blob: 3588a80854b27acb18d185d437662d03668eddae [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
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -080064void __lock_buffer(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -070065{
NeilBrown74316202014-07-07 15:16:04 +100066 wait_on_bit_lock_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
Linus Torvalds1da177e2005-04-16 15:20:36 -070067}
68EXPORT_SYMBOL(__lock_buffer);
69
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -080070void unlock_buffer(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -070071{
Nick Piggin51b07fc2008-10-18 20:27:00 -070072 clear_bit_unlock(BH_Lock, &bh->b_state);
Peter Zijlstra4e857c52014-03-17 18:06:10 +010073 smp_mb__after_atomic();
Linus Torvalds1da177e2005-04-16 15:20:36 -070074 wake_up_bit(&bh->b_state, BH_Lock);
75}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -070076EXPORT_SYMBOL(unlock_buffer);
Linus Torvalds1da177e2005-04-16 15:20:36 -070077
78/*
Mel Gormanb4597222013-07-03 15:02:05 -070079 * Returns if the page has dirty or writeback buffers. If all the buffers
80 * are unlocked and clean then the PageDirty information is stale. If
81 * any of the pages are locked, it is assumed they are locked for IO.
82 */
83void buffer_check_dirty_writeback(struct page *page,
84 bool *dirty, bool *writeback)
85{
86 struct buffer_head *head, *bh;
87 *dirty = false;
88 *writeback = false;
89
90 BUG_ON(!PageLocked(page));
91
92 if (!page_has_buffers(page))
93 return;
94
95 if (PageWriteback(page))
96 *writeback = true;
97
98 head = page_buffers(page);
99 bh = head;
100 do {
101 if (buffer_locked(bh))
102 *writeback = true;
103
104 if (buffer_dirty(bh))
105 *dirty = true;
106
107 bh = bh->b_this_page;
108 } while (bh != head);
109}
110EXPORT_SYMBOL(buffer_check_dirty_writeback);
111
112/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700113 * Block until a buffer comes unlocked. This doesn't stop it
114 * from becoming locked again - you have to lock it yourself
115 * if you want to preserve its state.
116 */
117void __wait_on_buffer(struct buffer_head * bh)
118{
NeilBrown74316202014-07-07 15:16:04 +1000119 wait_on_bit_io(&bh->b_state, BH_Lock, TASK_UNINTERRUPTIBLE);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700120}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700121EXPORT_SYMBOL(__wait_on_buffer);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700122
123static void
124__clear_page_buffers(struct page *page)
125{
126 ClearPagePrivate(page);
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700127 set_page_private(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700128 page_cache_release(page);
129}
130
Keith Mannthey08bafc02008-11-25 10:24:35 +0100131
132static int quiet_error(struct buffer_head *bh)
133{
134 if (!test_bit(BH_Quiet, &bh->b_state) && printk_ratelimit())
135 return 0;
136 return 1;
137}
138
139
Linus Torvalds1da177e2005-04-16 15:20:36 -0700140static void buffer_io_error(struct buffer_head *bh)
141{
142 char b[BDEVNAME_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700143 printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
144 bdevname(bh->b_bdev, b),
145 (unsigned long long)bh->b_blocknr);
146}
147
148/*
Dmitry Monakhov68671f32007-10-16 01:24:47 -0700149 * End-of-IO handler helper function which does not touch the bh after
150 * unlocking it.
151 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
152 * a race there is benign: unlock_buffer() only use the bh's address for
153 * hashing after unlocking the buffer, so it doesn't actually touch the bh
154 * itself.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700155 */
Dmitry Monakhov68671f32007-10-16 01:24:47 -0700156static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700157{
158 if (uptodate) {
159 set_buffer_uptodate(bh);
160 } else {
161 /* This happens, due to failed READA attempts. */
162 clear_buffer_uptodate(bh);
163 }
164 unlock_buffer(bh);
Dmitry Monakhov68671f32007-10-16 01:24:47 -0700165}
166
167/*
168 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
169 * unlock the buffer. This is what ll_rw_block uses too.
170 */
171void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
172{
173 __end_buffer_read_notouch(bh, uptodate);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700174 put_bh(bh);
175}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700176EXPORT_SYMBOL(end_buffer_read_sync);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700177
178void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
179{
180 char b[BDEVNAME_SIZE];
181
182 if (uptodate) {
183 set_buffer_uptodate(bh);
184 } else {
Christoph Hellwig0edd55f2010-08-18 05:29:23 -0400185 if (!quiet_error(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700186 buffer_io_error(bh);
187 printk(KERN_WARNING "lost page write due to "
188 "I/O error on %s\n",
189 bdevname(bh->b_bdev, b));
190 }
191 set_buffer_write_io_error(bh);
192 clear_buffer_uptodate(bh);
193 }
194 unlock_buffer(bh);
195 put_bh(bh);
196}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700197EXPORT_SYMBOL(end_buffer_write_sync);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700198
199/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700200 * Various filesystems appear to want __find_get_block to be non-blocking.
201 * But it's the page lock which protects the buffers. To get around this,
202 * we get exclusion from try_to_free_buffers with the blockdev mapping's
203 * private_lock.
204 *
205 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
206 * may be quite high. This code could TryLock the page, and if that
207 * succeeds, there is no need to take private_lock. (But if
208 * private_lock is contended then so is mapping->tree_lock).
209 */
210static struct buffer_head *
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -0800211__find_get_block_slow(struct block_device *bdev, sector_t block)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700212{
213 struct inode *bd_inode = bdev->bd_inode;
214 struct address_space *bd_mapping = bd_inode->i_mapping;
215 struct buffer_head *ret = NULL;
216 pgoff_t index;
217 struct buffer_head *bh;
218 struct buffer_head *head;
219 struct page *page;
220 int all_mapped = 1;
221
222 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
Mel Gorman2457aec2014-06-04 16:10:31 -0700223 page = find_get_page_flags(bd_mapping, index, FGP_ACCESSED);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700224 if (!page)
225 goto out;
226
227 spin_lock(&bd_mapping->private_lock);
228 if (!page_has_buffers(page))
229 goto out_unlock;
230 head = page_buffers(page);
231 bh = head;
232 do {
Nikanth Karthikesan97f76d32009-04-02 16:56:46 -0700233 if (!buffer_mapped(bh))
234 all_mapped = 0;
235 else if (bh->b_blocknr == block) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700236 ret = bh;
237 get_bh(bh);
238 goto out_unlock;
239 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700240 bh = bh->b_this_page;
241 } while (bh != head);
242
243 /* we might be here because some of the buffers on this page are
244 * not mapped. This is due to various races between
245 * file io on the block device and getblk. It gets dealt with
246 * elsewhere, don't buffer_error if we had some unmapped buffers
247 */
248 if (all_mapped) {
Tao Ma72a2ebd2011-10-31 17:09:00 -0700249 char b[BDEVNAME_SIZE];
250
Linus Torvalds1da177e2005-04-16 15:20:36 -0700251 printk("__find_get_block_slow() failed. "
252 "block=%llu, b_blocknr=%llu\n",
Badari Pulavarty205f87f2006-03-26 01:38:00 -0800253 (unsigned long long)block,
254 (unsigned long long)bh->b_blocknr);
255 printk("b_state=0x%08lx, b_size=%zu\n",
256 bh->b_state, bh->b_size);
Tao Ma72a2ebd2011-10-31 17:09:00 -0700257 printk("device %s blocksize: %d\n", bdevname(bdev, b),
258 1 << bd_inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700259 }
260out_unlock:
261 spin_unlock(&bd_mapping->private_lock);
262 page_cache_release(page);
263out:
264 return ret;
265}
266
Linus Torvalds1da177e2005-04-16 15:20:36 -0700267/*
Jens Axboe5b0830c2009-09-23 19:37:09 +0200268 * Kick the writeback threads then try to free up some ZONE_NORMAL memory.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700269 */
270static void free_more_memory(void)
271{
Mel Gorman19770b32008-04-28 02:12:18 -0700272 struct zone *zone;
Mel Gorman0e884602008-04-28 02:12:14 -0700273 int nid;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700274
Curt Wohlgemuth0e175a12011-10-07 21:54:10 -0600275 wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700276 yield();
277
Mel Gorman0e884602008-04-28 02:12:14 -0700278 for_each_online_node(nid) {
Mel Gorman19770b32008-04-28 02:12:18 -0700279 (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS),
280 gfp_zone(GFP_NOFS), NULL,
281 &zone);
282 if (zone)
Mel Gorman54a6eb52008-04-28 02:12:16 -0700283 try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0,
KAMEZAWA Hiroyuki327c0e92009-03-31 15:23:31 -0700284 GFP_NOFS, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700285 }
286}
287
288/*
289 * I/O completion handler for block_read_full_page() - pages
290 * which come unlocked at the end of I/O.
291 */
292static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
293{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700294 unsigned long flags;
Nick Piggina3972202005-07-07 17:56:56 -0700295 struct buffer_head *first;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700296 struct buffer_head *tmp;
297 struct page *page;
298 int page_uptodate = 1;
299
300 BUG_ON(!buffer_async_read(bh));
301
302 page = bh->b_page;
303 if (uptodate) {
304 set_buffer_uptodate(bh);
305 } else {
306 clear_buffer_uptodate(bh);
Keith Mannthey08bafc02008-11-25 10:24:35 +0100307 if (!quiet_error(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700308 buffer_io_error(bh);
309 SetPageError(page);
310 }
311
312 /*
313 * Be _very_ careful from here on. Bad things can happen if
314 * two buffer heads end IO at almost the same time and both
315 * decide that the page is now completely done.
316 */
Nick Piggina3972202005-07-07 17:56:56 -0700317 first = page_buffers(page);
318 local_irq_save(flags);
319 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700320 clear_buffer_async_read(bh);
321 unlock_buffer(bh);
322 tmp = bh;
323 do {
324 if (!buffer_uptodate(tmp))
325 page_uptodate = 0;
326 if (buffer_async_read(tmp)) {
327 BUG_ON(!buffer_locked(tmp));
328 goto still_busy;
329 }
330 tmp = tmp->b_this_page;
331 } while (tmp != bh);
Nick Piggina3972202005-07-07 17:56:56 -0700332 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
333 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700334
335 /*
336 * If none of the buffers had errors and they are all
337 * uptodate then we can set the page uptodate.
338 */
339 if (page_uptodate && !PageError(page))
340 SetPageUptodate(page);
341 unlock_page(page);
342 return;
343
344still_busy:
Nick Piggina3972202005-07-07 17:56:56 -0700345 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
346 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700347 return;
348}
349
350/*
351 * Completion handler for block_write_full_page() - pages which are unlocked
352 * during I/O, and which have PageWriteback cleared upon I/O completion.
353 */
Chris Mason35c80d52009-04-15 13:22:38 -0400354void end_buffer_async_write(struct buffer_head *bh, int uptodate)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700355{
356 char b[BDEVNAME_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700357 unsigned long flags;
Nick Piggina3972202005-07-07 17:56:56 -0700358 struct buffer_head *first;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700359 struct buffer_head *tmp;
360 struct page *page;
361
362 BUG_ON(!buffer_async_write(bh));
363
364 page = bh->b_page;
365 if (uptodate) {
366 set_buffer_uptodate(bh);
367 } else {
Keith Mannthey08bafc02008-11-25 10:24:35 +0100368 if (!quiet_error(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700369 buffer_io_error(bh);
370 printk(KERN_WARNING "lost page write due to "
371 "I/O error on %s\n",
372 bdevname(bh->b_bdev, b));
373 }
374 set_bit(AS_EIO, &page->mapping->flags);
Jan Kara58ff4072006-10-17 00:10:19 -0700375 set_buffer_write_io_error(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700376 clear_buffer_uptodate(bh);
377 SetPageError(page);
378 }
379
Nick Piggina3972202005-07-07 17:56:56 -0700380 first = page_buffers(page);
381 local_irq_save(flags);
382 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
383
Linus Torvalds1da177e2005-04-16 15:20:36 -0700384 clear_buffer_async_write(bh);
385 unlock_buffer(bh);
386 tmp = bh->b_this_page;
387 while (tmp != bh) {
388 if (buffer_async_write(tmp)) {
389 BUG_ON(!buffer_locked(tmp));
390 goto still_busy;
391 }
392 tmp = tmp->b_this_page;
393 }
Nick Piggina3972202005-07-07 17:56:56 -0700394 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
395 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700396 end_page_writeback(page);
397 return;
398
399still_busy:
Nick Piggina3972202005-07-07 17:56:56 -0700400 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
401 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700402 return;
403}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700404EXPORT_SYMBOL(end_buffer_async_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700405
406/*
407 * If a page's buffers are under async readin (end_buffer_async_read
408 * completion) then there is a possibility that another thread of
409 * control could lock one of the buffers after it has completed
410 * but while some of the other buffers have not completed. This
411 * locked buffer would confuse end_buffer_async_read() into not unlocking
412 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
413 * that this buffer is not under async I/O.
414 *
415 * The page comes unlocked when it has no locked buffer_async buffers
416 * left.
417 *
418 * PageLocked prevents anyone starting new async I/O reads any of
419 * the buffers.
420 *
421 * PageWriteback is used to prevent simultaneous writeout of the same
422 * page.
423 *
424 * PageLocked prevents anyone from starting writeback of a page which is
425 * under read I/O (PageWriteback is only ever set against a locked page).
426 */
427static void mark_buffer_async_read(struct buffer_head *bh)
428{
429 bh->b_end_io = end_buffer_async_read;
430 set_buffer_async_read(bh);
431}
432
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700433static void mark_buffer_async_write_endio(struct buffer_head *bh,
434 bh_end_io_t *handler)
Chris Mason35c80d52009-04-15 13:22:38 -0400435{
436 bh->b_end_io = handler;
437 set_buffer_async_write(bh);
438}
439
Linus Torvalds1da177e2005-04-16 15:20:36 -0700440void mark_buffer_async_write(struct buffer_head *bh)
441{
Chris Mason35c80d52009-04-15 13:22:38 -0400442 mark_buffer_async_write_endio(bh, end_buffer_async_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700443}
444EXPORT_SYMBOL(mark_buffer_async_write);
445
446
447/*
448 * fs/buffer.c contains helper functions for buffer-backed address space's
449 * fsync functions. A common requirement for buffer-based filesystems is
450 * that certain data from the backing blockdev needs to be written out for
451 * a successful fsync(). For example, ext2 indirect blocks need to be
452 * written back and waited upon before fsync() returns.
453 *
454 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
455 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
456 * management of a list of dependent buffers at ->i_mapping->private_list.
457 *
458 * Locking is a little subtle: try_to_free_buffers() will remove buffers
459 * from their controlling inode's queue when they are being freed. But
460 * try_to_free_buffers() will be operating against the *blockdev* mapping
461 * at the time, not against the S_ISREG file which depends on those buffers.
462 * So the locking for private_list is via the private_lock in the address_space
463 * which backs the buffers. Which is different from the address_space
464 * against which the buffers are listed. So for a particular address_space,
465 * mapping->private_lock does *not* protect mapping->private_list! In fact,
466 * mapping->private_list will always be protected by the backing blockdev's
467 * ->private_lock.
468 *
469 * Which introduces a requirement: all buffers on an address_space's
470 * ->private_list must be from the same address_space: the blockdev's.
471 *
472 * address_spaces which do not place buffers at ->private_list via these
473 * utility functions are free to use private_lock and private_list for
474 * whatever they want. The only requirement is that list_empty(private_list)
475 * be true at clear_inode() time.
476 *
477 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
478 * filesystems should do that. invalidate_inode_buffers() should just go
479 * BUG_ON(!list_empty).
480 *
481 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
482 * take an address_space, not an inode. And it should be called
483 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
484 * queued up.
485 *
486 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
487 * list if it is already on a list. Because if the buffer is on a list,
488 * it *must* already be on the right one. If not, the filesystem is being
489 * silly. This will save a ton of locking. But first we have to ensure
490 * that buffers are taken *off* the old inode's list when they are freed
491 * (presumably in truncate). That requires careful auditing of all
492 * filesystems (do it inside bforget()). It could also be done by bringing
493 * b_inode back.
494 */
495
496/*
497 * The buffer's backing address_space's private_lock must be held
498 */
Thomas Petazzonidbacefc2008-07-29 22:33:47 -0700499static void __remove_assoc_queue(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700500{
501 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -0700502 WARN_ON(!bh->b_assoc_map);
503 if (buffer_write_io_error(bh))
504 set_bit(AS_EIO, &bh->b_assoc_map->flags);
505 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700506}
507
508int inode_has_buffers(struct inode *inode)
509{
510 return !list_empty(&inode->i_data.private_list);
511}
512
513/*
514 * osync is designed to support O_SYNC io. It waits synchronously for
515 * all already-submitted IO to complete, but does not queue any new
516 * writes to the disk.
517 *
518 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
519 * you dirty the buffers, and then use osync_inode_buffers to wait for
520 * completion. Any other dirty buffers which are not yet queued for
521 * write will not be flushed to disk by the osync.
522 */
523static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
524{
525 struct buffer_head *bh;
526 struct list_head *p;
527 int err = 0;
528
529 spin_lock(lock);
530repeat:
531 list_for_each_prev(p, list) {
532 bh = BH_ENTRY(p);
533 if (buffer_locked(bh)) {
534 get_bh(bh);
535 spin_unlock(lock);
536 wait_on_buffer(bh);
537 if (!buffer_uptodate(bh))
538 err = -EIO;
539 brelse(bh);
540 spin_lock(lock);
541 goto repeat;
542 }
543 }
544 spin_unlock(lock);
545 return err;
546}
547
Al Viro01a05b32010-03-23 06:06:58 -0400548static void do_thaw_one(struct super_block *sb, void *unused)
549{
550 char b[BDEVNAME_SIZE];
551 while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
552 printk(KERN_WARNING "Emergency Thaw on %s\n",
553 bdevname(sb->s_bdev, b));
554}
555
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700556static void do_thaw_all(struct work_struct *work)
Eric Sandeenc2d75432009-03-31 15:23:46 -0700557{
Al Viro01a05b32010-03-23 06:06:58 -0400558 iterate_supers(do_thaw_one, NULL);
Jens Axboe053c5252009-04-08 13:44:08 +0200559 kfree(work);
Eric Sandeenc2d75432009-03-31 15:23:46 -0700560 printk(KERN_WARNING "Emergency Thaw complete\n");
561}
562
563/**
564 * emergency_thaw_all -- forcibly thaw every frozen filesystem
565 *
566 * Used for emergency unfreeze of all filesystems via SysRq
567 */
568void emergency_thaw_all(void)
569{
Jens Axboe053c5252009-04-08 13:44:08 +0200570 struct work_struct *work;
571
572 work = kmalloc(sizeof(*work), GFP_ATOMIC);
573 if (work) {
574 INIT_WORK(work, do_thaw_all);
575 schedule_work(work);
576 }
Eric Sandeenc2d75432009-03-31 15:23:46 -0700577}
578
Linus Torvalds1da177e2005-04-16 15:20:36 -0700579/**
Randy Dunlap78a4a502008-02-29 22:02:31 -0800580 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
Martin Waitz67be2dd2005-05-01 08:59:26 -0700581 * @mapping: the mapping which wants those buffers written
Linus Torvalds1da177e2005-04-16 15:20:36 -0700582 *
583 * Starts I/O against the buffers at mapping->private_list, and waits upon
584 * that I/O.
585 *
Martin Waitz67be2dd2005-05-01 08:59:26 -0700586 * Basically, this is a convenience function for fsync().
587 * @mapping is a file or directory which needs those buffers to be written for
588 * a successful fsync().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700589 */
590int sync_mapping_buffers(struct address_space *mapping)
591{
Rafael Aquini252aa6f2012-12-11 16:02:35 -0800592 struct address_space *buffer_mapping = mapping->private_data;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700593
594 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
595 return 0;
596
597 return fsync_buffers_list(&buffer_mapping->private_lock,
598 &mapping->private_list);
599}
600EXPORT_SYMBOL(sync_mapping_buffers);
601
602/*
603 * Called when we've recently written block `bblock', and it is known that
604 * `bblock' was for a buffer_boundary() buffer. This means that the block at
605 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
606 * dirty, schedule it for IO. So that indirects merge nicely with their data.
607 */
608void write_boundary_block(struct block_device *bdev,
609 sector_t bblock, unsigned blocksize)
610{
611 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
612 if (bh) {
613 if (buffer_dirty(bh))
614 ll_rw_block(WRITE, 1, &bh);
615 put_bh(bh);
616 }
617}
618
619void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
620{
621 struct address_space *mapping = inode->i_mapping;
622 struct address_space *buffer_mapping = bh->b_page->mapping;
623
624 mark_buffer_dirty(bh);
Rafael Aquini252aa6f2012-12-11 16:02:35 -0800625 if (!mapping->private_data) {
626 mapping->private_data = buffer_mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700627 } else {
Rafael Aquini252aa6f2012-12-11 16:02:35 -0800628 BUG_ON(mapping->private_data != buffer_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700629 }
Jan Kara535ee2f2008-02-08 04:21:59 -0800630 if (!bh->b_assoc_map) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700631 spin_lock(&buffer_mapping->private_lock);
632 list_move_tail(&bh->b_assoc_buffers,
633 &mapping->private_list);
Jan Kara58ff4072006-10-17 00:10:19 -0700634 bh->b_assoc_map = mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700635 spin_unlock(&buffer_mapping->private_lock);
636 }
637}
638EXPORT_SYMBOL(mark_buffer_dirty_inode);
639
640/*
Nick Piggin787d2212007-07-17 04:03:34 -0700641 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
642 * dirty.
643 *
644 * If warn is true, then emit a warning if the page is not uptodate and has
645 * not been truncated.
646 */
Linus Torvaldsa8e7d492009-03-19 11:32:05 -0700647static void __set_page_dirty(struct page *page,
Nick Piggin787d2212007-07-17 04:03:34 -0700648 struct address_space *mapping, int warn)
649{
KOSAKI Motohiro227d53b32014-02-06 12:04:28 -0800650 unsigned long flags;
651
652 spin_lock_irqsave(&mapping->tree_lock, flags);
Nick Piggin787d2212007-07-17 04:03:34 -0700653 if (page->mapping) { /* Race with truncate? */
654 WARN_ON_ONCE(warn && !PageUptodate(page));
Edward Shishkine3a7cca2009-03-31 15:19:39 -0700655 account_page_dirtied(page, mapping);
Nick Piggin787d2212007-07-17 04:03:34 -0700656 radix_tree_tag_set(&mapping->page_tree,
657 page_index(page), PAGECACHE_TAG_DIRTY);
658 }
KOSAKI Motohiro227d53b32014-02-06 12:04:28 -0800659 spin_unlock_irqrestore(&mapping->tree_lock, flags);
Nick Piggin787d2212007-07-17 04:03:34 -0700660 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
Nick Piggin787d2212007-07-17 04:03:34 -0700661}
662
663/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700664 * Add a page to the dirty page list.
665 *
666 * It is a sad fact of life that this function is called from several places
667 * deeply under spinlocking. It may not sleep.
668 *
669 * If the page has buffers, the uptodate buffers are set dirty, to preserve
670 * dirty-state coherency between the page and the buffers. It the page does
671 * not have buffers then when they are later attached they will all be set
672 * dirty.
673 *
674 * The buffers are dirtied before the page is dirtied. There's a small race
675 * window in which a writepage caller may see the page cleanness but not the
676 * buffer dirtiness. That's fine. If this code were to set the page dirty
677 * before the buffers, a concurrent writepage caller could clear the page dirty
678 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
679 * page on the dirty page list.
680 *
681 * We use private_lock to lock against try_to_free_buffers while using the
682 * page's buffer list. Also use this to protect against clean buffers being
683 * added to the page after it was set dirty.
684 *
685 * FIXME: may need to call ->reservepage here as well. That's rather up to the
686 * address_space though.
687 */
688int __set_page_dirty_buffers(struct page *page)
689{
Linus Torvaldsa8e7d492009-03-19 11:32:05 -0700690 int newly_dirty;
Nick Piggin787d2212007-07-17 04:03:34 -0700691 struct address_space *mapping = page_mapping(page);
Nick Pigginebf7a222006-10-10 04:36:54 +0200692
693 if (unlikely(!mapping))
694 return !TestSetPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700695
696 spin_lock(&mapping->private_lock);
697 if (page_has_buffers(page)) {
698 struct buffer_head *head = page_buffers(page);
699 struct buffer_head *bh = head;
700
701 do {
702 set_buffer_dirty(bh);
703 bh = bh->b_this_page;
704 } while (bh != head);
705 }
Linus Torvaldsa8e7d492009-03-19 11:32:05 -0700706 newly_dirty = !TestSetPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700707 spin_unlock(&mapping->private_lock);
708
Linus Torvaldsa8e7d492009-03-19 11:32:05 -0700709 if (newly_dirty)
710 __set_page_dirty(page, mapping, 1);
711 return newly_dirty;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700712}
713EXPORT_SYMBOL(__set_page_dirty_buffers);
714
715/*
716 * Write out and wait upon a list of buffers.
717 *
718 * We have conflicting pressures: we want to make sure that all
719 * initially dirty buffers get waited on, but that any subsequently
720 * dirtied buffers don't. After all, we don't want fsync to last
721 * forever if somebody is actively writing to the file.
722 *
723 * Do this in two main stages: first we copy dirty buffers to a
724 * temporary inode list, queueing the writes as we go. Then we clean
725 * up, waiting for those writes to complete.
726 *
727 * During this second stage, any subsequent updates to the file may end
728 * up refiling the buffer on the original inode's dirty list again, so
729 * there is a chance we will end up with a buffer queued for write but
730 * not yet completed on that list. So, as a final cleanup we go through
731 * the osync code to catch these locked, dirty buffers without requeuing
732 * any newly dirty buffers for write.
733 */
734static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
735{
736 struct buffer_head *bh;
737 struct list_head tmp;
Jens Axboe7eaceac2011-03-10 08:52:07 +0100738 struct address_space *mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700739 int err = 0, err2;
Jens Axboe4ee24912011-03-17 10:51:40 +0100740 struct blk_plug plug;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700741
742 INIT_LIST_HEAD(&tmp);
Jens Axboe4ee24912011-03-17 10:51:40 +0100743 blk_start_plug(&plug);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700744
745 spin_lock(lock);
746 while (!list_empty(list)) {
747 bh = BH_ENTRY(list->next);
Jan Kara535ee2f2008-02-08 04:21:59 -0800748 mapping = bh->b_assoc_map;
Jan Kara58ff4072006-10-17 00:10:19 -0700749 __remove_assoc_queue(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -0800750 /* Avoid race with mark_buffer_dirty_inode() which does
751 * a lockless check and we rely on seeing the dirty bit */
752 smp_mb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700753 if (buffer_dirty(bh) || buffer_locked(bh)) {
754 list_add(&bh->b_assoc_buffers, &tmp);
Jan Kara535ee2f2008-02-08 04:21:59 -0800755 bh->b_assoc_map = mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700756 if (buffer_dirty(bh)) {
757 get_bh(bh);
758 spin_unlock(lock);
759 /*
760 * Ensure any pending I/O completes so that
Christoph Hellwig9cb569d2010-08-11 17:06:24 +0200761 * write_dirty_buffer() actually writes the
762 * current contents - it is a noop if I/O is
763 * still in flight on potentially older
764 * contents.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700765 */
Jens Axboe721a9602011-03-09 11:56:30 +0100766 write_dirty_buffer(bh, WRITE_SYNC);
Jens Axboe9cf6b722009-04-06 14:48:03 +0200767
768 /*
769 * Kick off IO for the previous mapping. Note
770 * that we will not run the very last mapping,
771 * wait_on_buffer() will do that for us
772 * through sync_buffer().
773 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700774 brelse(bh);
775 spin_lock(lock);
776 }
777 }
778 }
779
Jens Axboe4ee24912011-03-17 10:51:40 +0100780 spin_unlock(lock);
781 blk_finish_plug(&plug);
782 spin_lock(lock);
783
Linus Torvalds1da177e2005-04-16 15:20:36 -0700784 while (!list_empty(&tmp)) {
785 bh = BH_ENTRY(tmp.prev);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700786 get_bh(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -0800787 mapping = bh->b_assoc_map;
788 __remove_assoc_queue(bh);
789 /* Avoid race with mark_buffer_dirty_inode() which does
790 * a lockless check and we rely on seeing the dirty bit */
791 smp_mb();
792 if (buffer_dirty(bh)) {
793 list_add(&bh->b_assoc_buffers,
Jan Karae3892292008-03-04 14:28:33 -0800794 &mapping->private_list);
Jan Kara535ee2f2008-02-08 04:21:59 -0800795 bh->b_assoc_map = mapping;
796 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700797 spin_unlock(lock);
798 wait_on_buffer(bh);
799 if (!buffer_uptodate(bh))
800 err = -EIO;
801 brelse(bh);
802 spin_lock(lock);
803 }
804
805 spin_unlock(lock);
806 err2 = osync_buffers_list(lock, list);
807 if (err)
808 return err;
809 else
810 return err2;
811}
812
813/*
814 * Invalidate any and all dirty buffers on a given inode. We are
815 * probably unmounting the fs, but that doesn't mean we have already
816 * done a sync(). Just drop the buffers from the inode list.
817 *
818 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
819 * assumes that all the buffers are against the blockdev. Not true
820 * for reiserfs.
821 */
822void invalidate_inode_buffers(struct inode *inode)
823{
824 if (inode_has_buffers(inode)) {
825 struct address_space *mapping = &inode->i_data;
826 struct list_head *list = &mapping->private_list;
Rafael Aquini252aa6f2012-12-11 16:02:35 -0800827 struct address_space *buffer_mapping = mapping->private_data;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700828
829 spin_lock(&buffer_mapping->private_lock);
830 while (!list_empty(list))
831 __remove_assoc_queue(BH_ENTRY(list->next));
832 spin_unlock(&buffer_mapping->private_lock);
833 }
834}
Jan Kara52b19ac2008-09-23 18:24:08 +0200835EXPORT_SYMBOL(invalidate_inode_buffers);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700836
837/*
838 * Remove any clean buffers from the inode's buffer list. This is called
839 * when we're trying to free the inode itself. Those buffers can pin it.
840 *
841 * Returns true if all buffers were removed.
842 */
843int remove_inode_buffers(struct inode *inode)
844{
845 int ret = 1;
846
847 if (inode_has_buffers(inode)) {
848 struct address_space *mapping = &inode->i_data;
849 struct list_head *list = &mapping->private_list;
Rafael Aquini252aa6f2012-12-11 16:02:35 -0800850 struct address_space *buffer_mapping = mapping->private_data;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700851
852 spin_lock(&buffer_mapping->private_lock);
853 while (!list_empty(list)) {
854 struct buffer_head *bh = BH_ENTRY(list->next);
855 if (buffer_dirty(bh)) {
856 ret = 0;
857 break;
858 }
859 __remove_assoc_queue(bh);
860 }
861 spin_unlock(&buffer_mapping->private_lock);
862 }
863 return ret;
864}
865
866/*
867 * Create the appropriate buffers when given a page for data area and
868 * the size of each buffer.. Use the bh->b_this_page linked list to
869 * follow the buffers created. Return NULL if unable to create more
870 * buffers.
871 *
872 * The retry flag is used to differentiate async IO (paging, swapping)
873 * which may not fail from ordinary buffer allocations.
874 */
875struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
876 int retry)
877{
878 struct buffer_head *bh, *head;
879 long offset;
880
881try_again:
882 head = NULL;
883 offset = PAGE_SIZE;
884 while ((offset -= size) >= 0) {
885 bh = alloc_buffer_head(GFP_NOFS);
886 if (!bh)
887 goto no_grow;
888
Linus Torvalds1da177e2005-04-16 15:20:36 -0700889 bh->b_this_page = head;
890 bh->b_blocknr = -1;
891 head = bh;
892
Linus Torvalds1da177e2005-04-16 15:20:36 -0700893 bh->b_size = size;
894
895 /* Link the buffer to its page */
896 set_bh_page(bh, page, offset);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700897 }
898 return head;
899/*
900 * In case anything failed, we just free everything we got.
901 */
902no_grow:
903 if (head) {
904 do {
905 bh = head;
906 head = head->b_this_page;
907 free_buffer_head(bh);
908 } while (head);
909 }
910
911 /*
912 * Return failure for non-async IO requests. Async IO requests
913 * are not allowed to fail, so we have to wait until buffer heads
914 * become available. But we don't want tasks sleeping with
915 * partially complete buffers, so all were released above.
916 */
917 if (!retry)
918 return NULL;
919
920 /* We're _really_ low on memory. Now we just
921 * wait for old buffer heads to become free due to
922 * finishing IO. Since this is an async request and
923 * the reserve list is empty, we're sure there are
924 * async buffer heads in use.
925 */
926 free_more_memory();
927 goto try_again;
928}
929EXPORT_SYMBOL_GPL(alloc_page_buffers);
930
931static inline void
932link_dev_buffers(struct page *page, struct buffer_head *head)
933{
934 struct buffer_head *bh, *tail;
935
936 bh = head;
937 do {
938 tail = bh;
939 bh = bh->b_this_page;
940 } while (bh);
941 tail->b_this_page = head;
942 attach_page_buffers(page, head);
943}
944
Linus Torvaldsbbec02702012-11-29 12:31:52 -0800945static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
946{
947 sector_t retval = ~((sector_t)0);
948 loff_t sz = i_size_read(bdev->bd_inode);
949
950 if (sz) {
951 unsigned int sizebits = blksize_bits(size);
952 retval = (sz >> sizebits);
953 }
954 return retval;
955}
956
Linus Torvalds1da177e2005-04-16 15:20:36 -0700957/*
958 * Initialise the state of a blockdev page's buffers.
959 */
Hugh Dickins676ce6d2012-08-23 12:17:36 +0200960static sector_t
Linus Torvalds1da177e2005-04-16 15:20:36 -0700961init_page_buffers(struct page *page, struct block_device *bdev,
962 sector_t block, int size)
963{
964 struct buffer_head *head = page_buffers(page);
965 struct buffer_head *bh = head;
966 int uptodate = PageUptodate(page);
Linus Torvaldsbbec02702012-11-29 12:31:52 -0800967 sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode), size);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700968
969 do {
970 if (!buffer_mapped(bh)) {
971 init_buffer(bh, NULL, NULL);
972 bh->b_bdev = bdev;
973 bh->b_blocknr = block;
974 if (uptodate)
975 set_buffer_uptodate(bh);
Jeff Moyer080399a2012-05-11 16:34:10 +0200976 if (block < end_block)
977 set_buffer_mapped(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700978 }
979 block++;
980 bh = bh->b_this_page;
981 } while (bh != head);
Hugh Dickins676ce6d2012-08-23 12:17:36 +0200982
983 /*
984 * Caller needs to validate requested block against end of device.
985 */
986 return end_block;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700987}
988
989/*
990 * Create the page-cache page that contains the requested block.
991 *
Hugh Dickins676ce6d2012-08-23 12:17:36 +0200992 * This is used purely for blockdev mappings.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700993 */
Hugh Dickins676ce6d2012-08-23 12:17:36 +0200994static int
Linus Torvalds1da177e2005-04-16 15:20:36 -0700995grow_dev_page(struct block_device *bdev, sector_t block,
Hugh Dickins676ce6d2012-08-23 12:17:36 +0200996 pgoff_t index, int size, int sizebits)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700997{
998 struct inode *inode = bdev->bd_inode;
999 struct page *page;
1000 struct buffer_head *bh;
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001001 sector_t end_block;
1002 int ret = 0; /* Will call free_more_memory() */
Johannes Weiner84235de2013-10-16 13:47:00 -07001003 gfp_t gfp_mask;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001004
Johannes Weiner84235de2013-10-16 13:47:00 -07001005 gfp_mask = mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS;
1006 gfp_mask |= __GFP_MOVABLE;
1007 /*
1008 * XXX: __getblk_slow() can not really deal with failure and
1009 * will endlessly loop on improvised global reclaim. Prefer
1010 * looping in the allocator rather than here, at least that
1011 * code knows what it's doing.
1012 */
1013 gfp_mask |= __GFP_NOFAIL;
1014
1015 page = find_or_create_page(inode->i_mapping, index, gfp_mask);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001016 if (!page)
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001017 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001018
Eric Sesterhenne827f922006-03-26 18:24:46 +02001019 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001020
1021 if (page_has_buffers(page)) {
1022 bh = page_buffers(page);
1023 if (bh->b_size == size) {
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001024 end_block = init_page_buffers(page, bdev,
Anton Altaparmakovf2d5a942014-09-22 01:53:03 +01001025 (sector_t)index << sizebits,
1026 size);
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001027 goto done;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001028 }
1029 if (!try_to_free_buffers(page))
1030 goto failed;
1031 }
1032
1033 /*
1034 * Allocate some buffers for this page
1035 */
1036 bh = alloc_page_buffers(page, size, 0);
1037 if (!bh)
1038 goto failed;
1039
1040 /*
1041 * Link the page to the buffers and initialise them. Take the
1042 * lock to be atomic wrt __find_get_block(), which does not
1043 * run under the page lock.
1044 */
1045 spin_lock(&inode->i_mapping->private_lock);
1046 link_dev_buffers(page, bh);
Anton Altaparmakovf2d5a942014-09-22 01:53:03 +01001047 end_block = init_page_buffers(page, bdev, (sector_t)index << sizebits,
1048 size);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001049 spin_unlock(&inode->i_mapping->private_lock);
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001050done:
1051 ret = (block < end_block) ? 1 : -ENXIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001052failed:
Linus Torvalds1da177e2005-04-16 15:20:36 -07001053 unlock_page(page);
1054 page_cache_release(page);
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001055 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001056}
1057
1058/*
1059 * Create buffers for the specified block device block's page. If
1060 * that page was dirty, the buffers are set dirty also.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001061 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001062static int
Linus Torvalds1da177e2005-04-16 15:20:36 -07001063grow_buffers(struct block_device *bdev, sector_t block, int size)
1064{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001065 pgoff_t index;
1066 int sizebits;
1067
1068 sizebits = -1;
1069 do {
1070 sizebits++;
1071 } while ((size << sizebits) < PAGE_SIZE);
1072
1073 index = block >> sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001074
Andrew Mortone5657932006-10-11 01:21:46 -07001075 /*
1076 * Check for a block which wants to lie outside our maximum possible
1077 * pagecache index. (this comparison is done using sector_t types).
1078 */
1079 if (unlikely(index != block >> sizebits)) {
1080 char b[BDEVNAME_SIZE];
1081
1082 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1083 "device %s\n",
Harvey Harrison8e24eea2008-04-30 00:55:09 -07001084 __func__, (unsigned long long)block,
Andrew Mortone5657932006-10-11 01:21:46 -07001085 bdevname(bdev, b));
1086 return -EIO;
1087 }
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001088
Linus Torvalds1da177e2005-04-16 15:20:36 -07001089 /* Create a page with the proper size buffers.. */
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001090 return grow_dev_page(bdev, block, index, size, sizebits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001091}
1092
Adrian Bunk75c96f82005-05-05 16:16:09 -07001093static struct buffer_head *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001094__getblk_slow(struct block_device *bdev, sector_t block, int size)
1095{
1096 /* Size must be multiple of hard sectorsize */
Martin K. Petersene1defc42009-05-22 17:17:49 -04001097 if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
Linus Torvalds1da177e2005-04-16 15:20:36 -07001098 (size < 512 || size > PAGE_SIZE))) {
1099 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1100 size);
Martin K. Petersene1defc42009-05-22 17:17:49 -04001101 printk(KERN_ERR "logical block size: %d\n",
1102 bdev_logical_block_size(bdev));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001103
1104 dump_stack();
1105 return NULL;
1106 }
1107
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001108 for (;;) {
1109 struct buffer_head *bh;
1110 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001111
1112 bh = __find_get_block(bdev, block, size);
1113 if (bh)
1114 return bh;
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001115
1116 ret = grow_buffers(bdev, block, size);
1117 if (ret < 0)
1118 return NULL;
1119 if (ret == 0)
1120 free_more_memory();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001121 }
1122}
1123
1124/*
1125 * The relationship between dirty buffers and dirty pages:
1126 *
1127 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1128 * the page is tagged dirty in its radix tree.
1129 *
1130 * At all times, the dirtiness of the buffers represents the dirtiness of
1131 * subsections of the page. If the page has buffers, the page dirty bit is
1132 * merely a hint about the true dirty state.
1133 *
1134 * When a page is set dirty in its entirety, all its buffers are marked dirty
1135 * (if the page has buffers).
1136 *
1137 * When a buffer is marked dirty, its page is dirtied, but the page's other
1138 * buffers are not.
1139 *
1140 * Also. When blockdev buffers are explicitly read with bread(), they
1141 * individually become uptodate. But their backing page remains not
1142 * uptodate - even if all of its buffers are uptodate. A subsequent
1143 * block_read_full_page() against that page will discover all the uptodate
1144 * buffers, will set the page uptodate and will perform no I/O.
1145 */
1146
1147/**
1148 * mark_buffer_dirty - mark a buffer_head as needing writeout
Martin Waitz67be2dd2005-05-01 08:59:26 -07001149 * @bh: the buffer_head to mark dirty
Linus Torvalds1da177e2005-04-16 15:20:36 -07001150 *
1151 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1152 * backing page dirty, then tag the page as dirty in its address_space's radix
1153 * tree and then attach the address_space's inode to its superblock's dirty
1154 * inode list.
1155 *
1156 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
Dave Chinner250df6e2011-03-22 22:23:36 +11001157 * mapping->tree_lock and mapping->host->i_lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001158 */
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -08001159void mark_buffer_dirty(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001160{
Nick Piggin787d2212007-07-17 04:03:34 -07001161 WARN_ON_ONCE(!buffer_uptodate(bh));
Linus Torvalds1be62dc2008-04-04 14:38:17 -07001162
Tejun Heo5305cb82013-01-11 13:06:36 -08001163 trace_block_dirty_buffer(bh);
1164
Linus Torvalds1be62dc2008-04-04 14:38:17 -07001165 /*
1166 * Very *carefully* optimize the it-is-already-dirty case.
1167 *
1168 * Don't let the final "is it dirty" escape to before we
1169 * perhaps modified the buffer.
1170 */
1171 if (buffer_dirty(bh)) {
1172 smp_mb();
1173 if (buffer_dirty(bh))
1174 return;
1175 }
1176
Linus Torvaldsa8e7d492009-03-19 11:32:05 -07001177 if (!test_set_buffer_dirty(bh)) {
1178 struct page *page = bh->b_page;
Linus Torvalds8e9d78e2009-08-21 17:40:08 -07001179 if (!TestSetPageDirty(page)) {
1180 struct address_space *mapping = page_mapping(page);
1181 if (mapping)
1182 __set_page_dirty(page, mapping, 0);
1183 }
Linus Torvaldsa8e7d492009-03-19 11:32:05 -07001184 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001185}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07001186EXPORT_SYMBOL(mark_buffer_dirty);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001187
1188/*
1189 * Decrement a buffer_head's reference count. If all buffers against a page
1190 * have zero reference count, are clean and unlocked, and if the page is clean
1191 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1192 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1193 * a page but it ends up not being freed, and buffers may later be reattached).
1194 */
1195void __brelse(struct buffer_head * buf)
1196{
1197 if (atomic_read(&buf->b_count)) {
1198 put_bh(buf);
1199 return;
1200 }
Arjan van de Ven5c752ad2008-07-25 19:45:40 -07001201 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
Linus Torvalds1da177e2005-04-16 15:20:36 -07001202}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07001203EXPORT_SYMBOL(__brelse);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001204
1205/*
1206 * bforget() is like brelse(), except it discards any
1207 * potentially dirty data.
1208 */
1209void __bforget(struct buffer_head *bh)
1210{
1211 clear_buffer_dirty(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -08001212 if (bh->b_assoc_map) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001213 struct address_space *buffer_mapping = bh->b_page->mapping;
1214
1215 spin_lock(&buffer_mapping->private_lock);
1216 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -07001217 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001218 spin_unlock(&buffer_mapping->private_lock);
1219 }
1220 __brelse(bh);
1221}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07001222EXPORT_SYMBOL(__bforget);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001223
1224static struct buffer_head *__bread_slow(struct buffer_head *bh)
1225{
1226 lock_buffer(bh);
1227 if (buffer_uptodate(bh)) {
1228 unlock_buffer(bh);
1229 return bh;
1230 } else {
1231 get_bh(bh);
1232 bh->b_end_io = end_buffer_read_sync;
1233 submit_bh(READ, bh);
1234 wait_on_buffer(bh);
1235 if (buffer_uptodate(bh))
1236 return bh;
1237 }
1238 brelse(bh);
1239 return NULL;
1240}
1241
1242/*
1243 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1244 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1245 * refcount elevated by one when they're in an LRU. A buffer can only appear
1246 * once in a particular CPU's LRU. A single buffer can be present in multiple
1247 * CPU's LRUs at the same time.
1248 *
1249 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1250 * sb_find_get_block().
1251 *
1252 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1253 * a local interrupt disable for that.
1254 */
1255
1256#define BH_LRU_SIZE 8
1257
1258struct bh_lru {
1259 struct buffer_head *bhs[BH_LRU_SIZE];
1260};
1261
1262static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1263
1264#ifdef CONFIG_SMP
1265#define bh_lru_lock() local_irq_disable()
1266#define bh_lru_unlock() local_irq_enable()
1267#else
1268#define bh_lru_lock() preempt_disable()
1269#define bh_lru_unlock() preempt_enable()
1270#endif
1271
1272static inline void check_irqs_on(void)
1273{
1274#ifdef irqs_disabled
1275 BUG_ON(irqs_disabled());
1276#endif
1277}
1278
1279/*
1280 * The LRU management algorithm is dopey-but-simple. Sorry.
1281 */
1282static void bh_lru_install(struct buffer_head *bh)
1283{
1284 struct buffer_head *evictee = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001285
1286 check_irqs_on();
1287 bh_lru_lock();
Christoph Lameterc7b92512010-12-06 11:16:28 -06001288 if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001289 struct buffer_head *bhs[BH_LRU_SIZE];
1290 int in;
1291 int out = 0;
1292
1293 get_bh(bh);
1294 bhs[out++] = bh;
1295 for (in = 0; in < BH_LRU_SIZE; in++) {
Christoph Lameterc7b92512010-12-06 11:16:28 -06001296 struct buffer_head *bh2 =
1297 __this_cpu_read(bh_lrus.bhs[in]);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001298
1299 if (bh2 == bh) {
1300 __brelse(bh2);
1301 } else {
1302 if (out >= BH_LRU_SIZE) {
1303 BUG_ON(evictee != NULL);
1304 evictee = bh2;
1305 } else {
1306 bhs[out++] = bh2;
1307 }
1308 }
1309 }
1310 while (out < BH_LRU_SIZE)
1311 bhs[out++] = NULL;
Christoph Lameterca6673b02013-12-03 17:32:53 -06001312 memcpy(this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001313 }
1314 bh_lru_unlock();
1315
1316 if (evictee)
1317 __brelse(evictee);
1318}
1319
1320/*
1321 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1322 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001323static struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001324lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001325{
1326 struct buffer_head *ret = NULL;
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001327 unsigned int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001328
1329 check_irqs_on();
1330 bh_lru_lock();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001331 for (i = 0; i < BH_LRU_SIZE; i++) {
Christoph Lameterc7b92512010-12-06 11:16:28 -06001332 struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001333
1334 if (bh && bh->b_bdev == bdev &&
1335 bh->b_blocknr == block && bh->b_size == size) {
1336 if (i) {
1337 while (i) {
Christoph Lameterc7b92512010-12-06 11:16:28 -06001338 __this_cpu_write(bh_lrus.bhs[i],
1339 __this_cpu_read(bh_lrus.bhs[i - 1]));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001340 i--;
1341 }
Christoph Lameterc7b92512010-12-06 11:16:28 -06001342 __this_cpu_write(bh_lrus.bhs[0], bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001343 }
1344 get_bh(bh);
1345 ret = bh;
1346 break;
1347 }
1348 }
1349 bh_lru_unlock();
1350 return ret;
1351}
1352
1353/*
1354 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1355 * it in the LRU and mark it as accessed. If it is not present then return
1356 * NULL
1357 */
1358struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001359__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001360{
1361 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1362
1363 if (bh == NULL) {
Mel Gorman2457aec2014-06-04 16:10:31 -07001364 /* __find_get_block_slow will mark the page accessed */
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001365 bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001366 if (bh)
1367 bh_lru_install(bh);
Mel Gorman2457aec2014-06-04 16:10:31 -07001368 } else
Linus Torvalds1da177e2005-04-16 15:20:36 -07001369 touch_buffer(bh);
Mel Gorman2457aec2014-06-04 16:10:31 -07001370
Linus Torvalds1da177e2005-04-16 15:20:36 -07001371 return bh;
1372}
1373EXPORT_SYMBOL(__find_get_block);
1374
1375/*
1376 * __getblk will locate (and, if necessary, create) the buffer_head
1377 * which corresponds to the passed block_device, block and size. The
1378 * returned buffer has its reference count incremented.
1379 *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001380 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1381 * attempt is failing. FIXME, perhaps?
1382 */
1383struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001384__getblk(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001385{
1386 struct buffer_head *bh = __find_get_block(bdev, block, size);
1387
1388 might_sleep();
1389 if (bh == NULL)
1390 bh = __getblk_slow(bdev, block, size);
1391 return bh;
1392}
1393EXPORT_SYMBOL(__getblk);
1394
1395/*
1396 * Do async read-ahead on a buffer..
1397 */
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001398void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001399{
1400 struct buffer_head *bh = __getblk(bdev, block, size);
Andrew Mortona3e713b2005-10-30 15:03:15 -08001401 if (likely(bh)) {
1402 ll_rw_block(READA, 1, &bh);
1403 brelse(bh);
1404 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001405}
1406EXPORT_SYMBOL(__breadahead);
1407
1408/**
1409 * __bread() - reads a specified block and returns the bh
Martin Waitz67be2dd2005-05-01 08:59:26 -07001410 * @bdev: the block_device to read from
Linus Torvalds1da177e2005-04-16 15:20:36 -07001411 * @block: number of block
1412 * @size: size (in bytes) to read
1413 *
1414 * Reads a specified block, and returns buffer head that contains it.
1415 * It returns NULL if the block was unreadable.
1416 */
1417struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001418__bread(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001419{
1420 struct buffer_head *bh = __getblk(bdev, block, size);
1421
Andrew Mortona3e713b2005-10-30 15:03:15 -08001422 if (likely(bh) && !buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001423 bh = __bread_slow(bh);
1424 return bh;
1425}
1426EXPORT_SYMBOL(__bread);
1427
1428/*
1429 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1430 * This doesn't race because it runs in each cpu either in irq
1431 * or with preempt disabled.
1432 */
1433static void invalidate_bh_lru(void *arg)
1434{
1435 struct bh_lru *b = &get_cpu_var(bh_lrus);
1436 int i;
1437
1438 for (i = 0; i < BH_LRU_SIZE; i++) {
1439 brelse(b->bhs[i]);
1440 b->bhs[i] = NULL;
1441 }
1442 put_cpu_var(bh_lrus);
1443}
Gilad Ben-Yossef42be35d2012-03-28 14:42:45 -07001444
1445static bool has_bh_in_lru(int cpu, void *dummy)
1446{
1447 struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1448 int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001449
Gilad Ben-Yossef42be35d2012-03-28 14:42:45 -07001450 for (i = 0; i < BH_LRU_SIZE; i++) {
1451 if (b->bhs[i])
1452 return 1;
1453 }
1454
1455 return 0;
1456}
1457
Peter Zijlstraf9a14392007-05-06 14:49:55 -07001458void invalidate_bh_lrus(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001459{
Gilad Ben-Yossef42be35d2012-03-28 14:42:45 -07001460 on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001461}
Nick Piggin9db55792008-02-08 04:19:49 -08001462EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001463
1464void set_bh_page(struct buffer_head *bh,
1465 struct page *page, unsigned long offset)
1466{
1467 bh->b_page = page;
Eric Sesterhenne827f922006-03-26 18:24:46 +02001468 BUG_ON(offset >= PAGE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001469 if (PageHighMem(page))
1470 /*
1471 * This catches illegal uses and preserves the offset:
1472 */
1473 bh->b_data = (char *)(0 + offset);
1474 else
1475 bh->b_data = page_address(page) + offset;
1476}
1477EXPORT_SYMBOL(set_bh_page);
1478
1479/*
1480 * Called when truncating a buffer on a page completely.
1481 */
Mel Gormane7470ee2014-06-04 16:10:29 -07001482
1483/* Bits that are cleared during an invalidate */
1484#define BUFFER_FLAGS_DISCARD \
1485 (1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \
1486 1 << BH_Delay | 1 << BH_Unwritten)
1487
Arjan van de Ven858119e2006-01-14 13:20:43 -08001488static void discard_buffer(struct buffer_head * bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001489{
Mel Gormane7470ee2014-06-04 16:10:29 -07001490 unsigned long b_state, b_state_old;
1491
Linus Torvalds1da177e2005-04-16 15:20:36 -07001492 lock_buffer(bh);
1493 clear_buffer_dirty(bh);
1494 bh->b_bdev = NULL;
Mel Gormane7470ee2014-06-04 16:10:29 -07001495 b_state = bh->b_state;
1496 for (;;) {
1497 b_state_old = cmpxchg(&bh->b_state, b_state,
1498 (b_state & ~BUFFER_FLAGS_DISCARD));
1499 if (b_state_old == b_state)
1500 break;
1501 b_state = b_state_old;
1502 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001503 unlock_buffer(bh);
1504}
1505
1506/**
Wang Sheng-Hui814e1d22011-09-01 08:22:57 +08001507 * block_invalidatepage - invalidate part or all of a buffer-backed page
Linus Torvalds1da177e2005-04-16 15:20:36 -07001508 *
1509 * @page: the page which is affected
Lukas Czernerd47992f2013-05-21 23:17:23 -04001510 * @offset: start of the range to invalidate
1511 * @length: length of the range to invalidate
Linus Torvalds1da177e2005-04-16 15:20:36 -07001512 *
1513 * block_invalidatepage() is called when all or part of the page has become
Wang Sheng-Hui814e1d22011-09-01 08:22:57 +08001514 * invalidated by a truncate operation.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001515 *
1516 * block_invalidatepage() does not have to release all buffers, but it must
1517 * ensure that no dirty buffer is left outside @offset and that no I/O
1518 * is underway against any of the blocks which are outside the truncation
1519 * point. Because the caller is about to free (and possibly reuse) those
1520 * blocks on-disk.
1521 */
Lukas Czernerd47992f2013-05-21 23:17:23 -04001522void block_invalidatepage(struct page *page, unsigned int offset,
1523 unsigned int length)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001524{
1525 struct buffer_head *head, *bh, *next;
1526 unsigned int curr_off = 0;
Lukas Czernerd47992f2013-05-21 23:17:23 -04001527 unsigned int stop = length + offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001528
1529 BUG_ON(!PageLocked(page));
1530 if (!page_has_buffers(page))
1531 goto out;
1532
Lukas Czernerd47992f2013-05-21 23:17:23 -04001533 /*
1534 * Check for overflow
1535 */
1536 BUG_ON(stop > PAGE_CACHE_SIZE || stop < length);
1537
Linus Torvalds1da177e2005-04-16 15:20:36 -07001538 head = page_buffers(page);
1539 bh = head;
1540 do {
1541 unsigned int next_off = curr_off + bh->b_size;
1542 next = bh->b_this_page;
1543
1544 /*
Lukas Czernerd47992f2013-05-21 23:17:23 -04001545 * Are we still fully in range ?
1546 */
1547 if (next_off > stop)
1548 goto out;
1549
1550 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001551 * is this block fully invalidated?
1552 */
1553 if (offset <= curr_off)
1554 discard_buffer(bh);
1555 curr_off = next_off;
1556 bh = next;
1557 } while (bh != head);
1558
1559 /*
1560 * We release buffers only if the entire page is being invalidated.
1561 * The get_block cached value has been unconditionally invalidated,
1562 * so real IO is not possible anymore.
1563 */
1564 if (offset == 0)
NeilBrown2ff28e22006-03-26 01:37:18 -08001565 try_to_release_page(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001566out:
NeilBrown2ff28e22006-03-26 01:37:18 -08001567 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001568}
1569EXPORT_SYMBOL(block_invalidatepage);
1570
Lukas Czernerd47992f2013-05-21 23:17:23 -04001571
Linus Torvalds1da177e2005-04-16 15:20:36 -07001572/*
1573 * We attach and possibly dirty the buffers atomically wrt
1574 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1575 * is already excluded via the page lock.
1576 */
1577void create_empty_buffers(struct page *page,
1578 unsigned long blocksize, unsigned long b_state)
1579{
1580 struct buffer_head *bh, *head, *tail;
1581
1582 head = alloc_page_buffers(page, blocksize, 1);
1583 bh = head;
1584 do {
1585 bh->b_state |= b_state;
1586 tail = bh;
1587 bh = bh->b_this_page;
1588 } while (bh);
1589 tail->b_this_page = head;
1590
1591 spin_lock(&page->mapping->private_lock);
1592 if (PageUptodate(page) || PageDirty(page)) {
1593 bh = head;
1594 do {
1595 if (PageDirty(page))
1596 set_buffer_dirty(bh);
1597 if (PageUptodate(page))
1598 set_buffer_uptodate(bh);
1599 bh = bh->b_this_page;
1600 } while (bh != head);
1601 }
1602 attach_page_buffers(page, head);
1603 spin_unlock(&page->mapping->private_lock);
1604}
1605EXPORT_SYMBOL(create_empty_buffers);
1606
1607/*
1608 * We are taking a block for data and we don't want any output from any
1609 * buffer-cache aliases starting from return from that function and
1610 * until the moment when something will explicitly mark the buffer
1611 * dirty (hopefully that will not happen until we will free that block ;-)
1612 * We don't even need to mark it not-uptodate - nobody can expect
1613 * anything from a newly allocated buffer anyway. We used to used
1614 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1615 * don't want to mark the alias unmapped, for example - it would confuse
1616 * anyone who might pick it with bread() afterwards...
1617 *
1618 * Also.. Note that bforget() doesn't lock the buffer. So there can
1619 * be writeout I/O going on against recently-freed buffers. We don't
1620 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1621 * only if we really need to. That happens here.
1622 */
1623void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1624{
1625 struct buffer_head *old_bh;
1626
1627 might_sleep();
1628
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001629 old_bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001630 if (old_bh) {
1631 clear_buffer_dirty(old_bh);
1632 wait_on_buffer(old_bh);
1633 clear_buffer_req(old_bh);
1634 __brelse(old_bh);
1635 }
1636}
1637EXPORT_SYMBOL(unmap_underlying_metadata);
1638
1639/*
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001640 * Size is a power-of-two in the range 512..PAGE_SIZE,
1641 * and the case we care about most is PAGE_SIZE.
1642 *
1643 * So this *could* possibly be written with those
1644 * constraints in mind (relevant mostly if some
1645 * architecture has a slow bit-scan instruction)
1646 */
1647static inline int block_size_bits(unsigned int blocksize)
1648{
1649 return ilog2(blocksize);
1650}
1651
1652static struct buffer_head *create_page_buffers(struct page *page, struct inode *inode, unsigned int b_state)
1653{
1654 BUG_ON(!PageLocked(page));
1655
1656 if (!page_has_buffers(page))
1657 create_empty_buffers(page, 1 << ACCESS_ONCE(inode->i_blkbits), b_state);
1658 return page_buffers(page);
1659}
1660
1661/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001662 * NOTE! All mapped/uptodate combinations are valid:
1663 *
1664 * Mapped Uptodate Meaning
1665 *
1666 * No No "unknown" - must do get_block()
1667 * No Yes "hole" - zero-filled
1668 * Yes No "allocated" - allocated on disk, not read in
1669 * Yes Yes "valid" - allocated and up-to-date in memory.
1670 *
1671 * "Dirty" is valid only with the last case (mapped+uptodate).
1672 */
1673
1674/*
1675 * While block_write_full_page is writing back the dirty buffers under
1676 * the page lock, whoever dirtied the buffers may decide to clean them
1677 * again at any time. We handle that by only looking at the buffer
1678 * state inside lock_buffer().
1679 *
1680 * If block_write_full_page() is called for regular writeback
1681 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1682 * locked buffer. This only can happen if someone has written the buffer
1683 * directly, with submit_bh(). At the address_space level PageWriteback
1684 * prevents this contention from occurring.
Theodore Ts'o6e34eed2009-04-07 18:12:43 -04001685 *
1686 * If block_write_full_page() is called with wbc->sync_mode ==
Jens Axboe721a9602011-03-09 11:56:30 +01001687 * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this
1688 * causes the writes to be flagged as synchronous writes.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001689 */
1690static int __block_write_full_page(struct inode *inode, struct page *page,
Chris Mason35c80d52009-04-15 13:22:38 -04001691 get_block_t *get_block, struct writeback_control *wbc,
1692 bh_end_io_t *handler)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001693{
1694 int err;
1695 sector_t block;
1696 sector_t last_block;
Andrew Mortonf0fbd5f2005-05-05 16:15:48 -07001697 struct buffer_head *bh, *head;
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001698 unsigned int blocksize, bbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001699 int nr_underway = 0;
Theodore Ts'o6e34eed2009-04-07 18:12:43 -04001700 int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
Jens Axboe721a9602011-03-09 11:56:30 +01001701 WRITE_SYNC : WRITE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001702
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001703 head = create_page_buffers(page, inode,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001704 (1 << BH_Dirty)|(1 << BH_Uptodate));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001705
1706 /*
1707 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1708 * here, and the (potentially unmapped) buffers may become dirty at
1709 * any time. If a buffer becomes dirty here after we've inspected it
1710 * then we just miss that fact, and the page stays dirty.
1711 *
1712 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1713 * handle that here by just cleaning them.
1714 */
1715
Linus Torvalds1da177e2005-04-16 15:20:36 -07001716 bh = head;
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001717 blocksize = bh->b_size;
1718 bbits = block_size_bits(blocksize);
1719
1720 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1721 last_block = (i_size_read(inode) - 1) >> bbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001722
1723 /*
1724 * Get all the dirty buffers mapped to disk addresses and
1725 * handle any aliases from the underlying blockdev's mapping.
1726 */
1727 do {
1728 if (block > last_block) {
1729 /*
1730 * mapped buffers outside i_size will occur, because
1731 * this page can be outside i_size when there is a
1732 * truncate in progress.
1733 */
1734 /*
1735 * The buffer was zeroed by block_write_full_page()
1736 */
1737 clear_buffer_dirty(bh);
1738 set_buffer_uptodate(bh);
Alex Tomas29a814d2008-07-11 19:27:31 -04001739 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1740 buffer_dirty(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001741 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001742 err = get_block(inode, block, bh, 1);
1743 if (err)
1744 goto recover;
Alex Tomas29a814d2008-07-11 19:27:31 -04001745 clear_buffer_delay(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001746 if (buffer_new(bh)) {
1747 /* blockdev mappings never come here */
1748 clear_buffer_new(bh);
1749 unmap_underlying_metadata(bh->b_bdev,
1750 bh->b_blocknr);
1751 }
1752 }
1753 bh = bh->b_this_page;
1754 block++;
1755 } while (bh != head);
1756
1757 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001758 if (!buffer_mapped(bh))
1759 continue;
1760 /*
1761 * If it's a fully non-blocking write attempt and we cannot
1762 * lock the buffer then redirty the page. Note that this can
Jens Axboe5b0830c2009-09-23 19:37:09 +02001763 * potentially cause a busy-wait loop from writeback threads
1764 * and kswapd activity, but those code paths have their own
1765 * higher-level throttling.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001766 */
Wu Fengguang1b430be2010-10-26 14:21:26 -07001767 if (wbc->sync_mode != WB_SYNC_NONE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001768 lock_buffer(bh);
Nick Pigginca5de402008-08-02 12:02:13 +02001769 } else if (!trylock_buffer(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001770 redirty_page_for_writepage(wbc, page);
1771 continue;
1772 }
1773 if (test_clear_buffer_dirty(bh)) {
Chris Mason35c80d52009-04-15 13:22:38 -04001774 mark_buffer_async_write_endio(bh, handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001775 } else {
1776 unlock_buffer(bh);
1777 }
1778 } while ((bh = bh->b_this_page) != head);
1779
1780 /*
1781 * The page and its buffers are protected by PageWriteback(), so we can
1782 * drop the bh refcounts early.
1783 */
1784 BUG_ON(PageWriteback(page));
1785 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001786
1787 do {
1788 struct buffer_head *next = bh->b_this_page;
1789 if (buffer_async_write(bh)) {
Theodore Ts'oa64c8612009-03-27 22:14:10 -04001790 submit_bh(write_op, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001791 nr_underway++;
1792 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001793 bh = next;
1794 } while (bh != head);
Andrew Morton05937ba2005-05-05 16:15:47 -07001795 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001796
1797 err = 0;
1798done:
1799 if (nr_underway == 0) {
1800 /*
1801 * The page was marked dirty, but the buffers were
1802 * clean. Someone wrote them back by hand with
1803 * ll_rw_block/submit_bh. A rare case.
1804 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001805 end_page_writeback(page);
Nick Piggin3d67f2d2007-05-06 14:49:05 -07001806
Linus Torvalds1da177e2005-04-16 15:20:36 -07001807 /*
1808 * The page and buffer_heads can be released at any time from
1809 * here on.
1810 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001811 }
1812 return err;
1813
1814recover:
1815 /*
1816 * ENOSPC, or some other error. We may already have added some
1817 * blocks to the file, so we need to write these out to avoid
1818 * exposing stale data.
1819 * The page is currently locked and not marked for writeback
1820 */
1821 bh = head;
1822 /* Recovery: lock and submit the mapped buffers */
1823 do {
Alex Tomas29a814d2008-07-11 19:27:31 -04001824 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1825 !buffer_delay(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001826 lock_buffer(bh);
Chris Mason35c80d52009-04-15 13:22:38 -04001827 mark_buffer_async_write_endio(bh, handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001828 } else {
1829 /*
1830 * The buffer may have been set dirty during
1831 * attachment to a dirty page.
1832 */
1833 clear_buffer_dirty(bh);
1834 }
1835 } while ((bh = bh->b_this_page) != head);
1836 SetPageError(page);
1837 BUG_ON(PageWriteback(page));
Andrew Morton7e4c3692007-05-08 00:23:27 -07001838 mapping_set_error(page->mapping, err);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001839 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001840 do {
1841 struct buffer_head *next = bh->b_this_page;
1842 if (buffer_async_write(bh)) {
1843 clear_buffer_dirty(bh);
Theodore Ts'oa64c8612009-03-27 22:14:10 -04001844 submit_bh(write_op, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001845 nr_underway++;
1846 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001847 bh = next;
1848 } while (bh != head);
Nick Pigginffda9d32007-02-20 13:57:54 -08001849 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001850 goto done;
1851}
1852
Nick Pigginafddba42007-10-16 01:25:01 -07001853/*
1854 * If a page has any new buffers, zero them out here, and mark them uptodate
1855 * and dirty so they'll be written out (in order to prevent uninitialised
1856 * block data from leaking). And clear the new bit.
1857 */
1858void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1859{
1860 unsigned int block_start, block_end;
1861 struct buffer_head *head, *bh;
1862
1863 BUG_ON(!PageLocked(page));
1864 if (!page_has_buffers(page))
1865 return;
1866
1867 bh = head = page_buffers(page);
1868 block_start = 0;
1869 do {
1870 block_end = block_start + bh->b_size;
1871
1872 if (buffer_new(bh)) {
1873 if (block_end > from && block_start < to) {
1874 if (!PageUptodate(page)) {
1875 unsigned start, size;
1876
1877 start = max(from, block_start);
1878 size = min(to, block_end) - start;
1879
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001880 zero_user(page, start, size);
Nick Pigginafddba42007-10-16 01:25:01 -07001881 set_buffer_uptodate(bh);
1882 }
1883
1884 clear_buffer_new(bh);
1885 mark_buffer_dirty(bh);
1886 }
1887 }
1888
1889 block_start = block_end;
1890 bh = bh->b_this_page;
1891 } while (bh != head);
1892}
1893EXPORT_SYMBOL(page_zero_new_buffers);
1894
Christoph Hellwigebdec242010-10-06 10:47:23 +02001895int __block_write_begin(struct page *page, loff_t pos, unsigned len,
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001896 get_block_t *get_block)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001897{
Christoph Hellwigebdec242010-10-06 10:47:23 +02001898 unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1899 unsigned to = from + len;
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001900 struct inode *inode = page->mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001901 unsigned block_start, block_end;
1902 sector_t block;
1903 int err = 0;
1904 unsigned blocksize, bbits;
1905 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1906
1907 BUG_ON(!PageLocked(page));
1908 BUG_ON(from > PAGE_CACHE_SIZE);
1909 BUG_ON(to > PAGE_CACHE_SIZE);
1910 BUG_ON(from > to);
1911
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001912 head = create_page_buffers(page, inode, 0);
1913 blocksize = head->b_size;
1914 bbits = block_size_bits(blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001915
Linus Torvalds1da177e2005-04-16 15:20:36 -07001916 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1917
1918 for(bh = head, block_start = 0; bh != head || !block_start;
1919 block++, block_start=block_end, bh = bh->b_this_page) {
1920 block_end = block_start + blocksize;
1921 if (block_end <= from || block_start >= to) {
1922 if (PageUptodate(page)) {
1923 if (!buffer_uptodate(bh))
1924 set_buffer_uptodate(bh);
1925 }
1926 continue;
1927 }
1928 if (buffer_new(bh))
1929 clear_buffer_new(bh);
1930 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001931 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001932 err = get_block(inode, block, bh, 1);
1933 if (err)
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001934 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001935 if (buffer_new(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001936 unmap_underlying_metadata(bh->b_bdev,
1937 bh->b_blocknr);
1938 if (PageUptodate(page)) {
Nick Piggin637aff42007-10-16 01:25:00 -07001939 clear_buffer_new(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001940 set_buffer_uptodate(bh);
Nick Piggin637aff42007-10-16 01:25:00 -07001941 mark_buffer_dirty(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001942 continue;
1943 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001944 if (block_end > to || block_start < from)
1945 zero_user_segments(page,
1946 to, block_end,
1947 block_start, from);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001948 continue;
1949 }
1950 }
1951 if (PageUptodate(page)) {
1952 if (!buffer_uptodate(bh))
1953 set_buffer_uptodate(bh);
1954 continue;
1955 }
1956 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
David Chinner33a266d2007-02-12 00:51:41 -08001957 !buffer_unwritten(bh) &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001958 (block_start < from || block_end > to)) {
1959 ll_rw_block(READ, 1, &bh);
1960 *wait_bh++=bh;
1961 }
1962 }
1963 /*
1964 * If we issued read requests - let them complete.
1965 */
1966 while(wait_bh > wait) {
1967 wait_on_buffer(*--wait_bh);
1968 if (!buffer_uptodate(*wait_bh))
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001969 err = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001970 }
Jan Karaf9f07b62011-06-14 00:58:27 +02001971 if (unlikely(err))
Nick Pigginafddba42007-10-16 01:25:01 -07001972 page_zero_new_buffers(page, from, to);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001973 return err;
1974}
Christoph Hellwigebdec242010-10-06 10:47:23 +02001975EXPORT_SYMBOL(__block_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001976
1977static int __block_commit_write(struct inode *inode, struct page *page,
1978 unsigned from, unsigned to)
1979{
1980 unsigned block_start, block_end;
1981 int partial = 0;
1982 unsigned blocksize;
1983 struct buffer_head *bh, *head;
1984
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001985 bh = head = page_buffers(page);
1986 blocksize = bh->b_size;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001987
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001988 block_start = 0;
1989 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001990 block_end = block_start + blocksize;
1991 if (block_end <= from || block_start >= to) {
1992 if (!buffer_uptodate(bh))
1993 partial = 1;
1994 } else {
1995 set_buffer_uptodate(bh);
1996 mark_buffer_dirty(bh);
1997 }
Nick Pigginafddba42007-10-16 01:25:01 -07001998 clear_buffer_new(bh);
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001999
2000 block_start = block_end;
2001 bh = bh->b_this_page;
2002 } while (bh != head);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002003
2004 /*
2005 * If this is a partial write which happened to make all buffers
2006 * uptodate then we can optimize away a bogus readpage() for
2007 * the next read(). Here we 'discover' whether the page went
2008 * uptodate as a result of this (potentially partial) write.
2009 */
2010 if (!partial)
2011 SetPageUptodate(page);
2012 return 0;
2013}
2014
2015/*
Christoph Hellwig155130a2010-06-04 11:29:58 +02002016 * block_write_begin takes care of the basic task of block allocation and
2017 * bringing partial write blocks uptodate first.
2018 *
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10002019 * The filesystem needs to handle block truncation upon failure.
Nick Pigginafddba42007-10-16 01:25:01 -07002020 */
Christoph Hellwig155130a2010-06-04 11:29:58 +02002021int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
2022 unsigned flags, struct page **pagep, get_block_t *get_block)
Nick Pigginafddba42007-10-16 01:25:01 -07002023{
Christoph Hellwig6e1db882010-06-04 11:29:57 +02002024 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
Nick Pigginafddba42007-10-16 01:25:01 -07002025 struct page *page;
Christoph Hellwig6e1db882010-06-04 11:29:57 +02002026 int status;
Nick Pigginafddba42007-10-16 01:25:01 -07002027
Christoph Hellwig6e1db882010-06-04 11:29:57 +02002028 page = grab_cache_page_write_begin(mapping, index, flags);
2029 if (!page)
2030 return -ENOMEM;
Nick Pigginafddba42007-10-16 01:25:01 -07002031
Christoph Hellwig6e1db882010-06-04 11:29:57 +02002032 status = __block_write_begin(page, pos, len, get_block);
Nick Pigginafddba42007-10-16 01:25:01 -07002033 if (unlikely(status)) {
Christoph Hellwig6e1db882010-06-04 11:29:57 +02002034 unlock_page(page);
2035 page_cache_release(page);
2036 page = NULL;
Nick Pigginafddba42007-10-16 01:25:01 -07002037 }
2038
Christoph Hellwig6e1db882010-06-04 11:29:57 +02002039 *pagep = page;
Nick Pigginafddba42007-10-16 01:25:01 -07002040 return status;
2041}
2042EXPORT_SYMBOL(block_write_begin);
2043
2044int block_write_end(struct file *file, struct address_space *mapping,
2045 loff_t pos, unsigned len, unsigned copied,
2046 struct page *page, void *fsdata)
2047{
2048 struct inode *inode = mapping->host;
2049 unsigned start;
2050
2051 start = pos & (PAGE_CACHE_SIZE - 1);
2052
2053 if (unlikely(copied < len)) {
2054 /*
2055 * The buffers that were written will now be uptodate, so we
2056 * don't have to worry about a readpage reading them and
2057 * overwriting a partial write. However if we have encountered
2058 * a short write and only partially written into a buffer, it
2059 * will not be marked uptodate, so a readpage might come in and
2060 * destroy our partial write.
2061 *
2062 * Do the simplest thing, and just treat any short write to a
2063 * non uptodate page as a zero-length write, and force the
2064 * caller to redo the whole thing.
2065 */
2066 if (!PageUptodate(page))
2067 copied = 0;
2068
2069 page_zero_new_buffers(page, start+copied, start+len);
2070 }
2071 flush_dcache_page(page);
2072
2073 /* This could be a short (even 0-length) commit */
2074 __block_commit_write(inode, page, start, start+copied);
2075
2076 return copied;
2077}
2078EXPORT_SYMBOL(block_write_end);
2079
2080int generic_write_end(struct file *file, struct address_space *mapping,
2081 loff_t pos, unsigned len, unsigned copied,
2082 struct page *page, void *fsdata)
2083{
2084 struct inode *inode = mapping->host;
Jan Karac7d206b2008-07-11 19:27:31 -04002085 int i_size_changed = 0;
Nick Pigginafddba42007-10-16 01:25:01 -07002086
2087 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2088
2089 /*
2090 * No need to use i_size_read() here, the i_size
2091 * cannot change under us because we hold i_mutex.
2092 *
2093 * But it's important to update i_size while still holding page lock:
2094 * page writeout could otherwise come in and zero beyond i_size.
2095 */
2096 if (pos+copied > inode->i_size) {
2097 i_size_write(inode, pos+copied);
Jan Karac7d206b2008-07-11 19:27:31 -04002098 i_size_changed = 1;
Nick Pigginafddba42007-10-16 01:25:01 -07002099 }
2100
2101 unlock_page(page);
2102 page_cache_release(page);
2103
Jan Karac7d206b2008-07-11 19:27:31 -04002104 /*
2105 * Don't mark the inode dirty under page lock. First, it unnecessarily
2106 * makes the holding time of page lock longer. Second, it forces lock
2107 * ordering of page lock and transaction start for journaling
2108 * filesystems.
2109 */
2110 if (i_size_changed)
2111 mark_inode_dirty(inode);
2112
Nick Pigginafddba42007-10-16 01:25:01 -07002113 return copied;
2114}
2115EXPORT_SYMBOL(generic_write_end);
2116
2117/*
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07002118 * block_is_partially_uptodate checks whether buffers within a page are
2119 * uptodate or not.
2120 *
2121 * Returns true if all buffers which correspond to a file portion
2122 * we want to read are uptodate.
2123 */
Al Viroc186afb42014-02-02 21:16:54 -05002124int block_is_partially_uptodate(struct page *page, unsigned long from,
2125 unsigned long count)
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07002126{
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07002127 unsigned block_start, block_end, blocksize;
2128 unsigned to;
2129 struct buffer_head *bh, *head;
2130 int ret = 1;
2131
2132 if (!page_has_buffers(page))
2133 return 0;
2134
Linus Torvalds45bce8f2012-11-29 10:21:43 -08002135 head = page_buffers(page);
2136 blocksize = head->b_size;
Al Viroc186afb42014-02-02 21:16:54 -05002137 to = min_t(unsigned, PAGE_CACHE_SIZE - from, count);
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07002138 to = from + to;
2139 if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
2140 return 0;
2141
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07002142 bh = head;
2143 block_start = 0;
2144 do {
2145 block_end = block_start + blocksize;
2146 if (block_end > from && block_start < to) {
2147 if (!buffer_uptodate(bh)) {
2148 ret = 0;
2149 break;
2150 }
2151 if (block_end >= to)
2152 break;
2153 }
2154 block_start = block_end;
2155 bh = bh->b_this_page;
2156 } while (bh != head);
2157
2158 return ret;
2159}
2160EXPORT_SYMBOL(block_is_partially_uptodate);
2161
2162/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002163 * Generic "read page" function for block devices that have the normal
2164 * get_block functionality. This is most of the block device filesystems.
2165 * Reads the page asynchronously --- the unlock_buffer() and
2166 * set/clear_buffer_uptodate() functions propagate buffer state into the
2167 * page struct once IO has completed.
2168 */
2169int block_read_full_page(struct page *page, get_block_t *get_block)
2170{
2171 struct inode *inode = page->mapping->host;
2172 sector_t iblock, lblock;
2173 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
Linus Torvalds45bce8f2012-11-29 10:21:43 -08002174 unsigned int blocksize, bbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002175 int nr, i;
2176 int fully_mapped = 1;
2177
Linus Torvalds45bce8f2012-11-29 10:21:43 -08002178 head = create_page_buffers(page, inode, 0);
2179 blocksize = head->b_size;
2180 bbits = block_size_bits(blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002181
Linus Torvalds45bce8f2012-11-29 10:21:43 -08002182 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
2183 lblock = (i_size_read(inode)+blocksize-1) >> bbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002184 bh = head;
2185 nr = 0;
2186 i = 0;
2187
2188 do {
2189 if (buffer_uptodate(bh))
2190 continue;
2191
2192 if (!buffer_mapped(bh)) {
Andrew Mortonc64610b2005-05-16 21:53:49 -07002193 int err = 0;
2194
Linus Torvalds1da177e2005-04-16 15:20:36 -07002195 fully_mapped = 0;
2196 if (iblock < lblock) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002197 WARN_ON(bh->b_size != blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002198 err = get_block(inode, iblock, bh, 0);
2199 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002200 SetPageError(page);
2201 }
2202 if (!buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002203 zero_user(page, i * blocksize, blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002204 if (!err)
2205 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002206 continue;
2207 }
2208 /*
2209 * get_block() might have updated the buffer
2210 * synchronously
2211 */
2212 if (buffer_uptodate(bh))
2213 continue;
2214 }
2215 arr[nr++] = bh;
2216 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2217
2218 if (fully_mapped)
2219 SetPageMappedToDisk(page);
2220
2221 if (!nr) {
2222 /*
2223 * All buffers are uptodate - we can set the page uptodate
2224 * as well. But not if get_block() returned an error.
2225 */
2226 if (!PageError(page))
2227 SetPageUptodate(page);
2228 unlock_page(page);
2229 return 0;
2230 }
2231
2232 /* Stage two: lock the buffers */
2233 for (i = 0; i < nr; i++) {
2234 bh = arr[i];
2235 lock_buffer(bh);
2236 mark_buffer_async_read(bh);
2237 }
2238
2239 /*
2240 * Stage 3: start the IO. Check for uptodateness
2241 * inside the buffer lock in case another process reading
2242 * the underlying blockdev brought it uptodate (the sct fix).
2243 */
2244 for (i = 0; i < nr; i++) {
2245 bh = arr[i];
2246 if (buffer_uptodate(bh))
2247 end_buffer_async_read(bh, 1);
2248 else
2249 submit_bh(READ, bh);
2250 }
2251 return 0;
2252}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002253EXPORT_SYMBOL(block_read_full_page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002254
2255/* utility function for filesystems that need to do work on expanding
Nick Piggin89e10782007-10-16 01:25:07 -07002256 * truncates. Uses filesystem pagecache writes to allow the filesystem to
Linus Torvalds1da177e2005-04-16 15:20:36 -07002257 * deal with the hole.
2258 */
Nick Piggin89e10782007-10-16 01:25:07 -07002259int generic_cont_expand_simple(struct inode *inode, loff_t size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002260{
2261 struct address_space *mapping = inode->i_mapping;
2262 struct page *page;
Nick Piggin89e10782007-10-16 01:25:07 -07002263 void *fsdata;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002264 int err;
2265
npiggin@suse.dec08d3b02009-08-21 02:35:06 +10002266 err = inode_newsize_ok(inode, size);
2267 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002268 goto out;
2269
Nick Piggin89e10782007-10-16 01:25:07 -07002270 err = pagecache_write_begin(NULL, mapping, size, 0,
2271 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2272 &page, &fsdata);
2273 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002274 goto out;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002275
Nick Piggin89e10782007-10-16 01:25:07 -07002276 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2277 BUG_ON(err > 0);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002278
Linus Torvalds1da177e2005-04-16 15:20:36 -07002279out:
2280 return err;
2281}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002282EXPORT_SYMBOL(generic_cont_expand_simple);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002283
Adrian Bunkf1e3af72008-04-29 00:59:01 -07002284static int cont_expand_zero(struct file *file, struct address_space *mapping,
2285 loff_t pos, loff_t *bytes)
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002286{
Nick Piggin89e10782007-10-16 01:25:07 -07002287 struct inode *inode = mapping->host;
2288 unsigned blocksize = 1 << inode->i_blkbits;
2289 struct page *page;
2290 void *fsdata;
2291 pgoff_t index, curidx;
2292 loff_t curpos;
2293 unsigned zerofrom, offset, len;
2294 int err = 0;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002295
Nick Piggin89e10782007-10-16 01:25:07 -07002296 index = pos >> PAGE_CACHE_SHIFT;
2297 offset = pos & ~PAGE_CACHE_MASK;
2298
2299 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
2300 zerofrom = curpos & ~PAGE_CACHE_MASK;
2301 if (zerofrom & (blocksize-1)) {
2302 *bytes |= (blocksize-1);
2303 (*bytes)++;
2304 }
2305 len = PAGE_CACHE_SIZE - zerofrom;
2306
2307 err = pagecache_write_begin(file, mapping, curpos, len,
2308 AOP_FLAG_UNINTERRUPTIBLE,
2309 &page, &fsdata);
2310 if (err)
2311 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002312 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002313 err = pagecache_write_end(file, mapping, curpos, len, len,
2314 page, fsdata);
2315 if (err < 0)
2316 goto out;
2317 BUG_ON(err != len);
2318 err = 0;
OGAWA Hirofumi061e9742008-04-28 02:16:28 -07002319
2320 balance_dirty_pages_ratelimited(mapping);
Nick Piggin89e10782007-10-16 01:25:07 -07002321 }
2322
2323 /* page covers the boundary, find the boundary offset */
2324 if (index == curidx) {
2325 zerofrom = curpos & ~PAGE_CACHE_MASK;
2326 /* if we will expand the thing last block will be filled */
2327 if (offset <= zerofrom) {
2328 goto out;
2329 }
2330 if (zerofrom & (blocksize-1)) {
2331 *bytes |= (blocksize-1);
2332 (*bytes)++;
2333 }
2334 len = offset - zerofrom;
2335
2336 err = pagecache_write_begin(file, mapping, curpos, len,
2337 AOP_FLAG_UNINTERRUPTIBLE,
2338 &page, &fsdata);
2339 if (err)
2340 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002341 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002342 err = pagecache_write_end(file, mapping, curpos, len, len,
2343 page, fsdata);
2344 if (err < 0)
2345 goto out;
2346 BUG_ON(err != len);
2347 err = 0;
2348 }
2349out:
2350 return err;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002351}
2352
Linus Torvalds1da177e2005-04-16 15:20:36 -07002353/*
2354 * For moronic filesystems that do not allow holes in file.
2355 * We may have to extend the file.
2356 */
Christoph Hellwig282dc172010-06-04 11:29:55 +02002357int cont_write_begin(struct file *file, struct address_space *mapping,
Nick Piggin89e10782007-10-16 01:25:07 -07002358 loff_t pos, unsigned len, unsigned flags,
2359 struct page **pagep, void **fsdata,
2360 get_block_t *get_block, loff_t *bytes)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002361{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002362 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002363 unsigned blocksize = 1 << inode->i_blkbits;
Nick Piggin89e10782007-10-16 01:25:07 -07002364 unsigned zerofrom;
2365 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002366
Nick Piggin89e10782007-10-16 01:25:07 -07002367 err = cont_expand_zero(file, mapping, pos, bytes);
2368 if (err)
Christoph Hellwig155130a2010-06-04 11:29:58 +02002369 return err;
Nick Piggin89e10782007-10-16 01:25:07 -07002370
2371 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2372 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2373 *bytes |= (blocksize-1);
2374 (*bytes)++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002375 }
2376
Christoph Hellwig155130a2010-06-04 11:29:58 +02002377 return block_write_begin(mapping, pos, len, flags, pagep, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002378}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002379EXPORT_SYMBOL(cont_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002380
Linus Torvalds1da177e2005-04-16 15:20:36 -07002381int block_commit_write(struct page *page, unsigned from, unsigned to)
2382{
2383 struct inode *inode = page->mapping->host;
2384 __block_commit_write(inode,page,from,to);
2385 return 0;
2386}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002387EXPORT_SYMBOL(block_commit_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002388
David Chinner54171692007-07-19 17:39:55 +10002389/*
2390 * block_page_mkwrite() is not allowed to change the file size as it gets
2391 * called from a page fault handler when a page is first dirtied. Hence we must
2392 * be careful to check for EOF conditions here. We set the page up correctly
2393 * for a written page which means we get ENOSPC checking when writing into
2394 * holes and correct delalloc and unwritten extent mapping on filesystems that
2395 * support these features.
2396 *
2397 * We are not allowed to take the i_mutex here so we have to play games to
2398 * protect against truncate races as the page could now be beyond EOF. Because
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10002399 * truncate writes the inode size before removing pages, once we have the
David Chinner54171692007-07-19 17:39:55 +10002400 * page lock we can determine safely if the page is beyond EOF. If it is not
2401 * beyond EOF, then the page is guaranteed safe against truncation until we
2402 * unlock the page.
Jan Karaea13a862011-05-24 00:23:35 +02002403 *
Jan Kara14da9202012-06-12 16:20:37 +02002404 * Direct callers of this function should protect against filesystem freezing
2405 * using sb_start_write() - sb_end_write() functions.
David Chinner54171692007-07-19 17:39:55 +10002406 */
Jan Kara24da4fa2011-05-24 00:23:34 +02002407int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2408 get_block_t get_block)
David Chinner54171692007-07-19 17:39:55 +10002409{
Nick Pigginc2ec1752009-03-31 15:23:21 -07002410 struct page *page = vmf->page;
Al Viro496ad9a2013-01-23 17:07:38 -05002411 struct inode *inode = file_inode(vma->vm_file);
David Chinner54171692007-07-19 17:39:55 +10002412 unsigned long end;
2413 loff_t size;
Jan Kara24da4fa2011-05-24 00:23:34 +02002414 int ret;
David Chinner54171692007-07-19 17:39:55 +10002415
2416 lock_page(page);
2417 size = i_size_read(inode);
2418 if ((page->mapping != inode->i_mapping) ||
Nick Piggin18336332007-07-20 00:31:45 -07002419 (page_offset(page) > size)) {
Jan Kara24da4fa2011-05-24 00:23:34 +02002420 /* We overload EFAULT to mean page got truncated */
2421 ret = -EFAULT;
2422 goto out_unlock;
David Chinner54171692007-07-19 17:39:55 +10002423 }
2424
2425 /* page is wholly or partially inside EOF */
2426 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
2427 end = size & ~PAGE_CACHE_MASK;
2428 else
2429 end = PAGE_CACHE_SIZE;
2430
Christoph Hellwigebdec242010-10-06 10:47:23 +02002431 ret = __block_write_begin(page, 0, end, get_block);
David Chinner54171692007-07-19 17:39:55 +10002432 if (!ret)
2433 ret = block_commit_write(page, 0, end);
2434
Jan Kara24da4fa2011-05-24 00:23:34 +02002435 if (unlikely(ret < 0))
2436 goto out_unlock;
Jan Karaea13a862011-05-24 00:23:35 +02002437 set_page_dirty(page);
Darrick J. Wong1d1d1a72013-02-21 16:42:51 -08002438 wait_for_stable_page(page);
Jan Kara24da4fa2011-05-24 00:23:34 +02002439 return 0;
2440out_unlock:
2441 unlock_page(page);
David Chinner54171692007-07-19 17:39:55 +10002442 return ret;
2443}
Jan Kara24da4fa2011-05-24 00:23:34 +02002444EXPORT_SYMBOL(__block_page_mkwrite);
2445
2446int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2447 get_block_t get_block)
2448{
Jan Karaea13a862011-05-24 00:23:35 +02002449 int ret;
Al Viro496ad9a2013-01-23 17:07:38 -05002450 struct super_block *sb = file_inode(vma->vm_file)->i_sb;
Jan Kara24da4fa2011-05-24 00:23:34 +02002451
Jan Kara14da9202012-06-12 16:20:37 +02002452 sb_start_pagefault(sb);
Theodore Ts'o041bbb6d2012-09-30 23:04:56 -04002453
2454 /*
2455 * Update file times before taking page lock. We may end up failing the
2456 * fault so this update may be superfluous but who really cares...
2457 */
2458 file_update_time(vma->vm_file);
2459
Jan Karaea13a862011-05-24 00:23:35 +02002460 ret = __block_page_mkwrite(vma, vmf, get_block);
Jan Kara14da9202012-06-12 16:20:37 +02002461 sb_end_pagefault(sb);
Jan Kara24da4fa2011-05-24 00:23:34 +02002462 return block_page_mkwrite_return(ret);
2463}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002464EXPORT_SYMBOL(block_page_mkwrite);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002465
2466/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002467 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
Linus Torvalds1da177e2005-04-16 15:20:36 -07002468 * immediately, while under the page lock. So it needs a special end_io
2469 * handler which does not touch the bh after unlocking it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002470 */
2471static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2472{
Dmitry Monakhov68671f32007-10-16 01:24:47 -07002473 __end_buffer_read_notouch(bh, uptodate);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002474}
2475
2476/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002477 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2478 * the page (converting it to circular linked list and taking care of page
2479 * dirty races).
2480 */
2481static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2482{
2483 struct buffer_head *bh;
2484
2485 BUG_ON(!PageLocked(page));
2486
2487 spin_lock(&page->mapping->private_lock);
2488 bh = head;
2489 do {
2490 if (PageDirty(page))
2491 set_buffer_dirty(bh);
2492 if (!bh->b_this_page)
2493 bh->b_this_page = head;
2494 bh = bh->b_this_page;
2495 } while (bh != head);
2496 attach_page_buffers(page, head);
2497 spin_unlock(&page->mapping->private_lock);
2498}
2499
2500/*
Christoph Hellwigea0f04e2010-06-04 11:29:54 +02002501 * On entry, the page is fully not uptodate.
2502 * On exit the page is fully uptodate in the areas outside (from,to)
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10002503 * The filesystem needs to handle block truncation upon failure.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002504 */
Christoph Hellwigea0f04e2010-06-04 11:29:54 +02002505int nobh_write_begin(struct address_space *mapping,
Nick Piggin03158cd2007-10-16 01:25:25 -07002506 loff_t pos, unsigned len, unsigned flags,
2507 struct page **pagep, void **fsdata,
Linus Torvalds1da177e2005-04-16 15:20:36 -07002508 get_block_t *get_block)
2509{
Nick Piggin03158cd2007-10-16 01:25:25 -07002510 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002511 const unsigned blkbits = inode->i_blkbits;
2512 const unsigned blocksize = 1 << blkbits;
Nick Piggina4b06722007-10-16 01:24:48 -07002513 struct buffer_head *head, *bh;
Nick Piggin03158cd2007-10-16 01:25:25 -07002514 struct page *page;
2515 pgoff_t index;
2516 unsigned from, to;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002517 unsigned block_in_page;
Nick Piggina4b06722007-10-16 01:24:48 -07002518 unsigned block_start, block_end;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002519 sector_t block_in_file;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002520 int nr_reads = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002521 int ret = 0;
2522 int is_mapped_to_disk = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002523
Nick Piggin03158cd2007-10-16 01:25:25 -07002524 index = pos >> PAGE_CACHE_SHIFT;
2525 from = pos & (PAGE_CACHE_SIZE - 1);
2526 to = from + len;
2527
Nick Piggin54566b22009-01-04 12:00:53 -08002528 page = grab_cache_page_write_begin(mapping, index, flags);
Nick Piggin03158cd2007-10-16 01:25:25 -07002529 if (!page)
2530 return -ENOMEM;
2531 *pagep = page;
2532 *fsdata = NULL;
2533
2534 if (page_has_buffers(page)) {
Namhyung Kim309f77a2010-10-25 15:01:12 +09002535 ret = __block_write_begin(page, pos, len, get_block);
2536 if (unlikely(ret))
2537 goto out_release;
2538 return ret;
Nick Piggin03158cd2007-10-16 01:25:25 -07002539 }
Nick Piggina4b06722007-10-16 01:24:48 -07002540
Linus Torvalds1da177e2005-04-16 15:20:36 -07002541 if (PageMappedToDisk(page))
2542 return 0;
2543
Nick Piggina4b06722007-10-16 01:24:48 -07002544 /*
2545 * Allocate buffers so that we can keep track of state, and potentially
2546 * attach them to the page if an error occurs. In the common case of
2547 * no error, they will just be freed again without ever being attached
2548 * to the page (which is all OK, because we're under the page lock).
2549 *
2550 * Be careful: the buffer linked list is a NULL terminated one, rather
2551 * than the circular one we're used to.
2552 */
2553 head = alloc_page_buffers(page, blocksize, 0);
Nick Piggin03158cd2007-10-16 01:25:25 -07002554 if (!head) {
2555 ret = -ENOMEM;
2556 goto out_release;
2557 }
Nick Piggina4b06722007-10-16 01:24:48 -07002558
Linus Torvalds1da177e2005-04-16 15:20:36 -07002559 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002560
2561 /*
2562 * We loop across all blocks in the page, whether or not they are
2563 * part of the affected region. This is so we can discover if the
2564 * page is fully mapped-to-disk.
2565 */
Nick Piggina4b06722007-10-16 01:24:48 -07002566 for (block_start = 0, block_in_page = 0, bh = head;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002567 block_start < PAGE_CACHE_SIZE;
Nick Piggina4b06722007-10-16 01:24:48 -07002568 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002569 int create;
2570
Nick Piggina4b06722007-10-16 01:24:48 -07002571 block_end = block_start + blocksize;
2572 bh->b_state = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002573 create = 1;
2574 if (block_start >= to)
2575 create = 0;
2576 ret = get_block(inode, block_in_file + block_in_page,
Nick Piggina4b06722007-10-16 01:24:48 -07002577 bh, create);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002578 if (ret)
2579 goto failed;
Nick Piggina4b06722007-10-16 01:24:48 -07002580 if (!buffer_mapped(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002581 is_mapped_to_disk = 0;
Nick Piggina4b06722007-10-16 01:24:48 -07002582 if (buffer_new(bh))
2583 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
2584 if (PageUptodate(page)) {
2585 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002586 continue;
Nick Piggina4b06722007-10-16 01:24:48 -07002587 }
2588 if (buffer_new(bh) || !buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002589 zero_user_segments(page, block_start, from,
2590 to, block_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002591 continue;
2592 }
Nick Piggina4b06722007-10-16 01:24:48 -07002593 if (buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002594 continue; /* reiserfs does this */
2595 if (block_start < from || block_end > to) {
Nick Piggina4b06722007-10-16 01:24:48 -07002596 lock_buffer(bh);
2597 bh->b_end_io = end_buffer_read_nobh;
2598 submit_bh(READ, bh);
2599 nr_reads++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002600 }
2601 }
2602
2603 if (nr_reads) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002604 /*
2605 * The page is locked, so these buffers are protected from
2606 * any VM or truncate activity. Hence we don't need to care
2607 * for the buffer_head refcounts.
2608 */
Nick Piggina4b06722007-10-16 01:24:48 -07002609 for (bh = head; bh; bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002610 wait_on_buffer(bh);
2611 if (!buffer_uptodate(bh))
2612 ret = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002613 }
2614 if (ret)
2615 goto failed;
2616 }
2617
2618 if (is_mapped_to_disk)
2619 SetPageMappedToDisk(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002620
Nick Piggin03158cd2007-10-16 01:25:25 -07002621 *fsdata = head; /* to be released by nobh_write_end */
Nick Piggina4b06722007-10-16 01:24:48 -07002622
Linus Torvalds1da177e2005-04-16 15:20:36 -07002623 return 0;
2624
2625failed:
Nick Piggin03158cd2007-10-16 01:25:25 -07002626 BUG_ON(!ret);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002627 /*
Nick Piggina4b06722007-10-16 01:24:48 -07002628 * Error recovery is a bit difficult. We need to zero out blocks that
2629 * were newly allocated, and dirty them to ensure they get written out.
2630 * Buffers need to be attached to the page at this point, otherwise
2631 * the handling of potential IO errors during writeout would be hard
2632 * (could try doing synchronous writeout, but what if that fails too?)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002633 */
Nick Piggin03158cd2007-10-16 01:25:25 -07002634 attach_nobh_buffers(page, head);
2635 page_zero_new_buffers(page, from, to);
Nick Piggina4b06722007-10-16 01:24:48 -07002636
Nick Piggin03158cd2007-10-16 01:25:25 -07002637out_release:
2638 unlock_page(page);
2639 page_cache_release(page);
2640 *pagep = NULL;
Nick Piggina4b06722007-10-16 01:24:48 -07002641
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10002642 return ret;
2643}
Nick Piggin03158cd2007-10-16 01:25:25 -07002644EXPORT_SYMBOL(nobh_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002645
Nick Piggin03158cd2007-10-16 01:25:25 -07002646int nobh_write_end(struct file *file, struct address_space *mapping,
2647 loff_t pos, unsigned len, unsigned copied,
2648 struct page *page, void *fsdata)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002649{
2650 struct inode *inode = page->mapping->host;
Nick Pigginefdc3132007-10-21 06:57:41 +02002651 struct buffer_head *head = fsdata;
Nick Piggin03158cd2007-10-16 01:25:25 -07002652 struct buffer_head *bh;
Dmitri Monakhov5b41e742008-03-28 14:15:52 -07002653 BUG_ON(fsdata != NULL && page_has_buffers(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002654
Dave Kleikampd4cf1092009-02-06 14:59:26 -06002655 if (unlikely(copied < len) && head)
Dmitri Monakhov5b41e742008-03-28 14:15:52 -07002656 attach_nobh_buffers(page, head);
2657 if (page_has_buffers(page))
2658 return generic_write_end(file, mapping, pos, len,
2659 copied, page, fsdata);
Nick Piggina4b06722007-10-16 01:24:48 -07002660
Nick Piggin22c8ca72007-02-20 13:58:09 -08002661 SetPageUptodate(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002662 set_page_dirty(page);
Nick Piggin03158cd2007-10-16 01:25:25 -07002663 if (pos+copied > inode->i_size) {
2664 i_size_write(inode, pos+copied);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002665 mark_inode_dirty(inode);
2666 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002667
2668 unlock_page(page);
2669 page_cache_release(page);
2670
Nick Piggin03158cd2007-10-16 01:25:25 -07002671 while (head) {
2672 bh = head;
2673 head = head->b_this_page;
2674 free_buffer_head(bh);
2675 }
2676
2677 return copied;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002678}
Nick Piggin03158cd2007-10-16 01:25:25 -07002679EXPORT_SYMBOL(nobh_write_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002680
2681/*
2682 * nobh_writepage() - based on block_full_write_page() except
2683 * that it tries to operate without attaching bufferheads to
2684 * the page.
2685 */
2686int nobh_writepage(struct page *page, get_block_t *get_block,
2687 struct writeback_control *wbc)
2688{
2689 struct inode * const inode = page->mapping->host;
2690 loff_t i_size = i_size_read(inode);
2691 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2692 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002693 int ret;
2694
2695 /* Is the page fully inside i_size? */
2696 if (page->index < end_index)
2697 goto out;
2698
2699 /* Is the page fully outside i_size? (truncate in progress) */
2700 offset = i_size & (PAGE_CACHE_SIZE-1);
2701 if (page->index >= end_index+1 || !offset) {
2702 /*
2703 * The page may have dirty, unmapped buffers. For example,
2704 * they may have been added in ext3_writepage(). Make them
2705 * freeable here, so the page does not leak.
2706 */
2707#if 0
2708 /* Not really sure about this - do we need this ? */
2709 if (page->mapping->a_ops->invalidatepage)
2710 page->mapping->a_ops->invalidatepage(page, offset);
2711#endif
2712 unlock_page(page);
2713 return 0; /* don't care */
2714 }
2715
2716 /*
2717 * The page straddles i_size. It must be zeroed out on each and every
2718 * writepage invocation because it may be mmapped. "A file is mapped
2719 * in multiples of the page size. For a file that is not a multiple of
2720 * the page size, the remaining memory is zeroed when mapped, and
2721 * writes to that region are not written out to the file."
2722 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002723 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002724out:
2725 ret = mpage_writepage(page, get_block, wbc);
2726 if (ret == -EAGAIN)
Chris Mason35c80d52009-04-15 13:22:38 -04002727 ret = __block_write_full_page(inode, page, get_block, wbc,
2728 end_buffer_async_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002729 return ret;
2730}
2731EXPORT_SYMBOL(nobh_writepage);
2732
Nick Piggin03158cd2007-10-16 01:25:25 -07002733int nobh_truncate_page(struct address_space *mapping,
2734 loff_t from, get_block_t *get_block)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002735{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002736 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2737 unsigned offset = from & (PAGE_CACHE_SIZE-1);
Nick Piggin03158cd2007-10-16 01:25:25 -07002738 unsigned blocksize;
2739 sector_t iblock;
2740 unsigned length, pos;
2741 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002742 struct page *page;
Nick Piggin03158cd2007-10-16 01:25:25 -07002743 struct buffer_head map_bh;
2744 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002745
Nick Piggin03158cd2007-10-16 01:25:25 -07002746 blocksize = 1 << inode->i_blkbits;
2747 length = offset & (blocksize - 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002748
Nick Piggin03158cd2007-10-16 01:25:25 -07002749 /* Block boundary? Nothing to do */
2750 if (!length)
2751 return 0;
2752
2753 length = blocksize - length;
2754 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2755
Linus Torvalds1da177e2005-04-16 15:20:36 -07002756 page = grab_cache_page(mapping, index);
Nick Piggin03158cd2007-10-16 01:25:25 -07002757 err = -ENOMEM;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002758 if (!page)
2759 goto out;
2760
Nick Piggin03158cd2007-10-16 01:25:25 -07002761 if (page_has_buffers(page)) {
2762has_buffers:
2763 unlock_page(page);
2764 page_cache_release(page);
2765 return block_truncate_page(mapping, from, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002766 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002767
2768 /* Find the buffer that contains "offset" */
2769 pos = blocksize;
2770 while (offset >= pos) {
2771 iblock++;
2772 pos += blocksize;
2773 }
2774
Theodore Ts'o460bcf52009-05-12 07:37:56 -04002775 map_bh.b_size = blocksize;
2776 map_bh.b_state = 0;
Nick Piggin03158cd2007-10-16 01:25:25 -07002777 err = get_block(inode, iblock, &map_bh, 0);
2778 if (err)
2779 goto unlock;
2780 /* unmapped? It's a hole - nothing to do */
2781 if (!buffer_mapped(&map_bh))
2782 goto unlock;
2783
2784 /* Ok, it's mapped. Make sure it's up-to-date */
2785 if (!PageUptodate(page)) {
2786 err = mapping->a_ops->readpage(NULL, page);
2787 if (err) {
2788 page_cache_release(page);
2789 goto out;
2790 }
2791 lock_page(page);
2792 if (!PageUptodate(page)) {
2793 err = -EIO;
2794 goto unlock;
2795 }
2796 if (page_has_buffers(page))
2797 goto has_buffers;
2798 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002799 zero_user(page, offset, length);
Nick Piggin03158cd2007-10-16 01:25:25 -07002800 set_page_dirty(page);
2801 err = 0;
2802
2803unlock:
Linus Torvalds1da177e2005-04-16 15:20:36 -07002804 unlock_page(page);
2805 page_cache_release(page);
2806out:
Nick Piggin03158cd2007-10-16 01:25:25 -07002807 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002808}
2809EXPORT_SYMBOL(nobh_truncate_page);
2810
2811int block_truncate_page(struct address_space *mapping,
2812 loff_t from, get_block_t *get_block)
2813{
2814 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2815 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2816 unsigned blocksize;
Andrew Morton54b21a72006-01-08 01:03:05 -08002817 sector_t iblock;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002818 unsigned length, pos;
2819 struct inode *inode = mapping->host;
2820 struct page *page;
2821 struct buffer_head *bh;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002822 int err;
2823
2824 blocksize = 1 << inode->i_blkbits;
2825 length = offset & (blocksize - 1);
2826
2827 /* Block boundary? Nothing to do */
2828 if (!length)
2829 return 0;
2830
2831 length = blocksize - length;
Andrew Morton54b21a72006-01-08 01:03:05 -08002832 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002833
2834 page = grab_cache_page(mapping, index);
2835 err = -ENOMEM;
2836 if (!page)
2837 goto out;
2838
2839 if (!page_has_buffers(page))
2840 create_empty_buffers(page, blocksize, 0);
2841
2842 /* Find the buffer that contains "offset" */
2843 bh = page_buffers(page);
2844 pos = blocksize;
2845 while (offset >= pos) {
2846 bh = bh->b_this_page;
2847 iblock++;
2848 pos += blocksize;
2849 }
2850
2851 err = 0;
2852 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002853 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002854 err = get_block(inode, iblock, bh, 0);
2855 if (err)
2856 goto unlock;
2857 /* unmapped? It's a hole - nothing to do */
2858 if (!buffer_mapped(bh))
2859 goto unlock;
2860 }
2861
2862 /* Ok, it's mapped. Make sure it's up-to-date */
2863 if (PageUptodate(page))
2864 set_buffer_uptodate(bh);
2865
David Chinner33a266d2007-02-12 00:51:41 -08002866 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002867 err = -EIO;
2868 ll_rw_block(READ, 1, &bh);
2869 wait_on_buffer(bh);
2870 /* Uhhuh. Read error. Complain and punt. */
2871 if (!buffer_uptodate(bh))
2872 goto unlock;
2873 }
2874
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002875 zero_user(page, offset, length);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002876 mark_buffer_dirty(bh);
2877 err = 0;
2878
2879unlock:
2880 unlock_page(page);
2881 page_cache_release(page);
2882out:
2883 return err;
2884}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002885EXPORT_SYMBOL(block_truncate_page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002886
2887/*
2888 * The generic ->writepage function for buffer-backed address_spaces
2889 */
Matthew Wilcox1b938c02014-06-04 16:07:43 -07002890int block_write_full_page(struct page *page, get_block_t *get_block,
2891 struct writeback_control *wbc)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002892{
2893 struct inode * const inode = page->mapping->host;
2894 loff_t i_size = i_size_read(inode);
2895 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2896 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002897
2898 /* Is the page fully inside i_size? */
2899 if (page->index < end_index)
Chris Mason35c80d52009-04-15 13:22:38 -04002900 return __block_write_full_page(inode, page, get_block, wbc,
Matthew Wilcox1b938c02014-06-04 16:07:43 -07002901 end_buffer_async_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002902
2903 /* Is the page fully outside i_size? (truncate in progress) */
2904 offset = i_size & (PAGE_CACHE_SIZE-1);
2905 if (page->index >= end_index+1 || !offset) {
2906 /*
2907 * The page may have dirty, unmapped buffers. For example,
2908 * they may have been added in ext3_writepage(). Make them
2909 * freeable here, so the page does not leak.
2910 */
Lukas Czernerd47992f2013-05-21 23:17:23 -04002911 do_invalidatepage(page, 0, PAGE_CACHE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002912 unlock_page(page);
2913 return 0; /* don't care */
2914 }
2915
2916 /*
2917 * The page straddles i_size. It must be zeroed out on each and every
Adam Buchbinder2a61aa42009-12-11 16:35:40 -05002918 * writepage invocation because it may be mmapped. "A file is mapped
Linus Torvalds1da177e2005-04-16 15:20:36 -07002919 * in multiples of the page size. For a file that is not a multiple of
2920 * the page size, the remaining memory is zeroed when mapped, and
2921 * writes to that region are not written out to the file."
2922 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002923 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Matthew Wilcox1b938c02014-06-04 16:07:43 -07002924 return __block_write_full_page(inode, page, get_block, wbc,
2925 end_buffer_async_write);
Chris Mason35c80d52009-04-15 13:22:38 -04002926}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002927EXPORT_SYMBOL(block_write_full_page);
Chris Mason35c80d52009-04-15 13:22:38 -04002928
Linus Torvalds1da177e2005-04-16 15:20:36 -07002929sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2930 get_block_t *get_block)
2931{
2932 struct buffer_head tmp;
2933 struct inode *inode = mapping->host;
2934 tmp.b_state = 0;
2935 tmp.b_blocknr = 0;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002936 tmp.b_size = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002937 get_block(inode, block, &tmp, 0);
2938 return tmp.b_blocknr;
2939}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002940EXPORT_SYMBOL(generic_block_bmap);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002941
NeilBrown6712ecf2007-09-27 12:47:43 +02002942static void end_bio_bh_io_sync(struct bio *bio, int err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002943{
2944 struct buffer_head *bh = bio->bi_private;
2945
Linus Torvalds1da177e2005-04-16 15:20:36 -07002946 if (err == -EOPNOTSUPP) {
2947 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002948 }
2949
Keith Mannthey08bafc02008-11-25 10:24:35 +01002950 if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags)))
2951 set_bit(BH_Quiet, &bh->b_state);
2952
Linus Torvalds1da177e2005-04-16 15:20:36 -07002953 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2954 bio_put(bio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002955}
2956
Linus Torvalds57302e02012-12-04 08:25:11 -08002957/*
2958 * This allows us to do IO even on the odd last sectors
2959 * of a device, even if the bh block size is some multiple
2960 * of the physical sector size.
2961 *
2962 * We'll just truncate the bio to the size of the device,
2963 * and clear the end of the buffer head manually.
2964 *
2965 * Truly out-of-range accesses will turn into actual IO
2966 * errors, this only handles the "we need to be able to
2967 * do IO at the final sector" case.
2968 */
2969static void guard_bh_eod(int rw, struct bio *bio, struct buffer_head *bh)
2970{
2971 sector_t maxsector;
2972 unsigned bytes;
2973
2974 maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
2975 if (!maxsector)
2976 return;
2977
2978 /*
2979 * If the *whole* IO is past the end of the device,
2980 * let it through, and the IO layer will turn it into
2981 * an EIO.
2982 */
Kent Overstreet4f024f32013-10-11 15:44:27 -07002983 if (unlikely(bio->bi_iter.bi_sector >= maxsector))
Linus Torvalds57302e02012-12-04 08:25:11 -08002984 return;
2985
Kent Overstreet4f024f32013-10-11 15:44:27 -07002986 maxsector -= bio->bi_iter.bi_sector;
2987 bytes = bio->bi_iter.bi_size;
Linus Torvalds57302e02012-12-04 08:25:11 -08002988 if (likely((bytes >> 9) <= maxsector))
2989 return;
2990
2991 /* Uhhuh. We've got a bh that straddles the device size! */
2992 bytes = maxsector << 9;
2993
2994 /* Truncate the bio.. */
Kent Overstreet4f024f32013-10-11 15:44:27 -07002995 bio->bi_iter.bi_size = bytes;
Linus Torvalds57302e02012-12-04 08:25:11 -08002996 bio->bi_io_vec[0].bv_len = bytes;
2997
2998 /* ..and clear the end of the buffer for reads */
Dan Carpenter27d7c2a2012-12-05 20:01:24 +03002999 if ((rw & RW_MASK) == READ) {
Linus Torvalds57302e02012-12-04 08:25:11 -08003000 void *kaddr = kmap_atomic(bh->b_page);
3001 memset(kaddr + bh_offset(bh) + bytes, 0, bh->b_size - bytes);
3002 kunmap_atomic(kaddr);
Linus Torvalds6d283db2013-01-14 13:17:50 -08003003 flush_dcache_page(bh->b_page);
Linus Torvalds57302e02012-12-04 08:25:11 -08003004 }
3005}
3006
Darrick J. Wong7136851112013-04-29 15:07:25 -07003007int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003008{
3009 struct bio *bio;
3010 int ret = 0;
3011
3012 BUG_ON(!buffer_locked(bh));
3013 BUG_ON(!buffer_mapped(bh));
3014 BUG_ON(!bh->b_end_io);
Aneesh Kumar K.V8fb0e342009-05-12 16:22:37 -04003015 BUG_ON(buffer_delay(bh));
3016 BUG_ON(buffer_unwritten(bh));
Linus Torvalds1da177e2005-04-16 15:20:36 -07003017
Jens Axboe48fd4f92008-08-22 10:00:36 +02003018 /*
Jens Axboe48fd4f92008-08-22 10:00:36 +02003019 * Only clear out a write error when rewriting
Linus Torvalds1da177e2005-04-16 15:20:36 -07003020 */
Jens Axboe48fd4f92008-08-22 10:00:36 +02003021 if (test_set_buffer_req(bh) && (rw & WRITE))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003022 clear_buffer_write_io_error(bh);
3023
3024 /*
3025 * from here on down, it's all bio -- do the initial mapping,
3026 * submit_bio -> generic_make_request may further map this bio around
3027 */
3028 bio = bio_alloc(GFP_NOIO, 1);
3029
Kent Overstreet4f024f32013-10-11 15:44:27 -07003030 bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003031 bio->bi_bdev = bh->b_bdev;
3032 bio->bi_io_vec[0].bv_page = bh->b_page;
3033 bio->bi_io_vec[0].bv_len = bh->b_size;
3034 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
3035
3036 bio->bi_vcnt = 1;
Kent Overstreet4f024f32013-10-11 15:44:27 -07003037 bio->bi_iter.bi_size = bh->b_size;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003038
3039 bio->bi_end_io = end_bio_bh_io_sync;
3040 bio->bi_private = bh;
Darrick J. Wong7136851112013-04-29 15:07:25 -07003041 bio->bi_flags |= bio_flags;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003042
Linus Torvalds57302e02012-12-04 08:25:11 -08003043 /* Take care of bh's that straddle the end of the device */
3044 guard_bh_eod(rw, bio, bh);
3045
Theodore Ts'o877f9622013-04-20 19:58:37 -04003046 if (buffer_meta(bh))
3047 rw |= REQ_META;
3048 if (buffer_prio(bh))
3049 rw |= REQ_PRIO;
3050
Linus Torvalds1da177e2005-04-16 15:20:36 -07003051 bio_get(bio);
3052 submit_bio(rw, bio);
3053
3054 if (bio_flagged(bio, BIO_EOPNOTSUPP))
3055 ret = -EOPNOTSUPP;
3056
3057 bio_put(bio);
3058 return ret;
3059}
Darrick J. Wong7136851112013-04-29 15:07:25 -07003060EXPORT_SYMBOL_GPL(_submit_bh);
3061
3062int submit_bh(int rw, struct buffer_head *bh)
3063{
3064 return _submit_bh(rw, bh, 0);
3065}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07003066EXPORT_SYMBOL(submit_bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003067
3068/**
3069 * ll_rw_block: low-level access to block devices (DEPRECATED)
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003070 * @rw: whether to %READ or %WRITE or maybe %READA (readahead)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003071 * @nr: number of &struct buffer_heads in the array
3072 * @bhs: array of pointers to &struct buffer_head
3073 *
Jan Karaa7662232005-09-06 15:19:10 -07003074 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
3075 * requests an I/O operation on them, either a %READ or a %WRITE. The third
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003076 * %READA option is described in the documentation for generic_make_request()
3077 * which ll_rw_block() calls.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003078 *
3079 * This function drops any buffer that it cannot get a lock on (with the
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003080 * BH_Lock state bit), any buffer that appears to be clean when doing a write
3081 * request, and any buffer that appears to be up-to-date when doing read
3082 * request. Further it marks as clean buffers that are processed for
3083 * writing (the buffer cache won't assume that they are actually clean
3084 * until the buffer gets unlocked).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003085 *
3086 * ll_rw_block sets b_end_io to simple completion handler that marks
Masanari Iidae2278672014-02-18 22:54:36 +09003087 * the buffer up-to-date (if appropriate), unlocks the buffer and wakes
Linus Torvalds1da177e2005-04-16 15:20:36 -07003088 * any waiters.
3089 *
3090 * All of the buffers must be for the same device, and must also be a
3091 * multiple of the current approved size for the device.
3092 */
3093void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
3094{
3095 int i;
3096
3097 for (i = 0; i < nr; i++) {
3098 struct buffer_head *bh = bhs[i];
3099
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003100 if (!trylock_buffer(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003101 continue;
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003102 if (rw == WRITE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003103 if (test_clear_buffer_dirty(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07003104 bh->b_end_io = end_buffer_write_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08003105 get_bh(bh);
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003106 submit_bh(WRITE, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003107 continue;
3108 }
3109 } else {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003110 if (!buffer_uptodate(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07003111 bh->b_end_io = end_buffer_read_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08003112 get_bh(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003113 submit_bh(rw, bh);
3114 continue;
3115 }
3116 }
3117 unlock_buffer(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003118 }
3119}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07003120EXPORT_SYMBOL(ll_rw_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003121
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003122void write_dirty_buffer(struct buffer_head *bh, int rw)
3123{
3124 lock_buffer(bh);
3125 if (!test_clear_buffer_dirty(bh)) {
3126 unlock_buffer(bh);
3127 return;
3128 }
3129 bh->b_end_io = end_buffer_write_sync;
3130 get_bh(bh);
3131 submit_bh(rw, bh);
3132}
3133EXPORT_SYMBOL(write_dirty_buffer);
3134
Linus Torvalds1da177e2005-04-16 15:20:36 -07003135/*
3136 * For a data-integrity writeout, we need to wait upon any in-progress I/O
3137 * and then start new I/O and then wait upon it. The caller must have a ref on
3138 * the buffer_head.
3139 */
Christoph Hellwig87e99512010-08-11 17:05:45 +02003140int __sync_dirty_buffer(struct buffer_head *bh, int rw)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003141{
3142 int ret = 0;
3143
3144 WARN_ON(atomic_read(&bh->b_count) < 1);
3145 lock_buffer(bh);
3146 if (test_clear_buffer_dirty(bh)) {
3147 get_bh(bh);
3148 bh->b_end_io = end_buffer_write_sync;
Christoph Hellwig87e99512010-08-11 17:05:45 +02003149 ret = submit_bh(rw, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003150 wait_on_buffer(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003151 if (!ret && !buffer_uptodate(bh))
3152 ret = -EIO;
3153 } else {
3154 unlock_buffer(bh);
3155 }
3156 return ret;
3157}
Christoph Hellwig87e99512010-08-11 17:05:45 +02003158EXPORT_SYMBOL(__sync_dirty_buffer);
3159
3160int sync_dirty_buffer(struct buffer_head *bh)
3161{
3162 return __sync_dirty_buffer(bh, WRITE_SYNC);
3163}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07003164EXPORT_SYMBOL(sync_dirty_buffer);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003165
3166/*
3167 * try_to_free_buffers() checks if all the buffers on this particular page
3168 * are unused, and releases them if so.
3169 *
3170 * Exclusion against try_to_free_buffers may be obtained by either
3171 * locking the page or by holding its mapping's private_lock.
3172 *
3173 * If the page is dirty but all the buffers are clean then we need to
3174 * be sure to mark the page clean as well. This is because the page
3175 * may be against a block device, and a later reattachment of buffers
3176 * to a dirty page will set *all* buffers dirty. Which would corrupt
3177 * filesystem data on the same device.
3178 *
3179 * The same applies to regular filesystem pages: if all the buffers are
3180 * clean then we set the page clean and proceed. To do that, we require
3181 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3182 * private_lock.
3183 *
3184 * try_to_free_buffers() is non-blocking.
3185 */
3186static inline int buffer_busy(struct buffer_head *bh)
3187{
3188 return atomic_read(&bh->b_count) |
3189 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3190}
3191
3192static int
3193drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3194{
3195 struct buffer_head *head = page_buffers(page);
3196 struct buffer_head *bh;
3197
3198 bh = head;
3199 do {
akpm@osdl.orgde7d5a32005-05-01 08:58:39 -07003200 if (buffer_write_io_error(bh) && page->mapping)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003201 set_bit(AS_EIO, &page->mapping->flags);
3202 if (buffer_busy(bh))
3203 goto failed;
3204 bh = bh->b_this_page;
3205 } while (bh != head);
3206
3207 do {
3208 struct buffer_head *next = bh->b_this_page;
3209
Jan Kara535ee2f2008-02-08 04:21:59 -08003210 if (bh->b_assoc_map)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003211 __remove_assoc_queue(bh);
3212 bh = next;
3213 } while (bh != head);
3214 *buffers_to_free = head;
3215 __clear_page_buffers(page);
3216 return 1;
3217failed:
3218 return 0;
3219}
3220
3221int try_to_free_buffers(struct page *page)
3222{
3223 struct address_space * const mapping = page->mapping;
3224 struct buffer_head *buffers_to_free = NULL;
3225 int ret = 0;
3226
3227 BUG_ON(!PageLocked(page));
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003228 if (PageWriteback(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003229 return 0;
3230
3231 if (mapping == NULL) { /* can this still happen? */
3232 ret = drop_buffers(page, &buffers_to_free);
3233 goto out;
3234 }
3235
3236 spin_lock(&mapping->private_lock);
3237 ret = drop_buffers(page, &buffers_to_free);
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003238
3239 /*
3240 * If the filesystem writes its buffers by hand (eg ext3)
3241 * then we can have clean buffers against a dirty page. We
3242 * clean the page here; otherwise the VM will never notice
3243 * that the filesystem did any IO at all.
3244 *
3245 * Also, during truncate, discard_buffer will have marked all
3246 * the page's buffers clean. We discover that here and clean
3247 * the page also.
Nick Piggin87df7242007-01-30 14:36:27 +11003248 *
3249 * private_lock must be held over this entire operation in order
3250 * to synchronise against __set_page_dirty_buffers and prevent the
3251 * dirty bit from being lost.
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003252 */
3253 if (ret)
3254 cancel_dirty_page(page, PAGE_CACHE_SIZE);
Nick Piggin87df7242007-01-30 14:36:27 +11003255 spin_unlock(&mapping->private_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003256out:
3257 if (buffers_to_free) {
3258 struct buffer_head *bh = buffers_to_free;
3259
3260 do {
3261 struct buffer_head *next = bh->b_this_page;
3262 free_buffer_head(bh);
3263 bh = next;
3264 } while (bh != buffers_to_free);
3265 }
3266 return ret;
3267}
3268EXPORT_SYMBOL(try_to_free_buffers);
3269
Linus Torvalds1da177e2005-04-16 15:20:36 -07003270/*
3271 * There are no bdflush tunables left. But distributions are
3272 * still running obsolete flush daemons, so we terminate them here.
3273 *
3274 * Use of bdflush() is deprecated and will be removed in a future kernel.
Jens Axboe5b0830c2009-09-23 19:37:09 +02003275 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003276 */
Heiko Carstensbdc480e2009-01-14 14:14:12 +01003277SYSCALL_DEFINE2(bdflush, int, func, long, data)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003278{
3279 static int msg_count;
3280
3281 if (!capable(CAP_SYS_ADMIN))
3282 return -EPERM;
3283
3284 if (msg_count < 5) {
3285 msg_count++;
3286 printk(KERN_INFO
3287 "warning: process `%s' used the obsolete bdflush"
3288 " system call\n", current->comm);
3289 printk(KERN_INFO "Fix your initscripts?\n");
3290 }
3291
3292 if (func == 1)
3293 do_exit(0);
3294 return 0;
3295}
3296
3297/*
3298 * Buffer-head allocation
3299 */
Shai Fultheima0a9b042012-05-15 12:29:52 +03003300static struct kmem_cache *bh_cachep __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003301
3302/*
3303 * Once the number of bh's in the machine exceeds this level, we start
3304 * stripping them in writeback.
3305 */
Zhang Yanfei43be5942013-02-22 16:35:46 -08003306static unsigned long max_buffer_heads;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003307
3308int buffer_heads_over_limit;
3309
3310struct bh_accounting {
3311 int nr; /* Number of live bh's */
3312 int ratelimit; /* Limit cacheline bouncing */
3313};
3314
3315static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3316
3317static void recalc_bh_state(void)
3318{
3319 int i;
3320 int tot = 0;
3321
Christoph Lameteree1be862010-12-06 11:40:05 -06003322 if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003323 return;
Christoph Lameterc7b92512010-12-06 11:16:28 -06003324 __this_cpu_write(bh_accounting.ratelimit, 0);
Eric Dumazet8a143422006-03-24 03:18:10 -08003325 for_each_online_cpu(i)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003326 tot += per_cpu(bh_accounting, i).nr;
3327 buffer_heads_over_limit = (tot > max_buffer_heads);
3328}
Christoph Lameterc7b92512010-12-06 11:16:28 -06003329
Al Virodd0fc662005-10-07 07:46:04 +01003330struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003331{
Richard Kennedy019b4d12010-03-10 15:20:33 -08003332 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003333 if (ret) {
Christoph Lametera35afb82007-05-16 22:10:57 -07003334 INIT_LIST_HEAD(&ret->b_assoc_buffers);
Christoph Lameterc7b92512010-12-06 11:16:28 -06003335 preempt_disable();
3336 __this_cpu_inc(bh_accounting.nr);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003337 recalc_bh_state();
Christoph Lameterc7b92512010-12-06 11:16:28 -06003338 preempt_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -07003339 }
3340 return ret;
3341}
3342EXPORT_SYMBOL(alloc_buffer_head);
3343
3344void free_buffer_head(struct buffer_head *bh)
3345{
3346 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3347 kmem_cache_free(bh_cachep, bh);
Christoph Lameterc7b92512010-12-06 11:16:28 -06003348 preempt_disable();
3349 __this_cpu_dec(bh_accounting.nr);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003350 recalc_bh_state();
Christoph Lameterc7b92512010-12-06 11:16:28 -06003351 preempt_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -07003352}
3353EXPORT_SYMBOL(free_buffer_head);
3354
Linus Torvalds1da177e2005-04-16 15:20:36 -07003355static void buffer_exit_cpu(int cpu)
3356{
3357 int i;
3358 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3359
3360 for (i = 0; i < BH_LRU_SIZE; i++) {
3361 brelse(b->bhs[i]);
3362 b->bhs[i] = NULL;
3363 }
Christoph Lameterc7b92512010-12-06 11:16:28 -06003364 this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
Eric Dumazet8a143422006-03-24 03:18:10 -08003365 per_cpu(bh_accounting, cpu).nr = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003366}
3367
3368static int buffer_cpu_notify(struct notifier_block *self,
3369 unsigned long action, void *hcpu)
3370{
Rafael J. Wysocki8bb78442007-05-09 02:35:10 -07003371 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003372 buffer_exit_cpu((unsigned long)hcpu);
3373 return NOTIFY_OK;
3374}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003375
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003376/**
Randy Dunlapa6b91912008-03-19 17:01:00 -07003377 * bh_uptodate_or_lock - Test whether the buffer is uptodate
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003378 * @bh: struct buffer_head
3379 *
3380 * Return true if the buffer is up-to-date and false,
3381 * with the buffer locked, if not.
3382 */
3383int bh_uptodate_or_lock(struct buffer_head *bh)
3384{
3385 if (!buffer_uptodate(bh)) {
3386 lock_buffer(bh);
3387 if (!buffer_uptodate(bh))
3388 return 0;
3389 unlock_buffer(bh);
3390 }
3391 return 1;
3392}
3393EXPORT_SYMBOL(bh_uptodate_or_lock);
3394
3395/**
Randy Dunlapa6b91912008-03-19 17:01:00 -07003396 * bh_submit_read - Submit a locked buffer for reading
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003397 * @bh: struct buffer_head
3398 *
3399 * Returns zero on success and -EIO on error.
3400 */
3401int bh_submit_read(struct buffer_head *bh)
3402{
3403 BUG_ON(!buffer_locked(bh));
3404
3405 if (buffer_uptodate(bh)) {
3406 unlock_buffer(bh);
3407 return 0;
3408 }
3409
3410 get_bh(bh);
3411 bh->b_end_io = end_buffer_read_sync;
3412 submit_bh(READ, bh);
3413 wait_on_buffer(bh);
3414 if (buffer_uptodate(bh))
3415 return 0;
3416 return -EIO;
3417}
3418EXPORT_SYMBOL(bh_submit_read);
3419
Linus Torvalds1da177e2005-04-16 15:20:36 -07003420void __init buffer_init(void)
3421{
Zhang Yanfei43be5942013-02-22 16:35:46 -08003422 unsigned long nrpages;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003423
Christoph Lameterb98938c2008-02-04 22:28:36 -08003424 bh_cachep = kmem_cache_create("buffer_head",
3425 sizeof(struct buffer_head), 0,
3426 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3427 SLAB_MEM_SPREAD),
Richard Kennedy019b4d12010-03-10 15:20:33 -08003428 NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003429
3430 /*
3431 * Limit the bh occupancy to 10% of ZONE_NORMAL
3432 */
3433 nrpages = (nr_free_buffer_pages() * 10) / 100;
3434 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3435 hotcpu_notifier(buffer_cpu_notify, 0);
3436}