blob: 6024877335caf2a9dfa6af1018c5da19b0e8a2ae [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>
Tejun Heo5305cb82013-01-11 13:06:36 -080044#include <trace/events/block.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070045
46static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
Linus Torvalds1da177e2005-04-16 15:20:36 -070047
48#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
49
Yan Honga3f3c292012-12-12 13:52:15 -080050void init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
Linus Torvalds1da177e2005-04-16 15:20:36 -070051{
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
Tejun Heof0059af2013-01-11 13:06:35 -080057inline void touch_buffer(struct buffer_head *bh)
58{
Tejun Heo5305cb82013-01-11 13:06:36 -080059 trace_block_touch_buffer(bh);
Tejun Heof0059af2013-01-11 13:06:35 -080060 mark_page_accessed(bh->b_page);
61}
62EXPORT_SYMBOL(touch_buffer);
63
Jens Axboe7eaceac2011-03-10 08:52:07 +010064static int sleep_on_buffer(void *word)
Linus Torvalds1da177e2005-04-16 15:20:36 -070065{
Linus Torvalds1da177e2005-04-16 15:20:36 -070066 io_schedule();
67 return 0;
68}
69
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -080070void __lock_buffer(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -070071{
Jens Axboe7eaceac2011-03-10 08:52:07 +010072 wait_on_bit_lock(&bh->b_state, BH_Lock, sleep_on_buffer,
Linus Torvalds1da177e2005-04-16 15:20:36 -070073 TASK_UNINTERRUPTIBLE);
74}
75EXPORT_SYMBOL(__lock_buffer);
76
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -080077void unlock_buffer(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -070078{
Nick Piggin51b07fc2008-10-18 20:27:00 -070079 clear_bit_unlock(BH_Lock, &bh->b_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -070080 smp_mb__after_clear_bit();
81 wake_up_bit(&bh->b_state, BH_Lock);
82}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -070083EXPORT_SYMBOL(unlock_buffer);
Linus Torvalds1da177e2005-04-16 15:20:36 -070084
85/*
Mel Gormanb4597222013-07-03 15:02:05 -070086 * Returns if the page has dirty or writeback buffers. If all the buffers
87 * are unlocked and clean then the PageDirty information is stale. If
88 * any of the pages are locked, it is assumed they are locked for IO.
89 */
90void buffer_check_dirty_writeback(struct page *page,
91 bool *dirty, bool *writeback)
92{
93 struct buffer_head *head, *bh;
94 *dirty = false;
95 *writeback = false;
96
97 BUG_ON(!PageLocked(page));
98
99 if (!page_has_buffers(page))
100 return;
101
102 if (PageWriteback(page))
103 *writeback = true;
104
105 head = page_buffers(page);
106 bh = head;
107 do {
108 if (buffer_locked(bh))
109 *writeback = true;
110
111 if (buffer_dirty(bh))
112 *dirty = true;
113
114 bh = bh->b_this_page;
115 } while (bh != head);
116}
117EXPORT_SYMBOL(buffer_check_dirty_writeback);
118
119/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700120 * Block until a buffer comes unlocked. This doesn't stop it
121 * from becoming locked again - you have to lock it yourself
122 * if you want to preserve its state.
123 */
124void __wait_on_buffer(struct buffer_head * bh)
125{
Jens Axboe7eaceac2011-03-10 08:52:07 +0100126 wait_on_bit(&bh->b_state, BH_Lock, sleep_on_buffer, TASK_UNINTERRUPTIBLE);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700127}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700128EXPORT_SYMBOL(__wait_on_buffer);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700129
130static void
131__clear_page_buffers(struct page *page)
132{
133 ClearPagePrivate(page);
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700134 set_page_private(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700135 page_cache_release(page);
136}
137
Keith Mannthey08bafc02008-11-25 10:24:35 +0100138
139static int quiet_error(struct buffer_head *bh)
140{
141 if (!test_bit(BH_Quiet, &bh->b_state) && printk_ratelimit())
142 return 0;
143 return 1;
144}
145
146
Linus Torvalds1da177e2005-04-16 15:20:36 -0700147static void buffer_io_error(struct buffer_head *bh)
148{
149 char b[BDEVNAME_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700150 printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
151 bdevname(bh->b_bdev, b),
152 (unsigned long long)bh->b_blocknr);
153}
154
155/*
Dmitry Monakhov68671f32007-10-16 01:24:47 -0700156 * End-of-IO handler helper function which does not touch the bh after
157 * unlocking it.
158 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
159 * a race there is benign: unlock_buffer() only use the bh's address for
160 * hashing after unlocking the buffer, so it doesn't actually touch the bh
161 * itself.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700162 */
Dmitry Monakhov68671f32007-10-16 01:24:47 -0700163static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700164{
165 if (uptodate) {
166 set_buffer_uptodate(bh);
167 } else {
168 /* This happens, due to failed READA attempts. */
169 clear_buffer_uptodate(bh);
170 }
171 unlock_buffer(bh);
Dmitry Monakhov68671f32007-10-16 01:24:47 -0700172}
173
174/*
175 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
176 * unlock the buffer. This is what ll_rw_block uses too.
177 */
178void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
179{
180 __end_buffer_read_notouch(bh, uptodate);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700181 put_bh(bh);
182}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700183EXPORT_SYMBOL(end_buffer_read_sync);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700184
185void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
186{
187 char b[BDEVNAME_SIZE];
188
189 if (uptodate) {
190 set_buffer_uptodate(bh);
191 } else {
Christoph Hellwig0edd55f2010-08-18 05:29:23 -0400192 if (!quiet_error(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700193 buffer_io_error(bh);
194 printk(KERN_WARNING "lost page write due to "
195 "I/O error on %s\n",
196 bdevname(bh->b_bdev, b));
197 }
198 set_buffer_write_io_error(bh);
199 clear_buffer_uptodate(bh);
200 }
201 unlock_buffer(bh);
202 put_bh(bh);
203}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700204EXPORT_SYMBOL(end_buffer_write_sync);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700205
206/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700207 * Various filesystems appear to want __find_get_block to be non-blocking.
208 * But it's the page lock which protects the buffers. To get around this,
209 * we get exclusion from try_to_free_buffers with the blockdev mapping's
210 * private_lock.
211 *
212 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
213 * may be quite high. This code could TryLock the page, and if that
214 * succeeds, there is no need to take private_lock. (But if
215 * private_lock is contended then so is mapping->tree_lock).
216 */
217static struct buffer_head *
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -0800218__find_get_block_slow(struct block_device *bdev, sector_t block)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700219{
220 struct inode *bd_inode = bdev->bd_inode;
221 struct address_space *bd_mapping = bd_inode->i_mapping;
222 struct buffer_head *ret = NULL;
223 pgoff_t index;
224 struct buffer_head *bh;
225 struct buffer_head *head;
226 struct page *page;
227 int all_mapped = 1;
228
229 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
230 page = find_get_page(bd_mapping, index);
231 if (!page)
232 goto out;
233
234 spin_lock(&bd_mapping->private_lock);
235 if (!page_has_buffers(page))
236 goto out_unlock;
237 head = page_buffers(page);
238 bh = head;
239 do {
Nikanth Karthikesan97f76d32009-04-02 16:56:46 -0700240 if (!buffer_mapped(bh))
241 all_mapped = 0;
242 else if (bh->b_blocknr == block) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700243 ret = bh;
244 get_bh(bh);
245 goto out_unlock;
246 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700247 bh = bh->b_this_page;
248 } while (bh != head);
249
250 /* we might be here because some of the buffers on this page are
251 * not mapped. This is due to various races between
252 * file io on the block device and getblk. It gets dealt with
253 * elsewhere, don't buffer_error if we had some unmapped buffers
254 */
255 if (all_mapped) {
Tao Ma72a2ebd2011-10-31 17:09:00 -0700256 char b[BDEVNAME_SIZE];
257
Linus Torvalds1da177e2005-04-16 15:20:36 -0700258 printk("__find_get_block_slow() failed. "
259 "block=%llu, b_blocknr=%llu\n",
Badari Pulavarty205f87f2006-03-26 01:38:00 -0800260 (unsigned long long)block,
261 (unsigned long long)bh->b_blocknr);
262 printk("b_state=0x%08lx, b_size=%zu\n",
263 bh->b_state, bh->b_size);
Tao Ma72a2ebd2011-10-31 17:09:00 -0700264 printk("device %s blocksize: %d\n", bdevname(bdev, b),
265 1 << bd_inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700266 }
267out_unlock:
268 spin_unlock(&bd_mapping->private_lock);
269 page_cache_release(page);
270out:
271 return ret;
272}
273
Linus Torvalds1da177e2005-04-16 15:20:36 -0700274/*
Jens Axboe5b0830c2009-09-23 19:37:09 +0200275 * Kick the writeback threads then try to free up some ZONE_NORMAL memory.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700276 */
277static void free_more_memory(void)
278{
Mel Gorman19770b32008-04-28 02:12:18 -0700279 struct zone *zone;
Mel Gorman0e884602008-04-28 02:12:14 -0700280 int nid;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700281
Curt Wohlgemuth0e175a12011-10-07 21:54:10 -0600282 wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700283 yield();
284
Mel Gorman0e884602008-04-28 02:12:14 -0700285 for_each_online_node(nid) {
Mel Gorman19770b32008-04-28 02:12:18 -0700286 (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS),
287 gfp_zone(GFP_NOFS), NULL,
288 &zone);
289 if (zone)
Mel Gorman54a6eb52008-04-28 02:12:16 -0700290 try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0,
KAMEZAWA Hiroyuki327c0e92009-03-31 15:23:31 -0700291 GFP_NOFS, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700292 }
293}
294
295/*
296 * I/O completion handler for block_read_full_page() - pages
297 * which come unlocked at the end of I/O.
298 */
299static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
300{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700301 unsigned long flags;
Nick Piggina3972202005-07-07 17:56:56 -0700302 struct buffer_head *first;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700303 struct buffer_head *tmp;
304 struct page *page;
305 int page_uptodate = 1;
306
307 BUG_ON(!buffer_async_read(bh));
308
309 page = bh->b_page;
310 if (uptodate) {
311 set_buffer_uptodate(bh);
312 } else {
313 clear_buffer_uptodate(bh);
Keith Mannthey08bafc02008-11-25 10:24:35 +0100314 if (!quiet_error(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700315 buffer_io_error(bh);
316 SetPageError(page);
317 }
318
319 /*
320 * Be _very_ careful from here on. Bad things can happen if
321 * two buffer heads end IO at almost the same time and both
322 * decide that the page is now completely done.
323 */
Nick Piggina3972202005-07-07 17:56:56 -0700324 first = page_buffers(page);
325 local_irq_save(flags);
326 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700327 clear_buffer_async_read(bh);
328 unlock_buffer(bh);
329 tmp = bh;
330 do {
331 if (!buffer_uptodate(tmp))
332 page_uptodate = 0;
333 if (buffer_async_read(tmp)) {
334 BUG_ON(!buffer_locked(tmp));
335 goto still_busy;
336 }
337 tmp = tmp->b_this_page;
338 } while (tmp != bh);
Nick Piggina3972202005-07-07 17:56:56 -0700339 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
340 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700341
342 /*
343 * If none of the buffers had errors and they are all
344 * uptodate then we can set the page uptodate.
345 */
346 if (page_uptodate && !PageError(page))
347 SetPageUptodate(page);
348 unlock_page(page);
349 return;
350
351still_busy:
Nick Piggina3972202005-07-07 17:56:56 -0700352 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
353 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700354 return;
355}
356
357/*
358 * Completion handler for block_write_full_page() - pages which are unlocked
359 * during I/O, and which have PageWriteback cleared upon I/O completion.
360 */
Chris Mason35c80d52009-04-15 13:22:38 -0400361void end_buffer_async_write(struct buffer_head *bh, int uptodate)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700362{
363 char b[BDEVNAME_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700364 unsigned long flags;
Nick Piggina3972202005-07-07 17:56:56 -0700365 struct buffer_head *first;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700366 struct buffer_head *tmp;
367 struct page *page;
368
369 BUG_ON(!buffer_async_write(bh));
370
371 page = bh->b_page;
372 if (uptodate) {
373 set_buffer_uptodate(bh);
374 } else {
Keith Mannthey08bafc02008-11-25 10:24:35 +0100375 if (!quiet_error(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700376 buffer_io_error(bh);
377 printk(KERN_WARNING "lost page write due to "
378 "I/O error on %s\n",
379 bdevname(bh->b_bdev, b));
380 }
381 set_bit(AS_EIO, &page->mapping->flags);
Jan Kara58ff4072006-10-17 00:10:19 -0700382 set_buffer_write_io_error(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700383 clear_buffer_uptodate(bh);
384 SetPageError(page);
385 }
386
Nick Piggina3972202005-07-07 17:56:56 -0700387 first = page_buffers(page);
388 local_irq_save(flags);
389 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
390
Linus Torvalds1da177e2005-04-16 15:20:36 -0700391 clear_buffer_async_write(bh);
392 unlock_buffer(bh);
393 tmp = bh->b_this_page;
394 while (tmp != bh) {
395 if (buffer_async_write(tmp)) {
396 BUG_ON(!buffer_locked(tmp));
397 goto still_busy;
398 }
399 tmp = tmp->b_this_page;
400 }
Nick Piggina3972202005-07-07 17:56:56 -0700401 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
402 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700403 end_page_writeback(page);
404 return;
405
406still_busy:
Nick Piggina3972202005-07-07 17:56:56 -0700407 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
408 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700409 return;
410}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700411EXPORT_SYMBOL(end_buffer_async_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700412
413/*
414 * If a page's buffers are under async readin (end_buffer_async_read
415 * completion) then there is a possibility that another thread of
416 * control could lock one of the buffers after it has completed
417 * but while some of the other buffers have not completed. This
418 * locked buffer would confuse end_buffer_async_read() into not unlocking
419 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
420 * that this buffer is not under async I/O.
421 *
422 * The page comes unlocked when it has no locked buffer_async buffers
423 * left.
424 *
425 * PageLocked prevents anyone starting new async I/O reads any of
426 * the buffers.
427 *
428 * PageWriteback is used to prevent simultaneous writeout of the same
429 * page.
430 *
431 * PageLocked prevents anyone from starting writeback of a page which is
432 * under read I/O (PageWriteback is only ever set against a locked page).
433 */
434static void mark_buffer_async_read(struct buffer_head *bh)
435{
436 bh->b_end_io = end_buffer_async_read;
437 set_buffer_async_read(bh);
438}
439
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700440static void mark_buffer_async_write_endio(struct buffer_head *bh,
441 bh_end_io_t *handler)
Chris Mason35c80d52009-04-15 13:22:38 -0400442{
443 bh->b_end_io = handler;
444 set_buffer_async_write(bh);
445}
446
Linus Torvalds1da177e2005-04-16 15:20:36 -0700447void mark_buffer_async_write(struct buffer_head *bh)
448{
Chris Mason35c80d52009-04-15 13:22:38 -0400449 mark_buffer_async_write_endio(bh, end_buffer_async_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700450}
451EXPORT_SYMBOL(mark_buffer_async_write);
452
453
454/*
455 * fs/buffer.c contains helper functions for buffer-backed address space's
456 * fsync functions. A common requirement for buffer-based filesystems is
457 * that certain data from the backing blockdev needs to be written out for
458 * a successful fsync(). For example, ext2 indirect blocks need to be
459 * written back and waited upon before fsync() returns.
460 *
461 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
462 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
463 * management of a list of dependent buffers at ->i_mapping->private_list.
464 *
465 * Locking is a little subtle: try_to_free_buffers() will remove buffers
466 * from their controlling inode's queue when they are being freed. But
467 * try_to_free_buffers() will be operating against the *blockdev* mapping
468 * at the time, not against the S_ISREG file which depends on those buffers.
469 * So the locking for private_list is via the private_lock in the address_space
470 * which backs the buffers. Which is different from the address_space
471 * against which the buffers are listed. So for a particular address_space,
472 * mapping->private_lock does *not* protect mapping->private_list! In fact,
473 * mapping->private_list will always be protected by the backing blockdev's
474 * ->private_lock.
475 *
476 * Which introduces a requirement: all buffers on an address_space's
477 * ->private_list must be from the same address_space: the blockdev's.
478 *
479 * address_spaces which do not place buffers at ->private_list via these
480 * utility functions are free to use private_lock and private_list for
481 * whatever they want. The only requirement is that list_empty(private_list)
482 * be true at clear_inode() time.
483 *
484 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
485 * filesystems should do that. invalidate_inode_buffers() should just go
486 * BUG_ON(!list_empty).
487 *
488 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
489 * take an address_space, not an inode. And it should be called
490 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
491 * queued up.
492 *
493 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
494 * list if it is already on a list. Because if the buffer is on a list,
495 * it *must* already be on the right one. If not, the filesystem is being
496 * silly. This will save a ton of locking. But first we have to ensure
497 * that buffers are taken *off* the old inode's list when they are freed
498 * (presumably in truncate). That requires careful auditing of all
499 * filesystems (do it inside bforget()). It could also be done by bringing
500 * b_inode back.
501 */
502
503/*
504 * The buffer's backing address_space's private_lock must be held
505 */
Thomas Petazzonidbacefc2008-07-29 22:33:47 -0700506static void __remove_assoc_queue(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700507{
508 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -0700509 WARN_ON(!bh->b_assoc_map);
510 if (buffer_write_io_error(bh))
511 set_bit(AS_EIO, &bh->b_assoc_map->flags);
512 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700513}
514
515int inode_has_buffers(struct inode *inode)
516{
517 return !list_empty(&inode->i_data.private_list);
518}
519
520/*
521 * osync is designed to support O_SYNC io. It waits synchronously for
522 * all already-submitted IO to complete, but does not queue any new
523 * writes to the disk.
524 *
525 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
526 * you dirty the buffers, and then use osync_inode_buffers to wait for
527 * completion. Any other dirty buffers which are not yet queued for
528 * write will not be flushed to disk by the osync.
529 */
530static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
531{
532 struct buffer_head *bh;
533 struct list_head *p;
534 int err = 0;
535
536 spin_lock(lock);
537repeat:
538 list_for_each_prev(p, list) {
539 bh = BH_ENTRY(p);
540 if (buffer_locked(bh)) {
541 get_bh(bh);
542 spin_unlock(lock);
543 wait_on_buffer(bh);
544 if (!buffer_uptodate(bh))
545 err = -EIO;
546 brelse(bh);
547 spin_lock(lock);
548 goto repeat;
549 }
550 }
551 spin_unlock(lock);
552 return err;
553}
554
Al Viro01a05b32010-03-23 06:06:58 -0400555static void do_thaw_one(struct super_block *sb, void *unused)
556{
557 char b[BDEVNAME_SIZE];
558 while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
559 printk(KERN_WARNING "Emergency Thaw on %s\n",
560 bdevname(sb->s_bdev, b));
561}
562
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700563static void do_thaw_all(struct work_struct *work)
Eric Sandeenc2d75432009-03-31 15:23:46 -0700564{
Al Viro01a05b32010-03-23 06:06:58 -0400565 iterate_supers(do_thaw_one, NULL);
Jens Axboe053c5252009-04-08 13:44:08 +0200566 kfree(work);
Eric Sandeenc2d75432009-03-31 15:23:46 -0700567 printk(KERN_WARNING "Emergency Thaw complete\n");
568}
569
570/**
571 * emergency_thaw_all -- forcibly thaw every frozen filesystem
572 *
573 * Used for emergency unfreeze of all filesystems via SysRq
574 */
575void emergency_thaw_all(void)
576{
Jens Axboe053c5252009-04-08 13:44:08 +0200577 struct work_struct *work;
578
579 work = kmalloc(sizeof(*work), GFP_ATOMIC);
580 if (work) {
581 INIT_WORK(work, do_thaw_all);
582 schedule_work(work);
583 }
Eric Sandeenc2d75432009-03-31 15:23:46 -0700584}
585
Linus Torvalds1da177e2005-04-16 15:20:36 -0700586/**
Randy Dunlap78a4a502008-02-29 22:02:31 -0800587 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
Martin Waitz67be2dd2005-05-01 08:59:26 -0700588 * @mapping: the mapping which wants those buffers written
Linus Torvalds1da177e2005-04-16 15:20:36 -0700589 *
590 * Starts I/O against the buffers at mapping->private_list, and waits upon
591 * that I/O.
592 *
Martin Waitz67be2dd2005-05-01 08:59:26 -0700593 * Basically, this is a convenience function for fsync().
594 * @mapping is a file or directory which needs those buffers to be written for
595 * a successful fsync().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700596 */
597int sync_mapping_buffers(struct address_space *mapping)
598{
Rafael Aquini252aa6f2012-12-11 16:02:35 -0800599 struct address_space *buffer_mapping = mapping->private_data;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700600
601 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
602 return 0;
603
604 return fsync_buffers_list(&buffer_mapping->private_lock,
605 &mapping->private_list);
606}
607EXPORT_SYMBOL(sync_mapping_buffers);
608
609/*
610 * Called when we've recently written block `bblock', and it is known that
611 * `bblock' was for a buffer_boundary() buffer. This means that the block at
612 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
613 * dirty, schedule it for IO. So that indirects merge nicely with their data.
614 */
615void write_boundary_block(struct block_device *bdev,
616 sector_t bblock, unsigned blocksize)
617{
618 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
619 if (bh) {
620 if (buffer_dirty(bh))
621 ll_rw_block(WRITE, 1, &bh);
622 put_bh(bh);
623 }
624}
625
626void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
627{
628 struct address_space *mapping = inode->i_mapping;
629 struct address_space *buffer_mapping = bh->b_page->mapping;
630
631 mark_buffer_dirty(bh);
Rafael Aquini252aa6f2012-12-11 16:02:35 -0800632 if (!mapping->private_data) {
633 mapping->private_data = buffer_mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700634 } else {
Rafael Aquini252aa6f2012-12-11 16:02:35 -0800635 BUG_ON(mapping->private_data != buffer_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700636 }
Jan Kara535ee2f2008-02-08 04:21:59 -0800637 if (!bh->b_assoc_map) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700638 spin_lock(&buffer_mapping->private_lock);
639 list_move_tail(&bh->b_assoc_buffers,
640 &mapping->private_list);
Jan Kara58ff4072006-10-17 00:10:19 -0700641 bh->b_assoc_map = mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700642 spin_unlock(&buffer_mapping->private_lock);
643 }
644}
645EXPORT_SYMBOL(mark_buffer_dirty_inode);
646
647/*
Nick Piggin787d2212007-07-17 04:03:34 -0700648 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
649 * dirty.
650 *
651 * If warn is true, then emit a warning if the page is not uptodate and has
652 * not been truncated.
653 */
Linus Torvaldsa8e7d492009-03-19 11:32:05 -0700654static void __set_page_dirty(struct page *page,
Nick Piggin787d2212007-07-17 04:03:34 -0700655 struct address_space *mapping, int warn)
656{
Nick Piggin19fd6232008-07-25 19:45:32 -0700657 spin_lock_irq(&mapping->tree_lock);
Nick Piggin787d2212007-07-17 04:03:34 -0700658 if (page->mapping) { /* Race with truncate? */
659 WARN_ON_ONCE(warn && !PageUptodate(page));
Edward Shishkine3a7cca2009-03-31 15:19:39 -0700660 account_page_dirtied(page, mapping);
Nick Piggin787d2212007-07-17 04:03:34 -0700661 radix_tree_tag_set(&mapping->page_tree,
662 page_index(page), PAGECACHE_TAG_DIRTY);
663 }
Nick Piggin19fd6232008-07-25 19:45:32 -0700664 spin_unlock_irq(&mapping->tree_lock);
Nick Piggin787d2212007-07-17 04:03:34 -0700665 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
Nick Piggin787d2212007-07-17 04:03:34 -0700666}
667
668/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700669 * Add a page to the dirty page list.
670 *
671 * It is a sad fact of life that this function is called from several places
672 * deeply under spinlocking. It may not sleep.
673 *
674 * If the page has buffers, the uptodate buffers are set dirty, to preserve
675 * dirty-state coherency between the page and the buffers. It the page does
676 * not have buffers then when they are later attached they will all be set
677 * dirty.
678 *
679 * The buffers are dirtied before the page is dirtied. There's a small race
680 * window in which a writepage caller may see the page cleanness but not the
681 * buffer dirtiness. That's fine. If this code were to set the page dirty
682 * before the buffers, a concurrent writepage caller could clear the page dirty
683 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
684 * page on the dirty page list.
685 *
686 * We use private_lock to lock against try_to_free_buffers while using the
687 * page's buffer list. Also use this to protect against clean buffers being
688 * added to the page after it was set dirty.
689 *
690 * FIXME: may need to call ->reservepage here as well. That's rather up to the
691 * address_space though.
692 */
693int __set_page_dirty_buffers(struct page *page)
694{
Linus Torvaldsa8e7d492009-03-19 11:32:05 -0700695 int newly_dirty;
Nick Piggin787d2212007-07-17 04:03:34 -0700696 struct address_space *mapping = page_mapping(page);
Nick Pigginebf7a222006-10-10 04:36:54 +0200697
698 if (unlikely(!mapping))
699 return !TestSetPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700700
701 spin_lock(&mapping->private_lock);
702 if (page_has_buffers(page)) {
703 struct buffer_head *head = page_buffers(page);
704 struct buffer_head *bh = head;
705
706 do {
707 set_buffer_dirty(bh);
708 bh = bh->b_this_page;
709 } while (bh != head);
710 }
Linus Torvaldsa8e7d492009-03-19 11:32:05 -0700711 newly_dirty = !TestSetPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700712 spin_unlock(&mapping->private_lock);
713
Linus Torvaldsa8e7d492009-03-19 11:32:05 -0700714 if (newly_dirty)
715 __set_page_dirty(page, mapping, 1);
716 return newly_dirty;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700717}
718EXPORT_SYMBOL(__set_page_dirty_buffers);
719
720/*
721 * Write out and wait upon a list of buffers.
722 *
723 * We have conflicting pressures: we want to make sure that all
724 * initially dirty buffers get waited on, but that any subsequently
725 * dirtied buffers don't. After all, we don't want fsync to last
726 * forever if somebody is actively writing to the file.
727 *
728 * Do this in two main stages: first we copy dirty buffers to a
729 * temporary inode list, queueing the writes as we go. Then we clean
730 * up, waiting for those writes to complete.
731 *
732 * During this second stage, any subsequent updates to the file may end
733 * up refiling the buffer on the original inode's dirty list again, so
734 * there is a chance we will end up with a buffer queued for write but
735 * not yet completed on that list. So, as a final cleanup we go through
736 * the osync code to catch these locked, dirty buffers without requeuing
737 * any newly dirty buffers for write.
738 */
739static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
740{
741 struct buffer_head *bh;
742 struct list_head tmp;
Jens Axboe7eaceac2011-03-10 08:52:07 +0100743 struct address_space *mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700744 int err = 0, err2;
Jens Axboe4ee24912011-03-17 10:51:40 +0100745 struct blk_plug plug;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700746
747 INIT_LIST_HEAD(&tmp);
Jens Axboe4ee24912011-03-17 10:51:40 +0100748 blk_start_plug(&plug);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700749
750 spin_lock(lock);
751 while (!list_empty(list)) {
752 bh = BH_ENTRY(list->next);
Jan Kara535ee2f2008-02-08 04:21:59 -0800753 mapping = bh->b_assoc_map;
Jan Kara58ff4072006-10-17 00:10:19 -0700754 __remove_assoc_queue(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -0800755 /* Avoid race with mark_buffer_dirty_inode() which does
756 * a lockless check and we rely on seeing the dirty bit */
757 smp_mb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700758 if (buffer_dirty(bh) || buffer_locked(bh)) {
759 list_add(&bh->b_assoc_buffers, &tmp);
Jan Kara535ee2f2008-02-08 04:21:59 -0800760 bh->b_assoc_map = mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700761 if (buffer_dirty(bh)) {
762 get_bh(bh);
763 spin_unlock(lock);
764 /*
765 * Ensure any pending I/O completes so that
Christoph Hellwig9cb569d2010-08-11 17:06:24 +0200766 * write_dirty_buffer() actually writes the
767 * current contents - it is a noop if I/O is
768 * still in flight on potentially older
769 * contents.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700770 */
Jens Axboe721a9602011-03-09 11:56:30 +0100771 write_dirty_buffer(bh, WRITE_SYNC);
Jens Axboe9cf6b722009-04-06 14:48:03 +0200772
773 /*
774 * Kick off IO for the previous mapping. Note
775 * that we will not run the very last mapping,
776 * wait_on_buffer() will do that for us
777 * through sync_buffer().
778 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700779 brelse(bh);
780 spin_lock(lock);
781 }
782 }
783 }
784
Jens Axboe4ee24912011-03-17 10:51:40 +0100785 spin_unlock(lock);
786 blk_finish_plug(&plug);
787 spin_lock(lock);
788
Linus Torvalds1da177e2005-04-16 15:20:36 -0700789 while (!list_empty(&tmp)) {
790 bh = BH_ENTRY(tmp.prev);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700791 get_bh(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -0800792 mapping = bh->b_assoc_map;
793 __remove_assoc_queue(bh);
794 /* Avoid race with mark_buffer_dirty_inode() which does
795 * a lockless check and we rely on seeing the dirty bit */
796 smp_mb();
797 if (buffer_dirty(bh)) {
798 list_add(&bh->b_assoc_buffers,
Jan Karae3892292008-03-04 14:28:33 -0800799 &mapping->private_list);
Jan Kara535ee2f2008-02-08 04:21:59 -0800800 bh->b_assoc_map = mapping;
801 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700802 spin_unlock(lock);
803 wait_on_buffer(bh);
804 if (!buffer_uptodate(bh))
805 err = -EIO;
806 brelse(bh);
807 spin_lock(lock);
808 }
809
810 spin_unlock(lock);
811 err2 = osync_buffers_list(lock, list);
812 if (err)
813 return err;
814 else
815 return err2;
816}
817
818/*
819 * Invalidate any and all dirty buffers on a given inode. We are
820 * probably unmounting the fs, but that doesn't mean we have already
821 * done a sync(). Just drop the buffers from the inode list.
822 *
823 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
824 * assumes that all the buffers are against the blockdev. Not true
825 * for reiserfs.
826 */
827void invalidate_inode_buffers(struct inode *inode)
828{
829 if (inode_has_buffers(inode)) {
830 struct address_space *mapping = &inode->i_data;
831 struct list_head *list = &mapping->private_list;
Rafael Aquini252aa6f2012-12-11 16:02:35 -0800832 struct address_space *buffer_mapping = mapping->private_data;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700833
834 spin_lock(&buffer_mapping->private_lock);
835 while (!list_empty(list))
836 __remove_assoc_queue(BH_ENTRY(list->next));
837 spin_unlock(&buffer_mapping->private_lock);
838 }
839}
Jan Kara52b19ac2008-09-23 18:24:08 +0200840EXPORT_SYMBOL(invalidate_inode_buffers);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700841
842/*
843 * Remove any clean buffers from the inode's buffer list. This is called
844 * when we're trying to free the inode itself. Those buffers can pin it.
845 *
846 * Returns true if all buffers were removed.
847 */
848int remove_inode_buffers(struct inode *inode)
849{
850 int ret = 1;
851
852 if (inode_has_buffers(inode)) {
853 struct address_space *mapping = &inode->i_data;
854 struct list_head *list = &mapping->private_list;
Rafael Aquini252aa6f2012-12-11 16:02:35 -0800855 struct address_space *buffer_mapping = mapping->private_data;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700856
857 spin_lock(&buffer_mapping->private_lock);
858 while (!list_empty(list)) {
859 struct buffer_head *bh = BH_ENTRY(list->next);
860 if (buffer_dirty(bh)) {
861 ret = 0;
862 break;
863 }
864 __remove_assoc_queue(bh);
865 }
866 spin_unlock(&buffer_mapping->private_lock);
867 }
868 return ret;
869}
870
871/*
872 * Create the appropriate buffers when given a page for data area and
873 * the size of each buffer.. Use the bh->b_this_page linked list to
874 * follow the buffers created. Return NULL if unable to create more
875 * buffers.
876 *
877 * The retry flag is used to differentiate async IO (paging, swapping)
878 * which may not fail from ordinary buffer allocations.
879 */
880struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
881 int retry)
882{
883 struct buffer_head *bh, *head;
884 long offset;
885
886try_again:
887 head = NULL;
888 offset = PAGE_SIZE;
889 while ((offset -= size) >= 0) {
890 bh = alloc_buffer_head(GFP_NOFS);
891 if (!bh)
892 goto no_grow;
893
Linus Torvalds1da177e2005-04-16 15:20:36 -0700894 bh->b_this_page = head;
895 bh->b_blocknr = -1;
896 head = bh;
897
Linus Torvalds1da177e2005-04-16 15:20:36 -0700898 bh->b_size = size;
899
900 /* Link the buffer to its page */
901 set_bh_page(bh, page, offset);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700902 }
903 return head;
904/*
905 * In case anything failed, we just free everything we got.
906 */
907no_grow:
908 if (head) {
909 do {
910 bh = head;
911 head = head->b_this_page;
912 free_buffer_head(bh);
913 } while (head);
914 }
915
916 /*
917 * Return failure for non-async IO requests. Async IO requests
918 * are not allowed to fail, so we have to wait until buffer heads
919 * become available. But we don't want tasks sleeping with
920 * partially complete buffers, so all were released above.
921 */
922 if (!retry)
923 return NULL;
924
925 /* We're _really_ low on memory. Now we just
926 * wait for old buffer heads to become free due to
927 * finishing IO. Since this is an async request and
928 * the reserve list is empty, we're sure there are
929 * async buffer heads in use.
930 */
931 free_more_memory();
932 goto try_again;
933}
934EXPORT_SYMBOL_GPL(alloc_page_buffers);
935
936static inline void
937link_dev_buffers(struct page *page, struct buffer_head *head)
938{
939 struct buffer_head *bh, *tail;
940
941 bh = head;
942 do {
943 tail = bh;
944 bh = bh->b_this_page;
945 } while (bh);
946 tail->b_this_page = head;
947 attach_page_buffers(page, head);
948}
949
Linus Torvaldsbbec02702012-11-29 12:31:52 -0800950static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
951{
952 sector_t retval = ~((sector_t)0);
953 loff_t sz = i_size_read(bdev->bd_inode);
954
955 if (sz) {
956 unsigned int sizebits = blksize_bits(size);
957 retval = (sz >> sizebits);
958 }
959 return retval;
960}
961
Linus Torvalds1da177e2005-04-16 15:20:36 -0700962/*
963 * Initialise the state of a blockdev page's buffers.
964 */
Hugh Dickins676ce6d2012-08-23 12:17:36 +0200965static sector_t
Linus Torvalds1da177e2005-04-16 15:20:36 -0700966init_page_buffers(struct page *page, struct block_device *bdev,
967 sector_t block, int size)
968{
969 struct buffer_head *head = page_buffers(page);
970 struct buffer_head *bh = head;
971 int uptodate = PageUptodate(page);
Linus Torvaldsbbec02702012-11-29 12:31:52 -0800972 sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode), size);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700973
974 do {
975 if (!buffer_mapped(bh)) {
976 init_buffer(bh, NULL, NULL);
977 bh->b_bdev = bdev;
978 bh->b_blocknr = block;
979 if (uptodate)
980 set_buffer_uptodate(bh);
Jeff Moyer080399a2012-05-11 16:34:10 +0200981 if (block < end_block)
982 set_buffer_mapped(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700983 }
984 block++;
985 bh = bh->b_this_page;
986 } while (bh != head);
Hugh Dickins676ce6d2012-08-23 12:17:36 +0200987
988 /*
989 * Caller needs to validate requested block against end of device.
990 */
991 return end_block;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700992}
993
994/*
995 * Create the page-cache page that contains the requested block.
996 *
Hugh Dickins676ce6d2012-08-23 12:17:36 +0200997 * This is used purely for blockdev mappings.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700998 */
Hugh Dickins676ce6d2012-08-23 12:17:36 +0200999static int
Linus Torvalds1da177e2005-04-16 15:20:36 -07001000grow_dev_page(struct block_device *bdev, sector_t block,
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001001 pgoff_t index, int size, int sizebits)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001002{
1003 struct inode *inode = bdev->bd_inode;
1004 struct page *page;
1005 struct buffer_head *bh;
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001006 sector_t end_block;
1007 int ret = 0; /* Will call free_more_memory() */
Johannes Weiner84235de2013-10-16 13:47:00 -07001008 gfp_t gfp_mask;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001009
Johannes Weiner84235de2013-10-16 13:47:00 -07001010 gfp_mask = mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS;
1011 gfp_mask |= __GFP_MOVABLE;
1012 /*
1013 * XXX: __getblk_slow() can not really deal with failure and
1014 * will endlessly loop on improvised global reclaim. Prefer
1015 * looping in the allocator rather than here, at least that
1016 * code knows what it's doing.
1017 */
1018 gfp_mask |= __GFP_NOFAIL;
1019
1020 page = find_or_create_page(inode->i_mapping, index, gfp_mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001021 if (!page)
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001022 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001023
Eric Sesterhenne827f922006-03-26 18:24:46 +02001024 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001025
1026 if (page_has_buffers(page)) {
1027 bh = page_buffers(page);
1028 if (bh->b_size == size) {
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001029 end_block = init_page_buffers(page, bdev,
1030 index << sizebits, size);
1031 goto done;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001032 }
1033 if (!try_to_free_buffers(page))
1034 goto failed;
1035 }
1036
1037 /*
1038 * Allocate some buffers for this page
1039 */
1040 bh = alloc_page_buffers(page, size, 0);
1041 if (!bh)
1042 goto failed;
1043
1044 /*
1045 * Link the page to the buffers and initialise them. Take the
1046 * lock to be atomic wrt __find_get_block(), which does not
1047 * run under the page lock.
1048 */
1049 spin_lock(&inode->i_mapping->private_lock);
1050 link_dev_buffers(page, bh);
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001051 end_block = init_page_buffers(page, bdev, index << sizebits, size);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001052 spin_unlock(&inode->i_mapping->private_lock);
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001053done:
1054 ret = (block < end_block) ? 1 : -ENXIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001055failed:
Linus Torvalds1da177e2005-04-16 15:20:36 -07001056 unlock_page(page);
1057 page_cache_release(page);
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001058 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001059}
1060
1061/*
1062 * Create buffers for the specified block device block's page. If
1063 * that page was dirty, the buffers are set dirty also.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001064 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001065static int
Linus Torvalds1da177e2005-04-16 15:20:36 -07001066grow_buffers(struct block_device *bdev, sector_t block, int size)
1067{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001068 pgoff_t index;
1069 int sizebits;
1070
1071 sizebits = -1;
1072 do {
1073 sizebits++;
1074 } while ((size << sizebits) < PAGE_SIZE);
1075
1076 index = block >> sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001077
Andrew Mortone5657932006-10-11 01:21:46 -07001078 /*
1079 * Check for a block which wants to lie outside our maximum possible
1080 * pagecache index. (this comparison is done using sector_t types).
1081 */
1082 if (unlikely(index != block >> sizebits)) {
1083 char b[BDEVNAME_SIZE];
1084
1085 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1086 "device %s\n",
Harvey Harrison8e24eea2008-04-30 00:55:09 -07001087 __func__, (unsigned long long)block,
Andrew Mortone5657932006-10-11 01:21:46 -07001088 bdevname(bdev, b));
1089 return -EIO;
1090 }
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001091
Linus Torvalds1da177e2005-04-16 15:20:36 -07001092 /* Create a page with the proper size buffers.. */
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001093 return grow_dev_page(bdev, block, index, size, sizebits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001094}
1095
Adrian Bunk75c96f82005-05-05 16:16:09 -07001096static struct buffer_head *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001097__getblk_slow(struct block_device *bdev, sector_t block, int size)
1098{
1099 /* Size must be multiple of hard sectorsize */
Martin K. Petersene1defc42009-05-22 17:17:49 -04001100 if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
Linus Torvalds1da177e2005-04-16 15:20:36 -07001101 (size < 512 || size > PAGE_SIZE))) {
1102 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1103 size);
Martin K. Petersene1defc42009-05-22 17:17:49 -04001104 printk(KERN_ERR "logical block size: %d\n",
1105 bdev_logical_block_size(bdev));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001106
1107 dump_stack();
1108 return NULL;
1109 }
1110
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001111 for (;;) {
1112 struct buffer_head *bh;
1113 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001114
1115 bh = __find_get_block(bdev, block, size);
1116 if (bh)
1117 return bh;
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001118
1119 ret = grow_buffers(bdev, block, size);
1120 if (ret < 0)
1121 return NULL;
1122 if (ret == 0)
1123 free_more_memory();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001124 }
1125}
1126
1127/*
1128 * The relationship between dirty buffers and dirty pages:
1129 *
1130 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1131 * the page is tagged dirty in its radix tree.
1132 *
1133 * At all times, the dirtiness of the buffers represents the dirtiness of
1134 * subsections of the page. If the page has buffers, the page dirty bit is
1135 * merely a hint about the true dirty state.
1136 *
1137 * When a page is set dirty in its entirety, all its buffers are marked dirty
1138 * (if the page has buffers).
1139 *
1140 * When a buffer is marked dirty, its page is dirtied, but the page's other
1141 * buffers are not.
1142 *
1143 * Also. When blockdev buffers are explicitly read with bread(), they
1144 * individually become uptodate. But their backing page remains not
1145 * uptodate - even if all of its buffers are uptodate. A subsequent
1146 * block_read_full_page() against that page will discover all the uptodate
1147 * buffers, will set the page uptodate and will perform no I/O.
1148 */
1149
1150/**
1151 * mark_buffer_dirty - mark a buffer_head as needing writeout
Martin Waitz67be2dd2005-05-01 08:59:26 -07001152 * @bh: the buffer_head to mark dirty
Linus Torvalds1da177e2005-04-16 15:20:36 -07001153 *
1154 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1155 * backing page dirty, then tag the page as dirty in its address_space's radix
1156 * tree and then attach the address_space's inode to its superblock's dirty
1157 * inode list.
1158 *
1159 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
Dave Chinner250df6e2011-03-22 22:23:36 +11001160 * mapping->tree_lock and mapping->host->i_lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001161 */
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -08001162void mark_buffer_dirty(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001163{
Nick Piggin787d2212007-07-17 04:03:34 -07001164 WARN_ON_ONCE(!buffer_uptodate(bh));
Linus Torvalds1be62dc2008-04-04 14:38:17 -07001165
Tejun Heo5305cb82013-01-11 13:06:36 -08001166 trace_block_dirty_buffer(bh);
1167
Linus Torvalds1be62dc2008-04-04 14:38:17 -07001168 /*
1169 * Very *carefully* optimize the it-is-already-dirty case.
1170 *
1171 * Don't let the final "is it dirty" escape to before we
1172 * perhaps modified the buffer.
1173 */
1174 if (buffer_dirty(bh)) {
1175 smp_mb();
1176 if (buffer_dirty(bh))
1177 return;
1178 }
1179
Linus Torvaldsa8e7d492009-03-19 11:32:05 -07001180 if (!test_set_buffer_dirty(bh)) {
1181 struct page *page = bh->b_page;
Linus Torvalds8e9d78e2009-08-21 17:40:08 -07001182 if (!TestSetPageDirty(page)) {
1183 struct address_space *mapping = page_mapping(page);
1184 if (mapping)
1185 __set_page_dirty(page, mapping, 0);
1186 }
Linus Torvaldsa8e7d492009-03-19 11:32:05 -07001187 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001188}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07001189EXPORT_SYMBOL(mark_buffer_dirty);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001190
1191/*
1192 * Decrement a buffer_head's reference count. If all buffers against a page
1193 * have zero reference count, are clean and unlocked, and if the page is clean
1194 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1195 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1196 * a page but it ends up not being freed, and buffers may later be reattached).
1197 */
1198void __brelse(struct buffer_head * buf)
1199{
1200 if (atomic_read(&buf->b_count)) {
1201 put_bh(buf);
1202 return;
1203 }
Arjan van de Ven5c752ad2008-07-25 19:45:40 -07001204 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
Linus Torvalds1da177e2005-04-16 15:20:36 -07001205}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07001206EXPORT_SYMBOL(__brelse);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001207
1208/*
1209 * bforget() is like brelse(), except it discards any
1210 * potentially dirty data.
1211 */
1212void __bforget(struct buffer_head *bh)
1213{
1214 clear_buffer_dirty(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -08001215 if (bh->b_assoc_map) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001216 struct address_space *buffer_mapping = bh->b_page->mapping;
1217
1218 spin_lock(&buffer_mapping->private_lock);
1219 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -07001220 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001221 spin_unlock(&buffer_mapping->private_lock);
1222 }
1223 __brelse(bh);
1224}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07001225EXPORT_SYMBOL(__bforget);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001226
1227static struct buffer_head *__bread_slow(struct buffer_head *bh)
1228{
1229 lock_buffer(bh);
1230 if (buffer_uptodate(bh)) {
1231 unlock_buffer(bh);
1232 return bh;
1233 } else {
1234 get_bh(bh);
1235 bh->b_end_io = end_buffer_read_sync;
1236 submit_bh(READ, bh);
1237 wait_on_buffer(bh);
1238 if (buffer_uptodate(bh))
1239 return bh;
1240 }
1241 brelse(bh);
1242 return NULL;
1243}
1244
1245/*
1246 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1247 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1248 * refcount elevated by one when they're in an LRU. A buffer can only appear
1249 * once in a particular CPU's LRU. A single buffer can be present in multiple
1250 * CPU's LRUs at the same time.
1251 *
1252 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1253 * sb_find_get_block().
1254 *
1255 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1256 * a local interrupt disable for that.
1257 */
1258
1259#define BH_LRU_SIZE 8
1260
1261struct bh_lru {
1262 struct buffer_head *bhs[BH_LRU_SIZE];
1263};
1264
1265static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1266
1267#ifdef CONFIG_SMP
1268#define bh_lru_lock() local_irq_disable()
1269#define bh_lru_unlock() local_irq_enable()
1270#else
1271#define bh_lru_lock() preempt_disable()
1272#define bh_lru_unlock() preempt_enable()
1273#endif
1274
1275static inline void check_irqs_on(void)
1276{
1277#ifdef irqs_disabled
1278 BUG_ON(irqs_disabled());
1279#endif
1280}
1281
1282/*
1283 * The LRU management algorithm is dopey-but-simple. Sorry.
1284 */
1285static void bh_lru_install(struct buffer_head *bh)
1286{
1287 struct buffer_head *evictee = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001288
1289 check_irqs_on();
1290 bh_lru_lock();
Christoph Lameterc7b92512010-12-06 11:16:28 -06001291 if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001292 struct buffer_head *bhs[BH_LRU_SIZE];
1293 int in;
1294 int out = 0;
1295
1296 get_bh(bh);
1297 bhs[out++] = bh;
1298 for (in = 0; in < BH_LRU_SIZE; in++) {
Christoph Lameterc7b92512010-12-06 11:16:28 -06001299 struct buffer_head *bh2 =
1300 __this_cpu_read(bh_lrus.bhs[in]);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001301
1302 if (bh2 == bh) {
1303 __brelse(bh2);
1304 } else {
1305 if (out >= BH_LRU_SIZE) {
1306 BUG_ON(evictee != NULL);
1307 evictee = bh2;
1308 } else {
1309 bhs[out++] = bh2;
1310 }
1311 }
1312 }
1313 while (out < BH_LRU_SIZE)
1314 bhs[out++] = NULL;
Christoph Lameterc7b92512010-12-06 11:16:28 -06001315 memcpy(__this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001316 }
1317 bh_lru_unlock();
1318
1319 if (evictee)
1320 __brelse(evictee);
1321}
1322
1323/*
1324 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1325 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001326static struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001327lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001328{
1329 struct buffer_head *ret = NULL;
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001330 unsigned int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001331
1332 check_irqs_on();
1333 bh_lru_lock();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001334 for (i = 0; i < BH_LRU_SIZE; i++) {
Christoph Lameterc7b92512010-12-06 11:16:28 -06001335 struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001336
1337 if (bh && bh->b_bdev == bdev &&
1338 bh->b_blocknr == block && bh->b_size == size) {
1339 if (i) {
1340 while (i) {
Christoph Lameterc7b92512010-12-06 11:16:28 -06001341 __this_cpu_write(bh_lrus.bhs[i],
1342 __this_cpu_read(bh_lrus.bhs[i - 1]));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001343 i--;
1344 }
Christoph Lameterc7b92512010-12-06 11:16:28 -06001345 __this_cpu_write(bh_lrus.bhs[0], bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001346 }
1347 get_bh(bh);
1348 ret = bh;
1349 break;
1350 }
1351 }
1352 bh_lru_unlock();
1353 return ret;
1354}
1355
1356/*
1357 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1358 * it in the LRU and mark it as accessed. If it is not present then return
1359 * NULL
1360 */
1361struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001362__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001363{
1364 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1365
1366 if (bh == NULL) {
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001367 bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001368 if (bh)
1369 bh_lru_install(bh);
1370 }
1371 if (bh)
1372 touch_buffer(bh);
1373 return bh;
1374}
1375EXPORT_SYMBOL(__find_get_block);
1376
1377/*
1378 * __getblk will locate (and, if necessary, create) the buffer_head
1379 * which corresponds to the passed block_device, block and size. The
1380 * returned buffer has its reference count incremented.
1381 *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001382 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1383 * attempt is failing. FIXME, perhaps?
1384 */
1385struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001386__getblk(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001387{
1388 struct buffer_head *bh = __find_get_block(bdev, block, size);
1389
1390 might_sleep();
1391 if (bh == NULL)
1392 bh = __getblk_slow(bdev, block, size);
1393 return bh;
1394}
1395EXPORT_SYMBOL(__getblk);
1396
1397/*
1398 * Do async read-ahead on a buffer..
1399 */
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001400void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001401{
1402 struct buffer_head *bh = __getblk(bdev, block, size);
Andrew Mortona3e713b2005-10-30 15:03:15 -08001403 if (likely(bh)) {
1404 ll_rw_block(READA, 1, &bh);
1405 brelse(bh);
1406 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001407}
1408EXPORT_SYMBOL(__breadahead);
1409
1410/**
1411 * __bread() - reads a specified block and returns the bh
Martin Waitz67be2dd2005-05-01 08:59:26 -07001412 * @bdev: the block_device to read from
Linus Torvalds1da177e2005-04-16 15:20:36 -07001413 * @block: number of block
1414 * @size: size (in bytes) to read
1415 *
1416 * Reads a specified block, and returns buffer head that contains it.
1417 * It returns NULL if the block was unreadable.
1418 */
1419struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001420__bread(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001421{
1422 struct buffer_head *bh = __getblk(bdev, block, size);
1423
Andrew Mortona3e713b2005-10-30 15:03:15 -08001424 if (likely(bh) && !buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001425 bh = __bread_slow(bh);
1426 return bh;
1427}
1428EXPORT_SYMBOL(__bread);
1429
1430/*
1431 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1432 * This doesn't race because it runs in each cpu either in irq
1433 * or with preempt disabled.
1434 */
1435static void invalidate_bh_lru(void *arg)
1436{
1437 struct bh_lru *b = &get_cpu_var(bh_lrus);
1438 int i;
1439
1440 for (i = 0; i < BH_LRU_SIZE; i++) {
1441 brelse(b->bhs[i]);
1442 b->bhs[i] = NULL;
1443 }
1444 put_cpu_var(bh_lrus);
1445}
Gilad Ben-Yossef42be35d2012-03-28 14:42:45 -07001446
1447static bool has_bh_in_lru(int cpu, void *dummy)
1448{
1449 struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1450 int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001451
Gilad Ben-Yossef42be35d2012-03-28 14:42:45 -07001452 for (i = 0; i < BH_LRU_SIZE; i++) {
1453 if (b->bhs[i])
1454 return 1;
1455 }
1456
1457 return 0;
1458}
1459
Peter Zijlstraf9a14392007-05-06 14:49:55 -07001460void invalidate_bh_lrus(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001461{
Gilad Ben-Yossef42be35d2012-03-28 14:42:45 -07001462 on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001463}
Nick Piggin9db55792008-02-08 04:19:49 -08001464EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001465
1466void set_bh_page(struct buffer_head *bh,
1467 struct page *page, unsigned long offset)
1468{
1469 bh->b_page = page;
Eric Sesterhenne827f922006-03-26 18:24:46 +02001470 BUG_ON(offset >= PAGE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001471 if (PageHighMem(page))
1472 /*
1473 * This catches illegal uses and preserves the offset:
1474 */
1475 bh->b_data = (char *)(0 + offset);
1476 else
1477 bh->b_data = page_address(page) + offset;
1478}
1479EXPORT_SYMBOL(set_bh_page);
1480
1481/*
1482 * Called when truncating a buffer on a page completely.
1483 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001484static void discard_buffer(struct buffer_head * bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001485{
1486 lock_buffer(bh);
1487 clear_buffer_dirty(bh);
1488 bh->b_bdev = NULL;
1489 clear_buffer_mapped(bh);
1490 clear_buffer_req(bh);
1491 clear_buffer_new(bh);
1492 clear_buffer_delay(bh);
David Chinner33a266d2007-02-12 00:51:41 -08001493 clear_buffer_unwritten(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001494 unlock_buffer(bh);
1495}
1496
1497/**
Wang Sheng-Hui814e1d22011-09-01 08:22:57 +08001498 * block_invalidatepage - invalidate part or all of a buffer-backed page
Linus Torvalds1da177e2005-04-16 15:20:36 -07001499 *
1500 * @page: the page which is affected
Lukas Czernerd47992f2013-05-21 23:17:23 -04001501 * @offset: start of the range to invalidate
1502 * @length: length of the range to invalidate
Linus Torvalds1da177e2005-04-16 15:20:36 -07001503 *
1504 * block_invalidatepage() is called when all or part of the page has become
Wang Sheng-Hui814e1d22011-09-01 08:22:57 +08001505 * invalidated by a truncate operation.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001506 *
1507 * block_invalidatepage() does not have to release all buffers, but it must
1508 * ensure that no dirty buffer is left outside @offset and that no I/O
1509 * is underway against any of the blocks which are outside the truncation
1510 * point. Because the caller is about to free (and possibly reuse) those
1511 * blocks on-disk.
1512 */
Lukas Czernerd47992f2013-05-21 23:17:23 -04001513void block_invalidatepage(struct page *page, unsigned int offset,
1514 unsigned int length)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001515{
1516 struct buffer_head *head, *bh, *next;
1517 unsigned int curr_off = 0;
Lukas Czernerd47992f2013-05-21 23:17:23 -04001518 unsigned int stop = length + offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001519
1520 BUG_ON(!PageLocked(page));
1521 if (!page_has_buffers(page))
1522 goto out;
1523
Lukas Czernerd47992f2013-05-21 23:17:23 -04001524 /*
1525 * Check for overflow
1526 */
1527 BUG_ON(stop > PAGE_CACHE_SIZE || stop < length);
1528
Linus Torvalds1da177e2005-04-16 15:20:36 -07001529 head = page_buffers(page);
1530 bh = head;
1531 do {
1532 unsigned int next_off = curr_off + bh->b_size;
1533 next = bh->b_this_page;
1534
1535 /*
Lukas Czernerd47992f2013-05-21 23:17:23 -04001536 * Are we still fully in range ?
1537 */
1538 if (next_off > stop)
1539 goto out;
1540
1541 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001542 * is this block fully invalidated?
1543 */
1544 if (offset <= curr_off)
1545 discard_buffer(bh);
1546 curr_off = next_off;
1547 bh = next;
1548 } while (bh != head);
1549
1550 /*
1551 * We release buffers only if the entire page is being invalidated.
1552 * The get_block cached value has been unconditionally invalidated,
1553 * so real IO is not possible anymore.
1554 */
1555 if (offset == 0)
NeilBrown2ff28e22006-03-26 01:37:18 -08001556 try_to_release_page(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001557out:
NeilBrown2ff28e22006-03-26 01:37:18 -08001558 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001559}
1560EXPORT_SYMBOL(block_invalidatepage);
1561
Lukas Czernerd47992f2013-05-21 23:17:23 -04001562
Linus Torvalds1da177e2005-04-16 15:20:36 -07001563/*
1564 * We attach and possibly dirty the buffers atomically wrt
1565 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1566 * is already excluded via the page lock.
1567 */
1568void create_empty_buffers(struct page *page,
1569 unsigned long blocksize, unsigned long b_state)
1570{
1571 struct buffer_head *bh, *head, *tail;
1572
1573 head = alloc_page_buffers(page, blocksize, 1);
1574 bh = head;
1575 do {
1576 bh->b_state |= b_state;
1577 tail = bh;
1578 bh = bh->b_this_page;
1579 } while (bh);
1580 tail->b_this_page = head;
1581
1582 spin_lock(&page->mapping->private_lock);
1583 if (PageUptodate(page) || PageDirty(page)) {
1584 bh = head;
1585 do {
1586 if (PageDirty(page))
1587 set_buffer_dirty(bh);
1588 if (PageUptodate(page))
1589 set_buffer_uptodate(bh);
1590 bh = bh->b_this_page;
1591 } while (bh != head);
1592 }
1593 attach_page_buffers(page, head);
1594 spin_unlock(&page->mapping->private_lock);
1595}
1596EXPORT_SYMBOL(create_empty_buffers);
1597
1598/*
1599 * We are taking a block for data and we don't want any output from any
1600 * buffer-cache aliases starting from return from that function and
1601 * until the moment when something will explicitly mark the buffer
1602 * dirty (hopefully that will not happen until we will free that block ;-)
1603 * We don't even need to mark it not-uptodate - nobody can expect
1604 * anything from a newly allocated buffer anyway. We used to used
1605 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1606 * don't want to mark the alias unmapped, for example - it would confuse
1607 * anyone who might pick it with bread() afterwards...
1608 *
1609 * Also.. Note that bforget() doesn't lock the buffer. So there can
1610 * be writeout I/O going on against recently-freed buffers. We don't
1611 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1612 * only if we really need to. That happens here.
1613 */
1614void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1615{
1616 struct buffer_head *old_bh;
1617
1618 might_sleep();
1619
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001620 old_bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001621 if (old_bh) {
1622 clear_buffer_dirty(old_bh);
1623 wait_on_buffer(old_bh);
1624 clear_buffer_req(old_bh);
1625 __brelse(old_bh);
1626 }
1627}
1628EXPORT_SYMBOL(unmap_underlying_metadata);
1629
1630/*
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001631 * Size is a power-of-two in the range 512..PAGE_SIZE,
1632 * and the case we care about most is PAGE_SIZE.
1633 *
1634 * So this *could* possibly be written with those
1635 * constraints in mind (relevant mostly if some
1636 * architecture has a slow bit-scan instruction)
1637 */
1638static inline int block_size_bits(unsigned int blocksize)
1639{
1640 return ilog2(blocksize);
1641}
1642
1643static struct buffer_head *create_page_buffers(struct page *page, struct inode *inode, unsigned int b_state)
1644{
1645 BUG_ON(!PageLocked(page));
1646
1647 if (!page_has_buffers(page))
1648 create_empty_buffers(page, 1 << ACCESS_ONCE(inode->i_blkbits), b_state);
1649 return page_buffers(page);
1650}
1651
1652/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001653 * NOTE! All mapped/uptodate combinations are valid:
1654 *
1655 * Mapped Uptodate Meaning
1656 *
1657 * No No "unknown" - must do get_block()
1658 * No Yes "hole" - zero-filled
1659 * Yes No "allocated" - allocated on disk, not read in
1660 * Yes Yes "valid" - allocated and up-to-date in memory.
1661 *
1662 * "Dirty" is valid only with the last case (mapped+uptodate).
1663 */
1664
1665/*
1666 * While block_write_full_page is writing back the dirty buffers under
1667 * the page lock, whoever dirtied the buffers may decide to clean them
1668 * again at any time. We handle that by only looking at the buffer
1669 * state inside lock_buffer().
1670 *
1671 * If block_write_full_page() is called for regular writeback
1672 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1673 * locked buffer. This only can happen if someone has written the buffer
1674 * directly, with submit_bh(). At the address_space level PageWriteback
1675 * prevents this contention from occurring.
Theodore Ts'o6e34eed2009-04-07 18:12:43 -04001676 *
1677 * If block_write_full_page() is called with wbc->sync_mode ==
Jens Axboe721a9602011-03-09 11:56:30 +01001678 * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this
1679 * causes the writes to be flagged as synchronous writes.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001680 */
1681static int __block_write_full_page(struct inode *inode, struct page *page,
Chris Mason35c80d52009-04-15 13:22:38 -04001682 get_block_t *get_block, struct writeback_control *wbc,
1683 bh_end_io_t *handler)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001684{
1685 int err;
1686 sector_t block;
1687 sector_t last_block;
Andrew Mortonf0fbd5f2005-05-05 16:15:48 -07001688 struct buffer_head *bh, *head;
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001689 unsigned int blocksize, bbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001690 int nr_underway = 0;
Theodore Ts'o6e34eed2009-04-07 18:12:43 -04001691 int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
Jens Axboe721a9602011-03-09 11:56:30 +01001692 WRITE_SYNC : WRITE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001693
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001694 head = create_page_buffers(page, inode,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001695 (1 << BH_Dirty)|(1 << BH_Uptodate));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001696
1697 /*
1698 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1699 * here, and the (potentially unmapped) buffers may become dirty at
1700 * any time. If a buffer becomes dirty here after we've inspected it
1701 * then we just miss that fact, and the page stays dirty.
1702 *
1703 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1704 * handle that here by just cleaning them.
1705 */
1706
Linus Torvalds1da177e2005-04-16 15:20:36 -07001707 bh = head;
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001708 blocksize = bh->b_size;
1709 bbits = block_size_bits(blocksize);
1710
1711 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1712 last_block = (i_size_read(inode) - 1) >> bbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001713
1714 /*
1715 * Get all the dirty buffers mapped to disk addresses and
1716 * handle any aliases from the underlying blockdev's mapping.
1717 */
1718 do {
1719 if (block > last_block) {
1720 /*
1721 * mapped buffers outside i_size will occur, because
1722 * this page can be outside i_size when there is a
1723 * truncate in progress.
1724 */
1725 /*
1726 * The buffer was zeroed by block_write_full_page()
1727 */
1728 clear_buffer_dirty(bh);
1729 set_buffer_uptodate(bh);
Alex Tomas29a814d2008-07-11 19:27:31 -04001730 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1731 buffer_dirty(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001732 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001733 err = get_block(inode, block, bh, 1);
1734 if (err)
1735 goto recover;
Alex Tomas29a814d2008-07-11 19:27:31 -04001736 clear_buffer_delay(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001737 if (buffer_new(bh)) {
1738 /* blockdev mappings never come here */
1739 clear_buffer_new(bh);
1740 unmap_underlying_metadata(bh->b_bdev,
1741 bh->b_blocknr);
1742 }
1743 }
1744 bh = bh->b_this_page;
1745 block++;
1746 } while (bh != head);
1747
1748 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001749 if (!buffer_mapped(bh))
1750 continue;
1751 /*
1752 * If it's a fully non-blocking write attempt and we cannot
1753 * lock the buffer then redirty the page. Note that this can
Jens Axboe5b0830c2009-09-23 19:37:09 +02001754 * potentially cause a busy-wait loop from writeback threads
1755 * and kswapd activity, but those code paths have their own
1756 * higher-level throttling.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001757 */
Wu Fengguang1b430be2010-10-26 14:21:26 -07001758 if (wbc->sync_mode != WB_SYNC_NONE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001759 lock_buffer(bh);
Nick Pigginca5de402008-08-02 12:02:13 +02001760 } else if (!trylock_buffer(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001761 redirty_page_for_writepage(wbc, page);
1762 continue;
1763 }
1764 if (test_clear_buffer_dirty(bh)) {
Chris Mason35c80d52009-04-15 13:22:38 -04001765 mark_buffer_async_write_endio(bh, handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001766 } else {
1767 unlock_buffer(bh);
1768 }
1769 } while ((bh = bh->b_this_page) != head);
1770
1771 /*
1772 * The page and its buffers are protected by PageWriteback(), so we can
1773 * drop the bh refcounts early.
1774 */
1775 BUG_ON(PageWriteback(page));
1776 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001777
1778 do {
1779 struct buffer_head *next = bh->b_this_page;
1780 if (buffer_async_write(bh)) {
Theodore Ts'oa64c8612009-03-27 22:14:10 -04001781 submit_bh(write_op, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001782 nr_underway++;
1783 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001784 bh = next;
1785 } while (bh != head);
Andrew Morton05937ba2005-05-05 16:15:47 -07001786 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001787
1788 err = 0;
1789done:
1790 if (nr_underway == 0) {
1791 /*
1792 * The page was marked dirty, but the buffers were
1793 * clean. Someone wrote them back by hand with
1794 * ll_rw_block/submit_bh. A rare case.
1795 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001796 end_page_writeback(page);
Nick Piggin3d67f2d2007-05-06 14:49:05 -07001797
Linus Torvalds1da177e2005-04-16 15:20:36 -07001798 /*
1799 * The page and buffer_heads can be released at any time from
1800 * here on.
1801 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001802 }
1803 return err;
1804
1805recover:
1806 /*
1807 * ENOSPC, or some other error. We may already have added some
1808 * blocks to the file, so we need to write these out to avoid
1809 * exposing stale data.
1810 * The page is currently locked and not marked for writeback
1811 */
1812 bh = head;
1813 /* Recovery: lock and submit the mapped buffers */
1814 do {
Alex Tomas29a814d2008-07-11 19:27:31 -04001815 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1816 !buffer_delay(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001817 lock_buffer(bh);
Chris Mason35c80d52009-04-15 13:22:38 -04001818 mark_buffer_async_write_endio(bh, handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001819 } else {
1820 /*
1821 * The buffer may have been set dirty during
1822 * attachment to a dirty page.
1823 */
1824 clear_buffer_dirty(bh);
1825 }
1826 } while ((bh = bh->b_this_page) != head);
1827 SetPageError(page);
1828 BUG_ON(PageWriteback(page));
Andrew Morton7e4c3692007-05-08 00:23:27 -07001829 mapping_set_error(page->mapping, err);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001830 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001831 do {
1832 struct buffer_head *next = bh->b_this_page;
1833 if (buffer_async_write(bh)) {
1834 clear_buffer_dirty(bh);
Theodore Ts'oa64c8612009-03-27 22:14:10 -04001835 submit_bh(write_op, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001836 nr_underway++;
1837 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001838 bh = next;
1839 } while (bh != head);
Nick Pigginffda9d32007-02-20 13:57:54 -08001840 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001841 goto done;
1842}
1843
Nick Pigginafddba42007-10-16 01:25:01 -07001844/*
1845 * If a page has any new buffers, zero them out here, and mark them uptodate
1846 * and dirty so they'll be written out (in order to prevent uninitialised
1847 * block data from leaking). And clear the new bit.
1848 */
1849void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1850{
1851 unsigned int block_start, block_end;
1852 struct buffer_head *head, *bh;
1853
1854 BUG_ON(!PageLocked(page));
1855 if (!page_has_buffers(page))
1856 return;
1857
1858 bh = head = page_buffers(page);
1859 block_start = 0;
1860 do {
1861 block_end = block_start + bh->b_size;
1862
1863 if (buffer_new(bh)) {
1864 if (block_end > from && block_start < to) {
1865 if (!PageUptodate(page)) {
1866 unsigned start, size;
1867
1868 start = max(from, block_start);
1869 size = min(to, block_end) - start;
1870
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001871 zero_user(page, start, size);
Nick Pigginafddba42007-10-16 01:25:01 -07001872 set_buffer_uptodate(bh);
1873 }
1874
1875 clear_buffer_new(bh);
1876 mark_buffer_dirty(bh);
1877 }
1878 }
1879
1880 block_start = block_end;
1881 bh = bh->b_this_page;
1882 } while (bh != head);
1883}
1884EXPORT_SYMBOL(page_zero_new_buffers);
1885
Christoph Hellwigebdec242010-10-06 10:47:23 +02001886int __block_write_begin(struct page *page, loff_t pos, unsigned len,
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001887 get_block_t *get_block)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001888{
Christoph Hellwigebdec242010-10-06 10:47:23 +02001889 unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1890 unsigned to = from + len;
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001891 struct inode *inode = page->mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001892 unsigned block_start, block_end;
1893 sector_t block;
1894 int err = 0;
1895 unsigned blocksize, bbits;
1896 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1897
1898 BUG_ON(!PageLocked(page));
1899 BUG_ON(from > PAGE_CACHE_SIZE);
1900 BUG_ON(to > PAGE_CACHE_SIZE);
1901 BUG_ON(from > to);
1902
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001903 head = create_page_buffers(page, inode, 0);
1904 blocksize = head->b_size;
1905 bbits = block_size_bits(blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001906
Linus Torvalds1da177e2005-04-16 15:20:36 -07001907 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1908
1909 for(bh = head, block_start = 0; bh != head || !block_start;
1910 block++, block_start=block_end, bh = bh->b_this_page) {
1911 block_end = block_start + blocksize;
1912 if (block_end <= from || block_start >= to) {
1913 if (PageUptodate(page)) {
1914 if (!buffer_uptodate(bh))
1915 set_buffer_uptodate(bh);
1916 }
1917 continue;
1918 }
1919 if (buffer_new(bh))
1920 clear_buffer_new(bh);
1921 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001922 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001923 err = get_block(inode, block, bh, 1);
1924 if (err)
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001925 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001926 if (buffer_new(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001927 unmap_underlying_metadata(bh->b_bdev,
1928 bh->b_blocknr);
1929 if (PageUptodate(page)) {
Nick Piggin637aff42007-10-16 01:25:00 -07001930 clear_buffer_new(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001931 set_buffer_uptodate(bh);
Nick Piggin637aff42007-10-16 01:25:00 -07001932 mark_buffer_dirty(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001933 continue;
1934 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001935 if (block_end > to || block_start < from)
1936 zero_user_segments(page,
1937 to, block_end,
1938 block_start, from);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001939 continue;
1940 }
1941 }
1942 if (PageUptodate(page)) {
1943 if (!buffer_uptodate(bh))
1944 set_buffer_uptodate(bh);
1945 continue;
1946 }
1947 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
David Chinner33a266d2007-02-12 00:51:41 -08001948 !buffer_unwritten(bh) &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001949 (block_start < from || block_end > to)) {
1950 ll_rw_block(READ, 1, &bh);
1951 *wait_bh++=bh;
1952 }
1953 }
1954 /*
1955 * If we issued read requests - let them complete.
1956 */
1957 while(wait_bh > wait) {
1958 wait_on_buffer(*--wait_bh);
1959 if (!buffer_uptodate(*wait_bh))
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001960 err = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001961 }
Jan Karaf9f07b62011-06-14 00:58:27 +02001962 if (unlikely(err))
Nick Pigginafddba42007-10-16 01:25:01 -07001963 page_zero_new_buffers(page, from, to);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001964 return err;
1965}
Christoph Hellwigebdec242010-10-06 10:47:23 +02001966EXPORT_SYMBOL(__block_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001967
1968static int __block_commit_write(struct inode *inode, struct page *page,
1969 unsigned from, unsigned to)
1970{
1971 unsigned block_start, block_end;
1972 int partial = 0;
1973 unsigned blocksize;
1974 struct buffer_head *bh, *head;
1975
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001976 bh = head = page_buffers(page);
1977 blocksize = bh->b_size;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001978
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001979 block_start = 0;
1980 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001981 block_end = block_start + blocksize;
1982 if (block_end <= from || block_start >= to) {
1983 if (!buffer_uptodate(bh))
1984 partial = 1;
1985 } else {
1986 set_buffer_uptodate(bh);
1987 mark_buffer_dirty(bh);
1988 }
Nick Pigginafddba42007-10-16 01:25:01 -07001989 clear_buffer_new(bh);
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001990
1991 block_start = block_end;
1992 bh = bh->b_this_page;
1993 } while (bh != head);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001994
1995 /*
1996 * If this is a partial write which happened to make all buffers
1997 * uptodate then we can optimize away a bogus readpage() for
1998 * the next read(). Here we 'discover' whether the page went
1999 * uptodate as a result of this (potentially partial) write.
2000 */
2001 if (!partial)
2002 SetPageUptodate(page);
2003 return 0;
2004}
2005
2006/*
Christoph Hellwig155130a2010-06-04 11:29:58 +02002007 * block_write_begin takes care of the basic task of block allocation and
2008 * bringing partial write blocks uptodate first.
2009 *
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10002010 * The filesystem needs to handle block truncation upon failure.
Nick Pigginafddba42007-10-16 01:25:01 -07002011 */
Christoph Hellwig155130a2010-06-04 11:29:58 +02002012int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
2013 unsigned flags, struct page **pagep, get_block_t *get_block)
Nick Pigginafddba42007-10-16 01:25:01 -07002014{
Christoph Hellwig6e1db882010-06-04 11:29:57 +02002015 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
Nick Pigginafddba42007-10-16 01:25:01 -07002016 struct page *page;
Christoph Hellwig6e1db882010-06-04 11:29:57 +02002017 int status;
Nick Pigginafddba42007-10-16 01:25:01 -07002018
Christoph Hellwig6e1db882010-06-04 11:29:57 +02002019 page = grab_cache_page_write_begin(mapping, index, flags);
2020 if (!page)
2021 return -ENOMEM;
Nick Pigginafddba42007-10-16 01:25:01 -07002022
Christoph Hellwig6e1db882010-06-04 11:29:57 +02002023 status = __block_write_begin(page, pos, len, get_block);
Nick Pigginafddba42007-10-16 01:25:01 -07002024 if (unlikely(status)) {
Christoph Hellwig6e1db882010-06-04 11:29:57 +02002025 unlock_page(page);
2026 page_cache_release(page);
2027 page = NULL;
Nick Pigginafddba42007-10-16 01:25:01 -07002028 }
2029
Christoph Hellwig6e1db882010-06-04 11:29:57 +02002030 *pagep = page;
Nick Pigginafddba42007-10-16 01:25:01 -07002031 return status;
2032}
2033EXPORT_SYMBOL(block_write_begin);
2034
2035int block_write_end(struct file *file, struct address_space *mapping,
2036 loff_t pos, unsigned len, unsigned copied,
2037 struct page *page, void *fsdata)
2038{
2039 struct inode *inode = mapping->host;
2040 unsigned start;
2041
2042 start = pos & (PAGE_CACHE_SIZE - 1);
2043
2044 if (unlikely(copied < len)) {
2045 /*
2046 * The buffers that were written will now be uptodate, so we
2047 * don't have to worry about a readpage reading them and
2048 * overwriting a partial write. However if we have encountered
2049 * a short write and only partially written into a buffer, it
2050 * will not be marked uptodate, so a readpage might come in and
2051 * destroy our partial write.
2052 *
2053 * Do the simplest thing, and just treat any short write to a
2054 * non uptodate page as a zero-length write, and force the
2055 * caller to redo the whole thing.
2056 */
2057 if (!PageUptodate(page))
2058 copied = 0;
2059
2060 page_zero_new_buffers(page, start+copied, start+len);
2061 }
2062 flush_dcache_page(page);
2063
2064 /* This could be a short (even 0-length) commit */
2065 __block_commit_write(inode, page, start, start+copied);
2066
2067 return copied;
2068}
2069EXPORT_SYMBOL(block_write_end);
2070
2071int generic_write_end(struct file *file, struct address_space *mapping,
2072 loff_t pos, unsigned len, unsigned copied,
2073 struct page *page, void *fsdata)
2074{
2075 struct inode *inode = mapping->host;
Jan Karac7d206b2008-07-11 19:27:31 -04002076 int i_size_changed = 0;
Nick Pigginafddba42007-10-16 01:25:01 -07002077
2078 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2079
2080 /*
2081 * No need to use i_size_read() here, the i_size
2082 * cannot change under us because we hold i_mutex.
2083 *
2084 * But it's important to update i_size while still holding page lock:
2085 * page writeout could otherwise come in and zero beyond i_size.
2086 */
2087 if (pos+copied > inode->i_size) {
2088 i_size_write(inode, pos+copied);
Jan Karac7d206b2008-07-11 19:27:31 -04002089 i_size_changed = 1;
Nick Pigginafddba42007-10-16 01:25:01 -07002090 }
2091
2092 unlock_page(page);
2093 page_cache_release(page);
2094
Jan Karac7d206b2008-07-11 19:27:31 -04002095 /*
2096 * Don't mark the inode dirty under page lock. First, it unnecessarily
2097 * makes the holding time of page lock longer. Second, it forces lock
2098 * ordering of page lock and transaction start for journaling
2099 * filesystems.
2100 */
2101 if (i_size_changed)
2102 mark_inode_dirty(inode);
2103
Nick Pigginafddba42007-10-16 01:25:01 -07002104 return copied;
2105}
2106EXPORT_SYMBOL(generic_write_end);
2107
2108/*
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07002109 * block_is_partially_uptodate checks whether buffers within a page are
2110 * uptodate or not.
2111 *
2112 * Returns true if all buffers which correspond to a file portion
2113 * we want to read are uptodate.
2114 */
2115int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
2116 unsigned long from)
2117{
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07002118 unsigned block_start, block_end, blocksize;
2119 unsigned to;
2120 struct buffer_head *bh, *head;
2121 int ret = 1;
2122
2123 if (!page_has_buffers(page))
2124 return 0;
2125
Linus Torvalds45bce8f2012-11-29 10:21:43 -08002126 head = page_buffers(page);
2127 blocksize = head->b_size;
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07002128 to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count);
2129 to = from + to;
2130 if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
2131 return 0;
2132
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07002133 bh = head;
2134 block_start = 0;
2135 do {
2136 block_end = block_start + blocksize;
2137 if (block_end > from && block_start < to) {
2138 if (!buffer_uptodate(bh)) {
2139 ret = 0;
2140 break;
2141 }
2142 if (block_end >= to)
2143 break;
2144 }
2145 block_start = block_end;
2146 bh = bh->b_this_page;
2147 } while (bh != head);
2148
2149 return ret;
2150}
2151EXPORT_SYMBOL(block_is_partially_uptodate);
2152
2153/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002154 * Generic "read page" function for block devices that have the normal
2155 * get_block functionality. This is most of the block device filesystems.
2156 * Reads the page asynchronously --- the unlock_buffer() and
2157 * set/clear_buffer_uptodate() functions propagate buffer state into the
2158 * page struct once IO has completed.
2159 */
2160int block_read_full_page(struct page *page, get_block_t *get_block)
2161{
2162 struct inode *inode = page->mapping->host;
2163 sector_t iblock, lblock;
2164 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
Linus Torvalds45bce8f2012-11-29 10:21:43 -08002165 unsigned int blocksize, bbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002166 int nr, i;
2167 int fully_mapped = 1;
2168
Linus Torvalds45bce8f2012-11-29 10:21:43 -08002169 head = create_page_buffers(page, inode, 0);
2170 blocksize = head->b_size;
2171 bbits = block_size_bits(blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002172
Linus Torvalds45bce8f2012-11-29 10:21:43 -08002173 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
2174 lblock = (i_size_read(inode)+blocksize-1) >> bbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002175 bh = head;
2176 nr = 0;
2177 i = 0;
2178
2179 do {
2180 if (buffer_uptodate(bh))
2181 continue;
2182
2183 if (!buffer_mapped(bh)) {
Andrew Mortonc64610b2005-05-16 21:53:49 -07002184 int err = 0;
2185
Linus Torvalds1da177e2005-04-16 15:20:36 -07002186 fully_mapped = 0;
2187 if (iblock < lblock) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002188 WARN_ON(bh->b_size != blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002189 err = get_block(inode, iblock, bh, 0);
2190 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002191 SetPageError(page);
2192 }
2193 if (!buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002194 zero_user(page, i * blocksize, blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002195 if (!err)
2196 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002197 continue;
2198 }
2199 /*
2200 * get_block() might have updated the buffer
2201 * synchronously
2202 */
2203 if (buffer_uptodate(bh))
2204 continue;
2205 }
2206 arr[nr++] = bh;
2207 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2208
2209 if (fully_mapped)
2210 SetPageMappedToDisk(page);
2211
2212 if (!nr) {
2213 /*
2214 * All buffers are uptodate - we can set the page uptodate
2215 * as well. But not if get_block() returned an error.
2216 */
2217 if (!PageError(page))
2218 SetPageUptodate(page);
2219 unlock_page(page);
2220 return 0;
2221 }
2222
2223 /* Stage two: lock the buffers */
2224 for (i = 0; i < nr; i++) {
2225 bh = arr[i];
2226 lock_buffer(bh);
2227 mark_buffer_async_read(bh);
2228 }
2229
2230 /*
2231 * Stage 3: start the IO. Check for uptodateness
2232 * inside the buffer lock in case another process reading
2233 * the underlying blockdev brought it uptodate (the sct fix).
2234 */
2235 for (i = 0; i < nr; i++) {
2236 bh = arr[i];
2237 if (buffer_uptodate(bh))
2238 end_buffer_async_read(bh, 1);
2239 else
2240 submit_bh(READ, bh);
2241 }
2242 return 0;
2243}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002244EXPORT_SYMBOL(block_read_full_page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002245
2246/* utility function for filesystems that need to do work on expanding
Nick Piggin89e10782007-10-16 01:25:07 -07002247 * truncates. Uses filesystem pagecache writes to allow the filesystem to
Linus Torvalds1da177e2005-04-16 15:20:36 -07002248 * deal with the hole.
2249 */
Nick Piggin89e10782007-10-16 01:25:07 -07002250int generic_cont_expand_simple(struct inode *inode, loff_t size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002251{
2252 struct address_space *mapping = inode->i_mapping;
2253 struct page *page;
Nick Piggin89e10782007-10-16 01:25:07 -07002254 void *fsdata;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002255 int err;
2256
npiggin@suse.dec08d3b02009-08-21 02:35:06 +10002257 err = inode_newsize_ok(inode, size);
2258 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002259 goto out;
2260
Nick Piggin89e10782007-10-16 01:25:07 -07002261 err = pagecache_write_begin(NULL, mapping, size, 0,
2262 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2263 &page, &fsdata);
2264 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002265 goto out;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002266
Nick Piggin89e10782007-10-16 01:25:07 -07002267 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2268 BUG_ON(err > 0);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002269
Linus Torvalds1da177e2005-04-16 15:20:36 -07002270out:
2271 return err;
2272}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002273EXPORT_SYMBOL(generic_cont_expand_simple);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002274
Adrian Bunkf1e3af72008-04-29 00:59:01 -07002275static int cont_expand_zero(struct file *file, struct address_space *mapping,
2276 loff_t pos, loff_t *bytes)
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002277{
Nick Piggin89e10782007-10-16 01:25:07 -07002278 struct inode *inode = mapping->host;
2279 unsigned blocksize = 1 << inode->i_blkbits;
2280 struct page *page;
2281 void *fsdata;
2282 pgoff_t index, curidx;
2283 loff_t curpos;
2284 unsigned zerofrom, offset, len;
2285 int err = 0;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002286
Nick Piggin89e10782007-10-16 01:25:07 -07002287 index = pos >> PAGE_CACHE_SHIFT;
2288 offset = pos & ~PAGE_CACHE_MASK;
2289
2290 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
2291 zerofrom = curpos & ~PAGE_CACHE_MASK;
2292 if (zerofrom & (blocksize-1)) {
2293 *bytes |= (blocksize-1);
2294 (*bytes)++;
2295 }
2296 len = PAGE_CACHE_SIZE - zerofrom;
2297
2298 err = pagecache_write_begin(file, mapping, curpos, len,
2299 AOP_FLAG_UNINTERRUPTIBLE,
2300 &page, &fsdata);
2301 if (err)
2302 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002303 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002304 err = pagecache_write_end(file, mapping, curpos, len, len,
2305 page, fsdata);
2306 if (err < 0)
2307 goto out;
2308 BUG_ON(err != len);
2309 err = 0;
OGAWA Hirofumi061e9742008-04-28 02:16:28 -07002310
2311 balance_dirty_pages_ratelimited(mapping);
Nick Piggin89e10782007-10-16 01:25:07 -07002312 }
2313
2314 /* page covers the boundary, find the boundary offset */
2315 if (index == curidx) {
2316 zerofrom = curpos & ~PAGE_CACHE_MASK;
2317 /* if we will expand the thing last block will be filled */
2318 if (offset <= zerofrom) {
2319 goto out;
2320 }
2321 if (zerofrom & (blocksize-1)) {
2322 *bytes |= (blocksize-1);
2323 (*bytes)++;
2324 }
2325 len = offset - zerofrom;
2326
2327 err = pagecache_write_begin(file, mapping, curpos, len,
2328 AOP_FLAG_UNINTERRUPTIBLE,
2329 &page, &fsdata);
2330 if (err)
2331 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002332 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002333 err = pagecache_write_end(file, mapping, curpos, len, len,
2334 page, fsdata);
2335 if (err < 0)
2336 goto out;
2337 BUG_ON(err != len);
2338 err = 0;
2339 }
2340out:
2341 return err;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002342}
2343
Linus Torvalds1da177e2005-04-16 15:20:36 -07002344/*
2345 * For moronic filesystems that do not allow holes in file.
2346 * We may have to extend the file.
2347 */
Christoph Hellwig282dc172010-06-04 11:29:55 +02002348int cont_write_begin(struct file *file, struct address_space *mapping,
Nick Piggin89e10782007-10-16 01:25:07 -07002349 loff_t pos, unsigned len, unsigned flags,
2350 struct page **pagep, void **fsdata,
2351 get_block_t *get_block, loff_t *bytes)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002352{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002353 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002354 unsigned blocksize = 1 << inode->i_blkbits;
Nick Piggin89e10782007-10-16 01:25:07 -07002355 unsigned zerofrom;
2356 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002357
Nick Piggin89e10782007-10-16 01:25:07 -07002358 err = cont_expand_zero(file, mapping, pos, bytes);
2359 if (err)
Christoph Hellwig155130a2010-06-04 11:29:58 +02002360 return err;
Nick Piggin89e10782007-10-16 01:25:07 -07002361
2362 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2363 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2364 *bytes |= (blocksize-1);
2365 (*bytes)++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002366 }
2367
Christoph Hellwig155130a2010-06-04 11:29:58 +02002368 return block_write_begin(mapping, pos, len, flags, pagep, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002369}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002370EXPORT_SYMBOL(cont_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002371
Linus Torvalds1da177e2005-04-16 15:20:36 -07002372int block_commit_write(struct page *page, unsigned from, unsigned to)
2373{
2374 struct inode *inode = page->mapping->host;
2375 __block_commit_write(inode,page,from,to);
2376 return 0;
2377}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002378EXPORT_SYMBOL(block_commit_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002379
David Chinner54171692007-07-19 17:39:55 +10002380/*
2381 * block_page_mkwrite() is not allowed to change the file size as it gets
2382 * called from a page fault handler when a page is first dirtied. Hence we must
2383 * be careful to check for EOF conditions here. We set the page up correctly
2384 * for a written page which means we get ENOSPC checking when writing into
2385 * holes and correct delalloc and unwritten extent mapping on filesystems that
2386 * support these features.
2387 *
2388 * We are not allowed to take the i_mutex here so we have to play games to
2389 * protect against truncate races as the page could now be beyond EOF. Because
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10002390 * truncate writes the inode size before removing pages, once we have the
David Chinner54171692007-07-19 17:39:55 +10002391 * page lock we can determine safely if the page is beyond EOF. If it is not
2392 * beyond EOF, then the page is guaranteed safe against truncation until we
2393 * unlock the page.
Jan Karaea13a862011-05-24 00:23:35 +02002394 *
Jan Kara14da9202012-06-12 16:20:37 +02002395 * Direct callers of this function should protect against filesystem freezing
2396 * using sb_start_write() - sb_end_write() functions.
David Chinner54171692007-07-19 17:39:55 +10002397 */
Jan Kara24da4fa2011-05-24 00:23:34 +02002398int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2399 get_block_t get_block)
David Chinner54171692007-07-19 17:39:55 +10002400{
Nick Pigginc2ec1752009-03-31 15:23:21 -07002401 struct page *page = vmf->page;
Al Viro496ad9a2013-01-23 17:07:38 -05002402 struct inode *inode = file_inode(vma->vm_file);
David Chinner54171692007-07-19 17:39:55 +10002403 unsigned long end;
2404 loff_t size;
Jan Kara24da4fa2011-05-24 00:23:34 +02002405 int ret;
David Chinner54171692007-07-19 17:39:55 +10002406
2407 lock_page(page);
2408 size = i_size_read(inode);
2409 if ((page->mapping != inode->i_mapping) ||
Nick Piggin18336332007-07-20 00:31:45 -07002410 (page_offset(page) > size)) {
Jan Kara24da4fa2011-05-24 00:23:34 +02002411 /* We overload EFAULT to mean page got truncated */
2412 ret = -EFAULT;
2413 goto out_unlock;
David Chinner54171692007-07-19 17:39:55 +10002414 }
2415
2416 /* page is wholly or partially inside EOF */
2417 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
2418 end = size & ~PAGE_CACHE_MASK;
2419 else
2420 end = PAGE_CACHE_SIZE;
2421
Christoph Hellwigebdec242010-10-06 10:47:23 +02002422 ret = __block_write_begin(page, 0, end, get_block);
David Chinner54171692007-07-19 17:39:55 +10002423 if (!ret)
2424 ret = block_commit_write(page, 0, end);
2425
Jan Kara24da4fa2011-05-24 00:23:34 +02002426 if (unlikely(ret < 0))
2427 goto out_unlock;
Jan Karaea13a862011-05-24 00:23:35 +02002428 set_page_dirty(page);
Darrick J. Wong1d1d1a72013-02-21 16:42:51 -08002429 wait_for_stable_page(page);
Jan Kara24da4fa2011-05-24 00:23:34 +02002430 return 0;
2431out_unlock:
2432 unlock_page(page);
David Chinner54171692007-07-19 17:39:55 +10002433 return ret;
2434}
Jan Kara24da4fa2011-05-24 00:23:34 +02002435EXPORT_SYMBOL(__block_page_mkwrite);
2436
2437int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2438 get_block_t get_block)
2439{
Jan Karaea13a862011-05-24 00:23:35 +02002440 int ret;
Al Viro496ad9a2013-01-23 17:07:38 -05002441 struct super_block *sb = file_inode(vma->vm_file)->i_sb;
Jan Kara24da4fa2011-05-24 00:23:34 +02002442
Jan Kara14da9202012-06-12 16:20:37 +02002443 sb_start_pagefault(sb);
Theodore Ts'o041bbb6d2012-09-30 23:04:56 -04002444
2445 /*
2446 * Update file times before taking page lock. We may end up failing the
2447 * fault so this update may be superfluous but who really cares...
2448 */
2449 file_update_time(vma->vm_file);
2450
Jan Karaea13a862011-05-24 00:23:35 +02002451 ret = __block_page_mkwrite(vma, vmf, get_block);
Jan Kara14da9202012-06-12 16:20:37 +02002452 sb_end_pagefault(sb);
Jan Kara24da4fa2011-05-24 00:23:34 +02002453 return block_page_mkwrite_return(ret);
2454}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002455EXPORT_SYMBOL(block_page_mkwrite);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002456
2457/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002458 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
Linus Torvalds1da177e2005-04-16 15:20:36 -07002459 * immediately, while under the page lock. So it needs a special end_io
2460 * handler which does not touch the bh after unlocking it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002461 */
2462static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2463{
Dmitry Monakhov68671f32007-10-16 01:24:47 -07002464 __end_buffer_read_notouch(bh, uptodate);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002465}
2466
2467/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002468 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2469 * the page (converting it to circular linked list and taking care of page
2470 * dirty races).
2471 */
2472static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2473{
2474 struct buffer_head *bh;
2475
2476 BUG_ON(!PageLocked(page));
2477
2478 spin_lock(&page->mapping->private_lock);
2479 bh = head;
2480 do {
2481 if (PageDirty(page))
2482 set_buffer_dirty(bh);
2483 if (!bh->b_this_page)
2484 bh->b_this_page = head;
2485 bh = bh->b_this_page;
2486 } while (bh != head);
2487 attach_page_buffers(page, head);
2488 spin_unlock(&page->mapping->private_lock);
2489}
2490
2491/*
Christoph Hellwigea0f04e2010-06-04 11:29:54 +02002492 * On entry, the page is fully not uptodate.
2493 * On exit the page is fully uptodate in the areas outside (from,to)
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10002494 * The filesystem needs to handle block truncation upon failure.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002495 */
Christoph Hellwigea0f04e2010-06-04 11:29:54 +02002496int nobh_write_begin(struct address_space *mapping,
Nick Piggin03158cd2007-10-16 01:25:25 -07002497 loff_t pos, unsigned len, unsigned flags,
2498 struct page **pagep, void **fsdata,
Linus Torvalds1da177e2005-04-16 15:20:36 -07002499 get_block_t *get_block)
2500{
Nick Piggin03158cd2007-10-16 01:25:25 -07002501 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002502 const unsigned blkbits = inode->i_blkbits;
2503 const unsigned blocksize = 1 << blkbits;
Nick Piggina4b06722007-10-16 01:24:48 -07002504 struct buffer_head *head, *bh;
Nick Piggin03158cd2007-10-16 01:25:25 -07002505 struct page *page;
2506 pgoff_t index;
2507 unsigned from, to;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002508 unsigned block_in_page;
Nick Piggina4b06722007-10-16 01:24:48 -07002509 unsigned block_start, block_end;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002510 sector_t block_in_file;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002511 int nr_reads = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002512 int ret = 0;
2513 int is_mapped_to_disk = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002514
Nick Piggin03158cd2007-10-16 01:25:25 -07002515 index = pos >> PAGE_CACHE_SHIFT;
2516 from = pos & (PAGE_CACHE_SIZE - 1);
2517 to = from + len;
2518
Nick Piggin54566b22009-01-04 12:00:53 -08002519 page = grab_cache_page_write_begin(mapping, index, flags);
Nick Piggin03158cd2007-10-16 01:25:25 -07002520 if (!page)
2521 return -ENOMEM;
2522 *pagep = page;
2523 *fsdata = NULL;
2524
2525 if (page_has_buffers(page)) {
Namhyung Kim309f77a2010-10-25 15:01:12 +09002526 ret = __block_write_begin(page, pos, len, get_block);
2527 if (unlikely(ret))
2528 goto out_release;
2529 return ret;
Nick Piggin03158cd2007-10-16 01:25:25 -07002530 }
Nick Piggina4b06722007-10-16 01:24:48 -07002531
Linus Torvalds1da177e2005-04-16 15:20:36 -07002532 if (PageMappedToDisk(page))
2533 return 0;
2534
Nick Piggina4b06722007-10-16 01:24:48 -07002535 /*
2536 * Allocate buffers so that we can keep track of state, and potentially
2537 * attach them to the page if an error occurs. In the common case of
2538 * no error, they will just be freed again without ever being attached
2539 * to the page (which is all OK, because we're under the page lock).
2540 *
2541 * Be careful: the buffer linked list is a NULL terminated one, rather
2542 * than the circular one we're used to.
2543 */
2544 head = alloc_page_buffers(page, blocksize, 0);
Nick Piggin03158cd2007-10-16 01:25:25 -07002545 if (!head) {
2546 ret = -ENOMEM;
2547 goto out_release;
2548 }
Nick Piggina4b06722007-10-16 01:24:48 -07002549
Linus Torvalds1da177e2005-04-16 15:20:36 -07002550 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002551
2552 /*
2553 * We loop across all blocks in the page, whether or not they are
2554 * part of the affected region. This is so we can discover if the
2555 * page is fully mapped-to-disk.
2556 */
Nick Piggina4b06722007-10-16 01:24:48 -07002557 for (block_start = 0, block_in_page = 0, bh = head;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002558 block_start < PAGE_CACHE_SIZE;
Nick Piggina4b06722007-10-16 01:24:48 -07002559 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002560 int create;
2561
Nick Piggina4b06722007-10-16 01:24:48 -07002562 block_end = block_start + blocksize;
2563 bh->b_state = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002564 create = 1;
2565 if (block_start >= to)
2566 create = 0;
2567 ret = get_block(inode, block_in_file + block_in_page,
Nick Piggina4b06722007-10-16 01:24:48 -07002568 bh, create);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002569 if (ret)
2570 goto failed;
Nick Piggina4b06722007-10-16 01:24:48 -07002571 if (!buffer_mapped(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002572 is_mapped_to_disk = 0;
Nick Piggina4b06722007-10-16 01:24:48 -07002573 if (buffer_new(bh))
2574 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
2575 if (PageUptodate(page)) {
2576 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002577 continue;
Nick Piggina4b06722007-10-16 01:24:48 -07002578 }
2579 if (buffer_new(bh) || !buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002580 zero_user_segments(page, block_start, from,
2581 to, block_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002582 continue;
2583 }
Nick Piggina4b06722007-10-16 01:24:48 -07002584 if (buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002585 continue; /* reiserfs does this */
2586 if (block_start < from || block_end > to) {
Nick Piggina4b06722007-10-16 01:24:48 -07002587 lock_buffer(bh);
2588 bh->b_end_io = end_buffer_read_nobh;
2589 submit_bh(READ, bh);
2590 nr_reads++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002591 }
2592 }
2593
2594 if (nr_reads) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002595 /*
2596 * The page is locked, so these buffers are protected from
2597 * any VM or truncate activity. Hence we don't need to care
2598 * for the buffer_head refcounts.
2599 */
Nick Piggina4b06722007-10-16 01:24:48 -07002600 for (bh = head; bh; bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002601 wait_on_buffer(bh);
2602 if (!buffer_uptodate(bh))
2603 ret = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002604 }
2605 if (ret)
2606 goto failed;
2607 }
2608
2609 if (is_mapped_to_disk)
2610 SetPageMappedToDisk(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002611
Nick Piggin03158cd2007-10-16 01:25:25 -07002612 *fsdata = head; /* to be released by nobh_write_end */
Nick Piggina4b06722007-10-16 01:24:48 -07002613
Linus Torvalds1da177e2005-04-16 15:20:36 -07002614 return 0;
2615
2616failed:
Nick Piggin03158cd2007-10-16 01:25:25 -07002617 BUG_ON(!ret);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002618 /*
Nick Piggina4b06722007-10-16 01:24:48 -07002619 * Error recovery is a bit difficult. We need to zero out blocks that
2620 * were newly allocated, and dirty them to ensure they get written out.
2621 * Buffers need to be attached to the page at this point, otherwise
2622 * the handling of potential IO errors during writeout would be hard
2623 * (could try doing synchronous writeout, but what if that fails too?)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002624 */
Nick Piggin03158cd2007-10-16 01:25:25 -07002625 attach_nobh_buffers(page, head);
2626 page_zero_new_buffers(page, from, to);
Nick Piggina4b06722007-10-16 01:24:48 -07002627
Nick Piggin03158cd2007-10-16 01:25:25 -07002628out_release:
2629 unlock_page(page);
2630 page_cache_release(page);
2631 *pagep = NULL;
Nick Piggina4b06722007-10-16 01:24:48 -07002632
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10002633 return ret;
2634}
Nick Piggin03158cd2007-10-16 01:25:25 -07002635EXPORT_SYMBOL(nobh_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002636
Nick Piggin03158cd2007-10-16 01:25:25 -07002637int nobh_write_end(struct file *file, struct address_space *mapping,
2638 loff_t pos, unsigned len, unsigned copied,
2639 struct page *page, void *fsdata)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002640{
2641 struct inode *inode = page->mapping->host;
Nick Pigginefdc3132007-10-21 06:57:41 +02002642 struct buffer_head *head = fsdata;
Nick Piggin03158cd2007-10-16 01:25:25 -07002643 struct buffer_head *bh;
Dmitri Monakhov5b41e742008-03-28 14:15:52 -07002644 BUG_ON(fsdata != NULL && page_has_buffers(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002645
Dave Kleikampd4cf1092009-02-06 14:59:26 -06002646 if (unlikely(copied < len) && head)
Dmitri Monakhov5b41e742008-03-28 14:15:52 -07002647 attach_nobh_buffers(page, head);
2648 if (page_has_buffers(page))
2649 return generic_write_end(file, mapping, pos, len,
2650 copied, page, fsdata);
Nick Piggina4b06722007-10-16 01:24:48 -07002651
Nick Piggin22c8ca72007-02-20 13:58:09 -08002652 SetPageUptodate(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002653 set_page_dirty(page);
Nick Piggin03158cd2007-10-16 01:25:25 -07002654 if (pos+copied > inode->i_size) {
2655 i_size_write(inode, pos+copied);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002656 mark_inode_dirty(inode);
2657 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002658
2659 unlock_page(page);
2660 page_cache_release(page);
2661
Nick Piggin03158cd2007-10-16 01:25:25 -07002662 while (head) {
2663 bh = head;
2664 head = head->b_this_page;
2665 free_buffer_head(bh);
2666 }
2667
2668 return copied;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002669}
Nick Piggin03158cd2007-10-16 01:25:25 -07002670EXPORT_SYMBOL(nobh_write_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002671
2672/*
2673 * nobh_writepage() - based on block_full_write_page() except
2674 * that it tries to operate without attaching bufferheads to
2675 * the page.
2676 */
2677int nobh_writepage(struct page *page, get_block_t *get_block,
2678 struct writeback_control *wbc)
2679{
2680 struct inode * const inode = page->mapping->host;
2681 loff_t i_size = i_size_read(inode);
2682 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2683 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002684 int ret;
2685
2686 /* Is the page fully inside i_size? */
2687 if (page->index < end_index)
2688 goto out;
2689
2690 /* Is the page fully outside i_size? (truncate in progress) */
2691 offset = i_size & (PAGE_CACHE_SIZE-1);
2692 if (page->index >= end_index+1 || !offset) {
2693 /*
2694 * The page may have dirty, unmapped buffers. For example,
2695 * they may have been added in ext3_writepage(). Make them
2696 * freeable here, so the page does not leak.
2697 */
2698#if 0
2699 /* Not really sure about this - do we need this ? */
2700 if (page->mapping->a_ops->invalidatepage)
2701 page->mapping->a_ops->invalidatepage(page, offset);
2702#endif
2703 unlock_page(page);
2704 return 0; /* don't care */
2705 }
2706
2707 /*
2708 * The page straddles i_size. It must be zeroed out on each and every
2709 * writepage invocation because it may be mmapped. "A file is mapped
2710 * in multiples of the page size. For a file that is not a multiple of
2711 * the page size, the remaining memory is zeroed when mapped, and
2712 * writes to that region are not written out to the file."
2713 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002714 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002715out:
2716 ret = mpage_writepage(page, get_block, wbc);
2717 if (ret == -EAGAIN)
Chris Mason35c80d52009-04-15 13:22:38 -04002718 ret = __block_write_full_page(inode, page, get_block, wbc,
2719 end_buffer_async_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002720 return ret;
2721}
2722EXPORT_SYMBOL(nobh_writepage);
2723
Nick Piggin03158cd2007-10-16 01:25:25 -07002724int nobh_truncate_page(struct address_space *mapping,
2725 loff_t from, get_block_t *get_block)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002726{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002727 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2728 unsigned offset = from & (PAGE_CACHE_SIZE-1);
Nick Piggin03158cd2007-10-16 01:25:25 -07002729 unsigned blocksize;
2730 sector_t iblock;
2731 unsigned length, pos;
2732 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002733 struct page *page;
Nick Piggin03158cd2007-10-16 01:25:25 -07002734 struct buffer_head map_bh;
2735 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002736
Nick Piggin03158cd2007-10-16 01:25:25 -07002737 blocksize = 1 << inode->i_blkbits;
2738 length = offset & (blocksize - 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002739
Nick Piggin03158cd2007-10-16 01:25:25 -07002740 /* Block boundary? Nothing to do */
2741 if (!length)
2742 return 0;
2743
2744 length = blocksize - length;
2745 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2746
Linus Torvalds1da177e2005-04-16 15:20:36 -07002747 page = grab_cache_page(mapping, index);
Nick Piggin03158cd2007-10-16 01:25:25 -07002748 err = -ENOMEM;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002749 if (!page)
2750 goto out;
2751
Nick Piggin03158cd2007-10-16 01:25:25 -07002752 if (page_has_buffers(page)) {
2753has_buffers:
2754 unlock_page(page);
2755 page_cache_release(page);
2756 return block_truncate_page(mapping, from, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002757 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002758
2759 /* Find the buffer that contains "offset" */
2760 pos = blocksize;
2761 while (offset >= pos) {
2762 iblock++;
2763 pos += blocksize;
2764 }
2765
Theodore Ts'o460bcf52009-05-12 07:37:56 -04002766 map_bh.b_size = blocksize;
2767 map_bh.b_state = 0;
Nick Piggin03158cd2007-10-16 01:25:25 -07002768 err = get_block(inode, iblock, &map_bh, 0);
2769 if (err)
2770 goto unlock;
2771 /* unmapped? It's a hole - nothing to do */
2772 if (!buffer_mapped(&map_bh))
2773 goto unlock;
2774
2775 /* Ok, it's mapped. Make sure it's up-to-date */
2776 if (!PageUptodate(page)) {
2777 err = mapping->a_ops->readpage(NULL, page);
2778 if (err) {
2779 page_cache_release(page);
2780 goto out;
2781 }
2782 lock_page(page);
2783 if (!PageUptodate(page)) {
2784 err = -EIO;
2785 goto unlock;
2786 }
2787 if (page_has_buffers(page))
2788 goto has_buffers;
2789 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002790 zero_user(page, offset, length);
Nick Piggin03158cd2007-10-16 01:25:25 -07002791 set_page_dirty(page);
2792 err = 0;
2793
2794unlock:
Linus Torvalds1da177e2005-04-16 15:20:36 -07002795 unlock_page(page);
2796 page_cache_release(page);
2797out:
Nick Piggin03158cd2007-10-16 01:25:25 -07002798 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002799}
2800EXPORT_SYMBOL(nobh_truncate_page);
2801
2802int block_truncate_page(struct address_space *mapping,
2803 loff_t from, get_block_t *get_block)
2804{
2805 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2806 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2807 unsigned blocksize;
Andrew Morton54b21a72006-01-08 01:03:05 -08002808 sector_t iblock;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002809 unsigned length, pos;
2810 struct inode *inode = mapping->host;
2811 struct page *page;
2812 struct buffer_head *bh;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002813 int err;
2814
2815 blocksize = 1 << inode->i_blkbits;
2816 length = offset & (blocksize - 1);
2817
2818 /* Block boundary? Nothing to do */
2819 if (!length)
2820 return 0;
2821
2822 length = blocksize - length;
Andrew Morton54b21a72006-01-08 01:03:05 -08002823 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002824
2825 page = grab_cache_page(mapping, index);
2826 err = -ENOMEM;
2827 if (!page)
2828 goto out;
2829
2830 if (!page_has_buffers(page))
2831 create_empty_buffers(page, blocksize, 0);
2832
2833 /* Find the buffer that contains "offset" */
2834 bh = page_buffers(page);
2835 pos = blocksize;
2836 while (offset >= pos) {
2837 bh = bh->b_this_page;
2838 iblock++;
2839 pos += blocksize;
2840 }
2841
2842 err = 0;
2843 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002844 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002845 err = get_block(inode, iblock, bh, 0);
2846 if (err)
2847 goto unlock;
2848 /* unmapped? It's a hole - nothing to do */
2849 if (!buffer_mapped(bh))
2850 goto unlock;
2851 }
2852
2853 /* Ok, it's mapped. Make sure it's up-to-date */
2854 if (PageUptodate(page))
2855 set_buffer_uptodate(bh);
2856
David Chinner33a266d2007-02-12 00:51:41 -08002857 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002858 err = -EIO;
2859 ll_rw_block(READ, 1, &bh);
2860 wait_on_buffer(bh);
2861 /* Uhhuh. Read error. Complain and punt. */
2862 if (!buffer_uptodate(bh))
2863 goto unlock;
2864 }
2865
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002866 zero_user(page, offset, length);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002867 mark_buffer_dirty(bh);
2868 err = 0;
2869
2870unlock:
2871 unlock_page(page);
2872 page_cache_release(page);
2873out:
2874 return err;
2875}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002876EXPORT_SYMBOL(block_truncate_page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002877
2878/*
2879 * The generic ->writepage function for buffer-backed address_spaces
Chris Mason35c80d52009-04-15 13:22:38 -04002880 * this form passes in the end_io handler used to finish the IO.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002881 */
Chris Mason35c80d52009-04-15 13:22:38 -04002882int block_write_full_page_endio(struct page *page, get_block_t *get_block,
2883 struct writeback_control *wbc, bh_end_io_t *handler)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002884{
2885 struct inode * const inode = page->mapping->host;
2886 loff_t i_size = i_size_read(inode);
2887 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2888 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002889
2890 /* Is the page fully inside i_size? */
2891 if (page->index < end_index)
Chris Mason35c80d52009-04-15 13:22:38 -04002892 return __block_write_full_page(inode, page, get_block, wbc,
2893 handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002894
2895 /* Is the page fully outside i_size? (truncate in progress) */
2896 offset = i_size & (PAGE_CACHE_SIZE-1);
2897 if (page->index >= end_index+1 || !offset) {
2898 /*
2899 * The page may have dirty, unmapped buffers. For example,
2900 * they may have been added in ext3_writepage(). Make them
2901 * freeable here, so the page does not leak.
2902 */
Lukas Czernerd47992f2013-05-21 23:17:23 -04002903 do_invalidatepage(page, 0, PAGE_CACHE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002904 unlock_page(page);
2905 return 0; /* don't care */
2906 }
2907
2908 /*
2909 * The page straddles i_size. It must be zeroed out on each and every
Adam Buchbinder2a61aa42009-12-11 16:35:40 -05002910 * writepage invocation because it may be mmapped. "A file is mapped
Linus Torvalds1da177e2005-04-16 15:20:36 -07002911 * in multiples of the page size. For a file that is not a multiple of
2912 * the page size, the remaining memory is zeroed when mapped, and
2913 * writes to that region are not written out to the file."
2914 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002915 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Chris Mason35c80d52009-04-15 13:22:38 -04002916 return __block_write_full_page(inode, page, get_block, wbc, handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002917}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002918EXPORT_SYMBOL(block_write_full_page_endio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002919
Chris Mason35c80d52009-04-15 13:22:38 -04002920/*
2921 * The generic ->writepage function for buffer-backed address_spaces
2922 */
2923int block_write_full_page(struct page *page, get_block_t *get_block,
2924 struct writeback_control *wbc)
2925{
2926 return block_write_full_page_endio(page, get_block, wbc,
2927 end_buffer_async_write);
2928}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002929EXPORT_SYMBOL(block_write_full_page);
Chris Mason35c80d52009-04-15 13:22:38 -04002930
Linus Torvalds1da177e2005-04-16 15:20:36 -07002931sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2932 get_block_t *get_block)
2933{
2934 struct buffer_head tmp;
2935 struct inode *inode = mapping->host;
2936 tmp.b_state = 0;
2937 tmp.b_blocknr = 0;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002938 tmp.b_size = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002939 get_block(inode, block, &tmp, 0);
2940 return tmp.b_blocknr;
2941}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002942EXPORT_SYMBOL(generic_block_bmap);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002943
NeilBrown6712ecf2007-09-27 12:47:43 +02002944static void end_bio_bh_io_sync(struct bio *bio, int err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002945{
2946 struct buffer_head *bh = bio->bi_private;
2947
Linus Torvalds1da177e2005-04-16 15:20:36 -07002948 if (err == -EOPNOTSUPP) {
2949 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002950 }
2951
Keith Mannthey08bafc02008-11-25 10:24:35 +01002952 if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags)))
2953 set_bit(BH_Quiet, &bh->b_state);
2954
Linus Torvalds1da177e2005-04-16 15:20:36 -07002955 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2956 bio_put(bio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002957}
2958
Linus Torvalds57302e02012-12-04 08:25:11 -08002959/*
2960 * This allows us to do IO even on the odd last sectors
2961 * of a device, even if the bh block size is some multiple
2962 * of the physical sector size.
2963 *
2964 * We'll just truncate the bio to the size of the device,
2965 * and clear the end of the buffer head manually.
2966 *
2967 * Truly out-of-range accesses will turn into actual IO
2968 * errors, this only handles the "we need to be able to
2969 * do IO at the final sector" case.
2970 */
2971static void guard_bh_eod(int rw, struct bio *bio, struct buffer_head *bh)
2972{
2973 sector_t maxsector;
2974 unsigned bytes;
2975
2976 maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
2977 if (!maxsector)
2978 return;
2979
2980 /*
2981 * If the *whole* IO is past the end of the device,
2982 * let it through, and the IO layer will turn it into
2983 * an EIO.
2984 */
2985 if (unlikely(bio->bi_sector >= maxsector))
2986 return;
2987
2988 maxsector -= bio->bi_sector;
2989 bytes = bio->bi_size;
2990 if (likely((bytes >> 9) <= maxsector))
2991 return;
2992
2993 /* Uhhuh. We've got a bh that straddles the device size! */
2994 bytes = maxsector << 9;
2995
2996 /* Truncate the bio.. */
2997 bio->bi_size = bytes;
2998 bio->bi_io_vec[0].bv_len = bytes;
2999
3000 /* ..and clear the end of the buffer for reads */
Dan Carpenter27d7c2a2012-12-05 20:01:24 +03003001 if ((rw & RW_MASK) == READ) {
Linus Torvalds57302e02012-12-04 08:25:11 -08003002 void *kaddr = kmap_atomic(bh->b_page);
3003 memset(kaddr + bh_offset(bh) + bytes, 0, bh->b_size - bytes);
3004 kunmap_atomic(kaddr);
Linus Torvalds6d283db2013-01-14 13:17:50 -08003005 flush_dcache_page(bh->b_page);
Linus Torvalds57302e02012-12-04 08:25:11 -08003006 }
3007}
3008
Darrick J. Wong7136851112013-04-29 15:07:25 -07003009int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003010{
3011 struct bio *bio;
3012 int ret = 0;
3013
3014 BUG_ON(!buffer_locked(bh));
3015 BUG_ON(!buffer_mapped(bh));
3016 BUG_ON(!bh->b_end_io);
Aneesh Kumar K.V8fb0e342009-05-12 16:22:37 -04003017 BUG_ON(buffer_delay(bh));
3018 BUG_ON(buffer_unwritten(bh));
Linus Torvalds1da177e2005-04-16 15:20:36 -07003019
Jens Axboe48fd4f92008-08-22 10:00:36 +02003020 /*
Jens Axboe48fd4f92008-08-22 10:00:36 +02003021 * Only clear out a write error when rewriting
Linus Torvalds1da177e2005-04-16 15:20:36 -07003022 */
Jens Axboe48fd4f92008-08-22 10:00:36 +02003023 if (test_set_buffer_req(bh) && (rw & WRITE))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003024 clear_buffer_write_io_error(bh);
3025
3026 /*
3027 * from here on down, it's all bio -- do the initial mapping,
3028 * submit_bio -> generic_make_request may further map this bio around
3029 */
3030 bio = bio_alloc(GFP_NOIO, 1);
3031
3032 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
3033 bio->bi_bdev = bh->b_bdev;
3034 bio->bi_io_vec[0].bv_page = bh->b_page;
3035 bio->bi_io_vec[0].bv_len = bh->b_size;
3036 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
3037
3038 bio->bi_vcnt = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003039 bio->bi_size = bh->b_size;
3040
3041 bio->bi_end_io = end_bio_bh_io_sync;
3042 bio->bi_private = bh;
Darrick J. Wong7136851112013-04-29 15:07:25 -07003043 bio->bi_flags |= bio_flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003044
Linus Torvalds57302e02012-12-04 08:25:11 -08003045 /* Take care of bh's that straddle the end of the device */
3046 guard_bh_eod(rw, bio, bh);
3047
Theodore Ts'o877f9622013-04-20 19:58:37 -04003048 if (buffer_meta(bh))
3049 rw |= REQ_META;
3050 if (buffer_prio(bh))
3051 rw |= REQ_PRIO;
3052
Linus Torvalds1da177e2005-04-16 15:20:36 -07003053 bio_get(bio);
3054 submit_bio(rw, bio);
3055
3056 if (bio_flagged(bio, BIO_EOPNOTSUPP))
3057 ret = -EOPNOTSUPP;
3058
3059 bio_put(bio);
3060 return ret;
3061}
Darrick J. Wong7136851112013-04-29 15:07:25 -07003062EXPORT_SYMBOL_GPL(_submit_bh);
3063
3064int submit_bh(int rw, struct buffer_head *bh)
3065{
3066 return _submit_bh(rw, bh, 0);
3067}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07003068EXPORT_SYMBOL(submit_bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003069
3070/**
3071 * ll_rw_block: low-level access to block devices (DEPRECATED)
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003072 * @rw: whether to %READ or %WRITE or maybe %READA (readahead)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003073 * @nr: number of &struct buffer_heads in the array
3074 * @bhs: array of pointers to &struct buffer_head
3075 *
Jan Karaa7662232005-09-06 15:19:10 -07003076 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
3077 * requests an I/O operation on them, either a %READ or a %WRITE. The third
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003078 * %READA option is described in the documentation for generic_make_request()
3079 * which ll_rw_block() calls.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003080 *
3081 * This function drops any buffer that it cannot get a lock on (with the
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003082 * BH_Lock state bit), any buffer that appears to be clean when doing a write
3083 * request, and any buffer that appears to be up-to-date when doing read
3084 * request. Further it marks as clean buffers that are processed for
3085 * writing (the buffer cache won't assume that they are actually clean
3086 * until the buffer gets unlocked).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003087 *
3088 * ll_rw_block sets b_end_io to simple completion handler that marks
3089 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
3090 * any waiters.
3091 *
3092 * All of the buffers must be for the same device, and must also be a
3093 * multiple of the current approved size for the device.
3094 */
3095void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
3096{
3097 int i;
3098
3099 for (i = 0; i < nr; i++) {
3100 struct buffer_head *bh = bhs[i];
3101
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003102 if (!trylock_buffer(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003103 continue;
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003104 if (rw == WRITE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003105 if (test_clear_buffer_dirty(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07003106 bh->b_end_io = end_buffer_write_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08003107 get_bh(bh);
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003108 submit_bh(WRITE, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003109 continue;
3110 }
3111 } else {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003112 if (!buffer_uptodate(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07003113 bh->b_end_io = end_buffer_read_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08003114 get_bh(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003115 submit_bh(rw, bh);
3116 continue;
3117 }
3118 }
3119 unlock_buffer(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003120 }
3121}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07003122EXPORT_SYMBOL(ll_rw_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003123
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003124void write_dirty_buffer(struct buffer_head *bh, int rw)
3125{
3126 lock_buffer(bh);
3127 if (!test_clear_buffer_dirty(bh)) {
3128 unlock_buffer(bh);
3129 return;
3130 }
3131 bh->b_end_io = end_buffer_write_sync;
3132 get_bh(bh);
3133 submit_bh(rw, bh);
3134}
3135EXPORT_SYMBOL(write_dirty_buffer);
3136
Linus Torvalds1da177e2005-04-16 15:20:36 -07003137/*
3138 * For a data-integrity writeout, we need to wait upon any in-progress I/O
3139 * and then start new I/O and then wait upon it. The caller must have a ref on
3140 * the buffer_head.
3141 */
Christoph Hellwig87e99512010-08-11 17:05:45 +02003142int __sync_dirty_buffer(struct buffer_head *bh, int rw)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003143{
3144 int ret = 0;
3145
3146 WARN_ON(atomic_read(&bh->b_count) < 1);
3147 lock_buffer(bh);
3148 if (test_clear_buffer_dirty(bh)) {
3149 get_bh(bh);
3150 bh->b_end_io = end_buffer_write_sync;
Christoph Hellwig87e99512010-08-11 17:05:45 +02003151 ret = submit_bh(rw, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003152 wait_on_buffer(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003153 if (!ret && !buffer_uptodate(bh))
3154 ret = -EIO;
3155 } else {
3156 unlock_buffer(bh);
3157 }
3158 return ret;
3159}
Christoph Hellwig87e99512010-08-11 17:05:45 +02003160EXPORT_SYMBOL(__sync_dirty_buffer);
3161
3162int sync_dirty_buffer(struct buffer_head *bh)
3163{
3164 return __sync_dirty_buffer(bh, WRITE_SYNC);
3165}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07003166EXPORT_SYMBOL(sync_dirty_buffer);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003167
3168/*
3169 * try_to_free_buffers() checks if all the buffers on this particular page
3170 * are unused, and releases them if so.
3171 *
3172 * Exclusion against try_to_free_buffers may be obtained by either
3173 * locking the page or by holding its mapping's private_lock.
3174 *
3175 * If the page is dirty but all the buffers are clean then we need to
3176 * be sure to mark the page clean as well. This is because the page
3177 * may be against a block device, and a later reattachment of buffers
3178 * to a dirty page will set *all* buffers dirty. Which would corrupt
3179 * filesystem data on the same device.
3180 *
3181 * The same applies to regular filesystem pages: if all the buffers are
3182 * clean then we set the page clean and proceed. To do that, we require
3183 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3184 * private_lock.
3185 *
3186 * try_to_free_buffers() is non-blocking.
3187 */
3188static inline int buffer_busy(struct buffer_head *bh)
3189{
3190 return atomic_read(&bh->b_count) |
3191 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3192}
3193
3194static int
3195drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3196{
3197 struct buffer_head *head = page_buffers(page);
3198 struct buffer_head *bh;
3199
3200 bh = head;
3201 do {
akpm@osdl.orgde7d5a32005-05-01 08:58:39 -07003202 if (buffer_write_io_error(bh) && page->mapping)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003203 set_bit(AS_EIO, &page->mapping->flags);
3204 if (buffer_busy(bh))
3205 goto failed;
3206 bh = bh->b_this_page;
3207 } while (bh != head);
3208
3209 do {
3210 struct buffer_head *next = bh->b_this_page;
3211
Jan Kara535ee2f2008-02-08 04:21:59 -08003212 if (bh->b_assoc_map)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003213 __remove_assoc_queue(bh);
3214 bh = next;
3215 } while (bh != head);
3216 *buffers_to_free = head;
3217 __clear_page_buffers(page);
3218 return 1;
3219failed:
3220 return 0;
3221}
3222
3223int try_to_free_buffers(struct page *page)
3224{
3225 struct address_space * const mapping = page->mapping;
3226 struct buffer_head *buffers_to_free = NULL;
3227 int ret = 0;
3228
3229 BUG_ON(!PageLocked(page));
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003230 if (PageWriteback(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003231 return 0;
3232
3233 if (mapping == NULL) { /* can this still happen? */
3234 ret = drop_buffers(page, &buffers_to_free);
3235 goto out;
3236 }
3237
3238 spin_lock(&mapping->private_lock);
3239 ret = drop_buffers(page, &buffers_to_free);
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003240
3241 /*
3242 * If the filesystem writes its buffers by hand (eg ext3)
3243 * then we can have clean buffers against a dirty page. We
3244 * clean the page here; otherwise the VM will never notice
3245 * that the filesystem did any IO at all.
3246 *
3247 * Also, during truncate, discard_buffer will have marked all
3248 * the page's buffers clean. We discover that here and clean
3249 * the page also.
Nick Piggin87df7242007-01-30 14:36:27 +11003250 *
3251 * private_lock must be held over this entire operation in order
3252 * to synchronise against __set_page_dirty_buffers and prevent the
3253 * dirty bit from being lost.
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003254 */
3255 if (ret)
3256 cancel_dirty_page(page, PAGE_CACHE_SIZE);
Nick Piggin87df7242007-01-30 14:36:27 +11003257 spin_unlock(&mapping->private_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003258out:
3259 if (buffers_to_free) {
3260 struct buffer_head *bh = buffers_to_free;
3261
3262 do {
3263 struct buffer_head *next = bh->b_this_page;
3264 free_buffer_head(bh);
3265 bh = next;
3266 } while (bh != buffers_to_free);
3267 }
3268 return ret;
3269}
3270EXPORT_SYMBOL(try_to_free_buffers);
3271
Linus Torvalds1da177e2005-04-16 15:20:36 -07003272/*
3273 * There are no bdflush tunables left. But distributions are
3274 * still running obsolete flush daemons, so we terminate them here.
3275 *
3276 * Use of bdflush() is deprecated and will be removed in a future kernel.
Jens Axboe5b0830c2009-09-23 19:37:09 +02003277 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003278 */
Heiko Carstensbdc480e2009-01-14 14:14:12 +01003279SYSCALL_DEFINE2(bdflush, int, func, long, data)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003280{
3281 static int msg_count;
3282
3283 if (!capable(CAP_SYS_ADMIN))
3284 return -EPERM;
3285
3286 if (msg_count < 5) {
3287 msg_count++;
3288 printk(KERN_INFO
3289 "warning: process `%s' used the obsolete bdflush"
3290 " system call\n", current->comm);
3291 printk(KERN_INFO "Fix your initscripts?\n");
3292 }
3293
3294 if (func == 1)
3295 do_exit(0);
3296 return 0;
3297}
3298
3299/*
3300 * Buffer-head allocation
3301 */
Shai Fultheima0a9b042012-05-15 12:29:52 +03003302static struct kmem_cache *bh_cachep __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003303
3304/*
3305 * Once the number of bh's in the machine exceeds this level, we start
3306 * stripping them in writeback.
3307 */
Zhang Yanfei43be5942013-02-22 16:35:46 -08003308static unsigned long max_buffer_heads;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003309
3310int buffer_heads_over_limit;
3311
3312struct bh_accounting {
3313 int nr; /* Number of live bh's */
3314 int ratelimit; /* Limit cacheline bouncing */
3315};
3316
3317static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3318
3319static void recalc_bh_state(void)
3320{
3321 int i;
3322 int tot = 0;
3323
Christoph Lameteree1be862010-12-06 11:40:05 -06003324 if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003325 return;
Christoph Lameterc7b92512010-12-06 11:16:28 -06003326 __this_cpu_write(bh_accounting.ratelimit, 0);
Eric Dumazet8a143422006-03-24 03:18:10 -08003327 for_each_online_cpu(i)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003328 tot += per_cpu(bh_accounting, i).nr;
3329 buffer_heads_over_limit = (tot > max_buffer_heads);
3330}
Christoph Lameterc7b92512010-12-06 11:16:28 -06003331
Al Virodd0fc662005-10-07 07:46:04 +01003332struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003333{
Richard Kennedy019b4d12010-03-10 15:20:33 -08003334 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003335 if (ret) {
Christoph Lametera35afb82007-05-16 22:10:57 -07003336 INIT_LIST_HEAD(&ret->b_assoc_buffers);
Christoph Lameterc7b92512010-12-06 11:16:28 -06003337 preempt_disable();
3338 __this_cpu_inc(bh_accounting.nr);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003339 recalc_bh_state();
Christoph Lameterc7b92512010-12-06 11:16:28 -06003340 preempt_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -07003341 }
3342 return ret;
3343}
3344EXPORT_SYMBOL(alloc_buffer_head);
3345
3346void free_buffer_head(struct buffer_head *bh)
3347{
3348 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3349 kmem_cache_free(bh_cachep, bh);
Christoph Lameterc7b92512010-12-06 11:16:28 -06003350 preempt_disable();
3351 __this_cpu_dec(bh_accounting.nr);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003352 recalc_bh_state();
Christoph Lameterc7b92512010-12-06 11:16:28 -06003353 preempt_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -07003354}
3355EXPORT_SYMBOL(free_buffer_head);
3356
Linus Torvalds1da177e2005-04-16 15:20:36 -07003357static void buffer_exit_cpu(int cpu)
3358{
3359 int i;
3360 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3361
3362 for (i = 0; i < BH_LRU_SIZE; i++) {
3363 brelse(b->bhs[i]);
3364 b->bhs[i] = NULL;
3365 }
Christoph Lameterc7b92512010-12-06 11:16:28 -06003366 this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
Eric Dumazet8a143422006-03-24 03:18:10 -08003367 per_cpu(bh_accounting, cpu).nr = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003368}
3369
3370static int buffer_cpu_notify(struct notifier_block *self,
3371 unsigned long action, void *hcpu)
3372{
Rafael J. Wysocki8bb78442007-05-09 02:35:10 -07003373 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003374 buffer_exit_cpu((unsigned long)hcpu);
3375 return NOTIFY_OK;
3376}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003377
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003378/**
Randy Dunlapa6b91912008-03-19 17:01:00 -07003379 * bh_uptodate_or_lock - Test whether the buffer is uptodate
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003380 * @bh: struct buffer_head
3381 *
3382 * Return true if the buffer is up-to-date and false,
3383 * with the buffer locked, if not.
3384 */
3385int bh_uptodate_or_lock(struct buffer_head *bh)
3386{
3387 if (!buffer_uptodate(bh)) {
3388 lock_buffer(bh);
3389 if (!buffer_uptodate(bh))
3390 return 0;
3391 unlock_buffer(bh);
3392 }
3393 return 1;
3394}
3395EXPORT_SYMBOL(bh_uptodate_or_lock);
3396
3397/**
Randy Dunlapa6b91912008-03-19 17:01:00 -07003398 * bh_submit_read - Submit a locked buffer for reading
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003399 * @bh: struct buffer_head
3400 *
3401 * Returns zero on success and -EIO on error.
3402 */
3403int bh_submit_read(struct buffer_head *bh)
3404{
3405 BUG_ON(!buffer_locked(bh));
3406
3407 if (buffer_uptodate(bh)) {
3408 unlock_buffer(bh);
3409 return 0;
3410 }
3411
3412 get_bh(bh);
3413 bh->b_end_io = end_buffer_read_sync;
3414 submit_bh(READ, bh);
3415 wait_on_buffer(bh);
3416 if (buffer_uptodate(bh))
3417 return 0;
3418 return -EIO;
3419}
3420EXPORT_SYMBOL(bh_submit_read);
3421
Linus Torvalds1da177e2005-04-16 15:20:36 -07003422void __init buffer_init(void)
3423{
Zhang Yanfei43be5942013-02-22 16:35:46 -08003424 unsigned long nrpages;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003425
Christoph Lameterb98938c2008-02-04 22:28:36 -08003426 bh_cachep = kmem_cache_create("buffer_head",
3427 sizeof(struct buffer_head), 0,
3428 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3429 SLAB_MEM_SPREAD),
Richard Kennedy019b4d12010-03-10 15:20:33 -08003430 NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003431
3432 /*
3433 * Limit the bh occupancy to 10% of ZONE_NORMAL
3434 */
3435 nrpages = (nr_free_buffer_pages() * 10) / 100;
3436 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3437 hotcpu_notifier(buffer_cpu_notify, 0);
3438}