Merge tag 'spi-for-linus' of git://git.secretlab.ca/git/linux-2.6
[GitHub/mt8127/android_kernel_alcatel_ttab.git] / fs / buffer.c
1 /*
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/kernel.h>
22 #include <linux/syscalls.h>
23 #include <linux/fs.h>
24 #include <linux/mm.h>
25 #include <linux/percpu.h>
26 #include <linux/slab.h>
27 #include <linux/capability.h>
28 #include <linux/blkdev.h>
29 #include <linux/file.h>
30 #include <linux/quotaops.h>
31 #include <linux/highmem.h>
32 #include <linux/export.h>
33 #include <linux/writeback.h>
34 #include <linux/hash.h>
35 #include <linux/suspend.h>
36 #include <linux/buffer_head.h>
37 #include <linux/task_io_accounting_ops.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 #include <linux/bit_spinlock.h>
44
45 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
46
47 #define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
48
49 inline void
50 init_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 EXPORT_SYMBOL(init_buffer);
56
57 static int sleep_on_buffer(void *word)
58 {
59 io_schedule();
60 return 0;
61 }
62
63 void __lock_buffer(struct buffer_head *bh)
64 {
65 wait_on_bit_lock(&bh->b_state, BH_Lock, sleep_on_buffer,
66 TASK_UNINTERRUPTIBLE);
67 }
68 EXPORT_SYMBOL(__lock_buffer);
69
70 void unlock_buffer(struct buffer_head *bh)
71 {
72 clear_bit_unlock(BH_Lock, &bh->b_state);
73 smp_mb__after_clear_bit();
74 wake_up_bit(&bh->b_state, BH_Lock);
75 }
76 EXPORT_SYMBOL(unlock_buffer);
77
78 /*
79 * Block until a buffer comes unlocked. This doesn't stop it
80 * from becoming locked again - you have to lock it yourself
81 * if you want to preserve its state.
82 */
83 void __wait_on_buffer(struct buffer_head * bh)
84 {
85 wait_on_bit(&bh->b_state, BH_Lock, sleep_on_buffer, TASK_UNINTERRUPTIBLE);
86 }
87 EXPORT_SYMBOL(__wait_on_buffer);
88
89 static void
90 __clear_page_buffers(struct page *page)
91 {
92 ClearPagePrivate(page);
93 set_page_private(page, 0);
94 page_cache_release(page);
95 }
96
97
98 static int quiet_error(struct buffer_head *bh)
99 {
100 if (!test_bit(BH_Quiet, &bh->b_state) && printk_ratelimit())
101 return 0;
102 return 1;
103 }
104
105
106 static void buffer_io_error(struct buffer_head *bh)
107 {
108 char b[BDEVNAME_SIZE];
109 printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
110 bdevname(bh->b_bdev, b),
111 (unsigned long long)bh->b_blocknr);
112 }
113
114 /*
115 * End-of-IO handler helper function which does not touch the bh after
116 * unlocking it.
117 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
118 * a race there is benign: unlock_buffer() only use the bh's address for
119 * hashing after unlocking the buffer, so it doesn't actually touch the bh
120 * itself.
121 */
122 static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
123 {
124 if (uptodate) {
125 set_buffer_uptodate(bh);
126 } else {
127 /* This happens, due to failed READA attempts. */
128 clear_buffer_uptodate(bh);
129 }
130 unlock_buffer(bh);
131 }
132
133 /*
134 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
135 * unlock the buffer. This is what ll_rw_block uses too.
136 */
137 void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
138 {
139 __end_buffer_read_notouch(bh, uptodate);
140 put_bh(bh);
141 }
142 EXPORT_SYMBOL(end_buffer_read_sync);
143
144 void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
145 {
146 char b[BDEVNAME_SIZE];
147
148 if (uptodate) {
149 set_buffer_uptodate(bh);
150 } else {
151 if (!quiet_error(bh)) {
152 buffer_io_error(bh);
153 printk(KERN_WARNING "lost page write due to "
154 "I/O error on %s\n",
155 bdevname(bh->b_bdev, b));
156 }
157 set_buffer_write_io_error(bh);
158 clear_buffer_uptodate(bh);
159 }
160 unlock_buffer(bh);
161 put_bh(bh);
162 }
163 EXPORT_SYMBOL(end_buffer_write_sync);
164
165 /*
166 * Various filesystems appear to want __find_get_block to be non-blocking.
167 * But it's the page lock which protects the buffers. To get around this,
168 * we get exclusion from try_to_free_buffers with the blockdev mapping's
169 * private_lock.
170 *
171 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
172 * may be quite high. This code could TryLock the page, and if that
173 * succeeds, there is no need to take private_lock. (But if
174 * private_lock is contended then so is mapping->tree_lock).
175 */
176 static struct buffer_head *
177 __find_get_block_slow(struct block_device *bdev, sector_t block)
178 {
179 struct inode *bd_inode = bdev->bd_inode;
180 struct address_space *bd_mapping = bd_inode->i_mapping;
181 struct buffer_head *ret = NULL;
182 pgoff_t index;
183 struct buffer_head *bh;
184 struct buffer_head *head;
185 struct page *page;
186 int all_mapped = 1;
187
188 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
189 page = find_get_page(bd_mapping, index);
190 if (!page)
191 goto out;
192
193 spin_lock(&bd_mapping->private_lock);
194 if (!page_has_buffers(page))
195 goto out_unlock;
196 head = page_buffers(page);
197 bh = head;
198 do {
199 if (!buffer_mapped(bh))
200 all_mapped = 0;
201 else if (bh->b_blocknr == block) {
202 ret = bh;
203 get_bh(bh);
204 goto out_unlock;
205 }
206 bh = bh->b_this_page;
207 } while (bh != head);
208
209 /* we might be here because some of the buffers on this page are
210 * not mapped. This is due to various races between
211 * file io on the block device and getblk. It gets dealt with
212 * elsewhere, don't buffer_error if we had some unmapped buffers
213 */
214 if (all_mapped) {
215 char b[BDEVNAME_SIZE];
216
217 printk("__find_get_block_slow() failed. "
218 "block=%llu, b_blocknr=%llu\n",
219 (unsigned long long)block,
220 (unsigned long long)bh->b_blocknr);
221 printk("b_state=0x%08lx, b_size=%zu\n",
222 bh->b_state, bh->b_size);
223 printk("device %s blocksize: %d\n", bdevname(bdev, b),
224 1 << bd_inode->i_blkbits);
225 }
226 out_unlock:
227 spin_unlock(&bd_mapping->private_lock);
228 page_cache_release(page);
229 out:
230 return ret;
231 }
232
233 /*
234 * Kick the writeback threads then try to free up some ZONE_NORMAL memory.
235 */
236 static void free_more_memory(void)
237 {
238 struct zone *zone;
239 int nid;
240
241 wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM);
242 yield();
243
244 for_each_online_node(nid) {
245 (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS),
246 gfp_zone(GFP_NOFS), NULL,
247 &zone);
248 if (zone)
249 try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0,
250 GFP_NOFS, NULL);
251 }
252 }
253
254 /*
255 * I/O completion handler for block_read_full_page() - pages
256 * which come unlocked at the end of I/O.
257 */
258 static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
259 {
260 unsigned long flags;
261 struct buffer_head *first;
262 struct buffer_head *tmp;
263 struct page *page;
264 int page_uptodate = 1;
265
266 BUG_ON(!buffer_async_read(bh));
267
268 page = bh->b_page;
269 if (uptodate) {
270 set_buffer_uptodate(bh);
271 } else {
272 clear_buffer_uptodate(bh);
273 if (!quiet_error(bh))
274 buffer_io_error(bh);
275 SetPageError(page);
276 }
277
278 /*
279 * Be _very_ careful from here on. Bad things can happen if
280 * two buffer heads end IO at almost the same time and both
281 * decide that the page is now completely done.
282 */
283 first = page_buffers(page);
284 local_irq_save(flags);
285 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
286 clear_buffer_async_read(bh);
287 unlock_buffer(bh);
288 tmp = bh;
289 do {
290 if (!buffer_uptodate(tmp))
291 page_uptodate = 0;
292 if (buffer_async_read(tmp)) {
293 BUG_ON(!buffer_locked(tmp));
294 goto still_busy;
295 }
296 tmp = tmp->b_this_page;
297 } while (tmp != bh);
298 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
299 local_irq_restore(flags);
300
301 /*
302 * If none of the buffers had errors and they are all
303 * uptodate then we can set the page uptodate.
304 */
305 if (page_uptodate && !PageError(page))
306 SetPageUptodate(page);
307 unlock_page(page);
308 return;
309
310 still_busy:
311 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
312 local_irq_restore(flags);
313 return;
314 }
315
316 /*
317 * Completion handler for block_write_full_page() - pages which are unlocked
318 * during I/O, and which have PageWriteback cleared upon I/O completion.
319 */
320 void end_buffer_async_write(struct buffer_head *bh, int uptodate)
321 {
322 char b[BDEVNAME_SIZE];
323 unsigned long flags;
324 struct buffer_head *first;
325 struct buffer_head *tmp;
326 struct page *page;
327
328 BUG_ON(!buffer_async_write(bh));
329
330 page = bh->b_page;
331 if (uptodate) {
332 set_buffer_uptodate(bh);
333 } else {
334 if (!quiet_error(bh)) {
335 buffer_io_error(bh);
336 printk(KERN_WARNING "lost page write due to "
337 "I/O error on %s\n",
338 bdevname(bh->b_bdev, b));
339 }
340 set_bit(AS_EIO, &page->mapping->flags);
341 set_buffer_write_io_error(bh);
342 clear_buffer_uptodate(bh);
343 SetPageError(page);
344 }
345
346 first = page_buffers(page);
347 local_irq_save(flags);
348 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
349
350 clear_buffer_async_write(bh);
351 unlock_buffer(bh);
352 tmp = bh->b_this_page;
353 while (tmp != bh) {
354 if (buffer_async_write(tmp)) {
355 BUG_ON(!buffer_locked(tmp));
356 goto still_busy;
357 }
358 tmp = tmp->b_this_page;
359 }
360 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
361 local_irq_restore(flags);
362 end_page_writeback(page);
363 return;
364
365 still_busy:
366 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
367 local_irq_restore(flags);
368 return;
369 }
370 EXPORT_SYMBOL(end_buffer_async_write);
371
372 /*
373 * If a page's buffers are under async readin (end_buffer_async_read
374 * completion) then there is a possibility that another thread of
375 * control could lock one of the buffers after it has completed
376 * but while some of the other buffers have not completed. This
377 * locked buffer would confuse end_buffer_async_read() into not unlocking
378 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
379 * that this buffer is not under async I/O.
380 *
381 * The page comes unlocked when it has no locked buffer_async buffers
382 * left.
383 *
384 * PageLocked prevents anyone starting new async I/O reads any of
385 * the buffers.
386 *
387 * PageWriteback is used to prevent simultaneous writeout of the same
388 * page.
389 *
390 * PageLocked prevents anyone from starting writeback of a page which is
391 * under read I/O (PageWriteback is only ever set against a locked page).
392 */
393 static void mark_buffer_async_read(struct buffer_head *bh)
394 {
395 bh->b_end_io = end_buffer_async_read;
396 set_buffer_async_read(bh);
397 }
398
399 static void mark_buffer_async_write_endio(struct buffer_head *bh,
400 bh_end_io_t *handler)
401 {
402 bh->b_end_io = handler;
403 set_buffer_async_write(bh);
404 }
405
406 void mark_buffer_async_write(struct buffer_head *bh)
407 {
408 mark_buffer_async_write_endio(bh, end_buffer_async_write);
409 }
410 EXPORT_SYMBOL(mark_buffer_async_write);
411
412
413 /*
414 * fs/buffer.c contains helper functions for buffer-backed address space's
415 * fsync functions. A common requirement for buffer-based filesystems is
416 * that certain data from the backing blockdev needs to be written out for
417 * a successful fsync(). For example, ext2 indirect blocks need to be
418 * written back and waited upon before fsync() returns.
419 *
420 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
421 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
422 * management of a list of dependent buffers at ->i_mapping->private_list.
423 *
424 * Locking is a little subtle: try_to_free_buffers() will remove buffers
425 * from their controlling inode's queue when they are being freed. But
426 * try_to_free_buffers() will be operating against the *blockdev* mapping
427 * at the time, not against the S_ISREG file which depends on those buffers.
428 * So the locking for private_list is via the private_lock in the address_space
429 * which backs the buffers. Which is different from the address_space
430 * against which the buffers are listed. So for a particular address_space,
431 * mapping->private_lock does *not* protect mapping->private_list! In fact,
432 * mapping->private_list will always be protected by the backing blockdev's
433 * ->private_lock.
434 *
435 * Which introduces a requirement: all buffers on an address_space's
436 * ->private_list must be from the same address_space: the blockdev's.
437 *
438 * address_spaces which do not place buffers at ->private_list via these
439 * utility functions are free to use private_lock and private_list for
440 * whatever they want. The only requirement is that list_empty(private_list)
441 * be true at clear_inode() time.
442 *
443 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
444 * filesystems should do that. invalidate_inode_buffers() should just go
445 * BUG_ON(!list_empty).
446 *
447 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
448 * take an address_space, not an inode. And it should be called
449 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
450 * queued up.
451 *
452 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
453 * list if it is already on a list. Because if the buffer is on a list,
454 * it *must* already be on the right one. If not, the filesystem is being
455 * silly. This will save a ton of locking. But first we have to ensure
456 * that buffers are taken *off* the old inode's list when they are freed
457 * (presumably in truncate). That requires careful auditing of all
458 * filesystems (do it inside bforget()). It could also be done by bringing
459 * b_inode back.
460 */
461
462 /*
463 * The buffer's backing address_space's private_lock must be held
464 */
465 static void __remove_assoc_queue(struct buffer_head *bh)
466 {
467 list_del_init(&bh->b_assoc_buffers);
468 WARN_ON(!bh->b_assoc_map);
469 if (buffer_write_io_error(bh))
470 set_bit(AS_EIO, &bh->b_assoc_map->flags);
471 bh->b_assoc_map = NULL;
472 }
473
474 int inode_has_buffers(struct inode *inode)
475 {
476 return !list_empty(&inode->i_data.private_list);
477 }
478
479 /*
480 * osync is designed to support O_SYNC io. It waits synchronously for
481 * all already-submitted IO to complete, but does not queue any new
482 * writes to the disk.
483 *
484 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
485 * you dirty the buffers, and then use osync_inode_buffers to wait for
486 * completion. Any other dirty buffers which are not yet queued for
487 * write will not be flushed to disk by the osync.
488 */
489 static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
490 {
491 struct buffer_head *bh;
492 struct list_head *p;
493 int err = 0;
494
495 spin_lock(lock);
496 repeat:
497 list_for_each_prev(p, list) {
498 bh = BH_ENTRY(p);
499 if (buffer_locked(bh)) {
500 get_bh(bh);
501 spin_unlock(lock);
502 wait_on_buffer(bh);
503 if (!buffer_uptodate(bh))
504 err = -EIO;
505 brelse(bh);
506 spin_lock(lock);
507 goto repeat;
508 }
509 }
510 spin_unlock(lock);
511 return err;
512 }
513
514 static void do_thaw_one(struct super_block *sb, void *unused)
515 {
516 char b[BDEVNAME_SIZE];
517 while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
518 printk(KERN_WARNING "Emergency Thaw on %s\n",
519 bdevname(sb->s_bdev, b));
520 }
521
522 static void do_thaw_all(struct work_struct *work)
523 {
524 iterate_supers(do_thaw_one, NULL);
525 kfree(work);
526 printk(KERN_WARNING "Emergency Thaw complete\n");
527 }
528
529 /**
530 * emergency_thaw_all -- forcibly thaw every frozen filesystem
531 *
532 * Used for emergency unfreeze of all filesystems via SysRq
533 */
534 void emergency_thaw_all(void)
535 {
536 struct work_struct *work;
537
538 work = kmalloc(sizeof(*work), GFP_ATOMIC);
539 if (work) {
540 INIT_WORK(work, do_thaw_all);
541 schedule_work(work);
542 }
543 }
544
545 /**
546 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
547 * @mapping: the mapping which wants those buffers written
548 *
549 * Starts I/O against the buffers at mapping->private_list, and waits upon
550 * that I/O.
551 *
552 * Basically, this is a convenience function for fsync().
553 * @mapping is a file or directory which needs those buffers to be written for
554 * a successful fsync().
555 */
556 int sync_mapping_buffers(struct address_space *mapping)
557 {
558 struct address_space *buffer_mapping = mapping->assoc_mapping;
559
560 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
561 return 0;
562
563 return fsync_buffers_list(&buffer_mapping->private_lock,
564 &mapping->private_list);
565 }
566 EXPORT_SYMBOL(sync_mapping_buffers);
567
568 /*
569 * Called when we've recently written block `bblock', and it is known that
570 * `bblock' was for a buffer_boundary() buffer. This means that the block at
571 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
572 * dirty, schedule it for IO. So that indirects merge nicely with their data.
573 */
574 void write_boundary_block(struct block_device *bdev,
575 sector_t bblock, unsigned blocksize)
576 {
577 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
578 if (bh) {
579 if (buffer_dirty(bh))
580 ll_rw_block(WRITE, 1, &bh);
581 put_bh(bh);
582 }
583 }
584
585 void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
586 {
587 struct address_space *mapping = inode->i_mapping;
588 struct address_space *buffer_mapping = bh->b_page->mapping;
589
590 mark_buffer_dirty(bh);
591 if (!mapping->assoc_mapping) {
592 mapping->assoc_mapping = buffer_mapping;
593 } else {
594 BUG_ON(mapping->assoc_mapping != buffer_mapping);
595 }
596 if (!bh->b_assoc_map) {
597 spin_lock(&buffer_mapping->private_lock);
598 list_move_tail(&bh->b_assoc_buffers,
599 &mapping->private_list);
600 bh->b_assoc_map = mapping;
601 spin_unlock(&buffer_mapping->private_lock);
602 }
603 }
604 EXPORT_SYMBOL(mark_buffer_dirty_inode);
605
606 /*
607 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
608 * dirty.
609 *
610 * If warn is true, then emit a warning if the page is not uptodate and has
611 * not been truncated.
612 */
613 static void __set_page_dirty(struct page *page,
614 struct address_space *mapping, int warn)
615 {
616 spin_lock_irq(&mapping->tree_lock);
617 if (page->mapping) { /* Race with truncate? */
618 WARN_ON_ONCE(warn && !PageUptodate(page));
619 account_page_dirtied(page, mapping);
620 radix_tree_tag_set(&mapping->page_tree,
621 page_index(page), PAGECACHE_TAG_DIRTY);
622 }
623 spin_unlock_irq(&mapping->tree_lock);
624 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
625 }
626
627 /*
628 * Add a page to the dirty page list.
629 *
630 * It is a sad fact of life that this function is called from several places
631 * deeply under spinlocking. It may not sleep.
632 *
633 * If the page has buffers, the uptodate buffers are set dirty, to preserve
634 * dirty-state coherency between the page and the buffers. It the page does
635 * not have buffers then when they are later attached they will all be set
636 * dirty.
637 *
638 * The buffers are dirtied before the page is dirtied. There's a small race
639 * window in which a writepage caller may see the page cleanness but not the
640 * buffer dirtiness. That's fine. If this code were to set the page dirty
641 * before the buffers, a concurrent writepage caller could clear the page dirty
642 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
643 * page on the dirty page list.
644 *
645 * We use private_lock to lock against try_to_free_buffers while using the
646 * page's buffer list. Also use this to protect against clean buffers being
647 * added to the page after it was set dirty.
648 *
649 * FIXME: may need to call ->reservepage here as well. That's rather up to the
650 * address_space though.
651 */
652 int __set_page_dirty_buffers(struct page *page)
653 {
654 int newly_dirty;
655 struct address_space *mapping = page_mapping(page);
656
657 if (unlikely(!mapping))
658 return !TestSetPageDirty(page);
659
660 spin_lock(&mapping->private_lock);
661 if (page_has_buffers(page)) {
662 struct buffer_head *head = page_buffers(page);
663 struct buffer_head *bh = head;
664
665 do {
666 set_buffer_dirty(bh);
667 bh = bh->b_this_page;
668 } while (bh != head);
669 }
670 newly_dirty = !TestSetPageDirty(page);
671 spin_unlock(&mapping->private_lock);
672
673 if (newly_dirty)
674 __set_page_dirty(page, mapping, 1);
675 return newly_dirty;
676 }
677 EXPORT_SYMBOL(__set_page_dirty_buffers);
678
679 /*
680 * Write out and wait upon a list of buffers.
681 *
682 * We have conflicting pressures: we want to make sure that all
683 * initially dirty buffers get waited on, but that any subsequently
684 * dirtied buffers don't. After all, we don't want fsync to last
685 * forever if somebody is actively writing to the file.
686 *
687 * Do this in two main stages: first we copy dirty buffers to a
688 * temporary inode list, queueing the writes as we go. Then we clean
689 * up, waiting for those writes to complete.
690 *
691 * During this second stage, any subsequent updates to the file may end
692 * up refiling the buffer on the original inode's dirty list again, so
693 * there is a chance we will end up with a buffer queued for write but
694 * not yet completed on that list. So, as a final cleanup we go through
695 * the osync code to catch these locked, dirty buffers without requeuing
696 * any newly dirty buffers for write.
697 */
698 static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
699 {
700 struct buffer_head *bh;
701 struct list_head tmp;
702 struct address_space *mapping;
703 int err = 0, err2;
704 struct blk_plug plug;
705
706 INIT_LIST_HEAD(&tmp);
707 blk_start_plug(&plug);
708
709 spin_lock(lock);
710 while (!list_empty(list)) {
711 bh = BH_ENTRY(list->next);
712 mapping = bh->b_assoc_map;
713 __remove_assoc_queue(bh);
714 /* Avoid race with mark_buffer_dirty_inode() which does
715 * a lockless check and we rely on seeing the dirty bit */
716 smp_mb();
717 if (buffer_dirty(bh) || buffer_locked(bh)) {
718 list_add(&bh->b_assoc_buffers, &tmp);
719 bh->b_assoc_map = mapping;
720 if (buffer_dirty(bh)) {
721 get_bh(bh);
722 spin_unlock(lock);
723 /*
724 * Ensure any pending I/O completes so that
725 * write_dirty_buffer() actually writes the
726 * current contents - it is a noop if I/O is
727 * still in flight on potentially older
728 * contents.
729 */
730 write_dirty_buffer(bh, WRITE_SYNC);
731
732 /*
733 * Kick off IO for the previous mapping. Note
734 * that we will not run the very last mapping,
735 * wait_on_buffer() will do that for us
736 * through sync_buffer().
737 */
738 brelse(bh);
739 spin_lock(lock);
740 }
741 }
742 }
743
744 spin_unlock(lock);
745 blk_finish_plug(&plug);
746 spin_lock(lock);
747
748 while (!list_empty(&tmp)) {
749 bh = BH_ENTRY(tmp.prev);
750 get_bh(bh);
751 mapping = bh->b_assoc_map;
752 __remove_assoc_queue(bh);
753 /* Avoid race with mark_buffer_dirty_inode() which does
754 * a lockless check and we rely on seeing the dirty bit */
755 smp_mb();
756 if (buffer_dirty(bh)) {
757 list_add(&bh->b_assoc_buffers,
758 &mapping->private_list);
759 bh->b_assoc_map = mapping;
760 }
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 }
768
769 spin_unlock(lock);
770 err2 = osync_buffers_list(lock, list);
771 if (err)
772 return err;
773 else
774 return err2;
775 }
776
777 /*
778 * Invalidate any and all dirty buffers on a given inode. We are
779 * probably unmounting the fs, but that doesn't mean we have already
780 * done a sync(). Just drop the buffers from the inode list.
781 *
782 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
783 * assumes that all the buffers are against the blockdev. Not true
784 * for reiserfs.
785 */
786 void invalidate_inode_buffers(struct inode *inode)
787 {
788 if (inode_has_buffers(inode)) {
789 struct address_space *mapping = &inode->i_data;
790 struct list_head *list = &mapping->private_list;
791 struct address_space *buffer_mapping = mapping->assoc_mapping;
792
793 spin_lock(&buffer_mapping->private_lock);
794 while (!list_empty(list))
795 __remove_assoc_queue(BH_ENTRY(list->next));
796 spin_unlock(&buffer_mapping->private_lock);
797 }
798 }
799 EXPORT_SYMBOL(invalidate_inode_buffers);
800
801 /*
802 * Remove any clean buffers from the inode's buffer list. This is called
803 * when we're trying to free the inode itself. Those buffers can pin it.
804 *
805 * Returns true if all buffers were removed.
806 */
807 int remove_inode_buffers(struct inode *inode)
808 {
809 int ret = 1;
810
811 if (inode_has_buffers(inode)) {
812 struct address_space *mapping = &inode->i_data;
813 struct list_head *list = &mapping->private_list;
814 struct address_space *buffer_mapping = mapping->assoc_mapping;
815
816 spin_lock(&buffer_mapping->private_lock);
817 while (!list_empty(list)) {
818 struct buffer_head *bh = BH_ENTRY(list->next);
819 if (buffer_dirty(bh)) {
820 ret = 0;
821 break;
822 }
823 __remove_assoc_queue(bh);
824 }
825 spin_unlock(&buffer_mapping->private_lock);
826 }
827 return ret;
828 }
829
830 /*
831 * Create the appropriate buffers when given a page for data area and
832 * the size of each buffer.. Use the bh->b_this_page linked list to
833 * follow the buffers created. Return NULL if unable to create more
834 * buffers.
835 *
836 * The retry flag is used to differentiate async IO (paging, swapping)
837 * which may not fail from ordinary buffer allocations.
838 */
839 struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
840 int retry)
841 {
842 struct buffer_head *bh, *head;
843 long offset;
844
845 try_again:
846 head = NULL;
847 offset = PAGE_SIZE;
848 while ((offset -= size) >= 0) {
849 bh = alloc_buffer_head(GFP_NOFS);
850 if (!bh)
851 goto no_grow;
852
853 bh->b_bdev = NULL;
854 bh->b_this_page = head;
855 bh->b_blocknr = -1;
856 head = bh;
857
858 bh->b_state = 0;
859 atomic_set(&bh->b_count, 0);
860 bh->b_size = size;
861
862 /* Link the buffer to its page */
863 set_bh_page(bh, page, offset);
864
865 init_buffer(bh, NULL, NULL);
866 }
867 return head;
868 /*
869 * In case anything failed, we just free everything we got.
870 */
871 no_grow:
872 if (head) {
873 do {
874 bh = head;
875 head = head->b_this_page;
876 free_buffer_head(bh);
877 } while (head);
878 }
879
880 /*
881 * Return failure for non-async IO requests. Async IO requests
882 * are not allowed to fail, so we have to wait until buffer heads
883 * become available. But we don't want tasks sleeping with
884 * partially complete buffers, so all were released above.
885 */
886 if (!retry)
887 return NULL;
888
889 /* We're _really_ low on memory. Now we just
890 * wait for old buffer heads to become free due to
891 * finishing IO. Since this is an async request and
892 * the reserve list is empty, we're sure there are
893 * async buffer heads in use.
894 */
895 free_more_memory();
896 goto try_again;
897 }
898 EXPORT_SYMBOL_GPL(alloc_page_buffers);
899
900 static inline void
901 link_dev_buffers(struct page *page, struct buffer_head *head)
902 {
903 struct buffer_head *bh, *tail;
904
905 bh = head;
906 do {
907 tail = bh;
908 bh = bh->b_this_page;
909 } while (bh);
910 tail->b_this_page = head;
911 attach_page_buffers(page, head);
912 }
913
914 /*
915 * Initialise the state of a blockdev page's buffers.
916 */
917 static void
918 init_page_buffers(struct page *page, struct block_device *bdev,
919 sector_t block, int size)
920 {
921 struct buffer_head *head = page_buffers(page);
922 struct buffer_head *bh = head;
923 int uptodate = PageUptodate(page);
924
925 do {
926 if (!buffer_mapped(bh)) {
927 init_buffer(bh, NULL, NULL);
928 bh->b_bdev = bdev;
929 bh->b_blocknr = block;
930 if (uptodate)
931 set_buffer_uptodate(bh);
932 set_buffer_mapped(bh);
933 }
934 block++;
935 bh = bh->b_this_page;
936 } while (bh != head);
937 }
938
939 /*
940 * Create the page-cache page that contains the requested block.
941 *
942 * This is user purely for blockdev mappings.
943 */
944 static struct page *
945 grow_dev_page(struct block_device *bdev, sector_t block,
946 pgoff_t index, int size)
947 {
948 struct inode *inode = bdev->bd_inode;
949 struct page *page;
950 struct buffer_head *bh;
951
952 page = find_or_create_page(inode->i_mapping, index,
953 (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE);
954 if (!page)
955 return NULL;
956
957 BUG_ON(!PageLocked(page));
958
959 if (page_has_buffers(page)) {
960 bh = page_buffers(page);
961 if (bh->b_size == size) {
962 init_page_buffers(page, bdev, block, size);
963 return page;
964 }
965 if (!try_to_free_buffers(page))
966 goto failed;
967 }
968
969 /*
970 * Allocate some buffers for this page
971 */
972 bh = alloc_page_buffers(page, size, 0);
973 if (!bh)
974 goto failed;
975
976 /*
977 * Link the page to the buffers and initialise them. Take the
978 * lock to be atomic wrt __find_get_block(), which does not
979 * run under the page lock.
980 */
981 spin_lock(&inode->i_mapping->private_lock);
982 link_dev_buffers(page, bh);
983 init_page_buffers(page, bdev, block, size);
984 spin_unlock(&inode->i_mapping->private_lock);
985 return page;
986
987 failed:
988 BUG();
989 unlock_page(page);
990 page_cache_release(page);
991 return NULL;
992 }
993
994 /*
995 * Create buffers for the specified block device block's page. If
996 * that page was dirty, the buffers are set dirty also.
997 */
998 static int
999 grow_buffers(struct block_device *bdev, sector_t block, int size)
1000 {
1001 struct page *page;
1002 pgoff_t index;
1003 int sizebits;
1004
1005 sizebits = -1;
1006 do {
1007 sizebits++;
1008 } while ((size << sizebits) < PAGE_SIZE);
1009
1010 index = block >> sizebits;
1011
1012 /*
1013 * Check for a block which wants to lie outside our maximum possible
1014 * pagecache index. (this comparison is done using sector_t types).
1015 */
1016 if (unlikely(index != block >> sizebits)) {
1017 char b[BDEVNAME_SIZE];
1018
1019 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1020 "device %s\n",
1021 __func__, (unsigned long long)block,
1022 bdevname(bdev, b));
1023 return -EIO;
1024 }
1025 block = index << sizebits;
1026 /* Create a page with the proper size buffers.. */
1027 page = grow_dev_page(bdev, block, index, size);
1028 if (!page)
1029 return 0;
1030 unlock_page(page);
1031 page_cache_release(page);
1032 return 1;
1033 }
1034
1035 static struct buffer_head *
1036 __getblk_slow(struct block_device *bdev, sector_t block, int size)
1037 {
1038 /* Size must be multiple of hard sectorsize */
1039 if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
1040 (size < 512 || size > PAGE_SIZE))) {
1041 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1042 size);
1043 printk(KERN_ERR "logical block size: %d\n",
1044 bdev_logical_block_size(bdev));
1045
1046 dump_stack();
1047 return NULL;
1048 }
1049
1050 for (;;) {
1051 struct buffer_head * bh;
1052 int ret;
1053
1054 bh = __find_get_block(bdev, block, size);
1055 if (bh)
1056 return bh;
1057
1058 ret = grow_buffers(bdev, block, size);
1059 if (ret < 0)
1060 return NULL;
1061 if (ret == 0)
1062 free_more_memory();
1063 }
1064 }
1065
1066 /*
1067 * The relationship between dirty buffers and dirty pages:
1068 *
1069 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1070 * the page is tagged dirty in its radix tree.
1071 *
1072 * At all times, the dirtiness of the buffers represents the dirtiness of
1073 * subsections of the page. If the page has buffers, the page dirty bit is
1074 * merely a hint about the true dirty state.
1075 *
1076 * When a page is set dirty in its entirety, all its buffers are marked dirty
1077 * (if the page has buffers).
1078 *
1079 * When a buffer is marked dirty, its page is dirtied, but the page's other
1080 * buffers are not.
1081 *
1082 * Also. When blockdev buffers are explicitly read with bread(), they
1083 * individually become uptodate. But their backing page remains not
1084 * uptodate - even if all of its buffers are uptodate. A subsequent
1085 * block_read_full_page() against that page will discover all the uptodate
1086 * buffers, will set the page uptodate and will perform no I/O.
1087 */
1088
1089 /**
1090 * mark_buffer_dirty - mark a buffer_head as needing writeout
1091 * @bh: the buffer_head to mark dirty
1092 *
1093 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1094 * backing page dirty, then tag the page as dirty in its address_space's radix
1095 * tree and then attach the address_space's inode to its superblock's dirty
1096 * inode list.
1097 *
1098 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1099 * mapping->tree_lock and mapping->host->i_lock.
1100 */
1101 void mark_buffer_dirty(struct buffer_head *bh)
1102 {
1103 WARN_ON_ONCE(!buffer_uptodate(bh));
1104
1105 /*
1106 * Very *carefully* optimize the it-is-already-dirty case.
1107 *
1108 * Don't let the final "is it dirty" escape to before we
1109 * perhaps modified the buffer.
1110 */
1111 if (buffer_dirty(bh)) {
1112 smp_mb();
1113 if (buffer_dirty(bh))
1114 return;
1115 }
1116
1117 if (!test_set_buffer_dirty(bh)) {
1118 struct page *page = bh->b_page;
1119 if (!TestSetPageDirty(page)) {
1120 struct address_space *mapping = page_mapping(page);
1121 if (mapping)
1122 __set_page_dirty(page, mapping, 0);
1123 }
1124 }
1125 }
1126 EXPORT_SYMBOL(mark_buffer_dirty);
1127
1128 /*
1129 * Decrement a buffer_head's reference count. If all buffers against a page
1130 * have zero reference count, are clean and unlocked, and if the page is clean
1131 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1132 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1133 * a page but it ends up not being freed, and buffers may later be reattached).
1134 */
1135 void __brelse(struct buffer_head * buf)
1136 {
1137 if (atomic_read(&buf->b_count)) {
1138 put_bh(buf);
1139 return;
1140 }
1141 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1142 }
1143 EXPORT_SYMBOL(__brelse);
1144
1145 /*
1146 * bforget() is like brelse(), except it discards any
1147 * potentially dirty data.
1148 */
1149 void __bforget(struct buffer_head *bh)
1150 {
1151 clear_buffer_dirty(bh);
1152 if (bh->b_assoc_map) {
1153 struct address_space *buffer_mapping = bh->b_page->mapping;
1154
1155 spin_lock(&buffer_mapping->private_lock);
1156 list_del_init(&bh->b_assoc_buffers);
1157 bh->b_assoc_map = NULL;
1158 spin_unlock(&buffer_mapping->private_lock);
1159 }
1160 __brelse(bh);
1161 }
1162 EXPORT_SYMBOL(__bforget);
1163
1164 static struct buffer_head *__bread_slow(struct buffer_head *bh)
1165 {
1166 lock_buffer(bh);
1167 if (buffer_uptodate(bh)) {
1168 unlock_buffer(bh);
1169 return bh;
1170 } else {
1171 get_bh(bh);
1172 bh->b_end_io = end_buffer_read_sync;
1173 submit_bh(READ, bh);
1174 wait_on_buffer(bh);
1175 if (buffer_uptodate(bh))
1176 return bh;
1177 }
1178 brelse(bh);
1179 return NULL;
1180 }
1181
1182 /*
1183 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1184 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1185 * refcount elevated by one when they're in an LRU. A buffer can only appear
1186 * once in a particular CPU's LRU. A single buffer can be present in multiple
1187 * CPU's LRUs at the same time.
1188 *
1189 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1190 * sb_find_get_block().
1191 *
1192 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1193 * a local interrupt disable for that.
1194 */
1195
1196 #define BH_LRU_SIZE 8
1197
1198 struct bh_lru {
1199 struct buffer_head *bhs[BH_LRU_SIZE];
1200 };
1201
1202 static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1203
1204 #ifdef CONFIG_SMP
1205 #define bh_lru_lock() local_irq_disable()
1206 #define bh_lru_unlock() local_irq_enable()
1207 #else
1208 #define bh_lru_lock() preempt_disable()
1209 #define bh_lru_unlock() preempt_enable()
1210 #endif
1211
1212 static inline void check_irqs_on(void)
1213 {
1214 #ifdef irqs_disabled
1215 BUG_ON(irqs_disabled());
1216 #endif
1217 }
1218
1219 /*
1220 * The LRU management algorithm is dopey-but-simple. Sorry.
1221 */
1222 static void bh_lru_install(struct buffer_head *bh)
1223 {
1224 struct buffer_head *evictee = NULL;
1225
1226 check_irqs_on();
1227 bh_lru_lock();
1228 if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
1229 struct buffer_head *bhs[BH_LRU_SIZE];
1230 int in;
1231 int out = 0;
1232
1233 get_bh(bh);
1234 bhs[out++] = bh;
1235 for (in = 0; in < BH_LRU_SIZE; in++) {
1236 struct buffer_head *bh2 =
1237 __this_cpu_read(bh_lrus.bhs[in]);
1238
1239 if (bh2 == bh) {
1240 __brelse(bh2);
1241 } else {
1242 if (out >= BH_LRU_SIZE) {
1243 BUG_ON(evictee != NULL);
1244 evictee = bh2;
1245 } else {
1246 bhs[out++] = bh2;
1247 }
1248 }
1249 }
1250 while (out < BH_LRU_SIZE)
1251 bhs[out++] = NULL;
1252 memcpy(__this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
1253 }
1254 bh_lru_unlock();
1255
1256 if (evictee)
1257 __brelse(evictee);
1258 }
1259
1260 /*
1261 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1262 */
1263 static struct buffer_head *
1264 lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1265 {
1266 struct buffer_head *ret = NULL;
1267 unsigned int i;
1268
1269 check_irqs_on();
1270 bh_lru_lock();
1271 for (i = 0; i < BH_LRU_SIZE; i++) {
1272 struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
1273
1274 if (bh && bh->b_bdev == bdev &&
1275 bh->b_blocknr == block && bh->b_size == size) {
1276 if (i) {
1277 while (i) {
1278 __this_cpu_write(bh_lrus.bhs[i],
1279 __this_cpu_read(bh_lrus.bhs[i - 1]));
1280 i--;
1281 }
1282 __this_cpu_write(bh_lrus.bhs[0], bh);
1283 }
1284 get_bh(bh);
1285 ret = bh;
1286 break;
1287 }
1288 }
1289 bh_lru_unlock();
1290 return ret;
1291 }
1292
1293 /*
1294 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1295 * it in the LRU and mark it as accessed. If it is not present then return
1296 * NULL
1297 */
1298 struct buffer_head *
1299 __find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1300 {
1301 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1302
1303 if (bh == NULL) {
1304 bh = __find_get_block_slow(bdev, block);
1305 if (bh)
1306 bh_lru_install(bh);
1307 }
1308 if (bh)
1309 touch_buffer(bh);
1310 return bh;
1311 }
1312 EXPORT_SYMBOL(__find_get_block);
1313
1314 /*
1315 * __getblk will locate (and, if necessary, create) the buffer_head
1316 * which corresponds to the passed block_device, block and size. The
1317 * returned buffer has its reference count incremented.
1318 *
1319 * __getblk() cannot fail - it just keeps trying. If you pass it an
1320 * illegal block number, __getblk() will happily return a buffer_head
1321 * which represents the non-existent block. Very weird.
1322 *
1323 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1324 * attempt is failing. FIXME, perhaps?
1325 */
1326 struct buffer_head *
1327 __getblk(struct block_device *bdev, sector_t block, unsigned size)
1328 {
1329 struct buffer_head *bh = __find_get_block(bdev, block, size);
1330
1331 might_sleep();
1332 if (bh == NULL)
1333 bh = __getblk_slow(bdev, block, size);
1334 return bh;
1335 }
1336 EXPORT_SYMBOL(__getblk);
1337
1338 /*
1339 * Do async read-ahead on a buffer..
1340 */
1341 void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1342 {
1343 struct buffer_head *bh = __getblk(bdev, block, size);
1344 if (likely(bh)) {
1345 ll_rw_block(READA, 1, &bh);
1346 brelse(bh);
1347 }
1348 }
1349 EXPORT_SYMBOL(__breadahead);
1350
1351 /**
1352 * __bread() - reads a specified block and returns the bh
1353 * @bdev: the block_device to read from
1354 * @block: number of block
1355 * @size: size (in bytes) to read
1356 *
1357 * Reads a specified block, and returns buffer head that contains it.
1358 * It returns NULL if the block was unreadable.
1359 */
1360 struct buffer_head *
1361 __bread(struct block_device *bdev, sector_t block, unsigned size)
1362 {
1363 struct buffer_head *bh = __getblk(bdev, block, size);
1364
1365 if (likely(bh) && !buffer_uptodate(bh))
1366 bh = __bread_slow(bh);
1367 return bh;
1368 }
1369 EXPORT_SYMBOL(__bread);
1370
1371 /*
1372 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1373 * This doesn't race because it runs in each cpu either in irq
1374 * or with preempt disabled.
1375 */
1376 static void invalidate_bh_lru(void *arg)
1377 {
1378 struct bh_lru *b = &get_cpu_var(bh_lrus);
1379 int i;
1380
1381 for (i = 0; i < BH_LRU_SIZE; i++) {
1382 brelse(b->bhs[i]);
1383 b->bhs[i] = NULL;
1384 }
1385 put_cpu_var(bh_lrus);
1386 }
1387
1388 static bool has_bh_in_lru(int cpu, void *dummy)
1389 {
1390 struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1391 int i;
1392
1393 for (i = 0; i < BH_LRU_SIZE; i++) {
1394 if (b->bhs[i])
1395 return 1;
1396 }
1397
1398 return 0;
1399 }
1400
1401 void invalidate_bh_lrus(void)
1402 {
1403 on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL);
1404 }
1405 EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1406
1407 void set_bh_page(struct buffer_head *bh,
1408 struct page *page, unsigned long offset)
1409 {
1410 bh->b_page = page;
1411 BUG_ON(offset >= PAGE_SIZE);
1412 if (PageHighMem(page))
1413 /*
1414 * This catches illegal uses and preserves the offset:
1415 */
1416 bh->b_data = (char *)(0 + offset);
1417 else
1418 bh->b_data = page_address(page) + offset;
1419 }
1420 EXPORT_SYMBOL(set_bh_page);
1421
1422 /*
1423 * Called when truncating a buffer on a page completely.
1424 */
1425 static void discard_buffer(struct buffer_head * bh)
1426 {
1427 lock_buffer(bh);
1428 clear_buffer_dirty(bh);
1429 bh->b_bdev = NULL;
1430 clear_buffer_mapped(bh);
1431 clear_buffer_req(bh);
1432 clear_buffer_new(bh);
1433 clear_buffer_delay(bh);
1434 clear_buffer_unwritten(bh);
1435 unlock_buffer(bh);
1436 }
1437
1438 /**
1439 * block_invalidatepage - invalidate part or all of a buffer-backed page
1440 *
1441 * @page: the page which is affected
1442 * @offset: the index of the truncation point
1443 *
1444 * block_invalidatepage() is called when all or part of the page has become
1445 * invalidated by a truncate operation.
1446 *
1447 * block_invalidatepage() does not have to release all buffers, but it must
1448 * ensure that no dirty buffer is left outside @offset and that no I/O
1449 * is underway against any of the blocks which are outside the truncation
1450 * point. Because the caller is about to free (and possibly reuse) those
1451 * blocks on-disk.
1452 */
1453 void block_invalidatepage(struct page *page, unsigned long offset)
1454 {
1455 struct buffer_head *head, *bh, *next;
1456 unsigned int curr_off = 0;
1457
1458 BUG_ON(!PageLocked(page));
1459 if (!page_has_buffers(page))
1460 goto out;
1461
1462 head = page_buffers(page);
1463 bh = head;
1464 do {
1465 unsigned int next_off = curr_off + bh->b_size;
1466 next = bh->b_this_page;
1467
1468 /*
1469 * is this block fully invalidated?
1470 */
1471 if (offset <= curr_off)
1472 discard_buffer(bh);
1473 curr_off = next_off;
1474 bh = next;
1475 } while (bh != head);
1476
1477 /*
1478 * We release buffers only if the entire page is being invalidated.
1479 * The get_block cached value has been unconditionally invalidated,
1480 * so real IO is not possible anymore.
1481 */
1482 if (offset == 0)
1483 try_to_release_page(page, 0);
1484 out:
1485 return;
1486 }
1487 EXPORT_SYMBOL(block_invalidatepage);
1488
1489 /*
1490 * We attach and possibly dirty the buffers atomically wrt
1491 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1492 * is already excluded via the page lock.
1493 */
1494 void create_empty_buffers(struct page *page,
1495 unsigned long blocksize, unsigned long b_state)
1496 {
1497 struct buffer_head *bh, *head, *tail;
1498
1499 head = alloc_page_buffers(page, blocksize, 1);
1500 bh = head;
1501 do {
1502 bh->b_state |= b_state;
1503 tail = bh;
1504 bh = bh->b_this_page;
1505 } while (bh);
1506 tail->b_this_page = head;
1507
1508 spin_lock(&page->mapping->private_lock);
1509 if (PageUptodate(page) || PageDirty(page)) {
1510 bh = head;
1511 do {
1512 if (PageDirty(page))
1513 set_buffer_dirty(bh);
1514 if (PageUptodate(page))
1515 set_buffer_uptodate(bh);
1516 bh = bh->b_this_page;
1517 } while (bh != head);
1518 }
1519 attach_page_buffers(page, head);
1520 spin_unlock(&page->mapping->private_lock);
1521 }
1522 EXPORT_SYMBOL(create_empty_buffers);
1523
1524 /*
1525 * We are taking a block for data and we don't want any output from any
1526 * buffer-cache aliases starting from return from that function and
1527 * until the moment when something will explicitly mark the buffer
1528 * dirty (hopefully that will not happen until we will free that block ;-)
1529 * We don't even need to mark it not-uptodate - nobody can expect
1530 * anything from a newly allocated buffer anyway. We used to used
1531 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1532 * don't want to mark the alias unmapped, for example - it would confuse
1533 * anyone who might pick it with bread() afterwards...
1534 *
1535 * Also.. Note that bforget() doesn't lock the buffer. So there can
1536 * be writeout I/O going on against recently-freed buffers. We don't
1537 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1538 * only if we really need to. That happens here.
1539 */
1540 void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1541 {
1542 struct buffer_head *old_bh;
1543
1544 might_sleep();
1545
1546 old_bh = __find_get_block_slow(bdev, block);
1547 if (old_bh) {
1548 clear_buffer_dirty(old_bh);
1549 wait_on_buffer(old_bh);
1550 clear_buffer_req(old_bh);
1551 __brelse(old_bh);
1552 }
1553 }
1554 EXPORT_SYMBOL(unmap_underlying_metadata);
1555
1556 /*
1557 * NOTE! All mapped/uptodate combinations are valid:
1558 *
1559 * Mapped Uptodate Meaning
1560 *
1561 * No No "unknown" - must do get_block()
1562 * No Yes "hole" - zero-filled
1563 * Yes No "allocated" - allocated on disk, not read in
1564 * Yes Yes "valid" - allocated and up-to-date in memory.
1565 *
1566 * "Dirty" is valid only with the last case (mapped+uptodate).
1567 */
1568
1569 /*
1570 * While block_write_full_page is writing back the dirty buffers under
1571 * the page lock, whoever dirtied the buffers may decide to clean them
1572 * again at any time. We handle that by only looking at the buffer
1573 * state inside lock_buffer().
1574 *
1575 * If block_write_full_page() is called for regular writeback
1576 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1577 * locked buffer. This only can happen if someone has written the buffer
1578 * directly, with submit_bh(). At the address_space level PageWriteback
1579 * prevents this contention from occurring.
1580 *
1581 * If block_write_full_page() is called with wbc->sync_mode ==
1582 * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this
1583 * causes the writes to be flagged as synchronous writes.
1584 */
1585 static int __block_write_full_page(struct inode *inode, struct page *page,
1586 get_block_t *get_block, struct writeback_control *wbc,
1587 bh_end_io_t *handler)
1588 {
1589 int err;
1590 sector_t block;
1591 sector_t last_block;
1592 struct buffer_head *bh, *head;
1593 const unsigned blocksize = 1 << inode->i_blkbits;
1594 int nr_underway = 0;
1595 int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
1596 WRITE_SYNC : WRITE);
1597
1598 BUG_ON(!PageLocked(page));
1599
1600 last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
1601
1602 if (!page_has_buffers(page)) {
1603 create_empty_buffers(page, blocksize,
1604 (1 << BH_Dirty)|(1 << BH_Uptodate));
1605 }
1606
1607 /*
1608 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1609 * here, and the (potentially unmapped) buffers may become dirty at
1610 * any time. If a buffer becomes dirty here after we've inspected it
1611 * then we just miss that fact, and the page stays dirty.
1612 *
1613 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1614 * handle that here by just cleaning them.
1615 */
1616
1617 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
1618 head = page_buffers(page);
1619 bh = head;
1620
1621 /*
1622 * Get all the dirty buffers mapped to disk addresses and
1623 * handle any aliases from the underlying blockdev's mapping.
1624 */
1625 do {
1626 if (block > last_block) {
1627 /*
1628 * mapped buffers outside i_size will occur, because
1629 * this page can be outside i_size when there is a
1630 * truncate in progress.
1631 */
1632 /*
1633 * The buffer was zeroed by block_write_full_page()
1634 */
1635 clear_buffer_dirty(bh);
1636 set_buffer_uptodate(bh);
1637 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1638 buffer_dirty(bh)) {
1639 WARN_ON(bh->b_size != blocksize);
1640 err = get_block(inode, block, bh, 1);
1641 if (err)
1642 goto recover;
1643 clear_buffer_delay(bh);
1644 if (buffer_new(bh)) {
1645 /* blockdev mappings never come here */
1646 clear_buffer_new(bh);
1647 unmap_underlying_metadata(bh->b_bdev,
1648 bh->b_blocknr);
1649 }
1650 }
1651 bh = bh->b_this_page;
1652 block++;
1653 } while (bh != head);
1654
1655 do {
1656 if (!buffer_mapped(bh))
1657 continue;
1658 /*
1659 * If it's a fully non-blocking write attempt and we cannot
1660 * lock the buffer then redirty the page. Note that this can
1661 * potentially cause a busy-wait loop from writeback threads
1662 * and kswapd activity, but those code paths have their own
1663 * higher-level throttling.
1664 */
1665 if (wbc->sync_mode != WB_SYNC_NONE) {
1666 lock_buffer(bh);
1667 } else if (!trylock_buffer(bh)) {
1668 redirty_page_for_writepage(wbc, page);
1669 continue;
1670 }
1671 if (test_clear_buffer_dirty(bh)) {
1672 mark_buffer_async_write_endio(bh, handler);
1673 } else {
1674 unlock_buffer(bh);
1675 }
1676 } while ((bh = bh->b_this_page) != head);
1677
1678 /*
1679 * The page and its buffers are protected by PageWriteback(), so we can
1680 * drop the bh refcounts early.
1681 */
1682 BUG_ON(PageWriteback(page));
1683 set_page_writeback(page);
1684
1685 do {
1686 struct buffer_head *next = bh->b_this_page;
1687 if (buffer_async_write(bh)) {
1688 submit_bh(write_op, bh);
1689 nr_underway++;
1690 }
1691 bh = next;
1692 } while (bh != head);
1693 unlock_page(page);
1694
1695 err = 0;
1696 done:
1697 if (nr_underway == 0) {
1698 /*
1699 * The page was marked dirty, but the buffers were
1700 * clean. Someone wrote them back by hand with
1701 * ll_rw_block/submit_bh. A rare case.
1702 */
1703 end_page_writeback(page);
1704
1705 /*
1706 * The page and buffer_heads can be released at any time from
1707 * here on.
1708 */
1709 }
1710 return err;
1711
1712 recover:
1713 /*
1714 * ENOSPC, or some other error. We may already have added some
1715 * blocks to the file, so we need to write these out to avoid
1716 * exposing stale data.
1717 * The page is currently locked and not marked for writeback
1718 */
1719 bh = head;
1720 /* Recovery: lock and submit the mapped buffers */
1721 do {
1722 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1723 !buffer_delay(bh)) {
1724 lock_buffer(bh);
1725 mark_buffer_async_write_endio(bh, handler);
1726 } else {
1727 /*
1728 * The buffer may have been set dirty during
1729 * attachment to a dirty page.
1730 */
1731 clear_buffer_dirty(bh);
1732 }
1733 } while ((bh = bh->b_this_page) != head);
1734 SetPageError(page);
1735 BUG_ON(PageWriteback(page));
1736 mapping_set_error(page->mapping, err);
1737 set_page_writeback(page);
1738 do {
1739 struct buffer_head *next = bh->b_this_page;
1740 if (buffer_async_write(bh)) {
1741 clear_buffer_dirty(bh);
1742 submit_bh(write_op, bh);
1743 nr_underway++;
1744 }
1745 bh = next;
1746 } while (bh != head);
1747 unlock_page(page);
1748 goto done;
1749 }
1750
1751 /*
1752 * If a page has any new buffers, zero them out here, and mark them uptodate
1753 * and dirty so they'll be written out (in order to prevent uninitialised
1754 * block data from leaking). And clear the new bit.
1755 */
1756 void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1757 {
1758 unsigned int block_start, block_end;
1759 struct buffer_head *head, *bh;
1760
1761 BUG_ON(!PageLocked(page));
1762 if (!page_has_buffers(page))
1763 return;
1764
1765 bh = head = page_buffers(page);
1766 block_start = 0;
1767 do {
1768 block_end = block_start + bh->b_size;
1769
1770 if (buffer_new(bh)) {
1771 if (block_end > from && block_start < to) {
1772 if (!PageUptodate(page)) {
1773 unsigned start, size;
1774
1775 start = max(from, block_start);
1776 size = min(to, block_end) - start;
1777
1778 zero_user(page, start, size);
1779 set_buffer_uptodate(bh);
1780 }
1781
1782 clear_buffer_new(bh);
1783 mark_buffer_dirty(bh);
1784 }
1785 }
1786
1787 block_start = block_end;
1788 bh = bh->b_this_page;
1789 } while (bh != head);
1790 }
1791 EXPORT_SYMBOL(page_zero_new_buffers);
1792
1793 int __block_write_begin(struct page *page, loff_t pos, unsigned len,
1794 get_block_t *get_block)
1795 {
1796 unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1797 unsigned to = from + len;
1798 struct inode *inode = page->mapping->host;
1799 unsigned block_start, block_end;
1800 sector_t block;
1801 int err = 0;
1802 unsigned blocksize, bbits;
1803 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1804
1805 BUG_ON(!PageLocked(page));
1806 BUG_ON(from > PAGE_CACHE_SIZE);
1807 BUG_ON(to > PAGE_CACHE_SIZE);
1808 BUG_ON(from > to);
1809
1810 blocksize = 1 << inode->i_blkbits;
1811 if (!page_has_buffers(page))
1812 create_empty_buffers(page, blocksize, 0);
1813 head = page_buffers(page);
1814
1815 bbits = inode->i_blkbits;
1816 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1817
1818 for(bh = head, block_start = 0; bh != head || !block_start;
1819 block++, block_start=block_end, bh = bh->b_this_page) {
1820 block_end = block_start + blocksize;
1821 if (block_end <= from || block_start >= to) {
1822 if (PageUptodate(page)) {
1823 if (!buffer_uptodate(bh))
1824 set_buffer_uptodate(bh);
1825 }
1826 continue;
1827 }
1828 if (buffer_new(bh))
1829 clear_buffer_new(bh);
1830 if (!buffer_mapped(bh)) {
1831 WARN_ON(bh->b_size != blocksize);
1832 err = get_block(inode, block, bh, 1);
1833 if (err)
1834 break;
1835 if (buffer_new(bh)) {
1836 unmap_underlying_metadata(bh->b_bdev,
1837 bh->b_blocknr);
1838 if (PageUptodate(page)) {
1839 clear_buffer_new(bh);
1840 set_buffer_uptodate(bh);
1841 mark_buffer_dirty(bh);
1842 continue;
1843 }
1844 if (block_end > to || block_start < from)
1845 zero_user_segments(page,
1846 to, block_end,
1847 block_start, from);
1848 continue;
1849 }
1850 }
1851 if (PageUptodate(page)) {
1852 if (!buffer_uptodate(bh))
1853 set_buffer_uptodate(bh);
1854 continue;
1855 }
1856 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1857 !buffer_unwritten(bh) &&
1858 (block_start < from || block_end > to)) {
1859 ll_rw_block(READ, 1, &bh);
1860 *wait_bh++=bh;
1861 }
1862 }
1863 /*
1864 * If we issued read requests - let them complete.
1865 */
1866 while(wait_bh > wait) {
1867 wait_on_buffer(*--wait_bh);
1868 if (!buffer_uptodate(*wait_bh))
1869 err = -EIO;
1870 }
1871 if (unlikely(err))
1872 page_zero_new_buffers(page, from, to);
1873 return err;
1874 }
1875 EXPORT_SYMBOL(__block_write_begin);
1876
1877 static int __block_commit_write(struct inode *inode, struct page *page,
1878 unsigned from, unsigned to)
1879 {
1880 unsigned block_start, block_end;
1881 int partial = 0;
1882 unsigned blocksize;
1883 struct buffer_head *bh, *head;
1884
1885 blocksize = 1 << inode->i_blkbits;
1886
1887 for(bh = head = page_buffers(page), block_start = 0;
1888 bh != head || !block_start;
1889 block_start=block_end, bh = bh->b_this_page) {
1890 block_end = block_start + blocksize;
1891 if (block_end <= from || block_start >= to) {
1892 if (!buffer_uptodate(bh))
1893 partial = 1;
1894 } else {
1895 set_buffer_uptodate(bh);
1896 mark_buffer_dirty(bh);
1897 }
1898 clear_buffer_new(bh);
1899 }
1900
1901 /*
1902 * If this is a partial write which happened to make all buffers
1903 * uptodate then we can optimize away a bogus readpage() for
1904 * the next read(). Here we 'discover' whether the page went
1905 * uptodate as a result of this (potentially partial) write.
1906 */
1907 if (!partial)
1908 SetPageUptodate(page);
1909 return 0;
1910 }
1911
1912 /*
1913 * block_write_begin takes care of the basic task of block allocation and
1914 * bringing partial write blocks uptodate first.
1915 *
1916 * The filesystem needs to handle block truncation upon failure.
1917 */
1918 int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
1919 unsigned flags, struct page **pagep, get_block_t *get_block)
1920 {
1921 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
1922 struct page *page;
1923 int status;
1924
1925 page = grab_cache_page_write_begin(mapping, index, flags);
1926 if (!page)
1927 return -ENOMEM;
1928
1929 status = __block_write_begin(page, pos, len, get_block);
1930 if (unlikely(status)) {
1931 unlock_page(page);
1932 page_cache_release(page);
1933 page = NULL;
1934 }
1935
1936 *pagep = page;
1937 return status;
1938 }
1939 EXPORT_SYMBOL(block_write_begin);
1940
1941 int block_write_end(struct file *file, struct address_space *mapping,
1942 loff_t pos, unsigned len, unsigned copied,
1943 struct page *page, void *fsdata)
1944 {
1945 struct inode *inode = mapping->host;
1946 unsigned start;
1947
1948 start = pos & (PAGE_CACHE_SIZE - 1);
1949
1950 if (unlikely(copied < len)) {
1951 /*
1952 * The buffers that were written will now be uptodate, so we
1953 * don't have to worry about a readpage reading them and
1954 * overwriting a partial write. However if we have encountered
1955 * a short write and only partially written into a buffer, it
1956 * will not be marked uptodate, so a readpage might come in and
1957 * destroy our partial write.
1958 *
1959 * Do the simplest thing, and just treat any short write to a
1960 * non uptodate page as a zero-length write, and force the
1961 * caller to redo the whole thing.
1962 */
1963 if (!PageUptodate(page))
1964 copied = 0;
1965
1966 page_zero_new_buffers(page, start+copied, start+len);
1967 }
1968 flush_dcache_page(page);
1969
1970 /* This could be a short (even 0-length) commit */
1971 __block_commit_write(inode, page, start, start+copied);
1972
1973 return copied;
1974 }
1975 EXPORT_SYMBOL(block_write_end);
1976
1977 int generic_write_end(struct file *file, struct address_space *mapping,
1978 loff_t pos, unsigned len, unsigned copied,
1979 struct page *page, void *fsdata)
1980 {
1981 struct inode *inode = mapping->host;
1982 int i_size_changed = 0;
1983
1984 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
1985
1986 /*
1987 * No need to use i_size_read() here, the i_size
1988 * cannot change under us because we hold i_mutex.
1989 *
1990 * But it's important to update i_size while still holding page lock:
1991 * page writeout could otherwise come in and zero beyond i_size.
1992 */
1993 if (pos+copied > inode->i_size) {
1994 i_size_write(inode, pos+copied);
1995 i_size_changed = 1;
1996 }
1997
1998 unlock_page(page);
1999 page_cache_release(page);
2000
2001 /*
2002 * Don't mark the inode dirty under page lock. First, it unnecessarily
2003 * makes the holding time of page lock longer. Second, it forces lock
2004 * ordering of page lock and transaction start for journaling
2005 * filesystems.
2006 */
2007 if (i_size_changed)
2008 mark_inode_dirty(inode);
2009
2010 return copied;
2011 }
2012 EXPORT_SYMBOL(generic_write_end);
2013
2014 /*
2015 * block_is_partially_uptodate checks whether buffers within a page are
2016 * uptodate or not.
2017 *
2018 * Returns true if all buffers which correspond to a file portion
2019 * we want to read are uptodate.
2020 */
2021 int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
2022 unsigned long from)
2023 {
2024 struct inode *inode = page->mapping->host;
2025 unsigned block_start, block_end, blocksize;
2026 unsigned to;
2027 struct buffer_head *bh, *head;
2028 int ret = 1;
2029
2030 if (!page_has_buffers(page))
2031 return 0;
2032
2033 blocksize = 1 << inode->i_blkbits;
2034 to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count);
2035 to = from + to;
2036 if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
2037 return 0;
2038
2039 head = page_buffers(page);
2040 bh = head;
2041 block_start = 0;
2042 do {
2043 block_end = block_start + blocksize;
2044 if (block_end > from && block_start < to) {
2045 if (!buffer_uptodate(bh)) {
2046 ret = 0;
2047 break;
2048 }
2049 if (block_end >= to)
2050 break;
2051 }
2052 block_start = block_end;
2053 bh = bh->b_this_page;
2054 } while (bh != head);
2055
2056 return ret;
2057 }
2058 EXPORT_SYMBOL(block_is_partially_uptodate);
2059
2060 /*
2061 * Generic "read page" function for block devices that have the normal
2062 * get_block functionality. This is most of the block device filesystems.
2063 * Reads the page asynchronously --- the unlock_buffer() and
2064 * set/clear_buffer_uptodate() functions propagate buffer state into the
2065 * page struct once IO has completed.
2066 */
2067 int block_read_full_page(struct page *page, get_block_t *get_block)
2068 {
2069 struct inode *inode = page->mapping->host;
2070 sector_t iblock, lblock;
2071 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2072 unsigned int blocksize;
2073 int nr, i;
2074 int fully_mapped = 1;
2075
2076 BUG_ON(!PageLocked(page));
2077 blocksize = 1 << inode->i_blkbits;
2078 if (!page_has_buffers(page))
2079 create_empty_buffers(page, blocksize, 0);
2080 head = page_buffers(page);
2081
2082 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2083 lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
2084 bh = head;
2085 nr = 0;
2086 i = 0;
2087
2088 do {
2089 if (buffer_uptodate(bh))
2090 continue;
2091
2092 if (!buffer_mapped(bh)) {
2093 int err = 0;
2094
2095 fully_mapped = 0;
2096 if (iblock < lblock) {
2097 WARN_ON(bh->b_size != blocksize);
2098 err = get_block(inode, iblock, bh, 0);
2099 if (err)
2100 SetPageError(page);
2101 }
2102 if (!buffer_mapped(bh)) {
2103 zero_user(page, i * blocksize, blocksize);
2104 if (!err)
2105 set_buffer_uptodate(bh);
2106 continue;
2107 }
2108 /*
2109 * get_block() might have updated the buffer
2110 * synchronously
2111 */
2112 if (buffer_uptodate(bh))
2113 continue;
2114 }
2115 arr[nr++] = bh;
2116 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2117
2118 if (fully_mapped)
2119 SetPageMappedToDisk(page);
2120
2121 if (!nr) {
2122 /*
2123 * All buffers are uptodate - we can set the page uptodate
2124 * as well. But not if get_block() returned an error.
2125 */
2126 if (!PageError(page))
2127 SetPageUptodate(page);
2128 unlock_page(page);
2129 return 0;
2130 }
2131
2132 /* Stage two: lock the buffers */
2133 for (i = 0; i < nr; i++) {
2134 bh = arr[i];
2135 lock_buffer(bh);
2136 mark_buffer_async_read(bh);
2137 }
2138
2139 /*
2140 * Stage 3: start the IO. Check for uptodateness
2141 * inside the buffer lock in case another process reading
2142 * the underlying blockdev brought it uptodate (the sct fix).
2143 */
2144 for (i = 0; i < nr; i++) {
2145 bh = arr[i];
2146 if (buffer_uptodate(bh))
2147 end_buffer_async_read(bh, 1);
2148 else
2149 submit_bh(READ, bh);
2150 }
2151 return 0;
2152 }
2153 EXPORT_SYMBOL(block_read_full_page);
2154
2155 /* utility function for filesystems that need to do work on expanding
2156 * truncates. Uses filesystem pagecache writes to allow the filesystem to
2157 * deal with the hole.
2158 */
2159 int generic_cont_expand_simple(struct inode *inode, loff_t size)
2160 {
2161 struct address_space *mapping = inode->i_mapping;
2162 struct page *page;
2163 void *fsdata;
2164 int err;
2165
2166 err = inode_newsize_ok(inode, size);
2167 if (err)
2168 goto out;
2169
2170 err = pagecache_write_begin(NULL, mapping, size, 0,
2171 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2172 &page, &fsdata);
2173 if (err)
2174 goto out;
2175
2176 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2177 BUG_ON(err > 0);
2178
2179 out:
2180 return err;
2181 }
2182 EXPORT_SYMBOL(generic_cont_expand_simple);
2183
2184 static int cont_expand_zero(struct file *file, struct address_space *mapping,
2185 loff_t pos, loff_t *bytes)
2186 {
2187 struct inode *inode = mapping->host;
2188 unsigned blocksize = 1 << inode->i_blkbits;
2189 struct page *page;
2190 void *fsdata;
2191 pgoff_t index, curidx;
2192 loff_t curpos;
2193 unsigned zerofrom, offset, len;
2194 int err = 0;
2195
2196 index = pos >> PAGE_CACHE_SHIFT;
2197 offset = pos & ~PAGE_CACHE_MASK;
2198
2199 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
2200 zerofrom = curpos & ~PAGE_CACHE_MASK;
2201 if (zerofrom & (blocksize-1)) {
2202 *bytes |= (blocksize-1);
2203 (*bytes)++;
2204 }
2205 len = PAGE_CACHE_SIZE - zerofrom;
2206
2207 err = pagecache_write_begin(file, mapping, curpos, len,
2208 AOP_FLAG_UNINTERRUPTIBLE,
2209 &page, &fsdata);
2210 if (err)
2211 goto out;
2212 zero_user(page, zerofrom, len);
2213 err = pagecache_write_end(file, mapping, curpos, len, len,
2214 page, fsdata);
2215 if (err < 0)
2216 goto out;
2217 BUG_ON(err != len);
2218 err = 0;
2219
2220 balance_dirty_pages_ratelimited(mapping);
2221 }
2222
2223 /* page covers the boundary, find the boundary offset */
2224 if (index == curidx) {
2225 zerofrom = curpos & ~PAGE_CACHE_MASK;
2226 /* if we will expand the thing last block will be filled */
2227 if (offset <= zerofrom) {
2228 goto out;
2229 }
2230 if (zerofrom & (blocksize-1)) {
2231 *bytes |= (blocksize-1);
2232 (*bytes)++;
2233 }
2234 len = offset - zerofrom;
2235
2236 err = pagecache_write_begin(file, mapping, curpos, len,
2237 AOP_FLAG_UNINTERRUPTIBLE,
2238 &page, &fsdata);
2239 if (err)
2240 goto out;
2241 zero_user(page, zerofrom, len);
2242 err = pagecache_write_end(file, mapping, curpos, len, len,
2243 page, fsdata);
2244 if (err < 0)
2245 goto out;
2246 BUG_ON(err != len);
2247 err = 0;
2248 }
2249 out:
2250 return err;
2251 }
2252
2253 /*
2254 * For moronic filesystems that do not allow holes in file.
2255 * We may have to extend the file.
2256 */
2257 int cont_write_begin(struct file *file, struct address_space *mapping,
2258 loff_t pos, unsigned len, unsigned flags,
2259 struct page **pagep, void **fsdata,
2260 get_block_t *get_block, loff_t *bytes)
2261 {
2262 struct inode *inode = mapping->host;
2263 unsigned blocksize = 1 << inode->i_blkbits;
2264 unsigned zerofrom;
2265 int err;
2266
2267 err = cont_expand_zero(file, mapping, pos, bytes);
2268 if (err)
2269 return err;
2270
2271 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2272 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2273 *bytes |= (blocksize-1);
2274 (*bytes)++;
2275 }
2276
2277 return block_write_begin(mapping, pos, len, flags, pagep, get_block);
2278 }
2279 EXPORT_SYMBOL(cont_write_begin);
2280
2281 int block_commit_write(struct page *page, unsigned from, unsigned to)
2282 {
2283 struct inode *inode = page->mapping->host;
2284 __block_commit_write(inode,page,from,to);
2285 return 0;
2286 }
2287 EXPORT_SYMBOL(block_commit_write);
2288
2289 /*
2290 * block_page_mkwrite() is not allowed to change the file size as it gets
2291 * called from a page fault handler when a page is first dirtied. Hence we must
2292 * be careful to check for EOF conditions here. We set the page up correctly
2293 * for a written page which means we get ENOSPC checking when writing into
2294 * holes and correct delalloc and unwritten extent mapping on filesystems that
2295 * support these features.
2296 *
2297 * We are not allowed to take the i_mutex here so we have to play games to
2298 * protect against truncate races as the page could now be beyond EOF. Because
2299 * truncate writes the inode size before removing pages, once we have the
2300 * page lock we can determine safely if the page is beyond EOF. If it is not
2301 * beyond EOF, then the page is guaranteed safe against truncation until we
2302 * unlock the page.
2303 *
2304 * Direct callers of this function should call vfs_check_frozen() so that page
2305 * fault does not busyloop until the fs is thawed.
2306 */
2307 int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2308 get_block_t get_block)
2309 {
2310 struct page *page = vmf->page;
2311 struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
2312 unsigned long end;
2313 loff_t size;
2314 int ret;
2315
2316 lock_page(page);
2317 size = i_size_read(inode);
2318 if ((page->mapping != inode->i_mapping) ||
2319 (page_offset(page) > size)) {
2320 /* We overload EFAULT to mean page got truncated */
2321 ret = -EFAULT;
2322 goto out_unlock;
2323 }
2324
2325 /* page is wholly or partially inside EOF */
2326 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
2327 end = size & ~PAGE_CACHE_MASK;
2328 else
2329 end = PAGE_CACHE_SIZE;
2330
2331 ret = __block_write_begin(page, 0, end, get_block);
2332 if (!ret)
2333 ret = block_commit_write(page, 0, end);
2334
2335 if (unlikely(ret < 0))
2336 goto out_unlock;
2337 /*
2338 * Freezing in progress? We check after the page is marked dirty and
2339 * with page lock held so if the test here fails, we are sure freezing
2340 * code will wait during syncing until the page fault is done - at that
2341 * point page will be dirty and unlocked so freezing code will write it
2342 * and writeprotect it again.
2343 */
2344 set_page_dirty(page);
2345 if (inode->i_sb->s_frozen != SB_UNFROZEN) {
2346 ret = -EAGAIN;
2347 goto out_unlock;
2348 }
2349 wait_on_page_writeback(page);
2350 return 0;
2351 out_unlock:
2352 unlock_page(page);
2353 return ret;
2354 }
2355 EXPORT_SYMBOL(__block_page_mkwrite);
2356
2357 int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2358 get_block_t get_block)
2359 {
2360 int ret;
2361 struct super_block *sb = vma->vm_file->f_path.dentry->d_inode->i_sb;
2362
2363 /*
2364 * This check is racy but catches the common case. The check in
2365 * __block_page_mkwrite() is reliable.
2366 */
2367 vfs_check_frozen(sb, SB_FREEZE_WRITE);
2368 ret = __block_page_mkwrite(vma, vmf, get_block);
2369 return block_page_mkwrite_return(ret);
2370 }
2371 EXPORT_SYMBOL(block_page_mkwrite);
2372
2373 /*
2374 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
2375 * immediately, while under the page lock. So it needs a special end_io
2376 * handler which does not touch the bh after unlocking it.
2377 */
2378 static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2379 {
2380 __end_buffer_read_notouch(bh, uptodate);
2381 }
2382
2383 /*
2384 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2385 * the page (converting it to circular linked list and taking care of page
2386 * dirty races).
2387 */
2388 static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2389 {
2390 struct buffer_head *bh;
2391
2392 BUG_ON(!PageLocked(page));
2393
2394 spin_lock(&page->mapping->private_lock);
2395 bh = head;
2396 do {
2397 if (PageDirty(page))
2398 set_buffer_dirty(bh);
2399 if (!bh->b_this_page)
2400 bh->b_this_page = head;
2401 bh = bh->b_this_page;
2402 } while (bh != head);
2403 attach_page_buffers(page, head);
2404 spin_unlock(&page->mapping->private_lock);
2405 }
2406
2407 /*
2408 * On entry, the page is fully not uptodate.
2409 * On exit the page is fully uptodate in the areas outside (from,to)
2410 * The filesystem needs to handle block truncation upon failure.
2411 */
2412 int nobh_write_begin(struct address_space *mapping,
2413 loff_t pos, unsigned len, unsigned flags,
2414 struct page **pagep, void **fsdata,
2415 get_block_t *get_block)
2416 {
2417 struct inode *inode = mapping->host;
2418 const unsigned blkbits = inode->i_blkbits;
2419 const unsigned blocksize = 1 << blkbits;
2420 struct buffer_head *head, *bh;
2421 struct page *page;
2422 pgoff_t index;
2423 unsigned from, to;
2424 unsigned block_in_page;
2425 unsigned block_start, block_end;
2426 sector_t block_in_file;
2427 int nr_reads = 0;
2428 int ret = 0;
2429 int is_mapped_to_disk = 1;
2430
2431 index = pos >> PAGE_CACHE_SHIFT;
2432 from = pos & (PAGE_CACHE_SIZE - 1);
2433 to = from + len;
2434
2435 page = grab_cache_page_write_begin(mapping, index, flags);
2436 if (!page)
2437 return -ENOMEM;
2438 *pagep = page;
2439 *fsdata = NULL;
2440
2441 if (page_has_buffers(page)) {
2442 ret = __block_write_begin(page, pos, len, get_block);
2443 if (unlikely(ret))
2444 goto out_release;
2445 return ret;
2446 }
2447
2448 if (PageMappedToDisk(page))
2449 return 0;
2450
2451 /*
2452 * Allocate buffers so that we can keep track of state, and potentially
2453 * attach them to the page if an error occurs. In the common case of
2454 * no error, they will just be freed again without ever being attached
2455 * to the page (which is all OK, because we're under the page lock).
2456 *
2457 * Be careful: the buffer linked list is a NULL terminated one, rather
2458 * than the circular one we're used to.
2459 */
2460 head = alloc_page_buffers(page, blocksize, 0);
2461 if (!head) {
2462 ret = -ENOMEM;
2463 goto out_release;
2464 }
2465
2466 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
2467
2468 /*
2469 * We loop across all blocks in the page, whether or not they are
2470 * part of the affected region. This is so we can discover if the
2471 * page is fully mapped-to-disk.
2472 */
2473 for (block_start = 0, block_in_page = 0, bh = head;
2474 block_start < PAGE_CACHE_SIZE;
2475 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
2476 int create;
2477
2478 block_end = block_start + blocksize;
2479 bh->b_state = 0;
2480 create = 1;
2481 if (block_start >= to)
2482 create = 0;
2483 ret = get_block(inode, block_in_file + block_in_page,
2484 bh, create);
2485 if (ret)
2486 goto failed;
2487 if (!buffer_mapped(bh))
2488 is_mapped_to_disk = 0;
2489 if (buffer_new(bh))
2490 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
2491 if (PageUptodate(page)) {
2492 set_buffer_uptodate(bh);
2493 continue;
2494 }
2495 if (buffer_new(bh) || !buffer_mapped(bh)) {
2496 zero_user_segments(page, block_start, from,
2497 to, block_end);
2498 continue;
2499 }
2500 if (buffer_uptodate(bh))
2501 continue; /* reiserfs does this */
2502 if (block_start < from || block_end > to) {
2503 lock_buffer(bh);
2504 bh->b_end_io = end_buffer_read_nobh;
2505 submit_bh(READ, bh);
2506 nr_reads++;
2507 }
2508 }
2509
2510 if (nr_reads) {
2511 /*
2512 * The page is locked, so these buffers are protected from
2513 * any VM or truncate activity. Hence we don't need to care
2514 * for the buffer_head refcounts.
2515 */
2516 for (bh = head; bh; bh = bh->b_this_page) {
2517 wait_on_buffer(bh);
2518 if (!buffer_uptodate(bh))
2519 ret = -EIO;
2520 }
2521 if (ret)
2522 goto failed;
2523 }
2524
2525 if (is_mapped_to_disk)
2526 SetPageMappedToDisk(page);
2527
2528 *fsdata = head; /* to be released by nobh_write_end */
2529
2530 return 0;
2531
2532 failed:
2533 BUG_ON(!ret);
2534 /*
2535 * Error recovery is a bit difficult. We need to zero out blocks that
2536 * were newly allocated, and dirty them to ensure they get written out.
2537 * Buffers need to be attached to the page at this point, otherwise
2538 * the handling of potential IO errors during writeout would be hard
2539 * (could try doing synchronous writeout, but what if that fails too?)
2540 */
2541 attach_nobh_buffers(page, head);
2542 page_zero_new_buffers(page, from, to);
2543
2544 out_release:
2545 unlock_page(page);
2546 page_cache_release(page);
2547 *pagep = NULL;
2548
2549 return ret;
2550 }
2551 EXPORT_SYMBOL(nobh_write_begin);
2552
2553 int nobh_write_end(struct file *file, struct address_space *mapping,
2554 loff_t pos, unsigned len, unsigned copied,
2555 struct page *page, void *fsdata)
2556 {
2557 struct inode *inode = page->mapping->host;
2558 struct buffer_head *head = fsdata;
2559 struct buffer_head *bh;
2560 BUG_ON(fsdata != NULL && page_has_buffers(page));
2561
2562 if (unlikely(copied < len) && head)
2563 attach_nobh_buffers(page, head);
2564 if (page_has_buffers(page))
2565 return generic_write_end(file, mapping, pos, len,
2566 copied, page, fsdata);
2567
2568 SetPageUptodate(page);
2569 set_page_dirty(page);
2570 if (pos+copied > inode->i_size) {
2571 i_size_write(inode, pos+copied);
2572 mark_inode_dirty(inode);
2573 }
2574
2575 unlock_page(page);
2576 page_cache_release(page);
2577
2578 while (head) {
2579 bh = head;
2580 head = head->b_this_page;
2581 free_buffer_head(bh);
2582 }
2583
2584 return copied;
2585 }
2586 EXPORT_SYMBOL(nobh_write_end);
2587
2588 /*
2589 * nobh_writepage() - based on block_full_write_page() except
2590 * that it tries to operate without attaching bufferheads to
2591 * the page.
2592 */
2593 int nobh_writepage(struct page *page, get_block_t *get_block,
2594 struct writeback_control *wbc)
2595 {
2596 struct inode * const inode = page->mapping->host;
2597 loff_t i_size = i_size_read(inode);
2598 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2599 unsigned offset;
2600 int ret;
2601
2602 /* Is the page fully inside i_size? */
2603 if (page->index < end_index)
2604 goto out;
2605
2606 /* Is the page fully outside i_size? (truncate in progress) */
2607 offset = i_size & (PAGE_CACHE_SIZE-1);
2608 if (page->index >= end_index+1 || !offset) {
2609 /*
2610 * The page may have dirty, unmapped buffers. For example,
2611 * they may have been added in ext3_writepage(). Make them
2612 * freeable here, so the page does not leak.
2613 */
2614 #if 0
2615 /* Not really sure about this - do we need this ? */
2616 if (page->mapping->a_ops->invalidatepage)
2617 page->mapping->a_ops->invalidatepage(page, offset);
2618 #endif
2619 unlock_page(page);
2620 return 0; /* don't care */
2621 }
2622
2623 /*
2624 * The page straddles i_size. It must be zeroed out on each and every
2625 * writepage invocation because it may be mmapped. "A file is mapped
2626 * in multiples of the page size. For a file that is not a multiple of
2627 * the page size, the remaining memory is zeroed when mapped, and
2628 * writes to that region are not written out to the file."
2629 */
2630 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2631 out:
2632 ret = mpage_writepage(page, get_block, wbc);
2633 if (ret == -EAGAIN)
2634 ret = __block_write_full_page(inode, page, get_block, wbc,
2635 end_buffer_async_write);
2636 return ret;
2637 }
2638 EXPORT_SYMBOL(nobh_writepage);
2639
2640 int nobh_truncate_page(struct address_space *mapping,
2641 loff_t from, get_block_t *get_block)
2642 {
2643 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2644 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2645 unsigned blocksize;
2646 sector_t iblock;
2647 unsigned length, pos;
2648 struct inode *inode = mapping->host;
2649 struct page *page;
2650 struct buffer_head map_bh;
2651 int err;
2652
2653 blocksize = 1 << inode->i_blkbits;
2654 length = offset & (blocksize - 1);
2655
2656 /* Block boundary? Nothing to do */
2657 if (!length)
2658 return 0;
2659
2660 length = blocksize - length;
2661 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2662
2663 page = grab_cache_page(mapping, index);
2664 err = -ENOMEM;
2665 if (!page)
2666 goto out;
2667
2668 if (page_has_buffers(page)) {
2669 has_buffers:
2670 unlock_page(page);
2671 page_cache_release(page);
2672 return block_truncate_page(mapping, from, get_block);
2673 }
2674
2675 /* Find the buffer that contains "offset" */
2676 pos = blocksize;
2677 while (offset >= pos) {
2678 iblock++;
2679 pos += blocksize;
2680 }
2681
2682 map_bh.b_size = blocksize;
2683 map_bh.b_state = 0;
2684 err = get_block(inode, iblock, &map_bh, 0);
2685 if (err)
2686 goto unlock;
2687 /* unmapped? It's a hole - nothing to do */
2688 if (!buffer_mapped(&map_bh))
2689 goto unlock;
2690
2691 /* Ok, it's mapped. Make sure it's up-to-date */
2692 if (!PageUptodate(page)) {
2693 err = mapping->a_ops->readpage(NULL, page);
2694 if (err) {
2695 page_cache_release(page);
2696 goto out;
2697 }
2698 lock_page(page);
2699 if (!PageUptodate(page)) {
2700 err = -EIO;
2701 goto unlock;
2702 }
2703 if (page_has_buffers(page))
2704 goto has_buffers;
2705 }
2706 zero_user(page, offset, length);
2707 set_page_dirty(page);
2708 err = 0;
2709
2710 unlock:
2711 unlock_page(page);
2712 page_cache_release(page);
2713 out:
2714 return err;
2715 }
2716 EXPORT_SYMBOL(nobh_truncate_page);
2717
2718 int block_truncate_page(struct address_space *mapping,
2719 loff_t from, get_block_t *get_block)
2720 {
2721 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2722 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2723 unsigned blocksize;
2724 sector_t iblock;
2725 unsigned length, pos;
2726 struct inode *inode = mapping->host;
2727 struct page *page;
2728 struct buffer_head *bh;
2729 int err;
2730
2731 blocksize = 1 << inode->i_blkbits;
2732 length = offset & (blocksize - 1);
2733
2734 /* Block boundary? Nothing to do */
2735 if (!length)
2736 return 0;
2737
2738 length = blocksize - length;
2739 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2740
2741 page = grab_cache_page(mapping, index);
2742 err = -ENOMEM;
2743 if (!page)
2744 goto out;
2745
2746 if (!page_has_buffers(page))
2747 create_empty_buffers(page, blocksize, 0);
2748
2749 /* Find the buffer that contains "offset" */
2750 bh = page_buffers(page);
2751 pos = blocksize;
2752 while (offset >= pos) {
2753 bh = bh->b_this_page;
2754 iblock++;
2755 pos += blocksize;
2756 }
2757
2758 err = 0;
2759 if (!buffer_mapped(bh)) {
2760 WARN_ON(bh->b_size != blocksize);
2761 err = get_block(inode, iblock, bh, 0);
2762 if (err)
2763 goto unlock;
2764 /* unmapped? It's a hole - nothing to do */
2765 if (!buffer_mapped(bh))
2766 goto unlock;
2767 }
2768
2769 /* Ok, it's mapped. Make sure it's up-to-date */
2770 if (PageUptodate(page))
2771 set_buffer_uptodate(bh);
2772
2773 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2774 err = -EIO;
2775 ll_rw_block(READ, 1, &bh);
2776 wait_on_buffer(bh);
2777 /* Uhhuh. Read error. Complain and punt. */
2778 if (!buffer_uptodate(bh))
2779 goto unlock;
2780 }
2781
2782 zero_user(page, offset, length);
2783 mark_buffer_dirty(bh);
2784 err = 0;
2785
2786 unlock:
2787 unlock_page(page);
2788 page_cache_release(page);
2789 out:
2790 return err;
2791 }
2792 EXPORT_SYMBOL(block_truncate_page);
2793
2794 /*
2795 * The generic ->writepage function for buffer-backed address_spaces
2796 * this form passes in the end_io handler used to finish the IO.
2797 */
2798 int block_write_full_page_endio(struct page *page, get_block_t *get_block,
2799 struct writeback_control *wbc, bh_end_io_t *handler)
2800 {
2801 struct inode * const inode = page->mapping->host;
2802 loff_t i_size = i_size_read(inode);
2803 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2804 unsigned offset;
2805
2806 /* Is the page fully inside i_size? */
2807 if (page->index < end_index)
2808 return __block_write_full_page(inode, page, get_block, wbc,
2809 handler);
2810
2811 /* Is the page fully outside i_size? (truncate in progress) */
2812 offset = i_size & (PAGE_CACHE_SIZE-1);
2813 if (page->index >= end_index+1 || !offset) {
2814 /*
2815 * The page may have dirty, unmapped buffers. For example,
2816 * they may have been added in ext3_writepage(). Make them
2817 * freeable here, so the page does not leak.
2818 */
2819 do_invalidatepage(page, 0);
2820 unlock_page(page);
2821 return 0; /* don't care */
2822 }
2823
2824 /*
2825 * The page straddles i_size. It must be zeroed out on each and every
2826 * writepage invocation because it may be mmapped. "A file is mapped
2827 * in multiples of the page size. For a file that is not a multiple of
2828 * the page size, the remaining memory is zeroed when mapped, and
2829 * writes to that region are not written out to the file."
2830 */
2831 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
2832 return __block_write_full_page(inode, page, get_block, wbc, handler);
2833 }
2834 EXPORT_SYMBOL(block_write_full_page_endio);
2835
2836 /*
2837 * The generic ->writepage function for buffer-backed address_spaces
2838 */
2839 int block_write_full_page(struct page *page, get_block_t *get_block,
2840 struct writeback_control *wbc)
2841 {
2842 return block_write_full_page_endio(page, get_block, wbc,
2843 end_buffer_async_write);
2844 }
2845 EXPORT_SYMBOL(block_write_full_page);
2846
2847 sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2848 get_block_t *get_block)
2849 {
2850 struct buffer_head tmp;
2851 struct inode *inode = mapping->host;
2852 tmp.b_state = 0;
2853 tmp.b_blocknr = 0;
2854 tmp.b_size = 1 << inode->i_blkbits;
2855 get_block(inode, block, &tmp, 0);
2856 return tmp.b_blocknr;
2857 }
2858 EXPORT_SYMBOL(generic_block_bmap);
2859
2860 static void end_bio_bh_io_sync(struct bio *bio, int err)
2861 {
2862 struct buffer_head *bh = bio->bi_private;
2863
2864 if (err == -EOPNOTSUPP) {
2865 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
2866 }
2867
2868 if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags)))
2869 set_bit(BH_Quiet, &bh->b_state);
2870
2871 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2872 bio_put(bio);
2873 }
2874
2875 int submit_bh(int rw, struct buffer_head * bh)
2876 {
2877 struct bio *bio;
2878 int ret = 0;
2879
2880 BUG_ON(!buffer_locked(bh));
2881 BUG_ON(!buffer_mapped(bh));
2882 BUG_ON(!bh->b_end_io);
2883 BUG_ON(buffer_delay(bh));
2884 BUG_ON(buffer_unwritten(bh));
2885
2886 /*
2887 * Only clear out a write error when rewriting
2888 */
2889 if (test_set_buffer_req(bh) && (rw & WRITE))
2890 clear_buffer_write_io_error(bh);
2891
2892 /*
2893 * from here on down, it's all bio -- do the initial mapping,
2894 * submit_bio -> generic_make_request may further map this bio around
2895 */
2896 bio = bio_alloc(GFP_NOIO, 1);
2897
2898 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2899 bio->bi_bdev = bh->b_bdev;
2900 bio->bi_io_vec[0].bv_page = bh->b_page;
2901 bio->bi_io_vec[0].bv_len = bh->b_size;
2902 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
2903
2904 bio->bi_vcnt = 1;
2905 bio->bi_idx = 0;
2906 bio->bi_size = bh->b_size;
2907
2908 bio->bi_end_io = end_bio_bh_io_sync;
2909 bio->bi_private = bh;
2910
2911 bio_get(bio);
2912 submit_bio(rw, bio);
2913
2914 if (bio_flagged(bio, BIO_EOPNOTSUPP))
2915 ret = -EOPNOTSUPP;
2916
2917 bio_put(bio);
2918 return ret;
2919 }
2920 EXPORT_SYMBOL(submit_bh);
2921
2922 /**
2923 * ll_rw_block: low-level access to block devices (DEPRECATED)
2924 * @rw: whether to %READ or %WRITE or maybe %READA (readahead)
2925 * @nr: number of &struct buffer_heads in the array
2926 * @bhs: array of pointers to &struct buffer_head
2927 *
2928 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
2929 * requests an I/O operation on them, either a %READ or a %WRITE. The third
2930 * %READA option is described in the documentation for generic_make_request()
2931 * which ll_rw_block() calls.
2932 *
2933 * This function drops any buffer that it cannot get a lock on (with the
2934 * BH_Lock state bit), any buffer that appears to be clean when doing a write
2935 * request, and any buffer that appears to be up-to-date when doing read
2936 * request. Further it marks as clean buffers that are processed for
2937 * writing (the buffer cache won't assume that they are actually clean
2938 * until the buffer gets unlocked).
2939 *
2940 * ll_rw_block sets b_end_io to simple completion handler that marks
2941 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
2942 * any waiters.
2943 *
2944 * All of the buffers must be for the same device, and must also be a
2945 * multiple of the current approved size for the device.
2946 */
2947 void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
2948 {
2949 int i;
2950
2951 for (i = 0; i < nr; i++) {
2952 struct buffer_head *bh = bhs[i];
2953
2954 if (!trylock_buffer(bh))
2955 continue;
2956 if (rw == WRITE) {
2957 if (test_clear_buffer_dirty(bh)) {
2958 bh->b_end_io = end_buffer_write_sync;
2959 get_bh(bh);
2960 submit_bh(WRITE, bh);
2961 continue;
2962 }
2963 } else {
2964 if (!buffer_uptodate(bh)) {
2965 bh->b_end_io = end_buffer_read_sync;
2966 get_bh(bh);
2967 submit_bh(rw, bh);
2968 continue;
2969 }
2970 }
2971 unlock_buffer(bh);
2972 }
2973 }
2974 EXPORT_SYMBOL(ll_rw_block);
2975
2976 void write_dirty_buffer(struct buffer_head *bh, int rw)
2977 {
2978 lock_buffer(bh);
2979 if (!test_clear_buffer_dirty(bh)) {
2980 unlock_buffer(bh);
2981 return;
2982 }
2983 bh->b_end_io = end_buffer_write_sync;
2984 get_bh(bh);
2985 submit_bh(rw, bh);
2986 }
2987 EXPORT_SYMBOL(write_dirty_buffer);
2988
2989 /*
2990 * For a data-integrity writeout, we need to wait upon any in-progress I/O
2991 * and then start new I/O and then wait upon it. The caller must have a ref on
2992 * the buffer_head.
2993 */
2994 int __sync_dirty_buffer(struct buffer_head *bh, int rw)
2995 {
2996 int ret = 0;
2997
2998 WARN_ON(atomic_read(&bh->b_count) < 1);
2999 lock_buffer(bh);
3000 if (test_clear_buffer_dirty(bh)) {
3001 get_bh(bh);
3002 bh->b_end_io = end_buffer_write_sync;
3003 ret = submit_bh(rw, bh);
3004 wait_on_buffer(bh);
3005 if (!ret && !buffer_uptodate(bh))
3006 ret = -EIO;
3007 } else {
3008 unlock_buffer(bh);
3009 }
3010 return ret;
3011 }
3012 EXPORT_SYMBOL(__sync_dirty_buffer);
3013
3014 int sync_dirty_buffer(struct buffer_head *bh)
3015 {
3016 return __sync_dirty_buffer(bh, WRITE_SYNC);
3017 }
3018 EXPORT_SYMBOL(sync_dirty_buffer);
3019
3020 /*
3021 * try_to_free_buffers() checks if all the buffers on this particular page
3022 * are unused, and releases them if so.
3023 *
3024 * Exclusion against try_to_free_buffers may be obtained by either
3025 * locking the page or by holding its mapping's private_lock.
3026 *
3027 * If the page is dirty but all the buffers are clean then we need to
3028 * be sure to mark the page clean as well. This is because the page
3029 * may be against a block device, and a later reattachment of buffers
3030 * to a dirty page will set *all* buffers dirty. Which would corrupt
3031 * filesystem data on the same device.
3032 *
3033 * The same applies to regular filesystem pages: if all the buffers are
3034 * clean then we set the page clean and proceed. To do that, we require
3035 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3036 * private_lock.
3037 *
3038 * try_to_free_buffers() is non-blocking.
3039 */
3040 static inline int buffer_busy(struct buffer_head *bh)
3041 {
3042 return atomic_read(&bh->b_count) |
3043 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3044 }
3045
3046 static int
3047 drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3048 {
3049 struct buffer_head *head = page_buffers(page);
3050 struct buffer_head *bh;
3051
3052 bh = head;
3053 do {
3054 if (buffer_write_io_error(bh) && page->mapping)
3055 set_bit(AS_EIO, &page->mapping->flags);
3056 if (buffer_busy(bh))
3057 goto failed;
3058 bh = bh->b_this_page;
3059 } while (bh != head);
3060
3061 do {
3062 struct buffer_head *next = bh->b_this_page;
3063
3064 if (bh->b_assoc_map)
3065 __remove_assoc_queue(bh);
3066 bh = next;
3067 } while (bh != head);
3068 *buffers_to_free = head;
3069 __clear_page_buffers(page);
3070 return 1;
3071 failed:
3072 return 0;
3073 }
3074
3075 int try_to_free_buffers(struct page *page)
3076 {
3077 struct address_space * const mapping = page->mapping;
3078 struct buffer_head *buffers_to_free = NULL;
3079 int ret = 0;
3080
3081 BUG_ON(!PageLocked(page));
3082 if (PageWriteback(page))
3083 return 0;
3084
3085 if (mapping == NULL) { /* can this still happen? */
3086 ret = drop_buffers(page, &buffers_to_free);
3087 goto out;
3088 }
3089
3090 spin_lock(&mapping->private_lock);
3091 ret = drop_buffers(page, &buffers_to_free);
3092
3093 /*
3094 * If the filesystem writes its buffers by hand (eg ext3)
3095 * then we can have clean buffers against a dirty page. We
3096 * clean the page here; otherwise the VM will never notice
3097 * that the filesystem did any IO at all.
3098 *
3099 * Also, during truncate, discard_buffer will have marked all
3100 * the page's buffers clean. We discover that here and clean
3101 * the page also.
3102 *
3103 * private_lock must be held over this entire operation in order
3104 * to synchronise against __set_page_dirty_buffers and prevent the
3105 * dirty bit from being lost.
3106 */
3107 if (ret)
3108 cancel_dirty_page(page, PAGE_CACHE_SIZE);
3109 spin_unlock(&mapping->private_lock);
3110 out:
3111 if (buffers_to_free) {
3112 struct buffer_head *bh = buffers_to_free;
3113
3114 do {
3115 struct buffer_head *next = bh->b_this_page;
3116 free_buffer_head(bh);
3117 bh = next;
3118 } while (bh != buffers_to_free);
3119 }
3120 return ret;
3121 }
3122 EXPORT_SYMBOL(try_to_free_buffers);
3123
3124 /*
3125 * There are no bdflush tunables left. But distributions are
3126 * still running obsolete flush daemons, so we terminate them here.
3127 *
3128 * Use of bdflush() is deprecated and will be removed in a future kernel.
3129 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
3130 */
3131 SYSCALL_DEFINE2(bdflush, int, func, long, data)
3132 {
3133 static int msg_count;
3134
3135 if (!capable(CAP_SYS_ADMIN))
3136 return -EPERM;
3137
3138 if (msg_count < 5) {
3139 msg_count++;
3140 printk(KERN_INFO
3141 "warning: process `%s' used the obsolete bdflush"
3142 " system call\n", current->comm);
3143 printk(KERN_INFO "Fix your initscripts?\n");
3144 }
3145
3146 if (func == 1)
3147 do_exit(0);
3148 return 0;
3149 }
3150
3151 /*
3152 * Buffer-head allocation
3153 */
3154 static struct kmem_cache *bh_cachep;
3155
3156 /*
3157 * Once the number of bh's in the machine exceeds this level, we start
3158 * stripping them in writeback.
3159 */
3160 static int max_buffer_heads;
3161
3162 int buffer_heads_over_limit;
3163
3164 struct bh_accounting {
3165 int nr; /* Number of live bh's */
3166 int ratelimit; /* Limit cacheline bouncing */
3167 };
3168
3169 static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3170
3171 static void recalc_bh_state(void)
3172 {
3173 int i;
3174 int tot = 0;
3175
3176 if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
3177 return;
3178 __this_cpu_write(bh_accounting.ratelimit, 0);
3179 for_each_online_cpu(i)
3180 tot += per_cpu(bh_accounting, i).nr;
3181 buffer_heads_over_limit = (tot > max_buffer_heads);
3182 }
3183
3184 struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
3185 {
3186 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
3187 if (ret) {
3188 INIT_LIST_HEAD(&ret->b_assoc_buffers);
3189 preempt_disable();
3190 __this_cpu_inc(bh_accounting.nr);
3191 recalc_bh_state();
3192 preempt_enable();
3193 }
3194 return ret;
3195 }
3196 EXPORT_SYMBOL(alloc_buffer_head);
3197
3198 void free_buffer_head(struct buffer_head *bh)
3199 {
3200 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3201 kmem_cache_free(bh_cachep, bh);
3202 preempt_disable();
3203 __this_cpu_dec(bh_accounting.nr);
3204 recalc_bh_state();
3205 preempt_enable();
3206 }
3207 EXPORT_SYMBOL(free_buffer_head);
3208
3209 static void buffer_exit_cpu(int cpu)
3210 {
3211 int i;
3212 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3213
3214 for (i = 0; i < BH_LRU_SIZE; i++) {
3215 brelse(b->bhs[i]);
3216 b->bhs[i] = NULL;
3217 }
3218 this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
3219 per_cpu(bh_accounting, cpu).nr = 0;
3220 }
3221
3222 static int buffer_cpu_notify(struct notifier_block *self,
3223 unsigned long action, void *hcpu)
3224 {
3225 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
3226 buffer_exit_cpu((unsigned long)hcpu);
3227 return NOTIFY_OK;
3228 }
3229
3230 /**
3231 * bh_uptodate_or_lock - Test whether the buffer is uptodate
3232 * @bh: struct buffer_head
3233 *
3234 * Return true if the buffer is up-to-date and false,
3235 * with the buffer locked, if not.
3236 */
3237 int bh_uptodate_or_lock(struct buffer_head *bh)
3238 {
3239 if (!buffer_uptodate(bh)) {
3240 lock_buffer(bh);
3241 if (!buffer_uptodate(bh))
3242 return 0;
3243 unlock_buffer(bh);
3244 }
3245 return 1;
3246 }
3247 EXPORT_SYMBOL(bh_uptodate_or_lock);
3248
3249 /**
3250 * bh_submit_read - Submit a locked buffer for reading
3251 * @bh: struct buffer_head
3252 *
3253 * Returns zero on success and -EIO on error.
3254 */
3255 int bh_submit_read(struct buffer_head *bh)
3256 {
3257 BUG_ON(!buffer_locked(bh));
3258
3259 if (buffer_uptodate(bh)) {
3260 unlock_buffer(bh);
3261 return 0;
3262 }
3263
3264 get_bh(bh);
3265 bh->b_end_io = end_buffer_read_sync;
3266 submit_bh(READ, bh);
3267 wait_on_buffer(bh);
3268 if (buffer_uptodate(bh))
3269 return 0;
3270 return -EIO;
3271 }
3272 EXPORT_SYMBOL(bh_submit_read);
3273
3274 void __init buffer_init(void)
3275 {
3276 int nrpages;
3277
3278 bh_cachep = kmem_cache_create("buffer_head",
3279 sizeof(struct buffer_head), 0,
3280 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3281 SLAB_MEM_SPREAD),
3282 NULL);
3283
3284 /*
3285 * Limit the bh occupancy to 10% of ZONE_NORMAL
3286 */
3287 nrpages = (nr_free_buffer_pages() * 10) / 100;
3288 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3289 hotcpu_notifier(buffer_cpu_notify, 0);
3290 }