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1 | /* |
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 | |
21 | #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> |
27 | #include <linux/capability.h> |
28 | #include <linux/blkdev.h> |
29 | #include <linux/file.h> |
30 | #include <linux/quotaops.h> |
31 | #include <linux/highmem.h> |
32 | #include <linux/module.h> |
33 | #include <linux/writeback.h> |
34 | #include <linux/hash.h> |
35 | #include <linux/suspend.h> |
36 | #include <linux/buffer_head.h> |
37 | #include <linux/task_io_accounting_ops.h> |
38 | #include <linux/bio.h> |
39 | #include <linux/notifier.h> |
40 | #include <linux/cpu.h> |
41 | #include <linux/bitops.h> |
42 | #include <linux/mpage.h> |
43 | #include <linux/bit_spinlock.h> |
44 | #include <linux/cleancache.h> |
45 | |
46 | static int fsync_buffers_list(spinlock_t *lock, struct list_head *list); |
47 | |
48 | #define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers) |
49 | |
50 | inline void |
51 | init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private) |
52 | { |
53 | bh->b_end_io = handler; |
54 | bh->b_private = private; |
55 | } |
56 | EXPORT_SYMBOL(init_buffer); |
57 | |
58 | static int sleep_on_buffer(void *word) |
59 | { |
60 | io_schedule(); |
61 | return 0; |
62 | } |
63 | |
64 | void __lock_buffer(struct buffer_head *bh) |
65 | { |
66 | wait_on_bit_lock(&bh->b_state, BH_Lock, sleep_on_buffer, |
67 | TASK_UNINTERRUPTIBLE); |
68 | } |
69 | EXPORT_SYMBOL(__lock_buffer); |
70 | |
71 | void unlock_buffer(struct buffer_head *bh) |
72 | { |
73 | clear_bit_unlock(BH_Lock, &bh->b_state); |
74 | smp_mb__after_clear_bit(); |
75 | wake_up_bit(&bh->b_state, BH_Lock); |
76 | } |
77 | EXPORT_SYMBOL(unlock_buffer); |
78 | |
79 | /* |
80 | * Block until a buffer comes unlocked. This doesn't stop it |
81 | * from becoming locked again - you have to lock it yourself |
82 | * if you want to preserve its state. |
83 | */ |
84 | void __wait_on_buffer(struct buffer_head * bh) |
85 | { |
86 | wait_on_bit(&bh->b_state, BH_Lock, sleep_on_buffer, TASK_UNINTERRUPTIBLE); |
87 | } |
88 | EXPORT_SYMBOL(__wait_on_buffer); |
89 | |
90 | static void |
91 | __clear_page_buffers(struct page *page) |
92 | { |
93 | ClearPagePrivate(page); |
94 | set_page_private(page, 0); |
95 | page_cache_release(page); |
96 | } |
97 | |
98 | |
99 | static int quiet_error(struct buffer_head *bh) |
100 | { |
101 | if (!test_bit(BH_Quiet, &bh->b_state) && printk_ratelimit()) |
102 | return 0; |
103 | return 1; |
104 | } |
105 | |
106 | |
107 | static void buffer_io_error(struct buffer_head *bh) |
108 | { |
109 | char b[BDEVNAME_SIZE]; |
110 | printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n", |
111 | bdevname(bh->b_bdev, b), |
112 | (unsigned long long)bh->b_blocknr); |
113 | } |
114 | |
115 | /* |
116 | * End-of-IO handler helper function which does not touch the bh after |
117 | * unlocking it. |
118 | * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but |
119 | * a race there is benign: unlock_buffer() only use the bh's address for |
120 | * hashing after unlocking the buffer, so it doesn't actually touch the bh |
121 | * itself. |
122 | */ |
123 | static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate) |
124 | { |
125 | if (uptodate) { |
126 | set_buffer_uptodate(bh); |
127 | } else { |
128 | /* This happens, due to failed READA attempts. */ |
129 | clear_buffer_uptodate(bh); |
130 | } |
131 | unlock_buffer(bh); |
132 | } |
133 | |
134 | /* |
135 | * Default synchronous end-of-IO handler.. Just mark it up-to-date and |
136 | * unlock the buffer. This is what ll_rw_block uses too. |
137 | */ |
138 | void end_buffer_read_sync(struct buffer_head *bh, int uptodate) |
139 | { |
140 | __end_buffer_read_notouch(bh, uptodate); |
141 | put_bh(bh); |
142 | } |
143 | EXPORT_SYMBOL(end_buffer_read_sync); |
144 | |
145 | void end_buffer_write_sync(struct buffer_head *bh, int uptodate) |
146 | { |
147 | char b[BDEVNAME_SIZE]; |
148 | |
149 | if (uptodate) { |
150 | set_buffer_uptodate(bh); |
151 | } else { |
152 | if (!quiet_error(bh)) { |
153 | buffer_io_error(bh); |
154 | printk(KERN_WARNING "lost page write due to " |
155 | "I/O error on %s\n", |
156 | bdevname(bh->b_bdev, b)); |
157 | } |
158 | set_buffer_write_io_error(bh); |
159 | clear_buffer_uptodate(bh); |
160 | } |
161 | unlock_buffer(bh); |
162 | put_bh(bh); |
163 | } |
164 | EXPORT_SYMBOL(end_buffer_write_sync); |
165 | |
166 | /* |
167 | * Various filesystems appear to want __find_get_block to be non-blocking. |
168 | * But it's the page lock which protects the buffers. To get around this, |
169 | * we get exclusion from try_to_free_buffers with the blockdev mapping's |
170 | * private_lock. |
171 | * |
172 | * Hack idea: for the blockdev mapping, i_bufferlist_lock contention |
173 | * may be quite high. This code could TryLock the page, and if that |
174 | * succeeds, there is no need to take private_lock. (But if |
175 | * private_lock is contended then so is mapping->tree_lock). |
176 | */ |
177 | static struct buffer_head * |
178 | __find_get_block_slow(struct block_device *bdev, sector_t block) |
179 | { |
180 | struct inode *bd_inode = bdev->bd_inode; |
181 | struct address_space *bd_mapping = bd_inode->i_mapping; |
182 | struct buffer_head *ret = NULL; |
183 | pgoff_t index; |
184 | struct buffer_head *bh; |
185 | struct buffer_head *head; |
186 | struct page *page; |
187 | int all_mapped = 1; |
188 | |
189 | index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits); |
190 | page = find_get_page(bd_mapping, index); |
191 | if (!page) |
192 | goto out; |
193 | |
194 | spin_lock(&bd_mapping->private_lock); |
195 | if (!page_has_buffers(page)) |
196 | goto out_unlock; |
197 | head = page_buffers(page); |
198 | bh = head; |
199 | do { |
200 | if (!buffer_mapped(bh)) |
201 | all_mapped = 0; |
202 | else if (bh->b_blocknr == block) { |
203 | ret = bh; |
204 | get_bh(bh); |
205 | goto out_unlock; |
206 | } |
207 | bh = bh->b_this_page; |
208 | } while (bh != head); |
209 | |
210 | /* we might be here because some of the buffers on this page are |
211 | * not mapped. This is due to various races between |
212 | * file io on the block device and getblk. It gets dealt with |
213 | * elsewhere, don't buffer_error if we had some unmapped buffers |
214 | */ |
215 | if (all_mapped) { |
216 | char b[BDEVNAME_SIZE]; |
217 | |
218 | printk("__find_get_block_slow() failed. " |
219 | "block=%llu, b_blocknr=%llu\n", |
220 | (unsigned long long)block, |
221 | (unsigned long long)bh->b_blocknr); |
222 | printk("b_state=0x%08lx, b_size=%zu\n", |
223 | bh->b_state, bh->b_size); |
224 | printk("device %s blocksize: %d\n", bdevname(bdev, b), |
225 | 1 << bd_inode->i_blkbits); |
226 | } |
227 | out_unlock: |
228 | spin_unlock(&bd_mapping->private_lock); |
229 | page_cache_release(page); |
230 | out: |
231 | return ret; |
232 | } |
233 | |
234 | /* If invalidate_buffers() will trash dirty buffers, it means some kind |
235 | of fs corruption is going on. Trashing dirty data always imply losing |
236 | information that was supposed to be just stored on the physical layer |
237 | by the user. |
238 | |
239 | Thus invalidate_buffers in general usage is not allwowed to trash |
240 | dirty buffers. For example ioctl(FLSBLKBUF) expects dirty data to |
241 | be preserved. These buffers are simply skipped. |
242 | |
243 | We also skip buffers which are still in use. For example this can |
244 | happen if a userspace program is reading the block device. |
245 | |
246 | NOTE: In the case where the user removed a removable-media-disk even if |
247 | there's still dirty data not synced on disk (due a bug in the device driver |
248 | or due an error of the user), by not destroying the dirty buffers we could |
249 | generate corruption also on the next media inserted, thus a parameter is |
250 | necessary to handle this case in the most safe way possible (trying |
251 | to not corrupt also the new disk inserted with the data belonging to |
252 | the old now corrupted disk). Also for the ramdisk the natural thing |
253 | to do in order to release the ramdisk memory is to destroy dirty buffers. |
254 | |
255 | These are two special cases. Normal usage imply the device driver |
256 | to issue a sync on the device (without waiting I/O completion) and |
257 | then an invalidate_buffers call that doesn't trash dirty buffers. |
258 | |
259 | For handling cache coherency with the blkdev pagecache the 'update' case |
260 | is been introduced. It is needed to re-read from disk any pinned |
261 | buffer. NOTE: re-reading from disk is destructive so we can do it only |
262 | when we assume nobody is changing the buffercache under our I/O and when |
263 | we think the disk contains more recent information than the buffercache. |
264 | The update == 1 pass marks the buffers we need to update, the update == 2 |
265 | pass does the actual I/O. */ |
266 | void invalidate_bdev(struct block_device *bdev) |
267 | { |
268 | struct address_space *mapping = bdev->bd_inode->i_mapping; |
269 | |
270 | if (mapping->nrpages == 0) |
271 | return; |
272 | |
273 | invalidate_bh_lrus(); |
274 | lru_add_drain_all(); /* make sure all lru add caches are flushed */ |
275 | invalidate_mapping_pages(mapping, 0, -1); |
276 | /* 99% of the time, we don't need to flush the cleancache on the bdev. |
277 | * But, for the strange corners, lets be cautious |
278 | */ |
279 | cleancache_flush_inode(mapping); |
280 | } |
281 | EXPORT_SYMBOL(invalidate_bdev); |
282 | |
283 | /* |
284 | * Kick the writeback threads then try to free up some ZONE_NORMAL memory. |
285 | */ |
286 | static void free_more_memory(void) |
287 | { |
288 | struct zone *zone; |
289 | int nid; |
290 | |
291 | wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM); |
292 | yield(); |
293 | |
294 | for_each_online_node(nid) { |
295 | (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS), |
296 | gfp_zone(GFP_NOFS), NULL, |
297 | &zone); |
298 | if (zone) |
299 | try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0, |
300 | GFP_NOFS, NULL); |
301 | } |
302 | } |
303 | |
304 | /* |
305 | * I/O completion handler for block_read_full_page() - pages |
306 | * which come unlocked at the end of I/O. |
307 | */ |
308 | static void end_buffer_async_read(struct buffer_head *bh, int uptodate) |
309 | { |
310 | unsigned long flags; |
311 | struct buffer_head *first; |
312 | struct buffer_head *tmp; |
313 | struct page *page; |
314 | int page_uptodate = 1; |
315 | |
316 | BUG_ON(!buffer_async_read(bh)); |
317 | |
318 | page = bh->b_page; |
319 | if (uptodate) { |
320 | set_buffer_uptodate(bh); |
321 | } else { |
322 | clear_buffer_uptodate(bh); |
323 | if (!quiet_error(bh)) |
324 | buffer_io_error(bh); |
325 | SetPageError(page); |
326 | } |
327 | |
328 | /* |
329 | * Be _very_ careful from here on. Bad things can happen if |
330 | * two buffer heads end IO at almost the same time and both |
331 | * decide that the page is now completely done. |
332 | */ |
333 | first = page_buffers(page); |
334 | local_irq_save(flags); |
335 | bit_spin_lock(BH_Uptodate_Lock, &first->b_state); |
336 | clear_buffer_async_read(bh); |
337 | unlock_buffer(bh); |
338 | tmp = bh; |
339 | do { |
340 | if (!buffer_uptodate(tmp)) |
341 | page_uptodate = 0; |
342 | if (buffer_async_read(tmp)) { |
343 | BUG_ON(!buffer_locked(tmp)); |
344 | goto still_busy; |
345 | } |
346 | tmp = tmp->b_this_page; |
347 | } while (tmp != bh); |
348 | bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
349 | local_irq_restore(flags); |
350 | |
351 | /* |
352 | * If none of the buffers had errors and they are all |
353 | * uptodate then we can set the page uptodate. |
354 | */ |
355 | if (page_uptodate && !PageError(page)) |
356 | SetPageUptodate(page); |
357 | unlock_page(page); |
358 | return; |
359 | |
360 | still_busy: |
361 | bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
362 | local_irq_restore(flags); |
363 | return; |
364 | } |
365 | |
366 | /* |
367 | * Completion handler for block_write_full_page() - pages which are unlocked |
368 | * during I/O, and which have PageWriteback cleared upon I/O completion. |
369 | */ |
370 | void end_buffer_async_write(struct buffer_head *bh, int uptodate) |
371 | { |
372 | char b[BDEVNAME_SIZE]; |
373 | unsigned long flags; |
374 | struct buffer_head *first; |
375 | struct buffer_head *tmp; |
376 | struct page *page; |
377 | |
378 | BUG_ON(!buffer_async_write(bh)); |
379 | |
380 | page = bh->b_page; |
381 | if (uptodate) { |
382 | set_buffer_uptodate(bh); |
383 | } else { |
384 | if (!quiet_error(bh)) { |
385 | buffer_io_error(bh); |
386 | printk(KERN_WARNING "lost page write due to " |
387 | "I/O error on %s\n", |
388 | bdevname(bh->b_bdev, b)); |
389 | } |
390 | set_bit(AS_EIO, &page->mapping->flags); |
391 | set_buffer_write_io_error(bh); |
392 | clear_buffer_uptodate(bh); |
393 | SetPageError(page); |
394 | } |
395 | |
396 | first = page_buffers(page); |
397 | local_irq_save(flags); |
398 | bit_spin_lock(BH_Uptodate_Lock, &first->b_state); |
399 | |
400 | clear_buffer_async_write(bh); |
401 | unlock_buffer(bh); |
402 | tmp = bh->b_this_page; |
403 | while (tmp != bh) { |
404 | if (buffer_async_write(tmp)) { |
405 | BUG_ON(!buffer_locked(tmp)); |
406 | goto still_busy; |
407 | } |
408 | tmp = tmp->b_this_page; |
409 | } |
410 | bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
411 | local_irq_restore(flags); |
412 | end_page_writeback(page); |
413 | return; |
414 | |
415 | still_busy: |
416 | bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
417 | local_irq_restore(flags); |
418 | return; |
419 | } |
420 | EXPORT_SYMBOL(end_buffer_async_write); |
421 | |
422 | /* |
423 | * If a page's buffers are under async readin (end_buffer_async_read |
424 | * completion) then there is a possibility that another thread of |
425 | * control could lock one of the buffers after it has completed |
426 | * but while some of the other buffers have not completed. This |
427 | * locked buffer would confuse end_buffer_async_read() into not unlocking |
428 | * the page. So the absence of BH_Async_Read tells end_buffer_async_read() |
429 | * that this buffer is not under async I/O. |
430 | * |
431 | * The page comes unlocked when it has no locked buffer_async buffers |
432 | * left. |
433 | * |
434 | * PageLocked prevents anyone starting new async I/O reads any of |
435 | * the buffers. |
436 | * |
437 | * PageWriteback is used to prevent simultaneous writeout of the same |
438 | * page. |
439 | * |
440 | * PageLocked prevents anyone from starting writeback of a page which is |
441 | * under read I/O (PageWriteback is only ever set against a locked page). |
442 | */ |
443 | static void mark_buffer_async_read(struct buffer_head *bh) |
444 | { |
445 | bh->b_end_io = end_buffer_async_read; |
446 | set_buffer_async_read(bh); |
447 | } |
448 | |
449 | static void mark_buffer_async_write_endio(struct buffer_head *bh, |
450 | bh_end_io_t *handler) |
451 | { |
452 | bh->b_end_io = handler; |
453 | set_buffer_async_write(bh); |
454 | } |
455 | |
456 | void mark_buffer_async_write(struct buffer_head *bh) |
457 | { |
458 | mark_buffer_async_write_endio(bh, end_buffer_async_write); |
459 | } |
460 | EXPORT_SYMBOL(mark_buffer_async_write); |
461 | |
462 | |
463 | /* |
464 | * fs/buffer.c contains helper functions for buffer-backed address space's |
465 | * fsync functions. A common requirement for buffer-based filesystems is |
466 | * that certain data from the backing blockdev needs to be written out for |
467 | * a successful fsync(). For example, ext2 indirect blocks need to be |
468 | * written back and waited upon before fsync() returns. |
469 | * |
470 | * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(), |
471 | * inode_has_buffers() and invalidate_inode_buffers() are provided for the |
472 | * management of a list of dependent buffers at ->i_mapping->private_list. |
473 | * |
474 | * Locking is a little subtle: try_to_free_buffers() will remove buffers |
475 | * from their controlling inode's queue when they are being freed. But |
476 | * try_to_free_buffers() will be operating against the *blockdev* mapping |
477 | * at the time, not against the S_ISREG file which depends on those buffers. |
478 | * So the locking for private_list is via the private_lock in the address_space |
479 | * which backs the buffers. Which is different from the address_space |
480 | * against which the buffers are listed. So for a particular address_space, |
481 | * mapping->private_lock does *not* protect mapping->private_list! In fact, |
482 | * mapping->private_list will always be protected by the backing blockdev's |
483 | * ->private_lock. |
484 | * |
485 | * Which introduces a requirement: all buffers on an address_space's |
486 | * ->private_list must be from the same address_space: the blockdev's. |
487 | * |
488 | * address_spaces which do not place buffers at ->private_list via these |
489 | * utility functions are free to use private_lock and private_list for |
490 | * whatever they want. The only requirement is that list_empty(private_list) |
491 | * be true at clear_inode() time. |
492 | * |
493 | * FIXME: clear_inode should not call invalidate_inode_buffers(). The |
494 | * filesystems should do that. invalidate_inode_buffers() should just go |
495 | * BUG_ON(!list_empty). |
496 | * |
497 | * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should |
498 | * take an address_space, not an inode. And it should be called |
499 | * mark_buffer_dirty_fsync() to clearly define why those buffers are being |
500 | * queued up. |
501 | * |
502 | * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the |
503 | * list if it is already on a list. Because if the buffer is on a list, |
504 | * it *must* already be on the right one. If not, the filesystem is being |
505 | * silly. This will save a ton of locking. But first we have to ensure |
506 | * that buffers are taken *off* the old inode's list when they are freed |
507 | * (presumably in truncate). That requires careful auditing of all |
508 | * filesystems (do it inside bforget()). It could also be done by bringing |
509 | * b_inode back. |
510 | */ |
511 | |
512 | /* |
513 | * The buffer's backing address_space's private_lock must be held |
514 | */ |
515 | static void __remove_assoc_queue(struct buffer_head *bh) |
516 | { |
517 | list_del_init(&bh->b_assoc_buffers); |
518 | WARN_ON(!bh->b_assoc_map); |
519 | if (buffer_write_io_error(bh)) |
520 | set_bit(AS_EIO, &bh->b_assoc_map->flags); |
521 | bh->b_assoc_map = NULL; |
522 | } |
523 | |
524 | int inode_has_buffers(struct inode *inode) |
525 | { |
526 | return !list_empty(&inode->i_data.private_list); |
527 | } |
528 | |
529 | /* |
530 | * osync is designed to support O_SYNC io. It waits synchronously for |
531 | * all already-submitted IO to complete, but does not queue any new |
532 | * writes to the disk. |
533 | * |
534 | * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as |
535 | * you dirty the buffers, and then use osync_inode_buffers to wait for |
536 | * completion. Any other dirty buffers which are not yet queued for |
537 | * write will not be flushed to disk by the osync. |
538 | */ |
539 | static int osync_buffers_list(spinlock_t *lock, struct list_head *list) |
540 | { |
541 | struct buffer_head *bh; |
542 | struct list_head *p; |
543 | int err = 0; |
544 | |
545 | spin_lock(lock); |
546 | repeat: |
547 | list_for_each_prev(p, list) { |
548 | bh = BH_ENTRY(p); |
549 | if (buffer_locked(bh)) { |
550 | get_bh(bh); |
551 | spin_unlock(lock); |
552 | wait_on_buffer(bh); |
553 | if (!buffer_uptodate(bh)) |
554 | err = -EIO; |
555 | brelse(bh); |
556 | spin_lock(lock); |
557 | goto repeat; |
558 | } |
559 | } |
560 | spin_unlock(lock); |
561 | return err; |
562 | } |
563 | |
564 | static void do_thaw_one(struct super_block *sb, void *unused) |
565 | { |
566 | char b[BDEVNAME_SIZE]; |
567 | while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb)) |
568 | printk(KERN_WARNING "Emergency Thaw on %s\n", |
569 | bdevname(sb->s_bdev, b)); |
570 | } |
571 | |
572 | static void do_thaw_all(struct work_struct *work) |
573 | { |
574 | iterate_supers(do_thaw_one, NULL); |
575 | kfree(work); |
576 | printk(KERN_WARNING "Emergency Thaw complete\n"); |
577 | } |
578 | |
579 | /** |
580 | * emergency_thaw_all -- forcibly thaw every frozen filesystem |
581 | * |
582 | * Used for emergency unfreeze of all filesystems via SysRq |
583 | */ |
584 | void emergency_thaw_all(void) |
585 | { |
586 | struct work_struct *work; |
587 | |
588 | work = kmalloc(sizeof(*work), GFP_ATOMIC); |
589 | if (work) { |
590 | INIT_WORK(work, do_thaw_all); |
591 | schedule_work(work); |
592 | } |
593 | } |
594 | |
595 | /** |
596 | * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers |
597 | * @mapping: the mapping which wants those buffers written |
598 | * |
599 | * Starts I/O against the buffers at mapping->private_list, and waits upon |
600 | * that I/O. |
601 | * |
602 | * Basically, this is a convenience function for fsync(). |
603 | * @mapping is a file or directory which needs those buffers to be written for |
604 | * a successful fsync(). |
605 | */ |
606 | int sync_mapping_buffers(struct address_space *mapping) |
607 | { |
608 | struct address_space *buffer_mapping = mapping->assoc_mapping; |
609 | |
610 | if (buffer_mapping == NULL || list_empty(&mapping->private_list)) |
611 | return 0; |
612 | |
613 | return fsync_buffers_list(&buffer_mapping->private_lock, |
614 | &mapping->private_list); |
615 | } |
616 | EXPORT_SYMBOL(sync_mapping_buffers); |
617 | |
618 | /* |
619 | * Called when we've recently written block `bblock', and it is known that |
620 | * `bblock' was for a buffer_boundary() buffer. This means that the block at |
621 | * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's |
622 | * dirty, schedule it for IO. So that indirects merge nicely with their data. |
623 | */ |
624 | void write_boundary_block(struct block_device *bdev, |
625 | sector_t bblock, unsigned blocksize) |
626 | { |
627 | struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize); |
628 | if (bh) { |
629 | if (buffer_dirty(bh)) |
630 | ll_rw_block(WRITE, 1, &bh); |
631 | put_bh(bh); |
632 | } |
633 | } |
634 | |
635 | void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode) |
636 | { |
637 | struct address_space *mapping = inode->i_mapping; |
638 | struct address_space *buffer_mapping = bh->b_page->mapping; |
639 | |
640 | mark_buffer_dirty(bh); |
641 | if (!mapping->assoc_mapping) { |
642 | mapping->assoc_mapping = buffer_mapping; |
643 | } else { |
644 | BUG_ON(mapping->assoc_mapping != buffer_mapping); |
645 | } |
646 | if (!bh->b_assoc_map) { |
647 | spin_lock(&buffer_mapping->private_lock); |
648 | list_move_tail(&bh->b_assoc_buffers, |
649 | &mapping->private_list); |
650 | bh->b_assoc_map = mapping; |
651 | spin_unlock(&buffer_mapping->private_lock); |
652 | } |
653 | } |
654 | EXPORT_SYMBOL(mark_buffer_dirty_inode); |
655 | |
656 | /* |
657 | * Mark the page dirty, and set it dirty in the radix tree, and mark the inode |
658 | * dirty. |
659 | * |
660 | * If warn is true, then emit a warning if the page is not uptodate and has |
661 | * not been truncated. |
662 | */ |
663 | static void __set_page_dirty(struct page *page, |
664 | struct address_space *mapping, int warn) |
665 | { |
666 | spin_lock_irq(&mapping->tree_lock); |
667 | if (page->mapping) { /* Race with truncate? */ |
668 | WARN_ON_ONCE(warn && !PageUptodate(page)); |
669 | account_page_dirtied(page, mapping); |
670 | radix_tree_tag_set(&mapping->page_tree, |
671 | page_index(page), PAGECACHE_TAG_DIRTY); |
672 | } |
673 | spin_unlock_irq(&mapping->tree_lock); |
674 | __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); |
675 | } |
676 | |
677 | /* |
678 | * Add a page to the dirty page list. |
679 | * |
680 | * It is a sad fact of life that this function is called from several places |
681 | * deeply under spinlocking. It may not sleep. |
682 | * |
683 | * If the page has buffers, the uptodate buffers are set dirty, to preserve |
684 | * dirty-state coherency between the page and the buffers. It the page does |
685 | * not have buffers then when they are later attached they will all be set |
686 | * dirty. |
687 | * |
688 | * The buffers are dirtied before the page is dirtied. There's a small race |
689 | * window in which a writepage caller may see the page cleanness but not the |
690 | * buffer dirtiness. That's fine. If this code were to set the page dirty |
691 | * before the buffers, a concurrent writepage caller could clear the page dirty |
692 | * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean |
693 | * page on the dirty page list. |
694 | * |
695 | * We use private_lock to lock against try_to_free_buffers while using the |
696 | * page's buffer list. Also use this to protect against clean buffers being |
697 | * added to the page after it was set dirty. |
698 | * |
699 | * FIXME: may need to call ->reservepage here as well. That's rather up to the |
700 | * address_space though. |
701 | */ |
702 | int __set_page_dirty_buffers(struct page *page) |
703 | { |
704 | int newly_dirty; |
705 | struct address_space *mapping = page_mapping(page); |
706 | |
707 | if (unlikely(!mapping)) |
708 | return !TestSetPageDirty(page); |
709 | |
710 | spin_lock(&mapping->private_lock); |
711 | if (page_has_buffers(page)) { |
712 | struct buffer_head *head = page_buffers(page); |
713 | struct buffer_head *bh = head; |
714 | |
715 | do { |
716 | set_buffer_dirty(bh); |
717 | bh = bh->b_this_page; |
718 | } while (bh != head); |
719 | } |
720 | newly_dirty = !TestSetPageDirty(page); |
721 | spin_unlock(&mapping->private_lock); |
722 | |
723 | if (newly_dirty) |
724 | __set_page_dirty(page, mapping, 1); |
725 | return newly_dirty; |
726 | } |
727 | EXPORT_SYMBOL(__set_page_dirty_buffers); |
728 | |
729 | /* |
730 | * Write out and wait upon a list of buffers. |
731 | * |
732 | * We have conflicting pressures: we want to make sure that all |
733 | * initially dirty buffers get waited on, but that any subsequently |
734 | * dirtied buffers don't. After all, we don't want fsync to last |
735 | * forever if somebody is actively writing to the file. |
736 | * |
737 | * Do this in two main stages: first we copy dirty buffers to a |
738 | * temporary inode list, queueing the writes as we go. Then we clean |
739 | * up, waiting for those writes to complete. |
740 | * |
741 | * During this second stage, any subsequent updates to the file may end |
742 | * up refiling the buffer on the original inode's dirty list again, so |
743 | * there is a chance we will end up with a buffer queued for write but |
744 | * not yet completed on that list. So, as a final cleanup we go through |
745 | * the osync code to catch these locked, dirty buffers without requeuing |
746 | * any newly dirty buffers for write. |
747 | */ |
748 | static int fsync_buffers_list(spinlock_t *lock, struct list_head *list) |
749 | { |
750 | struct buffer_head *bh; |
751 | struct list_head tmp; |
752 | struct address_space *mapping; |
753 | int err = 0, err2; |
754 | struct blk_plug plug; |
755 | |
756 | INIT_LIST_HEAD(&tmp); |
757 | blk_start_plug(&plug); |
758 | |
759 | spin_lock(lock); |
760 | while (!list_empty(list)) { |
761 | bh = BH_ENTRY(list->next); |
762 | mapping = bh->b_assoc_map; |
763 | __remove_assoc_queue(bh); |
764 | /* Avoid race with mark_buffer_dirty_inode() which does |
765 | * a lockless check and we rely on seeing the dirty bit */ |
766 | smp_mb(); |
767 | if (buffer_dirty(bh) || buffer_locked(bh)) { |
768 | list_add(&bh->b_assoc_buffers, &tmp); |
769 | bh->b_assoc_map = mapping; |
770 | if (buffer_dirty(bh)) { |
771 | get_bh(bh); |
772 | spin_unlock(lock); |
773 | /* |
774 | * Ensure any pending I/O completes so that |
775 | * write_dirty_buffer() actually writes the |
776 | * current contents - it is a noop if I/O is |
777 | * still in flight on potentially older |
778 | * contents. |
779 | */ |
780 | write_dirty_buffer(bh, WRITE_SYNC); |
781 | |
782 | /* |
783 | * Kick off IO for the previous mapping. Note |
784 | * that we will not run the very last mapping, |
785 | * wait_on_buffer() will do that for us |
786 | * through sync_buffer(). |
787 | */ |
788 | brelse(bh); |
789 | spin_lock(lock); |
790 | } |
791 | } |
792 | } |
793 | |
794 | spin_unlock(lock); |
795 | blk_finish_plug(&plug); |
796 | spin_lock(lock); |
797 | |
798 | while (!list_empty(&tmp)) { |
799 | bh = BH_ENTRY(tmp.prev); |
800 | get_bh(bh); |
801 | mapping = bh->b_assoc_map; |
802 | __remove_assoc_queue(bh); |
803 | /* Avoid race with mark_buffer_dirty_inode() which does |
804 | * a lockless check and we rely on seeing the dirty bit */ |
805 | smp_mb(); |
806 | if (buffer_dirty(bh)) { |
807 | list_add(&bh->b_assoc_buffers, |
808 | &mapping->private_list); |
809 | bh->b_assoc_map = mapping; |
810 | } |
811 | spin_unlock(lock); |
812 | wait_on_buffer(bh); |
813 | if (!buffer_uptodate(bh)) |
814 | err = -EIO; |
815 | brelse(bh); |
816 | spin_lock(lock); |
817 | } |
818 | |
819 | spin_unlock(lock); |
820 | err2 = osync_buffers_list(lock, list); |
821 | if (err) |
822 | return err; |
823 | else |
824 | return err2; |
825 | } |
826 | |
827 | /* |
828 | * Invalidate any and all dirty buffers on a given inode. We are |
829 | * probably unmounting the fs, but that doesn't mean we have already |
830 | * done a sync(). Just drop the buffers from the inode list. |
831 | * |
832 | * NOTE: we take the inode's blockdev's mapping's private_lock. Which |
833 | * assumes that all the buffers are against the blockdev. Not true |
834 | * for reiserfs. |
835 | */ |
836 | void invalidate_inode_buffers(struct inode *inode) |
837 | { |
838 | if (inode_has_buffers(inode)) { |
839 | struct address_space *mapping = &inode->i_data; |
840 | struct list_head *list = &mapping->private_list; |
841 | struct address_space *buffer_mapping = mapping->assoc_mapping; |
842 | |
843 | spin_lock(&buffer_mapping->private_lock); |
844 | while (!list_empty(list)) |
845 | __remove_assoc_queue(BH_ENTRY(list->next)); |
846 | spin_unlock(&buffer_mapping->private_lock); |
847 | } |
848 | } |
849 | EXPORT_SYMBOL(invalidate_inode_buffers); |
850 | |
851 | /* |
852 | * Remove any clean buffers from the inode's buffer list. This is called |
853 | * when we're trying to free the inode itself. Those buffers can pin it. |
854 | * |
855 | * Returns true if all buffers were removed. |
856 | */ |
857 | int remove_inode_buffers(struct inode *inode) |
858 | { |
859 | int ret = 1; |
860 | |
861 | if (inode_has_buffers(inode)) { |
862 | struct address_space *mapping = &inode->i_data; |
863 | struct list_head *list = &mapping->private_list; |
864 | struct address_space *buffer_mapping = mapping->assoc_mapping; |
865 | |
866 | spin_lock(&buffer_mapping->private_lock); |
867 | while (!list_empty(list)) { |
868 | struct buffer_head *bh = BH_ENTRY(list->next); |
869 | if (buffer_dirty(bh)) { |
870 | ret = 0; |
871 | break; |
872 | } |
873 | __remove_assoc_queue(bh); |
874 | } |
875 | spin_unlock(&buffer_mapping->private_lock); |
876 | } |
877 | return ret; |
878 | } |
879 | |
880 | /* |
881 | * Create the appropriate buffers when given a page for data area and |
882 | * the size of each buffer.. Use the bh->b_this_page linked list to |
883 | * follow the buffers created. Return NULL if unable to create more |
884 | * buffers. |
885 | * |
886 | * The retry flag is used to differentiate async IO (paging, swapping) |
887 | * which may not fail from ordinary buffer allocations. |
888 | */ |
889 | struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, |
890 | int retry) |
891 | { |
892 | struct buffer_head *bh, *head; |
893 | long offset; |
894 | |
895 | try_again: |
896 | head = NULL; |
897 | offset = PAGE_SIZE; |
898 | while ((offset -= size) >= 0) { |
899 | bh = alloc_buffer_head(GFP_NOFS); |
900 | if (!bh) |
901 | goto no_grow; |
902 | |
903 | bh->b_bdev = NULL; |
904 | bh->b_this_page = head; |
905 | bh->b_blocknr = -1; |
906 | head = bh; |
907 | |
908 | bh->b_state = 0; |
909 | atomic_set(&bh->b_count, 0); |
910 | bh->b_size = size; |
911 | |
912 | /* Link the buffer to its page */ |
913 | set_bh_page(bh, page, offset); |
914 | |
915 | init_buffer(bh, NULL, NULL); |
916 | } |
917 | return head; |
918 | /* |
919 | * In case anything failed, we just free everything we got. |
920 | */ |
921 | no_grow: |
922 | if (head) { |
923 | do { |
924 | bh = head; |
925 | head = head->b_this_page; |
926 | free_buffer_head(bh); |
927 | } while (head); |
928 | } |
929 | |
930 | /* |
931 | * Return failure for non-async IO requests. Async IO requests |
932 | * are not allowed to fail, so we have to wait until buffer heads |
933 | * become available. But we don't want tasks sleeping with |
934 | * partially complete buffers, so all were released above. |
935 | */ |
936 | if (!retry) |
937 | return NULL; |
938 | |
939 | /* We're _really_ low on memory. Now we just |
940 | * wait for old buffer heads to become free due to |
941 | * finishing IO. Since this is an async request and |
942 | * the reserve list is empty, we're sure there are |
943 | * async buffer heads in use. |
944 | */ |
945 | free_more_memory(); |
946 | goto try_again; |
947 | } |
948 | EXPORT_SYMBOL_GPL(alloc_page_buffers); |
949 | |
950 | static inline void |
951 | link_dev_buffers(struct page *page, struct buffer_head *head) |
952 | { |
953 | struct buffer_head *bh, *tail; |
954 | |
955 | bh = head; |
956 | do { |
957 | tail = bh; |
958 | bh = bh->b_this_page; |
959 | } while (bh); |
960 | tail->b_this_page = head; |
961 | attach_page_buffers(page, head); |
962 | } |
963 | |
964 | /* |
965 | * Initialise the state of a blockdev page's buffers. |
966 | */ |
967 | static void |
968 | init_page_buffers(struct page *page, struct block_device *bdev, |
969 | sector_t block, int size) |
970 | { |
971 | struct buffer_head *head = page_buffers(page); |
972 | struct buffer_head *bh = head; |
973 | int uptodate = PageUptodate(page); |
974 | |
975 | do { |
976 | if (!buffer_mapped(bh)) { |
977 | init_buffer(bh, NULL, NULL); |
978 | bh->b_bdev = bdev; |
979 | bh->b_blocknr = block; |
980 | if (uptodate) |
981 | set_buffer_uptodate(bh); |
982 | set_buffer_mapped(bh); |
983 | } |
984 | block++; |
985 | bh = bh->b_this_page; |
986 | } while (bh != head); |
987 | } |
988 | |
989 | /* |
990 | * Create the page-cache page that contains the requested block. |
991 | * |
992 | * This is user purely for blockdev mappings. |
993 | */ |
994 | static struct page * |
995 | grow_dev_page(struct block_device *bdev, sector_t block, |
996 | pgoff_t index, int size) |
997 | { |
998 | struct inode *inode = bdev->bd_inode; |
999 | struct page *page; |
1000 | struct buffer_head *bh; |
1001 | |
1002 | page = find_or_create_page(inode->i_mapping, index, |
1003 | (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE); |
1004 | if (!page) |
1005 | return NULL; |
1006 | |
1007 | BUG_ON(!PageLocked(page)); |
1008 | |
1009 | if (page_has_buffers(page)) { |
1010 | bh = page_buffers(page); |
1011 | if (bh->b_size == size) { |
1012 | init_page_buffers(page, bdev, block, size); |
1013 | return page; |
1014 | } |
1015 | if (!try_to_free_buffers(page)) |
1016 | goto failed; |
1017 | } |
1018 | |
1019 | /* |
1020 | * Allocate some buffers for this page |
1021 | */ |
1022 | bh = alloc_page_buffers(page, size, 0); |
1023 | if (!bh) |
1024 | goto failed; |
1025 | |
1026 | /* |
1027 | * Link the page to the buffers and initialise them. Take the |
1028 | * lock to be atomic wrt __find_get_block(), which does not |
1029 | * run under the page lock. |
1030 | */ |
1031 | spin_lock(&inode->i_mapping->private_lock); |
1032 | link_dev_buffers(page, bh); |
1033 | init_page_buffers(page, bdev, block, size); |
1034 | spin_unlock(&inode->i_mapping->private_lock); |
1035 | return page; |
1036 | |
1037 | failed: |
1038 | BUG(); |
1039 | unlock_page(page); |
1040 | page_cache_release(page); |
1041 | return NULL; |
1042 | } |
1043 | |
1044 | /* |
1045 | * Create buffers for the specified block device block's page. If |
1046 | * that page was dirty, the buffers are set dirty also. |
1047 | */ |
1048 | static int |
1049 | grow_buffers(struct block_device *bdev, sector_t block, int size) |
1050 | { |
1051 | struct page *page; |
1052 | pgoff_t index; |
1053 | int sizebits; |
1054 | |
1055 | sizebits = -1; |
1056 | do { |
1057 | sizebits++; |
1058 | } while ((size << sizebits) < PAGE_SIZE); |
1059 | |
1060 | index = block >> sizebits; |
1061 | |
1062 | /* |
1063 | * Check for a block which wants to lie outside our maximum possible |
1064 | * pagecache index. (this comparison is done using sector_t types). |
1065 | */ |
1066 | if (unlikely(index != block >> sizebits)) { |
1067 | char b[BDEVNAME_SIZE]; |
1068 | |
1069 | printk(KERN_ERR "%s: requested out-of-range block %llu for " |
1070 | "device %s\n", |
1071 | __func__, (unsigned long long)block, |
1072 | bdevname(bdev, b)); |
1073 | return -EIO; |
1074 | } |
1075 | block = index << sizebits; |
1076 | /* Create a page with the proper size buffers.. */ |
1077 | page = grow_dev_page(bdev, block, index, size); |
1078 | if (!page) |
1079 | return 0; |
1080 | unlock_page(page); |
1081 | page_cache_release(page); |
1082 | return 1; |
1083 | } |
1084 | |
1085 | static struct buffer_head * |
1086 | __getblk_slow(struct block_device *bdev, sector_t block, int size) |
1087 | { |
1088 | /* Size must be multiple of hard sectorsize */ |
1089 | if (unlikely(size & (bdev_logical_block_size(bdev)-1) || |
1090 | (size < 512 || size > PAGE_SIZE))) { |
1091 | printk(KERN_ERR "getblk(): invalid block size %d requested\n", |
1092 | size); |
1093 | printk(KERN_ERR "logical block size: %d\n", |
1094 | bdev_logical_block_size(bdev)); |
1095 | |
1096 | dump_stack(); |
1097 | return NULL; |
1098 | } |
1099 | |
1100 | for (;;) { |
1101 | struct buffer_head * bh; |
1102 | int ret; |
1103 | |
1104 | bh = __find_get_block(bdev, block, size); |
1105 | if (bh) |
1106 | return bh; |
1107 | |
1108 | ret = grow_buffers(bdev, block, size); |
1109 | if (ret < 0) |
1110 | return NULL; |
1111 | if (ret == 0) |
1112 | free_more_memory(); |
1113 | } |
1114 | } |
1115 | |
1116 | /* |
1117 | * The relationship between dirty buffers and dirty pages: |
1118 | * |
1119 | * Whenever a page has any dirty buffers, the page's dirty bit is set, and |
1120 | * the page is tagged dirty in its radix tree. |
1121 | * |
1122 | * At all times, the dirtiness of the buffers represents the dirtiness of |
1123 | * subsections of the page. If the page has buffers, the page dirty bit is |
1124 | * merely a hint about the true dirty state. |
1125 | * |
1126 | * When a page is set dirty in its entirety, all its buffers are marked dirty |
1127 | * (if the page has buffers). |
1128 | * |
1129 | * When a buffer is marked dirty, its page is dirtied, but the page's other |
1130 | * buffers are not. |
1131 | * |
1132 | * Also. When blockdev buffers are explicitly read with bread(), they |
1133 | * individually become uptodate. But their backing page remains not |
1134 | * uptodate - even if all of its buffers are uptodate. A subsequent |
1135 | * block_read_full_page() against that page will discover all the uptodate |
1136 | * buffers, will set the page uptodate and will perform no I/O. |
1137 | */ |
1138 | |
1139 | /** |
1140 | * mark_buffer_dirty - mark a buffer_head as needing writeout |
1141 | * @bh: the buffer_head to mark dirty |
1142 | * |
1143 | * mark_buffer_dirty() will set the dirty bit against the buffer, then set its |
1144 | * backing page dirty, then tag the page as dirty in its address_space's radix |
1145 | * tree and then attach the address_space's inode to its superblock's dirty |
1146 | * inode list. |
1147 | * |
1148 | * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock, |
1149 | * mapping->tree_lock and mapping->host->i_lock. |
1150 | */ |
1151 | void mark_buffer_dirty(struct buffer_head *bh) |
1152 | { |
1153 | WARN_ON_ONCE(!buffer_uptodate(bh)); |
1154 | |
1155 | /* |
1156 | * Very *carefully* optimize the it-is-already-dirty case. |
1157 | * |
1158 | * Don't let the final "is it dirty" escape to before we |
1159 | * perhaps modified the buffer. |
1160 | */ |
1161 | if (buffer_dirty(bh)) { |
1162 | smp_mb(); |
1163 | if (buffer_dirty(bh)) |
1164 | return; |
1165 | } |
1166 | |
1167 | if (!test_set_buffer_dirty(bh)) { |
1168 | struct page *page = bh->b_page; |
1169 | if (!TestSetPageDirty(page)) { |
1170 | struct address_space *mapping = page_mapping(page); |
1171 | if (mapping) |
1172 | __set_page_dirty(page, mapping, 0); |
1173 | } |
1174 | } |
1175 | } |
1176 | EXPORT_SYMBOL(mark_buffer_dirty); |
1177 | |
1178 | /* |
1179 | * Decrement a buffer_head's reference count. If all buffers against a page |
1180 | * have zero reference count, are clean and unlocked, and if the page is clean |
1181 | * and unlocked then try_to_free_buffers() may strip the buffers from the page |
1182 | * in preparation for freeing it (sometimes, rarely, buffers are removed from |
1183 | * a page but it ends up not being freed, and buffers may later be reattached). |
1184 | */ |
1185 | void __brelse(struct buffer_head * buf) |
1186 | { |
1187 | if (atomic_read(&buf->b_count)) { |
1188 | put_bh(buf); |
1189 | return; |
1190 | } |
1191 | WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n"); |
1192 | } |
1193 | EXPORT_SYMBOL(__brelse); |
1194 | |
1195 | /* |
1196 | * bforget() is like brelse(), except it discards any |
1197 | * potentially dirty data. |
1198 | */ |
1199 | void __bforget(struct buffer_head *bh) |
1200 | { |
1201 | clear_buffer_dirty(bh); |
1202 | if (bh->b_assoc_map) { |
1203 | struct address_space *buffer_mapping = bh->b_page->mapping; |
1204 | |
1205 | spin_lock(&buffer_mapping->private_lock); |
1206 | list_del_init(&bh->b_assoc_buffers); |
1207 | bh->b_assoc_map = NULL; |
1208 | spin_unlock(&buffer_mapping->private_lock); |
1209 | } |
1210 | __brelse(bh); |
1211 | } |
1212 | EXPORT_SYMBOL(__bforget); |
1213 | |
1214 | static struct buffer_head *__bread_slow(struct buffer_head *bh) |
1215 | { |
1216 | lock_buffer(bh); |
1217 | if (buffer_uptodate(bh)) { |
1218 | unlock_buffer(bh); |
1219 | return bh; |
1220 | } else { |
1221 | get_bh(bh); |
1222 | bh->b_end_io = end_buffer_read_sync; |
1223 | submit_bh(READ, bh); |
1224 | wait_on_buffer(bh); |
1225 | if (buffer_uptodate(bh)) |
1226 | return bh; |
1227 | } |
1228 | brelse(bh); |
1229 | return NULL; |
1230 | } |
1231 | |
1232 | /* |
1233 | * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block(). |
1234 | * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their |
1235 | * refcount elevated by one when they're in an LRU. A buffer can only appear |
1236 | * once in a particular CPU's LRU. A single buffer can be present in multiple |
1237 | * CPU's LRUs at the same time. |
1238 | * |
1239 | * This is a transparent caching front-end to sb_bread(), sb_getblk() and |
1240 | * sb_find_get_block(). |
1241 | * |
1242 | * The LRUs themselves only need locking against invalidate_bh_lrus. We use |
1243 | * a local interrupt disable for that. |
1244 | */ |
1245 | |
1246 | #define BH_LRU_SIZE 8 |
1247 | |
1248 | struct bh_lru { |
1249 | struct buffer_head *bhs[BH_LRU_SIZE]; |
1250 | }; |
1251 | |
1252 | static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }}; |
1253 | |
1254 | #ifdef CONFIG_SMP |
1255 | #define bh_lru_lock() local_irq_disable() |
1256 | #define bh_lru_unlock() local_irq_enable() |
1257 | #else |
1258 | #define bh_lru_lock() preempt_disable() |
1259 | #define bh_lru_unlock() preempt_enable() |
1260 | #endif |
1261 | |
1262 | static inline void check_irqs_on(void) |
1263 | { |
1264 | #ifdef irqs_disabled |
1265 | BUG_ON(irqs_disabled()); |
1266 | #endif |
1267 | } |
1268 | |
1269 | /* |
1270 | * The LRU management algorithm is dopey-but-simple. Sorry. |
1271 | */ |
1272 | static void bh_lru_install(struct buffer_head *bh) |
1273 | { |
1274 | struct buffer_head *evictee = NULL; |
1275 | |
1276 | check_irqs_on(); |
1277 | bh_lru_lock(); |
1278 | if (__this_cpu_read(bh_lrus.bhs[0]) != bh) { |
1279 | struct buffer_head *bhs[BH_LRU_SIZE]; |
1280 | int in; |
1281 | int out = 0; |
1282 | |
1283 | get_bh(bh); |
1284 | bhs[out++] = bh; |
1285 | for (in = 0; in < BH_LRU_SIZE; in++) { |
1286 | struct buffer_head *bh2 = |
1287 | __this_cpu_read(bh_lrus.bhs[in]); |
1288 | |
1289 | if (bh2 == bh) { |
1290 | __brelse(bh2); |
1291 | } else { |
1292 | if (out >= BH_LRU_SIZE) { |
1293 | BUG_ON(evictee != NULL); |
1294 | evictee = bh2; |
1295 | } else { |
1296 | bhs[out++] = bh2; |
1297 | } |
1298 | } |
1299 | } |
1300 | while (out < BH_LRU_SIZE) |
1301 | bhs[out++] = NULL; |
1302 | memcpy(__this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs)); |
1303 | } |
1304 | bh_lru_unlock(); |
1305 | |
1306 | if (evictee) |
1307 | __brelse(evictee); |
1308 | } |
1309 | |
1310 | /* |
1311 | * Look up the bh in this cpu's LRU. If it's there, move it to the head. |
1312 | */ |
1313 | static struct buffer_head * |
1314 | lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size) |
1315 | { |
1316 | struct buffer_head *ret = NULL; |
1317 | unsigned int i; |
1318 | |
1319 | check_irqs_on(); |
1320 | bh_lru_lock(); |
1321 | for (i = 0; i < BH_LRU_SIZE; i++) { |
1322 | struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]); |
1323 | |
1324 | if (bh && bh->b_bdev == bdev && |
1325 | bh->b_blocknr == block && bh->b_size == size) { |
1326 | if (i) { |
1327 | while (i) { |
1328 | __this_cpu_write(bh_lrus.bhs[i], |
1329 | __this_cpu_read(bh_lrus.bhs[i - 1])); |
1330 | i--; |
1331 | } |
1332 | __this_cpu_write(bh_lrus.bhs[0], bh); |
1333 | } |
1334 | get_bh(bh); |
1335 | ret = bh; |
1336 | break; |
1337 | } |
1338 | } |
1339 | bh_lru_unlock(); |
1340 | return ret; |
1341 | } |
1342 | |
1343 | /* |
1344 | * Perform a pagecache lookup for the matching buffer. If it's there, refresh |
1345 | * it in the LRU and mark it as accessed. If it is not present then return |
1346 | * NULL |
1347 | */ |
1348 | struct buffer_head * |
1349 | __find_get_block(struct block_device *bdev, sector_t block, unsigned size) |
1350 | { |
1351 | struct buffer_head *bh = lookup_bh_lru(bdev, block, size); |
1352 | |
1353 | if (bh == NULL) { |
1354 | bh = __find_get_block_slow(bdev, block); |
1355 | if (bh) |
1356 | bh_lru_install(bh); |
1357 | } |
1358 | if (bh) |
1359 | touch_buffer(bh); |
1360 | return bh; |
1361 | } |
1362 | EXPORT_SYMBOL(__find_get_block); |
1363 | |
1364 | /* |
1365 | * __getblk will locate (and, if necessary, create) the buffer_head |
1366 | * which corresponds to the passed block_device, block and size. The |
1367 | * returned buffer has its reference count incremented. |
1368 | * |
1369 | * __getblk() cannot fail - it just keeps trying. If you pass it an |
1370 | * illegal block number, __getblk() will happily return a buffer_head |
1371 | * which represents the non-existent block. Very weird. |
1372 | * |
1373 | * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers() |
1374 | * attempt is failing. FIXME, perhaps? |
1375 | */ |
1376 | struct buffer_head * |
1377 | __getblk(struct block_device *bdev, sector_t block, unsigned size) |
1378 | { |
1379 | struct buffer_head *bh = __find_get_block(bdev, block, size); |
1380 | |
1381 | might_sleep(); |
1382 | if (bh == NULL) |
1383 | bh = __getblk_slow(bdev, block, size); |
1384 | return bh; |
1385 | } |
1386 | EXPORT_SYMBOL(__getblk); |
1387 | |
1388 | /* |
1389 | * Do async read-ahead on a buffer.. |
1390 | */ |
1391 | void __breadahead(struct block_device *bdev, sector_t block, unsigned size) |
1392 | { |
1393 | struct buffer_head *bh = __getblk(bdev, block, size); |
1394 | if (likely(bh)) { |
1395 | ll_rw_block(READA, 1, &bh); |
1396 | brelse(bh); |
1397 | } |
1398 | } |
1399 | EXPORT_SYMBOL(__breadahead); |
1400 | |
1401 | /** |
1402 | * __bread() - reads a specified block and returns the bh |
1403 | * @bdev: the block_device to read from |
1404 | * @block: number of block |
1405 | * @size: size (in bytes) to read |
1406 | * |
1407 | * Reads a specified block, and returns buffer head that contains it. |
1408 | * It returns NULL if the block was unreadable. |
1409 | */ |
1410 | struct buffer_head * |
1411 | __bread(struct block_device *bdev, sector_t block, unsigned size) |
1412 | { |
1413 | struct buffer_head *bh = __getblk(bdev, block, size); |
1414 | |
1415 | if (likely(bh) && !buffer_uptodate(bh)) |
1416 | bh = __bread_slow(bh); |
1417 | return bh; |
1418 | } |
1419 | EXPORT_SYMBOL(__bread); |
1420 | |
1421 | /* |
1422 | * invalidate_bh_lrus() is called rarely - but not only at unmount. |
1423 | * This doesn't race because it runs in each cpu either in irq |
1424 | * or with preempt disabled. |
1425 | */ |
1426 | static void invalidate_bh_lru(void *arg) |
1427 | { |
1428 | struct bh_lru *b = &get_cpu_var(bh_lrus); |
1429 | int i; |
1430 | |
1431 | for (i = 0; i < BH_LRU_SIZE; i++) { |
1432 | brelse(b->bhs[i]); |
1433 | b->bhs[i] = NULL; |
1434 | } |
1435 | put_cpu_var(bh_lrus); |
1436 | } |
1437 | |
1438 | void invalidate_bh_lrus(void) |
1439 | { |
1440 | on_each_cpu(invalidate_bh_lru, NULL, 1); |
1441 | } |
1442 | EXPORT_SYMBOL_GPL(invalidate_bh_lrus); |
1443 | |
1444 | void set_bh_page(struct buffer_head *bh, |
1445 | struct page *page, unsigned long offset) |
1446 | { |
1447 | bh->b_page = page; |
1448 | BUG_ON(offset >= PAGE_SIZE); |
1449 | if (PageHighMem(page)) |
1450 | /* |
1451 | * This catches illegal uses and preserves the offset: |
1452 | */ |
1453 | bh->b_data = (char *)(0 + offset); |
1454 | else |
1455 | bh->b_data = page_address(page) + offset; |
1456 | } |
1457 | EXPORT_SYMBOL(set_bh_page); |
1458 | |
1459 | /* |
1460 | * Called when truncating a buffer on a page completely. |
1461 | */ |
1462 | static void discard_buffer(struct buffer_head * bh) |
1463 | { |
1464 | lock_buffer(bh); |
1465 | clear_buffer_dirty(bh); |
1466 | bh->b_bdev = NULL; |
1467 | clear_buffer_mapped(bh); |
1468 | clear_buffer_req(bh); |
1469 | clear_buffer_new(bh); |
1470 | clear_buffer_delay(bh); |
1471 | clear_buffer_unwritten(bh); |
1472 | unlock_buffer(bh); |
1473 | } |
1474 | |
1475 | /** |
1476 | * block_invalidatepage - invalidate part or all of a buffer-backed page |
1477 | * |
1478 | * @page: the page which is affected |
1479 | * @offset: the index of the truncation point |
1480 | * |
1481 | * block_invalidatepage() is called when all or part of the page has become |
1482 | * invalidated by a truncate operation. |
1483 | * |
1484 | * block_invalidatepage() does not have to release all buffers, but it must |
1485 | * ensure that no dirty buffer is left outside @offset and that no I/O |
1486 | * is underway against any of the blocks which are outside the truncation |
1487 | * point. Because the caller is about to free (and possibly reuse) those |
1488 | * blocks on-disk. |
1489 | */ |
1490 | void block_invalidatepage(struct page *page, unsigned long offset) |
1491 | { |
1492 | struct buffer_head *head, *bh, *next; |
1493 | unsigned int curr_off = 0; |
1494 | |
1495 | BUG_ON(!PageLocked(page)); |
1496 | if (!page_has_buffers(page)) |
1497 | goto out; |
1498 | |
1499 | head = page_buffers(page); |
1500 | bh = head; |
1501 | do { |
1502 | unsigned int next_off = curr_off + bh->b_size; |
1503 | next = bh->b_this_page; |
1504 | |
1505 | /* |
1506 | * is this block fully invalidated? |
1507 | */ |
1508 | if (offset <= curr_off) |
1509 | discard_buffer(bh); |
1510 | curr_off = next_off; |
1511 | bh = next; |
1512 | } while (bh != head); |
1513 | |
1514 | /* |
1515 | * We release buffers only if the entire page is being invalidated. |
1516 | * The get_block cached value has been unconditionally invalidated, |
1517 | * so real IO is not possible anymore. |
1518 | */ |
1519 | if (offset == 0) |
1520 | try_to_release_page(page, 0); |
1521 | out: |
1522 | return; |
1523 | } |
1524 | EXPORT_SYMBOL(block_invalidatepage); |
1525 | |
1526 | /* |
1527 | * We attach and possibly dirty the buffers atomically wrt |
1528 | * __set_page_dirty_buffers() via private_lock. try_to_free_buffers |
1529 | * is already excluded via the page lock. |
1530 | */ |
1531 | void create_empty_buffers(struct page *page, |
1532 | unsigned long blocksize, unsigned long b_state) |
1533 | { |
1534 | struct buffer_head *bh, *head, *tail; |
1535 | |
1536 | head = alloc_page_buffers(page, blocksize, 1); |
1537 | bh = head; |
1538 | do { |
1539 | bh->b_state |= b_state; |
1540 | tail = bh; |
1541 | bh = bh->b_this_page; |
1542 | } while (bh); |
1543 | tail->b_this_page = head; |
1544 | |
1545 | spin_lock(&page->mapping->private_lock); |
1546 | if (PageUptodate(page) || PageDirty(page)) { |
1547 | bh = head; |
1548 | do { |
1549 | if (PageDirty(page)) |
1550 | set_buffer_dirty(bh); |
1551 | if (PageUptodate(page)) |
1552 | set_buffer_uptodate(bh); |
1553 | bh = bh->b_this_page; |
1554 | } while (bh != head); |
1555 | } |
1556 | attach_page_buffers(page, head); |
1557 | spin_unlock(&page->mapping->private_lock); |
1558 | } |
1559 | EXPORT_SYMBOL(create_empty_buffers); |
1560 | |
1561 | /* |
1562 | * We are taking a block for data and we don't want any output from any |
1563 | * buffer-cache aliases starting from return from that function and |
1564 | * until the moment when something will explicitly mark the buffer |
1565 | * dirty (hopefully that will not happen until we will free that block ;-) |
1566 | * We don't even need to mark it not-uptodate - nobody can expect |
1567 | * anything from a newly allocated buffer anyway. We used to used |
1568 | * unmap_buffer() for such invalidation, but that was wrong. We definitely |
1569 | * don't want to mark the alias unmapped, for example - it would confuse |
1570 | * anyone who might pick it with bread() afterwards... |
1571 | * |
1572 | * Also.. Note that bforget() doesn't lock the buffer. So there can |
1573 | * be writeout I/O going on against recently-freed buffers. We don't |
1574 | * wait on that I/O in bforget() - it's more efficient to wait on the I/O |
1575 | * only if we really need to. That happens here. |
1576 | */ |
1577 | void unmap_underlying_metadata(struct block_device *bdev, sector_t block) |
1578 | { |
1579 | struct buffer_head *old_bh; |
1580 | |
1581 | might_sleep(); |
1582 | |
1583 | old_bh = __find_get_block_slow(bdev, block); |
1584 | if (old_bh) { |
1585 | clear_buffer_dirty(old_bh); |
1586 | wait_on_buffer(old_bh); |
1587 | clear_buffer_req(old_bh); |
1588 | __brelse(old_bh); |
1589 | } |
1590 | } |
1591 | EXPORT_SYMBOL(unmap_underlying_metadata); |
1592 | |
1593 | /* |
1594 | * NOTE! All mapped/uptodate combinations are valid: |
1595 | * |
1596 | * Mapped Uptodate Meaning |
1597 | * |
1598 | * No No "unknown" - must do get_block() |
1599 | * No Yes "hole" - zero-filled |
1600 | * Yes No "allocated" - allocated on disk, not read in |
1601 | * Yes Yes "valid" - allocated and up-to-date in memory. |
1602 | * |
1603 | * "Dirty" is valid only with the last case (mapped+uptodate). |
1604 | */ |
1605 | |
1606 | /* |
1607 | * While block_write_full_page is writing back the dirty buffers under |
1608 | * the page lock, whoever dirtied the buffers may decide to clean them |
1609 | * again at any time. We handle that by only looking at the buffer |
1610 | * state inside lock_buffer(). |
1611 | * |
1612 | * If block_write_full_page() is called for regular writeback |
1613 | * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a |
1614 | * locked buffer. This only can happen if someone has written the buffer |
1615 | * directly, with submit_bh(). At the address_space level PageWriteback |
1616 | * prevents this contention from occurring. |
1617 | * |
1618 | * If block_write_full_page() is called with wbc->sync_mode == |
1619 | * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this |
1620 | * causes the writes to be flagged as synchronous writes. |
1621 | */ |
1622 | static int __block_write_full_page(struct inode *inode, struct page *page, |
1623 | get_block_t *get_block, struct writeback_control *wbc, |
1624 | bh_end_io_t *handler) |
1625 | { |
1626 | int err; |
1627 | sector_t block; |
1628 | sector_t last_block; |
1629 | struct buffer_head *bh, *head; |
1630 | const unsigned blocksize = 1 << inode->i_blkbits; |
1631 | int nr_underway = 0; |
1632 | int write_op = (wbc->sync_mode == WB_SYNC_ALL ? |
1633 | WRITE_SYNC : WRITE); |
1634 | |
1635 | BUG_ON(!PageLocked(page)); |
1636 | |
1637 | last_block = (i_size_read(inode) - 1) >> inode->i_blkbits; |
1638 | |
1639 | if (!page_has_buffers(page)) { |
1640 | create_empty_buffers(page, blocksize, |
1641 | (1 << BH_Dirty)|(1 << BH_Uptodate)); |
1642 | } |
1643 | |
1644 | /* |
1645 | * Be very careful. We have no exclusion from __set_page_dirty_buffers |
1646 | * here, and the (potentially unmapped) buffers may become dirty at |
1647 | * any time. If a buffer becomes dirty here after we've inspected it |
1648 | * then we just miss that fact, and the page stays dirty. |
1649 | * |
1650 | * Buffers outside i_size may be dirtied by __set_page_dirty_buffers; |
1651 | * handle that here by just cleaning them. |
1652 | */ |
1653 | |
1654 | block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
1655 | head = page_buffers(page); |
1656 | bh = head; |
1657 | |
1658 | /* |
1659 | * Get all the dirty buffers mapped to disk addresses and |
1660 | * handle any aliases from the underlying blockdev's mapping. |
1661 | */ |
1662 | do { |
1663 | if (block > last_block) { |
1664 | /* |
1665 | * mapped buffers outside i_size will occur, because |
1666 | * this page can be outside i_size when there is a |
1667 | * truncate in progress. |
1668 | */ |
1669 | /* |
1670 | * The buffer was zeroed by block_write_full_page() |
1671 | */ |
1672 | clear_buffer_dirty(bh); |
1673 | set_buffer_uptodate(bh); |
1674 | } else if ((!buffer_mapped(bh) || buffer_delay(bh)) && |
1675 | buffer_dirty(bh)) { |
1676 | WARN_ON(bh->b_size != blocksize); |
1677 | err = get_block(inode, block, bh, 1); |
1678 | if (err) |
1679 | goto recover; |
1680 | clear_buffer_delay(bh); |
1681 | if (buffer_new(bh)) { |
1682 | /* blockdev mappings never come here */ |
1683 | clear_buffer_new(bh); |
1684 | unmap_underlying_metadata(bh->b_bdev, |
1685 | bh->b_blocknr); |
1686 | } |
1687 | } |
1688 | bh = bh->b_this_page; |
1689 | block++; |
1690 | } while (bh != head); |
1691 | |
1692 | do { |
1693 | if (!buffer_mapped(bh)) |
1694 | continue; |
1695 | /* |
1696 | * If it's a fully non-blocking write attempt and we cannot |
1697 | * lock the buffer then redirty the page. Note that this can |
1698 | * potentially cause a busy-wait loop from writeback threads |
1699 | * and kswapd activity, but those code paths have their own |
1700 | * higher-level throttling. |
1701 | */ |
1702 | if (wbc->sync_mode != WB_SYNC_NONE) { |
1703 | lock_buffer(bh); |
1704 | } else if (!trylock_buffer(bh)) { |
1705 | redirty_page_for_writepage(wbc, page); |
1706 | continue; |
1707 | } |
1708 | if (test_clear_buffer_dirty(bh)) { |
1709 | mark_buffer_async_write_endio(bh, handler); |
1710 | } else { |
1711 | unlock_buffer(bh); |
1712 | } |
1713 | } while ((bh = bh->b_this_page) != head); |
1714 | |
1715 | /* |
1716 | * The page and its buffers are protected by PageWriteback(), so we can |
1717 | * drop the bh refcounts early. |
1718 | */ |
1719 | BUG_ON(PageWriteback(page)); |
1720 | set_page_writeback(page); |
1721 | |
1722 | do { |
1723 | struct buffer_head *next = bh->b_this_page; |
1724 | if (buffer_async_write(bh)) { |
1725 | submit_bh(write_op, bh); |
1726 | nr_underway++; |
1727 | } |
1728 | bh = next; |
1729 | } while (bh != head); |
1730 | unlock_page(page); |
1731 | |
1732 | err = 0; |
1733 | done: |
1734 | if (nr_underway == 0) { |
1735 | /* |
1736 | * The page was marked dirty, but the buffers were |
1737 | * clean. Someone wrote them back by hand with |
1738 | * ll_rw_block/submit_bh. A rare case. |
1739 | */ |
1740 | end_page_writeback(page); |
1741 | |
1742 | /* |
1743 | * The page and buffer_heads can be released at any time from |
1744 | * here on. |
1745 | */ |
1746 | } |
1747 | return err; |
1748 | |
1749 | recover: |
1750 | /* |
1751 | * ENOSPC, or some other error. We may already have added some |
1752 | * blocks to the file, so we need to write these out to avoid |
1753 | * exposing stale data. |
1754 | * The page is currently locked and not marked for writeback |
1755 | */ |
1756 | bh = head; |
1757 | /* Recovery: lock and submit the mapped buffers */ |
1758 | do { |
1759 | if (buffer_mapped(bh) && buffer_dirty(bh) && |
1760 | !buffer_delay(bh)) { |
1761 | lock_buffer(bh); |
1762 | mark_buffer_async_write_endio(bh, handler); |
1763 | } else { |
1764 | /* |
1765 | * The buffer may have been set dirty during |
1766 | * attachment to a dirty page. |
1767 | */ |
1768 | clear_buffer_dirty(bh); |
1769 | } |
1770 | } while ((bh = bh->b_this_page) != head); |
1771 | SetPageError(page); |
1772 | BUG_ON(PageWriteback(page)); |
1773 | mapping_set_error(page->mapping, err); |
1774 | set_page_writeback(page); |
1775 | do { |
1776 | struct buffer_head *next = bh->b_this_page; |
1777 | if (buffer_async_write(bh)) { |
1778 | clear_buffer_dirty(bh); |
1779 | submit_bh(write_op, bh); |
1780 | nr_underway++; |
1781 | } |
1782 | bh = next; |
1783 | } while (bh != head); |
1784 | unlock_page(page); |
1785 | goto done; |
1786 | } |
1787 | |
1788 | /* |
1789 | * If a page has any new buffers, zero them out here, and mark them uptodate |
1790 | * and dirty so they'll be written out (in order to prevent uninitialised |
1791 | * block data from leaking). And clear the new bit. |
1792 | */ |
1793 | void page_zero_new_buffers(struct page *page, unsigned from, unsigned to) |
1794 | { |
1795 | unsigned int block_start, block_end; |
1796 | struct buffer_head *head, *bh; |
1797 | |
1798 | BUG_ON(!PageLocked(page)); |
1799 | if (!page_has_buffers(page)) |
1800 | return; |
1801 | |
1802 | bh = head = page_buffers(page); |
1803 | block_start = 0; |
1804 | do { |
1805 | block_end = block_start + bh->b_size; |
1806 | |
1807 | if (buffer_new(bh)) { |
1808 | if (block_end > from && block_start < to) { |
1809 | if (!PageUptodate(page)) { |
1810 | unsigned start, size; |
1811 | |
1812 | start = max(from, block_start); |
1813 | size = min(to, block_end) - start; |
1814 | |
1815 | zero_user(page, start, size); |
1816 | set_buffer_uptodate(bh); |
1817 | } |
1818 | |
1819 | clear_buffer_new(bh); |
1820 | mark_buffer_dirty(bh); |
1821 | } |
1822 | } |
1823 | |
1824 | block_start = block_end; |
1825 | bh = bh->b_this_page; |
1826 | } while (bh != head); |
1827 | } |
1828 | EXPORT_SYMBOL(page_zero_new_buffers); |
1829 | |
1830 | int __block_write_begin(struct page *page, loff_t pos, unsigned len, |
1831 | get_block_t *get_block) |
1832 | { |
1833 | unsigned from = pos & (PAGE_CACHE_SIZE - 1); |
1834 | unsigned to = from + len; |
1835 | struct inode *inode = page->mapping->host; |
1836 | unsigned block_start, block_end; |
1837 | sector_t block; |
1838 | int err = 0; |
1839 | unsigned blocksize, bbits; |
1840 | struct buffer_head *bh, *head, *wait[2], **wait_bh=wait; |
1841 | |
1842 | BUG_ON(!PageLocked(page)); |
1843 | BUG_ON(from > PAGE_CACHE_SIZE); |
1844 | BUG_ON(to > PAGE_CACHE_SIZE); |
1845 | BUG_ON(from > to); |
1846 | |
1847 | blocksize = 1 << inode->i_blkbits; |
1848 | if (!page_has_buffers(page)) |
1849 | create_empty_buffers(page, blocksize, 0); |
1850 | head = page_buffers(page); |
1851 | |
1852 | bbits = inode->i_blkbits; |
1853 | block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); |
1854 | |
1855 | for(bh = head, block_start = 0; bh != head || !block_start; |
1856 | block++, block_start=block_end, bh = bh->b_this_page) { |
1857 | block_end = block_start + blocksize; |
1858 | if (block_end <= from || block_start >= to) { |
1859 | if (PageUptodate(page)) { |
1860 | if (!buffer_uptodate(bh)) |
1861 | set_buffer_uptodate(bh); |
1862 | } |
1863 | continue; |
1864 | } |
1865 | if (buffer_new(bh)) |
1866 | clear_buffer_new(bh); |
1867 | if (!buffer_mapped(bh)) { |
1868 | WARN_ON(bh->b_size != blocksize); |
1869 | err = get_block(inode, block, bh, 1); |
1870 | if (err) |
1871 | break; |
1872 | if (buffer_new(bh)) { |
1873 | unmap_underlying_metadata(bh->b_bdev, |
1874 | bh->b_blocknr); |
1875 | if (PageUptodate(page)) { |
1876 | clear_buffer_new(bh); |
1877 | set_buffer_uptodate(bh); |
1878 | mark_buffer_dirty(bh); |
1879 | continue; |
1880 | } |
1881 | if (block_end > to || block_start < from) |
1882 | zero_user_segments(page, |
1883 | to, block_end, |
1884 | block_start, from); |
1885 | continue; |
1886 | } |
1887 | } |
1888 | if (PageUptodate(page)) { |
1889 | if (!buffer_uptodate(bh)) |
1890 | set_buffer_uptodate(bh); |
1891 | continue; |
1892 | } |
1893 | if (!buffer_uptodate(bh) && !buffer_delay(bh) && |
1894 | !buffer_unwritten(bh) && |
1895 | (block_start < from || block_end > to)) { |
1896 | ll_rw_block(READ, 1, &bh); |
1897 | *wait_bh++=bh; |
1898 | } |
1899 | } |
1900 | /* |
1901 | * If we issued read requests - let them complete. |
1902 | */ |
1903 | while(wait_bh > wait) { |
1904 | wait_on_buffer(*--wait_bh); |
1905 | if (!buffer_uptodate(*wait_bh)) |
1906 | err = -EIO; |
1907 | } |
1908 | if (unlikely(err)) |
1909 | page_zero_new_buffers(page, from, to); |
1910 | return err; |
1911 | } |
1912 | EXPORT_SYMBOL(__block_write_begin); |
1913 | |
1914 | static int __block_commit_write(struct inode *inode, struct page *page, |
1915 | unsigned from, unsigned to) |
1916 | { |
1917 | unsigned block_start, block_end; |
1918 | int partial = 0; |
1919 | unsigned blocksize; |
1920 | struct buffer_head *bh, *head; |
1921 | |
1922 | blocksize = 1 << inode->i_blkbits; |
1923 | |
1924 | for(bh = head = page_buffers(page), block_start = 0; |
1925 | bh != head || !block_start; |
1926 | block_start=block_end, bh = bh->b_this_page) { |
1927 | block_end = block_start + blocksize; |
1928 | if (block_end <= from || block_start >= to) { |
1929 | if (!buffer_uptodate(bh)) |
1930 | partial = 1; |
1931 | } else { |
1932 | set_buffer_uptodate(bh); |
1933 | mark_buffer_dirty(bh); |
1934 | } |
1935 | clear_buffer_new(bh); |
1936 | } |
1937 | |
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 | /* |
1950 | * block_write_begin takes care of the basic task of block allocation and |
1951 | * bringing partial write blocks uptodate first. |
1952 | * |
1953 | * The filesystem needs to handle block truncation upon failure. |
1954 | */ |
1955 | int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, |
1956 | unsigned flags, struct page **pagep, get_block_t *get_block) |
1957 | { |
1958 | pgoff_t index = pos >> PAGE_CACHE_SHIFT; |
1959 | struct page *page; |
1960 | int status; |
1961 | |
1962 | page = grab_cache_page_write_begin(mapping, index, flags); |
1963 | if (!page) |
1964 | return -ENOMEM; |
1965 | |
1966 | status = __block_write_begin(page, pos, len, get_block); |
1967 | if (unlikely(status)) { |
1968 | unlock_page(page); |
1969 | page_cache_release(page); |
1970 | page = NULL; |
1971 | } |
1972 | |
1973 | *pagep = page; |
1974 | return status; |
1975 | } |
1976 | EXPORT_SYMBOL(block_write_begin); |
1977 | |
1978 | int 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 | } |
2012 | EXPORT_SYMBOL(block_write_end); |
2013 | |
2014 | int 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; |
2019 | int i_size_changed = 0; |
2020 | |
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); |
2032 | i_size_changed = 1; |
2033 | } |
2034 | |
2035 | unlock_page(page); |
2036 | page_cache_release(page); |
2037 | |
2038 | /* |
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 | |
2047 | return copied; |
2048 | } |
2049 | EXPORT_SYMBOL(generic_write_end); |
2050 | |
2051 | /* |
2052 | * 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 | */ |
2058 | int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc, |
2059 | unsigned long from) |
2060 | { |
2061 | struct inode *inode = page->mapping->host; |
2062 | unsigned block_start, block_end, blocksize; |
2063 | unsigned to; |
2064 | struct buffer_head *bh, *head; |
2065 | int ret = 1; |
2066 | |
2067 | if (!page_has_buffers(page)) |
2068 | return 0; |
2069 | |
2070 | blocksize = 1 << inode->i_blkbits; |
2071 | 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 | |
2076 | head = page_buffers(page); |
2077 | bh = head; |
2078 | block_start = 0; |
2079 | do { |
2080 | block_end = block_start + blocksize; |
2081 | if (block_end > from && block_start < to) { |
2082 | if (!buffer_uptodate(bh)) { |
2083 | ret = 0; |
2084 | break; |
2085 | } |
2086 | if (block_end >= to) |
2087 | break; |
2088 | } |
2089 | block_start = block_end; |
2090 | bh = bh->b_this_page; |
2091 | } while (bh != head); |
2092 | |
2093 | return ret; |
2094 | } |
2095 | EXPORT_SYMBOL(block_is_partially_uptodate); |
2096 | |
2097 | /* |
2098 | * Generic "read page" function for block devices that have the normal |
2099 | * get_block functionality. This is most of the block device filesystems. |
2100 | * Reads the page asynchronously --- the unlock_buffer() and |
2101 | * set/clear_buffer_uptodate() functions propagate buffer state into the |
2102 | * page struct once IO has completed. |
2103 | */ |
2104 | int block_read_full_page(struct page *page, get_block_t *get_block) |
2105 | { |
2106 | struct inode *inode = page->mapping->host; |
2107 | sector_t iblock, lblock; |
2108 | struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE]; |
2109 | unsigned int blocksize; |
2110 | int nr, i; |
2111 | int fully_mapped = 1; |
2112 | |
2113 | BUG_ON(!PageLocked(page)); |
2114 | blocksize = 1 << inode->i_blkbits; |
2115 | if (!page_has_buffers(page)) |
2116 | create_empty_buffers(page, blocksize, 0); |
2117 | head = page_buffers(page); |
2118 | |
2119 | iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
2120 | lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits; |
2121 | bh = head; |
2122 | nr = 0; |
2123 | i = 0; |
2124 | |
2125 | do { |
2126 | if (buffer_uptodate(bh)) |
2127 | continue; |
2128 | |
2129 | if (!buffer_mapped(bh)) { |
2130 | int err = 0; |
2131 | |
2132 | fully_mapped = 0; |
2133 | if (iblock < lblock) { |
2134 | WARN_ON(bh->b_size != blocksize); |
2135 | err = get_block(inode, iblock, bh, 0); |
2136 | if (err) |
2137 | SetPageError(page); |
2138 | } |
2139 | if (!buffer_mapped(bh)) { |
2140 | zero_user(page, i * blocksize, blocksize); |
2141 | if (!err) |
2142 | set_buffer_uptodate(bh); |
2143 | continue; |
2144 | } |
2145 | /* |
2146 | * get_block() might have updated the buffer |
2147 | * synchronously |
2148 | */ |
2149 | if (buffer_uptodate(bh)) |
2150 | continue; |
2151 | } |
2152 | arr[nr++] = bh; |
2153 | } while (i++, iblock++, (bh = bh->b_this_page) != head); |
2154 | |
2155 | if (fully_mapped) |
2156 | SetPageMappedToDisk(page); |
2157 | |
2158 | if (!nr) { |
2159 | /* |
2160 | * All buffers are uptodate - we can set the page uptodate |
2161 | * as well. But not if get_block() returned an error. |
2162 | */ |
2163 | if (!PageError(page)) |
2164 | SetPageUptodate(page); |
2165 | unlock_page(page); |
2166 | return 0; |
2167 | } |
2168 | |
2169 | /* Stage two: lock the buffers */ |
2170 | for (i = 0; i < nr; i++) { |
2171 | bh = arr[i]; |
2172 | lock_buffer(bh); |
2173 | mark_buffer_async_read(bh); |
2174 | } |
2175 | |
2176 | /* |
2177 | * Stage 3: start the IO. Check for uptodateness |
2178 | * inside the buffer lock in case another process reading |
2179 | * the underlying blockdev brought it uptodate (the sct fix). |
2180 | */ |
2181 | for (i = 0; i < nr; i++) { |
2182 | bh = arr[i]; |
2183 | if (buffer_uptodate(bh)) |
2184 | end_buffer_async_read(bh, 1); |
2185 | else |
2186 | submit_bh(READ, bh); |
2187 | } |
2188 | return 0; |
2189 | } |
2190 | EXPORT_SYMBOL(block_read_full_page); |
2191 | |
2192 | /* utility function for filesystems that need to do work on expanding |
2193 | * truncates. Uses filesystem pagecache writes to allow the filesystem to |
2194 | * deal with the hole. |
2195 | */ |
2196 | int generic_cont_expand_simple(struct inode *inode, loff_t size) |
2197 | { |
2198 | struct address_space *mapping = inode->i_mapping; |
2199 | struct page *page; |
2200 | void *fsdata; |
2201 | int err; |
2202 | |
2203 | err = inode_newsize_ok(inode, size); |
2204 | if (err) |
2205 | goto out; |
2206 | |
2207 | err = pagecache_write_begin(NULL, mapping, size, 0, |
2208 | AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND, |
2209 | &page, &fsdata); |
2210 | if (err) |
2211 | goto out; |
2212 | |
2213 | err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata); |
2214 | BUG_ON(err > 0); |
2215 | |
2216 | out: |
2217 | return err; |
2218 | } |
2219 | EXPORT_SYMBOL(generic_cont_expand_simple); |
2220 | |
2221 | static int cont_expand_zero(struct file *file, struct address_space *mapping, |
2222 | loff_t pos, loff_t *bytes) |
2223 | { |
2224 | struct inode *inode = mapping->host; |
2225 | unsigned blocksize = 1 << inode->i_blkbits; |
2226 | struct page *page; |
2227 | void *fsdata; |
2228 | pgoff_t index, curidx; |
2229 | loff_t curpos; |
2230 | unsigned zerofrom, offset, len; |
2231 | int err = 0; |
2232 | |
2233 | index = pos >> PAGE_CACHE_SHIFT; |
2234 | offset = pos & ~PAGE_CACHE_MASK; |
2235 | |
2236 | while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) { |
2237 | zerofrom = curpos & ~PAGE_CACHE_MASK; |
2238 | if (zerofrom & (blocksize-1)) { |
2239 | *bytes |= (blocksize-1); |
2240 | (*bytes)++; |
2241 | } |
2242 | len = PAGE_CACHE_SIZE - zerofrom; |
2243 | |
2244 | err = pagecache_write_begin(file, mapping, curpos, len, |
2245 | AOP_FLAG_UNINTERRUPTIBLE, |
2246 | &page, &fsdata); |
2247 | if (err) |
2248 | goto out; |
2249 | zero_user(page, zerofrom, len); |
2250 | err = pagecache_write_end(file, mapping, curpos, len, len, |
2251 | page, fsdata); |
2252 | if (err < 0) |
2253 | goto out; |
2254 | BUG_ON(err != len); |
2255 | err = 0; |
2256 | |
2257 | balance_dirty_pages_ratelimited(mapping); |
2258 | } |
2259 | |
2260 | /* page covers the boundary, find the boundary offset */ |
2261 | if (index == curidx) { |
2262 | zerofrom = curpos & ~PAGE_CACHE_MASK; |
2263 | /* if we will expand the thing last block will be filled */ |
2264 | if (offset <= zerofrom) { |
2265 | goto out; |
2266 | } |
2267 | if (zerofrom & (blocksize-1)) { |
2268 | *bytes |= (blocksize-1); |
2269 | (*bytes)++; |
2270 | } |
2271 | len = offset - zerofrom; |
2272 | |
2273 | err = pagecache_write_begin(file, mapping, curpos, len, |
2274 | AOP_FLAG_UNINTERRUPTIBLE, |
2275 | &page, &fsdata); |
2276 | if (err) |
2277 | goto out; |
2278 | zero_user(page, zerofrom, len); |
2279 | err = pagecache_write_end(file, mapping, curpos, len, len, |
2280 | page, fsdata); |
2281 | if (err < 0) |
2282 | goto out; |
2283 | BUG_ON(err != len); |
2284 | err = 0; |
2285 | } |
2286 | out: |
2287 | return err; |
2288 | } |
2289 | |
2290 | /* |
2291 | * For moronic filesystems that do not allow holes in file. |
2292 | * We may have to extend the file. |
2293 | */ |
2294 | int cont_write_begin(struct file *file, struct address_space *mapping, |
2295 | loff_t pos, unsigned len, unsigned flags, |
2296 | struct page **pagep, void **fsdata, |
2297 | get_block_t *get_block, loff_t *bytes) |
2298 | { |
2299 | struct inode *inode = mapping->host; |
2300 | unsigned blocksize = 1 << inode->i_blkbits; |
2301 | unsigned zerofrom; |
2302 | int err; |
2303 | |
2304 | err = cont_expand_zero(file, mapping, pos, bytes); |
2305 | if (err) |
2306 | return err; |
2307 | |
2308 | zerofrom = *bytes & ~PAGE_CACHE_MASK; |
2309 | if (pos+len > *bytes && zerofrom & (blocksize-1)) { |
2310 | *bytes |= (blocksize-1); |
2311 | (*bytes)++; |
2312 | } |
2313 | |
2314 | return block_write_begin(mapping, pos, len, flags, pagep, get_block); |
2315 | } |
2316 | EXPORT_SYMBOL(cont_write_begin); |
2317 | |
2318 | int block_commit_write(struct page *page, unsigned from, unsigned to) |
2319 | { |
2320 | struct inode *inode = page->mapping->host; |
2321 | __block_commit_write(inode,page,from,to); |
2322 | return 0; |
2323 | } |
2324 | EXPORT_SYMBOL(block_commit_write); |
2325 | |
2326 | /* |
2327 | * block_page_mkwrite() is not allowed to change the file size as it gets |
2328 | * called from a page fault handler when a page is first dirtied. Hence we must |
2329 | * be careful to check for EOF conditions here. We set the page up correctly |
2330 | * for a written page which means we get ENOSPC checking when writing into |
2331 | * holes and correct delalloc and unwritten extent mapping on filesystems that |
2332 | * support these features. |
2333 | * |
2334 | * We are not allowed to take the i_mutex here so we have to play games to |
2335 | * protect against truncate races as the page could now be beyond EOF. Because |
2336 | * truncate writes the inode size before removing pages, once we have the |
2337 | * page lock we can determine safely if the page is beyond EOF. If it is not |
2338 | * beyond EOF, then the page is guaranteed safe against truncation until we |
2339 | * unlock the page. |
2340 | * |
2341 | * Direct callers of this function should call vfs_check_frozen() so that page |
2342 | * fault does not busyloop until the fs is thawed. |
2343 | */ |
2344 | int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, |
2345 | get_block_t get_block) |
2346 | { |
2347 | struct page *page = vmf->page; |
2348 | struct inode *inode = vma->vm_file->f_path.dentry->d_inode; |
2349 | unsigned long end; |
2350 | loff_t size; |
2351 | int ret; |
2352 | |
2353 | lock_page(page); |
2354 | size = i_size_read(inode); |
2355 | if ((page->mapping != inode->i_mapping) || |
2356 | (page_offset(page) > size)) { |
2357 | /* We overload EFAULT to mean page got truncated */ |
2358 | ret = -EFAULT; |
2359 | goto out_unlock; |
2360 | } |
2361 | |
2362 | /* page is wholly or partially inside EOF */ |
2363 | if (((page->index + 1) << PAGE_CACHE_SHIFT) > size) |
2364 | end = size & ~PAGE_CACHE_MASK; |
2365 | else |
2366 | end = PAGE_CACHE_SIZE; |
2367 | |
2368 | ret = __block_write_begin(page, 0, end, get_block); |
2369 | if (!ret) |
2370 | ret = block_commit_write(page, 0, end); |
2371 | |
2372 | if (unlikely(ret < 0)) |
2373 | goto out_unlock; |
2374 | /* |
2375 | * Freezing in progress? We check after the page is marked dirty and |
2376 | * with page lock held so if the test here fails, we are sure freezing |
2377 | * code will wait during syncing until the page fault is done - at that |
2378 | * point page will be dirty and unlocked so freezing code will write it |
2379 | * and writeprotect it again. |
2380 | */ |
2381 | set_page_dirty(page); |
2382 | if (inode->i_sb->s_frozen != SB_UNFROZEN) { |
2383 | ret = -EAGAIN; |
2384 | goto out_unlock; |
2385 | } |
2386 | wait_on_page_writeback(page); |
2387 | return 0; |
2388 | out_unlock: |
2389 | unlock_page(page); |
2390 | return ret; |
2391 | } |
2392 | EXPORT_SYMBOL(__block_page_mkwrite); |
2393 | |
2394 | int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, |
2395 | get_block_t get_block) |
2396 | { |
2397 | int ret; |
2398 | struct super_block *sb = vma->vm_file->f_path.dentry->d_inode->i_sb; |
2399 | |
2400 | /* |
2401 | * This check is racy but catches the common case. The check in |
2402 | * __block_page_mkwrite() is reliable. |
2403 | */ |
2404 | vfs_check_frozen(sb, SB_FREEZE_WRITE); |
2405 | ret = __block_page_mkwrite(vma, vmf, get_block); |
2406 | return block_page_mkwrite_return(ret); |
2407 | } |
2408 | EXPORT_SYMBOL(block_page_mkwrite); |
2409 | |
2410 | /* |
2411 | * nobh_write_begin()'s prereads are special: the buffer_heads are freed |
2412 | * immediately, while under the page lock. So it needs a special end_io |
2413 | * handler which does not touch the bh after unlocking it. |
2414 | */ |
2415 | static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate) |
2416 | { |
2417 | __end_buffer_read_notouch(bh, uptodate); |
2418 | } |
2419 | |
2420 | /* |
2421 | * Attach the singly-linked list of buffers created by nobh_write_begin, to |
2422 | * the page (converting it to circular linked list and taking care of page |
2423 | * dirty races). |
2424 | */ |
2425 | static void attach_nobh_buffers(struct page *page, struct buffer_head *head) |
2426 | { |
2427 | struct buffer_head *bh; |
2428 | |
2429 | BUG_ON(!PageLocked(page)); |
2430 | |
2431 | spin_lock(&page->mapping->private_lock); |
2432 | bh = head; |
2433 | do { |
2434 | if (PageDirty(page)) |
2435 | set_buffer_dirty(bh); |
2436 | if (!bh->b_this_page) |
2437 | bh->b_this_page = head; |
2438 | bh = bh->b_this_page; |
2439 | } while (bh != head); |
2440 | attach_page_buffers(page, head); |
2441 | spin_unlock(&page->mapping->private_lock); |
2442 | } |
2443 | |
2444 | /* |
2445 | * On entry, the page is fully not uptodate. |
2446 | * On exit the page is fully uptodate in the areas outside (from,to) |
2447 | * The filesystem needs to handle block truncation upon failure. |
2448 | */ |
2449 | int nobh_write_begin(struct address_space *mapping, |
2450 | loff_t pos, unsigned len, unsigned flags, |
2451 | struct page **pagep, void **fsdata, |
2452 | get_block_t *get_block) |
2453 | { |
2454 | struct inode *inode = mapping->host; |
2455 | const unsigned blkbits = inode->i_blkbits; |
2456 | const unsigned blocksize = 1 << blkbits; |
2457 | struct buffer_head *head, *bh; |
2458 | struct page *page; |
2459 | pgoff_t index; |
2460 | unsigned from, to; |
2461 | unsigned block_in_page; |
2462 | unsigned block_start, block_end; |
2463 | sector_t block_in_file; |
2464 | int nr_reads = 0; |
2465 | int ret = 0; |
2466 | int is_mapped_to_disk = 1; |
2467 | |
2468 | index = pos >> PAGE_CACHE_SHIFT; |
2469 | from = pos & (PAGE_CACHE_SIZE - 1); |
2470 | to = from + len; |
2471 | |
2472 | page = grab_cache_page_write_begin(mapping, index, flags); |
2473 | if (!page) |
2474 | return -ENOMEM; |
2475 | *pagep = page; |
2476 | *fsdata = NULL; |
2477 | |
2478 | if (page_has_buffers(page)) { |
2479 | ret = __block_write_begin(page, pos, len, get_block); |
2480 | if (unlikely(ret)) |
2481 | goto out_release; |
2482 | return ret; |
2483 | } |
2484 | |
2485 | if (PageMappedToDisk(page)) |
2486 | return 0; |
2487 | |
2488 | /* |
2489 | * Allocate buffers so that we can keep track of state, and potentially |
2490 | * attach them to the page if an error occurs. In the common case of |
2491 | * no error, they will just be freed again without ever being attached |
2492 | * to the page (which is all OK, because we're under the page lock). |
2493 | * |
2494 | * Be careful: the buffer linked list is a NULL terminated one, rather |
2495 | * than the circular one we're used to. |
2496 | */ |
2497 | head = alloc_page_buffers(page, blocksize, 0); |
2498 | if (!head) { |
2499 | ret = -ENOMEM; |
2500 | goto out_release; |
2501 | } |
2502 | |
2503 | block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); |
2504 | |
2505 | /* |
2506 | * We loop across all blocks in the page, whether or not they are |
2507 | * part of the affected region. This is so we can discover if the |
2508 | * page is fully mapped-to-disk. |
2509 | */ |
2510 | for (block_start = 0, block_in_page = 0, bh = head; |
2511 | block_start < PAGE_CACHE_SIZE; |
2512 | block_in_page++, block_start += blocksize, bh = bh->b_this_page) { |
2513 | int create; |
2514 | |
2515 | block_end = block_start + blocksize; |
2516 | bh->b_state = 0; |
2517 | create = 1; |
2518 | if (block_start >= to) |
2519 | create = 0; |
2520 | ret = get_block(inode, block_in_file + block_in_page, |
2521 | bh, create); |
2522 | if (ret) |
2523 | goto failed; |
2524 | if (!buffer_mapped(bh)) |
2525 | is_mapped_to_disk = 0; |
2526 | if (buffer_new(bh)) |
2527 | unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr); |
2528 | if (PageUptodate(page)) { |
2529 | set_buffer_uptodate(bh); |
2530 | continue; |
2531 | } |
2532 | if (buffer_new(bh) || !buffer_mapped(bh)) { |
2533 | zero_user_segments(page, block_start, from, |
2534 | to, block_end); |
2535 | continue; |
2536 | } |
2537 | if (buffer_uptodate(bh)) |
2538 | continue; /* reiserfs does this */ |
2539 | if (block_start < from || block_end > to) { |
2540 | lock_buffer(bh); |
2541 | bh->b_end_io = end_buffer_read_nobh; |
2542 | submit_bh(READ, bh); |
2543 | nr_reads++; |
2544 | } |
2545 | } |
2546 | |
2547 | if (nr_reads) { |
2548 | /* |
2549 | * The page is locked, so these buffers are protected from |
2550 | * any VM or truncate activity. Hence we don't need to care |
2551 | * for the buffer_head refcounts. |
2552 | */ |
2553 | for (bh = head; bh; bh = bh->b_this_page) { |
2554 | wait_on_buffer(bh); |
2555 | if (!buffer_uptodate(bh)) |
2556 | ret = -EIO; |
2557 | } |
2558 | if (ret) |
2559 | goto failed; |
2560 | } |
2561 | |
2562 | if (is_mapped_to_disk) |
2563 | SetPageMappedToDisk(page); |
2564 | |
2565 | *fsdata = head; /* to be released by nobh_write_end */ |
2566 | |
2567 | return 0; |
2568 | |
2569 | failed: |
2570 | BUG_ON(!ret); |
2571 | /* |
2572 | * Error recovery is a bit difficult. We need to zero out blocks that |
2573 | * were newly allocated, and dirty them to ensure they get written out. |
2574 | * Buffers need to be attached to the page at this point, otherwise |
2575 | * the handling of potential IO errors during writeout would be hard |
2576 | * (could try doing synchronous writeout, but what if that fails too?) |
2577 | */ |
2578 | attach_nobh_buffers(page, head); |
2579 | page_zero_new_buffers(page, from, to); |
2580 | |
2581 | out_release: |
2582 | unlock_page(page); |
2583 | page_cache_release(page); |
2584 | *pagep = NULL; |
2585 | |
2586 | return ret; |
2587 | } |
2588 | EXPORT_SYMBOL(nobh_write_begin); |
2589 | |
2590 | int nobh_write_end(struct file *file, struct address_space *mapping, |
2591 | loff_t pos, unsigned len, unsigned copied, |
2592 | struct page *page, void *fsdata) |
2593 | { |
2594 | struct inode *inode = page->mapping->host; |
2595 | struct buffer_head *head = fsdata; |
2596 | struct buffer_head *bh; |
2597 | BUG_ON(fsdata != NULL && page_has_buffers(page)); |
2598 | |
2599 | if (unlikely(copied < len) && head) |
2600 | attach_nobh_buffers(page, head); |
2601 | if (page_has_buffers(page)) |
2602 | return generic_write_end(file, mapping, pos, len, |
2603 | copied, page, fsdata); |
2604 | |
2605 | SetPageUptodate(page); |
2606 | set_page_dirty(page); |
2607 | if (pos+copied > inode->i_size) { |
2608 | i_size_write(inode, pos+copied); |
2609 | mark_inode_dirty(inode); |
2610 | } |
2611 | |
2612 | unlock_page(page); |
2613 | page_cache_release(page); |
2614 | |
2615 | while (head) { |
2616 | bh = head; |
2617 | head = head->b_this_page; |
2618 | free_buffer_head(bh); |
2619 | } |
2620 | |
2621 | return copied; |
2622 | } |
2623 | EXPORT_SYMBOL(nobh_write_end); |
2624 | |
2625 | /* |
2626 | * nobh_writepage() - based on block_full_write_page() except |
2627 | * that it tries to operate without attaching bufferheads to |
2628 | * the page. |
2629 | */ |
2630 | int nobh_writepage(struct page *page, get_block_t *get_block, |
2631 | struct writeback_control *wbc) |
2632 | { |
2633 | struct inode * const inode = page->mapping->host; |
2634 | loff_t i_size = i_size_read(inode); |
2635 | const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; |
2636 | unsigned offset; |
2637 | int ret; |
2638 | |
2639 | /* Is the page fully inside i_size? */ |
2640 | if (page->index < end_index) |
2641 | goto out; |
2642 | |
2643 | /* Is the page fully outside i_size? (truncate in progress) */ |
2644 | offset = i_size & (PAGE_CACHE_SIZE-1); |
2645 | if (page->index >= end_index+1 || !offset) { |
2646 | /* |
2647 | * The page may have dirty, unmapped buffers. For example, |
2648 | * they may have been added in ext3_writepage(). Make them |
2649 | * freeable here, so the page does not leak. |
2650 | */ |
2651 | #if 0 |
2652 | /* Not really sure about this - do we need this ? */ |
2653 | if (page->mapping->a_ops->invalidatepage) |
2654 | page->mapping->a_ops->invalidatepage(page, offset); |
2655 | #endif |
2656 | unlock_page(page); |
2657 | return 0; /* don't care */ |
2658 | } |
2659 | |
2660 | /* |
2661 | * The page straddles i_size. It must be zeroed out on each and every |
2662 | * writepage invocation because it may be mmapped. "A file is mapped |
2663 | * in multiples of the page size. For a file that is not a multiple of |
2664 | * the page size, the remaining memory is zeroed when mapped, and |
2665 | * writes to that region are not written out to the file." |
2666 | */ |
2667 | zero_user_segment(page, offset, PAGE_CACHE_SIZE); |
2668 | out: |
2669 | ret = mpage_writepage(page, get_block, wbc); |
2670 | if (ret == -EAGAIN) |
2671 | ret = __block_write_full_page(inode, page, get_block, wbc, |
2672 | end_buffer_async_write); |
2673 | return ret; |
2674 | } |
2675 | EXPORT_SYMBOL(nobh_writepage); |
2676 | |
2677 | int nobh_truncate_page(struct address_space *mapping, |
2678 | loff_t from, get_block_t *get_block) |
2679 | { |
2680 | pgoff_t index = from >> PAGE_CACHE_SHIFT; |
2681 | unsigned offset = from & (PAGE_CACHE_SIZE-1); |
2682 | unsigned blocksize; |
2683 | sector_t iblock; |
2684 | unsigned length, pos; |
2685 | struct inode *inode = mapping->host; |
2686 | struct page *page; |
2687 | struct buffer_head map_bh; |
2688 | int err; |
2689 | |
2690 | blocksize = 1 << inode->i_blkbits; |
2691 | length = offset & (blocksize - 1); |
2692 | |
2693 | /* Block boundary? Nothing to do */ |
2694 | if (!length) |
2695 | return 0; |
2696 | |
2697 | length = blocksize - length; |
2698 | iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
2699 | |
2700 | page = grab_cache_page(mapping, index); |
2701 | err = -ENOMEM; |
2702 | if (!page) |
2703 | goto out; |
2704 | |
2705 | if (page_has_buffers(page)) { |
2706 | has_buffers: |
2707 | unlock_page(page); |
2708 | page_cache_release(page); |
2709 | return block_truncate_page(mapping, from, get_block); |
2710 | } |
2711 | |
2712 | /* Find the buffer that contains "offset" */ |
2713 | pos = blocksize; |
2714 | while (offset >= pos) { |
2715 | iblock++; |
2716 | pos += blocksize; |
2717 | } |
2718 | |
2719 | map_bh.b_size = blocksize; |
2720 | map_bh.b_state = 0; |
2721 | err = get_block(inode, iblock, &map_bh, 0); |
2722 | if (err) |
2723 | goto unlock; |
2724 | /* unmapped? It's a hole - nothing to do */ |
2725 | if (!buffer_mapped(&map_bh)) |
2726 | goto unlock; |
2727 | |
2728 | /* Ok, it's mapped. Make sure it's up-to-date */ |
2729 | if (!PageUptodate(page)) { |
2730 | err = mapping->a_ops->readpage(NULL, page); |
2731 | if (err) { |
2732 | page_cache_release(page); |
2733 | goto out; |
2734 | } |
2735 | lock_page(page); |
2736 | if (!PageUptodate(page)) { |
2737 | err = -EIO; |
2738 | goto unlock; |
2739 | } |
2740 | if (page_has_buffers(page)) |
2741 | goto has_buffers; |
2742 | } |
2743 | zero_user(page, offset, length); |
2744 | set_page_dirty(page); |
2745 | err = 0; |
2746 | |
2747 | unlock: |
2748 | unlock_page(page); |
2749 | page_cache_release(page); |
2750 | out: |
2751 | return err; |
2752 | } |
2753 | EXPORT_SYMBOL(nobh_truncate_page); |
2754 | |
2755 | int block_truncate_page(struct address_space *mapping, |
2756 | loff_t from, get_block_t *get_block) |
2757 | { |
2758 | pgoff_t index = from >> PAGE_CACHE_SHIFT; |
2759 | unsigned offset = from & (PAGE_CACHE_SIZE-1); |
2760 | unsigned blocksize; |
2761 | sector_t iblock; |
2762 | unsigned length, pos; |
2763 | struct inode *inode = mapping->host; |
2764 | struct page *page; |
2765 | struct buffer_head *bh; |
2766 | int err; |
2767 | |
2768 | blocksize = 1 << inode->i_blkbits; |
2769 | length = offset & (blocksize - 1); |
2770 | |
2771 | /* Block boundary? Nothing to do */ |
2772 | if (!length) |
2773 | return 0; |
2774 | |
2775 | length = blocksize - length; |
2776 | iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
2777 | |
2778 | page = grab_cache_page(mapping, index); |
2779 | err = -ENOMEM; |
2780 | if (!page) |
2781 | goto out; |
2782 | |
2783 | if (!page_has_buffers(page)) |
2784 | create_empty_buffers(page, blocksize, 0); |
2785 | |
2786 | /* Find the buffer that contains "offset" */ |
2787 | bh = page_buffers(page); |
2788 | pos = blocksize; |
2789 | while (offset >= pos) { |
2790 | bh = bh->b_this_page; |
2791 | iblock++; |
2792 | pos += blocksize; |
2793 | } |
2794 | |
2795 | err = 0; |
2796 | if (!buffer_mapped(bh)) { |
2797 | WARN_ON(bh->b_size != blocksize); |
2798 | err = get_block(inode, iblock, bh, 0); |
2799 | if (err) |
2800 | goto unlock; |
2801 | /* unmapped? It's a hole - nothing to do */ |
2802 | if (!buffer_mapped(bh)) |
2803 | goto unlock; |
2804 | } |
2805 | |
2806 | /* Ok, it's mapped. Make sure it's up-to-date */ |
2807 | if (PageUptodate(page)) |
2808 | set_buffer_uptodate(bh); |
2809 | |
2810 | if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) { |
2811 | err = -EIO; |
2812 | ll_rw_block(READ, 1, &bh); |
2813 | wait_on_buffer(bh); |
2814 | /* Uhhuh. Read error. Complain and punt. */ |
2815 | if (!buffer_uptodate(bh)) |
2816 | goto unlock; |
2817 | } |
2818 | |
2819 | zero_user(page, offset, length); |
2820 | mark_buffer_dirty(bh); |
2821 | err = 0; |
2822 | |
2823 | unlock: |
2824 | unlock_page(page); |
2825 | page_cache_release(page); |
2826 | out: |
2827 | return err; |
2828 | } |
2829 | EXPORT_SYMBOL(block_truncate_page); |
2830 | |
2831 | /* |
2832 | * The generic ->writepage function for buffer-backed address_spaces |
2833 | * this form passes in the end_io handler used to finish the IO. |
2834 | */ |
2835 | int block_write_full_page_endio(struct page *page, get_block_t *get_block, |
2836 | struct writeback_control *wbc, bh_end_io_t *handler) |
2837 | { |
2838 | struct inode * const inode = page->mapping->host; |
2839 | loff_t i_size = i_size_read(inode); |
2840 | const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; |
2841 | unsigned offset; |
2842 | |
2843 | /* Is the page fully inside i_size? */ |
2844 | if (page->index < end_index) |
2845 | return __block_write_full_page(inode, page, get_block, wbc, |
2846 | handler); |
2847 | |
2848 | /* Is the page fully outside i_size? (truncate in progress) */ |
2849 | offset = i_size & (PAGE_CACHE_SIZE-1); |
2850 | if (page->index >= end_index+1 || !offset) { |
2851 | /* |
2852 | * The page may have dirty, unmapped buffers. For example, |
2853 | * they may have been added in ext3_writepage(). Make them |
2854 | * freeable here, so the page does not leak. |
2855 | */ |
2856 | do_invalidatepage(page, 0); |
2857 | unlock_page(page); |
2858 | return 0; /* don't care */ |
2859 | } |
2860 | |
2861 | /* |
2862 | * The page straddles i_size. It must be zeroed out on each and every |
2863 | * writepage invocation because it may be mmapped. "A file is mapped |
2864 | * in multiples of the page size. For a file that is not a multiple of |
2865 | * the page size, the remaining memory is zeroed when mapped, and |
2866 | * writes to that region are not written out to the file." |
2867 | */ |
2868 | zero_user_segment(page, offset, PAGE_CACHE_SIZE); |
2869 | return __block_write_full_page(inode, page, get_block, wbc, handler); |
2870 | } |
2871 | EXPORT_SYMBOL(block_write_full_page_endio); |
2872 | |
2873 | /* |
2874 | * The generic ->writepage function for buffer-backed address_spaces |
2875 | */ |
2876 | int block_write_full_page(struct page *page, get_block_t *get_block, |
2877 | struct writeback_control *wbc) |
2878 | { |
2879 | return block_write_full_page_endio(page, get_block, wbc, |
2880 | end_buffer_async_write); |
2881 | } |
2882 | EXPORT_SYMBOL(block_write_full_page); |
2883 | |
2884 | sector_t generic_block_bmap(struct address_space *mapping, sector_t block, |
2885 | get_block_t *get_block) |
2886 | { |
2887 | struct buffer_head tmp; |
2888 | struct inode *inode = mapping->host; |
2889 | tmp.b_state = 0; |
2890 | tmp.b_blocknr = 0; |
2891 | tmp.b_size = 1 << inode->i_blkbits; |
2892 | get_block(inode, block, &tmp, 0); |
2893 | return tmp.b_blocknr; |
2894 | } |
2895 | EXPORT_SYMBOL(generic_block_bmap); |
2896 | |
2897 | static void end_bio_bh_io_sync(struct bio *bio, int err) |
2898 | { |
2899 | struct buffer_head *bh = bio->bi_private; |
2900 | |
2901 | if (err == -EOPNOTSUPP) { |
2902 | set_bit(BIO_EOPNOTSUPP, &bio->bi_flags); |
2903 | } |
2904 | |
2905 | if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags))) |
2906 | set_bit(BH_Quiet, &bh->b_state); |
2907 | |
2908 | bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags)); |
2909 | bio_put(bio); |
2910 | } |
2911 | |
2912 | int submit_bh(int rw, struct buffer_head * bh) |
2913 | { |
2914 | struct bio *bio; |
2915 | int ret = 0; |
2916 | |
2917 | BUG_ON(!buffer_locked(bh)); |
2918 | BUG_ON(!buffer_mapped(bh)); |
2919 | BUG_ON(!bh->b_end_io); |
2920 | BUG_ON(buffer_delay(bh)); |
2921 | BUG_ON(buffer_unwritten(bh)); |
2922 | |
2923 | /* |
2924 | * Only clear out a write error when rewriting |
2925 | */ |
2926 | if (test_set_buffer_req(bh) && (rw & WRITE)) |
2927 | clear_buffer_write_io_error(bh); |
2928 | |
2929 | /* |
2930 | * from here on down, it's all bio -- do the initial mapping, |
2931 | * submit_bio -> generic_make_request may further map this bio around |
2932 | */ |
2933 | bio = bio_alloc(GFP_NOIO, 1); |
2934 | |
2935 | bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9); |
2936 | bio->bi_bdev = bh->b_bdev; |
2937 | bio->bi_io_vec[0].bv_page = bh->b_page; |
2938 | bio->bi_io_vec[0].bv_len = bh->b_size; |
2939 | bio->bi_io_vec[0].bv_offset = bh_offset(bh); |
2940 | |
2941 | bio->bi_vcnt = 1; |
2942 | bio->bi_idx = 0; |
2943 | bio->bi_size = bh->b_size; |
2944 | |
2945 | bio->bi_end_io = end_bio_bh_io_sync; |
2946 | bio->bi_private = bh; |
2947 | |
2948 | bio_get(bio); |
2949 | submit_bio(rw, bio); |
2950 | |
2951 | if (bio_flagged(bio, BIO_EOPNOTSUPP)) |
2952 | ret = -EOPNOTSUPP; |
2953 | |
2954 | bio_put(bio); |
2955 | return ret; |
2956 | } |
2957 | EXPORT_SYMBOL(submit_bh); |
2958 | |
2959 | /** |
2960 | * ll_rw_block: low-level access to block devices (DEPRECATED) |
2961 | * @rw: whether to %READ or %WRITE or maybe %READA (readahead) |
2962 | * @nr: number of &struct buffer_heads in the array |
2963 | * @bhs: array of pointers to &struct buffer_head |
2964 | * |
2965 | * ll_rw_block() takes an array of pointers to &struct buffer_heads, and |
2966 | * requests an I/O operation on them, either a %READ or a %WRITE. The third |
2967 | * %READA option is described in the documentation for generic_make_request() |
2968 | * which ll_rw_block() calls. |
2969 | * |
2970 | * This function drops any buffer that it cannot get a lock on (with the |
2971 | * BH_Lock state bit), any buffer that appears to be clean when doing a write |
2972 | * request, and any buffer that appears to be up-to-date when doing read |
2973 | * request. Further it marks as clean buffers that are processed for |
2974 | * writing (the buffer cache won't assume that they are actually clean |
2975 | * until the buffer gets unlocked). |
2976 | * |
2977 | * ll_rw_block sets b_end_io to simple completion handler that marks |
2978 | * the buffer up-to-date (if approriate), unlocks the buffer and wakes |
2979 | * any waiters. |
2980 | * |
2981 | * All of the buffers must be for the same device, and must also be a |
2982 | * multiple of the current approved size for the device. |
2983 | */ |
2984 | void ll_rw_block(int rw, int nr, struct buffer_head *bhs[]) |
2985 | { |
2986 | int i; |
2987 | |
2988 | for (i = 0; i < nr; i++) { |
2989 | struct buffer_head *bh = bhs[i]; |
2990 | |
2991 | if (!trylock_buffer(bh)) |
2992 | continue; |
2993 | if (rw == WRITE) { |
2994 | if (test_clear_buffer_dirty(bh)) { |
2995 | bh->b_end_io = end_buffer_write_sync; |
2996 | get_bh(bh); |
2997 | submit_bh(WRITE, bh); |
2998 | continue; |
2999 | } |
3000 | } else { |
3001 | if (!buffer_uptodate(bh)) { |
3002 | bh->b_end_io = end_buffer_read_sync; |
3003 | get_bh(bh); |
3004 | submit_bh(rw, bh); |
3005 | continue; |
3006 | } |
3007 | } |
3008 | unlock_buffer(bh); |
3009 | } |
3010 | } |
3011 | EXPORT_SYMBOL(ll_rw_block); |
3012 | |
3013 | void write_dirty_buffer(struct buffer_head *bh, int rw) |
3014 | { |
3015 | lock_buffer(bh); |
3016 | if (!test_clear_buffer_dirty(bh)) { |
3017 | unlock_buffer(bh); |
3018 | return; |
3019 | } |
3020 | bh->b_end_io = end_buffer_write_sync; |
3021 | get_bh(bh); |
3022 | submit_bh(rw, bh); |
3023 | } |
3024 | EXPORT_SYMBOL(write_dirty_buffer); |
3025 | |
3026 | /* |
3027 | * For a data-integrity writeout, we need to wait upon any in-progress I/O |
3028 | * and then start new I/O and then wait upon it. The caller must have a ref on |
3029 | * the buffer_head. |
3030 | */ |
3031 | int __sync_dirty_buffer(struct buffer_head *bh, int rw) |
3032 | { |
3033 | int ret = 0; |
3034 | |
3035 | WARN_ON(atomic_read(&bh->b_count) < 1); |
3036 | lock_buffer(bh); |
3037 | if (test_clear_buffer_dirty(bh)) { |
3038 | get_bh(bh); |
3039 | bh->b_end_io = end_buffer_write_sync; |
3040 | ret = submit_bh(rw, bh); |
3041 | wait_on_buffer(bh); |
3042 | if (!ret && !buffer_uptodate(bh)) |
3043 | ret = -EIO; |
3044 | } else { |
3045 | unlock_buffer(bh); |
3046 | } |
3047 | return ret; |
3048 | } |
3049 | EXPORT_SYMBOL(__sync_dirty_buffer); |
3050 | |
3051 | int sync_dirty_buffer(struct buffer_head *bh) |
3052 | { |
3053 | return __sync_dirty_buffer(bh, WRITE_SYNC); |
3054 | } |
3055 | EXPORT_SYMBOL(sync_dirty_buffer); |
3056 | |
3057 | /* |
3058 | * try_to_free_buffers() checks if all the buffers on this particular page |
3059 | * are unused, and releases them if so. |
3060 | * |
3061 | * Exclusion against try_to_free_buffers may be obtained by either |
3062 | * locking the page or by holding its mapping's private_lock. |
3063 | * |
3064 | * If the page is dirty but all the buffers are clean then we need to |
3065 | * be sure to mark the page clean as well. This is because the page |
3066 | * may be against a block device, and a later reattachment of buffers |
3067 | * to a dirty page will set *all* buffers dirty. Which would corrupt |
3068 | * filesystem data on the same device. |
3069 | * |
3070 | * The same applies to regular filesystem pages: if all the buffers are |
3071 | * clean then we set the page clean and proceed. To do that, we require |
3072 | * total exclusion from __set_page_dirty_buffers(). That is obtained with |
3073 | * private_lock. |
3074 | * |
3075 | * try_to_free_buffers() is non-blocking. |
3076 | */ |
3077 | static inline int buffer_busy(struct buffer_head *bh) |
3078 | { |
3079 | return atomic_read(&bh->b_count) | |
3080 | (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock))); |
3081 | } |
3082 | |
3083 | static int |
3084 | drop_buffers(struct page *page, struct buffer_head **buffers_to_free) |
3085 | { |
3086 | struct buffer_head *head = page_buffers(page); |
3087 | struct buffer_head *bh; |
3088 | |
3089 | bh = head; |
3090 | do { |
3091 | if (buffer_write_io_error(bh) && page->mapping) |
3092 | set_bit(AS_EIO, &page->mapping->flags); |
3093 | if (buffer_busy(bh)) |
3094 | goto failed; |
3095 | bh = bh->b_this_page; |
3096 | } while (bh != head); |
3097 | |
3098 | do { |
3099 | struct buffer_head *next = bh->b_this_page; |
3100 | |
3101 | if (bh->b_assoc_map) |
3102 | __remove_assoc_queue(bh); |
3103 | bh = next; |
3104 | } while (bh != head); |
3105 | *buffers_to_free = head; |
3106 | __clear_page_buffers(page); |
3107 | return 1; |
3108 | failed: |
3109 | return 0; |
3110 | } |
3111 | |
3112 | int try_to_free_buffers(struct page *page) |
3113 | { |
3114 | struct address_space * const mapping = page->mapping; |
3115 | struct buffer_head *buffers_to_free = NULL; |
3116 | int ret = 0; |
3117 | |
3118 | BUG_ON(!PageLocked(page)); |
3119 | if (PageWriteback(page)) |
3120 | return 0; |
3121 | |
3122 | if (mapping == NULL) { /* can this still happen? */ |
3123 | ret = drop_buffers(page, &buffers_to_free); |
3124 | goto out; |
3125 | } |
3126 | |
3127 | spin_lock(&mapping->private_lock); |
3128 | ret = drop_buffers(page, &buffers_to_free); |
3129 | |
3130 | /* |
3131 | * If the filesystem writes its buffers by hand (eg ext3) |
3132 | * then we can have clean buffers against a dirty page. We |
3133 | * clean the page here; otherwise the VM will never notice |
3134 | * that the filesystem did any IO at all. |
3135 | * |
3136 | * Also, during truncate, discard_buffer will have marked all |
3137 | * the page's buffers clean. We discover that here and clean |
3138 | * the page also. |
3139 | * |
3140 | * private_lock must be held over this entire operation in order |
3141 | * to synchronise against __set_page_dirty_buffers and prevent the |
3142 | * dirty bit from being lost. |
3143 | */ |
3144 | if (ret) |
3145 | cancel_dirty_page(page, PAGE_CACHE_SIZE); |
3146 | spin_unlock(&mapping->private_lock); |
3147 | out: |
3148 | if (buffers_to_free) { |
3149 | struct buffer_head *bh = buffers_to_free; |
3150 | |
3151 | do { |
3152 | struct buffer_head *next = bh->b_this_page; |
3153 | free_buffer_head(bh); |
3154 | bh = next; |
3155 | } while (bh != buffers_to_free); |
3156 | } |
3157 | return ret; |
3158 | } |
3159 | EXPORT_SYMBOL(try_to_free_buffers); |
3160 | |
3161 | /* |
3162 | * There are no bdflush tunables left. But distributions are |
3163 | * still running obsolete flush daemons, so we terminate them here. |
3164 | * |
3165 | * Use of bdflush() is deprecated and will be removed in a future kernel. |
3166 | * The `flush-X' kernel threads fully replace bdflush daemons and this call. |
3167 | */ |
3168 | SYSCALL_DEFINE2(bdflush, int, func, long, data) |
3169 | { |
3170 | static int msg_count; |
3171 | |
3172 | if (!capable(CAP_SYS_ADMIN)) |
3173 | return -EPERM; |
3174 | |
3175 | if (msg_count < 5) { |
3176 | msg_count++; |
3177 | printk(KERN_INFO |
3178 | "warning: process `%s' used the obsolete bdflush" |
3179 | " system call\n", current->comm); |
3180 | printk(KERN_INFO "Fix your initscripts?\n"); |
3181 | } |
3182 | |
3183 | if (func == 1) |
3184 | do_exit(0); |
3185 | return 0; |
3186 | } |
3187 | |
3188 | /* |
3189 | * Buffer-head allocation |
3190 | */ |
3191 | static struct kmem_cache *bh_cachep; |
3192 | |
3193 | /* |
3194 | * Once the number of bh's in the machine exceeds this level, we start |
3195 | * stripping them in writeback. |
3196 | */ |
3197 | static int max_buffer_heads; |
3198 | |
3199 | int buffer_heads_over_limit; |
3200 | |
3201 | struct bh_accounting { |
3202 | int nr; /* Number of live bh's */ |
3203 | int ratelimit; /* Limit cacheline bouncing */ |
3204 | }; |
3205 | |
3206 | static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0}; |
3207 | |
3208 | static void recalc_bh_state(void) |
3209 | { |
3210 | int i; |
3211 | int tot = 0; |
3212 | |
3213 | if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096) |
3214 | return; |
3215 | __this_cpu_write(bh_accounting.ratelimit, 0); |
3216 | for_each_online_cpu(i) |
3217 | tot += per_cpu(bh_accounting, i).nr; |
3218 | buffer_heads_over_limit = (tot > max_buffer_heads); |
3219 | } |
3220 | |
3221 | struct buffer_head *alloc_buffer_head(gfp_t gfp_flags) |
3222 | { |
3223 | struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags); |
3224 | if (ret) { |
3225 | INIT_LIST_HEAD(&ret->b_assoc_buffers); |
3226 | preempt_disable(); |
3227 | __this_cpu_inc(bh_accounting.nr); |
3228 | recalc_bh_state(); |
3229 | preempt_enable(); |
3230 | } |
3231 | return ret; |
3232 | } |
3233 | EXPORT_SYMBOL(alloc_buffer_head); |
3234 | |
3235 | void free_buffer_head(struct buffer_head *bh) |
3236 | { |
3237 | BUG_ON(!list_empty(&bh->b_assoc_buffers)); |
3238 | kmem_cache_free(bh_cachep, bh); |
3239 | preempt_disable(); |
3240 | __this_cpu_dec(bh_accounting.nr); |
3241 | recalc_bh_state(); |
3242 | preempt_enable(); |
3243 | } |
3244 | EXPORT_SYMBOL(free_buffer_head); |
3245 | |
3246 | static void buffer_exit_cpu(int cpu) |
3247 | { |
3248 | int i; |
3249 | struct bh_lru *b = &per_cpu(bh_lrus, cpu); |
3250 | |
3251 | for (i = 0; i < BH_LRU_SIZE; i++) { |
3252 | brelse(b->bhs[i]); |
3253 | b->bhs[i] = NULL; |
3254 | } |
3255 | this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr); |
3256 | per_cpu(bh_accounting, cpu).nr = 0; |
3257 | } |
3258 | |
3259 | static int buffer_cpu_notify(struct notifier_block *self, |
3260 | unsigned long action, void *hcpu) |
3261 | { |
3262 | if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) |
3263 | buffer_exit_cpu((unsigned long)hcpu); |
3264 | return NOTIFY_OK; |
3265 | } |
3266 | |
3267 | /** |
3268 | * bh_uptodate_or_lock - Test whether the buffer is uptodate |
3269 | * @bh: struct buffer_head |
3270 | * |
3271 | * Return true if the buffer is up-to-date and false, |
3272 | * with the buffer locked, if not. |
3273 | */ |
3274 | int bh_uptodate_or_lock(struct buffer_head *bh) |
3275 | { |
3276 | if (!buffer_uptodate(bh)) { |
3277 | lock_buffer(bh); |
3278 | if (!buffer_uptodate(bh)) |
3279 | return 0; |
3280 | unlock_buffer(bh); |
3281 | } |
3282 | return 1; |
3283 | } |
3284 | EXPORT_SYMBOL(bh_uptodate_or_lock); |
3285 | |
3286 | /** |
3287 | * bh_submit_read - Submit a locked buffer for reading |
3288 | * @bh: struct buffer_head |
3289 | * |
3290 | * Returns zero on success and -EIO on error. |
3291 | */ |
3292 | int bh_submit_read(struct buffer_head *bh) |
3293 | { |
3294 | BUG_ON(!buffer_locked(bh)); |
3295 | |
3296 | if (buffer_uptodate(bh)) { |
3297 | unlock_buffer(bh); |
3298 | return 0; |
3299 | } |
3300 | |
3301 | get_bh(bh); |
3302 | bh->b_end_io = end_buffer_read_sync; |
3303 | submit_bh(READ, bh); |
3304 | wait_on_buffer(bh); |
3305 | if (buffer_uptodate(bh)) |
3306 | return 0; |
3307 | return -EIO; |
3308 | } |
3309 | EXPORT_SYMBOL(bh_submit_read); |
3310 | |
3311 | void __init buffer_init(void) |
3312 | { |
3313 | int nrpages; |
3314 | |
3315 | bh_cachep = kmem_cache_create("buffer_head", |
3316 | sizeof(struct buffer_head), 0, |
3317 | (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC| |
3318 | SLAB_MEM_SPREAD), |
3319 | NULL); |
3320 | |
3321 | /* |
3322 | * Limit the bh occupancy to 10% of ZONE_NORMAL |
3323 | */ |
3324 | nrpages = (nr_free_buffer_pages() * 10) / 100; |
3325 | max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head)); |
3326 | hotcpu_notifier(buffer_cpu_notify, 0); |
3327 | } |
3328 |
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