&buffer_mapping->private_lock);
984 }
985}
986
987/*
988 * Remove any clean buffers from the inode's buffer list. This is called
989 * when we're trying to free the inode itself. Those buffers can pin it.
990 *
991 * Returns true if all buffers were removed.
992 */
993int remove_inode_buffers(struct inode *inode)
994{
995 int ret = 1;
996
997 if (inode_has_buffers(inode)) {
998 struct address_space *mapping = &inode->i_data;
999 struct list_head *list = &mapping->private_list;
1000 struct address_space *buffer_mapping = mapping->assoc_mapping;
1001
1002 spin_lock(&buffer_mapping->private_lock);
1003 while (!list_empty(list)) {
1004 struct buffer_head *bh = BH_ENTRY(list->next);
1005 if (buffer_dirty(bh)) {
1006 ret = 0;
1007 break;
1008 }
1009 __remove_assoc_queue(bh);
1010 }
1011 spin_unlock(&buffer_mapping->private_lock);
1012 }
1013 return ret;
1014}
1015
1016/*
1017 * Create the appropriate buffers when given a page for data area and
1018 * the size of each buffer.. Use the bh->b_this_page linked list to
1019 * follow the buffers created. Return NULL if unable to create more
1020 * buffers.
1021 *
1022 * The retry flag is used to differentiate async IO (paging, swapping)
1023 * which may not fail from ordinary buffer allocations.
1024 */
1025struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
1026 int retry)
1027{
1028 struct buffer_head *bh, *head;
1029 long offset;
1030
1031try_again:
1032 head = NULL;
1033 offset = PAGE_SIZE;
1034 while ((offset -= size) >= 0) {
1035 bh = alloc_buffer_head(GFP_NOFS);
1036 if (!bh)
1037 goto no_grow;
1038
1039 bh->b_bdev = NULL;
1040 bh->b_this_page = head;
1041 bh->b_blocknr = -1;
1042 head = bh;
1043
1044 bh->b_state = 0;
1045 atomic_set(&bh->b_count, 0);
1046 bh->b_size = size;
1047
1048 /* Link the buffer to its page */
1049 set_bh_page(bh, page, offset);
1050
1051 bh->b_end_io = NULL;
1052 }
1053 return head;
1054/*
1055 * In case anything failed, we just free everything we got.
1056 */
1057no_grow:
1058 if (head) {
1059 do {
1060 bh = head;
1061 head = head->b_this_page;
1062 free_buffer_head(bh);
1063 } while (head);
1064 }
1065
1066 /*
1067 * Return failure for non-async IO requests. Async IO requests
1068 * are not allowed to fail, so we have to wait until buffer heads
1069 * become available. But we don't want tasks sleeping with
1070 * partially complete buffers, so all were released above.
1071 */
1072 if (!retry)
1073 return NULL;
1074
1075 /* We're _really_ low on memory. Now we just
1076 * wait for old buffer heads to become free due to
1077 * finishing IO. Since this is an async request and
1078 * the reserve list is empty, we're sure there are
1079 * async buffer heads in use.
1080 */
1081 free_more_memory();
1082 goto try_again;
1083}
1084EXPORT_SYMBOL_GPL(alloc_page_buffers);
1085
1086static inline void
1087link_dev_buffers(struct page *page, struct buffer_head *head)
1088{
1089 struct buffer_head *bh, *tail;
1090
1091 bh = head;
1092 do {
1093 tail = bh;
1094 bh = bh->b_this_page;
1095 } while (bh);
1096 tail->b_this_page = head;
1097 attach_page_buffers(page, head);
1098}
1099
1100/*
1101 * Initialise the state of a blockdev page's buffers.
1102 */
1103static void
1104init_page_buffers(struct page *page, struct block_device *bdev,
1105 sector_t block, int size)
1106{
1107 struct buffer_head *head = page_buffers(page);
1108 struct buffer_head *bh = head;
1109 int uptodate = PageUptodate(page);
1110
1111 do {
1112 if (!buffer_mapped(bh)) {
1113 init_buffer(bh, NULL, NULL);
1114 bh->b_bdev = bdev;
1115 bh->b_blocknr = block;
1116 if (uptodate)
1117 set_buffer_uptodate(bh);
1118 set_buffer_mapped(bh);
1119 }
1120 block++;
1121 bh = bh->b_this_page;
1122 } while (bh != head);
1123}
1124
1125/*
1126 * Create the page-cache page that contains the requested block.
1127 *
1128 * This is user purely for blockdev mappings.
1129 */
1130static struct page *
1131grow_dev_page(struct block_device *bdev, sector_t block,
1132 pgoff_t index, int size)
1133{
1134 struct inode *inode = bdev->bd_inode;
1135 struct page *page;
1136 struct buffer_head *bh;
1137
1138 page = find_or_create_page(inode->i_mapping, index, GFP_NOFS);
1139 if (!page)
1140 return NULL;
1141
1142 if (!PageLocked(page))
1143 BUG();
1144
1145 if (page_has_buffers(page)) {
1146 bh = page_buffers(page);
1147 if (bh->b_size == size) {
1148 init_page_buffers(page, bdev, block, size);
1149 return page;
1150 }
1151 if (!try_to_free_buffers(page))
1152 goto failed;
1153 }
1154
1155 /*
1156 * Allocate some buffers for this page
1157 */
1158 bh = alloc_page_buffers(page, size, 0);
1159 if (!bh)
1160 goto failed;
1161
1162 /*
1163 * Link the page to the buffers and initialise them. Take the
1164 * lock to be atomic wrt __find_get_block(), which does not
1165 * run under the page lock.
1166 */
1167 spin_lock(&inode->i_mapping->private_lock);
1168 link_dev_buffers(page, bh);
1169 init_page_buffers(page, bdev, block, size);
1170 spin_unlock(&inode->i_mapping->private_lock);
1171 return page;
1172
1173failed:
1174 BUG();
1175 unlock_page(page);
1176 page_cache_release(page);
1177 return NULL;
1178}
1179
1180/*
1181 * Create buffers for the specified block device block's page. If
1182 * that page was dirty, the buffers are set dirty also.
1183 *
1184 * Except that's a bug. Attaching dirty buffers to a dirty
1185 * blockdev's page can result in filesystem corruption, because
1186 * some of those buffers may be aliases of filesystem data.
1187 * grow_dev_page() will go BUG() if this happens.
1188 */
1189static inline int
1190grow_buffers(struct block_device *bdev, sector_t block, int size)
1191{
1192 struct page *page;
1193 pgoff_t index;
1194 int sizebits;
1195
1196 sizebits = -1;
1197 do {
1198 sizebits++;
1199 } while ((size << sizebits) < PAGE_SIZE);
1200
1201 index = block >> sizebits;
1202 block = index << sizebits;
1203
1204 /* Create a page with the proper size buffers.. */
1205 page = grow_dev_page(bdev, block, index, size);
1206 if (!page)
1207 return 0;
1208 unlock_page(page);
1209 page_cache_release(page);
1210 return 1;
1211}
1212
1213struct buffer_head *
1214__getblk_slow(struct block_device *bdev, sector_t block, int size)
1215{
1216 /* Size must be multiple of hard sectorsize */
1217 if (unlikely(size & (bdev_hardsect_size(bdev)-1) ||
1218 (size < 512 || size > PAGE_SIZE))) {
1219 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1220 size);
1221 printk(KERN_ERR "hardsect size: %d\n",
1222 bdev_hardsect_size(bdev));
1223
1224 dump_stack();
1225 return NULL;
1226 }
1227
1228 for (;;) {
1229 struct buffer_head * bh;
1230
1231 bh = __find_get_block(bdev, block, size);
1232 if (bh)
1233 return bh;
1234
1235 if (!grow_buffers(bdev, block, size))
1236 free_more_memory();
1237 }
1238}
1239
1240/*
1241 * The relationship between dirty buffers and dirty pages:
1242 *
1243 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1244 * the page is tagged dirty in its radix tree.
1245 *
1246 * At all times, the dirtiness of the buffers represents the dirtiness of
1247 * subsections of the page. If the page has buffers, the page dirty bit is
1248 * merely a hint about the true dirty state.
1249 *
1250 * When a page is set dirty in its entirety, all its buffers are marked dirty
1251 * (if the page has buffers).
1252 *
1253 * When a buffer is marked dirty, its page is dirtied, but the page's other
1254 * buffers are not.
1255 *
1256 * Also. When blockdev buffers are explicitly read with bread(), they
1257 * individually become uptodate. But their backing page remains not
1258 * uptodate - even if all of its buffers are uptodate. A subsequent
1259 * block_read_full_page() against that page will discover all the uptodate
1260 * buffers, will set the page uptodate and will perform no I/O.
1261 */
1262
1263/**
1264 * mark_buffer_dirty - mark a buffer_head as needing writeout
Martin Waitz67be2dd2005-05-01 08:59:26 -07001265 * @bh: the buffer_head to mark dirty
Linus Torvalds1da177e2005-04-16 15:20:36 -07001266 *
1267 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1268 * backing page dirty, then tag the page as dirty in its address_space's radix
1269 * tree and then attach the address_space's inode to its superblock's dirty
1270 * inode list.
1271 *
1272 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1273 * mapping->tree_lock and the global inode_lock.
1274 */
1275void fastcall mark_buffer_dirty(struct buffer_head *bh)
1276{
1277 if (!buffer_dirty(bh) && !test_set_buffer_dirty(bh))
1278 __set_page_dirty_nobuffers(bh->b_page);
1279}
1280
1281/*
1282 * Decrement a buffer_head's reference count. If all buffers against a page
1283 * have zero reference count, are clean and unlocked, and if the page is clean
1284 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1285 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1286 * a page but it ends up not being freed, and buffers may later be reattached).
1287 */
1288void __brelse(struct buffer_head * buf)
1289{
1290 if (atomic_read(&buf->b_count)) {
1291 put_bh(buf);
1292 return;
1293 }
1294 printk(KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1295 WARN_ON(1);
1296}
1297
1298/*
1299 * bforget() is like brelse(), except it discards any
1300 * potentially dirty data.
1301 */
1302void __bforget(struct buffer_head *bh)
1303{
1304 clear_buffer_dirty(bh);
1305 if (!list_empty(&bh->b_assoc_buffers)) {
1306 struct address_space *buffer_mapping = bh->b_page->mapping;
1307
1308 spin_lock(&buffer_mapping->private_lock);
1309 list_del_init(&bh->b_assoc_buffers);
1310 spin_unlock(&buffer_mapping->private_lock);
1311 }
1312 __brelse(bh);
1313}
1314
1315static struct buffer_head *__bread_slow(struct buffer_head *bh)
1316{
1317 lock_buffer(bh);
1318 if (buffer_uptodate(bh)) {
1319 unlock_buffer(bh);
1320 return bh;
1321 } else {
1322 get_bh(bh);
1323 bh->b_end_io = end_buffer_read_sync;
1324 submit_bh(READ, bh);
1325 wait_on_buffer(bh);
1326 if (buffer_uptodate(bh))
1327 return bh;
1328 }
1329 brelse(bh);
1330 return NULL;
1331}
1332
1333/*
1334 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1335 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1336 * refcount elevated by one when they're in an LRU. A buffer can only appear
1337 * once in a particular CPU's LRU. A single buffer can be present in multiple
1338 * CPU's LRUs at the same time.
1339 *
1340 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1341 * sb_find_get_block().
1342 *
1343 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1344 * a local interrupt disable for that.
1345 */
1346
1347#define BH_LRU_SIZE 8
1348
1349struct bh_lru {
1350 struct buffer_head *bhs[BH_LRU_SIZE];
1351};
1352
1353static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1354
1355#ifdef CONFIG_SMP
1356#define bh_lru_lock() local_irq_disable()
1357#define bh_lru_unlock() local_irq_enable()
1358#else
1359#define bh_lru_lock() preempt_disable()
1360#define bh_lru_unlock() preempt_enable()
1361#endif
1362
1363static inline void check_irqs_on(void)
1364{
1365#ifdef irqs_disabled
1366 BUG_ON(irqs_disabled());
1367#endif
1368}
1369
1370/*
1371 * The LRU management algorithm is dopey-but-simple. Sorry.
1372 */
1373static void bh_lru_install(struct buffer_head *bh)
1374{
1375 struct buffer_head *evictee = NULL;
1376 struct bh_lru *lru;
1377
1378 check_irqs_on();
1379 bh_lru_lock();
1380 lru = &__get_cpu_var(bh_lrus);
1381 if (lru->bhs[0] != bh) {
1382 struct buffer_head *bhs[BH_LRU_SIZE];
1383 int in;
1384 int out = 0;
1385
1386 get_bh(bh);
1387 bhs[out++] = bh;
1388 for (in = 0; in < BH_LRU_SIZE; in++) {
1389 struct buffer_head *bh2 = lru->bhs[in];
1390
1391 if (bh2 == bh) {
1392 __brelse(bh2);
1393 } else {
1394 if (out >= BH_LRU_SIZE) {
1395 BUG_ON(evictee != NULL);
1396 evictee = bh2;
1397 } else {
1398 bhs[out++] = bh2;
1399 }
1400 }
1401 }
1402 while (out < BH_LRU_SIZE)
1403 bhs[out++] = NULL;
1404 memcpy(lru->bhs, bhs, sizeof(bhs));
1405 }
1406 bh_lru_unlock();
1407
1408 if (evictee)
1409 __brelse(evictee);
1410}
1411
1412/*
1413 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1414 */
1415static inline struct buffer_head *
1416lookup_bh_lru(struct block_device *bdev, sector_t block, int size)
1417{
1418 struct buffer_head *ret = NULL;
1419 struct bh_lru *lru;
1420 int i;
1421
1422 check_irqs_on();
1423 bh_lru_lock();
1424 lru = &__get_cpu_var(bh_lrus);
1425 for (i = 0; i < BH_LRU_SIZE; i++) {
1426 struct buffer_head *bh = lru->bhs[i];
1427
1428 if (bh && bh->b_bdev == bdev &&
1429 bh->b_blocknr == block && bh->b_size == size) {
1430 if (i) {
1431 while (i) {
1432 lru->bhs[i] = lru->bhs[i - 1];
1433 i--;
1434 }
1435 lru->bhs[0] = bh;
1436 }
1437 get_bh(bh);
1438 ret = bh;
1439 break;
1440 }
1441 }
1442 bh_lru_unlock();
1443 return ret;
1444}
1445
1446/*
1447 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1448 * it in the LRU and mark it as accessed. If it is not present then return
1449 * NULL
1450 */
1451struct buffer_head *
1452__find_get_block(struct block_device *bdev, sector_t block, int size)
1453{
1454 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1455
1456 if (bh == NULL) {
1457 bh = __find_get_block_slow(bdev, block, size);
1458 if (bh)
1459 bh_lru_install(bh);
1460 }
1461 if (bh)
1462 touch_buffer(bh);
1463 return bh;
1464}
1465EXPORT_SYMBOL(__find_get_block);
1466
1467/*
1468 * __getblk will locate (and, if necessary, create) the buffer_head
1469 * which corresponds to the passed block_device, block and size. The
1470 * returned buffer has its reference count incremented.
1471 *
1472 * __getblk() cannot fail - it just keeps trying. If you pass it an
1473 * illegal block number, __getblk() will happily return a buffer_head
1474 * which represents the non-existent block. Very weird.
1475 *
1476 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1477 * attempt is failing. FIXME, perhaps?
1478 */
1479struct buffer_head *
1480__getblk(struct block_device *bdev, sector_t block, int size)
1481{
1482 struct buffer_head *bh = __find_get_block(bdev, block, size);
1483
1484 might_sleep();
1485 if (bh == NULL)
1486 bh = __getblk_slow(bdev, block, size);
1487 return bh;
1488}
1489EXPORT_SYMBOL(__getblk);
1490
1491/*
1492 * Do async read-ahead on a buffer..
1493 */
1494void __breadahead(struct block_device *bdev, sector_t block, int size)
1495{
1496 struct buffer_head *bh = __getblk(bdev, block, size);
1497 ll_rw_block(READA, 1, &bh);
1498 brelse(bh);
1499}
1500EXPORT_SYMBOL(__breadahead);
1501
1502/**
1503 * __bread() - reads a specified block and returns the bh
Martin Waitz67be2dd2005-05-01 08:59:26 -07001504 * @bdev: the block_device to read from
Linus Torvalds1da177e2005-04-16 15:20:36 -07001505 * @block: number of block
1506 * @size: size (in bytes) to read
1507 *
1508 * Reads a specified block, and returns buffer head that contains it.
1509 * It returns NULL if the block was unreadable.
1510 */
1511struct buffer_head *
1512__bread(struct block_device *bdev, sector_t block, int size)
1513{
1514 struct buffer_head *bh = __getblk(bdev, block, size);
1515
1516 if (!buffer_uptodate(bh))
1517 bh = __bread_slow(bh);
1518 return bh;
1519}
1520EXPORT_SYMBOL(__bread);
1521
1522/*
1523 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1524 * This doesn't race because it runs in each cpu either in irq
1525 * or with preempt disabled.
1526 */
1527static void invalidate_bh_lru(void *arg)
1528{
1529 struct bh_lru *b = &get_cpu_var(bh_lrus);
1530 int i;
1531
1532 for (i = 0; i < BH_LRU_SIZE; i++) {
1533 brelse(b->bhs[i]);
1534 b->bhs[i] = NULL;
1535 }
1536 put_cpu_var(bh_lrus);
1537}
1538
1539static void invalidate_bh_lrus(void)
1540{
1541 on_each_cpu(invalidate_bh_lru, NULL, 1, 1);
1542}
1543
1544void set_bh_page(struct buffer_head *bh,
1545 struct page *page, unsigned long offset)
1546{
1547 bh->b_page = page;
1548 if (offset >= PAGE_SIZE)
1549 BUG();
1550 if (PageHighMem(page))
1551 /*
1552 * This catches illegal uses and preserves the offset:
1553 */
1554 bh->b_data = (char *)(0 + offset);
1555 else
1556 bh->b_data = page_address(page) + offset;
1557}
1558EXPORT_SYMBOL(set_bh_page);
1559
1560/*
1561 * Called when truncating a buffer on a page completely.
1562 */
1563static inline void discard_buffer(struct buffer_head * bh)
1564{
1565 lock_buffer(bh);
1566 clear_buffer_dirty(bh);
1567 bh->b_bdev = NULL;
1568 clear_buffer_mapped(bh);
1569 clear_buffer_req(bh);
1570 clear_buffer_new(bh);
1571 clear_buffer_delay(bh);
1572 unlock_buffer(bh);
1573}
1574
1575/**
1576 * try_to_release_page() - release old fs-specific metadata on a page
1577 *
1578 * @page: the page which the kernel is trying to free
1579 * @gfp_mask: memory allocation flags (and I/O mode)
1580 *
1581 * The address_space is to try to release any data against the page
1582 * (presumably at page->private). If the release was successful, return `1'.
1583 * Otherwise return zero.
1584 *
1585 * The @gfp_mask argument specifies whether I/O may be performed to release
1586 * this page (__GFP_IO), and whether the call may block (__GFP_WAIT).
1587 *
1588 * NOTE: @gfp_mask may go away, and this function may become non-blocking.
1589 */
1590int try_to_release_page(struct page *page, int gfp_mask)
1591{
1592 struct address_space * const mapping = page->mapping;
1593
1594 BUG_ON(!PageLocked(page));
1595 if (PageWriteback(page))
1596 return 0;
1597
1598 if (mapping && mapping->a_ops->releasepage)
1599 return mapping->a_ops->releasepage(page, gfp_mask);
1600 return try_to_free_buffers(page);
1601}
1602EXPORT_SYMBOL(try_to_release_page);
1603
1604/**
1605 * block_invalidatepage - invalidate part of all of a buffer-backed page
1606 *
1607 * @page: the page which is affected
1608 * @offset: the index of the truncation point
1609 *
1610 * block_invalidatepage() is called when all or part of the page has become
1611 * invalidatedby a truncate operation.
1612 *
1613 * block_invalidatepage() does not have to release all buffers, but it must
1614 * ensure that no dirty buffer is left outside @offset and that no I/O
1615 * is underway against any of the blocks which are outside the truncation
1616 * point. Because the caller is about to free (and possibly reuse) those
1617 * blocks on-disk.
1618 */
1619int block_invalidatepage(struct page *page, unsigned long offset)
1620{
1621 struct buffer_head *head, *bh, *next;
1622 unsigned int curr_off = 0;
1623 int ret = 1;
1624
1625 BUG_ON(!PageLocked(page));
1626 if (!page_has_buffers(page))
1627 goto out;
1628
1629 head = page_buffers(page);
1630 bh = head;
1631 do {
1632 unsigned int next_off = curr_off + bh->b_size;
1633 next = bh->b_this_page;
1634
1635 /*
1636 * is this block fully invalidated?
1637 */
1638 if (offset <= curr_off)
1639 discard_buffer(bh);
1640 curr_off = next_off;
1641 bh = next;
1642 } while (bh != head);
1643
1644 /*
1645 * We release buffers only if the entire page is being invalidated.
1646 * The get_block cached value has been unconditionally invalidated,
1647 * so real IO is not possible anymore.
1648 */
1649 if (offset == 0)
1650 ret = try_to_release_page(page, 0);
1651out:
1652 return ret;
1653}
1654EXPORT_SYMBOL(block_invalidatepage);
1655
1656/*
1657 * We attach and possibly dirty the buffers atomically wrt
1658 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1659 * is already excluded via the page lock.
1660 */
1661void create_empty_buffers(struct page *page,
1662 unsigned long blocksize, unsigned long b_state)
1663{
1664 struct buffer_head *bh, *head, *tail;
1665
1666 head = alloc_page_buffers(page, blocksize, 1);
1667 bh = head;
1668 do {
1669 bh->b_state |= b_state;
1670 tail = bh;
1671 bh = bh->b_this_page;
1672 } while (bh);
1673 tail->b_this_page = head;
1674
1675 spin_lock(&page->mapping->private_lock);
1676 if (PageUptodate(page) || PageDirty(page)) {
1677 bh = head;
1678 do {
1679 if (PageDirty(page))
1680 set_buffer_dirty(bh);
1681 if (PageUptodate(page))
1682 set_buffer_uptodate(bh);
1683 bh = bh->b_this_page;
1684 } while (bh != head);
1685 }
1686 attach_page_buffers(page, head);
1687 spin_unlock(&page->mapping->private_lock);
1688}
1689EXPORT_SYMBOL(create_empty_buffers);
1690
1691/*
1692 * We are taking a block for data and we don't want any output from any
1693 * buffer-cache aliases starting from return from that function and
1694 * until the moment when something will explicitly mark the buffer
1695 * dirty (hopefully that will not happen until we will free that block ;-)
1696 * We don't even need to mark it not-uptodate - nobody can expect
1697 * anything from a newly allocated buffer anyway. We used to used
1698 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1699 * don't want to mark the alias unmapped, for example - it would confuse
1700 * anyone who might pick it with bread() afterwards...
1701 *
1702 * Also.. Note that bforget() doesn't lock the buffer. So there can
1703 * be writeout I/O going on against recently-freed buffers. We don't
1704 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1705 * only if we really need to. That happens here.
1706 */
1707void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1708{
1709 struct buffer_head *old_bh;
1710
1711 might_sleep();
1712
1713 old_bh = __find_get_block_slow(bdev, block, 0);
1714 if (old_bh) {
1715 clear_buffer_dirty(old_bh);
1716 wait_on_buffer(old_bh);
1717 clear_buffer_req(old_bh);
1718 __brelse(old_bh);
1719 }
1720}
1721EXPORT_SYMBOL(unmap_underlying_metadata);
1722
1723/*
1724 * NOTE! All mapped/uptodate combinations are valid:
1725 *
1726 * Mapped Uptodate Meaning
1727 *
1728 * No No "unknown" - must do get_block()
1729 * No Yes "hole" - zero-filled
1730 * Yes No "allocated" - allocated on disk, not read in
1731 * Yes Yes "valid" - allocated and up-to-date in memory.
1732 *
1733 * "Dirty" is valid only with the last case (mapped+uptodate).
1734 */
1735
1736/*
1737 * While block_write_full_page is writing back the dirty buffers under
1738 * the page lock, whoever dirtied the buffers may decide to clean them
1739 * again at any time. We handle that by only looking at the buffer
1740 * state inside lock_buffer().
1741 *
1742 * If block_write_full_page() is called for regular writeback
1743 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1744 * locked buffer. This only can happen if someone has written the buffer
1745 * directly, with submit_bh(). At the address_space level PageWriteback
1746 * prevents this contention from occurring.
1747 */
1748static int __block_write_full_page(struct inode *inode, struct page *page,
1749 get_block_t *get_block, struct writeback_control *wbc)
1750{
1751 int err;
1752 sector_t block;
1753 sector_t last_block;
1754 struct buffer_head *bh, *head;
1755 int nr_underway = 0;
1756
1757 BUG_ON(!PageLocked(page));
1758
1759 last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
1760
1761 if (!page_has_buffers(page)) {
1762 create_empty_buffers(page, 1 << inode->i_blkbits,
1763 (1 << BH_Dirty)|(1 << BH_Uptodate));
1764 }
1765
1766 /*
1767 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1768 * here, and the (potentially unmapped) buffers may become dirty at
1769 * any time. If a buffer becomes dirty here after we've inspected it
1770 * then we just miss that fact, and the page stays dirty.
1771 *
1772 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1773 * handle that here by just cleaning them.
1774 */
1775
1776 block = page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
1777 head = page_buffers(page);
1778 bh = head;
1779
1780 /*
1781 * Get all the dirty buffers mapped to disk addresses and
1782 * handle any aliases from the underlying blockdev's mapping.
1783 */
1784 do {
1785 if (block > last_block) {
1786 /*
1787 * mapped buffers outside i_size will occur, because
1788 * this page can be outside i_size when there is a
1789 * truncate in progress.
1790 */
1791 /*
1792 * The buffer was zeroed by block_write_full_page()
1793 */
1794 clear_buffer_dirty(bh);
1795 set_buffer_uptodate(bh);
1796 } else if (!buffer_mapped(bh) && buffer_dirty(bh)) {
1797 err = get_block(inode, block, bh, 1);
1798 if (err)
1799 goto recover;
1800 if (buffer_new(bh)) {
1801 /* blockdev mappings never come here */
1802 clear_buffer_new(bh);
1803 unmap_underlying_metadata(bh->b_bdev,
1804 bh->b_blocknr);
1805 }
1806 }
1807 bh = bh->b_this_page;
1808 block++;
1809 } while (bh != head);
1810
1811 do {
1812 get_bh(bh);
1813 if (!buffer_mapped(bh))
1814 continue;
1815 /*
1816 * If it's a fully non-blocking write attempt and we cannot
1817 * lock the buffer then redirty the page. Note that this can
1818 * potentially cause a busy-wait loop from pdflush and kswapd
1819 * activity, but those code paths have their own higher-level
1820 * throttling.
1821 */
1822 if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) {
1823 lock_buffer(bh);
1824 } else if (test_set_buffer_locked(bh)) {
1825 redirty_page_for_writepage(wbc, page);
1826 continue;
1827 }
1828 if (test_clear_buffer_dirty(bh)) {
1829 mark_buffer_async_write(bh);
1830 } else {
1831 unlock_buffer(bh);
1832 }
1833 } while ((bh = bh->b_this_page) != head);
1834
1835 /*
1836 * The page and its buffers are protected by PageWriteback(), so we can
1837 * drop the bh refcounts early.
1838 */
1839 BUG_ON(PageWriteback(page));
1840 set_page_writeback(page);
1841 unlock_page(page);
1842
1843 do {
1844 struct buffer_head *next = bh->b_this_page;
1845 if (buffer_async_write(bh)) {
1846 submit_bh(WRITE, bh);
1847 nr_underway++;
1848 }
1849 put_bh(bh);
1850 bh = next;
1851 } while (bh != head);
1852
1853 err = 0;
1854done:
1855 if (nr_underway == 0) {
1856 /*
1857 * The page was marked dirty, but the buffers were
1858 * clean. Someone wrote them back by hand with
1859 * ll_rw_block/submit_bh. A rare case.
1860 */
1861 int uptodate = 1;
1862 do {
1863 if (!buffer_uptodate(bh)) {
1864 uptodate = 0;
1865 break;
1866 }
1867 bh = bh->b_this_page;
1868 } while (bh != head);
1869 if (uptodate)
1870 SetPageUptodate(page);
1871 end_page_writeback(page);
1872 /*
1873 * The page and buffer_heads can be released at any time from
1874 * here on.
1875 */
1876 wbc->pages_skipped++; /* We didn't write this page */
1877 }
1878 return err;
1879
1880recover:
1881 /*
1882 * ENOSPC, or some other error. We may already have added some
1883 * blocks to the file, so we need to write these out to avoid
1884 * exposing stale data.
1885 * The page is currently locked and not marked for writeback
1886 */
1887 bh = head;
1888 /* Recovery: lock and submit the mapped buffers */
1889 do {
1890 get_bh(bh);
1891 if (buffer_mapped(bh) && buffer_dirty(bh)) {
1892 lock_buffer(bh);
1893 mark_buffer_async_write(bh);
1894 } else {
1895 /*
1896 * The buffer may have been set dirty during
1897 * attachment to a dirty page.
1898 */
1899 clear_buffer_dirty(bh);
1900 }
1901 } while ((bh = bh->b_this_page) != head);
1902 SetPageError(page);
1903 BUG_ON(PageWriteback(page));
1904 set_page_writeback(page);
1905 unlock_page(page);
1906 do {
1907 struct buffer_head *next = bh->b_this_page;
1908 if (buffer_async_write(bh)) {
1909 clear_buffer_dirty(bh);
1910 submit_bh(WRITE, bh);
1911 nr_underway++;
1912 }
1913 put_bh(bh);
1914 bh = next;
1915 } while (bh != head);
1916 goto done;
1917}
1918
1919static int __block_prepare_write(struct inode *inode, struct page *page,
1920 unsigned from, unsigned to, get_block_t *get_block)
1921{
1922 unsigned block_start, block_end;
1923 sector_t block;
1924 int err = 0;
1925 unsigned blocksize, bbits;
1926 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1927
1928 BUG_ON(!PageLocked(page));
1929 BUG_ON(from > PAGE_CACHE_SIZE);
1930 BUG_ON(to > PAGE_CACHE_SIZE);
1931 BUG_ON(from > to);
1932
1933 blocksize = 1 << inode->i_blkbits;
1934 if (!page_has_buffers(page))
1935 create_empty_buffers(page, blocksize, 0);
1936 head = page_buffers(page);
1937
1938 bbits = inode->i_blkbits;
1939 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1940
1941 for(bh = head, block_start = 0; bh != head || !block_start;
1942 block++, block_start=block_end, bh = bh->b_this_page) {
1943 block_end = block_start + blocksize;
1944 if (block_end <= from || block_start >= to) {
1945 if (PageUptodate(page)) {
1946 if (!buffer_uptodate(bh))
1947 set_buffer_uptodate(bh);
1948 }
1949 continue;
1950 }
1951 if (buffer_new(bh))
1952 clear_buffer_new(bh);
1953 if (!buffer_mapped(bh)) {
1954 err = get_block(inode, block, bh, 1);
1955 if (err)
1956 goto out;
1957 if (buffer_new(bh)) {
1958 clear_buffer_new(bh);
1959 unmap_underlying_metadata(bh->b_bdev,
1960 bh->b_blocknr);
1961 if (PageUptodate(page)) {
1962 set_buffer_uptodate(bh);
1963 continue;
1964 }
1965 if (block_end > to || block_start < from) {
1966 void *kaddr;
1967
1968 kaddr = kmap_atomic(page, KM_USER0);
1969 if (block_end > to)
1970 memset(kaddr+to, 0,
1971 block_end-to);
1972 if (block_start < from)
1973 memset(kaddr+block_start,
1974 0, from-block_start);
1975 flush_dcache_page(page);
1976 kunmap_atomic(kaddr, KM_USER0);
1977 }
1978 continue;
1979 }
1980 }
1981 if (PageUptodate(page)) {
1982 if (!buffer_uptodate(bh))
1983 set_buffer_uptodate(bh);
1984 continue;
1985 }
1986 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1987 (block_start < from || block_end > to)) {
1988 ll_rw_block(READ, 1, &bh);
1989 *wait_bh++=bh;
1990 }
1991 }
1992 /*
1993 * If we issued read requests - let them complete.
1994 */
1995 while(wait_bh > wait) {
1996 wait_on_buffer(*--wait_bh);
1997 if (!buffer_uptodate(*wait_bh))
1998 return -EIO;
1999 }
2000 return 0;
2001out:
2002 /*
2003 * Zero out any newly allocated blocks to avoid exposing stale
2004 * data. If BH_New is set, we know that the block was newly
2005 * allocated in the above loop.
2006 */
2007 bh = head;
2008 block_start = 0;
2009 do {
2010 block_end = block_start+blocksize;
2011 if (block_end <= from)
2012 goto next_bh;
2013 if (block_start >= to)
2014 break;
2015 if (buffer_new(bh)) {
2016 void *kaddr;
2017
2018 clear_buffer_new(bh);
2019 kaddr = kmap_atomic(page, KM_USER0);
2020 memset(kaddr+block_start, 0, bh->b_size);
2021 kunmap_atomic(kaddr, KM_USER0);
2022 set_buffer_uptodate(bh);
2023 mark_buffer_dirty(bh);
2024 }
2025next_bh:
2026 block_start = block_end;
2027 bh = bh->b_this_page;
2028 } while (bh != head);
2029 return err;
2030}
2031
2032static int __block_commit_write(struct inode *inode, struct page *page,
2033 unsigned from, unsigned to)
2034{
2035 unsigned block_start, block_end;
2036 int partial = 0;
2037 unsigned blocksize;
2038 struct buffer_head *bh, *head;
2039
2040 blocksize = 1 << inode->i_blkbits;
2041
2042 for(bh = head = page_buffers(page), block_start = 0;
2043 bh != head || !block_start;
2044 block_start=block_end, bh = bh->b_this_page) {
2045 block_end = block_start + blocksize;
2046 if (block_end <= from || block_start >= to) {
2047 if (!buffer_uptodate(bh))
2048 partial = 1;
2049 } else {
2050 set_buffer_uptodate(bh);
2051 mark_buffer_dirty(bh);
2052 }
2053 }
2054
2055 /*
2056 * If this is a partial write which happened to make all buffers
2057 * uptodate then we can optimize away a bogus readpage() for
2058 * the next read(). Here we 'discover' whether the page went
2059 * uptodate as a result of this (potentially partial) write.
2060 */
2061 if (!partial)
2062 SetPageUptodate(page);
2063 return 0;
2064}
2065
2066/*
2067 * Generic "read page" function for block devices that have the normal
2068 * get_block functionality. This is most of the block device filesystems.
2069 * Reads the page asynchronously --- the unlock_buffer() and
2070 * set/clear_buffer_uptodate() functions propagate buffer state into the
2071 * page struct once IO has completed.
2072 */
2073int block_read_full_page(struct page *page, get_block_t *get_block)
2074{
2075 struct inode *inode = page->mapping->host;
2076 sector_t iblock, lblock;
2077 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2078 unsigned int blocksize;
2079 int nr, i;
2080 int fully_mapped = 1;
2081
Matt Mackallcd7619d2005-05-01 08:59:01 -07002082 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002083 blocksize = 1 << inode->i_blkbits;
2084 if (!page_has_buffers(page))
2085 create_empty_buffers(page, blocksize, 0);
2086 head = page_buffers(page);
2087
2088 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2089 lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
2090 bh = head;
2091 nr = 0;
2092 i = 0;
2093
2094 do {
2095 if (buffer_uptodate(bh))
2096 continue;
2097
2098 if (!buffer_mapped(bh)) {
2099 fully_mapped = 0;
2100 if (iblock < lblock) {
2101 if (get_block(inode, iblock, bh, 0))
2102 SetPageError(page);
2103 }
2104 if (!buffer_mapped(bh)) {
2105 void *kaddr = kmap_atomic(page, KM_USER0);
2106 memset(kaddr + i * blocksize, 0, blocksize);
2107 flush_dcache_page(page);
2108 kunmap_atomic(kaddr, KM_USER0);
2109 set_buffer_uptodate(bh);
2110 continue;
2111 }
2112 /*
2113 * get_block() might have updated the buffer
2114 * synchronously
2115 */
2116 if (buffer_uptodate(bh))
2117 continue;
2118 }
2119 arr[nr++] = bh;
2120 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2121
2122 if (fully_mapped)
2123 SetPageMappedToDisk(page);
2124
2125 if (!nr) {
2126 /*
2127 * All buffers are uptodate - we can set the page uptodate
2128 * as well. But not if get_block() returned an error.
2129 */
2130 if (!PageError(page))
2131 SetPageUptodate(page);
2132 unlock_page(page);
2133 return 0;
2134 }
2135
2136 /* Stage two: lock the buffers */
2137 for (i = 0; i < nr; i++) {
2138 bh = arr[i];
2139 lock_buffer(bh);
2140 mark_buffer_async_read(bh);
2141 }
2142
2143 /*
2144 * Stage 3: start the IO. Check for uptodateness
2145 * inside the buffer lock in case another process reading
2146 * the underlying blockdev brought it uptodate (the sct fix).
2147 */
2148 for (i = 0; i < nr; i++) {
2149 bh = arr[i];
2150 if (buffer_uptodate(bh))
2151 end_buffer_async_read(bh, 1);
2152 else
2153 submit_bh(READ, bh);
2154 }
2155 return 0;
2156}
2157
2158/* utility function for filesystems that need to do work on expanding
2159 * truncates. Uses prepare/commit_write to allow the filesystem to
2160 * deal with the hole.
2161 */
2162int generic_cont_expand(struct inode *inode, loff_t size)
2163{
2164 struct address_space *mapping = inode->i_mapping;
2165 struct page *page;
2166 unsigned long index, offset, limit;
2167 int err;
2168
2169 err = -EFBIG;
2170 limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
2171 if (limit != RLIM_INFINITY && size > (loff_t)limit) {
2172 send_sig(SIGXFSZ, current, 0);
2173 goto out;
2174 }
2175 if (size > inode->i_sb->s_maxbytes)
2176 goto out;
2177
2178 offset = (size & (PAGE_CACHE_SIZE-1)); /* Within page */
2179
2180 /* ugh. in prepare/commit_write, if from==to==start of block, we
2181 ** skip the prepare. make sure we never send an offset for the start
2182 ** of a block
2183 */
2184 if ((offset & (inode->i_sb->s_blocksize - 1)) == 0) {
2185 offset++;
2186 }
2187 index = size >> PAGE_CACHE_SHIFT;
2188 err = -ENOMEM;
2189 page = grab_cache_page(mapping, index);
2190 if (!page)
2191 goto out;
2192 err = mapping->a_ops->prepare_write(NULL, page, offset, offset);
2193 if (!err) {
2194 err = mapping->a_ops->commit_write(NULL, page, offset, offset);
2195 }
2196 unlock_page(page);
2197 page_cache_release(page);
2198 if (err > 0)
2199 err = 0;
2200out:
2201 return err;
2202}
2203
2204/*
2205 * For moronic filesystems that do not allow holes in file.
2206 * We may have to extend the file.
2207 */
2208
2209int cont_prepare_write(struct page *page, unsigned offset,
2210 unsigned to, get_block_t *get_block, loff_t *bytes)
2211{
2212 struct address_space *mapping = page->mapping;
2213 struct inode *inode = mapping->host;
2214 struct page *new_page;
2215 pgoff_t pgpos;
2216 long status;
2217 unsigned zerofrom;
2218 unsigned blocksize = 1 << inode->i_blkbits;
2219 void *kaddr;
2220
2221 while(page->index > (pgpos = *bytes>>PAGE_CACHE_SHIFT)) {
2222 status = -ENOMEM;
2223 new_page = grab_cache_page(mapping, pgpos);
2224 if (!new_page)
2225 goto out;
2226 /* we might sleep */
2227 if (*bytes>>PAGE_CACHE_SHIFT != pgpos) {
2228 unlock_page(new_page);
2229 page_cache_release(new_page);
2230 continue;
2231 }
2232 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2233 if (zerofrom & (blocksize-1)) {
2234 *bytes |= (blocksize-1);
2235 (*bytes)++;
2236 }
2237 status = __block_prepare_write(inode, new_page, zerofrom,
2238 PAGE_CACHE_SIZE, get_block);
2239 if (status)
2240 goto out_unmap;
2241 kaddr = kmap_atomic(new_page, KM_USER0);
2242 memset(kaddr+zerofrom, 0, PAGE_CACHE_SIZE-zerofrom);
2243 flush_dcache_page(new_page);
2244 kunmap_atomic(kaddr, KM_USER0);
2245 generic_commit_write(NULL, new_page, zerofrom, PAGE_CACHE_SIZE);
2246 unlock_page(new_page);
2247 page_cache_release(new_page);
2248 }
2249
2250 if (page->index < pgpos) {
2251 /* completely inside the area */
2252 zerofrom = offset;
2253 } else {
2254 /* page covers the boundary, find the boundary offset */
2255 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2256
2257 /* if we will expand the thing last block will be filled */
2258 if (to > zerofrom && (zerofrom & (blocksize-1))) {
2259 *bytes |= (blocksize-1);
2260 (*bytes)++;
2261 }
2262
2263 /* starting below the boundary? Nothing to zero out */
2264 if (offset <= zerofrom)
2265 zerofrom = offset;
2266 }
2267 status = __block_prepare_write(inode, page, zerofrom, to, get_block);
2268 if (status)
2269 goto out1;
2270 if (zerofrom < offset) {
2271 kaddr = kmap_atomic(page, KM_USER0);
2272 memset(kaddr+zerofrom, 0, offset-zerofrom);
2273 flush_dcache_page(page);
2274 kunmap_atomic(kaddr, KM_USER0);
2275 __block_commit_write(inode, page, zerofrom, offset);
2276 }
2277 return 0;
2278out1:
2279 ClearPageUptodate(page);
2280 return status;
2281
2282out_unmap:
2283 ClearPageUptodate(new_page);
2284 unlock_page(new_page);
2285 page_cache_release(new_page);
2286out:
2287 return status;
2288}
2289
2290int block_prepare_write(struct page *page, unsigned from, unsigned to,
2291 get_block_t *get_block)
2292{
2293 struct inode *inode = page->mapping->host;
2294 int err = __block_prepare_write(inode, page, from, to, get_block);
2295 if (err)
2296 ClearPageUptodate(page);
2297 return err;
2298}
2299
2300int block_commit_write(struct page *page, unsigned from, unsigned to)
2301{
2302 struct inode *inode = page->mapping->host;
2303 __block_commit_write(inode,page,from,to);
2304 return 0;
2305}
2306
2307int generic_commit_write(struct file *file, struct page *page,
2308 unsigned from, unsigned to)
2309{
2310 struct inode *inode = page->mapping->host;
2311 loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
2312 __block_commit_write(inode,page,from,to);
2313 /*
2314 * No need to use i_size_read() here, the i_size
2315 * cannot change under us because we hold i_sem.
2316 */
2317 if (pos > inode->i_size) {
2318 i_size_write(inode, pos);
2319 mark_inode_dirty(inode);
2320 }
2321 return 0;
2322}
2323
2324
2325/*
2326 * nobh_prepare_write()'s prereads are special: the buffer_heads are freed
2327 * immediately, while under the page lock. So it needs a special end_io
2328 * handler which does not touch the bh after unlocking it.
2329 *
2330 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
2331 * a race there is benign: unlock_buffer() only use the bh's address for
2332 * hashing after unlocking the buffer, so it doesn't actually touch the bh
2333 * itself.
2334 */
2335static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2336{
2337 if (uptodate) {
2338 set_buffer_uptodate(bh);
2339 } else {
2340 /* This happens, due to failed READA attempts. */
2341 clear_buffer_uptodate(bh);
2342 }
2343 unlock_buffer(bh);
2344}
2345
2346/*
2347 * On entry, the page is fully not uptodate.
2348 * On exit the page is fully uptodate in the areas outside (from,to)
2349 */
2350int nobh_prepare_write(struct page *page, unsigned from, unsigned to,
2351 get_block_t *get_block)
2352{
2353 struct inode *inode = page->mapping->host;
2354 const unsigned blkbits = inode->i_blkbits;
2355 const unsigned blocksize = 1 << blkbits;
2356 struct buffer_head map_bh;
2357 struct buffer_head *read_bh[MAX_BUF_PER_PAGE];
2358 unsigned block_in_page;
2359 unsigned block_start;
2360 sector_t block_in_file;
2361 char *kaddr;
2362 int nr_reads = 0;
2363 int i;
2364 int ret = 0;
2365 int is_mapped_to_disk = 1;
2366 int dirtied_it = 0;
2367
2368 if (PageMappedToDisk(page))
2369 return 0;
2370
2371 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
2372 map_bh.b_page = page;
2373
2374 /*
2375 * We loop across all blocks in the page, whether or not they are
2376 * part of the affected region. This is so we can discover if the
2377 * page is fully mapped-to-disk.
2378 */
2379 for (block_start = 0, block_in_page = 0;
2380 block_start < PAGE_CACHE_SIZE;
2381 block_in_page++, block_start += blocksize) {
2382 unsigned block_end = block_start + blocksize;
2383 int create;
2384
2385 map_bh.b_state = 0;
2386 create = 1;
2387 if (block_start >= to)
2388 create = 0;
2389 ret = get_block(inode, block_in_file + block_in_page,
2390 &map_bh, create);
2391 if (ret)
2392 goto failed;
2393 if (!buffer_mapped(&map_bh))
2394 is_mapped_to_disk = 0;
2395 if (buffer_new(&map_bh))
2396 unmap_underlying_metadata(map_bh.b_bdev,
2397 map_bh.b_blocknr);
2398 if (PageUptodate(page))
2399 continue;
2400 if (buffer_new(&map_bh) || !buffer_mapped(&map_bh)) {
2401 kaddr = kmap_atomic(page, KM_USER0);
2402 if (block_start < from) {
2403 memset(kaddr+block_start, 0, from-block_start);
2404 dirtied_it = 1;
2405 }
2406 if (block_end > to) {
2407 memset(kaddr + to, 0, block_end - to);
2408 dirtied_it = 1;
2409 }
2410 flush_dcache_page(page);
2411 kunmap_atomic(kaddr, KM_USER0);
2412 continue;
2413 }
2414 if (buffer_uptodate(&map_bh))
2415 continue; /* reiserfs does this */
2416 if (block_start < from || block_end > to) {
2417 struct buffer_head *bh = alloc_buffer_head(GFP_NOFS);
2418
2419 if (!bh) {
2420 ret = -ENOMEM;
2421 goto failed;
2422 }
2423 bh->b_state = map_bh.b_state;
2424 atomic_set(&bh->b_count, 0);
2425 bh->b_this_page = NULL;
2426 bh->b_page = page;
2427 bh->b_blocknr = map_bh.b_blocknr;
2428 bh->b_size = blocksize;
2429 bh->b_data = (char *)(long)block_start;
2430 bh->b_bdev = map_bh.b_bdev;
2431 bh->b_private = NULL;
2432 read_bh[nr_reads++] = bh;
2433 }
2434 }
2435
2436 if (nr_reads) {
2437 struct buffer_head *bh;
2438
2439 /*
2440 * The page is locked, so these buffers are protected from
2441 * any VM or truncate activity. Hence we don't need to care
2442 * for the buffer_head refcounts.
2443 */
2444 for (i = 0; i < nr_reads; i++) {
2445 bh = read_bh[i];
2446 lock_buffer(bh);
2447 bh->b_end_io = end_buffer_read_nobh;
2448 submit_bh(READ, bh);
2449 }
2450 for (i = 0; i < nr_reads; i++) {
2451 bh = read_bh[i];
2452 wait_on_buffer(bh);
2453 if (!buffer_uptodate(bh))
2454 ret = -EIO;
2455 free_buffer_head(bh);
2456 read_bh[i] = NULL;
2457 }
2458 if (ret)
2459 goto failed;
2460 }
2461
2462 if (is_mapped_to_disk)
2463 SetPageMappedToDisk(page);
2464 SetPageUptodate(page);
2465
2466 /*
2467 * Setting the page dirty here isn't necessary for the prepare_write
2468 * function - commit_write will do that. But if/when this function is
2469 * used within the pagefault handler to ensure that all mmapped pages
2470 * have backing space in the filesystem, we will need to dirty the page
2471 * if its contents were altered.
2472 */
2473 if (dirtied_it)
2474 set_page_dirty(page);
2475
2476 return 0;
2477
2478failed:
2479 for (i = 0; i < nr_reads; i++) {
2480 if (read_bh[i])
2481 free_buffer_head(read_bh[i]);
2482 }
2483
2484 /*
2485 * Error recovery is pretty slack. Clear the page and mark it dirty
2486 * so we'll later zero out any blocks which _were_ allocated.
2487 */
2488 kaddr = kmap_atomic(page, KM_USER0);
2489 memset(kaddr, 0, PAGE_CACHE_SIZE);
2490 kunmap_atomic(kaddr, KM_USER0);
2491 SetPageUptodate(page);
2492 set_page_dirty(page);
2493 return ret;
2494}
2495EXPORT_SYMBOL(nobh_prepare_write);
2496
2497int nobh_commit_write(struct file *file, struct page *page,
2498 unsigned from, unsigned to)
2499{
2500 struct inode *inode = page->mapping->host;
2501 loff_t pos = ((loff_t)page->index << PAGE_CACHE_SHIFT) + to;
2502
2503 set_page_dirty(page);
2504 if (pos > inode->i_size) {
2505 i_size_write(inode, pos);
2506 mark_inode_dirty(inode);
2507 }
2508 return 0;
2509}
2510EXPORT_SYMBOL(nobh_commit_write);
2511
2512/*
2513 * nobh_writepage() - based on block_full_write_page() except
2514 * that it tries to operate without attaching bufferheads to
2515 * the page.
2516 */
2517int nobh_writepage(struct page *page, get_block_t *get_block,
2518 struct writeback_control *wbc)
2519{
2520 struct inode * const inode = page->mapping->host;
2521 loff_t i_size = i_size_read(inode);
2522 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2523 unsigned offset;
2524 void *kaddr;
2525 int ret;
2526
2527 /* Is the page fully inside i_size? */
2528 if (page->index < end_index)
2529 goto out;
2530
2531 /* Is the page fully outside i_size? (truncate in progress) */
2532 offset = i_size & (PAGE_CACHE_SIZE-1);
2533 if (page->index >= end_index+1 || !offset) {
2534 /*
2535 * The page may have dirty, unmapped buffers. For example,
2536 * they may have been added in ext3_writepage(). Make them
2537 * freeable here, so the page does not leak.
2538 */
2539#if 0
2540 /* Not really sure about this - do we need this ? */
2541 if (page->mapping->a_ops->invalidatepage)
2542 page->mapping->a_ops->invalidatepage(page, offset);
2543#endif
2544 unlock_page(page);
2545 return 0; /* don't care */
2546 }
2547
2548 /*
2549 * The page straddles i_size. It must be zeroed out on each and every
2550 * writepage invocation because it may be mmapped. "A file is mapped
2551 * in multiples of the page size. For a file that is not a multiple of
2552 * the page size, the remaining memory is zeroed when mapped, and
2553 * writes to that region are not written out to the file."
2554 */
2555 kaddr = kmap_atomic(page, KM_USER0);
2556 memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
2557 flush_dcache_page(page);
2558 kunmap_atomic(kaddr, KM_USER0);
2559out:
2560 ret = mpage_writepage(page, get_block, wbc);
2561 if (ret == -EAGAIN)
2562 ret = __block_write_full_page(inode, page, get_block, wbc);
2563 return ret;
2564}
2565EXPORT_SYMBOL(nobh_writepage);
2566
2567/*
2568 * This function assumes that ->prepare_write() uses nobh_prepare_write().
2569 */
2570int nobh_truncate_page(struct address_space *mapping, loff_t from)
2571{
2572 struct inode *inode = mapping->host;
2573 unsigned blocksize = 1 << inode->i_blkbits;
2574 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2575 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2576 unsigned to;
2577 struct page *page;
2578 struct address_space_operations *a_ops = mapping->a_ops;
2579 char *kaddr;
2580 int ret = 0;
2581
2582 if ((offset & (blocksize - 1)) == 0)
2583 goto out;
2584
2585 ret = -ENOMEM;
2586 page = grab_cache_page(mapping, index);
2587 if (!page)
2588 goto out;
2589
2590 to = (offset + blocksize) & ~(blocksize - 1);
2591 ret = a_ops->prepare_write(NULL, page, offset, to);
2592 if (ret == 0) {
2593 kaddr = kmap_atomic(page, KM_USER0);
2594 memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
2595 flush_dcache_page(page);
2596 kunmap_atomic(kaddr, KM_USER0);
2597 set_page_dirty(page);
2598 }
2599 unlock_page(page);
2600 page_cache_release(page);
2601out:
2602 return ret;
2603}
2604EXPORT_SYMBOL(nobh_truncate_page);
2605
2606int block_truncate_page(struct address_space *mapping,
2607 loff_t from, get_block_t *get_block)
2608{
2609 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2610 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2611 unsigned blocksize;
2612 pgoff_t iblock;
2613 unsigned length, pos;
2614 struct inode *inode = mapping->host;
2615 struct page *page;
2616 struct buffer_head *bh;
2617 void *kaddr;
2618 int err;
2619
2620 blocksize = 1 << inode->i_blkbits;
2621 length = offset & (blocksize - 1);
2622
2623 /* Block boundary? Nothing to do */
2624 if (!length)
2625 return 0;
2626
2627 length = blocksize - length;
2628 iblock = index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2629
2630 page = grab_cache_page(mapping, index);
2631 err = -ENOMEM;
2632 if (!page)
2633 goto out;
2634
2635 if (!page_has_buffers(page))
2636 create_empty_buffers(page, blocksize, 0);
2637
2638 /* Find the buffer that contains "offset" */
2639 bh = page_buffers(page);
2640 pos = blocksize;
2641 while (offset >= pos) {
2642 bh = bh->b_this_page;
2643 iblock++;
2644 pos += blocksize;
2645 }
2646
2647 err = 0;
2648 if (!buffer_mapped(bh)) {
2649 err = get_block(inode, iblock, bh, 0);
2650 if (err)
2651 goto unlock;
2652 /* unmapped? It's a hole - nothing to do */
2653 if (!buffer_mapped(bh))
2654 goto unlock;
2655 }
2656
2657 /* Ok, it's mapped. Make sure it's up-to-date */
2658 if (PageUptodate(page))
2659 set_buffer_uptodate(bh);
2660
2661 if (!buffer_uptodate(bh) && !buffer_delay(bh)) {
2662 err = -EIO;
2663 ll_rw_block(READ, 1, &bh);
2664 wait_on_buffer(bh);
2665 /* Uhhuh. Read error. Complain and punt. */
2666 if (!buffer_uptodate(bh))
2667 goto unlock;
2668 }
2669
2670 kaddr = kmap_atomic(page, KM_USER0);
2671 memset(kaddr + offset, 0, length);
2672 flush_dcache_page(page);
2673 kunmap_atomic(kaddr, KM_USER0);
2674
2675 mark_buffer_dirty(bh);
2676 err = 0;
2677
2678unlock:
2679 unlock_page(page);
2680 page_cache_release(page);
2681out:
2682 return err;
2683}
2684
2685/*
2686 * The generic ->writepage function for buffer-backed address_spaces
2687 */
2688int block_write_full_page(struct page *page, get_block_t *get_block,
2689 struct writeback_control *wbc)
2690{
2691 struct inode * const inode = page->mapping->host;
2692 loff_t i_size = i_size_read(inode);
2693 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2694 unsigned offset;
2695 void *kaddr;
2696
2697 /* Is the page fully inside i_size? */
2698 if (page->index < end_index)
2699 return __block_write_full_page(inode, page, get_block, wbc);
2700
2701 /* Is the page fully outside i_size? (truncate in progress) */
2702 offset = i_size & (PAGE_CACHE_SIZE-1);
2703 if (page->index >= end_index+1 || !offset) {
2704 /*
2705 * The page may have dirty, unmapped buffers. For example,
2706 * they may have been added in ext3_writepage(). Make them
2707 * freeable here, so the page does not leak.
2708 */
2709 block_invalidatepage(page, 0);
2710 unlock_page(page);
2711 return 0; /* don't care */
2712 }
2713
2714 /*
2715 * The page straddles i_size. It must be zeroed out on each and every
2716 * writepage invokation because it may be mmapped. "A file is mapped
2717 * in multiples of the page size. For a file that is not a multiple of
2718 * the page size, the remaining memory is zeroed when mapped, and
2719 * writes to that region are not written out to the file."
2720 */
2721 kaddr = kmap_atomic(page, KM_USER0);
2722 memset(kaddr + offset, 0, PAGE_CACHE_SIZE - offset);
2723 flush_dcache_page(page);
2724 kunmap_atomic(kaddr, KM_USER0);
2725 return __block_write_full_page(inode, page, get_block, wbc);
2726}
2727
2728sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2729 get_block_t *get_block)
2730{
2731 struct buffer_head tmp;
2732 struct inode *inode = mapping->host;
2733 tmp.b_state = 0;
2734 tmp.b_blocknr = 0;
2735 get_block(inode, block, &tmp, 0);
2736 return tmp.b_blocknr;
2737}
2738
2739static int end_bio_bh_io_sync(struct bio *bio, unsigned int bytes_done, int err)
2740{
2741 struct buffer_head *bh = bio->bi_private;
2742
2743 if (bio->bi_size)
2744 return 1;
2745
2746 if (err == -EOPNOTSUPP) {
2747 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
2748 set_bit(BH_Eopnotsupp, &bh->b_state);
2749 }
2750
2751 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2752 bio_put(bio);
2753 return 0;
2754}
2755
2756int submit_bh(int rw, struct buffer_head * bh)
2757{
2758 struct bio *bio;
2759 int ret = 0;
2760
2761 BUG_ON(!buffer_locked(bh));
2762 BUG_ON(!buffer_mapped(bh));
2763 BUG_ON(!bh->b_end_io);
2764
2765 if (buffer_ordered(bh) && (rw == WRITE))
2766 rw = WRITE_BARRIER;
2767
2768 /*
2769 * Only clear out a write error when rewriting, should this
2770 * include WRITE_SYNC as well?
2771 */
2772 if (test_set_buffer_req(bh) && (rw == WRITE || rw == WRITE_BARRIER))
2773 clear_buffer_write_io_error(bh);
2774
2775 /*
2776 * from here on down, it's all bio -- do the initial mapping,
2777 * submit_bio -> generic_make_request may further map this bio around
2778 */
2779 bio = bio_alloc(GFP_NOIO, 1);
2780
2781 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2782 bio->bi_bdev = bh->b_bdev;
2783 bio->bi_io_vec[0].bv_page = bh->b_page;
2784 bio->bi_io_vec[0].bv_len = bh->b_size;
2785 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
2786
2787 bio->bi_vcnt = 1;
2788 bio->bi_idx = 0;
2789 bio->bi_size = bh->b_size;
2790
2791 bio->bi_end_io = end_bio_bh_io_sync;
2792 bio->bi_private = bh;
2793
2794 bio_get(bio);
2795 submit_bio(rw, bio);
2796
2797 if (bio_flagged(bio, BIO_EOPNOTSUPP))
2798 ret = -EOPNOTSUPP;
2799
2800 bio_put(bio);
2801 return ret;
2802}
2803
2804/**
2805 * ll_rw_block: low-level access to block devices (DEPRECATED)
2806 * @rw: whether to %READ or %WRITE or maybe %READA (readahead)
2807 * @nr: number of &struct buffer_heads in the array
2808 * @bhs: array of pointers to &struct buffer_head
2809 *
2810 * ll_rw_block() takes an array of pointers to &struct buffer_heads,
2811 * and requests an I/O operation on them, either a %READ or a %WRITE.
2812 * The third %READA option is described in the documentation for
2813 * generic_make_request() which ll_rw_block() calls.
2814 *
2815 * This function drops any buffer that it cannot get a lock on (with the
2816 * BH_Lock state bit), any buffer that appears to be clean when doing a
2817 * write request, and any buffer that appears to be up-to-date when doing
2818 * read request. Further it marks as clean buffers that are processed for
2819 * writing (the buffer cache won't assume that they are actually clean until
2820 * the buffer gets unlocked).
2821 *
2822 * ll_rw_block sets b_end_io to simple completion handler that marks
2823 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
2824 * any waiters.
2825 *
2826 * All of the buffers must be for the same device, and must also be a
2827 * multiple of the current approved size for the device.
2828 */
2829void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
2830{
2831 int i;
2832
2833 for (i = 0; i < nr; i++) {
2834 struct buffer_head *bh = bhs[i];
2835
2836 if (test_set_buffer_locked(bh))
2837 continue;
2838
2839 get_bh(bh);
2840 if (rw == WRITE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002841 if (test_clear_buffer_dirty(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07002842 bh->b_end_io = end_buffer_write_sync;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002843 submit_bh(WRITE, bh);
2844 continue;
2845 }
2846 } else {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002847 if (!buffer_uptodate(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07002848 bh->b_end_io = end_buffer_read_sync;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002849 submit_bh(rw, bh);
2850 continue;
2851 }
2852 }
2853 unlock_buffer(bh);
2854 put_bh(bh);
2855 }
2856}
2857
2858/*
2859 * For a data-integrity writeout, we need to wait upon any in-progress I/O
2860 * and then start new I/O and then wait upon it. The caller must have a ref on
2861 * the buffer_head.
2862 */
2863int sync_dirty_buffer(struct buffer_head *bh)
2864{
2865 int ret = 0;
2866
2867 WARN_ON(atomic_read(&bh->b_count) < 1);
2868 lock_buffer(bh);
2869 if (test_clear_buffer_dirty(bh)) {
2870 get_bh(bh);
2871 bh->b_end_io = end_buffer_write_sync;
2872 ret = submit_bh(WRITE, bh);
2873 wait_on_buffer(bh);
2874 if (buffer_eopnotsupp(bh)) {
2875 clear_buffer_eopnotsupp(bh);
2876 ret = -EOPNOTSUPP;
2877 }
2878 if (!ret && !buffer_uptodate(bh))
2879 ret = -EIO;
2880 } else {
2881 unlock_buffer(bh);
2882 }
2883 return ret;
2884}
2885
2886/*
2887 * try_to_free_buffers() checks if all the buffers on this particular page
2888 * are unused, and releases them if so.
2889 *
2890 * Exclusion against try_to_free_buffers may be obtained by either
2891 * locking the page or by holding its mapping's private_lock.
2892 *
2893 * If the page is dirty but all the buffers are clean then we need to
2894 * be sure to mark the page clean as well. This is because the page
2895 * may be against a block device, and a later reattachment of buffers
2896 * to a dirty page will set *all* buffers dirty. Which would corrupt
2897 * filesystem data on the same device.
2898 *
2899 * The same applies to regular filesystem pages: if all the buffers are
2900 * clean then we set the page clean and proceed. To do that, we require
2901 * total exclusion from __set_page_dirty_buffers(). That is obtained with
2902 * private_lock.
2903 *
2904 * try_to_free_buffers() is non-blocking.
2905 */
2906static inline int buffer_busy(struct buffer_head *bh)
2907{
2908 return atomic_read(&bh->b_count) |
2909 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
2910}
2911
2912static int
2913drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
2914{
2915 struct buffer_head *head = page_buffers(page);
2916 struct buffer_head *bh;
2917
2918 bh = head;
2919 do {
akpm@osdl.orgde7d5a32005-05-01 08:58:39 -07002920 if (buffer_write_io_error(bh) && page->mapping)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002921 set_bit(AS_EIO, &page->mapping->flags);
2922 if (buffer_busy(bh))
2923 goto failed;
2924 bh = bh->b_this_page;
2925 } while (bh != head);
2926
2927 do {
2928 struct buffer_head *next = bh->b_this_page;
2929
2930 if (!list_empty(&bh->b_assoc_buffers))
2931 __remove_assoc_queue(bh);
2932 bh = next;
2933 } while (bh != head);
2934 *buffers_to_free = head;
2935 __clear_page_buffers(page);
2936 return 1;
2937failed:
2938 return 0;
2939}
2940
2941int try_to_free_buffers(struct page *page)
2942{
2943 struct address_space * const mapping = page->mapping;
2944 struct buffer_head *buffers_to_free = NULL;
2945 int ret = 0;
2946
2947 BUG_ON(!PageLocked(page));
2948 if (PageWriteback(page))
2949 return 0;
2950
2951 if (mapping == NULL) { /* can this still happen? */
2952 ret = drop_buffers(page, &buffers_to_free);
2953 goto out;
2954 }
2955
2956 spin_lock(&mapping->private_lock);
2957 ret = drop_buffers(page, &buffers_to_free);
2958 if (ret) {
2959 /*
2960 * If the filesystem writes its buffers by hand (eg ext3)
2961 * then we can have clean buffers against a dirty page. We
2962 * clean the page here; otherwise later reattachment of buffers
2963 * could encounter a non-uptodate page, which is unresolvable.
2964 * This only applies in the rare case where try_to_free_buffers
2965 * succeeds but the page is not freed.
2966 */
2967 clear_page_dirty(page);
2968 }
2969 spin_unlock(&mapping->private_lock);
2970out:
2971 if (buffers_to_free) {
2972 struct buffer_head *bh = buffers_to_free;
2973
2974 do {
2975 struct buffer_head *next = bh->b_this_page;
2976 free_buffer_head(bh);
2977 bh = next;
2978 } while (bh != buffers_to_free);
2979 }
2980 return ret;
2981}
2982EXPORT_SYMBOL(try_to_free_buffers);
2983
2984int block_sync_page(struct page *page)
2985{
2986 struct address_space *mapping;
2987
2988 smp_mb();
2989 mapping = page_mapping(page);
2990 if (mapping)
2991 blk_run_backing_dev(mapping->backing_dev_info, page);
2992 return 0;
2993}
2994
2995/*
2996 * There are no bdflush tunables left. But distributions are
2997 * still running obsolete flush daemons, so we terminate them here.
2998 *
2999 * Use of bdflush() is deprecated and will be removed in a future kernel.
3000 * The `pdflush' kernel threads fully replace bdflush daemons and this call.
3001 */
3002asmlinkage long sys_bdflush(int func, long data)
3003{
3004 static int msg_count;
3005
3006 if (!capable(CAP_SYS_ADMIN))
3007 return -EPERM;
3008
3009 if (msg_count < 5) {
3010 msg_count++;
3011 printk(KERN_INFO
3012 "warning: process `%s' used the obsolete bdflush"
3013 " system call\n", current->comm);
3014 printk(KERN_INFO "Fix your initscripts?\n");
3015 }
3016
3017 if (func == 1)
3018 do_exit(0);
3019 return 0;
3020}
3021
3022/*
3023 * Buffer-head allocation
3024 */
3025static kmem_cache_t *bh_cachep;
3026
3027/*
3028 * Once the number of bh's in the machine exceeds this level, we start
3029 * stripping them in writeback.
3030 */
3031static int max_buffer_heads;
3032
3033int buffer_heads_over_limit;
3034
3035struct bh_accounting {
3036 int nr; /* Number of live bh's */
3037 int ratelimit; /* Limit cacheline bouncing */
3038};
3039
3040static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3041
3042static void recalc_bh_state(void)
3043{
3044 int i;
3045 int tot = 0;
3046
3047 if (__get_cpu_var(bh_accounting).ratelimit++ < 4096)
3048 return;
3049 __get_cpu_var(bh_accounting).ratelimit = 0;
3050 for_each_cpu(i)
3051 tot += per_cpu(bh_accounting, i).nr;
3052 buffer_heads_over_limit = (tot > max_buffer_heads);
3053}
3054
3055struct buffer_head *alloc_buffer_head(unsigned int __nocast gfp_flags)
3056{
3057 struct buffer_head *ret = kmem_cache_alloc(bh_cachep, gfp_flags);
3058 if (ret) {
3059 preempt_disable();
3060 __get_cpu_var(bh_accounting).nr++;
3061 recalc_bh_state();
3062 preempt_enable();
3063 }
3064 return ret;
3065}
3066EXPORT_SYMBOL(alloc_buffer_head);
3067
3068void free_buffer_head(struct buffer_head *bh)
3069{
3070 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3071 kmem_cache_free(bh_cachep, bh);
3072 preempt_disable();
3073 __get_cpu_var(bh_accounting).nr--;
3074 recalc_bh_state();
3075 preempt_enable();
3076}
3077EXPORT_SYMBOL(free_buffer_head);
3078
3079static void
3080init_buffer_head(void *data, kmem_cache_t *cachep, unsigned long flags)
3081{
3082 if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
3083 SLAB_CTOR_CONSTRUCTOR) {
3084 struct buffer_head * bh = (struct buffer_head *)data;
3085
3086 memset(bh, 0, sizeof(*bh));
3087 INIT_LIST_HEAD(&bh->b_assoc_buffers);
3088 }
3089}
3090
3091#ifdef CONFIG_HOTPLUG_CPU
3092static void buffer_exit_cpu(int cpu)
3093{
3094 int i;
3095 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3096
3097 for (i = 0; i < BH_LRU_SIZE; i++) {
3098 brelse(b->bhs[i]);
3099 b->bhs[i] = NULL;
3100 }
3101}
3102
3103static int buffer_cpu_notify(struct notifier_block *self,
3104 unsigned long action, void *hcpu)
3105{
3106 if (action == CPU_DEAD)
3107 buffer_exit_cpu((unsigned long)hcpu);
3108 return NOTIFY_OK;
3109}
3110#endif /* CONFIG_HOTPLUG_CPU */
3111
3112void __init buffer_init(void)
3113{
3114 int nrpages;
3115
3116 bh_cachep = kmem_cache_create("buffer_head",
3117 sizeof(struct buffer_head), 0,
3118 SLAB_PANIC, init_buffer_head, NULL);
3119
3120 /*
3121 * Limit the bh occupancy to 10% of ZONE_NORMAL
3122 */
3123 nrpages = (nr_free_buffer_pages() * 10) / 100;
3124 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3125 hotcpu_notifier(buffer_cpu_notify, 0);
3126}
3127
3128EXPORT_SYMBOL(__bforget);
3129EXPORT_SYMBOL(__brelse);
3130EXPORT_SYMBOL(__wait_on_buffer);
3131EXPORT_SYMBOL(block_commit_write);
3132EXPORT_SYMBOL(block_prepare_write);
3133EXPORT_SYMBOL(block_read_full_page);
3134EXPORT_SYMBOL(block_sync_page);
3135EXPORT_SYMBOL(block_truncate_page);
3136EXPORT_SYMBOL(block_write_full_page);
3137EXPORT_SYMBOL(cont_prepare_write);
3138EXPORT_SYMBOL(end_buffer_async_write);
3139EXPORT_SYMBOL(end_buffer_read_sync);
3140EXPORT_SYMBOL(end_buffer_write_sync);
3141EXPORT_SYMBOL(file_fsync);
3142EXPORT_SYMBOL(fsync_bdev);
3143EXPORT_SYMBOL(generic_block_bmap);
3144EXPORT_SYMBOL(generic_commit_write);
3145EXPORT_SYMBOL(generic_cont_expand);
3146EXPORT_SYMBOL(init_buffer);
3147EXPORT_SYMBOL(invalidate_bdev);
3148EXPORT_SYMBOL(ll_rw_block);
3149EXPORT_SYMBOL(mark_buffer_dirty);
3150EXPORT_SYMBOL(submit_bh);
3151EXPORT_SYMBOL(sync_dirty_buffer);
3152EXPORT_SYMBOL(unlock_buffer);