blob: c7062c896d7c20489f41ea838640a5cfa5387ca9 [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>
Paul Gortmaker630d9c42011-11-16 23:57:37 -050032#include <linux/export.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070033#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);
Jeff Moyer080399a2012-05-11 16:34:10 +0200924 sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700925
926 do {
927 if (!buffer_mapped(bh)) {
928 init_buffer(bh, NULL, NULL);
929 bh->b_bdev = bdev;
930 bh->b_blocknr = block;
931 if (uptodate)
932 set_buffer_uptodate(bh);
Jeff Moyer080399a2012-05-11 16:34:10 +0200933 if (block < end_block)
934 set_buffer_mapped(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700935 }
936 block++;
937 bh = bh->b_this_page;
938 } while (bh != head);
939}
940
941/*
942 * Create the page-cache page that contains the requested block.
943 *
944 * This is user purely for blockdev mappings.
945 */
946static struct page *
947grow_dev_page(struct block_device *bdev, sector_t block,
948 pgoff_t index, int size)
949{
950 struct inode *inode = bdev->bd_inode;
951 struct page *page;
952 struct buffer_head *bh;
953
Christoph Lameterea125892007-05-16 22:11:21 -0700954 page = find_or_create_page(inode->i_mapping, index,
Mel Gorman769848c2007-07-17 04:03:05 -0700955 (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700956 if (!page)
957 return NULL;
958
Eric Sesterhenne827f922006-03-26 18:24:46 +0200959 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700960
961 if (page_has_buffers(page)) {
962 bh = page_buffers(page);
963 if (bh->b_size == size) {
964 init_page_buffers(page, bdev, block, size);
965 return page;
966 }
967 if (!try_to_free_buffers(page))
968 goto failed;
969 }
970
971 /*
972 * Allocate some buffers for this page
973 */
974 bh = alloc_page_buffers(page, size, 0);
975 if (!bh)
976 goto failed;
977
978 /*
979 * Link the page to the buffers and initialise them. Take the
980 * lock to be atomic wrt __find_get_block(), which does not
981 * run under the page lock.
982 */
983 spin_lock(&inode->i_mapping->private_lock);
984 link_dev_buffers(page, bh);
985 init_page_buffers(page, bdev, block, size);
986 spin_unlock(&inode->i_mapping->private_lock);
987 return page;
988
989failed:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700990 unlock_page(page);
991 page_cache_release(page);
992 return NULL;
993}
994
995/*
996 * Create buffers for the specified block device block's page. If
997 * that page was dirty, the buffers are set dirty also.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700998 */
Arjan van de Ven858119e2006-01-14 13:20:43 -0800999static int
Linus Torvalds1da177e2005-04-16 15:20:36 -07001000grow_buffers(struct block_device *bdev, sector_t block, int size)
1001{
1002 struct page *page;
1003 pgoff_t index;
1004 int sizebits;
1005
1006 sizebits = -1;
1007 do {
1008 sizebits++;
1009 } while ((size << sizebits) < PAGE_SIZE);
1010
1011 index = block >> sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001012
Andrew Mortone5657932006-10-11 01:21:46 -07001013 /*
1014 * Check for a block which wants to lie outside our maximum possible
1015 * pagecache index. (this comparison is done using sector_t types).
1016 */
1017 if (unlikely(index != block >> sizebits)) {
1018 char b[BDEVNAME_SIZE];
1019
1020 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1021 "device %s\n",
Harvey Harrison8e24eea2008-04-30 00:55:09 -07001022 __func__, (unsigned long long)block,
Andrew Mortone5657932006-10-11 01:21:46 -07001023 bdevname(bdev, b));
1024 return -EIO;
1025 }
1026 block = index << sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001027 /* Create a page with the proper size buffers.. */
1028 page = grow_dev_page(bdev, block, index, size);
1029 if (!page)
1030 return 0;
1031 unlock_page(page);
1032 page_cache_release(page);
1033 return 1;
1034}
1035
Adrian Bunk75c96f82005-05-05 16:16:09 -07001036static struct buffer_head *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001037__getblk_slow(struct block_device *bdev, sector_t block, int size)
1038{
Jeff Moyer91f68c82012-07-12 09:43:14 -04001039 int ret;
1040 struct buffer_head *bh;
1041
Linus Torvalds1da177e2005-04-16 15:20:36 -07001042 /* Size must be multiple of hard sectorsize */
Martin K. Petersene1defc42009-05-22 17:17:49 -04001043 if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
Linus Torvalds1da177e2005-04-16 15:20:36 -07001044 (size < 512 || size > PAGE_SIZE))) {
1045 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1046 size);
Martin K. Petersene1defc42009-05-22 17:17:49 -04001047 printk(KERN_ERR "logical block size: %d\n",
1048 bdev_logical_block_size(bdev));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001049
1050 dump_stack();
1051 return NULL;
1052 }
1053
Jeff Moyer91f68c82012-07-12 09:43:14 -04001054retry:
1055 bh = __find_get_block(bdev, block, size);
1056 if (bh)
1057 return bh;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001058
Jeff Moyer91f68c82012-07-12 09:43:14 -04001059 ret = grow_buffers(bdev, block, size);
1060 if (ret == 0) {
1061 free_more_memory();
1062 goto retry;
1063 } else if (ret > 0) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001064 bh = __find_get_block(bdev, block, size);
1065 if (bh)
1066 return bh;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001067 }
Jeff Moyer91f68c82012-07-12 09:43:14 -04001068 return NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001069}
1070
1071/*
1072 * The relationship between dirty buffers and dirty pages:
1073 *
1074 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1075 * the page is tagged dirty in its radix tree.
1076 *
1077 * At all times, the dirtiness of the buffers represents the dirtiness of
1078 * subsections of the page. If the page has buffers, the page dirty bit is
1079 * merely a hint about the true dirty state.
1080 *
1081 * When a page is set dirty in its entirety, all its buffers are marked dirty
1082 * (if the page has buffers).
1083 *
1084 * When a buffer is marked dirty, its page is dirtied, but the page's other
1085 * buffers are not.
1086 *
1087 * Also. When blockdev buffers are explicitly read with bread(), they
1088 * individually become uptodate. But their backing page remains not
1089 * uptodate - even if all of its buffers are uptodate. A subsequent
1090 * block_read_full_page() against that page will discover all the uptodate
1091 * buffers, will set the page uptodate and will perform no I/O.
1092 */
1093
1094/**
1095 * mark_buffer_dirty - mark a buffer_head as needing writeout
Martin Waitz67be2dd2005-05-01 08:59:26 -07001096 * @bh: the buffer_head to mark dirty
Linus Torvalds1da177e2005-04-16 15:20:36 -07001097 *
1098 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1099 * backing page dirty, then tag the page as dirty in its address_space's radix
1100 * tree and then attach the address_space's inode to its superblock's dirty
1101 * inode list.
1102 *
1103 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
Dave Chinner250df6e2011-03-22 22:23:36 +11001104 * mapping->tree_lock and mapping->host->i_lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001105 */
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -08001106void mark_buffer_dirty(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001107{
Nick Piggin787d2212007-07-17 04:03:34 -07001108 WARN_ON_ONCE(!buffer_uptodate(bh));
Linus Torvalds1be62dc2008-04-04 14:38:17 -07001109
1110 /*
1111 * Very *carefully* optimize the it-is-already-dirty case.
1112 *
1113 * Don't let the final "is it dirty" escape to before we
1114 * perhaps modified the buffer.
1115 */
1116 if (buffer_dirty(bh)) {
1117 smp_mb();
1118 if (buffer_dirty(bh))
1119 return;
1120 }
1121
Linus Torvaldsa8e7d492009-03-19 11:32:05 -07001122 if (!test_set_buffer_dirty(bh)) {
1123 struct page *page = bh->b_page;
Linus Torvalds8e9d78e2009-08-21 17:40:08 -07001124 if (!TestSetPageDirty(page)) {
1125 struct address_space *mapping = page_mapping(page);
1126 if (mapping)
1127 __set_page_dirty(page, mapping, 0);
1128 }
Linus Torvaldsa8e7d492009-03-19 11:32:05 -07001129 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001130}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07001131EXPORT_SYMBOL(mark_buffer_dirty);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001132
1133/*
1134 * Decrement a buffer_head's reference count. If all buffers against a page
1135 * have zero reference count, are clean and unlocked, and if the page is clean
1136 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1137 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1138 * a page but it ends up not being freed, and buffers may later be reattached).
1139 */
1140void __brelse(struct buffer_head * buf)
1141{
1142 if (atomic_read(&buf->b_count)) {
1143 put_bh(buf);
1144 return;
1145 }
Arjan van de Ven5c752ad2008-07-25 19:45:40 -07001146 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
Linus Torvalds1da177e2005-04-16 15:20:36 -07001147}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07001148EXPORT_SYMBOL(__brelse);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001149
1150/*
1151 * bforget() is like brelse(), except it discards any
1152 * potentially dirty data.
1153 */
1154void __bforget(struct buffer_head *bh)
1155{
1156 clear_buffer_dirty(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -08001157 if (bh->b_assoc_map) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001158 struct address_space *buffer_mapping = bh->b_page->mapping;
1159
1160 spin_lock(&buffer_mapping->private_lock);
1161 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -07001162 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001163 spin_unlock(&buffer_mapping->private_lock);
1164 }
1165 __brelse(bh);
1166}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07001167EXPORT_SYMBOL(__bforget);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001168
1169static struct buffer_head *__bread_slow(struct buffer_head *bh)
1170{
1171 lock_buffer(bh);
1172 if (buffer_uptodate(bh)) {
1173 unlock_buffer(bh);
1174 return bh;
1175 } else {
1176 get_bh(bh);
1177 bh->b_end_io = end_buffer_read_sync;
1178 submit_bh(READ, bh);
1179 wait_on_buffer(bh);
1180 if (buffer_uptodate(bh))
1181 return bh;
1182 }
1183 brelse(bh);
1184 return NULL;
1185}
1186
1187/*
1188 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1189 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1190 * refcount elevated by one when they're in an LRU. A buffer can only appear
1191 * once in a particular CPU's LRU. A single buffer can be present in multiple
1192 * CPU's LRUs at the same time.
1193 *
1194 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1195 * sb_find_get_block().
1196 *
1197 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1198 * a local interrupt disable for that.
1199 */
1200
1201#define BH_LRU_SIZE 8
1202
1203struct bh_lru {
1204 struct buffer_head *bhs[BH_LRU_SIZE];
1205};
1206
1207static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1208
1209#ifdef CONFIG_SMP
1210#define bh_lru_lock() local_irq_disable()
1211#define bh_lru_unlock() local_irq_enable()
1212#else
1213#define bh_lru_lock() preempt_disable()
1214#define bh_lru_unlock() preempt_enable()
1215#endif
1216
1217static inline void check_irqs_on(void)
1218{
1219#ifdef irqs_disabled
1220 BUG_ON(irqs_disabled());
1221#endif
1222}
1223
1224/*
1225 * The LRU management algorithm is dopey-but-simple. Sorry.
1226 */
1227static void bh_lru_install(struct buffer_head *bh)
1228{
1229 struct buffer_head *evictee = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001230
1231 check_irqs_on();
1232 bh_lru_lock();
Christoph Lameterc7b92512010-12-06 11:16:28 -06001233 if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001234 struct buffer_head *bhs[BH_LRU_SIZE];
1235 int in;
1236 int out = 0;
1237
1238 get_bh(bh);
1239 bhs[out++] = bh;
1240 for (in = 0; in < BH_LRU_SIZE; in++) {
Christoph Lameterc7b92512010-12-06 11:16:28 -06001241 struct buffer_head *bh2 =
1242 __this_cpu_read(bh_lrus.bhs[in]);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001243
1244 if (bh2 == bh) {
1245 __brelse(bh2);
1246 } else {
1247 if (out >= BH_LRU_SIZE) {
1248 BUG_ON(evictee != NULL);
1249 evictee = bh2;
1250 } else {
1251 bhs[out++] = bh2;
1252 }
1253 }
1254 }
1255 while (out < BH_LRU_SIZE)
1256 bhs[out++] = NULL;
Christoph Lameterc7b92512010-12-06 11:16:28 -06001257 memcpy(__this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001258 }
1259 bh_lru_unlock();
1260
1261 if (evictee)
1262 __brelse(evictee);
1263}
1264
1265/*
1266 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1267 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001268static struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001269lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001270{
1271 struct buffer_head *ret = NULL;
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001272 unsigned int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001273
1274 check_irqs_on();
1275 bh_lru_lock();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001276 for (i = 0; i < BH_LRU_SIZE; i++) {
Christoph Lameterc7b92512010-12-06 11:16:28 -06001277 struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001278
1279 if (bh && bh->b_bdev == bdev &&
1280 bh->b_blocknr == block && bh->b_size == size) {
1281 if (i) {
1282 while (i) {
Christoph Lameterc7b92512010-12-06 11:16:28 -06001283 __this_cpu_write(bh_lrus.bhs[i],
1284 __this_cpu_read(bh_lrus.bhs[i - 1]));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001285 i--;
1286 }
Christoph Lameterc7b92512010-12-06 11:16:28 -06001287 __this_cpu_write(bh_lrus.bhs[0], bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001288 }
1289 get_bh(bh);
1290 ret = bh;
1291 break;
1292 }
1293 }
1294 bh_lru_unlock();
1295 return ret;
1296}
1297
1298/*
1299 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1300 * it in the LRU and mark it as accessed. If it is not present then return
1301 * NULL
1302 */
1303struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001304__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001305{
1306 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1307
1308 if (bh == NULL) {
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001309 bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001310 if (bh)
1311 bh_lru_install(bh);
1312 }
1313 if (bh)
1314 touch_buffer(bh);
1315 return bh;
1316}
1317EXPORT_SYMBOL(__find_get_block);
1318
1319/*
1320 * __getblk will locate (and, if necessary, create) the buffer_head
1321 * which corresponds to the passed block_device, block and size. The
1322 * returned buffer has its reference count incremented.
1323 *
1324 * __getblk() cannot fail - it just keeps trying. If you pass it an
1325 * illegal block number, __getblk() will happily return a buffer_head
1326 * which represents the non-existent block. Very weird.
1327 *
1328 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1329 * attempt is failing. FIXME, perhaps?
1330 */
1331struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001332__getblk(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001333{
1334 struct buffer_head *bh = __find_get_block(bdev, block, size);
1335
1336 might_sleep();
1337 if (bh == NULL)
1338 bh = __getblk_slow(bdev, block, size);
1339 return bh;
1340}
1341EXPORT_SYMBOL(__getblk);
1342
1343/*
1344 * Do async read-ahead on a buffer..
1345 */
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001346void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001347{
1348 struct buffer_head *bh = __getblk(bdev, block, size);
Andrew Mortona3e713b2005-10-30 15:03:15 -08001349 if (likely(bh)) {
1350 ll_rw_block(READA, 1, &bh);
1351 brelse(bh);
1352 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001353}
1354EXPORT_SYMBOL(__breadahead);
1355
1356/**
1357 * __bread() - reads a specified block and returns the bh
Martin Waitz67be2dd2005-05-01 08:59:26 -07001358 * @bdev: the block_device to read from
Linus Torvalds1da177e2005-04-16 15:20:36 -07001359 * @block: number of block
1360 * @size: size (in bytes) to read
1361 *
1362 * Reads a specified block, and returns buffer head that contains it.
1363 * It returns NULL if the block was unreadable.
1364 */
1365struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001366__bread(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001367{
1368 struct buffer_head *bh = __getblk(bdev, block, size);
1369
Andrew Mortona3e713b2005-10-30 15:03:15 -08001370 if (likely(bh) && !buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001371 bh = __bread_slow(bh);
1372 return bh;
1373}
1374EXPORT_SYMBOL(__bread);
1375
1376/*
1377 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1378 * This doesn't race because it runs in each cpu either in irq
1379 * or with preempt disabled.
1380 */
1381static void invalidate_bh_lru(void *arg)
1382{
1383 struct bh_lru *b = &get_cpu_var(bh_lrus);
1384 int i;
1385
1386 for (i = 0; i < BH_LRU_SIZE; i++) {
1387 brelse(b->bhs[i]);
1388 b->bhs[i] = NULL;
1389 }
1390 put_cpu_var(bh_lrus);
1391}
Gilad Ben-Yossef42be35d2012-03-28 14:42:45 -07001392
1393static bool has_bh_in_lru(int cpu, void *dummy)
1394{
1395 struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1396 int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001397
Gilad Ben-Yossef42be35d2012-03-28 14:42:45 -07001398 for (i = 0; i < BH_LRU_SIZE; i++) {
1399 if (b->bhs[i])
1400 return 1;
1401 }
1402
1403 return 0;
1404}
1405
Peter Zijlstraf9a14392007-05-06 14:49:55 -07001406void invalidate_bh_lrus(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001407{
Gilad Ben-Yossef42be35d2012-03-28 14:42:45 -07001408 on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001409}
Nick Piggin9db55792008-02-08 04:19:49 -08001410EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001411
1412void set_bh_page(struct buffer_head *bh,
1413 struct page *page, unsigned long offset)
1414{
1415 bh->b_page = page;
Eric Sesterhenne827f922006-03-26 18:24:46 +02001416 BUG_ON(offset >= PAGE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001417 if (PageHighMem(page))
1418 /*
1419 * This catches illegal uses and preserves the offset:
1420 */
1421 bh->b_data = (char *)(0 + offset);
1422 else
1423 bh->b_data = page_address(page) + offset;
1424}
1425EXPORT_SYMBOL(set_bh_page);
1426
1427/*
1428 * Called when truncating a buffer on a page completely.
1429 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001430static void discard_buffer(struct buffer_head * bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001431{
1432 lock_buffer(bh);
1433 clear_buffer_dirty(bh);
1434 bh->b_bdev = NULL;
1435 clear_buffer_mapped(bh);
1436 clear_buffer_req(bh);
1437 clear_buffer_new(bh);
1438 clear_buffer_delay(bh);
David Chinner33a266d2007-02-12 00:51:41 -08001439 clear_buffer_unwritten(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001440 unlock_buffer(bh);
1441}
1442
1443/**
Wang Sheng-Hui814e1d22011-09-01 08:22:57 +08001444 * block_invalidatepage - invalidate part or all of a buffer-backed page
Linus Torvalds1da177e2005-04-16 15:20:36 -07001445 *
1446 * @page: the page which is affected
1447 * @offset: the index of the truncation point
1448 *
1449 * block_invalidatepage() is called when all or part of the page has become
Wang Sheng-Hui814e1d22011-09-01 08:22:57 +08001450 * invalidated by a truncate operation.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001451 *
1452 * block_invalidatepage() does not have to release all buffers, but it must
1453 * ensure that no dirty buffer is left outside @offset and that no I/O
1454 * is underway against any of the blocks which are outside the truncation
1455 * point. Because the caller is about to free (and possibly reuse) those
1456 * blocks on-disk.
1457 */
NeilBrown2ff28e22006-03-26 01:37:18 -08001458void block_invalidatepage(struct page *page, unsigned long offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001459{
1460 struct buffer_head *head, *bh, *next;
1461 unsigned int curr_off = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001462
1463 BUG_ON(!PageLocked(page));
1464 if (!page_has_buffers(page))
1465 goto out;
1466
1467 head = page_buffers(page);
1468 bh = head;
1469 do {
1470 unsigned int next_off = curr_off + bh->b_size;
1471 next = bh->b_this_page;
1472
1473 /*
1474 * is this block fully invalidated?
1475 */
1476 if (offset <= curr_off)
1477 discard_buffer(bh);
1478 curr_off = next_off;
1479 bh = next;
1480 } while (bh != head);
1481
1482 /*
1483 * We release buffers only if the entire page is being invalidated.
1484 * The get_block cached value has been unconditionally invalidated,
1485 * so real IO is not possible anymore.
1486 */
1487 if (offset == 0)
NeilBrown2ff28e22006-03-26 01:37:18 -08001488 try_to_release_page(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001489out:
NeilBrown2ff28e22006-03-26 01:37:18 -08001490 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001491}
1492EXPORT_SYMBOL(block_invalidatepage);
1493
1494/*
1495 * We attach and possibly dirty the buffers atomically wrt
1496 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1497 * is already excluded via the page lock.
1498 */
1499void create_empty_buffers(struct page *page,
1500 unsigned long blocksize, unsigned long b_state)
1501{
1502 struct buffer_head *bh, *head, *tail;
1503
1504 head = alloc_page_buffers(page, blocksize, 1);
1505 bh = head;
1506 do {
1507 bh->b_state |= b_state;
1508 tail = bh;
1509 bh = bh->b_this_page;
1510 } while (bh);
1511 tail->b_this_page = head;
1512
1513 spin_lock(&page->mapping->private_lock);
1514 if (PageUptodate(page) || PageDirty(page)) {
1515 bh = head;
1516 do {
1517 if (PageDirty(page))
1518 set_buffer_dirty(bh);
1519 if (PageUptodate(page))
1520 set_buffer_uptodate(bh);
1521 bh = bh->b_this_page;
1522 } while (bh != head);
1523 }
1524 attach_page_buffers(page, head);
1525 spin_unlock(&page->mapping->private_lock);
1526}
1527EXPORT_SYMBOL(create_empty_buffers);
1528
1529/*
1530 * We are taking a block for data and we don't want any output from any
1531 * buffer-cache aliases starting from return from that function and
1532 * until the moment when something will explicitly mark the buffer
1533 * dirty (hopefully that will not happen until we will free that block ;-)
1534 * We don't even need to mark it not-uptodate - nobody can expect
1535 * anything from a newly allocated buffer anyway. We used to used
1536 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1537 * don't want to mark the alias unmapped, for example - it would confuse
1538 * anyone who might pick it with bread() afterwards...
1539 *
1540 * Also.. Note that bforget() doesn't lock the buffer. So there can
1541 * be writeout I/O going on against recently-freed buffers. We don't
1542 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1543 * only if we really need to. That happens here.
1544 */
1545void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1546{
1547 struct buffer_head *old_bh;
1548
1549 might_sleep();
1550
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001551 old_bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001552 if (old_bh) {
1553 clear_buffer_dirty(old_bh);
1554 wait_on_buffer(old_bh);
1555 clear_buffer_req(old_bh);
1556 __brelse(old_bh);
1557 }
1558}
1559EXPORT_SYMBOL(unmap_underlying_metadata);
1560
1561/*
1562 * NOTE! All mapped/uptodate combinations are valid:
1563 *
1564 * Mapped Uptodate Meaning
1565 *
1566 * No No "unknown" - must do get_block()
1567 * No Yes "hole" - zero-filled
1568 * Yes No "allocated" - allocated on disk, not read in
1569 * Yes Yes "valid" - allocated and up-to-date in memory.
1570 *
1571 * "Dirty" is valid only with the last case (mapped+uptodate).
1572 */
1573
1574/*
1575 * While block_write_full_page is writing back the dirty buffers under
1576 * the page lock, whoever dirtied the buffers may decide to clean them
1577 * again at any time. We handle that by only looking at the buffer
1578 * state inside lock_buffer().
1579 *
1580 * If block_write_full_page() is called for regular writeback
1581 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1582 * locked buffer. This only can happen if someone has written the buffer
1583 * directly, with submit_bh(). At the address_space level PageWriteback
1584 * prevents this contention from occurring.
Theodore Ts'o6e34eed2009-04-07 18:12:43 -04001585 *
1586 * If block_write_full_page() is called with wbc->sync_mode ==
Jens Axboe721a9602011-03-09 11:56:30 +01001587 * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this
1588 * causes the writes to be flagged as synchronous writes.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001589 */
1590static int __block_write_full_page(struct inode *inode, struct page *page,
Chris Mason35c80d52009-04-15 13:22:38 -04001591 get_block_t *get_block, struct writeback_control *wbc,
1592 bh_end_io_t *handler)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001593{
1594 int err;
1595 sector_t block;
1596 sector_t last_block;
Andrew Mortonf0fbd5f2005-05-05 16:15:48 -07001597 struct buffer_head *bh, *head;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001598 const unsigned blocksize = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001599 int nr_underway = 0;
Theodore Ts'o6e34eed2009-04-07 18:12:43 -04001600 int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
Jens Axboe721a9602011-03-09 11:56:30 +01001601 WRITE_SYNC : WRITE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001602
1603 BUG_ON(!PageLocked(page));
1604
1605 last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
1606
1607 if (!page_has_buffers(page)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001608 create_empty_buffers(page, blocksize,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001609 (1 << BH_Dirty)|(1 << BH_Uptodate));
1610 }
1611
1612 /*
1613 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1614 * here, and the (potentially unmapped) buffers may become dirty at
1615 * any time. If a buffer becomes dirty here after we've inspected it
1616 * then we just miss that fact, and the page stays dirty.
1617 *
1618 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1619 * handle that here by just cleaning them.
1620 */
1621
Andrew Morton54b21a72006-01-08 01:03:05 -08001622 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001623 head = page_buffers(page);
1624 bh = head;
1625
1626 /*
1627 * Get all the dirty buffers mapped to disk addresses and
1628 * handle any aliases from the underlying blockdev's mapping.
1629 */
1630 do {
1631 if (block > last_block) {
1632 /*
1633 * mapped buffers outside i_size will occur, because
1634 * this page can be outside i_size when there is a
1635 * truncate in progress.
1636 */
1637 /*
1638 * The buffer was zeroed by block_write_full_page()
1639 */
1640 clear_buffer_dirty(bh);
1641 set_buffer_uptodate(bh);
Alex Tomas29a814d2008-07-11 19:27:31 -04001642 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1643 buffer_dirty(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001644 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001645 err = get_block(inode, block, bh, 1);
1646 if (err)
1647 goto recover;
Alex Tomas29a814d2008-07-11 19:27:31 -04001648 clear_buffer_delay(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001649 if (buffer_new(bh)) {
1650 /* blockdev mappings never come here */
1651 clear_buffer_new(bh);
1652 unmap_underlying_metadata(bh->b_bdev,
1653 bh->b_blocknr);
1654 }
1655 }
1656 bh = bh->b_this_page;
1657 block++;
1658 } while (bh != head);
1659
1660 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001661 if (!buffer_mapped(bh))
1662 continue;
1663 /*
1664 * If it's a fully non-blocking write attempt and we cannot
1665 * lock the buffer then redirty the page. Note that this can
Jens Axboe5b0830c2009-09-23 19:37:09 +02001666 * potentially cause a busy-wait loop from writeback threads
1667 * and kswapd activity, but those code paths have their own
1668 * higher-level throttling.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001669 */
Wu Fengguang1b430be2010-10-26 14:21:26 -07001670 if (wbc->sync_mode != WB_SYNC_NONE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001671 lock_buffer(bh);
Nick Pigginca5de402008-08-02 12:02:13 +02001672 } else if (!trylock_buffer(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001673 redirty_page_for_writepage(wbc, page);
1674 continue;
1675 }
1676 if (test_clear_buffer_dirty(bh)) {
Chris Mason35c80d52009-04-15 13:22:38 -04001677 mark_buffer_async_write_endio(bh, handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001678 } else {
1679 unlock_buffer(bh);
1680 }
1681 } while ((bh = bh->b_this_page) != head);
1682
1683 /*
1684 * The page and its buffers are protected by PageWriteback(), so we can
1685 * drop the bh refcounts early.
1686 */
1687 BUG_ON(PageWriteback(page));
1688 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001689
1690 do {
1691 struct buffer_head *next = bh->b_this_page;
1692 if (buffer_async_write(bh)) {
Theodore Ts'oa64c8612009-03-27 22:14:10 -04001693 submit_bh(write_op, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001694 nr_underway++;
1695 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001696 bh = next;
1697 } while (bh != head);
Andrew Morton05937ba2005-05-05 16:15:47 -07001698 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001699
1700 err = 0;
1701done:
1702 if (nr_underway == 0) {
1703 /*
1704 * The page was marked dirty, but the buffers were
1705 * clean. Someone wrote them back by hand with
1706 * ll_rw_block/submit_bh. A rare case.
1707 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001708 end_page_writeback(page);
Nick Piggin3d67f2d2007-05-06 14:49:05 -07001709
Linus Torvalds1da177e2005-04-16 15:20:36 -07001710 /*
1711 * The page and buffer_heads can be released at any time from
1712 * here on.
1713 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001714 }
1715 return err;
1716
1717recover:
1718 /*
1719 * ENOSPC, or some other error. We may already have added some
1720 * blocks to the file, so we need to write these out to avoid
1721 * exposing stale data.
1722 * The page is currently locked and not marked for writeback
1723 */
1724 bh = head;
1725 /* Recovery: lock and submit the mapped buffers */
1726 do {
Alex Tomas29a814d2008-07-11 19:27:31 -04001727 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1728 !buffer_delay(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001729 lock_buffer(bh);
Chris Mason35c80d52009-04-15 13:22:38 -04001730 mark_buffer_async_write_endio(bh, handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001731 } else {
1732 /*
1733 * The buffer may have been set dirty during
1734 * attachment to a dirty page.
1735 */
1736 clear_buffer_dirty(bh);
1737 }
1738 } while ((bh = bh->b_this_page) != head);
1739 SetPageError(page);
1740 BUG_ON(PageWriteback(page));
Andrew Morton7e4c3692007-05-08 00:23:27 -07001741 mapping_set_error(page->mapping, err);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001742 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001743 do {
1744 struct buffer_head *next = bh->b_this_page;
1745 if (buffer_async_write(bh)) {
1746 clear_buffer_dirty(bh);
Theodore Ts'oa64c8612009-03-27 22:14:10 -04001747 submit_bh(write_op, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001748 nr_underway++;
1749 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001750 bh = next;
1751 } while (bh != head);
Nick Pigginffda9d32007-02-20 13:57:54 -08001752 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001753 goto done;
1754}
1755
Nick Pigginafddba42007-10-16 01:25:01 -07001756/*
1757 * If a page has any new buffers, zero them out here, and mark them uptodate
1758 * and dirty so they'll be written out (in order to prevent uninitialised
1759 * block data from leaking). And clear the new bit.
1760 */
1761void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1762{
1763 unsigned int block_start, block_end;
1764 struct buffer_head *head, *bh;
1765
1766 BUG_ON(!PageLocked(page));
1767 if (!page_has_buffers(page))
1768 return;
1769
1770 bh = head = page_buffers(page);
1771 block_start = 0;
1772 do {
1773 block_end = block_start + bh->b_size;
1774
1775 if (buffer_new(bh)) {
1776 if (block_end > from && block_start < to) {
1777 if (!PageUptodate(page)) {
1778 unsigned start, size;
1779
1780 start = max(from, block_start);
1781 size = min(to, block_end) - start;
1782
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001783 zero_user(page, start, size);
Nick Pigginafddba42007-10-16 01:25:01 -07001784 set_buffer_uptodate(bh);
1785 }
1786
1787 clear_buffer_new(bh);
1788 mark_buffer_dirty(bh);
1789 }
1790 }
1791
1792 block_start = block_end;
1793 bh = bh->b_this_page;
1794 } while (bh != head);
1795}
1796EXPORT_SYMBOL(page_zero_new_buffers);
1797
Christoph Hellwigebdec242010-10-06 10:47:23 +02001798int __block_write_begin(struct page *page, loff_t pos, unsigned len,
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001799 get_block_t *get_block)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001800{
Christoph Hellwigebdec242010-10-06 10:47:23 +02001801 unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1802 unsigned to = from + len;
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001803 struct inode *inode = page->mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001804 unsigned block_start, block_end;
1805 sector_t block;
1806 int err = 0;
1807 unsigned blocksize, bbits;
1808 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1809
1810 BUG_ON(!PageLocked(page));
1811 BUG_ON(from > PAGE_CACHE_SIZE);
1812 BUG_ON(to > PAGE_CACHE_SIZE);
1813 BUG_ON(from > to);
1814
1815 blocksize = 1 << inode->i_blkbits;
1816 if (!page_has_buffers(page))
1817 create_empty_buffers(page, blocksize, 0);
1818 head = page_buffers(page);
1819
1820 bbits = inode->i_blkbits;
1821 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1822
1823 for(bh = head, block_start = 0; bh != head || !block_start;
1824 block++, block_start=block_end, bh = bh->b_this_page) {
1825 block_end = block_start + blocksize;
1826 if (block_end <= from || block_start >= to) {
1827 if (PageUptodate(page)) {
1828 if (!buffer_uptodate(bh))
1829 set_buffer_uptodate(bh);
1830 }
1831 continue;
1832 }
1833 if (buffer_new(bh))
1834 clear_buffer_new(bh);
1835 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001836 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001837 err = get_block(inode, block, bh, 1);
1838 if (err)
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001839 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001840 if (buffer_new(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001841 unmap_underlying_metadata(bh->b_bdev,
1842 bh->b_blocknr);
1843 if (PageUptodate(page)) {
Nick Piggin637aff42007-10-16 01:25:00 -07001844 clear_buffer_new(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001845 set_buffer_uptodate(bh);
Nick Piggin637aff42007-10-16 01:25:00 -07001846 mark_buffer_dirty(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001847 continue;
1848 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001849 if (block_end > to || block_start < from)
1850 zero_user_segments(page,
1851 to, block_end,
1852 block_start, from);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001853 continue;
1854 }
1855 }
1856 if (PageUptodate(page)) {
1857 if (!buffer_uptodate(bh))
1858 set_buffer_uptodate(bh);
1859 continue;
1860 }
1861 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
David Chinner33a266d2007-02-12 00:51:41 -08001862 !buffer_unwritten(bh) &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001863 (block_start < from || block_end > to)) {
1864 ll_rw_block(READ, 1, &bh);
1865 *wait_bh++=bh;
1866 }
1867 }
1868 /*
1869 * If we issued read requests - let them complete.
1870 */
1871 while(wait_bh > wait) {
1872 wait_on_buffer(*--wait_bh);
1873 if (!buffer_uptodate(*wait_bh))
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001874 err = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001875 }
Jan Karaf9f07b62011-06-14 00:58:27 +02001876 if (unlikely(err))
Nick Pigginafddba42007-10-16 01:25:01 -07001877 page_zero_new_buffers(page, from, to);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001878 return err;
1879}
Christoph Hellwigebdec242010-10-06 10:47:23 +02001880EXPORT_SYMBOL(__block_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001881
1882static int __block_commit_write(struct inode *inode, struct page *page,
1883 unsigned from, unsigned to)
1884{
1885 unsigned block_start, block_end;
1886 int partial = 0;
1887 unsigned blocksize;
1888 struct buffer_head *bh, *head;
1889
1890 blocksize = 1 << inode->i_blkbits;
1891
1892 for(bh = head = page_buffers(page), block_start = 0;
1893 bh != head || !block_start;
1894 block_start=block_end, bh = bh->b_this_page) {
1895 block_end = block_start + blocksize;
1896 if (block_end <= from || block_start >= to) {
1897 if (!buffer_uptodate(bh))
1898 partial = 1;
1899 } else {
1900 set_buffer_uptodate(bh);
1901 mark_buffer_dirty(bh);
1902 }
Nick Pigginafddba42007-10-16 01:25:01 -07001903 clear_buffer_new(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001904 }
1905
1906 /*
1907 * If this is a partial write which happened to make all buffers
1908 * uptodate then we can optimize away a bogus readpage() for
1909 * the next read(). Here we 'discover' whether the page went
1910 * uptodate as a result of this (potentially partial) write.
1911 */
1912 if (!partial)
1913 SetPageUptodate(page);
1914 return 0;
1915}
1916
1917/*
Christoph Hellwig155130a2010-06-04 11:29:58 +02001918 * block_write_begin takes care of the basic task of block allocation and
1919 * bringing partial write blocks uptodate first.
1920 *
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10001921 * The filesystem needs to handle block truncation upon failure.
Nick Pigginafddba42007-10-16 01:25:01 -07001922 */
Christoph Hellwig155130a2010-06-04 11:29:58 +02001923int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
1924 unsigned flags, struct page **pagep, get_block_t *get_block)
Nick Pigginafddba42007-10-16 01:25:01 -07001925{
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001926 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
Nick Pigginafddba42007-10-16 01:25:01 -07001927 struct page *page;
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001928 int status;
Nick Pigginafddba42007-10-16 01:25:01 -07001929
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001930 page = grab_cache_page_write_begin(mapping, index, flags);
1931 if (!page)
1932 return -ENOMEM;
Nick Pigginafddba42007-10-16 01:25:01 -07001933
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001934 status = __block_write_begin(page, pos, len, get_block);
Nick Pigginafddba42007-10-16 01:25:01 -07001935 if (unlikely(status)) {
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001936 unlock_page(page);
1937 page_cache_release(page);
1938 page = NULL;
Nick Pigginafddba42007-10-16 01:25:01 -07001939 }
1940
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001941 *pagep = page;
Nick Pigginafddba42007-10-16 01:25:01 -07001942 return status;
1943}
1944EXPORT_SYMBOL(block_write_begin);
1945
1946int block_write_end(struct file *file, struct address_space *mapping,
1947 loff_t pos, unsigned len, unsigned copied,
1948 struct page *page, void *fsdata)
1949{
1950 struct inode *inode = mapping->host;
1951 unsigned start;
1952
1953 start = pos & (PAGE_CACHE_SIZE - 1);
1954
1955 if (unlikely(copied < len)) {
1956 /*
1957 * The buffers that were written will now be uptodate, so we
1958 * don't have to worry about a readpage reading them and
1959 * overwriting a partial write. However if we have encountered
1960 * a short write and only partially written into a buffer, it
1961 * will not be marked uptodate, so a readpage might come in and
1962 * destroy our partial write.
1963 *
1964 * Do the simplest thing, and just treat any short write to a
1965 * non uptodate page as a zero-length write, and force the
1966 * caller to redo the whole thing.
1967 */
1968 if (!PageUptodate(page))
1969 copied = 0;
1970
1971 page_zero_new_buffers(page, start+copied, start+len);
1972 }
1973 flush_dcache_page(page);
1974
1975 /* This could be a short (even 0-length) commit */
1976 __block_commit_write(inode, page, start, start+copied);
1977
1978 return copied;
1979}
1980EXPORT_SYMBOL(block_write_end);
1981
1982int generic_write_end(struct file *file, struct address_space *mapping,
1983 loff_t pos, unsigned len, unsigned copied,
1984 struct page *page, void *fsdata)
1985{
1986 struct inode *inode = mapping->host;
Jan Karac7d206b2008-07-11 19:27:31 -04001987 int i_size_changed = 0;
Nick Pigginafddba42007-10-16 01:25:01 -07001988
1989 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
1990
1991 /*
1992 * No need to use i_size_read() here, the i_size
1993 * cannot change under us because we hold i_mutex.
1994 *
1995 * But it's important to update i_size while still holding page lock:
1996 * page writeout could otherwise come in and zero beyond i_size.
1997 */
1998 if (pos+copied > inode->i_size) {
1999 i_size_write(inode, pos+copied);
Jan Karac7d206b2008-07-11 19:27:31 -04002000 i_size_changed = 1;
Nick Pigginafddba42007-10-16 01:25:01 -07002001 }
2002
2003 unlock_page(page);
2004 page_cache_release(page);
2005
Jan Karac7d206b2008-07-11 19:27:31 -04002006 /*
2007 * Don't mark the inode dirty under page lock. First, it unnecessarily
2008 * makes the holding time of page lock longer. Second, it forces lock
2009 * ordering of page lock and transaction start for journaling
2010 * filesystems.
2011 */
2012 if (i_size_changed)
2013 mark_inode_dirty(inode);
2014
Nick Pigginafddba42007-10-16 01:25:01 -07002015 return copied;
2016}
2017EXPORT_SYMBOL(generic_write_end);
2018
2019/*
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07002020 * block_is_partially_uptodate checks whether buffers within a page are
2021 * uptodate or not.
2022 *
2023 * Returns true if all buffers which correspond to a file portion
2024 * we want to read are uptodate.
2025 */
2026int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
2027 unsigned long from)
2028{
2029 struct inode *inode = page->mapping->host;
2030 unsigned block_start, block_end, blocksize;
2031 unsigned to;
2032 struct buffer_head *bh, *head;
2033 int ret = 1;
2034
2035 if (!page_has_buffers(page))
2036 return 0;
2037
2038 blocksize = 1 << inode->i_blkbits;
2039 to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count);
2040 to = from + to;
2041 if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
2042 return 0;
2043
2044 head = page_buffers(page);
2045 bh = head;
2046 block_start = 0;
2047 do {
2048 block_end = block_start + blocksize;
2049 if (block_end > from && block_start < to) {
2050 if (!buffer_uptodate(bh)) {
2051 ret = 0;
2052 break;
2053 }
2054 if (block_end >= to)
2055 break;
2056 }
2057 block_start = block_end;
2058 bh = bh->b_this_page;
2059 } while (bh != head);
2060
2061 return ret;
2062}
2063EXPORT_SYMBOL(block_is_partially_uptodate);
2064
2065/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002066 * Generic "read page" function for block devices that have the normal
2067 * get_block functionality. This is most of the block device filesystems.
2068 * Reads the page asynchronously --- the unlock_buffer() and
2069 * set/clear_buffer_uptodate() functions propagate buffer state into the
2070 * page struct once IO has completed.
2071 */
2072int block_read_full_page(struct page *page, get_block_t *get_block)
2073{
2074 struct inode *inode = page->mapping->host;
2075 sector_t iblock, lblock;
2076 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2077 unsigned int blocksize;
2078 int nr, i;
2079 int fully_mapped = 1;
2080
Matt Mackallcd7619d2005-05-01 08:59:01 -07002081 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002082 blocksize = 1 << inode->i_blkbits;
2083 if (!page_has_buffers(page))
2084 create_empty_buffers(page, blocksize, 0);
2085 head = page_buffers(page);
2086
2087 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2088 lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
2089 bh = head;
2090 nr = 0;
2091 i = 0;
2092
2093 do {
2094 if (buffer_uptodate(bh))
2095 continue;
2096
2097 if (!buffer_mapped(bh)) {
Andrew Mortonc64610b2005-05-16 21:53:49 -07002098 int err = 0;
2099
Linus Torvalds1da177e2005-04-16 15:20:36 -07002100 fully_mapped = 0;
2101 if (iblock < lblock) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002102 WARN_ON(bh->b_size != blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002103 err = get_block(inode, iblock, bh, 0);
2104 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002105 SetPageError(page);
2106 }
2107 if (!buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002108 zero_user(page, i * blocksize, blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002109 if (!err)
2110 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002111 continue;
2112 }
2113 /*
2114 * get_block() might have updated the buffer
2115 * synchronously
2116 */
2117 if (buffer_uptodate(bh))
2118 continue;
2119 }
2120 arr[nr++] = bh;
2121 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2122
2123 if (fully_mapped)
2124 SetPageMappedToDisk(page);
2125
2126 if (!nr) {
2127 /*
2128 * All buffers are uptodate - we can set the page uptodate
2129 * as well. But not if get_block() returned an error.
2130 */
2131 if (!PageError(page))
2132 SetPageUptodate(page);
2133 unlock_page(page);
2134 return 0;
2135 }
2136
2137 /* Stage two: lock the buffers */
2138 for (i = 0; i < nr; i++) {
2139 bh = arr[i];
2140 lock_buffer(bh);
2141 mark_buffer_async_read(bh);
2142 }
2143
2144 /*
2145 * Stage 3: start the IO. Check for uptodateness
2146 * inside the buffer lock in case another process reading
2147 * the underlying blockdev brought it uptodate (the sct fix).
2148 */
2149 for (i = 0; i < nr; i++) {
2150 bh = arr[i];
2151 if (buffer_uptodate(bh))
2152 end_buffer_async_read(bh, 1);
2153 else
2154 submit_bh(READ, bh);
2155 }
2156 return 0;
2157}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002158EXPORT_SYMBOL(block_read_full_page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002159
2160/* utility function for filesystems that need to do work on expanding
Nick Piggin89e10782007-10-16 01:25:07 -07002161 * truncates. Uses filesystem pagecache writes to allow the filesystem to
Linus Torvalds1da177e2005-04-16 15:20:36 -07002162 * deal with the hole.
2163 */
Nick Piggin89e10782007-10-16 01:25:07 -07002164int generic_cont_expand_simple(struct inode *inode, loff_t size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002165{
2166 struct address_space *mapping = inode->i_mapping;
2167 struct page *page;
Nick Piggin89e10782007-10-16 01:25:07 -07002168 void *fsdata;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002169 int err;
2170
npiggin@suse.dec08d3b02009-08-21 02:35:06 +10002171 err = inode_newsize_ok(inode, size);
2172 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002173 goto out;
2174
Nick Piggin89e10782007-10-16 01:25:07 -07002175 err = pagecache_write_begin(NULL, mapping, size, 0,
2176 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2177 &page, &fsdata);
2178 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002179 goto out;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002180
Nick Piggin89e10782007-10-16 01:25:07 -07002181 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2182 BUG_ON(err > 0);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002183
Linus Torvalds1da177e2005-04-16 15:20:36 -07002184out:
2185 return err;
2186}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002187EXPORT_SYMBOL(generic_cont_expand_simple);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002188
Adrian Bunkf1e3af72008-04-29 00:59:01 -07002189static int cont_expand_zero(struct file *file, struct address_space *mapping,
2190 loff_t pos, loff_t *bytes)
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002191{
Nick Piggin89e10782007-10-16 01:25:07 -07002192 struct inode *inode = mapping->host;
2193 unsigned blocksize = 1 << inode->i_blkbits;
2194 struct page *page;
2195 void *fsdata;
2196 pgoff_t index, curidx;
2197 loff_t curpos;
2198 unsigned zerofrom, offset, len;
2199 int err = 0;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002200
Nick Piggin89e10782007-10-16 01:25:07 -07002201 index = pos >> PAGE_CACHE_SHIFT;
2202 offset = pos & ~PAGE_CACHE_MASK;
2203
2204 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
2205 zerofrom = curpos & ~PAGE_CACHE_MASK;
2206 if (zerofrom & (blocksize-1)) {
2207 *bytes |= (blocksize-1);
2208 (*bytes)++;
2209 }
2210 len = PAGE_CACHE_SIZE - zerofrom;
2211
2212 err = pagecache_write_begin(file, mapping, curpos, len,
2213 AOP_FLAG_UNINTERRUPTIBLE,
2214 &page, &fsdata);
2215 if (err)
2216 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002217 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002218 err = pagecache_write_end(file, mapping, curpos, len, len,
2219 page, fsdata);
2220 if (err < 0)
2221 goto out;
2222 BUG_ON(err != len);
2223 err = 0;
OGAWA Hirofumi061e9742008-04-28 02:16:28 -07002224
2225 balance_dirty_pages_ratelimited(mapping);
Nick Piggin89e10782007-10-16 01:25:07 -07002226 }
2227
2228 /* page covers the boundary, find the boundary offset */
2229 if (index == curidx) {
2230 zerofrom = curpos & ~PAGE_CACHE_MASK;
2231 /* if we will expand the thing last block will be filled */
2232 if (offset <= zerofrom) {
2233 goto out;
2234 }
2235 if (zerofrom & (blocksize-1)) {
2236 *bytes |= (blocksize-1);
2237 (*bytes)++;
2238 }
2239 len = offset - zerofrom;
2240
2241 err = pagecache_write_begin(file, mapping, curpos, len,
2242 AOP_FLAG_UNINTERRUPTIBLE,
2243 &page, &fsdata);
2244 if (err)
2245 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002246 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002247 err = pagecache_write_end(file, mapping, curpos, len, len,
2248 page, fsdata);
2249 if (err < 0)
2250 goto out;
2251 BUG_ON(err != len);
2252 err = 0;
2253 }
2254out:
2255 return err;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002256}
2257
Linus Torvalds1da177e2005-04-16 15:20:36 -07002258/*
2259 * For moronic filesystems that do not allow holes in file.
2260 * We may have to extend the file.
2261 */
Christoph Hellwig282dc172010-06-04 11:29:55 +02002262int cont_write_begin(struct file *file, struct address_space *mapping,
Nick Piggin89e10782007-10-16 01:25:07 -07002263 loff_t pos, unsigned len, unsigned flags,
2264 struct page **pagep, void **fsdata,
2265 get_block_t *get_block, loff_t *bytes)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002266{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002267 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002268 unsigned blocksize = 1 << inode->i_blkbits;
Nick Piggin89e10782007-10-16 01:25:07 -07002269 unsigned zerofrom;
2270 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002271
Nick Piggin89e10782007-10-16 01:25:07 -07002272 err = cont_expand_zero(file, mapping, pos, bytes);
2273 if (err)
Christoph Hellwig155130a2010-06-04 11:29:58 +02002274 return err;
Nick Piggin89e10782007-10-16 01:25:07 -07002275
2276 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2277 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2278 *bytes |= (blocksize-1);
2279 (*bytes)++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002280 }
2281
Christoph Hellwig155130a2010-06-04 11:29:58 +02002282 return block_write_begin(mapping, pos, len, flags, pagep, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002283}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002284EXPORT_SYMBOL(cont_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002285
Linus Torvalds1da177e2005-04-16 15:20:36 -07002286int block_commit_write(struct page *page, unsigned from, unsigned to)
2287{
2288 struct inode *inode = page->mapping->host;
2289 __block_commit_write(inode,page,from,to);
2290 return 0;
2291}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002292EXPORT_SYMBOL(block_commit_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002293
David Chinner54171692007-07-19 17:39:55 +10002294/*
2295 * block_page_mkwrite() is not allowed to change the file size as it gets
2296 * called from a page fault handler when a page is first dirtied. Hence we must
2297 * be careful to check for EOF conditions here. We set the page up correctly
2298 * for a written page which means we get ENOSPC checking when writing into
2299 * holes and correct delalloc and unwritten extent mapping on filesystems that
2300 * support these features.
2301 *
2302 * We are not allowed to take the i_mutex here so we have to play games to
2303 * protect against truncate races as the page could now be beyond EOF. Because
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10002304 * truncate writes the inode size before removing pages, once we have the
David Chinner54171692007-07-19 17:39:55 +10002305 * page lock we can determine safely if the page is beyond EOF. If it is not
2306 * beyond EOF, then the page is guaranteed safe against truncation until we
2307 * unlock the page.
Jan Karaea13a862011-05-24 00:23:35 +02002308 *
2309 * Direct callers of this function should call vfs_check_frozen() so that page
2310 * fault does not busyloop until the fs is thawed.
David Chinner54171692007-07-19 17:39:55 +10002311 */
Jan Kara24da4fa2011-05-24 00:23:34 +02002312int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2313 get_block_t get_block)
David Chinner54171692007-07-19 17:39:55 +10002314{
Nick Pigginc2ec1752009-03-31 15:23:21 -07002315 struct page *page = vmf->page;
David Chinner54171692007-07-19 17:39:55 +10002316 struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
2317 unsigned long end;
2318 loff_t size;
Jan Kara24da4fa2011-05-24 00:23:34 +02002319 int ret;
David Chinner54171692007-07-19 17:39:55 +10002320
2321 lock_page(page);
2322 size = i_size_read(inode);
2323 if ((page->mapping != inode->i_mapping) ||
Nick Piggin18336332007-07-20 00:31:45 -07002324 (page_offset(page) > size)) {
Jan Kara24da4fa2011-05-24 00:23:34 +02002325 /* We overload EFAULT to mean page got truncated */
2326 ret = -EFAULT;
2327 goto out_unlock;
David Chinner54171692007-07-19 17:39:55 +10002328 }
2329
2330 /* page is wholly or partially inside EOF */
2331 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
2332 end = size & ~PAGE_CACHE_MASK;
2333 else
2334 end = PAGE_CACHE_SIZE;
2335
Christoph Hellwigebdec242010-10-06 10:47:23 +02002336 ret = __block_write_begin(page, 0, end, get_block);
David Chinner54171692007-07-19 17:39:55 +10002337 if (!ret)
2338 ret = block_commit_write(page, 0, end);
2339
Jan Kara24da4fa2011-05-24 00:23:34 +02002340 if (unlikely(ret < 0))
2341 goto out_unlock;
Jan Karaea13a862011-05-24 00:23:35 +02002342 /*
2343 * Freezing in progress? We check after the page is marked dirty and
2344 * with page lock held so if the test here fails, we are sure freezing
2345 * code will wait during syncing until the page fault is done - at that
2346 * point page will be dirty and unlocked so freezing code will write it
2347 * and writeprotect it again.
2348 */
2349 set_page_dirty(page);
2350 if (inode->i_sb->s_frozen != SB_UNFROZEN) {
2351 ret = -EAGAIN;
2352 goto out_unlock;
2353 }
Darrick J. Wongd76ee182011-05-27 12:23:41 -07002354 wait_on_page_writeback(page);
Jan Kara24da4fa2011-05-24 00:23:34 +02002355 return 0;
2356out_unlock:
2357 unlock_page(page);
David Chinner54171692007-07-19 17:39:55 +10002358 return ret;
2359}
Jan Kara24da4fa2011-05-24 00:23:34 +02002360EXPORT_SYMBOL(__block_page_mkwrite);
2361
2362int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2363 get_block_t get_block)
2364{
Jan Karaea13a862011-05-24 00:23:35 +02002365 int ret;
2366 struct super_block *sb = vma->vm_file->f_path.dentry->d_inode->i_sb;
Jan Kara24da4fa2011-05-24 00:23:34 +02002367
Jan Karaea13a862011-05-24 00:23:35 +02002368 /*
2369 * This check is racy but catches the common case. The check in
2370 * __block_page_mkwrite() is reliable.
2371 */
2372 vfs_check_frozen(sb, SB_FREEZE_WRITE);
2373 ret = __block_page_mkwrite(vma, vmf, get_block);
Jan Kara24da4fa2011-05-24 00:23:34 +02002374 return block_page_mkwrite_return(ret);
2375}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002376EXPORT_SYMBOL(block_page_mkwrite);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002377
2378/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002379 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
Linus Torvalds1da177e2005-04-16 15:20:36 -07002380 * immediately, while under the page lock. So it needs a special end_io
2381 * handler which does not touch the bh after unlocking it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002382 */
2383static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2384{
Dmitry Monakhov68671f32007-10-16 01:24:47 -07002385 __end_buffer_read_notouch(bh, uptodate);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002386}
2387
2388/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002389 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2390 * the page (converting it to circular linked list and taking care of page
2391 * dirty races).
2392 */
2393static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2394{
2395 struct buffer_head *bh;
2396
2397 BUG_ON(!PageLocked(page));
2398
2399 spin_lock(&page->mapping->private_lock);
2400 bh = head;
2401 do {
2402 if (PageDirty(page))
2403 set_buffer_dirty(bh);
2404 if (!bh->b_this_page)
2405 bh->b_this_page = head;
2406 bh = bh->b_this_page;
2407 } while (bh != head);
2408 attach_page_buffers(page, head);
2409 spin_unlock(&page->mapping->private_lock);
2410}
2411
2412/*
Christoph Hellwigea0f04e2010-06-04 11:29:54 +02002413 * On entry, the page is fully not uptodate.
2414 * On exit the page is fully uptodate in the areas outside (from,to)
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10002415 * The filesystem needs to handle block truncation upon failure.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002416 */
Christoph Hellwigea0f04e2010-06-04 11:29:54 +02002417int nobh_write_begin(struct address_space *mapping,
Nick Piggin03158cd2007-10-16 01:25:25 -07002418 loff_t pos, unsigned len, unsigned flags,
2419 struct page **pagep, void **fsdata,
Linus Torvalds1da177e2005-04-16 15:20:36 -07002420 get_block_t *get_block)
2421{
Nick Piggin03158cd2007-10-16 01:25:25 -07002422 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002423 const unsigned blkbits = inode->i_blkbits;
2424 const unsigned blocksize = 1 << blkbits;
Nick Piggina4b06722007-10-16 01:24:48 -07002425 struct buffer_head *head, *bh;
Nick Piggin03158cd2007-10-16 01:25:25 -07002426 struct page *page;
2427 pgoff_t index;
2428 unsigned from, to;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002429 unsigned block_in_page;
Nick Piggina4b06722007-10-16 01:24:48 -07002430 unsigned block_start, block_end;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002431 sector_t block_in_file;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002432 int nr_reads = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002433 int ret = 0;
2434 int is_mapped_to_disk = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002435
Nick Piggin03158cd2007-10-16 01:25:25 -07002436 index = pos >> PAGE_CACHE_SHIFT;
2437 from = pos & (PAGE_CACHE_SIZE - 1);
2438 to = from + len;
2439
Nick Piggin54566b22009-01-04 12:00:53 -08002440 page = grab_cache_page_write_begin(mapping, index, flags);
Nick Piggin03158cd2007-10-16 01:25:25 -07002441 if (!page)
2442 return -ENOMEM;
2443 *pagep = page;
2444 *fsdata = NULL;
2445
2446 if (page_has_buffers(page)) {
Namhyung Kim309f77a2010-10-25 15:01:12 +09002447 ret = __block_write_begin(page, pos, len, get_block);
2448 if (unlikely(ret))
2449 goto out_release;
2450 return ret;
Nick Piggin03158cd2007-10-16 01:25:25 -07002451 }
Nick Piggina4b06722007-10-16 01:24:48 -07002452
Linus Torvalds1da177e2005-04-16 15:20:36 -07002453 if (PageMappedToDisk(page))
2454 return 0;
2455
Nick Piggina4b06722007-10-16 01:24:48 -07002456 /*
2457 * Allocate buffers so that we can keep track of state, and potentially
2458 * attach them to the page if an error occurs. In the common case of
2459 * no error, they will just be freed again without ever being attached
2460 * to the page (which is all OK, because we're under the page lock).
2461 *
2462 * Be careful: the buffer linked list is a NULL terminated one, rather
2463 * than the circular one we're used to.
2464 */
2465 head = alloc_page_buffers(page, blocksize, 0);
Nick Piggin03158cd2007-10-16 01:25:25 -07002466 if (!head) {
2467 ret = -ENOMEM;
2468 goto out_release;
2469 }
Nick Piggina4b06722007-10-16 01:24:48 -07002470
Linus Torvalds1da177e2005-04-16 15:20:36 -07002471 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002472
2473 /*
2474 * We loop across all blocks in the page, whether or not they are
2475 * part of the affected region. This is so we can discover if the
2476 * page is fully mapped-to-disk.
2477 */
Nick Piggina4b06722007-10-16 01:24:48 -07002478 for (block_start = 0, block_in_page = 0, bh = head;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002479 block_start < PAGE_CACHE_SIZE;
Nick Piggina4b06722007-10-16 01:24:48 -07002480 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002481 int create;
2482
Nick Piggina4b06722007-10-16 01:24:48 -07002483 block_end = block_start + blocksize;
2484 bh->b_state = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002485 create = 1;
2486 if (block_start >= to)
2487 create = 0;
2488 ret = get_block(inode, block_in_file + block_in_page,
Nick Piggina4b06722007-10-16 01:24:48 -07002489 bh, create);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002490 if (ret)
2491 goto failed;
Nick Piggina4b06722007-10-16 01:24:48 -07002492 if (!buffer_mapped(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002493 is_mapped_to_disk = 0;
Nick Piggina4b06722007-10-16 01:24:48 -07002494 if (buffer_new(bh))
2495 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
2496 if (PageUptodate(page)) {
2497 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002498 continue;
Nick Piggina4b06722007-10-16 01:24:48 -07002499 }
2500 if (buffer_new(bh) || !buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002501 zero_user_segments(page, block_start, from,
2502 to, block_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002503 continue;
2504 }
Nick Piggina4b06722007-10-16 01:24:48 -07002505 if (buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002506 continue; /* reiserfs does this */
2507 if (block_start < from || block_end > to) {
Nick Piggina4b06722007-10-16 01:24:48 -07002508 lock_buffer(bh);
2509 bh->b_end_io = end_buffer_read_nobh;
2510 submit_bh(READ, bh);
2511 nr_reads++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002512 }
2513 }
2514
2515 if (nr_reads) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002516 /*
2517 * The page is locked, so these buffers are protected from
2518 * any VM or truncate activity. Hence we don't need to care
2519 * for the buffer_head refcounts.
2520 */
Nick Piggina4b06722007-10-16 01:24:48 -07002521 for (bh = head; bh; bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002522 wait_on_buffer(bh);
2523 if (!buffer_uptodate(bh))
2524 ret = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002525 }
2526 if (ret)
2527 goto failed;
2528 }
2529
2530 if (is_mapped_to_disk)
2531 SetPageMappedToDisk(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002532
Nick Piggin03158cd2007-10-16 01:25:25 -07002533 *fsdata = head; /* to be released by nobh_write_end */
Nick Piggina4b06722007-10-16 01:24:48 -07002534
Linus Torvalds1da177e2005-04-16 15:20:36 -07002535 return 0;
2536
2537failed:
Nick Piggin03158cd2007-10-16 01:25:25 -07002538 BUG_ON(!ret);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002539 /*
Nick Piggina4b06722007-10-16 01:24:48 -07002540 * Error recovery is a bit difficult. We need to zero out blocks that
2541 * were newly allocated, and dirty them to ensure they get written out.
2542 * Buffers need to be attached to the page at this point, otherwise
2543 * the handling of potential IO errors during writeout would be hard
2544 * (could try doing synchronous writeout, but what if that fails too?)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002545 */
Nick Piggin03158cd2007-10-16 01:25:25 -07002546 attach_nobh_buffers(page, head);
2547 page_zero_new_buffers(page, from, to);
Nick Piggina4b06722007-10-16 01:24:48 -07002548
Nick Piggin03158cd2007-10-16 01:25:25 -07002549out_release:
2550 unlock_page(page);
2551 page_cache_release(page);
2552 *pagep = NULL;
Nick Piggina4b06722007-10-16 01:24:48 -07002553
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10002554 return ret;
2555}
Nick Piggin03158cd2007-10-16 01:25:25 -07002556EXPORT_SYMBOL(nobh_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002557
Nick Piggin03158cd2007-10-16 01:25:25 -07002558int nobh_write_end(struct file *file, struct address_space *mapping,
2559 loff_t pos, unsigned len, unsigned copied,
2560 struct page *page, void *fsdata)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002561{
2562 struct inode *inode = page->mapping->host;
Nick Pigginefdc3132007-10-21 06:57:41 +02002563 struct buffer_head *head = fsdata;
Nick Piggin03158cd2007-10-16 01:25:25 -07002564 struct buffer_head *bh;
Dmitri Monakhov5b41e742008-03-28 14:15:52 -07002565 BUG_ON(fsdata != NULL && page_has_buffers(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002566
Dave Kleikampd4cf1092009-02-06 14:59:26 -06002567 if (unlikely(copied < len) && head)
Dmitri Monakhov5b41e742008-03-28 14:15:52 -07002568 attach_nobh_buffers(page, head);
2569 if (page_has_buffers(page))
2570 return generic_write_end(file, mapping, pos, len,
2571 copied, page, fsdata);
Nick Piggina4b06722007-10-16 01:24:48 -07002572
Nick Piggin22c8ca72007-02-20 13:58:09 -08002573 SetPageUptodate(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002574 set_page_dirty(page);
Nick Piggin03158cd2007-10-16 01:25:25 -07002575 if (pos+copied > inode->i_size) {
2576 i_size_write(inode, pos+copied);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002577 mark_inode_dirty(inode);
2578 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002579
2580 unlock_page(page);
2581 page_cache_release(page);
2582
Nick Piggin03158cd2007-10-16 01:25:25 -07002583 while (head) {
2584 bh = head;
2585 head = head->b_this_page;
2586 free_buffer_head(bh);
2587 }
2588
2589 return copied;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002590}
Nick Piggin03158cd2007-10-16 01:25:25 -07002591EXPORT_SYMBOL(nobh_write_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002592
2593/*
2594 * nobh_writepage() - based on block_full_write_page() except
2595 * that it tries to operate without attaching bufferheads to
2596 * the page.
2597 */
2598int nobh_writepage(struct page *page, get_block_t *get_block,
2599 struct writeback_control *wbc)
2600{
2601 struct inode * const inode = page->mapping->host;
2602 loff_t i_size = i_size_read(inode);
2603 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2604 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002605 int ret;
2606
2607 /* Is the page fully inside i_size? */
2608 if (page->index < end_index)
2609 goto out;
2610
2611 /* Is the page fully outside i_size? (truncate in progress) */
2612 offset = i_size & (PAGE_CACHE_SIZE-1);
2613 if (page->index >= end_index+1 || !offset) {
2614 /*
2615 * The page may have dirty, unmapped buffers. For example,
2616 * they may have been added in ext3_writepage(). Make them
2617 * freeable here, so the page does not leak.
2618 */
2619#if 0
2620 /* Not really sure about this - do we need this ? */
2621 if (page->mapping->a_ops->invalidatepage)
2622 page->mapping->a_ops->invalidatepage(page, offset);
2623#endif
2624 unlock_page(page);
2625 return 0; /* don't care */
2626 }
2627
2628 /*
2629 * The page straddles i_size. It must be zeroed out on each and every
2630 * writepage invocation because it may be mmapped. "A file is mapped
2631 * in multiples of the page size. For a file that is not a multiple of
2632 * the page size, the remaining memory is zeroed when mapped, and
2633 * writes to that region are not written out to the file."
2634 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002635 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002636out:
2637 ret = mpage_writepage(page, get_block, wbc);
2638 if (ret == -EAGAIN)
Chris Mason35c80d52009-04-15 13:22:38 -04002639 ret = __block_write_full_page(inode, page, get_block, wbc,
2640 end_buffer_async_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002641 return ret;
2642}
2643EXPORT_SYMBOL(nobh_writepage);
2644
Nick Piggin03158cd2007-10-16 01:25:25 -07002645int nobh_truncate_page(struct address_space *mapping,
2646 loff_t from, get_block_t *get_block)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002647{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002648 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2649 unsigned offset = from & (PAGE_CACHE_SIZE-1);
Nick Piggin03158cd2007-10-16 01:25:25 -07002650 unsigned blocksize;
2651 sector_t iblock;
2652 unsigned length, pos;
2653 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002654 struct page *page;
Nick Piggin03158cd2007-10-16 01:25:25 -07002655 struct buffer_head map_bh;
2656 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002657
Nick Piggin03158cd2007-10-16 01:25:25 -07002658 blocksize = 1 << inode->i_blkbits;
2659 length = offset & (blocksize - 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002660
Nick Piggin03158cd2007-10-16 01:25:25 -07002661 /* Block boundary? Nothing to do */
2662 if (!length)
2663 return 0;
2664
2665 length = blocksize - length;
2666 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2667
Linus Torvalds1da177e2005-04-16 15:20:36 -07002668 page = grab_cache_page(mapping, index);
Nick Piggin03158cd2007-10-16 01:25:25 -07002669 err = -ENOMEM;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002670 if (!page)
2671 goto out;
2672
Nick Piggin03158cd2007-10-16 01:25:25 -07002673 if (page_has_buffers(page)) {
2674has_buffers:
2675 unlock_page(page);
2676 page_cache_release(page);
2677 return block_truncate_page(mapping, from, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002678 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002679
2680 /* Find the buffer that contains "offset" */
2681 pos = blocksize;
2682 while (offset >= pos) {
2683 iblock++;
2684 pos += blocksize;
2685 }
2686
Theodore Ts'o460bcf52009-05-12 07:37:56 -04002687 map_bh.b_size = blocksize;
2688 map_bh.b_state = 0;
Nick Piggin03158cd2007-10-16 01:25:25 -07002689 err = get_block(inode, iblock, &map_bh, 0);
2690 if (err)
2691 goto unlock;
2692 /* unmapped? It's a hole - nothing to do */
2693 if (!buffer_mapped(&map_bh))
2694 goto unlock;
2695
2696 /* Ok, it's mapped. Make sure it's up-to-date */
2697 if (!PageUptodate(page)) {
2698 err = mapping->a_ops->readpage(NULL, page);
2699 if (err) {
2700 page_cache_release(page);
2701 goto out;
2702 }
2703 lock_page(page);
2704 if (!PageUptodate(page)) {
2705 err = -EIO;
2706 goto unlock;
2707 }
2708 if (page_has_buffers(page))
2709 goto has_buffers;
2710 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002711 zero_user(page, offset, length);
Nick Piggin03158cd2007-10-16 01:25:25 -07002712 set_page_dirty(page);
2713 err = 0;
2714
2715unlock:
Linus Torvalds1da177e2005-04-16 15:20:36 -07002716 unlock_page(page);
2717 page_cache_release(page);
2718out:
Nick Piggin03158cd2007-10-16 01:25:25 -07002719 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002720}
2721EXPORT_SYMBOL(nobh_truncate_page);
2722
2723int block_truncate_page(struct address_space *mapping,
2724 loff_t from, get_block_t *get_block)
2725{
2726 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2727 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2728 unsigned blocksize;
Andrew Morton54b21a72006-01-08 01:03:05 -08002729 sector_t iblock;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002730 unsigned length, pos;
2731 struct inode *inode = mapping->host;
2732 struct page *page;
2733 struct buffer_head *bh;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002734 int err;
2735
2736 blocksize = 1 << inode->i_blkbits;
2737 length = offset & (blocksize - 1);
2738
2739 /* Block boundary? Nothing to do */
2740 if (!length)
2741 return 0;
2742
2743 length = blocksize - length;
Andrew Morton54b21a72006-01-08 01:03:05 -08002744 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002745
2746 page = grab_cache_page(mapping, index);
2747 err = -ENOMEM;
2748 if (!page)
2749 goto out;
2750
2751 if (!page_has_buffers(page))
2752 create_empty_buffers(page, blocksize, 0);
2753
2754 /* Find the buffer that contains "offset" */
2755 bh = page_buffers(page);
2756 pos = blocksize;
2757 while (offset >= pos) {
2758 bh = bh->b_this_page;
2759 iblock++;
2760 pos += blocksize;
2761 }
2762
2763 err = 0;
2764 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002765 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002766 err = get_block(inode, iblock, bh, 0);
2767 if (err)
2768 goto unlock;
2769 /* unmapped? It's a hole - nothing to do */
2770 if (!buffer_mapped(bh))
2771 goto unlock;
2772 }
2773
2774 /* Ok, it's mapped. Make sure it's up-to-date */
2775 if (PageUptodate(page))
2776 set_buffer_uptodate(bh);
2777
David Chinner33a266d2007-02-12 00:51:41 -08002778 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002779 err = -EIO;
2780 ll_rw_block(READ, 1, &bh);
2781 wait_on_buffer(bh);
2782 /* Uhhuh. Read error. Complain and punt. */
2783 if (!buffer_uptodate(bh))
2784 goto unlock;
2785 }
2786
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002787 zero_user(page, offset, length);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002788 mark_buffer_dirty(bh);
2789 err = 0;
2790
2791unlock:
2792 unlock_page(page);
2793 page_cache_release(page);
2794out:
2795 return err;
2796}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002797EXPORT_SYMBOL(block_truncate_page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002798
2799/*
2800 * The generic ->writepage function for buffer-backed address_spaces
Chris Mason35c80d52009-04-15 13:22:38 -04002801 * this form passes in the end_io handler used to finish the IO.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002802 */
Chris Mason35c80d52009-04-15 13:22:38 -04002803int block_write_full_page_endio(struct page *page, get_block_t *get_block,
2804 struct writeback_control *wbc, bh_end_io_t *handler)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002805{
2806 struct inode * const inode = page->mapping->host;
2807 loff_t i_size = i_size_read(inode);
2808 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2809 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002810
2811 /* Is the page fully inside i_size? */
2812 if (page->index < end_index)
Chris Mason35c80d52009-04-15 13:22:38 -04002813 return __block_write_full_page(inode, page, get_block, wbc,
2814 handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002815
2816 /* Is the page fully outside i_size? (truncate in progress) */
2817 offset = i_size & (PAGE_CACHE_SIZE-1);
2818 if (page->index >= end_index+1 || !offset) {
2819 /*
2820 * The page may have dirty, unmapped buffers. For example,
2821 * they may have been added in ext3_writepage(). Make them
2822 * freeable here, so the page does not leak.
2823 */
Jan Karaaaa40592005-10-30 15:00:16 -08002824 do_invalidatepage(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002825 unlock_page(page);
2826 return 0; /* don't care */
2827 }
2828
2829 /*
2830 * The page straddles i_size. It must be zeroed out on each and every
Adam Buchbinder2a61aa42009-12-11 16:35:40 -05002831 * writepage invocation because it may be mmapped. "A file is mapped
Linus Torvalds1da177e2005-04-16 15:20:36 -07002832 * in multiples of the page size. For a file that is not a multiple of
2833 * the page size, the remaining memory is zeroed when mapped, and
2834 * writes to that region are not written out to the file."
2835 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002836 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Chris Mason35c80d52009-04-15 13:22:38 -04002837 return __block_write_full_page(inode, page, get_block, wbc, handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002838}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002839EXPORT_SYMBOL(block_write_full_page_endio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002840
Chris Mason35c80d52009-04-15 13:22:38 -04002841/*
2842 * The generic ->writepage function for buffer-backed address_spaces
2843 */
2844int block_write_full_page(struct page *page, get_block_t *get_block,
2845 struct writeback_control *wbc)
2846{
2847 return block_write_full_page_endio(page, get_block, wbc,
2848 end_buffer_async_write);
2849}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002850EXPORT_SYMBOL(block_write_full_page);
Chris Mason35c80d52009-04-15 13:22:38 -04002851
Linus Torvalds1da177e2005-04-16 15:20:36 -07002852sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2853 get_block_t *get_block)
2854{
2855 struct buffer_head tmp;
2856 struct inode *inode = mapping->host;
2857 tmp.b_state = 0;
2858 tmp.b_blocknr = 0;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002859 tmp.b_size = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002860 get_block(inode, block, &tmp, 0);
2861 return tmp.b_blocknr;
2862}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002863EXPORT_SYMBOL(generic_block_bmap);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002864
NeilBrown6712ecf2007-09-27 12:47:43 +02002865static void end_bio_bh_io_sync(struct bio *bio, int err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002866{
2867 struct buffer_head *bh = bio->bi_private;
2868
Linus Torvalds1da177e2005-04-16 15:20:36 -07002869 if (err == -EOPNOTSUPP) {
2870 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002871 }
2872
Keith Mannthey08bafc02008-11-25 10:24:35 +01002873 if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags)))
2874 set_bit(BH_Quiet, &bh->b_state);
2875
Linus Torvalds1da177e2005-04-16 15:20:36 -07002876 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2877 bio_put(bio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002878}
2879
2880int submit_bh(int rw, struct buffer_head * bh)
2881{
2882 struct bio *bio;
2883 int ret = 0;
2884
2885 BUG_ON(!buffer_locked(bh));
2886 BUG_ON(!buffer_mapped(bh));
2887 BUG_ON(!bh->b_end_io);
Aneesh Kumar K.V8fb0e342009-05-12 16:22:37 -04002888 BUG_ON(buffer_delay(bh));
2889 BUG_ON(buffer_unwritten(bh));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002890
Jens Axboe48fd4f92008-08-22 10:00:36 +02002891 /*
Jens Axboe48fd4f92008-08-22 10:00:36 +02002892 * Only clear out a write error when rewriting
Linus Torvalds1da177e2005-04-16 15:20:36 -07002893 */
Jens Axboe48fd4f92008-08-22 10:00:36 +02002894 if (test_set_buffer_req(bh) && (rw & WRITE))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002895 clear_buffer_write_io_error(bh);
2896
2897 /*
2898 * from here on down, it's all bio -- do the initial mapping,
2899 * submit_bio -> generic_make_request may further map this bio around
2900 */
2901 bio = bio_alloc(GFP_NOIO, 1);
2902
2903 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2904 bio->bi_bdev = bh->b_bdev;
2905 bio->bi_io_vec[0].bv_page = bh->b_page;
2906 bio->bi_io_vec[0].bv_len = bh->b_size;
2907 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
2908
2909 bio->bi_vcnt = 1;
2910 bio->bi_idx = 0;
2911 bio->bi_size = bh->b_size;
2912
2913 bio->bi_end_io = end_bio_bh_io_sync;
2914 bio->bi_private = bh;
2915
2916 bio_get(bio);
2917 submit_bio(rw, bio);
2918
2919 if (bio_flagged(bio, BIO_EOPNOTSUPP))
2920 ret = -EOPNOTSUPP;
2921
2922 bio_put(bio);
2923 return ret;
2924}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002925EXPORT_SYMBOL(submit_bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002926
2927/**
2928 * ll_rw_block: low-level access to block devices (DEPRECATED)
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02002929 * @rw: whether to %READ or %WRITE or maybe %READA (readahead)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002930 * @nr: number of &struct buffer_heads in the array
2931 * @bhs: array of pointers to &struct buffer_head
2932 *
Jan Karaa7662232005-09-06 15:19:10 -07002933 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
2934 * requests an I/O operation on them, either a %READ or a %WRITE. The third
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02002935 * %READA option is described in the documentation for generic_make_request()
2936 * which ll_rw_block() calls.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002937 *
2938 * This function drops any buffer that it cannot get a lock on (with the
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02002939 * BH_Lock state bit), any buffer that appears to be clean when doing a write
2940 * request, and any buffer that appears to be up-to-date when doing read
2941 * request. Further it marks as clean buffers that are processed for
2942 * writing (the buffer cache won't assume that they are actually clean
2943 * until the buffer gets unlocked).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002944 *
2945 * ll_rw_block sets b_end_io to simple completion handler that marks
2946 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
2947 * any waiters.
2948 *
2949 * All of the buffers must be for the same device, and must also be a
2950 * multiple of the current approved size for the device.
2951 */
2952void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
2953{
2954 int i;
2955
2956 for (i = 0; i < nr; i++) {
2957 struct buffer_head *bh = bhs[i];
2958
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02002959 if (!trylock_buffer(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002960 continue;
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02002961 if (rw == WRITE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002962 if (test_clear_buffer_dirty(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07002963 bh->b_end_io = end_buffer_write_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08002964 get_bh(bh);
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02002965 submit_bh(WRITE, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002966 continue;
2967 }
2968 } else {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002969 if (!buffer_uptodate(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07002970 bh->b_end_io = end_buffer_read_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08002971 get_bh(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002972 submit_bh(rw, bh);
2973 continue;
2974 }
2975 }
2976 unlock_buffer(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002977 }
2978}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002979EXPORT_SYMBOL(ll_rw_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002980
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02002981void write_dirty_buffer(struct buffer_head *bh, int rw)
2982{
2983 lock_buffer(bh);
2984 if (!test_clear_buffer_dirty(bh)) {
2985 unlock_buffer(bh);
2986 return;
2987 }
2988 bh->b_end_io = end_buffer_write_sync;
2989 get_bh(bh);
2990 submit_bh(rw, bh);
2991}
2992EXPORT_SYMBOL(write_dirty_buffer);
2993
Linus Torvalds1da177e2005-04-16 15:20:36 -07002994/*
2995 * For a data-integrity writeout, we need to wait upon any in-progress I/O
2996 * and then start new I/O and then wait upon it. The caller must have a ref on
2997 * the buffer_head.
2998 */
Christoph Hellwig87e99512010-08-11 17:05:45 +02002999int __sync_dirty_buffer(struct buffer_head *bh, int rw)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003000{
3001 int ret = 0;
3002
3003 WARN_ON(atomic_read(&bh->b_count) < 1);
3004 lock_buffer(bh);
3005 if (test_clear_buffer_dirty(bh)) {
3006 get_bh(bh);
3007 bh->b_end_io = end_buffer_write_sync;
Christoph Hellwig87e99512010-08-11 17:05:45 +02003008 ret = submit_bh(rw, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003009 wait_on_buffer(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003010 if (!ret && !buffer_uptodate(bh))
3011 ret = -EIO;
3012 } else {
3013 unlock_buffer(bh);
3014 }
3015 return ret;
3016}
Christoph Hellwig87e99512010-08-11 17:05:45 +02003017EXPORT_SYMBOL(__sync_dirty_buffer);
3018
3019int sync_dirty_buffer(struct buffer_head *bh)
3020{
3021 return __sync_dirty_buffer(bh, WRITE_SYNC);
3022}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07003023EXPORT_SYMBOL(sync_dirty_buffer);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003024
3025/*
3026 * try_to_free_buffers() checks if all the buffers on this particular page
3027 * are unused, and releases them if so.
3028 *
3029 * Exclusion against try_to_free_buffers may be obtained by either
3030 * locking the page or by holding its mapping's private_lock.
3031 *
3032 * If the page is dirty but all the buffers are clean then we need to
3033 * be sure to mark the page clean as well. This is because the page
3034 * may be against a block device, and a later reattachment of buffers
3035 * to a dirty page will set *all* buffers dirty. Which would corrupt
3036 * filesystem data on the same device.
3037 *
3038 * The same applies to regular filesystem pages: if all the buffers are
3039 * clean then we set the page clean and proceed. To do that, we require
3040 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3041 * private_lock.
3042 *
3043 * try_to_free_buffers() is non-blocking.
3044 */
3045static inline int buffer_busy(struct buffer_head *bh)
3046{
3047 return atomic_read(&bh->b_count) |
3048 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3049}
3050
3051static int
3052drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3053{
3054 struct buffer_head *head = page_buffers(page);
3055 struct buffer_head *bh;
3056
3057 bh = head;
3058 do {
akpm@osdl.orgde7d5a32005-05-01 08:58:39 -07003059 if (buffer_write_io_error(bh) && page->mapping)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003060 set_bit(AS_EIO, &page->mapping->flags);
3061 if (buffer_busy(bh))
3062 goto failed;
3063 bh = bh->b_this_page;
3064 } while (bh != head);
3065
3066 do {
3067 struct buffer_head *next = bh->b_this_page;
3068
Jan Kara535ee2f2008-02-08 04:21:59 -08003069 if (bh->b_assoc_map)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003070 __remove_assoc_queue(bh);
3071 bh = next;
3072 } while (bh != head);
3073 *buffers_to_free = head;
3074 __clear_page_buffers(page);
3075 return 1;
3076failed:
3077 return 0;
3078}
3079
3080int try_to_free_buffers(struct page *page)
3081{
3082 struct address_space * const mapping = page->mapping;
3083 struct buffer_head *buffers_to_free = NULL;
3084 int ret = 0;
3085
3086 BUG_ON(!PageLocked(page));
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003087 if (PageWriteback(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003088 return 0;
3089
3090 if (mapping == NULL) { /* can this still happen? */
3091 ret = drop_buffers(page, &buffers_to_free);
3092 goto out;
3093 }
3094
3095 spin_lock(&mapping->private_lock);
3096 ret = drop_buffers(page, &buffers_to_free);
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003097
3098 /*
3099 * If the filesystem writes its buffers by hand (eg ext3)
3100 * then we can have clean buffers against a dirty page. We
3101 * clean the page here; otherwise the VM will never notice
3102 * that the filesystem did any IO at all.
3103 *
3104 * Also, during truncate, discard_buffer will have marked all
3105 * the page's buffers clean. We discover that here and clean
3106 * the page also.
Nick Piggin87df7242007-01-30 14:36:27 +11003107 *
3108 * private_lock must be held over this entire operation in order
3109 * to synchronise against __set_page_dirty_buffers and prevent the
3110 * dirty bit from being lost.
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003111 */
3112 if (ret)
3113 cancel_dirty_page(page, PAGE_CACHE_SIZE);
Nick Piggin87df7242007-01-30 14:36:27 +11003114 spin_unlock(&mapping->private_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003115out:
3116 if (buffers_to_free) {
3117 struct buffer_head *bh = buffers_to_free;
3118
3119 do {
3120 struct buffer_head *next = bh->b_this_page;
3121 free_buffer_head(bh);
3122 bh = next;
3123 } while (bh != buffers_to_free);
3124 }
3125 return ret;
3126}
3127EXPORT_SYMBOL(try_to_free_buffers);
3128
Linus Torvalds1da177e2005-04-16 15:20:36 -07003129/*
3130 * There are no bdflush tunables left. But distributions are
3131 * still running obsolete flush daemons, so we terminate them here.
3132 *
3133 * Use of bdflush() is deprecated and will be removed in a future kernel.
Jens Axboe5b0830c2009-09-23 19:37:09 +02003134 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003135 */
Heiko Carstensbdc480e2009-01-14 14:14:12 +01003136SYSCALL_DEFINE2(bdflush, int, func, long, data)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003137{
3138 static int msg_count;
3139
3140 if (!capable(CAP_SYS_ADMIN))
3141 return -EPERM;
3142
3143 if (msg_count < 5) {
3144 msg_count++;
3145 printk(KERN_INFO
3146 "warning: process `%s' used the obsolete bdflush"
3147 " system call\n", current->comm);
3148 printk(KERN_INFO "Fix your initscripts?\n");
3149 }
3150
3151 if (func == 1)
3152 do_exit(0);
3153 return 0;
3154}
3155
3156/*
3157 * Buffer-head allocation
3158 */
Shai Fultheima0a9b042012-05-15 12:29:52 +03003159static struct kmem_cache *bh_cachep __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003160
3161/*
3162 * Once the number of bh's in the machine exceeds this level, we start
3163 * stripping them in writeback.
3164 */
3165static int max_buffer_heads;
3166
3167int buffer_heads_over_limit;
3168
3169struct bh_accounting {
3170 int nr; /* Number of live bh's */
3171 int ratelimit; /* Limit cacheline bouncing */
3172};
3173
3174static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3175
3176static void recalc_bh_state(void)
3177{
3178 int i;
3179 int tot = 0;
3180
Christoph Lameteree1be862010-12-06 11:40:05 -06003181 if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003182 return;
Christoph Lameterc7b92512010-12-06 11:16:28 -06003183 __this_cpu_write(bh_accounting.ratelimit, 0);
Eric Dumazet8a143422006-03-24 03:18:10 -08003184 for_each_online_cpu(i)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003185 tot += per_cpu(bh_accounting, i).nr;
3186 buffer_heads_over_limit = (tot > max_buffer_heads);
3187}
Christoph Lameterc7b92512010-12-06 11:16:28 -06003188
Al Virodd0fc662005-10-07 07:46:04 +01003189struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003190{
Richard Kennedy019b4d12010-03-10 15:20:33 -08003191 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003192 if (ret) {
Christoph Lametera35afb82007-05-16 22:10:57 -07003193 INIT_LIST_HEAD(&ret->b_assoc_buffers);
Christoph Lameterc7b92512010-12-06 11:16:28 -06003194 preempt_disable();
3195 __this_cpu_inc(bh_accounting.nr);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003196 recalc_bh_state();
Christoph Lameterc7b92512010-12-06 11:16:28 -06003197 preempt_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -07003198 }
3199 return ret;
3200}
3201EXPORT_SYMBOL(alloc_buffer_head);
3202
3203void free_buffer_head(struct buffer_head *bh)
3204{
3205 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3206 kmem_cache_free(bh_cachep, bh);
Christoph Lameterc7b92512010-12-06 11:16:28 -06003207 preempt_disable();
3208 __this_cpu_dec(bh_accounting.nr);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003209 recalc_bh_state();
Christoph Lameterc7b92512010-12-06 11:16:28 -06003210 preempt_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -07003211}
3212EXPORT_SYMBOL(free_buffer_head);
3213
Linus Torvalds1da177e2005-04-16 15:20:36 -07003214static void buffer_exit_cpu(int cpu)
3215{
3216 int i;
3217 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3218
3219 for (i = 0; i < BH_LRU_SIZE; i++) {
3220 brelse(b->bhs[i]);
3221 b->bhs[i] = NULL;
3222 }
Christoph Lameterc7b92512010-12-06 11:16:28 -06003223 this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
Eric Dumazet8a143422006-03-24 03:18:10 -08003224 per_cpu(bh_accounting, cpu).nr = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003225}
3226
3227static int buffer_cpu_notify(struct notifier_block *self,
3228 unsigned long action, void *hcpu)
3229{
Rafael J. Wysocki8bb78442007-05-09 02:35:10 -07003230 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003231 buffer_exit_cpu((unsigned long)hcpu);
3232 return NOTIFY_OK;
3233}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003234
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003235/**
Randy Dunlapa6b91912008-03-19 17:01:00 -07003236 * bh_uptodate_or_lock - Test whether the buffer is uptodate
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003237 * @bh: struct buffer_head
3238 *
3239 * Return true if the buffer is up-to-date and false,
3240 * with the buffer locked, if not.
3241 */
3242int bh_uptodate_or_lock(struct buffer_head *bh)
3243{
3244 if (!buffer_uptodate(bh)) {
3245 lock_buffer(bh);
3246 if (!buffer_uptodate(bh))
3247 return 0;
3248 unlock_buffer(bh);
3249 }
3250 return 1;
3251}
3252EXPORT_SYMBOL(bh_uptodate_or_lock);
3253
3254/**
Randy Dunlapa6b91912008-03-19 17:01:00 -07003255 * bh_submit_read - Submit a locked buffer for reading
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003256 * @bh: struct buffer_head
3257 *
3258 * Returns zero on success and -EIO on error.
3259 */
3260int bh_submit_read(struct buffer_head *bh)
3261{
3262 BUG_ON(!buffer_locked(bh));
3263
3264 if (buffer_uptodate(bh)) {
3265 unlock_buffer(bh);
3266 return 0;
3267 }
3268
3269 get_bh(bh);
3270 bh->b_end_io = end_buffer_read_sync;
3271 submit_bh(READ, bh);
3272 wait_on_buffer(bh);
3273 if (buffer_uptodate(bh))
3274 return 0;
3275 return -EIO;
3276}
3277EXPORT_SYMBOL(bh_submit_read);
3278
Linus Torvalds1da177e2005-04-16 15:20:36 -07003279void __init buffer_init(void)
3280{
3281 int nrpages;
3282
Christoph Lameterb98938c2008-02-04 22:28:36 -08003283 bh_cachep = kmem_cache_create("buffer_head",
3284 sizeof(struct buffer_head), 0,
3285 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3286 SLAB_MEM_SPREAD),
Richard Kennedy019b4d12010-03-10 15:20:33 -08003287 NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003288
3289 /*
3290 * Limit the bh occupancy to 10% of ZONE_NORMAL
3291 */
3292 nrpages = (nr_free_buffer_pages() * 10) / 100;
3293 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3294 hotcpu_notifier(buffer_cpu_notify, 0);
3295}