blob: 1a30db77af3257505eae9706db2c366146666751 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/fs/buffer.c
3 *
4 * Copyright (C) 1991, 1992, 2002 Linus Torvalds
5 */
6
7/*
8 * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95
9 *
10 * Removed a lot of unnecessary code and simplified things now that
11 * the buffer cache isn't our primary cache - Andrew Tridgell 12/96
12 *
13 * Speed up hash, lru, and free list operations. Use gfp() for allocating
14 * hash table, use SLAB cache for buffer heads. SMP threading. -DaveM
15 *
16 * Added 32k buffer block sizes - these are required older ARM systems. - RMK
17 *
18 * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de>
19 */
20
Linus Torvalds1da177e2005-04-16 15:20:36 -070021#include <linux/kernel.h>
22#include <linux/syscalls.h>
23#include <linux/fs.h>
24#include <linux/mm.h>
25#include <linux/percpu.h>
26#include <linux/slab.h>
Randy Dunlap16f7e0f2006-01-11 12:17:46 -080027#include <linux/capability.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070028#include <linux/blkdev.h>
29#include <linux/file.h>
30#include <linux/quotaops.h>
31#include <linux/highmem.h>
32#include <linux/module.h>
33#include <linux/writeback.h>
34#include <linux/hash.h>
35#include <linux/suspend.h>
36#include <linux/buffer_head.h>
Andrew Morton55e829a2006-12-10 02:19:27 -080037#include <linux/task_io_accounting_ops.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070038#include <linux/bio.h>
39#include <linux/notifier.h>
40#include <linux/cpu.h>
41#include <linux/bitops.h>
42#include <linux/mpage.h>
Ingo Molnarfb1c8f92005-09-10 00:25:56 -070043#include <linux/bit_spinlock.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070044
45static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
Linus Torvalds1da177e2005-04-16 15:20:36 -070046
47#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
48
49inline void
50init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
51{
52 bh->b_end_io = handler;
53 bh->b_private = private;
54}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -070055EXPORT_SYMBOL(init_buffer);
Linus Torvalds1da177e2005-04-16 15:20:36 -070056
Jens Axboe7eaceac2011-03-10 08:52:07 +010057static int sleep_on_buffer(void *word)
Linus Torvalds1da177e2005-04-16 15:20:36 -070058{
Linus Torvalds1da177e2005-04-16 15:20:36 -070059 io_schedule();
60 return 0;
61}
62
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -080063void __lock_buffer(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -070064{
Jens Axboe7eaceac2011-03-10 08:52:07 +010065 wait_on_bit_lock(&bh->b_state, BH_Lock, sleep_on_buffer,
Linus Torvalds1da177e2005-04-16 15:20:36 -070066 TASK_UNINTERRUPTIBLE);
67}
68EXPORT_SYMBOL(__lock_buffer);
69
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -080070void unlock_buffer(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -070071{
Nick Piggin51b07fc2008-10-18 20:27:00 -070072 clear_bit_unlock(BH_Lock, &bh->b_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -070073 smp_mb__after_clear_bit();
74 wake_up_bit(&bh->b_state, BH_Lock);
75}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -070076EXPORT_SYMBOL(unlock_buffer);
Linus Torvalds1da177e2005-04-16 15:20:36 -070077
78/*
79 * Block until a buffer comes unlocked. This doesn't stop it
80 * from becoming locked again - you have to lock it yourself
81 * if you want to preserve its state.
82 */
83void __wait_on_buffer(struct buffer_head * bh)
84{
Jens Axboe7eaceac2011-03-10 08:52:07 +010085 wait_on_bit(&bh->b_state, BH_Lock, sleep_on_buffer, TASK_UNINTERRUPTIBLE);
Linus Torvalds1da177e2005-04-16 15:20:36 -070086}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -070087EXPORT_SYMBOL(__wait_on_buffer);
Linus Torvalds1da177e2005-04-16 15:20:36 -070088
89static void
90__clear_page_buffers(struct page *page)
91{
92 ClearPagePrivate(page);
Hugh Dickins4c21e2f2005-10-29 18:16:40 -070093 set_page_private(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -070094 page_cache_release(page);
95}
96
Keith Mannthey08bafc02008-11-25 10:24:35 +010097
98static int quiet_error(struct buffer_head *bh)
99{
100 if (!test_bit(BH_Quiet, &bh->b_state) && printk_ratelimit())
101 return 0;
102 return 1;
103}
104
105
Linus Torvalds1da177e2005-04-16 15:20:36 -0700106static void buffer_io_error(struct buffer_head *bh)
107{
108 char b[BDEVNAME_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109 printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
110 bdevname(bh->b_bdev, b),
111 (unsigned long long)bh->b_blocknr);
112}
113
114/*
Dmitry Monakhov68671f32007-10-16 01:24:47 -0700115 * End-of-IO handler helper function which does not touch the bh after
116 * unlocking it.
117 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
118 * a race there is benign: unlock_buffer() only use the bh's address for
119 * hashing after unlocking the buffer, so it doesn't actually touch the bh
120 * itself.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700121 */
Dmitry Monakhov68671f32007-10-16 01:24:47 -0700122static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700123{
124 if (uptodate) {
125 set_buffer_uptodate(bh);
126 } else {
127 /* This happens, due to failed READA attempts. */
128 clear_buffer_uptodate(bh);
129 }
130 unlock_buffer(bh);
Dmitry Monakhov68671f32007-10-16 01:24:47 -0700131}
132
133/*
134 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
135 * unlock the buffer. This is what ll_rw_block uses too.
136 */
137void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
138{
139 __end_buffer_read_notouch(bh, uptodate);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700140 put_bh(bh);
141}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700142EXPORT_SYMBOL(end_buffer_read_sync);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700143
144void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
145{
146 char b[BDEVNAME_SIZE];
147
148 if (uptodate) {
149 set_buffer_uptodate(bh);
150 } else {
Christoph Hellwig0edd55f2010-08-18 05:29:23 -0400151 if (!quiet_error(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700152 buffer_io_error(bh);
153 printk(KERN_WARNING "lost page write due to "
154 "I/O error on %s\n",
155 bdevname(bh->b_bdev, b));
156 }
157 set_buffer_write_io_error(bh);
158 clear_buffer_uptodate(bh);
159 }
160 unlock_buffer(bh);
161 put_bh(bh);
162}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700163EXPORT_SYMBOL(end_buffer_write_sync);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700164
165/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700166 * Various filesystems appear to want __find_get_block to be non-blocking.
167 * But it's the page lock which protects the buffers. To get around this,
168 * we get exclusion from try_to_free_buffers with the blockdev mapping's
169 * private_lock.
170 *
171 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
172 * may be quite high. This code could TryLock the page, and if that
173 * succeeds, there is no need to take private_lock. (But if
174 * private_lock is contended then so is mapping->tree_lock).
175 */
176static struct buffer_head *
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -0800177__find_get_block_slow(struct block_device *bdev, sector_t block)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700178{
179 struct inode *bd_inode = bdev->bd_inode;
180 struct address_space *bd_mapping = bd_inode->i_mapping;
181 struct buffer_head *ret = NULL;
182 pgoff_t index;
183 struct buffer_head *bh;
184 struct buffer_head *head;
185 struct page *page;
186 int all_mapped = 1;
187
188 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
189 page = find_get_page(bd_mapping, index);
190 if (!page)
191 goto out;
192
193 spin_lock(&bd_mapping->private_lock);
194 if (!page_has_buffers(page))
195 goto out_unlock;
196 head = page_buffers(page);
197 bh = head;
198 do {
Nikanth Karthikesan97f76d32009-04-02 16:56:46 -0700199 if (!buffer_mapped(bh))
200 all_mapped = 0;
201 else if (bh->b_blocknr == block) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700202 ret = bh;
203 get_bh(bh);
204 goto out_unlock;
205 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700206 bh = bh->b_this_page;
207 } while (bh != head);
208
209 /* we might be here because some of the buffers on this page are
210 * not mapped. This is due to various races between
211 * file io on the block device and getblk. It gets dealt with
212 * elsewhere, don't buffer_error if we had some unmapped buffers
213 */
214 if (all_mapped) {
Tao Ma72a2ebd2011-10-31 17:09:00 -0700215 char b[BDEVNAME_SIZE];
216
Linus Torvalds1da177e2005-04-16 15:20:36 -0700217 printk("__find_get_block_slow() failed. "
218 "block=%llu, b_blocknr=%llu\n",
Badari Pulavarty205f87f2006-03-26 01:38:00 -0800219 (unsigned long long)block,
220 (unsigned long long)bh->b_blocknr);
221 printk("b_state=0x%08lx, b_size=%zu\n",
222 bh->b_state, bh->b_size);
Tao Ma72a2ebd2011-10-31 17:09:00 -0700223 printk("device %s blocksize: %d\n", bdevname(bdev, b),
224 1 << bd_inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700225 }
226out_unlock:
227 spin_unlock(&bd_mapping->private_lock);
228 page_cache_release(page);
229out:
230 return ret;
231}
232
Linus Torvalds1da177e2005-04-16 15:20:36 -0700233/*
Jens Axboe5b0830c2009-09-23 19:37:09 +0200234 * Kick the writeback threads then try to free up some ZONE_NORMAL memory.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700235 */
236static void free_more_memory(void)
237{
Mel Gorman19770b32008-04-28 02:12:18 -0700238 struct zone *zone;
Mel Gorman0e884602008-04-28 02:12:14 -0700239 int nid;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700240
Curt Wohlgemuth0e175a12011-10-07 21:54:10 -0600241 wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700242 yield();
243
Mel Gorman0e884602008-04-28 02:12:14 -0700244 for_each_online_node(nid) {
Mel Gorman19770b32008-04-28 02:12:18 -0700245 (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS),
246 gfp_zone(GFP_NOFS), NULL,
247 &zone);
248 if (zone)
Mel Gorman54a6eb52008-04-28 02:12:16 -0700249 try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0,
KAMEZAWA Hiroyuki327c0e92009-03-31 15:23:31 -0700250 GFP_NOFS, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700251 }
252}
253
254/*
255 * I/O completion handler for block_read_full_page() - pages
256 * which come unlocked at the end of I/O.
257 */
258static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
259{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700260 unsigned long flags;
Nick Piggina3972202005-07-07 17:56:56 -0700261 struct buffer_head *first;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700262 struct buffer_head *tmp;
263 struct page *page;
264 int page_uptodate = 1;
265
266 BUG_ON(!buffer_async_read(bh));
267
268 page = bh->b_page;
269 if (uptodate) {
270 set_buffer_uptodate(bh);
271 } else {
272 clear_buffer_uptodate(bh);
Keith Mannthey08bafc02008-11-25 10:24:35 +0100273 if (!quiet_error(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700274 buffer_io_error(bh);
275 SetPageError(page);
276 }
277
278 /*
279 * Be _very_ careful from here on. Bad things can happen if
280 * two buffer heads end IO at almost the same time and both
281 * decide that the page is now completely done.
282 */
Nick Piggina3972202005-07-07 17:56:56 -0700283 first = page_buffers(page);
284 local_irq_save(flags);
285 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700286 clear_buffer_async_read(bh);
287 unlock_buffer(bh);
288 tmp = bh;
289 do {
290 if (!buffer_uptodate(tmp))
291 page_uptodate = 0;
292 if (buffer_async_read(tmp)) {
293 BUG_ON(!buffer_locked(tmp));
294 goto still_busy;
295 }
296 tmp = tmp->b_this_page;
297 } while (tmp != bh);
Nick Piggina3972202005-07-07 17:56:56 -0700298 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
299 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700300
301 /*
302 * If none of the buffers had errors and they are all
303 * uptodate then we can set the page uptodate.
304 */
305 if (page_uptodate && !PageError(page))
306 SetPageUptodate(page);
307 unlock_page(page);
308 return;
309
310still_busy:
Nick Piggina3972202005-07-07 17:56:56 -0700311 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
312 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700313 return;
314}
315
316/*
317 * Completion handler for block_write_full_page() - pages which are unlocked
318 * during I/O, and which have PageWriteback cleared upon I/O completion.
319 */
Chris Mason35c80d52009-04-15 13:22:38 -0400320void end_buffer_async_write(struct buffer_head *bh, int uptodate)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700321{
322 char b[BDEVNAME_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700323 unsigned long flags;
Nick Piggina3972202005-07-07 17:56:56 -0700324 struct buffer_head *first;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700325 struct buffer_head *tmp;
326 struct page *page;
327
328 BUG_ON(!buffer_async_write(bh));
329
330 page = bh->b_page;
331 if (uptodate) {
332 set_buffer_uptodate(bh);
333 } else {
Keith Mannthey08bafc02008-11-25 10:24:35 +0100334 if (!quiet_error(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700335 buffer_io_error(bh);
336 printk(KERN_WARNING "lost page write due to "
337 "I/O error on %s\n",
338 bdevname(bh->b_bdev, b));
339 }
340 set_bit(AS_EIO, &page->mapping->flags);
Jan Kara58ff4072006-10-17 00:10:19 -0700341 set_buffer_write_io_error(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700342 clear_buffer_uptodate(bh);
343 SetPageError(page);
344 }
345
Nick Piggina3972202005-07-07 17:56:56 -0700346 first = page_buffers(page);
347 local_irq_save(flags);
348 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
349
Linus Torvalds1da177e2005-04-16 15:20:36 -0700350 clear_buffer_async_write(bh);
351 unlock_buffer(bh);
352 tmp = bh->b_this_page;
353 while (tmp != bh) {
354 if (buffer_async_write(tmp)) {
355 BUG_ON(!buffer_locked(tmp));
356 goto still_busy;
357 }
358 tmp = tmp->b_this_page;
359 }
Nick Piggina3972202005-07-07 17:56:56 -0700360 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
361 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700362 end_page_writeback(page);
363 return;
364
365still_busy:
Nick Piggina3972202005-07-07 17:56:56 -0700366 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
367 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700368 return;
369}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700370EXPORT_SYMBOL(end_buffer_async_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700371
372/*
373 * If a page's buffers are under async readin (end_buffer_async_read
374 * completion) then there is a possibility that another thread of
375 * control could lock one of the buffers after it has completed
376 * but while some of the other buffers have not completed. This
377 * locked buffer would confuse end_buffer_async_read() into not unlocking
378 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
379 * that this buffer is not under async I/O.
380 *
381 * The page comes unlocked when it has no locked buffer_async buffers
382 * left.
383 *
384 * PageLocked prevents anyone starting new async I/O reads any of
385 * the buffers.
386 *
387 * PageWriteback is used to prevent simultaneous writeout of the same
388 * page.
389 *
390 * PageLocked prevents anyone from starting writeback of a page which is
391 * under read I/O (PageWriteback is only ever set against a locked page).
392 */
393static void mark_buffer_async_read(struct buffer_head *bh)
394{
395 bh->b_end_io = end_buffer_async_read;
396 set_buffer_async_read(bh);
397}
398
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700399static void mark_buffer_async_write_endio(struct buffer_head *bh,
400 bh_end_io_t *handler)
Chris Mason35c80d52009-04-15 13:22:38 -0400401{
402 bh->b_end_io = handler;
403 set_buffer_async_write(bh);
404}
405
Linus Torvalds1da177e2005-04-16 15:20:36 -0700406void mark_buffer_async_write(struct buffer_head *bh)
407{
Chris Mason35c80d52009-04-15 13:22:38 -0400408 mark_buffer_async_write_endio(bh, end_buffer_async_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700409}
410EXPORT_SYMBOL(mark_buffer_async_write);
411
412
413/*
414 * fs/buffer.c contains helper functions for buffer-backed address space's
415 * fsync functions. A common requirement for buffer-based filesystems is
416 * that certain data from the backing blockdev needs to be written out for
417 * a successful fsync(). For example, ext2 indirect blocks need to be
418 * written back and waited upon before fsync() returns.
419 *
420 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
421 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
422 * management of a list of dependent buffers at ->i_mapping->private_list.
423 *
424 * Locking is a little subtle: try_to_free_buffers() will remove buffers
425 * from their controlling inode's queue when they are being freed. But
426 * try_to_free_buffers() will be operating against the *blockdev* mapping
427 * at the time, not against the S_ISREG file which depends on those buffers.
428 * So the locking for private_list is via the private_lock in the address_space
429 * which backs the buffers. Which is different from the address_space
430 * against which the buffers are listed. So for a particular address_space,
431 * mapping->private_lock does *not* protect mapping->private_list! In fact,
432 * mapping->private_list will always be protected by the backing blockdev's
433 * ->private_lock.
434 *
435 * Which introduces a requirement: all buffers on an address_space's
436 * ->private_list must be from the same address_space: the blockdev's.
437 *
438 * address_spaces which do not place buffers at ->private_list via these
439 * utility functions are free to use private_lock and private_list for
440 * whatever they want. The only requirement is that list_empty(private_list)
441 * be true at clear_inode() time.
442 *
443 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
444 * filesystems should do that. invalidate_inode_buffers() should just go
445 * BUG_ON(!list_empty).
446 *
447 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
448 * take an address_space, not an inode. And it should be called
449 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
450 * queued up.
451 *
452 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
453 * list if it is already on a list. Because if the buffer is on a list,
454 * it *must* already be on the right one. If not, the filesystem is being
455 * silly. This will save a ton of locking. But first we have to ensure
456 * that buffers are taken *off* the old inode's list when they are freed
457 * (presumably in truncate). That requires careful auditing of all
458 * filesystems (do it inside bforget()). It could also be done by bringing
459 * b_inode back.
460 */
461
462/*
463 * The buffer's backing address_space's private_lock must be held
464 */
Thomas Petazzonidbacefc2008-07-29 22:33:47 -0700465static void __remove_assoc_queue(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700466{
467 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -0700468 WARN_ON(!bh->b_assoc_map);
469 if (buffer_write_io_error(bh))
470 set_bit(AS_EIO, &bh->b_assoc_map->flags);
471 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700472}
473
474int inode_has_buffers(struct inode *inode)
475{
476 return !list_empty(&inode->i_data.private_list);
477}
478
479/*
480 * osync is designed to support O_SYNC io. It waits synchronously for
481 * all already-submitted IO to complete, but does not queue any new
482 * writes to the disk.
483 *
484 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
485 * you dirty the buffers, and then use osync_inode_buffers to wait for
486 * completion. Any other dirty buffers which are not yet queued for
487 * write will not be flushed to disk by the osync.
488 */
489static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
490{
491 struct buffer_head *bh;
492 struct list_head *p;
493 int err = 0;
494
495 spin_lock(lock);
496repeat:
497 list_for_each_prev(p, list) {
498 bh = BH_ENTRY(p);
499 if (buffer_locked(bh)) {
500 get_bh(bh);
501 spin_unlock(lock);
502 wait_on_buffer(bh);
503 if (!buffer_uptodate(bh))
504 err = -EIO;
505 brelse(bh);
506 spin_lock(lock);
507 goto repeat;
508 }
509 }
510 spin_unlock(lock);
511 return err;
512}
513
Al Viro01a05b32010-03-23 06:06:58 -0400514static void do_thaw_one(struct super_block *sb, void *unused)
515{
516 char b[BDEVNAME_SIZE];
517 while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
518 printk(KERN_WARNING "Emergency Thaw on %s\n",
519 bdevname(sb->s_bdev, b));
520}
521
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700522static void do_thaw_all(struct work_struct *work)
Eric Sandeenc2d75432009-03-31 15:23:46 -0700523{
Al Viro01a05b32010-03-23 06:06:58 -0400524 iterate_supers(do_thaw_one, NULL);
Jens Axboe053c5252009-04-08 13:44:08 +0200525 kfree(work);
Eric Sandeenc2d75432009-03-31 15:23:46 -0700526 printk(KERN_WARNING "Emergency Thaw complete\n");
527}
528
529/**
530 * emergency_thaw_all -- forcibly thaw every frozen filesystem
531 *
532 * Used for emergency unfreeze of all filesystems via SysRq
533 */
534void emergency_thaw_all(void)
535{
Jens Axboe053c5252009-04-08 13:44:08 +0200536 struct work_struct *work;
537
538 work = kmalloc(sizeof(*work), GFP_ATOMIC);
539 if (work) {
540 INIT_WORK(work, do_thaw_all);
541 schedule_work(work);
542 }
Eric Sandeenc2d75432009-03-31 15:23:46 -0700543}
544
Linus Torvalds1da177e2005-04-16 15:20:36 -0700545/**
Randy Dunlap78a4a502008-02-29 22:02:31 -0800546 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
Martin Waitz67be2dd2005-05-01 08:59:26 -0700547 * @mapping: the mapping which wants those buffers written
Linus Torvalds1da177e2005-04-16 15:20:36 -0700548 *
549 * Starts I/O against the buffers at mapping->private_list, and waits upon
550 * that I/O.
551 *
Martin Waitz67be2dd2005-05-01 08:59:26 -0700552 * Basically, this is a convenience function for fsync().
553 * @mapping is a file or directory which needs those buffers to be written for
554 * a successful fsync().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700555 */
556int sync_mapping_buffers(struct address_space *mapping)
557{
558 struct address_space *buffer_mapping = mapping->assoc_mapping;
559
560 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
561 return 0;
562
563 return fsync_buffers_list(&buffer_mapping->private_lock,
564 &mapping->private_list);
565}
566EXPORT_SYMBOL(sync_mapping_buffers);
567
568/*
569 * Called when we've recently written block `bblock', and it is known that
570 * `bblock' was for a buffer_boundary() buffer. This means that the block at
571 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
572 * dirty, schedule it for IO. So that indirects merge nicely with their data.
573 */
574void write_boundary_block(struct block_device *bdev,
575 sector_t bblock, unsigned blocksize)
576{
577 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
578 if (bh) {
579 if (buffer_dirty(bh))
580 ll_rw_block(WRITE, 1, &bh);
581 put_bh(bh);
582 }
583}
584
585void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
586{
587 struct address_space *mapping = inode->i_mapping;
588 struct address_space *buffer_mapping = bh->b_page->mapping;
589
590 mark_buffer_dirty(bh);
591 if (!mapping->assoc_mapping) {
592 mapping->assoc_mapping = buffer_mapping;
593 } else {
Eric Sesterhenne827f922006-03-26 18:24:46 +0200594 BUG_ON(mapping->assoc_mapping != buffer_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700595 }
Jan Kara535ee2f2008-02-08 04:21:59 -0800596 if (!bh->b_assoc_map) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700597 spin_lock(&buffer_mapping->private_lock);
598 list_move_tail(&bh->b_assoc_buffers,
599 &mapping->private_list);
Jan Kara58ff4072006-10-17 00:10:19 -0700600 bh->b_assoc_map = mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700601 spin_unlock(&buffer_mapping->private_lock);
602 }
603}
604EXPORT_SYMBOL(mark_buffer_dirty_inode);
605
606/*
Nick Piggin787d2212007-07-17 04:03:34 -0700607 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
608 * dirty.
609 *
610 * If warn is true, then emit a warning if the page is not uptodate and has
611 * not been truncated.
612 */
Linus Torvaldsa8e7d492009-03-19 11:32:05 -0700613static void __set_page_dirty(struct page *page,
Nick Piggin787d2212007-07-17 04:03:34 -0700614 struct address_space *mapping, int warn)
615{
Nick Piggin19fd6232008-07-25 19:45:32 -0700616 spin_lock_irq(&mapping->tree_lock);
Nick Piggin787d2212007-07-17 04:03:34 -0700617 if (page->mapping) { /* Race with truncate? */
618 WARN_ON_ONCE(warn && !PageUptodate(page));
Edward Shishkine3a7cca2009-03-31 15:19:39 -0700619 account_page_dirtied(page, mapping);
Nick Piggin787d2212007-07-17 04:03:34 -0700620 radix_tree_tag_set(&mapping->page_tree,
621 page_index(page), PAGECACHE_TAG_DIRTY);
622 }
Nick Piggin19fd6232008-07-25 19:45:32 -0700623 spin_unlock_irq(&mapping->tree_lock);
Nick Piggin787d2212007-07-17 04:03:34 -0700624 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
Nick Piggin787d2212007-07-17 04:03:34 -0700625}
626
627/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700628 * Add a page to the dirty page list.
629 *
630 * It is a sad fact of life that this function is called from several places
631 * deeply under spinlocking. It may not sleep.
632 *
633 * If the page has buffers, the uptodate buffers are set dirty, to preserve
634 * dirty-state coherency between the page and the buffers. It the page does
635 * not have buffers then when they are later attached they will all be set
636 * dirty.
637 *
638 * The buffers are dirtied before the page is dirtied. There's a small race
639 * window in which a writepage caller may see the page cleanness but not the
640 * buffer dirtiness. That's fine. If this code were to set the page dirty
641 * before the buffers, a concurrent writepage caller could clear the page dirty
642 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
643 * page on the dirty page list.
644 *
645 * We use private_lock to lock against try_to_free_buffers while using the
646 * page's buffer list. Also use this to protect against clean buffers being
647 * added to the page after it was set dirty.
648 *
649 * FIXME: may need to call ->reservepage here as well. That's rather up to the
650 * address_space though.
651 */
652int __set_page_dirty_buffers(struct page *page)
653{
Linus Torvaldsa8e7d492009-03-19 11:32:05 -0700654 int newly_dirty;
Nick Piggin787d2212007-07-17 04:03:34 -0700655 struct address_space *mapping = page_mapping(page);
Nick Pigginebf7a222006-10-10 04:36:54 +0200656
657 if (unlikely(!mapping))
658 return !TestSetPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700659
660 spin_lock(&mapping->private_lock);
661 if (page_has_buffers(page)) {
662 struct buffer_head *head = page_buffers(page);
663 struct buffer_head *bh = head;
664
665 do {
666 set_buffer_dirty(bh);
667 bh = bh->b_this_page;
668 } while (bh != head);
669 }
Linus Torvaldsa8e7d492009-03-19 11:32:05 -0700670 newly_dirty = !TestSetPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700671 spin_unlock(&mapping->private_lock);
672
Linus Torvaldsa8e7d492009-03-19 11:32:05 -0700673 if (newly_dirty)
674 __set_page_dirty(page, mapping, 1);
675 return newly_dirty;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700676}
677EXPORT_SYMBOL(__set_page_dirty_buffers);
678
679/*
680 * Write out and wait upon a list of buffers.
681 *
682 * We have conflicting pressures: we want to make sure that all
683 * initially dirty buffers get waited on, but that any subsequently
684 * dirtied buffers don't. After all, we don't want fsync to last
685 * forever if somebody is actively writing to the file.
686 *
687 * Do this in two main stages: first we copy dirty buffers to a
688 * temporary inode list, queueing the writes as we go. Then we clean
689 * up, waiting for those writes to complete.
690 *
691 * During this second stage, any subsequent updates to the file may end
692 * up refiling the buffer on the original inode's dirty list again, so
693 * there is a chance we will end up with a buffer queued for write but
694 * not yet completed on that list. So, as a final cleanup we go through
695 * the osync code to catch these locked, dirty buffers without requeuing
696 * any newly dirty buffers for write.
697 */
698static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
699{
700 struct buffer_head *bh;
701 struct list_head tmp;
Jens Axboe7eaceac2011-03-10 08:52:07 +0100702 struct address_space *mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700703 int err = 0, err2;
Jens Axboe4ee24912011-03-17 10:51:40 +0100704 struct blk_plug plug;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700705
706 INIT_LIST_HEAD(&tmp);
Jens Axboe4ee24912011-03-17 10:51:40 +0100707 blk_start_plug(&plug);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700708
709 spin_lock(lock);
710 while (!list_empty(list)) {
711 bh = BH_ENTRY(list->next);
Jan Kara535ee2f2008-02-08 04:21:59 -0800712 mapping = bh->b_assoc_map;
Jan Kara58ff4072006-10-17 00:10:19 -0700713 __remove_assoc_queue(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -0800714 /* Avoid race with mark_buffer_dirty_inode() which does
715 * a lockless check and we rely on seeing the dirty bit */
716 smp_mb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700717 if (buffer_dirty(bh) || buffer_locked(bh)) {
718 list_add(&bh->b_assoc_buffers, &tmp);
Jan Kara535ee2f2008-02-08 04:21:59 -0800719 bh->b_assoc_map = mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700720 if (buffer_dirty(bh)) {
721 get_bh(bh);
722 spin_unlock(lock);
723 /*
724 * Ensure any pending I/O completes so that
Christoph Hellwig9cb569d2010-08-11 17:06:24 +0200725 * write_dirty_buffer() actually writes the
726 * current contents - it is a noop if I/O is
727 * still in flight on potentially older
728 * contents.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700729 */
Jens Axboe721a9602011-03-09 11:56:30 +0100730 write_dirty_buffer(bh, WRITE_SYNC);
Jens Axboe9cf6b722009-04-06 14:48:03 +0200731
732 /*
733 * Kick off IO for the previous mapping. Note
734 * that we will not run the very last mapping,
735 * wait_on_buffer() will do that for us
736 * through sync_buffer().
737 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700738 brelse(bh);
739 spin_lock(lock);
740 }
741 }
742 }
743
Jens Axboe4ee24912011-03-17 10:51:40 +0100744 spin_unlock(lock);
745 blk_finish_plug(&plug);
746 spin_lock(lock);
747
Linus Torvalds1da177e2005-04-16 15:20:36 -0700748 while (!list_empty(&tmp)) {
749 bh = BH_ENTRY(tmp.prev);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700750 get_bh(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -0800751 mapping = bh->b_assoc_map;
752 __remove_assoc_queue(bh);
753 /* Avoid race with mark_buffer_dirty_inode() which does
754 * a lockless check and we rely on seeing the dirty bit */
755 smp_mb();
756 if (buffer_dirty(bh)) {
757 list_add(&bh->b_assoc_buffers,
Jan Karae3892292008-03-04 14:28:33 -0800758 &mapping->private_list);
Jan Kara535ee2f2008-02-08 04:21:59 -0800759 bh->b_assoc_map = mapping;
760 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700761 spin_unlock(lock);
762 wait_on_buffer(bh);
763 if (!buffer_uptodate(bh))
764 err = -EIO;
765 brelse(bh);
766 spin_lock(lock);
767 }
768
769 spin_unlock(lock);
770 err2 = osync_buffers_list(lock, list);
771 if (err)
772 return err;
773 else
774 return err2;
775}
776
777/*
778 * Invalidate any and all dirty buffers on a given inode. We are
779 * probably unmounting the fs, but that doesn't mean we have already
780 * done a sync(). Just drop the buffers from the inode list.
781 *
782 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
783 * assumes that all the buffers are against the blockdev. Not true
784 * for reiserfs.
785 */
786void invalidate_inode_buffers(struct inode *inode)
787{
788 if (inode_has_buffers(inode)) {
789 struct address_space *mapping = &inode->i_data;
790 struct list_head *list = &mapping->private_list;
791 struct address_space *buffer_mapping = mapping->assoc_mapping;
792
793 spin_lock(&buffer_mapping->private_lock);
794 while (!list_empty(list))
795 __remove_assoc_queue(BH_ENTRY(list->next));
796 spin_unlock(&buffer_mapping->private_lock);
797 }
798}
Jan Kara52b19ac2008-09-23 18:24:08 +0200799EXPORT_SYMBOL(invalidate_inode_buffers);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700800
801/*
802 * Remove any clean buffers from the inode's buffer list. This is called
803 * when we're trying to free the inode itself. Those buffers can pin it.
804 *
805 * Returns true if all buffers were removed.
806 */
807int remove_inode_buffers(struct inode *inode)
808{
809 int ret = 1;
810
811 if (inode_has_buffers(inode)) {
812 struct address_space *mapping = &inode->i_data;
813 struct list_head *list = &mapping->private_list;
814 struct address_space *buffer_mapping = mapping->assoc_mapping;
815
816 spin_lock(&buffer_mapping->private_lock);
817 while (!list_empty(list)) {
818 struct buffer_head *bh = BH_ENTRY(list->next);
819 if (buffer_dirty(bh)) {
820 ret = 0;
821 break;
822 }
823 __remove_assoc_queue(bh);
824 }
825 spin_unlock(&buffer_mapping->private_lock);
826 }
827 return ret;
828}
829
830/*
831 * Create the appropriate buffers when given a page for data area and
832 * the size of each buffer.. Use the bh->b_this_page linked list to
833 * follow the buffers created. Return NULL if unable to create more
834 * buffers.
835 *
836 * The retry flag is used to differentiate async IO (paging, swapping)
837 * which may not fail from ordinary buffer allocations.
838 */
839struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
840 int retry)
841{
842 struct buffer_head *bh, *head;
843 long offset;
844
845try_again:
846 head = NULL;
847 offset = PAGE_SIZE;
848 while ((offset -= size) >= 0) {
849 bh = alloc_buffer_head(GFP_NOFS);
850 if (!bh)
851 goto no_grow;
852
853 bh->b_bdev = NULL;
854 bh->b_this_page = head;
855 bh->b_blocknr = -1;
856 head = bh;
857
858 bh->b_state = 0;
859 atomic_set(&bh->b_count, 0);
860 bh->b_size = size;
861
862 /* Link the buffer to its page */
863 set_bh_page(bh, page, offset);
864
Nathan Scott01ffe332006-01-17 09:02:07 +1100865 init_buffer(bh, NULL, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700866 }
867 return head;
868/*
869 * In case anything failed, we just free everything we got.
870 */
871no_grow:
872 if (head) {
873 do {
874 bh = head;
875 head = head->b_this_page;
876 free_buffer_head(bh);
877 } while (head);
878 }
879
880 /*
881 * Return failure for non-async IO requests. Async IO requests
882 * are not allowed to fail, so we have to wait until buffer heads
883 * become available. But we don't want tasks sleeping with
884 * partially complete buffers, so all were released above.
885 */
886 if (!retry)
887 return NULL;
888
889 /* We're _really_ low on memory. Now we just
890 * wait for old buffer heads to become free due to
891 * finishing IO. Since this is an async request and
892 * the reserve list is empty, we're sure there are
893 * async buffer heads in use.
894 */
895 free_more_memory();
896 goto try_again;
897}
898EXPORT_SYMBOL_GPL(alloc_page_buffers);
899
900static inline void
901link_dev_buffers(struct page *page, struct buffer_head *head)
902{
903 struct buffer_head *bh, *tail;
904
905 bh = head;
906 do {
907 tail = bh;
908 bh = bh->b_this_page;
909 } while (bh);
910 tail->b_this_page = head;
911 attach_page_buffers(page, head);
912}
913
914/*
915 * Initialise the state of a blockdev page's buffers.
916 */
917static void
918init_page_buffers(struct page *page, struct block_device *bdev,
919 sector_t block, int size)
920{
921 struct buffer_head *head = page_buffers(page);
922 struct buffer_head *bh = head;
923 int uptodate = PageUptodate(page);
924
925 do {
926 if (!buffer_mapped(bh)) {
927 init_buffer(bh, NULL, NULL);
928 bh->b_bdev = bdev;
929 bh->b_blocknr = block;
930 if (uptodate)
931 set_buffer_uptodate(bh);
932 set_buffer_mapped(bh);
933 }
934 block++;
935 bh = bh->b_this_page;
936 } while (bh != head);
937}
938
939/*
940 * Create the page-cache page that contains the requested block.
941 *
942 * This is user purely for blockdev mappings.
943 */
944static struct page *
945grow_dev_page(struct block_device *bdev, sector_t block,
946 pgoff_t index, int size)
947{
948 struct inode *inode = bdev->bd_inode;
949 struct page *page;
950 struct buffer_head *bh;
951
Christoph Lameterea125892007-05-16 22:11:21 -0700952 page = find_or_create_page(inode->i_mapping, index,
Mel Gorman769848c2007-07-17 04:03:05 -0700953 (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700954 if (!page)
955 return NULL;
956
Eric Sesterhenne827f922006-03-26 18:24:46 +0200957 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700958
959 if (page_has_buffers(page)) {
960 bh = page_buffers(page);
961 if (bh->b_size == size) {
962 init_page_buffers(page, bdev, block, size);
963 return page;
964 }
965 if (!try_to_free_buffers(page))
966 goto failed;
967 }
968
969 /*
970 * Allocate some buffers for this page
971 */
972 bh = alloc_page_buffers(page, size, 0);
973 if (!bh)
974 goto failed;
975
976 /*
977 * Link the page to the buffers and initialise them. Take the
978 * lock to be atomic wrt __find_get_block(), which does not
979 * run under the page lock.
980 */
981 spin_lock(&inode->i_mapping->private_lock);
982 link_dev_buffers(page, bh);
983 init_page_buffers(page, bdev, block, size);
984 spin_unlock(&inode->i_mapping->private_lock);
985 return page;
986
987failed:
988 BUG();
989 unlock_page(page);
990 page_cache_release(page);
991 return NULL;
992}
993
994/*
995 * Create buffers for the specified block device block's page. If
996 * that page was dirty, the buffers are set dirty also.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700997 */
Arjan van de Ven858119e2006-01-14 13:20:43 -0800998static int
Linus Torvalds1da177e2005-04-16 15:20:36 -0700999grow_buffers(struct block_device *bdev, sector_t block, int size)
1000{
1001 struct page *page;
1002 pgoff_t index;
1003 int sizebits;
1004
1005 sizebits = -1;
1006 do {
1007 sizebits++;
1008 } while ((size << sizebits) < PAGE_SIZE);
1009
1010 index = block >> sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001011
Andrew Mortone5657932006-10-11 01:21:46 -07001012 /*
1013 * Check for a block which wants to lie outside our maximum possible
1014 * pagecache index. (this comparison is done using sector_t types).
1015 */
1016 if (unlikely(index != block >> sizebits)) {
1017 char b[BDEVNAME_SIZE];
1018
1019 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1020 "device %s\n",
Harvey Harrison8e24eea2008-04-30 00:55:09 -07001021 __func__, (unsigned long long)block,
Andrew Mortone5657932006-10-11 01:21:46 -07001022 bdevname(bdev, b));
1023 return -EIO;
1024 }
1025 block = index << sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001026 /* Create a page with the proper size buffers.. */
1027 page = grow_dev_page(bdev, block, index, size);
1028 if (!page)
1029 return 0;
1030 unlock_page(page);
1031 page_cache_release(page);
1032 return 1;
1033}
1034
Adrian Bunk75c96f82005-05-05 16:16:09 -07001035static struct buffer_head *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001036__getblk_slow(struct block_device *bdev, sector_t block, int size)
1037{
1038 /* Size must be multiple of hard sectorsize */
Martin K. Petersene1defc42009-05-22 17:17:49 -04001039 if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
Linus Torvalds1da177e2005-04-16 15:20:36 -07001040 (size < 512 || size > PAGE_SIZE))) {
1041 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1042 size);
Martin K. Petersene1defc42009-05-22 17:17:49 -04001043 printk(KERN_ERR "logical block size: %d\n",
1044 bdev_logical_block_size(bdev));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001045
1046 dump_stack();
1047 return NULL;
1048 }
1049
1050 for (;;) {
1051 struct buffer_head * bh;
Andrew Mortone5657932006-10-11 01:21:46 -07001052 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001053
1054 bh = __find_get_block(bdev, block, size);
1055 if (bh)
1056 return bh;
1057
Andrew Mortone5657932006-10-11 01:21:46 -07001058 ret = grow_buffers(bdev, block, size);
1059 if (ret < 0)
1060 return NULL;
1061 if (ret == 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001062 free_more_memory();
1063 }
1064}
1065
1066/*
1067 * The relationship between dirty buffers and dirty pages:
1068 *
1069 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1070 * the page is tagged dirty in its radix tree.
1071 *
1072 * At all times, the dirtiness of the buffers represents the dirtiness of
1073 * subsections of the page. If the page has buffers, the page dirty bit is
1074 * merely a hint about the true dirty state.
1075 *
1076 * When a page is set dirty in its entirety, all its buffers are marked dirty
1077 * (if the page has buffers).
1078 *
1079 * When a buffer is marked dirty, its page is dirtied, but the page's other
1080 * buffers are not.
1081 *
1082 * Also. When blockdev buffers are explicitly read with bread(), they
1083 * individually become uptodate. But their backing page remains not
1084 * uptodate - even if all of its buffers are uptodate. A subsequent
1085 * block_read_full_page() against that page will discover all the uptodate
1086 * buffers, will set the page uptodate and will perform no I/O.
1087 */
1088
1089/**
1090 * mark_buffer_dirty - mark a buffer_head as needing writeout
Martin Waitz67be2dd2005-05-01 08:59:26 -07001091 * @bh: the buffer_head to mark dirty
Linus Torvalds1da177e2005-04-16 15:20:36 -07001092 *
1093 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1094 * backing page dirty, then tag the page as dirty in its address_space's radix
1095 * tree and then attach the address_space's inode to its superblock's dirty
1096 * inode list.
1097 *
1098 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
Dave Chinner250df6e2011-03-22 22:23:36 +11001099 * mapping->tree_lock and mapping->host->i_lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001100 */
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -08001101void mark_buffer_dirty(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001102{
Nick Piggin787d2212007-07-17 04:03:34 -07001103 WARN_ON_ONCE(!buffer_uptodate(bh));
Linus Torvalds1be62dc2008-04-04 14:38:17 -07001104
1105 /*
1106 * Very *carefully* optimize the it-is-already-dirty case.
1107 *
1108 * Don't let the final "is it dirty" escape to before we
1109 * perhaps modified the buffer.
1110 */
1111 if (buffer_dirty(bh)) {
1112 smp_mb();
1113 if (buffer_dirty(bh))
1114 return;
1115 }
1116
Linus Torvaldsa8e7d492009-03-19 11:32:05 -07001117 if (!test_set_buffer_dirty(bh)) {
1118 struct page *page = bh->b_page;
Linus Torvalds8e9d78e2009-08-21 17:40:08 -07001119 if (!TestSetPageDirty(page)) {
1120 struct address_space *mapping = page_mapping(page);
1121 if (mapping)
1122 __set_page_dirty(page, mapping, 0);
1123 }
Linus Torvaldsa8e7d492009-03-19 11:32:05 -07001124 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001125}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07001126EXPORT_SYMBOL(mark_buffer_dirty);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001127
1128/*
1129 * Decrement a buffer_head's reference count. If all buffers against a page
1130 * have zero reference count, are clean and unlocked, and if the page is clean
1131 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1132 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1133 * a page but it ends up not being freed, and buffers may later be reattached).
1134 */
1135void __brelse(struct buffer_head * buf)
1136{
1137 if (atomic_read(&buf->b_count)) {
1138 put_bh(buf);
1139 return;
1140 }
Arjan van de Ven5c752ad2008-07-25 19:45:40 -07001141 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
Linus Torvalds1da177e2005-04-16 15:20:36 -07001142}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07001143EXPORT_SYMBOL(__brelse);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001144
1145/*
1146 * bforget() is like brelse(), except it discards any
1147 * potentially dirty data.
1148 */
1149void __bforget(struct buffer_head *bh)
1150{
1151 clear_buffer_dirty(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -08001152 if (bh->b_assoc_map) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001153 struct address_space *buffer_mapping = bh->b_page->mapping;
1154
1155 spin_lock(&buffer_mapping->private_lock);
1156 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -07001157 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001158 spin_unlock(&buffer_mapping->private_lock);
1159 }
1160 __brelse(bh);
1161}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07001162EXPORT_SYMBOL(__bforget);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001163
1164static struct buffer_head *__bread_slow(struct buffer_head *bh)
1165{
1166 lock_buffer(bh);
1167 if (buffer_uptodate(bh)) {
1168 unlock_buffer(bh);
1169 return bh;
1170 } else {
1171 get_bh(bh);
1172 bh->b_end_io = end_buffer_read_sync;
1173 submit_bh(READ, bh);
1174 wait_on_buffer(bh);
1175 if (buffer_uptodate(bh))
1176 return bh;
1177 }
1178 brelse(bh);
1179 return NULL;
1180}
1181
1182/*
1183 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1184 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1185 * refcount elevated by one when they're in an LRU. A buffer can only appear
1186 * once in a particular CPU's LRU. A single buffer can be present in multiple
1187 * CPU's LRUs at the same time.
1188 *
1189 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1190 * sb_find_get_block().
1191 *
1192 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1193 * a local interrupt disable for that.
1194 */
1195
1196#define BH_LRU_SIZE 8
1197
1198struct bh_lru {
1199 struct buffer_head *bhs[BH_LRU_SIZE];
1200};
1201
1202static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1203
1204#ifdef CONFIG_SMP
1205#define bh_lru_lock() local_irq_disable()
1206#define bh_lru_unlock() local_irq_enable()
1207#else
1208#define bh_lru_lock() preempt_disable()
1209#define bh_lru_unlock() preempt_enable()
1210#endif
1211
1212static inline void check_irqs_on(void)
1213{
1214#ifdef irqs_disabled
1215 BUG_ON(irqs_disabled());
1216#endif
1217}
1218
1219/*
1220 * The LRU management algorithm is dopey-but-simple. Sorry.
1221 */
1222static void bh_lru_install(struct buffer_head *bh)
1223{
1224 struct buffer_head *evictee = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001225
1226 check_irqs_on();
1227 bh_lru_lock();
Christoph Lameterc7b92512010-12-06 11:16:28 -06001228 if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001229 struct buffer_head *bhs[BH_LRU_SIZE];
1230 int in;
1231 int out = 0;
1232
1233 get_bh(bh);
1234 bhs[out++] = bh;
1235 for (in = 0; in < BH_LRU_SIZE; in++) {
Christoph Lameterc7b92512010-12-06 11:16:28 -06001236 struct buffer_head *bh2 =
1237 __this_cpu_read(bh_lrus.bhs[in]);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001238
1239 if (bh2 == bh) {
1240 __brelse(bh2);
1241 } else {
1242 if (out >= BH_LRU_SIZE) {
1243 BUG_ON(evictee != NULL);
1244 evictee = bh2;
1245 } else {
1246 bhs[out++] = bh2;
1247 }
1248 }
1249 }
1250 while (out < BH_LRU_SIZE)
1251 bhs[out++] = NULL;
Christoph Lameterc7b92512010-12-06 11:16:28 -06001252 memcpy(__this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001253 }
1254 bh_lru_unlock();
1255
1256 if (evictee)
1257 __brelse(evictee);
1258}
1259
1260/*
1261 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1262 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001263static struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001264lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001265{
1266 struct buffer_head *ret = NULL;
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001267 unsigned int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001268
1269 check_irqs_on();
1270 bh_lru_lock();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001271 for (i = 0; i < BH_LRU_SIZE; i++) {
Christoph Lameterc7b92512010-12-06 11:16:28 -06001272 struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001273
1274 if (bh && bh->b_bdev == bdev &&
1275 bh->b_blocknr == block && bh->b_size == size) {
1276 if (i) {
1277 while (i) {
Christoph Lameterc7b92512010-12-06 11:16:28 -06001278 __this_cpu_write(bh_lrus.bhs[i],
1279 __this_cpu_read(bh_lrus.bhs[i - 1]));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001280 i--;
1281 }
Christoph Lameterc7b92512010-12-06 11:16:28 -06001282 __this_cpu_write(bh_lrus.bhs[0], bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001283 }
1284 get_bh(bh);
1285 ret = bh;
1286 break;
1287 }
1288 }
1289 bh_lru_unlock();
1290 return ret;
1291}
1292
1293/*
1294 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1295 * it in the LRU and mark it as accessed. If it is not present then return
1296 * NULL
1297 */
1298struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001299__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001300{
1301 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1302
1303 if (bh == NULL) {
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001304 bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001305 if (bh)
1306 bh_lru_install(bh);
1307 }
1308 if (bh)
1309 touch_buffer(bh);
1310 return bh;
1311}
1312EXPORT_SYMBOL(__find_get_block);
1313
1314/*
1315 * __getblk will locate (and, if necessary, create) the buffer_head
1316 * which corresponds to the passed block_device, block and size. The
1317 * returned buffer has its reference count incremented.
1318 *
1319 * __getblk() cannot fail - it just keeps trying. If you pass it an
1320 * illegal block number, __getblk() will happily return a buffer_head
1321 * which represents the non-existent block. Very weird.
1322 *
1323 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1324 * attempt is failing. FIXME, perhaps?
1325 */
1326struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001327__getblk(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001328{
1329 struct buffer_head *bh = __find_get_block(bdev, block, size);
1330
1331 might_sleep();
1332 if (bh == NULL)
1333 bh = __getblk_slow(bdev, block, size);
1334 return bh;
1335}
1336EXPORT_SYMBOL(__getblk);
1337
1338/*
1339 * Do async read-ahead on a buffer..
1340 */
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001341void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001342{
1343 struct buffer_head *bh = __getblk(bdev, block, size);
Andrew Mortona3e713b2005-10-30 15:03:15 -08001344 if (likely(bh)) {
1345 ll_rw_block(READA, 1, &bh);
1346 brelse(bh);
1347 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001348}
1349EXPORT_SYMBOL(__breadahead);
1350
1351/**
1352 * __bread() - reads a specified block and returns the bh
Martin Waitz67be2dd2005-05-01 08:59:26 -07001353 * @bdev: the block_device to read from
Linus Torvalds1da177e2005-04-16 15:20:36 -07001354 * @block: number of block
1355 * @size: size (in bytes) to read
1356 *
1357 * Reads a specified block, and returns buffer head that contains it.
1358 * It returns NULL if the block was unreadable.
1359 */
1360struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001361__bread(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001362{
1363 struct buffer_head *bh = __getblk(bdev, block, size);
1364
Andrew Mortona3e713b2005-10-30 15:03:15 -08001365 if (likely(bh) && !buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001366 bh = __bread_slow(bh);
1367 return bh;
1368}
1369EXPORT_SYMBOL(__bread);
1370
1371/*
1372 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1373 * This doesn't race because it runs in each cpu either in irq
1374 * or with preempt disabled.
1375 */
1376static void invalidate_bh_lru(void *arg)
1377{
1378 struct bh_lru *b = &get_cpu_var(bh_lrus);
1379 int i;
1380
1381 for (i = 0; i < BH_LRU_SIZE; i++) {
1382 brelse(b->bhs[i]);
1383 b->bhs[i] = NULL;
1384 }
1385 put_cpu_var(bh_lrus);
1386}
1387
Peter Zijlstraf9a14392007-05-06 14:49:55 -07001388void invalidate_bh_lrus(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001389{
Jens Axboe15c8b6c2008-05-09 09:39:44 +02001390 on_each_cpu(invalidate_bh_lru, NULL, 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001391}
Nick Piggin9db55792008-02-08 04:19:49 -08001392EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001393
1394void set_bh_page(struct buffer_head *bh,
1395 struct page *page, unsigned long offset)
1396{
1397 bh->b_page = page;
Eric Sesterhenne827f922006-03-26 18:24:46 +02001398 BUG_ON(offset >= PAGE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001399 if (PageHighMem(page))
1400 /*
1401 * This catches illegal uses and preserves the offset:
1402 */
1403 bh->b_data = (char *)(0 + offset);
1404 else
1405 bh->b_data = page_address(page) + offset;
1406}
1407EXPORT_SYMBOL(set_bh_page);
1408
1409/*
1410 * Called when truncating a buffer on a page completely.
1411 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001412static void discard_buffer(struct buffer_head * bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001413{
1414 lock_buffer(bh);
1415 clear_buffer_dirty(bh);
1416 bh->b_bdev = NULL;
1417 clear_buffer_mapped(bh);
1418 clear_buffer_req(bh);
1419 clear_buffer_new(bh);
1420 clear_buffer_delay(bh);
David Chinner33a266d2007-02-12 00:51:41 -08001421 clear_buffer_unwritten(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001422 unlock_buffer(bh);
1423}
1424
1425/**
Wang Sheng-Hui814e1d22011-09-01 08:22:57 +08001426 * block_invalidatepage - invalidate part or all of a buffer-backed page
Linus Torvalds1da177e2005-04-16 15:20:36 -07001427 *
1428 * @page: the page which is affected
1429 * @offset: the index of the truncation point
1430 *
1431 * block_invalidatepage() is called when all or part of the page has become
Wang Sheng-Hui814e1d22011-09-01 08:22:57 +08001432 * invalidated by a truncate operation.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001433 *
1434 * block_invalidatepage() does not have to release all buffers, but it must
1435 * ensure that no dirty buffer is left outside @offset and that no I/O
1436 * is underway against any of the blocks which are outside the truncation
1437 * point. Because the caller is about to free (and possibly reuse) those
1438 * blocks on-disk.
1439 */
NeilBrown2ff28e22006-03-26 01:37:18 -08001440void block_invalidatepage(struct page *page, unsigned long offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001441{
1442 struct buffer_head *head, *bh, *next;
1443 unsigned int curr_off = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001444
1445 BUG_ON(!PageLocked(page));
1446 if (!page_has_buffers(page))
1447 goto out;
1448
1449 head = page_buffers(page);
1450 bh = head;
1451 do {
1452 unsigned int next_off = curr_off + bh->b_size;
1453 next = bh->b_this_page;
1454
1455 /*
1456 * is this block fully invalidated?
1457 */
1458 if (offset <= curr_off)
1459 discard_buffer(bh);
1460 curr_off = next_off;
1461 bh = next;
1462 } while (bh != head);
1463
1464 /*
1465 * We release buffers only if the entire page is being invalidated.
1466 * The get_block cached value has been unconditionally invalidated,
1467 * so real IO is not possible anymore.
1468 */
1469 if (offset == 0)
NeilBrown2ff28e22006-03-26 01:37:18 -08001470 try_to_release_page(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001471out:
NeilBrown2ff28e22006-03-26 01:37:18 -08001472 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001473}
1474EXPORT_SYMBOL(block_invalidatepage);
1475
1476/*
1477 * We attach and possibly dirty the buffers atomically wrt
1478 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1479 * is already excluded via the page lock.
1480 */
1481void create_empty_buffers(struct page *page,
1482 unsigned long blocksize, unsigned long b_state)
1483{
1484 struct buffer_head *bh, *head, *tail;
1485
1486 head = alloc_page_buffers(page, blocksize, 1);
1487 bh = head;
1488 do {
1489 bh->b_state |= b_state;
1490 tail = bh;
1491 bh = bh->b_this_page;
1492 } while (bh);
1493 tail->b_this_page = head;
1494
1495 spin_lock(&page->mapping->private_lock);
1496 if (PageUptodate(page) || PageDirty(page)) {
1497 bh = head;
1498 do {
1499 if (PageDirty(page))
1500 set_buffer_dirty(bh);
1501 if (PageUptodate(page))
1502 set_buffer_uptodate(bh);
1503 bh = bh->b_this_page;
1504 } while (bh != head);
1505 }
1506 attach_page_buffers(page, head);
1507 spin_unlock(&page->mapping->private_lock);
1508}
1509EXPORT_SYMBOL(create_empty_buffers);
1510
1511/*
1512 * We are taking a block for data and we don't want any output from any
1513 * buffer-cache aliases starting from return from that function and
1514 * until the moment when something will explicitly mark the buffer
1515 * dirty (hopefully that will not happen until we will free that block ;-)
1516 * We don't even need to mark it not-uptodate - nobody can expect
1517 * anything from a newly allocated buffer anyway. We used to used
1518 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1519 * don't want to mark the alias unmapped, for example - it would confuse
1520 * anyone who might pick it with bread() afterwards...
1521 *
1522 * Also.. Note that bforget() doesn't lock the buffer. So there can
1523 * be writeout I/O going on against recently-freed buffers. We don't
1524 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1525 * only if we really need to. That happens here.
1526 */
1527void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1528{
1529 struct buffer_head *old_bh;
1530
1531 might_sleep();
1532
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001533 old_bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001534 if (old_bh) {
1535 clear_buffer_dirty(old_bh);
1536 wait_on_buffer(old_bh);
1537 clear_buffer_req(old_bh);
1538 __brelse(old_bh);
1539 }
1540}
1541EXPORT_SYMBOL(unmap_underlying_metadata);
1542
1543/*
1544 * NOTE! All mapped/uptodate combinations are valid:
1545 *
1546 * Mapped Uptodate Meaning
1547 *
1548 * No No "unknown" - must do get_block()
1549 * No Yes "hole" - zero-filled
1550 * Yes No "allocated" - allocated on disk, not read in
1551 * Yes Yes "valid" - allocated and up-to-date in memory.
1552 *
1553 * "Dirty" is valid only with the last case (mapped+uptodate).
1554 */
1555
1556/*
1557 * While block_write_full_page is writing back the dirty buffers under
1558 * the page lock, whoever dirtied the buffers may decide to clean them
1559 * again at any time. We handle that by only looking at the buffer
1560 * state inside lock_buffer().
1561 *
1562 * If block_write_full_page() is called for regular writeback
1563 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1564 * locked buffer. This only can happen if someone has written the buffer
1565 * directly, with submit_bh(). At the address_space level PageWriteback
1566 * prevents this contention from occurring.
Theodore Ts'o6e34eed2009-04-07 18:12:43 -04001567 *
1568 * If block_write_full_page() is called with wbc->sync_mode ==
Jens Axboe721a9602011-03-09 11:56:30 +01001569 * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this
1570 * causes the writes to be flagged as synchronous writes.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001571 */
1572static int __block_write_full_page(struct inode *inode, struct page *page,
Chris Mason35c80d52009-04-15 13:22:38 -04001573 get_block_t *get_block, struct writeback_control *wbc,
1574 bh_end_io_t *handler)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001575{
1576 int err;
1577 sector_t block;
1578 sector_t last_block;
Andrew Mortonf0fbd5f2005-05-05 16:15:48 -07001579 struct buffer_head *bh, *head;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001580 const unsigned blocksize = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001581 int nr_underway = 0;
Theodore Ts'o6e34eed2009-04-07 18:12:43 -04001582 int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
Jens Axboe721a9602011-03-09 11:56:30 +01001583 WRITE_SYNC : WRITE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001584
1585 BUG_ON(!PageLocked(page));
1586
1587 last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
1588
1589 if (!page_has_buffers(page)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001590 create_empty_buffers(page, blocksize,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001591 (1 << BH_Dirty)|(1 << BH_Uptodate));
1592 }
1593
1594 /*
1595 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1596 * here, and the (potentially unmapped) buffers may become dirty at
1597 * any time. If a buffer becomes dirty here after we've inspected it
1598 * then we just miss that fact, and the page stays dirty.
1599 *
1600 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1601 * handle that here by just cleaning them.
1602 */
1603
Andrew Morton54b21a72006-01-08 01:03:05 -08001604 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001605 head = page_buffers(page);
1606 bh = head;
1607
1608 /*
1609 * Get all the dirty buffers mapped to disk addresses and
1610 * handle any aliases from the underlying blockdev's mapping.
1611 */
1612 do {
1613 if (block > last_block) {
1614 /*
1615 * mapped buffers outside i_size will occur, because
1616 * this page can be outside i_size when there is a
1617 * truncate in progress.
1618 */
1619 /*
1620 * The buffer was zeroed by block_write_full_page()
1621 */
1622 clear_buffer_dirty(bh);
1623 set_buffer_uptodate(bh);
Alex Tomas29a814d2008-07-11 19:27:31 -04001624 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1625 buffer_dirty(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001626 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001627 err = get_block(inode, block, bh, 1);
1628 if (err)
1629 goto recover;
Alex Tomas29a814d2008-07-11 19:27:31 -04001630 clear_buffer_delay(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001631 if (buffer_new(bh)) {
1632 /* blockdev mappings never come here */
1633 clear_buffer_new(bh);
1634 unmap_underlying_metadata(bh->b_bdev,
1635 bh->b_blocknr);
1636 }
1637 }
1638 bh = bh->b_this_page;
1639 block++;
1640 } while (bh != head);
1641
1642 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001643 if (!buffer_mapped(bh))
1644 continue;
1645 /*
1646 * If it's a fully non-blocking write attempt and we cannot
1647 * lock the buffer then redirty the page. Note that this can
Jens Axboe5b0830c2009-09-23 19:37:09 +02001648 * potentially cause a busy-wait loop from writeback threads
1649 * and kswapd activity, but those code paths have their own
1650 * higher-level throttling.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001651 */
Wu Fengguang1b430be2010-10-26 14:21:26 -07001652 if (wbc->sync_mode != WB_SYNC_NONE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001653 lock_buffer(bh);
Nick Pigginca5de402008-08-02 12:02:13 +02001654 } else if (!trylock_buffer(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001655 redirty_page_for_writepage(wbc, page);
1656 continue;
1657 }
1658 if (test_clear_buffer_dirty(bh)) {
Chris Mason35c80d52009-04-15 13:22:38 -04001659 mark_buffer_async_write_endio(bh, handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001660 } else {
1661 unlock_buffer(bh);
1662 }
1663 } while ((bh = bh->b_this_page) != head);
1664
1665 /*
1666 * The page and its buffers are protected by PageWriteback(), so we can
1667 * drop the bh refcounts early.
1668 */
1669 BUG_ON(PageWriteback(page));
1670 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001671
1672 do {
1673 struct buffer_head *next = bh->b_this_page;
1674 if (buffer_async_write(bh)) {
Theodore Ts'oa64c8612009-03-27 22:14:10 -04001675 submit_bh(write_op, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001676 nr_underway++;
1677 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001678 bh = next;
1679 } while (bh != head);
Andrew Morton05937ba2005-05-05 16:15:47 -07001680 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001681
1682 err = 0;
1683done:
1684 if (nr_underway == 0) {
1685 /*
1686 * The page was marked dirty, but the buffers were
1687 * clean. Someone wrote them back by hand with
1688 * ll_rw_block/submit_bh. A rare case.
1689 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001690 end_page_writeback(page);
Nick Piggin3d67f2d2007-05-06 14:49:05 -07001691
Linus Torvalds1da177e2005-04-16 15:20:36 -07001692 /*
1693 * The page and buffer_heads can be released at any time from
1694 * here on.
1695 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001696 }
1697 return err;
1698
1699recover:
1700 /*
1701 * ENOSPC, or some other error. We may already have added some
1702 * blocks to the file, so we need to write these out to avoid
1703 * exposing stale data.
1704 * The page is currently locked and not marked for writeback
1705 */
1706 bh = head;
1707 /* Recovery: lock and submit the mapped buffers */
1708 do {
Alex Tomas29a814d2008-07-11 19:27:31 -04001709 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1710 !buffer_delay(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001711 lock_buffer(bh);
Chris Mason35c80d52009-04-15 13:22:38 -04001712 mark_buffer_async_write_endio(bh, handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001713 } else {
1714 /*
1715 * The buffer may have been set dirty during
1716 * attachment to a dirty page.
1717 */
1718 clear_buffer_dirty(bh);
1719 }
1720 } while ((bh = bh->b_this_page) != head);
1721 SetPageError(page);
1722 BUG_ON(PageWriteback(page));
Andrew Morton7e4c3692007-05-08 00:23:27 -07001723 mapping_set_error(page->mapping, err);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001724 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001725 do {
1726 struct buffer_head *next = bh->b_this_page;
1727 if (buffer_async_write(bh)) {
1728 clear_buffer_dirty(bh);
Theodore Ts'oa64c8612009-03-27 22:14:10 -04001729 submit_bh(write_op, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001730 nr_underway++;
1731 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001732 bh = next;
1733 } while (bh != head);
Nick Pigginffda9d32007-02-20 13:57:54 -08001734 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001735 goto done;
1736}
1737
Nick Pigginafddba42007-10-16 01:25:01 -07001738/*
1739 * If a page has any new buffers, zero them out here, and mark them uptodate
1740 * and dirty so they'll be written out (in order to prevent uninitialised
1741 * block data from leaking). And clear the new bit.
1742 */
1743void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1744{
1745 unsigned int block_start, block_end;
1746 struct buffer_head *head, *bh;
1747
1748 BUG_ON(!PageLocked(page));
1749 if (!page_has_buffers(page))
1750 return;
1751
1752 bh = head = page_buffers(page);
1753 block_start = 0;
1754 do {
1755 block_end = block_start + bh->b_size;
1756
1757 if (buffer_new(bh)) {
1758 if (block_end > from && block_start < to) {
1759 if (!PageUptodate(page)) {
1760 unsigned start, size;
1761
1762 start = max(from, block_start);
1763 size = min(to, block_end) - start;
1764
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001765 zero_user(page, start, size);
Nick Pigginafddba42007-10-16 01:25:01 -07001766 set_buffer_uptodate(bh);
1767 }
1768
1769 clear_buffer_new(bh);
1770 mark_buffer_dirty(bh);
1771 }
1772 }
1773
1774 block_start = block_end;
1775 bh = bh->b_this_page;
1776 } while (bh != head);
1777}
1778EXPORT_SYMBOL(page_zero_new_buffers);
1779
Christoph Hellwigebdec242010-10-06 10:47:23 +02001780int __block_write_begin(struct page *page, loff_t pos, unsigned len,
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001781 get_block_t *get_block)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001782{
Christoph Hellwigebdec242010-10-06 10:47:23 +02001783 unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1784 unsigned to = from + len;
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001785 struct inode *inode = page->mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001786 unsigned block_start, block_end;
1787 sector_t block;
1788 int err = 0;
1789 unsigned blocksize, bbits;
1790 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1791
1792 BUG_ON(!PageLocked(page));
1793 BUG_ON(from > PAGE_CACHE_SIZE);
1794 BUG_ON(to > PAGE_CACHE_SIZE);
1795 BUG_ON(from > to);
1796
1797 blocksize = 1 << inode->i_blkbits;
1798 if (!page_has_buffers(page))
1799 create_empty_buffers(page, blocksize, 0);
1800 head = page_buffers(page);
1801
1802 bbits = inode->i_blkbits;
1803 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1804
1805 for(bh = head, block_start = 0; bh != head || !block_start;
1806 block++, block_start=block_end, bh = bh->b_this_page) {
1807 block_end = block_start + blocksize;
1808 if (block_end <= from || block_start >= to) {
1809 if (PageUptodate(page)) {
1810 if (!buffer_uptodate(bh))
1811 set_buffer_uptodate(bh);
1812 }
1813 continue;
1814 }
1815 if (buffer_new(bh))
1816 clear_buffer_new(bh);
1817 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001818 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001819 err = get_block(inode, block, bh, 1);
1820 if (err)
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001821 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001822 if (buffer_new(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001823 unmap_underlying_metadata(bh->b_bdev,
1824 bh->b_blocknr);
1825 if (PageUptodate(page)) {
Nick Piggin637aff42007-10-16 01:25:00 -07001826 clear_buffer_new(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001827 set_buffer_uptodate(bh);
Nick Piggin637aff42007-10-16 01:25:00 -07001828 mark_buffer_dirty(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001829 continue;
1830 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001831 if (block_end > to || block_start < from)
1832 zero_user_segments(page,
1833 to, block_end,
1834 block_start, from);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001835 continue;
1836 }
1837 }
1838 if (PageUptodate(page)) {
1839 if (!buffer_uptodate(bh))
1840 set_buffer_uptodate(bh);
1841 continue;
1842 }
1843 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
David Chinner33a266d2007-02-12 00:51:41 -08001844 !buffer_unwritten(bh) &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001845 (block_start < from || block_end > to)) {
1846 ll_rw_block(READ, 1, &bh);
1847 *wait_bh++=bh;
1848 }
1849 }
1850 /*
1851 * If we issued read requests - let them complete.
1852 */
1853 while(wait_bh > wait) {
1854 wait_on_buffer(*--wait_bh);
1855 if (!buffer_uptodate(*wait_bh))
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001856 err = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001857 }
Jan Karaf9f07b62011-06-14 00:58:27 +02001858 if (unlikely(err))
Nick Pigginafddba42007-10-16 01:25:01 -07001859 page_zero_new_buffers(page, from, to);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001860 return err;
1861}
Christoph Hellwigebdec242010-10-06 10:47:23 +02001862EXPORT_SYMBOL(__block_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001863
1864static int __block_commit_write(struct inode *inode, struct page *page,
1865 unsigned from, unsigned to)
1866{
1867 unsigned block_start, block_end;
1868 int partial = 0;
1869 unsigned blocksize;
1870 struct buffer_head *bh, *head;
1871
1872 blocksize = 1 << inode->i_blkbits;
1873
1874 for(bh = head = page_buffers(page), block_start = 0;
1875 bh != head || !block_start;
1876 block_start=block_end, bh = bh->b_this_page) {
1877 block_end = block_start + blocksize;
1878 if (block_end <= from || block_start >= to) {
1879 if (!buffer_uptodate(bh))
1880 partial = 1;
1881 } else {
1882 set_buffer_uptodate(bh);
1883 mark_buffer_dirty(bh);
1884 }
Nick Pigginafddba42007-10-16 01:25:01 -07001885 clear_buffer_new(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001886 }
1887
1888 /*
1889 * If this is a partial write which happened to make all buffers
1890 * uptodate then we can optimize away a bogus readpage() for
1891 * the next read(). Here we 'discover' whether the page went
1892 * uptodate as a result of this (potentially partial) write.
1893 */
1894 if (!partial)
1895 SetPageUptodate(page);
1896 return 0;
1897}
1898
1899/*
Christoph Hellwig155130a2010-06-04 11:29:58 +02001900 * block_write_begin takes care of the basic task of block allocation and
1901 * bringing partial write blocks uptodate first.
1902 *
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10001903 * The filesystem needs to handle block truncation upon failure.
Nick Pigginafddba42007-10-16 01:25:01 -07001904 */
Christoph Hellwig155130a2010-06-04 11:29:58 +02001905int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
1906 unsigned flags, struct page **pagep, get_block_t *get_block)
Nick Pigginafddba42007-10-16 01:25:01 -07001907{
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001908 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
Nick Pigginafddba42007-10-16 01:25:01 -07001909 struct page *page;
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001910 int status;
Nick Pigginafddba42007-10-16 01:25:01 -07001911
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001912 page = grab_cache_page_write_begin(mapping, index, flags);
1913 if (!page)
1914 return -ENOMEM;
Nick Pigginafddba42007-10-16 01:25:01 -07001915
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001916 status = __block_write_begin(page, pos, len, get_block);
Nick Pigginafddba42007-10-16 01:25:01 -07001917 if (unlikely(status)) {
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001918 unlock_page(page);
1919 page_cache_release(page);
1920 page = NULL;
Nick Pigginafddba42007-10-16 01:25:01 -07001921 }
1922
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001923 *pagep = page;
Nick Pigginafddba42007-10-16 01:25:01 -07001924 return status;
1925}
1926EXPORT_SYMBOL(block_write_begin);
1927
1928int block_write_end(struct file *file, struct address_space *mapping,
1929 loff_t pos, unsigned len, unsigned copied,
1930 struct page *page, void *fsdata)
1931{
1932 struct inode *inode = mapping->host;
1933 unsigned start;
1934
1935 start = pos & (PAGE_CACHE_SIZE - 1);
1936
1937 if (unlikely(copied < len)) {
1938 /*
1939 * The buffers that were written will now be uptodate, so we
1940 * don't have to worry about a readpage reading them and
1941 * overwriting a partial write. However if we have encountered
1942 * a short write and only partially written into a buffer, it
1943 * will not be marked uptodate, so a readpage might come in and
1944 * destroy our partial write.
1945 *
1946 * Do the simplest thing, and just treat any short write to a
1947 * non uptodate page as a zero-length write, and force the
1948 * caller to redo the whole thing.
1949 */
1950 if (!PageUptodate(page))
1951 copied = 0;
1952
1953 page_zero_new_buffers(page, start+copied, start+len);
1954 }
1955 flush_dcache_page(page);
1956
1957 /* This could be a short (even 0-length) commit */
1958 __block_commit_write(inode, page, start, start+copied);
1959
1960 return copied;
1961}
1962EXPORT_SYMBOL(block_write_end);
1963
1964int generic_write_end(struct file *file, struct address_space *mapping,
1965 loff_t pos, unsigned len, unsigned copied,
1966 struct page *page, void *fsdata)
1967{
1968 struct inode *inode = mapping->host;
Jan Karac7d206b2008-07-11 19:27:31 -04001969 int i_size_changed = 0;
Nick Pigginafddba42007-10-16 01:25:01 -07001970
1971 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
1972
1973 /*
1974 * No need to use i_size_read() here, the i_size
1975 * cannot change under us because we hold i_mutex.
1976 *
1977 * But it's important to update i_size while still holding page lock:
1978 * page writeout could otherwise come in and zero beyond i_size.
1979 */
1980 if (pos+copied > inode->i_size) {
1981 i_size_write(inode, pos+copied);
Jan Karac7d206b2008-07-11 19:27:31 -04001982 i_size_changed = 1;
Nick Pigginafddba42007-10-16 01:25:01 -07001983 }
1984
1985 unlock_page(page);
1986 page_cache_release(page);
1987
Jan Karac7d206b2008-07-11 19:27:31 -04001988 /*
1989 * Don't mark the inode dirty under page lock. First, it unnecessarily
1990 * makes the holding time of page lock longer. Second, it forces lock
1991 * ordering of page lock and transaction start for journaling
1992 * filesystems.
1993 */
1994 if (i_size_changed)
1995 mark_inode_dirty(inode);
1996
Nick Pigginafddba42007-10-16 01:25:01 -07001997 return copied;
1998}
1999EXPORT_SYMBOL(generic_write_end);
2000
2001/*
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07002002 * block_is_partially_uptodate checks whether buffers within a page are
2003 * uptodate or not.
2004 *
2005 * Returns true if all buffers which correspond to a file portion
2006 * we want to read are uptodate.
2007 */
2008int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
2009 unsigned long from)
2010{
2011 struct inode *inode = page->mapping->host;
2012 unsigned block_start, block_end, blocksize;
2013 unsigned to;
2014 struct buffer_head *bh, *head;
2015 int ret = 1;
2016
2017 if (!page_has_buffers(page))
2018 return 0;
2019
2020 blocksize = 1 << inode->i_blkbits;
2021 to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count);
2022 to = from + to;
2023 if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
2024 return 0;
2025
2026 head = page_buffers(page);
2027 bh = head;
2028 block_start = 0;
2029 do {
2030 block_end = block_start + blocksize;
2031 if (block_end > from && block_start < to) {
2032 if (!buffer_uptodate(bh)) {
2033 ret = 0;
2034 break;
2035 }
2036 if (block_end >= to)
2037 break;
2038 }
2039 block_start = block_end;
2040 bh = bh->b_this_page;
2041 } while (bh != head);
2042
2043 return ret;
2044}
2045EXPORT_SYMBOL(block_is_partially_uptodate);
2046
2047/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002048 * Generic "read page" function for block devices that have the normal
2049 * get_block functionality. This is most of the block device filesystems.
2050 * Reads the page asynchronously --- the unlock_buffer() and
2051 * set/clear_buffer_uptodate() functions propagate buffer state into the
2052 * page struct once IO has completed.
2053 */
2054int block_read_full_page(struct page *page, get_block_t *get_block)
2055{
2056 struct inode *inode = page->mapping->host;
2057 sector_t iblock, lblock;
2058 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2059 unsigned int blocksize;
2060 int nr, i;
2061 int fully_mapped = 1;
2062
Matt Mackallcd7619d2005-05-01 08:59:01 -07002063 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002064 blocksize = 1 << inode->i_blkbits;
2065 if (!page_has_buffers(page))
2066 create_empty_buffers(page, blocksize, 0);
2067 head = page_buffers(page);
2068
2069 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2070 lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
2071 bh = head;
2072 nr = 0;
2073 i = 0;
2074
2075 do {
2076 if (buffer_uptodate(bh))
2077 continue;
2078
2079 if (!buffer_mapped(bh)) {
Andrew Mortonc64610b2005-05-16 21:53:49 -07002080 int err = 0;
2081
Linus Torvalds1da177e2005-04-16 15:20:36 -07002082 fully_mapped = 0;
2083 if (iblock < lblock) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002084 WARN_ON(bh->b_size != blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002085 err = get_block(inode, iblock, bh, 0);
2086 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002087 SetPageError(page);
2088 }
2089 if (!buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002090 zero_user(page, i * blocksize, blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002091 if (!err)
2092 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002093 continue;
2094 }
2095 /*
2096 * get_block() might have updated the buffer
2097 * synchronously
2098 */
2099 if (buffer_uptodate(bh))
2100 continue;
2101 }
2102 arr[nr++] = bh;
2103 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2104
2105 if (fully_mapped)
2106 SetPageMappedToDisk(page);
2107
2108 if (!nr) {
2109 /*
2110 * All buffers are uptodate - we can set the page uptodate
2111 * as well. But not if get_block() returned an error.
2112 */
2113 if (!PageError(page))
2114 SetPageUptodate(page);
2115 unlock_page(page);
2116 return 0;
2117 }
2118
2119 /* Stage two: lock the buffers */
2120 for (i = 0; i < nr; i++) {
2121 bh = arr[i];
2122 lock_buffer(bh);
2123 mark_buffer_async_read(bh);
2124 }
2125
2126 /*
2127 * Stage 3: start the IO. Check for uptodateness
2128 * inside the buffer lock in case another process reading
2129 * the underlying blockdev brought it uptodate (the sct fix).
2130 */
2131 for (i = 0; i < nr; i++) {
2132 bh = arr[i];
2133 if (buffer_uptodate(bh))
2134 end_buffer_async_read(bh, 1);
2135 else
2136 submit_bh(READ, bh);
2137 }
2138 return 0;
2139}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002140EXPORT_SYMBOL(block_read_full_page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002141
2142/* utility function for filesystems that need to do work on expanding
Nick Piggin89e10782007-10-16 01:25:07 -07002143 * truncates. Uses filesystem pagecache writes to allow the filesystem to
Linus Torvalds1da177e2005-04-16 15:20:36 -07002144 * deal with the hole.
2145 */
Nick Piggin89e10782007-10-16 01:25:07 -07002146int generic_cont_expand_simple(struct inode *inode, loff_t size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002147{
2148 struct address_space *mapping = inode->i_mapping;
2149 struct page *page;
Nick Piggin89e10782007-10-16 01:25:07 -07002150 void *fsdata;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002151 int err;
2152
npiggin@suse.dec08d3b02009-08-21 02:35:06 +10002153 err = inode_newsize_ok(inode, size);
2154 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002155 goto out;
2156
Nick Piggin89e10782007-10-16 01:25:07 -07002157 err = pagecache_write_begin(NULL, mapping, size, 0,
2158 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2159 &page, &fsdata);
2160 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002161 goto out;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002162
Nick Piggin89e10782007-10-16 01:25:07 -07002163 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2164 BUG_ON(err > 0);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002165
Linus Torvalds1da177e2005-04-16 15:20:36 -07002166out:
2167 return err;
2168}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002169EXPORT_SYMBOL(generic_cont_expand_simple);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002170
Adrian Bunkf1e3af72008-04-29 00:59:01 -07002171static int cont_expand_zero(struct file *file, struct address_space *mapping,
2172 loff_t pos, loff_t *bytes)
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002173{
Nick Piggin89e10782007-10-16 01:25:07 -07002174 struct inode *inode = mapping->host;
2175 unsigned blocksize = 1 << inode->i_blkbits;
2176 struct page *page;
2177 void *fsdata;
2178 pgoff_t index, curidx;
2179 loff_t curpos;
2180 unsigned zerofrom, offset, len;
2181 int err = 0;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002182
Nick Piggin89e10782007-10-16 01:25:07 -07002183 index = pos >> PAGE_CACHE_SHIFT;
2184 offset = pos & ~PAGE_CACHE_MASK;
2185
2186 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
2187 zerofrom = curpos & ~PAGE_CACHE_MASK;
2188 if (zerofrom & (blocksize-1)) {
2189 *bytes |= (blocksize-1);
2190 (*bytes)++;
2191 }
2192 len = PAGE_CACHE_SIZE - zerofrom;
2193
2194 err = pagecache_write_begin(file, mapping, curpos, len,
2195 AOP_FLAG_UNINTERRUPTIBLE,
2196 &page, &fsdata);
2197 if (err)
2198 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002199 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002200 err = pagecache_write_end(file, mapping, curpos, len, len,
2201 page, fsdata);
2202 if (err < 0)
2203 goto out;
2204 BUG_ON(err != len);
2205 err = 0;
OGAWA Hirofumi061e9742008-04-28 02:16:28 -07002206
2207 balance_dirty_pages_ratelimited(mapping);
Nick Piggin89e10782007-10-16 01:25:07 -07002208 }
2209
2210 /* page covers the boundary, find the boundary offset */
2211 if (index == curidx) {
2212 zerofrom = curpos & ~PAGE_CACHE_MASK;
2213 /* if we will expand the thing last block will be filled */
2214 if (offset <= zerofrom) {
2215 goto out;
2216 }
2217 if (zerofrom & (blocksize-1)) {
2218 *bytes |= (blocksize-1);
2219 (*bytes)++;
2220 }
2221 len = offset - zerofrom;
2222
2223 err = pagecache_write_begin(file, mapping, curpos, len,
2224 AOP_FLAG_UNINTERRUPTIBLE,
2225 &page, &fsdata);
2226 if (err)
2227 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002228 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002229 err = pagecache_write_end(file, mapping, curpos, len, len,
2230 page, fsdata);
2231 if (err < 0)
2232 goto out;
2233 BUG_ON(err != len);
2234 err = 0;
2235 }
2236out:
2237 return err;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002238}
2239
Linus Torvalds1da177e2005-04-16 15:20:36 -07002240/*
2241 * For moronic filesystems that do not allow holes in file.
2242 * We may have to extend the file.
2243 */
Christoph Hellwig282dc172010-06-04 11:29:55 +02002244int cont_write_begin(struct file *file, struct address_space *mapping,
Nick Piggin89e10782007-10-16 01:25:07 -07002245 loff_t pos, unsigned len, unsigned flags,
2246 struct page **pagep, void **fsdata,
2247 get_block_t *get_block, loff_t *bytes)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002248{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002249 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002250 unsigned blocksize = 1 << inode->i_blkbits;
Nick Piggin89e10782007-10-16 01:25:07 -07002251 unsigned zerofrom;
2252 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002253
Nick Piggin89e10782007-10-16 01:25:07 -07002254 err = cont_expand_zero(file, mapping, pos, bytes);
2255 if (err)
Christoph Hellwig155130a2010-06-04 11:29:58 +02002256 return err;
Nick Piggin89e10782007-10-16 01:25:07 -07002257
2258 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2259 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2260 *bytes |= (blocksize-1);
2261 (*bytes)++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002262 }
2263
Christoph Hellwig155130a2010-06-04 11:29:58 +02002264 return block_write_begin(mapping, pos, len, flags, pagep, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002265}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002266EXPORT_SYMBOL(cont_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002267
Linus Torvalds1da177e2005-04-16 15:20:36 -07002268int block_commit_write(struct page *page, unsigned from, unsigned to)
2269{
2270 struct inode *inode = page->mapping->host;
2271 __block_commit_write(inode,page,from,to);
2272 return 0;
2273}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002274EXPORT_SYMBOL(block_commit_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002275
David Chinner54171692007-07-19 17:39:55 +10002276/*
2277 * block_page_mkwrite() is not allowed to change the file size as it gets
2278 * called from a page fault handler when a page is first dirtied. Hence we must
2279 * be careful to check for EOF conditions here. We set the page up correctly
2280 * for a written page which means we get ENOSPC checking when writing into
2281 * holes and correct delalloc and unwritten extent mapping on filesystems that
2282 * support these features.
2283 *
2284 * We are not allowed to take the i_mutex here so we have to play games to
2285 * protect against truncate races as the page could now be beyond EOF. Because
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10002286 * truncate writes the inode size before removing pages, once we have the
David Chinner54171692007-07-19 17:39:55 +10002287 * page lock we can determine safely if the page is beyond EOF. If it is not
2288 * beyond EOF, then the page is guaranteed safe against truncation until we
2289 * unlock the page.
Jan Karaea13a862011-05-24 00:23:35 +02002290 *
2291 * Direct callers of this function should call vfs_check_frozen() so that page
2292 * fault does not busyloop until the fs is thawed.
David Chinner54171692007-07-19 17:39:55 +10002293 */
Jan Kara24da4fa2011-05-24 00:23:34 +02002294int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2295 get_block_t get_block)
David Chinner54171692007-07-19 17:39:55 +10002296{
Nick Pigginc2ec1752009-03-31 15:23:21 -07002297 struct page *page = vmf->page;
David Chinner54171692007-07-19 17:39:55 +10002298 struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
2299 unsigned long end;
2300 loff_t size;
Jan Kara24da4fa2011-05-24 00:23:34 +02002301 int ret;
David Chinner54171692007-07-19 17:39:55 +10002302
2303 lock_page(page);
2304 size = i_size_read(inode);
2305 if ((page->mapping != inode->i_mapping) ||
Nick Piggin18336332007-07-20 00:31:45 -07002306 (page_offset(page) > size)) {
Jan Kara24da4fa2011-05-24 00:23:34 +02002307 /* We overload EFAULT to mean page got truncated */
2308 ret = -EFAULT;
2309 goto out_unlock;
David Chinner54171692007-07-19 17:39:55 +10002310 }
2311
2312 /* page is wholly or partially inside EOF */
2313 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
2314 end = size & ~PAGE_CACHE_MASK;
2315 else
2316 end = PAGE_CACHE_SIZE;
2317
Christoph Hellwigebdec242010-10-06 10:47:23 +02002318 ret = __block_write_begin(page, 0, end, get_block);
David Chinner54171692007-07-19 17:39:55 +10002319 if (!ret)
2320 ret = block_commit_write(page, 0, end);
2321
Jan Kara24da4fa2011-05-24 00:23:34 +02002322 if (unlikely(ret < 0))
2323 goto out_unlock;
Jan Karaea13a862011-05-24 00:23:35 +02002324 /*
2325 * Freezing in progress? We check after the page is marked dirty and
2326 * with page lock held so if the test here fails, we are sure freezing
2327 * code will wait during syncing until the page fault is done - at that
2328 * point page will be dirty and unlocked so freezing code will write it
2329 * and writeprotect it again.
2330 */
2331 set_page_dirty(page);
2332 if (inode->i_sb->s_frozen != SB_UNFROZEN) {
2333 ret = -EAGAIN;
2334 goto out_unlock;
2335 }
Darrick J. Wongd76ee182011-05-27 12:23:41 -07002336 wait_on_page_writeback(page);
Jan Kara24da4fa2011-05-24 00:23:34 +02002337 return 0;
2338out_unlock:
2339 unlock_page(page);
David Chinner54171692007-07-19 17:39:55 +10002340 return ret;
2341}
Jan Kara24da4fa2011-05-24 00:23:34 +02002342EXPORT_SYMBOL(__block_page_mkwrite);
2343
2344int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2345 get_block_t get_block)
2346{
Jan Karaea13a862011-05-24 00:23:35 +02002347 int ret;
2348 struct super_block *sb = vma->vm_file->f_path.dentry->d_inode->i_sb;
Jan Kara24da4fa2011-05-24 00:23:34 +02002349
Jan Karaea13a862011-05-24 00:23:35 +02002350 /*
2351 * This check is racy but catches the common case. The check in
2352 * __block_page_mkwrite() is reliable.
2353 */
2354 vfs_check_frozen(sb, SB_FREEZE_WRITE);
2355 ret = __block_page_mkwrite(vma, vmf, get_block);
Jan Kara24da4fa2011-05-24 00:23:34 +02002356 return block_page_mkwrite_return(ret);
2357}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002358EXPORT_SYMBOL(block_page_mkwrite);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002359
2360/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002361 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
Linus Torvalds1da177e2005-04-16 15:20:36 -07002362 * immediately, while under the page lock. So it needs a special end_io
2363 * handler which does not touch the bh after unlocking it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002364 */
2365static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2366{
Dmitry Monakhov68671f32007-10-16 01:24:47 -07002367 __end_buffer_read_notouch(bh, uptodate);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002368}
2369
2370/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002371 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2372 * the page (converting it to circular linked list and taking care of page
2373 * dirty races).
2374 */
2375static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2376{
2377 struct buffer_head *bh;
2378
2379 BUG_ON(!PageLocked(page));
2380
2381 spin_lock(&page->mapping->private_lock);
2382 bh = head;
2383 do {
2384 if (PageDirty(page))
2385 set_buffer_dirty(bh);
2386 if (!bh->b_this_page)
2387 bh->b_this_page = head;
2388 bh = bh->b_this_page;
2389 } while (bh != head);
2390 attach_page_buffers(page, head);
2391 spin_unlock(&page->mapping->private_lock);
2392}
2393
2394/*
Christoph Hellwigea0f04e2010-06-04 11:29:54 +02002395 * On entry, the page is fully not uptodate.
2396 * On exit the page is fully uptodate in the areas outside (from,to)
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10002397 * The filesystem needs to handle block truncation upon failure.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002398 */
Christoph Hellwigea0f04e2010-06-04 11:29:54 +02002399int nobh_write_begin(struct address_space *mapping,
Nick Piggin03158cd2007-10-16 01:25:25 -07002400 loff_t pos, unsigned len, unsigned flags,
2401 struct page **pagep, void **fsdata,
Linus Torvalds1da177e2005-04-16 15:20:36 -07002402 get_block_t *get_block)
2403{
Nick Piggin03158cd2007-10-16 01:25:25 -07002404 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002405 const unsigned blkbits = inode->i_blkbits;
2406 const unsigned blocksize = 1 << blkbits;
Nick Piggina4b06722007-10-16 01:24:48 -07002407 struct buffer_head *head, *bh;
Nick Piggin03158cd2007-10-16 01:25:25 -07002408 struct page *page;
2409 pgoff_t index;
2410 unsigned from, to;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002411 unsigned block_in_page;
Nick Piggina4b06722007-10-16 01:24:48 -07002412 unsigned block_start, block_end;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002413 sector_t block_in_file;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002414 int nr_reads = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002415 int ret = 0;
2416 int is_mapped_to_disk = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002417
Nick Piggin03158cd2007-10-16 01:25:25 -07002418 index = pos >> PAGE_CACHE_SHIFT;
2419 from = pos & (PAGE_CACHE_SIZE - 1);
2420 to = from + len;
2421
Nick Piggin54566b22009-01-04 12:00:53 -08002422 page = grab_cache_page_write_begin(mapping, index, flags);
Nick Piggin03158cd2007-10-16 01:25:25 -07002423 if (!page)
2424 return -ENOMEM;
2425 *pagep = page;
2426 *fsdata = NULL;
2427
2428 if (page_has_buffers(page)) {
Namhyung Kim309f77a2010-10-25 15:01:12 +09002429 ret = __block_write_begin(page, pos, len, get_block);
2430 if (unlikely(ret))
2431 goto out_release;
2432 return ret;
Nick Piggin03158cd2007-10-16 01:25:25 -07002433 }
Nick Piggina4b06722007-10-16 01:24:48 -07002434
Linus Torvalds1da177e2005-04-16 15:20:36 -07002435 if (PageMappedToDisk(page))
2436 return 0;
2437
Nick Piggina4b06722007-10-16 01:24:48 -07002438 /*
2439 * Allocate buffers so that we can keep track of state, and potentially
2440 * attach them to the page if an error occurs. In the common case of
2441 * no error, they will just be freed again without ever being attached
2442 * to the page (which is all OK, because we're under the page lock).
2443 *
2444 * Be careful: the buffer linked list is a NULL terminated one, rather
2445 * than the circular one we're used to.
2446 */
2447 head = alloc_page_buffers(page, blocksize, 0);
Nick Piggin03158cd2007-10-16 01:25:25 -07002448 if (!head) {
2449 ret = -ENOMEM;
2450 goto out_release;
2451 }
Nick Piggina4b06722007-10-16 01:24:48 -07002452
Linus Torvalds1da177e2005-04-16 15:20:36 -07002453 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002454
2455 /*
2456 * We loop across all blocks in the page, whether or not they are
2457 * part of the affected region. This is so we can discover if the
2458 * page is fully mapped-to-disk.
2459 */
Nick Piggina4b06722007-10-16 01:24:48 -07002460 for (block_start = 0, block_in_page = 0, bh = head;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002461 block_start < PAGE_CACHE_SIZE;
Nick Piggina4b06722007-10-16 01:24:48 -07002462 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002463 int create;
2464
Nick Piggina4b06722007-10-16 01:24:48 -07002465 block_end = block_start + blocksize;
2466 bh->b_state = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002467 create = 1;
2468 if (block_start >= to)
2469 create = 0;
2470 ret = get_block(inode, block_in_file + block_in_page,
Nick Piggina4b06722007-10-16 01:24:48 -07002471 bh, create);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002472 if (ret)
2473 goto failed;
Nick Piggina4b06722007-10-16 01:24:48 -07002474 if (!buffer_mapped(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002475 is_mapped_to_disk = 0;
Nick Piggina4b06722007-10-16 01:24:48 -07002476 if (buffer_new(bh))
2477 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
2478 if (PageUptodate(page)) {
2479 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002480 continue;
Nick Piggina4b06722007-10-16 01:24:48 -07002481 }
2482 if (buffer_new(bh) || !buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002483 zero_user_segments(page, block_start, from,
2484 to, block_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002485 continue;
2486 }
Nick Piggina4b06722007-10-16 01:24:48 -07002487 if (buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002488 continue; /* reiserfs does this */
2489 if (block_start < from || block_end > to) {
Nick Piggina4b06722007-10-16 01:24:48 -07002490 lock_buffer(bh);
2491 bh->b_end_io = end_buffer_read_nobh;
2492 submit_bh(READ, bh);
2493 nr_reads++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002494 }
2495 }
2496
2497 if (nr_reads) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002498 /*
2499 * The page is locked, so these buffers are protected from
2500 * any VM or truncate activity. Hence we don't need to care
2501 * for the buffer_head refcounts.
2502 */
Nick Piggina4b06722007-10-16 01:24:48 -07002503 for (bh = head; bh; bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002504 wait_on_buffer(bh);
2505 if (!buffer_uptodate(bh))
2506 ret = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002507 }
2508 if (ret)
2509 goto failed;
2510 }
2511
2512 if (is_mapped_to_disk)
2513 SetPageMappedToDisk(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002514
Nick Piggin03158cd2007-10-16 01:25:25 -07002515 *fsdata = head; /* to be released by nobh_write_end */
Nick Piggina4b06722007-10-16 01:24:48 -07002516
Linus Torvalds1da177e2005-04-16 15:20:36 -07002517 return 0;
2518
2519failed:
Nick Piggin03158cd2007-10-16 01:25:25 -07002520 BUG_ON(!ret);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002521 /*
Nick Piggina4b06722007-10-16 01:24:48 -07002522 * Error recovery is a bit difficult. We need to zero out blocks that
2523 * were newly allocated, and dirty them to ensure they get written out.
2524 * Buffers need to be attached to the page at this point, otherwise
2525 * the handling of potential IO errors during writeout would be hard
2526 * (could try doing synchronous writeout, but what if that fails too?)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002527 */
Nick Piggin03158cd2007-10-16 01:25:25 -07002528 attach_nobh_buffers(page, head);
2529 page_zero_new_buffers(page, from, to);
Nick Piggina4b06722007-10-16 01:24:48 -07002530
Nick Piggin03158cd2007-10-16 01:25:25 -07002531out_release:
2532 unlock_page(page);
2533 page_cache_release(page);
2534 *pagep = NULL;
Nick Piggina4b06722007-10-16 01:24:48 -07002535
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10002536 return ret;
2537}
Nick Piggin03158cd2007-10-16 01:25:25 -07002538EXPORT_SYMBOL(nobh_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002539
Nick Piggin03158cd2007-10-16 01:25:25 -07002540int nobh_write_end(struct file *file, struct address_space *mapping,
2541 loff_t pos, unsigned len, unsigned copied,
2542 struct page *page, void *fsdata)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002543{
2544 struct inode *inode = page->mapping->host;
Nick Pigginefdc3132007-10-21 06:57:41 +02002545 struct buffer_head *head = fsdata;
Nick Piggin03158cd2007-10-16 01:25:25 -07002546 struct buffer_head *bh;
Dmitri Monakhov5b41e742008-03-28 14:15:52 -07002547 BUG_ON(fsdata != NULL && page_has_buffers(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002548
Dave Kleikampd4cf1092009-02-06 14:59:26 -06002549 if (unlikely(copied < len) && head)
Dmitri Monakhov5b41e742008-03-28 14:15:52 -07002550 attach_nobh_buffers(page, head);
2551 if (page_has_buffers(page))
2552 return generic_write_end(file, mapping, pos, len,
2553 copied, page, fsdata);
Nick Piggina4b06722007-10-16 01:24:48 -07002554
Nick Piggin22c8ca72007-02-20 13:58:09 -08002555 SetPageUptodate(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002556 set_page_dirty(page);
Nick Piggin03158cd2007-10-16 01:25:25 -07002557 if (pos+copied > inode->i_size) {
2558 i_size_write(inode, pos+copied);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002559 mark_inode_dirty(inode);
2560 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002561
2562 unlock_page(page);
2563 page_cache_release(page);
2564
Nick Piggin03158cd2007-10-16 01:25:25 -07002565 while (head) {
2566 bh = head;
2567 head = head->b_this_page;
2568 free_buffer_head(bh);
2569 }
2570
2571 return copied;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002572}
Nick Piggin03158cd2007-10-16 01:25:25 -07002573EXPORT_SYMBOL(nobh_write_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002574
2575/*
2576 * nobh_writepage() - based on block_full_write_page() except
2577 * that it tries to operate without attaching bufferheads to
2578 * the page.
2579 */
2580int nobh_writepage(struct page *page, get_block_t *get_block,
2581 struct writeback_control *wbc)
2582{
2583 struct inode * const inode = page->mapping->host;
2584 loff_t i_size = i_size_read(inode);
2585 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2586 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002587 int ret;
2588
2589 /* Is the page fully inside i_size? */
2590 if (page->index < end_index)
2591 goto out;
2592
2593 /* Is the page fully outside i_size? (truncate in progress) */
2594 offset = i_size & (PAGE_CACHE_SIZE-1);
2595 if (page->index >= end_index+1 || !offset) {
2596 /*
2597 * The page may have dirty, unmapped buffers. For example,
2598 * they may have been added in ext3_writepage(). Make them
2599 * freeable here, so the page does not leak.
2600 */
2601#if 0
2602 /* Not really sure about this - do we need this ? */
2603 if (page->mapping->a_ops->invalidatepage)
2604 page->mapping->a_ops->invalidatepage(page, offset);
2605#endif
2606 unlock_page(page);
2607 return 0; /* don't care */
2608 }
2609
2610 /*
2611 * The page straddles i_size. It must be zeroed out on each and every
2612 * writepage invocation because it may be mmapped. "A file is mapped
2613 * in multiples of the page size. For a file that is not a multiple of
2614 * the page size, the remaining memory is zeroed when mapped, and
2615 * writes to that region are not written out to the file."
2616 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002617 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002618out:
2619 ret = mpage_writepage(page, get_block, wbc);
2620 if (ret == -EAGAIN)
Chris Mason35c80d52009-04-15 13:22:38 -04002621 ret = __block_write_full_page(inode, page, get_block, wbc,
2622 end_buffer_async_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002623 return ret;
2624}
2625EXPORT_SYMBOL(nobh_writepage);
2626
Nick Piggin03158cd2007-10-16 01:25:25 -07002627int nobh_truncate_page(struct address_space *mapping,
2628 loff_t from, get_block_t *get_block)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002629{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002630 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2631 unsigned offset = from & (PAGE_CACHE_SIZE-1);
Nick Piggin03158cd2007-10-16 01:25:25 -07002632 unsigned blocksize;
2633 sector_t iblock;
2634 unsigned length, pos;
2635 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002636 struct page *page;
Nick Piggin03158cd2007-10-16 01:25:25 -07002637 struct buffer_head map_bh;
2638 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002639
Nick Piggin03158cd2007-10-16 01:25:25 -07002640 blocksize = 1 << inode->i_blkbits;
2641 length = offset & (blocksize - 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002642
Nick Piggin03158cd2007-10-16 01:25:25 -07002643 /* Block boundary? Nothing to do */
2644 if (!length)
2645 return 0;
2646
2647 length = blocksize - length;
2648 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2649
Linus Torvalds1da177e2005-04-16 15:20:36 -07002650 page = grab_cache_page(mapping, index);
Nick Piggin03158cd2007-10-16 01:25:25 -07002651 err = -ENOMEM;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002652 if (!page)
2653 goto out;
2654
Nick Piggin03158cd2007-10-16 01:25:25 -07002655 if (page_has_buffers(page)) {
2656has_buffers:
2657 unlock_page(page);
2658 page_cache_release(page);
2659 return block_truncate_page(mapping, from, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002660 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002661
2662 /* Find the buffer that contains "offset" */
2663 pos = blocksize;
2664 while (offset >= pos) {
2665 iblock++;
2666 pos += blocksize;
2667 }
2668
Theodore Ts'o460bcf52009-05-12 07:37:56 -04002669 map_bh.b_size = blocksize;
2670 map_bh.b_state = 0;
Nick Piggin03158cd2007-10-16 01:25:25 -07002671 err = get_block(inode, iblock, &map_bh, 0);
2672 if (err)
2673 goto unlock;
2674 /* unmapped? It's a hole - nothing to do */
2675 if (!buffer_mapped(&map_bh))
2676 goto unlock;
2677
2678 /* Ok, it's mapped. Make sure it's up-to-date */
2679 if (!PageUptodate(page)) {
2680 err = mapping->a_ops->readpage(NULL, page);
2681 if (err) {
2682 page_cache_release(page);
2683 goto out;
2684 }
2685 lock_page(page);
2686 if (!PageUptodate(page)) {
2687 err = -EIO;
2688 goto unlock;
2689 }
2690 if (page_has_buffers(page))
2691 goto has_buffers;
2692 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002693 zero_user(page, offset, length);
Nick Piggin03158cd2007-10-16 01:25:25 -07002694 set_page_dirty(page);
2695 err = 0;
2696
2697unlock:
Linus Torvalds1da177e2005-04-16 15:20:36 -07002698 unlock_page(page);
2699 page_cache_release(page);
2700out:
Nick Piggin03158cd2007-10-16 01:25:25 -07002701 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002702}
2703EXPORT_SYMBOL(nobh_truncate_page);
2704
2705int block_truncate_page(struct address_space *mapping,
2706 loff_t from, get_block_t *get_block)
2707{
2708 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2709 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2710 unsigned blocksize;
Andrew Morton54b21a72006-01-08 01:03:05 -08002711 sector_t iblock;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002712 unsigned length, pos;
2713 struct inode *inode = mapping->host;
2714 struct page *page;
2715 struct buffer_head *bh;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002716 int err;
2717
2718 blocksize = 1 << inode->i_blkbits;
2719 length = offset & (blocksize - 1);
2720
2721 /* Block boundary? Nothing to do */
2722 if (!length)
2723 return 0;
2724
2725 length = blocksize - length;
Andrew Morton54b21a72006-01-08 01:03:05 -08002726 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002727
2728 page = grab_cache_page(mapping, index);
2729 err = -ENOMEM;
2730 if (!page)
2731 goto out;
2732
2733 if (!page_has_buffers(page))
2734 create_empty_buffers(page, blocksize, 0);
2735
2736 /* Find the buffer that contains "offset" */
2737 bh = page_buffers(page);
2738 pos = blocksize;
2739 while (offset >= pos) {
2740 bh = bh->b_this_page;
2741 iblock++;
2742 pos += blocksize;
2743 }
2744
2745 err = 0;
2746 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002747 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002748 err = get_block(inode, iblock, bh, 0);
2749 if (err)
2750 goto unlock;
2751 /* unmapped? It's a hole - nothing to do */
2752 if (!buffer_mapped(bh))
2753 goto unlock;
2754 }
2755
2756 /* Ok, it's mapped. Make sure it's up-to-date */
2757 if (PageUptodate(page))
2758 set_buffer_uptodate(bh);
2759
David Chinner33a266d2007-02-12 00:51:41 -08002760 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002761 err = -EIO;
2762 ll_rw_block(READ, 1, &bh);
2763 wait_on_buffer(bh);
2764 /* Uhhuh. Read error. Complain and punt. */
2765 if (!buffer_uptodate(bh))
2766 goto unlock;
2767 }
2768
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002769 zero_user(page, offset, length);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002770 mark_buffer_dirty(bh);
2771 err = 0;
2772
2773unlock:
2774 unlock_page(page);
2775 page_cache_release(page);
2776out:
2777 return err;
2778}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002779EXPORT_SYMBOL(block_truncate_page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002780
2781/*
2782 * The generic ->writepage function for buffer-backed address_spaces
Chris Mason35c80d52009-04-15 13:22:38 -04002783 * this form passes in the end_io handler used to finish the IO.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002784 */
Chris Mason35c80d52009-04-15 13:22:38 -04002785int block_write_full_page_endio(struct page *page, get_block_t *get_block,
2786 struct writeback_control *wbc, bh_end_io_t *handler)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002787{
2788 struct inode * const inode = page->mapping->host;
2789 loff_t i_size = i_size_read(inode);
2790 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2791 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002792
2793 /* Is the page fully inside i_size? */
2794 if (page->index < end_index)
Chris Mason35c80d52009-04-15 13:22:38 -04002795 return __block_write_full_page(inode, page, get_block, wbc,
2796 handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002797
2798 /* Is the page fully outside i_size? (truncate in progress) */
2799 offset = i_size & (PAGE_CACHE_SIZE-1);
2800 if (page->index >= end_index+1 || !offset) {
2801 /*
2802 * The page may have dirty, unmapped buffers. For example,
2803 * they may have been added in ext3_writepage(). Make them
2804 * freeable here, so the page does not leak.
2805 */
Jan Karaaaa40592005-10-30 15:00:16 -08002806 do_invalidatepage(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002807 unlock_page(page);
2808 return 0; /* don't care */
2809 }
2810
2811 /*
2812 * The page straddles i_size. It must be zeroed out on each and every
Adam Buchbinder2a61aa42009-12-11 16:35:40 -05002813 * writepage invocation because it may be mmapped. "A file is mapped
Linus Torvalds1da177e2005-04-16 15:20:36 -07002814 * in multiples of the page size. For a file that is not a multiple of
2815 * the page size, the remaining memory is zeroed when mapped, and
2816 * writes to that region are not written out to the file."
2817 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002818 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Chris Mason35c80d52009-04-15 13:22:38 -04002819 return __block_write_full_page(inode, page, get_block, wbc, handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002820}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002821EXPORT_SYMBOL(block_write_full_page_endio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002822
Chris Mason35c80d52009-04-15 13:22:38 -04002823/*
2824 * The generic ->writepage function for buffer-backed address_spaces
2825 */
2826int block_write_full_page(struct page *page, get_block_t *get_block,
2827 struct writeback_control *wbc)
2828{
2829 return block_write_full_page_endio(page, get_block, wbc,
2830 end_buffer_async_write);
2831}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002832EXPORT_SYMBOL(block_write_full_page);
Chris Mason35c80d52009-04-15 13:22:38 -04002833
Linus Torvalds1da177e2005-04-16 15:20:36 -07002834sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2835 get_block_t *get_block)
2836{
2837 struct buffer_head tmp;
2838 struct inode *inode = mapping->host;
2839 tmp.b_state = 0;
2840 tmp.b_blocknr = 0;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002841 tmp.b_size = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002842 get_block(inode, block, &tmp, 0);
2843 return tmp.b_blocknr;
2844}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002845EXPORT_SYMBOL(generic_block_bmap);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002846
NeilBrown6712ecf2007-09-27 12:47:43 +02002847static void end_bio_bh_io_sync(struct bio *bio, int err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002848{
2849 struct buffer_head *bh = bio->bi_private;
2850
Linus Torvalds1da177e2005-04-16 15:20:36 -07002851 if (err == -EOPNOTSUPP) {
2852 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002853 }
2854
Keith Mannthey08bafc02008-11-25 10:24:35 +01002855 if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags)))
2856 set_bit(BH_Quiet, &bh->b_state);
2857
Linus Torvalds1da177e2005-04-16 15:20:36 -07002858 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2859 bio_put(bio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002860}
2861
2862int submit_bh(int rw, struct buffer_head * bh)
2863{
2864 struct bio *bio;
2865 int ret = 0;
2866
2867 BUG_ON(!buffer_locked(bh));
2868 BUG_ON(!buffer_mapped(bh));
2869 BUG_ON(!bh->b_end_io);
Aneesh Kumar K.V8fb0e342009-05-12 16:22:37 -04002870 BUG_ON(buffer_delay(bh));
2871 BUG_ON(buffer_unwritten(bh));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002872
Jens Axboe48fd4f92008-08-22 10:00:36 +02002873 /*
Jens Axboe48fd4f92008-08-22 10:00:36 +02002874 * Only clear out a write error when rewriting
Linus Torvalds1da177e2005-04-16 15:20:36 -07002875 */
Jens Axboe48fd4f92008-08-22 10:00:36 +02002876 if (test_set_buffer_req(bh) && (rw & WRITE))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002877 clear_buffer_write_io_error(bh);
2878
2879 /*
2880 * from here on down, it's all bio -- do the initial mapping,
2881 * submit_bio -> generic_make_request may further map this bio around
2882 */
2883 bio = bio_alloc(GFP_NOIO, 1);
2884
2885 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2886 bio->bi_bdev = bh->b_bdev;
2887 bio->bi_io_vec[0].bv_page = bh->b_page;
2888 bio->bi_io_vec[0].bv_len = bh->b_size;
2889 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
2890
2891 bio->bi_vcnt = 1;
2892 bio->bi_idx = 0;
2893 bio->bi_size = bh->b_size;
2894
2895 bio->bi_end_io = end_bio_bh_io_sync;
2896 bio->bi_private = bh;
2897
2898 bio_get(bio);
2899 submit_bio(rw, bio);
2900
2901 if (bio_flagged(bio, BIO_EOPNOTSUPP))
2902 ret = -EOPNOTSUPP;
2903
2904 bio_put(bio);
2905 return ret;
2906}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002907EXPORT_SYMBOL(submit_bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002908
2909/**
2910 * ll_rw_block: low-level access to block devices (DEPRECATED)
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02002911 * @rw: whether to %READ or %WRITE or maybe %READA (readahead)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002912 * @nr: number of &struct buffer_heads in the array
2913 * @bhs: array of pointers to &struct buffer_head
2914 *
Jan Karaa7662232005-09-06 15:19:10 -07002915 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
2916 * requests an I/O operation on them, either a %READ or a %WRITE. The third
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02002917 * %READA option is described in the documentation for generic_make_request()
2918 * which ll_rw_block() calls.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002919 *
2920 * This function drops any buffer that it cannot get a lock on (with the
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02002921 * BH_Lock state bit), any buffer that appears to be clean when doing a write
2922 * request, and any buffer that appears to be up-to-date when doing read
2923 * request. Further it marks as clean buffers that are processed for
2924 * writing (the buffer cache won't assume that they are actually clean
2925 * until the buffer gets unlocked).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002926 *
2927 * ll_rw_block sets b_end_io to simple completion handler that marks
2928 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
2929 * any waiters.
2930 *
2931 * All of the buffers must be for the same device, and must also be a
2932 * multiple of the current approved size for the device.
2933 */
2934void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
2935{
2936 int i;
2937
2938 for (i = 0; i < nr; i++) {
2939 struct buffer_head *bh = bhs[i];
2940
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02002941 if (!trylock_buffer(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002942 continue;
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02002943 if (rw == WRITE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002944 if (test_clear_buffer_dirty(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07002945 bh->b_end_io = end_buffer_write_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08002946 get_bh(bh);
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02002947 submit_bh(WRITE, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002948 continue;
2949 }
2950 } else {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002951 if (!buffer_uptodate(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07002952 bh->b_end_io = end_buffer_read_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08002953 get_bh(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002954 submit_bh(rw, bh);
2955 continue;
2956 }
2957 }
2958 unlock_buffer(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002959 }
2960}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002961EXPORT_SYMBOL(ll_rw_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002962
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02002963void write_dirty_buffer(struct buffer_head *bh, int rw)
2964{
2965 lock_buffer(bh);
2966 if (!test_clear_buffer_dirty(bh)) {
2967 unlock_buffer(bh);
2968 return;
2969 }
2970 bh->b_end_io = end_buffer_write_sync;
2971 get_bh(bh);
2972 submit_bh(rw, bh);
2973}
2974EXPORT_SYMBOL(write_dirty_buffer);
2975
Linus Torvalds1da177e2005-04-16 15:20:36 -07002976/*
2977 * For a data-integrity writeout, we need to wait upon any in-progress I/O
2978 * and then start new I/O and then wait upon it. The caller must have a ref on
2979 * the buffer_head.
2980 */
Christoph Hellwig87e99512010-08-11 17:05:45 +02002981int __sync_dirty_buffer(struct buffer_head *bh, int rw)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002982{
2983 int ret = 0;
2984
2985 WARN_ON(atomic_read(&bh->b_count) < 1);
2986 lock_buffer(bh);
2987 if (test_clear_buffer_dirty(bh)) {
2988 get_bh(bh);
2989 bh->b_end_io = end_buffer_write_sync;
Christoph Hellwig87e99512010-08-11 17:05:45 +02002990 ret = submit_bh(rw, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002991 wait_on_buffer(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002992 if (!ret && !buffer_uptodate(bh))
2993 ret = -EIO;
2994 } else {
2995 unlock_buffer(bh);
2996 }
2997 return ret;
2998}
Christoph Hellwig87e99512010-08-11 17:05:45 +02002999EXPORT_SYMBOL(__sync_dirty_buffer);
3000
3001int sync_dirty_buffer(struct buffer_head *bh)
3002{
3003 return __sync_dirty_buffer(bh, WRITE_SYNC);
3004}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07003005EXPORT_SYMBOL(sync_dirty_buffer);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003006
3007/*
3008 * try_to_free_buffers() checks if all the buffers on this particular page
3009 * are unused, and releases them if so.
3010 *
3011 * Exclusion against try_to_free_buffers may be obtained by either
3012 * locking the page or by holding its mapping's private_lock.
3013 *
3014 * If the page is dirty but all the buffers are clean then we need to
3015 * be sure to mark the page clean as well. This is because the page
3016 * may be against a block device, and a later reattachment of buffers
3017 * to a dirty page will set *all* buffers dirty. Which would corrupt
3018 * filesystem data on the same device.
3019 *
3020 * The same applies to regular filesystem pages: if all the buffers are
3021 * clean then we set the page clean and proceed. To do that, we require
3022 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3023 * private_lock.
3024 *
3025 * try_to_free_buffers() is non-blocking.
3026 */
3027static inline int buffer_busy(struct buffer_head *bh)
3028{
3029 return atomic_read(&bh->b_count) |
3030 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3031}
3032
3033static int
3034drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3035{
3036 struct buffer_head *head = page_buffers(page);
3037 struct buffer_head *bh;
3038
3039 bh = head;
3040 do {
akpm@osdl.orgde7d5a32005-05-01 08:58:39 -07003041 if (buffer_write_io_error(bh) && page->mapping)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003042 set_bit(AS_EIO, &page->mapping->flags);
3043 if (buffer_busy(bh))
3044 goto failed;
3045 bh = bh->b_this_page;
3046 } while (bh != head);
3047
3048 do {
3049 struct buffer_head *next = bh->b_this_page;
3050
Jan Kara535ee2f2008-02-08 04:21:59 -08003051 if (bh->b_assoc_map)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003052 __remove_assoc_queue(bh);
3053 bh = next;
3054 } while (bh != head);
3055 *buffers_to_free = head;
3056 __clear_page_buffers(page);
3057 return 1;
3058failed:
3059 return 0;
3060}
3061
3062int try_to_free_buffers(struct page *page)
3063{
3064 struct address_space * const mapping = page->mapping;
3065 struct buffer_head *buffers_to_free = NULL;
3066 int ret = 0;
3067
3068 BUG_ON(!PageLocked(page));
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003069 if (PageWriteback(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003070 return 0;
3071
3072 if (mapping == NULL) { /* can this still happen? */
3073 ret = drop_buffers(page, &buffers_to_free);
3074 goto out;
3075 }
3076
3077 spin_lock(&mapping->private_lock);
3078 ret = drop_buffers(page, &buffers_to_free);
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003079
3080 /*
3081 * If the filesystem writes its buffers by hand (eg ext3)
3082 * then we can have clean buffers against a dirty page. We
3083 * clean the page here; otherwise the VM will never notice
3084 * that the filesystem did any IO at all.
3085 *
3086 * Also, during truncate, discard_buffer will have marked all
3087 * the page's buffers clean. We discover that here and clean
3088 * the page also.
Nick Piggin87df7242007-01-30 14:36:27 +11003089 *
3090 * private_lock must be held over this entire operation in order
3091 * to synchronise against __set_page_dirty_buffers and prevent the
3092 * dirty bit from being lost.
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003093 */
3094 if (ret)
3095 cancel_dirty_page(page, PAGE_CACHE_SIZE);
Nick Piggin87df7242007-01-30 14:36:27 +11003096 spin_unlock(&mapping->private_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003097out:
3098 if (buffers_to_free) {
3099 struct buffer_head *bh = buffers_to_free;
3100
3101 do {
3102 struct buffer_head *next = bh->b_this_page;
3103 free_buffer_head(bh);
3104 bh = next;
3105 } while (bh != buffers_to_free);
3106 }
3107 return ret;
3108}
3109EXPORT_SYMBOL(try_to_free_buffers);
3110
Linus Torvalds1da177e2005-04-16 15:20:36 -07003111/*
3112 * There are no bdflush tunables left. But distributions are
3113 * still running obsolete flush daemons, so we terminate them here.
3114 *
3115 * Use of bdflush() is deprecated and will be removed in a future kernel.
Jens Axboe5b0830c2009-09-23 19:37:09 +02003116 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003117 */
Heiko Carstensbdc480e2009-01-14 14:14:12 +01003118SYSCALL_DEFINE2(bdflush, int, func, long, data)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003119{
3120 static int msg_count;
3121
3122 if (!capable(CAP_SYS_ADMIN))
3123 return -EPERM;
3124
3125 if (msg_count < 5) {
3126 msg_count++;
3127 printk(KERN_INFO
3128 "warning: process `%s' used the obsolete bdflush"
3129 " system call\n", current->comm);
3130 printk(KERN_INFO "Fix your initscripts?\n");
3131 }
3132
3133 if (func == 1)
3134 do_exit(0);
3135 return 0;
3136}
3137
3138/*
3139 * Buffer-head allocation
3140 */
Christoph Lametere18b8902006-12-06 20:33:20 -08003141static struct kmem_cache *bh_cachep;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003142
3143/*
3144 * Once the number of bh's in the machine exceeds this level, we start
3145 * stripping them in writeback.
3146 */
3147static int max_buffer_heads;
3148
3149int buffer_heads_over_limit;
3150
3151struct bh_accounting {
3152 int nr; /* Number of live bh's */
3153 int ratelimit; /* Limit cacheline bouncing */
3154};
3155
3156static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3157
3158static void recalc_bh_state(void)
3159{
3160 int i;
3161 int tot = 0;
3162
Christoph Lameteree1be862010-12-06 11:40:05 -06003163 if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003164 return;
Christoph Lameterc7b92512010-12-06 11:16:28 -06003165 __this_cpu_write(bh_accounting.ratelimit, 0);
Eric Dumazet8a143422006-03-24 03:18:10 -08003166 for_each_online_cpu(i)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003167 tot += per_cpu(bh_accounting, i).nr;
3168 buffer_heads_over_limit = (tot > max_buffer_heads);
3169}
Christoph Lameterc7b92512010-12-06 11:16:28 -06003170
Al Virodd0fc662005-10-07 07:46:04 +01003171struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003172{
Richard Kennedy019b4d12010-03-10 15:20:33 -08003173 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003174 if (ret) {
Christoph Lametera35afb82007-05-16 22:10:57 -07003175 INIT_LIST_HEAD(&ret->b_assoc_buffers);
Christoph Lameterc7b92512010-12-06 11:16:28 -06003176 preempt_disable();
3177 __this_cpu_inc(bh_accounting.nr);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003178 recalc_bh_state();
Christoph Lameterc7b92512010-12-06 11:16:28 -06003179 preempt_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -07003180 }
3181 return ret;
3182}
3183EXPORT_SYMBOL(alloc_buffer_head);
3184
3185void free_buffer_head(struct buffer_head *bh)
3186{
3187 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3188 kmem_cache_free(bh_cachep, bh);
Christoph Lameterc7b92512010-12-06 11:16:28 -06003189 preempt_disable();
3190 __this_cpu_dec(bh_accounting.nr);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003191 recalc_bh_state();
Christoph Lameterc7b92512010-12-06 11:16:28 -06003192 preempt_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -07003193}
3194EXPORT_SYMBOL(free_buffer_head);
3195
Linus Torvalds1da177e2005-04-16 15:20:36 -07003196static void buffer_exit_cpu(int cpu)
3197{
3198 int i;
3199 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3200
3201 for (i = 0; i < BH_LRU_SIZE; i++) {
3202 brelse(b->bhs[i]);
3203 b->bhs[i] = NULL;
3204 }
Christoph Lameterc7b92512010-12-06 11:16:28 -06003205 this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
Eric Dumazet8a143422006-03-24 03:18:10 -08003206 per_cpu(bh_accounting, cpu).nr = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003207}
3208
3209static int buffer_cpu_notify(struct notifier_block *self,
3210 unsigned long action, void *hcpu)
3211{
Rafael J. Wysocki8bb78442007-05-09 02:35:10 -07003212 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003213 buffer_exit_cpu((unsigned long)hcpu);
3214 return NOTIFY_OK;
3215}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003216
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003217/**
Randy Dunlapa6b91912008-03-19 17:01:00 -07003218 * bh_uptodate_or_lock - Test whether the buffer is uptodate
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003219 * @bh: struct buffer_head
3220 *
3221 * Return true if the buffer is up-to-date and false,
3222 * with the buffer locked, if not.
3223 */
3224int bh_uptodate_or_lock(struct buffer_head *bh)
3225{
3226 if (!buffer_uptodate(bh)) {
3227 lock_buffer(bh);
3228 if (!buffer_uptodate(bh))
3229 return 0;
3230 unlock_buffer(bh);
3231 }
3232 return 1;
3233}
3234EXPORT_SYMBOL(bh_uptodate_or_lock);
3235
3236/**
Randy Dunlapa6b91912008-03-19 17:01:00 -07003237 * bh_submit_read - Submit a locked buffer for reading
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003238 * @bh: struct buffer_head
3239 *
3240 * Returns zero on success and -EIO on error.
3241 */
3242int bh_submit_read(struct buffer_head *bh)
3243{
3244 BUG_ON(!buffer_locked(bh));
3245
3246 if (buffer_uptodate(bh)) {
3247 unlock_buffer(bh);
3248 return 0;
3249 }
3250
3251 get_bh(bh);
3252 bh->b_end_io = end_buffer_read_sync;
3253 submit_bh(READ, bh);
3254 wait_on_buffer(bh);
3255 if (buffer_uptodate(bh))
3256 return 0;
3257 return -EIO;
3258}
3259EXPORT_SYMBOL(bh_submit_read);
3260
Linus Torvalds1da177e2005-04-16 15:20:36 -07003261void __init buffer_init(void)
3262{
3263 int nrpages;
3264
Christoph Lameterb98938c2008-02-04 22:28:36 -08003265 bh_cachep = kmem_cache_create("buffer_head",
3266 sizeof(struct buffer_head), 0,
3267 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3268 SLAB_MEM_SPREAD),
Richard Kennedy019b4d12010-03-10 15:20:33 -08003269 NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003270
3271 /*
3272 * Limit the bh occupancy to 10% of ZONE_NORMAL
3273 */
3274 nrpages = (nr_free_buffer_pages() * 10) / 100;
3275 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3276 hotcpu_notifier(buffer_cpu_notify, 0);
3277}