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1 | /* |
2 | * linux/fs/buffer.c |
3 | * |
4 | * Copyright (C) 1991, 1992, 2002 Linus Torvalds |
5 | */ |
6 | |
7 | /* |
8 | * Start bdflush() with kernel_thread not syscall - Paul Gortmaker, 12/95 |
9 | * |
10 | * Removed a lot of unnecessary code and simplified things now that |
11 | * the buffer cache isn't our primary cache - Andrew Tridgell 12/96 |
12 | * |
13 | * Speed up hash, lru, and free list operations. Use gfp() for allocating |
14 | * hash table, use SLAB cache for buffer heads. SMP threading. -DaveM |
15 | * |
16 | * Added 32k buffer block sizes - these are required older ARM systems. - RMK |
17 | * |
18 | * async buffer flushing, 1999 Andrea Arcangeli <andrea@suse.de> |
19 | */ |
20 | |
21 | #include <linux/kernel.h> |
22 | #include <linux/syscalls.h> |
23 | #include <linux/fs.h> |
24 | #include <linux/mm.h> |
25 | #include <linux/percpu.h> |
26 | #include <linux/slab.h> |
27 | #include <linux/capability.h> |
28 | #include <linux/blkdev.h> |
29 | #include <linux/file.h> |
30 | #include <linux/quotaops.h> |
31 | #include <linux/highmem.h> |
32 | #include <linux/module.h> |
33 | #include <linux/writeback.h> |
34 | #include <linux/hash.h> |
35 | #include <linux/suspend.h> |
36 | #include <linux/buffer_head.h> |
37 | #include <linux/task_io_accounting_ops.h> |
38 | #include <linux/bio.h> |
39 | #include <linux/notifier.h> |
40 | #include <linux/cpu.h> |
41 | #include <linux/bitops.h> |
42 | #include <linux/mpage.h> |
43 | #include <linux/bit_spinlock.h> |
44 | |
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 (!buffer_eopnotsupp(bh) && !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 | invalidate_mapping_pages(mapping, 0, -1); |
279 | } |
280 | EXPORT_SYMBOL(invalidate_bdev); |
281 | |
282 | /* |
283 | * Kick the writeback threads then try to free up some ZONE_NORMAL memory. |
284 | */ |
285 | static void free_more_memory(void) |
286 | { |
287 | struct zone *zone; |
288 | int nid; |
289 | |
290 | wakeup_flusher_threads(1024); |
291 | yield(); |
292 | |
293 | for_each_online_node(nid) { |
294 | (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS), |
295 | gfp_zone(GFP_NOFS), NULL, |
296 | &zone); |
297 | if (zone) |
298 | try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0, |
299 | GFP_NOFS, NULL); |
300 | } |
301 | } |
302 | |
303 | /* |
304 | * I/O completion handler for block_read_full_page() - pages |
305 | * which come unlocked at the end of I/O. |
306 | */ |
307 | static void end_buffer_async_read(struct buffer_head *bh, int uptodate) |
308 | { |
309 | unsigned long flags; |
310 | struct buffer_head *first; |
311 | struct buffer_head *tmp; |
312 | struct page *page; |
313 | int page_uptodate = 1; |
314 | |
315 | BUG_ON(!buffer_async_read(bh)); |
316 | |
317 | page = bh->b_page; |
318 | if (uptodate) { |
319 | set_buffer_uptodate(bh); |
320 | } else { |
321 | clear_buffer_uptodate(bh); |
322 | if (!quiet_error(bh)) |
323 | buffer_io_error(bh); |
324 | SetPageError(page); |
325 | } |
326 | |
327 | /* |
328 | * Be _very_ careful from here on. Bad things can happen if |
329 | * two buffer heads end IO at almost the same time and both |
330 | * decide that the page is now completely done. |
331 | */ |
332 | first = page_buffers(page); |
333 | local_irq_save(flags); |
334 | bit_spin_lock(BH_Uptodate_Lock, &first->b_state); |
335 | clear_buffer_async_read(bh); |
336 | unlock_buffer(bh); |
337 | tmp = bh; |
338 | do { |
339 | if (!buffer_uptodate(tmp)) |
340 | page_uptodate = 0; |
341 | if (buffer_async_read(tmp)) { |
342 | BUG_ON(!buffer_locked(tmp)); |
343 | goto still_busy; |
344 | } |
345 | tmp = tmp->b_this_page; |
346 | } while (tmp != bh); |
347 | bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
348 | local_irq_restore(flags); |
349 | |
350 | /* |
351 | * If none of the buffers had errors and they are all |
352 | * uptodate then we can set the page uptodate. |
353 | */ |
354 | if (page_uptodate && !PageError(page)) |
355 | SetPageUptodate(page); |
356 | unlock_page(page); |
357 | return; |
358 | |
359 | still_busy: |
360 | bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
361 | local_irq_restore(flags); |
362 | return; |
363 | } |
364 | |
365 | /* |
366 | * Completion handler for block_write_full_page() - pages which are unlocked |
367 | * during I/O, and which have PageWriteback cleared upon I/O completion. |
368 | */ |
369 | void end_buffer_async_write(struct buffer_head *bh, int uptodate) |
370 | { |
371 | char b[BDEVNAME_SIZE]; |
372 | unsigned long flags; |
373 | struct buffer_head *first; |
374 | struct buffer_head *tmp; |
375 | struct page *page; |
376 | |
377 | BUG_ON(!buffer_async_write(bh)); |
378 | |
379 | page = bh->b_page; |
380 | if (uptodate) { |
381 | set_buffer_uptodate(bh); |
382 | } else { |
383 | if (!quiet_error(bh)) { |
384 | buffer_io_error(bh); |
385 | printk(KERN_WARNING "lost page write due to " |
386 | "I/O error on %s\n", |
387 | bdevname(bh->b_bdev, b)); |
388 | } |
389 | set_bit(AS_EIO, &page->mapping->flags); |
390 | set_buffer_write_io_error(bh); |
391 | clear_buffer_uptodate(bh); |
392 | SetPageError(page); |
393 | } |
394 | |
395 | first = page_buffers(page); |
396 | local_irq_save(flags); |
397 | bit_spin_lock(BH_Uptodate_Lock, &first->b_state); |
398 | |
399 | clear_buffer_async_write(bh); |
400 | unlock_buffer(bh); |
401 | tmp = bh->b_this_page; |
402 | while (tmp != bh) { |
403 | if (buffer_async_write(tmp)) { |
404 | BUG_ON(!buffer_locked(tmp)); |
405 | goto still_busy; |
406 | } |
407 | tmp = tmp->b_this_page; |
408 | } |
409 | bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
410 | local_irq_restore(flags); |
411 | end_page_writeback(page); |
412 | return; |
413 | |
414 | still_busy: |
415 | bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
416 | local_irq_restore(flags); |
417 | return; |
418 | } |
419 | EXPORT_SYMBOL(end_buffer_async_write); |
420 | |
421 | /* |
422 | * If a page's buffers are under async readin (end_buffer_async_read |
423 | * completion) then there is a possibility that another thread of |
424 | * control could lock one of the buffers after it has completed |
425 | * but while some of the other buffers have not completed. This |
426 | * locked buffer would confuse end_buffer_async_read() into not unlocking |
427 | * the page. So the absence of BH_Async_Read tells end_buffer_async_read() |
428 | * that this buffer is not under async I/O. |
429 | * |
430 | * The page comes unlocked when it has no locked buffer_async buffers |
431 | * left. |
432 | * |
433 | * PageLocked prevents anyone starting new async I/O reads any of |
434 | * the buffers. |
435 | * |
436 | * PageWriteback is used to prevent simultaneous writeout of the same |
437 | * page. |
438 | * |
439 | * PageLocked prevents anyone from starting writeback of a page which is |
440 | * under read I/O (PageWriteback is only ever set against a locked page). |
441 | */ |
442 | static void mark_buffer_async_read(struct buffer_head *bh) |
443 | { |
444 | bh->b_end_io = end_buffer_async_read; |
445 | set_buffer_async_read(bh); |
446 | } |
447 | |
448 | static void mark_buffer_async_write_endio(struct buffer_head *bh, |
449 | bh_end_io_t *handler) |
450 | { |
451 | bh->b_end_io = handler; |
452 | set_buffer_async_write(bh); |
453 | } |
454 | |
455 | void mark_buffer_async_write(struct buffer_head *bh) |
456 | { |
457 | mark_buffer_async_write_endio(bh, end_buffer_async_write); |
458 | } |
459 | EXPORT_SYMBOL(mark_buffer_async_write); |
460 | |
461 | |
462 | /* |
463 | * fs/buffer.c contains helper functions for buffer-backed address space's |
464 | * fsync functions. A common requirement for buffer-based filesystems is |
465 | * that certain data from the backing blockdev needs to be written out for |
466 | * a successful fsync(). For example, ext2 indirect blocks need to be |
467 | * written back and waited upon before fsync() returns. |
468 | * |
469 | * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(), |
470 | * inode_has_buffers() and invalidate_inode_buffers() are provided for the |
471 | * management of a list of dependent buffers at ->i_mapping->private_list. |
472 | * |
473 | * Locking is a little subtle: try_to_free_buffers() will remove buffers |
474 | * from their controlling inode's queue when they are being freed. But |
475 | * try_to_free_buffers() will be operating against the *blockdev* mapping |
476 | * at the time, not against the S_ISREG file which depends on those buffers. |
477 | * So the locking for private_list is via the private_lock in the address_space |
478 | * which backs the buffers. Which is different from the address_space |
479 | * against which the buffers are listed. So for a particular address_space, |
480 | * mapping->private_lock does *not* protect mapping->private_list! In fact, |
481 | * mapping->private_list will always be protected by the backing blockdev's |
482 | * ->private_lock. |
483 | * |
484 | * Which introduces a requirement: all buffers on an address_space's |
485 | * ->private_list must be from the same address_space: the blockdev's. |
486 | * |
487 | * address_spaces which do not place buffers at ->private_list via these |
488 | * utility functions are free to use private_lock and private_list for |
489 | * whatever they want. The only requirement is that list_empty(private_list) |
490 | * be true at clear_inode() time. |
491 | * |
492 | * FIXME: clear_inode should not call invalidate_inode_buffers(). The |
493 | * filesystems should do that. invalidate_inode_buffers() should just go |
494 | * BUG_ON(!list_empty). |
495 | * |
496 | * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should |
497 | * take an address_space, not an inode. And it should be called |
498 | * mark_buffer_dirty_fsync() to clearly define why those buffers are being |
499 | * queued up. |
500 | * |
501 | * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the |
502 | * list if it is already on a list. Because if the buffer is on a list, |
503 | * it *must* already be on the right one. If not, the filesystem is being |
504 | * silly. This will save a ton of locking. But first we have to ensure |
505 | * that buffers are taken *off* the old inode's list when they are freed |
506 | * (presumably in truncate). That requires careful auditing of all |
507 | * filesystems (do it inside bforget()). It could also be done by bringing |
508 | * b_inode back. |
509 | */ |
510 | |
511 | /* |
512 | * The buffer's backing address_space's private_lock must be held |
513 | */ |
514 | static void __remove_assoc_queue(struct buffer_head *bh) |
515 | { |
516 | list_del_init(&bh->b_assoc_buffers); |
517 | WARN_ON(!bh->b_assoc_map); |
518 | if (buffer_write_io_error(bh)) |
519 | set_bit(AS_EIO, &bh->b_assoc_map->flags); |
520 | bh->b_assoc_map = NULL; |
521 | } |
522 | |
523 | int inode_has_buffers(struct inode *inode) |
524 | { |
525 | return !list_empty(&inode->i_data.private_list); |
526 | } |
527 | |
528 | /* |
529 | * osync is designed to support O_SYNC io. It waits synchronously for |
530 | * all already-submitted IO to complete, but does not queue any new |
531 | * writes to the disk. |
532 | * |
533 | * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as |
534 | * you dirty the buffers, and then use osync_inode_buffers to wait for |
535 | * completion. Any other dirty buffers which are not yet queued for |
536 | * write will not be flushed to disk by the osync. |
537 | */ |
538 | static int osync_buffers_list(spinlock_t *lock, struct list_head *list) |
539 | { |
540 | struct buffer_head *bh; |
541 | struct list_head *p; |
542 | int err = 0; |
543 | |
544 | spin_lock(lock); |
545 | repeat: |
546 | list_for_each_prev(p, list) { |
547 | bh = BH_ENTRY(p); |
548 | if (buffer_locked(bh)) { |
549 | get_bh(bh); |
550 | spin_unlock(lock); |
551 | wait_on_buffer(bh); |
552 | if (!buffer_uptodate(bh)) |
553 | err = -EIO; |
554 | brelse(bh); |
555 | spin_lock(lock); |
556 | goto repeat; |
557 | } |
558 | } |
559 | spin_unlock(lock); |
560 | return err; |
561 | } |
562 | |
563 | static void do_thaw_all(struct work_struct *work) |
564 | { |
565 | struct super_block *sb; |
566 | char b[BDEVNAME_SIZE]; |
567 | |
568 | spin_lock(&sb_lock); |
569 | restart: |
570 | list_for_each_entry(sb, &super_blocks, s_list) { |
571 | sb->s_count++; |
572 | spin_unlock(&sb_lock); |
573 | down_read(&sb->s_umount); |
574 | while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb)) |
575 | printk(KERN_WARNING "Emergency Thaw on %s\n", |
576 | bdevname(sb->s_bdev, b)); |
577 | up_read(&sb->s_umount); |
578 | spin_lock(&sb_lock); |
579 | if (__put_super_and_need_restart(sb)) |
580 | goto restart; |
581 | } |
582 | spin_unlock(&sb_lock); |
583 | kfree(work); |
584 | printk(KERN_WARNING "Emergency Thaw complete\n"); |
585 | } |
586 | |
587 | /** |
588 | * emergency_thaw_all -- forcibly thaw every frozen filesystem |
589 | * |
590 | * Used for emergency unfreeze of all filesystems via SysRq |
591 | */ |
592 | void emergency_thaw_all(void) |
593 | { |
594 | struct work_struct *work; |
595 | |
596 | work = kmalloc(sizeof(*work), GFP_ATOMIC); |
597 | if (work) { |
598 | INIT_WORK(work, do_thaw_all); |
599 | schedule_work(work); |
600 | } |
601 | } |
602 | |
603 | /** |
604 | * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers |
605 | * @mapping: the mapping which wants those buffers written |
606 | * |
607 | * Starts I/O against the buffers at mapping->private_list, and waits upon |
608 | * that I/O. |
609 | * |
610 | * Basically, this is a convenience function for fsync(). |
611 | * @mapping is a file or directory which needs those buffers to be written for |
612 | * a successful fsync(). |
613 | */ |
614 | int sync_mapping_buffers(struct address_space *mapping) |
615 | { |
616 | struct address_space *buffer_mapping = mapping->assoc_mapping; |
617 | |
618 | if (buffer_mapping == NULL || list_empty(&mapping->private_list)) |
619 | return 0; |
620 | |
621 | return fsync_buffers_list(&buffer_mapping->private_lock, |
622 | &mapping->private_list); |
623 | } |
624 | EXPORT_SYMBOL(sync_mapping_buffers); |
625 | |
626 | /* |
627 | * Called when we've recently written block `bblock', and it is known that |
628 | * `bblock' was for a buffer_boundary() buffer. This means that the block at |
629 | * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's |
630 | * dirty, schedule it for IO. So that indirects merge nicely with their data. |
631 | */ |
632 | void write_boundary_block(struct block_device *bdev, |
633 | sector_t bblock, unsigned blocksize) |
634 | { |
635 | struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize); |
636 | if (bh) { |
637 | if (buffer_dirty(bh)) |
638 | ll_rw_block(WRITE, 1, &bh); |
639 | put_bh(bh); |
640 | } |
641 | } |
642 | |
643 | void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode) |
644 | { |
645 | struct address_space *mapping = inode->i_mapping; |
646 | struct address_space *buffer_mapping = bh->b_page->mapping; |
647 | |
648 | mark_buffer_dirty(bh); |
649 | if (!mapping->assoc_mapping) { |
650 | mapping->assoc_mapping = buffer_mapping; |
651 | } else { |
652 | BUG_ON(mapping->assoc_mapping != buffer_mapping); |
653 | } |
654 | if (!bh->b_assoc_map) { |
655 | spin_lock(&buffer_mapping->private_lock); |
656 | list_move_tail(&bh->b_assoc_buffers, |
657 | &mapping->private_list); |
658 | bh->b_assoc_map = mapping; |
659 | spin_unlock(&buffer_mapping->private_lock); |
660 | } |
661 | } |
662 | EXPORT_SYMBOL(mark_buffer_dirty_inode); |
663 | |
664 | /* |
665 | * Mark the page dirty, and set it dirty in the radix tree, and mark the inode |
666 | * dirty. |
667 | * |
668 | * If warn is true, then emit a warning if the page is not uptodate and has |
669 | * not been truncated. |
670 | */ |
671 | static void __set_page_dirty(struct page *page, |
672 | struct address_space *mapping, int warn) |
673 | { |
674 | spin_lock_irq(&mapping->tree_lock); |
675 | if (page->mapping) { /* Race with truncate? */ |
676 | WARN_ON_ONCE(warn && !PageUptodate(page)); |
677 | account_page_dirtied(page, mapping); |
678 | radix_tree_tag_set(&mapping->page_tree, |
679 | page_index(page), PAGECACHE_TAG_DIRTY); |
680 | } |
681 | spin_unlock_irq(&mapping->tree_lock); |
682 | __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); |
683 | } |
684 | |
685 | /* |
686 | * Add a page to the dirty page list. |
687 | * |
688 | * It is a sad fact of life that this function is called from several places |
689 | * deeply under spinlocking. It may not sleep. |
690 | * |
691 | * If the page has buffers, the uptodate buffers are set dirty, to preserve |
692 | * dirty-state coherency between the page and the buffers. It the page does |
693 | * not have buffers then when they are later attached they will all be set |
694 | * dirty. |
695 | * |
696 | * The buffers are dirtied before the page is dirtied. There's a small race |
697 | * window in which a writepage caller may see the page cleanness but not the |
698 | * buffer dirtiness. That's fine. If this code were to set the page dirty |
699 | * before the buffers, a concurrent writepage caller could clear the page dirty |
700 | * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean |
701 | * page on the dirty page list. |
702 | * |
703 | * We use private_lock to lock against try_to_free_buffers while using the |
704 | * page's buffer list. Also use this to protect against clean buffers being |
705 | * added to the page after it was set dirty. |
706 | * |
707 | * FIXME: may need to call ->reservepage here as well. That's rather up to the |
708 | * address_space though. |
709 | */ |
710 | int __set_page_dirty_buffers(struct page *page) |
711 | { |
712 | int newly_dirty; |
713 | struct address_space *mapping = page_mapping(page); |
714 | |
715 | if (unlikely(!mapping)) |
716 | return !TestSetPageDirty(page); |
717 | |
718 | spin_lock(&mapping->private_lock); |
719 | if (page_has_buffers(page)) { |
720 | struct buffer_head *head = page_buffers(page); |
721 | struct buffer_head *bh = head; |
722 | |
723 | do { |
724 | set_buffer_dirty(bh); |
725 | bh = bh->b_this_page; |
726 | } while (bh != head); |
727 | } |
728 | newly_dirty = !TestSetPageDirty(page); |
729 | spin_unlock(&mapping->private_lock); |
730 | |
731 | if (newly_dirty) |
732 | __set_page_dirty(page, mapping, 1); |
733 | return newly_dirty; |
734 | } |
735 | EXPORT_SYMBOL(__set_page_dirty_buffers); |
736 | |
737 | /* |
738 | * Write out and wait upon a list of buffers. |
739 | * |
740 | * We have conflicting pressures: we want to make sure that all |
741 | * initially dirty buffers get waited on, but that any subsequently |
742 | * dirtied buffers don't. After all, we don't want fsync to last |
743 | * forever if somebody is actively writing to the file. |
744 | * |
745 | * Do this in two main stages: first we copy dirty buffers to a |
746 | * temporary inode list, queueing the writes as we go. Then we clean |
747 | * up, waiting for those writes to complete. |
748 | * |
749 | * During this second stage, any subsequent updates to the file may end |
750 | * up refiling the buffer on the original inode's dirty list again, so |
751 | * there is a chance we will end up with a buffer queued for write but |
752 | * not yet completed on that list. So, as a final cleanup we go through |
753 | * the osync code to catch these locked, dirty buffers without requeuing |
754 | * any newly dirty buffers for write. |
755 | */ |
756 | static int fsync_buffers_list(spinlock_t *lock, struct list_head *list) |
757 | { |
758 | struct buffer_head *bh; |
759 | struct list_head tmp; |
760 | struct address_space *mapping, *prev_mapping = NULL; |
761 | int err = 0, err2; |
762 | |
763 | INIT_LIST_HEAD(&tmp); |
764 | |
765 | spin_lock(lock); |
766 | while (!list_empty(list)) { |
767 | bh = BH_ENTRY(list->next); |
768 | mapping = bh->b_assoc_map; |
769 | __remove_assoc_queue(bh); |
770 | /* Avoid race with mark_buffer_dirty_inode() which does |
771 | * a lockless check and we rely on seeing the dirty bit */ |
772 | smp_mb(); |
773 | if (buffer_dirty(bh) || buffer_locked(bh)) { |
774 | list_add(&bh->b_assoc_buffers, &tmp); |
775 | bh->b_assoc_map = mapping; |
776 | if (buffer_dirty(bh)) { |
777 | get_bh(bh); |
778 | spin_unlock(lock); |
779 | /* |
780 | * Ensure any pending I/O completes so that |
781 | * ll_rw_block() actually writes the current |
782 | * contents - it is a noop if I/O is still in |
783 | * flight on potentially older contents. |
784 | */ |
785 | ll_rw_block(SWRITE_SYNC_PLUG, 1, &bh); |
786 | |
787 | /* |
788 | * Kick off IO for the previous mapping. Note |
789 | * that we will not run the very last mapping, |
790 | * wait_on_buffer() will do that for us |
791 | * through sync_buffer(). |
792 | */ |
793 | if (prev_mapping && prev_mapping != mapping) |
794 | blk_run_address_space(prev_mapping); |
795 | prev_mapping = mapping; |
796 | |
797 | brelse(bh); |
798 | spin_lock(lock); |
799 | } |
800 | } |
801 | } |
802 | |
803 | while (!list_empty(&tmp)) { |
804 | bh = BH_ENTRY(tmp.prev); |
805 | get_bh(bh); |
806 | mapping = bh->b_assoc_map; |
807 | __remove_assoc_queue(bh); |
808 | /* Avoid race with mark_buffer_dirty_inode() which does |
809 | * a lockless check and we rely on seeing the dirty bit */ |
810 | smp_mb(); |
811 | if (buffer_dirty(bh)) { |
812 | list_add(&bh->b_assoc_buffers, |
813 | &mapping->private_list); |
814 | bh->b_assoc_map = mapping; |
815 | } |
816 | spin_unlock(lock); |
817 | wait_on_buffer(bh); |
818 | if (!buffer_uptodate(bh)) |
819 | err = -EIO; |
820 | brelse(bh); |
821 | spin_lock(lock); |
822 | } |
823 | |
824 | spin_unlock(lock); |
825 | err2 = osync_buffers_list(lock, list); |
826 | if (err) |
827 | return err; |
828 | else |
829 | return err2; |
830 | } |
831 | |
832 | /* |
833 | * Invalidate any and all dirty buffers on a given inode. We are |
834 | * probably unmounting the fs, but that doesn't mean we have already |
835 | * done a sync(). Just drop the buffers from the inode list. |
836 | * |
837 | * NOTE: we take the inode's blockdev's mapping's private_lock. Which |
838 | * assumes that all the buffers are against the blockdev. Not true |
839 | * for reiserfs. |
840 | */ |
841 | void invalidate_inode_buffers(struct inode *inode) |
842 | { |
843 | if (inode_has_buffers(inode)) { |
844 | struct address_space *mapping = &inode->i_data; |
845 | struct list_head *list = &mapping->private_list; |
846 | struct address_space *buffer_mapping = mapping->assoc_mapping; |
847 | |
848 | spin_lock(&buffer_mapping->private_lock); |
849 | while (!list_empty(list)) |
850 | __remove_assoc_queue(BH_ENTRY(list->next)); |
851 | spin_unlock(&buffer_mapping->private_lock); |
852 | } |
853 | } |
854 | EXPORT_SYMBOL(invalidate_inode_buffers); |
855 | |
856 | /* |
857 | * Remove any clean buffers from the inode's buffer list. This is called |
858 | * when we're trying to free the inode itself. Those buffers can pin it. |
859 | * |
860 | * Returns true if all buffers were removed. |
861 | */ |
862 | int remove_inode_buffers(struct inode *inode) |
863 | { |
864 | int ret = 1; |
865 | |
866 | if (inode_has_buffers(inode)) { |
867 | struct address_space *mapping = &inode->i_data; |
868 | struct list_head *list = &mapping->private_list; |
869 | struct address_space *buffer_mapping = mapping->assoc_mapping; |
870 | |
871 | spin_lock(&buffer_mapping->private_lock); |
872 | while (!list_empty(list)) { |
873 | struct buffer_head *bh = BH_ENTRY(list->next); |
874 | if (buffer_dirty(bh)) { |
875 | ret = 0; |
876 | break; |
877 | } |
878 | __remove_assoc_queue(bh); |
879 | } |
880 | spin_unlock(&buffer_mapping->private_lock); |
881 | } |
882 | return ret; |
883 | } |
884 | |
885 | /* |
886 | * Create the appropriate buffers when given a page for data area and |
887 | * the size of each buffer.. Use the bh->b_this_page linked list to |
888 | * follow the buffers created. Return NULL if unable to create more |
889 | * buffers. |
890 | * |
891 | * The retry flag is used to differentiate async IO (paging, swapping) |
892 | * which may not fail from ordinary buffer allocations. |
893 | */ |
894 | struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, |
895 | int retry) |
896 | { |
897 | struct buffer_head *bh, *head; |
898 | long offset; |
899 | |
900 | try_again: |
901 | head = NULL; |
902 | offset = PAGE_SIZE; |
903 | while ((offset -= size) >= 0) { |
904 | bh = alloc_buffer_head(GFP_NOFS); |
905 | if (!bh) |
906 | goto no_grow; |
907 | |
908 | bh->b_bdev = NULL; |
909 | bh->b_this_page = head; |
910 | bh->b_blocknr = -1; |
911 | head = bh; |
912 | |
913 | bh->b_state = 0; |
914 | atomic_set(&bh->b_count, 0); |
915 | bh->b_private = NULL; |
916 | bh->b_size = size; |
917 | |
918 | /* Link the buffer to its page */ |
919 | set_bh_page(bh, page, offset); |
920 | |
921 | init_buffer(bh, NULL, NULL); |
922 | } |
923 | return head; |
924 | /* |
925 | * In case anything failed, we just free everything we got. |
926 | */ |
927 | no_grow: |
928 | if (head) { |
929 | do { |
930 | bh = head; |
931 | head = head->b_this_page; |
932 | free_buffer_head(bh); |
933 | } while (head); |
934 | } |
935 | |
936 | /* |
937 | * Return failure for non-async IO requests. Async IO requests |
938 | * are not allowed to fail, so we have to wait until buffer heads |
939 | * become available. But we don't want tasks sleeping with |
940 | * partially complete buffers, so all were released above. |
941 | */ |
942 | if (!retry) |
943 | return NULL; |
944 | |
945 | /* We're _really_ low on memory. Now we just |
946 | * wait for old buffer heads to become free due to |
947 | * finishing IO. Since this is an async request and |
948 | * the reserve list is empty, we're sure there are |
949 | * async buffer heads in use. |
950 | */ |
951 | free_more_memory(); |
952 | goto try_again; |
953 | } |
954 | EXPORT_SYMBOL_GPL(alloc_page_buffers); |
955 | |
956 | static inline void |
957 | link_dev_buffers(struct page *page, struct buffer_head *head) |
958 | { |
959 | struct buffer_head *bh, *tail; |
960 | |
961 | bh = head; |
962 | do { |
963 | tail = bh; |
964 | bh = bh->b_this_page; |
965 | } while (bh); |
966 | tail->b_this_page = head; |
967 | attach_page_buffers(page, head); |
968 | } |
969 | |
970 | /* |
971 | * Initialise the state of a blockdev page's buffers. |
972 | */ |
973 | static void |
974 | init_page_buffers(struct page *page, struct block_device *bdev, |
975 | sector_t block, int size) |
976 | { |
977 | struct buffer_head *head = page_buffers(page); |
978 | struct buffer_head *bh = head; |
979 | int uptodate = PageUptodate(page); |
980 | |
981 | do { |
982 | if (!buffer_mapped(bh)) { |
983 | init_buffer(bh, NULL, NULL); |
984 | bh->b_bdev = bdev; |
985 | bh->b_blocknr = block; |
986 | if (uptodate) |
987 | set_buffer_uptodate(bh); |
988 | set_buffer_mapped(bh); |
989 | } |
990 | block++; |
991 | bh = bh->b_this_page; |
992 | } while (bh != head); |
993 | } |
994 | |
995 | /* |
996 | * Create the page-cache page that contains the requested block. |
997 | * |
998 | * This is user purely for blockdev mappings. |
999 | */ |
1000 | static struct page * |
1001 | grow_dev_page(struct block_device *bdev, sector_t block, |
1002 | pgoff_t index, int size) |
1003 | { |
1004 | struct inode *inode = bdev->bd_inode; |
1005 | struct page *page; |
1006 | struct buffer_head *bh; |
1007 | |
1008 | page = find_or_create_page(inode->i_mapping, index, |
1009 | (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE); |
1010 | if (!page) |
1011 | return NULL; |
1012 | |
1013 | BUG_ON(!PageLocked(page)); |
1014 | |
1015 | if (page_has_buffers(page)) { |
1016 | bh = page_buffers(page); |
1017 | if (bh->b_size == size) { |
1018 | init_page_buffers(page, bdev, block, size); |
1019 | return page; |
1020 | } |
1021 | if (!try_to_free_buffers(page)) |
1022 | goto failed; |
1023 | } |
1024 | |
1025 | /* |
1026 | * Allocate some buffers for this page |
1027 | */ |
1028 | bh = alloc_page_buffers(page, size, 0); |
1029 | if (!bh) |
1030 | goto failed; |
1031 | |
1032 | /* |
1033 | * Link the page to the buffers and initialise them. Take the |
1034 | * lock to be atomic wrt __find_get_block(), which does not |
1035 | * run under the page lock. |
1036 | */ |
1037 | spin_lock(&inode->i_mapping->private_lock); |
1038 | link_dev_buffers(page, bh); |
1039 | init_page_buffers(page, bdev, block, size); |
1040 | spin_unlock(&inode->i_mapping->private_lock); |
1041 | return page; |
1042 | |
1043 | failed: |
1044 | BUG(); |
1045 | unlock_page(page); |
1046 | page_cache_release(page); |
1047 | return NULL; |
1048 | } |
1049 | |
1050 | /* |
1051 | * Create buffers for the specified block device block's page. If |
1052 | * that page was dirty, the buffers are set dirty also. |
1053 | */ |
1054 | static int |
1055 | grow_buffers(struct block_device *bdev, sector_t block, int size) |
1056 | { |
1057 | struct page *page; |
1058 | pgoff_t index; |
1059 | int sizebits; |
1060 | |
1061 | sizebits = -1; |
1062 | do { |
1063 | sizebits++; |
1064 | } while ((size << sizebits) < PAGE_SIZE); |
1065 | |
1066 | index = block >> sizebits; |
1067 | |
1068 | /* |
1069 | * Check for a block which wants to lie outside our maximum possible |
1070 | * pagecache index. (this comparison is done using sector_t types). |
1071 | */ |
1072 | if (unlikely(index != block >> sizebits)) { |
1073 | char b[BDEVNAME_SIZE]; |
1074 | |
1075 | printk(KERN_ERR "%s: requested out-of-range block %llu for " |
1076 | "device %s\n", |
1077 | __func__, (unsigned long long)block, |
1078 | bdevname(bdev, b)); |
1079 | return -EIO; |
1080 | } |
1081 | block = index << sizebits; |
1082 | /* Create a page with the proper size buffers.. */ |
1083 | page = grow_dev_page(bdev, block, index, size); |
1084 | if (!page) |
1085 | return 0; |
1086 | unlock_page(page); |
1087 | page_cache_release(page); |
1088 | return 1; |
1089 | } |
1090 | |
1091 | static struct buffer_head * |
1092 | __getblk_slow(struct block_device *bdev, sector_t block, int size) |
1093 | { |
1094 | /* Size must be multiple of hard sectorsize */ |
1095 | if (unlikely(size & (bdev_logical_block_size(bdev)-1) || |
1096 | (size < 512 || size > PAGE_SIZE))) { |
1097 | printk(KERN_ERR "getblk(): invalid block size %d requested\n", |
1098 | size); |
1099 | printk(KERN_ERR "logical block size: %d\n", |
1100 | bdev_logical_block_size(bdev)); |
1101 | |
1102 | dump_stack(); |
1103 | return NULL; |
1104 | } |
1105 | |
1106 | for (;;) { |
1107 | struct buffer_head * bh; |
1108 | int ret; |
1109 | |
1110 | bh = __find_get_block(bdev, block, size); |
1111 | if (bh) |
1112 | return bh; |
1113 | |
1114 | ret = grow_buffers(bdev, block, size); |
1115 | if (ret < 0) |
1116 | return NULL; |
1117 | if (ret == 0) |
1118 | free_more_memory(); |
1119 | } |
1120 | } |
1121 | |
1122 | /* |
1123 | * The relationship between dirty buffers and dirty pages: |
1124 | * |
1125 | * Whenever a page has any dirty buffers, the page's dirty bit is set, and |
1126 | * the page is tagged dirty in its radix tree. |
1127 | * |
1128 | * At all times, the dirtiness of the buffers represents the dirtiness of |
1129 | * subsections of the page. If the page has buffers, the page dirty bit is |
1130 | * merely a hint about the true dirty state. |
1131 | * |
1132 | * When a page is set dirty in its entirety, all its buffers are marked dirty |
1133 | * (if the page has buffers). |
1134 | * |
1135 | * When a buffer is marked dirty, its page is dirtied, but the page's other |
1136 | * buffers are not. |
1137 | * |
1138 | * Also. When blockdev buffers are explicitly read with bread(), they |
1139 | * individually become uptodate. But their backing page remains not |
1140 | * uptodate - even if all of its buffers are uptodate. A subsequent |
1141 | * block_read_full_page() against that page will discover all the uptodate |
1142 | * buffers, will set the page uptodate and will perform no I/O. |
1143 | */ |
1144 | |
1145 | /** |
1146 | * mark_buffer_dirty - mark a buffer_head as needing writeout |
1147 | * @bh: the buffer_head to mark dirty |
1148 | * |
1149 | * mark_buffer_dirty() will set the dirty bit against the buffer, then set its |
1150 | * backing page dirty, then tag the page as dirty in its address_space's radix |
1151 | * tree and then attach the address_space's inode to its superblock's dirty |
1152 | * inode list. |
1153 | * |
1154 | * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock, |
1155 | * mapping->tree_lock and the global inode_lock. |
1156 | */ |
1157 | void mark_buffer_dirty(struct buffer_head *bh) |
1158 | { |
1159 | WARN_ON_ONCE(!buffer_uptodate(bh)); |
1160 | |
1161 | /* |
1162 | * Very *carefully* optimize the it-is-already-dirty case. |
1163 | * |
1164 | * Don't let the final "is it dirty" escape to before we |
1165 | * perhaps modified the buffer. |
1166 | */ |
1167 | if (buffer_dirty(bh)) { |
1168 | smp_mb(); |
1169 | if (buffer_dirty(bh)) |
1170 | return; |
1171 | } |
1172 | |
1173 | if (!test_set_buffer_dirty(bh)) { |
1174 | struct page *page = bh->b_page; |
1175 | if (!TestSetPageDirty(page)) { |
1176 | struct address_space *mapping = page_mapping(page); |
1177 | if (mapping) |
1178 | __set_page_dirty(page, mapping, 0); |
1179 | } |
1180 | } |
1181 | } |
1182 | EXPORT_SYMBOL(mark_buffer_dirty); |
1183 | |
1184 | /* |
1185 | * Decrement a buffer_head's reference count. If all buffers against a page |
1186 | * have zero reference count, are clean and unlocked, and if the page is clean |
1187 | * and unlocked then try_to_free_buffers() may strip the buffers from the page |
1188 | * in preparation for freeing it (sometimes, rarely, buffers are removed from |
1189 | * a page but it ends up not being freed, and buffers may later be reattached). |
1190 | */ |
1191 | void __brelse(struct buffer_head * buf) |
1192 | { |
1193 | if (atomic_read(&buf->b_count)) { |
1194 | put_bh(buf); |
1195 | return; |
1196 | } |
1197 | WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n"); |
1198 | } |
1199 | EXPORT_SYMBOL(__brelse); |
1200 | |
1201 | /* |
1202 | * bforget() is like brelse(), except it discards any |
1203 | * potentially dirty data. |
1204 | */ |
1205 | void __bforget(struct buffer_head *bh) |
1206 | { |
1207 | clear_buffer_dirty(bh); |
1208 | if (bh->b_assoc_map) { |
1209 | struct address_space *buffer_mapping = bh->b_page->mapping; |
1210 | |
1211 | spin_lock(&buffer_mapping->private_lock); |
1212 | list_del_init(&bh->b_assoc_buffers); |
1213 | bh->b_assoc_map = NULL; |
1214 | spin_unlock(&buffer_mapping->private_lock); |
1215 | } |
1216 | __brelse(bh); |
1217 | } |
1218 | EXPORT_SYMBOL(__bforget); |
1219 | |
1220 | static struct buffer_head *__bread_slow(struct buffer_head *bh) |
1221 | { |
1222 | lock_buffer(bh); |
1223 | if (buffer_uptodate(bh)) { |
1224 | unlock_buffer(bh); |
1225 | return bh; |
1226 | } else { |
1227 | get_bh(bh); |
1228 | bh->b_end_io = end_buffer_read_sync; |
1229 | submit_bh(READ, bh); |
1230 | wait_on_buffer(bh); |
1231 | if (buffer_uptodate(bh)) |
1232 | return bh; |
1233 | } |
1234 | brelse(bh); |
1235 | return NULL; |
1236 | } |
1237 | |
1238 | /* |
1239 | * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block(). |
1240 | * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their |
1241 | * refcount elevated by one when they're in an LRU. A buffer can only appear |
1242 | * once in a particular CPU's LRU. A single buffer can be present in multiple |
1243 | * CPU's LRUs at the same time. |
1244 | * |
1245 | * This is a transparent caching front-end to sb_bread(), sb_getblk() and |
1246 | * sb_find_get_block(). |
1247 | * |
1248 | * The LRUs themselves only need locking against invalidate_bh_lrus. We use |
1249 | * a local interrupt disable for that. |
1250 | */ |
1251 | |
1252 | #define BH_LRU_SIZE 8 |
1253 | |
1254 | struct bh_lru { |
1255 | struct buffer_head *bhs[BH_LRU_SIZE]; |
1256 | }; |
1257 | |
1258 | static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }}; |
1259 | |
1260 | #ifdef CONFIG_SMP |
1261 | #define bh_lru_lock() local_irq_disable() |
1262 | #define bh_lru_unlock() local_irq_enable() |
1263 | #else |
1264 | #define bh_lru_lock() preempt_disable() |
1265 | #define bh_lru_unlock() preempt_enable() |
1266 | #endif |
1267 | |
1268 | static inline void check_irqs_on(void) |
1269 | { |
1270 | #ifdef irqs_disabled |
1271 | BUG_ON(irqs_disabled()); |
1272 | #endif |
1273 | } |
1274 | |
1275 | /* |
1276 | * The LRU management algorithm is dopey-but-simple. Sorry. |
1277 | */ |
1278 | static void bh_lru_install(struct buffer_head *bh) |
1279 | { |
1280 | struct buffer_head *evictee = NULL; |
1281 | struct bh_lru *lru; |
1282 | |
1283 | check_irqs_on(); |
1284 | bh_lru_lock(); |
1285 | lru = &__get_cpu_var(bh_lrus); |
1286 | if (lru->bhs[0] != bh) { |
1287 | struct buffer_head *bhs[BH_LRU_SIZE]; |
1288 | int in; |
1289 | int out = 0; |
1290 | |
1291 | get_bh(bh); |
1292 | bhs[out++] = bh; |
1293 | for (in = 0; in < BH_LRU_SIZE; in++) { |
1294 | struct buffer_head *bh2 = lru->bhs[in]; |
1295 | |
1296 | if (bh2 == bh) { |
1297 | __brelse(bh2); |
1298 | } else { |
1299 | if (out >= BH_LRU_SIZE) { |
1300 | BUG_ON(evictee != NULL); |
1301 | evictee = bh2; |
1302 | } else { |
1303 | bhs[out++] = bh2; |
1304 | } |
1305 | } |
1306 | } |
1307 | while (out < BH_LRU_SIZE) |
1308 | bhs[out++] = NULL; |
1309 | memcpy(lru->bhs, bhs, sizeof(bhs)); |
1310 | } |
1311 | bh_lru_unlock(); |
1312 | |
1313 | if (evictee) |
1314 | __brelse(evictee); |
1315 | } |
1316 | |
1317 | /* |
1318 | * Look up the bh in this cpu's LRU. If it's there, move it to the head. |
1319 | */ |
1320 | static struct buffer_head * |
1321 | lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size) |
1322 | { |
1323 | struct buffer_head *ret = NULL; |
1324 | struct bh_lru *lru; |
1325 | unsigned int i; |
1326 | |
1327 | check_irqs_on(); |
1328 | bh_lru_lock(); |
1329 | lru = &__get_cpu_var(bh_lrus); |
1330 | for (i = 0; i < BH_LRU_SIZE; i++) { |
1331 | struct buffer_head *bh = lru->bhs[i]; |
1332 | |
1333 | if (bh && bh->b_bdev == bdev && |
1334 | bh->b_blocknr == block && bh->b_size == size) { |
1335 | if (i) { |
1336 | while (i) { |
1337 | lru->bhs[i] = lru->bhs[i - 1]; |
1338 | i--; |
1339 | } |
1340 | lru->bhs[0] = bh; |
1341 | } |
1342 | get_bh(bh); |
1343 | ret = bh; |
1344 | break; |
1345 | } |
1346 | } |
1347 | bh_lru_unlock(); |
1348 | return ret; |
1349 | } |
1350 | |
1351 | /* |
1352 | * Perform a pagecache lookup for the matching buffer. If it's there, refresh |
1353 | * it in the LRU and mark it as accessed. If it is not present then return |
1354 | * NULL |
1355 | */ |
1356 | struct buffer_head * |
1357 | __find_get_block(struct block_device *bdev, sector_t block, unsigned size) |
1358 | { |
1359 | struct buffer_head *bh = lookup_bh_lru(bdev, block, size); |
1360 | |
1361 | if (bh == NULL) { |
1362 | bh = __find_get_block_slow(bdev, block); |
1363 | if (bh) |
1364 | bh_lru_install(bh); |
1365 | } |
1366 | if (bh) |
1367 | touch_buffer(bh); |
1368 | return bh; |
1369 | } |
1370 | EXPORT_SYMBOL(__find_get_block); |
1371 | |
1372 | /* |
1373 | * __getblk will locate (and, if necessary, create) the buffer_head |
1374 | * which corresponds to the passed block_device, block and size. The |
1375 | * returned buffer has its reference count incremented. |
1376 | * |
1377 | * __getblk() cannot fail - it just keeps trying. If you pass it an |
1378 | * illegal block number, __getblk() will happily return a buffer_head |
1379 | * which represents the non-existent block. Very weird. |
1380 | * |
1381 | * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers() |
1382 | * attempt is failing. FIXME, perhaps? |
1383 | */ |
1384 | struct buffer_head * |
1385 | __getblk(struct block_device *bdev, sector_t block, unsigned size) |
1386 | { |
1387 | struct buffer_head *bh = __find_get_block(bdev, block, size); |
1388 | |
1389 | might_sleep(); |
1390 | if (bh == NULL) |
1391 | bh = __getblk_slow(bdev, block, size); |
1392 | return bh; |
1393 | } |
1394 | EXPORT_SYMBOL(__getblk); |
1395 | |
1396 | /* |
1397 | * Do async read-ahead on a buffer.. |
1398 | */ |
1399 | void __breadahead(struct block_device *bdev, sector_t block, unsigned size) |
1400 | { |
1401 | struct buffer_head *bh = __getblk(bdev, block, size); |
1402 | if (likely(bh)) { |
1403 | ll_rw_block(READA, 1, &bh); |
1404 | brelse(bh); |
1405 | } |
1406 | } |
1407 | EXPORT_SYMBOL(__breadahead); |
1408 | |
1409 | /** |
1410 | * __bread() - reads a specified block and returns the bh |
1411 | * @bdev: the block_device to read from |
1412 | * @block: number of block |
1413 | * @size: size (in bytes) to read |
1414 | * |
1415 | * Reads a specified block, and returns buffer head that contains it. |
1416 | * It returns NULL if the block was unreadable. |
1417 | */ |
1418 | struct buffer_head * |
1419 | __bread(struct block_device *bdev, sector_t block, unsigned size) |
1420 | { |
1421 | struct buffer_head *bh = __getblk(bdev, block, size); |
1422 | |
1423 | if (likely(bh) && !buffer_uptodate(bh)) |
1424 | bh = __bread_slow(bh); |
1425 | return bh; |
1426 | } |
1427 | EXPORT_SYMBOL(__bread); |
1428 | |
1429 | /* |
1430 | * invalidate_bh_lrus() is called rarely - but not only at unmount. |
1431 | * This doesn't race because it runs in each cpu either in irq |
1432 | * or with preempt disabled. |
1433 | */ |
1434 | static void invalidate_bh_lru(void *arg) |
1435 | { |
1436 | struct bh_lru *b = &get_cpu_var(bh_lrus); |
1437 | int i; |
1438 | |
1439 | for (i = 0; i < BH_LRU_SIZE; i++) { |
1440 | brelse(b->bhs[i]); |
1441 | b->bhs[i] = NULL; |
1442 | } |
1443 | put_cpu_var(bh_lrus); |
1444 | } |
1445 | |
1446 | void invalidate_bh_lrus(void) |
1447 | { |
1448 | on_each_cpu(invalidate_bh_lru, NULL, 1); |
1449 | } |
1450 | EXPORT_SYMBOL_GPL(invalidate_bh_lrus); |
1451 | |
1452 | void set_bh_page(struct buffer_head *bh, |
1453 | struct page *page, unsigned long offset) |
1454 | { |
1455 | bh->b_page = page; |
1456 | BUG_ON(offset >= PAGE_SIZE); |
1457 | if (PageHighMem(page)) |
1458 | /* |
1459 | * This catches illegal uses and preserves the offset: |
1460 | */ |
1461 | bh->b_data = (char *)(0 + offset); |
1462 | else |
1463 | bh->b_data = page_address(page) + offset; |
1464 | } |
1465 | EXPORT_SYMBOL(set_bh_page); |
1466 | |
1467 | /* |
1468 | * Called when truncating a buffer on a page completely. |
1469 | */ |
1470 | static void discard_buffer(struct buffer_head * bh) |
1471 | { |
1472 | lock_buffer(bh); |
1473 | clear_buffer_dirty(bh); |
1474 | bh->b_bdev = NULL; |
1475 | clear_buffer_mapped(bh); |
1476 | clear_buffer_req(bh); |
1477 | clear_buffer_new(bh); |
1478 | clear_buffer_delay(bh); |
1479 | clear_buffer_unwritten(bh); |
1480 | unlock_buffer(bh); |
1481 | } |
1482 | |
1483 | /** |
1484 | * block_invalidatepage - invalidate part of all of a buffer-backed page |
1485 | * |
1486 | * @page: the page which is affected |
1487 | * @offset: the index of the truncation point |
1488 | * |
1489 | * block_invalidatepage() is called when all or part of the page has become |
1490 | * invalidatedby a truncate operation. |
1491 | * |
1492 | * block_invalidatepage() does not have to release all buffers, but it must |
1493 | * ensure that no dirty buffer is left outside @offset and that no I/O |
1494 | * is underway against any of the blocks which are outside the truncation |
1495 | * point. Because the caller is about to free (and possibly reuse) those |
1496 | * blocks on-disk. |
1497 | */ |
1498 | void block_invalidatepage(struct page *page, unsigned long offset) |
1499 | { |
1500 | struct buffer_head *head, *bh, *next; |
1501 | unsigned int curr_off = 0; |
1502 | |
1503 | BUG_ON(!PageLocked(page)); |
1504 | if (!page_has_buffers(page)) |
1505 | goto out; |
1506 | |
1507 | head = page_buffers(page); |
1508 | bh = head; |
1509 | do { |
1510 | unsigned int next_off = curr_off + bh->b_size; |
1511 | next = bh->b_this_page; |
1512 | |
1513 | /* |
1514 | * is this block fully invalidated? |
1515 | */ |
1516 | if (offset <= curr_off) |
1517 | discard_buffer(bh); |
1518 | curr_off = next_off; |
1519 | bh = next; |
1520 | } while (bh != head); |
1521 | |
1522 | /* |
1523 | * We release buffers only if the entire page is being invalidated. |
1524 | * The get_block cached value has been unconditionally invalidated, |
1525 | * so real IO is not possible anymore. |
1526 | */ |
1527 | if (offset == 0) |
1528 | try_to_release_page(page, 0); |
1529 | out: |
1530 | return; |
1531 | } |
1532 | EXPORT_SYMBOL(block_invalidatepage); |
1533 | |
1534 | /* |
1535 | * We attach and possibly dirty the buffers atomically wrt |
1536 | * __set_page_dirty_buffers() via private_lock. try_to_free_buffers |
1537 | * is already excluded via the page lock. |
1538 | */ |
1539 | void create_empty_buffers(struct page *page, |
1540 | unsigned long blocksize, unsigned long b_state) |
1541 | { |
1542 | struct buffer_head *bh, *head, *tail; |
1543 | |
1544 | head = alloc_page_buffers(page, blocksize, 1); |
1545 | bh = head; |
1546 | do { |
1547 | bh->b_state |= b_state; |
1548 | tail = bh; |
1549 | bh = bh->b_this_page; |
1550 | } while (bh); |
1551 | tail->b_this_page = head; |
1552 | |
1553 | spin_lock(&page->mapping->private_lock); |
1554 | if (PageUptodate(page) || PageDirty(page)) { |
1555 | bh = head; |
1556 | do { |
1557 | if (PageDirty(page)) |
1558 | set_buffer_dirty(bh); |
1559 | if (PageUptodate(page)) |
1560 | set_buffer_uptodate(bh); |
1561 | bh = bh->b_this_page; |
1562 | } while (bh != head); |
1563 | } |
1564 | attach_page_buffers(page, head); |
1565 | spin_unlock(&page->mapping->private_lock); |
1566 | } |
1567 | EXPORT_SYMBOL(create_empty_buffers); |
1568 | |
1569 | /* |
1570 | * We are taking a block for data and we don't want any output from any |
1571 | * buffer-cache aliases starting from return from that function and |
1572 | * until the moment when something will explicitly mark the buffer |
1573 | * dirty (hopefully that will not happen until we will free that block ;-) |
1574 | * We don't even need to mark it not-uptodate - nobody can expect |
1575 | * anything from a newly allocated buffer anyway. We used to used |
1576 | * unmap_buffer() for such invalidation, but that was wrong. We definitely |
1577 | * don't want to mark the alias unmapped, for example - it would confuse |
1578 | * anyone who might pick it with bread() afterwards... |
1579 | * |
1580 | * Also.. Note that bforget() doesn't lock the buffer. So there can |
1581 | * be writeout I/O going on against recently-freed buffers. We don't |
1582 | * wait on that I/O in bforget() - it's more efficient to wait on the I/O |
1583 | * only if we really need to. That happens here. |
1584 | */ |
1585 | void unmap_underlying_metadata(struct block_device *bdev, sector_t block) |
1586 | { |
1587 | struct buffer_head *old_bh; |
1588 | |
1589 | might_sleep(); |
1590 | |
1591 | old_bh = __find_get_block_slow(bdev, block); |
1592 | if (old_bh) { |
1593 | clear_buffer_dirty(old_bh); |
1594 | wait_on_buffer(old_bh); |
1595 | clear_buffer_req(old_bh); |
1596 | __brelse(old_bh); |
1597 | } |
1598 | } |
1599 | EXPORT_SYMBOL(unmap_underlying_metadata); |
1600 | |
1601 | /* |
1602 | * NOTE! All mapped/uptodate combinations are valid: |
1603 | * |
1604 | * Mapped Uptodate Meaning |
1605 | * |
1606 | * No No "unknown" - must do get_block() |
1607 | * No Yes "hole" - zero-filled |
1608 | * Yes No "allocated" - allocated on disk, not read in |
1609 | * Yes Yes "valid" - allocated and up-to-date in memory. |
1610 | * |
1611 | * "Dirty" is valid only with the last case (mapped+uptodate). |
1612 | */ |
1613 | |
1614 | /* |
1615 | * While block_write_full_page is writing back the dirty buffers under |
1616 | * the page lock, whoever dirtied the buffers may decide to clean them |
1617 | * again at any time. We handle that by only looking at the buffer |
1618 | * state inside lock_buffer(). |
1619 | * |
1620 | * If block_write_full_page() is called for regular writeback |
1621 | * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a |
1622 | * locked buffer. This only can happen if someone has written the buffer |
1623 | * directly, with submit_bh(). At the address_space level PageWriteback |
1624 | * prevents this contention from occurring. |
1625 | * |
1626 | * If block_write_full_page() is called with wbc->sync_mode == |
1627 | * WB_SYNC_ALL, the writes are posted using WRITE_SYNC_PLUG; this |
1628 | * causes the writes to be flagged as synchronous writes, but the |
1629 | * block device queue will NOT be unplugged, since usually many pages |
1630 | * will be pushed to the out before the higher-level caller actually |
1631 | * waits for the writes to be completed. The various wait functions, |
1632 | * such as wait_on_writeback_range() will ultimately call sync_page() |
1633 | * which will ultimately call blk_run_backing_dev(), which will end up |
1634 | * unplugging the device queue. |
1635 | */ |
1636 | static int __block_write_full_page(struct inode *inode, struct page *page, |
1637 | get_block_t *get_block, struct writeback_control *wbc, |
1638 | bh_end_io_t *handler) |
1639 | { |
1640 | int err; |
1641 | sector_t block; |
1642 | sector_t last_block; |
1643 | struct buffer_head *bh, *head; |
1644 | const unsigned blocksize = 1 << inode->i_blkbits; |
1645 | int nr_underway = 0; |
1646 | int write_op = (wbc->sync_mode == WB_SYNC_ALL ? |
1647 | WRITE_SYNC_PLUG : WRITE); |
1648 | |
1649 | BUG_ON(!PageLocked(page)); |
1650 | |
1651 | last_block = (i_size_read(inode) - 1) >> inode->i_blkbits; |
1652 | |
1653 | if (!page_has_buffers(page)) { |
1654 | create_empty_buffers(page, blocksize, |
1655 | (1 << BH_Dirty)|(1 << BH_Uptodate)); |
1656 | } |
1657 | |
1658 | /* |
1659 | * Be very careful. We have no exclusion from __set_page_dirty_buffers |
1660 | * here, and the (potentially unmapped) buffers may become dirty at |
1661 | * any time. If a buffer becomes dirty here after we've inspected it |
1662 | * then we just miss that fact, and the page stays dirty. |
1663 | * |
1664 | * Buffers outside i_size may be dirtied by __set_page_dirty_buffers; |
1665 | * handle that here by just cleaning them. |
1666 | */ |
1667 | |
1668 | block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
1669 | head = page_buffers(page); |
1670 | bh = head; |
1671 | |
1672 | /* |
1673 | * Get all the dirty buffers mapped to disk addresses and |
1674 | * handle any aliases from the underlying blockdev's mapping. |
1675 | */ |
1676 | do { |
1677 | if (block > last_block) { |
1678 | /* |
1679 | * mapped buffers outside i_size will occur, because |
1680 | * this page can be outside i_size when there is a |
1681 | * truncate in progress. |
1682 | */ |
1683 | /* |
1684 | * The buffer was zeroed by block_write_full_page() |
1685 | */ |
1686 | clear_buffer_dirty(bh); |
1687 | set_buffer_uptodate(bh); |
1688 | } else if ((!buffer_mapped(bh) || buffer_delay(bh)) && |
1689 | buffer_dirty(bh)) { |
1690 | WARN_ON(bh->b_size != blocksize); |
1691 | err = get_block(inode, block, bh, 1); |
1692 | if (err) |
1693 | goto recover; |
1694 | clear_buffer_delay(bh); |
1695 | if (buffer_new(bh)) { |
1696 | /* blockdev mappings never come here */ |
1697 | clear_buffer_new(bh); |
1698 | unmap_underlying_metadata(bh->b_bdev, |
1699 | bh->b_blocknr); |
1700 | } |
1701 | } |
1702 | bh = bh->b_this_page; |
1703 | block++; |
1704 | } while (bh != head); |
1705 | |
1706 | do { |
1707 | if (!buffer_mapped(bh)) |
1708 | continue; |
1709 | /* |
1710 | * If it's a fully non-blocking write attempt and we cannot |
1711 | * lock the buffer then redirty the page. Note that this can |
1712 | * potentially cause a busy-wait loop from writeback threads |
1713 | * and kswapd activity, but those code paths have their own |
1714 | * higher-level throttling. |
1715 | */ |
1716 | if (wbc->sync_mode != WB_SYNC_NONE || !wbc->nonblocking) { |
1717 | lock_buffer(bh); |
1718 | } else if (!trylock_buffer(bh)) { |
1719 | redirty_page_for_writepage(wbc, page); |
1720 | continue; |
1721 | } |
1722 | if (test_clear_buffer_dirty(bh)) { |
1723 | mark_buffer_async_write_endio(bh, handler); |
1724 | } else { |
1725 | unlock_buffer(bh); |
1726 | } |
1727 | } while ((bh = bh->b_this_page) != head); |
1728 | |
1729 | /* |
1730 | * The page and its buffers are protected by PageWriteback(), so we can |
1731 | * drop the bh refcounts early. |
1732 | */ |
1733 | BUG_ON(PageWriteback(page)); |
1734 | set_page_writeback(page); |
1735 | |
1736 | do { |
1737 | struct buffer_head *next = bh->b_this_page; |
1738 | if (buffer_async_write(bh)) { |
1739 | submit_bh(write_op, bh); |
1740 | nr_underway++; |
1741 | } |
1742 | bh = next; |
1743 | } while (bh != head); |
1744 | unlock_page(page); |
1745 | |
1746 | err = 0; |
1747 | done: |
1748 | if (nr_underway == 0) { |
1749 | /* |
1750 | * The page was marked dirty, but the buffers were |
1751 | * clean. Someone wrote them back by hand with |
1752 | * ll_rw_block/submit_bh. A rare case. |
1753 | */ |
1754 | end_page_writeback(page); |
1755 | |
1756 | /* |
1757 | * The page and buffer_heads can be released at any time from |
1758 | * here on. |
1759 | */ |
1760 | } |
1761 | return err; |
1762 | |
1763 | recover: |
1764 | /* |
1765 | * ENOSPC, or some other error. We may already have added some |
1766 | * blocks to the file, so we need to write these out to avoid |
1767 | * exposing stale data. |
1768 | * The page is currently locked and not marked for writeback |
1769 | */ |
1770 | bh = head; |
1771 | /* Recovery: lock and submit the mapped buffers */ |
1772 | do { |
1773 | if (buffer_mapped(bh) && buffer_dirty(bh) && |
1774 | !buffer_delay(bh)) { |
1775 | lock_buffer(bh); |
1776 | mark_buffer_async_write_endio(bh, handler); |
1777 | } else { |
1778 | /* |
1779 | * The buffer may have been set dirty during |
1780 | * attachment to a dirty page. |
1781 | */ |
1782 | clear_buffer_dirty(bh); |
1783 | } |
1784 | } while ((bh = bh->b_this_page) != head); |
1785 | SetPageError(page); |
1786 | BUG_ON(PageWriteback(page)); |
1787 | mapping_set_error(page->mapping, err); |
1788 | set_page_writeback(page); |
1789 | do { |
1790 | struct buffer_head *next = bh->b_this_page; |
1791 | if (buffer_async_write(bh)) { |
1792 | clear_buffer_dirty(bh); |
1793 | submit_bh(write_op, bh); |
1794 | nr_underway++; |
1795 | } |
1796 | bh = next; |
1797 | } while (bh != head); |
1798 | unlock_page(page); |
1799 | goto done; |
1800 | } |
1801 | |
1802 | /* |
1803 | * If a page has any new buffers, zero them out here, and mark them uptodate |
1804 | * and dirty so they'll be written out (in order to prevent uninitialised |
1805 | * block data from leaking). And clear the new bit. |
1806 | */ |
1807 | void page_zero_new_buffers(struct page *page, unsigned from, unsigned to) |
1808 | { |
1809 | unsigned int block_start, block_end; |
1810 | struct buffer_head *head, *bh; |
1811 | |
1812 | BUG_ON(!PageLocked(page)); |
1813 | if (!page_has_buffers(page)) |
1814 | return; |
1815 | |
1816 | bh = head = page_buffers(page); |
1817 | block_start = 0; |
1818 | do { |
1819 | block_end = block_start + bh->b_size; |
1820 | |
1821 | if (buffer_new(bh)) { |
1822 | if (block_end > from && block_start < to) { |
1823 | if (!PageUptodate(page)) { |
1824 | unsigned start, size; |
1825 | |
1826 | start = max(from, block_start); |
1827 | size = min(to, block_end) - start; |
1828 | |
1829 | zero_user(page, start, size); |
1830 | set_buffer_uptodate(bh); |
1831 | } |
1832 | |
1833 | clear_buffer_new(bh); |
1834 | mark_buffer_dirty(bh); |
1835 | } |
1836 | } |
1837 | |
1838 | block_start = block_end; |
1839 | bh = bh->b_this_page; |
1840 | } while (bh != head); |
1841 | } |
1842 | EXPORT_SYMBOL(page_zero_new_buffers); |
1843 | |
1844 | static int __block_prepare_write(struct inode *inode, struct page *page, |
1845 | unsigned from, unsigned to, get_block_t *get_block) |
1846 | { |
1847 | unsigned block_start, block_end; |
1848 | sector_t block; |
1849 | int err = 0; |
1850 | unsigned blocksize, bbits; |
1851 | struct buffer_head *bh, *head, *wait[2], **wait_bh=wait; |
1852 | |
1853 | BUG_ON(!PageLocked(page)); |
1854 | BUG_ON(from > PAGE_CACHE_SIZE); |
1855 | BUG_ON(to > PAGE_CACHE_SIZE); |
1856 | BUG_ON(from > to); |
1857 | |
1858 | blocksize = 1 << inode->i_blkbits; |
1859 | if (!page_has_buffers(page)) |
1860 | create_empty_buffers(page, blocksize, 0); |
1861 | head = page_buffers(page); |
1862 | |
1863 | bbits = inode->i_blkbits; |
1864 | block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); |
1865 | |
1866 | for(bh = head, block_start = 0; bh != head || !block_start; |
1867 | block++, block_start=block_end, bh = bh->b_this_page) { |
1868 | block_end = block_start + blocksize; |
1869 | if (block_end <= from || block_start >= to) { |
1870 | if (PageUptodate(page)) { |
1871 | if (!buffer_uptodate(bh)) |
1872 | set_buffer_uptodate(bh); |
1873 | } |
1874 | continue; |
1875 | } |
1876 | if (buffer_new(bh)) |
1877 | clear_buffer_new(bh); |
1878 | if (!buffer_mapped(bh)) { |
1879 | WARN_ON(bh->b_size != blocksize); |
1880 | err = get_block(inode, block, bh, 1); |
1881 | if (err) |
1882 | break; |
1883 | if (buffer_new(bh)) { |
1884 | unmap_underlying_metadata(bh->b_bdev, |
1885 | bh->b_blocknr); |
1886 | if (PageUptodate(page)) { |
1887 | clear_buffer_new(bh); |
1888 | set_buffer_uptodate(bh); |
1889 | mark_buffer_dirty(bh); |
1890 | continue; |
1891 | } |
1892 | if (block_end > to || block_start < from) |
1893 | zero_user_segments(page, |
1894 | to, block_end, |
1895 | block_start, from); |
1896 | continue; |
1897 | } |
1898 | } |
1899 | if (PageUptodate(page)) { |
1900 | if (!buffer_uptodate(bh)) |
1901 | set_buffer_uptodate(bh); |
1902 | continue; |
1903 | } |
1904 | if (!buffer_uptodate(bh) && !buffer_delay(bh) && |
1905 | !buffer_unwritten(bh) && |
1906 | (block_start < from || block_end > to)) { |
1907 | ll_rw_block(READ, 1, &bh); |
1908 | *wait_bh++=bh; |
1909 | } |
1910 | } |
1911 | /* |
1912 | * If we issued read requests - let them complete. |
1913 | */ |
1914 | while(wait_bh > wait) { |
1915 | wait_on_buffer(*--wait_bh); |
1916 | if (!buffer_uptodate(*wait_bh)) |
1917 | err = -EIO; |
1918 | } |
1919 | if (unlikely(err)) |
1920 | page_zero_new_buffers(page, from, to); |
1921 | return err; |
1922 | } |
1923 | |
1924 | static int __block_commit_write(struct inode *inode, struct page *page, |
1925 | unsigned from, unsigned to) |
1926 | { |
1927 | unsigned block_start, block_end; |
1928 | int partial = 0; |
1929 | unsigned blocksize; |
1930 | struct buffer_head *bh, *head; |
1931 | |
1932 | blocksize = 1 << inode->i_blkbits; |
1933 | |
1934 | for(bh = head = page_buffers(page), block_start = 0; |
1935 | bh != head || !block_start; |
1936 | block_start=block_end, bh = bh->b_this_page) { |
1937 | block_end = block_start + blocksize; |
1938 | if (block_end <= from || block_start >= to) { |
1939 | if (!buffer_uptodate(bh)) |
1940 | partial = 1; |
1941 | } else { |
1942 | set_buffer_uptodate(bh); |
1943 | mark_buffer_dirty(bh); |
1944 | } |
1945 | clear_buffer_new(bh); |
1946 | } |
1947 | |
1948 | /* |
1949 | * If this is a partial write which happened to make all buffers |
1950 | * uptodate then we can optimize away a bogus readpage() for |
1951 | * the next read(). Here we 'discover' whether the page went |
1952 | * uptodate as a result of this (potentially partial) write. |
1953 | */ |
1954 | if (!partial) |
1955 | SetPageUptodate(page); |
1956 | return 0; |
1957 | } |
1958 | |
1959 | /* |
1960 | * block_write_begin takes care of the basic task of block allocation and |
1961 | * bringing partial write blocks uptodate first. |
1962 | * |
1963 | * If *pagep is not NULL, then block_write_begin uses the locked page |
1964 | * at *pagep rather than allocating its own. In this case, the page will |
1965 | * not be unlocked or deallocated on failure. |
1966 | */ |
1967 | int block_write_begin(struct file *file, struct address_space *mapping, |
1968 | loff_t pos, unsigned len, unsigned flags, |
1969 | struct page **pagep, void **fsdata, |
1970 | get_block_t *get_block) |
1971 | { |
1972 | struct inode *inode = mapping->host; |
1973 | int status = 0; |
1974 | struct page *page; |
1975 | pgoff_t index; |
1976 | unsigned start, end; |
1977 | int ownpage = 0; |
1978 | |
1979 | index = pos >> PAGE_CACHE_SHIFT; |
1980 | start = pos & (PAGE_CACHE_SIZE - 1); |
1981 | end = start + len; |
1982 | |
1983 | page = *pagep; |
1984 | if (page == NULL) { |
1985 | ownpage = 1; |
1986 | page = grab_cache_page_write_begin(mapping, index, flags); |
1987 | if (!page) { |
1988 | status = -ENOMEM; |
1989 | goto out; |
1990 | } |
1991 | *pagep = page; |
1992 | } else |
1993 | BUG_ON(!PageLocked(page)); |
1994 | |
1995 | status = __block_prepare_write(inode, page, start, end, get_block); |
1996 | if (unlikely(status)) { |
1997 | ClearPageUptodate(page); |
1998 | |
1999 | if (ownpage) { |
2000 | unlock_page(page); |
2001 | page_cache_release(page); |
2002 | *pagep = NULL; |
2003 | |
2004 | /* |
2005 | * prepare_write() may have instantiated a few blocks |
2006 | * outside i_size. Trim these off again. Don't need |
2007 | * i_size_read because we hold i_mutex. |
2008 | */ |
2009 | if (pos + len > inode->i_size) |
2010 | vmtruncate(inode, inode->i_size); |
2011 | } |
2012 | } |
2013 | |
2014 | out: |
2015 | return status; |
2016 | } |
2017 | EXPORT_SYMBOL(block_write_begin); |
2018 | |
2019 | int block_write_end(struct file *file, struct address_space *mapping, |
2020 | loff_t pos, unsigned len, unsigned copied, |
2021 | struct page *page, void *fsdata) |
2022 | { |
2023 | struct inode *inode = mapping->host; |
2024 | unsigned start; |
2025 | |
2026 | start = pos & (PAGE_CACHE_SIZE - 1); |
2027 | |
2028 | if (unlikely(copied < len)) { |
2029 | /* |
2030 | * The buffers that were written will now be uptodate, so we |
2031 | * don't have to worry about a readpage reading them and |
2032 | * overwriting a partial write. However if we have encountered |
2033 | * a short write and only partially written into a buffer, it |
2034 | * will not be marked uptodate, so a readpage might come in and |
2035 | * destroy our partial write. |
2036 | * |
2037 | * Do the simplest thing, and just treat any short write to a |
2038 | * non uptodate page as a zero-length write, and force the |
2039 | * caller to redo the whole thing. |
2040 | */ |
2041 | if (!PageUptodate(page)) |
2042 | copied = 0; |
2043 | |
2044 | page_zero_new_buffers(page, start+copied, start+len); |
2045 | } |
2046 | flush_dcache_page(page); |
2047 | |
2048 | /* This could be a short (even 0-length) commit */ |
2049 | __block_commit_write(inode, page, start, start+copied); |
2050 | |
2051 | return copied; |
2052 | } |
2053 | EXPORT_SYMBOL(block_write_end); |
2054 | |
2055 | int generic_write_end(struct file *file, struct address_space *mapping, |
2056 | loff_t pos, unsigned len, unsigned copied, |
2057 | struct page *page, void *fsdata) |
2058 | { |
2059 | struct inode *inode = mapping->host; |
2060 | int i_size_changed = 0; |
2061 | |
2062 | copied = block_write_end(file, mapping, pos, len, copied, page, fsdata); |
2063 | |
2064 | /* |
2065 | * No need to use i_size_read() here, the i_size |
2066 | * cannot change under us because we hold i_mutex. |
2067 | * |
2068 | * But it's important to update i_size while still holding page lock: |
2069 | * page writeout could otherwise come in and zero beyond i_size. |
2070 | */ |
2071 | if (pos+copied > inode->i_size) { |
2072 | i_size_write(inode, pos+copied); |
2073 | i_size_changed = 1; |
2074 | } |
2075 | |
2076 | unlock_page(page); |
2077 | page_cache_release(page); |
2078 | |
2079 | /* |
2080 | * Don't mark the inode dirty under page lock. First, it unnecessarily |
2081 | * makes the holding time of page lock longer. Second, it forces lock |
2082 | * ordering of page lock and transaction start for journaling |
2083 | * filesystems. |
2084 | */ |
2085 | if (i_size_changed) |
2086 | mark_inode_dirty(inode); |
2087 | |
2088 | return copied; |
2089 | } |
2090 | EXPORT_SYMBOL(generic_write_end); |
2091 | |
2092 | /* |
2093 | * block_is_partially_uptodate checks whether buffers within a page are |
2094 | * uptodate or not. |
2095 | * |
2096 | * Returns true if all buffers which correspond to a file portion |
2097 | * we want to read are uptodate. |
2098 | */ |
2099 | int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc, |
2100 | unsigned long from) |
2101 | { |
2102 | struct inode *inode = page->mapping->host; |
2103 | unsigned block_start, block_end, blocksize; |
2104 | unsigned to; |
2105 | struct buffer_head *bh, *head; |
2106 | int ret = 1; |
2107 | |
2108 | if (!page_has_buffers(page)) |
2109 | return 0; |
2110 | |
2111 | blocksize = 1 << inode->i_blkbits; |
2112 | to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count); |
2113 | to = from + to; |
2114 | if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize) |
2115 | return 0; |
2116 | |
2117 | head = page_buffers(page); |
2118 | bh = head; |
2119 | block_start = 0; |
2120 | do { |
2121 | block_end = block_start + blocksize; |
2122 | if (block_end > from && block_start < to) { |
2123 | if (!buffer_uptodate(bh)) { |
2124 | ret = 0; |
2125 | break; |
2126 | } |
2127 | if (block_end >= to) |
2128 | break; |
2129 | } |
2130 | block_start = block_end; |
2131 | bh = bh->b_this_page; |
2132 | } while (bh != head); |
2133 | |
2134 | return ret; |
2135 | } |
2136 | EXPORT_SYMBOL(block_is_partially_uptodate); |
2137 | |
2138 | /* |
2139 | * Generic "read page" function for block devices that have the normal |
2140 | * get_block functionality. This is most of the block device filesystems. |
2141 | * Reads the page asynchronously --- the unlock_buffer() and |
2142 | * set/clear_buffer_uptodate() functions propagate buffer state into the |
2143 | * page struct once IO has completed. |
2144 | */ |
2145 | int block_read_full_page(struct page *page, get_block_t *get_block) |
2146 | { |
2147 | struct inode *inode = page->mapping->host; |
2148 | sector_t iblock, lblock; |
2149 | struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE]; |
2150 | unsigned int blocksize; |
2151 | int nr, i; |
2152 | int fully_mapped = 1; |
2153 | |
2154 | BUG_ON(!PageLocked(page)); |
2155 | blocksize = 1 << inode->i_blkbits; |
2156 | if (!page_has_buffers(page)) |
2157 | create_empty_buffers(page, blocksize, 0); |
2158 | head = page_buffers(page); |
2159 | |
2160 | iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
2161 | lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits; |
2162 | bh = head; |
2163 | nr = 0; |
2164 | i = 0; |
2165 | |
2166 | do { |
2167 | if (buffer_uptodate(bh)) |
2168 | continue; |
2169 | |
2170 | if (!buffer_mapped(bh)) { |
2171 | int err = 0; |
2172 | |
2173 | fully_mapped = 0; |
2174 | if (iblock < lblock) { |
2175 | WARN_ON(bh->b_size != blocksize); |
2176 | err = get_block(inode, iblock, bh, 0); |
2177 | if (err) |
2178 | SetPageError(page); |
2179 | } |
2180 | if (!buffer_mapped(bh)) { |
2181 | zero_user(page, i * blocksize, blocksize); |
2182 | if (!err) |
2183 | set_buffer_uptodate(bh); |
2184 | continue; |
2185 | } |
2186 | /* |
2187 | * get_block() might have updated the buffer |
2188 | * synchronously |
2189 | */ |
2190 | if (buffer_uptodate(bh)) |
2191 | continue; |
2192 | } |
2193 | arr[nr++] = bh; |
2194 | } while (i++, iblock++, (bh = bh->b_this_page) != head); |
2195 | |
2196 | if (fully_mapped) |
2197 | SetPageMappedToDisk(page); |
2198 | |
2199 | if (!nr) { |
2200 | /* |
2201 | * All buffers are uptodate - we can set the page uptodate |
2202 | * as well. But not if get_block() returned an error. |
2203 | */ |
2204 | if (!PageError(page)) |
2205 | SetPageUptodate(page); |
2206 | unlock_page(page); |
2207 | return 0; |
2208 | } |
2209 | |
2210 | /* Stage two: lock the buffers */ |
2211 | for (i = 0; i < nr; i++) { |
2212 | bh = arr[i]; |
2213 | lock_buffer(bh); |
2214 | mark_buffer_async_read(bh); |
2215 | } |
2216 | |
2217 | /* |
2218 | * Stage 3: start the IO. Check for uptodateness |
2219 | * inside the buffer lock in case another process reading |
2220 | * the underlying blockdev brought it uptodate (the sct fix). |
2221 | */ |
2222 | for (i = 0; i < nr; i++) { |
2223 | bh = arr[i]; |
2224 | if (buffer_uptodate(bh)) |
2225 | end_buffer_async_read(bh, 1); |
2226 | else |
2227 | submit_bh(READ, bh); |
2228 | } |
2229 | return 0; |
2230 | } |
2231 | EXPORT_SYMBOL(block_read_full_page); |
2232 | |
2233 | /* utility function for filesystems that need to do work on expanding |
2234 | * truncates. Uses filesystem pagecache writes to allow the filesystem to |
2235 | * deal with the hole. |
2236 | */ |
2237 | int generic_cont_expand_simple(struct inode *inode, loff_t size) |
2238 | { |
2239 | struct address_space *mapping = inode->i_mapping; |
2240 | struct page *page; |
2241 | void *fsdata; |
2242 | int err; |
2243 | |
2244 | err = inode_newsize_ok(inode, size); |
2245 | if (err) |
2246 | goto out; |
2247 | |
2248 | err = pagecache_write_begin(NULL, mapping, size, 0, |
2249 | AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND, |
2250 | &page, &fsdata); |
2251 | if (err) |
2252 | goto out; |
2253 | |
2254 | err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata); |
2255 | BUG_ON(err > 0); |
2256 | |
2257 | out: |
2258 | return err; |
2259 | } |
2260 | EXPORT_SYMBOL(generic_cont_expand_simple); |
2261 | |
2262 | static int cont_expand_zero(struct file *file, struct address_space *mapping, |
2263 | loff_t pos, loff_t *bytes) |
2264 | { |
2265 | struct inode *inode = mapping->host; |
2266 | unsigned blocksize = 1 << inode->i_blkbits; |
2267 | struct page *page; |
2268 | void *fsdata; |
2269 | pgoff_t index, curidx; |
2270 | loff_t curpos; |
2271 | unsigned zerofrom, offset, len; |
2272 | int err = 0; |
2273 | |
2274 | index = pos >> PAGE_CACHE_SHIFT; |
2275 | offset = pos & ~PAGE_CACHE_MASK; |
2276 | |
2277 | while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) { |
2278 | zerofrom = curpos & ~PAGE_CACHE_MASK; |
2279 | if (zerofrom & (blocksize-1)) { |
2280 | *bytes |= (blocksize-1); |
2281 | (*bytes)++; |
2282 | } |
2283 | len = PAGE_CACHE_SIZE - zerofrom; |
2284 | |
2285 | err = pagecache_write_begin(file, mapping, curpos, len, |
2286 | AOP_FLAG_UNINTERRUPTIBLE, |
2287 | &page, &fsdata); |
2288 | if (err) |
2289 | goto out; |
2290 | zero_user(page, zerofrom, len); |
2291 | err = pagecache_write_end(file, mapping, curpos, len, len, |
2292 | page, fsdata); |
2293 | if (err < 0) |
2294 | goto out; |
2295 | BUG_ON(err != len); |
2296 | err = 0; |
2297 | |
2298 | balance_dirty_pages_ratelimited(mapping); |
2299 | } |
2300 | |
2301 | /* page covers the boundary, find the boundary offset */ |
2302 | if (index == curidx) { |
2303 | zerofrom = curpos & ~PAGE_CACHE_MASK; |
2304 | /* if we will expand the thing last block will be filled */ |
2305 | if (offset <= zerofrom) { |
2306 | goto out; |
2307 | } |
2308 | if (zerofrom & (blocksize-1)) { |
2309 | *bytes |= (blocksize-1); |
2310 | (*bytes)++; |
2311 | } |
2312 | len = offset - zerofrom; |
2313 | |
2314 | err = pagecache_write_begin(file, mapping, curpos, len, |
2315 | AOP_FLAG_UNINTERRUPTIBLE, |
2316 | &page, &fsdata); |
2317 | if (err) |
2318 | goto out; |
2319 | zero_user(page, zerofrom, len); |
2320 | err = pagecache_write_end(file, mapping, curpos, len, len, |
2321 | page, fsdata); |
2322 | if (err < 0) |
2323 | goto out; |
2324 | BUG_ON(err != len); |
2325 | err = 0; |
2326 | } |
2327 | out: |
2328 | return err; |
2329 | } |
2330 | |
2331 | /* |
2332 | * For moronic filesystems that do not allow holes in file. |
2333 | * We may have to extend the file. |
2334 | */ |
2335 | int cont_write_begin(struct file *file, struct address_space *mapping, |
2336 | loff_t pos, unsigned len, unsigned flags, |
2337 | struct page **pagep, void **fsdata, |
2338 | get_block_t *get_block, loff_t *bytes) |
2339 | { |
2340 | struct inode *inode = mapping->host; |
2341 | unsigned blocksize = 1 << inode->i_blkbits; |
2342 | unsigned zerofrom; |
2343 | int err; |
2344 | |
2345 | err = cont_expand_zero(file, mapping, pos, bytes); |
2346 | if (err) |
2347 | goto out; |
2348 | |
2349 | zerofrom = *bytes & ~PAGE_CACHE_MASK; |
2350 | if (pos+len > *bytes && zerofrom & (blocksize-1)) { |
2351 | *bytes |= (blocksize-1); |
2352 | (*bytes)++; |
2353 | } |
2354 | |
2355 | *pagep = NULL; |
2356 | err = block_write_begin(file, mapping, pos, len, |
2357 | flags, pagep, fsdata, get_block); |
2358 | out: |
2359 | return err; |
2360 | } |
2361 | EXPORT_SYMBOL(cont_write_begin); |
2362 | |
2363 | int block_prepare_write(struct page *page, unsigned from, unsigned to, |
2364 | get_block_t *get_block) |
2365 | { |
2366 | struct inode *inode = page->mapping->host; |
2367 | int err = __block_prepare_write(inode, page, from, to, get_block); |
2368 | if (err) |
2369 | ClearPageUptodate(page); |
2370 | return err; |
2371 | } |
2372 | EXPORT_SYMBOL(block_prepare_write); |
2373 | |
2374 | int block_commit_write(struct page *page, unsigned from, unsigned to) |
2375 | { |
2376 | struct inode *inode = page->mapping->host; |
2377 | __block_commit_write(inode,page,from,to); |
2378 | return 0; |
2379 | } |
2380 | EXPORT_SYMBOL(block_commit_write); |
2381 | |
2382 | /* |
2383 | * block_page_mkwrite() is not allowed to change the file size as it gets |
2384 | * called from a page fault handler when a page is first dirtied. Hence we must |
2385 | * be careful to check for EOF conditions here. We set the page up correctly |
2386 | * for a written page which means we get ENOSPC checking when writing into |
2387 | * holes and correct delalloc and unwritten extent mapping on filesystems that |
2388 | * support these features. |
2389 | * |
2390 | * We are not allowed to take the i_mutex here so we have to play games to |
2391 | * protect against truncate races as the page could now be beyond EOF. Because |
2392 | * vmtruncate() writes the inode size before removing pages, once we have the |
2393 | * page lock we can determine safely if the page is beyond EOF. If it is not |
2394 | * beyond EOF, then the page is guaranteed safe against truncation until we |
2395 | * unlock the page. |
2396 | */ |
2397 | int |
2398 | block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, |
2399 | get_block_t get_block) |
2400 | { |
2401 | struct page *page = vmf->page; |
2402 | struct inode *inode = vma->vm_file->f_path.dentry->d_inode; |
2403 | unsigned long end; |
2404 | loff_t size; |
2405 | int ret = VM_FAULT_NOPAGE; /* make the VM retry the fault */ |
2406 | |
2407 | lock_page(page); |
2408 | size = i_size_read(inode); |
2409 | if ((page->mapping != inode->i_mapping) || |
2410 | (page_offset(page) > size)) { |
2411 | /* page got truncated out from underneath us */ |
2412 | unlock_page(page); |
2413 | goto out; |
2414 | } |
2415 | |
2416 | /* page is wholly or partially inside EOF */ |
2417 | if (((page->index + 1) << PAGE_CACHE_SHIFT) > size) |
2418 | end = size & ~PAGE_CACHE_MASK; |
2419 | else |
2420 | end = PAGE_CACHE_SIZE; |
2421 | |
2422 | ret = block_prepare_write(page, 0, end, get_block); |
2423 | if (!ret) |
2424 | ret = block_commit_write(page, 0, end); |
2425 | |
2426 | if (unlikely(ret)) { |
2427 | unlock_page(page); |
2428 | if (ret == -ENOMEM) |
2429 | ret = VM_FAULT_OOM; |
2430 | else /* -ENOSPC, -EIO, etc */ |
2431 | ret = VM_FAULT_SIGBUS; |
2432 | } else |
2433 | ret = VM_FAULT_LOCKED; |
2434 | |
2435 | out: |
2436 | return ret; |
2437 | } |
2438 | EXPORT_SYMBOL(block_page_mkwrite); |
2439 | |
2440 | /* |
2441 | * nobh_write_begin()'s prereads are special: the buffer_heads are freed |
2442 | * immediately, while under the page lock. So it needs a special end_io |
2443 | * handler which does not touch the bh after unlocking it. |
2444 | */ |
2445 | static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate) |
2446 | { |
2447 | __end_buffer_read_notouch(bh, uptodate); |
2448 | } |
2449 | |
2450 | /* |
2451 | * Attach the singly-linked list of buffers created by nobh_write_begin, to |
2452 | * the page (converting it to circular linked list and taking care of page |
2453 | * dirty races). |
2454 | */ |
2455 | static void attach_nobh_buffers(struct page *page, struct buffer_head *head) |
2456 | { |
2457 | struct buffer_head *bh; |
2458 | |
2459 | BUG_ON(!PageLocked(page)); |
2460 | |
2461 | spin_lock(&page->mapping->private_lock); |
2462 | bh = head; |
2463 | do { |
2464 | if (PageDirty(page)) |
2465 | set_buffer_dirty(bh); |
2466 | if (!bh->b_this_page) |
2467 | bh->b_this_page = head; |
2468 | bh = bh->b_this_page; |
2469 | } while (bh != head); |
2470 | attach_page_buffers(page, head); |
2471 | spin_unlock(&page->mapping->private_lock); |
2472 | } |
2473 | |
2474 | /* |
2475 | * On entry, the page is fully not uptodate. |
2476 | * On exit the page is fully uptodate in the areas outside (from,to) |
2477 | */ |
2478 | int nobh_write_begin(struct file *file, struct address_space *mapping, |
2479 | loff_t pos, unsigned len, unsigned flags, |
2480 | struct page **pagep, void **fsdata, |
2481 | get_block_t *get_block) |
2482 | { |
2483 | struct inode *inode = mapping->host; |
2484 | const unsigned blkbits = inode->i_blkbits; |
2485 | const unsigned blocksize = 1 << blkbits; |
2486 | struct buffer_head *head, *bh; |
2487 | struct page *page; |
2488 | pgoff_t index; |
2489 | unsigned from, to; |
2490 | unsigned block_in_page; |
2491 | unsigned block_start, block_end; |
2492 | sector_t block_in_file; |
2493 | int nr_reads = 0; |
2494 | int ret = 0; |
2495 | int is_mapped_to_disk = 1; |
2496 | |
2497 | index = pos >> PAGE_CACHE_SHIFT; |
2498 | from = pos & (PAGE_CACHE_SIZE - 1); |
2499 | to = from + len; |
2500 | |
2501 | page = grab_cache_page_write_begin(mapping, index, flags); |
2502 | if (!page) |
2503 | return -ENOMEM; |
2504 | *pagep = page; |
2505 | *fsdata = NULL; |
2506 | |
2507 | if (page_has_buffers(page)) { |
2508 | unlock_page(page); |
2509 | page_cache_release(page); |
2510 | *pagep = NULL; |
2511 | return block_write_begin(file, mapping, pos, len, flags, pagep, |
2512 | fsdata, get_block); |
2513 | } |
2514 | |
2515 | if (PageMappedToDisk(page)) |
2516 | return 0; |
2517 | |
2518 | /* |
2519 | * Allocate buffers so that we can keep track of state, and potentially |
2520 | * attach them to the page if an error occurs. In the common case of |
2521 | * no error, they will just be freed again without ever being attached |
2522 | * to the page (which is all OK, because we're under the page lock). |
2523 | * |
2524 | * Be careful: the buffer linked list is a NULL terminated one, rather |
2525 | * than the circular one we're used to. |
2526 | */ |
2527 | head = alloc_page_buffers(page, blocksize, 0); |
2528 | if (!head) { |
2529 | ret = -ENOMEM; |
2530 | goto out_release; |
2531 | } |
2532 | |
2533 | block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); |
2534 | |
2535 | /* |
2536 | * We loop across all blocks in the page, whether or not they are |
2537 | * part of the affected region. This is so we can discover if the |
2538 | * page is fully mapped-to-disk. |
2539 | */ |
2540 | for (block_start = 0, block_in_page = 0, bh = head; |
2541 | block_start < PAGE_CACHE_SIZE; |
2542 | block_in_page++, block_start += blocksize, bh = bh->b_this_page) { |
2543 | int create; |
2544 | |
2545 | block_end = block_start + blocksize; |
2546 | bh->b_state = 0; |
2547 | create = 1; |
2548 | if (block_start >= to) |
2549 | create = 0; |
2550 | ret = get_block(inode, block_in_file + block_in_page, |
2551 | bh, create); |
2552 | if (ret) |
2553 | goto failed; |
2554 | if (!buffer_mapped(bh)) |
2555 | is_mapped_to_disk = 0; |
2556 | if (buffer_new(bh)) |
2557 | unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr); |
2558 | if (PageUptodate(page)) { |
2559 | set_buffer_uptodate(bh); |
2560 | continue; |
2561 | } |
2562 | if (buffer_new(bh) || !buffer_mapped(bh)) { |
2563 | zero_user_segments(page, block_start, from, |
2564 | to, block_end); |
2565 | continue; |
2566 | } |
2567 | if (buffer_uptodate(bh)) |
2568 | continue; /* reiserfs does this */ |
2569 | if (block_start < from || block_end > to) { |
2570 | lock_buffer(bh); |
2571 | bh->b_end_io = end_buffer_read_nobh; |
2572 | submit_bh(READ, bh); |
2573 | nr_reads++; |
2574 | } |
2575 | } |
2576 | |
2577 | if (nr_reads) { |
2578 | /* |
2579 | * The page is locked, so these buffers are protected from |
2580 | * any VM or truncate activity. Hence we don't need to care |
2581 | * for the buffer_head refcounts. |
2582 | */ |
2583 | for (bh = head; bh; bh = bh->b_this_page) { |
2584 | wait_on_buffer(bh); |
2585 | if (!buffer_uptodate(bh)) |
2586 | ret = -EIO; |
2587 | } |
2588 | if (ret) |
2589 | goto failed; |
2590 | } |
2591 | |
2592 | if (is_mapped_to_disk) |
2593 | SetPageMappedToDisk(page); |
2594 | |
2595 | *fsdata = head; /* to be released by nobh_write_end */ |
2596 | |
2597 | return 0; |
2598 | |
2599 | failed: |
2600 | BUG_ON(!ret); |
2601 | /* |
2602 | * Error recovery is a bit difficult. We need to zero out blocks that |
2603 | * were newly allocated, and dirty them to ensure they get written out. |
2604 | * Buffers need to be attached to the page at this point, otherwise |
2605 | * the handling of potential IO errors during writeout would be hard |
2606 | * (could try doing synchronous writeout, but what if that fails too?) |
2607 | */ |
2608 | attach_nobh_buffers(page, head); |
2609 | page_zero_new_buffers(page, from, to); |
2610 | |
2611 | out_release: |
2612 | unlock_page(page); |
2613 | page_cache_release(page); |
2614 | *pagep = NULL; |
2615 | |
2616 | if (pos + len > inode->i_size) |
2617 | vmtruncate(inode, inode->i_size); |
2618 | |
2619 | return ret; |
2620 | } |
2621 | EXPORT_SYMBOL(nobh_write_begin); |
2622 | |
2623 | int nobh_write_end(struct file *file, struct address_space *mapping, |
2624 | loff_t pos, unsigned len, unsigned copied, |
2625 | struct page *page, void *fsdata) |
2626 | { |
2627 | struct inode *inode = page->mapping->host; |
2628 | struct buffer_head *head = fsdata; |
2629 | struct buffer_head *bh; |
2630 | BUG_ON(fsdata != NULL && page_has_buffers(page)); |
2631 | |
2632 | if (unlikely(copied < len) && head) |
2633 | attach_nobh_buffers(page, head); |
2634 | if (page_has_buffers(page)) |
2635 | return generic_write_end(file, mapping, pos, len, |
2636 | copied, page, fsdata); |
2637 | |
2638 | SetPageUptodate(page); |
2639 | set_page_dirty(page); |
2640 | if (pos+copied > inode->i_size) { |
2641 | i_size_write(inode, pos+copied); |
2642 | mark_inode_dirty(inode); |
2643 | } |
2644 | |
2645 | unlock_page(page); |
2646 | page_cache_release(page); |
2647 | |
2648 | while (head) { |
2649 | bh = head; |
2650 | head = head->b_this_page; |
2651 | free_buffer_head(bh); |
2652 | } |
2653 | |
2654 | return copied; |
2655 | } |
2656 | EXPORT_SYMBOL(nobh_write_end); |
2657 | |
2658 | /* |
2659 | * nobh_writepage() - based on block_full_write_page() except |
2660 | * that it tries to operate without attaching bufferheads to |
2661 | * the page. |
2662 | */ |
2663 | int nobh_writepage(struct page *page, get_block_t *get_block, |
2664 | struct writeback_control *wbc) |
2665 | { |
2666 | struct inode * const inode = page->mapping->host; |
2667 | loff_t i_size = i_size_read(inode); |
2668 | const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; |
2669 | unsigned offset; |
2670 | int ret; |
2671 | |
2672 | /* Is the page fully inside i_size? */ |
2673 | if (page->index < end_index) |
2674 | goto out; |
2675 | |
2676 | /* Is the page fully outside i_size? (truncate in progress) */ |
2677 | offset = i_size & (PAGE_CACHE_SIZE-1); |
2678 | if (page->index >= end_index+1 || !offset) { |
2679 | /* |
2680 | * The page may have dirty, unmapped buffers. For example, |
2681 | * they may have been added in ext3_writepage(). Make them |
2682 | * freeable here, so the page does not leak. |
2683 | */ |
2684 | #if 0 |
2685 | /* Not really sure about this - do we need this ? */ |
2686 | if (page->mapping->a_ops->invalidatepage) |
2687 | page->mapping->a_ops->invalidatepage(page, offset); |
2688 | #endif |
2689 | unlock_page(page); |
2690 | return 0; /* don't care */ |
2691 | } |
2692 | |
2693 | /* |
2694 | * The page straddles i_size. It must be zeroed out on each and every |
2695 | * writepage invocation because it may be mmapped. "A file is mapped |
2696 | * in multiples of the page size. For a file that is not a multiple of |
2697 | * the page size, the remaining memory is zeroed when mapped, and |
2698 | * writes to that region are not written out to the file." |
2699 | */ |
2700 | zero_user_segment(page, offset, PAGE_CACHE_SIZE); |
2701 | out: |
2702 | ret = mpage_writepage(page, get_block, wbc); |
2703 | if (ret == -EAGAIN) |
2704 | ret = __block_write_full_page(inode, page, get_block, wbc, |
2705 | end_buffer_async_write); |
2706 | return ret; |
2707 | } |
2708 | EXPORT_SYMBOL(nobh_writepage); |
2709 | |
2710 | int nobh_truncate_page(struct address_space *mapping, |
2711 | loff_t from, get_block_t *get_block) |
2712 | { |
2713 | pgoff_t index = from >> PAGE_CACHE_SHIFT; |
2714 | unsigned offset = from & (PAGE_CACHE_SIZE-1); |
2715 | unsigned blocksize; |
2716 | sector_t iblock; |
2717 | unsigned length, pos; |
2718 | struct inode *inode = mapping->host; |
2719 | struct page *page; |
2720 | struct buffer_head map_bh; |
2721 | int err; |
2722 | |
2723 | blocksize = 1 << inode->i_blkbits; |
2724 | length = offset & (blocksize - 1); |
2725 | |
2726 | /* Block boundary? Nothing to do */ |
2727 | if (!length) |
2728 | return 0; |
2729 | |
2730 | length = blocksize - length; |
2731 | iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
2732 | |
2733 | page = grab_cache_page(mapping, index); |
2734 | err = -ENOMEM; |
2735 | if (!page) |
2736 | goto out; |
2737 | |
2738 | if (page_has_buffers(page)) { |
2739 | has_buffers: |
2740 | unlock_page(page); |
2741 | page_cache_release(page); |
2742 | return block_truncate_page(mapping, from, get_block); |
2743 | } |
2744 | |
2745 | /* Find the buffer that contains "offset" */ |
2746 | pos = blocksize; |
2747 | while (offset >= pos) { |
2748 | iblock++; |
2749 | pos += blocksize; |
2750 | } |
2751 | |
2752 | map_bh.b_size = blocksize; |
2753 | map_bh.b_state = 0; |
2754 | err = get_block(inode, iblock, &map_bh, 0); |
2755 | if (err) |
2756 | goto unlock; |
2757 | /* unmapped? It's a hole - nothing to do */ |
2758 | if (!buffer_mapped(&map_bh)) |
2759 | goto unlock; |
2760 | |
2761 | /* Ok, it's mapped. Make sure it's up-to-date */ |
2762 | if (!PageUptodate(page)) { |
2763 | err = mapping->a_ops->readpage(NULL, page); |
2764 | if (err) { |
2765 | page_cache_release(page); |
2766 | goto out; |
2767 | } |
2768 | lock_page(page); |
2769 | if (!PageUptodate(page)) { |
2770 | err = -EIO; |
2771 | goto unlock; |
2772 | } |
2773 | if (page_has_buffers(page)) |
2774 | goto has_buffers; |
2775 | } |
2776 | zero_user(page, offset, length); |
2777 | set_page_dirty(page); |
2778 | err = 0; |
2779 | |
2780 | unlock: |
2781 | unlock_page(page); |
2782 | page_cache_release(page); |
2783 | out: |
2784 | return err; |
2785 | } |
2786 | EXPORT_SYMBOL(nobh_truncate_page); |
2787 | |
2788 | int block_truncate_page(struct address_space *mapping, |
2789 | loff_t from, get_block_t *get_block) |
2790 | { |
2791 | pgoff_t index = from >> PAGE_CACHE_SHIFT; |
2792 | unsigned offset = from & (PAGE_CACHE_SIZE-1); |
2793 | unsigned blocksize; |
2794 | sector_t iblock; |
2795 | unsigned length, pos; |
2796 | struct inode *inode = mapping->host; |
2797 | struct page *page; |
2798 | struct buffer_head *bh; |
2799 | int err; |
2800 | |
2801 | blocksize = 1 << inode->i_blkbits; |
2802 | length = offset & (blocksize - 1); |
2803 | |
2804 | /* Block boundary? Nothing to do */ |
2805 | if (!length) |
2806 | return 0; |
2807 | |
2808 | length = blocksize - length; |
2809 | iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
2810 | |
2811 | page = grab_cache_page(mapping, index); |
2812 | err = -ENOMEM; |
2813 | if (!page) |
2814 | goto out; |
2815 | |
2816 | if (!page_has_buffers(page)) |
2817 | create_empty_buffers(page, blocksize, 0); |
2818 | |
2819 | /* Find the buffer that contains "offset" */ |
2820 | bh = page_buffers(page); |
2821 | pos = blocksize; |
2822 | while (offset >= pos) { |
2823 | bh = bh->b_this_page; |
2824 | iblock++; |
2825 | pos += blocksize; |
2826 | } |
2827 | |
2828 | err = 0; |
2829 | if (!buffer_mapped(bh)) { |
2830 | WARN_ON(bh->b_size != blocksize); |
2831 | err = get_block(inode, iblock, bh, 0); |
2832 | if (err) |
2833 | goto unlock; |
2834 | /* unmapped? It's a hole - nothing to do */ |
2835 | if (!buffer_mapped(bh)) |
2836 | goto unlock; |
2837 | } |
2838 | |
2839 | /* Ok, it's mapped. Make sure it's up-to-date */ |
2840 | if (PageUptodate(page)) |
2841 | set_buffer_uptodate(bh); |
2842 | |
2843 | if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) { |
2844 | err = -EIO; |
2845 | ll_rw_block(READ, 1, &bh); |
2846 | wait_on_buffer(bh); |
2847 | /* Uhhuh. Read error. Complain and punt. */ |
2848 | if (!buffer_uptodate(bh)) |
2849 | goto unlock; |
2850 | } |
2851 | |
2852 | zero_user(page, offset, length); |
2853 | mark_buffer_dirty(bh); |
2854 | err = 0; |
2855 | |
2856 | unlock: |
2857 | unlock_page(page); |
2858 | page_cache_release(page); |
2859 | out: |
2860 | return err; |
2861 | } |
2862 | EXPORT_SYMBOL(block_truncate_page); |
2863 | |
2864 | /* |
2865 | * The generic ->writepage function for buffer-backed address_spaces |
2866 | * this form passes in the end_io handler used to finish the IO. |
2867 | */ |
2868 | int block_write_full_page_endio(struct page *page, get_block_t *get_block, |
2869 | struct writeback_control *wbc, bh_end_io_t *handler) |
2870 | { |
2871 | struct inode * const inode = page->mapping->host; |
2872 | loff_t i_size = i_size_read(inode); |
2873 | const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; |
2874 | unsigned offset; |
2875 | |
2876 | /* Is the page fully inside i_size? */ |
2877 | if (page->index < end_index) |
2878 | return __block_write_full_page(inode, page, get_block, wbc, |
2879 | handler); |
2880 | |
2881 | /* Is the page fully outside i_size? (truncate in progress) */ |
2882 | offset = i_size & (PAGE_CACHE_SIZE-1); |
2883 | if (page->index >= end_index+1 || !offset) { |
2884 | /* |
2885 | * The page may have dirty, unmapped buffers. For example, |
2886 | * they may have been added in ext3_writepage(). Make them |
2887 | * freeable here, so the page does not leak. |
2888 | */ |
2889 | do_invalidatepage(page, 0); |
2890 | unlock_page(page); |
2891 | return 0; /* don't care */ |
2892 | } |
2893 | |
2894 | /* |
2895 | * The page straddles i_size. It must be zeroed out on each and every |
2896 | * writepage invocation because it may be mmapped. "A file is mapped |
2897 | * in multiples of the page size. For a file that is not a multiple of |
2898 | * the page size, the remaining memory is zeroed when mapped, and |
2899 | * writes to that region are not written out to the file." |
2900 | */ |
2901 | zero_user_segment(page, offset, PAGE_CACHE_SIZE); |
2902 | return __block_write_full_page(inode, page, get_block, wbc, handler); |
2903 | } |
2904 | EXPORT_SYMBOL(block_write_full_page_endio); |
2905 | |
2906 | /* |
2907 | * The generic ->writepage function for buffer-backed address_spaces |
2908 | */ |
2909 | int block_write_full_page(struct page *page, get_block_t *get_block, |
2910 | struct writeback_control *wbc) |
2911 | { |
2912 | return block_write_full_page_endio(page, get_block, wbc, |
2913 | end_buffer_async_write); |
2914 | } |
2915 | EXPORT_SYMBOL(block_write_full_page); |
2916 | |
2917 | sector_t generic_block_bmap(struct address_space *mapping, sector_t block, |
2918 | get_block_t *get_block) |
2919 | { |
2920 | struct buffer_head tmp; |
2921 | struct inode *inode = mapping->host; |
2922 | tmp.b_state = 0; |
2923 | tmp.b_blocknr = 0; |
2924 | tmp.b_size = 1 << inode->i_blkbits; |
2925 | get_block(inode, block, &tmp, 0); |
2926 | return tmp.b_blocknr; |
2927 | } |
2928 | EXPORT_SYMBOL(generic_block_bmap); |
2929 | |
2930 | static void end_bio_bh_io_sync(struct bio *bio, int err) |
2931 | { |
2932 | struct buffer_head *bh = bio->bi_private; |
2933 | |
2934 | if (err == -EOPNOTSUPP) { |
2935 | set_bit(BIO_EOPNOTSUPP, &bio->bi_flags); |
2936 | set_bit(BH_Eopnotsupp, &bh->b_state); |
2937 | } |
2938 | |
2939 | if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags))) |
2940 | set_bit(BH_Quiet, &bh->b_state); |
2941 | |
2942 | bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags)); |
2943 | bio_put(bio); |
2944 | } |
2945 | |
2946 | int submit_bh(int rw, struct buffer_head * bh) |
2947 | { |
2948 | struct bio *bio; |
2949 | int ret = 0; |
2950 | |
2951 | BUG_ON(!buffer_locked(bh)); |
2952 | BUG_ON(!buffer_mapped(bh)); |
2953 | BUG_ON(!bh->b_end_io); |
2954 | BUG_ON(buffer_delay(bh)); |
2955 | BUG_ON(buffer_unwritten(bh)); |
2956 | |
2957 | /* |
2958 | * Mask in barrier bit for a write (could be either a WRITE or a |
2959 | * WRITE_SYNC |
2960 | */ |
2961 | if (buffer_ordered(bh) && (rw & WRITE)) |
2962 | rw |= WRITE_BARRIER; |
2963 | |
2964 | /* |
2965 | * Only clear out a write error when rewriting |
2966 | */ |
2967 | if (test_set_buffer_req(bh) && (rw & WRITE)) |
2968 | clear_buffer_write_io_error(bh); |
2969 | |
2970 | /* |
2971 | * from here on down, it's all bio -- do the initial mapping, |
2972 | * submit_bio -> generic_make_request may further map this bio around |
2973 | */ |
2974 | bio = bio_alloc(GFP_NOIO, 1); |
2975 | |
2976 | bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9); |
2977 | bio->bi_bdev = bh->b_bdev; |
2978 | bio->bi_io_vec[0].bv_page = bh->b_page; |
2979 | bio->bi_io_vec[0].bv_len = bh->b_size; |
2980 | bio->bi_io_vec[0].bv_offset = bh_offset(bh); |
2981 | |
2982 | bio->bi_vcnt = 1; |
2983 | bio->bi_idx = 0; |
2984 | bio->bi_size = bh->b_size; |
2985 | |
2986 | bio->bi_end_io = end_bio_bh_io_sync; |
2987 | bio->bi_private = bh; |
2988 | |
2989 | bio_get(bio); |
2990 | submit_bio(rw, bio); |
2991 | |
2992 | if (bio_flagged(bio, BIO_EOPNOTSUPP)) |
2993 | ret = -EOPNOTSUPP; |
2994 | |
2995 | bio_put(bio); |
2996 | return ret; |
2997 | } |
2998 | EXPORT_SYMBOL(submit_bh); |
2999 | |
3000 | /** |
3001 | * ll_rw_block: low-level access to block devices (DEPRECATED) |
3002 | * @rw: whether to %READ or %WRITE or %SWRITE or maybe %READA (readahead) |
3003 | * @nr: number of &struct buffer_heads in the array |
3004 | * @bhs: array of pointers to &struct buffer_head |
3005 | * |
3006 | * ll_rw_block() takes an array of pointers to &struct buffer_heads, and |
3007 | * requests an I/O operation on them, either a %READ or a %WRITE. The third |
3008 | * %SWRITE is like %WRITE only we make sure that the *current* data in buffers |
3009 | * are sent to disk. The fourth %READA option is described in the documentation |
3010 | * for generic_make_request() which ll_rw_block() calls. |
3011 | * |
3012 | * This function drops any buffer that it cannot get a lock on (with the |
3013 | * BH_Lock state bit) unless SWRITE is required, any buffer that appears to be |
3014 | * clean when doing a write request, and any buffer that appears to be |
3015 | * up-to-date when doing read request. Further it marks as clean buffers that |
3016 | * are processed for writing (the buffer cache won't assume that they are |
3017 | * actually clean until the buffer gets unlocked). |
3018 | * |
3019 | * ll_rw_block sets b_end_io to simple completion handler that marks |
3020 | * the buffer up-to-date (if approriate), unlocks the buffer and wakes |
3021 | * any waiters. |
3022 | * |
3023 | * All of the buffers must be for the same device, and must also be a |
3024 | * multiple of the current approved size for the device. |
3025 | */ |
3026 | void ll_rw_block(int rw, int nr, struct buffer_head *bhs[]) |
3027 | { |
3028 | int i; |
3029 | |
3030 | for (i = 0; i < nr; i++) { |
3031 | struct buffer_head *bh = bhs[i]; |
3032 | |
3033 | if (rw == SWRITE || rw == SWRITE_SYNC || rw == SWRITE_SYNC_PLUG) |
3034 | lock_buffer(bh); |
3035 | else if (!trylock_buffer(bh)) |
3036 | continue; |
3037 | |
3038 | if (rw == WRITE || rw == SWRITE || rw == SWRITE_SYNC || |
3039 | rw == SWRITE_SYNC_PLUG) { |
3040 | if (test_clear_buffer_dirty(bh)) { |
3041 | bh->b_end_io = end_buffer_write_sync; |
3042 | get_bh(bh); |
3043 | if (rw == SWRITE_SYNC) |
3044 | submit_bh(WRITE_SYNC, bh); |
3045 | else |
3046 | submit_bh(WRITE, bh); |
3047 | continue; |
3048 | } |
3049 | } else { |
3050 | if (!buffer_uptodate(bh)) { |
3051 | bh->b_end_io = end_buffer_read_sync; |
3052 | get_bh(bh); |
3053 | submit_bh(rw, bh); |
3054 | continue; |
3055 | } |
3056 | } |
3057 | unlock_buffer(bh); |
3058 | } |
3059 | } |
3060 | EXPORT_SYMBOL(ll_rw_block); |
3061 | |
3062 | /* |
3063 | * For a data-integrity writeout, we need to wait upon any in-progress I/O |
3064 | * and then start new I/O and then wait upon it. The caller must have a ref on |
3065 | * the buffer_head. |
3066 | */ |
3067 | int sync_dirty_buffer(struct buffer_head *bh) |
3068 | { |
3069 | int ret = 0; |
3070 | |
3071 | WARN_ON(atomic_read(&bh->b_count) < 1); |
3072 | lock_buffer(bh); |
3073 | if (test_clear_buffer_dirty(bh)) { |
3074 | get_bh(bh); |
3075 | bh->b_end_io = end_buffer_write_sync; |
3076 | ret = submit_bh(WRITE_SYNC, bh); |
3077 | wait_on_buffer(bh); |
3078 | if (buffer_eopnotsupp(bh)) { |
3079 | clear_buffer_eopnotsupp(bh); |
3080 | ret = -EOPNOTSUPP; |
3081 | } |
3082 | if (!ret && !buffer_uptodate(bh)) |
3083 | ret = -EIO; |
3084 | } else { |
3085 | unlock_buffer(bh); |
3086 | } |
3087 | return ret; |
3088 | } |
3089 | EXPORT_SYMBOL(sync_dirty_buffer); |
3090 | |
3091 | /* |
3092 | * try_to_free_buffers() checks if all the buffers on this particular page |
3093 | * are unused, and releases them if so. |
3094 | * |
3095 | * Exclusion against try_to_free_buffers may be obtained by either |
3096 | * locking the page or by holding its mapping's private_lock. |
3097 | * |
3098 | * If the page is dirty but all the buffers are clean then we need to |
3099 | * be sure to mark the page clean as well. This is because the page |
3100 | * may be against a block device, and a later reattachment of buffers |
3101 | * to a dirty page will set *all* buffers dirty. Which would corrupt |
3102 | * filesystem data on the same device. |
3103 | * |
3104 | * The same applies to regular filesystem pages: if all the buffers are |
3105 | * clean then we set the page clean and proceed. To do that, we require |
3106 | * total exclusion from __set_page_dirty_buffers(). That is obtained with |
3107 | * private_lock. |
3108 | * |
3109 | * try_to_free_buffers() is non-blocking. |
3110 | */ |
3111 | static inline int buffer_busy(struct buffer_head *bh) |
3112 | { |
3113 | return atomic_read(&bh->b_count) | |
3114 | (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock))); |
3115 | } |
3116 | |
3117 | static int |
3118 | drop_buffers(struct page *page, struct buffer_head **buffers_to_free) |
3119 | { |
3120 | struct buffer_head *head = page_buffers(page); |
3121 | struct buffer_head *bh; |
3122 | |
3123 | bh = head; |
3124 | do { |
3125 | if (buffer_write_io_error(bh) && page->mapping) |
3126 | set_bit(AS_EIO, &page->mapping->flags); |
3127 | if (buffer_busy(bh)) |
3128 | goto failed; |
3129 | bh = bh->b_this_page; |
3130 | } while (bh != head); |
3131 | |
3132 | do { |
3133 | struct buffer_head *next = bh->b_this_page; |
3134 | |
3135 | if (bh->b_assoc_map) |
3136 | __remove_assoc_queue(bh); |
3137 | bh = next; |
3138 | } while (bh != head); |
3139 | *buffers_to_free = head; |
3140 | __clear_page_buffers(page); |
3141 | return 1; |
3142 | failed: |
3143 | return 0; |
3144 | } |
3145 | |
3146 | int try_to_free_buffers(struct page *page) |
3147 | { |
3148 | struct address_space * const mapping = page->mapping; |
3149 | struct buffer_head *buffers_to_free = NULL; |
3150 | int ret = 0; |
3151 | |
3152 | BUG_ON(!PageLocked(page)); |
3153 | if (PageWriteback(page)) |
3154 | return 0; |
3155 | |
3156 | if (mapping == NULL) { /* can this still happen? */ |
3157 | ret = drop_buffers(page, &buffers_to_free); |
3158 | goto out; |
3159 | } |
3160 | |
3161 | spin_lock(&mapping->private_lock); |
3162 | ret = drop_buffers(page, &buffers_to_free); |
3163 | |
3164 | /* |
3165 | * If the filesystem writes its buffers by hand (eg ext3) |
3166 | * then we can have clean buffers against a dirty page. We |
3167 | * clean the page here; otherwise the VM will never notice |
3168 | * that the filesystem did any IO at all. |
3169 | * |
3170 | * Also, during truncate, discard_buffer will have marked all |
3171 | * the page's buffers clean. We discover that here and clean |
3172 | * the page also. |
3173 | * |
3174 | * private_lock must be held over this entire operation in order |
3175 | * to synchronise against __set_page_dirty_buffers and prevent the |
3176 | * dirty bit from being lost. |
3177 | */ |
3178 | if (ret) |
3179 | cancel_dirty_page(page, PAGE_CACHE_SIZE); |
3180 | spin_unlock(&mapping->private_lock); |
3181 | out: |
3182 | if (buffers_to_free) { |
3183 | struct buffer_head *bh = buffers_to_free; |
3184 | |
3185 | do { |
3186 | struct buffer_head *next = bh->b_this_page; |
3187 | free_buffer_head(bh); |
3188 | bh = next; |
3189 | } while (bh != buffers_to_free); |
3190 | } |
3191 | return ret; |
3192 | } |
3193 | EXPORT_SYMBOL(try_to_free_buffers); |
3194 | |
3195 | void block_sync_page(struct page *page) |
3196 | { |
3197 | struct address_space *mapping; |
3198 | |
3199 | smp_mb(); |
3200 | mapping = page_mapping(page); |
3201 | if (mapping) |
3202 | blk_run_backing_dev(mapping->backing_dev_info, page); |
3203 | } |
3204 | EXPORT_SYMBOL(block_sync_page); |
3205 | |
3206 | /* |
3207 | * There are no bdflush tunables left. But distributions are |
3208 | * still running obsolete flush daemons, so we terminate them here. |
3209 | * |
3210 | * Use of bdflush() is deprecated and will be removed in a future kernel. |
3211 | * The `flush-X' kernel threads fully replace bdflush daemons and this call. |
3212 | */ |
3213 | SYSCALL_DEFINE2(bdflush, int, func, long, data) |
3214 | { |
3215 | static int msg_count; |
3216 | |
3217 | if (!capable(CAP_SYS_ADMIN)) |
3218 | return -EPERM; |
3219 | |
3220 | if (msg_count < 5) { |
3221 | msg_count++; |
3222 | printk(KERN_INFO |
3223 | "warning: process `%s' used the obsolete bdflush" |
3224 | " system call\n", current->comm); |
3225 | printk(KERN_INFO "Fix your initscripts?\n"); |
3226 | } |
3227 | |
3228 | if (func == 1) |
3229 | do_exit(0); |
3230 | return 0; |
3231 | } |
3232 | |
3233 | /* |
3234 | * Buffer-head allocation |
3235 | */ |
3236 | static struct kmem_cache *bh_cachep; |
3237 | |
3238 | /* |
3239 | * Once the number of bh's in the machine exceeds this level, we start |
3240 | * stripping them in writeback. |
3241 | */ |
3242 | static int max_buffer_heads; |
3243 | |
3244 | int buffer_heads_over_limit; |
3245 | |
3246 | struct bh_accounting { |
3247 | int nr; /* Number of live bh's */ |
3248 | int ratelimit; /* Limit cacheline bouncing */ |
3249 | }; |
3250 | |
3251 | static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0}; |
3252 | |
3253 | static void recalc_bh_state(void) |
3254 | { |
3255 | int i; |
3256 | int tot = 0; |
3257 | |
3258 | if (__get_cpu_var(bh_accounting).ratelimit++ < 4096) |
3259 | return; |
3260 | __get_cpu_var(bh_accounting).ratelimit = 0; |
3261 | for_each_online_cpu(i) |
3262 | tot += per_cpu(bh_accounting, i).nr; |
3263 | buffer_heads_over_limit = (tot > max_buffer_heads); |
3264 | } |
3265 | |
3266 | struct buffer_head *alloc_buffer_head(gfp_t gfp_flags) |
3267 | { |
3268 | struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags); |
3269 | if (ret) { |
3270 | INIT_LIST_HEAD(&ret->b_assoc_buffers); |
3271 | get_cpu_var(bh_accounting).nr++; |
3272 | recalc_bh_state(); |
3273 | put_cpu_var(bh_accounting); |
3274 | } |
3275 | return ret; |
3276 | } |
3277 | EXPORT_SYMBOL(alloc_buffer_head); |
3278 | |
3279 | void free_buffer_head(struct buffer_head *bh) |
3280 | { |
3281 | BUG_ON(!list_empty(&bh->b_assoc_buffers)); |
3282 | kmem_cache_free(bh_cachep, bh); |
3283 | get_cpu_var(bh_accounting).nr--; |
3284 | recalc_bh_state(); |
3285 | put_cpu_var(bh_accounting); |
3286 | } |
3287 | EXPORT_SYMBOL(free_buffer_head); |
3288 | |
3289 | static void buffer_exit_cpu(int cpu) |
3290 | { |
3291 | int i; |
3292 | struct bh_lru *b = &per_cpu(bh_lrus, cpu); |
3293 | |
3294 | for (i = 0; i < BH_LRU_SIZE; i++) { |
3295 | brelse(b->bhs[i]); |
3296 | b->bhs[i] = NULL; |
3297 | } |
3298 | get_cpu_var(bh_accounting).nr += per_cpu(bh_accounting, cpu).nr; |
3299 | per_cpu(bh_accounting, cpu).nr = 0; |
3300 | put_cpu_var(bh_accounting); |
3301 | } |
3302 | |
3303 | static int buffer_cpu_notify(struct notifier_block *self, |
3304 | unsigned long action, void *hcpu) |
3305 | { |
3306 | if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) |
3307 | buffer_exit_cpu((unsigned long)hcpu); |
3308 | return NOTIFY_OK; |
3309 | } |
3310 | |
3311 | /** |
3312 | * bh_uptodate_or_lock - Test whether the buffer is uptodate |
3313 | * @bh: struct buffer_head |
3314 | * |
3315 | * Return true if the buffer is up-to-date and false, |
3316 | * with the buffer locked, if not. |
3317 | */ |
3318 | int bh_uptodate_or_lock(struct buffer_head *bh) |
3319 | { |
3320 | if (!buffer_uptodate(bh)) { |
3321 | lock_buffer(bh); |
3322 | if (!buffer_uptodate(bh)) |
3323 | return 0; |
3324 | unlock_buffer(bh); |
3325 | } |
3326 | return 1; |
3327 | } |
3328 | EXPORT_SYMBOL(bh_uptodate_or_lock); |
3329 | |
3330 | /** |
3331 | * bh_submit_read - Submit a locked buffer for reading |
3332 | * @bh: struct buffer_head |
3333 | * |
3334 | * Returns zero on success and -EIO on error. |
3335 | */ |
3336 | int bh_submit_read(struct buffer_head *bh) |
3337 | { |
3338 | BUG_ON(!buffer_locked(bh)); |
3339 | |
3340 | if (buffer_uptodate(bh)) { |
3341 | unlock_buffer(bh); |
3342 | return 0; |
3343 | } |
3344 | |
3345 | get_bh(bh); |
3346 | bh->b_end_io = end_buffer_read_sync; |
3347 | submit_bh(READ, bh); |
3348 | wait_on_buffer(bh); |
3349 | if (buffer_uptodate(bh)) |
3350 | return 0; |
3351 | return -EIO; |
3352 | } |
3353 | EXPORT_SYMBOL(bh_submit_read); |
3354 | |
3355 | void __init buffer_init(void) |
3356 | { |
3357 | int nrpages; |
3358 | |
3359 | bh_cachep = kmem_cache_create("buffer_head", |
3360 | sizeof(struct buffer_head), 0, |
3361 | (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC| |
3362 | SLAB_MEM_SPREAD), |
3363 | NULL); |
3364 | |
3365 | /* |
3366 | * Limit the bh occupancy to 10% of ZONE_NORMAL |
3367 | */ |
3368 | nrpages = (nr_free_buffer_pages() * 10) / 100; |
3369 | max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head)); |
3370 | hotcpu_notifier(buffer_cpu_notify, 0); |
3371 | } |
3372 |
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