blob: b4dcb34c9635ae61b747bb9d4816477a49a8d90a [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * linux/fs/buffer.c
3 *
4 * Copyright (C) 1991, 1992, 2002 Linus Torvalds
5 */
6
7/*
8 * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95
9 *
10 * Removed a lot of unnecessary code and simplified things now that
11 * the buffer cache isn't our primary cache - Andrew Tridgell 12/96
12 *
13 * Speed up hash, lru, and free list operations. Use gfp() for allocating
14 * hash table, use SLAB cache for buffer heads. SMP threading. -DaveM
15 *
16 * Added 32k buffer block sizes - these are required older ARM systems. - RMK
17 *
18 * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de>
19 */
20
Linus Torvalds1da177e2005-04-16 15:20:36 -070021#include <linux/kernel.h>
22#include <linux/syscalls.h>
23#include <linux/fs.h>
24#include <linux/mm.h>
25#include <linux/percpu.h>
26#include <linux/slab.h>
Randy Dunlap16f7e0f2006-01-11 12:17:46 -080027#include <linux/capability.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070028#include <linux/blkdev.h>
29#include <linux/file.h>
30#include <linux/quotaops.h>
31#include <linux/highmem.h>
Paul Gortmaker630d9c42011-11-16 23:57:37 -050032#include <linux/export.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070033#include <linux/writeback.h>
34#include <linux/hash.h>
35#include <linux/suspend.h>
36#include <linux/buffer_head.h>
Andrew Morton55e829a2006-12-10 02:19:27 -080037#include <linux/task_io_accounting_ops.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070038#include <linux/bio.h>
39#include <linux/notifier.h>
40#include <linux/cpu.h>
41#include <linux/bitops.h>
42#include <linux/mpage.h>
Ingo Molnarfb1c8f92005-09-10 00:25:56 -070043#include <linux/bit_spinlock.h>
Tejun Heo5305cb82013-01-11 13:06:36 -080044#include <trace/events/block.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070045
46static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
Linus Torvalds1da177e2005-04-16 15:20:36 -070047
48#define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
49
Yan Honga3f3c292012-12-12 13:52:15 -080050void init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
Linus Torvalds1da177e2005-04-16 15:20:36 -070051{
52 bh->b_end_io = handler;
53 bh->b_private = private;
54}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -070055EXPORT_SYMBOL(init_buffer);
Linus Torvalds1da177e2005-04-16 15:20:36 -070056
Tejun Heof0059af2013-01-11 13:06:35 -080057inline void touch_buffer(struct buffer_head *bh)
58{
Tejun Heo5305cb82013-01-11 13:06:36 -080059 trace_block_touch_buffer(bh);
Tejun Heof0059af2013-01-11 13:06:35 -080060 mark_page_accessed(bh->b_page);
61}
62EXPORT_SYMBOL(touch_buffer);
63
Jens Axboe7eaceac2011-03-10 08:52:07 +010064static int sleep_on_buffer(void *word)
Linus Torvalds1da177e2005-04-16 15:20:36 -070065{
Linus Torvalds1da177e2005-04-16 15:20:36 -070066 io_schedule();
67 return 0;
68}
69
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -080070void __lock_buffer(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -070071{
Jens Axboe7eaceac2011-03-10 08:52:07 +010072 wait_on_bit_lock(&bh->b_state, BH_Lock, sleep_on_buffer,
Linus Torvalds1da177e2005-04-16 15:20:36 -070073 TASK_UNINTERRUPTIBLE);
74}
75EXPORT_SYMBOL(__lock_buffer);
76
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -080077void unlock_buffer(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -070078{
Nick Piggin51b07fc2008-10-18 20:27:00 -070079 clear_bit_unlock(BH_Lock, &bh->b_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -070080 smp_mb__after_clear_bit();
81 wake_up_bit(&bh->b_state, BH_Lock);
82}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -070083EXPORT_SYMBOL(unlock_buffer);
Linus Torvalds1da177e2005-04-16 15:20:36 -070084
85/*
86 * Block until a buffer comes unlocked. This doesn't stop it
87 * from becoming locked again - you have to lock it yourself
88 * if you want to preserve its state.
89 */
90void __wait_on_buffer(struct buffer_head * bh)
91{
Jens Axboe7eaceac2011-03-10 08:52:07 +010092 wait_on_bit(&bh->b_state, BH_Lock, sleep_on_buffer, TASK_UNINTERRUPTIBLE);
Linus Torvalds1da177e2005-04-16 15:20:36 -070093}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -070094EXPORT_SYMBOL(__wait_on_buffer);
Linus Torvalds1da177e2005-04-16 15:20:36 -070095
96static void
97__clear_page_buffers(struct page *page)
98{
99 ClearPagePrivate(page);
Hugh Dickins4c21e2f2005-10-29 18:16:40 -0700100 set_page_private(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700101 page_cache_release(page);
102}
103
Keith Mannthey08bafc02008-11-25 10:24:35 +0100104
105static int quiet_error(struct buffer_head *bh)
106{
107 if (!test_bit(BH_Quiet, &bh->b_state) && printk_ratelimit())
108 return 0;
109 return 1;
110}
111
112
Linus Torvalds1da177e2005-04-16 15:20:36 -0700113static void buffer_io_error(struct buffer_head *bh)
114{
115 char b[BDEVNAME_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700116 printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n",
117 bdevname(bh->b_bdev, b),
118 (unsigned long long)bh->b_blocknr);
119}
120
121/*
Dmitry Monakhov68671f32007-10-16 01:24:47 -0700122 * End-of-IO handler helper function which does not touch the bh after
123 * unlocking it.
124 * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
125 * a race there is benign: unlock_buffer() only use the bh's address for
126 * hashing after unlocking the buffer, so it doesn't actually touch the bh
127 * itself.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700128 */
Dmitry Monakhov68671f32007-10-16 01:24:47 -0700129static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700130{
131 if (uptodate) {
132 set_buffer_uptodate(bh);
133 } else {
134 /* This happens, due to failed READA attempts. */
135 clear_buffer_uptodate(bh);
136 }
137 unlock_buffer(bh);
Dmitry Monakhov68671f32007-10-16 01:24:47 -0700138}
139
140/*
141 * Default synchronous end-of-IO handler.. Just mark it up-to-date and
142 * unlock the buffer. This is what ll_rw_block uses too.
143 */
144void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
145{
146 __end_buffer_read_notouch(bh, uptodate);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700147 put_bh(bh);
148}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700149EXPORT_SYMBOL(end_buffer_read_sync);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700150
151void end_buffer_write_sync(struct buffer_head *bh, int uptodate)
152{
153 char b[BDEVNAME_SIZE];
154
155 if (uptodate) {
156 set_buffer_uptodate(bh);
157 } else {
Christoph Hellwig0edd55f2010-08-18 05:29:23 -0400158 if (!quiet_error(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700159 buffer_io_error(bh);
160 printk(KERN_WARNING "lost page write due to "
161 "I/O error on %s\n",
162 bdevname(bh->b_bdev, b));
163 }
164 set_buffer_write_io_error(bh);
165 clear_buffer_uptodate(bh);
166 }
167 unlock_buffer(bh);
168 put_bh(bh);
169}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700170EXPORT_SYMBOL(end_buffer_write_sync);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700171
172/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700173 * Various filesystems appear to want __find_get_block to be non-blocking.
174 * But it's the page lock which protects the buffers. To get around this,
175 * we get exclusion from try_to_free_buffers with the blockdev mapping's
176 * private_lock.
177 *
178 * Hack idea: for the blockdev mapping, i_bufferlist_lock contention
179 * may be quite high. This code could TryLock the page, and if that
180 * succeeds, there is no need to take private_lock. (But if
181 * private_lock is contended then so is mapping->tree_lock).
182 */
183static struct buffer_head *
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -0800184__find_get_block_slow(struct block_device *bdev, sector_t block)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700185{
186 struct inode *bd_inode = bdev->bd_inode;
187 struct address_space *bd_mapping = bd_inode->i_mapping;
188 struct buffer_head *ret = NULL;
189 pgoff_t index;
190 struct buffer_head *bh;
191 struct buffer_head *head;
192 struct page *page;
193 int all_mapped = 1;
194
195 index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits);
196 page = find_get_page(bd_mapping, index);
197 if (!page)
198 goto out;
199
200 spin_lock(&bd_mapping->private_lock);
201 if (!page_has_buffers(page))
202 goto out_unlock;
203 head = page_buffers(page);
204 bh = head;
205 do {
Nikanth Karthikesan97f76d32009-04-02 16:56:46 -0700206 if (!buffer_mapped(bh))
207 all_mapped = 0;
208 else if (bh->b_blocknr == block) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700209 ret = bh;
210 get_bh(bh);
211 goto out_unlock;
212 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700213 bh = bh->b_this_page;
214 } while (bh != head);
215
216 /* we might be here because some of the buffers on this page are
217 * not mapped. This is due to various races between
218 * file io on the block device and getblk. It gets dealt with
219 * elsewhere, don't buffer_error if we had some unmapped buffers
220 */
221 if (all_mapped) {
Tao Ma72a2ebd2011-10-31 17:09:00 -0700222 char b[BDEVNAME_SIZE];
223
Linus Torvalds1da177e2005-04-16 15:20:36 -0700224 printk("__find_get_block_slow() failed. "
225 "block=%llu, b_blocknr=%llu\n",
Badari Pulavarty205f87f2006-03-26 01:38:00 -0800226 (unsigned long long)block,
227 (unsigned long long)bh->b_blocknr);
228 printk("b_state=0x%08lx, b_size=%zu\n",
229 bh->b_state, bh->b_size);
Tao Ma72a2ebd2011-10-31 17:09:00 -0700230 printk("device %s blocksize: %d\n", bdevname(bdev, b),
231 1 << bd_inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700232 }
233out_unlock:
234 spin_unlock(&bd_mapping->private_lock);
235 page_cache_release(page);
236out:
237 return ret;
238}
239
Linus Torvalds1da177e2005-04-16 15:20:36 -0700240/*
Jens Axboe5b0830c2009-09-23 19:37:09 +0200241 * Kick the writeback threads then try to free up some ZONE_NORMAL memory.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700242 */
243static void free_more_memory(void)
244{
Mel Gorman19770b32008-04-28 02:12:18 -0700245 struct zone *zone;
Mel Gorman0e884602008-04-28 02:12:14 -0700246 int nid;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700247
Curt Wohlgemuth0e175a12011-10-07 21:54:10 -0600248 wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700249 yield();
250
Mel Gorman0e884602008-04-28 02:12:14 -0700251 for_each_online_node(nid) {
Mel Gorman19770b32008-04-28 02:12:18 -0700252 (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS),
253 gfp_zone(GFP_NOFS), NULL,
254 &zone);
255 if (zone)
Mel Gorman54a6eb52008-04-28 02:12:16 -0700256 try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0,
KAMEZAWA Hiroyuki327c0e92009-03-31 15:23:31 -0700257 GFP_NOFS, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700258 }
259}
260
261/*
262 * I/O completion handler for block_read_full_page() - pages
263 * which come unlocked at the end of I/O.
264 */
265static void end_buffer_async_read(struct buffer_head *bh, int uptodate)
266{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700267 unsigned long flags;
Nick Piggina3972202005-07-07 17:56:56 -0700268 struct buffer_head *first;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700269 struct buffer_head *tmp;
270 struct page *page;
271 int page_uptodate = 1;
272
273 BUG_ON(!buffer_async_read(bh));
274
275 page = bh->b_page;
276 if (uptodate) {
277 set_buffer_uptodate(bh);
278 } else {
279 clear_buffer_uptodate(bh);
Keith Mannthey08bafc02008-11-25 10:24:35 +0100280 if (!quiet_error(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700281 buffer_io_error(bh);
282 SetPageError(page);
283 }
284
285 /*
286 * Be _very_ careful from here on. Bad things can happen if
287 * two buffer heads end IO at almost the same time and both
288 * decide that the page is now completely done.
289 */
Nick Piggina3972202005-07-07 17:56:56 -0700290 first = page_buffers(page);
291 local_irq_save(flags);
292 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700293 clear_buffer_async_read(bh);
294 unlock_buffer(bh);
295 tmp = bh;
296 do {
297 if (!buffer_uptodate(tmp))
298 page_uptodate = 0;
299 if (buffer_async_read(tmp)) {
300 BUG_ON(!buffer_locked(tmp));
301 goto still_busy;
302 }
303 tmp = tmp->b_this_page;
304 } while (tmp != bh);
Nick Piggina3972202005-07-07 17:56:56 -0700305 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
306 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700307
308 /*
309 * If none of the buffers had errors and they are all
310 * uptodate then we can set the page uptodate.
311 */
312 if (page_uptodate && !PageError(page))
313 SetPageUptodate(page);
314 unlock_page(page);
315 return;
316
317still_busy:
Nick Piggina3972202005-07-07 17:56:56 -0700318 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
319 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700320 return;
321}
322
323/*
324 * Completion handler for block_write_full_page() - pages which are unlocked
325 * during I/O, and which have PageWriteback cleared upon I/O completion.
326 */
Chris Mason35c80d52009-04-15 13:22:38 -0400327void end_buffer_async_write(struct buffer_head *bh, int uptodate)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700328{
329 char b[BDEVNAME_SIZE];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700330 unsigned long flags;
Nick Piggina3972202005-07-07 17:56:56 -0700331 struct buffer_head *first;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700332 struct buffer_head *tmp;
333 struct page *page;
334
335 BUG_ON(!buffer_async_write(bh));
336
337 page = bh->b_page;
338 if (uptodate) {
339 set_buffer_uptodate(bh);
340 } else {
Keith Mannthey08bafc02008-11-25 10:24:35 +0100341 if (!quiet_error(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700342 buffer_io_error(bh);
343 printk(KERN_WARNING "lost page write due to "
344 "I/O error on %s\n",
345 bdevname(bh->b_bdev, b));
346 }
347 set_bit(AS_EIO, &page->mapping->flags);
Jan Kara58ff4072006-10-17 00:10:19 -0700348 set_buffer_write_io_error(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700349 clear_buffer_uptodate(bh);
350 SetPageError(page);
351 }
352
Nick Piggina3972202005-07-07 17:56:56 -0700353 first = page_buffers(page);
354 local_irq_save(flags);
355 bit_spin_lock(BH_Uptodate_Lock, &first->b_state);
356
Linus Torvalds1da177e2005-04-16 15:20:36 -0700357 clear_buffer_async_write(bh);
358 unlock_buffer(bh);
359 tmp = bh->b_this_page;
360 while (tmp != bh) {
361 if (buffer_async_write(tmp)) {
362 BUG_ON(!buffer_locked(tmp));
363 goto still_busy;
364 }
365 tmp = tmp->b_this_page;
366 }
Nick Piggina3972202005-07-07 17:56:56 -0700367 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
368 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700369 end_page_writeback(page);
370 return;
371
372still_busy:
Nick Piggina3972202005-07-07 17:56:56 -0700373 bit_spin_unlock(BH_Uptodate_Lock, &first->b_state);
374 local_irq_restore(flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700375 return;
376}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700377EXPORT_SYMBOL(end_buffer_async_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700378
379/*
380 * If a page's buffers are under async readin (end_buffer_async_read
381 * completion) then there is a possibility that another thread of
382 * control could lock one of the buffers after it has completed
383 * but while some of the other buffers have not completed. This
384 * locked buffer would confuse end_buffer_async_read() into not unlocking
385 * the page. So the absence of BH_Async_Read tells end_buffer_async_read()
386 * that this buffer is not under async I/O.
387 *
388 * The page comes unlocked when it has no locked buffer_async buffers
389 * left.
390 *
391 * PageLocked prevents anyone starting new async I/O reads any of
392 * the buffers.
393 *
394 * PageWriteback is used to prevent simultaneous writeout of the same
395 * page.
396 *
397 * PageLocked prevents anyone from starting writeback of a page which is
398 * under read I/O (PageWriteback is only ever set against a locked page).
399 */
400static void mark_buffer_async_read(struct buffer_head *bh)
401{
402 bh->b_end_io = end_buffer_async_read;
403 set_buffer_async_read(bh);
404}
405
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700406static void mark_buffer_async_write_endio(struct buffer_head *bh,
407 bh_end_io_t *handler)
Chris Mason35c80d52009-04-15 13:22:38 -0400408{
409 bh->b_end_io = handler;
410 set_buffer_async_write(bh);
411}
412
Linus Torvalds1da177e2005-04-16 15:20:36 -0700413void mark_buffer_async_write(struct buffer_head *bh)
414{
Chris Mason35c80d52009-04-15 13:22:38 -0400415 mark_buffer_async_write_endio(bh, end_buffer_async_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700416}
417EXPORT_SYMBOL(mark_buffer_async_write);
418
419
420/*
421 * fs/buffer.c contains helper functions for buffer-backed address space's
422 * fsync functions. A common requirement for buffer-based filesystems is
423 * that certain data from the backing blockdev needs to be written out for
424 * a successful fsync(). For example, ext2 indirect blocks need to be
425 * written back and waited upon before fsync() returns.
426 *
427 * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(),
428 * inode_has_buffers() and invalidate_inode_buffers() are provided for the
429 * management of a list of dependent buffers at ->i_mapping->private_list.
430 *
431 * Locking is a little subtle: try_to_free_buffers() will remove buffers
432 * from their controlling inode's queue when they are being freed. But
433 * try_to_free_buffers() will be operating against the *blockdev* mapping
434 * at the time, not against the S_ISREG file which depends on those buffers.
435 * So the locking for private_list is via the private_lock in the address_space
436 * which backs the buffers. Which is different from the address_space
437 * against which the buffers are listed. So for a particular address_space,
438 * mapping->private_lock does *not* protect mapping->private_list! In fact,
439 * mapping->private_list will always be protected by the backing blockdev's
440 * ->private_lock.
441 *
442 * Which introduces a requirement: all buffers on an address_space's
443 * ->private_list must be from the same address_space: the blockdev's.
444 *
445 * address_spaces which do not place buffers at ->private_list via these
446 * utility functions are free to use private_lock and private_list for
447 * whatever they want. The only requirement is that list_empty(private_list)
448 * be true at clear_inode() time.
449 *
450 * FIXME: clear_inode should not call invalidate_inode_buffers(). The
451 * filesystems should do that. invalidate_inode_buffers() should just go
452 * BUG_ON(!list_empty).
453 *
454 * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should
455 * take an address_space, not an inode. And it should be called
456 * mark_buffer_dirty_fsync() to clearly define why those buffers are being
457 * queued up.
458 *
459 * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the
460 * list if it is already on a list. Because if the buffer is on a list,
461 * it *must* already be on the right one. If not, the filesystem is being
462 * silly. This will save a ton of locking. But first we have to ensure
463 * that buffers are taken *off* the old inode's list when they are freed
464 * (presumably in truncate). That requires careful auditing of all
465 * filesystems (do it inside bforget()). It could also be done by bringing
466 * b_inode back.
467 */
468
469/*
470 * The buffer's backing address_space's private_lock must be held
471 */
Thomas Petazzonidbacefc2008-07-29 22:33:47 -0700472static void __remove_assoc_queue(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700473{
474 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -0700475 WARN_ON(!bh->b_assoc_map);
476 if (buffer_write_io_error(bh))
477 set_bit(AS_EIO, &bh->b_assoc_map->flags);
478 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700479}
480
481int inode_has_buffers(struct inode *inode)
482{
483 return !list_empty(&inode->i_data.private_list);
484}
485
486/*
487 * osync is designed to support O_SYNC io. It waits synchronously for
488 * all already-submitted IO to complete, but does not queue any new
489 * writes to the disk.
490 *
491 * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as
492 * you dirty the buffers, and then use osync_inode_buffers to wait for
493 * completion. Any other dirty buffers which are not yet queued for
494 * write will not be flushed to disk by the osync.
495 */
496static int osync_buffers_list(spinlock_t *lock, struct list_head *list)
497{
498 struct buffer_head *bh;
499 struct list_head *p;
500 int err = 0;
501
502 spin_lock(lock);
503repeat:
504 list_for_each_prev(p, list) {
505 bh = BH_ENTRY(p);
506 if (buffer_locked(bh)) {
507 get_bh(bh);
508 spin_unlock(lock);
509 wait_on_buffer(bh);
510 if (!buffer_uptodate(bh))
511 err = -EIO;
512 brelse(bh);
513 spin_lock(lock);
514 goto repeat;
515 }
516 }
517 spin_unlock(lock);
518 return err;
519}
520
Al Viro01a05b32010-03-23 06:06:58 -0400521static void do_thaw_one(struct super_block *sb, void *unused)
522{
523 char b[BDEVNAME_SIZE];
524 while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb))
525 printk(KERN_WARNING "Emergency Thaw on %s\n",
526 bdevname(sb->s_bdev, b));
527}
528
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -0700529static void do_thaw_all(struct work_struct *work)
Eric Sandeenc2d75432009-03-31 15:23:46 -0700530{
Al Viro01a05b32010-03-23 06:06:58 -0400531 iterate_supers(do_thaw_one, NULL);
Jens Axboe053c5252009-04-08 13:44:08 +0200532 kfree(work);
Eric Sandeenc2d75432009-03-31 15:23:46 -0700533 printk(KERN_WARNING "Emergency Thaw complete\n");
534}
535
536/**
537 * emergency_thaw_all -- forcibly thaw every frozen filesystem
538 *
539 * Used for emergency unfreeze of all filesystems via SysRq
540 */
541void emergency_thaw_all(void)
542{
Jens Axboe053c5252009-04-08 13:44:08 +0200543 struct work_struct *work;
544
545 work = kmalloc(sizeof(*work), GFP_ATOMIC);
546 if (work) {
547 INIT_WORK(work, do_thaw_all);
548 schedule_work(work);
549 }
Eric Sandeenc2d75432009-03-31 15:23:46 -0700550}
551
Linus Torvalds1da177e2005-04-16 15:20:36 -0700552/**
Randy Dunlap78a4a502008-02-29 22:02:31 -0800553 * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers
Martin Waitz67be2dd2005-05-01 08:59:26 -0700554 * @mapping: the mapping which wants those buffers written
Linus Torvalds1da177e2005-04-16 15:20:36 -0700555 *
556 * Starts I/O against the buffers at mapping->private_list, and waits upon
557 * that I/O.
558 *
Martin Waitz67be2dd2005-05-01 08:59:26 -0700559 * Basically, this is a convenience function for fsync().
560 * @mapping is a file or directory which needs those buffers to be written for
561 * a successful fsync().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700562 */
563int sync_mapping_buffers(struct address_space *mapping)
564{
Rafael Aquini252aa6f2012-12-11 16:02:35 -0800565 struct address_space *buffer_mapping = mapping->private_data;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700566
567 if (buffer_mapping == NULL || list_empty(&mapping->private_list))
568 return 0;
569
570 return fsync_buffers_list(&buffer_mapping->private_lock,
571 &mapping->private_list);
572}
573EXPORT_SYMBOL(sync_mapping_buffers);
574
575/*
576 * Called when we've recently written block `bblock', and it is known that
577 * `bblock' was for a buffer_boundary() buffer. This means that the block at
578 * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's
579 * dirty, schedule it for IO. So that indirects merge nicely with their data.
580 */
581void write_boundary_block(struct block_device *bdev,
582 sector_t bblock, unsigned blocksize)
583{
584 struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize);
585 if (bh) {
586 if (buffer_dirty(bh))
587 ll_rw_block(WRITE, 1, &bh);
588 put_bh(bh);
589 }
590}
591
592void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
593{
594 struct address_space *mapping = inode->i_mapping;
595 struct address_space *buffer_mapping = bh->b_page->mapping;
596
597 mark_buffer_dirty(bh);
Rafael Aquini252aa6f2012-12-11 16:02:35 -0800598 if (!mapping->private_data) {
599 mapping->private_data = buffer_mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700600 } else {
Rafael Aquini252aa6f2012-12-11 16:02:35 -0800601 BUG_ON(mapping->private_data != buffer_mapping);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700602 }
Jan Kara535ee2f2008-02-08 04:21:59 -0800603 if (!bh->b_assoc_map) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700604 spin_lock(&buffer_mapping->private_lock);
605 list_move_tail(&bh->b_assoc_buffers,
606 &mapping->private_list);
Jan Kara58ff4072006-10-17 00:10:19 -0700607 bh->b_assoc_map = mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700608 spin_unlock(&buffer_mapping->private_lock);
609 }
610}
611EXPORT_SYMBOL(mark_buffer_dirty_inode);
612
613/*
Nick Piggin787d2212007-07-17 04:03:34 -0700614 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode
615 * dirty.
616 *
617 * If warn is true, then emit a warning if the page is not uptodate and has
618 * not been truncated.
619 */
Linus Torvaldsa8e7d492009-03-19 11:32:05 -0700620static void __set_page_dirty(struct page *page,
Nick Piggin787d2212007-07-17 04:03:34 -0700621 struct address_space *mapping, int warn)
622{
Nick Piggin19fd6232008-07-25 19:45:32 -0700623 spin_lock_irq(&mapping->tree_lock);
Nick Piggin787d2212007-07-17 04:03:34 -0700624 if (page->mapping) { /* Race with truncate? */
625 WARN_ON_ONCE(warn && !PageUptodate(page));
Edward Shishkine3a7cca2009-03-31 15:19:39 -0700626 account_page_dirtied(page, mapping);
Nick Piggin787d2212007-07-17 04:03:34 -0700627 radix_tree_tag_set(&mapping->page_tree,
628 page_index(page), PAGECACHE_TAG_DIRTY);
629 }
Nick Piggin19fd6232008-07-25 19:45:32 -0700630 spin_unlock_irq(&mapping->tree_lock);
Nick Piggin787d2212007-07-17 04:03:34 -0700631 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
Nick Piggin787d2212007-07-17 04:03:34 -0700632}
633
634/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700635 * Add a page to the dirty page list.
636 *
637 * It is a sad fact of life that this function is called from several places
638 * deeply under spinlocking. It may not sleep.
639 *
640 * If the page has buffers, the uptodate buffers are set dirty, to preserve
641 * dirty-state coherency between the page and the buffers. It the page does
642 * not have buffers then when they are later attached they will all be set
643 * dirty.
644 *
645 * The buffers are dirtied before the page is dirtied. There's a small race
646 * window in which a writepage caller may see the page cleanness but not the
647 * buffer dirtiness. That's fine. If this code were to set the page dirty
648 * before the buffers, a concurrent writepage caller could clear the page dirty
649 * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
650 * page on the dirty page list.
651 *
652 * We use private_lock to lock against try_to_free_buffers while using the
653 * page's buffer list. Also use this to protect against clean buffers being
654 * added to the page after it was set dirty.
655 *
656 * FIXME: may need to call ->reservepage here as well. That's rather up to the
657 * address_space though.
658 */
659int __set_page_dirty_buffers(struct page *page)
660{
Linus Torvaldsa8e7d492009-03-19 11:32:05 -0700661 int newly_dirty;
Nick Piggin787d2212007-07-17 04:03:34 -0700662 struct address_space *mapping = page_mapping(page);
Nick Pigginebf7a222006-10-10 04:36:54 +0200663
664 if (unlikely(!mapping))
665 return !TestSetPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700666
667 spin_lock(&mapping->private_lock);
668 if (page_has_buffers(page)) {
669 struct buffer_head *head = page_buffers(page);
670 struct buffer_head *bh = head;
671
672 do {
673 set_buffer_dirty(bh);
674 bh = bh->b_this_page;
675 } while (bh != head);
676 }
Linus Torvaldsa8e7d492009-03-19 11:32:05 -0700677 newly_dirty = !TestSetPageDirty(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700678 spin_unlock(&mapping->private_lock);
679
Linus Torvaldsa8e7d492009-03-19 11:32:05 -0700680 if (newly_dirty)
681 __set_page_dirty(page, mapping, 1);
682 return newly_dirty;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700683}
684EXPORT_SYMBOL(__set_page_dirty_buffers);
685
686/*
687 * Write out and wait upon a list of buffers.
688 *
689 * We have conflicting pressures: we want to make sure that all
690 * initially dirty buffers get waited on, but that any subsequently
691 * dirtied buffers don't. After all, we don't want fsync to last
692 * forever if somebody is actively writing to the file.
693 *
694 * Do this in two main stages: first we copy dirty buffers to a
695 * temporary inode list, queueing the writes as we go. Then we clean
696 * up, waiting for those writes to complete.
697 *
698 * During this second stage, any subsequent updates to the file may end
699 * up refiling the buffer on the original inode's dirty list again, so
700 * there is a chance we will end up with a buffer queued for write but
701 * not yet completed on that list. So, as a final cleanup we go through
702 * the osync code to catch these locked, dirty buffers without requeuing
703 * any newly dirty buffers for write.
704 */
705static int fsync_buffers_list(spinlock_t *lock, struct list_head *list)
706{
707 struct buffer_head *bh;
708 struct list_head tmp;
Jens Axboe7eaceac2011-03-10 08:52:07 +0100709 struct address_space *mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700710 int err = 0, err2;
Jens Axboe4ee24912011-03-17 10:51:40 +0100711 struct blk_plug plug;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700712
713 INIT_LIST_HEAD(&tmp);
Jens Axboe4ee24912011-03-17 10:51:40 +0100714 blk_start_plug(&plug);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700715
716 spin_lock(lock);
717 while (!list_empty(list)) {
718 bh = BH_ENTRY(list->next);
Jan Kara535ee2f2008-02-08 04:21:59 -0800719 mapping = bh->b_assoc_map;
Jan Kara58ff4072006-10-17 00:10:19 -0700720 __remove_assoc_queue(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -0800721 /* Avoid race with mark_buffer_dirty_inode() which does
722 * a lockless check and we rely on seeing the dirty bit */
723 smp_mb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700724 if (buffer_dirty(bh) || buffer_locked(bh)) {
725 list_add(&bh->b_assoc_buffers, &tmp);
Jan Kara535ee2f2008-02-08 04:21:59 -0800726 bh->b_assoc_map = mapping;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700727 if (buffer_dirty(bh)) {
728 get_bh(bh);
729 spin_unlock(lock);
730 /*
731 * Ensure any pending I/O completes so that
Christoph Hellwig9cb569d2010-08-11 17:06:24 +0200732 * write_dirty_buffer() actually writes the
733 * current contents - it is a noop if I/O is
734 * still in flight on potentially older
735 * contents.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700736 */
Jens Axboe721a9602011-03-09 11:56:30 +0100737 write_dirty_buffer(bh, WRITE_SYNC);
Jens Axboe9cf6b722009-04-06 14:48:03 +0200738
739 /*
740 * Kick off IO for the previous mapping. Note
741 * that we will not run the very last mapping,
742 * wait_on_buffer() will do that for us
743 * through sync_buffer().
744 */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700745 brelse(bh);
746 spin_lock(lock);
747 }
748 }
749 }
750
Jens Axboe4ee24912011-03-17 10:51:40 +0100751 spin_unlock(lock);
752 blk_finish_plug(&plug);
753 spin_lock(lock);
754
Linus Torvalds1da177e2005-04-16 15:20:36 -0700755 while (!list_empty(&tmp)) {
756 bh = BH_ENTRY(tmp.prev);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700757 get_bh(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -0800758 mapping = bh->b_assoc_map;
759 __remove_assoc_queue(bh);
760 /* Avoid race with mark_buffer_dirty_inode() which does
761 * a lockless check and we rely on seeing the dirty bit */
762 smp_mb();
763 if (buffer_dirty(bh)) {
764 list_add(&bh->b_assoc_buffers,
Jan Karae3892292008-03-04 14:28:33 -0800765 &mapping->private_list);
Jan Kara535ee2f2008-02-08 04:21:59 -0800766 bh->b_assoc_map = mapping;
767 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700768 spin_unlock(lock);
769 wait_on_buffer(bh);
770 if (!buffer_uptodate(bh))
771 err = -EIO;
772 brelse(bh);
773 spin_lock(lock);
774 }
775
776 spin_unlock(lock);
777 err2 = osync_buffers_list(lock, list);
778 if (err)
779 return err;
780 else
781 return err2;
782}
783
784/*
785 * Invalidate any and all dirty buffers on a given inode. We are
786 * probably unmounting the fs, but that doesn't mean we have already
787 * done a sync(). Just drop the buffers from the inode list.
788 *
789 * NOTE: we take the inode's blockdev's mapping's private_lock. Which
790 * assumes that all the buffers are against the blockdev. Not true
791 * for reiserfs.
792 */
793void invalidate_inode_buffers(struct inode *inode)
794{
795 if (inode_has_buffers(inode)) {
796 struct address_space *mapping = &inode->i_data;
797 struct list_head *list = &mapping->private_list;
Rafael Aquini252aa6f2012-12-11 16:02:35 -0800798 struct address_space *buffer_mapping = mapping->private_data;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700799
800 spin_lock(&buffer_mapping->private_lock);
801 while (!list_empty(list))
802 __remove_assoc_queue(BH_ENTRY(list->next));
803 spin_unlock(&buffer_mapping->private_lock);
804 }
805}
Jan Kara52b19ac2008-09-23 18:24:08 +0200806EXPORT_SYMBOL(invalidate_inode_buffers);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700807
808/*
809 * Remove any clean buffers from the inode's buffer list. This is called
810 * when we're trying to free the inode itself. Those buffers can pin it.
811 *
812 * Returns true if all buffers were removed.
813 */
814int remove_inode_buffers(struct inode *inode)
815{
816 int ret = 1;
817
818 if (inode_has_buffers(inode)) {
819 struct address_space *mapping = &inode->i_data;
820 struct list_head *list = &mapping->private_list;
Rafael Aquini252aa6f2012-12-11 16:02:35 -0800821 struct address_space *buffer_mapping = mapping->private_data;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700822
823 spin_lock(&buffer_mapping->private_lock);
824 while (!list_empty(list)) {
825 struct buffer_head *bh = BH_ENTRY(list->next);
826 if (buffer_dirty(bh)) {
827 ret = 0;
828 break;
829 }
830 __remove_assoc_queue(bh);
831 }
832 spin_unlock(&buffer_mapping->private_lock);
833 }
834 return ret;
835}
836
837/*
838 * Create the appropriate buffers when given a page for data area and
839 * the size of each buffer.. Use the bh->b_this_page linked list to
840 * follow the buffers created. Return NULL if unable to create more
841 * buffers.
842 *
843 * The retry flag is used to differentiate async IO (paging, swapping)
844 * which may not fail from ordinary buffer allocations.
845 */
846struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
847 int retry)
848{
849 struct buffer_head *bh, *head;
850 long offset;
851
852try_again:
853 head = NULL;
854 offset = PAGE_SIZE;
855 while ((offset -= size) >= 0) {
856 bh = alloc_buffer_head(GFP_NOFS);
857 if (!bh)
858 goto no_grow;
859
Linus Torvalds1da177e2005-04-16 15:20:36 -0700860 bh->b_this_page = head;
861 bh->b_blocknr = -1;
862 head = bh;
863
Linus Torvalds1da177e2005-04-16 15:20:36 -0700864 bh->b_size = size;
865
866 /* Link the buffer to its page */
867 set_bh_page(bh, page, offset);
868
Nathan Scott01ffe332006-01-17 09:02:07 +1100869 init_buffer(bh, NULL, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700870 }
871 return head;
872/*
873 * In case anything failed, we just free everything we got.
874 */
875no_grow:
876 if (head) {
877 do {
878 bh = head;
879 head = head->b_this_page;
880 free_buffer_head(bh);
881 } while (head);
882 }
883
884 /*
885 * Return failure for non-async IO requests. Async IO requests
886 * are not allowed to fail, so we have to wait until buffer heads
887 * become available. But we don't want tasks sleeping with
888 * partially complete buffers, so all were released above.
889 */
890 if (!retry)
891 return NULL;
892
893 /* We're _really_ low on memory. Now we just
894 * wait for old buffer heads to become free due to
895 * finishing IO. Since this is an async request and
896 * the reserve list is empty, we're sure there are
897 * async buffer heads in use.
898 */
899 free_more_memory();
900 goto try_again;
901}
902EXPORT_SYMBOL_GPL(alloc_page_buffers);
903
904static inline void
905link_dev_buffers(struct page *page, struct buffer_head *head)
906{
907 struct buffer_head *bh, *tail;
908
909 bh = head;
910 do {
911 tail = bh;
912 bh = bh->b_this_page;
913 } while (bh);
914 tail->b_this_page = head;
915 attach_page_buffers(page, head);
916}
917
Linus Torvaldsbbec02702012-11-29 12:31:52 -0800918static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
919{
920 sector_t retval = ~((sector_t)0);
921 loff_t sz = i_size_read(bdev->bd_inode);
922
923 if (sz) {
924 unsigned int sizebits = blksize_bits(size);
925 retval = (sz >> sizebits);
926 }
927 return retval;
928}
929
Linus Torvalds1da177e2005-04-16 15:20:36 -0700930/*
931 * Initialise the state of a blockdev page's buffers.
932 */
Hugh Dickins676ce6d2012-08-23 12:17:36 +0200933static sector_t
Linus Torvalds1da177e2005-04-16 15:20:36 -0700934init_page_buffers(struct page *page, struct block_device *bdev,
935 sector_t block, int size)
936{
937 struct buffer_head *head = page_buffers(page);
938 struct buffer_head *bh = head;
939 int uptodate = PageUptodate(page);
Linus Torvaldsbbec02702012-11-29 12:31:52 -0800940 sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode), size);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700941
942 do {
943 if (!buffer_mapped(bh)) {
944 init_buffer(bh, NULL, NULL);
945 bh->b_bdev = bdev;
946 bh->b_blocknr = block;
947 if (uptodate)
948 set_buffer_uptodate(bh);
Jeff Moyer080399a2012-05-11 16:34:10 +0200949 if (block < end_block)
950 set_buffer_mapped(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700951 }
952 block++;
953 bh = bh->b_this_page;
954 } while (bh != head);
Hugh Dickins676ce6d2012-08-23 12:17:36 +0200955
956 /*
957 * Caller needs to validate requested block against end of device.
958 */
959 return end_block;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700960}
961
962/*
963 * Create the page-cache page that contains the requested block.
964 *
Hugh Dickins676ce6d2012-08-23 12:17:36 +0200965 * This is used purely for blockdev mappings.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700966 */
Hugh Dickins676ce6d2012-08-23 12:17:36 +0200967static int
Linus Torvalds1da177e2005-04-16 15:20:36 -0700968grow_dev_page(struct block_device *bdev, sector_t block,
Hugh Dickins676ce6d2012-08-23 12:17:36 +0200969 pgoff_t index, int size, int sizebits)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700970{
971 struct inode *inode = bdev->bd_inode;
972 struct page *page;
973 struct buffer_head *bh;
Hugh Dickins676ce6d2012-08-23 12:17:36 +0200974 sector_t end_block;
975 int ret = 0; /* Will call free_more_memory() */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700976
Christoph Lameterea125892007-05-16 22:11:21 -0700977 page = find_or_create_page(inode->i_mapping, index,
Mel Gorman769848c2007-07-17 04:03:05 -0700978 (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700979 if (!page)
Hugh Dickins676ce6d2012-08-23 12:17:36 +0200980 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700981
Eric Sesterhenne827f922006-03-26 18:24:46 +0200982 BUG_ON(!PageLocked(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700983
984 if (page_has_buffers(page)) {
985 bh = page_buffers(page);
986 if (bh->b_size == size) {
Hugh Dickins676ce6d2012-08-23 12:17:36 +0200987 end_block = init_page_buffers(page, bdev,
988 index << sizebits, size);
989 goto done;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700990 }
991 if (!try_to_free_buffers(page))
992 goto failed;
993 }
994
995 /*
996 * Allocate some buffers for this page
997 */
998 bh = alloc_page_buffers(page, size, 0);
999 if (!bh)
1000 goto failed;
1001
1002 /*
1003 * Link the page to the buffers and initialise them. Take the
1004 * lock to be atomic wrt __find_get_block(), which does not
1005 * run under the page lock.
1006 */
1007 spin_lock(&inode->i_mapping->private_lock);
1008 link_dev_buffers(page, bh);
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001009 end_block = init_page_buffers(page, bdev, index << sizebits, size);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001010 spin_unlock(&inode->i_mapping->private_lock);
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001011done:
1012 ret = (block < end_block) ? 1 : -ENXIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001013failed:
Linus Torvalds1da177e2005-04-16 15:20:36 -07001014 unlock_page(page);
1015 page_cache_release(page);
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001016 return ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001017}
1018
1019/*
1020 * Create buffers for the specified block device block's page. If
1021 * that page was dirty, the buffers are set dirty also.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001022 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001023static int
Linus Torvalds1da177e2005-04-16 15:20:36 -07001024grow_buffers(struct block_device *bdev, sector_t block, int size)
1025{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001026 pgoff_t index;
1027 int sizebits;
1028
1029 sizebits = -1;
1030 do {
1031 sizebits++;
1032 } while ((size << sizebits) < PAGE_SIZE);
1033
1034 index = block >> sizebits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001035
Andrew Mortone5657932006-10-11 01:21:46 -07001036 /*
1037 * Check for a block which wants to lie outside our maximum possible
1038 * pagecache index. (this comparison is done using sector_t types).
1039 */
1040 if (unlikely(index != block >> sizebits)) {
1041 char b[BDEVNAME_SIZE];
1042
1043 printk(KERN_ERR "%s: requested out-of-range block %llu for "
1044 "device %s\n",
Harvey Harrison8e24eea2008-04-30 00:55:09 -07001045 __func__, (unsigned long long)block,
Andrew Mortone5657932006-10-11 01:21:46 -07001046 bdevname(bdev, b));
1047 return -EIO;
1048 }
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001049
Linus Torvalds1da177e2005-04-16 15:20:36 -07001050 /* Create a page with the proper size buffers.. */
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001051 return grow_dev_page(bdev, block, index, size, sizebits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001052}
1053
Adrian Bunk75c96f82005-05-05 16:16:09 -07001054static struct buffer_head *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001055__getblk_slow(struct block_device *bdev, sector_t block, int size)
1056{
1057 /* Size must be multiple of hard sectorsize */
Martin K. Petersene1defc42009-05-22 17:17:49 -04001058 if (unlikely(size & (bdev_logical_block_size(bdev)-1) ||
Linus Torvalds1da177e2005-04-16 15:20:36 -07001059 (size < 512 || size > PAGE_SIZE))) {
1060 printk(KERN_ERR "getblk(): invalid block size %d requested\n",
1061 size);
Martin K. Petersene1defc42009-05-22 17:17:49 -04001062 printk(KERN_ERR "logical block size: %d\n",
1063 bdev_logical_block_size(bdev));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001064
1065 dump_stack();
1066 return NULL;
1067 }
1068
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001069 for (;;) {
1070 struct buffer_head *bh;
1071 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001072
1073 bh = __find_get_block(bdev, block, size);
1074 if (bh)
1075 return bh;
Hugh Dickins676ce6d2012-08-23 12:17:36 +02001076
1077 ret = grow_buffers(bdev, block, size);
1078 if (ret < 0)
1079 return NULL;
1080 if (ret == 0)
1081 free_more_memory();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001082 }
1083}
1084
1085/*
1086 * The relationship between dirty buffers and dirty pages:
1087 *
1088 * Whenever a page has any dirty buffers, the page's dirty bit is set, and
1089 * the page is tagged dirty in its radix tree.
1090 *
1091 * At all times, the dirtiness of the buffers represents the dirtiness of
1092 * subsections of the page. If the page has buffers, the page dirty bit is
1093 * merely a hint about the true dirty state.
1094 *
1095 * When a page is set dirty in its entirety, all its buffers are marked dirty
1096 * (if the page has buffers).
1097 *
1098 * When a buffer is marked dirty, its page is dirtied, but the page's other
1099 * buffers are not.
1100 *
1101 * Also. When blockdev buffers are explicitly read with bread(), they
1102 * individually become uptodate. But their backing page remains not
1103 * uptodate - even if all of its buffers are uptodate. A subsequent
1104 * block_read_full_page() against that page will discover all the uptodate
1105 * buffers, will set the page uptodate and will perform no I/O.
1106 */
1107
1108/**
1109 * mark_buffer_dirty - mark a buffer_head as needing writeout
Martin Waitz67be2dd2005-05-01 08:59:26 -07001110 * @bh: the buffer_head to mark dirty
Linus Torvalds1da177e2005-04-16 15:20:36 -07001111 *
1112 * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
1113 * backing page dirty, then tag the page as dirty in its address_space's radix
1114 * tree and then attach the address_space's inode to its superblock's dirty
1115 * inode list.
1116 *
1117 * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock,
Dave Chinner250df6e2011-03-22 22:23:36 +11001118 * mapping->tree_lock and mapping->host->i_lock.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001119 */
Harvey Harrisonfc9b52c2008-02-08 04:19:52 -08001120void mark_buffer_dirty(struct buffer_head *bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001121{
Nick Piggin787d2212007-07-17 04:03:34 -07001122 WARN_ON_ONCE(!buffer_uptodate(bh));
Linus Torvalds1be62dc2008-04-04 14:38:17 -07001123
Tejun Heo5305cb82013-01-11 13:06:36 -08001124 trace_block_dirty_buffer(bh);
1125
Linus Torvalds1be62dc2008-04-04 14:38:17 -07001126 /*
1127 * Very *carefully* optimize the it-is-already-dirty case.
1128 *
1129 * Don't let the final "is it dirty" escape to before we
1130 * perhaps modified the buffer.
1131 */
1132 if (buffer_dirty(bh)) {
1133 smp_mb();
1134 if (buffer_dirty(bh))
1135 return;
1136 }
1137
Linus Torvaldsa8e7d492009-03-19 11:32:05 -07001138 if (!test_set_buffer_dirty(bh)) {
1139 struct page *page = bh->b_page;
Linus Torvalds8e9d78e2009-08-21 17:40:08 -07001140 if (!TestSetPageDirty(page)) {
1141 struct address_space *mapping = page_mapping(page);
1142 if (mapping)
1143 __set_page_dirty(page, mapping, 0);
1144 }
Linus Torvaldsa8e7d492009-03-19 11:32:05 -07001145 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001146}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07001147EXPORT_SYMBOL(mark_buffer_dirty);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001148
1149/*
1150 * Decrement a buffer_head's reference count. If all buffers against a page
1151 * have zero reference count, are clean and unlocked, and if the page is clean
1152 * and unlocked then try_to_free_buffers() may strip the buffers from the page
1153 * in preparation for freeing it (sometimes, rarely, buffers are removed from
1154 * a page but it ends up not being freed, and buffers may later be reattached).
1155 */
1156void __brelse(struct buffer_head * buf)
1157{
1158 if (atomic_read(&buf->b_count)) {
1159 put_bh(buf);
1160 return;
1161 }
Arjan van de Ven5c752ad2008-07-25 19:45:40 -07001162 WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n");
Linus Torvalds1da177e2005-04-16 15:20:36 -07001163}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07001164EXPORT_SYMBOL(__brelse);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001165
1166/*
1167 * bforget() is like brelse(), except it discards any
1168 * potentially dirty data.
1169 */
1170void __bforget(struct buffer_head *bh)
1171{
1172 clear_buffer_dirty(bh);
Jan Kara535ee2f2008-02-08 04:21:59 -08001173 if (bh->b_assoc_map) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001174 struct address_space *buffer_mapping = bh->b_page->mapping;
1175
1176 spin_lock(&buffer_mapping->private_lock);
1177 list_del_init(&bh->b_assoc_buffers);
Jan Kara58ff4072006-10-17 00:10:19 -07001178 bh->b_assoc_map = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001179 spin_unlock(&buffer_mapping->private_lock);
1180 }
1181 __brelse(bh);
1182}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07001183EXPORT_SYMBOL(__bforget);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001184
1185static struct buffer_head *__bread_slow(struct buffer_head *bh)
1186{
1187 lock_buffer(bh);
1188 if (buffer_uptodate(bh)) {
1189 unlock_buffer(bh);
1190 return bh;
1191 } else {
1192 get_bh(bh);
1193 bh->b_end_io = end_buffer_read_sync;
1194 submit_bh(READ, bh);
1195 wait_on_buffer(bh);
1196 if (buffer_uptodate(bh))
1197 return bh;
1198 }
1199 brelse(bh);
1200 return NULL;
1201}
1202
1203/*
1204 * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block().
1205 * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their
1206 * refcount elevated by one when they're in an LRU. A buffer can only appear
1207 * once in a particular CPU's LRU. A single buffer can be present in multiple
1208 * CPU's LRUs at the same time.
1209 *
1210 * This is a transparent caching front-end to sb_bread(), sb_getblk() and
1211 * sb_find_get_block().
1212 *
1213 * The LRUs themselves only need locking against invalidate_bh_lrus. We use
1214 * a local interrupt disable for that.
1215 */
1216
1217#define BH_LRU_SIZE 8
1218
1219struct bh_lru {
1220 struct buffer_head *bhs[BH_LRU_SIZE];
1221};
1222
1223static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }};
1224
1225#ifdef CONFIG_SMP
1226#define bh_lru_lock() local_irq_disable()
1227#define bh_lru_unlock() local_irq_enable()
1228#else
1229#define bh_lru_lock() preempt_disable()
1230#define bh_lru_unlock() preempt_enable()
1231#endif
1232
1233static inline void check_irqs_on(void)
1234{
1235#ifdef irqs_disabled
1236 BUG_ON(irqs_disabled());
1237#endif
1238}
1239
1240/*
1241 * The LRU management algorithm is dopey-but-simple. Sorry.
1242 */
1243static void bh_lru_install(struct buffer_head *bh)
1244{
1245 struct buffer_head *evictee = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001246
1247 check_irqs_on();
1248 bh_lru_lock();
Christoph Lameterc7b92512010-12-06 11:16:28 -06001249 if (__this_cpu_read(bh_lrus.bhs[0]) != bh) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001250 struct buffer_head *bhs[BH_LRU_SIZE];
1251 int in;
1252 int out = 0;
1253
1254 get_bh(bh);
1255 bhs[out++] = bh;
1256 for (in = 0; in < BH_LRU_SIZE; in++) {
Christoph Lameterc7b92512010-12-06 11:16:28 -06001257 struct buffer_head *bh2 =
1258 __this_cpu_read(bh_lrus.bhs[in]);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001259
1260 if (bh2 == bh) {
1261 __brelse(bh2);
1262 } else {
1263 if (out >= BH_LRU_SIZE) {
1264 BUG_ON(evictee != NULL);
1265 evictee = bh2;
1266 } else {
1267 bhs[out++] = bh2;
1268 }
1269 }
1270 }
1271 while (out < BH_LRU_SIZE)
1272 bhs[out++] = NULL;
Christoph Lameterc7b92512010-12-06 11:16:28 -06001273 memcpy(__this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001274 }
1275 bh_lru_unlock();
1276
1277 if (evictee)
1278 __brelse(evictee);
1279}
1280
1281/*
1282 * Look up the bh in this cpu's LRU. If it's there, move it to the head.
1283 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001284static struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001285lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001286{
1287 struct buffer_head *ret = NULL;
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001288 unsigned int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001289
1290 check_irqs_on();
1291 bh_lru_lock();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001292 for (i = 0; i < BH_LRU_SIZE; i++) {
Christoph Lameterc7b92512010-12-06 11:16:28 -06001293 struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001294
1295 if (bh && bh->b_bdev == bdev &&
1296 bh->b_blocknr == block && bh->b_size == size) {
1297 if (i) {
1298 while (i) {
Christoph Lameterc7b92512010-12-06 11:16:28 -06001299 __this_cpu_write(bh_lrus.bhs[i],
1300 __this_cpu_read(bh_lrus.bhs[i - 1]));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001301 i--;
1302 }
Christoph Lameterc7b92512010-12-06 11:16:28 -06001303 __this_cpu_write(bh_lrus.bhs[0], bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001304 }
1305 get_bh(bh);
1306 ret = bh;
1307 break;
1308 }
1309 }
1310 bh_lru_unlock();
1311 return ret;
1312}
1313
1314/*
1315 * Perform a pagecache lookup for the matching buffer. If it's there, refresh
1316 * it in the LRU and mark it as accessed. If it is not present then return
1317 * NULL
1318 */
1319struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001320__find_get_block(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001321{
1322 struct buffer_head *bh = lookup_bh_lru(bdev, block, size);
1323
1324 if (bh == NULL) {
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001325 bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001326 if (bh)
1327 bh_lru_install(bh);
1328 }
1329 if (bh)
1330 touch_buffer(bh);
1331 return bh;
1332}
1333EXPORT_SYMBOL(__find_get_block);
1334
1335/*
1336 * __getblk will locate (and, if necessary, create) the buffer_head
1337 * which corresponds to the passed block_device, block and size. The
1338 * returned buffer has its reference count incremented.
1339 *
Linus Torvalds1da177e2005-04-16 15:20:36 -07001340 * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers()
1341 * attempt is failing. FIXME, perhaps?
1342 */
1343struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001344__getblk(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001345{
1346 struct buffer_head *bh = __find_get_block(bdev, block, size);
1347
1348 might_sleep();
1349 if (bh == NULL)
1350 bh = __getblk_slow(bdev, block, size);
1351 return bh;
1352}
1353EXPORT_SYMBOL(__getblk);
1354
1355/*
1356 * Do async read-ahead on a buffer..
1357 */
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001358void __breadahead(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001359{
1360 struct buffer_head *bh = __getblk(bdev, block, size);
Andrew Mortona3e713b2005-10-30 15:03:15 -08001361 if (likely(bh)) {
1362 ll_rw_block(READA, 1, &bh);
1363 brelse(bh);
1364 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001365}
1366EXPORT_SYMBOL(__breadahead);
1367
1368/**
1369 * __bread() - reads a specified block and returns the bh
Martin Waitz67be2dd2005-05-01 08:59:26 -07001370 * @bdev: the block_device to read from
Linus Torvalds1da177e2005-04-16 15:20:36 -07001371 * @block: number of block
1372 * @size: size (in bytes) to read
1373 *
1374 * Reads a specified block, and returns buffer head that contains it.
1375 * It returns NULL if the block was unreadable.
1376 */
1377struct buffer_head *
Tomasz Kvarsin3991d3b2007-02-12 00:52:14 -08001378__bread(struct block_device *bdev, sector_t block, unsigned size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001379{
1380 struct buffer_head *bh = __getblk(bdev, block, size);
1381
Andrew Mortona3e713b2005-10-30 15:03:15 -08001382 if (likely(bh) && !buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001383 bh = __bread_slow(bh);
1384 return bh;
1385}
1386EXPORT_SYMBOL(__bread);
1387
1388/*
1389 * invalidate_bh_lrus() is called rarely - but not only at unmount.
1390 * This doesn't race because it runs in each cpu either in irq
1391 * or with preempt disabled.
1392 */
1393static void invalidate_bh_lru(void *arg)
1394{
1395 struct bh_lru *b = &get_cpu_var(bh_lrus);
1396 int i;
1397
1398 for (i = 0; i < BH_LRU_SIZE; i++) {
1399 brelse(b->bhs[i]);
1400 b->bhs[i] = NULL;
1401 }
1402 put_cpu_var(bh_lrus);
1403}
Gilad Ben-Yossef42be35d2012-03-28 14:42:45 -07001404
1405static bool has_bh_in_lru(int cpu, void *dummy)
1406{
1407 struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu);
1408 int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001409
Gilad Ben-Yossef42be35d2012-03-28 14:42:45 -07001410 for (i = 0; i < BH_LRU_SIZE; i++) {
1411 if (b->bhs[i])
1412 return 1;
1413 }
1414
1415 return 0;
1416}
1417
Peter Zijlstraf9a14392007-05-06 14:49:55 -07001418void invalidate_bh_lrus(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001419{
Gilad Ben-Yossef42be35d2012-03-28 14:42:45 -07001420 on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001421}
Nick Piggin9db55792008-02-08 04:19:49 -08001422EXPORT_SYMBOL_GPL(invalidate_bh_lrus);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001423
1424void set_bh_page(struct buffer_head *bh,
1425 struct page *page, unsigned long offset)
1426{
1427 bh->b_page = page;
Eric Sesterhenne827f922006-03-26 18:24:46 +02001428 BUG_ON(offset >= PAGE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001429 if (PageHighMem(page))
1430 /*
1431 * This catches illegal uses and preserves the offset:
1432 */
1433 bh->b_data = (char *)(0 + offset);
1434 else
1435 bh->b_data = page_address(page) + offset;
1436}
1437EXPORT_SYMBOL(set_bh_page);
1438
1439/*
1440 * Called when truncating a buffer on a page completely.
1441 */
Arjan van de Ven858119e2006-01-14 13:20:43 -08001442static void discard_buffer(struct buffer_head * bh)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001443{
1444 lock_buffer(bh);
1445 clear_buffer_dirty(bh);
1446 bh->b_bdev = NULL;
1447 clear_buffer_mapped(bh);
1448 clear_buffer_req(bh);
1449 clear_buffer_new(bh);
1450 clear_buffer_delay(bh);
David Chinner33a266d2007-02-12 00:51:41 -08001451 clear_buffer_unwritten(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001452 unlock_buffer(bh);
1453}
1454
1455/**
Wang Sheng-Hui814e1d22011-09-01 08:22:57 +08001456 * block_invalidatepage - invalidate part or all of a buffer-backed page
Linus Torvalds1da177e2005-04-16 15:20:36 -07001457 *
1458 * @page: the page which is affected
1459 * @offset: the index of the truncation point
1460 *
1461 * block_invalidatepage() is called when all or part of the page has become
Wang Sheng-Hui814e1d22011-09-01 08:22:57 +08001462 * invalidated by a truncate operation.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001463 *
1464 * block_invalidatepage() does not have to release all buffers, but it must
1465 * ensure that no dirty buffer is left outside @offset and that no I/O
1466 * is underway against any of the blocks which are outside the truncation
1467 * point. Because the caller is about to free (and possibly reuse) those
1468 * blocks on-disk.
1469 */
NeilBrown2ff28e22006-03-26 01:37:18 -08001470void block_invalidatepage(struct page *page, unsigned long offset)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001471{
1472 struct buffer_head *head, *bh, *next;
1473 unsigned int curr_off = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001474
1475 BUG_ON(!PageLocked(page));
1476 if (!page_has_buffers(page))
1477 goto out;
1478
1479 head = page_buffers(page);
1480 bh = head;
1481 do {
1482 unsigned int next_off = curr_off + bh->b_size;
1483 next = bh->b_this_page;
1484
1485 /*
1486 * is this block fully invalidated?
1487 */
1488 if (offset <= curr_off)
1489 discard_buffer(bh);
1490 curr_off = next_off;
1491 bh = next;
1492 } while (bh != head);
1493
1494 /*
1495 * We release buffers only if the entire page is being invalidated.
1496 * The get_block cached value has been unconditionally invalidated,
1497 * so real IO is not possible anymore.
1498 */
1499 if (offset == 0)
NeilBrown2ff28e22006-03-26 01:37:18 -08001500 try_to_release_page(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001501out:
NeilBrown2ff28e22006-03-26 01:37:18 -08001502 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001503}
1504EXPORT_SYMBOL(block_invalidatepage);
1505
1506/*
1507 * We attach and possibly dirty the buffers atomically wrt
1508 * __set_page_dirty_buffers() via private_lock. try_to_free_buffers
1509 * is already excluded via the page lock.
1510 */
1511void create_empty_buffers(struct page *page,
1512 unsigned long blocksize, unsigned long b_state)
1513{
1514 struct buffer_head *bh, *head, *tail;
1515
1516 head = alloc_page_buffers(page, blocksize, 1);
1517 bh = head;
1518 do {
1519 bh->b_state |= b_state;
1520 tail = bh;
1521 bh = bh->b_this_page;
1522 } while (bh);
1523 tail->b_this_page = head;
1524
1525 spin_lock(&page->mapping->private_lock);
1526 if (PageUptodate(page) || PageDirty(page)) {
1527 bh = head;
1528 do {
1529 if (PageDirty(page))
1530 set_buffer_dirty(bh);
1531 if (PageUptodate(page))
1532 set_buffer_uptodate(bh);
1533 bh = bh->b_this_page;
1534 } while (bh != head);
1535 }
1536 attach_page_buffers(page, head);
1537 spin_unlock(&page->mapping->private_lock);
1538}
1539EXPORT_SYMBOL(create_empty_buffers);
1540
1541/*
1542 * We are taking a block for data and we don't want any output from any
1543 * buffer-cache aliases starting from return from that function and
1544 * until the moment when something will explicitly mark the buffer
1545 * dirty (hopefully that will not happen until we will free that block ;-)
1546 * We don't even need to mark it not-uptodate - nobody can expect
1547 * anything from a newly allocated buffer anyway. We used to used
1548 * unmap_buffer() for such invalidation, but that was wrong. We definitely
1549 * don't want to mark the alias unmapped, for example - it would confuse
1550 * anyone who might pick it with bread() afterwards...
1551 *
1552 * Also.. Note that bforget() doesn't lock the buffer. So there can
1553 * be writeout I/O going on against recently-freed buffers. We don't
1554 * wait on that I/O in bforget() - it's more efficient to wait on the I/O
1555 * only if we really need to. That happens here.
1556 */
1557void unmap_underlying_metadata(struct block_device *bdev, sector_t block)
1558{
1559 struct buffer_head *old_bh;
1560
1561 might_sleep();
1562
Coywolf Qi Hunt385fd4c2005-11-07 00:59:39 -08001563 old_bh = __find_get_block_slow(bdev, block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001564 if (old_bh) {
1565 clear_buffer_dirty(old_bh);
1566 wait_on_buffer(old_bh);
1567 clear_buffer_req(old_bh);
1568 __brelse(old_bh);
1569 }
1570}
1571EXPORT_SYMBOL(unmap_underlying_metadata);
1572
1573/*
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001574 * Size is a power-of-two in the range 512..PAGE_SIZE,
1575 * and the case we care about most is PAGE_SIZE.
1576 *
1577 * So this *could* possibly be written with those
1578 * constraints in mind (relevant mostly if some
1579 * architecture has a slow bit-scan instruction)
1580 */
1581static inline int block_size_bits(unsigned int blocksize)
1582{
1583 return ilog2(blocksize);
1584}
1585
1586static struct buffer_head *create_page_buffers(struct page *page, struct inode *inode, unsigned int b_state)
1587{
1588 BUG_ON(!PageLocked(page));
1589
1590 if (!page_has_buffers(page))
1591 create_empty_buffers(page, 1 << ACCESS_ONCE(inode->i_blkbits), b_state);
1592 return page_buffers(page);
1593}
1594
1595/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07001596 * NOTE! All mapped/uptodate combinations are valid:
1597 *
1598 * Mapped Uptodate Meaning
1599 *
1600 * No No "unknown" - must do get_block()
1601 * No Yes "hole" - zero-filled
1602 * Yes No "allocated" - allocated on disk, not read in
1603 * Yes Yes "valid" - allocated and up-to-date in memory.
1604 *
1605 * "Dirty" is valid only with the last case (mapped+uptodate).
1606 */
1607
1608/*
1609 * While block_write_full_page is writing back the dirty buffers under
1610 * the page lock, whoever dirtied the buffers may decide to clean them
1611 * again at any time. We handle that by only looking at the buffer
1612 * state inside lock_buffer().
1613 *
1614 * If block_write_full_page() is called for regular writeback
1615 * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a
1616 * locked buffer. This only can happen if someone has written the buffer
1617 * directly, with submit_bh(). At the address_space level PageWriteback
1618 * prevents this contention from occurring.
Theodore Ts'o6e34eed2009-04-07 18:12:43 -04001619 *
1620 * If block_write_full_page() is called with wbc->sync_mode ==
Jens Axboe721a9602011-03-09 11:56:30 +01001621 * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this
1622 * causes the writes to be flagged as synchronous writes.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001623 */
1624static int __block_write_full_page(struct inode *inode, struct page *page,
Chris Mason35c80d52009-04-15 13:22:38 -04001625 get_block_t *get_block, struct writeback_control *wbc,
1626 bh_end_io_t *handler)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001627{
1628 int err;
1629 sector_t block;
1630 sector_t last_block;
Andrew Mortonf0fbd5f2005-05-05 16:15:48 -07001631 struct buffer_head *bh, *head;
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001632 unsigned int blocksize, bbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001633 int nr_underway = 0;
Theodore Ts'o6e34eed2009-04-07 18:12:43 -04001634 int write_op = (wbc->sync_mode == WB_SYNC_ALL ?
Jens Axboe721a9602011-03-09 11:56:30 +01001635 WRITE_SYNC : WRITE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001636
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001637 head = create_page_buffers(page, inode,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001638 (1 << BH_Dirty)|(1 << BH_Uptodate));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001639
1640 /*
1641 * Be very careful. We have no exclusion from __set_page_dirty_buffers
1642 * here, and the (potentially unmapped) buffers may become dirty at
1643 * any time. If a buffer becomes dirty here after we've inspected it
1644 * then we just miss that fact, and the page stays dirty.
1645 *
1646 * Buffers outside i_size may be dirtied by __set_page_dirty_buffers;
1647 * handle that here by just cleaning them.
1648 */
1649
Linus Torvalds1da177e2005-04-16 15:20:36 -07001650 bh = head;
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001651 blocksize = bh->b_size;
1652 bbits = block_size_bits(blocksize);
1653
1654 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1655 last_block = (i_size_read(inode) - 1) >> bbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001656
1657 /*
1658 * Get all the dirty buffers mapped to disk addresses and
1659 * handle any aliases from the underlying blockdev's mapping.
1660 */
1661 do {
1662 if (block > last_block) {
1663 /*
1664 * mapped buffers outside i_size will occur, because
1665 * this page can be outside i_size when there is a
1666 * truncate in progress.
1667 */
1668 /*
1669 * The buffer was zeroed by block_write_full_page()
1670 */
1671 clear_buffer_dirty(bh);
1672 set_buffer_uptodate(bh);
Alex Tomas29a814d2008-07-11 19:27:31 -04001673 } else if ((!buffer_mapped(bh) || buffer_delay(bh)) &&
1674 buffer_dirty(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001675 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001676 err = get_block(inode, block, bh, 1);
1677 if (err)
1678 goto recover;
Alex Tomas29a814d2008-07-11 19:27:31 -04001679 clear_buffer_delay(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001680 if (buffer_new(bh)) {
1681 /* blockdev mappings never come here */
1682 clear_buffer_new(bh);
1683 unmap_underlying_metadata(bh->b_bdev,
1684 bh->b_blocknr);
1685 }
1686 }
1687 bh = bh->b_this_page;
1688 block++;
1689 } while (bh != head);
1690
1691 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001692 if (!buffer_mapped(bh))
1693 continue;
1694 /*
1695 * If it's a fully non-blocking write attempt and we cannot
1696 * lock the buffer then redirty the page. Note that this can
Jens Axboe5b0830c2009-09-23 19:37:09 +02001697 * potentially cause a busy-wait loop from writeback threads
1698 * and kswapd activity, but those code paths have their own
1699 * higher-level throttling.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001700 */
Wu Fengguang1b430be2010-10-26 14:21:26 -07001701 if (wbc->sync_mode != WB_SYNC_NONE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001702 lock_buffer(bh);
Nick Pigginca5de402008-08-02 12:02:13 +02001703 } else if (!trylock_buffer(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001704 redirty_page_for_writepage(wbc, page);
1705 continue;
1706 }
1707 if (test_clear_buffer_dirty(bh)) {
Chris Mason35c80d52009-04-15 13:22:38 -04001708 mark_buffer_async_write_endio(bh, handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001709 } else {
1710 unlock_buffer(bh);
1711 }
1712 } while ((bh = bh->b_this_page) != head);
1713
1714 /*
1715 * The page and its buffers are protected by PageWriteback(), so we can
1716 * drop the bh refcounts early.
1717 */
1718 BUG_ON(PageWriteback(page));
1719 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001720
1721 do {
1722 struct buffer_head *next = bh->b_this_page;
1723 if (buffer_async_write(bh)) {
Theodore Ts'oa64c8612009-03-27 22:14:10 -04001724 submit_bh(write_op, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001725 nr_underway++;
1726 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001727 bh = next;
1728 } while (bh != head);
Andrew Morton05937ba2005-05-05 16:15:47 -07001729 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001730
1731 err = 0;
1732done:
1733 if (nr_underway == 0) {
1734 /*
1735 * The page was marked dirty, but the buffers were
1736 * clean. Someone wrote them back by hand with
1737 * ll_rw_block/submit_bh. A rare case.
1738 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001739 end_page_writeback(page);
Nick Piggin3d67f2d2007-05-06 14:49:05 -07001740
Linus Torvalds1da177e2005-04-16 15:20:36 -07001741 /*
1742 * The page and buffer_heads can be released at any time from
1743 * here on.
1744 */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001745 }
1746 return err;
1747
1748recover:
1749 /*
1750 * ENOSPC, or some other error. We may already have added some
1751 * blocks to the file, so we need to write these out to avoid
1752 * exposing stale data.
1753 * The page is currently locked and not marked for writeback
1754 */
1755 bh = head;
1756 /* Recovery: lock and submit the mapped buffers */
1757 do {
Alex Tomas29a814d2008-07-11 19:27:31 -04001758 if (buffer_mapped(bh) && buffer_dirty(bh) &&
1759 !buffer_delay(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001760 lock_buffer(bh);
Chris Mason35c80d52009-04-15 13:22:38 -04001761 mark_buffer_async_write_endio(bh, handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001762 } else {
1763 /*
1764 * The buffer may have been set dirty during
1765 * attachment to a dirty page.
1766 */
1767 clear_buffer_dirty(bh);
1768 }
1769 } while ((bh = bh->b_this_page) != head);
1770 SetPageError(page);
1771 BUG_ON(PageWriteback(page));
Andrew Morton7e4c3692007-05-08 00:23:27 -07001772 mapping_set_error(page->mapping, err);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001773 set_page_writeback(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001774 do {
1775 struct buffer_head *next = bh->b_this_page;
1776 if (buffer_async_write(bh)) {
1777 clear_buffer_dirty(bh);
Theodore Ts'oa64c8612009-03-27 22:14:10 -04001778 submit_bh(write_op, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001779 nr_underway++;
1780 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001781 bh = next;
1782 } while (bh != head);
Nick Pigginffda9d32007-02-20 13:57:54 -08001783 unlock_page(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001784 goto done;
1785}
1786
Nick Pigginafddba42007-10-16 01:25:01 -07001787/*
1788 * If a page has any new buffers, zero them out here, and mark them uptodate
1789 * and dirty so they'll be written out (in order to prevent uninitialised
1790 * block data from leaking). And clear the new bit.
1791 */
1792void page_zero_new_buffers(struct page *page, unsigned from, unsigned to)
1793{
1794 unsigned int block_start, block_end;
1795 struct buffer_head *head, *bh;
1796
1797 BUG_ON(!PageLocked(page));
1798 if (!page_has_buffers(page))
1799 return;
1800
1801 bh = head = page_buffers(page);
1802 block_start = 0;
1803 do {
1804 block_end = block_start + bh->b_size;
1805
1806 if (buffer_new(bh)) {
1807 if (block_end > from && block_start < to) {
1808 if (!PageUptodate(page)) {
1809 unsigned start, size;
1810
1811 start = max(from, block_start);
1812 size = min(to, block_end) - start;
1813
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001814 zero_user(page, start, size);
Nick Pigginafddba42007-10-16 01:25:01 -07001815 set_buffer_uptodate(bh);
1816 }
1817
1818 clear_buffer_new(bh);
1819 mark_buffer_dirty(bh);
1820 }
1821 }
1822
1823 block_start = block_end;
1824 bh = bh->b_this_page;
1825 } while (bh != head);
1826}
1827EXPORT_SYMBOL(page_zero_new_buffers);
1828
Christoph Hellwigebdec242010-10-06 10:47:23 +02001829int __block_write_begin(struct page *page, loff_t pos, unsigned len,
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001830 get_block_t *get_block)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001831{
Christoph Hellwigebdec242010-10-06 10:47:23 +02001832 unsigned from = pos & (PAGE_CACHE_SIZE - 1);
1833 unsigned to = from + len;
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001834 struct inode *inode = page->mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001835 unsigned block_start, block_end;
1836 sector_t block;
1837 int err = 0;
1838 unsigned blocksize, bbits;
1839 struct buffer_head *bh, *head, *wait[2], **wait_bh=wait;
1840
1841 BUG_ON(!PageLocked(page));
1842 BUG_ON(from > PAGE_CACHE_SIZE);
1843 BUG_ON(to > PAGE_CACHE_SIZE);
1844 BUG_ON(from > to);
1845
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001846 head = create_page_buffers(page, inode, 0);
1847 blocksize = head->b_size;
1848 bbits = block_size_bits(blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001849
Linus Torvalds1da177e2005-04-16 15:20:36 -07001850 block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
1851
1852 for(bh = head, block_start = 0; bh != head || !block_start;
1853 block++, block_start=block_end, bh = bh->b_this_page) {
1854 block_end = block_start + blocksize;
1855 if (block_end <= from || block_start >= to) {
1856 if (PageUptodate(page)) {
1857 if (!buffer_uptodate(bh))
1858 set_buffer_uptodate(bh);
1859 }
1860 continue;
1861 }
1862 if (buffer_new(bh))
1863 clear_buffer_new(bh);
1864 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08001865 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001866 err = get_block(inode, block, bh, 1);
1867 if (err)
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001868 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001869 if (buffer_new(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001870 unmap_underlying_metadata(bh->b_bdev,
1871 bh->b_blocknr);
1872 if (PageUptodate(page)) {
Nick Piggin637aff42007-10-16 01:25:00 -07001873 clear_buffer_new(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001874 set_buffer_uptodate(bh);
Nick Piggin637aff42007-10-16 01:25:00 -07001875 mark_buffer_dirty(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001876 continue;
1877 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08001878 if (block_end > to || block_start < from)
1879 zero_user_segments(page,
1880 to, block_end,
1881 block_start, from);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001882 continue;
1883 }
1884 }
1885 if (PageUptodate(page)) {
1886 if (!buffer_uptodate(bh))
1887 set_buffer_uptodate(bh);
1888 continue;
1889 }
1890 if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
David Chinner33a266d2007-02-12 00:51:41 -08001891 !buffer_unwritten(bh) &&
Linus Torvalds1da177e2005-04-16 15:20:36 -07001892 (block_start < from || block_end > to)) {
1893 ll_rw_block(READ, 1, &bh);
1894 *wait_bh++=bh;
1895 }
1896 }
1897 /*
1898 * If we issued read requests - let them complete.
1899 */
1900 while(wait_bh > wait) {
1901 wait_on_buffer(*--wait_bh);
1902 if (!buffer_uptodate(*wait_bh))
Nick Pigginf3ddbdc2005-05-05 16:15:45 -07001903 err = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001904 }
Jan Karaf9f07b62011-06-14 00:58:27 +02001905 if (unlikely(err))
Nick Pigginafddba42007-10-16 01:25:01 -07001906 page_zero_new_buffers(page, from, to);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001907 return err;
1908}
Christoph Hellwigebdec242010-10-06 10:47:23 +02001909EXPORT_SYMBOL(__block_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001910
1911static int __block_commit_write(struct inode *inode, struct page *page,
1912 unsigned from, unsigned to)
1913{
1914 unsigned block_start, block_end;
1915 int partial = 0;
1916 unsigned blocksize;
1917 struct buffer_head *bh, *head;
1918
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001919 bh = head = page_buffers(page);
1920 blocksize = bh->b_size;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001921
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001922 block_start = 0;
1923 do {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001924 block_end = block_start + blocksize;
1925 if (block_end <= from || block_start >= to) {
1926 if (!buffer_uptodate(bh))
1927 partial = 1;
1928 } else {
1929 set_buffer_uptodate(bh);
1930 mark_buffer_dirty(bh);
1931 }
Nick Pigginafddba42007-10-16 01:25:01 -07001932 clear_buffer_new(bh);
Linus Torvalds45bce8f2012-11-29 10:21:43 -08001933
1934 block_start = block_end;
1935 bh = bh->b_this_page;
1936 } while (bh != head);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001937
1938 /*
1939 * If this is a partial write which happened to make all buffers
1940 * uptodate then we can optimize away a bogus readpage() for
1941 * the next read(). Here we 'discover' whether the page went
1942 * uptodate as a result of this (potentially partial) write.
1943 */
1944 if (!partial)
1945 SetPageUptodate(page);
1946 return 0;
1947}
1948
1949/*
Christoph Hellwig155130a2010-06-04 11:29:58 +02001950 * block_write_begin takes care of the basic task of block allocation and
1951 * bringing partial write blocks uptodate first.
1952 *
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10001953 * The filesystem needs to handle block truncation upon failure.
Nick Pigginafddba42007-10-16 01:25:01 -07001954 */
Christoph Hellwig155130a2010-06-04 11:29:58 +02001955int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
1956 unsigned flags, struct page **pagep, get_block_t *get_block)
Nick Pigginafddba42007-10-16 01:25:01 -07001957{
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001958 pgoff_t index = pos >> PAGE_CACHE_SHIFT;
Nick Pigginafddba42007-10-16 01:25:01 -07001959 struct page *page;
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001960 int status;
Nick Pigginafddba42007-10-16 01:25:01 -07001961
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001962 page = grab_cache_page_write_begin(mapping, index, flags);
1963 if (!page)
1964 return -ENOMEM;
Nick Pigginafddba42007-10-16 01:25:01 -07001965
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001966 status = __block_write_begin(page, pos, len, get_block);
Nick Pigginafddba42007-10-16 01:25:01 -07001967 if (unlikely(status)) {
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001968 unlock_page(page);
1969 page_cache_release(page);
1970 page = NULL;
Nick Pigginafddba42007-10-16 01:25:01 -07001971 }
1972
Christoph Hellwig6e1db882010-06-04 11:29:57 +02001973 *pagep = page;
Nick Pigginafddba42007-10-16 01:25:01 -07001974 return status;
1975}
1976EXPORT_SYMBOL(block_write_begin);
1977
1978int block_write_end(struct file *file, struct address_space *mapping,
1979 loff_t pos, unsigned len, unsigned copied,
1980 struct page *page, void *fsdata)
1981{
1982 struct inode *inode = mapping->host;
1983 unsigned start;
1984
1985 start = pos & (PAGE_CACHE_SIZE - 1);
1986
1987 if (unlikely(copied < len)) {
1988 /*
1989 * The buffers that were written will now be uptodate, so we
1990 * don't have to worry about a readpage reading them and
1991 * overwriting a partial write. However if we have encountered
1992 * a short write and only partially written into a buffer, it
1993 * will not be marked uptodate, so a readpage might come in and
1994 * destroy our partial write.
1995 *
1996 * Do the simplest thing, and just treat any short write to a
1997 * non uptodate page as a zero-length write, and force the
1998 * caller to redo the whole thing.
1999 */
2000 if (!PageUptodate(page))
2001 copied = 0;
2002
2003 page_zero_new_buffers(page, start+copied, start+len);
2004 }
2005 flush_dcache_page(page);
2006
2007 /* This could be a short (even 0-length) commit */
2008 __block_commit_write(inode, page, start, start+copied);
2009
2010 return copied;
2011}
2012EXPORT_SYMBOL(block_write_end);
2013
2014int generic_write_end(struct file *file, struct address_space *mapping,
2015 loff_t pos, unsigned len, unsigned copied,
2016 struct page *page, void *fsdata)
2017{
2018 struct inode *inode = mapping->host;
Jan Karac7d206b2008-07-11 19:27:31 -04002019 int i_size_changed = 0;
Nick Pigginafddba42007-10-16 01:25:01 -07002020
2021 copied = block_write_end(file, mapping, pos, len, copied, page, fsdata);
2022
2023 /*
2024 * No need to use i_size_read() here, the i_size
2025 * cannot change under us because we hold i_mutex.
2026 *
2027 * But it's important to update i_size while still holding page lock:
2028 * page writeout could otherwise come in and zero beyond i_size.
2029 */
2030 if (pos+copied > inode->i_size) {
2031 i_size_write(inode, pos+copied);
Jan Karac7d206b2008-07-11 19:27:31 -04002032 i_size_changed = 1;
Nick Pigginafddba42007-10-16 01:25:01 -07002033 }
2034
2035 unlock_page(page);
2036 page_cache_release(page);
2037
Jan Karac7d206b2008-07-11 19:27:31 -04002038 /*
2039 * Don't mark the inode dirty under page lock. First, it unnecessarily
2040 * makes the holding time of page lock longer. Second, it forces lock
2041 * ordering of page lock and transaction start for journaling
2042 * filesystems.
2043 */
2044 if (i_size_changed)
2045 mark_inode_dirty(inode);
2046
Nick Pigginafddba42007-10-16 01:25:01 -07002047 return copied;
2048}
2049EXPORT_SYMBOL(generic_write_end);
2050
2051/*
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07002052 * block_is_partially_uptodate checks whether buffers within a page are
2053 * uptodate or not.
2054 *
2055 * Returns true if all buffers which correspond to a file portion
2056 * we want to read are uptodate.
2057 */
2058int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc,
2059 unsigned long from)
2060{
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07002061 unsigned block_start, block_end, blocksize;
2062 unsigned to;
2063 struct buffer_head *bh, *head;
2064 int ret = 1;
2065
2066 if (!page_has_buffers(page))
2067 return 0;
2068
Linus Torvalds45bce8f2012-11-29 10:21:43 -08002069 head = page_buffers(page);
2070 blocksize = head->b_size;
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07002071 to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count);
2072 to = from + to;
2073 if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize)
2074 return 0;
2075
Hisashi Hifumi8ab22b92008-07-28 15:46:36 -07002076 bh = head;
2077 block_start = 0;
2078 do {
2079 block_end = block_start + blocksize;
2080 if (block_end > from && block_start < to) {
2081 if (!buffer_uptodate(bh)) {
2082 ret = 0;
2083 break;
2084 }
2085 if (block_end >= to)
2086 break;
2087 }
2088 block_start = block_end;
2089 bh = bh->b_this_page;
2090 } while (bh != head);
2091
2092 return ret;
2093}
2094EXPORT_SYMBOL(block_is_partially_uptodate);
2095
2096/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07002097 * Generic "read page" function for block devices that have the normal
2098 * get_block functionality. This is most of the block device filesystems.
2099 * Reads the page asynchronously --- the unlock_buffer() and
2100 * set/clear_buffer_uptodate() functions propagate buffer state into the
2101 * page struct once IO has completed.
2102 */
2103int block_read_full_page(struct page *page, get_block_t *get_block)
2104{
2105 struct inode *inode = page->mapping->host;
2106 sector_t iblock, lblock;
2107 struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE];
Linus Torvalds45bce8f2012-11-29 10:21:43 -08002108 unsigned int blocksize, bbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002109 int nr, i;
2110 int fully_mapped = 1;
2111
Linus Torvalds45bce8f2012-11-29 10:21:43 -08002112 head = create_page_buffers(page, inode, 0);
2113 blocksize = head->b_size;
2114 bbits = block_size_bits(blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002115
Linus Torvalds45bce8f2012-11-29 10:21:43 -08002116 iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits);
2117 lblock = (i_size_read(inode)+blocksize-1) >> bbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002118 bh = head;
2119 nr = 0;
2120 i = 0;
2121
2122 do {
2123 if (buffer_uptodate(bh))
2124 continue;
2125
2126 if (!buffer_mapped(bh)) {
Andrew Mortonc64610b2005-05-16 21:53:49 -07002127 int err = 0;
2128
Linus Torvalds1da177e2005-04-16 15:20:36 -07002129 fully_mapped = 0;
2130 if (iblock < lblock) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002131 WARN_ON(bh->b_size != blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002132 err = get_block(inode, iblock, bh, 0);
2133 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002134 SetPageError(page);
2135 }
2136 if (!buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002137 zero_user(page, i * blocksize, blocksize);
Andrew Mortonc64610b2005-05-16 21:53:49 -07002138 if (!err)
2139 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002140 continue;
2141 }
2142 /*
2143 * get_block() might have updated the buffer
2144 * synchronously
2145 */
2146 if (buffer_uptodate(bh))
2147 continue;
2148 }
2149 arr[nr++] = bh;
2150 } while (i++, iblock++, (bh = bh->b_this_page) != head);
2151
2152 if (fully_mapped)
2153 SetPageMappedToDisk(page);
2154
2155 if (!nr) {
2156 /*
2157 * All buffers are uptodate - we can set the page uptodate
2158 * as well. But not if get_block() returned an error.
2159 */
2160 if (!PageError(page))
2161 SetPageUptodate(page);
2162 unlock_page(page);
2163 return 0;
2164 }
2165
2166 /* Stage two: lock the buffers */
2167 for (i = 0; i < nr; i++) {
2168 bh = arr[i];
2169 lock_buffer(bh);
2170 mark_buffer_async_read(bh);
2171 }
2172
2173 /*
2174 * Stage 3: start the IO. Check for uptodateness
2175 * inside the buffer lock in case another process reading
2176 * the underlying blockdev brought it uptodate (the sct fix).
2177 */
2178 for (i = 0; i < nr; i++) {
2179 bh = arr[i];
2180 if (buffer_uptodate(bh))
2181 end_buffer_async_read(bh, 1);
2182 else
2183 submit_bh(READ, bh);
2184 }
2185 return 0;
2186}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002187EXPORT_SYMBOL(block_read_full_page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002188
2189/* utility function for filesystems that need to do work on expanding
Nick Piggin89e10782007-10-16 01:25:07 -07002190 * truncates. Uses filesystem pagecache writes to allow the filesystem to
Linus Torvalds1da177e2005-04-16 15:20:36 -07002191 * deal with the hole.
2192 */
Nick Piggin89e10782007-10-16 01:25:07 -07002193int generic_cont_expand_simple(struct inode *inode, loff_t size)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002194{
2195 struct address_space *mapping = inode->i_mapping;
2196 struct page *page;
Nick Piggin89e10782007-10-16 01:25:07 -07002197 void *fsdata;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002198 int err;
2199
npiggin@suse.dec08d3b02009-08-21 02:35:06 +10002200 err = inode_newsize_ok(inode, size);
2201 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002202 goto out;
2203
Nick Piggin89e10782007-10-16 01:25:07 -07002204 err = pagecache_write_begin(NULL, mapping, size, 0,
2205 AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND,
2206 &page, &fsdata);
2207 if (err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002208 goto out;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002209
Nick Piggin89e10782007-10-16 01:25:07 -07002210 err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata);
2211 BUG_ON(err > 0);
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002212
Linus Torvalds1da177e2005-04-16 15:20:36 -07002213out:
2214 return err;
2215}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002216EXPORT_SYMBOL(generic_cont_expand_simple);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002217
Adrian Bunkf1e3af72008-04-29 00:59:01 -07002218static int cont_expand_zero(struct file *file, struct address_space *mapping,
2219 loff_t pos, loff_t *bytes)
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002220{
Nick Piggin89e10782007-10-16 01:25:07 -07002221 struct inode *inode = mapping->host;
2222 unsigned blocksize = 1 << inode->i_blkbits;
2223 struct page *page;
2224 void *fsdata;
2225 pgoff_t index, curidx;
2226 loff_t curpos;
2227 unsigned zerofrom, offset, len;
2228 int err = 0;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002229
Nick Piggin89e10782007-10-16 01:25:07 -07002230 index = pos >> PAGE_CACHE_SHIFT;
2231 offset = pos & ~PAGE_CACHE_MASK;
2232
2233 while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) {
2234 zerofrom = curpos & ~PAGE_CACHE_MASK;
2235 if (zerofrom & (blocksize-1)) {
2236 *bytes |= (blocksize-1);
2237 (*bytes)++;
2238 }
2239 len = PAGE_CACHE_SIZE - zerofrom;
2240
2241 err = pagecache_write_begin(file, mapping, curpos, len,
2242 AOP_FLAG_UNINTERRUPTIBLE,
2243 &page, &fsdata);
2244 if (err)
2245 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002246 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002247 err = pagecache_write_end(file, mapping, curpos, len, len,
2248 page, fsdata);
2249 if (err < 0)
2250 goto out;
2251 BUG_ON(err != len);
2252 err = 0;
OGAWA Hirofumi061e9742008-04-28 02:16:28 -07002253
2254 balance_dirty_pages_ratelimited(mapping);
Nick Piggin89e10782007-10-16 01:25:07 -07002255 }
2256
2257 /* page covers the boundary, find the boundary offset */
2258 if (index == curidx) {
2259 zerofrom = curpos & ~PAGE_CACHE_MASK;
2260 /* if we will expand the thing last block will be filled */
2261 if (offset <= zerofrom) {
2262 goto out;
2263 }
2264 if (zerofrom & (blocksize-1)) {
2265 *bytes |= (blocksize-1);
2266 (*bytes)++;
2267 }
2268 len = offset - zerofrom;
2269
2270 err = pagecache_write_begin(file, mapping, curpos, len,
2271 AOP_FLAG_UNINTERRUPTIBLE,
2272 &page, &fsdata);
2273 if (err)
2274 goto out;
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002275 zero_user(page, zerofrom, len);
Nick Piggin89e10782007-10-16 01:25:07 -07002276 err = pagecache_write_end(file, mapping, curpos, len, len,
2277 page, fsdata);
2278 if (err < 0)
2279 goto out;
2280 BUG_ON(err != len);
2281 err = 0;
2282 }
2283out:
2284 return err;
OGAWA Hirofumi05eb0b52006-01-08 01:02:13 -08002285}
2286
Linus Torvalds1da177e2005-04-16 15:20:36 -07002287/*
2288 * For moronic filesystems that do not allow holes in file.
2289 * We may have to extend the file.
2290 */
Christoph Hellwig282dc172010-06-04 11:29:55 +02002291int cont_write_begin(struct file *file, struct address_space *mapping,
Nick Piggin89e10782007-10-16 01:25:07 -07002292 loff_t pos, unsigned len, unsigned flags,
2293 struct page **pagep, void **fsdata,
2294 get_block_t *get_block, loff_t *bytes)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002295{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002296 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002297 unsigned blocksize = 1 << inode->i_blkbits;
Nick Piggin89e10782007-10-16 01:25:07 -07002298 unsigned zerofrom;
2299 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002300
Nick Piggin89e10782007-10-16 01:25:07 -07002301 err = cont_expand_zero(file, mapping, pos, bytes);
2302 if (err)
Christoph Hellwig155130a2010-06-04 11:29:58 +02002303 return err;
Nick Piggin89e10782007-10-16 01:25:07 -07002304
2305 zerofrom = *bytes & ~PAGE_CACHE_MASK;
2306 if (pos+len > *bytes && zerofrom & (blocksize-1)) {
2307 *bytes |= (blocksize-1);
2308 (*bytes)++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002309 }
2310
Christoph Hellwig155130a2010-06-04 11:29:58 +02002311 return block_write_begin(mapping, pos, len, flags, pagep, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002312}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002313EXPORT_SYMBOL(cont_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002314
Linus Torvalds1da177e2005-04-16 15:20:36 -07002315int block_commit_write(struct page *page, unsigned from, unsigned to)
2316{
2317 struct inode *inode = page->mapping->host;
2318 __block_commit_write(inode,page,from,to);
2319 return 0;
2320}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002321EXPORT_SYMBOL(block_commit_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002322
David Chinner54171692007-07-19 17:39:55 +10002323/*
2324 * block_page_mkwrite() is not allowed to change the file size as it gets
2325 * called from a page fault handler when a page is first dirtied. Hence we must
2326 * be careful to check for EOF conditions here. We set the page up correctly
2327 * for a written page which means we get ENOSPC checking when writing into
2328 * holes and correct delalloc and unwritten extent mapping on filesystems that
2329 * support these features.
2330 *
2331 * We are not allowed to take the i_mutex here so we have to play games to
2332 * protect against truncate races as the page could now be beyond EOF. Because
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10002333 * truncate writes the inode size before removing pages, once we have the
David Chinner54171692007-07-19 17:39:55 +10002334 * page lock we can determine safely if the page is beyond EOF. If it is not
2335 * beyond EOF, then the page is guaranteed safe against truncation until we
2336 * unlock the page.
Jan Karaea13a862011-05-24 00:23:35 +02002337 *
Jan Kara14da9202012-06-12 16:20:37 +02002338 * Direct callers of this function should protect against filesystem freezing
2339 * using sb_start_write() - sb_end_write() functions.
David Chinner54171692007-07-19 17:39:55 +10002340 */
Jan Kara24da4fa2011-05-24 00:23:34 +02002341int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2342 get_block_t get_block)
David Chinner54171692007-07-19 17:39:55 +10002343{
Nick Pigginc2ec1752009-03-31 15:23:21 -07002344 struct page *page = vmf->page;
Al Viro496ad9a2013-01-23 17:07:38 -05002345 struct inode *inode = file_inode(vma->vm_file);
David Chinner54171692007-07-19 17:39:55 +10002346 unsigned long end;
2347 loff_t size;
Jan Kara24da4fa2011-05-24 00:23:34 +02002348 int ret;
David Chinner54171692007-07-19 17:39:55 +10002349
2350 lock_page(page);
2351 size = i_size_read(inode);
2352 if ((page->mapping != inode->i_mapping) ||
Nick Piggin18336332007-07-20 00:31:45 -07002353 (page_offset(page) > size)) {
Jan Kara24da4fa2011-05-24 00:23:34 +02002354 /* We overload EFAULT to mean page got truncated */
2355 ret = -EFAULT;
2356 goto out_unlock;
David Chinner54171692007-07-19 17:39:55 +10002357 }
2358
2359 /* page is wholly or partially inside EOF */
2360 if (((page->index + 1) << PAGE_CACHE_SHIFT) > size)
2361 end = size & ~PAGE_CACHE_MASK;
2362 else
2363 end = PAGE_CACHE_SIZE;
2364
Christoph Hellwigebdec242010-10-06 10:47:23 +02002365 ret = __block_write_begin(page, 0, end, get_block);
David Chinner54171692007-07-19 17:39:55 +10002366 if (!ret)
2367 ret = block_commit_write(page, 0, end);
2368
Jan Kara24da4fa2011-05-24 00:23:34 +02002369 if (unlikely(ret < 0))
2370 goto out_unlock;
Jan Karaea13a862011-05-24 00:23:35 +02002371 set_page_dirty(page);
Darrick J. Wong1d1d1a72013-02-21 16:42:51 -08002372 wait_for_stable_page(page);
Jan Kara24da4fa2011-05-24 00:23:34 +02002373 return 0;
2374out_unlock:
2375 unlock_page(page);
David Chinner54171692007-07-19 17:39:55 +10002376 return ret;
2377}
Jan Kara24da4fa2011-05-24 00:23:34 +02002378EXPORT_SYMBOL(__block_page_mkwrite);
2379
2380int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
2381 get_block_t get_block)
2382{
Jan Karaea13a862011-05-24 00:23:35 +02002383 int ret;
Al Viro496ad9a2013-01-23 17:07:38 -05002384 struct super_block *sb = file_inode(vma->vm_file)->i_sb;
Jan Kara24da4fa2011-05-24 00:23:34 +02002385
Jan Kara14da9202012-06-12 16:20:37 +02002386 sb_start_pagefault(sb);
Theodore Ts'o041bbb6d2012-09-30 23:04:56 -04002387
2388 /*
2389 * Update file times before taking page lock. We may end up failing the
2390 * fault so this update may be superfluous but who really cares...
2391 */
2392 file_update_time(vma->vm_file);
2393
Jan Karaea13a862011-05-24 00:23:35 +02002394 ret = __block_page_mkwrite(vma, vmf, get_block);
Jan Kara14da9202012-06-12 16:20:37 +02002395 sb_end_pagefault(sb);
Jan Kara24da4fa2011-05-24 00:23:34 +02002396 return block_page_mkwrite_return(ret);
2397}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002398EXPORT_SYMBOL(block_page_mkwrite);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002399
2400/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002401 * nobh_write_begin()'s prereads are special: the buffer_heads are freed
Linus Torvalds1da177e2005-04-16 15:20:36 -07002402 * immediately, while under the page lock. So it needs a special end_io
2403 * handler which does not touch the bh after unlocking it.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002404 */
2405static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
2406{
Dmitry Monakhov68671f32007-10-16 01:24:47 -07002407 __end_buffer_read_notouch(bh, uptodate);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002408}
2409
2410/*
Nick Piggin03158cd2007-10-16 01:25:25 -07002411 * Attach the singly-linked list of buffers created by nobh_write_begin, to
2412 * the page (converting it to circular linked list and taking care of page
2413 * dirty races).
2414 */
2415static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
2416{
2417 struct buffer_head *bh;
2418
2419 BUG_ON(!PageLocked(page));
2420
2421 spin_lock(&page->mapping->private_lock);
2422 bh = head;
2423 do {
2424 if (PageDirty(page))
2425 set_buffer_dirty(bh);
2426 if (!bh->b_this_page)
2427 bh->b_this_page = head;
2428 bh = bh->b_this_page;
2429 } while (bh != head);
2430 attach_page_buffers(page, head);
2431 spin_unlock(&page->mapping->private_lock);
2432}
2433
2434/*
Christoph Hellwigea0f04e2010-06-04 11:29:54 +02002435 * On entry, the page is fully not uptodate.
2436 * On exit the page is fully uptodate in the areas outside (from,to)
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10002437 * The filesystem needs to handle block truncation upon failure.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002438 */
Christoph Hellwigea0f04e2010-06-04 11:29:54 +02002439int nobh_write_begin(struct address_space *mapping,
Nick Piggin03158cd2007-10-16 01:25:25 -07002440 loff_t pos, unsigned len, unsigned flags,
2441 struct page **pagep, void **fsdata,
Linus Torvalds1da177e2005-04-16 15:20:36 -07002442 get_block_t *get_block)
2443{
Nick Piggin03158cd2007-10-16 01:25:25 -07002444 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002445 const unsigned blkbits = inode->i_blkbits;
2446 const unsigned blocksize = 1 << blkbits;
Nick Piggina4b06722007-10-16 01:24:48 -07002447 struct buffer_head *head, *bh;
Nick Piggin03158cd2007-10-16 01:25:25 -07002448 struct page *page;
2449 pgoff_t index;
2450 unsigned from, to;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002451 unsigned block_in_page;
Nick Piggina4b06722007-10-16 01:24:48 -07002452 unsigned block_start, block_end;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002453 sector_t block_in_file;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002454 int nr_reads = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002455 int ret = 0;
2456 int is_mapped_to_disk = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002457
Nick Piggin03158cd2007-10-16 01:25:25 -07002458 index = pos >> PAGE_CACHE_SHIFT;
2459 from = pos & (PAGE_CACHE_SIZE - 1);
2460 to = from + len;
2461
Nick Piggin54566b22009-01-04 12:00:53 -08002462 page = grab_cache_page_write_begin(mapping, index, flags);
Nick Piggin03158cd2007-10-16 01:25:25 -07002463 if (!page)
2464 return -ENOMEM;
2465 *pagep = page;
2466 *fsdata = NULL;
2467
2468 if (page_has_buffers(page)) {
Namhyung Kim309f77a2010-10-25 15:01:12 +09002469 ret = __block_write_begin(page, pos, len, get_block);
2470 if (unlikely(ret))
2471 goto out_release;
2472 return ret;
Nick Piggin03158cd2007-10-16 01:25:25 -07002473 }
Nick Piggina4b06722007-10-16 01:24:48 -07002474
Linus Torvalds1da177e2005-04-16 15:20:36 -07002475 if (PageMappedToDisk(page))
2476 return 0;
2477
Nick Piggina4b06722007-10-16 01:24:48 -07002478 /*
2479 * Allocate buffers so that we can keep track of state, and potentially
2480 * attach them to the page if an error occurs. In the common case of
2481 * no error, they will just be freed again without ever being attached
2482 * to the page (which is all OK, because we're under the page lock).
2483 *
2484 * Be careful: the buffer linked list is a NULL terminated one, rather
2485 * than the circular one we're used to.
2486 */
2487 head = alloc_page_buffers(page, blocksize, 0);
Nick Piggin03158cd2007-10-16 01:25:25 -07002488 if (!head) {
2489 ret = -ENOMEM;
2490 goto out_release;
2491 }
Nick Piggina4b06722007-10-16 01:24:48 -07002492
Linus Torvalds1da177e2005-04-16 15:20:36 -07002493 block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002494
2495 /*
2496 * We loop across all blocks in the page, whether or not they are
2497 * part of the affected region. This is so we can discover if the
2498 * page is fully mapped-to-disk.
2499 */
Nick Piggina4b06722007-10-16 01:24:48 -07002500 for (block_start = 0, block_in_page = 0, bh = head;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002501 block_start < PAGE_CACHE_SIZE;
Nick Piggina4b06722007-10-16 01:24:48 -07002502 block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002503 int create;
2504
Nick Piggina4b06722007-10-16 01:24:48 -07002505 block_end = block_start + blocksize;
2506 bh->b_state = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002507 create = 1;
2508 if (block_start >= to)
2509 create = 0;
2510 ret = get_block(inode, block_in_file + block_in_page,
Nick Piggina4b06722007-10-16 01:24:48 -07002511 bh, create);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002512 if (ret)
2513 goto failed;
Nick Piggina4b06722007-10-16 01:24:48 -07002514 if (!buffer_mapped(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002515 is_mapped_to_disk = 0;
Nick Piggina4b06722007-10-16 01:24:48 -07002516 if (buffer_new(bh))
2517 unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr);
2518 if (PageUptodate(page)) {
2519 set_buffer_uptodate(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002520 continue;
Nick Piggina4b06722007-10-16 01:24:48 -07002521 }
2522 if (buffer_new(bh) || !buffer_mapped(bh)) {
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002523 zero_user_segments(page, block_start, from,
2524 to, block_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002525 continue;
2526 }
Nick Piggina4b06722007-10-16 01:24:48 -07002527 if (buffer_uptodate(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002528 continue; /* reiserfs does this */
2529 if (block_start < from || block_end > to) {
Nick Piggina4b06722007-10-16 01:24:48 -07002530 lock_buffer(bh);
2531 bh->b_end_io = end_buffer_read_nobh;
2532 submit_bh(READ, bh);
2533 nr_reads++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002534 }
2535 }
2536
2537 if (nr_reads) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002538 /*
2539 * The page is locked, so these buffers are protected from
2540 * any VM or truncate activity. Hence we don't need to care
2541 * for the buffer_head refcounts.
2542 */
Nick Piggina4b06722007-10-16 01:24:48 -07002543 for (bh = head; bh; bh = bh->b_this_page) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002544 wait_on_buffer(bh);
2545 if (!buffer_uptodate(bh))
2546 ret = -EIO;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002547 }
2548 if (ret)
2549 goto failed;
2550 }
2551
2552 if (is_mapped_to_disk)
2553 SetPageMappedToDisk(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002554
Nick Piggin03158cd2007-10-16 01:25:25 -07002555 *fsdata = head; /* to be released by nobh_write_end */
Nick Piggina4b06722007-10-16 01:24:48 -07002556
Linus Torvalds1da177e2005-04-16 15:20:36 -07002557 return 0;
2558
2559failed:
Nick Piggin03158cd2007-10-16 01:25:25 -07002560 BUG_ON(!ret);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002561 /*
Nick Piggina4b06722007-10-16 01:24:48 -07002562 * Error recovery is a bit difficult. We need to zero out blocks that
2563 * were newly allocated, and dirty them to ensure they get written out.
2564 * Buffers need to be attached to the page at this point, otherwise
2565 * the handling of potential IO errors during writeout would be hard
2566 * (could try doing synchronous writeout, but what if that fails too?)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002567 */
Nick Piggin03158cd2007-10-16 01:25:25 -07002568 attach_nobh_buffers(page, head);
2569 page_zero_new_buffers(page, from, to);
Nick Piggina4b06722007-10-16 01:24:48 -07002570
Nick Piggin03158cd2007-10-16 01:25:25 -07002571out_release:
2572 unlock_page(page);
2573 page_cache_release(page);
2574 *pagep = NULL;
Nick Piggina4b06722007-10-16 01:24:48 -07002575
npiggin@suse.de7bb46a62010-05-27 01:05:33 +10002576 return ret;
2577}
Nick Piggin03158cd2007-10-16 01:25:25 -07002578EXPORT_SYMBOL(nobh_write_begin);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002579
Nick Piggin03158cd2007-10-16 01:25:25 -07002580int nobh_write_end(struct file *file, struct address_space *mapping,
2581 loff_t pos, unsigned len, unsigned copied,
2582 struct page *page, void *fsdata)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002583{
2584 struct inode *inode = page->mapping->host;
Nick Pigginefdc3132007-10-21 06:57:41 +02002585 struct buffer_head *head = fsdata;
Nick Piggin03158cd2007-10-16 01:25:25 -07002586 struct buffer_head *bh;
Dmitri Monakhov5b41e742008-03-28 14:15:52 -07002587 BUG_ON(fsdata != NULL && page_has_buffers(page));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002588
Dave Kleikampd4cf1092009-02-06 14:59:26 -06002589 if (unlikely(copied < len) && head)
Dmitri Monakhov5b41e742008-03-28 14:15:52 -07002590 attach_nobh_buffers(page, head);
2591 if (page_has_buffers(page))
2592 return generic_write_end(file, mapping, pos, len,
2593 copied, page, fsdata);
Nick Piggina4b06722007-10-16 01:24:48 -07002594
Nick Piggin22c8ca72007-02-20 13:58:09 -08002595 SetPageUptodate(page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002596 set_page_dirty(page);
Nick Piggin03158cd2007-10-16 01:25:25 -07002597 if (pos+copied > inode->i_size) {
2598 i_size_write(inode, pos+copied);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002599 mark_inode_dirty(inode);
2600 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002601
2602 unlock_page(page);
2603 page_cache_release(page);
2604
Nick Piggin03158cd2007-10-16 01:25:25 -07002605 while (head) {
2606 bh = head;
2607 head = head->b_this_page;
2608 free_buffer_head(bh);
2609 }
2610
2611 return copied;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002612}
Nick Piggin03158cd2007-10-16 01:25:25 -07002613EXPORT_SYMBOL(nobh_write_end);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002614
2615/*
2616 * nobh_writepage() - based on block_full_write_page() except
2617 * that it tries to operate without attaching bufferheads to
2618 * the page.
2619 */
2620int nobh_writepage(struct page *page, get_block_t *get_block,
2621 struct writeback_control *wbc)
2622{
2623 struct inode * const inode = page->mapping->host;
2624 loff_t i_size = i_size_read(inode);
2625 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2626 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002627 int ret;
2628
2629 /* Is the page fully inside i_size? */
2630 if (page->index < end_index)
2631 goto out;
2632
2633 /* Is the page fully outside i_size? (truncate in progress) */
2634 offset = i_size & (PAGE_CACHE_SIZE-1);
2635 if (page->index >= end_index+1 || !offset) {
2636 /*
2637 * The page may have dirty, unmapped buffers. For example,
2638 * they may have been added in ext3_writepage(). Make them
2639 * freeable here, so the page does not leak.
2640 */
2641#if 0
2642 /* Not really sure about this - do we need this ? */
2643 if (page->mapping->a_ops->invalidatepage)
2644 page->mapping->a_ops->invalidatepage(page, offset);
2645#endif
2646 unlock_page(page);
2647 return 0; /* don't care */
2648 }
2649
2650 /*
2651 * The page straddles i_size. It must be zeroed out on each and every
2652 * writepage invocation because it may be mmapped. "A file is mapped
2653 * in multiples of the page size. For a file that is not a multiple of
2654 * the page size, the remaining memory is zeroed when mapped, and
2655 * writes to that region are not written out to the file."
2656 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002657 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002658out:
2659 ret = mpage_writepage(page, get_block, wbc);
2660 if (ret == -EAGAIN)
Chris Mason35c80d52009-04-15 13:22:38 -04002661 ret = __block_write_full_page(inode, page, get_block, wbc,
2662 end_buffer_async_write);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002663 return ret;
2664}
2665EXPORT_SYMBOL(nobh_writepage);
2666
Nick Piggin03158cd2007-10-16 01:25:25 -07002667int nobh_truncate_page(struct address_space *mapping,
2668 loff_t from, get_block_t *get_block)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002669{
Linus Torvalds1da177e2005-04-16 15:20:36 -07002670 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2671 unsigned offset = from & (PAGE_CACHE_SIZE-1);
Nick Piggin03158cd2007-10-16 01:25:25 -07002672 unsigned blocksize;
2673 sector_t iblock;
2674 unsigned length, pos;
2675 struct inode *inode = mapping->host;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002676 struct page *page;
Nick Piggin03158cd2007-10-16 01:25:25 -07002677 struct buffer_head map_bh;
2678 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002679
Nick Piggin03158cd2007-10-16 01:25:25 -07002680 blocksize = 1 << inode->i_blkbits;
2681 length = offset & (blocksize - 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002682
Nick Piggin03158cd2007-10-16 01:25:25 -07002683 /* Block boundary? Nothing to do */
2684 if (!length)
2685 return 0;
2686
2687 length = blocksize - length;
2688 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
2689
Linus Torvalds1da177e2005-04-16 15:20:36 -07002690 page = grab_cache_page(mapping, index);
Nick Piggin03158cd2007-10-16 01:25:25 -07002691 err = -ENOMEM;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002692 if (!page)
2693 goto out;
2694
Nick Piggin03158cd2007-10-16 01:25:25 -07002695 if (page_has_buffers(page)) {
2696has_buffers:
2697 unlock_page(page);
2698 page_cache_release(page);
2699 return block_truncate_page(mapping, from, get_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002700 }
Nick Piggin03158cd2007-10-16 01:25:25 -07002701
2702 /* Find the buffer that contains "offset" */
2703 pos = blocksize;
2704 while (offset >= pos) {
2705 iblock++;
2706 pos += blocksize;
2707 }
2708
Theodore Ts'o460bcf52009-05-12 07:37:56 -04002709 map_bh.b_size = blocksize;
2710 map_bh.b_state = 0;
Nick Piggin03158cd2007-10-16 01:25:25 -07002711 err = get_block(inode, iblock, &map_bh, 0);
2712 if (err)
2713 goto unlock;
2714 /* unmapped? It's a hole - nothing to do */
2715 if (!buffer_mapped(&map_bh))
2716 goto unlock;
2717
2718 /* Ok, it's mapped. Make sure it's up-to-date */
2719 if (!PageUptodate(page)) {
2720 err = mapping->a_ops->readpage(NULL, page);
2721 if (err) {
2722 page_cache_release(page);
2723 goto out;
2724 }
2725 lock_page(page);
2726 if (!PageUptodate(page)) {
2727 err = -EIO;
2728 goto unlock;
2729 }
2730 if (page_has_buffers(page))
2731 goto has_buffers;
2732 }
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002733 zero_user(page, offset, length);
Nick Piggin03158cd2007-10-16 01:25:25 -07002734 set_page_dirty(page);
2735 err = 0;
2736
2737unlock:
Linus Torvalds1da177e2005-04-16 15:20:36 -07002738 unlock_page(page);
2739 page_cache_release(page);
2740out:
Nick Piggin03158cd2007-10-16 01:25:25 -07002741 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002742}
2743EXPORT_SYMBOL(nobh_truncate_page);
2744
2745int block_truncate_page(struct address_space *mapping,
2746 loff_t from, get_block_t *get_block)
2747{
2748 pgoff_t index = from >> PAGE_CACHE_SHIFT;
2749 unsigned offset = from & (PAGE_CACHE_SIZE-1);
2750 unsigned blocksize;
Andrew Morton54b21a72006-01-08 01:03:05 -08002751 sector_t iblock;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002752 unsigned length, pos;
2753 struct inode *inode = mapping->host;
2754 struct page *page;
2755 struct buffer_head *bh;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002756 int err;
2757
2758 blocksize = 1 << inode->i_blkbits;
2759 length = offset & (blocksize - 1);
2760
2761 /* Block boundary? Nothing to do */
2762 if (!length)
2763 return 0;
2764
2765 length = blocksize - length;
Andrew Morton54b21a72006-01-08 01:03:05 -08002766 iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002767
2768 page = grab_cache_page(mapping, index);
2769 err = -ENOMEM;
2770 if (!page)
2771 goto out;
2772
2773 if (!page_has_buffers(page))
2774 create_empty_buffers(page, blocksize, 0);
2775
2776 /* Find the buffer that contains "offset" */
2777 bh = page_buffers(page);
2778 pos = blocksize;
2779 while (offset >= pos) {
2780 bh = bh->b_this_page;
2781 iblock++;
2782 pos += blocksize;
2783 }
2784
2785 err = 0;
2786 if (!buffer_mapped(bh)) {
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002787 WARN_ON(bh->b_size != blocksize);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002788 err = get_block(inode, iblock, bh, 0);
2789 if (err)
2790 goto unlock;
2791 /* unmapped? It's a hole - nothing to do */
2792 if (!buffer_mapped(bh))
2793 goto unlock;
2794 }
2795
2796 /* Ok, it's mapped. Make sure it's up-to-date */
2797 if (PageUptodate(page))
2798 set_buffer_uptodate(bh);
2799
David Chinner33a266d2007-02-12 00:51:41 -08002800 if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002801 err = -EIO;
2802 ll_rw_block(READ, 1, &bh);
2803 wait_on_buffer(bh);
2804 /* Uhhuh. Read error. Complain and punt. */
2805 if (!buffer_uptodate(bh))
2806 goto unlock;
2807 }
2808
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002809 zero_user(page, offset, length);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002810 mark_buffer_dirty(bh);
2811 err = 0;
2812
2813unlock:
2814 unlock_page(page);
2815 page_cache_release(page);
2816out:
2817 return err;
2818}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002819EXPORT_SYMBOL(block_truncate_page);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002820
2821/*
2822 * The generic ->writepage function for buffer-backed address_spaces
Chris Mason35c80d52009-04-15 13:22:38 -04002823 * this form passes in the end_io handler used to finish the IO.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002824 */
Chris Mason35c80d52009-04-15 13:22:38 -04002825int block_write_full_page_endio(struct page *page, get_block_t *get_block,
2826 struct writeback_control *wbc, bh_end_io_t *handler)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002827{
2828 struct inode * const inode = page->mapping->host;
2829 loff_t i_size = i_size_read(inode);
2830 const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT;
2831 unsigned offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002832
2833 /* Is the page fully inside i_size? */
2834 if (page->index < end_index)
Chris Mason35c80d52009-04-15 13:22:38 -04002835 return __block_write_full_page(inode, page, get_block, wbc,
2836 handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002837
2838 /* Is the page fully outside i_size? (truncate in progress) */
2839 offset = i_size & (PAGE_CACHE_SIZE-1);
2840 if (page->index >= end_index+1 || !offset) {
2841 /*
2842 * The page may have dirty, unmapped buffers. For example,
2843 * they may have been added in ext3_writepage(). Make them
2844 * freeable here, so the page does not leak.
2845 */
Jan Karaaaa40592005-10-30 15:00:16 -08002846 do_invalidatepage(page, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002847 unlock_page(page);
2848 return 0; /* don't care */
2849 }
2850
2851 /*
2852 * The page straddles i_size. It must be zeroed out on each and every
Adam Buchbinder2a61aa42009-12-11 16:35:40 -05002853 * writepage invocation because it may be mmapped. "A file is mapped
Linus Torvalds1da177e2005-04-16 15:20:36 -07002854 * in multiples of the page size. For a file that is not a multiple of
2855 * the page size, the remaining memory is zeroed when mapped, and
2856 * writes to that region are not written out to the file."
2857 */
Christoph Lametereebd2aa2008-02-04 22:28:29 -08002858 zero_user_segment(page, offset, PAGE_CACHE_SIZE);
Chris Mason35c80d52009-04-15 13:22:38 -04002859 return __block_write_full_page(inode, page, get_block, wbc, handler);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002860}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002861EXPORT_SYMBOL(block_write_full_page_endio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002862
Chris Mason35c80d52009-04-15 13:22:38 -04002863/*
2864 * The generic ->writepage function for buffer-backed address_spaces
2865 */
2866int block_write_full_page(struct page *page, get_block_t *get_block,
2867 struct writeback_control *wbc)
2868{
2869 return block_write_full_page_endio(page, get_block, wbc,
2870 end_buffer_async_write);
2871}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002872EXPORT_SYMBOL(block_write_full_page);
Chris Mason35c80d52009-04-15 13:22:38 -04002873
Linus Torvalds1da177e2005-04-16 15:20:36 -07002874sector_t generic_block_bmap(struct address_space *mapping, sector_t block,
2875 get_block_t *get_block)
2876{
2877 struct buffer_head tmp;
2878 struct inode *inode = mapping->host;
2879 tmp.b_state = 0;
2880 tmp.b_blocknr = 0;
Badari Pulavartyb0cf2322006-03-26 01:38:00 -08002881 tmp.b_size = 1 << inode->i_blkbits;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002882 get_block(inode, block, &tmp, 0);
2883 return tmp.b_blocknr;
2884}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07002885EXPORT_SYMBOL(generic_block_bmap);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002886
NeilBrown6712ecf2007-09-27 12:47:43 +02002887static void end_bio_bh_io_sync(struct bio *bio, int err)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002888{
2889 struct buffer_head *bh = bio->bi_private;
2890
Linus Torvalds1da177e2005-04-16 15:20:36 -07002891 if (err == -EOPNOTSUPP) {
2892 set_bit(BIO_EOPNOTSUPP, &bio->bi_flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002893 }
2894
Keith Mannthey08bafc02008-11-25 10:24:35 +01002895 if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags)))
2896 set_bit(BH_Quiet, &bh->b_state);
2897
Linus Torvalds1da177e2005-04-16 15:20:36 -07002898 bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags));
2899 bio_put(bio);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002900}
2901
Linus Torvalds57302e02012-12-04 08:25:11 -08002902/*
2903 * This allows us to do IO even on the odd last sectors
2904 * of a device, even if the bh block size is some multiple
2905 * of the physical sector size.
2906 *
2907 * We'll just truncate the bio to the size of the device,
2908 * and clear the end of the buffer head manually.
2909 *
2910 * Truly out-of-range accesses will turn into actual IO
2911 * errors, this only handles the "we need to be able to
2912 * do IO at the final sector" case.
2913 */
2914static void guard_bh_eod(int rw, struct bio *bio, struct buffer_head *bh)
2915{
2916 sector_t maxsector;
2917 unsigned bytes;
2918
2919 maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
2920 if (!maxsector)
2921 return;
2922
2923 /*
2924 * If the *whole* IO is past the end of the device,
2925 * let it through, and the IO layer will turn it into
2926 * an EIO.
2927 */
2928 if (unlikely(bio->bi_sector >= maxsector))
2929 return;
2930
2931 maxsector -= bio->bi_sector;
2932 bytes = bio->bi_size;
2933 if (likely((bytes >> 9) <= maxsector))
2934 return;
2935
2936 /* Uhhuh. We've got a bh that straddles the device size! */
2937 bytes = maxsector << 9;
2938
2939 /* Truncate the bio.. */
2940 bio->bi_size = bytes;
2941 bio->bi_io_vec[0].bv_len = bytes;
2942
2943 /* ..and clear the end of the buffer for reads */
Dan Carpenter27d7c2a2012-12-05 20:01:24 +03002944 if ((rw & RW_MASK) == READ) {
Linus Torvalds57302e02012-12-04 08:25:11 -08002945 void *kaddr = kmap_atomic(bh->b_page);
2946 memset(kaddr + bh_offset(bh) + bytes, 0, bh->b_size - bytes);
2947 kunmap_atomic(kaddr);
Linus Torvalds6d283db2013-01-14 13:17:50 -08002948 flush_dcache_page(bh->b_page);
Linus Torvalds57302e02012-12-04 08:25:11 -08002949 }
2950}
2951
Linus Torvalds1da177e2005-04-16 15:20:36 -07002952int submit_bh(int rw, struct buffer_head * bh)
2953{
2954 struct bio *bio;
2955 int ret = 0;
2956
2957 BUG_ON(!buffer_locked(bh));
2958 BUG_ON(!buffer_mapped(bh));
2959 BUG_ON(!bh->b_end_io);
Aneesh Kumar K.V8fb0e342009-05-12 16:22:37 -04002960 BUG_ON(buffer_delay(bh));
2961 BUG_ON(buffer_unwritten(bh));
Linus Torvalds1da177e2005-04-16 15:20:36 -07002962
Jens Axboe48fd4f92008-08-22 10:00:36 +02002963 /*
Jens Axboe48fd4f92008-08-22 10:00:36 +02002964 * Only clear out a write error when rewriting
Linus Torvalds1da177e2005-04-16 15:20:36 -07002965 */
Jens Axboe48fd4f92008-08-22 10:00:36 +02002966 if (test_set_buffer_req(bh) && (rw & WRITE))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002967 clear_buffer_write_io_error(bh);
2968
2969 /*
2970 * from here on down, it's all bio -- do the initial mapping,
2971 * submit_bio -> generic_make_request may further map this bio around
2972 */
2973 bio = bio_alloc(GFP_NOIO, 1);
2974
2975 bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9);
2976 bio->bi_bdev = bh->b_bdev;
2977 bio->bi_io_vec[0].bv_page = bh->b_page;
2978 bio->bi_io_vec[0].bv_len = bh->b_size;
2979 bio->bi_io_vec[0].bv_offset = bh_offset(bh);
2980
2981 bio->bi_vcnt = 1;
2982 bio->bi_idx = 0;
2983 bio->bi_size = bh->b_size;
2984
2985 bio->bi_end_io = end_bio_bh_io_sync;
2986 bio->bi_private = bh;
2987
Linus Torvalds57302e02012-12-04 08:25:11 -08002988 /* Take care of bh's that straddle the end of the device */
2989 guard_bh_eod(rw, bio, bh);
2990
Linus Torvalds1da177e2005-04-16 15:20:36 -07002991 bio_get(bio);
2992 submit_bio(rw, bio);
2993
2994 if (bio_flagged(bio, BIO_EOPNOTSUPP))
2995 ret = -EOPNOTSUPP;
2996
2997 bio_put(bio);
2998 return ret;
2999}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07003000EXPORT_SYMBOL(submit_bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003001
3002/**
3003 * ll_rw_block: low-level access to block devices (DEPRECATED)
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003004 * @rw: whether to %READ or %WRITE or maybe %READA (readahead)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003005 * @nr: number of &struct buffer_heads in the array
3006 * @bhs: array of pointers to &struct buffer_head
3007 *
Jan Karaa7662232005-09-06 15:19:10 -07003008 * ll_rw_block() takes an array of pointers to &struct buffer_heads, and
3009 * requests an I/O operation on them, either a %READ or a %WRITE. The third
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003010 * %READA option is described in the documentation for generic_make_request()
3011 * which ll_rw_block() calls.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003012 *
3013 * This function drops any buffer that it cannot get a lock on (with the
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003014 * BH_Lock state bit), any buffer that appears to be clean when doing a write
3015 * request, and any buffer that appears to be up-to-date when doing read
3016 * request. Further it marks as clean buffers that are processed for
3017 * writing (the buffer cache won't assume that they are actually clean
3018 * until the buffer gets unlocked).
Linus Torvalds1da177e2005-04-16 15:20:36 -07003019 *
3020 * ll_rw_block sets b_end_io to simple completion handler that marks
3021 * the buffer up-to-date (if approriate), unlocks the buffer and wakes
3022 * any waiters.
3023 *
3024 * All of the buffers must be for the same device, and must also be a
3025 * multiple of the current approved size for the device.
3026 */
3027void ll_rw_block(int rw, int nr, struct buffer_head *bhs[])
3028{
3029 int i;
3030
3031 for (i = 0; i < nr; i++) {
3032 struct buffer_head *bh = bhs[i];
3033
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003034 if (!trylock_buffer(bh))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003035 continue;
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003036 if (rw == WRITE) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003037 if (test_clear_buffer_dirty(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07003038 bh->b_end_io = end_buffer_write_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08003039 get_bh(bh);
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003040 submit_bh(WRITE, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003041 continue;
3042 }
3043 } else {
Linus Torvalds1da177e2005-04-16 15:20:36 -07003044 if (!buffer_uptodate(bh)) {
akpm@osdl.org76c30732005-04-16 15:24:07 -07003045 bh->b_end_io = end_buffer_read_sync;
OGAWA Hirofumie60e5c52006-02-03 03:04:43 -08003046 get_bh(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003047 submit_bh(rw, bh);
3048 continue;
3049 }
3050 }
3051 unlock_buffer(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003052 }
3053}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07003054EXPORT_SYMBOL(ll_rw_block);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003055
Christoph Hellwig9cb569d2010-08-11 17:06:24 +02003056void write_dirty_buffer(struct buffer_head *bh, int rw)
3057{
3058 lock_buffer(bh);
3059 if (!test_clear_buffer_dirty(bh)) {
3060 unlock_buffer(bh);
3061 return;
3062 }
3063 bh->b_end_io = end_buffer_write_sync;
3064 get_bh(bh);
3065 submit_bh(rw, bh);
3066}
3067EXPORT_SYMBOL(write_dirty_buffer);
3068
Linus Torvalds1da177e2005-04-16 15:20:36 -07003069/*
3070 * For a data-integrity writeout, we need to wait upon any in-progress I/O
3071 * and then start new I/O and then wait upon it. The caller must have a ref on
3072 * the buffer_head.
3073 */
Christoph Hellwig87e99512010-08-11 17:05:45 +02003074int __sync_dirty_buffer(struct buffer_head *bh, int rw)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003075{
3076 int ret = 0;
3077
3078 WARN_ON(atomic_read(&bh->b_count) < 1);
3079 lock_buffer(bh);
3080 if (test_clear_buffer_dirty(bh)) {
3081 get_bh(bh);
3082 bh->b_end_io = end_buffer_write_sync;
Christoph Hellwig87e99512010-08-11 17:05:45 +02003083 ret = submit_bh(rw, bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003084 wait_on_buffer(bh);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003085 if (!ret && !buffer_uptodate(bh))
3086 ret = -EIO;
3087 } else {
3088 unlock_buffer(bh);
3089 }
3090 return ret;
3091}
Christoph Hellwig87e99512010-08-11 17:05:45 +02003092EXPORT_SYMBOL(__sync_dirty_buffer);
3093
3094int sync_dirty_buffer(struct buffer_head *bh)
3095{
3096 return __sync_dirty_buffer(bh, WRITE_SYNC);
3097}
H Hartley Sweeten1fe72ea2009-09-22 16:43:51 -07003098EXPORT_SYMBOL(sync_dirty_buffer);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003099
3100/*
3101 * try_to_free_buffers() checks if all the buffers on this particular page
3102 * are unused, and releases them if so.
3103 *
3104 * Exclusion against try_to_free_buffers may be obtained by either
3105 * locking the page or by holding its mapping's private_lock.
3106 *
3107 * If the page is dirty but all the buffers are clean then we need to
3108 * be sure to mark the page clean as well. This is because the page
3109 * may be against a block device, and a later reattachment of buffers
3110 * to a dirty page will set *all* buffers dirty. Which would corrupt
3111 * filesystem data on the same device.
3112 *
3113 * The same applies to regular filesystem pages: if all the buffers are
3114 * clean then we set the page clean and proceed. To do that, we require
3115 * total exclusion from __set_page_dirty_buffers(). That is obtained with
3116 * private_lock.
3117 *
3118 * try_to_free_buffers() is non-blocking.
3119 */
3120static inline int buffer_busy(struct buffer_head *bh)
3121{
3122 return atomic_read(&bh->b_count) |
3123 (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock)));
3124}
3125
3126static int
3127drop_buffers(struct page *page, struct buffer_head **buffers_to_free)
3128{
3129 struct buffer_head *head = page_buffers(page);
3130 struct buffer_head *bh;
3131
3132 bh = head;
3133 do {
akpm@osdl.orgde7d5a32005-05-01 08:58:39 -07003134 if (buffer_write_io_error(bh) && page->mapping)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003135 set_bit(AS_EIO, &page->mapping->flags);
3136 if (buffer_busy(bh))
3137 goto failed;
3138 bh = bh->b_this_page;
3139 } while (bh != head);
3140
3141 do {
3142 struct buffer_head *next = bh->b_this_page;
3143
Jan Kara535ee2f2008-02-08 04:21:59 -08003144 if (bh->b_assoc_map)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003145 __remove_assoc_queue(bh);
3146 bh = next;
3147 } while (bh != head);
3148 *buffers_to_free = head;
3149 __clear_page_buffers(page);
3150 return 1;
3151failed:
3152 return 0;
3153}
3154
3155int try_to_free_buffers(struct page *page)
3156{
3157 struct address_space * const mapping = page->mapping;
3158 struct buffer_head *buffers_to_free = NULL;
3159 int ret = 0;
3160
3161 BUG_ON(!PageLocked(page));
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003162 if (PageWriteback(page))
Linus Torvalds1da177e2005-04-16 15:20:36 -07003163 return 0;
3164
3165 if (mapping == NULL) { /* can this still happen? */
3166 ret = drop_buffers(page, &buffers_to_free);
3167 goto out;
3168 }
3169
3170 spin_lock(&mapping->private_lock);
3171 ret = drop_buffers(page, &buffers_to_free);
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003172
3173 /*
3174 * If the filesystem writes its buffers by hand (eg ext3)
3175 * then we can have clean buffers against a dirty page. We
3176 * clean the page here; otherwise the VM will never notice
3177 * that the filesystem did any IO at all.
3178 *
3179 * Also, during truncate, discard_buffer will have marked all
3180 * the page's buffers clean. We discover that here and clean
3181 * the page also.
Nick Piggin87df7242007-01-30 14:36:27 +11003182 *
3183 * private_lock must be held over this entire operation in order
3184 * to synchronise against __set_page_dirty_buffers and prevent the
3185 * dirty bit from being lost.
Linus Torvaldsecdfc972007-01-26 12:47:06 -08003186 */
3187 if (ret)
3188 cancel_dirty_page(page, PAGE_CACHE_SIZE);
Nick Piggin87df7242007-01-30 14:36:27 +11003189 spin_unlock(&mapping->private_lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003190out:
3191 if (buffers_to_free) {
3192 struct buffer_head *bh = buffers_to_free;
3193
3194 do {
3195 struct buffer_head *next = bh->b_this_page;
3196 free_buffer_head(bh);
3197 bh = next;
3198 } while (bh != buffers_to_free);
3199 }
3200 return ret;
3201}
3202EXPORT_SYMBOL(try_to_free_buffers);
3203
Linus Torvalds1da177e2005-04-16 15:20:36 -07003204/*
3205 * There are no bdflush tunables left. But distributions are
3206 * still running obsolete flush daemons, so we terminate them here.
3207 *
3208 * Use of bdflush() is deprecated and will be removed in a future kernel.
Jens Axboe5b0830c2009-09-23 19:37:09 +02003209 * The `flush-X' kernel threads fully replace bdflush daemons and this call.
Linus Torvalds1da177e2005-04-16 15:20:36 -07003210 */
Heiko Carstensbdc480e2009-01-14 14:14:12 +01003211SYSCALL_DEFINE2(bdflush, int, func, long, data)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003212{
3213 static int msg_count;
3214
3215 if (!capable(CAP_SYS_ADMIN))
3216 return -EPERM;
3217
3218 if (msg_count < 5) {
3219 msg_count++;
3220 printk(KERN_INFO
3221 "warning: process `%s' used the obsolete bdflush"
3222 " system call\n", current->comm);
3223 printk(KERN_INFO "Fix your initscripts?\n");
3224 }
3225
3226 if (func == 1)
3227 do_exit(0);
3228 return 0;
3229}
3230
3231/*
3232 * Buffer-head allocation
3233 */
Shai Fultheima0a9b042012-05-15 12:29:52 +03003234static struct kmem_cache *bh_cachep __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003235
3236/*
3237 * Once the number of bh's in the machine exceeds this level, we start
3238 * stripping them in writeback.
3239 */
Zhang Yanfei43be5942013-02-22 16:35:46 -08003240static unsigned long max_buffer_heads;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003241
3242int buffer_heads_over_limit;
3243
3244struct bh_accounting {
3245 int nr; /* Number of live bh's */
3246 int ratelimit; /* Limit cacheline bouncing */
3247};
3248
3249static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0};
3250
3251static void recalc_bh_state(void)
3252{
3253 int i;
3254 int tot = 0;
3255
Christoph Lameteree1be862010-12-06 11:40:05 -06003256 if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003257 return;
Christoph Lameterc7b92512010-12-06 11:16:28 -06003258 __this_cpu_write(bh_accounting.ratelimit, 0);
Eric Dumazet8a143422006-03-24 03:18:10 -08003259 for_each_online_cpu(i)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003260 tot += per_cpu(bh_accounting, i).nr;
3261 buffer_heads_over_limit = (tot > max_buffer_heads);
3262}
Christoph Lameterc7b92512010-12-06 11:16:28 -06003263
Al Virodd0fc662005-10-07 07:46:04 +01003264struct buffer_head *alloc_buffer_head(gfp_t gfp_flags)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003265{
Richard Kennedy019b4d12010-03-10 15:20:33 -08003266 struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003267 if (ret) {
Christoph Lametera35afb82007-05-16 22:10:57 -07003268 INIT_LIST_HEAD(&ret->b_assoc_buffers);
Christoph Lameterc7b92512010-12-06 11:16:28 -06003269 preempt_disable();
3270 __this_cpu_inc(bh_accounting.nr);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003271 recalc_bh_state();
Christoph Lameterc7b92512010-12-06 11:16:28 -06003272 preempt_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -07003273 }
3274 return ret;
3275}
3276EXPORT_SYMBOL(alloc_buffer_head);
3277
3278void free_buffer_head(struct buffer_head *bh)
3279{
3280 BUG_ON(!list_empty(&bh->b_assoc_buffers));
3281 kmem_cache_free(bh_cachep, bh);
Christoph Lameterc7b92512010-12-06 11:16:28 -06003282 preempt_disable();
3283 __this_cpu_dec(bh_accounting.nr);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003284 recalc_bh_state();
Christoph Lameterc7b92512010-12-06 11:16:28 -06003285 preempt_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -07003286}
3287EXPORT_SYMBOL(free_buffer_head);
3288
Linus Torvalds1da177e2005-04-16 15:20:36 -07003289static void buffer_exit_cpu(int cpu)
3290{
3291 int i;
3292 struct bh_lru *b = &per_cpu(bh_lrus, cpu);
3293
3294 for (i = 0; i < BH_LRU_SIZE; i++) {
3295 brelse(b->bhs[i]);
3296 b->bhs[i] = NULL;
3297 }
Christoph Lameterc7b92512010-12-06 11:16:28 -06003298 this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr);
Eric Dumazet8a143422006-03-24 03:18:10 -08003299 per_cpu(bh_accounting, cpu).nr = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003300}
3301
3302static int buffer_cpu_notify(struct notifier_block *self,
3303 unsigned long action, void *hcpu)
3304{
Rafael J. Wysocki8bb78442007-05-09 02:35:10 -07003305 if (action == CPU_DEAD || action == CPU_DEAD_FROZEN)
Linus Torvalds1da177e2005-04-16 15:20:36 -07003306 buffer_exit_cpu((unsigned long)hcpu);
3307 return NOTIFY_OK;
3308}
Linus Torvalds1da177e2005-04-16 15:20:36 -07003309
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003310/**
Randy Dunlapa6b91912008-03-19 17:01:00 -07003311 * bh_uptodate_or_lock - Test whether the buffer is uptodate
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003312 * @bh: struct buffer_head
3313 *
3314 * Return true if the buffer is up-to-date and false,
3315 * with the buffer locked, if not.
3316 */
3317int bh_uptodate_or_lock(struct buffer_head *bh)
3318{
3319 if (!buffer_uptodate(bh)) {
3320 lock_buffer(bh);
3321 if (!buffer_uptodate(bh))
3322 return 0;
3323 unlock_buffer(bh);
3324 }
3325 return 1;
3326}
3327EXPORT_SYMBOL(bh_uptodate_or_lock);
3328
3329/**
Randy Dunlapa6b91912008-03-19 17:01:00 -07003330 * bh_submit_read - Submit a locked buffer for reading
Aneesh Kumar K.V389d1b02008-01-28 23:58:26 -05003331 * @bh: struct buffer_head
3332 *
3333 * Returns zero on success and -EIO on error.
3334 */
3335int bh_submit_read(struct buffer_head *bh)
3336{
3337 BUG_ON(!buffer_locked(bh));
3338
3339 if (buffer_uptodate(bh)) {
3340 unlock_buffer(bh);
3341 return 0;
3342 }
3343
3344 get_bh(bh);
3345 bh->b_end_io = end_buffer_read_sync;
3346 submit_bh(READ, bh);
3347 wait_on_buffer(bh);
3348 if (buffer_uptodate(bh))
3349 return 0;
3350 return -EIO;
3351}
3352EXPORT_SYMBOL(bh_submit_read);
3353
Linus Torvalds1da177e2005-04-16 15:20:36 -07003354void __init buffer_init(void)
3355{
Zhang Yanfei43be5942013-02-22 16:35:46 -08003356 unsigned long nrpages;
Linus Torvalds1da177e2005-04-16 15:20:36 -07003357
Christoph Lameterb98938c2008-02-04 22:28:36 -08003358 bh_cachep = kmem_cache_create("buffer_head",
3359 sizeof(struct buffer_head), 0,
3360 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
3361 SLAB_MEM_SPREAD),
Richard Kennedy019b4d12010-03-10 15:20:33 -08003362 NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07003363
3364 /*
3365 * Limit the bh occupancy to 10% of ZONE_NORMAL
3366 */
3367 nrpages = (nr_free_buffer_pages() * 10) / 100;
3368 max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head));
3369 hotcpu_notifier(buffer_cpu_notify, 0);
3370}