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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/export.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 sleep_on_buffer(void *word) |
58 | { |
59 | io_schedule(); |
60 | return 0; |
61 | } |
62 | |
63 | void __lock_buffer(struct buffer_head *bh) |
64 | { |
65 | wait_on_bit_lock(&bh->b_state, BH_Lock, sleep_on_buffer, |
66 | TASK_UNINTERRUPTIBLE); |
67 | } |
68 | EXPORT_SYMBOL(__lock_buffer); |
69 | |
70 | void unlock_buffer(struct buffer_head *bh) |
71 | { |
72 | clear_bit_unlock(BH_Lock, &bh->b_state); |
73 | smp_mb__after_clear_bit(); |
74 | wake_up_bit(&bh->b_state, BH_Lock); |
75 | } |
76 | EXPORT_SYMBOL(unlock_buffer); |
77 | |
78 | /* |
79 | * Block until a buffer comes unlocked. This doesn't stop it |
80 | * from becoming locked again - you have to lock it yourself |
81 | * if you want to preserve its state. |
82 | */ |
83 | void __wait_on_buffer(struct buffer_head * bh) |
84 | { |
85 | wait_on_bit(&bh->b_state, BH_Lock, sleep_on_buffer, TASK_UNINTERRUPTIBLE); |
86 | } |
87 | EXPORT_SYMBOL(__wait_on_buffer); |
88 | |
89 | static void |
90 | __clear_page_buffers(struct page *page) |
91 | { |
92 | ClearPagePrivate(page); |
93 | set_page_private(page, 0); |
94 | page_cache_release(page); |
95 | } |
96 | |
97 | |
98 | static int quiet_error(struct buffer_head *bh) |
99 | { |
100 | if (!test_bit(BH_Quiet, &bh->b_state) && printk_ratelimit()) |
101 | return 0; |
102 | return 1; |
103 | } |
104 | |
105 | |
106 | static void buffer_io_error(struct buffer_head *bh) |
107 | { |
108 | char b[BDEVNAME_SIZE]; |
109 | printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n", |
110 | bdevname(bh->b_bdev, b), |
111 | (unsigned long long)bh->b_blocknr); |
112 | } |
113 | |
114 | /* |
115 | * End-of-IO handler helper function which does not touch the bh after |
116 | * unlocking it. |
117 | * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but |
118 | * a race there is benign: unlock_buffer() only use the bh's address for |
119 | * hashing after unlocking the buffer, so it doesn't actually touch the bh |
120 | * itself. |
121 | */ |
122 | static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate) |
123 | { |
124 | if (uptodate) { |
125 | set_buffer_uptodate(bh); |
126 | } else { |
127 | /* This happens, due to failed READA attempts. */ |
128 | clear_buffer_uptodate(bh); |
129 | } |
130 | unlock_buffer(bh); |
131 | } |
132 | |
133 | /* |
134 | * Default synchronous end-of-IO handler.. Just mark it up-to-date and |
135 | * unlock the buffer. This is what ll_rw_block uses too. |
136 | */ |
137 | void end_buffer_read_sync(struct buffer_head *bh, int uptodate) |
138 | { |
139 | __end_buffer_read_notouch(bh, uptodate); |
140 | put_bh(bh); |
141 | } |
142 | EXPORT_SYMBOL(end_buffer_read_sync); |
143 | |
144 | void end_buffer_write_sync(struct buffer_head *bh, int uptodate) |
145 | { |
146 | char b[BDEVNAME_SIZE]; |
147 | |
148 | if (uptodate) { |
149 | set_buffer_uptodate(bh); |
150 | } else { |
151 | if (!quiet_error(bh)) { |
152 | buffer_io_error(bh); |
153 | printk(KERN_WARNING "lost page write due to " |
154 | "I/O error on %s\n", |
155 | bdevname(bh->b_bdev, b)); |
156 | } |
157 | set_buffer_write_io_error(bh); |
158 | clear_buffer_uptodate(bh); |
159 | } |
160 | unlock_buffer(bh); |
161 | put_bh(bh); |
162 | } |
163 | EXPORT_SYMBOL(end_buffer_write_sync); |
164 | |
165 | /* |
166 | * Various filesystems appear to want __find_get_block to be non-blocking. |
167 | * But it's the page lock which protects the buffers. To get around this, |
168 | * we get exclusion from try_to_free_buffers with the blockdev mapping's |
169 | * private_lock. |
170 | * |
171 | * Hack idea: for the blockdev mapping, i_bufferlist_lock contention |
172 | * may be quite high. This code could TryLock the page, and if that |
173 | * succeeds, there is no need to take private_lock. (But if |
174 | * private_lock is contended then so is mapping->tree_lock). |
175 | */ |
176 | static struct buffer_head * |
177 | __find_get_block_slow(struct block_device *bdev, sector_t block) |
178 | { |
179 | struct inode *bd_inode = bdev->bd_inode; |
180 | struct address_space *bd_mapping = bd_inode->i_mapping; |
181 | struct buffer_head *ret = NULL; |
182 | pgoff_t index; |
183 | struct buffer_head *bh; |
184 | struct buffer_head *head; |
185 | struct page *page; |
186 | int all_mapped = 1; |
187 | |
188 | index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits); |
189 | page = find_get_page(bd_mapping, index); |
190 | if (!page) |
191 | goto out; |
192 | |
193 | spin_lock(&bd_mapping->private_lock); |
194 | if (!page_has_buffers(page)) |
195 | goto out_unlock; |
196 | head = page_buffers(page); |
197 | bh = head; |
198 | do { |
199 | if (!buffer_mapped(bh)) |
200 | all_mapped = 0; |
201 | else if (bh->b_blocknr == block) { |
202 | ret = bh; |
203 | get_bh(bh); |
204 | goto out_unlock; |
205 | } |
206 | bh = bh->b_this_page; |
207 | } while (bh != head); |
208 | |
209 | /* we might be here because some of the buffers on this page are |
210 | * not mapped. This is due to various races between |
211 | * file io on the block device and getblk. It gets dealt with |
212 | * elsewhere, don't buffer_error if we had some unmapped buffers |
213 | */ |
214 | if (all_mapped) { |
215 | char b[BDEVNAME_SIZE]; |
216 | |
217 | printk("__find_get_block_slow() failed. " |
218 | "block=%llu, b_blocknr=%llu\n", |
219 | (unsigned long long)block, |
220 | (unsigned long long)bh->b_blocknr); |
221 | printk("b_state=0x%08lx, b_size=%zu\n", |
222 | bh->b_state, bh->b_size); |
223 | printk("device %s blocksize: %d\n", bdevname(bdev, b), |
224 | 1 << bd_inode->i_blkbits); |
225 | } |
226 | out_unlock: |
227 | spin_unlock(&bd_mapping->private_lock); |
228 | page_cache_release(page); |
229 | out: |
230 | return ret; |
231 | } |
232 | |
233 | /* |
234 | * Kick the writeback threads then try to free up some ZONE_NORMAL memory. |
235 | */ |
236 | static void free_more_memory(void) |
237 | { |
238 | struct zone *zone; |
239 | int nid; |
240 | |
241 | wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM); |
242 | yield(); |
243 | |
244 | for_each_online_node(nid) { |
245 | (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS), |
246 | gfp_zone(GFP_NOFS), NULL, |
247 | &zone); |
248 | if (zone) |
249 | try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0, |
250 | GFP_NOFS, NULL); |
251 | } |
252 | } |
253 | |
254 | /* |
255 | * I/O completion handler for block_read_full_page() - pages |
256 | * which come unlocked at the end of I/O. |
257 | */ |
258 | static void end_buffer_async_read(struct buffer_head *bh, int uptodate) |
259 | { |
260 | unsigned long flags; |
261 | struct buffer_head *first; |
262 | struct buffer_head *tmp; |
263 | struct page *page; |
264 | int page_uptodate = 1; |
265 | |
266 | BUG_ON(!buffer_async_read(bh)); |
267 | |
268 | page = bh->b_page; |
269 | if (uptodate) { |
270 | set_buffer_uptodate(bh); |
271 | } else { |
272 | clear_buffer_uptodate(bh); |
273 | if (!quiet_error(bh)) |
274 | buffer_io_error(bh); |
275 | SetPageError(page); |
276 | } |
277 | |
278 | /* |
279 | * Be _very_ careful from here on. Bad things can happen if |
280 | * two buffer heads end IO at almost the same time and both |
281 | * decide that the page is now completely done. |
282 | */ |
283 | first = page_buffers(page); |
284 | local_irq_save(flags); |
285 | bit_spin_lock(BH_Uptodate_Lock, &first->b_state); |
286 | clear_buffer_async_read(bh); |
287 | unlock_buffer(bh); |
288 | tmp = bh; |
289 | do { |
290 | if (!buffer_uptodate(tmp)) |
291 | page_uptodate = 0; |
292 | if (buffer_async_read(tmp)) { |
293 | BUG_ON(!buffer_locked(tmp)); |
294 | goto still_busy; |
295 | } |
296 | tmp = tmp->b_this_page; |
297 | } while (tmp != bh); |
298 | bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
299 | local_irq_restore(flags); |
300 | |
301 | /* |
302 | * If none of the buffers had errors and they are all |
303 | * uptodate then we can set the page uptodate. |
304 | */ |
305 | if (page_uptodate && !PageError(page)) |
306 | SetPageUptodate(page); |
307 | unlock_page(page); |
308 | return; |
309 | |
310 | still_busy: |
311 | bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
312 | local_irq_restore(flags); |
313 | return; |
314 | } |
315 | |
316 | /* |
317 | * Completion handler for block_write_full_page() - pages which are unlocked |
318 | * during I/O, and which have PageWriteback cleared upon I/O completion. |
319 | */ |
320 | void end_buffer_async_write(struct buffer_head *bh, int uptodate) |
321 | { |
322 | char b[BDEVNAME_SIZE]; |
323 | unsigned long flags; |
324 | struct buffer_head *first; |
325 | struct buffer_head *tmp; |
326 | struct page *page; |
327 | |
328 | BUG_ON(!buffer_async_write(bh)); |
329 | |
330 | page = bh->b_page; |
331 | if (uptodate) { |
332 | set_buffer_uptodate(bh); |
333 | } else { |
334 | if (!quiet_error(bh)) { |
335 | buffer_io_error(bh); |
336 | printk(KERN_WARNING "lost page write due to " |
337 | "I/O error on %s\n", |
338 | bdevname(bh->b_bdev, b)); |
339 | } |
340 | set_bit(AS_EIO, &page->mapping->flags); |
341 | set_buffer_write_io_error(bh); |
342 | clear_buffer_uptodate(bh); |
343 | SetPageError(page); |
344 | } |
345 | |
346 | first = page_buffers(page); |
347 | local_irq_save(flags); |
348 | bit_spin_lock(BH_Uptodate_Lock, &first->b_state); |
349 | |
350 | clear_buffer_async_write(bh); |
351 | unlock_buffer(bh); |
352 | tmp = bh->b_this_page; |
353 | while (tmp != bh) { |
354 | if (buffer_async_write(tmp)) { |
355 | BUG_ON(!buffer_locked(tmp)); |
356 | goto still_busy; |
357 | } |
358 | tmp = tmp->b_this_page; |
359 | } |
360 | bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
361 | local_irq_restore(flags); |
362 | end_page_writeback(page); |
363 | return; |
364 | |
365 | still_busy: |
366 | bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
367 | local_irq_restore(flags); |
368 | return; |
369 | } |
370 | EXPORT_SYMBOL(end_buffer_async_write); |
371 | |
372 | /* |
373 | * If a page's buffers are under async readin (end_buffer_async_read |
374 | * completion) then there is a possibility that another thread of |
375 | * control could lock one of the buffers after it has completed |
376 | * but while some of the other buffers have not completed. This |
377 | * locked buffer would confuse end_buffer_async_read() into not unlocking |
378 | * the page. So the absence of BH_Async_Read tells end_buffer_async_read() |
379 | * that this buffer is not under async I/O. |
380 | * |
381 | * The page comes unlocked when it has no locked buffer_async buffers |
382 | * left. |
383 | * |
384 | * PageLocked prevents anyone starting new async I/O reads any of |
385 | * the buffers. |
386 | * |
387 | * PageWriteback is used to prevent simultaneous writeout of the same |
388 | * page. |
389 | * |
390 | * PageLocked prevents anyone from starting writeback of a page which is |
391 | * under read I/O (PageWriteback is only ever set against a locked page). |
392 | */ |
393 | static void mark_buffer_async_read(struct buffer_head *bh) |
394 | { |
395 | bh->b_end_io = end_buffer_async_read; |
396 | set_buffer_async_read(bh); |
397 | } |
398 | |
399 | static void mark_buffer_async_write_endio(struct buffer_head *bh, |
400 | bh_end_io_t *handler) |
401 | { |
402 | bh->b_end_io = handler; |
403 | set_buffer_async_write(bh); |
404 | } |
405 | |
406 | void mark_buffer_async_write(struct buffer_head *bh) |
407 | { |
408 | mark_buffer_async_write_endio(bh, end_buffer_async_write); |
409 | } |
410 | EXPORT_SYMBOL(mark_buffer_async_write); |
411 | |
412 | |
413 | /* |
414 | * fs/buffer.c contains helper functions for buffer-backed address space's |
415 | * fsync functions. A common requirement for buffer-based filesystems is |
416 | * that certain data from the backing blockdev needs to be written out for |
417 | * a successful fsync(). For example, ext2 indirect blocks need to be |
418 | * written back and waited upon before fsync() returns. |
419 | * |
420 | * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(), |
421 | * inode_has_buffers() and invalidate_inode_buffers() are provided for the |
422 | * management of a list of dependent buffers at ->i_mapping->private_list. |
423 | * |
424 | * Locking is a little subtle: try_to_free_buffers() will remove buffers |
425 | * from their controlling inode's queue when they are being freed. But |
426 | * try_to_free_buffers() will be operating against the *blockdev* mapping |
427 | * at the time, not against the S_ISREG file which depends on those buffers. |
428 | * So the locking for private_list is via the private_lock in the address_space |
429 | * which backs the buffers. Which is different from the address_space |
430 | * against which the buffers are listed. So for a particular address_space, |
431 | * mapping->private_lock does *not* protect mapping->private_list! In fact, |
432 | * mapping->private_list will always be protected by the backing blockdev's |
433 | * ->private_lock. |
434 | * |
435 | * Which introduces a requirement: all buffers on an address_space's |
436 | * ->private_list must be from the same address_space: the blockdev's. |
437 | * |
438 | * address_spaces which do not place buffers at ->private_list via these |
439 | * utility functions are free to use private_lock and private_list for |
440 | * whatever they want. The only requirement is that list_empty(private_list) |
441 | * be true at clear_inode() time. |
442 | * |
443 | * FIXME: clear_inode should not call invalidate_inode_buffers(). The |
444 | * filesystems should do that. invalidate_inode_buffers() should just go |
445 | * BUG_ON(!list_empty). |
446 | * |
447 | * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should |
448 | * take an address_space, not an inode. And it should be called |
449 | * mark_buffer_dirty_fsync() to clearly define why those buffers are being |
450 | * queued up. |
451 | * |
452 | * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the |
453 | * list if it is already on a list. Because if the buffer is on a list, |
454 | * it *must* already be on the right one. If not, the filesystem is being |
455 | * silly. This will save a ton of locking. But first we have to ensure |
456 | * that buffers are taken *off* the old inode's list when they are freed |
457 | * (presumably in truncate). That requires careful auditing of all |
458 | * filesystems (do it inside bforget()). It could also be done by bringing |
459 | * b_inode back. |
460 | */ |
461 | |
462 | /* |
463 | * The buffer's backing address_space's private_lock must be held |
464 | */ |
465 | static void __remove_assoc_queue(struct buffer_head *bh) |
466 | { |
467 | list_del_init(&bh->b_assoc_buffers); |
468 | WARN_ON(!bh->b_assoc_map); |
469 | if (buffer_write_io_error(bh)) |
470 | set_bit(AS_EIO, &bh->b_assoc_map->flags); |
471 | bh->b_assoc_map = NULL; |
472 | } |
473 | |
474 | int inode_has_buffers(struct inode *inode) |
475 | { |
476 | return !list_empty(&inode->i_data.private_list); |
477 | } |
478 | |
479 | /* |
480 | * osync is designed to support O_SYNC io. It waits synchronously for |
481 | * all already-submitted IO to complete, but does not queue any new |
482 | * writes to the disk. |
483 | * |
484 | * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as |
485 | * you dirty the buffers, and then use osync_inode_buffers to wait for |
486 | * completion. Any other dirty buffers which are not yet queued for |
487 | * write will not be flushed to disk by the osync. |
488 | */ |
489 | static int osync_buffers_list(spinlock_t *lock, struct list_head *list) |
490 | { |
491 | struct buffer_head *bh; |
492 | struct list_head *p; |
493 | int err = 0; |
494 | |
495 | spin_lock(lock); |
496 | repeat: |
497 | list_for_each_prev(p, list) { |
498 | bh = BH_ENTRY(p); |
499 | if (buffer_locked(bh)) { |
500 | get_bh(bh); |
501 | spin_unlock(lock); |
502 | wait_on_buffer(bh); |
503 | if (!buffer_uptodate(bh)) |
504 | err = -EIO; |
505 | brelse(bh); |
506 | spin_lock(lock); |
507 | goto repeat; |
508 | } |
509 | } |
510 | spin_unlock(lock); |
511 | return err; |
512 | } |
513 | |
514 | static void do_thaw_one(struct super_block *sb, void *unused) |
515 | { |
516 | char b[BDEVNAME_SIZE]; |
517 | while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb)) |
518 | printk(KERN_WARNING "Emergency Thaw on %s\n", |
519 | bdevname(sb->s_bdev, b)); |
520 | } |
521 | |
522 | static void do_thaw_all(struct work_struct *work) |
523 | { |
524 | iterate_supers(do_thaw_one, NULL); |
525 | kfree(work); |
526 | printk(KERN_WARNING "Emergency Thaw complete\n"); |
527 | } |
528 | |
529 | /** |
530 | * emergency_thaw_all -- forcibly thaw every frozen filesystem |
531 | * |
532 | * Used for emergency unfreeze of all filesystems via SysRq |
533 | */ |
534 | void emergency_thaw_all(void) |
535 | { |
536 | struct work_struct *work; |
537 | |
538 | work = kmalloc(sizeof(*work), GFP_ATOMIC); |
539 | if (work) { |
540 | INIT_WORK(work, do_thaw_all); |
541 | schedule_work(work); |
542 | } |
543 | } |
544 | |
545 | /** |
546 | * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers |
547 | * @mapping: the mapping which wants those buffers written |
548 | * |
549 | * Starts I/O against the buffers at mapping->private_list, and waits upon |
550 | * that I/O. |
551 | * |
552 | * Basically, this is a convenience function for fsync(). |
553 | * @mapping is a file or directory which needs those buffers to be written for |
554 | * a successful fsync(). |
555 | */ |
556 | int sync_mapping_buffers(struct address_space *mapping) |
557 | { |
558 | struct address_space *buffer_mapping = mapping->assoc_mapping; |
559 | |
560 | if (buffer_mapping == NULL || list_empty(&mapping->private_list)) |
561 | return 0; |
562 | |
563 | return fsync_buffers_list(&buffer_mapping->private_lock, |
564 | &mapping->private_list); |
565 | } |
566 | EXPORT_SYMBOL(sync_mapping_buffers); |
567 | |
568 | /* |
569 | * Called when we've recently written block `bblock', and it is known that |
570 | * `bblock' was for a buffer_boundary() buffer. This means that the block at |
571 | * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's |
572 | * dirty, schedule it for IO. So that indirects merge nicely with their data. |
573 | */ |
574 | void write_boundary_block(struct block_device *bdev, |
575 | sector_t bblock, unsigned blocksize) |
576 | { |
577 | struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize); |
578 | if (bh) { |
579 | if (buffer_dirty(bh)) |
580 | ll_rw_block(WRITE, 1, &bh); |
581 | put_bh(bh); |
582 | } |
583 | } |
584 | |
585 | void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode) |
586 | { |
587 | struct address_space *mapping = inode->i_mapping; |
588 | struct address_space *buffer_mapping = bh->b_page->mapping; |
589 | |
590 | mark_buffer_dirty(bh); |
591 | if (!mapping->assoc_mapping) { |
592 | mapping->assoc_mapping = buffer_mapping; |
593 | } else { |
594 | BUG_ON(mapping->assoc_mapping != buffer_mapping); |
595 | } |
596 | if (!bh->b_assoc_map) { |
597 | spin_lock(&buffer_mapping->private_lock); |
598 | list_move_tail(&bh->b_assoc_buffers, |
599 | &mapping->private_list); |
600 | bh->b_assoc_map = mapping; |
601 | spin_unlock(&buffer_mapping->private_lock); |
602 | } |
603 | } |
604 | EXPORT_SYMBOL(mark_buffer_dirty_inode); |
605 | |
606 | /* |
607 | * Mark the page dirty, and set it dirty in the radix tree, and mark the inode |
608 | * dirty. |
609 | * |
610 | * If warn is true, then emit a warning if the page is not uptodate and has |
611 | * not been truncated. |
612 | */ |
613 | static void __set_page_dirty(struct page *page, |
614 | struct address_space *mapping, int warn) |
615 | { |
616 | spin_lock_irq(&mapping->tree_lock); |
617 | if (page->mapping) { /* Race with truncate? */ |
618 | WARN_ON_ONCE(warn && !PageUptodate(page)); |
619 | account_page_dirtied(page, mapping); |
620 | radix_tree_tag_set(&mapping->page_tree, |
621 | page_index(page), PAGECACHE_TAG_DIRTY); |
622 | } |
623 | spin_unlock_irq(&mapping->tree_lock); |
624 | __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); |
625 | } |
626 | |
627 | /* |
628 | * Add a page to the dirty page list. |
629 | * |
630 | * It is a sad fact of life that this function is called from several places |
631 | * deeply under spinlocking. It may not sleep. |
632 | * |
633 | * If the page has buffers, the uptodate buffers are set dirty, to preserve |
634 | * dirty-state coherency between the page and the buffers. It the page does |
635 | * not have buffers then when they are later attached they will all be set |
636 | * dirty. |
637 | * |
638 | * The buffers are dirtied before the page is dirtied. There's a small race |
639 | * window in which a writepage caller may see the page cleanness but not the |
640 | * buffer dirtiness. That's fine. If this code were to set the page dirty |
641 | * before the buffers, a concurrent writepage caller could clear the page dirty |
642 | * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean |
643 | * page on the dirty page list. |
644 | * |
645 | * We use private_lock to lock against try_to_free_buffers while using the |
646 | * page's buffer list. Also use this to protect against clean buffers being |
647 | * added to the page after it was set dirty. |
648 | * |
649 | * FIXME: may need to call ->reservepage here as well. That's rather up to the |
650 | * address_space though. |
651 | */ |
652 | int __set_page_dirty_buffers(struct page *page) |
653 | { |
654 | int newly_dirty; |
655 | struct address_space *mapping = page_mapping(page); |
656 | |
657 | if (unlikely(!mapping)) |
658 | return !TestSetPageDirty(page); |
659 | |
660 | spin_lock(&mapping->private_lock); |
661 | if (page_has_buffers(page)) { |
662 | struct buffer_head *head = page_buffers(page); |
663 | struct buffer_head *bh = head; |
664 | |
665 | do { |
666 | set_buffer_dirty(bh); |
667 | bh = bh->b_this_page; |
668 | } while (bh != head); |
669 | } |
670 | newly_dirty = !TestSetPageDirty(page); |
671 | spin_unlock(&mapping->private_lock); |
672 | |
673 | if (newly_dirty) |
674 | __set_page_dirty(page, mapping, 1); |
675 | return newly_dirty; |
676 | } |
677 | EXPORT_SYMBOL(__set_page_dirty_buffers); |
678 | |
679 | /* |
680 | * Write out and wait upon a list of buffers. |
681 | * |
682 | * We have conflicting pressures: we want to make sure that all |
683 | * initially dirty buffers get waited on, but that any subsequently |
684 | * dirtied buffers don't. After all, we don't want fsync to last |
685 | * forever if somebody is actively writing to the file. |
686 | * |
687 | * Do this in two main stages: first we copy dirty buffers to a |
688 | * temporary inode list, queueing the writes as we go. Then we clean |
689 | * up, waiting for those writes to complete. |
690 | * |
691 | * During this second stage, any subsequent updates to the file may end |
692 | * up refiling the buffer on the original inode's dirty list again, so |
693 | * there is a chance we will end up with a buffer queued for write but |
694 | * not yet completed on that list. So, as a final cleanup we go through |
695 | * the osync code to catch these locked, dirty buffers without requeuing |
696 | * any newly dirty buffers for write. |
697 | */ |
698 | static int fsync_buffers_list(spinlock_t *lock, struct list_head *list) |
699 | { |
700 | struct buffer_head *bh; |
701 | struct list_head tmp; |
702 | struct address_space *mapping; |
703 | int err = 0, err2; |
704 | struct blk_plug plug; |
705 | |
706 | INIT_LIST_HEAD(&tmp); |
707 | blk_start_plug(&plug); |
708 | |
709 | spin_lock(lock); |
710 | while (!list_empty(list)) { |
711 | bh = BH_ENTRY(list->next); |
712 | mapping = bh->b_assoc_map; |
713 | __remove_assoc_queue(bh); |
714 | /* Avoid race with mark_buffer_dirty_inode() which does |
715 | * a lockless check and we rely on seeing the dirty bit */ |
716 | smp_mb(); |
717 | if (buffer_dirty(bh) || buffer_locked(bh)) { |
718 | list_add(&bh->b_assoc_buffers, &tmp); |
719 | bh->b_assoc_map = mapping; |
720 | if (buffer_dirty(bh)) { |
721 | get_bh(bh); |
722 | spin_unlock(lock); |
723 | /* |
724 | * Ensure any pending I/O completes so that |
725 | * write_dirty_buffer() actually writes the |
726 | * current contents - it is a noop if I/O is |
727 | * still in flight on potentially older |
728 | * contents. |
729 | */ |
730 | write_dirty_buffer(bh, WRITE_SYNC); |
731 | |
732 | /* |
733 | * Kick off IO for the previous mapping. Note |
734 | * that we will not run the very last mapping, |
735 | * wait_on_buffer() will do that for us |
736 | * through sync_buffer(). |
737 | */ |
738 | brelse(bh); |
739 | spin_lock(lock); |
740 | } |
741 | } |
742 | } |
743 | |
744 | spin_unlock(lock); |
745 | blk_finish_plug(&plug); |
746 | spin_lock(lock); |
747 | |
748 | while (!list_empty(&tmp)) { |
749 | bh = BH_ENTRY(tmp.prev); |
750 | get_bh(bh); |
751 | mapping = bh->b_assoc_map; |
752 | __remove_assoc_queue(bh); |
753 | /* Avoid race with mark_buffer_dirty_inode() which does |
754 | * a lockless check and we rely on seeing the dirty bit */ |
755 | smp_mb(); |
756 | if (buffer_dirty(bh)) { |
757 | list_add(&bh->b_assoc_buffers, |
758 | &mapping->private_list); |
759 | bh->b_assoc_map = mapping; |
760 | } |
761 | spin_unlock(lock); |
762 | wait_on_buffer(bh); |
763 | if (!buffer_uptodate(bh)) |
764 | err = -EIO; |
765 | brelse(bh); |
766 | spin_lock(lock); |
767 | } |
768 | |
769 | spin_unlock(lock); |
770 | err2 = osync_buffers_list(lock, list); |
771 | if (err) |
772 | return err; |
773 | else |
774 | return err2; |
775 | } |
776 | |
777 | /* |
778 | * Invalidate any and all dirty buffers on a given inode. We are |
779 | * probably unmounting the fs, but that doesn't mean we have already |
780 | * done a sync(). Just drop the buffers from the inode list. |
781 | * |
782 | * NOTE: we take the inode's blockdev's mapping's private_lock. Which |
783 | * assumes that all the buffers are against the blockdev. Not true |
784 | * for reiserfs. |
785 | */ |
786 | void invalidate_inode_buffers(struct inode *inode) |
787 | { |
788 | if (inode_has_buffers(inode)) { |
789 | struct address_space *mapping = &inode->i_data; |
790 | struct list_head *list = &mapping->private_list; |
791 | struct address_space *buffer_mapping = mapping->assoc_mapping; |
792 | |
793 | spin_lock(&buffer_mapping->private_lock); |
794 | while (!list_empty(list)) |
795 | __remove_assoc_queue(BH_ENTRY(list->next)); |
796 | spin_unlock(&buffer_mapping->private_lock); |
797 | } |
798 | } |
799 | EXPORT_SYMBOL(invalidate_inode_buffers); |
800 | |
801 | /* |
802 | * Remove any clean buffers from the inode's buffer list. This is called |
803 | * when we're trying to free the inode itself. Those buffers can pin it. |
804 | * |
805 | * Returns true if all buffers were removed. |
806 | */ |
807 | int remove_inode_buffers(struct inode *inode) |
808 | { |
809 | int ret = 1; |
810 | |
811 | if (inode_has_buffers(inode)) { |
812 | struct address_space *mapping = &inode->i_data; |
813 | struct list_head *list = &mapping->private_list; |
814 | struct address_space *buffer_mapping = mapping->assoc_mapping; |
815 | |
816 | spin_lock(&buffer_mapping->private_lock); |
817 | while (!list_empty(list)) { |
818 | struct buffer_head *bh = BH_ENTRY(list->next); |
819 | if (buffer_dirty(bh)) { |
820 | ret = 0; |
821 | break; |
822 | } |
823 | __remove_assoc_queue(bh); |
824 | } |
825 | spin_unlock(&buffer_mapping->private_lock); |
826 | } |
827 | return ret; |
828 | } |
829 | |
830 | /* |
831 | * Create the appropriate buffers when given a page for data area and |
832 | * the size of each buffer.. Use the bh->b_this_page linked list to |
833 | * follow the buffers created. Return NULL if unable to create more |
834 | * buffers. |
835 | * |
836 | * The retry flag is used to differentiate async IO (paging, swapping) |
837 | * which may not fail from ordinary buffer allocations. |
838 | */ |
839 | struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, |
840 | int retry) |
841 | { |
842 | struct buffer_head *bh, *head; |
843 | long offset; |
844 | |
845 | try_again: |
846 | head = NULL; |
847 | offset = PAGE_SIZE; |
848 | while ((offset -= size) >= 0) { |
849 | bh = alloc_buffer_head(GFP_NOFS); |
850 | if (!bh) |
851 | goto no_grow; |
852 | |
853 | bh->b_bdev = NULL; |
854 | bh->b_this_page = head; |
855 | bh->b_blocknr = -1; |
856 | head = bh; |
857 | |
858 | bh->b_state = 0; |
859 | atomic_set(&bh->b_count, 0); |
860 | bh->b_size = size; |
861 | |
862 | /* Link the buffer to its page */ |
863 | set_bh_page(bh, page, offset); |
864 | |
865 | init_buffer(bh, NULL, NULL); |
866 | } |
867 | return head; |
868 | /* |
869 | * In case anything failed, we just free everything we got. |
870 | */ |
871 | no_grow: |
872 | if (head) { |
873 | do { |
874 | bh = head; |
875 | head = head->b_this_page; |
876 | free_buffer_head(bh); |
877 | } while (head); |
878 | } |
879 | |
880 | /* |
881 | * Return failure for non-async IO requests. Async IO requests |
882 | * are not allowed to fail, so we have to wait until buffer heads |
883 | * become available. But we don't want tasks sleeping with |
884 | * partially complete buffers, so all were released above. |
885 | */ |
886 | if (!retry) |
887 | return NULL; |
888 | |
889 | /* We're _really_ low on memory. Now we just |
890 | * wait for old buffer heads to become free due to |
891 | * finishing IO. Since this is an async request and |
892 | * the reserve list is empty, we're sure there are |
893 | * async buffer heads in use. |
894 | */ |
895 | free_more_memory(); |
896 | goto try_again; |
897 | } |
898 | EXPORT_SYMBOL_GPL(alloc_page_buffers); |
899 | |
900 | static inline void |
901 | link_dev_buffers(struct page *page, struct buffer_head *head) |
902 | { |
903 | struct buffer_head *bh, *tail; |
904 | |
905 | bh = head; |
906 | do { |
907 | tail = bh; |
908 | bh = bh->b_this_page; |
909 | } while (bh); |
910 | tail->b_this_page = head; |
911 | attach_page_buffers(page, head); |
912 | } |
913 | |
914 | /* |
915 | * Initialise the state of a blockdev page's buffers. |
916 | */ |
917 | static void |
918 | init_page_buffers(struct page *page, struct block_device *bdev, |
919 | sector_t block, int size) |
920 | { |
921 | struct buffer_head *head = page_buffers(page); |
922 | struct buffer_head *bh = head; |
923 | int uptodate = PageUptodate(page); |
924 | sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode)); |
925 | |
926 | do { |
927 | if (!buffer_mapped(bh)) { |
928 | init_buffer(bh, NULL, NULL); |
929 | bh->b_bdev = bdev; |
930 | bh->b_blocknr = block; |
931 | if (uptodate) |
932 | set_buffer_uptodate(bh); |
933 | if (block < end_block) |
934 | set_buffer_mapped(bh); |
935 | } |
936 | block++; |
937 | bh = bh->b_this_page; |
938 | } while (bh != head); |
939 | } |
940 | |
941 | /* |
942 | * Create the page-cache page that contains the requested block. |
943 | * |
944 | * This is user purely for blockdev mappings. |
945 | */ |
946 | static struct page * |
947 | grow_dev_page(struct block_device *bdev, sector_t block, |
948 | pgoff_t index, int size) |
949 | { |
950 | struct inode *inode = bdev->bd_inode; |
951 | struct page *page; |
952 | struct buffer_head *bh; |
953 | |
954 | page = find_or_create_page(inode->i_mapping, index, |
955 | (mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS)|__GFP_MOVABLE); |
956 | if (!page) |
957 | return NULL; |
958 | |
959 | BUG_ON(!PageLocked(page)); |
960 | |
961 | if (page_has_buffers(page)) { |
962 | bh = page_buffers(page); |
963 | if (bh->b_size == size) { |
964 | init_page_buffers(page, bdev, block, size); |
965 | return page; |
966 | } |
967 | if (!try_to_free_buffers(page)) |
968 | goto failed; |
969 | } |
970 | |
971 | /* |
972 | * Allocate some buffers for this page |
973 | */ |
974 | bh = alloc_page_buffers(page, size, 0); |
975 | if (!bh) |
976 | goto failed; |
977 | |
978 | /* |
979 | * Link the page to the buffers and initialise them. Take the |
980 | * lock to be atomic wrt __find_get_block(), which does not |
981 | * run under the page lock. |
982 | */ |
983 | spin_lock(&inode->i_mapping->private_lock); |
984 | link_dev_buffers(page, bh); |
985 | init_page_buffers(page, bdev, block, size); |
986 | spin_unlock(&inode->i_mapping->private_lock); |
987 | return page; |
988 | |
989 | failed: |
990 | unlock_page(page); |
991 | page_cache_release(page); |
992 | return NULL; |
993 | } |
994 | |
995 | /* |
996 | * Create buffers for the specified block device block's page. If |
997 | * that page was dirty, the buffers are set dirty also. |
998 | */ |
999 | static int |
1000 | grow_buffers(struct block_device *bdev, sector_t block, int size) |
1001 | { |
1002 | struct page *page; |
1003 | pgoff_t index; |
1004 | int sizebits; |
1005 | |
1006 | sizebits = -1; |
1007 | do { |
1008 | sizebits++; |
1009 | } while ((size << sizebits) < PAGE_SIZE); |
1010 | |
1011 | index = block >> sizebits; |
1012 | |
1013 | /* |
1014 | * Check for a block which wants to lie outside our maximum possible |
1015 | * pagecache index. (this comparison is done using sector_t types). |
1016 | */ |
1017 | if (unlikely(index != block >> sizebits)) { |
1018 | char b[BDEVNAME_SIZE]; |
1019 | |
1020 | printk(KERN_ERR "%s: requested out-of-range block %llu for " |
1021 | "device %s\n", |
1022 | __func__, (unsigned long long)block, |
1023 | bdevname(bdev, b)); |
1024 | return -EIO; |
1025 | } |
1026 | block = index << sizebits; |
1027 | /* Create a page with the proper size buffers.. */ |
1028 | page = grow_dev_page(bdev, block, index, size); |
1029 | if (!page) |
1030 | return 0; |
1031 | unlock_page(page); |
1032 | page_cache_release(page); |
1033 | return 1; |
1034 | } |
1035 | |
1036 | static struct buffer_head * |
1037 | __getblk_slow(struct block_device *bdev, sector_t block, int size) |
1038 | { |
1039 | int ret; |
1040 | struct buffer_head *bh; |
1041 | |
1042 | /* Size must be multiple of hard sectorsize */ |
1043 | if (unlikely(size & (bdev_logical_block_size(bdev)-1) || |
1044 | (size < 512 || size > PAGE_SIZE))) { |
1045 | printk(KERN_ERR "getblk(): invalid block size %d requested\n", |
1046 | size); |
1047 | printk(KERN_ERR "logical block size: %d\n", |
1048 | bdev_logical_block_size(bdev)); |
1049 | |
1050 | dump_stack(); |
1051 | return NULL; |
1052 | } |
1053 | |
1054 | retry: |
1055 | bh = __find_get_block(bdev, block, size); |
1056 | if (bh) |
1057 | return bh; |
1058 | |
1059 | ret = grow_buffers(bdev, block, size); |
1060 | if (ret == 0) { |
1061 | free_more_memory(); |
1062 | goto retry; |
1063 | } else if (ret > 0) { |
1064 | bh = __find_get_block(bdev, block, size); |
1065 | if (bh) |
1066 | return bh; |
1067 | } |
1068 | return NULL; |
1069 | } |
1070 | |
1071 | /* |
1072 | * The relationship between dirty buffers and dirty pages: |
1073 | * |
1074 | * Whenever a page has any dirty buffers, the page's dirty bit is set, and |
1075 | * the page is tagged dirty in its radix tree. |
1076 | * |
1077 | * At all times, the dirtiness of the buffers represents the dirtiness of |
1078 | * subsections of the page. If the page has buffers, the page dirty bit is |
1079 | * merely a hint about the true dirty state. |
1080 | * |
1081 | * When a page is set dirty in its entirety, all its buffers are marked dirty |
1082 | * (if the page has buffers). |
1083 | * |
1084 | * When a buffer is marked dirty, its page is dirtied, but the page's other |
1085 | * buffers are not. |
1086 | * |
1087 | * Also. When blockdev buffers are explicitly read with bread(), they |
1088 | * individually become uptodate. But their backing page remains not |
1089 | * uptodate - even if all of its buffers are uptodate. A subsequent |
1090 | * block_read_full_page() against that page will discover all the uptodate |
1091 | * buffers, will set the page uptodate and will perform no I/O. |
1092 | */ |
1093 | |
1094 | /** |
1095 | * mark_buffer_dirty - mark a buffer_head as needing writeout |
1096 | * @bh: the buffer_head to mark dirty |
1097 | * |
1098 | * mark_buffer_dirty() will set the dirty bit against the buffer, then set its |
1099 | * backing page dirty, then tag the page as dirty in its address_space's radix |
1100 | * tree and then attach the address_space's inode to its superblock's dirty |
1101 | * inode list. |
1102 | * |
1103 | * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock, |
1104 | * mapping->tree_lock and mapping->host->i_lock. |
1105 | */ |
1106 | void mark_buffer_dirty(struct buffer_head *bh) |
1107 | { |
1108 | WARN_ON_ONCE(!buffer_uptodate(bh)); |
1109 | |
1110 | /* |
1111 | * Very *carefully* optimize the it-is-already-dirty case. |
1112 | * |
1113 | * Don't let the final "is it dirty" escape to before we |
1114 | * perhaps modified the buffer. |
1115 | */ |
1116 | if (buffer_dirty(bh)) { |
1117 | smp_mb(); |
1118 | if (buffer_dirty(bh)) |
1119 | return; |
1120 | } |
1121 | |
1122 | if (!test_set_buffer_dirty(bh)) { |
1123 | struct page *page = bh->b_page; |
1124 | if (!TestSetPageDirty(page)) { |
1125 | struct address_space *mapping = page_mapping(page); |
1126 | if (mapping) |
1127 | __set_page_dirty(page, mapping, 0); |
1128 | } |
1129 | } |
1130 | } |
1131 | EXPORT_SYMBOL(mark_buffer_dirty); |
1132 | |
1133 | /* |
1134 | * Decrement a buffer_head's reference count. If all buffers against a page |
1135 | * have zero reference count, are clean and unlocked, and if the page is clean |
1136 | * and unlocked then try_to_free_buffers() may strip the buffers from the page |
1137 | * in preparation for freeing it (sometimes, rarely, buffers are removed from |
1138 | * a page but it ends up not being freed, and buffers may later be reattached). |
1139 | */ |
1140 | void __brelse(struct buffer_head * buf) |
1141 | { |
1142 | if (atomic_read(&buf->b_count)) { |
1143 | put_bh(buf); |
1144 | return; |
1145 | } |
1146 | WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n"); |
1147 | } |
1148 | EXPORT_SYMBOL(__brelse); |
1149 | |
1150 | /* |
1151 | * bforget() is like brelse(), except it discards any |
1152 | * potentially dirty data. |
1153 | */ |
1154 | void __bforget(struct buffer_head *bh) |
1155 | { |
1156 | clear_buffer_dirty(bh); |
1157 | if (bh->b_assoc_map) { |
1158 | struct address_space *buffer_mapping = bh->b_page->mapping; |
1159 | |
1160 | spin_lock(&buffer_mapping->private_lock); |
1161 | list_del_init(&bh->b_assoc_buffers); |
1162 | bh->b_assoc_map = NULL; |
1163 | spin_unlock(&buffer_mapping->private_lock); |
1164 | } |
1165 | __brelse(bh); |
1166 | } |
1167 | EXPORT_SYMBOL(__bforget); |
1168 | |
1169 | static struct buffer_head *__bread_slow(struct buffer_head *bh) |
1170 | { |
1171 | lock_buffer(bh); |
1172 | if (buffer_uptodate(bh)) { |
1173 | unlock_buffer(bh); |
1174 | return bh; |
1175 | } else { |
1176 | get_bh(bh); |
1177 | bh->b_end_io = end_buffer_read_sync; |
1178 | submit_bh(READ, bh); |
1179 | wait_on_buffer(bh); |
1180 | if (buffer_uptodate(bh)) |
1181 | return bh; |
1182 | } |
1183 | brelse(bh); |
1184 | return NULL; |
1185 | } |
1186 | |
1187 | /* |
1188 | * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block(). |
1189 | * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their |
1190 | * refcount elevated by one when they're in an LRU. A buffer can only appear |
1191 | * once in a particular CPU's LRU. A single buffer can be present in multiple |
1192 | * CPU's LRUs at the same time. |
1193 | * |
1194 | * This is a transparent caching front-end to sb_bread(), sb_getblk() and |
1195 | * sb_find_get_block(). |
1196 | * |
1197 | * The LRUs themselves only need locking against invalidate_bh_lrus. We use |
1198 | * a local interrupt disable for that. |
1199 | */ |
1200 | |
1201 | #define BH_LRU_SIZE 8 |
1202 | |
1203 | struct bh_lru { |
1204 | struct buffer_head *bhs[BH_LRU_SIZE]; |
1205 | }; |
1206 | |
1207 | static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }}; |
1208 | |
1209 | #ifdef CONFIG_SMP |
1210 | #define bh_lru_lock() local_irq_disable() |
1211 | #define bh_lru_unlock() local_irq_enable() |
1212 | #else |
1213 | #define bh_lru_lock() preempt_disable() |
1214 | #define bh_lru_unlock() preempt_enable() |
1215 | #endif |
1216 | |
1217 | static inline void check_irqs_on(void) |
1218 | { |
1219 | #ifdef irqs_disabled |
1220 | BUG_ON(irqs_disabled()); |
1221 | #endif |
1222 | } |
1223 | |
1224 | /* |
1225 | * The LRU management algorithm is dopey-but-simple. Sorry. |
1226 | */ |
1227 | static void bh_lru_install(struct buffer_head *bh) |
1228 | { |
1229 | struct buffer_head *evictee = NULL; |
1230 | |
1231 | check_irqs_on(); |
1232 | bh_lru_lock(); |
1233 | if (__this_cpu_read(bh_lrus.bhs[0]) != bh) { |
1234 | struct buffer_head *bhs[BH_LRU_SIZE]; |
1235 | int in; |
1236 | int out = 0; |
1237 | |
1238 | get_bh(bh); |
1239 | bhs[out++] = bh; |
1240 | for (in = 0; in < BH_LRU_SIZE; in++) { |
1241 | struct buffer_head *bh2 = |
1242 | __this_cpu_read(bh_lrus.bhs[in]); |
1243 | |
1244 | if (bh2 == bh) { |
1245 | __brelse(bh2); |
1246 | } else { |
1247 | if (out >= BH_LRU_SIZE) { |
1248 | BUG_ON(evictee != NULL); |
1249 | evictee = bh2; |
1250 | } else { |
1251 | bhs[out++] = bh2; |
1252 | } |
1253 | } |
1254 | } |
1255 | while (out < BH_LRU_SIZE) |
1256 | bhs[out++] = NULL; |
1257 | memcpy(__this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs)); |
1258 | } |
1259 | bh_lru_unlock(); |
1260 | |
1261 | if (evictee) |
1262 | __brelse(evictee); |
1263 | } |
1264 | |
1265 | /* |
1266 | * Look up the bh in this cpu's LRU. If it's there, move it to the head. |
1267 | */ |
1268 | static struct buffer_head * |
1269 | lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size) |
1270 | { |
1271 | struct buffer_head *ret = NULL; |
1272 | unsigned int i; |
1273 | |
1274 | check_irqs_on(); |
1275 | bh_lru_lock(); |
1276 | for (i = 0; i < BH_LRU_SIZE; i++) { |
1277 | struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]); |
1278 | |
1279 | if (bh && bh->b_bdev == bdev && |
1280 | bh->b_blocknr == block && bh->b_size == size) { |
1281 | if (i) { |
1282 | while (i) { |
1283 | __this_cpu_write(bh_lrus.bhs[i], |
1284 | __this_cpu_read(bh_lrus.bhs[i - 1])); |
1285 | i--; |
1286 | } |
1287 | __this_cpu_write(bh_lrus.bhs[0], bh); |
1288 | } |
1289 | get_bh(bh); |
1290 | ret = bh; |
1291 | break; |
1292 | } |
1293 | } |
1294 | bh_lru_unlock(); |
1295 | return ret; |
1296 | } |
1297 | |
1298 | /* |
1299 | * Perform a pagecache lookup for the matching buffer. If it's there, refresh |
1300 | * it in the LRU and mark it as accessed. If it is not present then return |
1301 | * NULL |
1302 | */ |
1303 | struct buffer_head * |
1304 | __find_get_block(struct block_device *bdev, sector_t block, unsigned size) |
1305 | { |
1306 | struct buffer_head *bh = lookup_bh_lru(bdev, block, size); |
1307 | |
1308 | if (bh == NULL) { |
1309 | bh = __find_get_block_slow(bdev, block); |
1310 | if (bh) |
1311 | bh_lru_install(bh); |
1312 | } |
1313 | if (bh) |
1314 | touch_buffer(bh); |
1315 | return bh; |
1316 | } |
1317 | EXPORT_SYMBOL(__find_get_block); |
1318 | |
1319 | /* |
1320 | * __getblk will locate (and, if necessary, create) the buffer_head |
1321 | * which corresponds to the passed block_device, block and size. The |
1322 | * returned buffer has its reference count incremented. |
1323 | * |
1324 | * __getblk() cannot fail - it just keeps trying. If you pass it an |
1325 | * illegal block number, __getblk() will happily return a buffer_head |
1326 | * which represents the non-existent block. Very weird. |
1327 | * |
1328 | * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers() |
1329 | * attempt is failing. FIXME, perhaps? |
1330 | */ |
1331 | struct buffer_head * |
1332 | __getblk(struct block_device *bdev, sector_t block, unsigned size) |
1333 | { |
1334 | struct buffer_head *bh = __find_get_block(bdev, block, size); |
1335 | |
1336 | might_sleep(); |
1337 | if (bh == NULL) |
1338 | bh = __getblk_slow(bdev, block, size); |
1339 | return bh; |
1340 | } |
1341 | EXPORT_SYMBOL(__getblk); |
1342 | |
1343 | /* |
1344 | * Do async read-ahead on a buffer.. |
1345 | */ |
1346 | void __breadahead(struct block_device *bdev, sector_t block, unsigned size) |
1347 | { |
1348 | struct buffer_head *bh = __getblk(bdev, block, size); |
1349 | if (likely(bh)) { |
1350 | ll_rw_block(READA, 1, &bh); |
1351 | brelse(bh); |
1352 | } |
1353 | } |
1354 | EXPORT_SYMBOL(__breadahead); |
1355 | |
1356 | /** |
1357 | * __bread() - reads a specified block and returns the bh |
1358 | * @bdev: the block_device to read from |
1359 | * @block: number of block |
1360 | * @size: size (in bytes) to read |
1361 | * |
1362 | * Reads a specified block, and returns buffer head that contains it. |
1363 | * It returns NULL if the block was unreadable. |
1364 | */ |
1365 | struct buffer_head * |
1366 | __bread(struct block_device *bdev, sector_t block, unsigned size) |
1367 | { |
1368 | struct buffer_head *bh = __getblk(bdev, block, size); |
1369 | |
1370 | if (likely(bh) && !buffer_uptodate(bh)) |
1371 | bh = __bread_slow(bh); |
1372 | return bh; |
1373 | } |
1374 | EXPORT_SYMBOL(__bread); |
1375 | |
1376 | /* |
1377 | * invalidate_bh_lrus() is called rarely - but not only at unmount. |
1378 | * This doesn't race because it runs in each cpu either in irq |
1379 | * or with preempt disabled. |
1380 | */ |
1381 | static void invalidate_bh_lru(void *arg) |
1382 | { |
1383 | struct bh_lru *b = &get_cpu_var(bh_lrus); |
1384 | int i; |
1385 | |
1386 | for (i = 0; i < BH_LRU_SIZE; i++) { |
1387 | brelse(b->bhs[i]); |
1388 | b->bhs[i] = NULL; |
1389 | } |
1390 | put_cpu_var(bh_lrus); |
1391 | } |
1392 | |
1393 | static bool has_bh_in_lru(int cpu, void *dummy) |
1394 | { |
1395 | struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu); |
1396 | int i; |
1397 | |
1398 | for (i = 0; i < BH_LRU_SIZE; i++) { |
1399 | if (b->bhs[i]) |
1400 | return 1; |
1401 | } |
1402 | |
1403 | return 0; |
1404 | } |
1405 | |
1406 | void invalidate_bh_lrus(void) |
1407 | { |
1408 | on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL); |
1409 | } |
1410 | EXPORT_SYMBOL_GPL(invalidate_bh_lrus); |
1411 | |
1412 | void set_bh_page(struct buffer_head *bh, |
1413 | struct page *page, unsigned long offset) |
1414 | { |
1415 | bh->b_page = page; |
1416 | BUG_ON(offset >= PAGE_SIZE); |
1417 | if (PageHighMem(page)) |
1418 | /* |
1419 | * This catches illegal uses and preserves the offset: |
1420 | */ |
1421 | bh->b_data = (char *)(0 + offset); |
1422 | else |
1423 | bh->b_data = page_address(page) + offset; |
1424 | } |
1425 | EXPORT_SYMBOL(set_bh_page); |
1426 | |
1427 | /* |
1428 | * Called when truncating a buffer on a page completely. |
1429 | */ |
1430 | static void discard_buffer(struct buffer_head * bh) |
1431 | { |
1432 | lock_buffer(bh); |
1433 | clear_buffer_dirty(bh); |
1434 | bh->b_bdev = NULL; |
1435 | clear_buffer_mapped(bh); |
1436 | clear_buffer_req(bh); |
1437 | clear_buffer_new(bh); |
1438 | clear_buffer_delay(bh); |
1439 | clear_buffer_unwritten(bh); |
1440 | unlock_buffer(bh); |
1441 | } |
1442 | |
1443 | /** |
1444 | * block_invalidatepage - invalidate part or all of a buffer-backed page |
1445 | * |
1446 | * @page: the page which is affected |
1447 | * @offset: the index of the truncation point |
1448 | * |
1449 | * block_invalidatepage() is called when all or part of the page has become |
1450 | * invalidated by a truncate operation. |
1451 | * |
1452 | * block_invalidatepage() does not have to release all buffers, but it must |
1453 | * ensure that no dirty buffer is left outside @offset and that no I/O |
1454 | * is underway against any of the blocks which are outside the truncation |
1455 | * point. Because the caller is about to free (and possibly reuse) those |
1456 | * blocks on-disk. |
1457 | */ |
1458 | void block_invalidatepage(struct page *page, unsigned long offset) |
1459 | { |
1460 | struct buffer_head *head, *bh, *next; |
1461 | unsigned int curr_off = 0; |
1462 | |
1463 | BUG_ON(!PageLocked(page)); |
1464 | if (!page_has_buffers(page)) |
1465 | goto out; |
1466 | |
1467 | head = page_buffers(page); |
1468 | bh = head; |
1469 | do { |
1470 | unsigned int next_off = curr_off + bh->b_size; |
1471 | next = bh->b_this_page; |
1472 | |
1473 | /* |
1474 | * is this block fully invalidated? |
1475 | */ |
1476 | if (offset <= curr_off) |
1477 | discard_buffer(bh); |
1478 | curr_off = next_off; |
1479 | bh = next; |
1480 | } while (bh != head); |
1481 | |
1482 | /* |
1483 | * We release buffers only if the entire page is being invalidated. |
1484 | * The get_block cached value has been unconditionally invalidated, |
1485 | * so real IO is not possible anymore. |
1486 | */ |
1487 | if (offset == 0) |
1488 | try_to_release_page(page, 0); |
1489 | out: |
1490 | return; |
1491 | } |
1492 | EXPORT_SYMBOL(block_invalidatepage); |
1493 | |
1494 | /* |
1495 | * We attach and possibly dirty the buffers atomically wrt |
1496 | * __set_page_dirty_buffers() via private_lock. try_to_free_buffers |
1497 | * is already excluded via the page lock. |
1498 | */ |
1499 | void create_empty_buffers(struct page *page, |
1500 | unsigned long blocksize, unsigned long b_state) |
1501 | { |
1502 | struct buffer_head *bh, *head, *tail; |
1503 | |
1504 | head = alloc_page_buffers(page, blocksize, 1); |
1505 | bh = head; |
1506 | do { |
1507 | bh->b_state |= b_state; |
1508 | tail = bh; |
1509 | bh = bh->b_this_page; |
1510 | } while (bh); |
1511 | tail->b_this_page = head; |
1512 | |
1513 | spin_lock(&page->mapping->private_lock); |
1514 | if (PageUptodate(page) || PageDirty(page)) { |
1515 | bh = head; |
1516 | do { |
1517 | if (PageDirty(page)) |
1518 | set_buffer_dirty(bh); |
1519 | if (PageUptodate(page)) |
1520 | set_buffer_uptodate(bh); |
1521 | bh = bh->b_this_page; |
1522 | } while (bh != head); |
1523 | } |
1524 | attach_page_buffers(page, head); |
1525 | spin_unlock(&page->mapping->private_lock); |
1526 | } |
1527 | EXPORT_SYMBOL(create_empty_buffers); |
1528 | |
1529 | /* |
1530 | * We are taking a block for data and we don't want any output from any |
1531 | * buffer-cache aliases starting from return from that function and |
1532 | * until the moment when something will explicitly mark the buffer |
1533 | * dirty (hopefully that will not happen until we will free that block ;-) |
1534 | * We don't even need to mark it not-uptodate - nobody can expect |
1535 | * anything from a newly allocated buffer anyway. We used to used |
1536 | * unmap_buffer() for such invalidation, but that was wrong. We definitely |
1537 | * don't want to mark the alias unmapped, for example - it would confuse |
1538 | * anyone who might pick it with bread() afterwards... |
1539 | * |
1540 | * Also.. Note that bforget() doesn't lock the buffer. So there can |
1541 | * be writeout I/O going on against recently-freed buffers. We don't |
1542 | * wait on that I/O in bforget() - it's more efficient to wait on the I/O |
1543 | * only if we really need to. That happens here. |
1544 | */ |
1545 | void unmap_underlying_metadata(struct block_device *bdev, sector_t block) |
1546 | { |
1547 | struct buffer_head *old_bh; |
1548 | |
1549 | might_sleep(); |
1550 | |
1551 | old_bh = __find_get_block_slow(bdev, block); |
1552 | if (old_bh) { |
1553 | clear_buffer_dirty(old_bh); |
1554 | wait_on_buffer(old_bh); |
1555 | clear_buffer_req(old_bh); |
1556 | __brelse(old_bh); |
1557 | } |
1558 | } |
1559 | EXPORT_SYMBOL(unmap_underlying_metadata); |
1560 | |
1561 | /* |
1562 | * NOTE! All mapped/uptodate combinations are valid: |
1563 | * |
1564 | * Mapped Uptodate Meaning |
1565 | * |
1566 | * No No "unknown" - must do get_block() |
1567 | * No Yes "hole" - zero-filled |
1568 | * Yes No "allocated" - allocated on disk, not read in |
1569 | * Yes Yes "valid" - allocated and up-to-date in memory. |
1570 | * |
1571 | * "Dirty" is valid only with the last case (mapped+uptodate). |
1572 | */ |
1573 | |
1574 | /* |
1575 | * While block_write_full_page is writing back the dirty buffers under |
1576 | * the page lock, whoever dirtied the buffers may decide to clean them |
1577 | * again at any time. We handle that by only looking at the buffer |
1578 | * state inside lock_buffer(). |
1579 | * |
1580 | * If block_write_full_page() is called for regular writeback |
1581 | * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a |
1582 | * locked buffer. This only can happen if someone has written the buffer |
1583 | * directly, with submit_bh(). At the address_space level PageWriteback |
1584 | * prevents this contention from occurring. |
1585 | * |
1586 | * If block_write_full_page() is called with wbc->sync_mode == |
1587 | * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this |
1588 | * causes the writes to be flagged as synchronous writes. |
1589 | */ |
1590 | static int __block_write_full_page(struct inode *inode, struct page *page, |
1591 | get_block_t *get_block, struct writeback_control *wbc, |
1592 | bh_end_io_t *handler) |
1593 | { |
1594 | int err; |
1595 | sector_t block; |
1596 | sector_t last_block; |
1597 | struct buffer_head *bh, *head; |
1598 | const unsigned blocksize = 1 << inode->i_blkbits; |
1599 | int nr_underway = 0; |
1600 | int write_op = (wbc->sync_mode == WB_SYNC_ALL ? |
1601 | WRITE_SYNC : WRITE); |
1602 | |
1603 | BUG_ON(!PageLocked(page)); |
1604 | |
1605 | last_block = (i_size_read(inode) - 1) >> inode->i_blkbits; |
1606 | |
1607 | if (!page_has_buffers(page)) { |
1608 | create_empty_buffers(page, blocksize, |
1609 | (1 << BH_Dirty)|(1 << BH_Uptodate)); |
1610 | } |
1611 | |
1612 | /* |
1613 | * Be very careful. We have no exclusion from __set_page_dirty_buffers |
1614 | * here, and the (potentially unmapped) buffers may become dirty at |
1615 | * any time. If a buffer becomes dirty here after we've inspected it |
1616 | * then we just miss that fact, and the page stays dirty. |
1617 | * |
1618 | * Buffers outside i_size may be dirtied by __set_page_dirty_buffers; |
1619 | * handle that here by just cleaning them. |
1620 | */ |
1621 | |
1622 | block = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
1623 | head = page_buffers(page); |
1624 | bh = head; |
1625 | |
1626 | /* |
1627 | * Get all the dirty buffers mapped to disk addresses and |
1628 | * handle any aliases from the underlying blockdev's mapping. |
1629 | */ |
1630 | do { |
1631 | if (block > last_block) { |
1632 | /* |
1633 | * mapped buffers outside i_size will occur, because |
1634 | * this page can be outside i_size when there is a |
1635 | * truncate in progress. |
1636 | */ |
1637 | /* |
1638 | * The buffer was zeroed by block_write_full_page() |
1639 | */ |
1640 | clear_buffer_dirty(bh); |
1641 | set_buffer_uptodate(bh); |
1642 | } else if ((!buffer_mapped(bh) || buffer_delay(bh)) && |
1643 | buffer_dirty(bh)) { |
1644 | WARN_ON(bh->b_size != blocksize); |
1645 | err = get_block(inode, block, bh, 1); |
1646 | if (err) |
1647 | goto recover; |
1648 | clear_buffer_delay(bh); |
1649 | if (buffer_new(bh)) { |
1650 | /* blockdev mappings never come here */ |
1651 | clear_buffer_new(bh); |
1652 | unmap_underlying_metadata(bh->b_bdev, |
1653 | bh->b_blocknr); |
1654 | } |
1655 | } |
1656 | bh = bh->b_this_page; |
1657 | block++; |
1658 | } while (bh != head); |
1659 | |
1660 | do { |
1661 | if (!buffer_mapped(bh)) |
1662 | continue; |
1663 | /* |
1664 | * If it's a fully non-blocking write attempt and we cannot |
1665 | * lock the buffer then redirty the page. Note that this can |
1666 | * potentially cause a busy-wait loop from writeback threads |
1667 | * and kswapd activity, but those code paths have their own |
1668 | * higher-level throttling. |
1669 | */ |
1670 | if (wbc->sync_mode != WB_SYNC_NONE) { |
1671 | lock_buffer(bh); |
1672 | } else if (!trylock_buffer(bh)) { |
1673 | redirty_page_for_writepage(wbc, page); |
1674 | continue; |
1675 | } |
1676 | if (test_clear_buffer_dirty(bh)) { |
1677 | mark_buffer_async_write_endio(bh, handler); |
1678 | } else { |
1679 | unlock_buffer(bh); |
1680 | } |
1681 | } while ((bh = bh->b_this_page) != head); |
1682 | |
1683 | /* |
1684 | * The page and its buffers are protected by PageWriteback(), so we can |
1685 | * drop the bh refcounts early. |
1686 | */ |
1687 | BUG_ON(PageWriteback(page)); |
1688 | set_page_writeback(page); |
1689 | |
1690 | do { |
1691 | struct buffer_head *next = bh->b_this_page; |
1692 | if (buffer_async_write(bh)) { |
1693 | submit_bh(write_op, bh); |
1694 | nr_underway++; |
1695 | } |
1696 | bh = next; |
1697 | } while (bh != head); |
1698 | unlock_page(page); |
1699 | |
1700 | err = 0; |
1701 | done: |
1702 | if (nr_underway == 0) { |
1703 | /* |
1704 | * The page was marked dirty, but the buffers were |
1705 | * clean. Someone wrote them back by hand with |
1706 | * ll_rw_block/submit_bh. A rare case. |
1707 | */ |
1708 | end_page_writeback(page); |
1709 | |
1710 | /* |
1711 | * The page and buffer_heads can be released at any time from |
1712 | * here on. |
1713 | */ |
1714 | } |
1715 | return err; |
1716 | |
1717 | recover: |
1718 | /* |
1719 | * ENOSPC, or some other error. We may already have added some |
1720 | * blocks to the file, so we need to write these out to avoid |
1721 | * exposing stale data. |
1722 | * The page is currently locked and not marked for writeback |
1723 | */ |
1724 | bh = head; |
1725 | /* Recovery: lock and submit the mapped buffers */ |
1726 | do { |
1727 | if (buffer_mapped(bh) && buffer_dirty(bh) && |
1728 | !buffer_delay(bh)) { |
1729 | lock_buffer(bh); |
1730 | mark_buffer_async_write_endio(bh, handler); |
1731 | } else { |
1732 | /* |
1733 | * The buffer may have been set dirty during |
1734 | * attachment to a dirty page. |
1735 | */ |
1736 | clear_buffer_dirty(bh); |
1737 | } |
1738 | } while ((bh = bh->b_this_page) != head); |
1739 | SetPageError(page); |
1740 | BUG_ON(PageWriteback(page)); |
1741 | mapping_set_error(page->mapping, err); |
1742 | set_page_writeback(page); |
1743 | do { |
1744 | struct buffer_head *next = bh->b_this_page; |
1745 | if (buffer_async_write(bh)) { |
1746 | clear_buffer_dirty(bh); |
1747 | submit_bh(write_op, bh); |
1748 | nr_underway++; |
1749 | } |
1750 | bh = next; |
1751 | } while (bh != head); |
1752 | unlock_page(page); |
1753 | goto done; |
1754 | } |
1755 | |
1756 | /* |
1757 | * If a page has any new buffers, zero them out here, and mark them uptodate |
1758 | * and dirty so they'll be written out (in order to prevent uninitialised |
1759 | * block data from leaking). And clear the new bit. |
1760 | */ |
1761 | void page_zero_new_buffers(struct page *page, unsigned from, unsigned to) |
1762 | { |
1763 | unsigned int block_start, block_end; |
1764 | struct buffer_head *head, *bh; |
1765 | |
1766 | BUG_ON(!PageLocked(page)); |
1767 | if (!page_has_buffers(page)) |
1768 | return; |
1769 | |
1770 | bh = head = page_buffers(page); |
1771 | block_start = 0; |
1772 | do { |
1773 | block_end = block_start + bh->b_size; |
1774 | |
1775 | if (buffer_new(bh)) { |
1776 | if (block_end > from && block_start < to) { |
1777 | if (!PageUptodate(page)) { |
1778 | unsigned start, size; |
1779 | |
1780 | start = max(from, block_start); |
1781 | size = min(to, block_end) - start; |
1782 | |
1783 | zero_user(page, start, size); |
1784 | set_buffer_uptodate(bh); |
1785 | } |
1786 | |
1787 | clear_buffer_new(bh); |
1788 | mark_buffer_dirty(bh); |
1789 | } |
1790 | } |
1791 | |
1792 | block_start = block_end; |
1793 | bh = bh->b_this_page; |
1794 | } while (bh != head); |
1795 | } |
1796 | EXPORT_SYMBOL(page_zero_new_buffers); |
1797 | |
1798 | int __block_write_begin(struct page *page, loff_t pos, unsigned len, |
1799 | get_block_t *get_block) |
1800 | { |
1801 | unsigned from = pos & (PAGE_CACHE_SIZE - 1); |
1802 | unsigned to = from + len; |
1803 | struct inode *inode = page->mapping->host; |
1804 | unsigned block_start, block_end; |
1805 | sector_t block; |
1806 | int err = 0; |
1807 | unsigned blocksize, bbits; |
1808 | struct buffer_head *bh, *head, *wait[2], **wait_bh=wait; |
1809 | |
1810 | BUG_ON(!PageLocked(page)); |
1811 | BUG_ON(from > PAGE_CACHE_SIZE); |
1812 | BUG_ON(to > PAGE_CACHE_SIZE); |
1813 | BUG_ON(from > to); |
1814 | |
1815 | blocksize = 1 << inode->i_blkbits; |
1816 | if (!page_has_buffers(page)) |
1817 | create_empty_buffers(page, blocksize, 0); |
1818 | head = page_buffers(page); |
1819 | |
1820 | bbits = inode->i_blkbits; |
1821 | block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); |
1822 | |
1823 | for(bh = head, block_start = 0; bh != head || !block_start; |
1824 | block++, block_start=block_end, bh = bh->b_this_page) { |
1825 | block_end = block_start + blocksize; |
1826 | if (block_end <= from || block_start >= to) { |
1827 | if (PageUptodate(page)) { |
1828 | if (!buffer_uptodate(bh)) |
1829 | set_buffer_uptodate(bh); |
1830 | } |
1831 | continue; |
1832 | } |
1833 | if (buffer_new(bh)) |
1834 | clear_buffer_new(bh); |
1835 | if (!buffer_mapped(bh)) { |
1836 | WARN_ON(bh->b_size != blocksize); |
1837 | err = get_block(inode, block, bh, 1); |
1838 | if (err) |
1839 | break; |
1840 | if (buffer_new(bh)) { |
1841 | unmap_underlying_metadata(bh->b_bdev, |
1842 | bh->b_blocknr); |
1843 | if (PageUptodate(page)) { |
1844 | clear_buffer_new(bh); |
1845 | set_buffer_uptodate(bh); |
1846 | mark_buffer_dirty(bh); |
1847 | continue; |
1848 | } |
1849 | if (block_end > to || block_start < from) |
1850 | zero_user_segments(page, |
1851 | to, block_end, |
1852 | block_start, from); |
1853 | continue; |
1854 | } |
1855 | } |
1856 | if (PageUptodate(page)) { |
1857 | if (!buffer_uptodate(bh)) |
1858 | set_buffer_uptodate(bh); |
1859 | continue; |
1860 | } |
1861 | if (!buffer_uptodate(bh) && !buffer_delay(bh) && |
1862 | !buffer_unwritten(bh) && |
1863 | (block_start < from || block_end > to)) { |
1864 | ll_rw_block(READ, 1, &bh); |
1865 | *wait_bh++=bh; |
1866 | } |
1867 | } |
1868 | /* |
1869 | * If we issued read requests - let them complete. |
1870 | */ |
1871 | while(wait_bh > wait) { |
1872 | wait_on_buffer(*--wait_bh); |
1873 | if (!buffer_uptodate(*wait_bh)) |
1874 | err = -EIO; |
1875 | } |
1876 | if (unlikely(err)) |
1877 | page_zero_new_buffers(page, from, to); |
1878 | return err; |
1879 | } |
1880 | EXPORT_SYMBOL(__block_write_begin); |
1881 | |
1882 | static int __block_commit_write(struct inode *inode, struct page *page, |
1883 | unsigned from, unsigned to) |
1884 | { |
1885 | unsigned block_start, block_end; |
1886 | int partial = 0; |
1887 | unsigned blocksize; |
1888 | struct buffer_head *bh, *head; |
1889 | |
1890 | blocksize = 1 << inode->i_blkbits; |
1891 | |
1892 | for(bh = head = page_buffers(page), block_start = 0; |
1893 | bh != head || !block_start; |
1894 | block_start=block_end, bh = bh->b_this_page) { |
1895 | block_end = block_start + blocksize; |
1896 | if (block_end <= from || block_start >= to) { |
1897 | if (!buffer_uptodate(bh)) |
1898 | partial = 1; |
1899 | } else { |
1900 | set_buffer_uptodate(bh); |
1901 | mark_buffer_dirty(bh); |
1902 | } |
1903 | clear_buffer_new(bh); |
1904 | } |
1905 | |
1906 | /* |
1907 | * If this is a partial write which happened to make all buffers |
1908 | * uptodate then we can optimize away a bogus readpage() for |
1909 | * the next read(). Here we 'discover' whether the page went |
1910 | * uptodate as a result of this (potentially partial) write. |
1911 | */ |
1912 | if (!partial) |
1913 | SetPageUptodate(page); |
1914 | return 0; |
1915 | } |
1916 | |
1917 | /* |
1918 | * block_write_begin takes care of the basic task of block allocation and |
1919 | * bringing partial write blocks uptodate first. |
1920 | * |
1921 | * The filesystem needs to handle block truncation upon failure. |
1922 | */ |
1923 | int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, |
1924 | unsigned flags, struct page **pagep, get_block_t *get_block) |
1925 | { |
1926 | pgoff_t index = pos >> PAGE_CACHE_SHIFT; |
1927 | struct page *page; |
1928 | int status; |
1929 | |
1930 | page = grab_cache_page_write_begin(mapping, index, flags); |
1931 | if (!page) |
1932 | return -ENOMEM; |
1933 | |
1934 | status = __block_write_begin(page, pos, len, get_block); |
1935 | if (unlikely(status)) { |
1936 | unlock_page(page); |
1937 | page_cache_release(page); |
1938 | page = NULL; |
1939 | } |
1940 | |
1941 | *pagep = page; |
1942 | return status; |
1943 | } |
1944 | EXPORT_SYMBOL(block_write_begin); |
1945 | |
1946 | int block_write_end(struct file *file, struct address_space *mapping, |
1947 | loff_t pos, unsigned len, unsigned copied, |
1948 | struct page *page, void *fsdata) |
1949 | { |
1950 | struct inode *inode = mapping->host; |
1951 | unsigned start; |
1952 | |
1953 | start = pos & (PAGE_CACHE_SIZE - 1); |
1954 | |
1955 | if (unlikely(copied < len)) { |
1956 | /* |
1957 | * The buffers that were written will now be uptodate, so we |
1958 | * don't have to worry about a readpage reading them and |
1959 | * overwriting a partial write. However if we have encountered |
1960 | * a short write and only partially written into a buffer, it |
1961 | * will not be marked uptodate, so a readpage might come in and |
1962 | * destroy our partial write. |
1963 | * |
1964 | * Do the simplest thing, and just treat any short write to a |
1965 | * non uptodate page as a zero-length write, and force the |
1966 | * caller to redo the whole thing. |
1967 | */ |
1968 | if (!PageUptodate(page)) |
1969 | copied = 0; |
1970 | |
1971 | page_zero_new_buffers(page, start+copied, start+len); |
1972 | } |
1973 | flush_dcache_page(page); |
1974 | |
1975 | /* This could be a short (even 0-length) commit */ |
1976 | __block_commit_write(inode, page, start, start+copied); |
1977 | |
1978 | return copied; |
1979 | } |
1980 | EXPORT_SYMBOL(block_write_end); |
1981 | |
1982 | int generic_write_end(struct file *file, struct address_space *mapping, |
1983 | loff_t pos, unsigned len, unsigned copied, |
1984 | struct page *page, void *fsdata) |
1985 | { |
1986 | struct inode *inode = mapping->host; |
1987 | int i_size_changed = 0; |
1988 | |
1989 | copied = block_write_end(file, mapping, pos, len, copied, page, fsdata); |
1990 | |
1991 | /* |
1992 | * No need to use i_size_read() here, the i_size |
1993 | * cannot change under us because we hold i_mutex. |
1994 | * |
1995 | * But it's important to update i_size while still holding page lock: |
1996 | * page writeout could otherwise come in and zero beyond i_size. |
1997 | */ |
1998 | if (pos+copied > inode->i_size) { |
1999 | i_size_write(inode, pos+copied); |
2000 | i_size_changed = 1; |
2001 | } |
2002 | |
2003 | unlock_page(page); |
2004 | page_cache_release(page); |
2005 | |
2006 | /* |
2007 | * Don't mark the inode dirty under page lock. First, it unnecessarily |
2008 | * makes the holding time of page lock longer. Second, it forces lock |
2009 | * ordering of page lock and transaction start for journaling |
2010 | * filesystems. |
2011 | */ |
2012 | if (i_size_changed) |
2013 | mark_inode_dirty(inode); |
2014 | |
2015 | return copied; |
2016 | } |
2017 | EXPORT_SYMBOL(generic_write_end); |
2018 | |
2019 | /* |
2020 | * block_is_partially_uptodate checks whether buffers within a page are |
2021 | * uptodate or not. |
2022 | * |
2023 | * Returns true if all buffers which correspond to a file portion |
2024 | * we want to read are uptodate. |
2025 | */ |
2026 | int block_is_partially_uptodate(struct page *page, read_descriptor_t *desc, |
2027 | unsigned long from) |
2028 | { |
2029 | struct inode *inode = page->mapping->host; |
2030 | unsigned block_start, block_end, blocksize; |
2031 | unsigned to; |
2032 | struct buffer_head *bh, *head; |
2033 | int ret = 1; |
2034 | |
2035 | if (!page_has_buffers(page)) |
2036 | return 0; |
2037 | |
2038 | blocksize = 1 << inode->i_blkbits; |
2039 | to = min_t(unsigned, PAGE_CACHE_SIZE - from, desc->count); |
2040 | to = from + to; |
2041 | if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize) |
2042 | return 0; |
2043 | |
2044 | head = page_buffers(page); |
2045 | bh = head; |
2046 | block_start = 0; |
2047 | do { |
2048 | block_end = block_start + blocksize; |
2049 | if (block_end > from && block_start < to) { |
2050 | if (!buffer_uptodate(bh)) { |
2051 | ret = 0; |
2052 | break; |
2053 | } |
2054 | if (block_end >= to) |
2055 | break; |
2056 | } |
2057 | block_start = block_end; |
2058 | bh = bh->b_this_page; |
2059 | } while (bh != head); |
2060 | |
2061 | return ret; |
2062 | } |
2063 | EXPORT_SYMBOL(block_is_partially_uptodate); |
2064 | |
2065 | /* |
2066 | * Generic "read page" function for block devices that have the normal |
2067 | * get_block functionality. This is most of the block device filesystems. |
2068 | * Reads the page asynchronously --- the unlock_buffer() and |
2069 | * set/clear_buffer_uptodate() functions propagate buffer state into the |
2070 | * page struct once IO has completed. |
2071 | */ |
2072 | int block_read_full_page(struct page *page, get_block_t *get_block) |
2073 | { |
2074 | struct inode *inode = page->mapping->host; |
2075 | sector_t iblock, lblock; |
2076 | struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE]; |
2077 | unsigned int blocksize; |
2078 | int nr, i; |
2079 | int fully_mapped = 1; |
2080 | |
2081 | BUG_ON(!PageLocked(page)); |
2082 | blocksize = 1 << inode->i_blkbits; |
2083 | if (!page_has_buffers(page)) |
2084 | create_empty_buffers(page, blocksize, 0); |
2085 | head = page_buffers(page); |
2086 | |
2087 | iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
2088 | lblock = (i_size_read(inode)+blocksize-1) >> inode->i_blkbits; |
2089 | bh = head; |
2090 | nr = 0; |
2091 | i = 0; |
2092 | |
2093 | do { |
2094 | if (buffer_uptodate(bh)) |
2095 | continue; |
2096 | |
2097 | if (!buffer_mapped(bh)) { |
2098 | int err = 0; |
2099 | |
2100 | fully_mapped = 0; |
2101 | if (iblock < lblock) { |
2102 | WARN_ON(bh->b_size != blocksize); |
2103 | err = get_block(inode, iblock, bh, 0); |
2104 | if (err) |
2105 | SetPageError(page); |
2106 | } |
2107 | if (!buffer_mapped(bh)) { |
2108 | zero_user(page, i * blocksize, blocksize); |
2109 | if (!err) |
2110 | set_buffer_uptodate(bh); |
2111 | continue; |
2112 | } |
2113 | /* |
2114 | * get_block() might have updated the buffer |
2115 | * synchronously |
2116 | */ |
2117 | if (buffer_uptodate(bh)) |
2118 | continue; |
2119 | } |
2120 | arr[nr++] = bh; |
2121 | } while (i++, iblock++, (bh = bh->b_this_page) != head); |
2122 | |
2123 | if (fully_mapped) |
2124 | SetPageMappedToDisk(page); |
2125 | |
2126 | if (!nr) { |
2127 | /* |
2128 | * All buffers are uptodate - we can set the page uptodate |
2129 | * as well. But not if get_block() returned an error. |
2130 | */ |
2131 | if (!PageError(page)) |
2132 | SetPageUptodate(page); |
2133 | unlock_page(page); |
2134 | return 0; |
2135 | } |
2136 | |
2137 | /* Stage two: lock the buffers */ |
2138 | for (i = 0; i < nr; i++) { |
2139 | bh = arr[i]; |
2140 | lock_buffer(bh); |
2141 | mark_buffer_async_read(bh); |
2142 | } |
2143 | |
2144 | /* |
2145 | * Stage 3: start the IO. Check for uptodateness |
2146 | * inside the buffer lock in case another process reading |
2147 | * the underlying blockdev brought it uptodate (the sct fix). |
2148 | */ |
2149 | for (i = 0; i < nr; i++) { |
2150 | bh = arr[i]; |
2151 | if (buffer_uptodate(bh)) |
2152 | end_buffer_async_read(bh, 1); |
2153 | else |
2154 | submit_bh(READ, bh); |
2155 | } |
2156 | return 0; |
2157 | } |
2158 | EXPORT_SYMBOL(block_read_full_page); |
2159 | |
2160 | /* utility function for filesystems that need to do work on expanding |
2161 | * truncates. Uses filesystem pagecache writes to allow the filesystem to |
2162 | * deal with the hole. |
2163 | */ |
2164 | int generic_cont_expand_simple(struct inode *inode, loff_t size) |
2165 | { |
2166 | struct address_space *mapping = inode->i_mapping; |
2167 | struct page *page; |
2168 | void *fsdata; |
2169 | int err; |
2170 | |
2171 | err = inode_newsize_ok(inode, size); |
2172 | if (err) |
2173 | goto out; |
2174 | |
2175 | err = pagecache_write_begin(NULL, mapping, size, 0, |
2176 | AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND, |
2177 | &page, &fsdata); |
2178 | if (err) |
2179 | goto out; |
2180 | |
2181 | err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata); |
2182 | BUG_ON(err > 0); |
2183 | |
2184 | out: |
2185 | return err; |
2186 | } |
2187 | EXPORT_SYMBOL(generic_cont_expand_simple); |
2188 | |
2189 | static int cont_expand_zero(struct file *file, struct address_space *mapping, |
2190 | loff_t pos, loff_t *bytes) |
2191 | { |
2192 | struct inode *inode = mapping->host; |
2193 | unsigned blocksize = 1 << inode->i_blkbits; |
2194 | struct page *page; |
2195 | void *fsdata; |
2196 | pgoff_t index, curidx; |
2197 | loff_t curpos; |
2198 | unsigned zerofrom, offset, len; |
2199 | int err = 0; |
2200 | |
2201 | index = pos >> PAGE_CACHE_SHIFT; |
2202 | offset = pos & ~PAGE_CACHE_MASK; |
2203 | |
2204 | while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) { |
2205 | zerofrom = curpos & ~PAGE_CACHE_MASK; |
2206 | if (zerofrom & (blocksize-1)) { |
2207 | *bytes |= (blocksize-1); |
2208 | (*bytes)++; |
2209 | } |
2210 | len = PAGE_CACHE_SIZE - zerofrom; |
2211 | |
2212 | err = pagecache_write_begin(file, mapping, curpos, len, |
2213 | AOP_FLAG_UNINTERRUPTIBLE, |
2214 | &page, &fsdata); |
2215 | if (err) |
2216 | goto out; |
2217 | zero_user(page, zerofrom, len); |
2218 | err = pagecache_write_end(file, mapping, curpos, len, len, |
2219 | page, fsdata); |
2220 | if (err < 0) |
2221 | goto out; |
2222 | BUG_ON(err != len); |
2223 | err = 0; |
2224 | |
2225 | balance_dirty_pages_ratelimited(mapping); |
2226 | } |
2227 | |
2228 | /* page covers the boundary, find the boundary offset */ |
2229 | if (index == curidx) { |
2230 | zerofrom = curpos & ~PAGE_CACHE_MASK; |
2231 | /* if we will expand the thing last block will be filled */ |
2232 | if (offset <= zerofrom) { |
2233 | goto out; |
2234 | } |
2235 | if (zerofrom & (blocksize-1)) { |
2236 | *bytes |= (blocksize-1); |
2237 | (*bytes)++; |
2238 | } |
2239 | len = offset - zerofrom; |
2240 | |
2241 | err = pagecache_write_begin(file, mapping, curpos, len, |
2242 | AOP_FLAG_UNINTERRUPTIBLE, |
2243 | &page, &fsdata); |
2244 | if (err) |
2245 | goto out; |
2246 | zero_user(page, zerofrom, len); |
2247 | err = pagecache_write_end(file, mapping, curpos, len, len, |
2248 | page, fsdata); |
2249 | if (err < 0) |
2250 | goto out; |
2251 | BUG_ON(err != len); |
2252 | err = 0; |
2253 | } |
2254 | out: |
2255 | return err; |
2256 | } |
2257 | |
2258 | /* |
2259 | * For moronic filesystems that do not allow holes in file. |
2260 | * We may have to extend the file. |
2261 | */ |
2262 | int cont_write_begin(struct file *file, struct address_space *mapping, |
2263 | loff_t pos, unsigned len, unsigned flags, |
2264 | struct page **pagep, void **fsdata, |
2265 | get_block_t *get_block, loff_t *bytes) |
2266 | { |
2267 | struct inode *inode = mapping->host; |
2268 | unsigned blocksize = 1 << inode->i_blkbits; |
2269 | unsigned zerofrom; |
2270 | int err; |
2271 | |
2272 | err = cont_expand_zero(file, mapping, pos, bytes); |
2273 | if (err) |
2274 | return err; |
2275 | |
2276 | zerofrom = *bytes & ~PAGE_CACHE_MASK; |
2277 | if (pos+len > *bytes && zerofrom & (blocksize-1)) { |
2278 | *bytes |= (blocksize-1); |
2279 | (*bytes)++; |
2280 | } |
2281 | |
2282 | return block_write_begin(mapping, pos, len, flags, pagep, get_block); |
2283 | } |
2284 | EXPORT_SYMBOL(cont_write_begin); |
2285 | |
2286 | int block_commit_write(struct page *page, unsigned from, unsigned to) |
2287 | { |
2288 | struct inode *inode = page->mapping->host; |
2289 | __block_commit_write(inode,page,from,to); |
2290 | return 0; |
2291 | } |
2292 | EXPORT_SYMBOL(block_commit_write); |
2293 | |
2294 | /* |
2295 | * block_page_mkwrite() is not allowed to change the file size as it gets |
2296 | * called from a page fault handler when a page is first dirtied. Hence we must |
2297 | * be careful to check for EOF conditions here. We set the page up correctly |
2298 | * for a written page which means we get ENOSPC checking when writing into |
2299 | * holes and correct delalloc and unwritten extent mapping on filesystems that |
2300 | * support these features. |
2301 | * |
2302 | * We are not allowed to take the i_mutex here so we have to play games to |
2303 | * protect against truncate races as the page could now be beyond EOF. Because |
2304 | * truncate writes the inode size before removing pages, once we have the |
2305 | * page lock we can determine safely if the page is beyond EOF. If it is not |
2306 | * beyond EOF, then the page is guaranteed safe against truncation until we |
2307 | * unlock the page. |
2308 | * |
2309 | * Direct callers of this function should call vfs_check_frozen() so that page |
2310 | * fault does not busyloop until the fs is thawed. |
2311 | */ |
2312 | int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, |
2313 | get_block_t get_block) |
2314 | { |
2315 | struct page *page = vmf->page; |
2316 | struct inode *inode = vma->vm_file->f_path.dentry->d_inode; |
2317 | unsigned long end; |
2318 | loff_t size; |
2319 | int ret; |
2320 | |
2321 | lock_page(page); |
2322 | size = i_size_read(inode); |
2323 | if ((page->mapping != inode->i_mapping) || |
2324 | (page_offset(page) > size)) { |
2325 | /* We overload EFAULT to mean page got truncated */ |
2326 | ret = -EFAULT; |
2327 | goto out_unlock; |
2328 | } |
2329 | |
2330 | /* page is wholly or partially inside EOF */ |
2331 | if (((page->index + 1) << PAGE_CACHE_SHIFT) > size) |
2332 | end = size & ~PAGE_CACHE_MASK; |
2333 | else |
2334 | end = PAGE_CACHE_SIZE; |
2335 | |
2336 | ret = __block_write_begin(page, 0, end, get_block); |
2337 | if (!ret) |
2338 | ret = block_commit_write(page, 0, end); |
2339 | |
2340 | if (unlikely(ret < 0)) |
2341 | goto out_unlock; |
2342 | /* |
2343 | * Freezing in progress? We check after the page is marked dirty and |
2344 | * with page lock held so if the test here fails, we are sure freezing |
2345 | * code will wait during syncing until the page fault is done - at that |
2346 | * point page will be dirty and unlocked so freezing code will write it |
2347 | * and writeprotect it again. |
2348 | */ |
2349 | set_page_dirty(page); |
2350 | if (inode->i_sb->s_frozen != SB_UNFROZEN) { |
2351 | ret = -EAGAIN; |
2352 | goto out_unlock; |
2353 | } |
2354 | wait_on_page_writeback(page); |
2355 | return 0; |
2356 | out_unlock: |
2357 | unlock_page(page); |
2358 | return ret; |
2359 | } |
2360 | EXPORT_SYMBOL(__block_page_mkwrite); |
2361 | |
2362 | int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, |
2363 | get_block_t get_block) |
2364 | { |
2365 | int ret; |
2366 | struct super_block *sb = vma->vm_file->f_path.dentry->d_inode->i_sb; |
2367 | |
2368 | /* |
2369 | * This check is racy but catches the common case. The check in |
2370 | * __block_page_mkwrite() is reliable. |
2371 | */ |
2372 | vfs_check_frozen(sb, SB_FREEZE_WRITE); |
2373 | ret = __block_page_mkwrite(vma, vmf, get_block); |
2374 | return block_page_mkwrite_return(ret); |
2375 | } |
2376 | EXPORT_SYMBOL(block_page_mkwrite); |
2377 | |
2378 | /* |
2379 | * nobh_write_begin()'s prereads are special: the buffer_heads are freed |
2380 | * immediately, while under the page lock. So it needs a special end_io |
2381 | * handler which does not touch the bh after unlocking it. |
2382 | */ |
2383 | static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate) |
2384 | { |
2385 | __end_buffer_read_notouch(bh, uptodate); |
2386 | } |
2387 | |
2388 | /* |
2389 | * Attach the singly-linked list of buffers created by nobh_write_begin, to |
2390 | * the page (converting it to circular linked list and taking care of page |
2391 | * dirty races). |
2392 | */ |
2393 | static void attach_nobh_buffers(struct page *page, struct buffer_head *head) |
2394 | { |
2395 | struct buffer_head *bh; |
2396 | |
2397 | BUG_ON(!PageLocked(page)); |
2398 | |
2399 | spin_lock(&page->mapping->private_lock); |
2400 | bh = head; |
2401 | do { |
2402 | if (PageDirty(page)) |
2403 | set_buffer_dirty(bh); |
2404 | if (!bh->b_this_page) |
2405 | bh->b_this_page = head; |
2406 | bh = bh->b_this_page; |
2407 | } while (bh != head); |
2408 | attach_page_buffers(page, head); |
2409 | spin_unlock(&page->mapping->private_lock); |
2410 | } |
2411 | |
2412 | /* |
2413 | * On entry, the page is fully not uptodate. |
2414 | * On exit the page is fully uptodate in the areas outside (from,to) |
2415 | * The filesystem needs to handle block truncation upon failure. |
2416 | */ |
2417 | int nobh_write_begin(struct address_space *mapping, |
2418 | loff_t pos, unsigned len, unsigned flags, |
2419 | struct page **pagep, void **fsdata, |
2420 | get_block_t *get_block) |
2421 | { |
2422 | struct inode *inode = mapping->host; |
2423 | const unsigned blkbits = inode->i_blkbits; |
2424 | const unsigned blocksize = 1 << blkbits; |
2425 | struct buffer_head *head, *bh; |
2426 | struct page *page; |
2427 | pgoff_t index; |
2428 | unsigned from, to; |
2429 | unsigned block_in_page; |
2430 | unsigned block_start, block_end; |
2431 | sector_t block_in_file; |
2432 | int nr_reads = 0; |
2433 | int ret = 0; |
2434 | int is_mapped_to_disk = 1; |
2435 | |
2436 | index = pos >> PAGE_CACHE_SHIFT; |
2437 | from = pos & (PAGE_CACHE_SIZE - 1); |
2438 | to = from + len; |
2439 | |
2440 | page = grab_cache_page_write_begin(mapping, index, flags); |
2441 | if (!page) |
2442 | return -ENOMEM; |
2443 | *pagep = page; |
2444 | *fsdata = NULL; |
2445 | |
2446 | if (page_has_buffers(page)) { |
2447 | ret = __block_write_begin(page, pos, len, get_block); |
2448 | if (unlikely(ret)) |
2449 | goto out_release; |
2450 | return ret; |
2451 | } |
2452 | |
2453 | if (PageMappedToDisk(page)) |
2454 | return 0; |
2455 | |
2456 | /* |
2457 | * Allocate buffers so that we can keep track of state, and potentially |
2458 | * attach them to the page if an error occurs. In the common case of |
2459 | * no error, they will just be freed again without ever being attached |
2460 | * to the page (which is all OK, because we're under the page lock). |
2461 | * |
2462 | * Be careful: the buffer linked list is a NULL terminated one, rather |
2463 | * than the circular one we're used to. |
2464 | */ |
2465 | head = alloc_page_buffers(page, blocksize, 0); |
2466 | if (!head) { |
2467 | ret = -ENOMEM; |
2468 | goto out_release; |
2469 | } |
2470 | |
2471 | block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); |
2472 | |
2473 | /* |
2474 | * We loop across all blocks in the page, whether or not they are |
2475 | * part of the affected region. This is so we can discover if the |
2476 | * page is fully mapped-to-disk. |
2477 | */ |
2478 | for (block_start = 0, block_in_page = 0, bh = head; |
2479 | block_start < PAGE_CACHE_SIZE; |
2480 | block_in_page++, block_start += blocksize, bh = bh->b_this_page) { |
2481 | int create; |
2482 | |
2483 | block_end = block_start + blocksize; |
2484 | bh->b_state = 0; |
2485 | create = 1; |
2486 | if (block_start >= to) |
2487 | create = 0; |
2488 | ret = get_block(inode, block_in_file + block_in_page, |
2489 | bh, create); |
2490 | if (ret) |
2491 | goto failed; |
2492 | if (!buffer_mapped(bh)) |
2493 | is_mapped_to_disk = 0; |
2494 | if (buffer_new(bh)) |
2495 | unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr); |
2496 | if (PageUptodate(page)) { |
2497 | set_buffer_uptodate(bh); |
2498 | continue; |
2499 | } |
2500 | if (buffer_new(bh) || !buffer_mapped(bh)) { |
2501 | zero_user_segments(page, block_start, from, |
2502 | to, block_end); |
2503 | continue; |
2504 | } |
2505 | if (buffer_uptodate(bh)) |
2506 | continue; /* reiserfs does this */ |
2507 | if (block_start < from || block_end > to) { |
2508 | lock_buffer(bh); |
2509 | bh->b_end_io = end_buffer_read_nobh; |
2510 | submit_bh(READ, bh); |
2511 | nr_reads++; |
2512 | } |
2513 | } |
2514 | |
2515 | if (nr_reads) { |
2516 | /* |
2517 | * The page is locked, so these buffers are protected from |
2518 | * any VM or truncate activity. Hence we don't need to care |
2519 | * for the buffer_head refcounts. |
2520 | */ |
2521 | for (bh = head; bh; bh = bh->b_this_page) { |
2522 | wait_on_buffer(bh); |
2523 | if (!buffer_uptodate(bh)) |
2524 | ret = -EIO; |
2525 | } |
2526 | if (ret) |
2527 | goto failed; |
2528 | } |
2529 | |
2530 | if (is_mapped_to_disk) |
2531 | SetPageMappedToDisk(page); |
2532 | |
2533 | *fsdata = head; /* to be released by nobh_write_end */ |
2534 | |
2535 | return 0; |
2536 | |
2537 | failed: |
2538 | BUG_ON(!ret); |
2539 | /* |
2540 | * Error recovery is a bit difficult. We need to zero out blocks that |
2541 | * were newly allocated, and dirty them to ensure they get written out. |
2542 | * Buffers need to be attached to the page at this point, otherwise |
2543 | * the handling of potential IO errors during writeout would be hard |
2544 | * (could try doing synchronous writeout, but what if that fails too?) |
2545 | */ |
2546 | attach_nobh_buffers(page, head); |
2547 | page_zero_new_buffers(page, from, to); |
2548 | |
2549 | out_release: |
2550 | unlock_page(page); |
2551 | page_cache_release(page); |
2552 | *pagep = NULL; |
2553 | |
2554 | return ret; |
2555 | } |
2556 | EXPORT_SYMBOL(nobh_write_begin); |
2557 | |
2558 | int nobh_write_end(struct file *file, struct address_space *mapping, |
2559 | loff_t pos, unsigned len, unsigned copied, |
2560 | struct page *page, void *fsdata) |
2561 | { |
2562 | struct inode *inode = page->mapping->host; |
2563 | struct buffer_head *head = fsdata; |
2564 | struct buffer_head *bh; |
2565 | BUG_ON(fsdata != NULL && page_has_buffers(page)); |
2566 | |
2567 | if (unlikely(copied < len) && head) |
2568 | attach_nobh_buffers(page, head); |
2569 | if (page_has_buffers(page)) |
2570 | return generic_write_end(file, mapping, pos, len, |
2571 | copied, page, fsdata); |
2572 | |
2573 | SetPageUptodate(page); |
2574 | set_page_dirty(page); |
2575 | if (pos+copied > inode->i_size) { |
2576 | i_size_write(inode, pos+copied); |
2577 | mark_inode_dirty(inode); |
2578 | } |
2579 | |
2580 | unlock_page(page); |
2581 | page_cache_release(page); |
2582 | |
2583 | while (head) { |
2584 | bh = head; |
2585 | head = head->b_this_page; |
2586 | free_buffer_head(bh); |
2587 | } |
2588 | |
2589 | return copied; |
2590 | } |
2591 | EXPORT_SYMBOL(nobh_write_end); |
2592 | |
2593 | /* |
2594 | * nobh_writepage() - based on block_full_write_page() except |
2595 | * that it tries to operate without attaching bufferheads to |
2596 | * the page. |
2597 | */ |
2598 | int nobh_writepage(struct page *page, get_block_t *get_block, |
2599 | struct writeback_control *wbc) |
2600 | { |
2601 | struct inode * const inode = page->mapping->host; |
2602 | loff_t i_size = i_size_read(inode); |
2603 | const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; |
2604 | unsigned offset; |
2605 | int ret; |
2606 | |
2607 | /* Is the page fully inside i_size? */ |
2608 | if (page->index < end_index) |
2609 | goto out; |
2610 | |
2611 | /* Is the page fully outside i_size? (truncate in progress) */ |
2612 | offset = i_size & (PAGE_CACHE_SIZE-1); |
2613 | if (page->index >= end_index+1 || !offset) { |
2614 | /* |
2615 | * The page may have dirty, unmapped buffers. For example, |
2616 | * they may have been added in ext3_writepage(). Make them |
2617 | * freeable here, so the page does not leak. |
2618 | */ |
2619 | #if 0 |
2620 | /* Not really sure about this - do we need this ? */ |
2621 | if (page->mapping->a_ops->invalidatepage) |
2622 | page->mapping->a_ops->invalidatepage(page, offset); |
2623 | #endif |
2624 | unlock_page(page); |
2625 | return 0; /* don't care */ |
2626 | } |
2627 | |
2628 | /* |
2629 | * The page straddles i_size. It must be zeroed out on each and every |
2630 | * writepage invocation because it may be mmapped. "A file is mapped |
2631 | * in multiples of the page size. For a file that is not a multiple of |
2632 | * the page size, the remaining memory is zeroed when mapped, and |
2633 | * writes to that region are not written out to the file." |
2634 | */ |
2635 | zero_user_segment(page, offset, PAGE_CACHE_SIZE); |
2636 | out: |
2637 | ret = mpage_writepage(page, get_block, wbc); |
2638 | if (ret == -EAGAIN) |
2639 | ret = __block_write_full_page(inode, page, get_block, wbc, |
2640 | end_buffer_async_write); |
2641 | return ret; |
2642 | } |
2643 | EXPORT_SYMBOL(nobh_writepage); |
2644 | |
2645 | int nobh_truncate_page(struct address_space *mapping, |
2646 | loff_t from, get_block_t *get_block) |
2647 | { |
2648 | pgoff_t index = from >> PAGE_CACHE_SHIFT; |
2649 | unsigned offset = from & (PAGE_CACHE_SIZE-1); |
2650 | unsigned blocksize; |
2651 | sector_t iblock; |
2652 | unsigned length, pos; |
2653 | struct inode *inode = mapping->host; |
2654 | struct page *page; |
2655 | struct buffer_head map_bh; |
2656 | int err; |
2657 | |
2658 | blocksize = 1 << inode->i_blkbits; |
2659 | length = offset & (blocksize - 1); |
2660 | |
2661 | /* Block boundary? Nothing to do */ |
2662 | if (!length) |
2663 | return 0; |
2664 | |
2665 | length = blocksize - length; |
2666 | iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
2667 | |
2668 | page = grab_cache_page(mapping, index); |
2669 | err = -ENOMEM; |
2670 | if (!page) |
2671 | goto out; |
2672 | |
2673 | if (page_has_buffers(page)) { |
2674 | has_buffers: |
2675 | unlock_page(page); |
2676 | page_cache_release(page); |
2677 | return block_truncate_page(mapping, from, get_block); |
2678 | } |
2679 | |
2680 | /* Find the buffer that contains "offset" */ |
2681 | pos = blocksize; |
2682 | while (offset >= pos) { |
2683 | iblock++; |
2684 | pos += blocksize; |
2685 | } |
2686 | |
2687 | map_bh.b_size = blocksize; |
2688 | map_bh.b_state = 0; |
2689 | err = get_block(inode, iblock, &map_bh, 0); |
2690 | if (err) |
2691 | goto unlock; |
2692 | /* unmapped? It's a hole - nothing to do */ |
2693 | if (!buffer_mapped(&map_bh)) |
2694 | goto unlock; |
2695 | |
2696 | /* Ok, it's mapped. Make sure it's up-to-date */ |
2697 | if (!PageUptodate(page)) { |
2698 | err = mapping->a_ops->readpage(NULL, page); |
2699 | if (err) { |
2700 | page_cache_release(page); |
2701 | goto out; |
2702 | } |
2703 | lock_page(page); |
2704 | if (!PageUptodate(page)) { |
2705 | err = -EIO; |
2706 | goto unlock; |
2707 | } |
2708 | if (page_has_buffers(page)) |
2709 | goto has_buffers; |
2710 | } |
2711 | zero_user(page, offset, length); |
2712 | set_page_dirty(page); |
2713 | err = 0; |
2714 | |
2715 | unlock: |
2716 | unlock_page(page); |
2717 | page_cache_release(page); |
2718 | out: |
2719 | return err; |
2720 | } |
2721 | EXPORT_SYMBOL(nobh_truncate_page); |
2722 | |
2723 | int block_truncate_page(struct address_space *mapping, |
2724 | loff_t from, get_block_t *get_block) |
2725 | { |
2726 | pgoff_t index = from >> PAGE_CACHE_SHIFT; |
2727 | unsigned offset = from & (PAGE_CACHE_SIZE-1); |
2728 | unsigned blocksize; |
2729 | sector_t iblock; |
2730 | unsigned length, pos; |
2731 | struct inode *inode = mapping->host; |
2732 | struct page *page; |
2733 | struct buffer_head *bh; |
2734 | int err; |
2735 | |
2736 | blocksize = 1 << inode->i_blkbits; |
2737 | length = offset & (blocksize - 1); |
2738 | |
2739 | /* Block boundary? Nothing to do */ |
2740 | if (!length) |
2741 | return 0; |
2742 | |
2743 | length = blocksize - length; |
2744 | iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
2745 | |
2746 | page = grab_cache_page(mapping, index); |
2747 | err = -ENOMEM; |
2748 | if (!page) |
2749 | goto out; |
2750 | |
2751 | if (!page_has_buffers(page)) |
2752 | create_empty_buffers(page, blocksize, 0); |
2753 | |
2754 | /* Find the buffer that contains "offset" */ |
2755 | bh = page_buffers(page); |
2756 | pos = blocksize; |
2757 | while (offset >= pos) { |
2758 | bh = bh->b_this_page; |
2759 | iblock++; |
2760 | pos += blocksize; |
2761 | } |
2762 | |
2763 | err = 0; |
2764 | if (!buffer_mapped(bh)) { |
2765 | WARN_ON(bh->b_size != blocksize); |
2766 | err = get_block(inode, iblock, bh, 0); |
2767 | if (err) |
2768 | goto unlock; |
2769 | /* unmapped? It's a hole - nothing to do */ |
2770 | if (!buffer_mapped(bh)) |
2771 | goto unlock; |
2772 | } |
2773 | |
2774 | /* Ok, it's mapped. Make sure it's up-to-date */ |
2775 | if (PageUptodate(page)) |
2776 | set_buffer_uptodate(bh); |
2777 | |
2778 | if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) { |
2779 | err = -EIO; |
2780 | ll_rw_block(READ, 1, &bh); |
2781 | wait_on_buffer(bh); |
2782 | /* Uhhuh. Read error. Complain and punt. */ |
2783 | if (!buffer_uptodate(bh)) |
2784 | goto unlock; |
2785 | } |
2786 | |
2787 | zero_user(page, offset, length); |
2788 | mark_buffer_dirty(bh); |
2789 | err = 0; |
2790 | |
2791 | unlock: |
2792 | unlock_page(page); |
2793 | page_cache_release(page); |
2794 | out: |
2795 | return err; |
2796 | } |
2797 | EXPORT_SYMBOL(block_truncate_page); |
2798 | |
2799 | /* |
2800 | * The generic ->writepage function for buffer-backed address_spaces |
2801 | * this form passes in the end_io handler used to finish the IO. |
2802 | */ |
2803 | int block_write_full_page_endio(struct page *page, get_block_t *get_block, |
2804 | struct writeback_control *wbc, bh_end_io_t *handler) |
2805 | { |
2806 | struct inode * const inode = page->mapping->host; |
2807 | loff_t i_size = i_size_read(inode); |
2808 | const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; |
2809 | unsigned offset; |
2810 | |
2811 | /* Is the page fully inside i_size? */ |
2812 | if (page->index < end_index) |
2813 | return __block_write_full_page(inode, page, get_block, wbc, |
2814 | handler); |
2815 | |
2816 | /* Is the page fully outside i_size? (truncate in progress) */ |
2817 | offset = i_size & (PAGE_CACHE_SIZE-1); |
2818 | if (page->index >= end_index+1 || !offset) { |
2819 | /* |
2820 | * The page may have dirty, unmapped buffers. For example, |
2821 | * they may have been added in ext3_writepage(). Make them |
2822 | * freeable here, so the page does not leak. |
2823 | */ |
2824 | do_invalidatepage(page, 0); |
2825 | unlock_page(page); |
2826 | return 0; /* don't care */ |
2827 | } |
2828 | |
2829 | /* |
2830 | * The page straddles i_size. It must be zeroed out on each and every |
2831 | * writepage invocation because it may be mmapped. "A file is mapped |
2832 | * in multiples of the page size. For a file that is not a multiple of |
2833 | * the page size, the remaining memory is zeroed when mapped, and |
2834 | * writes to that region are not written out to the file." |
2835 | */ |
2836 | zero_user_segment(page, offset, PAGE_CACHE_SIZE); |
2837 | return __block_write_full_page(inode, page, get_block, wbc, handler); |
2838 | } |
2839 | EXPORT_SYMBOL(block_write_full_page_endio); |
2840 | |
2841 | /* |
2842 | * The generic ->writepage function for buffer-backed address_spaces |
2843 | */ |
2844 | int block_write_full_page(struct page *page, get_block_t *get_block, |
2845 | struct writeback_control *wbc) |
2846 | { |
2847 | return block_write_full_page_endio(page, get_block, wbc, |
2848 | end_buffer_async_write); |
2849 | } |
2850 | EXPORT_SYMBOL(block_write_full_page); |
2851 | |
2852 | sector_t generic_block_bmap(struct address_space *mapping, sector_t block, |
2853 | get_block_t *get_block) |
2854 | { |
2855 | struct buffer_head tmp; |
2856 | struct inode *inode = mapping->host; |
2857 | tmp.b_state = 0; |
2858 | tmp.b_blocknr = 0; |
2859 | tmp.b_size = 1 << inode->i_blkbits; |
2860 | get_block(inode, block, &tmp, 0); |
2861 | return tmp.b_blocknr; |
2862 | } |
2863 | EXPORT_SYMBOL(generic_block_bmap); |
2864 | |
2865 | static void end_bio_bh_io_sync(struct bio *bio, int err) |
2866 | { |
2867 | struct buffer_head *bh = bio->bi_private; |
2868 | |
2869 | if (err == -EOPNOTSUPP) { |
2870 | set_bit(BIO_EOPNOTSUPP, &bio->bi_flags); |
2871 | } |
2872 | |
2873 | if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags))) |
2874 | set_bit(BH_Quiet, &bh->b_state); |
2875 | |
2876 | bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags)); |
2877 | bio_put(bio); |
2878 | } |
2879 | |
2880 | int submit_bh(int rw, struct buffer_head * bh) |
2881 | { |
2882 | struct bio *bio; |
2883 | int ret = 0; |
2884 | |
2885 | BUG_ON(!buffer_locked(bh)); |
2886 | BUG_ON(!buffer_mapped(bh)); |
2887 | BUG_ON(!bh->b_end_io); |
2888 | BUG_ON(buffer_delay(bh)); |
2889 | BUG_ON(buffer_unwritten(bh)); |
2890 | |
2891 | /* |
2892 | * Only clear out a write error when rewriting |
2893 | */ |
2894 | if (test_set_buffer_req(bh) && (rw & WRITE)) |
2895 | clear_buffer_write_io_error(bh); |
2896 | |
2897 | /* |
2898 | * from here on down, it's all bio -- do the initial mapping, |
2899 | * submit_bio -> generic_make_request may further map this bio around |
2900 | */ |
2901 | bio = bio_alloc(GFP_NOIO, 1); |
2902 | |
2903 | bio->bi_sector = bh->b_blocknr * (bh->b_size >> 9); |
2904 | bio->bi_bdev = bh->b_bdev; |
2905 | bio->bi_io_vec[0].bv_page = bh->b_page; |
2906 | bio->bi_io_vec[0].bv_len = bh->b_size; |
2907 | bio->bi_io_vec[0].bv_offset = bh_offset(bh); |
2908 | |
2909 | bio->bi_vcnt = 1; |
2910 | bio->bi_idx = 0; |
2911 | bio->bi_size = bh->b_size; |
2912 | |
2913 | bio->bi_end_io = end_bio_bh_io_sync; |
2914 | bio->bi_private = bh; |
2915 | |
2916 | bio_get(bio); |
2917 | submit_bio(rw, bio); |
2918 | |
2919 | if (bio_flagged(bio, BIO_EOPNOTSUPP)) |
2920 | ret = -EOPNOTSUPP; |
2921 | |
2922 | bio_put(bio); |
2923 | return ret; |
2924 | } |
2925 | EXPORT_SYMBOL(submit_bh); |
2926 | |
2927 | /** |
2928 | * ll_rw_block: low-level access to block devices (DEPRECATED) |
2929 | * @rw: whether to %READ or %WRITE or maybe %READA (readahead) |
2930 | * @nr: number of &struct buffer_heads in the array |
2931 | * @bhs: array of pointers to &struct buffer_head |
2932 | * |
2933 | * ll_rw_block() takes an array of pointers to &struct buffer_heads, and |
2934 | * requests an I/O operation on them, either a %READ or a %WRITE. The third |
2935 | * %READA option is described in the documentation for generic_make_request() |
2936 | * which ll_rw_block() calls. |
2937 | * |
2938 | * This function drops any buffer that it cannot get a lock on (with the |
2939 | * BH_Lock state bit), any buffer that appears to be clean when doing a write |
2940 | * request, and any buffer that appears to be up-to-date when doing read |
2941 | * request. Further it marks as clean buffers that are processed for |
2942 | * writing (the buffer cache won't assume that they are actually clean |
2943 | * until the buffer gets unlocked). |
2944 | * |
2945 | * ll_rw_block sets b_end_io to simple completion handler that marks |
2946 | * the buffer up-to-date (if approriate), unlocks the buffer and wakes |
2947 | * any waiters. |
2948 | * |
2949 | * All of the buffers must be for the same device, and must also be a |
2950 | * multiple of the current approved size for the device. |
2951 | */ |
2952 | void ll_rw_block(int rw, int nr, struct buffer_head *bhs[]) |
2953 | { |
2954 | int i; |
2955 | |
2956 | for (i = 0; i < nr; i++) { |
2957 | struct buffer_head *bh = bhs[i]; |
2958 | |
2959 | if (!trylock_buffer(bh)) |
2960 | continue; |
2961 | if (rw == WRITE) { |
2962 | if (test_clear_buffer_dirty(bh)) { |
2963 | bh->b_end_io = end_buffer_write_sync; |
2964 | get_bh(bh); |
2965 | submit_bh(WRITE, bh); |
2966 | continue; |
2967 | } |
2968 | } else { |
2969 | if (!buffer_uptodate(bh)) { |
2970 | bh->b_end_io = end_buffer_read_sync; |
2971 | get_bh(bh); |
2972 | submit_bh(rw, bh); |
2973 | continue; |
2974 | } |
2975 | } |
2976 | unlock_buffer(bh); |
2977 | } |
2978 | } |
2979 | EXPORT_SYMBOL(ll_rw_block); |
2980 | |
2981 | void write_dirty_buffer(struct buffer_head *bh, int rw) |
2982 | { |
2983 | lock_buffer(bh); |
2984 | if (!test_clear_buffer_dirty(bh)) { |
2985 | unlock_buffer(bh); |
2986 | return; |
2987 | } |
2988 | bh->b_end_io = end_buffer_write_sync; |
2989 | get_bh(bh); |
2990 | submit_bh(rw, bh); |
2991 | } |
2992 | EXPORT_SYMBOL(write_dirty_buffer); |
2993 | |
2994 | /* |
2995 | * For a data-integrity writeout, we need to wait upon any in-progress I/O |
2996 | * and then start new I/O and then wait upon it. The caller must have a ref on |
2997 | * the buffer_head. |
2998 | */ |
2999 | int __sync_dirty_buffer(struct buffer_head *bh, int rw) |
3000 | { |
3001 | int ret = 0; |
3002 | |
3003 | WARN_ON(atomic_read(&bh->b_count) < 1); |
3004 | lock_buffer(bh); |
3005 | if (test_clear_buffer_dirty(bh)) { |
3006 | get_bh(bh); |
3007 | bh->b_end_io = end_buffer_write_sync; |
3008 | ret = submit_bh(rw, bh); |
3009 | wait_on_buffer(bh); |
3010 | if (!ret && !buffer_uptodate(bh)) |
3011 | ret = -EIO; |
3012 | } else { |
3013 | unlock_buffer(bh); |
3014 | } |
3015 | return ret; |
3016 | } |
3017 | EXPORT_SYMBOL(__sync_dirty_buffer); |
3018 | |
3019 | int sync_dirty_buffer(struct buffer_head *bh) |
3020 | { |
3021 | return __sync_dirty_buffer(bh, WRITE_SYNC); |
3022 | } |
3023 | EXPORT_SYMBOL(sync_dirty_buffer); |
3024 | |
3025 | /* |
3026 | * try_to_free_buffers() checks if all the buffers on this particular page |
3027 | * are unused, and releases them if so. |
3028 | * |
3029 | * Exclusion against try_to_free_buffers may be obtained by either |
3030 | * locking the page or by holding its mapping's private_lock. |
3031 | * |
3032 | * If the page is dirty but all the buffers are clean then we need to |
3033 | * be sure to mark the page clean as well. This is because the page |
3034 | * may be against a block device, and a later reattachment of buffers |
3035 | * to a dirty page will set *all* buffers dirty. Which would corrupt |
3036 | * filesystem data on the same device. |
3037 | * |
3038 | * The same applies to regular filesystem pages: if all the buffers are |
3039 | * clean then we set the page clean and proceed. To do that, we require |
3040 | * total exclusion from __set_page_dirty_buffers(). That is obtained with |
3041 | * private_lock. |
3042 | * |
3043 | * try_to_free_buffers() is non-blocking. |
3044 | */ |
3045 | static inline int buffer_busy(struct buffer_head *bh) |
3046 | { |
3047 | return atomic_read(&bh->b_count) | |
3048 | (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock))); |
3049 | } |
3050 | |
3051 | static int |
3052 | drop_buffers(struct page *page, struct buffer_head **buffers_to_free) |
3053 | { |
3054 | struct buffer_head *head = page_buffers(page); |
3055 | struct buffer_head *bh; |
3056 | |
3057 | bh = head; |
3058 | do { |
3059 | if (buffer_write_io_error(bh) && page->mapping) |
3060 | set_bit(AS_EIO, &page->mapping->flags); |
3061 | if (buffer_busy(bh)) |
3062 | goto failed; |
3063 | bh = bh->b_this_page; |
3064 | } while (bh != head); |
3065 | |
3066 | do { |
3067 | struct buffer_head *next = bh->b_this_page; |
3068 | |
3069 | if (bh->b_assoc_map) |
3070 | __remove_assoc_queue(bh); |
3071 | bh = next; |
3072 | } while (bh != head); |
3073 | *buffers_to_free = head; |
3074 | __clear_page_buffers(page); |
3075 | return 1; |
3076 | failed: |
3077 | return 0; |
3078 | } |
3079 | |
3080 | int try_to_free_buffers(struct page *page) |
3081 | { |
3082 | struct address_space * const mapping = page->mapping; |
3083 | struct buffer_head *buffers_to_free = NULL; |
3084 | int ret = 0; |
3085 | |
3086 | BUG_ON(!PageLocked(page)); |
3087 | if (PageWriteback(page)) |
3088 | return 0; |
3089 | |
3090 | if (mapping == NULL) { /* can this still happen? */ |
3091 | ret = drop_buffers(page, &buffers_to_free); |
3092 | goto out; |
3093 | } |
3094 | |
3095 | spin_lock(&mapping->private_lock); |
3096 | ret = drop_buffers(page, &buffers_to_free); |
3097 | |
3098 | /* |
3099 | * If the filesystem writes its buffers by hand (eg ext3) |
3100 | * then we can have clean buffers against a dirty page. We |
3101 | * clean the page here; otherwise the VM will never notice |
3102 | * that the filesystem did any IO at all. |
3103 | * |
3104 | * Also, during truncate, discard_buffer will have marked all |
3105 | * the page's buffers clean. We discover that here and clean |
3106 | * the page also. |
3107 | * |
3108 | * private_lock must be held over this entire operation in order |
3109 | * to synchronise against __set_page_dirty_buffers and prevent the |
3110 | * dirty bit from being lost. |
3111 | */ |
3112 | if (ret) |
3113 | cancel_dirty_page(page, PAGE_CACHE_SIZE); |
3114 | spin_unlock(&mapping->private_lock); |
3115 | out: |
3116 | if (buffers_to_free) { |
3117 | struct buffer_head *bh = buffers_to_free; |
3118 | |
3119 | do { |
3120 | struct buffer_head *next = bh->b_this_page; |
3121 | free_buffer_head(bh); |
3122 | bh = next; |
3123 | } while (bh != buffers_to_free); |
3124 | } |
3125 | return ret; |
3126 | } |
3127 | EXPORT_SYMBOL(try_to_free_buffers); |
3128 | |
3129 | /* |
3130 | * There are no bdflush tunables left. But distributions are |
3131 | * still running obsolete flush daemons, so we terminate them here. |
3132 | * |
3133 | * Use of bdflush() is deprecated and will be removed in a future kernel. |
3134 | * The `flush-X' kernel threads fully replace bdflush daemons and this call. |
3135 | */ |
3136 | SYSCALL_DEFINE2(bdflush, int, func, long, data) |
3137 | { |
3138 | static int msg_count; |
3139 | |
3140 | if (!capable(CAP_SYS_ADMIN)) |
3141 | return -EPERM; |
3142 | |
3143 | if (msg_count < 5) { |
3144 | msg_count++; |
3145 | printk(KERN_INFO |
3146 | "warning: process `%s' used the obsolete bdflush" |
3147 | " system call\n", current->comm); |
3148 | printk(KERN_INFO "Fix your initscripts?\n"); |
3149 | } |
3150 | |
3151 | if (func == 1) |
3152 | do_exit(0); |
3153 | return 0; |
3154 | } |
3155 | |
3156 | /* |
3157 | * Buffer-head allocation |
3158 | */ |
3159 | static struct kmem_cache *bh_cachep __read_mostly; |
3160 | |
3161 | /* |
3162 | * Once the number of bh's in the machine exceeds this level, we start |
3163 | * stripping them in writeback. |
3164 | */ |
3165 | static int max_buffer_heads; |
3166 | |
3167 | int buffer_heads_over_limit; |
3168 | |
3169 | struct bh_accounting { |
3170 | int nr; /* Number of live bh's */ |
3171 | int ratelimit; /* Limit cacheline bouncing */ |
3172 | }; |
3173 | |
3174 | static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0}; |
3175 | |
3176 | static void recalc_bh_state(void) |
3177 | { |
3178 | int i; |
3179 | int tot = 0; |
3180 | |
3181 | if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096) |
3182 | return; |
3183 | __this_cpu_write(bh_accounting.ratelimit, 0); |
3184 | for_each_online_cpu(i) |
3185 | tot += per_cpu(bh_accounting, i).nr; |
3186 | buffer_heads_over_limit = (tot > max_buffer_heads); |
3187 | } |
3188 | |
3189 | struct buffer_head *alloc_buffer_head(gfp_t gfp_flags) |
3190 | { |
3191 | struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags); |
3192 | if (ret) { |
3193 | INIT_LIST_HEAD(&ret->b_assoc_buffers); |
3194 | preempt_disable(); |
3195 | __this_cpu_inc(bh_accounting.nr); |
3196 | recalc_bh_state(); |
3197 | preempt_enable(); |
3198 | } |
3199 | return ret; |
3200 | } |
3201 | EXPORT_SYMBOL(alloc_buffer_head); |
3202 | |
3203 | void free_buffer_head(struct buffer_head *bh) |
3204 | { |
3205 | BUG_ON(!list_empty(&bh->b_assoc_buffers)); |
3206 | kmem_cache_free(bh_cachep, bh); |
3207 | preempt_disable(); |
3208 | __this_cpu_dec(bh_accounting.nr); |
3209 | recalc_bh_state(); |
3210 | preempt_enable(); |
3211 | } |
3212 | EXPORT_SYMBOL(free_buffer_head); |
3213 | |
3214 | static void buffer_exit_cpu(int cpu) |
3215 | { |
3216 | int i; |
3217 | struct bh_lru *b = &per_cpu(bh_lrus, cpu); |
3218 | |
3219 | for (i = 0; i < BH_LRU_SIZE; i++) { |
3220 | brelse(b->bhs[i]); |
3221 | b->bhs[i] = NULL; |
3222 | } |
3223 | this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr); |
3224 | per_cpu(bh_accounting, cpu).nr = 0; |
3225 | } |
3226 | |
3227 | static int buffer_cpu_notify(struct notifier_block *self, |
3228 | unsigned long action, void *hcpu) |
3229 | { |
3230 | if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) |
3231 | buffer_exit_cpu((unsigned long)hcpu); |
3232 | return NOTIFY_OK; |
3233 | } |
3234 | |
3235 | /** |
3236 | * bh_uptodate_or_lock - Test whether the buffer is uptodate |
3237 | * @bh: struct buffer_head |
3238 | * |
3239 | * Return true if the buffer is up-to-date and false, |
3240 | * with the buffer locked, if not. |
3241 | */ |
3242 | int bh_uptodate_or_lock(struct buffer_head *bh) |
3243 | { |
3244 | if (!buffer_uptodate(bh)) { |
3245 | lock_buffer(bh); |
3246 | if (!buffer_uptodate(bh)) |
3247 | return 0; |
3248 | unlock_buffer(bh); |
3249 | } |
3250 | return 1; |
3251 | } |
3252 | EXPORT_SYMBOL(bh_uptodate_or_lock); |
3253 | |
3254 | /** |
3255 | * bh_submit_read - Submit a locked buffer for reading |
3256 | * @bh: struct buffer_head |
3257 | * |
3258 | * Returns zero on success and -EIO on error. |
3259 | */ |
3260 | int bh_submit_read(struct buffer_head *bh) |
3261 | { |
3262 | BUG_ON(!buffer_locked(bh)); |
3263 | |
3264 | if (buffer_uptodate(bh)) { |
3265 | unlock_buffer(bh); |
3266 | return 0; |
3267 | } |
3268 | |
3269 | get_bh(bh); |
3270 | bh->b_end_io = end_buffer_read_sync; |
3271 | submit_bh(READ, bh); |
3272 | wait_on_buffer(bh); |
3273 | if (buffer_uptodate(bh)) |
3274 | return 0; |
3275 | return -EIO; |
3276 | } |
3277 | EXPORT_SYMBOL(bh_submit_read); |
3278 | |
3279 | void __init buffer_init(void) |
3280 | { |
3281 | int nrpages; |
3282 | |
3283 | bh_cachep = kmem_cache_create("buffer_head", |
3284 | sizeof(struct buffer_head), 0, |
3285 | (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC| |
3286 | SLAB_MEM_SPREAD), |
3287 | NULL); |
3288 | |
3289 | /* |
3290 | * Limit the bh occupancy to 10% of ZONE_NORMAL |
3291 | */ |
3292 | nrpages = (nr_free_buffer_pages() * 10) / 100; |
3293 | max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head)); |
3294 | hotcpu_notifier(buffer_cpu_notify, 0); |
3295 | } |
3296 |
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