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/sched/signal.h>
23#include <linux/syscalls.h>
24#include <linux/fs.h>
25#include <linux/iomap.h>
26#include <linux/mm.h>
27#include <linux/percpu.h>
28#include <linux/slab.h>
29#include <linux/capability.h>
30#include <linux/blkdev.h>
31#include <linux/file.h>
32#include <linux/quotaops.h>
33#include <linux/highmem.h>
34#include <linux/export.h>
35#include <linux/backing-dev.h>
36#include <linux/writeback.h>
37#include <linux/hash.h>
38#include <linux/suspend.h>
39#include <linux/buffer_head.h>
40#include <linux/task_io_accounting_ops.h>
41#include <linux/bio.h>
42#include <linux/cpu.h>
43#include <linux/bitops.h>
44#include <linux/mpage.h>
45#include <linux/bit_spinlock.h>
46#include <linux/pagevec.h>
47#include <linux/sched/mm.h>
48#include <trace/events/block.h>
49
50static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
51static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
52 enum rw_hint hint, struct writeback_control *wbc);
53
54#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
55
56inline void touch_buffer(struct buffer_head *bh)
57{
58 trace_block_touch_buffer(bh);
59 mark_page_accessed(bh->b_page);
60}
61EXPORT_SYMBOL(touch_buffer);
62
63void __lock_buffer(struct buffer_head *bh)
64{
65 wait_on_bit_lock_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
66}
67EXPORT_SYMBOL(__lock_buffer);
68
69void unlock_buffer(struct buffer_head *bh)
70{
71 clear_bit_unlock(BH_Lock, &bh->b_state);
72 smp_mb__after_atomic();
73 wake_up_bit(&bh->b_state, BH_Lock);
74}
75EXPORT_SYMBOL(unlock_buffer);
76
77/*
78 * Returns if the page has dirty or writeback buffers. If all the buffers
79 * are unlocked and clean then the PageDirty information is stale. If
80 * any of the pages are locked, it is assumed they are locked for IO.
81 */
82void buffer_check_dirty_writeback(struct page *page,
83 bool *dirty, bool *writeback)
84{
85 struct buffer_head *head, *bh;
86 *dirty = false;
87 *writeback = false;
88
89 BUG_ON(!PageLocked(page));
90
91 if (!page_has_buffers(page))
92 return;
93
94 if (PageWriteback(page))
95 *writeback = true;
96
97 head = page_buffers(page);
98 bh = head;
99 do {
100 if (buffer_locked(bh))
101 *writeback = true;
102
103 if (buffer_dirty(bh))
104 *dirty = true;
105
106 bh = bh->b_this_page;
107 } while (bh != head);
108}
109EXPORT_SYMBOL(buffer_check_dirty_writeback);
110
111/*
112 * Block until a buffer comes unlocked. This doesn't stop it
113 * from becoming locked again - you have to lock it yourself
114 * if you want to preserve its state.
115 */
116void __wait_on_buffer(struct buffer_head * bh)
117{
118 wait_on_bit_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
119}
120EXPORT_SYMBOL(__wait_on_buffer);
121
122static void
123__clear_page_buffers(struct page *page)
124{
125 ClearPagePrivate(page);
126 set_page_private(page, 0);
127 put_page(page);
128}
129
130static void buffer_io_error(struct buffer_head *bh, char *msg)
131{
132 if (!test_bit(BH_Quiet, &bh->b_state))
133 printk_ratelimited(KERN_ERR
134 "Buffer I/O error on dev %pg, logical block %llu%s\n",
135 bh->b_bdev, (unsigned long long)bh->b_blocknr, msg);
136}
137
138/*
139 * End-of-IO handler helper function which does not touch the bh after
140 * unlocking it.
141 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
142 * a race there is benign: unlock_buffer() only use the bh's address for
143 * hashing after unlocking the buffer, so it doesn't actually touch the bh
144 * itself.
145 */
146static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
147{
148 if (uptodate) {
149 set_buffer_uptodate(bh);
150 } else {
151 /* This happens, due to failed read-ahead attempts. */
152 clear_buffer_uptodate(bh);
153 }
154 unlock_buffer(bh);
155}
156
157/*
158 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
159 * unlock the buffer. This is what ll_rw_block uses too.
160 */
161void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
162{
163 __end_buffer_read_notouch(bh, uptodate);
164 put_bh(bh);
165}
166EXPORT_SYMBOL(end_buffer_read_sync);
167
168void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
169{
170 if (uptodate) {
171 set_buffer_uptodate(bh);
172 } else {
173 buffer_io_error(bh, ", lost sync page write");
174 mark_buffer_write_io_error(bh);
175 clear_buffer_uptodate(bh);
176 }
177 unlock_buffer(bh);
178 put_bh(bh);
179}
180EXPORT_SYMBOL(end_buffer_write_sync);
181
182/*
183 * Various filesystems appear to want __find_get_block to be non-blocking.
184 * But it's the page lock which protects the buffers. To get around this,
185 * we get exclusion from try_to_free_buffers with the blockdev mapping's
186 * private_lock.
187 *
188 * Hack idea: for the blockdev mapping, private_lock contention
189 * may be quite high. This code could TryLock the page, and if that
190 * succeeds, there is no need to take private_lock.
191 */
192static struct buffer_head *
193__find_get_block_slow(struct block_device *bdev, sector_t block)
194{
195 struct inode *bd_inode = bdev->bd_inode;
196 struct address_space *bd_mapping = bd_inode->i_mapping;
197 struct buffer_head *ret = NULL;
198 pgoff_t index;
199 struct buffer_head *bh;
200 struct buffer_head *head;
201 struct page *page;
202 int all_mapped = 1;
203 static DEFINE_RATELIMIT_STATE(last_warned, HZ, 1);
204
205 index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
206 page = find_get_page_flags(bd_mapping, index, FGP_ACCESSED);
207 if (!page)
208 goto out;
209
210 spin_lock(&bd_mapping->private_lock);
211 if (!page_has_buffers(page))
212 goto out_unlock;
213 head = page_buffers(page);
214 bh = head;
215 do {
216 if (!buffer_mapped(bh))
217 all_mapped = 0;
218 else if (bh->b_blocknr == block) {
219 ret = bh;
220 get_bh(bh);
221 goto out_unlock;
222 }
223 bh = bh->b_this_page;
224 } while (bh != head);
225
226 /* we might be here because some of the buffers on this page are
227 * not mapped. This is due to various races between
228 * file io on the block device and getblk. It gets dealt with
229 * elsewhere, don't buffer_error if we had some unmapped buffers
230 */
231 ratelimit_set_flags(&last_warned, RATELIMIT_MSG_ON_RELEASE);
232 if (all_mapped && __ratelimit(&last_warned)) {
233 printk("__find_get_block_slow() failed. block=%llu, "
234 "b_blocknr=%llu, b_state=0x%08lx, b_size=%zu, "
235 "device %pg blocksize: %d\n",
236 (unsigned long long)block,
237 (unsigned long long)bh->b_blocknr,
238 bh->b_state, bh->b_size, bdev,
239 1 << bd_inode->i_blkbits);
240 }
241out_unlock:
242 spin_unlock(&bd_mapping->private_lock);
243 put_page(page);
244out:
245 return ret;
246}
247
248/*
249 * I/O completion handler for block_read_full_page() - pages
250 * which come unlocked at the end of I/O.
251 */
252static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
253{
254 unsigned long flags;
255 struct buffer_head *first;
256 struct buffer_head *tmp;
257 struct page *page;
258 int page_uptodate = 1;
259
260 BUG_ON(!buffer_async_read(bh));
261
262 page = bh->b_page;
263 if (uptodate) {
264 set_buffer_uptodate(bh);
265 } else {
266 clear_buffer_uptodate(bh);
267 buffer_io_error(bh, ", async page read");
268 SetPageError(page);
269 }
270
271 /*
272 * Be _very_ careful from here on. Bad things can happen if
273 * two buffer heads end IO at almost the same time and both
274 * decide that the page is now completely done.
275 */
276 first = page_buffers(page);
277 local_irq_save(flags);
278 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
279 clear_buffer_async_read(bh);
280 unlock_buffer(bh);
281 tmp = bh;
282 do {
283 if (!buffer_uptodate(tmp))
284 page_uptodate = 0;
285 if (buffer_async_read(tmp)) {
286 BUG_ON(!buffer_locked(tmp));
287 goto still_busy;
288 }
289 tmp = tmp->b_this_page;
290 } while (tmp != bh);
291 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
292 local_irq_restore(flags);
293
294 /*
295 * If none of the buffers had errors and they are all
296 * uptodate then we can set the page uptodate.
297 */
298 if (page_uptodate && !PageError(page))
299 SetPageUptodate(page);
300 unlock_page(page);
301 return;
302
303still_busy:
304 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
305 local_irq_restore(flags);
306 return;
307}
308
309/*
310 * Completion handler for block_write_full_page() - pages which are unlocked
311 * during I/O, and which have PageWriteback cleared upon I/O completion.
312 */
313void end_buffer_async_write(struct buffer_head *bh, int uptodate)
314{
315 unsigned long flags;
316 struct buffer_head *first;
317 struct buffer_head *tmp;
318 struct page *page;
319
320 BUG_ON(!buffer_async_write(bh));
321
322 page = bh->b_page;
323 if (uptodate) {
324 set_buffer_uptodate(bh);
325 } else {
326 buffer_io_error(bh, ", lost async page write");
327 mark_buffer_write_io_error(bh);
328 clear_buffer_uptodate(bh);
329 SetPageError(page);
330 }
331
332 first = page_buffers(page);
333 local_irq_save(flags);
334 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
335
336 clear_buffer_async_write(bh);
337 unlock_buffer(bh);
338 tmp = bh->b_this_page;
339 while (tmp != bh) {
340 if (buffer_async_write(tmp)) {
341 BUG_ON(!buffer_locked(tmp));
342 goto still_busy;
343 }
344 tmp = tmp->b_this_page;
345 }
346 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
347 local_irq_restore(flags);
348 end_page_writeback(page);
349 return;
350
351still_busy:
352 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
353 local_irq_restore(flags);
354 return;
355}
356EXPORT_SYMBOL(end_buffer_async_write);
357
358/*
359 * If a page's buffers are under async readin (end_buffer_async_read
360 * completion) then there is a possibility that another thread of
361 * control could lock one of the buffers after it has completed
362 * but while some of the other buffers have not completed. This
363 * locked buffer would confuse end_buffer_async_read() into not unlocking
364 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
365 * that this buffer is not under async I/O.
366 *
367 * The page comes unlocked when it has no locked buffer_async buffers
368 * left.
369 *
370 * PageLocked prevents anyone starting new async I/O reads any of
371 * the buffers.
372 *
373 * PageWriteback is used to prevent simultaneous writeout of the same
374 * page.
375 *
376 * PageLocked prevents anyone from starting writeback of a page which is
377 * under read I/O (PageWriteback is only ever set against a locked page).
378 */
379static void mark_buffer_async_read(struct buffer_head *bh)
380{
381 bh->b_end_io = end_buffer_async_read;
382 set_buffer_async_read(bh);
383}
384
385static void mark_buffer_async_write_endio(struct buffer_head *bh,
386 bh_end_io_t *handler)
387{
388 bh->b_end_io = handler;
389 set_buffer_async_write(bh);
390}
391
392void mark_buffer_async_write(struct buffer_head *bh)
393{
394 mark_buffer_async_write_endio(bh, end_buffer_async_write);
395}
396EXPORT_SYMBOL(mark_buffer_async_write);
397
398
399/*
400 * fs/buffer.c contains helper functions for buffer-backed address space's
401 * fsync functions. A common requirement for buffer-based filesystems is
402 * that certain data from the backing blockdev needs to be written out for
403 * a successful fsync(). For example, ext2 indirect blocks need to be
404 * written back and waited upon before fsync() returns.
405 *
406 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
407 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
408 * management of a list of dependent buffers at ->i_mapping->private_list.
409 *
410 * Locking is a little subtle: try_to_free_buffers() will remove buffers
411 * from their controlling inode's queue when they are being freed. But
412 * try_to_free_buffers() will be operating against the *blockdev* mapping
413 * at the time, not against the S_ISREG file which depends on those buffers.
414 * So the locking for private_list is via the private_lock in the address_space
415 * which backs the buffers. Which is different from the address_space
416 * against which the buffers are listed. So for a particular address_space,
417 * mapping->private_lock does *not* protect mapping->private_list! In fact,
418 * mapping->private_list will always be protected by the backing blockdev's
419 * ->private_lock.
420 *
421 * Which introduces a requirement: all buffers on an address_space's
422 * ->private_list must be from the same address_space: the blockdev's.
423 *
424 * address_spaces which do not place buffers at ->private_list via these
425 * utility functions are free to use private_lock and private_list for
426 * whatever they want. The only requirement is that list_empty(private_list)
427 * be true at clear_inode() time.
428 *
429 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
430 * filesystems should do that. invalidate_inode_buffers() should just go
431 * BUG_ON(!list_empty).
432 *
433 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
434 * take an address_space, not an inode. And it should be called
435 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
436 * queued up.
437 *
438 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
439 * list if it is already on a list. Because if the buffer is on a list,
440 * it *must* already be on the right one. If not, the filesystem is being
441 * silly. This will save a ton of locking. But first we have to ensure
442 * that buffers are taken *off* the old inode's list when they are freed
443 * (presumably in truncate). That requires careful auditing of all
444 * filesystems (do it inside bforget()). It could also be done by bringing
445 * b_inode back.
446 */
447
448/*
449 * The buffer's backing address_space's private_lock must be held
450 */
451static void __remove_assoc_queue(struct buffer_head *bh)
452{
453 list_del_init(&bh->b_assoc_buffers);
454 WARN_ON(!bh->b_assoc_map);
455 bh->b_assoc_map = NULL;
456}
457
458int inode_has_buffers(struct inode *inode)
459{
460 return !list_empty(&inode->i_data.private_list);
461}
462
463/*
464 * osync is designed to support O_SYNC io. It waits synchronously for
465 * all already-submitted IO to complete, but does not queue any new
466 * writes to the disk.
467 *
468 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
469 * you dirty the buffers, and then use osync_inode_buffers to wait for
470 * completion. Any other dirty buffers which are not yet queued for
471 * write will not be flushed to disk by the osync.
472 */
473static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
474{
475 struct buffer_head *bh;
476 struct list_head *p;
477 int err = 0;
478
479 spin_lock(lock);
480repeat:
481 list_for_each_prev(p, list) {
482 bh = BH_ENTRY(p);
483 if (buffer_locked(bh)) {
484 get_bh(bh);
485 spin_unlock(lock);
486 wait_on_buffer(bh);
487 if (!buffer_uptodate(bh))
488 err = -EIO;
489 brelse(bh);
490 spin_lock(lock);
491 goto repeat;
492 }
493 }
494 spin_unlock(lock);
495 return err;
496}
497
498void emergency_thaw_bdev(struct super_block *sb)
499{
500 while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
501 printk(KERN_WARNING "Emergency Thaw on %pg\n", sb->s_bdev);
502}
503
504/**
505 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
506 * @mapping: the mapping which wants those buffers written
507 *
508 * Starts I/O against the buffers at mapping->private_list, and waits upon
509 * that I/O.
510 *
511 * Basically, this is a convenience function for fsync().
512 * @mapping is a file or directory which needs those buffers to be written for
513 * a successful fsync().
514 */
515int sync_mapping_buffers(struct address_space *mapping)
516{
517 struct address_space *buffer_mapping = mapping->private_data;
518
519 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
520 return 0;
521
522 return fsync_buffers_list(&buffer_mapping->private_lock,
523 &mapping->private_list);
524}
525EXPORT_SYMBOL(sync_mapping_buffers);
526
527/*
528 * Called when we've recently written block `bblock', and it is known that
529 * `bblock' was for a buffer_boundary() buffer. This means that the block at
530 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
531 * dirty, schedule it for IO. So that indirects merge nicely with their data.
532 */
533void write_boundary_block(struct block_device *bdev,
534 sector_t bblock, unsigned blocksize)
535{
536 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
537 if (bh) {
538 if (buffer_dirty(bh))
539 ll_rw_block(REQ_OP_WRITE, 0, 1, &bh);
540 put_bh(bh);
541 }
542}
543
544void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
545{
546 struct address_space *mapping = inode->i_mapping;
547 struct address_space *buffer_mapping = bh->b_page->mapping;
548
549 mark_buffer_dirty(bh);
550 if (!mapping->private_data) {
551 mapping->private_data = buffer_mapping;
552 } else {
553 BUG_ON(mapping->private_data != buffer_mapping);
554 }
555 if (!bh->b_assoc_map) {
556 spin_lock(&buffer_mapping->private_lock);
557 list_move_tail(&bh->b_assoc_buffers,
558 &mapping->private_list);
559 bh->b_assoc_map = mapping;
560 spin_unlock(&buffer_mapping->private_lock);
561 }
562}
563EXPORT_SYMBOL(mark_buffer_dirty_inode);
564
565/*
566 * Mark the page dirty, and set it dirty in the page cache, and mark the inode
567 * dirty.
568 *
569 * If warn is true, then emit a warning if the page is not uptodate and has
570 * not been truncated.
571 *
572 * The caller must hold lock_page_memcg().
573 */
574void __set_page_dirty(struct page *page, struct address_space *mapping,
575 int warn)
576{
577 unsigned long flags;
578
579 xa_lock_irqsave(&mapping->i_pages, flags);
580 if (page->mapping) { /* Race with truncate? */
581 WARN_ON_ONCE(warn && !PageUptodate(page));
582 account_page_dirtied(page, mapping);
583 __xa_set_mark(&mapping->i_pages, page_index(page),
584 PAGECACHE_TAG_DIRTY);
585 }
586 xa_unlock_irqrestore(&mapping->i_pages, flags);
587}
588EXPORT_SYMBOL_GPL(__set_page_dirty);
589
590/*
591 * Add a page to the dirty page list.
592 *
593 * It is a sad fact of life that this function is called from several places
594 * deeply under spinlocking. It may not sleep.
595 *
596 * If the page has buffers, the uptodate buffers are set dirty, to preserve
597 * dirty-state coherency between the page and the buffers. It the page does
598 * not have buffers then when they are later attached they will all be set
599 * dirty.
600 *
601 * The buffers are dirtied before the page is dirtied. There's a small race
602 * window in which a writepage caller may see the page cleanness but not the
603 * buffer dirtiness. That's fine. If this code were to set the page dirty
604 * before the buffers, a concurrent writepage caller could clear the page dirty
605 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
606 * page on the dirty page list.
607 *
608 * We use private_lock to lock against try_to_free_buffers while using the
609 * page's buffer list. Also use this to protect against clean buffers being
610 * added to the page after it was set dirty.
611 *
612 * FIXME: may need to call ->reservepage here as well. That's rather up to the
613 * address_space though.
614 */
615int __set_page_dirty_buffers(struct page *page)
616{
617 int newly_dirty;
618 struct address_space *mapping = page_mapping(page);
619
620 if (unlikely(!mapping))
621 return !TestSetPageDirty(page);
622
623 spin_lock(&mapping->private_lock);
624 if (page_has_buffers(page)) {
625 struct buffer_head *head = page_buffers(page);
626 struct buffer_head *bh = head;
627
628 do {
629 set_buffer_dirty(bh);
630 bh = bh->b_this_page;
631 } while (bh != head);
632 }
633 /*
634 * Lock out page->mem_cgroup migration to keep PageDirty
635 * synchronized with per-memcg dirty page counters.
636 */
637 lock_page_memcg(page);
638 newly_dirty = !TestSetPageDirty(page);
639 spin_unlock(&mapping->private_lock);
640
641 if (newly_dirty)
642 __set_page_dirty(page, mapping, 1);
643
644 unlock_page_memcg(page);
645
646 if (newly_dirty)
647 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
648
649 return newly_dirty;
650}
651EXPORT_SYMBOL(__set_page_dirty_buffers);
652
653/*
654 * Write out and wait upon a list of buffers.
655 *
656 * We have conflicting pressures: we want to make sure that all
657 * initially dirty buffers get waited on, but that any subsequently
658 * dirtied buffers don't. After all, we don't want fsync to last
659 * forever if somebody is actively writing to the file.
660 *
661 * Do this in two main stages: first we copy dirty buffers to a
662 * temporary inode list, queueing the writes as we go. Then we clean
663 * up, waiting for those writes to complete.
664 *
665 * During this second stage, any subsequent updates to the file may end
666 * up refiling the buffer on the original inode's dirty list again, so
667 * there is a chance we will end up with a buffer queued for write but
668 * not yet completed on that list. So, as a final cleanup we go through
669 * the osync code to catch these locked, dirty buffers without requeuing
670 * any newly dirty buffers for write.
671 */
672static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
673{
674 struct buffer_head *bh;
675 struct list_head tmp;
676 struct address_space *mapping;
677 int err = 0, err2;
678 struct blk_plug plug;
679
680 INIT_LIST_HEAD(&tmp);
681 blk_start_plug(&plug);
682
683 spin_lock(lock);
684 while (!list_empty(list)) {
685 bh = BH_ENTRY(list->next);
686 mapping = bh->b_assoc_map;
687 __remove_assoc_queue(bh);
688 /* Avoid race with mark_buffer_dirty_inode() which does
689 * a lockless check and we rely on seeing the dirty bit */
690 smp_mb();
691 if (buffer_dirty(bh) || buffer_locked(bh)) {
692 list_add(&bh->b_assoc_buffers, &tmp);
693 bh->b_assoc_map = mapping;
694 if (buffer_dirty(bh)) {
695 get_bh(bh);
696 spin_unlock(lock);
697 /*
698 * Ensure any pending I/O completes so that
699 * write_dirty_buffer() actually writes the
700 * current contents - it is a noop if I/O is
701 * still in flight on potentially older
702 * contents.
703 */
704 write_dirty_buffer(bh, REQ_SYNC);
705
706 /*
707 * Kick off IO for the previous mapping. Note
708 * that we will not run the very last mapping,
709 * wait_on_buffer() will do that for us
710 * through sync_buffer().
711 */
712 brelse(bh);
713 spin_lock(lock);
714 }
715 }
716 }
717
718 spin_unlock(lock);
719 blk_finish_plug(&plug);
720 spin_lock(lock);
721
722 while (!list_empty(&tmp)) {
723 bh = BH_ENTRY(tmp.prev);
724 get_bh(bh);
725 mapping = bh->b_assoc_map;
726 __remove_assoc_queue(bh);
727 /* Avoid race with mark_buffer_dirty_inode() which does
728 * a lockless check and we rely on seeing the dirty bit */
729 smp_mb();
730 if (buffer_dirty(bh)) {
731 list_add(&bh->b_assoc_buffers,
732 &mapping->private_list);
733 bh->b_assoc_map = mapping;
734 }
735 spin_unlock(lock);
736 wait_on_buffer(bh);
737 if (!buffer_uptodate(bh))
738 err = -EIO;
739 brelse(bh);
740 spin_lock(lock);
741 }
742
743 spin_unlock(lock);
744 err2 = osync_buffers_list(lock, list);
745 if (err)
746 return err;
747 else
748 return err2;
749}
750
751/*
752 * Invalidate any and all dirty buffers on a given inode. We are
753 * probably unmounting the fs, but that doesn't mean we have already
754 * done a sync(). Just drop the buffers from the inode list.
755 *
756 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
757 * assumes that all the buffers are against the blockdev. Not true
758 * for reiserfs.
759 */
760void invalidate_inode_buffers(struct inode *inode)
761{
762 if (inode_has_buffers(inode)) {
763 struct address_space *mapping = &inode->i_data;
764 struct list_head *list = &mapping->private_list;
765 struct address_space *buffer_mapping = mapping->private_data;
766
767 spin_lock(&buffer_mapping->private_lock);
768 while (!list_empty(list))
769 __remove_assoc_queue(BH_ENTRY(list->next));
770 spin_unlock(&buffer_mapping->private_lock);
771 }
772}
773EXPORT_SYMBOL(invalidate_inode_buffers);
774
775/*
776 * Remove any clean buffers from the inode's buffer list. This is called
777 * when we're trying to free the inode itself. Those buffers can pin it.
778 *
779 * Returns true if all buffers were removed.
780 */
781int remove_inode_buffers(struct inode *inode)
782{
783 int ret = 1;
784
785 if (inode_has_buffers(inode)) {
786 struct address_space *mapping = &inode->i_data;
787 struct list_head *list = &mapping->private_list;
788 struct address_space *buffer_mapping = mapping->private_data;
789
790 spin_lock(&buffer_mapping->private_lock);
791 while (!list_empty(list)) {
792 struct buffer_head *bh = BH_ENTRY(list->next);
793 if (buffer_dirty(bh)) {
794 ret = 0;
795 break;
796 }
797 __remove_assoc_queue(bh);
798 }
799 spin_unlock(&buffer_mapping->private_lock);
800 }
801 return ret;
802}
803
804/*
805 * Create the appropriate buffers when given a page for data area and
806 * the size of each buffer.. Use the bh->b_this_page linked list to
807 * follow the buffers created. Return NULL if unable to create more
808 * buffers.
809 *
810 * The retry flag is used to differentiate async IO (paging, swapping)
811 * which may not fail from ordinary buffer allocations.
812 */
813struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
814 bool retry)
815{
816 struct buffer_head *bh, *head;
817 gfp_t gfp = GFP_NOFS | __GFP_ACCOUNT;
818 long offset;
819 struct mem_cgroup *memcg;
820
821 if (retry)
822 gfp |= __GFP_NOFAIL;
823
824 memcg = get_mem_cgroup_from_page(page);
825 memalloc_use_memcg(memcg);
826
827 head = NULL;
828 offset = PAGE_SIZE;
829 while ((offset -= size) >= 0) {
830 bh = alloc_buffer_head(gfp);
831 if (!bh)
832 goto no_grow;
833
834 bh->b_this_page = head;
835 bh->b_blocknr = -1;
836 head = bh;
837
838 bh->b_size = size;
839
840 /* Link the buffer to its page */
841 set_bh_page(bh, page, offset);
842 }
843out:
844 memalloc_unuse_memcg();
845 mem_cgroup_put(memcg);
846 return head;
847/*
848 * In case anything failed, we just free everything we got.
849 */
850no_grow:
851 if (head) {
852 do {
853 bh = head;
854 head = head->b_this_page;
855 free_buffer_head(bh);
856 } while (head);
857 }
858
859 goto out;
860}
861EXPORT_SYMBOL_GPL(alloc_page_buffers);
862
863static inline void
864link_dev_buffers(struct page *page, struct buffer_head *head)
865{
866 struct buffer_head *bh, *tail;
867
868 bh = head;
869 do {
870 tail = bh;
871 bh = bh->b_this_page;
872 } while (bh);
873 tail->b_this_page = head;
874 attach_page_buffers(page, head);
875}
876
877static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
878{
879 sector_t retval = ~((sector_t)0);
880 loff_t sz = i_size_read(bdev->bd_inode);
881
882 if (sz) {
883 unsigned int sizebits = blksize_bits(size);
884 retval = (sz >> sizebits);
885 }
886 return retval;
887}
888
889/*
890 * Initialise the state of a blockdev page's buffers.
891 */
892static sector_t
893init_page_buffers(struct page *page, struct block_device *bdev,
894 sector_t block, int size)
895{
896 struct buffer_head *head = page_buffers(page);
897 struct buffer_head *bh = head;
898 int uptodate = PageUptodate(page);
899 sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode), size);
900
901 do {
902 if (!buffer_mapped(bh)) {
903 bh->b_end_io = NULL;
904 bh->b_private = NULL;
905 bh->b_bdev = bdev;
906 bh->b_blocknr = block;
907 if (uptodate)
908 set_buffer_uptodate(bh);
909 if (block < end_block)
910 set_buffer_mapped(bh);
911 }
912 block++;
913 bh = bh->b_this_page;
914 } while (bh != head);
915
916 /*
917 * Caller needs to validate requested block against end of device.
918 */
919 return end_block;
920}
921
922/*
923 * Create the page-cache page that contains the requested block.
924 *
925 * This is used purely for blockdev mappings.
926 */
927static int
928grow_dev_page(struct block_device *bdev, sector_t block,
929 pgoff_t index, int size, int sizebits, gfp_t gfp)
930{
931 struct inode *inode = bdev->bd_inode;
932 struct page *page;
933 struct buffer_head *bh;
934 sector_t end_block;
935 int ret = 0; /* Will call free_more_memory() */
936 gfp_t gfp_mask;
937
938 gfp_mask = mapping_gfp_constraint(inode->i_mapping, ~__GFP_FS) | gfp;
939
940 /*
941 * XXX: __getblk_slow() can not really deal with failure and
942 * will endlessly loop on improvised global reclaim. Prefer
943 * looping in the allocator rather than here, at least that
944 * code knows what it's doing.
945 */
946 gfp_mask |= __GFP_NOFAIL;
947
948 page = find_or_create_page(inode->i_mapping, index, gfp_mask);
949
950 BUG_ON(!PageLocked(page));
951
952 if (page_has_buffers(page)) {
953 bh = page_buffers(page);
954 if (bh->b_size == size) {
955 end_block = init_page_buffers(page, bdev,
956 (sector_t)index << sizebits,
957 size);
958 goto done;
959 }
960 if (!try_to_free_buffers(page))
961 goto failed;
962 }
963
964 /*
965 * Allocate some buffers for this page
966 */
967 bh = alloc_page_buffers(page, size, true);
968
969 /*
970 * Link the page to the buffers and initialise them. Take the
971 * lock to be atomic wrt __find_get_block(), which does not
972 * run under the page lock.
973 */
974 spin_lock(&inode->i_mapping->private_lock);
975 link_dev_buffers(page, bh);
976 end_block = init_page_buffers(page, bdev, (sector_t)index << sizebits,
977 size);
978 spin_unlock(&inode->i_mapping->private_lock);
979done:
980 ret = (block < end_block) ? 1 : -ENXIO;
981failed:
982 unlock_page(page);
983 put_page(page);
984 return ret;
985}
986
987/*
988 * Create buffers for the specified block device block's page. If
989 * that page was dirty, the buffers are set dirty also.
990 */
991static int
992grow_buffers(struct block_device *bdev, sector_t block, int size, gfp_t gfp)
993{
994 pgoff_t index;
995 int sizebits;
996
997 sizebits = -1;
998 do {
999 sizebits++;
1000 } while ((size << sizebits) < PAGE_SIZE);
1001
1002 index = block >> sizebits;
1003
1004 /*
1005 * Check for a block which wants to lie outside our maximum possible
1006 * pagecache index. (this comparison is done using sector_t types).
1007 */
1008 if (unlikely(index != block >> sizebits)) {
1009 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1010 "device %pg\n",
1011 __func__, (unsigned long long)block,
1012 bdev);
1013 return -EIO;
1014 }
1015
1016 /* Create a page with the proper size buffers.. */
1017 return grow_dev_page(bdev, block, index, size, sizebits, gfp);
1018}
1019
1020static struct buffer_head *
1021__getblk_slow(struct block_device *bdev, sector_t block,
1022 unsigned size, gfp_t gfp)
1023{
1024 /* Size must be multiple of hard sectorsize */
1025 if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
1026 (size < 512 || size > PAGE_SIZE))) {
1027 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1028 size);
1029 printk(KERN_ERR "logical block size: %d\n",
1030 bdev_logical_block_size(bdev));
1031
1032 dump_stack();
1033 return NULL;
1034 }
1035
1036 for (;;) {
1037 struct buffer_head *bh;
1038 int ret;
1039
1040 bh = __find_get_block(bdev, block, size);
1041 if (bh)
1042 return bh;
1043
1044 ret = grow_buffers(bdev, block, size, gfp);
1045 if (ret < 0)
1046 return NULL;
1047 }
1048}
1049
1050/*
1051 * The relationship between dirty buffers and dirty pages:
1052 *
1053 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1054 * the page is tagged dirty in the page cache.
1055 *
1056 * At all times, the dirtiness of the buffers represents the dirtiness of
1057 * subsections of the page. If the page has buffers, the page dirty bit is
1058 * merely a hint about the true dirty state.
1059 *
1060 * When a page is set dirty in its entirety, all its buffers are marked dirty
1061 * (if the page has buffers).
1062 *
1063 * When a buffer is marked dirty, its page is dirtied, but the page's other
1064 * buffers are not.
1065 *
1066 * Also. When blockdev buffers are explicitly read with bread(), they
1067 * individually become uptodate. But their backing page remains not
1068 * uptodate - even if all of its buffers are uptodate. A subsequent
1069 * block_read_full_page() against that page will discover all the uptodate
1070 * buffers, will set the page uptodate and will perform no I/O.
1071 */
1072
1073/**
1074 * mark_buffer_dirty - mark a buffer_head as needing writeout
1075 * @bh: the buffer_head to mark dirty
1076 *
1077 * mark_buffer_dirty() will set the dirty bit against the buffer, then set
1078 * its backing page dirty, then tag the page as dirty in the page cache
1079 * and then attach the address_space's inode to its superblock's dirty
1080 * inode list.
1081 *
1082 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
1083 * i_pages lock and mapping->host->i_lock.
1084 */
1085void mark_buffer_dirty(struct buffer_head *bh)
1086{
1087 WARN_ON_ONCE(!buffer_uptodate(bh));
1088
1089 trace_block_dirty_buffer(bh);
1090
1091 /*
1092 * Very *carefully* optimize the it-is-already-dirty case.
1093 *
1094 * Don't let the final "is it dirty" escape to before we
1095 * perhaps modified the buffer.
1096 */
1097 if (buffer_dirty(bh)) {
1098 smp_mb();
1099 if (buffer_dirty(bh))
1100 return;
1101 }
1102
1103 if (!test_set_buffer_dirty(bh)) {
1104 struct page *page = bh->b_page;
1105 struct address_space *mapping = NULL;
1106
1107 lock_page_memcg(page);
1108 if (!TestSetPageDirty(page)) {
1109 mapping = page_mapping(page);
1110 if (mapping)
1111 __set_page_dirty(page, mapping, 0);
1112 }
1113 unlock_page_memcg(page);
1114 if (mapping)
1115 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
1116 }
1117}
1118EXPORT_SYMBOL(mark_buffer_dirty);
1119
1120void mark_buffer_write_io_error(struct buffer_head *bh)
1121{
1122 set_buffer_write_io_error(bh);
1123 /* FIXME: do we need to set this in both places? */
1124 if (bh->b_page && bh->b_page->mapping)
1125 mapping_set_error(bh->b_page->mapping, -EIO);
1126 if (bh->b_assoc_map)
1127 mapping_set_error(bh->b_assoc_map, -EIO);
1128}
1129EXPORT_SYMBOL(mark_buffer_write_io_error);
1130
1131/*
1132 * Decrement a buffer_head's reference count. If all buffers against a page
1133 * have zero reference count, are clean and unlocked, and if the page is clean
1134 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1135 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1136 * a page but it ends up not being freed, and buffers may later be reattached).
1137 */
1138void __brelse(struct buffer_head * buf)
1139{
1140 if (atomic_read(&buf->b_count)) {
1141 put_bh(buf);
1142 return;
1143 }
1144 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
1145}
1146EXPORT_SYMBOL(__brelse);
1147
1148/*
1149 * bforget() is like brelse(), except it discards any
1150 * potentially dirty data.
1151 */
1152void __bforget(struct buffer_head *bh)
1153{
1154 clear_buffer_dirty(bh);
1155 if (bh->b_assoc_map) {
1156 struct address_space *buffer_mapping = bh->b_page->mapping;
1157
1158 spin_lock(&buffer_mapping->private_lock);
1159 list_del_init(&bh->b_assoc_buffers);
1160 bh->b_assoc_map = NULL;
1161 spin_unlock(&buffer_mapping->private_lock);
1162 }
1163 __brelse(bh);
1164}
1165EXPORT_SYMBOL(__bforget);
1166
1167static struct buffer_head *__bread_slow(struct buffer_head *bh)
1168{
1169 lock_buffer(bh);
1170 if (buffer_uptodate(bh)) {
1171 unlock_buffer(bh);
1172 return bh;
1173 } else {
1174 get_bh(bh);
1175 bh->b_end_io = end_buffer_read_sync;
1176 submit_bh(REQ_OP_READ, 0, bh);
1177 wait_on_buffer(bh);
1178 if (buffer_uptodate(bh))
1179 return bh;
1180 }
1181 brelse(bh);
1182 return NULL;
1183}
1184
1185/*
1186 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1187 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1188 * refcount elevated by one when they're in an LRU. A buffer can only appear
1189 * once in a particular CPU's LRU. A single buffer can be present in multiple
1190 * CPU's LRUs at the same time.
1191 *
1192 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1193 * sb_find_get_block().
1194 *
1195 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1196 * a local interrupt disable for that.
1197 */
1198
1199#define BH_LRU_SIZE 16
1200
1201struct bh_lru {
1202 struct buffer_head *bhs[BH_LRU_SIZE];
1203};
1204
1205static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1206
1207#ifdef CONFIG_SMP
1208#define bh_lru_lock() local_irq_disable()
1209#define bh_lru_unlock() local_irq_enable()
1210#else
1211#define bh_lru_lock() preempt_disable()
1212#define bh_lru_unlock() preempt_enable()
1213#endif
1214
1215static inline void check_irqs_on(void)
1216{
1217#ifdef irqs_disabled
1218 BUG_ON(irqs_disabled());
1219#endif
1220}
1221
1222/*
1223 * Install a buffer_head into this cpu's LRU. If not already in the LRU, it is
1224 * inserted at the front, and the buffer_head at the back if any is evicted.
1225 * Or, if already in the LRU it is moved to the front.
1226 */
1227static void bh_lru_install(struct buffer_head *bh)
1228{
1229 struct buffer_head *evictee = bh;
1230 struct bh_lru *b;
1231 int i;
1232
1233 check_irqs_on();
1234 bh_lru_lock();
1235
1236 b = this_cpu_ptr(&bh_lrus);
1237 for (i = 0; i < BH_LRU_SIZE; i++) {
1238 swap(evictee, b->bhs[i]);
1239 if (evictee == bh) {
1240 bh_lru_unlock();
1241 return;
1242 }
1243 }
1244
1245 get_bh(bh);
1246 bh_lru_unlock();
1247 brelse(evictee);
1248}
1249
1250/*
1251 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1252 */
1253static struct buffer_head *
1254lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
1255{
1256 struct buffer_head *ret = NULL;
1257 unsigned int i;
1258
1259 check_irqs_on();
1260 bh_lru_lock();
1261 for (i = 0; i < BH_LRU_SIZE; i++) {
1262 struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
1263
1264 if (bh && bh->b_blocknr == block && bh->b_bdev == bdev &&
1265 bh->b_size == size) {
1266 if (i) {
1267 while (i) {
1268 __this_cpu_write(bh_lrus.bhs[i],
1269 __this_cpu_read(bh_lrus.bhs[i - 1]));
1270 i--;
1271 }
1272 __this_cpu_write(bh_lrus.bhs[0], bh);
1273 }
1274 get_bh(bh);
1275 ret = bh;
1276 break;
1277 }
1278 }
1279 bh_lru_unlock();
1280 return ret;
1281}
1282
1283/*
1284 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1285 * it in the LRU and mark it as accessed. If it is not present then return
1286 * NULL
1287 */
1288struct buffer_head *
1289__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
1290{
1291 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1292
1293 if (bh == NULL) {
1294 /* __find_get_block_slow will mark the page accessed */
1295 bh = __find_get_block_slow(bdev, block);
1296 if (bh)
1297 bh_lru_install(bh);
1298 } else
1299 touch_buffer(bh);
1300
1301 return bh;
1302}
1303EXPORT_SYMBOL(__find_get_block);
1304
1305/*
1306 * __getblk_gfp() will locate (and, if necessary, create) the buffer_head
1307 * which corresponds to the passed block_device, block and size. The
1308 * returned buffer has its reference count incremented.
1309 *
1310 * __getblk_gfp() will lock up the machine if grow_dev_page's
1311 * try_to_free_buffers() attempt is failing. FIXME, perhaps?
1312 */
1313struct buffer_head *
1314__getblk_gfp(struct block_device *bdev, sector_t block,
1315 unsigned size, gfp_t gfp)
1316{
1317 struct buffer_head *bh = __find_get_block(bdev, block, size);
1318
1319 might_sleep();
1320 if (bh == NULL)
1321 bh = __getblk_slow(bdev, block, size, gfp);
1322 return bh;
1323}
1324EXPORT_SYMBOL(__getblk_gfp);
1325
1326/*
1327 * Do async read-ahead on a buffer..
1328 */
1329void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
1330{
1331 struct buffer_head *bh = __getblk(bdev, block, size);
1332 if (likely(bh)) {
1333 ll_rw_block(REQ_OP_READ, REQ_RAHEAD, 1, &bh);
1334 brelse(bh);
1335 }
1336}
1337EXPORT_SYMBOL(__breadahead);
1338
1339/**
1340 * __bread_gfp() - reads a specified block and returns the bh
1341 * @bdev: the block_device to read from
1342 * @block: number of block
1343 * @size: size (in bytes) to read
1344 * @gfp: page allocation flag
1345 *
1346 * Reads a specified block, and returns buffer head that contains it.
1347 * The page cache can be allocated from non-movable area
1348 * not to prevent page migration if you set gfp to zero.
1349 * It returns NULL if the block was unreadable.
1350 */
1351struct buffer_head *
1352__bread_gfp(struct block_device *bdev, sector_t block,
1353 unsigned size, gfp_t gfp)
1354{
1355 struct buffer_head *bh = __getblk_gfp(bdev, block, size, gfp);
1356
1357 if (likely(bh) && !buffer_uptodate(bh))
1358 bh = __bread_slow(bh);
1359 return bh;
1360}
1361EXPORT_SYMBOL(__bread_gfp);
1362
1363/*
1364 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1365 * This doesn't race because it runs in each cpu either in irq
1366 * or with preempt disabled.
1367 */
1368static void invalidate_bh_lru(void *arg)
1369{
1370 struct bh_lru *b = &get_cpu_var(bh_lrus);
1371 int i;
1372
1373 for (i = 0; i < BH_LRU_SIZE; i++) {
1374 brelse(b->bhs[i]);
1375 b->bhs[i] = NULL;
1376 }
1377 put_cpu_var(bh_lrus);
1378}
1379
1380static bool has_bh_in_lru(int cpu, void *dummy)
1381{
1382 struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1383 int i;
1384
1385 for (i = 0; i < BH_LRU_SIZE; i++) {
1386 if (b->bhs[i])
1387 return 1;
1388 }
1389
1390 return 0;
1391}
1392
1393void invalidate_bh_lrus(void)
1394{
1395 on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL);
1396}
1397EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
1398
1399void set_bh_page(struct buffer_head *bh,
1400 struct page *page, unsigned long offset)
1401{
1402 bh->b_page = page;
1403 BUG_ON(offset >= PAGE_SIZE);
1404 if (PageHighMem(page))
1405 /*
1406 * This catches illegal uses and preserves the offset:
1407 */
1408 bh->b_data = (char *)(0 + offset);
1409 else
1410 bh->b_data = page_address(page) + offset;
1411}
1412EXPORT_SYMBOL(set_bh_page);
1413
1414/*
1415 * Called when truncating a buffer on a page completely.
1416 */
1417
1418/* Bits that are cleared during an invalidate */
1419#define BUFFER_FLAGS_DISCARD \
1420 (1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \
1421 1 << BH_Delay | 1 << BH_Unwritten)
1422
1423static void discard_buffer(struct buffer_head * bh)
1424{
1425 unsigned long b_state, b_state_old;
1426
1427 lock_buffer(bh);
1428 clear_buffer_dirty(bh);
1429 bh->b_bdev = NULL;
1430 b_state = bh->b_state;
1431 for (;;) {
1432 b_state_old = cmpxchg(&bh->b_state, b_state,
1433 (b_state & ~BUFFER_FLAGS_DISCARD));
1434 if (b_state_old == b_state)
1435 break;
1436 b_state = b_state_old;
1437 }
1438 unlock_buffer(bh);
1439}
1440
1441/**
1442 * block_invalidatepage - invalidate part or all of a buffer-backed page
1443 *
1444 * @page: the page which is affected
1445 * @offset: start of the range to invalidate
1446 * @length: length of the range to invalidate
1447 *
1448 * block_invalidatepage() is called when all or part of the page has become
1449 * invalidated by a truncate operation.
1450 *
1451 * block_invalidatepage() does not have to release all buffers, but it must
1452 * ensure that no dirty buffer is left outside @offset and that no I/O
1453 * is underway against any of the blocks which are outside the truncation
1454 * point. Because the caller is about to free (and possibly reuse) those
1455 * blocks on-disk.
1456 */
1457void block_invalidatepage(struct page *page, unsigned int offset,
1458 unsigned int length)
1459{
1460 struct buffer_head *head, *bh, *next;
1461 unsigned int curr_off = 0;
1462 unsigned int stop = length + offset;
1463
1464 BUG_ON(!PageLocked(page));
1465 if (!page_has_buffers(page))
1466 goto out;
1467
1468 /*
1469 * Check for overflow
1470 */
1471 BUG_ON(stop > PAGE_SIZE || stop < length);
1472
1473 head = page_buffers(page);
1474 bh = head;
1475 do {
1476 unsigned int next_off = curr_off + bh->b_size;
1477 next = bh->b_this_page;
1478
1479 /*
1480 * Are we still fully in range ?
1481 */
1482 if (next_off > stop)
1483 goto out;
1484
1485 /*
1486 * is this block fully invalidated?
1487 */
1488 if (offset <= curr_off)
1489 discard_buffer(bh);
1490 curr_off = next_off;
1491 bh = next;
1492 } while (bh != head);
1493
1494 /*
1495 * We release buffers only if the entire page is being invalidated.
1496 * The get_block cached value has been unconditionally invalidated,
1497 * so real IO is not possible anymore.
1498 */
1499 if (length == PAGE_SIZE)
1500 try_to_release_page(page, 0);
1501out:
1502 return;
1503}
1504EXPORT_SYMBOL(block_invalidatepage);
1505
1506
1507/*
1508 * We attach and possibly dirty the buffers atomically wrt
1509 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1510 * is already excluded via the page lock.
1511 */
1512void create_empty_buffers(struct page *page,
1513 unsigned long blocksize, unsigned long b_state)
1514{
1515 struct buffer_head *bh, *head, *tail;
1516
1517 head = alloc_page_buffers(page, blocksize, true);
1518 bh = head;
1519 do {
1520 bh->b_state |= b_state;
1521 tail = bh;
1522 bh = bh->b_this_page;
1523 } while (bh);
1524 tail->b_this_page = head;
1525
1526 spin_lock(&page->mapping->private_lock);
1527 if (PageUptodate(page) || PageDirty(page)) {
1528 bh = head;
1529 do {
1530 if (PageDirty(page))
1531 set_buffer_dirty(bh);
1532 if (PageUptodate(page))
1533 set_buffer_uptodate(bh);
1534 bh = bh->b_this_page;
1535 } while (bh != head);
1536 }
1537 attach_page_buffers(page, head);
1538 spin_unlock(&page->mapping->private_lock);
1539}
1540EXPORT_SYMBOL(create_empty_buffers);
1541
1542/**
1543 * clean_bdev_aliases: clean a range of buffers in block device
1544 * @bdev: Block device to clean buffers in
1545 * @block: Start of a range of blocks to clean
1546 * @len: Number of blocks to clean
1547 *
1548 * We are taking a range of blocks for data and we don't want writeback of any
1549 * buffer-cache aliases starting from return from this function and until the
1550 * moment when something will explicitly mark the buffer dirty (hopefully that
1551 * will not happen until we will free that block ;-) We don't even need to mark
1552 * it not-uptodate - nobody can expect anything from a newly allocated buffer
1553 * anyway. We used to use unmap_buffer() for such invalidation, but that was
1554 * wrong. We definitely don't want to mark the alias unmapped, for example - it
1555 * would confuse anyone who might pick it with bread() afterwards...
1556 *
1557 * Also.. Note that bforget() doesn't lock the buffer. So there can be
1558 * writeout I/O going on against recently-freed buffers. We don't wait on that
1559 * I/O in bforget() - it's more efficient to wait on the I/O only if we really
1560 * need to. That happens here.
1561 */
1562void clean_bdev_aliases(struct block_device *bdev, sector_t block, sector_t len)
1563{
1564 struct inode *bd_inode = bdev->bd_inode;
1565 struct address_space *bd_mapping = bd_inode->i_mapping;
1566 struct pagevec pvec;
1567 pgoff_t index = block >> (PAGE_SHIFT - bd_inode->i_blkbits);
1568 pgoff_t end;
1569 int i, count;
1570 struct buffer_head *bh;
1571 struct buffer_head *head;
1572
1573 end = (block + len - 1) >> (PAGE_SHIFT - bd_inode->i_blkbits);
1574 pagevec_init(&pvec);
1575 while (pagevec_lookup_range(&pvec, bd_mapping, &index, end)) {
1576 count = pagevec_count(&pvec);
1577 for (i = 0; i < count; i++) {
1578 struct page *page = pvec.pages[i];
1579
1580 if (!page_has_buffers(page))
1581 continue;
1582 /*
1583 * We use page lock instead of bd_mapping->private_lock
1584 * to pin buffers here since we can afford to sleep and
1585 * it scales better than a global spinlock lock.
1586 */
1587 lock_page(page);
1588 /* Recheck when the page is locked which pins bhs */
1589 if (!page_has_buffers(page))
1590 goto unlock_page;
1591 head = page_buffers(page);
1592 bh = head;
1593 do {
1594 if (!buffer_mapped(bh) || (bh->b_blocknr < block))
1595 goto next;
1596 if (bh->b_blocknr >= block + len)
1597 break;
1598 clear_buffer_dirty(bh);
1599 wait_on_buffer(bh);
1600 clear_buffer_req(bh);
1601next:
1602 bh = bh->b_this_page;
1603 } while (bh != head);
1604unlock_page:
1605 unlock_page(page);
1606 }
1607 pagevec_release(&pvec);
1608 cond_resched();
1609 /* End of range already reached? */
1610 if (index > end || !index)
1611 break;
1612 }
1613}
1614EXPORT_SYMBOL(clean_bdev_aliases);
1615
1616/*
1617 * Size is a power-of-two in the range 512..PAGE_SIZE,
1618 * and the case we care about most is PAGE_SIZE.
1619 *
1620 * So this *could* possibly be written with those
1621 * constraints in mind (relevant mostly if some
1622 * architecture has a slow bit-scan instruction)
1623 */
1624static inline int block_size_bits(unsigned int blocksize)
1625{
1626 return ilog2(blocksize);
1627}
1628
1629static struct buffer_head *create_page_buffers(struct page *page, struct inode *inode, unsigned int b_state)
1630{
1631 BUG_ON(!PageLocked(page));
1632
1633 if (!page_has_buffers(page))
1634 create_empty_buffers(page, 1 << READ_ONCE(inode->i_blkbits),
1635 b_state);
1636 return page_buffers(page);
1637}
1638
1639/*
1640 * NOTE! All mapped/uptodate combinations are valid:
1641 *
1642 * Mapped Uptodate Meaning
1643 *
1644 * No No "unknown" - must do get_block()
1645 * No Yes "hole" - zero-filled
1646 * Yes No "allocated" - allocated on disk, not read in
1647 * Yes Yes "valid" - allocated and up-to-date in memory.
1648 *
1649 * "Dirty" is valid only with the last case (mapped+uptodate).
1650 */
1651
1652/*
1653 * While block_write_full_page is writing back the dirty buffers under
1654 * the page lock, whoever dirtied the buffers may decide to clean them
1655 * again at any time. We handle that by only looking at the buffer
1656 * state inside lock_buffer().
1657 *
1658 * If block_write_full_page() is called for regular writeback
1659 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1660 * locked buffer. This only can happen if someone has written the buffer
1661 * directly, with submit_bh(). At the address_space level PageWriteback
1662 * prevents this contention from occurring.
1663 *
1664 * If block_write_full_page() is called with wbc->sync_mode ==
1665 * WB_SYNC_ALL, the writes are posted using REQ_SYNC; this
1666 * causes the writes to be flagged as synchronous writes.
1667 */
1668int __block_write_full_page(struct inode *inode, struct page *page,
1669 get_block_t *get_block, struct writeback_control *wbc,
1670 bh_end_io_t *handler)
1671{
1672 int err;
1673 sector_t block;
1674 sector_t last_block;
1675 struct buffer_head *bh, *head;
1676 unsigned int blocksize, bbits;
1677 int nr_underway = 0;
1678 int write_flags = wbc_to_write_flags(wbc);
1679
1680 head = create_page_buffers(page, inode,
1681 (1 << BH_Dirty)|(1 << BH_Uptodate));
1682
1683 /*
1684 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1685 * here, and the (potentially unmapped) buffers may become dirty at
1686 * any time. If a buffer becomes dirty here after we've inspected it
1687 * then we just miss that fact, and the page stays dirty.
1688 *
1689 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1690 * handle that here by just cleaning them.
1691 */
1692
1693 bh = head;
1694 blocksize = bh->b_size;
1695 bbits = block_size_bits(blocksize);
1696
1697 block = (sector_t)page->index << (PAGE_SHIFT - bbits);
1698 last_block = (i_size_read(inode) - 1) >> bbits;
1699
1700 /*
1701 * Get all the dirty buffers mapped to disk addresses and
1702 * handle any aliases from the underlying blockdev's mapping.
1703 */
1704 do {
1705 if (block > last_block) {
1706 /*
1707 * mapped buffers outside i_size will occur, because
1708 * this page can be outside i_size when there is a
1709 * truncate in progress.
1710 */
1711 /*
1712 * The buffer was zeroed by block_write_full_page()
1713 */
1714 clear_buffer_dirty(bh);
1715 set_buffer_uptodate(bh);
1716 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1717 buffer_dirty(bh)) {
1718 WARN_ON(bh->b_size != blocksize);
1719 err = get_block(inode, block, bh, 1);
1720 if (err)
1721 goto recover;
1722 clear_buffer_delay(bh);
1723 if (buffer_new(bh)) {
1724 /* blockdev mappings never come here */
1725 clear_buffer_new(bh);
1726 clean_bdev_bh_alias(bh);
1727 }
1728 }
1729 bh = bh->b_this_page;
1730 block++;
1731 } while (bh != head);
1732
1733 do {
1734 if (!buffer_mapped(bh))
1735 continue;
1736 /*
1737 * If it's a fully non-blocking write attempt and we cannot
1738 * lock the buffer then redirty the page. Note that this can
1739 * potentially cause a busy-wait loop from writeback threads
1740 * and kswapd activity, but those code paths have their own
1741 * higher-level throttling.
1742 */
1743 if (wbc->sync_mode != WB_SYNC_NONE) {
1744 lock_buffer(bh);
1745 } else if (!trylock_buffer(bh)) {
1746 redirty_page_for_writepage(wbc, page);
1747 continue;
1748 }
1749 if (test_clear_buffer_dirty(bh)) {
1750 mark_buffer_async_write_endio(bh, handler);
1751 } else {
1752 unlock_buffer(bh);
1753 }
1754 } while ((bh = bh->b_this_page) != head);
1755
1756 /*
1757 * The page and its buffers are protected by PageWriteback(), so we can
1758 * drop the bh refcounts early.
1759 */
1760 BUG_ON(PageWriteback(page));
1761 set_page_writeback(page);
1762
1763 do {
1764 struct buffer_head *next = bh->b_this_page;
1765 if (buffer_async_write(bh)) {
1766 submit_bh_wbc(REQ_OP_WRITE, write_flags, bh,
1767 inode->i_write_hint, wbc);
1768 nr_underway++;
1769 }
1770 bh = next;
1771 } while (bh != head);
1772 unlock_page(page);
1773
1774 err = 0;
1775done:
1776 if (nr_underway == 0) {
1777 /*
1778 * The page was marked dirty, but the buffers were
1779 * clean. Someone wrote them back by hand with
1780 * ll_rw_block/submit_bh. A rare case.
1781 */
1782 end_page_writeback(page);
1783
1784 /*
1785 * The page and buffer_heads can be released at any time from
1786 * here on.
1787 */
1788 }
1789 return err;
1790
1791recover:
1792 /*
1793 * ENOSPC, or some other error. We may already have added some
1794 * blocks to the file, so we need to write these out to avoid
1795 * exposing stale data.
1796 * The page is currently locked and not marked for writeback
1797 */
1798 bh = head;
1799 /* Recovery: lock and submit the mapped buffers */
1800 do {
1801 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1802 !buffer_delay(bh)) {
1803 lock_buffer(bh);
1804 mark_buffer_async_write_endio(bh, handler);
1805 } else {
1806 /*
1807 * The buffer may have been set dirty during
1808 * attachment to a dirty page.
1809 */
1810 clear_buffer_dirty(bh);
1811 }
1812 } while ((bh = bh->b_this_page) != head);
1813 SetPageError(page);
1814 BUG_ON(PageWriteback(page));
1815 mapping_set_error(page->mapping, err);
1816 set_page_writeback(page);
1817 do {
1818 struct buffer_head *next = bh->b_this_page;
1819 if (buffer_async_write(bh)) {
1820 clear_buffer_dirty(bh);
1821 submit_bh_wbc(REQ_OP_WRITE, write_flags, bh,
1822 inode->i_write_hint, wbc);
1823 nr_underway++;
1824 }
1825 bh = next;
1826 } while (bh != head);
1827 unlock_page(page);
1828 goto done;
1829}
1830EXPORT_SYMBOL(__block_write_full_page);
1831
1832/*
1833 * If a page has any new buffers, zero them out here, and mark them uptodate
1834 * and dirty so they'll be written out (in order to prevent uninitialised
1835 * block data from leaking). And clear the new bit.
1836 */
1837void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1838{
1839 unsigned int block_start, block_end;
1840 struct buffer_head *head, *bh;
1841
1842 BUG_ON(!PageLocked(page));
1843 if (!page_has_buffers(page))
1844 return;
1845
1846 bh = head = page_buffers(page);
1847 block_start = 0;
1848 do {
1849 block_end = block_start + bh->b_size;
1850
1851 if (buffer_new(bh)) {
1852 if (block_end > from && block_start < to) {
1853 if (!PageUptodate(page)) {
1854 unsigned start, size;
1855
1856 start = max(from, block_start);
1857 size = min(to, block_end) - start;
1858
1859 zero_user(page, start, size);
1860 set_buffer_uptodate(bh);
1861 }
1862
1863 clear_buffer_new(bh);
1864 mark_buffer_dirty(bh);
1865 }
1866 }
1867
1868 block_start = block_end;
1869 bh = bh->b_this_page;
1870 } while (bh != head);
1871}
1872EXPORT_SYMBOL(page_zero_new_buffers);
1873
1874static void
1875iomap_to_bh(struct inode *inode, sector_t block, struct buffer_head *bh,
1876 struct iomap *iomap)
1877{
1878 loff_t offset = block << inode->i_blkbits;
1879
1880 bh->b_bdev = iomap->bdev;
1881
1882 /*
1883 * Block points to offset in file we need to map, iomap contains
1884 * the offset at which the map starts. If the map ends before the
1885 * current block, then do not map the buffer and let the caller
1886 * handle it.
1887 */
1888 BUG_ON(offset >= iomap->offset + iomap->length);
1889
1890 switch (iomap->type) {
1891 case IOMAP_HOLE:
1892 /*
1893 * If the buffer is not up to date or beyond the current EOF,
1894 * we need to mark it as new to ensure sub-block zeroing is
1895 * executed if necessary.
1896 */
1897 if (!buffer_uptodate(bh) ||
1898 (offset >= i_size_read(inode)))
1899 set_buffer_new(bh);
1900 break;
1901 case IOMAP_DELALLOC:
1902 if (!buffer_uptodate(bh) ||
1903 (offset >= i_size_read(inode)))
1904 set_buffer_new(bh);
1905 set_buffer_uptodate(bh);
1906 set_buffer_mapped(bh);
1907 set_buffer_delay(bh);
1908 break;
1909 case IOMAP_UNWRITTEN:
1910 /*
1911 * For unwritten regions, we always need to ensure that regions
1912 * in the block we are not writing to are zeroed. Mark the
1913 * buffer as new to ensure this.
1914 */
1915 set_buffer_new(bh);
1916 set_buffer_unwritten(bh);
1917 /* FALLTHRU */
1918 case IOMAP_MAPPED:
1919 if ((iomap->flags & IOMAP_F_NEW) ||
1920 offset >= i_size_read(inode))
1921 set_buffer_new(bh);
1922 bh->b_blocknr = (iomap->addr + offset - iomap->offset) >>
1923 inode->i_blkbits;
1924 set_buffer_mapped(bh);
1925 break;
1926 }
1927}
1928
1929int __block_write_begin_int(struct page *page, loff_t pos, unsigned len,
1930 get_block_t *get_block, struct iomap *iomap)
1931{
1932 unsigned from = pos & (PAGE_SIZE - 1);
1933 unsigned to = from + len;
1934 struct inode *inode = page->mapping->host;
1935 unsigned block_start, block_end;
1936 sector_t block;
1937 int err = 0;
1938 unsigned blocksize, bbits;
1939 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1940
1941 BUG_ON(!PageLocked(page));
1942 BUG_ON(from > PAGE_SIZE);
1943 BUG_ON(to > PAGE_SIZE);
1944 BUG_ON(from > to);
1945
1946 head = create_page_buffers(page, inode, 0);
1947 blocksize = head->b_size;
1948 bbits = block_size_bits(blocksize);
1949
1950 block = (sector_t)page->index << (PAGE_SHIFT - bbits);
1951
1952 for(bh = head, block_start = 0; bh != head || !block_start;
1953 block++, block_start=block_end, bh = bh->b_this_page) {
1954 block_end = block_start + blocksize;
1955 if (block_end <= from || block_start >= to) {
1956 if (PageUptodate(page)) {
1957 if (!buffer_uptodate(bh))
1958 set_buffer_uptodate(bh);
1959 }
1960 continue;
1961 }
1962 if (buffer_new(bh))
1963 clear_buffer_new(bh);
1964 if (!buffer_mapped(bh)) {
1965 WARN_ON(bh->b_size != blocksize);
1966 if (get_block) {
1967 err = get_block(inode, block, bh, 1);
1968 if (err)
1969 break;
1970 } else {
1971 iomap_to_bh(inode, block, bh, iomap);
1972 }
1973
1974 if (buffer_new(bh)) {
1975 clean_bdev_bh_alias(bh);
1976 if (PageUptodate(page)) {
1977 clear_buffer_new(bh);
1978 set_buffer_uptodate(bh);
1979 mark_buffer_dirty(bh);
1980 continue;
1981 }
1982 if (block_end > to || block_start < from)
1983 zero_user_segments(page,
1984 to, block_end,
1985 block_start, from);
1986 continue;
1987 }
1988 }
1989 if (PageUptodate(page)) {
1990 if (!buffer_uptodate(bh))
1991 set_buffer_uptodate(bh);
1992 continue;
1993 }
1994 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
1995 !buffer_unwritten(bh) &&
1996 (block_start < from || block_end > to)) {
1997 ll_rw_block(REQ_OP_READ, 0, 1, &bh);
1998 *wait_bh++=bh;
1999 }
2000 }
2001 /*
2002 * If we issued read requests - let them complete.
2003 */
2004 while(wait_bh > wait) {
2005 wait_on_buffer(*--wait_bh);
2006 if (!buffer_uptodate(*wait_bh))
2007 err = -EIO;
2008 }
2009 if (unlikely(err))
2010 page_zero_new_buffers(page, from, to);
2011 return err;
2012}
2013
2014int __block_write_begin(struct page *page, loff_t pos, unsigned len,
2015 get_block_t *get_block)
2016{
2017 return __block_write_begin_int(page, pos, len, get_block, NULL);
2018}
2019EXPORT_SYMBOL(__block_write_begin);
2020
2021static int __block_commit_write(struct inode *inode, struct page *page,
2022 unsigned from, unsigned to)
2023{
2024 unsigned block_start, block_end;
2025 int partial = 0;
2026 unsigned blocksize;
2027 struct buffer_head *bh, *head;
2028
2029 bh = head = page_buffers(page);
2030 blocksize = bh->b_size;
2031
2032 block_start = 0;
2033 do {
2034 block_end = block_start + blocksize;
2035 if (block_end <= from || block_start >= to) {
2036 if (!buffer_uptodate(bh))
2037 partial = 1;
2038 } else {
2039 set_buffer_uptodate(bh);
2040 mark_buffer_dirty(bh);
2041 }
2042 clear_buffer_new(bh);
2043
2044 block_start = block_end;
2045 bh = bh->b_this_page;
2046 } while (bh != head);
2047
2048 /*
2049 * If this is a partial write which happened to make all buffers
2050 * uptodate then we can optimize away a bogus readpage() for
2051 * the next read(). Here we 'discover' whether the page went
2052 * uptodate as a result of this (potentially partial) write.
2053 */
2054 if (!partial)
2055 SetPageUptodate(page);
2056 return 0;
2057}
2058
2059/*
2060 * block_write_begin takes care of the basic task of block allocation and
2061 * bringing partial write blocks uptodate first.
2062 *
2063 * The filesystem needs to handle block truncation upon failure.
2064 */
2065int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
2066 unsigned flags, struct page **pagep, get_block_t *get_block)
2067{
2068 pgoff_t index = pos >> PAGE_SHIFT;
2069 struct page *page;
2070 int status;
2071
2072 page = grab_cache_page_write_begin(mapping, index, flags);
2073 if (!page)
2074 return -ENOMEM;
2075
2076 status = __block_write_begin(page, pos, len, get_block);
2077 if (unlikely(status)) {
2078 unlock_page(page);
2079 put_page(page);
2080 page = NULL;
2081 }
2082
2083 *pagep = page;
2084 return status;
2085}
2086EXPORT_SYMBOL(block_write_begin);
2087
2088int __generic_write_end(struct inode *inode, loff_t pos, unsigned copied,
2089 struct page *page)
2090{
2091 loff_t old_size = inode->i_size;
2092 bool i_size_changed = false;
2093
2094 /*
2095 * No need to use i_size_read() here, the i_size cannot change under us
2096 * because we hold i_rwsem.
2097 *
2098 * But it's important to update i_size while still holding page lock:
2099 * page writeout could otherwise come in and zero beyond i_size.
2100 */
2101 if (pos + copied > inode->i_size) {
2102 i_size_write(inode, pos + copied);
2103 i_size_changed = true;
2104 }
2105
2106 unlock_page(page);
2107 put_page(page);
2108
2109 if (old_size < pos)
2110 pagecache_isize_extended(inode, old_size, pos);
2111 /*
2112 * Don't mark the inode dirty under page lock. First, it unnecessarily
2113 * makes the holding time of page lock longer. Second, it forces lock
2114 * ordering of page lock and transaction start for journaling
2115 * filesystems.
2116 */
2117 if (i_size_changed)
2118 mark_inode_dirty(inode);
2119 return copied;
2120}
2121
2122int block_write_end(struct file *file, struct address_space *mapping,
2123 loff_t pos, unsigned len, unsigned copied,
2124 struct page *page, void *fsdata)
2125{
2126 struct inode *inode = mapping->host;
2127 unsigned start;
2128
2129 start = pos & (PAGE_SIZE - 1);
2130
2131 if (unlikely(copied < len)) {
2132 /*
2133 * The buffers that were written will now be uptodate, so we
2134 * don't have to worry about a readpage reading them and
2135 * overwriting a partial write. However if we have encountered
2136 * a short write and only partially written into a buffer, it
2137 * will not be marked uptodate, so a readpage might come in and
2138 * destroy our partial write.
2139 *
2140 * Do the simplest thing, and just treat any short write to a
2141 * non uptodate page as a zero-length write, and force the
2142 * caller to redo the whole thing.
2143 */
2144 if (!PageUptodate(page))
2145 copied = 0;
2146
2147 page_zero_new_buffers(page, start+copied, start+len);
2148 }
2149 flush_dcache_page(page);
2150
2151 /* This could be a short (even 0-length) commit */
2152 __block_commit_write(inode, page, start, start+copied);
2153
2154 return copied;
2155}
2156EXPORT_SYMBOL(block_write_end);
2157
2158int generic_write_end(struct file *file, struct address_space *mapping,
2159 loff_t pos, unsigned len, unsigned copied,
2160 struct page *page, void *fsdata)
2161{
2162 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2163 return __generic_write_end(mapping->host, pos, copied, page);
2164}
2165EXPORT_SYMBOL(generic_write_end);
2166
2167/*
2168 * block_is_partially_uptodate checks whether buffers within a page are
2169 * uptodate or not.
2170 *
2171 * Returns true if all buffers which correspond to a file portion
2172 * we want to read are uptodate.
2173 */
2174int block_is_partially_uptodate(struct page *page, unsigned long from,
2175 unsigned long count)
2176{
2177 unsigned block_start, block_end, blocksize;
2178 unsigned to;
2179 struct buffer_head *bh, *head;
2180 int ret = 1;
2181
2182 if (!page_has_buffers(page))
2183 return 0;
2184
2185 head = page_buffers(page);
2186 blocksize = head->b_size;
2187 to = min_t(unsigned, PAGE_SIZE - from, count);
2188 to = from + to;
2189 if (from < blocksize && to > PAGE_SIZE - blocksize)
2190 return 0;
2191
2192 bh = head;
2193 block_start = 0;
2194 do {
2195 block_end = block_start + blocksize;
2196 if (block_end > from && block_start < to) {
2197 if (!buffer_uptodate(bh)) {
2198 ret = 0;
2199 break;
2200 }
2201 if (block_end >= to)
2202 break;
2203 }
2204 block_start = block_end;
2205 bh = bh->b_this_page;
2206 } while (bh != head);
2207
2208 return ret;
2209}
2210EXPORT_SYMBOL(block_is_partially_uptodate);
2211
2212/*
2213 * Generic "read page" function for block devices that have the normal
2214 * get_block functionality. This is most of the block device filesystems.
2215 * Reads the page asynchronously --- the unlock_buffer() and
2216 * set/clear_buffer_uptodate() functions propagate buffer state into the
2217 * page struct once IO has completed.
2218 */
2219int block_read_full_page(struct page *page, get_block_t *get_block)
2220{
2221 struct inode *inode = page->mapping->host;
2222 sector_t iblock, lblock;
2223 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2224 unsigned int blocksize, bbits;
2225 int nr, i;
2226 int fully_mapped = 1;
2227
2228 head = create_page_buffers(page, inode, 0);
2229 blocksize = head->b_size;
2230 bbits = block_size_bits(blocksize);
2231
2232 iblock = (sector_t)page->index << (PAGE_SHIFT - bbits);
2233 lblock = (i_size_read(inode)+blocksize-1) >> bbits;
2234 bh = head;
2235 nr = 0;
2236 i = 0;
2237
2238 do {
2239 if (buffer_uptodate(bh))
2240 continue;
2241
2242 if (!buffer_mapped(bh)) {
2243 int err = 0;
2244
2245 fully_mapped = 0;
2246 if (iblock < lblock) {
2247 WARN_ON(bh->b_size != blocksize);
2248 err = get_block(inode, iblock, bh, 0);
2249 if (err)
2250 SetPageError(page);
2251 }
2252 if (!buffer_mapped(bh)) {
2253 zero_user(page, i * blocksize, blocksize);
2254 if (!err)
2255 set_buffer_uptodate(bh);
2256 continue;
2257 }
2258 /*
2259 * get_block() might have updated the buffer
2260 * synchronously
2261 */
2262 if (buffer_uptodate(bh))
2263 continue;
2264 }
2265 arr[nr++] = bh;
2266 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2267
2268 if (fully_mapped)
2269 SetPageMappedToDisk(page);
2270
2271 if (!nr) {
2272 /*
2273 * All buffers are uptodate - we can set the page uptodate
2274 * as well. But not if get_block() returned an error.
2275 */
2276 if (!PageError(page))
2277 SetPageUptodate(page);
2278 unlock_page(page);
2279 return 0;
2280 }
2281
2282 /* Stage two: lock the buffers */
2283 for (i = 0; i < nr; i++) {
2284 bh = arr[i];
2285 lock_buffer(bh);
2286 mark_buffer_async_read(bh);
2287 }
2288
2289 /*
2290 * Stage 3: start the IO. Check for uptodateness
2291 * inside the buffer lock in case another process reading
2292 * the underlying blockdev brought it uptodate (the sct fix).
2293 */
2294 for (i = 0; i < nr; i++) {
2295 bh = arr[i];
2296 if (buffer_uptodate(bh))
2297 end_buffer_async_read(bh, 1);
2298 else
2299 submit_bh(REQ_OP_READ, 0, bh);
2300 }
2301 return 0;
2302}
2303EXPORT_SYMBOL(block_read_full_page);
2304
2305/* utility function for filesystems that need to do work on expanding
2306 * truncates. Uses filesystem pagecache writes to allow the filesystem to
2307 * deal with the hole.
2308 */
2309int generic_cont_expand_simple(struct inode *inode, loff_t size)
2310{
2311 struct address_space *mapping = inode->i_mapping;
2312 struct page *page;
2313 void *fsdata;
2314 int err;
2315
2316 err = inode_newsize_ok(inode, size);
2317 if (err)
2318 goto out;
2319
2320 err = pagecache_write_begin(NULL, mapping, size, 0,
2321 AOP_FLAG_CONT_EXPAND, &page, &fsdata);
2322 if (err)
2323 goto out;
2324
2325 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2326 BUG_ON(err > 0);
2327
2328out:
2329 return err;
2330}
2331EXPORT_SYMBOL(generic_cont_expand_simple);
2332
2333static int cont_expand_zero(struct file *file, struct address_space *mapping,
2334 loff_t pos, loff_t *bytes)
2335{
2336 struct inode *inode = mapping->host;
2337 unsigned int blocksize = i_blocksize(inode);
2338 struct page *page;
2339 void *fsdata;
2340 pgoff_t index, curidx;
2341 loff_t curpos;
2342 unsigned zerofrom, offset, len;
2343 int err = 0;
2344
2345 index = pos >> PAGE_SHIFT;
2346 offset = pos & ~PAGE_MASK;
2347
2348 while (index > (curidx = (curpos = *bytes)>>PAGE_SHIFT)) {
2349 zerofrom = curpos & ~PAGE_MASK;
2350 if (zerofrom & (blocksize-1)) {
2351 *bytes |= (blocksize-1);
2352 (*bytes)++;
2353 }
2354 len = PAGE_SIZE - zerofrom;
2355
2356 err = pagecache_write_begin(file, mapping, curpos, len, 0,
2357 &page, &fsdata);
2358 if (err)
2359 goto out;
2360 zero_user(page, zerofrom, len);
2361 err = pagecache_write_end(file, mapping, curpos, len, len,
2362 page, fsdata);
2363 if (err < 0)
2364 goto out;
2365 BUG_ON(err != len);
2366 err = 0;
2367
2368 balance_dirty_pages_ratelimited(mapping);
2369
2370 if (fatal_signal_pending(current)) {
2371 err = -EINTR;
2372 goto out;
2373 }
2374 }
2375
2376 /* page covers the boundary, find the boundary offset */
2377 if (index == curidx) {
2378 zerofrom = curpos & ~PAGE_MASK;
2379 /* if we will expand the thing last block will be filled */
2380 if (offset <= zerofrom) {
2381 goto out;
2382 }
2383 if (zerofrom & (blocksize-1)) {
2384 *bytes |= (blocksize-1);
2385 (*bytes)++;
2386 }
2387 len = offset - zerofrom;
2388
2389 err = pagecache_write_begin(file, mapping, curpos, len, 0,
2390 &page, &fsdata);
2391 if (err)
2392 goto out;
2393 zero_user(page, zerofrom, len);
2394 err = pagecache_write_end(file, mapping, curpos, len, len,
2395 page, fsdata);
2396 if (err < 0)
2397 goto out;
2398 BUG_ON(err != len);
2399 err = 0;
2400 }
2401out:
2402 return err;
2403}
2404
2405/*
2406 * For moronic filesystems that do not allow holes in file.
2407 * We may have to extend the file.
2408 */
2409int cont_write_begin(struct file *file, struct address_space *mapping,
2410 loff_t pos, unsigned len, unsigned flags,
2411 struct page **pagep, void **fsdata,
2412 get_block_t *get_block, loff_t *bytes)
2413{
2414 struct inode *inode = mapping->host;
2415 unsigned int blocksize = i_blocksize(inode);
2416 unsigned int zerofrom;
2417 int err;
2418
2419 err = cont_expand_zero(file, mapping, pos, bytes);
2420 if (err)
2421 return err;
2422
2423 zerofrom = *bytes & ~PAGE_MASK;
2424 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2425 *bytes |= (blocksize-1);
2426 (*bytes)++;
2427 }
2428
2429 return block_write_begin(mapping, pos, len, flags, pagep, get_block);
2430}
2431EXPORT_SYMBOL(cont_write_begin);
2432
2433int block_commit_write(struct page *page, unsigned from, unsigned to)
2434{
2435 struct inode *inode = page->mapping->host;
2436 __block_commit_write(inode,page,from,to);
2437 return 0;
2438}
2439EXPORT_SYMBOL(block_commit_write);
2440
2441/*
2442 * block_page_mkwrite() is not allowed to change the file size as it gets
2443 * called from a page fault handler when a page is first dirtied. Hence we must
2444 * be careful to check for EOF conditions here. We set the page up correctly
2445 * for a written page which means we get ENOSPC checking when writing into
2446 * holes and correct delalloc and unwritten extent mapping on filesystems that
2447 * support these features.
2448 *
2449 * We are not allowed to take the i_mutex here so we have to play games to
2450 * protect against truncate races as the page could now be beyond EOF. Because
2451 * truncate writes the inode size before removing pages, once we have the
2452 * page lock we can determine safely if the page is beyond EOF. If it is not
2453 * beyond EOF, then the page is guaranteed safe against truncation until we
2454 * unlock the page.
2455 *
2456 * Direct callers of this function should protect against filesystem freezing
2457 * using sb_start_pagefault() - sb_end_pagefault() functions.
2458 */
2459int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2460 get_block_t get_block)
2461{
2462 struct page *page = vmf->page;
2463 struct inode *inode = file_inode(vma->vm_file);
2464 unsigned long end;
2465 loff_t size;
2466 int ret;
2467
2468 lock_page(page);
2469 size = i_size_read(inode);
2470 if ((page->mapping != inode->i_mapping) ||
2471 (page_offset(page) > size)) {
2472 /* We overload EFAULT to mean page got truncated */
2473 ret = -EFAULT;
2474 goto out_unlock;
2475 }
2476
2477 /* page is wholly or partially inside EOF */
2478 if (((page->index + 1) << PAGE_SHIFT) > size)
2479 end = size & ~PAGE_MASK;
2480 else
2481 end = PAGE_SIZE;
2482
2483 ret = __block_write_begin(page, 0, end, get_block);
2484 if (!ret)
2485 ret = block_commit_write(page, 0, end);
2486
2487 if (unlikely(ret < 0))
2488 goto out_unlock;
2489 set_page_dirty(page);
2490 wait_for_stable_page(page);
2491 return 0;
2492out_unlock:
2493 unlock_page(page);
2494 return ret;
2495}
2496EXPORT_SYMBOL(block_page_mkwrite);
2497
2498/*
2499 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
2500 * immediately, while under the page lock. So it needs a special end_io
2501 * handler which does not touch the bh after unlocking it.
2502 */
2503static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2504{
2505 __end_buffer_read_notouch(bh, uptodate);
2506}
2507
2508/*
2509 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2510 * the page (converting it to circular linked list and taking care of page
2511 * dirty races).
2512 */
2513static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2514{
2515 struct buffer_head *bh;
2516
2517 BUG_ON(!PageLocked(page));
2518
2519 spin_lock(&page->mapping->private_lock);
2520 bh = head;
2521 do {
2522 if (PageDirty(page))
2523 set_buffer_dirty(bh);
2524 if (!bh->b_this_page)
2525 bh->b_this_page = head;
2526 bh = bh->b_this_page;
2527 } while (bh != head);
2528 attach_page_buffers(page, head);
2529 spin_unlock(&page->mapping->private_lock);
2530}
2531
2532/*
2533 * On entry, the page is fully not uptodate.
2534 * On exit the page is fully uptodate in the areas outside (from,to)
2535 * The filesystem needs to handle block truncation upon failure.
2536 */
2537int nobh_write_begin(struct address_space *mapping,
2538 loff_t pos, unsigned len, unsigned flags,
2539 struct page **pagep, void **fsdata,
2540 get_block_t *get_block)
2541{
2542 struct inode *inode = mapping->host;
2543 const unsigned blkbits = inode->i_blkbits;
2544 const unsigned blocksize = 1 << blkbits;
2545 struct buffer_head *head, *bh;
2546 struct page *page;
2547 pgoff_t index;
2548 unsigned from, to;
2549 unsigned block_in_page;
2550 unsigned block_start, block_end;
2551 sector_t block_in_file;
2552 int nr_reads = 0;
2553 int ret = 0;
2554 int is_mapped_to_disk = 1;
2555
2556 index = pos >> PAGE_SHIFT;
2557 from = pos & (PAGE_SIZE - 1);
2558 to = from + len;
2559
2560 page = grab_cache_page_write_begin(mapping, index, flags);
2561 if (!page)
2562 return -ENOMEM;
2563 *pagep = page;
2564 *fsdata = NULL;
2565
2566 if (page_has_buffers(page)) {
2567 ret = __block_write_begin(page, pos, len, get_block);
2568 if (unlikely(ret))
2569 goto out_release;
2570 return ret;
2571 }
2572
2573 if (PageMappedToDisk(page))
2574 return 0;
2575
2576 /*
2577 * Allocate buffers so that we can keep track of state, and potentially
2578 * attach them to the page if an error occurs. In the common case of
2579 * no error, they will just be freed again without ever being attached
2580 * to the page (which is all OK, because we're under the page lock).
2581 *
2582 * Be careful: the buffer linked list is a NULL terminated one, rather
2583 * than the circular one we're used to.
2584 */
2585 head = alloc_page_buffers(page, blocksize, false);
2586 if (!head) {
2587 ret = -ENOMEM;
2588 goto out_release;
2589 }
2590
2591 block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
2592
2593 /*
2594 * We loop across all blocks in the page, whether or not they are
2595 * part of the affected region. This is so we can discover if the
2596 * page is fully mapped-to-disk.
2597 */
2598 for (block_start = 0, block_in_page = 0, bh = head;
2599 block_start < PAGE_SIZE;
2600 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
2601 int create;
2602
2603 block_end = block_start + blocksize;
2604 bh->b_state = 0;
2605 create = 1;
2606 if (block_start >= to)
2607 create = 0;
2608 ret = get_block(inode, block_in_file + block_in_page,
2609 bh, create);
2610 if (ret)
2611 goto failed;
2612 if (!buffer_mapped(bh))
2613 is_mapped_to_disk = 0;
2614 if (buffer_new(bh))
2615 clean_bdev_bh_alias(bh);
2616 if (PageUptodate(page)) {
2617 set_buffer_uptodate(bh);
2618 continue;
2619 }
2620 if (buffer_new(bh) || !buffer_mapped(bh)) {
2621 zero_user_segments(page, block_start, from,
2622 to, block_end);
2623 continue;
2624 }
2625 if (buffer_uptodate(bh))
2626 continue; /* reiserfs does this */
2627 if (block_start < from || block_end > to) {
2628 lock_buffer(bh);
2629 bh->b_end_io = end_buffer_read_nobh;
2630 submit_bh(REQ_OP_READ, 0, bh);
2631 nr_reads++;
2632 }
2633 }
2634
2635 if (nr_reads) {
2636 /*
2637 * The page is locked, so these buffers are protected from
2638 * any VM or truncate activity. Hence we don't need to care
2639 * for the buffer_head refcounts.
2640 */
2641 for (bh = head; bh; bh = bh->b_this_page) {
2642 wait_on_buffer(bh);
2643 if (!buffer_uptodate(bh))
2644 ret = -EIO;
2645 }
2646 if (ret)
2647 goto failed;
2648 }
2649
2650 if (is_mapped_to_disk)
2651 SetPageMappedToDisk(page);
2652
2653 *fsdata = head; /* to be released by nobh_write_end */
2654
2655 return 0;
2656
2657failed:
2658 BUG_ON(!ret);
2659 /*
2660 * Error recovery is a bit difficult. We need to zero out blocks that
2661 * were newly allocated, and dirty them to ensure they get written out.
2662 * Buffers need to be attached to the page at this point, otherwise
2663 * the handling of potential IO errors during writeout would be hard
2664 * (could try doing synchronous writeout, but what if that fails too?)
2665 */
2666 attach_nobh_buffers(page, head);
2667 page_zero_new_buffers(page, from, to);
2668
2669out_release:
2670 unlock_page(page);
2671 put_page(page);
2672 *pagep = NULL;
2673
2674 return ret;
2675}
2676EXPORT_SYMBOL(nobh_write_begin);
2677
2678int nobh_write_end(struct file *file, struct address_space *mapping,
2679 loff_t pos, unsigned len, unsigned copied,
2680 struct page *page, void *fsdata)
2681{
2682 struct inode *inode = page->mapping->host;
2683 struct buffer_head *head = fsdata;
2684 struct buffer_head *bh;
2685 BUG_ON(fsdata != NULL && page_has_buffers(page));
2686
2687 if (unlikely(copied < len) && head)
2688 attach_nobh_buffers(page, head);
2689 if (page_has_buffers(page))
2690 return generic_write_end(file, mapping, pos, len,
2691 copied, page, fsdata);
2692
2693 SetPageUptodate(page);
2694 set_page_dirty(page);
2695 if (pos+copied > inode->i_size) {
2696 i_size_write(inode, pos+copied);
2697 mark_inode_dirty(inode);
2698 }
2699
2700 unlock_page(page);
2701 put_page(page);
2702
2703 while (head) {
2704 bh = head;
2705 head = head->b_this_page;
2706 free_buffer_head(bh);
2707 }
2708
2709 return copied;
2710}
2711EXPORT_SYMBOL(nobh_write_end);
2712
2713/*
2714 * nobh_writepage() - based on block_full_write_page() except
2715 * that it tries to operate without attaching bufferheads to
2716 * the page.
2717 */
2718int nobh_writepage(struct page *page, get_block_t *get_block,
2719 struct writeback_control *wbc)
2720{
2721 struct inode * const inode = page->mapping->host;
2722 loff_t i_size = i_size_read(inode);
2723 const pgoff_t end_index = i_size >> PAGE_SHIFT;
2724 unsigned offset;
2725 int ret;
2726
2727 /* Is the page fully inside i_size? */
2728 if (page->index < end_index)
2729 goto out;
2730
2731 /* Is the page fully outside i_size? (truncate in progress) */
2732 offset = i_size & (PAGE_SIZE-1);
2733 if (page->index >= end_index+1 || !offset) {
2734 /*
2735 * The page may have dirty, unmapped buffers. For example,
2736 * they may have been added in ext3_writepage(). Make them
2737 * freeable here, so the page does not leak.
2738 */
2739#if 0
2740 /* Not really sure about this - do we need this ? */
2741 if (page->mapping->a_ops->invalidatepage)
2742 page->mapping->a_ops->invalidatepage(page, offset);
2743#endif
2744 unlock_page(page);
2745 return 0; /* don't care */
2746 }
2747
2748 /*
2749 * The page straddles i_size. It must be zeroed out on each and every
2750 * writepage invocation because it may be mmapped. "A file is mapped
2751 * in multiples of the page size. For a file that is not a multiple of
2752 * the page size, the remaining memory is zeroed when mapped, and
2753 * writes to that region are not written out to the file."
2754 */
2755 zero_user_segment(page, offset, PAGE_SIZE);
2756out:
2757 ret = mpage_writepage(page, get_block, wbc);
2758 if (ret == -EAGAIN)
2759 ret = __block_write_full_page(inode, page, get_block, wbc,
2760 end_buffer_async_write);
2761 return ret;
2762}
2763EXPORT_SYMBOL(nobh_writepage);
2764
2765int nobh_truncate_page(struct address_space *mapping,
2766 loff_t from, get_block_t *get_block)
2767{
2768 pgoff_t index = from >> PAGE_SHIFT;
2769 unsigned offset = from & (PAGE_SIZE-1);
2770 unsigned blocksize;
2771 sector_t iblock;
2772 unsigned length, pos;
2773 struct inode *inode = mapping->host;
2774 struct page *page;
2775 struct buffer_head map_bh;
2776 int err;
2777
2778 blocksize = i_blocksize(inode);
2779 length = offset & (blocksize - 1);
2780
2781 /* Block boundary? Nothing to do */
2782 if (!length)
2783 return 0;
2784
2785 length = blocksize - length;
2786 iblock = (sector_t)index << (PAGE_SHIFT - inode->i_blkbits);
2787
2788 page = grab_cache_page(mapping, index);
2789 err = -ENOMEM;
2790 if (!page)
2791 goto out;
2792
2793 if (page_has_buffers(page)) {
2794has_buffers:
2795 unlock_page(page);
2796 put_page(page);
2797 return block_truncate_page(mapping, from, get_block);
2798 }
2799
2800 /* Find the buffer that contains "offset" */
2801 pos = blocksize;
2802 while (offset >= pos) {
2803 iblock++;
2804 pos += blocksize;
2805 }
2806
2807 map_bh.b_size = blocksize;
2808 map_bh.b_state = 0;
2809 err = get_block(inode, iblock, &map_bh, 0);
2810 if (err)
2811 goto unlock;
2812 /* unmapped? It's a hole - nothing to do */
2813 if (!buffer_mapped(&map_bh))
2814 goto unlock;
2815
2816 /* Ok, it's mapped. Make sure it's up-to-date */
2817 if (!PageUptodate(page)) {
2818 err = mapping->a_ops->readpage(NULL, page);
2819 if (err) {
2820 put_page(page);
2821 goto out;
2822 }
2823 lock_page(page);
2824 if (!PageUptodate(page)) {
2825 err = -EIO;
2826 goto unlock;
2827 }
2828 if (page_has_buffers(page))
2829 goto has_buffers;
2830 }
2831 zero_user(page, offset, length);
2832 set_page_dirty(page);
2833 err = 0;
2834
2835unlock:
2836 unlock_page(page);
2837 put_page(page);
2838out:
2839 return err;
2840}
2841EXPORT_SYMBOL(nobh_truncate_page);
2842
2843int block_truncate_page(struct address_space *mapping,
2844 loff_t from, get_block_t *get_block)
2845{
2846 pgoff_t index = from >> PAGE_SHIFT;
2847 unsigned offset = from & (PAGE_SIZE-1);
2848 unsigned blocksize;
2849 sector_t iblock;
2850 unsigned length, pos;
2851 struct inode *inode = mapping->host;
2852 struct page *page;
2853 struct buffer_head *bh;
2854 int err;
2855
2856 blocksize = i_blocksize(inode);
2857 length = offset & (blocksize - 1);
2858
2859 /* Block boundary? Nothing to do */
2860 if (!length)
2861 return 0;
2862
2863 length = blocksize - length;
2864 iblock = (sector_t)index << (PAGE_SHIFT - inode->i_blkbits);
2865
2866 page = grab_cache_page(mapping, index);
2867 err = -ENOMEM;
2868 if (!page)
2869 goto out;
2870
2871 if (!page_has_buffers(page))
2872 create_empty_buffers(page, blocksize, 0);
2873
2874 /* Find the buffer that contains "offset" */
2875 bh = page_buffers(page);
2876 pos = blocksize;
2877 while (offset >= pos) {
2878 bh = bh->b_this_page;
2879 iblock++;
2880 pos += blocksize;
2881 }
2882
2883 err = 0;
2884 if (!buffer_mapped(bh)) {
2885 WARN_ON(bh->b_size != blocksize);
2886 err = get_block(inode, iblock, bh, 0);
2887 if (err)
2888 goto unlock;
2889 /* unmapped? It's a hole - nothing to do */
2890 if (!buffer_mapped(bh))
2891 goto unlock;
2892 }
2893
2894 /* Ok, it's mapped. Make sure it's up-to-date */
2895 if (PageUptodate(page))
2896 set_buffer_uptodate(bh);
2897
2898 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
2899 err = -EIO;
2900 ll_rw_block(REQ_OP_READ, 0, 1, &bh);
2901 wait_on_buffer(bh);
2902 /* Uhhuh. Read error. Complain and punt. */
2903 if (!buffer_uptodate(bh))
2904 goto unlock;
2905 }
2906
2907 zero_user(page, offset, length);
2908 mark_buffer_dirty(bh);
2909 err = 0;
2910
2911unlock:
2912 unlock_page(page);
2913 put_page(page);
2914out:
2915 return err;
2916}
2917EXPORT_SYMBOL(block_truncate_page);
2918
2919/*
2920 * The generic ->writepage function for buffer-backed address_spaces
2921 */
2922int block_write_full_page(struct page *page, get_block_t *get_block,
2923 struct writeback_control *wbc)
2924{
2925 struct inode * const inode = page->mapping->host;
2926 loff_t i_size = i_size_read(inode);
2927 const pgoff_t end_index = i_size >> PAGE_SHIFT;
2928 unsigned offset;
2929
2930 /* Is the page fully inside i_size? */
2931 if (page->index < end_index)
2932 return __block_write_full_page(inode, page, get_block, wbc,
2933 end_buffer_async_write);
2934
2935 /* Is the page fully outside i_size? (truncate in progress) */
2936 offset = i_size & (PAGE_SIZE-1);
2937 if (page->index >= end_index+1 || !offset) {
2938 /*
2939 * The page may have dirty, unmapped buffers. For example,
2940 * they may have been added in ext3_writepage(). Make them
2941 * freeable here, so the page does not leak.
2942 */
2943 do_invalidatepage(page, 0, PAGE_SIZE);
2944 unlock_page(page);
2945 return 0; /* don't care */
2946 }
2947
2948 /*
2949 * The page straddles i_size. It must be zeroed out on each and every
2950 * writepage invocation because it may be mmapped. "A file is mapped
2951 * in multiples of the page size. For a file that is not a multiple of
2952 * the page size, the remaining memory is zeroed when mapped, and
2953 * writes to that region are not written out to the file."
2954 */
2955 zero_user_segment(page, offset, PAGE_SIZE);
2956 return __block_write_full_page(inode, page, get_block, wbc,
2957 end_buffer_async_write);
2958}
2959EXPORT_SYMBOL(block_write_full_page);
2960
2961sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2962 get_block_t *get_block)
2963{
2964 struct inode *inode = mapping->host;
2965 struct buffer_head tmp = {
2966 .b_size = i_blocksize(inode),
2967 };
2968
2969 get_block(inode, block, &tmp, 0);
2970 return tmp.b_blocknr;
2971}
2972EXPORT_SYMBOL(generic_block_bmap);
2973
2974static void end_bio_bh_io_sync(struct bio *bio)
2975{
2976 struct buffer_head *bh = bio->bi_private;
2977
2978 if (unlikely(bio_flagged(bio, BIO_QUIET)))
2979 set_bit(BH_Quiet, &bh->b_state);
2980
2981 bh->b_end_io(bh, !bio->bi_status);
2982 bio_put(bio);
2983}
2984
2985/*
2986 * This allows us to do IO even on the odd last sectors
2987 * of a device, even if the block size is some multiple
2988 * of the physical sector size.
2989 *
2990 * We'll just truncate the bio to the size of the device,
2991 * and clear the end of the buffer head manually.
2992 *
2993 * Truly out-of-range accesses will turn into actual IO
2994 * errors, this only handles the "we need to be able to
2995 * do IO at the final sector" case.
2996 */
2997void guard_bio_eod(int op, struct bio *bio)
2998{
2999 sector_t maxsector;
3000 struct bio_vec *bvec = bio_last_bvec_all(bio);
3001 unsigned truncated_bytes;
3002 struct hd_struct *part;
3003
3004 rcu_read_lock();
3005 part = __disk_get_part(bio->bi_disk, bio->bi_partno);
3006 if (part)
3007 maxsector = part_nr_sects_read(part);
3008 else
3009 maxsector = get_capacity(bio->bi_disk);
3010 rcu_read_unlock();
3011
3012 if (!maxsector)
3013 return;
3014
3015 /*
3016 * If the *whole* IO is past the end of the device,
3017 * let it through, and the IO layer will turn it into
3018 * an EIO.
3019 */
3020 if (unlikely(bio->bi_iter.bi_sector >= maxsector))
3021 return;
3022
3023 maxsector -= bio->bi_iter.bi_sector;
3024 if (likely((bio->bi_iter.bi_size >> 9) <= maxsector))
3025 return;
3026
3027 /* Uhhuh. We've got a bio that straddles the device size! */
3028 truncated_bytes = bio->bi_iter.bi_size - (maxsector << 9);
3029
3030 /*
3031 * The bio contains more than one segment which spans EOD, just return
3032 * and let IO layer turn it into an EIO
3033 */
3034 if (truncated_bytes > bvec->bv_len)
3035 return;
3036
3037 /* Truncate the bio.. */
3038 bio->bi_iter.bi_size -= truncated_bytes;
3039 bvec->bv_len -= truncated_bytes;
3040
3041 /* ..and clear the end of the buffer for reads */
3042 if (op == REQ_OP_READ) {
3043 struct bio_vec bv;
3044
3045 mp_bvec_last_segment(bvec, &bv);
3046 zero_user(bv.bv_page, bv.bv_offset + bv.bv_len,
3047 truncated_bytes);
3048 }
3049}
3050
3051static int submit_bh_wbc(int op, int op_flags, struct buffer_head *bh,
3052 enum rw_hint write_hint, struct writeback_control *wbc)
3053{
3054 struct bio *bio;
3055
3056 BUG_ON(!buffer_locked(bh));
3057 BUG_ON(!buffer_mapped(bh));
3058 BUG_ON(!bh->b_end_io);
3059 BUG_ON(buffer_delay(bh));
3060 BUG_ON(buffer_unwritten(bh));
3061
3062 /*
3063 * Only clear out a write error when rewriting
3064 */
3065 if (test_set_buffer_req(bh) && (op == REQ_OP_WRITE))
3066 clear_buffer_write_io_error(bh);
3067
3068 /*
3069 * from here on down, it's all bio -- do the initial mapping,
3070 * submit_bio -> generic_make_request may further map this bio around
3071 */
3072 bio = bio_alloc(GFP_NOIO, 1);
3073
3074 bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
3075 bio_set_dev(bio, bh->b_bdev);
3076 bio->bi_write_hint = write_hint;
3077
3078 bio_add_page(bio, bh->b_page, bh->b_size, bh_offset(bh));
3079 BUG_ON(bio->bi_iter.bi_size != bh->b_size);
3080
3081 bio->bi_end_io = end_bio_bh_io_sync;
3082 bio->bi_private = bh;
3083
3084 /* Take care of bh's that straddle the end of the device */
3085 guard_bio_eod(op, bio);
3086
3087 if (buffer_meta(bh))
3088 op_flags |= REQ_META;
3089 if (buffer_prio(bh))
3090 op_flags |= REQ_PRIO;
3091 bio_set_op_attrs(bio, op, op_flags);
3092
3093 if (wbc) {
3094 wbc_init_bio(wbc, bio);
3095 wbc_account_io(wbc, bh->b_page, bh->b_size);
3096 }
3097
3098 submit_bio(bio);
3099 return 0;
3100}
3101
3102int submit_bh(int op, int op_flags, struct buffer_head *bh)
3103{
3104 return submit_bh_wbc(op, op_flags, bh, 0, NULL);
3105}
3106EXPORT_SYMBOL(submit_bh);
3107
3108/**
3109 * ll_rw_block: low-level access to block devices (DEPRECATED)
3110 * @op: whether to %READ or %WRITE
3111 * @op_flags: req_flag_bits
3112 * @nr: number of &struct buffer_heads in the array
3113 * @bhs: array of pointers to &struct buffer_head
3114 *
3115 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
3116 * requests an I/O operation on them, either a %REQ_OP_READ or a %REQ_OP_WRITE.
3117 * @op_flags contains flags modifying the detailed I/O behavior, most notably
3118 * %REQ_RAHEAD.
3119 *
3120 * This function drops any buffer that it cannot get a lock on (with the
3121 * BH_Lock state bit), any buffer that appears to be clean when doing a write
3122 * request, and any buffer that appears to be up-to-date when doing read
3123 * request. Further it marks as clean buffers that are processed for
3124 * writing (the buffer cache won't assume that they are actually clean
3125 * until the buffer gets unlocked).
3126 *
3127 * ll_rw_block sets b_end_io to simple completion handler that marks
3128 * the buffer up-to-date (if appropriate), unlocks the buffer and wakes
3129 * any waiters.
3130 *
3131 * All of the buffers must be for the same device, and must also be a
3132 * multiple of the current approved size for the device.
3133 */
3134void ll_rw_block(int op, int op_flags, int nr, struct buffer_head *bhs[])
3135{
3136 int i;
3137
3138 for (i = 0; i < nr; i++) {
3139 struct buffer_head *bh = bhs[i];
3140
3141 if (!trylock_buffer(bh))
3142 continue;
3143 if (op == WRITE) {
3144 if (test_clear_buffer_dirty(bh)) {
3145 bh->b_end_io = end_buffer_write_sync;
3146 get_bh(bh);
3147 submit_bh(op, op_flags, bh);
3148 continue;
3149 }
3150 } else {
3151 if (!buffer_uptodate(bh)) {
3152 bh->b_end_io = end_buffer_read_sync;
3153 get_bh(bh);
3154 submit_bh(op, op_flags, bh);
3155 continue;
3156 }
3157 }
3158 unlock_buffer(bh);
3159 }
3160}
3161EXPORT_SYMBOL(ll_rw_block);
3162
3163void write_dirty_buffer(struct buffer_head *bh, int op_flags)
3164{
3165 lock_buffer(bh);
3166 if (!test_clear_buffer_dirty(bh)) {
3167 unlock_buffer(bh);
3168 return;
3169 }
3170 bh->b_end_io = end_buffer_write_sync;
3171 get_bh(bh);
3172 submit_bh(REQ_OP_WRITE, op_flags, bh);
3173}
3174EXPORT_SYMBOL(write_dirty_buffer);
3175
3176/*
3177 * For a data-integrity writeout, we need to wait upon any in-progress I/O
3178 * and then start new I/O and then wait upon it. The caller must have a ref on
3179 * the buffer_head.
3180 */
3181int __sync_dirty_buffer(struct buffer_head *bh, int op_flags)
3182{
3183 int ret = 0;
3184
3185 WARN_ON(atomic_read(&bh->b_count) < 1);
3186 lock_buffer(bh);
3187 if (test_clear_buffer_dirty(bh)) {
3188 get_bh(bh);
3189 bh->b_end_io = end_buffer_write_sync;
3190 ret = submit_bh(REQ_OP_WRITE, op_flags, bh);
3191 wait_on_buffer(bh);
3192 if (!ret && !buffer_uptodate(bh))
3193 ret = -EIO;
3194 } else {
3195 unlock_buffer(bh);
3196 }
3197 return ret;
3198}
3199EXPORT_SYMBOL(__sync_dirty_buffer);
3200
3201int sync_dirty_buffer(struct buffer_head *bh)
3202{
3203 return __sync_dirty_buffer(bh, REQ_SYNC);
3204}
3205EXPORT_SYMBOL(sync_dirty_buffer);
3206
3207/*
3208 * try_to_free_buffers() checks if all the buffers on this particular page
3209 * are unused, and releases them if so.
3210 *
3211 * Exclusion against try_to_free_buffers may be obtained by either
3212 * locking the page or by holding its mapping's private_lock.
3213 *
3214 * If the page is dirty but all the buffers are clean then we need to
3215 * be sure to mark the page clean as well. This is because the page
3216 * may be against a block device, and a later reattachment of buffers
3217 * to a dirty page will set *all* buffers dirty. Which would corrupt
3218 * filesystem data on the same device.
3219 *
3220 * The same applies to regular filesystem pages: if all the buffers are
3221 * clean then we set the page clean and proceed. To do that, we require
3222 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3223 * private_lock.
3224 *
3225 * try_to_free_buffers() is non-blocking.
3226 */
3227static inline int buffer_busy(struct buffer_head *bh)
3228{
3229 return atomic_read(&bh->b_count) |
3230 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3231}
3232
3233static int
3234drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3235{
3236 struct buffer_head *head = page_buffers(page);
3237 struct buffer_head *bh;
3238
3239 bh = head;
3240 do {
3241 if (buffer_busy(bh))
3242 goto failed;
3243 bh = bh->b_this_page;
3244 } while (bh != head);
3245
3246 do {
3247 struct buffer_head *next = bh->b_this_page;
3248
3249 if (bh->b_assoc_map)
3250 __remove_assoc_queue(bh);
3251 bh = next;
3252 } while (bh != head);
3253 *buffers_to_free = head;
3254 __clear_page_buffers(page);
3255 return 1;
3256failed:
3257 return 0;
3258}
3259
3260int try_to_free_buffers(struct page *page)
3261{
3262 struct address_space * const mapping = page->mapping;
3263 struct buffer_head *buffers_to_free = NULL;
3264 int ret = 0;
3265
3266 BUG_ON(!PageLocked(page));
3267 if (PageWriteback(page))
3268 return 0;
3269
3270 if (mapping == NULL) { /* can this still happen? */
3271 ret = drop_buffers(page, &buffers_to_free);
3272 goto out;
3273 }
3274
3275 spin_lock(&mapping->private_lock);
3276 ret = drop_buffers(page, &buffers_to_free);
3277
3278 /*
3279 * If the filesystem writes its buffers by hand (eg ext3)
3280 * then we can have clean buffers against a dirty page. We
3281 * clean the page here; otherwise the VM will never notice
3282 * that the filesystem did any IO at all.
3283 *
3284 * Also, during truncate, discard_buffer will have marked all
3285 * the page's buffers clean. We discover that here and clean
3286 * the page also.
3287 *
3288 * private_lock must be held over this entire operation in order
3289 * to synchronise against __set_page_dirty_buffers and prevent the
3290 * dirty bit from being lost.
3291 */
3292 if (ret)
3293 cancel_dirty_page(page);
3294 spin_unlock(&mapping->private_lock);
3295out:
3296 if (buffers_to_free) {
3297 struct buffer_head *bh = buffers_to_free;
3298
3299 do {
3300 struct buffer_head *next = bh->b_this_page;
3301 free_buffer_head(bh);
3302 bh = next;
3303 } while (bh != buffers_to_free);
3304 }
3305 return ret;
3306}
3307EXPORT_SYMBOL(try_to_free_buffers);
3308
3309/*
3310 * There are no bdflush tunables left. But distributions are
3311 * still running obsolete flush daemons, so we terminate them here.
3312 *
3313 * Use of bdflush() is deprecated and will be removed in a future kernel.
3314 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
3315 */
3316SYSCALL_DEFINE2(bdflush, int, func, long, data)
3317{
3318 static int msg_count;
3319
3320 if (!capable(CAP_SYS_ADMIN))
3321 return -EPERM;
3322
3323 if (msg_count < 5) {
3324 msg_count++;
3325 printk(KERN_INFO
3326 "warning: process `%s' used the obsolete bdflush"
3327 " system call\n", current->comm);
3328 printk(KERN_INFO "Fix your initscripts?\n");
3329 }
3330
3331 if (func == 1)
3332 do_exit(0);
3333 return 0;
3334}
3335
3336/*
3337 * Buffer-head allocation
3338 */
3339static struct kmem_cache *bh_cachep __read_mostly;
3340
3341/*
3342 * Once the number of bh's in the machine exceeds this level, we start
3343 * stripping them in writeback.
3344 */
3345static unsigned long max_buffer_heads;
3346
3347int buffer_heads_over_limit;
3348
3349struct bh_accounting {
3350 int nr; /* Number of live bh's */
3351 int ratelimit; /* Limit cacheline bouncing */
3352};
3353
3354static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3355
3356static void recalc_bh_state(void)
3357{
3358 int i;
3359 int tot = 0;
3360
3361 if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
3362 return;
3363