Root/
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 | |
45 | static int fsync_buffers_list(spinlock_t *lock, struct list_head *list); |
46 | |
47 | #define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers) |
48 | |
49 | inline void |
50 | init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private) |
51 | { |
52 | bh->b_end_io = handler; |
53 | bh->b_private = private; |
54 | } |
55 | EXPORT_SYMBOL(init_buffer); |
56 | |
57 | static int sync_buffer(void *word) |
58 | { |
59 | struct block_device *bd; |
60 | struct buffer_head *bh |
61 | = container_of(word, struct buffer_head, b_state); |
62 | |
63 | smp_mb(); |
64 | bd = bh->b_bdev; |
65 | if (bd) |
66 | blk_run_address_space(bd->bd_inode->i_mapping); |
67 | io_schedule(); |
68 | return 0; |
69 | } |
70 | |
71 | void __lock_buffer(struct buffer_head *bh) |
72 | { |
73 | wait_on_bit_lock(&bh->b_state, BH_Lock, sync_buffer, |
74 | TASK_UNINTERRUPTIBLE); |
75 | } |
76 | EXPORT_SYMBOL(__lock_buffer); |
77 | |
78 | void unlock_buffer(struct buffer_head *bh) |
79 | { |
80 | clear_bit_unlock(BH_Lock, &bh->b_state); |
81 | smp_mb__after_clear_bit(); |
82 | wake_up_bit(&bh->b_state, BH_Lock); |
83 | } |
84 | EXPORT_SYMBOL(unlock_buffer); |
85 | |
86 | /* |
87 | * Block until a buffer comes unlocked. This doesn't stop it |
88 | * from becoming locked again - you have to lock it yourself |
89 | * if you want to preserve its state. |
90 | */ |
91 | void __wait_on_buffer(struct buffer_head * bh) |
92 | { |
93 | wait_on_bit(&bh->b_state, BH_Lock, sync_buffer, TASK_UNINTERRUPTIBLE); |
94 | } |
95 | EXPORT_SYMBOL(__wait_on_buffer); |
96 | |
97 | static void |
98 | __clear_page_buffers(struct page *page) |
99 | { |
100 | ClearPagePrivate(page); |
101 | set_page_private(page, 0); |
102 | page_cache_release(page); |
103 | } |
104 | |
105 | |
106 | static int quiet_error(struct buffer_head *bh) |
107 | { |
108 | if (!test_bit(BH_Quiet, &bh->b_state) && printk_ratelimit()) |
109 | return 0; |
110 | return 1; |
111 | } |
112 | |
113 | |
114 | static void buffer_io_error(struct buffer_head *bh) |
115 | { |
116 | char b[BDEVNAME_SIZE]; |
117 | printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n", |
118 | bdevname(bh->b_bdev, b), |
119 | (unsigned long long)bh->b_blocknr); |
120 | } |
121 | |
122 | /* |
123 | * End-of-IO handler helper function which does not touch the bh after |
124 | * unlocking it. |
125 | * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but |
126 | * a race there is benign: unlock_buffer() only use the bh's address for |
127 | * hashing after unlocking the buffer, so it doesn't actually touch the bh |
128 | * itself. |
129 | */ |
130 | static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate) |
131 | { |
132 | if (uptodate) { |
133 | set_buffer_uptodate(bh); |
134 | } else { |
135 | /* This happens, due to failed READA attempts. */ |
136 | clear_buffer_uptodate(bh); |
137 | } |
138 | unlock_buffer(bh); |
139 | } |
140 | |
141 | /* |
142 | * Default synchronous end-of-IO handler.. Just mark it up-to-date and |
143 | * unlock the buffer. This is what ll_rw_block uses too. |
144 | */ |
145 | void end_buffer_read_sync(struct buffer_head *bh, int uptodate) |
146 | { |
147 | __end_buffer_read_notouch(bh, uptodate); |
148 | put_bh(bh); |
149 | } |
150 | EXPORT_SYMBOL(end_buffer_read_sync); |
151 | |
152 | void end_buffer_write_sync(struct buffer_head *bh, int uptodate) |
153 | { |
154 | char b[BDEVNAME_SIZE]; |
155 | |
156 | if (uptodate) { |
157 | set_buffer_uptodate(bh); |
158 | } else { |
159 | if (!quiet_error(bh)) { |
160 | buffer_io_error(bh); |
161 | printk(KERN_WARNING "lost page write due to " |
162 | "I/O error on %s\n", |
163 | bdevname(bh->b_bdev, b)); |
164 | } |
165 | set_buffer_write_io_error(bh); |
166 | clear_buffer_uptodate(bh); |
167 | } |
168 | unlock_buffer(bh); |
169 | put_bh(bh); |
170 | } |
171 | EXPORT_SYMBOL(end_buffer_write_sync); |
172 | |
173 | /* |
174 | * Various filesystems appear to want __find_get_block to be non-blocking. |
175 | * But it's the page lock which protects the buffers. To get around this, |
176 | * we get exclusion from try_to_free_buffers with the blockdev mapping's |
177 | * private_lock. |
178 | * |
179 | * Hack idea: for the blockdev mapping, i_bufferlist_lock contention |
180 | * may be quite high. This code could TryLock the page, and if that |
181 | * succeeds, there is no need to take private_lock. (But if |
182 | * private_lock is contended then so is mapping->tree_lock). |
183 | */ |
184 | static struct buffer_head * |
185 | __find_get_block_slow(struct block_device *bdev, sector_t block) |
186 | { |
187 | struct inode *bd_inode = bdev->bd_inode; |
188 | struct address_space *bd_mapping = bd_inode->i_mapping; |
189 | struct buffer_head *ret = NULL; |
190 | pgoff_t index; |
191 | struct buffer_head *bh; |
192 | struct buffer_head *head; |
193 | struct page *page; |
194 | int all_mapped = 1; |
195 | |
196 | index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits); |
197 | page = find_get_page(bd_mapping, index); |
198 | if (!page) |
199 | goto out; |
200 | |
201 | spin_lock(&bd_mapping->private_lock); |
202 | if (!page_has_buffers(page)) |
203 | goto out_unlock; |
204 | head = page_buffers(page); |
205 | bh = head; |
206 | do { |
207 | if (!buffer_mapped(bh)) |
208 | all_mapped = 0; |
209 | else if (bh->b_blocknr == block) { |
210 | ret = bh; |
211 | get_bh(bh); |
212 | goto out_unlock; |
213 | } |
214 | bh = bh->b_this_page; |
215 | } while (bh != head); |
216 | |
217 | /* we might be here because some of the buffers on this page are |
218 | * not mapped. This is due to various races between |
219 | * file io on the block device and getblk. It gets dealt with |
220 | * elsewhere, don't buffer_error if we had some unmapped buffers |
221 | */ |
222 | if (all_mapped) { |
223 | printk("__find_get_block_slow() failed. " |
224 | "block=%llu, b_blocknr=%llu\n", |
225 | (unsigned long long)block, |
226 | (unsigned long long)bh->b_blocknr); |
227 | printk("b_state=0x%08lx, b_size=%zu\n", |
228 | bh->b_state, bh->b_size); |
229 | printk("device blocksize: %d\n", 1 << bd_inode->i_blkbits); |
230 | } |
231 | out_unlock: |
232 | spin_unlock(&bd_mapping->private_lock); |
233 | page_cache_release(page); |
234 | out: |
235 | return ret; |
236 | } |
237 | |
238 | /* If invalidate_buffers() will trash dirty buffers, it means some kind |
239 | of fs corruption is going on. Trashing dirty data always imply losing |
240 | information that was supposed to be just stored on the physical layer |
241 | by the user. |
242 | |
243 | Thus invalidate_buffers in general usage is not allwowed to trash |
244 | dirty buffers. For example ioctl(FLSBLKBUF) expects dirty data to |
245 | be preserved. These buffers are simply skipped. |
246 | |
247 | We also skip buffers which are still in use. For example this can |
248 | happen if a userspace program is reading the block device. |
249 | |
250 | NOTE: In the case where the user removed a removable-media-disk even if |
251 | there's still dirty data not synced on disk (due a bug in the device driver |
252 | or due an error of the user), by not destroying the dirty buffers we could |
253 | generate corruption also on the next media inserted, thus a parameter is |
254 | necessary to handle this case in the most safe way possible (trying |
255 | to not corrupt also the new disk inserted with the data belonging to |
256 | the old now corrupted disk). Also for the ramdisk the natural thing |
257 | to do in order to release the ramdisk memory is to destroy dirty buffers. |
258 | |
259 | These are two special cases. Normal usage imply the device driver |
260 | to issue a sync on the device (without waiting I/O completion) and |
261 | then an invalidate_buffers call that doesn't trash dirty buffers. |
262 | |
263 | For handling cache coherency with the blkdev pagecache the 'update' case |
264 | is been introduced. It is needed to re-read from disk any pinned |
265 | buffer. NOTE: re-reading from disk is destructive so we can do it only |
266 | when we assume nobody is changing the buffercache under our I/O and when |
267 | we think the disk contains more recent information than the buffercache. |
268 | The update == 1 pass marks the buffers we need to update, the update == 2 |
269 | pass does the actual I/O. */ |
270 | void invalidate_bdev(struct block_device *bdev) |
271 | { |
272 | struct address_space *mapping = bdev->bd_inode->i_mapping; |
273 | |
274 | if (mapping->nrpages == 0) |
275 | return; |
276 | |
277 | invalidate_bh_lrus(); |
278 | lru_add_drain_all(); /* make sure all lru add caches are flushed */ |
279 | invalidate_mapping_pages(mapping, 0, -1); |
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); |
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, *prev_mapping = NULL; |
753 | int err = 0, err2; |
754 | |
755 | INIT_LIST_HEAD(&tmp); |
756 | |
757 | spin_lock(lock); |
758 | while (!list_empty(list)) { |
759 | bh = BH_ENTRY(list->next); |
760 | mapping = bh->b_assoc_map; |
761 | __remove_assoc_queue(bh); |
762 | /* Avoid race with mark_buffer_dirty_inode() which does |
763 | * a lockless check and we rely on seeing the dirty bit */ |
764 | smp_mb(); |
765 | if (buffer_dirty(bh) || buffer_locked(bh)) { |
766 | list_add(&bh->b_assoc_buffers, &tmp); |
767 | bh->b_assoc_map = mapping; |
768 | if (buffer_dirty(bh)) { |
769 | get_bh(bh); |
770 | spin_unlock(lock); |
771 | /* |
772 | * Ensure any pending I/O completes so that |
773 | * write_dirty_buffer() actually writes the |
774 | * current contents - it is a noop if I/O is |
775 | * still in flight on potentially older |
776 | * contents. |
777 | */ |
778 | write_dirty_buffer(bh, WRITE_SYNC_PLUG); |
779 | |
780 | /* |
781 | * Kick off IO for the previous mapping. Note |
782 | * that we will not run the very last mapping, |
783 | * wait_on_buffer() will do that for us |
784 | * through sync_buffer(). |
785 | */ |
786 | if (prev_mapping && prev_mapping != mapping) |
787 | blk_run_address_space(prev_mapping); |
788 | prev_mapping = mapping; |
789 | |
790 | brelse(bh); |
791 | spin_lock(lock); |
792 | } |
793 | } |
794 | } |
795 | |
796 | while (!list_empty(&tmp)) { |
797 | bh = BH_ENTRY(tmp.prev); |
798 | get_bh(bh); |
799 | mapping = bh->b_assoc_map; |
800 | __remove_assoc_queue(bh); |
801 | /* Avoid race with mark_buffer_dirty_inode() which does |
802 | * a lockless check and we rely on seeing the dirty bit */ |
803 | smp_mb(); |
804 | if (buffer_dirty(bh)) { |
805 | list_add(&bh->b_assoc_buffers, |
806 | &mapping->private_list); |
807 | bh->b_assoc_map = mapping; |
808 | } |
809 | spin_unlock(lock); |
810 | wait_on_buffer(bh); |
811 | if (!buffer_uptodate(bh)) |
812 | err = -EIO; |
813 | brelse(bh); |
814 | spin_lock(lock); |
815 | } |
816 | |
817 | spin_unlock(lock); |
818 | err2 = osync_buffers_list(lock, list); |
819 | if (err) |
820 | return err; |
821 | else |
822 | return err2; |
823 | } |
824 | |
825 | /* |
826 | * Invalidate any and all dirty buffers on a given inode. We are |
827 | * probably unmounting the fs, but that doesn't mean we have already |
828 | * done a sync(). Just drop the buffers from the inode list. |
829 | * |
830 | * NOTE: we take the inode's blockdev's mapping's private_lock. Which |
831 | * assumes that all the buffers are against the blockdev. Not true |
832 | * for reiserfs. |
833 | */ |
834 | void invalidate_inode_buffers(struct inode *inode) |
835 | { |
836 | if (inode_has_buffers(inode)) { |
837 | struct address_space *mapping = &inode->i_data; |
838 | struct list_head *list = &mapping->private_list; |
839 | struct address_space *buffer_mapping = mapping->assoc_mapping; |
840 | |
841 | spin_lock(&buffer_mapping->private_lock); |
842 | while (!list_empty(list)) |
843 | __remove_assoc_queue(BH_ENTRY(list->next)); |
844 | spin_unlock(&buffer_mapping->private_lock); |
845 | } |
846 | } |
847 | EXPORT_SYMBOL(invalidate_inode_buffers); |
848 | |
849 | /* |
850 | * Remove any clean buffers from the inode's buffer list. This is called |
851 | * when we're trying to free the inode itself. Those buffers can pin it. |
852 | * |
853 | * Returns true if all buffers were removed. |
854 | */ |
855 | int remove_inode_buffers(struct inode *inode) |
856 | { |
857 | int ret = 1; |
858 | |
859 | if (inode_has_buffers(inode)) { |
860 | struct address_space *mapping = &inode->i_data; |
861 | struct list_head *list = &mapping->private_list; |
862 | struct address_space *buffer_mapping = mapping->assoc_mapping; |
863 | |
864 | spin_lock(&buffer_mapping->private_lock); |
865 | while (!list_empty(list)) { |
866 | struct buffer_head *bh = BH_ENTRY(list->next); |
867 | if (buffer_dirty(bh)) { |
868 | ret = 0; |
869 | break; |
870 | } |
871 | __remove_assoc_queue(bh); |
872 | } |
873 | spin_unlock(&buffer_mapping->private_lock); |
874 | } |
875 | return ret; |
876 | } |
877 | |
878 | /* |
879 | * Create the appropriate buffers when given a page for data area and |
880 | * the size of each buffer.. Use the bh->b_this_page linked list to |
881 | * follow the buffers created. Return NULL if unable to create more |
882 | * buffers. |
883 | * |
884 | * The retry flag is used to differentiate async IO (paging, swapping) |
885 | * which may not fail from ordinary buffer allocations. |
886 | */ |
887 | struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, |
888 | int retry) |
889 | { |
890 | struct buffer_head *bh, *head; |
891 | long offset; |
892 | |
893 | try_again: |
894 | head = NULL; |
895 | offset = PAGE_SIZE; |
896 | while ((offset -= size) >= 0) { |
897 | bh = alloc_buffer_head(GFP_NOFS); |
898 | if (!bh) |
899 | goto no_grow; |
900 | |
901 | bh->b_bdev = NULL; |
902 | bh->b_this_page = head; |
903 | bh->b_blocknr = -1; |
904 | head = bh; |
905 | |
906 | bh->b_state = 0; |
907 | atomic_set(&bh->b_count, 0); |
908 | bh->b_size = size; |
909 | |
910 | /* Link the buffer to its page */ |
911 | set_bh_page(bh, page, offset); |
912 | |
913 | init_buffer(bh, NULL, NULL); |
914 | } |
915 | return head; |
916 | /* |
917 | * In case anything failed, we just free everything we got. |
918 | */ |
919 | no_grow: |
920 | if (head) { |
921 | do { |
922 | bh = head; |
923 | head = head->b_this_page; |
924 | free_buffer_head(bh); |
925 | } while (head); |
926 | } |
927 | |
928 | /* |
929 | * Return failure for non-async IO requests. Async IO requests |
930 | * are not allowed to fail, so we have to wait until buffer heads |
931 | * become available. But we don't want tasks sleeping with |
932 | * partially complete buffers, so all were released above. |
933 | */ |
934 | if (!retry) |
935 | return NULL; |
936 | |
937 | /* We're _really_ low on memory. Now we just |
938 | * wait for old buffer heads to become free due to |
939 | * finishing IO. Since this is an async request and |
940 | * the reserve list is empty, we're sure there are |
941 | * async buffer heads in use. |
942 | */ |
943 | free_more_memory(); |
944 | goto try_again; |
945 | } |
946 | EXPORT_SYMBOL_GPL(alloc_page_buffers); |
947 | |
948 | static inline void |
949 | link_dev_buffers(struct page *page, struct buffer_head *head) |
950 | { |
951 | struct buffer_head *bh, *tail; |
952 | |
953 | bh = head; |
954 | do { |
955 | tail = bh; |
956 | bh = bh->b_this_page; |
957 | } while (bh); |
958 | tail->b_this_page = head; |
959 | attach_page_buffers(page, head); |
960 | } |
961 | |
962 | /* |
963 | * Initialise the state of a blockdev page's buffers. |
964 | */ |
965 | static void |
966 | init_page_buffers(struct page *page, struct block_device *bdev, |
967 | sector_t block, int size) |
968 | { |
969 | struct buffer_head *head = page_buffers(page); |
970 | struct buffer_head *bh = head; |
971 | int uptodate = PageUptodate(page); |
972 | |
973 | do { |
974 | if (!buffer_mapped(bh)) { |
975 | init_buffer(bh, NULL, NULL); |
976 | bh->b_bdev = bdev; |
977 | bh->b_blocknr = block; |
978 | if (uptodate) |
979 | set_buffer_uptodate(bh); |
980 | set_buffer_mapped(bh); |
981 | } |
982 | block++; |
983 | bh = bh->b_this_page; |
984 | } while (bh != head); |
985 | } |
986 | |
987 | /* |
988 | * Create the page-cache page that contains the requested block. |
989 | * |
990 | * This is user purely for blockdev mappings. |
991 | */ |
992 | static struct page * |
993 | grow_dev_page(struct block_device *bdev, sector_t block, |
994 | pgoff_t index, int size) |
995 | { |
996 | struct inode *inode = bdev->bd_inode; |
997 | struct page *page; |
998 | struct buffer_head *bh; |
999 | |
1000 | page = find_or_create_page(inode->i_mapping, index, |
1001 | (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE); |
1002 | if (!page) |
1003 | return NULL; |
1004 | |
1005 | BUG_ON(!PageLocked(page)); |
1006 | |
1007 | if (page_has_buffers(page)) { |
1008 | bh = page_buffers(page); |
1009 | if (bh->b_size == size) { |
1010 | init_page_buffers(page, bdev, block, size); |
1011 | return page; |
1012 | } |
1013 | if (!try_to_free_buffers(page)) |
1014 | goto failed; |
1015 | } |
1016 | |
1017 | /* |
1018 | * Allocate some buffers for this page |
1019 | */ |
1020 | bh = alloc_page_buffers(page, size, 0); |
1021 | if (!bh) |
1022 | goto failed; |
1023 | |
1024 | /* |
1025 | * Link the page to the buffers and initialise them. Take the |
1026 | * lock to be atomic wrt __find_get_block(), which does not |
1027 | * run under the page lock. |
1028 | */ |
1029 | spin_lock(&inode->i_mapping->private_lock); |
1030 | link_dev_buffers(page, bh); |
1031 | init_page_buffers(page, bdev, block, size); |
1032 | spin_unlock(&inode->i_mapping->private_lock); |
1033 | return page; |
1034 | |
1035 | failed: |
1036 | BUG(); |
1037 | unlock_page(page); |
1038 | page_cache_release(page); |
1039 | return NULL; |
1040 | } |
1041 | |
1042 | /* |
1043 | * Create buffers for the specified block device block's page. If |
1044 | * that page was dirty, the buffers are set dirty also. |
1045 | */ |
1046 | static int |
1047 | grow_buffers(struct block_device *bdev, sector_t block, int size) |
1048 | { |
1049 | struct page *page; |
1050 | pgoff_t index; |
1051 | int sizebits; |
1052 | |
1053 | sizebits = -1; |
1054 | do { |
1055 | sizebits++; |
1056 | } while ((size << sizebits) < PAGE_SIZE); |
1057 | |
1058 | index = block >> sizebits; |
1059 | |
1060 | /* |
1061 | * Check for a block which wants to lie outside our maximum possible |
1062 | * pagecache index. (this comparison is done using sector_t types). |
1063 | */ |
1064 | if (unlikely(index != block >> sizebits)) { |
1065 | char b[BDEVNAME_SIZE]; |
1066 | |
1067 | printk(KERN_ERR "%s: requested out-of-range block %llu for " |
1068 | "device %s\n", |
1069 | __func__, (unsigned long long)block, |
1070 | bdevname(bdev, b)); |
1071 | return -EIO; |
1072 | } |
1073 | block = index << sizebits; |
1074 | /* Create a page with the proper size buffers.. */ |
1075 | page = grow_dev_page(bdev, block, index, size); |
1076 | if (!page) |
1077 | return 0; |
1078 | unlock_page(page); |
1079 | page_cache_release(page); |
1080 | return 1; |
1081 | } |
1082 | |
1083 | static struct buffer_head * |
1084 | __getblk_slow(struct block_device *bdev, sector_t block, int size) |
1085 | { |
1086 | /* Size must be multiple of hard sectorsize */ |
1087 | if (unlikely(size & (bdev_logical_block_size(bdev)-1) || |
1088 | (size < 512 || size > PAGE_SIZE))) { |
1089 | printk(KERN_ERR "getblk(): invalid block size %d requested\n", |
1090 | size); |
1091 | printk(KERN_ERR "logical block size: %d\n", |
1092 | bdev_logical_block_size(bdev)); |
1093 | |
1094 | dump_stack(); |
1095 | return NULL; |
1096 | } |
1097 | |
1098 | for (;;) { |
1099 | struct buffer_head * bh; |
1100 | int ret; |
1101 | |
1102 | bh = __find_get_block(bdev, block, size); |
1103 | if (bh) |
1104 | return bh; |
1105 | |
1106 | ret = grow_buffers(bdev, block, size); |
1107 | if (ret < 0) |
1108 | return NULL; |
1109 | if (ret == 0) |
1110 | free_more_memory(); |
1111 | } |
1112 | } |
1113 | |
1114 | /* |
1115 | * The relationship between dirty buffers and dirty pages: |
1116 | * |
1117 | * Whenever a page has any dirty buffers, the page's dirty bit is set, and |
1118 | * the page is tagged dirty in its radix tree. |
1119 | * |
1120 | * At all times, the dirtiness of the buffers represents the dirtiness of |
1121 | * subsections of the page. If the page has buffers, the page dirty bit is |
1122 | * merely a hint about the true dirty state. |
1123 | * |
1124 | * When a page is set dirty in its entirety, all its buffers are marked dirty |
1125 | * (if the page has buffers). |
1126 | * |
1127 | * When a buffer is marked dirty, its page is dirtied, but the page's other |
1128 | * buffers are not. |
1129 | * |
1130 | * Also. When blockdev buffers are explicitly read with bread(), they |
1131 | * individually become uptodate. But their backing page remains not |
1132 | * uptodate - even if all of its buffers are uptodate. A subsequent |
1133 | * block_read_full_page() against that page will discover all the uptodate |
1134 | * buffers, will set the page uptodate and will perform no I/O. |
1135 | */ |
1136 | |
1137 | /** |
1138 | * mark_buffer_dirty - mark a buffer_head as needing writeout |
1139 | * @bh: the buffer_head to mark dirty |
1140 | * |
1141 | * mark_buffer_dirty() will set the dirty bit against the buffer, then set its |
1142 | * backing page dirty, then tag the page as dirty in its address_space's radix |
1143 | * tree and then attach the address_space's inode to its superblock's dirty |
1144 | * inode list. |
1145 | * |
1146 | * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock, |
1147 | * mapping->tree_lock and the global inode_lock. |
1148 | */ |
1149 | void mark_buffer_dirty(struct buffer_head *bh) |
1150 | { |
1151 | WARN_ON_ONCE(!buffer_uptodate(bh)); |
1152 | |
1153 | /* |
1154 | * Very *carefully* optimize the it-is-already-dirty case. |
1155 | * |
1156 | * Don't let the final "is it dirty" escape to before we |
1157 | * perhaps modified the buffer. |
1158 | */ |
1159 | if (buffer_dirty(bh)) { |
1160 | smp_mb(); |
1161 | if (buffer_dirty(bh)) |
1162 | return; |
1163 | } |
1164 | |
1165 | if (!test_set_buffer_dirty(bh)) { |
1166 | struct page *page = bh->b_page; |
1167 | if (!TestSetPageDirty(page)) { |
1168 | struct address_space *mapping = page_mapping(page); |
1169 | if (mapping) |
1170 | __set_page_dirty(page, mapping, 0); |
1171 | } |
1172 | } |
1173 | } |
1174 | EXPORT_SYMBOL(mark_buffer_dirty); |
1175 | |
1176 | /* |
1177 | * Decrement a buffer_head's reference count. If all buffers against a page |
1178 | * have zero reference count, are clean and unlocked, and if the page is clean |
1179 | * and unlocked then try_to_free_buffers() may strip the buffers from the page |
1180 | * in preparation for freeing it (sometimes, rarely, buffers are removed from |
1181 | * a page but it ends up not being freed, and buffers may later be reattached). |
1182 | */ |
1183 | void __brelse(struct buffer_head * buf) |
1184 | { |
1185 | if (atomic_read(&buf->b_count)) { |
1186 | put_bh(buf); |
1187 | return; |
1188 | } |
1189 | WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n"); |
1190 | } |
1191 | EXPORT_SYMBOL(__brelse); |
1192 | |
1193 | /* |
1194 | * bforget() is like brelse(), except it discards any |
1195 | * potentially dirty data. |
1196 | */ |
1197 | void __bforget(struct buffer_head *bh) |
1198 | { |
1199 | clear_buffer_dirty(bh); |
1200 | if (bh->b_assoc_map) { |
1201 | struct address_space *buffer_mapping = bh->b_page->mapping; |
1202 | |
1203 | spin_lock(&buffer_mapping->private_lock); |
1204 | list_del_init(&bh->b_assoc_buffers); |
1205 | bh->b_assoc_map = NULL; |
1206 | spin_unlock(&buffer_mapping->private_lock); |
1207 | } |
1208 | __brelse(bh); |
1209 | } |
1210 | EXPORT_SYMBOL(__bforget); |
1211 | |
1212 | static struct buffer_head *__bread_slow(struct buffer_head *bh) |
1213 | { |
1214 | lock_buffer(bh); |
1215 | if (buffer_uptodate(bh)) { |
1216 | unlock_buffer(bh); |
1217 | return bh; |
1218 | } else { |
1219 | get_bh(bh); |
1220 | bh->b_end_io = end_buffer_read_sync; |
1221 | submit_bh(READ, bh); |
1222 | wait_on_buffer(bh); |
1223 | if (buffer_uptodate(bh)) |
1224 | return bh; |
1225 | } |
1226 | brelse(bh); |
1227 | return NULL; |
1228 | } |
1229 | |
1230 | /* |
1231 | * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block(). |
1232 | * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their |
1233 | * refcount elevated by one when they're in an LRU. A buffer can only appear |
1234 | * once in a particular CPU's LRU. A single buffer can be present in multiple |
1235 | * CPU's LRUs at the same time. |
1236 | * |
1237 | * This is a transparent caching front-end to sb_bread(), sb_getblk() and |
1238 | * sb_find_get_block(). |
1239 | * |
1240 | * The LRUs themselves only need locking against invalidate_bh_lrus. We use |
1241 | * a local interrupt disable for that. |
1242 | */ |
1243 | |
1244 | #define BH_LRU_SIZE 8 |
1245 | |
1246 | struct bh_lru { |
1247 | struct buffer_head *bhs[BH_LRU_SIZE]; |
1248 | }; |
1249 | |
1250 | static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }}; |
1251 | |
1252 | #ifdef CONFIG_SMP |
1253 | #define bh_lru_lock() local_irq_disable() |
1254 | #define bh_lru_unlock() local_irq_enable() |
1255 | #else |
1256 | #define bh_lru_lock() preempt_disable() |
1257 | #define bh_lru_unlock() preempt_enable() |
1258 | #endif |
1259 | |
1260 | static inline void check_irqs_on(void) |
1261 | { |
1262 | #ifdef irqs_disabled |
1263 | BUG_ON(irqs_disabled()); |
1264 | #endif |
1265 | } |
1266 | |
1267 | /* |
1268 | * The LRU management algorithm is dopey-but-simple. Sorry. |
1269 | */ |
1270 | static void bh_lru_install(struct buffer_head *bh) |
1271 | { |
1272 | struct buffer_head *evictee = NULL; |
1273 | |
1274 | check_irqs_on(); |
1275 | bh_lru_lock(); |
1276 | if (__this_cpu_read(bh_lrus.bhs[0]) != bh) { |
1277 | struct buffer_head *bhs[BH_LRU_SIZE]; |
1278 | int in; |
1279 | int out = 0; |
1280 | |
1281 | get_bh(bh); |
1282 | bhs[out++] = bh; |
1283 | for (in = 0; in < BH_LRU_SIZE; in++) { |
1284 | struct buffer_head *bh2 = |
1285 | __this_cpu_read(bh_lrus.bhs[in]); |
1286 | |
1287 | if (bh2 == bh) { |
1288 | __brelse(bh2); |
1289 | } else { |
1290 | if (out >= BH_LRU_SIZE) { |
1291 | BUG_ON(evictee != NULL); |
1292 | evictee = bh2; |
1293 | } else { |
1294 | bhs[out++] = bh2; |
1295 | } |
1296 | } |
1297 | } |
1298 | while (out < BH_LRU_SIZE) |
1299 | bhs[out++] = NULL; |
1300 | memcpy(__this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs)); |
1301 | } |
1302 | bh_lru_unlock(); |
1303 | |
1304 | if (evictee) |
1305 | __brelse(evictee); |
1306 | } |
1307 | |
1308 | /* |
1309 | * Look up the bh in this cpu's LRU. If it's there, move it to the head. |
1310 | */ |
1311 | static struct buffer_head * |
1312 | lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size) |
1313 | { |
1314 | struct buffer_head *ret = NULL; |
1315 | unsigned int i; |
1316 | |
1317 | check_irqs_on(); |
1318 | bh_lru_lock(); |
1319 | for (i = 0; i < BH_LRU_SIZE; i++) { |
1320 | struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]); |
1321 | |
1322 | if (bh && bh->b_bdev == bdev && |
1323 | bh->b_blocknr == block && bh->b_size == size) { |
1324 | if (i) { |
1325 | while (i) { |
1326 | __this_cpu_write(bh_lrus.bhs[i], |
1327 | __this_cpu_read(bh_lrus.bhs[i - 1])); |
1328 | i--; |
1329 | } |
1330 | __this_cpu_write(bh_lrus.bhs[0], bh); |
1331 | } |
1332 | get_bh(bh); |
1333 | ret = bh; |
1334 | break; |
1335 | } |
1336 | } |
1337 | bh_lru_unlock(); |
1338 | return ret; |
1339 | } |
1340 | |
1341 | /* |
1342 | * Perform a pagecache lookup for the matching buffer. If it's there, refresh |
1343 | * it in the LRU and mark it as accessed. If it is not present then return |
1344 | * NULL |
1345 | */ |
1346 | struct buffer_head * |
1347 | __find_get_block(struct block_device *bdev, sector_t block, unsigned size) |
1348 | { |
1349 | struct buffer_head *bh = lookup_bh_lru(bdev, block, size); |
1350 | |
1351 | if (bh == NULL) { |
1352 | bh = __find_get_block_slow(bdev, block); |
1353 | if (bh) |
1354 | bh_lru_install(bh); |
1355 | } |
1356 | if (bh) |
1357 | touch_buffer(bh); |
1358 | return bh; |
1359 | } |
1360 | EXPORT_SYMBOL(__find_get_block); |
1361 | |
1362 | /* |
1363 | * __getblk will locate (and, if necessary, create) the buffer_head |
1364 | * which corresponds to the passed block_device, block and size. The |
1365 | * returned buffer has its reference count incremented. |
1366 | * |
1367 | * __getblk() cannot fail - it just keeps trying. If you pass it an |
1368 | * illegal block number, __getblk() will happily return a buffer_head |
1369 | * which represents the non-existent block. Very weird. |
1370 | * |
1371 | * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers() |
1372 | * attempt is failing. FIXME, perhaps? |
1373 | */ |
1374 | struct buffer_head * |
1375 | __getblk(struct block_device *bdev, sector_t block, unsigned size) |
1376 | { |
1377 | struct buffer_head *bh = __find_get_block(bdev, block, size); |
1378 | |
1379 | might_sleep(); |
1380 | if (bh == NULL) |
1381 | bh = __getblk_slow(bdev, block, size); |
1382 | return bh; |
1383 | } |
1384 | EXPORT_SYMBOL(__getblk); |
1385 | |
1386 | /* |
1387 | * Do async read-ahead on a buffer.. |
1388 | */ |
1389 | void __breadahead(struct block_device *bdev, sector_t block, unsigned size) |
1390 | { |
1391 | struct buffer_head *bh = __getblk(bdev, block, size); |
1392 | if (likely(bh)) { |
1393 | ll_rw_block(READA, 1, &bh); |
1394 | brelse(bh); |
1395 | } |
1396 | } |
1397 | EXPORT_SYMBOL(__breadahead); |
1398 | |
1399 | /** |
1400 | * __bread() - reads a specified block and returns the bh |
1401 | * @bdev: the block_device to read from |
1402 | * @block: number of block |
1403 | * @size: size (in bytes) to read |
1404 | * |
1405 | * Reads a specified block, and returns buffer head that contains it. |
1406 | * It returns NULL if the block was unreadable. |
1407 | */ |
1408 | struct buffer_head * |
1409 | __bread(struct block_device *bdev, sector_t block, unsigned size) |
1410 | { |
1411 | struct buffer_head *bh = __getblk(bdev, block, size); |
1412 | |
1413 | if (likely(bh) && !buffer_uptodate(bh)) |
1414 | bh = __bread_slow(bh); |
1415 | return bh; |
1416 | } |
1417 | EXPORT_SYMBOL(__bread); |
1418 | |
1419 | /* |
1420 | * invalidate_bh_lrus() is called rarely - but not only at unmount. |
1421 | * This doesn't race because it runs in each cpu either in irq |
1422 | * or with preempt disabled. |
1423 | */ |
1424 | static void invalidate_bh_lru(void *arg) |
1425 | { |
1426 | struct bh_lru *b = &get_cpu_var(bh_lrus); |
1427 | int i; |
1428 | |
1429 | for (i = 0; i < BH_LRU_SIZE; i++) { |
1430 | brelse(b->bhs[i]); |
1431 | b->bhs[i] = NULL; |
1432 | } |
1433 | put_cpu_var(bh_lrus); |
1434 | } |
1435 | |
1436 | void invalidate_bh_lrus(void) |
1437 | { |
1438 | on_each_cpu(invalidate_bh_lru, NULL, 1); |
1439 | } |
1440 | EXPORT_SYMBOL_GPL(invalidate_bh_lrus); |
1441 | |
1442 | void set_bh_page(struct buffer_head *bh, |
1443 | struct page *page, unsigned long offset) |
1444 | { |
1445 | bh->b_page = page; |
1446 | BUG_ON(offset >= PAGE_SIZE); |
1447 | if (PageHighMem(page)) |
1448 | /* |
1449 | * This catches illegal uses and preserves the offset: |
1450 | */ |
1451 | bh->b_data = (char *)(0 + offset); |
1452 | else |
1453 | bh->b_data = page_address(page) + offset; |
1454 | } |
1455 | EXPORT_SYMBOL(set_bh_page); |
1456 | |
1457 | /* |
1458 | * Called when truncating a buffer on a page completely. |
1459 | */ |
1460 | static void discard_buffer(struct buffer_head * bh) |
1461 | { |
1462 | lock_buffer(bh); |
1463 | clear_buffer_dirty(bh); |
1464 | bh->b_bdev = NULL; |
1465 | clear_buffer_mapped(bh); |
1466 | clear_buffer_req(bh); |
1467 | clear_buffer_new(bh); |
1468 | clear_buffer_delay(bh); |
1469 | clear_buffer_unwritten(bh); |
1470 | unlock_buffer(bh); |
1471 | } |
1472 | |
1473 | /** |
1474 | * block_invalidatepage - invalidate part of all of a buffer-backed page |
1475 | * |
1476 | * @page: the page which is affected |
1477 | * @offset: the index of the truncation point |
1478 | * |
1479 | * block_invalidatepage() is called when all or part of the page has become |
1480 | * invalidatedby a truncate operation. |
1481 | * |
1482 | * block_invalidatepage() does not have to release all buffers, but it must |
1483 | * ensure that no dirty buffer is left outside @offset and that no I/O |
1484 | * is underway against any of the blocks which are outside the truncation |
1485 | * point. Because the caller is about to free (and possibly reuse) those |
1486 | * blocks on-disk. |
1487 | */ |
1488 | void block_invalidatepage(struct page *page, unsigned long offset) |
1489 | { |
1490 | struct buffer_head *head, *bh, *next; |
1491 | unsigned int curr_off = 0; |
1492 | |
1493 | BUG_ON(!PageLocked(page)); |
1494 | if (!page_has_buffers(page)) |
1495 | goto out; |
1496 | |
1497 | head = page_buffers(page); |
1498 | bh = head; |
1499 | do { |
1500 | unsigned int next_off = curr_off + bh->b_size; |
1501 | next = bh->b_this_page; |
1502 | |
1503 | /* |
1504 | * is this block fully invalidated? |
1505 | */ |
1506 | if (offset <= curr_off) |
1507 | discard_buffer(bh); |
1508 | curr_off = next_off; |
1509 | bh = next; |
1510 | } while (bh != head); |
1511 | |
1512 | /* |
1513 | * We release buffers only if the entire page is being invalidated. |
1514 | * The get_block cached value has been unconditionally invalidated, |
1515 | * so real IO is not possible anymore. |
1516 | */ |
1517 | if (offset == 0) |
1518 | try_to_release_page(page, 0); |
1519 | out: |
1520 | return; |
1521 | } |
1522 | EXPORT_SYMBOL(block_invalidatepage); |
1523 | |
1524 | /* |
1525 | * We attach and possibly dirty the buffers atomically wrt |
1526 | * __set_page_dirty_buffers() via private_lock. try_to_free_buffers |
1527 | * is already excluded via the page lock. |
1528 | */ |
1529 | void create_empty_buffers(struct page *page, |
1530 | unsigned long blocksize, unsigned long b_state) |
1531 | { |
1532 | struct buffer_head *bh, *head, *tail; |
1533 | |
1534 | head = alloc_page_buffers(page, blocksize, 1); |
1535 | bh = head; |
1536 | do { |
1537 | bh->b_state |= b_state; |
1538 | tail = bh; |
1539 | bh = bh->b_this_page; |
1540 | } while (bh); |
1541 | tail->b_this_page = head; |
1542 | |
1543 | spin_lock(&page->mapping->private_lock); |
1544 | if (PageUptodate(page) || PageDirty(page)) { |
1545 | bh = head; |
1546 | do { |
1547 | if (PageDirty(page)) |
1548 | set_buffer_dirty(bh); |
1549 | if (PageUptodate(page)) |
1550 | set_buffer_uptodate(bh); |
1551 | bh = bh->b_this_page; |
1552 | } while (bh != head); |
1553 | } |
1554 | attach_page_buffers(page, head); |
1555 | spin_unlock(&page->mapping->private_lock); |
1556 | } |
1557 | EXPORT_SYMBOL(create_empty_buffers); |
1558 | |
1559 | /* |
1560 | * We are taking a block for data and we don't want any output from any |
1561 | * buffer-cache aliases starting from return from that function and |
1562 | * until the moment when something will explicitly mark the buffer |
1563 | * dirty (hopefully that will not happen until we will free that block ;-) |
1564 | * We don't even need to mark it not-uptodate - nobody can expect |
1565 | * anything from a newly allocated buffer anyway. We used to used |
1566 | * unmap_buffer() for such invalidation, but that was wrong. We definitely |
1567 | * don't want to mark the alias unmapped, for example - it would confuse |
1568 | * anyone who might pick it with bread() afterwards... |
1569 | * |
1570 | * Also.. Note that bforget() doesn't lock the buffer. So there can |
1571 | * be writeout I/O going on against recently-freed buffers. We don't |
1572 | * wait on that I/O in bforget() - it's more efficient to wait on the I/O |
1573 | * only if we really need to. That happens here. |
1574 | */ |
1575 | void unmap_underlying_metadata(struct block_device *bdev, sector_t block) |
1576 | { |
1577 | struct buffer_head *old_bh; |
1578 | |
1579 | might_sleep(); |
1580 | |
1581 | old_bh = __find_get_block_slow(bdev, block); |
1582 | if (old_bh) { |
1583 | clear_buffer_dirty(old_bh); |
1584 | wait_on_buffer(old_bh); |
1585 | clear_buffer_req(old_bh); |
1586 | __brelse(old_bh); |
1587 | } |
1588 | } |
1589 | EXPORT_SYMBOL(unmap_underlying_metadata); |
1590 | |
1591 | /* |
1592 | * NOTE! All mapped/uptodate combinations are valid: |
1593 | * |
1594 | * Mapped Uptodate Meaning |
1595 | * |
1596 | * No No "unknown" - must do get_block() |
1597 | * No Yes "hole" - zero-filled |
1598 | * Yes No "allocated" - allocated on disk, not read in |
1599 | * Yes Yes "valid" - allocated and up-to-date in memory. |
1600 | * |
1601 | * "Dirty" is valid only with the last case (mapped+uptodate). |
1602 | */ |
1603 | |
1604 | /* |
1605 | * While block_write_full_page is writing back the dirty buffers under |
1606 | * the page lock, whoever dirtied the buffers may decide to clean them |
1607 | * again at any time. We handle that by only looking at the buffer |
1608 | * state inside lock_buffer(). |
1609 | * |
1610 | * If block_write_full_page() is called for regular writeback |
1611 | * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a |
1612 | * locked buffer. This only can happen if someone has written the buffer |
1613 | * directly, with submit_bh(). At the address_space level PageWriteback |
1614 | * prevents this contention from occurring. |
1615 | * |
1616 | * If block_write_full_page() is called with wbc->sync_mode == |
1617 | * WB_SYNC_ALL, the writes are posted using WRITE_SYNC_PLUG; this |
1618 | * causes the writes to be flagged as synchronous writes, but the |
1619 | * block device queue will NOT be unplugged, since usually many pages |
1620 | * will be pushed to the out before the higher-level caller actually |
1621 | * waits for the writes to be completed. The various wait functions, |
1622 | * such as wait_on_writeback_range() will ultimately call sync_page() |
1623 | * which will ultimately call blk_run_backing_dev(), which will end up |
1624 | * unplugging the device queue. |
1625 | */ |
1626 | static int __block_write_full_page(struct inode *inode, struct page *page, |
1627 | get_block_t *get_block, struct writeback_control *wbc, |
1628 | bh_end_io_t *handler) |
1629 | { |
1630 | int err; |
1631 | sector_t block; |
1632 | sector_t last_block; |
1633 | struct buffer_head *bh, *head; |
1634 | const unsigned blocksize = 1 << inode->i_blkbits; |
1635 | int nr_underway = 0; |
1636 | int write_op = (wbc->sync_mode == WB_SYNC_ALL ? |
1637 | WRITE_SYNC_PLUG : WRITE); |
1638 | |
1639 | BUG_ON(!PageLocked(page)); |
1640 | |
1641 | last_block = (i_size_read(inode) - 1) >> inode->i_blkbits; |
1642 | |
1643 | if (!page_has_buffers(page)) { |
1644 | create_empty_buffers(page, blocksize, |
1645 | (1 << BH_Dirty)|(1 << BH_Uptodate)); |
1646 | } |
1647 | |
1648 | /* |
1649 | * Be very careful. We have no exclusion from __set_page_dirty_buffers |
1650 | * here, and the (potentially unmapped) buffers may become dirty at |
1651 | * any time. If a buffer becomes dirty here after we've inspected it |
1652 | * then we just miss that fact, and the page stays dirty. |
1653 | * |
1654 | * Buffers outside i_size may be dirtied by __set_page_dirty_buffers; |
1655 | * handle that here by just cleaning them. |
1656 | */ |
1657 | |
1658 | block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
1659 | head = page_buffers(page); |
1660 | bh = head; |
1661 | |
1662 | /* |
1663 | * Get all the dirty buffers mapped to disk addresses and |
1664 | * handle any aliases from the underlying blockdev's mapping. |
1665 | */ |
1666 | do { |
1667 | if (block > last_block) { |
1668 | /* |
1669 | * mapped buffers outside i_size will occur, because |
1670 | * this page can be outside i_size when there is a |
1671 | * truncate in progress. |
1672 | */ |
1673 | /* |
1674 | * The buffer was zeroed by block_write_full_page() |
1675 | */ |
1676 | clear_buffer_dirty(bh); |
1677 | set_buffer_uptodate(bh); |
1678 | } else if ((!buffer_mapped(bh) || buffer_delay(bh)) && |
1679 | buffer_dirty(bh)) { |
1680 | WARN_ON(bh->b_size != blocksize); |
1681 | err = get_block(inode, block, bh, 1); |
1682 | if (err) |
1683 | goto recover; |
1684 | clear_buffer_delay(bh); |
1685 | if (buffer_new(bh)) { |
1686 | /* blockdev mappings never come here */ |
1687 | clear_buffer_new(bh); |
1688 | unmap_underlying_metadata(bh->b_bdev, |
1689 | bh->b_blocknr); |
1690 | } |
1691 | } |
1692 | bh = bh->b_this_page; |
1693 | block++; |
1694 | } while (bh != head); |
1695 | |
1696 | do { |
1697 | if (!buffer_mapped(bh)) |
1698 | continue; |
1699 | /* |
1700 | * If it's a fully non-blocking write attempt and we cannot |
1701 | * lock the buffer then redirty the page. Note that this can |
1702 | * potentially cause a busy-wait loop from writeback threads |
1703 | * and kswapd activity, but those code paths have their own |
1704 | * higher-level throttling. |
1705 | */ |
1706 | if (wbc->sync_mode != WB_SYNC_NONE) { |
1707 | lock_buffer(bh); |
1708 | } else if (!trylock_buffer(bh)) { |
1709 | redirty_page_for_writepage(wbc, page); |
1710 | continue; |
1711 | } |
1712 | if (test_clear_buffer_dirty(bh)) { |
1713 | mark_buffer_async_write_endio(bh, handler); |
1714 | } else { |
1715 | unlock_buffer(bh); |
1716 | } |
1717 | } while ((bh = bh->b_this_page) != head); |
1718 | |
1719 | /* |
1720 | * The page and its buffers are protected by PageWriteback(), so we can |
1721 | * drop the bh refcounts early. |
1722 | */ |
1723 | BUG_ON(PageWriteback(page)); |
1724 | set_page_writeback(page); |
1725 | |
1726 | do { |
1727 | struct buffer_head *next = bh->b_this_page; |
1728 | if (buffer_async_write(bh)) { |
1729 | submit_bh(write_op, bh); |
1730 | nr_underway++; |
1731 | } |
1732 | bh = next; |
1733 | } while (bh != head); |
1734 | unlock_page(page); |
1735 | |
1736 | err = 0; |
1737 | done: |
1738 | if (nr_underway == 0) { |
1739 | /* |
1740 | * The page was marked dirty, but the buffers were |
1741 | * clean. Someone wrote them back by hand with |
1742 | * ll_rw_block/submit_bh. A rare case. |
1743 | */ |
1744 | end_page_writeback(page); |
1745 | |
1746 | /* |
1747 | * The page and buffer_heads can be released at any time from |
1748 | * here on. |
1749 | */ |
1750 | } |
1751 | return err; |
1752 | |
1753 | recover: |
1754 | /* |
1755 | * ENOSPC, or some other error. We may already have added some |
1756 | * blocks to the file, so we need to write these out to avoid |
1757 | * exposing stale data. |
1758 | * The page is currently locked and not marked for writeback |
1759 | */ |
1760 | bh = head; |
1761 | /* Recovery: lock and submit the mapped buffers */ |
1762 | do { |
1763 | if (buffer_mapped(bh) && buffer_dirty(bh) && |
1764 | !buffer_delay(bh)) { |
1765 | lock_buffer(bh); |
1766 | mark_buffer_async_write_endio(bh, handler); |
1767 | } else { |
1768 | /* |
1769 | * The buffer may have been set dirty during |
1770 | * attachment to a dirty page. |
1771 | */ |
1772 | clear_buffer_dirty(bh); |
1773 | } |
1774 | } while ((bh = bh->b_this_page) != head); |
1775 | SetPageError(page); |
1776 | BUG_ON(PageWriteback(page)); |
1777 | mapping_set_error(page->mapping, err); |
1778 | set_page_writeback(page); |
1779 | do { |
1780 | struct buffer_head *next = bh->b_this_page; |
1781 | if (buffer_async_write(bh)) { |
1782 | clear_buffer_dirty(bh); |
1783 | submit_bh(write_op, bh); |
1784 | nr_underway++; |
1785 | } |
1786 | bh = next; |
1787 | } while (bh != head); |
1788 | unlock_page(page); |
1789 | goto done; |
1790 | } |
1791 | |
1792 | /* |
1793 | * If a page has any new buffers, zero them out here, and mark them uptodate |
1794 | * and dirty so they'll be written out (in order to prevent uninitialised |
1795 | * block data from leaking). And clear the new bit. |
1796 | */ |
1797 | void page_zero_new_buffers(struct page *page, unsigned from, unsigned to) |
1798 | { |
1799 | unsigned int block_start, block_end; |
1800 | struct buffer_head *head, *bh; |
1801 | |
1802 | BUG_ON(!PageLocked(page)); |
1803 | if (!page_has_buffers(page)) |
1804 | return; |
1805 | |
1806 | bh = head = page_buffers(page); |
1807 | block_start = 0; |
1808 | do { |
1809 | block_end = block_start + bh->b_size; |
1810 | |
1811 | if (buffer_new(bh)) { |
1812 | if (block_end > from && block_start < to) { |
1813 | if (!PageUptodate(page)) { |
1814 | unsigned start, size; |
1815 | |
1816 | start = max(from, block_start); |
1817 | size = min(to, block_end) - start; |
1818 | |
1819 | zero_user(page, start, size); |
1820 | set_buffer_uptodate(bh); |
1821 | } |
1822 | |
1823 | clear_buffer_new(bh); |
1824 | mark_buffer_dirty(bh); |
1825 | } |
1826 | } |
1827 | |
1828 | block_start = block_end; |
1829 | bh = bh->b_this_page; |
1830 | } while (bh != head); |
1831 | } |
1832 | EXPORT_SYMBOL(page_zero_new_buffers); |
1833 | |
1834 | int __block_write_begin(struct page *page, loff_t pos, unsigned len, |
1835 | get_block_t *get_block) |
1836 | { |
1837 | unsigned from = pos & (PAGE_CACHE_SIZE - 1); |
1838 | unsigned to = from + len; |
1839 | struct inode *inode = page->mapping->host; |
1840 | unsigned block_start, block_end; |
1841 | sector_t block; |
1842 | int err = 0; |
1843 | unsigned blocksize, bbits; |
1844 | struct buffer_head *bh, *head, *wait[2], **wait_bh=wait; |
1845 | |
1846 | BUG_ON(!PageLocked(page)); |
1847 | BUG_ON(from > PAGE_CACHE_SIZE); |
1848 | BUG_ON(to > PAGE_CACHE_SIZE); |
1849 | BUG_ON(from > to); |
1850 | |
1851 | blocksize = 1 << inode->i_blkbits; |
1852 | if (!page_has_buffers(page)) |
1853 | create_empty_buffers(page, blocksize, 0); |
1854 | head = page_buffers(page); |
1855 | |
1856 | bbits = inode->i_blkbits; |
1857 | block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); |
1858 | |
1859 | for(bh = head, block_start = 0; bh != head || !block_start; |
1860 | block++, block_start=block_end, bh = bh->b_this_page) { |
1861 | block_end = block_start + blocksize; |
1862 | if (block_end <= from || block_start >= to) { |
1863 | if (PageUptodate(page)) { |
1864 | if (!buffer_uptodate(bh)) |
1865 | set_buffer_uptodate(bh); |
1866 | } |
1867 | continue; |
1868 | } |
1869 | if (buffer_new(bh)) |
1870 | clear_buffer_new(bh); |
1871 | if (!buffer_mapped(bh)) { |
1872 | WARN_ON(bh->b_size != blocksize); |
1873 | err = get_block(inode, block, bh, 1); |
1874 | if (err) |
1875 | break; |
1876 | if (buffer_new(bh)) { |
1877 | unmap_underlying_metadata(bh->b_bdev, |
1878 | bh->b_blocknr); |
1879 | if (PageUptodate(page)) { |
1880 | clear_buffer_new(bh); |
1881 | set_buffer_uptodate(bh); |
1882 | mark_buffer_dirty(bh); |
1883 | continue; |
1884 | } |
1885 | if (block_end > to || block_start < from) |
1886 | zero_user_segments(page, |
1887 | to, block_end, |
1888 | block_start, from); |
1889 | continue; |
1890 | } |
1891 | } |
1892 | if (PageUptodate(page)) { |
1893 | if (!buffer_uptodate(bh)) |
1894 | set_buffer_uptodate(bh); |
1895 | continue; |
1896 | } |
1897 | if (!buffer_uptodate(bh) && !buffer_delay(bh) && |
1898 | !buffer_unwritten(bh) && |
1899 | (block_start < from || block_end > to)) { |
1900 | ll_rw_block(READ, 1, &bh); |
1901 | *wait_bh++=bh; |
1902 | } |
1903 | } |
1904 | /* |
1905 | * If we issued read requests - let them complete. |
1906 | */ |
1907 | while(wait_bh > wait) { |
1908 | wait_on_buffer(*--wait_bh); |
1909 | if (!buffer_uptodate(*wait_bh)) |
1910 | err = -EIO; |
1911 | } |
1912 | if (unlikely(err)) { |
1913 | page_zero_new_buffers(page, from, to); |
1914 | ClearPageUptodate(page); |
1915 | } |
1916 | return err; |
1917 | } |
1918 | EXPORT_SYMBOL(__block_write_begin); |
1919 | |
1920 | static int __block_commit_write(struct inode *inode, struct page *page, |
1921 | unsigned from, unsigned to) |
1922 | { |
1923 | unsigned block_start, block_end; |
1924 | int partial = 0; |
1925 | unsigned blocksize; |
1926 | struct buffer_head *bh, *head; |
1927 | |
1928 | blocksize = 1 << inode->i_blkbits; |
1929 | |
1930 | for(bh = head = page_buffers(page), block_start = 0; |
1931 | bh != head || !block_start; |
1932 | block_start=block_end, bh = bh->b_this_page) { |
1933 | block_end = block_start + blocksize; |
1934 | if (block_end <= from || block_start >= to) { |
1935 | if (!buffer_uptodate(bh)) |
1936 | partial = 1; |
1937 | } else { |
1938 | set_buffer_uptodate(bh); |
1939 | mark_buffer_dirty(bh); |
1940 | } |
1941 | clear_buffer_new(bh); |
1942 | } |
1943 | |
1944 | /* |
1945 | * If this is a partial write which happened to make all buffers |
1946 | * uptodate then we can optimize away a bogus readpage() for |
1947 | * the next read(). Here we 'discover' whether the page went |
1948 | * uptodate as a result of this (potentially partial) write. |
1949 | */ |
1950 | if (!partial) |
1951 | SetPageUptodate(page); |
1952 | return 0; |
1953 | } |
1954 | |
1955 | /* |
1956 | * block_write_begin takes care of the basic task of block allocation and |
1957 | * bringing partial write blocks uptodate first. |
1958 | * |
1959 | * The filesystem needs to handle block truncation upon failure. |
1960 | */ |
1961 | int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, |
1962 | unsigned flags, struct page **pagep, get_block_t *get_block) |
1963 | { |
1964 | pgoff_t index = pos >> PAGE_CACHE_SHIFT; |
1965 | struct page *page; |
1966 | int status; |
1967 | |
1968 | page = grab_cache_page_write_begin(mapping, index, flags); |
1969 | if (!page) |
1970 | return -ENOMEM; |
1971 | |
1972 | status = __block_write_begin(page, pos, len, get_block); |
1973 | if (unlikely(status)) { |
1974 | unlock_page(page); |
1975 | page_cache_release(page); |
1976 | page = NULL; |
1977 | } |
1978 | |
1979 | *pagep = page; |
1980 | return status; |
1981 | } |
1982 | EXPORT_SYMBOL(block_write_begin); |
1983 | |
1984 | int block_write_end(struct file *file, struct address_space *mapping, |
1985 | loff_t pos, unsigned len, unsigned copied, |
1986 | struct page *page, void *fsdata) |
1987 | { |
1988 | struct inode *inode = mapping->host; |
1989 | unsigned start; |
1990 | |
1991 | start = pos & (PAGE_CACHE_SIZE - 1); |
1992 | |
1993 | if (unlikely(copied < len)) { |
1994 | /* |
1995 | * The buffers that were written will now be uptodate, so we |
1996 | * don't have to worry about a readpage reading them and |
1997 | * overwriting a partial write. However if we have encountered |
1998 | * a short write and only partially written into a buffer, it |
1999 | * will not be marked uptodate, so a readpage might come in and |
2000 | * destroy our partial write. |
2001 | * |
2002 | * Do the simplest thing, and just treat any short write to a |
2003 | * non uptodate page as a zero-length write, and force the |
2004 | * caller to redo the whole thing. |
2005 | */ |
2006 | if (!PageUptodate(page)) |
2007 | copied = 0; |
2008 | |
2009 | page_zero_new_buffers(page, start+copied, start+len); |
2010 | } |
2011 | flush_dcache_page(page); |
2012 | |
2013 | /* This could be a short (even 0-length) commit */ |
2014 | __block_commit_write(inode, page, start, start+copied); |
2015 | |
2016 | return copied; |
2017 | } |
2018 | EXPORT_SYMBOL(block_write_end); |
2019 | |
2020 | int generic_write_end(struct file *file, struct address_space *mapping, |
2021 | loff_t pos, unsigned len, unsigned copied, |
2022 | struct page *page, void *fsdata) |
2023 | { |
2024 | struct inode *inode = mapping->host; |
2025 | int i_size_changed = 0; |
2026 | |
2027 | copied = block_write_end(file, mapping, pos, len, copied, page, fsdata); |
2028 | |
2029 | /* |
2030 | * No need to use i_size_read() here, the i_size |
2031 | * cannot change under us because we hold i_mutex. |
2032 | * |
2033 | * But it's important to update i_size while still holding page lock: |
2034 | * page writeout could otherwise come in and zero beyond i_size. |
2035 | */ |
2036 | if (pos+copied > inode->i_size) { |
2037 | i_size_write(inode, pos+copied); |
2038 | i_size_changed = 1; |
2039 | } |
2040 | |
2041 | unlock_page(page); |
2042 | page_cache_release(page); |
2043 | |
2044 | /* |
2045 | * Don't mark the inode dirty under page lock. First, it unnecessarily |
2046 | * makes the holding time of page lock longer. Second, it forces lock |
2047 | * ordering of page lock and transaction start for journaling |
2048 | * filesystems. |
2049 | */ |
2050 | if (i_size_changed) |
2051 | mark_inode_dirty(inode); |
2052 | |
2053 | return copied; |
2054 | } |
2055 | EXPORT_SYMBOL(generic_write_end); |
2056 | |
2057 | /* |
2058 | * block_is_partially_uptodate checks whether buffers within a page are |
2059 | * uptodate or not. |
2060 | * |
2061 | * Returns true if all buffers which correspond to a file portion |
2062 | * we want to read are uptodate. |
2063 | */ |
2064 | int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc, |
2065 | unsigned long from) |
2066 | { |
2067 | struct inode *inode = page->mapping->host; |
2068 | unsigned block_start, block_end, blocksize; |
2069 | unsigned to; |
2070 | struct buffer_head *bh, *head; |
2071 | int ret = 1; |
2072 | |
2073 | if (!page_has_buffers(page)) |
2074 | return 0; |
2075 | |
2076 | blocksize = 1 << inode->i_blkbits; |
2077 | to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count); |
2078 | to = from + to; |
2079 | if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize) |
2080 | return 0; |
2081 | |
2082 | head = page_buffers(page); |
2083 | bh = head; |
2084 | block_start = 0; |
2085 | do { |
2086 | block_end = block_start + blocksize; |
2087 | if (block_end > from && block_start < to) { |
2088 | if (!buffer_uptodate(bh)) { |
2089 | ret = 0; |
2090 | break; |
2091 | } |
2092 | if (block_end >= to) |
2093 | break; |
2094 | } |
2095 | block_start = block_end; |
2096 | bh = bh->b_this_page; |
2097 | } while (bh != head); |
2098 | |
2099 | return ret; |
2100 | } |
2101 | EXPORT_SYMBOL(block_is_partially_uptodate); |
2102 | |
2103 | /* |
2104 | * Generic "read page" function for block devices that have the normal |
2105 | * get_block functionality. This is most of the block device filesystems. |
2106 | * Reads the page asynchronously --- the unlock_buffer() and |
2107 | * set/clear_buffer_uptodate() functions propagate buffer state into the |
2108 | * page struct once IO has completed. |
2109 | */ |
2110 | int block_read_full_page(struct page *page, get_block_t *get_block) |
2111 | { |
2112 | struct inode *inode = page->mapping->host; |
2113 | sector_t iblock, lblock; |
2114 | struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE]; |
2115 | unsigned int blocksize; |
2116 | int nr, i; |
2117 | int fully_mapped = 1; |
2118 | |
2119 | BUG_ON(!PageLocked(page)); |
2120 | blocksize = 1 << inode->i_blkbits; |
2121 | if (!page_has_buffers(page)) |
2122 | create_empty_buffers(page, blocksize, 0); |
2123 | head = page_buffers(page); |
2124 | |
2125 | iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
2126 | lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits; |
2127 | bh = head; |
2128 | nr = 0; |
2129 | i = 0; |
2130 | |
2131 | do { |
2132 | if (buffer_uptodate(bh)) |
2133 | continue; |
2134 | |
2135 | if (!buffer_mapped(bh)) { |
2136 | int err = 0; |
2137 | |
2138 | fully_mapped = 0; |
2139 | if (iblock < lblock) { |
2140 | WARN_ON(bh->b_size != blocksize); |
2141 | err = get_block(inode, iblock, bh, 0); |
2142 | if (err) |
2143 | SetPageError(page); |
2144 | } |
2145 | if (!buffer_mapped(bh)) { |
2146 | zero_user(page, i * blocksize, blocksize); |
2147 | if (!err) |
2148 | set_buffer_uptodate(bh); |
2149 | continue; |
2150 | } |
2151 | /* |
2152 | * get_block() might have updated the buffer |
2153 | * synchronously |
2154 | */ |
2155 | if (buffer_uptodate(bh)) |
2156 | continue; |
2157 | } |
2158 | arr[nr++] = bh; |
2159 | } while (i++, iblock++, (bh = bh->b_this_page) != head); |
2160 | |
2161 | if (fully_mapped) |
2162 | SetPageMappedToDisk(page); |
2163 | |
2164 | if (!nr) { |
2165 | /* |
2166 | * All buffers are uptodate - we can set the page uptodate |
2167 | * as well. But not if get_block() returned an error. |
2168 | */ |
2169 | if (!PageError(page)) |
2170 | SetPageUptodate(page); |
2171 | unlock_page(page); |
2172 | return 0; |
2173 | } |
2174 | |
2175 | /* Stage two: lock the buffers */ |
2176 | for (i = 0; i < nr; i++) { |
2177 | bh = arr[i]; |
2178 | lock_buffer(bh); |
2179 | mark_buffer_async_read(bh); |
2180 | } |
2181 | |
2182 | /* |
2183 | * Stage 3: start the IO. Check for uptodateness |
2184 | * inside the buffer lock in case another process reading |
2185 | * the underlying blockdev brought it uptodate (the sct fix). |
2186 | */ |
2187 | for (i = 0; i < nr; i++) { |
2188 | bh = arr[i]; |
2189 | if (buffer_uptodate(bh)) |
2190 | end_buffer_async_read(bh, 1); |
2191 | else |
2192 | submit_bh(READ, bh); |
2193 | } |
2194 | return 0; |
2195 | } |
2196 | EXPORT_SYMBOL(block_read_full_page); |
2197 | |
2198 | /* utility function for filesystems that need to do work on expanding |
2199 | * truncates. Uses filesystem pagecache writes to allow the filesystem to |
2200 | * deal with the hole. |
2201 | */ |
2202 | int generic_cont_expand_simple(struct inode *inode, loff_t size) |
2203 | { |
2204 | struct address_space *mapping = inode->i_mapping; |
2205 | struct page *page; |
2206 | void *fsdata; |
2207 | int err; |
2208 | |
2209 | err = inode_newsize_ok(inode, size); |
2210 | if (err) |
2211 | goto out; |
2212 | |
2213 | err = pagecache_write_begin(NULL, mapping, size, 0, |
2214 | AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND, |
2215 | &page, &fsdata); |
2216 | if (err) |
2217 | goto out; |
2218 | |
2219 | err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata); |
2220 | BUG_ON(err > 0); |
2221 | |
2222 | out: |
2223 | return err; |
2224 | } |
2225 | EXPORT_SYMBOL(generic_cont_expand_simple); |
2226 | |
2227 | static int cont_expand_zero(struct file *file, struct address_space *mapping, |
2228 | loff_t pos, loff_t *bytes) |
2229 | { |
2230 | struct inode *inode = mapping->host; |
2231 | unsigned blocksize = 1 << inode->i_blkbits; |
2232 | struct page *page; |
2233 | void *fsdata; |
2234 | pgoff_t index, curidx; |
2235 | loff_t curpos; |
2236 | unsigned zerofrom, offset, len; |
2237 | int err = 0; |
2238 | |
2239 | index = pos >> PAGE_CACHE_SHIFT; |
2240 | offset = pos & ~PAGE_CACHE_MASK; |
2241 | |
2242 | while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) { |
2243 | zerofrom = curpos & ~PAGE_CACHE_MASK; |
2244 | if (zerofrom & (blocksize-1)) { |
2245 | *bytes |= (blocksize-1); |
2246 | (*bytes)++; |
2247 | } |
2248 | len = PAGE_CACHE_SIZE - zerofrom; |
2249 | |
2250 | err = pagecache_write_begin(file, mapping, curpos, len, |
2251 | AOP_FLAG_UNINTERRUPTIBLE, |
2252 | &page, &fsdata); |
2253 | if (err) |
2254 | goto out; |
2255 | zero_user(page, zerofrom, len); |
2256 | err = pagecache_write_end(file, mapping, curpos, len, len, |
2257 | page, fsdata); |
2258 | if (err < 0) |
2259 | goto out; |
2260 | BUG_ON(err != len); |
2261 | err = 0; |
2262 | |
2263 | balance_dirty_pages_ratelimited(mapping); |
2264 | } |
2265 | |
2266 | /* page covers the boundary, find the boundary offset */ |
2267 | if (index == curidx) { |
2268 | zerofrom = curpos & ~PAGE_CACHE_MASK; |
2269 | /* if we will expand the thing last block will be filled */ |
2270 | if (offset <= zerofrom) { |
2271 | goto out; |
2272 | } |
2273 | if (zerofrom & (blocksize-1)) { |
2274 | *bytes |= (blocksize-1); |
2275 | (*bytes)++; |
2276 | } |
2277 | len = offset - zerofrom; |
2278 | |
2279 | err = pagecache_write_begin(file, mapping, curpos, len, |
2280 | AOP_FLAG_UNINTERRUPTIBLE, |
2281 | &page, &fsdata); |
2282 | if (err) |
2283 | goto out; |
2284 | zero_user(page, zerofrom, len); |
2285 | err = pagecache_write_end(file, mapping, curpos, len, len, |
2286 | page, fsdata); |
2287 | if (err < 0) |
2288 | goto out; |
2289 | BUG_ON(err != len); |
2290 | err = 0; |
2291 | } |
2292 | out: |
2293 | return err; |
2294 | } |
2295 | |
2296 | /* |
2297 | * For moronic filesystems that do not allow holes in file. |
2298 | * We may have to extend the file. |
2299 | */ |
2300 | int cont_write_begin(struct file *file, struct address_space *mapping, |
2301 | loff_t pos, unsigned len, unsigned flags, |
2302 | struct page **pagep, void **fsdata, |
2303 | get_block_t *get_block, loff_t *bytes) |
2304 | { |
2305 | struct inode *inode = mapping->host; |
2306 | unsigned blocksize = 1 << inode->i_blkbits; |
2307 | unsigned zerofrom; |
2308 | int err; |
2309 | |
2310 | err = cont_expand_zero(file, mapping, pos, bytes); |
2311 | if (err) |
2312 | return err; |
2313 | |
2314 | zerofrom = *bytes & ~PAGE_CACHE_MASK; |
2315 | if (pos+len > *bytes && zerofrom & (blocksize-1)) { |
2316 | *bytes |= (blocksize-1); |
2317 | (*bytes)++; |
2318 | } |
2319 | |
2320 | return block_write_begin(mapping, pos, len, flags, pagep, get_block); |
2321 | } |
2322 | EXPORT_SYMBOL(cont_write_begin); |
2323 | |
2324 | int block_commit_write(struct page *page, unsigned from, unsigned to) |
2325 | { |
2326 | struct inode *inode = page->mapping->host; |
2327 | __block_commit_write(inode,page,from,to); |
2328 | return 0; |
2329 | } |
2330 | EXPORT_SYMBOL(block_commit_write); |
2331 | |
2332 | /* |
2333 | * block_page_mkwrite() is not allowed to change the file size as it gets |
2334 | * called from a page fault handler when a page is first dirtied. Hence we must |
2335 | * be careful to check for EOF conditions here. We set the page up correctly |
2336 | * for a written page which means we get ENOSPC checking when writing into |
2337 | * holes and correct delalloc and unwritten extent mapping on filesystems that |
2338 | * support these features. |
2339 | * |
2340 | * We are not allowed to take the i_mutex here so we have to play games to |
2341 | * protect against truncate races as the page could now be beyond EOF. Because |
2342 | * truncate writes the inode size before removing pages, once we have the |
2343 | * page lock we can determine safely if the page is beyond EOF. If it is not |
2344 | * beyond EOF, then the page is guaranteed safe against truncation until we |
2345 | * unlock the page. |
2346 | */ |
2347 | int |
2348 | block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, |
2349 | get_block_t get_block) |
2350 | { |
2351 | struct page *page = vmf->page; |
2352 | struct inode *inode = vma->vm_file->f_path.dentry->d_inode; |
2353 | unsigned long end; |
2354 | loff_t size; |
2355 | int ret = VM_FAULT_NOPAGE; /* make the VM retry the fault */ |
2356 | |
2357 | lock_page(page); |
2358 | size = i_size_read(inode); |
2359 | if ((page->mapping != inode->i_mapping) || |
2360 | (page_offset(page) > size)) { |
2361 | /* page got truncated out from underneath us */ |
2362 | unlock_page(page); |
2363 | goto out; |
2364 | } |
2365 | |
2366 | /* page is wholly or partially inside EOF */ |
2367 | if (((page->index + 1) << PAGE_CACHE_SHIFT) > size) |
2368 | end = size & ~PAGE_CACHE_MASK; |
2369 | else |
2370 | end = PAGE_CACHE_SIZE; |
2371 | |
2372 | ret = __block_write_begin(page, 0, end, get_block); |
2373 | if (!ret) |
2374 | ret = block_commit_write(page, 0, end); |
2375 | |
2376 | if (unlikely(ret)) { |
2377 | unlock_page(page); |
2378 | if (ret == -ENOMEM) |
2379 | ret = VM_FAULT_OOM; |
2380 | else /* -ENOSPC, -EIO, etc */ |
2381 | ret = VM_FAULT_SIGBUS; |
2382 | } else |
2383 | ret = VM_FAULT_LOCKED; |
2384 | |
2385 | out: |
2386 | return ret; |
2387 | } |
2388 | EXPORT_SYMBOL(block_page_mkwrite); |
2389 | |
2390 | /* |
2391 | * nobh_write_begin()'s prereads are special: the buffer_heads are freed |
2392 | * immediately, while under the page lock. So it needs a special end_io |
2393 | * handler which does not touch the bh after unlocking it. |
2394 | */ |
2395 | static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate) |
2396 | { |
2397 | __end_buffer_read_notouch(bh, uptodate); |
2398 | } |
2399 | |
2400 | /* |
2401 | * Attach the singly-linked list of buffers created by nobh_write_begin, to |
2402 | * the page (converting it to circular linked list and taking care of page |
2403 | * dirty races). |
2404 | */ |
2405 | static void attach_nobh_buffers(struct page *page, struct buffer_head *head) |
2406 | { |
2407 | struct buffer_head *bh; |
2408 | |
2409 | BUG_ON(!PageLocked(page)); |
2410 | |
2411 | spin_lock(&page->mapping->private_lock); |
2412 | bh = head; |
2413 | do { |
2414 | if (PageDirty(page)) |
2415 | set_buffer_dirty(bh); |
2416 | if (!bh->b_this_page) |
2417 | bh->b_this_page = head; |
2418 | bh = bh->b_this_page; |
2419 | } while (bh != head); |
2420 | attach_page_buffers(page, head); |
2421 | spin_unlock(&page->mapping->private_lock); |
2422 | } |
2423 | |
2424 | /* |
2425 | * On entry, the page is fully not uptodate. |
2426 | * On exit the page is fully uptodate in the areas outside (from,to) |
2427 | * The filesystem needs to handle block truncation upon failure. |
2428 | */ |
2429 | int nobh_write_begin(struct address_space *mapping, |
2430 | loff_t pos, unsigned len, unsigned flags, |
2431 | struct page **pagep, void **fsdata, |
2432 | get_block_t *get_block) |
2433 | { |
2434 | struct inode *inode = mapping->host; |
2435 | const unsigned blkbits = inode->i_blkbits; |
2436 | const unsigned blocksize = 1 << blkbits; |
2437 | struct buffer_head *head, *bh; |
2438 | struct page *page; |
2439 | pgoff_t index; |
2440 | unsigned from, to; |
2441 | unsigned block_in_page; |
2442 | unsigned block_start, block_end; |
2443 | sector_t block_in_file; |
2444 | int nr_reads = 0; |
2445 | int ret = 0; |
2446 | int is_mapped_to_disk = 1; |
2447 | |
2448 | index = pos >> PAGE_CACHE_SHIFT; |
2449 | from = pos & (PAGE_CACHE_SIZE - 1); |
2450 | to = from + len; |
2451 | |
2452 | page = grab_cache_page_write_begin(mapping, index, flags); |
2453 | if (!page) |
2454 | return -ENOMEM; |
2455 | *pagep = page; |
2456 | *fsdata = NULL; |
2457 | |
2458 | if (page_has_buffers(page)) { |
2459 | ret = __block_write_begin(page, pos, len, get_block); |
2460 | if (unlikely(ret)) |
2461 | goto out_release; |
2462 | return ret; |
2463 | } |
2464 | |
2465 | if (PageMappedToDisk(page)) |
2466 | return 0; |
2467 | |
2468 | /* |
2469 | * Allocate buffers so that we can keep track of state, and potentially |
2470 | * attach them to the page if an error occurs. In the common case of |
2471 | * no error, they will just be freed again without ever being attached |
2472 | * to the page (which is all OK, because we're under the page lock). |
2473 | * |
2474 | * Be careful: the buffer linked list is a NULL terminated one, rather |
2475 | * than the circular one we're used to. |
2476 | */ |
2477 | head = alloc_page_buffers(page, blocksize, 0); |
2478 | if (!head) { |
2479 | ret = -ENOMEM; |
2480 | goto out_release; |
2481 | } |
2482 | |
2483 | block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); |
2484 | |
2485 | /* |
2486 | * We loop across all blocks in the page, whether or not they are |
2487 | * part of the affected region. This is so we can discover if the |
2488 | * page is fully mapped-to-disk. |
2489 | */ |
2490 | for (block_start = 0, block_in_page = 0, bh = head; |
2491 | block_start < PAGE_CACHE_SIZE; |
2492 | block_in_page++, block_start += blocksize, bh = bh->b_this_page) { |
2493 | int create; |
2494 | |
2495 | block_end = block_start + blocksize; |
2496 | bh->b_state = 0; |
2497 | create = 1; |
2498 | if (block_start >= to) |
2499 | create = 0; |
2500 | ret = get_block(inode, block_in_file + block_in_page, |
2501 | bh, create); |
2502 | if (ret) |
2503 | goto failed; |
2504 | if (!buffer_mapped(bh)) |
2505 | is_mapped_to_disk = 0; |
2506 | if (buffer_new(bh)) |
2507 | unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr); |
2508 | if (PageUptodate(page)) { |
2509 | set_buffer_uptodate(bh); |
2510 | continue; |
2511 | } |
2512 | if (buffer_new(bh) || !buffer_mapped(bh)) { |
2513 | zero_user_segments(page, block_start, from, |
2514 | to, block_end); |
2515 | continue; |
2516 | } |
2517 | if (buffer_uptodate(bh)) |
2518 | continue; /* reiserfs does this */ |
2519 | if (block_start < from || block_end > to) { |
2520 | lock_buffer(bh); |
2521 | bh->b_end_io = end_buffer_read_nobh; |
2522 | submit_bh(READ, bh); |
2523 | nr_reads++; |
2524 | } |
2525 | } |
2526 | |
2527 | if (nr_reads) { |
2528 | /* |
2529 | * The page is locked, so these buffers are protected from |
2530 | * any VM or truncate activity. Hence we don't need to care |
2531 | * for the buffer_head refcounts. |
2532 | */ |
2533 | for (bh = head; bh; bh = bh->b_this_page) { |
2534 | wait_on_buffer(bh); |
2535 | if (!buffer_uptodate(bh)) |
2536 | ret = -EIO; |
2537 | } |
2538 | if (ret) |
2539 | goto failed; |
2540 | } |
2541 | |
2542 | if (is_mapped_to_disk) |
2543 | SetPageMappedToDisk(page); |
2544 | |
2545 | *fsdata = head; /* to be released by nobh_write_end */ |
2546 | |
2547 | return 0; |
2548 | |
2549 | failed: |
2550 | BUG_ON(!ret); |
2551 | /* |
2552 | * Error recovery is a bit difficult. We need to zero out blocks that |
2553 | * were newly allocated, and dirty them to ensure they get written out. |
2554 | * Buffers need to be attached to the page at this point, otherwise |
2555 | * the handling of potential IO errors during writeout would be hard |
2556 | * (could try doing synchronous writeout, but what if that fails too?) |
2557 | */ |
2558 | attach_nobh_buffers(page, head); |
2559 | page_zero_new_buffers(page, from, to); |
2560 | |
2561 | out_release: |
2562 | unlock_page(page); |
2563 | page_cache_release(page); |
2564 | *pagep = NULL; |
2565 | |
2566 | return ret; |
2567 | } |
2568 | EXPORT_SYMBOL(nobh_write_begin); |
2569 | |
2570 | int nobh_write_end(struct file *file, struct address_space *mapping, |
2571 | loff_t pos, unsigned len, unsigned copied, |
2572 | struct page *page, void *fsdata) |
2573 | { |
2574 | struct inode *inode = page->mapping->host; |
2575 | struct buffer_head *head = fsdata; |
2576 | struct buffer_head *bh; |
2577 | BUG_ON(fsdata != NULL && page_has_buffers(page)); |
2578 | |
2579 | if (unlikely(copied < len) && head) |
2580 | attach_nobh_buffers(page, head); |
2581 | if (page_has_buffers(page)) |
2582 | return generic_write_end(file, mapping, pos, len, |
2583 | copied, page, fsdata); |
2584 | |
2585 | SetPageUptodate(page); |
2586 | set_page_dirty(page); |
2587 | if (pos+copied > inode->i_size) { |
2588 | i_size_write(inode, pos+copied); |
2589 | mark_inode_dirty(inode); |
2590 | } |
2591 | |
2592 | unlock_page(page); |
2593 | page_cache_release(page); |
2594 | |
2595 | while (head) { |
2596 | bh = head; |
2597 | head = head->b_this_page; |
2598 | free_buffer_head(bh); |
2599 | } |
2600 | |
2601 | return copied; |
2602 | } |
2603 | EXPORT_SYMBOL(nobh_write_end); |
2604 | |
2605 | /* |
2606 | * nobh_writepage() - based on block_full_write_page() except |
2607 | * that it tries to operate without attaching bufferheads to |
2608 | * the page. |
2609 | */ |
2610 | int nobh_writepage(struct page *page, get_block_t *get_block, |
2611 | struct writeback_control *wbc) |
2612 | { |
2613 | struct inode * const inode = page->mapping->host; |
2614 | loff_t i_size = i_size_read(inode); |
2615 | const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; |
2616 | unsigned offset; |
2617 | int ret; |
2618 | |
2619 | /* Is the page fully inside i_size? */ |
2620 | if (page->index < end_index) |
2621 | goto out; |
2622 | |
2623 | /* Is the page fully outside i_size? (truncate in progress) */ |
2624 | offset = i_size & (PAGE_CACHE_SIZE-1); |
2625 | if (page->index >= end_index+1 || !offset) { |
2626 | /* |
2627 | * The page may have dirty, unmapped buffers. For example, |
2628 | * they may have been added in ext3_writepage(). Make them |
2629 | * freeable here, so the page does not leak. |
2630 | */ |
2631 | #if 0 |
2632 | /* Not really sure about this - do we need this ? */ |
2633 | if (page->mapping->a_ops->invalidatepage) |
2634 | page->mapping->a_ops->invalidatepage(page, offset); |
2635 | #endif |
2636 | unlock_page(page); |
2637 | return 0; /* don't care */ |
2638 | } |
2639 | |
2640 | /* |
2641 | * The page straddles i_size. It must be zeroed out on each and every |
2642 | * writepage invocation because it may be mmapped. "A file is mapped |
2643 | * in multiples of the page size. For a file that is not a multiple of |
2644 | * the page size, the remaining memory is zeroed when mapped, and |
2645 | * writes to that region are not written out to the file." |
2646 | */ |
2647 | zero_user_segment(page, offset, PAGE_CACHE_SIZE); |
2648 | out: |
2649 | ret = mpage_writepage(page, get_block, wbc); |
2650 | if (ret == -EAGAIN) |
2651 | ret = __block_write_full_page(inode, page, get_block, wbc, |
2652 | end_buffer_async_write); |
2653 | return ret; |
2654 | } |
2655 | EXPORT_SYMBOL(nobh_writepage); |
2656 | |
2657 | int nobh_truncate_page(struct address_space *mapping, |
2658 | loff_t from, get_block_t *get_block) |
2659 | { |
2660 | pgoff_t index = from >> PAGE_CACHE_SHIFT; |
2661 | unsigned offset = from & (PAGE_CACHE_SIZE-1); |
2662 | unsigned blocksize; |
2663 | sector_t iblock; |
2664 | unsigned length, pos; |
2665 | struct inode *inode = mapping->host; |
2666 | struct page *page; |
2667 | struct buffer_head map_bh; |
2668 | int err; |
2669 | |
2670 | blocksize = 1 << inode->i_blkbits; |
2671 | length = offset & (blocksize - 1); |
2672 | |
2673 | /* Block boundary? Nothing to do */ |
2674 | if (!length) |
2675 | return 0; |
2676 | |
2677 | length = blocksize - length; |
2678 | iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
2679 | |
2680 | page = grab_cache_page(mapping, index); |
2681 | err = -ENOMEM; |
2682 | if (!page) |
2683 | goto out; |
2684 | |
2685 | if (page_has_buffers(page)) { |
2686 | has_buffers: |
2687 | unlock_page(page); |
2688 | page_cache_release(page); |
2689 | return block_truncate_page(mapping, from, get_block); |
2690 | } |
2691 | |
2692 | /* Find the buffer that contains "offset" */ |
2693 | pos = blocksize; |
2694 | while (offset >= pos) { |
2695 | iblock++; |
2696 | pos += blocksize; |
2697 | } |
2698 | |
2699 | map_bh.b_size = blocksize; |
2700 | map_bh.b_state = 0; |
2701 | err = get_block(inode, iblock, &map_bh, 0); |
2702 | if (err) |
2703 | goto unlock; |
2704 | /* unmapped? It's a hole - nothing to do */ |
2705 | if (!buffer_mapped(&map_bh)) |
2706 | goto unlock; |
2707 | |
2708 | /* Ok, it's mapped. Make sure it's up-to-date */ |
2709 | if (!PageUptodate(page)) { |
2710 | err = mapping->a_ops->readpage(NULL, page); |
2711 | if (err) { |
2712 | page_cache_release(page); |
2713 | goto out; |
2714 | } |
2715 | lock_page(page); |
2716 | if (!PageUptodate(page)) { |
2717 | err = -EIO; |
2718 | goto unlock; |
2719 | } |
2720 | if (page_has_buffers(page)) |
2721 | goto has_buffers; |
2722 | } |
2723 | zero_user(page, offset, length); |
2724 | set_page_dirty(page); |
2725 | err = 0; |
2726 | |
2727 | unlock: |
2728 | unlock_page(page); |
2729 | page_cache_release(page); |
2730 | out: |
2731 | return err; |
2732 | } |
2733 | EXPORT_SYMBOL(nobh_truncate_page); |
2734 | |
2735 | int block_truncate_page(struct address_space *mapping, |
2736 | loff_t from, get_block_t *get_block) |
2737 | { |
2738 | pgoff_t index = from >> PAGE_CACHE_SHIFT; |
2739 | unsigned offset = from & (PAGE_CACHE_SIZE-1); |
2740 | unsigned blocksize; |
2741 | sector_t iblock; |
2742 | unsigned length, pos; |
2743 | struct inode *inode = mapping->host; |
2744 | struct page *page; |
2745 | struct buffer_head *bh; |
2746 | int err; |
2747 | |
2748 | blocksize = 1 << inode->i_blkbits; |
2749 | length = offset & (blocksize - 1); |
2750 | |
2751 | /* Block boundary? Nothing to do */ |
2752 | if (!length) |
2753 | return 0; |
2754 | |
2755 | length = blocksize - length; |
2756 | iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
2757 | |
2758 | page = grab_cache_page(mapping, index); |
2759 | err = -ENOMEM; |
2760 | if (!page) |
2761 | goto out; |
2762 | |
2763 | if (!page_has_buffers(page)) |
2764 | create_empty_buffers(page, blocksize, 0); |
2765 | |
2766 | /* Find the buffer that contains "offset" */ |
2767 | bh = page_buffers(page); |
2768 | pos = blocksize; |
2769 | while (offset >= pos) { |
2770 | bh = bh->b_this_page; |
2771 | iblock++; |
2772 | pos += blocksize; |
2773 | } |
2774 | |
2775 | err = 0; |
2776 | if (!buffer_mapped(bh)) { |
2777 | WARN_ON(bh->b_size != blocksize); |
2778 | err = get_block(inode, iblock, bh, 0); |
2779 | if (err) |
2780 | goto unlock; |
2781 | /* unmapped? It's a hole - nothing to do */ |
2782 | if (!buffer_mapped(bh)) |
2783 | goto unlock; |
2784 | } |
2785 | |
2786 | /* Ok, it's mapped. Make sure it's up-to-date */ |
2787 | if (PageUptodate(page)) |
2788 | set_buffer_uptodate(bh); |
2789 | |
2790 | if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) { |
2791 | err = -EIO; |
2792 | ll_rw_block(READ, 1, &bh); |
2793 | wait_on_buffer(bh); |
2794 | /* Uhhuh. Read error. Complain and punt. */ |
2795 | if (!buffer_uptodate(bh)) |
2796 | goto unlock; |
2797 | } |
2798 | |
2799 | zero_user(page, offset, length); |
2800 | mark_buffer_dirty(bh); |
2801 | err = 0; |
2802 | |
2803 | unlock: |
2804 | unlock_page(page); |
2805 | page_cache_release(page); |
2806 | out: |
2807 | return err; |
2808 | } |
2809 | EXPORT_SYMBOL(block_truncate_page); |
2810 | |
2811 | /* |
2812 | * The generic ->writepage function for buffer-backed address_spaces |
2813 | * this form passes in the end_io handler used to finish the IO. |
2814 | */ |
2815 | int block_write_full_page_endio(struct page *page, get_block_t *get_block, |
2816 | struct writeback_control *wbc, bh_end_io_t *handler) |
2817 | { |
2818 | struct inode * const inode = page->mapping->host; |
2819 | loff_t i_size = i_size_read(inode); |
2820 | const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; |
2821 | unsigned offset; |
2822 | |
2823 | /* Is the page fully inside i_size? */ |
2824 | if (page->index < end_index) |
2825 | return __block_write_full_page(inode, page, get_block, wbc, |
2826 | handler); |
2827 | |
2828 | /* Is the page fully outside i_size? (truncate in progress) */ |
2829 | offset = i_size & (PAGE_CACHE_SIZE-1); |
2830 | if (page->index >= end_index+1 || !offset) { |
2831 | /* |
2832 | * The page may have dirty, unmapped buffers. For example, |
2833 | * they may have been added in ext3_writepage(). Make them |
2834 | * freeable here, so the page does not leak. |
2835 | */ |
2836 | do_invalidatepage(page, 0); |
2837 | unlock_page(page); |
2838 | return 0; /* don't care */ |
2839 | } |
2840 | |
2841 | /* |
2842 | * The page straddles i_size. It must be zeroed out on each and every |
2843 | * writepage invocation because it may be mmapped. "A file is mapped |
2844 | * in multiples of the page size. For a file that is not a multiple of |
2845 | * the page size, the remaining memory is zeroed when mapped, and |
2846 | * writes to that region are not written out to the file." |
2847 | */ |
2848 | zero_user_segment(page, offset, PAGE_CACHE_SIZE); |
2849 | return __block_write_full_page(inode, page, get_block, wbc, handler); |
2850 | } |
2851 | EXPORT_SYMBOL(block_write_full_page_endio); |
2852 | |
2853 | /* |
2854 | * The generic ->writepage function for buffer-backed address_spaces |
2855 | */ |
2856 | int block_write_full_page(struct page *page, get_block_t *get_block, |
2857 | struct writeback_control *wbc) |
2858 | { |
2859 | return block_write_full_page_endio(page, get_block, wbc, |
2860 | end_buffer_async_write); |
2861 | } |
2862 | EXPORT_SYMBOL(block_write_full_page); |
2863 | |
2864 | sector_t generic_block_bmap(struct address_space *mapping, sector_t block, |
2865 | get_block_t *get_block) |
2866 | { |
2867 | struct buffer_head tmp; |
2868 | struct inode *inode = mapping->host; |
2869 | tmp.b_state = 0; |
2870 | tmp.b_blocknr = 0; |
2871 | tmp.b_size = 1 << inode->i_blkbits; |
2872 | get_block(inode, block, &tmp, 0); |
2873 | return tmp.b_blocknr; |
2874 | } |
2875 | EXPORT_SYMBOL(generic_block_bmap); |
2876 | |
2877 | static void end_bio_bh_io_sync(struct bio *bio, int err) |
2878 | { |
2879 | struct buffer_head *bh = bio->bi_private; |
2880 | |
2881 | if (err == -EOPNOTSUPP) { |
2882 | set_bit(BIO_EOPNOTSUPP, &bio->bi_flags); |
2883 | } |
2884 | |
2885 | if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags))) |
2886 | set_bit(BH_Quiet, &bh->b_state); |
2887 | |
2888 | bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags)); |
2889 | bio_put(bio); |
2890 | } |
2891 | |
2892 | int submit_bh(int rw, struct buffer_head * bh) |
2893 | { |
2894 | struct bio *bio; |
2895 | int ret = 0; |
2896 | |
2897 | BUG_ON(!buffer_locked(bh)); |
2898 | BUG_ON(!buffer_mapped(bh)); |
2899 | BUG_ON(!bh->b_end_io); |
2900 | BUG_ON(buffer_delay(bh)); |
2901 | BUG_ON(buffer_unwritten(bh)); |
2902 | |
2903 | /* |
2904 | * Only clear out a write error when rewriting |
2905 | */ |
2906 | if (test_set_buffer_req(bh) && (rw & WRITE)) |
2907 | clear_buffer_write_io_error(bh); |
2908 | |
2909 | /* |
2910 | * from here on down, it's all bio -- do the initial mapping, |
2911 | * submit_bio -> generic_make_request may further map this bio around |
2912 | */ |
2913 | bio = bio_alloc(GFP_NOIO, 1); |
2914 | |
2915 | bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9); |
2916 | bio->bi_bdev = bh->b_bdev; |
2917 | bio->bi_io_vec[0].bv_page = bh->b_page; |
2918 | bio->bi_io_vec[0].bv_len = bh->b_size; |
2919 | bio->bi_io_vec[0].bv_offset = bh_offset(bh); |
2920 | |
2921 | bio->bi_vcnt = 1; |
2922 | bio->bi_idx = 0; |
2923 | bio->bi_size = bh->b_size; |
2924 | |
2925 | bio->bi_end_io = end_bio_bh_io_sync; |
2926 | bio->bi_private = bh; |
2927 | |
2928 | bio_get(bio); |
2929 | submit_bio(rw, bio); |
2930 | |
2931 | if (bio_flagged(bio, BIO_EOPNOTSUPP)) |
2932 | ret = -EOPNOTSUPP; |
2933 | |
2934 | bio_put(bio); |
2935 | return ret; |
2936 | } |
2937 | EXPORT_SYMBOL(submit_bh); |
2938 | |
2939 | /** |
2940 | * ll_rw_block: low-level access to block devices (DEPRECATED) |
2941 | * @rw: whether to %READ or %WRITE or maybe %READA (readahead) |
2942 | * @nr: number of &struct buffer_heads in the array |
2943 | * @bhs: array of pointers to &struct buffer_head |
2944 | * |
2945 | * ll_rw_block() takes an array of pointers to &struct buffer_heads, and |
2946 | * requests an I/O operation on them, either a %READ or a %WRITE. The third |
2947 | * %READA option is described in the documentation for generic_make_request() |
2948 | * which ll_rw_block() calls. |
2949 | * |
2950 | * This function drops any buffer that it cannot get a lock on (with the |
2951 | * BH_Lock state bit), any buffer that appears to be clean when doing a write |
2952 | * request, and any buffer that appears to be up-to-date when doing read |
2953 | * request. Further it marks as clean buffers that are processed for |
2954 | * writing (the buffer cache won't assume that they are actually clean |
2955 | * until the buffer gets unlocked). |
2956 | * |
2957 | * ll_rw_block sets b_end_io to simple completion handler that marks |
2958 | * the buffer up-to-date (if approriate), unlocks the buffer and wakes |
2959 | * any waiters. |
2960 | * |
2961 | * All of the buffers must be for the same device, and must also be a |
2962 | * multiple of the current approved size for the device. |
2963 | */ |
2964 | void ll_rw_block(int rw, int nr, struct buffer_head *bhs[]) |
2965 | { |
2966 | int i; |
2967 | |
2968 | for (i = 0; i < nr; i++) { |
2969 | struct buffer_head *bh = bhs[i]; |
2970 | |
2971 | if (!trylock_buffer(bh)) |
2972 | continue; |
2973 | if (rw == WRITE) { |
2974 | if (test_clear_buffer_dirty(bh)) { |
2975 | bh->b_end_io = end_buffer_write_sync; |
2976 | get_bh(bh); |
2977 | submit_bh(WRITE, bh); |
2978 | continue; |
2979 | } |
2980 | } else { |
2981 | if (!buffer_uptodate(bh)) { |
2982 | bh->b_end_io = end_buffer_read_sync; |
2983 | get_bh(bh); |
2984 | submit_bh(rw, bh); |
2985 | continue; |
2986 | } |
2987 | } |
2988 | unlock_buffer(bh); |
2989 | } |
2990 | } |
2991 | EXPORT_SYMBOL(ll_rw_block); |
2992 | |
2993 | void write_dirty_buffer(struct buffer_head *bh, int rw) |
2994 | { |
2995 | lock_buffer(bh); |
2996 | if (!test_clear_buffer_dirty(bh)) { |
2997 | unlock_buffer(bh); |
2998 | return; |
2999 | } |
3000 | bh->b_end_io = end_buffer_write_sync; |
3001 | get_bh(bh); |
3002 | submit_bh(rw, bh); |
3003 | } |
3004 | EXPORT_SYMBOL(write_dirty_buffer); |
3005 | |
3006 | /* |
3007 | * For a data-integrity writeout, we need to wait upon any in-progress I/O |
3008 | * and then start new I/O and then wait upon it. The caller must have a ref on |
3009 | * the buffer_head. |
3010 | */ |
3011 | int __sync_dirty_buffer(struct buffer_head *bh, int rw) |
3012 | { |
3013 | int ret = 0; |
3014 | |
3015 | WARN_ON(atomic_read(&bh->b_count) < 1); |
3016 | lock_buffer(bh); |
3017 | if (test_clear_buffer_dirty(bh)) { |
3018 | get_bh(bh); |
3019 | bh->b_end_io = end_buffer_write_sync; |
3020 | ret = submit_bh(rw, bh); |
3021 | wait_on_buffer(bh); |
3022 | if (!ret && !buffer_uptodate(bh)) |
3023 | ret = -EIO; |
3024 | } else { |
3025 | unlock_buffer(bh); |
3026 | } |
3027 | return ret; |
3028 | } |
3029 | EXPORT_SYMBOL(__sync_dirty_buffer); |
3030 | |
3031 | int sync_dirty_buffer(struct buffer_head *bh) |
3032 | { |
3033 | return __sync_dirty_buffer(bh, WRITE_SYNC); |
3034 | } |
3035 | EXPORT_SYMBOL(sync_dirty_buffer); |
3036 | |
3037 | /* |
3038 | * try_to_free_buffers() checks if all the buffers on this particular page |
3039 | * are unused, and releases them if so. |
3040 | * |
3041 | * Exclusion against try_to_free_buffers may be obtained by either |
3042 | * locking the page or by holding its mapping's private_lock. |
3043 | * |
3044 | * If the page is dirty but all the buffers are clean then we need to |
3045 | * be sure to mark the page clean as well. This is because the page |
3046 | * may be against a block device, and a later reattachment of buffers |
3047 | * to a dirty page will set *all* buffers dirty. Which would corrupt |
3048 | * filesystem data on the same device. |
3049 | * |
3050 | * The same applies to regular filesystem pages: if all the buffers are |
3051 | * clean then we set the page clean and proceed. To do that, we require |
3052 | * total exclusion from __set_page_dirty_buffers(). That is obtained with |
3053 | * private_lock. |
3054 | * |
3055 | * try_to_free_buffers() is non-blocking. |
3056 | */ |
3057 | static inline int buffer_busy(struct buffer_head *bh) |
3058 | { |
3059 | return atomic_read(&bh->b_count) | |
3060 | (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock))); |
3061 | } |
3062 | |
3063 | static int |
3064 | drop_buffers(struct page *page, struct buffer_head **buffers_to_free) |
3065 | { |
3066 | struct buffer_head *head = page_buffers(page); |
3067 | struct buffer_head *bh; |
3068 | |
3069 | bh = head; |
3070 | do { |
3071 | if (buffer_write_io_error(bh) && page->mapping) |
3072 | set_bit(AS_EIO, &page->mapping->flags); |
3073 | if (buffer_busy(bh)) |
3074 | goto failed; |
3075 | bh = bh->b_this_page; |
3076 | } while (bh != head); |
3077 | |
3078 | do { |
3079 | struct buffer_head *next = bh->b_this_page; |
3080 | |
3081 | if (bh->b_assoc_map) |
3082 | __remove_assoc_queue(bh); |
3083 | bh = next; |
3084 | } while (bh != head); |
3085 | *buffers_to_free = head; |
3086 | __clear_page_buffers(page); |
3087 | return 1; |
3088 | failed: |
3089 | return 0; |
3090 | } |
3091 | |
3092 | int try_to_free_buffers(struct page *page) |
3093 | { |
3094 | struct address_space * const mapping = page->mapping; |
3095 | struct buffer_head *buffers_to_free = NULL; |
3096 | int ret = 0; |
3097 | |
3098 | BUG_ON(!PageLocked(page)); |
3099 | if (PageWriteback(page)) |
3100 | return 0; |
3101 | |
3102 | if (mapping == NULL) { /* can this still happen? */ |
3103 | ret = drop_buffers(page, &buffers_to_free); |
3104 | goto out; |
3105 | } |
3106 | |
3107 | spin_lock(&mapping->private_lock); |
3108 | ret = drop_buffers(page, &buffers_to_free); |
3109 | |
3110 | /* |
3111 | * If the filesystem writes its buffers by hand (eg ext3) |
3112 | * then we can have clean buffers against a dirty page. We |
3113 | * clean the page here; otherwise the VM will never notice |
3114 | * that the filesystem did any IO at all. |
3115 | * |
3116 | * Also, during truncate, discard_buffer will have marked all |
3117 | * the page's buffers clean. We discover that here and clean |
3118 | * the page also. |
3119 | * |
3120 | * private_lock must be held over this entire operation in order |
3121 | * to synchronise against __set_page_dirty_buffers and prevent the |
3122 | * dirty bit from being lost. |
3123 | */ |
3124 | if (ret) |
3125 | cancel_dirty_page(page, PAGE_CACHE_SIZE); |
3126 | spin_unlock(&mapping->private_lock); |
3127 | out: |
3128 | if (buffers_to_free) { |
3129 | struct buffer_head *bh = buffers_to_free; |
3130 | |
3131 | do { |
3132 | struct buffer_head *next = bh->b_this_page; |
3133 | free_buffer_head(bh); |
3134 | bh = next; |
3135 | } while (bh != buffers_to_free); |
3136 | } |
3137 | return ret; |
3138 | } |
3139 | EXPORT_SYMBOL(try_to_free_buffers); |
3140 | |
3141 | void block_sync_page(struct page *page) |
3142 | { |
3143 | struct address_space *mapping; |
3144 | |
3145 | smp_mb(); |
3146 | mapping = page_mapping(page); |
3147 | if (mapping) |
3148 | blk_run_backing_dev(mapping->backing_dev_info, page); |
3149 | } |
3150 | EXPORT_SYMBOL(block_sync_page); |
3151 | |
3152 | /* |
3153 | * There are no bdflush tunables left. But distributions are |
3154 | * still running obsolete flush daemons, so we terminate them here. |
3155 | * |
3156 | * Use of bdflush() is deprecated and will be removed in a future kernel. |
3157 | * The `flush-X' kernel threads fully replace bdflush daemons and this call. |
3158 | */ |
3159 | SYSCALL_DEFINE2(bdflush, int, func, long, data) |
3160 | { |
3161 | static int msg_count; |
3162 | |
3163 | if (!capable(CAP_SYS_ADMIN)) |
3164 | return -EPERM; |
3165 | |
3166 | if (msg_count < 5) { |
3167 | msg_count++; |
3168 | printk(KERN_INFO |
3169 | "warning: process `%s' used the obsolete bdflush" |
3170 | " system call\n", current->comm); |
3171 | printk(KERN_INFO "Fix your initscripts?\n"); |
3172 | } |
3173 | |
3174 | if (func == 1) |
3175 | do_exit(0); |
3176 | return 0; |
3177 | } |
3178 | |
3179 | /* |
3180 | * Buffer-head allocation |
3181 | */ |
3182 | static struct kmem_cache *bh_cachep; |
3183 | |
3184 | /* |
3185 | * Once the number of bh's in the machine exceeds this level, we start |
3186 | * stripping them in writeback. |
3187 | */ |
3188 | static int max_buffer_heads; |
3189 | |
3190 | int buffer_heads_over_limit; |
3191 | |
3192 | struct bh_accounting { |
3193 | int nr; /* Number of live bh's */ |
3194 | int ratelimit; /* Limit cacheline bouncing */ |
3195 | }; |
3196 | |
3197 | static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0}; |
3198 | |
3199 | static void recalc_bh_state(void) |
3200 | { |
3201 | int i; |
3202 | int tot = 0; |
3203 | |
3204 | if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096) |
3205 | return; |
3206 | __this_cpu_write(bh_accounting.ratelimit, 0); |
3207 | for_each_online_cpu(i) |
3208 | tot += per_cpu(bh_accounting, i).nr; |
3209 | buffer_heads_over_limit = (tot > max_buffer_heads); |
3210 | } |
3211 | |
3212 | struct buffer_head *alloc_buffer_head(gfp_t gfp_flags) |
3213 | { |
3214 | struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags); |
3215 | if (ret) { |
3216 | INIT_LIST_HEAD(&ret->b_assoc_buffers); |
3217 | preempt_disable(); |
3218 | __this_cpu_inc(bh_accounting.nr); |
3219 | recalc_bh_state(); |
3220 | preempt_enable(); |
3221 | } |
3222 | return ret; |
3223 | } |
3224 | EXPORT_SYMBOL(alloc_buffer_head); |
3225 | |
3226 | void free_buffer_head(struct buffer_head *bh) |
3227 | { |
3228 | BUG_ON(!list_empty(&bh->b_assoc_buffers)); |
3229 | kmem_cache_free(bh_cachep, bh); |
3230 | preempt_disable(); |
3231 | __this_cpu_dec(bh_accounting.nr); |
3232 | recalc_bh_state(); |
3233 | preempt_enable(); |
3234 | } |
3235 | EXPORT_SYMBOL(free_buffer_head); |
3236 | |
3237 | static void buffer_exit_cpu(int cpu) |
3238 | { |
3239 | int i; |
3240 | struct bh_lru *b = &per_cpu(bh_lrus, cpu); |
3241 | |
3242 | for (i = 0; i < BH_LRU_SIZE; i++) { |
3243 | brelse(b->bhs[i]); |
3244 | b->bhs[i] = NULL; |
3245 | } |
3246 | this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr); |
3247 | per_cpu(bh_accounting, cpu).nr = 0; |
3248 | } |
3249 | |
3250 | static int buffer_cpu_notify(struct notifier_block *self, |
3251 | unsigned long action, void *hcpu) |
3252 | { |
3253 | if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) |
3254 | buffer_exit_cpu((unsigned long)hcpu); |
3255 | return NOTIFY_OK; |
3256 | } |
3257 | |
3258 | /** |
3259 | * bh_uptodate_or_lock - Test whether the buffer is uptodate |
3260 | * @bh: struct buffer_head |
3261 | * |
3262 | * Return true if the buffer is up-to-date and false, |
3263 | * with the buffer locked, if not. |
3264 | */ |
3265 | int bh_uptodate_or_lock(struct buffer_head *bh) |
3266 | { |
3267 | if (!buffer_uptodate(bh)) { |
3268 | lock_buffer(bh); |
3269 | if (!buffer_uptodate(bh)) |
3270 | return 0; |
3271 | unlock_buffer(bh); |
3272 | } |
3273 | return 1; |
3274 | } |
3275 | EXPORT_SYMBOL(bh_uptodate_or_lock); |
3276 | |
3277 | /** |
3278 | * bh_submit_read - Submit a locked buffer for reading |
3279 | * @bh: struct buffer_head |
3280 | * |
3281 | * Returns zero on success and -EIO on error. |
3282 | */ |
3283 | int bh_submit_read(struct buffer_head *bh) |
3284 | { |
3285 | BUG_ON(!buffer_locked(bh)); |
3286 | |
3287 | if (buffer_uptodate(bh)) { |
3288 | unlock_buffer(bh); |
3289 | return 0; |
3290 | } |
3291 | |
3292 | get_bh(bh); |
3293 | bh->b_end_io = end_buffer_read_sync; |
3294 | submit_bh(READ, bh); |
3295 | wait_on_buffer(bh); |
3296 | if (buffer_uptodate(bh)) |
3297 | return 0; |
3298 | return -EIO; |
3299 | } |
3300 | EXPORT_SYMBOL(bh_submit_read); |
3301 | |
3302 | void __init buffer_init(void) |
3303 | { |
3304 | int nrpages; |
3305 | |
3306 | bh_cachep = kmem_cache_create("buffer_head", |
3307 | sizeof(struct buffer_head), 0, |
3308 | (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC| |
3309 | SLAB_MEM_SPREAD), |
3310 | NULL); |
3311 | |
3312 | /* |
3313 | * Limit the bh occupancy to 10% of ZONE_NORMAL |
3314 | */ |
3315 | nrpages = (nr_free_buffer_pages() * 10) / 100; |
3316 | max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head)); |
3317 | hotcpu_notifier(buffer_cpu_notify, 0); |
3318 | } |
3319 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.11
jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master
Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9