blob: 35ac651f1937cfd114e675be49ed858a62a3662b [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{
1039 /* Size must be multiple of hard sectorsize */
Martin K. Petersene1defc42009-05-22 17:17:49 -04001040 if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
Linus Torvalds1da177e2005-04-16 15:20:36 -07001041 (size < 512 || size > PAGE_SIZE))) {
1042 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1043 size);
Martin K. Petersene1defc42009-05-22 17:17:49 -04001044 printk(KERN_ERR "logical block size: %d\n",
1045 bdev_logical_block_size(bdev));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001046
1047 dump_stack();
1048 return NULL;
1049 }
1050
1051 for (;;) {
1052 struct buffer_head * bh;
Andrew Mortone5657932006-10-11 01:21:46 -07001053 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001054
1055 bh = __find_get_block(bdev, block, size);
1056 if (bh)
1057 return bh;
1058
Andrew Mortone5657932006-10-11 01:21:46 -07001059 ret = grow_buffers(bdev, block, size);
1060 if (ret < 0)
1061 return NULL;
1062 if (ret == 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001063 free_more_memory();
1064 }
1065}
1066
1067/*
1068 * The relationship between dirty buffers and dirty pages:
1069 *
1070 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1071 * the page is tagged dirty in its radix tree.
1072 *
1073 * At all times, the dirtiness of the buffers represents the dirtiness of
1074 * subsections of the page. If the page has buffers, the page dirty bit is
1075 * merely a hint about the true dirty state.
1076 *
1077 * When a page is set dirty in its entirety, all its buffers are marked dirty
1078 * (if the page has buffers).
1079 *
1080 * When a buffer is marked dirty, its page is dirtied, but the page's other
1081 * buffers are not.
1082 *
1083 * Also. When blockdev buffers are explicitly read with bread(), they
1084 * individually become uptodate. But their backing page remains not
1085 * uptodate - even if all of its buffers are uptodate. A subsequent
1086 * block_read_full_page() against that page will discover all the uptodate
1087 * buffers, will set the page uptodate and will perform no I/O.
1088 */
1089
1090/**
1091 * mark_buffer_dirty - mark a buffer_head as needing writeout
Martin Waitz67be2dd2005-05-01 08:59:26 -07001092 * @bh: the buffer_head to mark dirty
Linus Torvalds1da177e2005-04-16 15:20:36 -07001093 *
1094 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1095 * backing page dirty, then tag the page as dirty in its address_space's radix
1096 * tree and then attach the address_space's inode to its superblock's dirty
1097 * inode list.
1098 *
1099 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
Dave Chinner250df6e2011-03-22 22:23:36 +11001100 * mapping->tree_lock and mapping->host->i_lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001101 */
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -08001102void mark_buffer_dirty(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001103{
Nick Piggin787d2212007-07-17 04:03:34 -07001104 WARN_ON_ONCE(!buffer_uptodate(bh));
Linus Torvalds1be62dc2008-04-04 14:38:17 -07001105
1106 /*
1107 * Very *carefully* optimize the it-is-already-dirty case.
1108 *
1109 * Don't let the final "is it dirty" escape to before we
1110 * perhaps modified the buffer.
1111 */
1112 if (buffer_dirty(bh)) {
1113 smp_mb();
1114 if (buffer_dirty(bh))
1115 return;
1116 }
1117
Linus Torvaldsa8e7d492009-03-19 11:32:05 -07001118 if (!test_set_buffer_dirty(bh)) {
1119 struct page *page = bh->b_page;
Linus Torvalds8e9d78e2009-08-21 17:40:08 -07001120 if (!TestSetPageDirty(page)) {
1121 struct address_space *mapping = page_mapping(page);
1122 if (mapping)
1123 __set_page_dirty(page, mapping, 0);
1124 }
Linus Torvaldsa8e7d492009-03-19 11:32:05 -07001125 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001126}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07001127EXPORT_SYMBOL(mark_buffer_dirty);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001128
1129/*
1130 * Decrement a buffer_head's reference count. If all buffers against a page
1131 * have zero reference count, are clean and unlocked, and if the page is clean
1132 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1133 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1134 * a page but it ends up not being freed, and buffers may later be reattached).
1135 */
1136void __brelse(struct buffer_head * buf)
1137{
1138 if (atomic_read(&buf->b_count)) {
1139 put_bh(buf);
1140 return;
1141 }
Arjan van de Ven5c752ad2008-07-25 19:45:40 -07001142 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
Linus Torvalds1da177e2005-04-16 15:20:36 -07001143}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07001144EXPORT_SYMBOL(__brelse);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001145
1146/*
1147 * bforget() is like brelse(), except it discards any
1148 * potentially dirty data.
1149 */
1150void __bforget(struct buffer_head *bh)
1151{
1152 clear_buffer_dirty(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -08001153 if (bh->b_assoc_map) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001154 struct address_space *buffer_mapping = bh->b_page->mapping;
1155
1156 spin_lock(&buffer_mapping->private_lock);
1157 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -07001158 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001159 spin_unlock(&buffer_mapping->private_lock);
1160 }
1161 __brelse(bh);
1162}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07001163EXPORT_SYMBOL(__bforget);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001164
1165static struct buffer_head *__bread_slow(struct buffer_head *bh)
1166{
1167 lock_buffer(bh);
1168 if (buffer_uptodate(bh)) {
1169 unlock_buffer(bh);
1170 return bh;
1171 } else {
1172 get_bh(bh);
1173 bh->b_end_io = end_buffer_read_sync;
1174 submit_bh(READ, bh);
1175 wait_on_buffer(bh);
1176 if (buffer_uptodate(bh))
1177 return bh;
1178 }
1179 brelse(bh);
1180 return NULL;
1181}
1182
1183/*
1184 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1185 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1186 * refcount elevated by one when they're in an LRU. A buffer can only appear
1187 * once in a particular CPU's LRU. A single buffer can be present in multiple
1188 * CPU's LRUs at the same time.
1189 *
1190 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1191 * sb_find_get_block().
1192 *
1193 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1194 * a local interrupt disable for that.
1195 */
1196
1197#define BH_LRU_SIZE 8
1198
1199struct bh_lru {
1200 struct buffer_head *bhs[BH_LRU_SIZE];
1201};
1202
1203static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1204
1205#ifdef CONFIG_SMP
1206#define bh_lru_lock() local_irq_disable()
1207#define bh_lru_unlock() local_irq_enable()
1208#else
1209#define bh_lru_lock() preempt_disable()
1210#define bh_lru_unlock() preempt_enable()
1211#endif
1212
1213static inline void check_irqs_on(void)
1214{
1215#ifdef irqs_disabled
1216 BUG_ON(irqs_disabled());
1217#endif
1218}
1219
1220/*
1221 * The LRU management algorithm is dopey-but-simple. Sorry.
1222 */
1223static void bh_lru_install(struct buffer_head *bh)
1224{
1225 struct buffer_head *evictee = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001226
1227 check_irqs_on();
1228 bh_lru_lock();
Christoph Lameterc7b92512010-12-06 11:16:28 -06001229 if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001230 struct buffer_head *bhs[BH_LRU_SIZE];
1231 int in;
1232 int out = 0;
1233
1234 get_bh(bh);
1235 bhs[out++] = bh;
1236 for (in = 0; in < BH_LRU_SIZE; in++) {
Christoph Lameterc7b92512010-12-06 11:16:28 -06001237 struct buffer_head *bh2 =
1238 __this_cpu_read(bh_lrus.bhs[in]);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001239
1240 if (bh2 == bh) {
1241 __brelse(bh2);
1242 } else {
1243 if (out >= BH_LRU_SIZE) {
1244 BUG_ON(evictee != NULL);
1245 evictee = bh2;
1246 } else {
1247 bhs[out++] = bh2;
1248 }
1249 }
1250 }
1251 while (out < BH_LRU_SIZE)
1252 bhs[out++] = NULL;
Christoph Lameterc7b92512010-12-06 11:16:28 -06001253 memcpy(__this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001254 }
1255 bh_lru_unlock();
1256
1257 if (evictee)
1258 __brelse(evictee);
1259}
1260
1261/*
1262 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1263 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001264static struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001265lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001266{
1267 struct buffer_head *ret = NULL;
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001268 unsigned int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001269
1270 check_irqs_on();
1271 bh_lru_lock();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001272 for (i = 0; i < BH_LRU_SIZE; i++) {
Christoph Lameterc7b92512010-12-06 11:16:28 -06001273 struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001274
1275 if (bh && bh->b_bdev == bdev &&
1276 bh->b_blocknr == block && bh->b_size == size) {
1277 if (i) {
1278 while (i) {
Christoph Lameterc7b92512010-12-06 11:16:28 -06001279 __this_cpu_write(bh_lrus.bhs[i],
1280 __this_cpu_read(bh_lrus.bhs[i - 1]));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001281 i--;
1282 }
Christoph Lameterc7b92512010-12-06 11:16:28 -06001283 __this_cpu_write(bh_lrus.bhs[0], bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001284 }
1285 get_bh(bh);
1286 ret = bh;
1287 break;
1288 }
1289 }
1290 bh_lru_unlock();
1291 return ret;
1292}
1293
1294/*
1295 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1296 * it in the LRU and mark it as accessed. If it is not present then return
1297 * NULL
1298 */
1299struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001300__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001301{
1302 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1303
1304 if (bh == NULL) {
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001305 bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001306 if (bh)
1307 bh_lru_install(bh);
1308 }
1309 if (bh)
1310 touch_buffer(bh);
1311 return bh;
1312}
1313EXPORT_SYMBOL(__find_get_block);
1314
1315/*
1316 * __getblk will locate (and, if necessary, create) the buffer_head
1317 * which corresponds to the passed block_device, block and size. The
1318 * returned buffer has its reference count incremented.
1319 *
1320 * __getblk() cannot fail - it just keeps trying. If you pass it an
1321 * illegal block number, __getblk() will happily return a buffer_head
1322 * which represents the non-existent block. Very weird.
1323 *
1324 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1325 * attempt is failing. FIXME, perhaps?
1326 */
1327struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001328__getblk(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001329{
1330 struct buffer_head *bh = __find_get_block(bdev, block, size);
1331
1332 might_sleep();
1333 if (bh == NULL)
1334 bh = __getblk_slow(bdev, block, size);
1335 return bh;
1336}
1337EXPORT_SYMBOL(__getblk);
1338
1339/*
1340 * Do async read-ahead on a buffer..
1341 */
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001342void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001343{
1344 struct buffer_head *bh = __getblk(bdev, block, size);
Andrew Mortona3e713b2005-10-30 15:03:15 -08001345 if (likely(bh)) {
1346 ll_rw_block(READA, 1, &bh);
1347 brelse(bh);
1348 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001349}
1350EXPORT_SYMBOL(__breadahead);
1351
1352/**
1353 * __bread() - reads a specified block and returns the bh
Martin Waitz67be2dd2005-05-01 08:59:26 -07001354 * @bdev: the block_device to read from
Linus Torvalds1da177e2005-04-16 15:20:36 -07001355 * @block: number of block
1356 * @size: size (in bytes) to read
1357 *
1358 * Reads a specified block, and returns buffer head that contains it.
1359 * It returns NULL if the block was unreadable.
1360 */
1361struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001362__bread(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001363{
1364 struct buffer_head *bh = __getblk(bdev, block, size);
1365
Andrew Mortona3e713b2005-10-30 15:03:15 -08001366 if (likely(bh) && !buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001367 bh = __bread_slow(bh);
1368 return bh;
1369}
1370EXPORT_SYMBOL(__bread);
1371
1372/*
1373 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1374 * This doesn't race because it runs in each cpu either in irq
1375 * or with preempt disabled.
1376 */
1377static void invalidate_bh_lru(void *arg)
1378{
1379 struct bh_lru *b = &get_cpu_var(bh_lrus);
1380 int i;
1381
1382 for (i = 0; i < BH_LRU_SIZE; i++) {
1383 brelse(b->bhs[i]);
1384 b->bhs[i] = NULL;
1385 }
1386 put_cpu_var(bh_lrus);
1387}
Gilad Ben-Yossef42be35d2012-03-28 14:42:45 -07001388
1389static bool has_bh_in_lru(int cpu, void *dummy)
1390{
1391 struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1392 int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001393
Gilad Ben-Yossef42be35d2012-03-28 14:42:45 -07001394 for (i = 0; i < BH_LRU_SIZE; i++) {
1395 if (b->bhs[i])
1396 return 1;
1397 }
1398
1399 return 0;
1400}
1401
Laura Abbott96760382012-08-30 18:01:17 -07001402static void __evict_bh_lru(void *arg)
1403{
1404 struct bh_lru *b = &get_cpu_var(bh_lrus);
1405 struct buffer_head *bh = arg;
1406 int i;
1407
1408 for (i = 0; i < BH_LRU_SIZE; i++) {
1409 if (b->bhs[i] == bh) {
1410 brelse(b->bhs[i]);
1411 b->bhs[i] = NULL;
1412 goto out;
1413 }
1414 }
1415out:
1416 put_cpu_var(bh_lrus);
1417}
1418
1419static bool bh_exists_in_lru(int cpu, void *arg)
1420{
1421 struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1422 struct buffer_head *bh = arg;
1423 int i;
1424
1425 for (i = 0; i < BH_LRU_SIZE; i++) {
1426 if (b->bhs[i] == bh)
1427 return 1;
1428 }
1429
1430 return 0;
1431
1432}
Peter Zijlstraf9a14392007-05-06 14:49:55 -07001433void invalidate_bh_lrus(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001434{
Gilad Ben-Yossef42be35d2012-03-28 14:42:45 -07001435 on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001436}
Nick Piggin9db55792008-02-08 04:19:49 -08001437EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001438
Laura Abbott96760382012-08-30 18:01:17 -07001439void evict_bh_lrus(struct buffer_head *bh)
1440{
1441 on_each_cpu_cond(bh_exists_in_lru, __evict_bh_lru, bh, 1, GFP_ATOMIC);
1442}
1443EXPORT_SYMBOL_GPL(evict_bh_lrus);
1444
Linus Torvalds1da177e2005-04-16 15:20:36 -07001445void set_bh_page(struct buffer_head *bh,
1446 struct page *page, unsigned long offset)
1447{
1448 bh->b_page = page;
Eric Sesterhenne827f922006-03-26 18:24:46 +02001449 BUG_ON(offset >= PAGE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001450 if (PageHighMem(page))
1451 /*
1452 * This catches illegal uses and preserves the offset:
1453 */
1454 bh->b_data = (char *)(0 + offset);
1455 else
1456 bh->b_data = page_address(page) + offset;
1457}
1458EXPORT_SYMBOL(set_bh_page);
1459
1460/*
1461 * Called when truncating a buffer on a page completely.
1462 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001463static void discard_buffer(struct buffer_head * bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001464{
1465 lock_buffer(bh);
1466 clear_buffer_dirty(bh);
1467 bh->b_bdev = NULL;
1468 clear_buffer_mapped(bh);
1469 clear_buffer_req(bh);
1470 clear_buffer_new(bh);
1471 clear_buffer_delay(bh);
David Chinner33a266d2007-02-12 00:51:41 -08001472 clear_buffer_unwritten(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001473 unlock_buffer(bh);
1474}
1475
1476/**
Wang Sheng-Hui814e1d22011-09-01 08:22:57 +08001477 * block_invalidatepage - invalidate part or all of a buffer-backed page
Linus Torvalds1da177e2005-04-16 15:20:36 -07001478 *
1479 * @page: the page which is affected
1480 * @offset: the index of the truncation point
1481 *
1482 * block_invalidatepage() is called when all or part of the page has become
Wang Sheng-Hui814e1d22011-09-01 08:22:57 +08001483 * invalidated by a truncate operation.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001484 *
1485 * block_invalidatepage() does not have to release all buffers, but it must
1486 * ensure that no dirty buffer is left outside @offset and that no I/O
1487 * is underway against any of the blocks which are outside the truncation
1488 * point. Because the caller is about to free (and possibly reuse) those
1489 * blocks on-disk.
1490 */
NeilBrown2ff28e22006-03-26 01:37:18 -08001491void block_invalidatepage(struct page *page, unsigned long offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001492{
1493 struct buffer_head *head, *bh, *next;
1494 unsigned int curr_off = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001495
1496 BUG_ON(!PageLocked(page));
1497 if (!page_has_buffers(page))
1498 goto out;
1499
1500 head = page_buffers(page);
1501 bh = head;
1502 do {
1503 unsigned int next_off = curr_off + bh->b_size;
1504 next = bh->b_this_page;
1505
1506 /*
1507 * is this block fully invalidated?
1508 */
1509 if (offset <= curr_off)
1510 discard_buffer(bh);
1511 curr_off = next_off;
1512 bh = next;
1513 } while (bh != head);
1514
1515 /*
1516 * We release buffers only if the entire page is being invalidated.
1517 * The get_block cached value has been unconditionally invalidated,
1518 * so real IO is not possible anymore.
1519 */
1520 if (offset == 0)
NeilBrown2ff28e22006-03-26 01:37:18 -08001521 try_to_release_page(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001522out:
NeilBrown2ff28e22006-03-26 01:37:18 -08001523 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001524}
1525EXPORT_SYMBOL(block_invalidatepage);
1526
1527/*
1528 * We attach and possibly dirty the buffers atomically wrt
1529 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1530 * is already excluded via the page lock.
1531 */
1532void create_empty_buffers(struct page *page,
1533 unsigned long blocksize, unsigned long b_state)
1534{
1535 struct buffer_head *bh, *head, *tail;
1536
1537 head = alloc_page_buffers(page, blocksize, 1);
1538 bh = head;
1539 do {
1540 bh->b_state |= b_state;
1541 tail = bh;
1542 bh = bh->b_this_page;
1543 } while (bh);
1544 tail->b_this_page = head;
1545
1546 spin_lock(&page->mapping->private_lock);
1547 if (PageUptodate(page) || PageDirty(page)) {
1548 bh = head;
1549 do {
1550 if (PageDirty(page))
1551 set_buffer_dirty(bh);
1552 if (PageUptodate(page))
1553 set_buffer_uptodate(bh);
1554 bh = bh->b_this_page;
1555 } while (bh != head);
1556 }
1557 attach_page_buffers(page, head);
1558 spin_unlock(&page->mapping->private_lock);
1559}
1560EXPORT_SYMBOL(create_empty_buffers);
1561
1562/*
1563 * We are taking a block for data and we don't want any output from any
1564 * buffer-cache aliases starting from return from that function and
1565 * until the moment when something will explicitly mark the buffer
1566 * dirty (hopefully that will not happen until we will free that block ;-)
1567 * We don't even need to mark it not-uptodate - nobody can expect
1568 * anything from a newly allocated buffer anyway. We used to used
1569 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1570 * don't want to mark the alias unmapped, for example - it would confuse
1571 * anyone who might pick it with bread() afterwards...
1572 *
1573 * Also.. Note that bforget() doesn't lock the buffer. So there can
1574 * be writeout I/O going on against recently-freed buffers. We don't
1575 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1576 * only if we really need to. That happens here.
1577 */
1578void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1579{
1580 struct buffer_head *old_bh;
1581
1582 might_sleep();
1583
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001584 old_bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001585 if (old_bh) {
1586 clear_buffer_dirty(old_bh);
1587 wait_on_buffer(old_bh);
1588 clear_buffer_req(old_bh);
1589 __brelse(old_bh);
1590 }
1591}
1592EXPORT_SYMBOL(unmap_underlying_metadata);
1593
1594/*
1595 * NOTE! All mapped/uptodate combinations are valid:
1596 *
1597 * Mapped Uptodate Meaning
1598 *
1599 * No No "unknown" - must do get_block()
1600 * No Yes "hole" - zero-filled
1601 * Yes No "allocated" - allocated on disk, not read in
1602 * Yes Yes "valid" - allocated and up-to-date in memory.
1603 *
1604 * "Dirty" is valid only with the last case (mapped+uptodate).
1605 */
1606
1607/*
1608 * While block_write_full_page is writing back the dirty buffers under
1609 * the page lock, whoever dirtied the buffers may decide to clean them
1610 * again at any time. We handle that by only looking at the buffer
1611 * state inside lock_buffer().
1612 *
1613 * If block_write_full_page() is called for regular writeback
1614 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1615 * locked buffer. This only can happen if someone has written the buffer
1616 * directly, with submit_bh(). At the address_space level PageWriteback
1617 * prevents this contention from occurring.
Theodore Ts'o6e34eed2009-04-07 18:12:43 -04001618 *
1619 * If block_write_full_page() is called with wbc->sync_mode ==
Jens Axboe721a9602011-03-09 11:56:30 +01001620 * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this
1621 * causes the writes to be flagged as synchronous writes.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001622 */
1623static int __block_write_full_page(struct inode *inode, struct page *page,
Chris Mason35c80d52009-04-15 13:22:38 -04001624 get_block_t *get_block, struct writeback_control *wbc,
1625 bh_end_io_t *handler)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001626{
1627 int err;
1628 sector_t block;
1629 sector_t last_block;
Andrew Mortonf0fbd5f2005-05-05 16:15:48 -07001630 struct buffer_head *bh, *head;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001631 const unsigned blocksize = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001632 int nr_underway = 0;
Theodore Ts'o6e34eed2009-04-07 18:12:43 -04001633 int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
Jens Axboe721a9602011-03-09 11:56:30 +01001634 WRITE_SYNC : WRITE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001635
1636 BUG_ON(!PageLocked(page));
1637
1638 last_block = (i_size_read(inode) - 1) >> inode->i_blkbits;
1639
1640 if (!page_has_buffers(page)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001641 create_empty_buffers(page, blocksize,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001642 (1 << BH_Dirty)|(1 << BH_Uptodate));
1643 }
1644
1645 /*
1646 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1647 * here, and the (potentially unmapped) buffers may become dirty at
1648 * any time. If a buffer becomes dirty here after we've inspected it
1649 * then we just miss that fact, and the page stays dirty.
1650 *
1651 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1652 * handle that here by just cleaning them.
1653 */
1654
Andrew Morton54b21a72006-01-08 01:03:05 -08001655 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001656 head = page_buffers(page);
1657 bh = head;
1658
1659 /*
1660 * Get all the dirty buffers mapped to disk addresses and
1661 * handle any aliases from the underlying blockdev's mapping.
1662 */
1663 do {
1664 if (block > last_block) {
1665 /*
1666 * mapped buffers outside i_size will occur, because
1667 * this page can be outside i_size when there is a
1668 * truncate in progress.
1669 */
1670 /*
1671 * The buffer was zeroed by block_write_full_page()
1672 */
1673 clear_buffer_dirty(bh);
1674 set_buffer_uptodate(bh);
Alex Tomas29a814d2008-07-11 19:27:31 -04001675 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1676 buffer_dirty(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001677 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001678 err = get_block(inode, block, bh, 1);
1679 if (err)
1680 goto recover;
Alex Tomas29a814d2008-07-11 19:27:31 -04001681 clear_buffer_delay(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001682 if (buffer_new(bh)) {
1683 /* blockdev mappings never come here */
1684 clear_buffer_new(bh);
1685 unmap_underlying_metadata(bh->b_bdev,
1686 bh->b_blocknr);
1687 }
1688 }
1689 bh = bh->b_this_page;
1690 block++;
1691 } while (bh != head);
1692
1693 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001694 if (!buffer_mapped(bh))
1695 continue;
1696 /*
1697 * If it's a fully non-blocking write attempt and we cannot
1698 * lock the buffer then redirty the page. Note that this can
Jens Axboe5b0830c2009-09-23 19:37:09 +02001699 * potentially cause a busy-wait loop from writeback threads
1700 * and kswapd activity, but those code paths have their own
1701 * higher-level throttling.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001702 */
Wu Fengguang1b430be2010-10-26 14:21:26 -07001703 if (wbc->sync_mode != WB_SYNC_NONE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001704 lock_buffer(bh);
Nick Pigginca5de402008-08-02 12:02:13 +02001705 } else if (!trylock_buffer(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001706 redirty_page_for_writepage(wbc, page);
1707 continue;
1708 }
1709 if (test_clear_buffer_dirty(bh)) {
Chris Mason35c80d52009-04-15 13:22:38 -04001710 mark_buffer_async_write_endio(bh, handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001711 } else {
1712 unlock_buffer(bh);
1713 }
1714 } while ((bh = bh->b_this_page) != head);
1715
1716 /*
1717 * The page and its buffers are protected by PageWriteback(), so we can
1718 * drop the bh refcounts early.
1719 */
1720 BUG_ON(PageWriteback(page));
1721 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001722
1723 do {
1724 struct buffer_head *next = bh->b_this_page;
1725 if (buffer_async_write(bh)) {
Theodore Ts'oa64c8612009-03-27 22:14:10 -04001726 submit_bh(write_op, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001727 nr_underway++;
1728 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001729 bh = next;
1730 } while (bh != head);
Andrew Morton05937ba2005-05-05 16:15:47 -07001731 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001732
1733 err = 0;
1734done:
1735 if (nr_underway == 0) {
1736 /*
1737 * The page was marked dirty, but the buffers were
1738 * clean. Someone wrote them back by hand with
1739 * ll_rw_block/submit_bh. A rare case.
1740 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001741 end_page_writeback(page);
Nick Piggin3d67f2d2007-05-06 14:49:05 -07001742
Linus Torvalds1da177e2005-04-16 15:20:36 -07001743 /*
1744 * The page and buffer_heads can be released at any time from
1745 * here on.
1746 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001747 }
1748 return err;
1749
1750recover:
1751 /*
1752 * ENOSPC, or some other error. We may already have added some
1753 * blocks to the file, so we need to write these out to avoid
1754 * exposing stale data.
1755 * The page is currently locked and not marked for writeback
1756 */
1757 bh = head;
1758 /* Recovery: lock and submit the mapped buffers */
1759 do {
Alex Tomas29a814d2008-07-11 19:27:31 -04001760 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1761 !buffer_delay(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001762 lock_buffer(bh);
Chris Mason35c80d52009-04-15 13:22:38 -04001763 mark_buffer_async_write_endio(bh, handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001764 } else {
1765 /*
1766 * The buffer may have been set dirty during
1767 * attachment to a dirty page.
1768 */
1769 clear_buffer_dirty(bh);
1770 }
1771 } while ((bh = bh->b_this_page) != head);
1772 SetPageError(page);
1773 BUG_ON(PageWriteback(page));
Andrew Morton7e4c3692007-05-08 00:23:27 -07001774 mapping_set_error(page->mapping, err);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001775 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001776 do {
1777 struct buffer_head *next = bh->b_this_page;
1778 if (buffer_async_write(bh)) {
1779 clear_buffer_dirty(bh);
Theodore Ts'oa64c8612009-03-27 22:14:10 -04001780 submit_bh(write_op, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001781 nr_underway++;
1782 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001783 bh = next;
1784 } while (bh != head);
Nick Pigginffda9d32007-02-20 13:57:54 -08001785 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001786 goto done;
1787}
1788
Nick Pigginafddba42007-10-16 01:25:01 -07001789/*
1790 * If a page has any new buffers, zero them out here, and mark them uptodate
1791 * and dirty so they'll be written out (in order to prevent uninitialised
1792 * block data from leaking). And clear the new bit.
1793 */
1794void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1795{
1796 unsigned int block_start, block_end;
1797 struct buffer_head *head, *bh;
1798
1799 BUG_ON(!PageLocked(page));
1800 if (!page_has_buffers(page))
1801 return;
1802
1803 bh = head = page_buffers(page);
1804 block_start = 0;
1805 do {
1806 block_end = block_start + bh->b_size;
1807
1808 if (buffer_new(bh)) {
1809 if (block_end > from && block_start < to) {
1810 if (!PageUptodate(page)) {
1811 unsigned start, size;
1812
1813 start = max(from, block_start);
1814 size = min(to, block_end) - start;
1815
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001816 zero_user(page, start, size);
Nick Pigginafddba42007-10-16 01:25:01 -07001817 set_buffer_uptodate(bh);
1818 }
1819
1820 clear_buffer_new(bh);
1821 mark_buffer_dirty(bh);
1822 }
1823 }
1824
1825 block_start = block_end;
1826 bh = bh->b_this_page;
1827 } while (bh != head);
1828}
1829EXPORT_SYMBOL(page_zero_new_buffers);
1830
Christoph Hellwigebdec242010-10-06 10:47:23 +02001831int __block_write_begin(struct page *page, loff_t pos, unsigned len,
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001832 get_block_t *get_block)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001833{
Christoph Hellwigebdec242010-10-06 10:47:23 +02001834 unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1835 unsigned to = from + len;
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001836 struct inode *inode = page->mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001837 unsigned block_start, block_end;
1838 sector_t block;
1839 int err = 0;
1840 unsigned blocksize, bbits;
1841 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1842
1843 BUG_ON(!PageLocked(page));
1844 BUG_ON(from > PAGE_CACHE_SIZE);
1845 BUG_ON(to > PAGE_CACHE_SIZE);
1846 BUG_ON(from > to);
1847
1848 blocksize = 1 << inode->i_blkbits;
1849 if (!page_has_buffers(page))
1850 create_empty_buffers(page, blocksize, 0);
1851 head = page_buffers(page);
1852
1853 bbits = inode->i_blkbits;
1854 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1855
1856 for(bh = head, block_start = 0; bh != head || !block_start;
1857 block++, block_start=block_end, bh = bh->b_this_page) {
1858 block_end = block_start + blocksize;
1859 if (block_end <= from || block_start >= to) {
1860 if (PageUptodate(page)) {
1861 if (!buffer_uptodate(bh))
1862 set_buffer_uptodate(bh);
1863 }
1864 continue;
1865 }
1866 if (buffer_new(bh))
1867 clear_buffer_new(bh);
1868 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001869 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001870 err = get_block(inode, block, bh, 1);
1871 if (err)
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001872 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001873 if (buffer_new(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001874 unmap_underlying_metadata(bh->b_bdev,
1875 bh->b_blocknr);
1876 if (PageUptodate(page)) {
Nick Piggin637aff42007-10-16 01:25:00 -07001877 clear_buffer_new(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001878 set_buffer_uptodate(bh);
Nick Piggin637aff42007-10-16 01:25:00 -07001879 mark_buffer_dirty(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001880 continue;
1881 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001882 if (block_end > to || block_start < from)
1883 zero_user_segments(page,
1884 to, block_end,
1885 block_start, from);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001886 continue;
1887 }
1888 }
1889 if (PageUptodate(page)) {
1890 if (!buffer_uptodate(bh))
1891 set_buffer_uptodate(bh);
1892 continue;
1893 }
1894 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
David Chinner33a266d2007-02-12 00:51:41 -08001895 !buffer_unwritten(bh) &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001896 (block_start < from || block_end > to)) {
1897 ll_rw_block(READ, 1, &bh);
1898 *wait_bh++=bh;
1899 }
1900 }
1901 /*
1902 * If we issued read requests - let them complete.
1903 */
1904 while(wait_bh > wait) {
1905 wait_on_buffer(*--wait_bh);
1906 if (!buffer_uptodate(*wait_bh))
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001907 err = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001908 }
Jan Karaf9f07b62011-06-14 00:58:27 +02001909 if (unlikely(err))
Nick Pigginafddba42007-10-16 01:25:01 -07001910 page_zero_new_buffers(page, from, to);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001911 return err;
1912}
Christoph Hellwigebdec242010-10-06 10:47:23 +02001913EXPORT_SYMBOL(__block_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001914
1915static int __block_commit_write(struct inode *inode, struct page *page,
1916 unsigned from, unsigned to)
1917{
1918 unsigned block_start, block_end;
1919 int partial = 0;
1920 unsigned blocksize;
1921 struct buffer_head *bh, *head;
1922
1923 blocksize = 1 << inode->i_blkbits;
1924
1925 for(bh = head = page_buffers(page), block_start = 0;
1926 bh != head || !block_start;
1927 block_start=block_end, bh = bh->b_this_page) {
1928 block_end = block_start + blocksize;
1929 if (block_end <= from || block_start >= to) {
1930 if (!buffer_uptodate(bh))
1931 partial = 1;
1932 } else {
1933 set_buffer_uptodate(bh);
1934 mark_buffer_dirty(bh);
1935 }
Nick Pigginafddba42007-10-16 01:25:01 -07001936 clear_buffer_new(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001937 }
1938
1939 /*
1940 * If this is a partial write which happened to make all buffers
1941 * uptodate then we can optimize away a bogus readpage() for
1942 * the next read(). Here we 'discover' whether the page went
1943 * uptodate as a result of this (potentially partial) write.
1944 */
1945 if (!partial)
1946 SetPageUptodate(page);
1947 return 0;
1948}
1949
1950/*
Christoph Hellwig155130a2010-06-04 11:29:58 +02001951 * block_write_begin takes care of the basic task of block allocation and
1952 * bringing partial write blocks uptodate first.
1953 *
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10001954 * The filesystem needs to handle block truncation upon failure.
Nick Pigginafddba42007-10-16 01:25:01 -07001955 */
Christoph Hellwig155130a2010-06-04 11:29:58 +02001956int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
1957 unsigned flags, struct page **pagep, get_block_t *get_block)
Nick Pigginafddba42007-10-16 01:25:01 -07001958{
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001959 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
Nick Pigginafddba42007-10-16 01:25:01 -07001960 struct page *page;
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001961 int status;
Nick Pigginafddba42007-10-16 01:25:01 -07001962
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001963 page = grab_cache_page_write_begin(mapping, index, flags);
1964 if (!page)
1965 return -ENOMEM;
Nick Pigginafddba42007-10-16 01:25:01 -07001966
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001967 status = __block_write_begin(page, pos, len, get_block);
Nick Pigginafddba42007-10-16 01:25:01 -07001968 if (unlikely(status)) {
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001969 unlock_page(page);
1970 page_cache_release(page);
1971 page = NULL;
Nick Pigginafddba42007-10-16 01:25:01 -07001972 }
1973
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001974 *pagep = page;
Nick Pigginafddba42007-10-16 01:25:01 -07001975 return status;
1976}
1977EXPORT_SYMBOL(block_write_begin);
1978
1979int block_write_end(struct file *file, struct address_space *mapping,
1980 loff_t pos, unsigned len, unsigned copied,
1981 struct page *page, void *fsdata)
1982{
1983 struct inode *inode = mapping->host;
1984 unsigned start;
1985
1986 start = pos & (PAGE_CACHE_SIZE - 1);
1987
1988 if (unlikely(copied < len)) {
1989 /*
1990 * The buffers that were written will now be uptodate, so we
1991 * don't have to worry about a readpage reading them and
1992 * overwriting a partial write. However if we have encountered
1993 * a short write and only partially written into a buffer, it
1994 * will not be marked uptodate, so a readpage might come in and
1995 * destroy our partial write.
1996 *
1997 * Do the simplest thing, and just treat any short write to a
1998 * non uptodate page as a zero-length write, and force the
1999 * caller to redo the whole thing.
2000 */
2001 if (!PageUptodate(page))
2002 copied = 0;
2003
2004 page_zero_new_buffers(page, start+copied, start+len);
2005 }
2006 flush_dcache_page(page);
2007
2008 /* This could be a short (even 0-length) commit */
2009 __block_commit_write(inode, page, start, start+copied);
2010
2011 return copied;
2012}
2013EXPORT_SYMBOL(block_write_end);
2014
2015int generic_write_end(struct file *file, struct address_space *mapping,
2016 loff_t pos, unsigned len, unsigned copied,
2017 struct page *page, void *fsdata)
2018{
2019 struct inode *inode = mapping->host;
Jan Karac7d206b2008-07-11 19:27:31 -04002020 int i_size_changed = 0;
Nick Pigginafddba42007-10-16 01:25:01 -07002021
2022 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2023
2024 /*
2025 * No need to use i_size_read() here, the i_size
2026 * cannot change under us because we hold i_mutex.
2027 *
2028 * But it's important to update i_size while still holding page lock:
2029 * page writeout could otherwise come in and zero beyond i_size.
2030 */
2031 if (pos+copied > inode->i_size) {
2032 i_size_write(inode, pos+copied);
Jan Karac7d206b2008-07-11 19:27:31 -04002033 i_size_changed = 1;
Nick Pigginafddba42007-10-16 01:25:01 -07002034 }
2035
2036 unlock_page(page);
2037 page_cache_release(page);
2038
Jan Karac7d206b2008-07-11 19:27:31 -04002039 /*
2040 * Don't mark the inode dirty under page lock. First, it unnecessarily
2041 * makes the holding time of page lock longer. Second, it forces lock
2042 * ordering of page lock and transaction start for journaling
2043 * filesystems.
2044 */
2045 if (i_size_changed)
2046 mark_inode_dirty(inode);
2047
Nick Pigginafddba42007-10-16 01:25:01 -07002048 return copied;
2049}
2050EXPORT_SYMBOL(generic_write_end);
2051
2052/*
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07002053 * block_is_partially_uptodate checks whether buffers within a page are
2054 * uptodate or not.
2055 *
2056 * Returns true if all buffers which correspond to a file portion
2057 * we want to read are uptodate.
2058 */
2059int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
2060 unsigned long from)
2061{
2062 struct inode *inode = page->mapping->host;
2063 unsigned block_start, block_end, blocksize;
2064 unsigned to;
2065 struct buffer_head *bh, *head;
2066 int ret = 1;
2067
2068 if (!page_has_buffers(page))
2069 return 0;
2070
2071 blocksize = 1 << inode->i_blkbits;
2072 to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count);
2073 to = from + to;
2074 if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
2075 return 0;
2076
2077 head = page_buffers(page);
2078 bh = head;
2079 block_start = 0;
2080 do {
2081 block_end = block_start + blocksize;
2082 if (block_end > from && block_start < to) {
2083 if (!buffer_uptodate(bh)) {
2084 ret = 0;
2085 break;
2086 }
2087 if (block_end >= to)
2088 break;
2089 }
2090 block_start = block_end;
2091 bh = bh->b_this_page;
2092 } while (bh != head);
2093
2094 return ret;
2095}
2096EXPORT_SYMBOL(block_is_partially_uptodate);
2097
2098/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002099 * Generic "read page" function for block devices that have the normal
2100 * get_block functionality. This is most of the block device filesystems.
2101 * Reads the page asynchronously --- the unlock_buffer() and
2102 * set/clear_buffer_uptodate() functions propagate buffer state into the
2103 * page struct once IO has completed.
2104 */
2105int block_read_full_page(struct page *page, get_block_t *get_block)
2106{
2107 struct inode *inode = page->mapping->host;
2108 sector_t iblock, lblock;
2109 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
2110 unsigned int blocksize;
2111 int nr, i;
2112 int fully_mapped = 1;
2113
Matt Mackallcd7619d2005-05-01 08:59:01 -07002114 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002115 blocksize = 1 << inode->i_blkbits;
2116 if (!page_has_buffers(page))
2117 create_empty_buffers(page, blocksize, 0);
2118 head = page_buffers(page);
2119
2120 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2121 lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits;
2122 bh = head;
2123 nr = 0;
2124 i = 0;
2125
2126 do {
2127 if (buffer_uptodate(bh))
2128 continue;
2129
2130 if (!buffer_mapped(bh)) {
Andrew Mortonc64610b2005-05-16 21:53:49 -07002131 int err = 0;
2132
Linus Torvalds1da177e2005-04-16 15:20:36 -07002133 fully_mapped = 0;
2134 if (iblock < lblock) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002135 WARN_ON(bh->b_size != blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002136 err = get_block(inode, iblock, bh, 0);
2137 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002138 SetPageError(page);
2139 }
2140 if (!buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002141 zero_user(page, i * blocksize, blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002142 if (!err)
2143 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002144 continue;
2145 }
2146 /*
2147 * get_block() might have updated the buffer
2148 * synchronously
2149 */
2150 if (buffer_uptodate(bh))
2151 continue;
2152 }
2153 arr[nr++] = bh;
2154 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2155
2156 if (fully_mapped)
2157 SetPageMappedToDisk(page);
2158
2159 if (!nr) {
2160 /*
2161 * All buffers are uptodate - we can set the page uptodate
2162 * as well. But not if get_block() returned an error.
2163 */
2164 if (!PageError(page))
2165 SetPageUptodate(page);
2166 unlock_page(page);
2167 return 0;
2168 }
2169
2170 /* Stage two: lock the buffers */
2171 for (i = 0; i < nr; i++) {
2172 bh = arr[i];
2173 lock_buffer(bh);
2174 mark_buffer_async_read(bh);
2175 }
2176
2177 /*
2178 * Stage 3: start the IO. Check for uptodateness
2179 * inside the buffer lock in case another process reading
2180 * the underlying blockdev brought it uptodate (the sct fix).
2181 */
2182 for (i = 0; i < nr; i++) {
2183 bh = arr[i];
2184 if (buffer_uptodate(bh))
2185 end_buffer_async_read(bh, 1);
2186 else
2187 submit_bh(READ, bh);
2188 }
2189 return 0;
2190}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002191EXPORT_SYMBOL(block_read_full_page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002192
2193/* utility function for filesystems that need to do work on expanding
Nick Piggin89e10782007-10-16 01:25:07 -07002194 * truncates. Uses filesystem pagecache writes to allow the filesystem to
Linus Torvalds1da177e2005-04-16 15:20:36 -07002195 * deal with the hole.
2196 */
Nick Piggin89e10782007-10-16 01:25:07 -07002197int generic_cont_expand_simple(struct inode *inode, loff_t size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002198{
2199 struct address_space *mapping = inode->i_mapping;
2200 struct page *page;
Nick Piggin89e10782007-10-16 01:25:07 -07002201 void *fsdata;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002202 int err;
2203
npiggin@suse.dec08d3b02009-08-21 02:35:06 +10002204 err = inode_newsize_ok(inode, size);
2205 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002206 goto out;
2207
Nick Piggin89e10782007-10-16 01:25:07 -07002208 err = pagecache_write_begin(NULL, mapping, size, 0,
2209 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2210 &page, &fsdata);
2211 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002212 goto out;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002213
Nick Piggin89e10782007-10-16 01:25:07 -07002214 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2215 BUG_ON(err > 0);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002216
Linus Torvalds1da177e2005-04-16 15:20:36 -07002217out:
2218 return err;
2219}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002220EXPORT_SYMBOL(generic_cont_expand_simple);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002221
Adrian Bunkf1e3af72008-04-29 00:59:01 -07002222static int cont_expand_zero(struct file *file, struct address_space *mapping,
2223 loff_t pos, loff_t *bytes)
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002224{
Nick Piggin89e10782007-10-16 01:25:07 -07002225 struct inode *inode = mapping->host;
2226 unsigned blocksize = 1 << inode->i_blkbits;
2227 struct page *page;
2228 void *fsdata;
2229 pgoff_t index, curidx;
2230 loff_t curpos;
2231 unsigned zerofrom, offset, len;
2232 int err = 0;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002233
Nick Piggin89e10782007-10-16 01:25:07 -07002234 index = pos >> PAGE_CACHE_SHIFT;
2235 offset = pos & ~PAGE_CACHE_MASK;
2236
2237 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
2238 zerofrom = curpos & ~PAGE_CACHE_MASK;
2239 if (zerofrom & (blocksize-1)) {
2240 *bytes |= (blocksize-1);
2241 (*bytes)++;
2242 }
2243 len = PAGE_CACHE_SIZE - zerofrom;
2244
2245 err = pagecache_write_begin(file, mapping, curpos, len,
2246 AOP_FLAG_UNINTERRUPTIBLE,
2247 &page, &fsdata);
2248 if (err)
2249 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002250 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002251 err = pagecache_write_end(file, mapping, curpos, len, len,
2252 page, fsdata);
2253 if (err < 0)
2254 goto out;
2255 BUG_ON(err != len);
2256 err = 0;
OGAWA Hirofumi061e9742008-04-28 02:16:28 -07002257
2258 balance_dirty_pages_ratelimited(mapping);
Nick Piggin89e10782007-10-16 01:25:07 -07002259 }
2260
2261 /* page covers the boundary, find the boundary offset */
2262 if (index == curidx) {
2263 zerofrom = curpos & ~PAGE_CACHE_MASK;
2264 /* if we will expand the thing last block will be filled */
2265 if (offset <= zerofrom) {
2266 goto out;
2267 }
2268 if (zerofrom & (blocksize-1)) {
2269 *bytes |= (blocksize-1);
2270 (*bytes)++;
2271 }
2272 len = offset - zerofrom;
2273
2274 err = pagecache_write_begin(file, mapping, curpos, len,
2275 AOP_FLAG_UNINTERRUPTIBLE,
2276 &page, &fsdata);
2277 if (err)
2278 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002279 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002280 err = pagecache_write_end(file, mapping, curpos, len, len,
2281 page, fsdata);
2282 if (err < 0)
2283 goto out;
2284 BUG_ON(err != len);
2285 err = 0;
2286 }
2287out:
2288 return err;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002289}
2290
Linus Torvalds1da177e2005-04-16 15:20:36 -07002291/*
2292 * For moronic filesystems that do not allow holes in file.
2293 * We may have to extend the file.
2294 */
Christoph Hellwig282dc172010-06-04 11:29:55 +02002295int cont_write_begin(struct file *file, struct address_space *mapping,
Nick Piggin89e10782007-10-16 01:25:07 -07002296 loff_t pos, unsigned len, unsigned flags,
2297 struct page **pagep, void **fsdata,
2298 get_block_t *get_block, loff_t *bytes)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002299{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002300 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002301 unsigned blocksize = 1 << inode->i_blkbits;
Nick Piggin89e10782007-10-16 01:25:07 -07002302 unsigned zerofrom;
2303 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002304
Nick Piggin89e10782007-10-16 01:25:07 -07002305 err = cont_expand_zero(file, mapping, pos, bytes);
2306 if (err)
Christoph Hellwig155130a2010-06-04 11:29:58 +02002307 return err;
Nick Piggin89e10782007-10-16 01:25:07 -07002308
2309 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2310 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2311 *bytes |= (blocksize-1);
2312 (*bytes)++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002313 }
2314
Christoph Hellwig155130a2010-06-04 11:29:58 +02002315 return block_write_begin(mapping, pos, len, flags, pagep, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002316}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002317EXPORT_SYMBOL(cont_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002318
Linus Torvalds1da177e2005-04-16 15:20:36 -07002319int block_commit_write(struct page *page, unsigned from, unsigned to)
2320{
2321 struct inode *inode = page->mapping->host;
2322 __block_commit_write(inode,page,from,to);
2323 return 0;
2324}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002325EXPORT_SYMBOL(block_commit_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002326
David Chinner54171692007-07-19 17:39:55 +10002327/*
2328 * block_page_mkwrite() is not allowed to change the file size as it gets
2329 * called from a page fault handler when a page is first dirtied. Hence we must
2330 * be careful to check for EOF conditions here. We set the page up correctly
2331 * for a written page which means we get ENOSPC checking when writing into
2332 * holes and correct delalloc and unwritten extent mapping on filesystems that
2333 * support these features.
2334 *
2335 * We are not allowed to take the i_mutex here so we have to play games to
2336 * protect against truncate races as the page could now be beyond EOF. Because
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10002337 * truncate writes the inode size before removing pages, once we have the
David Chinner54171692007-07-19 17:39:55 +10002338 * page lock we can determine safely if the page is beyond EOF. If it is not
2339 * beyond EOF, then the page is guaranteed safe against truncation until we
2340 * unlock the page.
Jan Karaea13a862011-05-24 00:23:35 +02002341 *
2342 * Direct callers of this function should call vfs_check_frozen() so that page
2343 * fault does not busyloop until the fs is thawed.
David Chinner54171692007-07-19 17:39:55 +10002344 */
Jan Kara24da4fa2011-05-24 00:23:34 +02002345int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2346 get_block_t get_block)
David Chinner54171692007-07-19 17:39:55 +10002347{
Nick Pigginc2ec1752009-03-31 15:23:21 -07002348 struct page *page = vmf->page;
David Chinner54171692007-07-19 17:39:55 +10002349 struct inode *inode = vma->vm_file->f_path.dentry->d_inode;
2350 unsigned long end;
2351 loff_t size;
Jan Kara24da4fa2011-05-24 00:23:34 +02002352 int ret;
David Chinner54171692007-07-19 17:39:55 +10002353
2354 lock_page(page);
2355 size = i_size_read(inode);
2356 if ((page->mapping != inode->i_mapping) ||
Nick Piggin18336332007-07-20 00:31:45 -07002357 (page_offset(page) > size)) {
Jan Kara24da4fa2011-05-24 00:23:34 +02002358 /* We overload EFAULT to mean page got truncated */
2359 ret = -EFAULT;
2360 goto out_unlock;
David Chinner54171692007-07-19 17:39:55 +10002361 }
2362
2363 /* page is wholly or partially inside EOF */
2364 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
2365 end = size & ~PAGE_CACHE_MASK;
2366 else
2367 end = PAGE_CACHE_SIZE;
2368
Christoph Hellwigebdec242010-10-06 10:47:23 +02002369 ret = __block_write_begin(page, 0, end, get_block);
David Chinner54171692007-07-19 17:39:55 +10002370 if (!ret)
2371 ret = block_commit_write(page, 0, end);
2372
Jan Kara24da4fa2011-05-24 00:23:34 +02002373 if (unlikely(ret < 0))
2374 goto out_unlock;
Jan Karaea13a862011-05-24 00:23:35 +02002375 /*
2376 * Freezing in progress? We check after the page is marked dirty and
2377 * with page lock held so if the test here fails, we are sure freezing
2378 * code will wait during syncing until the page fault is done - at that
2379 * point page will be dirty and unlocked so freezing code will write it
2380 * and writeprotect it again.
2381 */
2382 set_page_dirty(page);
2383 if (inode->i_sb->s_frozen != SB_UNFROZEN) {
2384 ret = -EAGAIN;
2385 goto out_unlock;
2386 }
Darrick J. Wongd76ee182011-05-27 12:23:41 -07002387 wait_on_page_writeback(page);
Jan Kara24da4fa2011-05-24 00:23:34 +02002388 return 0;
2389out_unlock:
2390 unlock_page(page);
David Chinner54171692007-07-19 17:39:55 +10002391 return ret;
2392}
Jan Kara24da4fa2011-05-24 00:23:34 +02002393EXPORT_SYMBOL(__block_page_mkwrite);
2394
2395int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2396 get_block_t get_block)
2397{
Jan Karaea13a862011-05-24 00:23:35 +02002398 int ret;
2399 struct super_block *sb = vma->vm_file->f_path.dentry->d_inode->i_sb;
Jan Kara24da4fa2011-05-24 00:23:34 +02002400
Jan Karaea13a862011-05-24 00:23:35 +02002401 /*
2402 * This check is racy but catches the common case. The check in
2403 * __block_page_mkwrite() is reliable.
2404 */
2405 vfs_check_frozen(sb, SB_FREEZE_WRITE);
2406 ret = __block_page_mkwrite(vma, vmf, get_block);
Jan Kara24da4fa2011-05-24 00:23:34 +02002407 return block_page_mkwrite_return(ret);
2408}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002409EXPORT_SYMBOL(block_page_mkwrite);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002410
2411/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002412 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
Linus Torvalds1da177e2005-04-16 15:20:36 -07002413 * immediately, while under the page lock. So it needs a special end_io
2414 * handler which does not touch the bh after unlocking it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002415 */
2416static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2417{
Dmitry Monakhov68671f32007-10-16 01:24:47 -07002418 __end_buffer_read_notouch(bh, uptodate);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002419}
2420
2421/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002422 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2423 * the page (converting it to circular linked list and taking care of page
2424 * dirty races).
2425 */
2426static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2427{
2428 struct buffer_head *bh;
2429
2430 BUG_ON(!PageLocked(page));
2431
2432 spin_lock(&page->mapping->private_lock);
2433 bh = head;
2434 do {
2435 if (PageDirty(page))
2436 set_buffer_dirty(bh);
2437 if (!bh->b_this_page)
2438 bh->b_this_page = head;
2439 bh = bh->b_this_page;
2440 } while (bh != head);
2441 attach_page_buffers(page, head);
2442 spin_unlock(&page->mapping->private_lock);
2443}
2444
2445/*
Christoph Hellwigea0f04e2010-06-04 11:29:54 +02002446 * On entry, the page is fully not uptodate.
2447 * On exit the page is fully uptodate in the areas outside (from,to)
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10002448 * The filesystem needs to handle block truncation upon failure.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002449 */
Christoph Hellwigea0f04e2010-06-04 11:29:54 +02002450int nobh_write_begin(struct address_space *mapping,
Nick Piggin03158cd2007-10-16 01:25:25 -07002451 loff_t pos, unsigned len, unsigned flags,
2452 struct page **pagep, void **fsdata,
Linus Torvalds1da177e2005-04-16 15:20:36 -07002453 get_block_t *get_block)
2454{
Nick Piggin03158cd2007-10-16 01:25:25 -07002455 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002456 const unsigned blkbits = inode->i_blkbits;
2457 const unsigned blocksize = 1 << blkbits;
Nick Piggina4b06722007-10-16 01:24:48 -07002458 struct buffer_head *head, *bh;
Nick Piggin03158cd2007-10-16 01:25:25 -07002459 struct page *page;
2460 pgoff_t index;
2461 unsigned from, to;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002462 unsigned block_in_page;
Nick Piggina4b06722007-10-16 01:24:48 -07002463 unsigned block_start, block_end;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002464 sector_t block_in_file;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002465 int nr_reads = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002466 int ret = 0;
2467 int is_mapped_to_disk = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002468
Nick Piggin03158cd2007-10-16 01:25:25 -07002469 index = pos >> PAGE_CACHE_SHIFT;
2470 from = pos & (PAGE_CACHE_SIZE - 1);
2471 to = from + len;
2472
Nick Piggin54566b22009-01-04 12:00:53 -08002473 page = grab_cache_page_write_begin(mapping, index, flags);
Nick Piggin03158cd2007-10-16 01:25:25 -07002474 if (!page)
2475 return -ENOMEM;
2476 *pagep = page;
2477 *fsdata = NULL;
2478
2479 if (page_has_buffers(page)) {
Namhyung Kim309f77a2010-10-25 15:01:12 +09002480 ret = __block_write_begin(page, pos, len, get_block);
2481 if (unlikely(ret))
2482 goto out_release;
2483 return ret;
Nick Piggin03158cd2007-10-16 01:25:25 -07002484 }
Nick Piggina4b06722007-10-16 01:24:48 -07002485
Linus Torvalds1da177e2005-04-16 15:20:36 -07002486 if (PageMappedToDisk(page))
2487 return 0;
2488
Nick Piggina4b06722007-10-16 01:24:48 -07002489 /*
2490 * Allocate buffers so that we can keep track of state, and potentially
2491 * attach them to the page if an error occurs. In the common case of
2492 * no error, they will just be freed again without ever being attached
2493 * to the page (which is all OK, because we're under the page lock).
2494 *
2495 * Be careful: the buffer linked list is a NULL terminated one, rather
2496 * than the circular one we're used to.
2497 */
2498 head = alloc_page_buffers(page, blocksize, 0);
Nick Piggin03158cd2007-10-16 01:25:25 -07002499 if (!head) {
2500 ret = -ENOMEM;
2501 goto out_release;
2502 }
Nick Piggina4b06722007-10-16 01:24:48 -07002503
Linus Torvalds1da177e2005-04-16 15:20:36 -07002504 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002505
2506 /*
2507 * We loop across all blocks in the page, whether or not they are
2508 * part of the affected region. This is so we can discover if the
2509 * page is fully mapped-to-disk.
2510 */
Nick Piggina4b06722007-10-16 01:24:48 -07002511 for (block_start = 0, block_in_page = 0, bh = head;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002512 block_start < PAGE_CACHE_SIZE;
Nick Piggina4b06722007-10-16 01:24:48 -07002513 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002514 int create;
2515
Nick Piggina4b06722007-10-16 01:24:48 -07002516 block_end = block_start + blocksize;
2517 bh->b_state = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002518 create = 1;
2519 if (block_start >= to)
2520 create = 0;
2521 ret = get_block(inode, block_in_file + block_in_page,
Nick Piggina4b06722007-10-16 01:24:48 -07002522 bh, create);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002523 if (ret)
2524 goto failed;
Nick Piggina4b06722007-10-16 01:24:48 -07002525 if (!buffer_mapped(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002526 is_mapped_to_disk = 0;
Nick Piggina4b06722007-10-16 01:24:48 -07002527 if (buffer_new(bh))
2528 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
2529 if (PageUptodate(page)) {
2530 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002531 continue;
Nick Piggina4b06722007-10-16 01:24:48 -07002532 }
2533 if (buffer_new(bh) || !buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002534 zero_user_segments(page, block_start, from,
2535 to, block_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002536 continue;
2537 }
Nick Piggina4b06722007-10-16 01:24:48 -07002538 if (buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002539 continue; /* reiserfs does this */
2540 if (block_start < from || block_end > to) {
Nick Piggina4b06722007-10-16 01:24:48 -07002541 lock_buffer(bh);
2542 bh->b_end_io = end_buffer_read_nobh;
2543 submit_bh(READ, bh);
2544 nr_reads++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002545 }
2546 }
2547
2548 if (nr_reads) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002549 /*
2550 * The page is locked, so these buffers are protected from
2551 * any VM or truncate activity. Hence we don't need to care
2552 * for the buffer_head refcounts.
2553 */
Nick Piggina4b06722007-10-16 01:24:48 -07002554 for (bh = head; bh; bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002555 wait_on_buffer(bh);
2556 if (!buffer_uptodate(bh))
2557 ret = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002558 }
2559 if (ret)
2560 goto failed;
2561 }
2562
2563 if (is_mapped_to_disk)
2564 SetPageMappedToDisk(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002565
Nick Piggin03158cd2007-10-16 01:25:25 -07002566 *fsdata = head; /* to be released by nobh_write_end */
Nick Piggina4b06722007-10-16 01:24:48 -07002567
Linus Torvalds1da177e2005-04-16 15:20:36 -07002568 return 0;
2569
2570failed:
Nick Piggin03158cd2007-10-16 01:25:25 -07002571 BUG_ON(!ret);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002572 /*
Nick Piggina4b06722007-10-16 01:24:48 -07002573 * Error recovery is a bit difficult. We need to zero out blocks that
2574 * were newly allocated, and dirty them to ensure they get written out.
2575 * Buffers need to be attached to the page at this point, otherwise
2576 * the handling of potential IO errors during writeout would be hard
2577 * (could try doing synchronous writeout, but what if that fails too?)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002578 */
Nick Piggin03158cd2007-10-16 01:25:25 -07002579 attach_nobh_buffers(page, head);
2580 page_zero_new_buffers(page, from, to);
Nick Piggina4b06722007-10-16 01:24:48 -07002581
Nick Piggin03158cd2007-10-16 01:25:25 -07002582out_release:
2583 unlock_page(page);
2584 page_cache_release(page);
2585 *pagep = NULL;
Nick Piggina4b06722007-10-16 01:24:48 -07002586
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10002587 return ret;
2588}
Nick Piggin03158cd2007-10-16 01:25:25 -07002589EXPORT_SYMBOL(nobh_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002590
Nick Piggin03158cd2007-10-16 01:25:25 -07002591int nobh_write_end(struct file *file, struct address_space *mapping,
2592 loff_t pos, unsigned len, unsigned copied,
2593 struct page *page, void *fsdata)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002594{
2595 struct inode *inode = page->mapping->host;
Nick Pigginefdc3132007-10-21 06:57:41 +02002596 struct buffer_head *head = fsdata;
Nick Piggin03158cd2007-10-16 01:25:25 -07002597 struct buffer_head *bh;
Dmitri Monakhov5b41e742008-03-28 14:15:52 -07002598 BUG_ON(fsdata != NULL && page_has_buffers(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002599
Dave Kleikampd4cf1092009-02-06 14:59:26 -06002600 if (unlikely(copied < len) && head)
Dmitri Monakhov5b41e742008-03-28 14:15:52 -07002601 attach_nobh_buffers(page, head);
2602 if (page_has_buffers(page))
2603 return generic_write_end(file, mapping, pos, len,
2604 copied, page, fsdata);
Nick Piggina4b06722007-10-16 01:24:48 -07002605
Nick Piggin22c8ca72007-02-20 13:58:09 -08002606 SetPageUptodate(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002607 set_page_dirty(page);
Nick Piggin03158cd2007-10-16 01:25:25 -07002608 if (pos+copied > inode->i_size) {
2609 i_size_write(inode, pos+copied);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002610 mark_inode_dirty(inode);
2611 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002612
2613 unlock_page(page);
2614 page_cache_release(page);
2615
Nick Piggin03158cd2007-10-16 01:25:25 -07002616 while (head) {
2617 bh = head;
2618 head = head->b_this_page;
2619 free_buffer_head(bh);
2620 }
2621
2622 return copied;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002623}
Nick Piggin03158cd2007-10-16 01:25:25 -07002624EXPORT_SYMBOL(nobh_write_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002625
2626/*
2627 * nobh_writepage() - based on block_full_write_page() except
2628 * that it tries to operate without attaching bufferheads to
2629 * the page.
2630 */
2631int nobh_writepage(struct page *page, get_block_t *get_block,
2632 struct writeback_control *wbc)
2633{
2634 struct inode * const inode = page->mapping->host;
2635 loff_t i_size = i_size_read(inode);
2636 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2637 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002638 int ret;
2639
2640 /* Is the page fully inside i_size? */
2641 if (page->index < end_index)
2642 goto out;
2643
2644 /* Is the page fully outside i_size? (truncate in progress) */
2645 offset = i_size & (PAGE_CACHE_SIZE-1);
2646 if (page->index >= end_index+1 || !offset) {
2647 /*
2648 * The page may have dirty, unmapped buffers. For example,
2649 * they may have been added in ext3_writepage(). Make them
2650 * freeable here, so the page does not leak.
2651 */
2652#if 0
2653 /* Not really sure about this - do we need this ? */
2654 if (page->mapping->a_ops->invalidatepage)
2655 page->mapping->a_ops->invalidatepage(page, offset);
2656#endif
2657 unlock_page(page);
2658 return 0; /* don't care */
2659 }
2660
2661 /*
2662 * The page straddles i_size. It must be zeroed out on each and every
2663 * writepage invocation because it may be mmapped. "A file is mapped
2664 * in multiples of the page size. For a file that is not a multiple of
2665 * the page size, the remaining memory is zeroed when mapped, and
2666 * writes to that region are not written out to the file."
2667 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002668 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002669out:
2670 ret = mpage_writepage(page, get_block, wbc);
2671 if (ret == -EAGAIN)
Chris Mason35c80d52009-04-15 13:22:38 -04002672 ret = __block_write_full_page(inode, page, get_block, wbc,
2673 end_buffer_async_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002674 return ret;
2675}
2676EXPORT_SYMBOL(nobh_writepage);
2677
Nick Piggin03158cd2007-10-16 01:25:25 -07002678int nobh_truncate_page(struct address_space *mapping,
2679 loff_t from, get_block_t *get_block)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002680{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002681 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2682 unsigned offset = from & (PAGE_CACHE_SIZE-1);
Nick Piggin03158cd2007-10-16 01:25:25 -07002683 unsigned blocksize;
2684 sector_t iblock;
2685 unsigned length, pos;
2686 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002687 struct page *page;
Nick Piggin03158cd2007-10-16 01:25:25 -07002688 struct buffer_head map_bh;
2689 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002690
Nick Piggin03158cd2007-10-16 01:25:25 -07002691 blocksize = 1 << inode->i_blkbits;
2692 length = offset & (blocksize - 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002693
Nick Piggin03158cd2007-10-16 01:25:25 -07002694 /* Block boundary? Nothing to do */
2695 if (!length)
2696 return 0;
2697
2698 length = blocksize - length;
2699 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2700
Linus Torvalds1da177e2005-04-16 15:20:36 -07002701 page = grab_cache_page(mapping, index);
Nick Piggin03158cd2007-10-16 01:25:25 -07002702 err = -ENOMEM;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002703 if (!page)
2704 goto out;
2705
Nick Piggin03158cd2007-10-16 01:25:25 -07002706 if (page_has_buffers(page)) {
2707has_buffers:
2708 unlock_page(page);
2709 page_cache_release(page);
2710 return block_truncate_page(mapping, from, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002711 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002712
2713 /* Find the buffer that contains "offset" */
2714 pos = blocksize;
2715 while (offset >= pos) {
2716 iblock++;
2717 pos += blocksize;
2718 }
2719
Theodore Ts'o460bcf52009-05-12 07:37:56 -04002720 map_bh.b_size = blocksize;
2721 map_bh.b_state = 0;
Nick Piggin03158cd2007-10-16 01:25:25 -07002722 err = get_block(inode, iblock, &map_bh, 0);
2723 if (err)
2724 goto unlock;
2725 /* unmapped? It's a hole - nothing to do */
2726 if (!buffer_mapped(&map_bh))
2727 goto unlock;
2728
2729 /* Ok, it's mapped. Make sure it's up-to-date */
2730 if (!PageUptodate(page)) {
2731 err = mapping->a_ops->readpage(NULL, page);
2732 if (err) {
2733 page_cache_release(page);
2734 goto out;
2735 }
2736 lock_page(page);
2737 if (!PageUptodate(page)) {
2738 err = -EIO;
2739 goto unlock;
2740 }
2741 if (page_has_buffers(page))
2742 goto has_buffers;
2743 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002744 zero_user(page, offset, length);
Nick Piggin03158cd2007-10-16 01:25:25 -07002745 set_page_dirty(page);
2746 err = 0;
2747
2748unlock:
Linus Torvalds1da177e2005-04-16 15:20:36 -07002749 unlock_page(page);
2750 page_cache_release(page);
2751out:
Nick Piggin03158cd2007-10-16 01:25:25 -07002752 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002753}
2754EXPORT_SYMBOL(nobh_truncate_page);
2755
2756int block_truncate_page(struct address_space *mapping,
2757 loff_t from, get_block_t *get_block)
2758{
2759 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2760 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2761 unsigned blocksize;
Andrew Morton54b21a72006-01-08 01:03:05 -08002762 sector_t iblock;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002763 unsigned length, pos;
2764 struct inode *inode = mapping->host;
2765 struct page *page;
2766 struct buffer_head *bh;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002767 int err;
2768
2769 blocksize = 1 << inode->i_blkbits;
2770 length = offset & (blocksize - 1);
2771
2772 /* Block boundary? Nothing to do */
2773 if (!length)
2774 return 0;
2775
2776 length = blocksize - length;
Andrew Morton54b21a72006-01-08 01:03:05 -08002777 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002778
2779 page = grab_cache_page(mapping, index);
2780 err = -ENOMEM;
2781 if (!page)
2782 goto out;
2783
2784 if (!page_has_buffers(page))
2785 create_empty_buffers(page, blocksize, 0);
2786
2787 /* Find the buffer that contains "offset" */
2788 bh = page_buffers(page);
2789 pos = blocksize;
2790 while (offset >= pos) {
2791 bh = bh->b_this_page;
2792 iblock++;
2793 pos += blocksize;
2794 }
2795
2796 err = 0;
2797 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002798 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002799 err = get_block(inode, iblock, bh, 0);
2800 if (err)
2801 goto unlock;
2802 /* unmapped? It's a hole - nothing to do */
2803 if (!buffer_mapped(bh))
2804 goto unlock;
2805 }
2806
2807 /* Ok, it's mapped. Make sure it's up-to-date */
2808 if (PageUptodate(page))
2809 set_buffer_uptodate(bh);
2810
David Chinner33a266d2007-02-12 00:51:41 -08002811 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002812 err = -EIO;
2813 ll_rw_block(READ, 1, &bh);
2814 wait_on_buffer(bh);
2815 /* Uhhuh. Read error. Complain and punt. */
2816 if (!buffer_uptodate(bh))
2817 goto unlock;
2818 }
2819
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002820 zero_user(page, offset, length);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002821 mark_buffer_dirty(bh);
2822 err = 0;
2823
2824unlock:
2825 unlock_page(page);
2826 page_cache_release(page);
2827out:
2828 return err;
2829}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002830EXPORT_SYMBOL(block_truncate_page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002831
2832/*
2833 * The generic ->writepage function for buffer-backed address_spaces
Chris Mason35c80d52009-04-15 13:22:38 -04002834 * this form passes in the end_io handler used to finish the IO.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002835 */
Chris Mason35c80d52009-04-15 13:22:38 -04002836int block_write_full_page_endio(struct page *page, get_block_t *get_block,
2837 struct writeback_control *wbc, bh_end_io_t *handler)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002838{
2839 struct inode * const inode = page->mapping->host;
2840 loff_t i_size = i_size_read(inode);
2841 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2842 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002843
2844 /* Is the page fully inside i_size? */
2845 if (page->index < end_index)
Chris Mason35c80d52009-04-15 13:22:38 -04002846 return __block_write_full_page(inode, page, get_block, wbc,
2847 handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002848
2849 /* Is the page fully outside i_size? (truncate in progress) */
2850 offset = i_size & (PAGE_CACHE_SIZE-1);
2851 if (page->index >= end_index+1 || !offset) {
2852 /*
2853 * The page may have dirty, unmapped buffers. For example,
2854 * they may have been added in ext3_writepage(). Make them
2855 * freeable here, so the page does not leak.
2856 */
Jan Karaaaa40592005-10-30 15:00:16 -08002857 do_invalidatepage(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002858 unlock_page(page);
2859 return 0; /* don't care */
2860 }
2861
2862 /*
2863 * The page straddles i_size. It must be zeroed out on each and every
Adam Buchbinder2a61aa42009-12-11 16:35:40 -05002864 * writepage invocation because it may be mmapped. "A file is mapped
Linus Torvalds1da177e2005-04-16 15:20:36 -07002865 * in multiples of the page size. For a file that is not a multiple of
2866 * the page size, the remaining memory is zeroed when mapped, and
2867 * writes to that region are not written out to the file."
2868 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002869 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Chris Mason35c80d52009-04-15 13:22:38 -04002870 return __block_write_full_page(inode, page, get_block, wbc, handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002871}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002872EXPORT_SYMBOL(block_write_full_page_endio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002873
Chris Mason35c80d52009-04-15 13:22:38 -04002874/*
2875 * The generic ->writepage function for buffer-backed address_spaces
2876 */
2877int block_write_full_page(struct page *page, get_block_t *get_block,
2878 struct writeback_control *wbc)
2879{
2880 return block_write_full_page_endio(page, get_block, wbc,
2881 end_buffer_async_write);
2882}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002883EXPORT_SYMBOL(block_write_full_page);
Chris Mason35c80d52009-04-15 13:22:38 -04002884
Linus Torvalds1da177e2005-04-16 15:20:36 -07002885sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2886 get_block_t *get_block)
2887{
2888 struct buffer_head tmp;
2889 struct inode *inode = mapping->host;
2890 tmp.b_state = 0;
2891 tmp.b_blocknr = 0;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002892 tmp.b_size = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002893 get_block(inode, block, &tmp, 0);
2894 return tmp.b_blocknr;
2895}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002896EXPORT_SYMBOL(generic_block_bmap);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002897
NeilBrown6712ecf2007-09-27 12:47:43 +02002898static void end_bio_bh_io_sync(struct bio *bio, int err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002899{
2900 struct buffer_head *bh = bio->bi_private;
2901
Linus Torvalds1da177e2005-04-16 15:20:36 -07002902 if (err == -EOPNOTSUPP) {
2903 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002904 }
2905
Keith Mannthey08bafc02008-11-25 10:24:35 +01002906 if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags)))
2907 set_bit(BH_Quiet, &bh->b_state);
2908
Linus Torvalds1da177e2005-04-16 15:20:36 -07002909 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2910 bio_put(bio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002911}
2912
2913int submit_bh(int rw, struct buffer_head * bh)
2914{
2915 struct bio *bio;
2916 int ret = 0;
2917
2918 BUG_ON(!buffer_locked(bh));
2919 BUG_ON(!buffer_mapped(bh));
2920 BUG_ON(!bh->b_end_io);
Aneesh Kumar K.V8fb0e342009-05-12 16:22:37 -04002921 BUG_ON(buffer_delay(bh));
2922 BUG_ON(buffer_unwritten(bh));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002923
Jens Axboe48fd4f92008-08-22 10:00:36 +02002924 /*
Jens Axboe48fd4f92008-08-22 10:00:36 +02002925 * Only clear out a write error when rewriting
Linus Torvalds1da177e2005-04-16 15:20:36 -07002926 */
Jens Axboe48fd4f92008-08-22 10:00:36 +02002927 if (test_set_buffer_req(bh) && (rw & WRITE))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002928 clear_buffer_write_io_error(bh);
2929
2930 /*
2931 * from here on down, it's all bio -- do the initial mapping,
2932 * submit_bio -> generic_make_request may further map this bio around
2933 */
2934 bio = bio_alloc(GFP_NOIO, 1);
2935
2936 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2937 bio->bi_bdev = bh->b_bdev;
2938 bio->bi_io_vec[0].bv_page = bh->b_page;
2939 bio->bi_io_vec[0].bv_len = bh->b_size;
2940 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
2941
2942 bio->bi_vcnt = 1;
2943 bio->bi_idx = 0;
2944 bio->bi_size = bh->b_size;
2945
2946 bio->bi_end_io = end_bio_bh_io_sync;
2947 bio->bi_private = bh;
2948
2949 bio_get(bio);
2950 submit_bio(rw, bio);
2951
2952 if (bio_flagged(bio, BIO_EOPNOTSUPP))
2953 ret = -EOPNOTSUPP;
2954
2955 bio_put(bio);
2956 return ret;
2957}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002958EXPORT_SYMBOL(submit_bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002959
2960/**
2961 * ll_rw_block: low-level access to block devices (DEPRECATED)
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02002962 * @rw: whether to %READ or %WRITE or maybe %READA (readahead)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002963 * @nr: number of &struct buffer_heads in the array
2964 * @bhs: array of pointers to &struct buffer_head
2965 *
Jan Karaa7662232005-09-06 15:19:10 -07002966 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
2967 * requests an I/O operation on them, either a %READ or a %WRITE. The third
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02002968 * %READA option is described in the documentation for generic_make_request()
2969 * which ll_rw_block() calls.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002970 *
2971 * This function drops any buffer that it cannot get a lock on (with the
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02002972 * BH_Lock state bit), any buffer that appears to be clean when doing a write
2973 * request, and any buffer that appears to be up-to-date when doing read
2974 * request. Further it marks as clean buffers that are processed for
2975 * writing (the buffer cache won't assume that they are actually clean
2976 * until the buffer gets unlocked).
Linus Torvalds1da177e2005-04-16 15:20:36 -07002977 *
2978 * ll_rw_block sets b_end_io to simple completion handler that marks
2979 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
2980 * any waiters.
2981 *
2982 * All of the buffers must be for the same device, and must also be a
2983 * multiple of the current approved size for the device.
2984 */
2985void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
2986{
2987 int i;
2988
2989 for (i = 0; i < nr; i++) {
2990 struct buffer_head *bh = bhs[i];
2991
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02002992 if (!trylock_buffer(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002993 continue;
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02002994 if (rw == WRITE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002995 if (test_clear_buffer_dirty(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07002996 bh->b_end_io = end_buffer_write_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08002997 get_bh(bh);
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02002998 submit_bh(WRITE, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002999 continue;
3000 }
3001 } else {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003002 if (!buffer_uptodate(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07003003 bh->b_end_io = end_buffer_read_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08003004 get_bh(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003005 submit_bh(rw, bh);
3006 continue;
3007 }
3008 }
3009 unlock_buffer(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003010 }
3011}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07003012EXPORT_SYMBOL(ll_rw_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003013
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003014void write_dirty_buffer(struct buffer_head *bh, int rw)
3015{
3016 lock_buffer(bh);
3017 if (!test_clear_buffer_dirty(bh)) {
3018 unlock_buffer(bh);
3019 return;
3020 }
3021 bh->b_end_io = end_buffer_write_sync;
3022 get_bh(bh);
3023 submit_bh(rw, bh);
3024}
3025EXPORT_SYMBOL(write_dirty_buffer);
3026
Linus Torvalds1da177e2005-04-16 15:20:36 -07003027/*
3028 * For a data-integrity writeout, we need to wait upon any in-progress I/O
3029 * and then start new I/O and then wait upon it. The caller must have a ref on
3030 * the buffer_head.
3031 */
Christoph Hellwig87e99512010-08-11 17:05:45 +02003032int __sync_dirty_buffer(struct buffer_head *bh, int rw)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003033{
3034 int ret = 0;
3035
3036 WARN_ON(atomic_read(&bh->b_count) < 1);
3037 lock_buffer(bh);
3038 if (test_clear_buffer_dirty(bh)) {
3039 get_bh(bh);
3040 bh->b_end_io = end_buffer_write_sync;
Christoph Hellwig87e99512010-08-11 17:05:45 +02003041 ret = submit_bh(rw, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003042 wait_on_buffer(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003043 if (!ret && !buffer_uptodate(bh))
3044 ret = -EIO;
3045 } else {
3046 unlock_buffer(bh);
3047 }
3048 return ret;
3049}
Christoph Hellwig87e99512010-08-11 17:05:45 +02003050EXPORT_SYMBOL(__sync_dirty_buffer);
3051
3052int sync_dirty_buffer(struct buffer_head *bh)
3053{
3054 return __sync_dirty_buffer(bh, WRITE_SYNC);
3055}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07003056EXPORT_SYMBOL(sync_dirty_buffer);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003057
3058/*
3059 * try_to_free_buffers() checks if all the buffers on this particular page
3060 * are unused, and releases them if so.
3061 *
3062 * Exclusion against try_to_free_buffers may be obtained by either
3063 * locking the page or by holding its mapping's private_lock.
3064 *
3065 * If the page is dirty but all the buffers are clean then we need to
3066 * be sure to mark the page clean as well. This is because the page
3067 * may be against a block device, and a later reattachment of buffers
3068 * to a dirty page will set *all* buffers dirty. Which would corrupt
3069 * filesystem data on the same device.
3070 *
3071 * The same applies to regular filesystem pages: if all the buffers are
3072 * clean then we set the page clean and proceed. To do that, we require
3073 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3074 * private_lock.
3075 *
3076 * try_to_free_buffers() is non-blocking.
3077 */
3078static inline int buffer_busy(struct buffer_head *bh)
3079{
3080 return atomic_read(&bh->b_count) |
3081 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3082}
3083
3084static int
3085drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3086{
3087 struct buffer_head *head = page_buffers(page);
3088 struct buffer_head *bh;
3089
3090 bh = head;
3091 do {
akpm@osdl.orgde7d5a32005-05-01 08:58:39 -07003092 if (buffer_write_io_error(bh) && page->mapping)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003093 set_bit(AS_EIO, &page->mapping->flags);
Laura Abbott96760382012-08-30 18:01:17 -07003094 if (buffer_busy(bh)) {
3095 /*
3096 * Check if the busy failure was due to an
3097 * outstanding LRU reference
3098 */
3099 evict_bh_lrus(bh);
3100 if (buffer_busy(bh))
3101 goto failed;
3102 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07003103 bh = bh->b_this_page;
3104 } while (bh != head);
3105
3106 do {
3107 struct buffer_head *next = bh->b_this_page;
3108
Jan Kara535ee2f2008-02-08 04:21:59 -08003109 if (bh->b_assoc_map)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003110 __remove_assoc_queue(bh);
3111 bh = next;
3112 } while (bh != head);
3113 *buffers_to_free = head;
3114 __clear_page_buffers(page);
3115 return 1;
3116failed:
3117 return 0;
3118}
3119
3120int try_to_free_buffers(struct page *page)
3121{
3122 struct address_space * const mapping = page->mapping;
3123 struct buffer_head *buffers_to_free = NULL;
3124 int ret = 0;
3125
3126 BUG_ON(!PageLocked(page));
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003127 if (PageWriteback(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003128 return 0;
3129
3130 if (mapping == NULL) { /* can this still happen? */
3131 ret = drop_buffers(page, &buffers_to_free);
3132 goto out;
3133 }
3134
3135 spin_lock(&mapping->private_lock);
3136 ret = drop_buffers(page, &buffers_to_free);
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003137
3138 /*
3139 * If the filesystem writes its buffers by hand (eg ext3)
3140 * then we can have clean buffers against a dirty page. We
3141 * clean the page here; otherwise the VM will never notice
3142 * that the filesystem did any IO at all.
3143 *
3144 * Also, during truncate, discard_buffer will have marked all
3145 * the page's buffers clean. We discover that here and clean
3146 * the page also.
Nick Piggin87df7242007-01-30 14:36:27 +11003147 *
3148 * private_lock must be held over this entire operation in order
3149 * to synchronise against __set_page_dirty_buffers and prevent the
3150 * dirty bit from being lost.
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003151 */
3152 if (ret)
3153 cancel_dirty_page(page, PAGE_CACHE_SIZE);
Nick Piggin87df7242007-01-30 14:36:27 +11003154 spin_unlock(&mapping->private_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003155out:
3156 if (buffers_to_free) {
3157 struct buffer_head *bh = buffers_to_free;
3158
3159 do {
3160 struct buffer_head *next = bh->b_this_page;
3161 free_buffer_head(bh);
3162 bh = next;
3163 } while (bh != buffers_to_free);
3164 }
3165 return ret;
3166}
3167EXPORT_SYMBOL(try_to_free_buffers);
3168
Linus Torvalds1da177e2005-04-16 15:20:36 -07003169/*
3170 * There are no bdflush tunables left. But distributions are
3171 * still running obsolete flush daemons, so we terminate them here.
3172 *
3173 * Use of bdflush() is deprecated and will be removed in a future kernel.
Jens Axboe5b0830c2009-09-23 19:37:09 +02003174 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003175 */
Heiko Carstensbdc480e2009-01-14 14:14:12 +01003176SYSCALL_DEFINE2(bdflush, int, func, long, data)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003177{
3178 static int msg_count;
3179
3180 if (!capable(CAP_SYS_ADMIN))
3181 return -EPERM;
3182
3183 if (msg_count < 5) {
3184 msg_count++;
3185 printk(KERN_INFO
3186 "warning: process `%s' used the obsolete bdflush"
3187 " system call\n", current->comm);
3188 printk(KERN_INFO "Fix your initscripts?\n");
3189 }
3190
3191 if (func == 1)
3192 do_exit(0);
3193 return 0;
3194}
3195
3196/*
3197 * Buffer-head allocation
3198 */
Christoph Lametere18b8902006-12-06 20:33:20 -08003199static struct kmem_cache *bh_cachep;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003200
3201/*
3202 * Once the number of bh's in the machine exceeds this level, we start
3203 * stripping them in writeback.
3204 */
3205static int max_buffer_heads;
3206
3207int buffer_heads_over_limit;
3208
3209struct bh_accounting {
3210 int nr; /* Number of live bh's */
3211 int ratelimit; /* Limit cacheline bouncing */
3212};
3213
3214static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3215
3216static void recalc_bh_state(void)
3217{
3218 int i;
3219 int tot = 0;
3220
Christoph Lameteree1be862010-12-06 11:40:05 -06003221 if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003222 return;
Christoph Lameterc7b92512010-12-06 11:16:28 -06003223 __this_cpu_write(bh_accounting.ratelimit, 0);
Eric Dumazet8a143422006-03-24 03:18:10 -08003224 for_each_online_cpu(i)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003225 tot += per_cpu(bh_accounting, i).nr;
3226 buffer_heads_over_limit = (tot > max_buffer_heads);
3227}
Christoph Lameterc7b92512010-12-06 11:16:28 -06003228
Al Virodd0fc662005-10-07 07:46:04 +01003229struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003230{
Richard Kennedy019b4d12010-03-10 15:20:33 -08003231 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003232 if (ret) {
Christoph Lametera35afb82007-05-16 22:10:57 -07003233 INIT_LIST_HEAD(&ret->b_assoc_buffers);
Christoph Lameterc7b92512010-12-06 11:16:28 -06003234 preempt_disable();
3235 __this_cpu_inc(bh_accounting.nr);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003236 recalc_bh_state();
Christoph Lameterc7b92512010-12-06 11:16:28 -06003237 preempt_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -07003238 }
3239 return ret;
3240}
3241EXPORT_SYMBOL(alloc_buffer_head);
3242
3243void free_buffer_head(struct buffer_head *bh)
3244{
3245 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3246 kmem_cache_free(bh_cachep, bh);
Christoph Lameterc7b92512010-12-06 11:16:28 -06003247 preempt_disable();
3248 __this_cpu_dec(bh_accounting.nr);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003249 recalc_bh_state();
Christoph Lameterc7b92512010-12-06 11:16:28 -06003250 preempt_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -07003251}
3252EXPORT_SYMBOL(free_buffer_head);
3253
Linus Torvalds1da177e2005-04-16 15:20:36 -07003254static void buffer_exit_cpu(int cpu)
3255{
3256 int i;
3257 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3258
3259 for (i = 0; i < BH_LRU_SIZE; i++) {
3260 brelse(b->bhs[i]);
3261 b->bhs[i] = NULL;
3262 }
Christoph Lameterc7b92512010-12-06 11:16:28 -06003263 this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
Eric Dumazet8a143422006-03-24 03:18:10 -08003264 per_cpu(bh_accounting, cpu).nr = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003265}
3266
3267static int buffer_cpu_notify(struct notifier_block *self,
3268 unsigned long action, void *hcpu)
3269{
Rafael J. Wysocki8bb78442007-05-09 02:35:10 -07003270 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003271 buffer_exit_cpu((unsigned long)hcpu);
3272 return NOTIFY_OK;
3273}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003274
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003275/**
Randy Dunlapa6b91912008-03-19 17:01:00 -07003276 * bh_uptodate_or_lock - Test whether the buffer is uptodate
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003277 * @bh: struct buffer_head
3278 *
3279 * Return true if the buffer is up-to-date and false,
3280 * with the buffer locked, if not.
3281 */
3282int bh_uptodate_or_lock(struct buffer_head *bh)
3283{
3284 if (!buffer_uptodate(bh)) {
3285 lock_buffer(bh);
3286 if (!buffer_uptodate(bh))
3287 return 0;
3288 unlock_buffer(bh);
3289 }
3290 return 1;
3291}
3292EXPORT_SYMBOL(bh_uptodate_or_lock);
3293
3294/**
Randy Dunlapa6b91912008-03-19 17:01:00 -07003295 * bh_submit_read - Submit a locked buffer for reading
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003296 * @bh: struct buffer_head
3297 *
3298 * Returns zero on success and -EIO on error.
3299 */
3300int bh_submit_read(struct buffer_head *bh)
3301{
3302 BUG_ON(!buffer_locked(bh));
3303
3304 if (buffer_uptodate(bh)) {
3305 unlock_buffer(bh);
3306 return 0;
3307 }
3308
3309 get_bh(bh);
3310 bh->b_end_io = end_buffer_read_sync;
3311 submit_bh(READ, bh);
3312 wait_on_buffer(bh);
3313 if (buffer_uptodate(bh))
3314 return 0;
3315 return -EIO;
3316}
3317EXPORT_SYMBOL(bh_submit_read);
3318
Linus Torvalds1da177e2005-04-16 15:20:36 -07003319void __init buffer_init(void)
3320{
3321 int nrpages;
3322
Christoph Lameterb98938c2008-02-04 22:28:36 -08003323 bh_cachep = kmem_cache_create("buffer_head",
3324 sizeof(struct buffer_head), 0,
3325 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3326 SLAB_MEM_SPREAD),
Richard Kennedy019b4d12010-03-10 15:20:33 -08003327 NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003328
3329 /*
3330 * Limit the bh occupancy to 10% of ZONE_NORMAL
3331 */
3332 nrpages = (nr_free_buffer_pages() * 10) / 100;
3333 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3334 hotcpu_notifier(buffer_cpu_notify, 0);
3335}