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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 | #include <trace/events/block.h> |
45 | |
46 | static int fsync_buffers_list(spinlock_t *lock, struct list_head *list); |
47 | |
48 | #define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers) |
49 | |
50 | void 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 | inline void touch_buffer(struct buffer_head *bh) |
58 | { |
59 | trace_block_touch_buffer(bh); |
60 | mark_page_accessed(bh->b_page); |
61 | } |
62 | EXPORT_SYMBOL(touch_buffer); |
63 | |
64 | static int sleep_on_buffer(void *word) |
65 | { |
66 | io_schedule(); |
67 | return 0; |
68 | } |
69 | |
70 | void __lock_buffer(struct buffer_head *bh) |
71 | { |
72 | wait_on_bit_lock(&bh->b_state, BH_Lock, sleep_on_buffer, |
73 | TASK_UNINTERRUPTIBLE); |
74 | } |
75 | EXPORT_SYMBOL(__lock_buffer); |
76 | |
77 | void unlock_buffer(struct buffer_head *bh) |
78 | { |
79 | clear_bit_unlock(BH_Lock, &bh->b_state); |
80 | smp_mb__after_atomic(); |
81 | wake_up_bit(&bh->b_state, BH_Lock); |
82 | } |
83 | EXPORT_SYMBOL(unlock_buffer); |
84 | |
85 | /* |
86 | * Returns if the page has dirty or writeback buffers. If all the buffers |
87 | * are unlocked and clean then the PageDirty information is stale. If |
88 | * any of the pages are locked, it is assumed they are locked for IO. |
89 | */ |
90 | void buffer_check_dirty_writeback(struct page *page, |
91 | bool *dirty, bool *writeback) |
92 | { |
93 | struct buffer_head *head, *bh; |
94 | *dirty = false; |
95 | *writeback = false; |
96 | |
97 | BUG_ON(!PageLocked(page)); |
98 | |
99 | if (!page_has_buffers(page)) |
100 | return; |
101 | |
102 | if (PageWriteback(page)) |
103 | *writeback = true; |
104 | |
105 | head = page_buffers(page); |
106 | bh = head; |
107 | do { |
108 | if (buffer_locked(bh)) |
109 | *writeback = true; |
110 | |
111 | if (buffer_dirty(bh)) |
112 | *dirty = true; |
113 | |
114 | bh = bh->b_this_page; |
115 | } while (bh != head); |
116 | } |
117 | EXPORT_SYMBOL(buffer_check_dirty_writeback); |
118 | |
119 | /* |
120 | * Block until a buffer comes unlocked. This doesn't stop it |
121 | * from becoming locked again - you have to lock it yourself |
122 | * if you want to preserve its state. |
123 | */ |
124 | void __wait_on_buffer(struct buffer_head * bh) |
125 | { |
126 | wait_on_bit(&bh->b_state, BH_Lock, sleep_on_buffer, TASK_UNINTERRUPTIBLE); |
127 | } |
128 | EXPORT_SYMBOL(__wait_on_buffer); |
129 | |
130 | static void |
131 | __clear_page_buffers(struct page *page) |
132 | { |
133 | ClearPagePrivate(page); |
134 | set_page_private(page, 0); |
135 | page_cache_release(page); |
136 | } |
137 | |
138 | |
139 | static int quiet_error(struct buffer_head *bh) |
140 | { |
141 | if (!test_bit(BH_Quiet, &bh->b_state) && printk_ratelimit()) |
142 | return 0; |
143 | return 1; |
144 | } |
145 | |
146 | |
147 | static void buffer_io_error(struct buffer_head *bh) |
148 | { |
149 | char b[BDEVNAME_SIZE]; |
150 | printk(KERN_ERR "Buffer I/O error on device %s, logical block %Lu\n", |
151 | bdevname(bh->b_bdev, b), |
152 | (unsigned long long)bh->b_blocknr); |
153 | } |
154 | |
155 | /* |
156 | * End-of-IO handler helper function which does not touch the bh after |
157 | * unlocking it. |
158 | * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but |
159 | * a race there is benign: unlock_buffer() only use the bh's address for |
160 | * hashing after unlocking the buffer, so it doesn't actually touch the bh |
161 | * itself. |
162 | */ |
163 | static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate) |
164 | { |
165 | if (uptodate) { |
166 | set_buffer_uptodate(bh); |
167 | } else { |
168 | /* This happens, due to failed READA attempts. */ |
169 | clear_buffer_uptodate(bh); |
170 | } |
171 | unlock_buffer(bh); |
172 | } |
173 | |
174 | /* |
175 | * Default synchronous end-of-IO handler.. Just mark it up-to-date and |
176 | * unlock the buffer. This is what ll_rw_block uses too. |
177 | */ |
178 | void end_buffer_read_sync(struct buffer_head *bh, int uptodate) |
179 | { |
180 | __end_buffer_read_notouch(bh, uptodate); |
181 | put_bh(bh); |
182 | } |
183 | EXPORT_SYMBOL(end_buffer_read_sync); |
184 | |
185 | void end_buffer_write_sync(struct buffer_head *bh, int uptodate) |
186 | { |
187 | char b[BDEVNAME_SIZE]; |
188 | |
189 | if (uptodate) { |
190 | set_buffer_uptodate(bh); |
191 | } else { |
192 | if (!quiet_error(bh)) { |
193 | buffer_io_error(bh); |
194 | printk(KERN_WARNING "lost page write due to " |
195 | "I/O error on %s\n", |
196 | bdevname(bh->b_bdev, b)); |
197 | } |
198 | set_buffer_write_io_error(bh); |
199 | clear_buffer_uptodate(bh); |
200 | } |
201 | unlock_buffer(bh); |
202 | put_bh(bh); |
203 | } |
204 | EXPORT_SYMBOL(end_buffer_write_sync); |
205 | |
206 | /* |
207 | * Various filesystems appear to want __find_get_block to be non-blocking. |
208 | * But it's the page lock which protects the buffers. To get around this, |
209 | * we get exclusion from try_to_free_buffers with the blockdev mapping's |
210 | * private_lock. |
211 | * |
212 | * Hack idea: for the blockdev mapping, i_bufferlist_lock contention |
213 | * may be quite high. This code could TryLock the page, and if that |
214 | * succeeds, there is no need to take private_lock. (But if |
215 | * private_lock is contended then so is mapping->tree_lock). |
216 | */ |
217 | static struct buffer_head * |
218 | __find_get_block_slow(struct block_device *bdev, sector_t block) |
219 | { |
220 | struct inode *bd_inode = bdev->bd_inode; |
221 | struct address_space *bd_mapping = bd_inode->i_mapping; |
222 | struct buffer_head *ret = NULL; |
223 | pgoff_t index; |
224 | struct buffer_head *bh; |
225 | struct buffer_head *head; |
226 | struct page *page; |
227 | int all_mapped = 1; |
228 | |
229 | index = block >> (PAGE_CACHE_SHIFT - bd_inode->i_blkbits); |
230 | page = find_get_page_flags(bd_mapping, index, FGP_ACCESSED); |
231 | if (!page) |
232 | goto out; |
233 | |
234 | spin_lock(&bd_mapping->private_lock); |
235 | if (!page_has_buffers(page)) |
236 | goto out_unlock; |
237 | head = page_buffers(page); |
238 | bh = head; |
239 | do { |
240 | if (!buffer_mapped(bh)) |
241 | all_mapped = 0; |
242 | else if (bh->b_blocknr == block) { |
243 | ret = bh; |
244 | get_bh(bh); |
245 | goto out_unlock; |
246 | } |
247 | bh = bh->b_this_page; |
248 | } while (bh != head); |
249 | |
250 | /* we might be here because some of the buffers on this page are |
251 | * not mapped. This is due to various races between |
252 | * file io on the block device and getblk. It gets dealt with |
253 | * elsewhere, don't buffer_error if we had some unmapped buffers |
254 | */ |
255 | if (all_mapped) { |
256 | char b[BDEVNAME_SIZE]; |
257 | |
258 | printk("__find_get_block_slow() failed. " |
259 | "block=%llu, b_blocknr=%llu\n", |
260 | (unsigned long long)block, |
261 | (unsigned long long)bh->b_blocknr); |
262 | printk("b_state=0x%08lx, b_size=%zu\n", |
263 | bh->b_state, bh->b_size); |
264 | printk("device %s blocksize: %d\n", bdevname(bdev, b), |
265 | 1 << bd_inode->i_blkbits); |
266 | } |
267 | out_unlock: |
268 | spin_unlock(&bd_mapping->private_lock); |
269 | page_cache_release(page); |
270 | out: |
271 | return ret; |
272 | } |
273 | |
274 | /* |
275 | * Kick the writeback threads then try to free up some ZONE_NORMAL memory. |
276 | */ |
277 | static void free_more_memory(void) |
278 | { |
279 | struct zone *zone; |
280 | int nid; |
281 | |
282 | wakeup_flusher_threads(1024, WB_REASON_FREE_MORE_MEM); |
283 | yield(); |
284 | |
285 | for_each_online_node(nid) { |
286 | (void)first_zones_zonelist(node_zonelist(nid, GFP_NOFS), |
287 | gfp_zone(GFP_NOFS), NULL, |
288 | &zone); |
289 | if (zone) |
290 | try_to_free_pages(node_zonelist(nid, GFP_NOFS), 0, |
291 | GFP_NOFS, NULL); |
292 | } |
293 | } |
294 | |
295 | /* |
296 | * I/O completion handler for block_read_full_page() - pages |
297 | * which come unlocked at the end of I/O. |
298 | */ |
299 | static void end_buffer_async_read(struct buffer_head *bh, int uptodate) |
300 | { |
301 | unsigned long flags; |
302 | struct buffer_head *first; |
303 | struct buffer_head *tmp; |
304 | struct page *page; |
305 | int page_uptodate = 1; |
306 | |
307 | BUG_ON(!buffer_async_read(bh)); |
308 | |
309 | page = bh->b_page; |
310 | if (uptodate) { |
311 | set_buffer_uptodate(bh); |
312 | } else { |
313 | clear_buffer_uptodate(bh); |
314 | if (!quiet_error(bh)) |
315 | buffer_io_error(bh); |
316 | SetPageError(page); |
317 | } |
318 | |
319 | /* |
320 | * Be _very_ careful from here on. Bad things can happen if |
321 | * two buffer heads end IO at almost the same time and both |
322 | * decide that the page is now completely done. |
323 | */ |
324 | first = page_buffers(page); |
325 | local_irq_save(flags); |
326 | bit_spin_lock(BH_Uptodate_Lock, &first->b_state); |
327 | clear_buffer_async_read(bh); |
328 | unlock_buffer(bh); |
329 | tmp = bh; |
330 | do { |
331 | if (!buffer_uptodate(tmp)) |
332 | page_uptodate = 0; |
333 | if (buffer_async_read(tmp)) { |
334 | BUG_ON(!buffer_locked(tmp)); |
335 | goto still_busy; |
336 | } |
337 | tmp = tmp->b_this_page; |
338 | } while (tmp != bh); |
339 | bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
340 | local_irq_restore(flags); |
341 | |
342 | /* |
343 | * If none of the buffers had errors and they are all |
344 | * uptodate then we can set the page uptodate. |
345 | */ |
346 | if (page_uptodate && !PageError(page)) |
347 | SetPageUptodate(page); |
348 | unlock_page(page); |
349 | return; |
350 | |
351 | still_busy: |
352 | bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
353 | local_irq_restore(flags); |
354 | return; |
355 | } |
356 | |
357 | /* |
358 | * Completion handler for block_write_full_page() - pages which are unlocked |
359 | * during I/O, and which have PageWriteback cleared upon I/O completion. |
360 | */ |
361 | void end_buffer_async_write(struct buffer_head *bh, int uptodate) |
362 | { |
363 | char b[BDEVNAME_SIZE]; |
364 | unsigned long flags; |
365 | struct buffer_head *first; |
366 | struct buffer_head *tmp; |
367 | struct page *page; |
368 | |
369 | BUG_ON(!buffer_async_write(bh)); |
370 | |
371 | page = bh->b_page; |
372 | if (uptodate) { |
373 | set_buffer_uptodate(bh); |
374 | } else { |
375 | if (!quiet_error(bh)) { |
376 | buffer_io_error(bh); |
377 | printk(KERN_WARNING "lost page write due to " |
378 | "I/O error on %s\n", |
379 | bdevname(bh->b_bdev, b)); |
380 | } |
381 | set_bit(AS_EIO, &page->mapping->flags); |
382 | set_buffer_write_io_error(bh); |
383 | clear_buffer_uptodate(bh); |
384 | SetPageError(page); |
385 | } |
386 | |
387 | first = page_buffers(page); |
388 | local_irq_save(flags); |
389 | bit_spin_lock(BH_Uptodate_Lock, &first->b_state); |
390 | |
391 | clear_buffer_async_write(bh); |
392 | unlock_buffer(bh); |
393 | tmp = bh->b_this_page; |
394 | while (tmp != bh) { |
395 | if (buffer_async_write(tmp)) { |
396 | BUG_ON(!buffer_locked(tmp)); |
397 | goto still_busy; |
398 | } |
399 | tmp = tmp->b_this_page; |
400 | } |
401 | bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
402 | local_irq_restore(flags); |
403 | end_page_writeback(page); |
404 | return; |
405 | |
406 | still_busy: |
407 | bit_spin_unlock(BH_Uptodate_Lock, &first->b_state); |
408 | local_irq_restore(flags); |
409 | return; |
410 | } |
411 | EXPORT_SYMBOL(end_buffer_async_write); |
412 | |
413 | /* |
414 | * If a page's buffers are under async readin (end_buffer_async_read |
415 | * completion) then there is a possibility that another thread of |
416 | * control could lock one of the buffers after it has completed |
417 | * but while some of the other buffers have not completed. This |
418 | * locked buffer would confuse end_buffer_async_read() into not unlocking |
419 | * the page. So the absence of BH_Async_Read tells end_buffer_async_read() |
420 | * that this buffer is not under async I/O. |
421 | * |
422 | * The page comes unlocked when it has no locked buffer_async buffers |
423 | * left. |
424 | * |
425 | * PageLocked prevents anyone starting new async I/O reads any of |
426 | * the buffers. |
427 | * |
428 | * PageWriteback is used to prevent simultaneous writeout of the same |
429 | * page. |
430 | * |
431 | * PageLocked prevents anyone from starting writeback of a page which is |
432 | * under read I/O (PageWriteback is only ever set against a locked page). |
433 | */ |
434 | static void mark_buffer_async_read(struct buffer_head *bh) |
435 | { |
436 | bh->b_end_io = end_buffer_async_read; |
437 | set_buffer_async_read(bh); |
438 | } |
439 | |
440 | static void mark_buffer_async_write_endio(struct buffer_head *bh, |
441 | bh_end_io_t *handler) |
442 | { |
443 | bh->b_end_io = handler; |
444 | set_buffer_async_write(bh); |
445 | } |
446 | |
447 | void mark_buffer_async_write(struct buffer_head *bh) |
448 | { |
449 | mark_buffer_async_write_endio(bh, end_buffer_async_write); |
450 | } |
451 | EXPORT_SYMBOL(mark_buffer_async_write); |
452 | |
453 | |
454 | /* |
455 | * fs/buffer.c contains helper functions for buffer-backed address space's |
456 | * fsync functions. A common requirement for buffer-based filesystems is |
457 | * that certain data from the backing blockdev needs to be written out for |
458 | * a successful fsync(). For example, ext2 indirect blocks need to be |
459 | * written back and waited upon before fsync() returns. |
460 | * |
461 | * The functions mark_buffer_inode_dirty(), fsync_inode_buffers(), |
462 | * inode_has_buffers() and invalidate_inode_buffers() are provided for the |
463 | * management of a list of dependent buffers at ->i_mapping->private_list. |
464 | * |
465 | * Locking is a little subtle: try_to_free_buffers() will remove buffers |
466 | * from their controlling inode's queue when they are being freed. But |
467 | * try_to_free_buffers() will be operating against the *blockdev* mapping |
468 | * at the time, not against the S_ISREG file which depends on those buffers. |
469 | * So the locking for private_list is via the private_lock in the address_space |
470 | * which backs the buffers. Which is different from the address_space |
471 | * against which the buffers are listed. So for a particular address_space, |
472 | * mapping->private_lock does *not* protect mapping->private_list! In fact, |
473 | * mapping->private_list will always be protected by the backing blockdev's |
474 | * ->private_lock. |
475 | * |
476 | * Which introduces a requirement: all buffers on an address_space's |
477 | * ->private_list must be from the same address_space: the blockdev's. |
478 | * |
479 | * address_spaces which do not place buffers at ->private_list via these |
480 | * utility functions are free to use private_lock and private_list for |
481 | * whatever they want. The only requirement is that list_empty(private_list) |
482 | * be true at clear_inode() time. |
483 | * |
484 | * FIXME: clear_inode should not call invalidate_inode_buffers(). The |
485 | * filesystems should do that. invalidate_inode_buffers() should just go |
486 | * BUG_ON(!list_empty). |
487 | * |
488 | * FIXME: mark_buffer_dirty_inode() is a data-plane operation. It should |
489 | * take an address_space, not an inode. And it should be called |
490 | * mark_buffer_dirty_fsync() to clearly define why those buffers are being |
491 | * queued up. |
492 | * |
493 | * FIXME: mark_buffer_dirty_inode() doesn't need to add the buffer to the |
494 | * list if it is already on a list. Because if the buffer is on a list, |
495 | * it *must* already be on the right one. If not, the filesystem is being |
496 | * silly. This will save a ton of locking. But first we have to ensure |
497 | * that buffers are taken *off* the old inode's list when they are freed |
498 | * (presumably in truncate). That requires careful auditing of all |
499 | * filesystems (do it inside bforget()). It could also be done by bringing |
500 | * b_inode back. |
501 | */ |
502 | |
503 | /* |
504 | * The buffer's backing address_space's private_lock must be held |
505 | */ |
506 | static void __remove_assoc_queue(struct buffer_head *bh) |
507 | { |
508 | list_del_init(&bh->b_assoc_buffers); |
509 | WARN_ON(!bh->b_assoc_map); |
510 | if (buffer_write_io_error(bh)) |
511 | set_bit(AS_EIO, &bh->b_assoc_map->flags); |
512 | bh->b_assoc_map = NULL; |
513 | } |
514 | |
515 | int inode_has_buffers(struct inode *inode) |
516 | { |
517 | return !list_empty(&inode->i_data.private_list); |
518 | } |
519 | |
520 | /* |
521 | * osync is designed to support O_SYNC io. It waits synchronously for |
522 | * all already-submitted IO to complete, but does not queue any new |
523 | * writes to the disk. |
524 | * |
525 | * To do O_SYNC writes, just queue the buffer writes with ll_rw_block as |
526 | * you dirty the buffers, and then use osync_inode_buffers to wait for |
527 | * completion. Any other dirty buffers which are not yet queued for |
528 | * write will not be flushed to disk by the osync. |
529 | */ |
530 | static int osync_buffers_list(spinlock_t *lock, struct list_head *list) |
531 | { |
532 | struct buffer_head *bh; |
533 | struct list_head *p; |
534 | int err = 0; |
535 | |
536 | spin_lock(lock); |
537 | repeat: |
538 | list_for_each_prev(p, list) { |
539 | bh = BH_ENTRY(p); |
540 | if (buffer_locked(bh)) { |
541 | get_bh(bh); |
542 | spin_unlock(lock); |
543 | wait_on_buffer(bh); |
544 | if (!buffer_uptodate(bh)) |
545 | err = -EIO; |
546 | brelse(bh); |
547 | spin_lock(lock); |
548 | goto repeat; |
549 | } |
550 | } |
551 | spin_unlock(lock); |
552 | return err; |
553 | } |
554 | |
555 | static void do_thaw_one(struct super_block *sb, void *unused) |
556 | { |
557 | char b[BDEVNAME_SIZE]; |
558 | while (sb->s_bdev && !thaw_bdev(sb->s_bdev, sb)) |
559 | printk(KERN_WARNING "Emergency Thaw on %s\n", |
560 | bdevname(sb->s_bdev, b)); |
561 | } |
562 | |
563 | static void do_thaw_all(struct work_struct *work) |
564 | { |
565 | iterate_supers(do_thaw_one, NULL); |
566 | kfree(work); |
567 | printk(KERN_WARNING "Emergency Thaw complete\n"); |
568 | } |
569 | |
570 | /** |
571 | * emergency_thaw_all -- forcibly thaw every frozen filesystem |
572 | * |
573 | * Used for emergency unfreeze of all filesystems via SysRq |
574 | */ |
575 | void emergency_thaw_all(void) |
576 | { |
577 | struct work_struct *work; |
578 | |
579 | work = kmalloc(sizeof(*work), GFP_ATOMIC); |
580 | if (work) { |
581 | INIT_WORK(work, do_thaw_all); |
582 | schedule_work(work); |
583 | } |
584 | } |
585 | |
586 | /** |
587 | * sync_mapping_buffers - write out & wait upon a mapping's "associated" buffers |
588 | * @mapping: the mapping which wants those buffers written |
589 | * |
590 | * Starts I/O against the buffers at mapping->private_list, and waits upon |
591 | * that I/O. |
592 | * |
593 | * Basically, this is a convenience function for fsync(). |
594 | * @mapping is a file or directory which needs those buffers to be written for |
595 | * a successful fsync(). |
596 | */ |
597 | int sync_mapping_buffers(struct address_space *mapping) |
598 | { |
599 | struct address_space *buffer_mapping = mapping->private_data; |
600 | |
601 | if (buffer_mapping == NULL || list_empty(&mapping->private_list)) |
602 | return 0; |
603 | |
604 | return fsync_buffers_list(&buffer_mapping->private_lock, |
605 | &mapping->private_list); |
606 | } |
607 | EXPORT_SYMBOL(sync_mapping_buffers); |
608 | |
609 | /* |
610 | * Called when we've recently written block `bblock', and it is known that |
611 | * `bblock' was for a buffer_boundary() buffer. This means that the block at |
612 | * `bblock + 1' is probably a dirty indirect block. Hunt it down and, if it's |
613 | * dirty, schedule it for IO. So that indirects merge nicely with their data. |
614 | */ |
615 | void write_boundary_block(struct block_device *bdev, |
616 | sector_t bblock, unsigned blocksize) |
617 | { |
618 | struct buffer_head *bh = __find_get_block(bdev, bblock + 1, blocksize); |
619 | if (bh) { |
620 | if (buffer_dirty(bh)) |
621 | ll_rw_block(WRITE, 1, &bh); |
622 | put_bh(bh); |
623 | } |
624 | } |
625 | |
626 | void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode) |
627 | { |
628 | struct address_space *mapping = inode->i_mapping; |
629 | struct address_space *buffer_mapping = bh->b_page->mapping; |
630 | |
631 | mark_buffer_dirty(bh); |
632 | if (!mapping->private_data) { |
633 | mapping->private_data = buffer_mapping; |
634 | } else { |
635 | BUG_ON(mapping->private_data != buffer_mapping); |
636 | } |
637 | if (!bh->b_assoc_map) { |
638 | spin_lock(&buffer_mapping->private_lock); |
639 | list_move_tail(&bh->b_assoc_buffers, |
640 | &mapping->private_list); |
641 | bh->b_assoc_map = mapping; |
642 | spin_unlock(&buffer_mapping->private_lock); |
643 | } |
644 | } |
645 | EXPORT_SYMBOL(mark_buffer_dirty_inode); |
646 | |
647 | /* |
648 | * Mark the page dirty, and set it dirty in the radix tree, and mark the inode |
649 | * dirty. |
650 | * |
651 | * If warn is true, then emit a warning if the page is not uptodate and has |
652 | * not been truncated. |
653 | */ |
654 | static void __set_page_dirty(struct page *page, |
655 | struct address_space *mapping, int warn) |
656 | { |
657 | unsigned long flags; |
658 | |
659 | spin_lock_irqsave(&mapping->tree_lock, flags); |
660 | if (page->mapping) { /* Race with truncate? */ |
661 | WARN_ON_ONCE(warn && !PageUptodate(page)); |
662 | account_page_dirtied(page, mapping); |
663 | radix_tree_tag_set(&mapping->page_tree, |
664 | page_index(page), PAGECACHE_TAG_DIRTY); |
665 | } |
666 | spin_unlock_irqrestore(&mapping->tree_lock, flags); |
667 | __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); |
668 | } |
669 | |
670 | /* |
671 | * Add a page to the dirty page list. |
672 | * |
673 | * It is a sad fact of life that this function is called from several places |
674 | * deeply under spinlocking. It may not sleep. |
675 | * |
676 | * If the page has buffers, the uptodate buffers are set dirty, to preserve |
677 | * dirty-state coherency between the page and the buffers. It the page does |
678 | * not have buffers then when they are later attached they will all be set |
679 | * dirty. |
680 | * |
681 | * The buffers are dirtied before the page is dirtied. There's a small race |
682 | * window in which a writepage caller may see the page cleanness but not the |
683 | * buffer dirtiness. That's fine. If this code were to set the page dirty |
684 | * before the buffers, a concurrent writepage caller could clear the page dirty |
685 | * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean |
686 | * page on the dirty page list. |
687 | * |
688 | * We use private_lock to lock against try_to_free_buffers while using the |
689 | * page's buffer list. Also use this to protect against clean buffers being |
690 | * added to the page after it was set dirty. |
691 | * |
692 | * FIXME: may need to call ->reservepage here as well. That's rather up to the |
693 | * address_space though. |
694 | */ |
695 | int __set_page_dirty_buffers(struct page *page) |
696 | { |
697 | int newly_dirty; |
698 | struct address_space *mapping = page_mapping(page); |
699 | |
700 | if (unlikely(!mapping)) |
701 | return !TestSetPageDirty(page); |
702 | |
703 | spin_lock(&mapping->private_lock); |
704 | if (page_has_buffers(page)) { |
705 | struct buffer_head *head = page_buffers(page); |
706 | struct buffer_head *bh = head; |
707 | |
708 | do { |
709 | set_buffer_dirty(bh); |
710 | bh = bh->b_this_page; |
711 | } while (bh != head); |
712 | } |
713 | newly_dirty = !TestSetPageDirty(page); |
714 | spin_unlock(&mapping->private_lock); |
715 | |
716 | if (newly_dirty) |
717 | __set_page_dirty(page, mapping, 1); |
718 | return newly_dirty; |
719 | } |
720 | EXPORT_SYMBOL(__set_page_dirty_buffers); |
721 | |
722 | /* |
723 | * Write out and wait upon a list of buffers. |
724 | * |
725 | * We have conflicting pressures: we want to make sure that all |
726 | * initially dirty buffers get waited on, but that any subsequently |
727 | * dirtied buffers don't. After all, we don't want fsync to last |
728 | * forever if somebody is actively writing to the file. |
729 | * |
730 | * Do this in two main stages: first we copy dirty buffers to a |
731 | * temporary inode list, queueing the writes as we go. Then we clean |
732 | * up, waiting for those writes to complete. |
733 | * |
734 | * During this second stage, any subsequent updates to the file may end |
735 | * up refiling the buffer on the original inode's dirty list again, so |
736 | * there is a chance we will end up with a buffer queued for write but |
737 | * not yet completed on that list. So, as a final cleanup we go through |
738 | * the osync code to catch these locked, dirty buffers without requeuing |
739 | * any newly dirty buffers for write. |
740 | */ |
741 | static int fsync_buffers_list(spinlock_t *lock, struct list_head *list) |
742 | { |
743 | struct buffer_head *bh; |
744 | struct list_head tmp; |
745 | struct address_space *mapping; |
746 | int err = 0, err2; |
747 | struct blk_plug plug; |
748 | |
749 | INIT_LIST_HEAD(&tmp); |
750 | blk_start_plug(&plug); |
751 | |
752 | spin_lock(lock); |
753 | while (!list_empty(list)) { |
754 | bh = BH_ENTRY(list->next); |
755 | mapping = bh->b_assoc_map; |
756 | __remove_assoc_queue(bh); |
757 | /* Avoid race with mark_buffer_dirty_inode() which does |
758 | * a lockless check and we rely on seeing the dirty bit */ |
759 | smp_mb(); |
760 | if (buffer_dirty(bh) || buffer_locked(bh)) { |
761 | list_add(&bh->b_assoc_buffers, &tmp); |
762 | bh->b_assoc_map = mapping; |
763 | if (buffer_dirty(bh)) { |
764 | get_bh(bh); |
765 | spin_unlock(lock); |
766 | /* |
767 | * Ensure any pending I/O completes so that |
768 | * write_dirty_buffer() actually writes the |
769 | * current contents - it is a noop if I/O is |
770 | * still in flight on potentially older |
771 | * contents. |
772 | */ |
773 | write_dirty_buffer(bh, WRITE_SYNC); |
774 | |
775 | /* |
776 | * Kick off IO for the previous mapping. Note |
777 | * that we will not run the very last mapping, |
778 | * wait_on_buffer() will do that for us |
779 | * through sync_buffer(). |
780 | */ |
781 | brelse(bh); |
782 | spin_lock(lock); |
783 | } |
784 | } |
785 | } |
786 | |
787 | spin_unlock(lock); |
788 | blk_finish_plug(&plug); |
789 | spin_lock(lock); |
790 | |
791 | while (!list_empty(&tmp)) { |
792 | bh = BH_ENTRY(tmp.prev); |
793 | get_bh(bh); |
794 | mapping = bh->b_assoc_map; |
795 | __remove_assoc_queue(bh); |
796 | /* Avoid race with mark_buffer_dirty_inode() which does |
797 | * a lockless check and we rely on seeing the dirty bit */ |
798 | smp_mb(); |
799 | if (buffer_dirty(bh)) { |
800 | list_add(&bh->b_assoc_buffers, |
801 | &mapping->private_list); |
802 | bh->b_assoc_map = mapping; |
803 | } |
804 | spin_unlock(lock); |
805 | wait_on_buffer(bh); |
806 | if (!buffer_uptodate(bh)) |
807 | err = -EIO; |
808 | brelse(bh); |
809 | spin_lock(lock); |
810 | } |
811 | |
812 | spin_unlock(lock); |
813 | err2 = osync_buffers_list(lock, list); |
814 | if (err) |
815 | return err; |
816 | else |
817 | return err2; |
818 | } |
819 | |
820 | /* |
821 | * Invalidate any and all dirty buffers on a given inode. We are |
822 | * probably unmounting the fs, but that doesn't mean we have already |
823 | * done a sync(). Just drop the buffers from the inode list. |
824 | * |
825 | * NOTE: we take the inode's blockdev's mapping's private_lock. Which |
826 | * assumes that all the buffers are against the blockdev. Not true |
827 | * for reiserfs. |
828 | */ |
829 | void invalidate_inode_buffers(struct inode *inode) |
830 | { |
831 | if (inode_has_buffers(inode)) { |
832 | struct address_space *mapping = &inode->i_data; |
833 | struct list_head *list = &mapping->private_list; |
834 | struct address_space *buffer_mapping = mapping->private_data; |
835 | |
836 | spin_lock(&buffer_mapping->private_lock); |
837 | while (!list_empty(list)) |
838 | __remove_assoc_queue(BH_ENTRY(list->next)); |
839 | spin_unlock(&buffer_mapping->private_lock); |
840 | } |
841 | } |
842 | EXPORT_SYMBOL(invalidate_inode_buffers); |
843 | |
844 | /* |
845 | * Remove any clean buffers from the inode's buffer list. This is called |
846 | * when we're trying to free the inode itself. Those buffers can pin it. |
847 | * |
848 | * Returns true if all buffers were removed. |
849 | */ |
850 | int remove_inode_buffers(struct inode *inode) |
851 | { |
852 | int ret = 1; |
853 | |
854 | if (inode_has_buffers(inode)) { |
855 | struct address_space *mapping = &inode->i_data; |
856 | struct list_head *list = &mapping->private_list; |
857 | struct address_space *buffer_mapping = mapping->private_data; |
858 | |
859 | spin_lock(&buffer_mapping->private_lock); |
860 | while (!list_empty(list)) { |
861 | struct buffer_head *bh = BH_ENTRY(list->next); |
862 | if (buffer_dirty(bh)) { |
863 | ret = 0; |
864 | break; |
865 | } |
866 | __remove_assoc_queue(bh); |
867 | } |
868 | spin_unlock(&buffer_mapping->private_lock); |
869 | } |
870 | return ret; |
871 | } |
872 | |
873 | /* |
874 | * Create the appropriate buffers when given a page for data area and |
875 | * the size of each buffer.. Use the bh->b_this_page linked list to |
876 | * follow the buffers created. Return NULL if unable to create more |
877 | * buffers. |
878 | * |
879 | * The retry flag is used to differentiate async IO (paging, swapping) |
880 | * which may not fail from ordinary buffer allocations. |
881 | */ |
882 | struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size, |
883 | int retry) |
884 | { |
885 | struct buffer_head *bh, *head; |
886 | long offset; |
887 | |
888 | try_again: |
889 | head = NULL; |
890 | offset = PAGE_SIZE; |
891 | while ((offset -= size) >= 0) { |
892 | bh = alloc_buffer_head(GFP_NOFS); |
893 | if (!bh) |
894 | goto no_grow; |
895 | |
896 | bh->b_this_page = head; |
897 | bh->b_blocknr = -1; |
898 | head = bh; |
899 | |
900 | bh->b_size = size; |
901 | |
902 | /* Link the buffer to its page */ |
903 | set_bh_page(bh, page, offset); |
904 | } |
905 | return head; |
906 | /* |
907 | * In case anything failed, we just free everything we got. |
908 | */ |
909 | no_grow: |
910 | if (head) { |
911 | do { |
912 | bh = head; |
913 | head = head->b_this_page; |
914 | free_buffer_head(bh); |
915 | } while (head); |
916 | } |
917 | |
918 | /* |
919 | * Return failure for non-async IO requests. Async IO requests |
920 | * are not allowed to fail, so we have to wait until buffer heads |
921 | * become available. But we don't want tasks sleeping with |
922 | * partially complete buffers, so all were released above. |
923 | */ |
924 | if (!retry) |
925 | return NULL; |
926 | |
927 | /* We're _really_ low on memory. Now we just |
928 | * wait for old buffer heads to become free due to |
929 | * finishing IO. Since this is an async request and |
930 | * the reserve list is empty, we're sure there are |
931 | * async buffer heads in use. |
932 | */ |
933 | free_more_memory(); |
934 | goto try_again; |
935 | } |
936 | EXPORT_SYMBOL_GPL(alloc_page_buffers); |
937 | |
938 | static inline void |
939 | link_dev_buffers(struct page *page, struct buffer_head *head) |
940 | { |
941 | struct buffer_head *bh, *tail; |
942 | |
943 | bh = head; |
944 | do { |
945 | tail = bh; |
946 | bh = bh->b_this_page; |
947 | } while (bh); |
948 | tail->b_this_page = head; |
949 | attach_page_buffers(page, head); |
950 | } |
951 | |
952 | static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size) |
953 | { |
954 | sector_t retval = ~((sector_t)0); |
955 | loff_t sz = i_size_read(bdev->bd_inode); |
956 | |
957 | if (sz) { |
958 | unsigned int sizebits = blksize_bits(size); |
959 | retval = (sz >> sizebits); |
960 | } |
961 | return retval; |
962 | } |
963 | |
964 | /* |
965 | * Initialise the state of a blockdev page's buffers. |
966 | */ |
967 | static sector_t |
968 | init_page_buffers(struct page *page, struct block_device *bdev, |
969 | sector_t block, int size) |
970 | { |
971 | struct buffer_head *head = page_buffers(page); |
972 | struct buffer_head *bh = head; |
973 | int uptodate = PageUptodate(page); |
974 | sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode), size); |
975 | |
976 | do { |
977 | if (!buffer_mapped(bh)) { |
978 | init_buffer(bh, NULL, NULL); |
979 | bh->b_bdev = bdev; |
980 | bh->b_blocknr = block; |
981 | if (uptodate) |
982 | set_buffer_uptodate(bh); |
983 | if (block < end_block) |
984 | set_buffer_mapped(bh); |
985 | } |
986 | block++; |
987 | bh = bh->b_this_page; |
988 | } while (bh != head); |
989 | |
990 | /* |
991 | * Caller needs to validate requested block against end of device. |
992 | */ |
993 | return end_block; |
994 | } |
995 | |
996 | /* |
997 | * Create the page-cache page that contains the requested block. |
998 | * |
999 | * This is used purely for blockdev mappings. |
1000 | */ |
1001 | static int |
1002 | grow_dev_page(struct block_device *bdev, sector_t block, |
1003 | pgoff_t index, int size, int sizebits) |
1004 | { |
1005 | struct inode *inode = bdev->bd_inode; |
1006 | struct page *page; |
1007 | struct buffer_head *bh; |
1008 | sector_t end_block; |
1009 | int ret = 0; /* Will call free_more_memory() */ |
1010 | gfp_t gfp_mask; |
1011 | |
1012 | gfp_mask = mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS; |
1013 | gfp_mask |= __GFP_MOVABLE; |
1014 | /* |
1015 | * XXX: __getblk_slow() can not really deal with failure and |
1016 | * will endlessly loop on improvised global reclaim. Prefer |
1017 | * looping in the allocator rather than here, at least that |
1018 | * code knows what it's doing. |
1019 | */ |
1020 | gfp_mask |= __GFP_NOFAIL; |
1021 | |
1022 | page = find_or_create_page(inode->i_mapping, index, gfp_mask); |
1023 | if (!page) |
1024 | return ret; |
1025 | |
1026 | BUG_ON(!PageLocked(page)); |
1027 | |
1028 | if (page_has_buffers(page)) { |
1029 | bh = page_buffers(page); |
1030 | if (bh->b_size == size) { |
1031 | end_block = init_page_buffers(page, bdev, |
1032 | index << sizebits, size); |
1033 | goto done; |
1034 | } |
1035 | if (!try_to_free_buffers(page)) |
1036 | goto failed; |
1037 | } |
1038 | |
1039 | /* |
1040 | * Allocate some buffers for this page |
1041 | */ |
1042 | bh = alloc_page_buffers(page, size, 0); |
1043 | if (!bh) |
1044 | goto failed; |
1045 | |
1046 | /* |
1047 | * Link the page to the buffers and initialise them. Take the |
1048 | * lock to be atomic wrt __find_get_block(), which does not |
1049 | * run under the page lock. |
1050 | */ |
1051 | spin_lock(&inode->i_mapping->private_lock); |
1052 | link_dev_buffers(page, bh); |
1053 | end_block = init_page_buffers(page, bdev, index << sizebits, size); |
1054 | spin_unlock(&inode->i_mapping->private_lock); |
1055 | done: |
1056 | ret = (block < end_block) ? 1 : -ENXIO; |
1057 | failed: |
1058 | unlock_page(page); |
1059 | page_cache_release(page); |
1060 | return ret; |
1061 | } |
1062 | |
1063 | /* |
1064 | * Create buffers for the specified block device block's page. If |
1065 | * that page was dirty, the buffers are set dirty also. |
1066 | */ |
1067 | static int |
1068 | grow_buffers(struct block_device *bdev, sector_t block, int size) |
1069 | { |
1070 | pgoff_t index; |
1071 | int sizebits; |
1072 | |
1073 | sizebits = -1; |
1074 | do { |
1075 | sizebits++; |
1076 | } while ((size << sizebits) < PAGE_SIZE); |
1077 | |
1078 | index = block >> sizebits; |
1079 | |
1080 | /* |
1081 | * Check for a block which wants to lie outside our maximum possible |
1082 | * pagecache index. (this comparison is done using sector_t types). |
1083 | */ |
1084 | if (unlikely(index != block >> sizebits)) { |
1085 | char b[BDEVNAME_SIZE]; |
1086 | |
1087 | printk(KERN_ERR "%s: requested out-of-range block %llu for " |
1088 | "device %s\n", |
1089 | __func__, (unsigned long long)block, |
1090 | bdevname(bdev, b)); |
1091 | return -EIO; |
1092 | } |
1093 | |
1094 | /* Create a page with the proper size buffers.. */ |
1095 | return grow_dev_page(bdev, block, index, size, sizebits); |
1096 | } |
1097 | |
1098 | static struct buffer_head * |
1099 | __getblk_slow(struct block_device *bdev, sector_t block, int size) |
1100 | { |
1101 | /* Size must be multiple of hard sectorsize */ |
1102 | if (unlikely(size & (bdev_logical_block_size(bdev)-1) || |
1103 | (size < 512 || size > PAGE_SIZE))) { |
1104 | printk(KERN_ERR "getblk(): invalid block size %d requested\n", |
1105 | size); |
1106 | printk(KERN_ERR "logical block size: %d\n", |
1107 | bdev_logical_block_size(bdev)); |
1108 | |
1109 | dump_stack(); |
1110 | return NULL; |
1111 | } |
1112 | |
1113 | for (;;) { |
1114 | struct buffer_head *bh; |
1115 | int ret; |
1116 | |
1117 | bh = __find_get_block(bdev, block, size); |
1118 | if (bh) |
1119 | return bh; |
1120 | |
1121 | ret = grow_buffers(bdev, block, size); |
1122 | if (ret < 0) |
1123 | return NULL; |
1124 | if (ret == 0) |
1125 | free_more_memory(); |
1126 | } |
1127 | } |
1128 | |
1129 | /* |
1130 | * The relationship between dirty buffers and dirty pages: |
1131 | * |
1132 | * Whenever a page has any dirty buffers, the page's dirty bit is set, and |
1133 | * the page is tagged dirty in its radix tree. |
1134 | * |
1135 | * At all times, the dirtiness of the buffers represents the dirtiness of |
1136 | * subsections of the page. If the page has buffers, the page dirty bit is |
1137 | * merely a hint about the true dirty state. |
1138 | * |
1139 | * When a page is set dirty in its entirety, all its buffers are marked dirty |
1140 | * (if the page has buffers). |
1141 | * |
1142 | * When a buffer is marked dirty, its page is dirtied, but the page's other |
1143 | * buffers are not. |
1144 | * |
1145 | * Also. When blockdev buffers are explicitly read with bread(), they |
1146 | * individually become uptodate. But their backing page remains not |
1147 | * uptodate - even if all of its buffers are uptodate. A subsequent |
1148 | * block_read_full_page() against that page will discover all the uptodate |
1149 | * buffers, will set the page uptodate and will perform no I/O. |
1150 | */ |
1151 | |
1152 | /** |
1153 | * mark_buffer_dirty - mark a buffer_head as needing writeout |
1154 | * @bh: the buffer_head to mark dirty |
1155 | * |
1156 | * mark_buffer_dirty() will set the dirty bit against the buffer, then set its |
1157 | * backing page dirty, then tag the page as dirty in its address_space's radix |
1158 | * tree and then attach the address_space's inode to its superblock's dirty |
1159 | * inode list. |
1160 | * |
1161 | * mark_buffer_dirty() is atomic. It takes bh->b_page->mapping->private_lock, |
1162 | * mapping->tree_lock and mapping->host->i_lock. |
1163 | */ |
1164 | void mark_buffer_dirty(struct buffer_head *bh) |
1165 | { |
1166 | WARN_ON_ONCE(!buffer_uptodate(bh)); |
1167 | |
1168 | trace_block_dirty_buffer(bh); |
1169 | |
1170 | /* |
1171 | * Very *carefully* optimize the it-is-already-dirty case. |
1172 | * |
1173 | * Don't let the final "is it dirty" escape to before we |
1174 | * perhaps modified the buffer. |
1175 | */ |
1176 | if (buffer_dirty(bh)) { |
1177 | smp_mb(); |
1178 | if (buffer_dirty(bh)) |
1179 | return; |
1180 | } |
1181 | |
1182 | if (!test_set_buffer_dirty(bh)) { |
1183 | struct page *page = bh->b_page; |
1184 | if (!TestSetPageDirty(page)) { |
1185 | struct address_space *mapping = page_mapping(page); |
1186 | if (mapping) |
1187 | __set_page_dirty(page, mapping, 0); |
1188 | } |
1189 | } |
1190 | } |
1191 | EXPORT_SYMBOL(mark_buffer_dirty); |
1192 | |
1193 | /* |
1194 | * Decrement a buffer_head's reference count. If all buffers against a page |
1195 | * have zero reference count, are clean and unlocked, and if the page is clean |
1196 | * and unlocked then try_to_free_buffers() may strip the buffers from the page |
1197 | * in preparation for freeing it (sometimes, rarely, buffers are removed from |
1198 | * a page but it ends up not being freed, and buffers may later be reattached). |
1199 | */ |
1200 | void __brelse(struct buffer_head * buf) |
1201 | { |
1202 | if (atomic_read(&buf->b_count)) { |
1203 | put_bh(buf); |
1204 | return; |
1205 | } |
1206 | WARN(1, KERN_ERR "VFS: brelse: Trying to free free buffer\n"); |
1207 | } |
1208 | EXPORT_SYMBOL(__brelse); |
1209 | |
1210 | /* |
1211 | * bforget() is like brelse(), except it discards any |
1212 | * potentially dirty data. |
1213 | */ |
1214 | void __bforget(struct buffer_head *bh) |
1215 | { |
1216 | clear_buffer_dirty(bh); |
1217 | if (bh->b_assoc_map) { |
1218 | struct address_space *buffer_mapping = bh->b_page->mapping; |
1219 | |
1220 | spin_lock(&buffer_mapping->private_lock); |
1221 | list_del_init(&bh->b_assoc_buffers); |
1222 | bh->b_assoc_map = NULL; |
1223 | spin_unlock(&buffer_mapping->private_lock); |
1224 | } |
1225 | __brelse(bh); |
1226 | } |
1227 | EXPORT_SYMBOL(__bforget); |
1228 | |
1229 | static struct buffer_head *__bread_slow(struct buffer_head *bh) |
1230 | { |
1231 | lock_buffer(bh); |
1232 | if (buffer_uptodate(bh)) { |
1233 | unlock_buffer(bh); |
1234 | return bh; |
1235 | } else { |
1236 | get_bh(bh); |
1237 | bh->b_end_io = end_buffer_read_sync; |
1238 | submit_bh(READ, bh); |
1239 | wait_on_buffer(bh); |
1240 | if (buffer_uptodate(bh)) |
1241 | return bh; |
1242 | } |
1243 | brelse(bh); |
1244 | return NULL; |
1245 | } |
1246 | |
1247 | /* |
1248 | * Per-cpu buffer LRU implementation. To reduce the cost of __find_get_block(). |
1249 | * The bhs[] array is sorted - newest buffer is at bhs[0]. Buffers have their |
1250 | * refcount elevated by one when they're in an LRU. A buffer can only appear |
1251 | * once in a particular CPU's LRU. A single buffer can be present in multiple |
1252 | * CPU's LRUs at the same time. |
1253 | * |
1254 | * This is a transparent caching front-end to sb_bread(), sb_getblk() and |
1255 | * sb_find_get_block(). |
1256 | * |
1257 | * The LRUs themselves only need locking against invalidate_bh_lrus. We use |
1258 | * a local interrupt disable for that. |
1259 | */ |
1260 | |
1261 | #define BH_LRU_SIZE 8 |
1262 | |
1263 | struct bh_lru { |
1264 | struct buffer_head *bhs[BH_LRU_SIZE]; |
1265 | }; |
1266 | |
1267 | static DEFINE_PER_CPU(struct bh_lru, bh_lrus) = {{ NULL }}; |
1268 | |
1269 | #ifdef CONFIG_SMP |
1270 | #define bh_lru_lock() local_irq_disable() |
1271 | #define bh_lru_unlock() local_irq_enable() |
1272 | #else |
1273 | #define bh_lru_lock() preempt_disable() |
1274 | #define bh_lru_unlock() preempt_enable() |
1275 | #endif |
1276 | |
1277 | static inline void check_irqs_on(void) |
1278 | { |
1279 | #ifdef irqs_disabled |
1280 | BUG_ON(irqs_disabled()); |
1281 | #endif |
1282 | } |
1283 | |
1284 | /* |
1285 | * The LRU management algorithm is dopey-but-simple. Sorry. |
1286 | */ |
1287 | static void bh_lru_install(struct buffer_head *bh) |
1288 | { |
1289 | struct buffer_head *evictee = NULL; |
1290 | |
1291 | check_irqs_on(); |
1292 | bh_lru_lock(); |
1293 | if (__this_cpu_read(bh_lrus.bhs[0]) != bh) { |
1294 | struct buffer_head *bhs[BH_LRU_SIZE]; |
1295 | int in; |
1296 | int out = 0; |
1297 | |
1298 | get_bh(bh); |
1299 | bhs[out++] = bh; |
1300 | for (in = 0; in < BH_LRU_SIZE; in++) { |
1301 | struct buffer_head *bh2 = |
1302 | __this_cpu_read(bh_lrus.bhs[in]); |
1303 | |
1304 | if (bh2 == bh) { |
1305 | __brelse(bh2); |
1306 | } else { |
1307 | if (out >= BH_LRU_SIZE) { |
1308 | BUG_ON(evictee != NULL); |
1309 | evictee = bh2; |
1310 | } else { |
1311 | bhs[out++] = bh2; |
1312 | } |
1313 | } |
1314 | } |
1315 | while (out < BH_LRU_SIZE) |
1316 | bhs[out++] = NULL; |
1317 | memcpy(this_cpu_ptr(&bh_lrus.bhs), bhs, sizeof(bhs)); |
1318 | } |
1319 | bh_lru_unlock(); |
1320 | |
1321 | if (evictee) |
1322 | __brelse(evictee); |
1323 | } |
1324 | |
1325 | /* |
1326 | * Look up the bh in this cpu's LRU. If it's there, move it to the head. |
1327 | */ |
1328 | static struct buffer_head * |
1329 | lookup_bh_lru(struct block_device *bdev, sector_t block, unsigned size) |
1330 | { |
1331 | struct buffer_head *ret = NULL; |
1332 | unsigned int i; |
1333 | |
1334 | check_irqs_on(); |
1335 | bh_lru_lock(); |
1336 | for (i = 0; i < BH_LRU_SIZE; i++) { |
1337 | struct buffer_head *bh = __this_cpu_read(bh_lrus.bhs[i]); |
1338 | |
1339 | if (bh && bh->b_bdev == bdev && |
1340 | bh->b_blocknr == block && bh->b_size == size) { |
1341 | if (i) { |
1342 | while (i) { |
1343 | __this_cpu_write(bh_lrus.bhs[i], |
1344 | __this_cpu_read(bh_lrus.bhs[i - 1])); |
1345 | i--; |
1346 | } |
1347 | __this_cpu_write(bh_lrus.bhs[0], bh); |
1348 | } |
1349 | get_bh(bh); |
1350 | ret = bh; |
1351 | break; |
1352 | } |
1353 | } |
1354 | bh_lru_unlock(); |
1355 | return ret; |
1356 | } |
1357 | |
1358 | /* |
1359 | * Perform a pagecache lookup for the matching buffer. If it's there, refresh |
1360 | * it in the LRU and mark it as accessed. If it is not present then return |
1361 | * NULL |
1362 | */ |
1363 | struct buffer_head * |
1364 | __find_get_block(struct block_device *bdev, sector_t block, unsigned size) |
1365 | { |
1366 | struct buffer_head *bh = lookup_bh_lru(bdev, block, size); |
1367 | |
1368 | if (bh == NULL) { |
1369 | /* __find_get_block_slow will mark the page accessed */ |
1370 | bh = __find_get_block_slow(bdev, block); |
1371 | if (bh) |
1372 | bh_lru_install(bh); |
1373 | } else |
1374 | touch_buffer(bh); |
1375 | |
1376 | return bh; |
1377 | } |
1378 | EXPORT_SYMBOL(__find_get_block); |
1379 | |
1380 | /* |
1381 | * __getblk will locate (and, if necessary, create) the buffer_head |
1382 | * which corresponds to the passed block_device, block and size. The |
1383 | * returned buffer has its reference count incremented. |
1384 | * |
1385 | * __getblk() will lock up the machine if grow_dev_page's try_to_free_buffers() |
1386 | * attempt is failing. FIXME, perhaps? |
1387 | */ |
1388 | struct buffer_head * |
1389 | __getblk(struct block_device *bdev, sector_t block, unsigned size) |
1390 | { |
1391 | struct buffer_head *bh = __find_get_block(bdev, block, size); |
1392 | |
1393 | might_sleep(); |
1394 | if (bh == NULL) |
1395 | bh = __getblk_slow(bdev, block, size); |
1396 | return bh; |
1397 | } |
1398 | EXPORT_SYMBOL(__getblk); |
1399 | |
1400 | /* |
1401 | * Do async read-ahead on a buffer.. |
1402 | */ |
1403 | void __breadahead(struct block_device *bdev, sector_t block, unsigned size) |
1404 | { |
1405 | struct buffer_head *bh = __getblk(bdev, block, size); |
1406 | if (likely(bh)) { |
1407 | ll_rw_block(READA, 1, &bh); |
1408 | brelse(bh); |
1409 | } |
1410 | } |
1411 | EXPORT_SYMBOL(__breadahead); |
1412 | |
1413 | /** |
1414 | * __bread() - reads a specified block and returns the bh |
1415 | * @bdev: the block_device to read from |
1416 | * @block: number of block |
1417 | * @size: size (in bytes) to read |
1418 | * |
1419 | * Reads a specified block, and returns buffer head that contains it. |
1420 | * It returns NULL if the block was unreadable. |
1421 | */ |
1422 | struct buffer_head * |
1423 | __bread(struct block_device *bdev, sector_t block, unsigned size) |
1424 | { |
1425 | struct buffer_head *bh = __getblk(bdev, block, size); |
1426 | |
1427 | if (likely(bh) && !buffer_uptodate(bh)) |
1428 | bh = __bread_slow(bh); |
1429 | return bh; |
1430 | } |
1431 | EXPORT_SYMBOL(__bread); |
1432 | |
1433 | /* |
1434 | * invalidate_bh_lrus() is called rarely - but not only at unmount. |
1435 | * This doesn't race because it runs in each cpu either in irq |
1436 | * or with preempt disabled. |
1437 | */ |
1438 | static void invalidate_bh_lru(void *arg) |
1439 | { |
1440 | struct bh_lru *b = &get_cpu_var(bh_lrus); |
1441 | int i; |
1442 | |
1443 | for (i = 0; i < BH_LRU_SIZE; i++) { |
1444 | brelse(b->bhs[i]); |
1445 | b->bhs[i] = NULL; |
1446 | } |
1447 | put_cpu_var(bh_lrus); |
1448 | } |
1449 | |
1450 | static bool has_bh_in_lru(int cpu, void *dummy) |
1451 | { |
1452 | struct bh_lru *b = per_cpu_ptr(&bh_lrus, cpu); |
1453 | int i; |
1454 | |
1455 | for (i = 0; i < BH_LRU_SIZE; i++) { |
1456 | if (b->bhs[i]) |
1457 | return 1; |
1458 | } |
1459 | |
1460 | return 0; |
1461 | } |
1462 | |
1463 | void invalidate_bh_lrus(void) |
1464 | { |
1465 | on_each_cpu_cond(has_bh_in_lru, invalidate_bh_lru, NULL, 1, GFP_KERNEL); |
1466 | } |
1467 | EXPORT_SYMBOL_GPL(invalidate_bh_lrus); |
1468 | |
1469 | void set_bh_page(struct buffer_head *bh, |
1470 | struct page *page, unsigned long offset) |
1471 | { |
1472 | bh->b_page = page; |
1473 | BUG_ON(offset >= PAGE_SIZE); |
1474 | if (PageHighMem(page)) |
1475 | /* |
1476 | * This catches illegal uses and preserves the offset: |
1477 | */ |
1478 | bh->b_data = (char *)(0 + offset); |
1479 | else |
1480 | bh->b_data = page_address(page) + offset; |
1481 | } |
1482 | EXPORT_SYMBOL(set_bh_page); |
1483 | |
1484 | /* |
1485 | * Called when truncating a buffer on a page completely. |
1486 | */ |
1487 | |
1488 | /* Bits that are cleared during an invalidate */ |
1489 | #define BUFFER_FLAGS_DISCARD \ |
1490 | (1 << BH_Mapped | 1 << BH_New | 1 << BH_Req | \ |
1491 | 1 << BH_Delay | 1 << BH_Unwritten) |
1492 | |
1493 | static void discard_buffer(struct buffer_head * bh) |
1494 | { |
1495 | unsigned long b_state, b_state_old; |
1496 | |
1497 | lock_buffer(bh); |
1498 | clear_buffer_dirty(bh); |
1499 | bh->b_bdev = NULL; |
1500 | b_state = bh->b_state; |
1501 | for (;;) { |
1502 | b_state_old = cmpxchg(&bh->b_state, b_state, |
1503 | (b_state & ~BUFFER_FLAGS_DISCARD)); |
1504 | if (b_state_old == b_state) |
1505 | break; |
1506 | b_state = b_state_old; |
1507 | } |
1508 | unlock_buffer(bh); |
1509 | } |
1510 | |
1511 | /** |
1512 | * block_invalidatepage - invalidate part or all of a buffer-backed page |
1513 | * |
1514 | * @page: the page which is affected |
1515 | * @offset: start of the range to invalidate |
1516 | * @length: length of the range to invalidate |
1517 | * |
1518 | * block_invalidatepage() is called when all or part of the page has become |
1519 | * invalidated by a truncate operation. |
1520 | * |
1521 | * block_invalidatepage() does not have to release all buffers, but it must |
1522 | * ensure that no dirty buffer is left outside @offset and that no I/O |
1523 | * is underway against any of the blocks which are outside the truncation |
1524 | * point. Because the caller is about to free (and possibly reuse) those |
1525 | * blocks on-disk. |
1526 | */ |
1527 | void block_invalidatepage(struct page *page, unsigned int offset, |
1528 | unsigned int length) |
1529 | { |
1530 | struct buffer_head *head, *bh, *next; |
1531 | unsigned int curr_off = 0; |
1532 | unsigned int stop = length + offset; |
1533 | |
1534 | BUG_ON(!PageLocked(page)); |
1535 | if (!page_has_buffers(page)) |
1536 | goto out; |
1537 | |
1538 | /* |
1539 | * Check for overflow |
1540 | */ |
1541 | BUG_ON(stop > PAGE_CACHE_SIZE || stop < length); |
1542 | |
1543 | head = page_buffers(page); |
1544 | bh = head; |
1545 | do { |
1546 | unsigned int next_off = curr_off + bh->b_size; |
1547 | next = bh->b_this_page; |
1548 | |
1549 | /* |
1550 | * Are we still fully in range ? |
1551 | */ |
1552 | if (next_off > stop) |
1553 | goto out; |
1554 | |
1555 | /* |
1556 | * is this block fully invalidated? |
1557 | */ |
1558 | if (offset <= curr_off) |
1559 | discard_buffer(bh); |
1560 | curr_off = next_off; |
1561 | bh = next; |
1562 | } while (bh != head); |
1563 | |
1564 | /* |
1565 | * We release buffers only if the entire page is being invalidated. |
1566 | * The get_block cached value has been unconditionally invalidated, |
1567 | * so real IO is not possible anymore. |
1568 | */ |
1569 | if (offset == 0) |
1570 | try_to_release_page(page, 0); |
1571 | out: |
1572 | return; |
1573 | } |
1574 | EXPORT_SYMBOL(block_invalidatepage); |
1575 | |
1576 | |
1577 | /* |
1578 | * We attach and possibly dirty the buffers atomically wrt |
1579 | * __set_page_dirty_buffers() via private_lock. try_to_free_buffers |
1580 | * is already excluded via the page lock. |
1581 | */ |
1582 | void create_empty_buffers(struct page *page, |
1583 | unsigned long blocksize, unsigned long b_state) |
1584 | { |
1585 | struct buffer_head *bh, *head, *tail; |
1586 | |
1587 | head = alloc_page_buffers(page, blocksize, 1); |
1588 | bh = head; |
1589 | do { |
1590 | bh->b_state |= b_state; |
1591 | tail = bh; |
1592 | bh = bh->b_this_page; |
1593 | } while (bh); |
1594 | tail->b_this_page = head; |
1595 | |
1596 | spin_lock(&page->mapping->private_lock); |
1597 | if (PageUptodate(page) || PageDirty(page)) { |
1598 | bh = head; |
1599 | do { |
1600 | if (PageDirty(page)) |
1601 | set_buffer_dirty(bh); |
1602 | if (PageUptodate(page)) |
1603 | set_buffer_uptodate(bh); |
1604 | bh = bh->b_this_page; |
1605 | } while (bh != head); |
1606 | } |
1607 | attach_page_buffers(page, head); |
1608 | spin_unlock(&page->mapping->private_lock); |
1609 | } |
1610 | EXPORT_SYMBOL(create_empty_buffers); |
1611 | |
1612 | /* |
1613 | * We are taking a block for data and we don't want any output from any |
1614 | * buffer-cache aliases starting from return from that function and |
1615 | * until the moment when something will explicitly mark the buffer |
1616 | * dirty (hopefully that will not happen until we will free that block ;-) |
1617 | * We don't even need to mark it not-uptodate - nobody can expect |
1618 | * anything from a newly allocated buffer anyway. We used to used |
1619 | * unmap_buffer() for such invalidation, but that was wrong. We definitely |
1620 | * don't want to mark the alias unmapped, for example - it would confuse |
1621 | * anyone who might pick it with bread() afterwards... |
1622 | * |
1623 | * Also.. Note that bforget() doesn't lock the buffer. So there can |
1624 | * be writeout I/O going on against recently-freed buffers. We don't |
1625 | * wait on that I/O in bforget() - it's more efficient to wait on the I/O |
1626 | * only if we really need to. That happens here. |
1627 | */ |
1628 | void unmap_underlying_metadata(struct block_device *bdev, sector_t block) |
1629 | { |
1630 | struct buffer_head *old_bh; |
1631 | |
1632 | might_sleep(); |
1633 | |
1634 | old_bh = __find_get_block_slow(bdev, block); |
1635 | if (old_bh) { |
1636 | clear_buffer_dirty(old_bh); |
1637 | wait_on_buffer(old_bh); |
1638 | clear_buffer_req(old_bh); |
1639 | __brelse(old_bh); |
1640 | } |
1641 | } |
1642 | EXPORT_SYMBOL(unmap_underlying_metadata); |
1643 | |
1644 | /* |
1645 | * Size is a power-of-two in the range 512..PAGE_SIZE, |
1646 | * and the case we care about most is PAGE_SIZE. |
1647 | * |
1648 | * So this *could* possibly be written with those |
1649 | * constraints in mind (relevant mostly if some |
1650 | * architecture has a slow bit-scan instruction) |
1651 | */ |
1652 | static inline int block_size_bits(unsigned int blocksize) |
1653 | { |
1654 | return ilog2(blocksize); |
1655 | } |
1656 | |
1657 | static struct buffer_head *create_page_buffers(struct page *page, struct inode *inode, unsigned int b_state) |
1658 | { |
1659 | BUG_ON(!PageLocked(page)); |
1660 | |
1661 | if (!page_has_buffers(page)) |
1662 | create_empty_buffers(page, 1 << ACCESS_ONCE(inode->i_blkbits), b_state); |
1663 | return page_buffers(page); |
1664 | } |
1665 | |
1666 | /* |
1667 | * NOTE! All mapped/uptodate combinations are valid: |
1668 | * |
1669 | * Mapped Uptodate Meaning |
1670 | * |
1671 | * No No "unknown" - must do get_block() |
1672 | * No Yes "hole" - zero-filled |
1673 | * Yes No "allocated" - allocated on disk, not read in |
1674 | * Yes Yes "valid" - allocated and up-to-date in memory. |
1675 | * |
1676 | * "Dirty" is valid only with the last case (mapped+uptodate). |
1677 | */ |
1678 | |
1679 | /* |
1680 | * While block_write_full_page is writing back the dirty buffers under |
1681 | * the page lock, whoever dirtied the buffers may decide to clean them |
1682 | * again at any time. We handle that by only looking at the buffer |
1683 | * state inside lock_buffer(). |
1684 | * |
1685 | * If block_write_full_page() is called for regular writeback |
1686 | * (wbc->sync_mode == WB_SYNC_NONE) then it will redirty a page which has a |
1687 | * locked buffer. This only can happen if someone has written the buffer |
1688 | * directly, with submit_bh(). At the address_space level PageWriteback |
1689 | * prevents this contention from occurring. |
1690 | * |
1691 | * If block_write_full_page() is called with wbc->sync_mode == |
1692 | * WB_SYNC_ALL, the writes are posted using WRITE_SYNC; this |
1693 | * causes the writes to be flagged as synchronous writes. |
1694 | */ |
1695 | static int __block_write_full_page(struct inode *inode, struct page *page, |
1696 | get_block_t *get_block, struct writeback_control *wbc, |
1697 | bh_end_io_t *handler) |
1698 | { |
1699 | int err; |
1700 | sector_t block; |
1701 | sector_t last_block; |
1702 | struct buffer_head *bh, *head; |
1703 | unsigned int blocksize, bbits; |
1704 | int nr_underway = 0; |
1705 | int write_op = (wbc->sync_mode == WB_SYNC_ALL ? |
1706 | WRITE_SYNC : WRITE); |
1707 | |
1708 | head = create_page_buffers(page, inode, |
1709 | (1 << BH_Dirty)|(1 << BH_Uptodate)); |
1710 | |
1711 | /* |
1712 | * Be very careful. We have no exclusion from __set_page_dirty_buffers |
1713 | * here, and the (potentially unmapped) buffers may become dirty at |
1714 | * any time. If a buffer becomes dirty here after we've inspected it |
1715 | * then we just miss that fact, and the page stays dirty. |
1716 | * |
1717 | * Buffers outside i_size may be dirtied by __set_page_dirty_buffers; |
1718 | * handle that here by just cleaning them. |
1719 | */ |
1720 | |
1721 | bh = head; |
1722 | blocksize = bh->b_size; |
1723 | bbits = block_size_bits(blocksize); |
1724 | |
1725 | block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); |
1726 | last_block = (i_size_read(inode) - 1) >> bbits; |
1727 | |
1728 | /* |
1729 | * Get all the dirty buffers mapped to disk addresses and |
1730 | * handle any aliases from the underlying blockdev's mapping. |
1731 | */ |
1732 | do { |
1733 | if (block > last_block) { |
1734 | /* |
1735 | * mapped buffers outside i_size will occur, because |
1736 | * this page can be outside i_size when there is a |
1737 | * truncate in progress. |
1738 | */ |
1739 | /* |
1740 | * The buffer was zeroed by block_write_full_page() |
1741 | */ |
1742 | clear_buffer_dirty(bh); |
1743 | set_buffer_uptodate(bh); |
1744 | } else if ((!buffer_mapped(bh) || buffer_delay(bh)) && |
1745 | buffer_dirty(bh)) { |
1746 | WARN_ON(bh->b_size != blocksize); |
1747 | err = get_block(inode, block, bh, 1); |
1748 | if (err) |
1749 | goto recover; |
1750 | clear_buffer_delay(bh); |
1751 | if (buffer_new(bh)) { |
1752 | /* blockdev mappings never come here */ |
1753 | clear_buffer_new(bh); |
1754 | unmap_underlying_metadata(bh->b_bdev, |
1755 | bh->b_blocknr); |
1756 | } |
1757 | } |
1758 | bh = bh->b_this_page; |
1759 | block++; |
1760 | } while (bh != head); |
1761 | |
1762 | do { |
1763 | if (!buffer_mapped(bh)) |
1764 | continue; |
1765 | /* |
1766 | * If it's a fully non-blocking write attempt and we cannot |
1767 | * lock the buffer then redirty the page. Note that this can |
1768 | * potentially cause a busy-wait loop from writeback threads |
1769 | * and kswapd activity, but those code paths have their own |
1770 | * higher-level throttling. |
1771 | */ |
1772 | if (wbc->sync_mode != WB_SYNC_NONE) { |
1773 | lock_buffer(bh); |
1774 | } else if (!trylock_buffer(bh)) { |
1775 | redirty_page_for_writepage(wbc, page); |
1776 | continue; |
1777 | } |
1778 | if (test_clear_buffer_dirty(bh)) { |
1779 | mark_buffer_async_write_endio(bh, handler); |
1780 | } else { |
1781 | unlock_buffer(bh); |
1782 | } |
1783 | } while ((bh = bh->b_this_page) != head); |
1784 | |
1785 | /* |
1786 | * The page and its buffers are protected by PageWriteback(), so we can |
1787 | * drop the bh refcounts early. |
1788 | */ |
1789 | BUG_ON(PageWriteback(page)); |
1790 | set_page_writeback(page); |
1791 | |
1792 | do { |
1793 | struct buffer_head *next = bh->b_this_page; |
1794 | if (buffer_async_write(bh)) { |
1795 | submit_bh(write_op, bh); |
1796 | nr_underway++; |
1797 | } |
1798 | bh = next; |
1799 | } while (bh != head); |
1800 | unlock_page(page); |
1801 | |
1802 | err = 0; |
1803 | done: |
1804 | if (nr_underway == 0) { |
1805 | /* |
1806 | * The page was marked dirty, but the buffers were |
1807 | * clean. Someone wrote them back by hand with |
1808 | * ll_rw_block/submit_bh. A rare case. |
1809 | */ |
1810 | end_page_writeback(page); |
1811 | |
1812 | /* |
1813 | * The page and buffer_heads can be released at any time from |
1814 | * here on. |
1815 | */ |
1816 | } |
1817 | return err; |
1818 | |
1819 | recover: |
1820 | /* |
1821 | * ENOSPC, or some other error. We may already have added some |
1822 | * blocks to the file, so we need to write these out to avoid |
1823 | * exposing stale data. |
1824 | * The page is currently locked and not marked for writeback |
1825 | */ |
1826 | bh = head; |
1827 | /* Recovery: lock and submit the mapped buffers */ |
1828 | do { |
1829 | if (buffer_mapped(bh) && buffer_dirty(bh) && |
1830 | !buffer_delay(bh)) { |
1831 | lock_buffer(bh); |
1832 | mark_buffer_async_write_endio(bh, handler); |
1833 | } else { |
1834 | /* |
1835 | * The buffer may have been set dirty during |
1836 | * attachment to a dirty page. |
1837 | */ |
1838 | clear_buffer_dirty(bh); |
1839 | } |
1840 | } while ((bh = bh->b_this_page) != head); |
1841 | SetPageError(page); |
1842 | BUG_ON(PageWriteback(page)); |
1843 | mapping_set_error(page->mapping, err); |
1844 | set_page_writeback(page); |
1845 | do { |
1846 | struct buffer_head *next = bh->b_this_page; |
1847 | if (buffer_async_write(bh)) { |
1848 | clear_buffer_dirty(bh); |
1849 | submit_bh(write_op, bh); |
1850 | nr_underway++; |
1851 | } |
1852 | bh = next; |
1853 | } while (bh != head); |
1854 | unlock_page(page); |
1855 | goto done; |
1856 | } |
1857 | |
1858 | /* |
1859 | * If a page has any new buffers, zero them out here, and mark them uptodate |
1860 | * and dirty so they'll be written out (in order to prevent uninitialised |
1861 | * block data from leaking). And clear the new bit. |
1862 | */ |
1863 | void page_zero_new_buffers(struct page *page, unsigned from, unsigned to) |
1864 | { |
1865 | unsigned int block_start, block_end; |
1866 | struct buffer_head *head, *bh; |
1867 | |
1868 | BUG_ON(!PageLocked(page)); |
1869 | if (!page_has_buffers(page)) |
1870 | return; |
1871 | |
1872 | bh = head = page_buffers(page); |
1873 | block_start = 0; |
1874 | do { |
1875 | block_end = block_start + bh->b_size; |
1876 | |
1877 | if (buffer_new(bh)) { |
1878 | if (block_end > from && block_start < to) { |
1879 | if (!PageUptodate(page)) { |
1880 | unsigned start, size; |
1881 | |
1882 | start = max(from, block_start); |
1883 | size = min(to, block_end) - start; |
1884 | |
1885 | zero_user(page, start, size); |
1886 | set_buffer_uptodate(bh); |
1887 | } |
1888 | |
1889 | clear_buffer_new(bh); |
1890 | mark_buffer_dirty(bh); |
1891 | } |
1892 | } |
1893 | |
1894 | block_start = block_end; |
1895 | bh = bh->b_this_page; |
1896 | } while (bh != head); |
1897 | } |
1898 | EXPORT_SYMBOL(page_zero_new_buffers); |
1899 | |
1900 | int __block_write_begin(struct page *page, loff_t pos, unsigned len, |
1901 | get_block_t *get_block) |
1902 | { |
1903 | unsigned from = pos & (PAGE_CACHE_SIZE - 1); |
1904 | unsigned to = from + len; |
1905 | struct inode *inode = page->mapping->host; |
1906 | unsigned block_start, block_end; |
1907 | sector_t block; |
1908 | int err = 0; |
1909 | unsigned blocksize, bbits; |
1910 | struct buffer_head *bh, *head, *wait[2], **wait_bh=wait; |
1911 | |
1912 | BUG_ON(!PageLocked(page)); |
1913 | BUG_ON(from > PAGE_CACHE_SIZE); |
1914 | BUG_ON(to > PAGE_CACHE_SIZE); |
1915 | BUG_ON(from > to); |
1916 | |
1917 | head = create_page_buffers(page, inode, 0); |
1918 | blocksize = head->b_size; |
1919 | bbits = block_size_bits(blocksize); |
1920 | |
1921 | block = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); |
1922 | |
1923 | for(bh = head, block_start = 0; bh != head || !block_start; |
1924 | block++, block_start=block_end, bh = bh->b_this_page) { |
1925 | block_end = block_start + blocksize; |
1926 | if (block_end <= from || block_start >= to) { |
1927 | if (PageUptodate(page)) { |
1928 | if (!buffer_uptodate(bh)) |
1929 | set_buffer_uptodate(bh); |
1930 | } |
1931 | continue; |
1932 | } |
1933 | if (buffer_new(bh)) |
1934 | clear_buffer_new(bh); |
1935 | if (!buffer_mapped(bh)) { |
1936 | WARN_ON(bh->b_size != blocksize); |
1937 | err = get_block(inode, block, bh, 1); |
1938 | if (err) |
1939 | break; |
1940 | if (buffer_new(bh)) { |
1941 | unmap_underlying_metadata(bh->b_bdev, |
1942 | bh->b_blocknr); |
1943 | if (PageUptodate(page)) { |
1944 | clear_buffer_new(bh); |
1945 | set_buffer_uptodate(bh); |
1946 | mark_buffer_dirty(bh); |
1947 | continue; |
1948 | } |
1949 | if (block_end > to || block_start < from) |
1950 | zero_user_segments(page, |
1951 | to, block_end, |
1952 | block_start, from); |
1953 | continue; |
1954 | } |
1955 | } |
1956 | if (PageUptodate(page)) { |
1957 | if (!buffer_uptodate(bh)) |
1958 | set_buffer_uptodate(bh); |
1959 | continue; |
1960 | } |
1961 | if (!buffer_uptodate(bh) && !buffer_delay(bh) && |
1962 | !buffer_unwritten(bh) && |
1963 | (block_start < from || block_end > to)) { |
1964 | ll_rw_block(READ, 1, &bh); |
1965 | *wait_bh++=bh; |
1966 | } |
1967 | } |
1968 | /* |
1969 | * If we issued read requests - let them complete. |
1970 | */ |
1971 | while(wait_bh > wait) { |
1972 | wait_on_buffer(*--wait_bh); |
1973 | if (!buffer_uptodate(*wait_bh)) |
1974 | err = -EIO; |
1975 | } |
1976 | if (unlikely(err)) |
1977 | page_zero_new_buffers(page, from, to); |
1978 | return err; |
1979 | } |
1980 | EXPORT_SYMBOL(__block_write_begin); |
1981 | |
1982 | static int __block_commit_write(struct inode *inode, struct page *page, |
1983 | unsigned from, unsigned to) |
1984 | { |
1985 | unsigned block_start, block_end; |
1986 | int partial = 0; |
1987 | unsigned blocksize; |
1988 | struct buffer_head *bh, *head; |
1989 | |
1990 | bh = head = page_buffers(page); |
1991 | blocksize = bh->b_size; |
1992 | |
1993 | block_start = 0; |
1994 | do { |
1995 | block_end = block_start + blocksize; |
1996 | if (block_end <= from || block_start >= to) { |
1997 | if (!buffer_uptodate(bh)) |
1998 | partial = 1; |
1999 | } else { |
2000 | set_buffer_uptodate(bh); |
2001 | mark_buffer_dirty(bh); |
2002 | } |
2003 | clear_buffer_new(bh); |
2004 | |
2005 | block_start = block_end; |
2006 | bh = bh->b_this_page; |
2007 | } while (bh != head); |
2008 | |
2009 | /* |
2010 | * If this is a partial write which happened to make all buffers |
2011 | * uptodate then we can optimize away a bogus readpage() for |
2012 | * the next read(). Here we 'discover' whether the page went |
2013 | * uptodate as a result of this (potentially partial) write. |
2014 | */ |
2015 | if (!partial) |
2016 | SetPageUptodate(page); |
2017 | return 0; |
2018 | } |
2019 | |
2020 | /* |
2021 | * block_write_begin takes care of the basic task of block allocation and |
2022 | * bringing partial write blocks uptodate first. |
2023 | * |
2024 | * The filesystem needs to handle block truncation upon failure. |
2025 | */ |
2026 | int block_write_begin(struct address_space *mapping, loff_t pos, unsigned len, |
2027 | unsigned flags, struct page **pagep, get_block_t *get_block) |
2028 | { |
2029 | pgoff_t index = pos >> PAGE_CACHE_SHIFT; |
2030 | struct page *page; |
2031 | int status; |
2032 | |
2033 | page = grab_cache_page_write_begin(mapping, index, flags); |
2034 | if (!page) |
2035 | return -ENOMEM; |
2036 | |
2037 | status = __block_write_begin(page, pos, len, get_block); |
2038 | if (unlikely(status)) { |
2039 | unlock_page(page); |
2040 | page_cache_release(page); |
2041 | page = NULL; |
2042 | } |
2043 | |
2044 | *pagep = page; |
2045 | return status; |
2046 | } |
2047 | EXPORT_SYMBOL(block_write_begin); |
2048 | |
2049 | int block_write_end(struct file *file, struct address_space *mapping, |
2050 | loff_t pos, unsigned len, unsigned copied, |
2051 | struct page *page, void *fsdata) |
2052 | { |
2053 | struct inode *inode = mapping->host; |
2054 | unsigned start; |
2055 | |
2056 | start = pos & (PAGE_CACHE_SIZE - 1); |
2057 | |
2058 | if (unlikely(copied < len)) { |
2059 | /* |
2060 | * The buffers that were written will now be uptodate, so we |
2061 | * don't have to worry about a readpage reading them and |
2062 | * overwriting a partial write. However if we have encountered |
2063 | * a short write and only partially written into a buffer, it |
2064 | * will not be marked uptodate, so a readpage might come in and |
2065 | * destroy our partial write. |
2066 | * |
2067 | * Do the simplest thing, and just treat any short write to a |
2068 | * non uptodate page as a zero-length write, and force the |
2069 | * caller to redo the whole thing. |
2070 | */ |
2071 | if (!PageUptodate(page)) |
2072 | copied = 0; |
2073 | |
2074 | page_zero_new_buffers(page, start+copied, start+len); |
2075 | } |
2076 | flush_dcache_page(page); |
2077 | |
2078 | /* This could be a short (even 0-length) commit */ |
2079 | __block_commit_write(inode, page, start, start+copied); |
2080 | |
2081 | return copied; |
2082 | } |
2083 | EXPORT_SYMBOL(block_write_end); |
2084 | |
2085 | int generic_write_end(struct file *file, struct address_space *mapping, |
2086 | loff_t pos, unsigned len, unsigned copied, |
2087 | struct page *page, void *fsdata) |
2088 | { |
2089 | struct inode *inode = mapping->host; |
2090 | int i_size_changed = 0; |
2091 | |
2092 | copied = block_write_end(file, mapping, pos, len, copied, page, fsdata); |
2093 | |
2094 | /* |
2095 | * No need to use i_size_read() here, the i_size |
2096 | * cannot change under us because we hold i_mutex. |
2097 | * |
2098 | * But it's important to update i_size while still holding page lock: |
2099 | * page writeout could otherwise come in and zero beyond i_size. |
2100 | */ |
2101 | if (pos+copied > inode->i_size) { |
2102 | i_size_write(inode, pos+copied); |
2103 | i_size_changed = 1; |
2104 | } |
2105 | |
2106 | unlock_page(page); |
2107 | page_cache_release(page); |
2108 | |
2109 | /* |
2110 | * Don't mark the inode dirty under page lock. First, it unnecessarily |
2111 | * makes the holding time of page lock longer. Second, it forces lock |
2112 | * ordering of page lock and transaction start for journaling |
2113 | * filesystems. |
2114 | */ |
2115 | if (i_size_changed) |
2116 | mark_inode_dirty(inode); |
2117 | |
2118 | return copied; |
2119 | } |
2120 | EXPORT_SYMBOL(generic_write_end); |
2121 | |
2122 | /* |
2123 | * block_is_partially_uptodate checks whether buffers within a page are |
2124 | * uptodate or not. |
2125 | * |
2126 | * Returns true if all buffers which correspond to a file portion |
2127 | * we want to read are uptodate. |
2128 | */ |
2129 | int block_is_partially_uptodate(struct page *page, unsigned long from, |
2130 | unsigned long count) |
2131 | { |
2132 | unsigned block_start, block_end, blocksize; |
2133 | unsigned to; |
2134 | struct buffer_head *bh, *head; |
2135 | int ret = 1; |
2136 | |
2137 | if (!page_has_buffers(page)) |
2138 | return 0; |
2139 | |
2140 | head = page_buffers(page); |
2141 | blocksize = head->b_size; |
2142 | to = min_t(unsigned, PAGE_CACHE_SIZE - from, count); |
2143 | to = from + to; |
2144 | if (from < blocksize && to > PAGE_CACHE_SIZE - blocksize) |
2145 | return 0; |
2146 | |
2147 | bh = head; |
2148 | block_start = 0; |
2149 | do { |
2150 | block_end = block_start + blocksize; |
2151 | if (block_end > from && block_start < to) { |
2152 | if (!buffer_uptodate(bh)) { |
2153 | ret = 0; |
2154 | break; |
2155 | } |
2156 | if (block_end >= to) |
2157 | break; |
2158 | } |
2159 | block_start = block_end; |
2160 | bh = bh->b_this_page; |
2161 | } while (bh != head); |
2162 | |
2163 | return ret; |
2164 | } |
2165 | EXPORT_SYMBOL(block_is_partially_uptodate); |
2166 | |
2167 | /* |
2168 | * Generic "read page" function for block devices that have the normal |
2169 | * get_block functionality. This is most of the block device filesystems. |
2170 | * Reads the page asynchronously --- the unlock_buffer() and |
2171 | * set/clear_buffer_uptodate() functions propagate buffer state into the |
2172 | * page struct once IO has completed. |
2173 | */ |
2174 | int block_read_full_page(struct page *page, get_block_t *get_block) |
2175 | { |
2176 | struct inode *inode = page->mapping->host; |
2177 | sector_t iblock, lblock; |
2178 | struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE]; |
2179 | unsigned int blocksize, bbits; |
2180 | int nr, i; |
2181 | int fully_mapped = 1; |
2182 | |
2183 | head = create_page_buffers(page, inode, 0); |
2184 | blocksize = head->b_size; |
2185 | bbits = block_size_bits(blocksize); |
2186 | |
2187 | iblock = (sector_t)page->index << (PAGE_CACHE_SHIFT - bbits); |
2188 | lblock = (i_size_read(inode)+blocksize-1) >> bbits; |
2189 | bh = head; |
2190 | nr = 0; |
2191 | i = 0; |
2192 | |
2193 | do { |
2194 | if (buffer_uptodate(bh)) |
2195 | continue; |
2196 | |
2197 | if (!buffer_mapped(bh)) { |
2198 | int err = 0; |
2199 | |
2200 | fully_mapped = 0; |
2201 | if (iblock < lblock) { |
2202 | WARN_ON(bh->b_size != blocksize); |
2203 | err = get_block(inode, iblock, bh, 0); |
2204 | if (err) |
2205 | SetPageError(page); |
2206 | } |
2207 | if (!buffer_mapped(bh)) { |
2208 | zero_user(page, i * blocksize, blocksize); |
2209 | if (!err) |
2210 | set_buffer_uptodate(bh); |
2211 | continue; |
2212 | } |
2213 | /* |
2214 | * get_block() might have updated the buffer |
2215 | * synchronously |
2216 | */ |
2217 | if (buffer_uptodate(bh)) |
2218 | continue; |
2219 | } |
2220 | arr[nr++] = bh; |
2221 | } while (i++, iblock++, (bh = bh->b_this_page) != head); |
2222 | |
2223 | if (fully_mapped) |
2224 | SetPageMappedToDisk(page); |
2225 | |
2226 | if (!nr) { |
2227 | /* |
2228 | * All buffers are uptodate - we can set the page uptodate |
2229 | * as well. But not if get_block() returned an error. |
2230 | */ |
2231 | if (!PageError(page)) |
2232 | SetPageUptodate(page); |
2233 | unlock_page(page); |
2234 | return 0; |
2235 | } |
2236 | |
2237 | /* Stage two: lock the buffers */ |
2238 | for (i = 0; i < nr; i++) { |
2239 | bh = arr[i]; |
2240 | lock_buffer(bh); |
2241 | mark_buffer_async_read(bh); |
2242 | } |
2243 | |
2244 | /* |
2245 | * Stage 3: start the IO. Check for uptodateness |
2246 | * inside the buffer lock in case another process reading |
2247 | * the underlying blockdev brought it uptodate (the sct fix). |
2248 | */ |
2249 | for (i = 0; i < nr; i++) { |
2250 | bh = arr[i]; |
2251 | if (buffer_uptodate(bh)) |
2252 | end_buffer_async_read(bh, 1); |
2253 | else |
2254 | submit_bh(READ, bh); |
2255 | } |
2256 | return 0; |
2257 | } |
2258 | EXPORT_SYMBOL(block_read_full_page); |
2259 | |
2260 | /* utility function for filesystems that need to do work on expanding |
2261 | * truncates. Uses filesystem pagecache writes to allow the filesystem to |
2262 | * deal with the hole. |
2263 | */ |
2264 | int generic_cont_expand_simple(struct inode *inode, loff_t size) |
2265 | { |
2266 | struct address_space *mapping = inode->i_mapping; |
2267 | struct page *page; |
2268 | void *fsdata; |
2269 | int err; |
2270 | |
2271 | err = inode_newsize_ok(inode, size); |
2272 | if (err) |
2273 | goto out; |
2274 | |
2275 | err = pagecache_write_begin(NULL, mapping, size, 0, |
2276 | AOP_FLAG_UNINTERRUPTIBLE|AOP_FLAG_CONT_EXPAND, |
2277 | &page, &fsdata); |
2278 | if (err) |
2279 | goto out; |
2280 | |
2281 | err = pagecache_write_end(NULL, mapping, size, 0, 0, page, fsdata); |
2282 | BUG_ON(err > 0); |
2283 | |
2284 | out: |
2285 | return err; |
2286 | } |
2287 | EXPORT_SYMBOL(generic_cont_expand_simple); |
2288 | |
2289 | static int cont_expand_zero(struct file *file, struct address_space *mapping, |
2290 | loff_t pos, loff_t *bytes) |
2291 | { |
2292 | struct inode *inode = mapping->host; |
2293 | unsigned blocksize = 1 << inode->i_blkbits; |
2294 | struct page *page; |
2295 | void *fsdata; |
2296 | pgoff_t index, curidx; |
2297 | loff_t curpos; |
2298 | unsigned zerofrom, offset, len; |
2299 | int err = 0; |
2300 | |
2301 | index = pos >> PAGE_CACHE_SHIFT; |
2302 | offset = pos & ~PAGE_CACHE_MASK; |
2303 | |
2304 | while (index > (curidx = (curpos = *bytes)>>PAGE_CACHE_SHIFT)) { |
2305 | zerofrom = curpos & ~PAGE_CACHE_MASK; |
2306 | if (zerofrom & (blocksize-1)) { |
2307 | *bytes |= (blocksize-1); |
2308 | (*bytes)++; |
2309 | } |
2310 | len = PAGE_CACHE_SIZE - zerofrom; |
2311 | |
2312 | err = pagecache_write_begin(file, mapping, curpos, len, |
2313 | AOP_FLAG_UNINTERRUPTIBLE, |
2314 | &page, &fsdata); |
2315 | if (err) |
2316 | goto out; |
2317 | zero_user(page, zerofrom, len); |
2318 | err = pagecache_write_end(file, mapping, curpos, len, len, |
2319 | page, fsdata); |
2320 | if (err < 0) |
2321 | goto out; |
2322 | BUG_ON(err != len); |
2323 | err = 0; |
2324 | |
2325 | balance_dirty_pages_ratelimited(mapping); |
2326 | } |
2327 | |
2328 | /* page covers the boundary, find the boundary offset */ |
2329 | if (index == curidx) { |
2330 | zerofrom = curpos & ~PAGE_CACHE_MASK; |
2331 | /* if we will expand the thing last block will be filled */ |
2332 | if (offset <= zerofrom) { |
2333 | goto out; |
2334 | } |
2335 | if (zerofrom & (blocksize-1)) { |
2336 | *bytes |= (blocksize-1); |
2337 | (*bytes)++; |
2338 | } |
2339 | len = offset - zerofrom; |
2340 | |
2341 | err = pagecache_write_begin(file, mapping, curpos, len, |
2342 | AOP_FLAG_UNINTERRUPTIBLE, |
2343 | &page, &fsdata); |
2344 | if (err) |
2345 | goto out; |
2346 | zero_user(page, zerofrom, len); |
2347 | err = pagecache_write_end(file, mapping, curpos, len, len, |
2348 | page, fsdata); |
2349 | if (err < 0) |
2350 | goto out; |
2351 | BUG_ON(err != len); |
2352 | err = 0; |
2353 | } |
2354 | out: |
2355 | return err; |
2356 | } |
2357 | |
2358 | /* |
2359 | * For moronic filesystems that do not allow holes in file. |
2360 | * We may have to extend the file. |
2361 | */ |
2362 | int cont_write_begin(struct file *file, struct address_space *mapping, |
2363 | loff_t pos, unsigned len, unsigned flags, |
2364 | struct page **pagep, void **fsdata, |
2365 | get_block_t *get_block, loff_t *bytes) |
2366 | { |
2367 | struct inode *inode = mapping->host; |
2368 | unsigned blocksize = 1 << inode->i_blkbits; |
2369 | unsigned zerofrom; |
2370 | int err; |
2371 | |
2372 | err = cont_expand_zero(file, mapping, pos, bytes); |
2373 | if (err) |
2374 | return err; |
2375 | |
2376 | zerofrom = *bytes & ~PAGE_CACHE_MASK; |
2377 | if (pos+len > *bytes && zerofrom & (blocksize-1)) { |
2378 | *bytes |= (blocksize-1); |
2379 | (*bytes)++; |
2380 | } |
2381 | |
2382 | return block_write_begin(mapping, pos, len, flags, pagep, get_block); |
2383 | } |
2384 | EXPORT_SYMBOL(cont_write_begin); |
2385 | |
2386 | int block_commit_write(struct page *page, unsigned from, unsigned to) |
2387 | { |
2388 | struct inode *inode = page->mapping->host; |
2389 | __block_commit_write(inode,page,from,to); |
2390 | return 0; |
2391 | } |
2392 | EXPORT_SYMBOL(block_commit_write); |
2393 | |
2394 | /* |
2395 | * block_page_mkwrite() is not allowed to change the file size as it gets |
2396 | * called from a page fault handler when a page is first dirtied. Hence we must |
2397 | * be careful to check for EOF conditions here. We set the page up correctly |
2398 | * for a written page which means we get ENOSPC checking when writing into |
2399 | * holes and correct delalloc and unwritten extent mapping on filesystems that |
2400 | * support these features. |
2401 | * |
2402 | * We are not allowed to take the i_mutex here so we have to play games to |
2403 | * protect against truncate races as the page could now be beyond EOF. Because |
2404 | * truncate writes the inode size before removing pages, once we have the |
2405 | * page lock we can determine safely if the page is beyond EOF. If it is not |
2406 | * beyond EOF, then the page is guaranteed safe against truncation until we |
2407 | * unlock the page. |
2408 | * |
2409 | * Direct callers of this function should protect against filesystem freezing |
2410 | * using sb_start_write() - sb_end_write() functions. |
2411 | */ |
2412 | int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, |
2413 | get_block_t get_block) |
2414 | { |
2415 | struct page *page = vmf->page; |
2416 | struct inode *inode = file_inode(vma->vm_file); |
2417 | unsigned long end; |
2418 | loff_t size; |
2419 | int ret; |
2420 | |
2421 | lock_page(page); |
2422 | size = i_size_read(inode); |
2423 | if ((page->mapping != inode->i_mapping) || |
2424 | (page_offset(page) > size)) { |
2425 | /* We overload EFAULT to mean page got truncated */ |
2426 | ret = -EFAULT; |
2427 | goto out_unlock; |
2428 | } |
2429 | |
2430 | /* page is wholly or partially inside EOF */ |
2431 | if (((page->index + 1) << PAGE_CACHE_SHIFT) > size) |
2432 | end = size & ~PAGE_CACHE_MASK; |
2433 | else |
2434 | end = PAGE_CACHE_SIZE; |
2435 | |
2436 | ret = __block_write_begin(page, 0, end, get_block); |
2437 | if (!ret) |
2438 | ret = block_commit_write(page, 0, end); |
2439 | |
2440 | if (unlikely(ret < 0)) |
2441 | goto out_unlock; |
2442 | set_page_dirty(page); |
2443 | wait_for_stable_page(page); |
2444 | return 0; |
2445 | out_unlock: |
2446 | unlock_page(page); |
2447 | return ret; |
2448 | } |
2449 | EXPORT_SYMBOL(__block_page_mkwrite); |
2450 | |
2451 | int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf, |
2452 | get_block_t get_block) |
2453 | { |
2454 | int ret; |
2455 | struct super_block *sb = file_inode(vma->vm_file)->i_sb; |
2456 | |
2457 | sb_start_pagefault(sb); |
2458 | |
2459 | /* |
2460 | * Update file times before taking page lock. We may end up failing the |
2461 | * fault so this update may be superfluous but who really cares... |
2462 | */ |
2463 | file_update_time(vma->vm_file); |
2464 | |
2465 | ret = __block_page_mkwrite(vma, vmf, get_block); |
2466 | sb_end_pagefault(sb); |
2467 | return block_page_mkwrite_return(ret); |
2468 | } |
2469 | EXPORT_SYMBOL(block_page_mkwrite); |
2470 | |
2471 | /* |
2472 | * nobh_write_begin()'s prereads are special: the buffer_heads are freed |
2473 | * immediately, while under the page lock. So it needs a special end_io |
2474 | * handler which does not touch the bh after unlocking it. |
2475 | */ |
2476 | static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate) |
2477 | { |
2478 | __end_buffer_read_notouch(bh, uptodate); |
2479 | } |
2480 | |
2481 | /* |
2482 | * Attach the singly-linked list of buffers created by nobh_write_begin, to |
2483 | * the page (converting it to circular linked list and taking care of page |
2484 | * dirty races). |
2485 | */ |
2486 | static void attach_nobh_buffers(struct page *page, struct buffer_head *head) |
2487 | { |
2488 | struct buffer_head *bh; |
2489 | |
2490 | BUG_ON(!PageLocked(page)); |
2491 | |
2492 | spin_lock(&page->mapping->private_lock); |
2493 | bh = head; |
2494 | do { |
2495 | if (PageDirty(page)) |
2496 | set_buffer_dirty(bh); |
2497 | if (!bh->b_this_page) |
2498 | bh->b_this_page = head; |
2499 | bh = bh->b_this_page; |
2500 | } while (bh != head); |
2501 | attach_page_buffers(page, head); |
2502 | spin_unlock(&page->mapping->private_lock); |
2503 | } |
2504 | |
2505 | /* |
2506 | * On entry, the page is fully not uptodate. |
2507 | * On exit the page is fully uptodate in the areas outside (from,to) |
2508 | * The filesystem needs to handle block truncation upon failure. |
2509 | */ |
2510 | int nobh_write_begin(struct address_space *mapping, |
2511 | loff_t pos, unsigned len, unsigned flags, |
2512 | struct page **pagep, void **fsdata, |
2513 | get_block_t *get_block) |
2514 | { |
2515 | struct inode *inode = mapping->host; |
2516 | const unsigned blkbits = inode->i_blkbits; |
2517 | const unsigned blocksize = 1 << blkbits; |
2518 | struct buffer_head *head, *bh; |
2519 | struct page *page; |
2520 | pgoff_t index; |
2521 | unsigned from, to; |
2522 | unsigned block_in_page; |
2523 | unsigned block_start, block_end; |
2524 | sector_t block_in_file; |
2525 | int nr_reads = 0; |
2526 | int ret = 0; |
2527 | int is_mapped_to_disk = 1; |
2528 | |
2529 | index = pos >> PAGE_CACHE_SHIFT; |
2530 | from = pos & (PAGE_CACHE_SIZE - 1); |
2531 | to = from + len; |
2532 | |
2533 | page = grab_cache_page_write_begin(mapping, index, flags); |
2534 | if (!page) |
2535 | return -ENOMEM; |
2536 | *pagep = page; |
2537 | *fsdata = NULL; |
2538 | |
2539 | if (page_has_buffers(page)) { |
2540 | ret = __block_write_begin(page, pos, len, get_block); |
2541 | if (unlikely(ret)) |
2542 | goto out_release; |
2543 | return ret; |
2544 | } |
2545 | |
2546 | if (PageMappedToDisk(page)) |
2547 | return 0; |
2548 | |
2549 | /* |
2550 | * Allocate buffers so that we can keep track of state, and potentially |
2551 | * attach them to the page if an error occurs. In the common case of |
2552 | * no error, they will just be freed again without ever being attached |
2553 | * to the page (which is all OK, because we're under the page lock). |
2554 | * |
2555 | * Be careful: the buffer linked list is a NULL terminated one, rather |
2556 | * than the circular one we're used to. |
2557 | */ |
2558 | head = alloc_page_buffers(page, blocksize, 0); |
2559 | if (!head) { |
2560 | ret = -ENOMEM; |
2561 | goto out_release; |
2562 | } |
2563 | |
2564 | block_in_file = (sector_t)page->index << (PAGE_CACHE_SHIFT - blkbits); |
2565 | |
2566 | /* |
2567 | * We loop across all blocks in the page, whether or not they are |
2568 | * part of the affected region. This is so we can discover if the |
2569 | * page is fully mapped-to-disk. |
2570 | */ |
2571 | for (block_start = 0, block_in_page = 0, bh = head; |
2572 | block_start < PAGE_CACHE_SIZE; |
2573 | block_in_page++, block_start += blocksize, bh = bh->b_this_page) { |
2574 | int create; |
2575 | |
2576 | block_end = block_start + blocksize; |
2577 | bh->b_state = 0; |
2578 | create = 1; |
2579 | if (block_start >= to) |
2580 | create = 0; |
2581 | ret = get_block(inode, block_in_file + block_in_page, |
2582 | bh, create); |
2583 | if (ret) |
2584 | goto failed; |
2585 | if (!buffer_mapped(bh)) |
2586 | is_mapped_to_disk = 0; |
2587 | if (buffer_new(bh)) |
2588 | unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr); |
2589 | if (PageUptodate(page)) { |
2590 | set_buffer_uptodate(bh); |
2591 | continue; |
2592 | } |
2593 | if (buffer_new(bh) || !buffer_mapped(bh)) { |
2594 | zero_user_segments(page, block_start, from, |
2595 | to, block_end); |
2596 | continue; |
2597 | } |
2598 | if (buffer_uptodate(bh)) |
2599 | continue; /* reiserfs does this */ |
2600 | if (block_start < from || block_end > to) { |
2601 | lock_buffer(bh); |
2602 | bh->b_end_io = end_buffer_read_nobh; |
2603 | submit_bh(READ, bh); |
2604 | nr_reads++; |
2605 | } |
2606 | } |
2607 | |
2608 | if (nr_reads) { |
2609 | /* |
2610 | * The page is locked, so these buffers are protected from |
2611 | * any VM or truncate activity. Hence we don't need to care |
2612 | * for the buffer_head refcounts. |
2613 | */ |
2614 | for (bh = head; bh; bh = bh->b_this_page) { |
2615 | wait_on_buffer(bh); |
2616 | if (!buffer_uptodate(bh)) |
2617 | ret = -EIO; |
2618 | } |
2619 | if (ret) |
2620 | goto failed; |
2621 | } |
2622 | |
2623 | if (is_mapped_to_disk) |
2624 | SetPageMappedToDisk(page); |
2625 | |
2626 | *fsdata = head; /* to be released by nobh_write_end */ |
2627 | |
2628 | return 0; |
2629 | |
2630 | failed: |
2631 | BUG_ON(!ret); |
2632 | /* |
2633 | * Error recovery is a bit difficult. We need to zero out blocks that |
2634 | * were newly allocated, and dirty them to ensure they get written out. |
2635 | * Buffers need to be attached to the page at this point, otherwise |
2636 | * the handling of potential IO errors during writeout would be hard |
2637 | * (could try doing synchronous writeout, but what if that fails too?) |
2638 | */ |
2639 | attach_nobh_buffers(page, head); |
2640 | page_zero_new_buffers(page, from, to); |
2641 | |
2642 | out_release: |
2643 | unlock_page(page); |
2644 | page_cache_release(page); |
2645 | *pagep = NULL; |
2646 | |
2647 | return ret; |
2648 | } |
2649 | EXPORT_SYMBOL(nobh_write_begin); |
2650 | |
2651 | int nobh_write_end(struct file *file, struct address_space *mapping, |
2652 | loff_t pos, unsigned len, unsigned copied, |
2653 | struct page *page, void *fsdata) |
2654 | { |
2655 | struct inode *inode = page->mapping->host; |
2656 | struct buffer_head *head = fsdata; |
2657 | struct buffer_head *bh; |
2658 | BUG_ON(fsdata != NULL && page_has_buffers(page)); |
2659 | |
2660 | if (unlikely(copied < len) && head) |
2661 | attach_nobh_buffers(page, head); |
2662 | if (page_has_buffers(page)) |
2663 | return generic_write_end(file, mapping, pos, len, |
2664 | copied, page, fsdata); |
2665 | |
2666 | SetPageUptodate(page); |
2667 | set_page_dirty(page); |
2668 | if (pos+copied > inode->i_size) { |
2669 | i_size_write(inode, pos+copied); |
2670 | mark_inode_dirty(inode); |
2671 | } |
2672 | |
2673 | unlock_page(page); |
2674 | page_cache_release(page); |
2675 | |
2676 | while (head) { |
2677 | bh = head; |
2678 | head = head->b_this_page; |
2679 | free_buffer_head(bh); |
2680 | } |
2681 | |
2682 | return copied; |
2683 | } |
2684 | EXPORT_SYMBOL(nobh_write_end); |
2685 | |
2686 | /* |
2687 | * nobh_writepage() - based on block_full_write_page() except |
2688 | * that it tries to operate without attaching bufferheads to |
2689 | * the page. |
2690 | */ |
2691 | int nobh_writepage(struct page *page, get_block_t *get_block, |
2692 | struct writeback_control *wbc) |
2693 | { |
2694 | struct inode * const inode = page->mapping->host; |
2695 | loff_t i_size = i_size_read(inode); |
2696 | const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; |
2697 | unsigned offset; |
2698 | int ret; |
2699 | |
2700 | /* Is the page fully inside i_size? */ |
2701 | if (page->index < end_index) |
2702 | goto out; |
2703 | |
2704 | /* Is the page fully outside i_size? (truncate in progress) */ |
2705 | offset = i_size & (PAGE_CACHE_SIZE-1); |
2706 | if (page->index >= end_index+1 || !offset) { |
2707 | /* |
2708 | * The page may have dirty, unmapped buffers. For example, |
2709 | * they may have been added in ext3_writepage(). Make them |
2710 | * freeable here, so the page does not leak. |
2711 | */ |
2712 | #if 0 |
2713 | /* Not really sure about this - do we need this ? */ |
2714 | if (page->mapping->a_ops->invalidatepage) |
2715 | page->mapping->a_ops->invalidatepage(page, offset); |
2716 | #endif |
2717 | unlock_page(page); |
2718 | return 0; /* don't care */ |
2719 | } |
2720 | |
2721 | /* |
2722 | * The page straddles i_size. It must be zeroed out on each and every |
2723 | * writepage invocation because it may be mmapped. "A file is mapped |
2724 | * in multiples of the page size. For a file that is not a multiple of |
2725 | * the page size, the remaining memory is zeroed when mapped, and |
2726 | * writes to that region are not written out to the file." |
2727 | */ |
2728 | zero_user_segment(page, offset, PAGE_CACHE_SIZE); |
2729 | out: |
2730 | ret = mpage_writepage(page, get_block, wbc); |
2731 | if (ret == -EAGAIN) |
2732 | ret = __block_write_full_page(inode, page, get_block, wbc, |
2733 | end_buffer_async_write); |
2734 | return ret; |
2735 | } |
2736 | EXPORT_SYMBOL(nobh_writepage); |
2737 | |
2738 | int nobh_truncate_page(struct address_space *mapping, |
2739 | loff_t from, get_block_t *get_block) |
2740 | { |
2741 | pgoff_t index = from >> PAGE_CACHE_SHIFT; |
2742 | unsigned offset = from & (PAGE_CACHE_SIZE-1); |
2743 | unsigned blocksize; |
2744 | sector_t iblock; |
2745 | unsigned length, pos; |
2746 | struct inode *inode = mapping->host; |
2747 | struct page *page; |
2748 | struct buffer_head map_bh; |
2749 | int err; |
2750 | |
2751 | blocksize = 1 << inode->i_blkbits; |
2752 | length = offset & (blocksize - 1); |
2753 | |
2754 | /* Block boundary? Nothing to do */ |
2755 | if (!length) |
2756 | return 0; |
2757 | |
2758 | length = blocksize - length; |
2759 | iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
2760 | |
2761 | page = grab_cache_page(mapping, index); |
2762 | err = -ENOMEM; |
2763 | if (!page) |
2764 | goto out; |
2765 | |
2766 | if (page_has_buffers(page)) { |
2767 | has_buffers: |
2768 | unlock_page(page); |
2769 | page_cache_release(page); |
2770 | return block_truncate_page(mapping, from, get_block); |
2771 | } |
2772 | |
2773 | /* Find the buffer that contains "offset" */ |
2774 | pos = blocksize; |
2775 | while (offset >= pos) { |
2776 | iblock++; |
2777 | pos += blocksize; |
2778 | } |
2779 | |
2780 | map_bh.b_size = blocksize; |
2781 | map_bh.b_state = 0; |
2782 | err = get_block(inode, iblock, &map_bh, 0); |
2783 | if (err) |
2784 | goto unlock; |
2785 | /* unmapped? It's a hole - nothing to do */ |
2786 | if (!buffer_mapped(&map_bh)) |
2787 | goto unlock; |
2788 | |
2789 | /* Ok, it's mapped. Make sure it's up-to-date */ |
2790 | if (!PageUptodate(page)) { |
2791 | err = mapping->a_ops->readpage(NULL, page); |
2792 | if (err) { |
2793 | page_cache_release(page); |
2794 | goto out; |
2795 | } |
2796 | lock_page(page); |
2797 | if (!PageUptodate(page)) { |
2798 | err = -EIO; |
2799 | goto unlock; |
2800 | } |
2801 | if (page_has_buffers(page)) |
2802 | goto has_buffers; |
2803 | } |
2804 | zero_user(page, offset, length); |
2805 | set_page_dirty(page); |
2806 | err = 0; |
2807 | |
2808 | unlock: |
2809 | unlock_page(page); |
2810 | page_cache_release(page); |
2811 | out: |
2812 | return err; |
2813 | } |
2814 | EXPORT_SYMBOL(nobh_truncate_page); |
2815 | |
2816 | int block_truncate_page(struct address_space *mapping, |
2817 | loff_t from, get_block_t *get_block) |
2818 | { |
2819 | pgoff_t index = from >> PAGE_CACHE_SHIFT; |
2820 | unsigned offset = from & (PAGE_CACHE_SIZE-1); |
2821 | unsigned blocksize; |
2822 | sector_t iblock; |
2823 | unsigned length, pos; |
2824 | struct inode *inode = mapping->host; |
2825 | struct page *page; |
2826 | struct buffer_head *bh; |
2827 | int err; |
2828 | |
2829 | blocksize = 1 << inode->i_blkbits; |
2830 | length = offset & (blocksize - 1); |
2831 | |
2832 | /* Block boundary? Nothing to do */ |
2833 | if (!length) |
2834 | return 0; |
2835 | |
2836 | length = blocksize - length; |
2837 | iblock = (sector_t)index << (PAGE_CACHE_SHIFT - inode->i_blkbits); |
2838 | |
2839 | page = grab_cache_page(mapping, index); |
2840 | err = -ENOMEM; |
2841 | if (!page) |
2842 | goto out; |
2843 | |
2844 | if (!page_has_buffers(page)) |
2845 | create_empty_buffers(page, blocksize, 0); |
2846 | |
2847 | /* Find the buffer that contains "offset" */ |
2848 | bh = page_buffers(page); |
2849 | pos = blocksize; |
2850 | while (offset >= pos) { |
2851 | bh = bh->b_this_page; |
2852 | iblock++; |
2853 | pos += blocksize; |
2854 | } |
2855 | |
2856 | err = 0; |
2857 | if (!buffer_mapped(bh)) { |
2858 | WARN_ON(bh->b_size != blocksize); |
2859 | err = get_block(inode, iblock, bh, 0); |
2860 | if (err) |
2861 | goto unlock; |
2862 | /* unmapped? It's a hole - nothing to do */ |
2863 | if (!buffer_mapped(bh)) |
2864 | goto unlock; |
2865 | } |
2866 | |
2867 | /* Ok, it's mapped. Make sure it's up-to-date */ |
2868 | if (PageUptodate(page)) |
2869 | set_buffer_uptodate(bh); |
2870 | |
2871 | if (!buffer_uptodate(bh) && !buffer_delay(bh) && !buffer_unwritten(bh)) { |
2872 | err = -EIO; |
2873 | ll_rw_block(READ, 1, &bh); |
2874 | wait_on_buffer(bh); |
2875 | /* Uhhuh. Read error. Complain and punt. */ |
2876 | if (!buffer_uptodate(bh)) |
2877 | goto unlock; |
2878 | } |
2879 | |
2880 | zero_user(page, offset, length); |
2881 | mark_buffer_dirty(bh); |
2882 | err = 0; |
2883 | |
2884 | unlock: |
2885 | unlock_page(page); |
2886 | page_cache_release(page); |
2887 | out: |
2888 | return err; |
2889 | } |
2890 | EXPORT_SYMBOL(block_truncate_page); |
2891 | |
2892 | /* |
2893 | * The generic ->writepage function for buffer-backed address_spaces |
2894 | */ |
2895 | int block_write_full_page(struct page *page, get_block_t *get_block, |
2896 | struct writeback_control *wbc) |
2897 | { |
2898 | struct inode * const inode = page->mapping->host; |
2899 | loff_t i_size = i_size_read(inode); |
2900 | const pgoff_t end_index = i_size >> PAGE_CACHE_SHIFT; |
2901 | unsigned offset; |
2902 | |
2903 | /* Is the page fully inside i_size? */ |
2904 | if (page->index < end_index) |
2905 | return __block_write_full_page(inode, page, get_block, wbc, |
2906 | end_buffer_async_write); |
2907 | |
2908 | /* Is the page fully outside i_size? (truncate in progress) */ |
2909 | offset = i_size & (PAGE_CACHE_SIZE-1); |
2910 | if (page->index >= end_index+1 || !offset) { |
2911 | /* |
2912 | * The page may have dirty, unmapped buffers. For example, |
2913 | * they may have been added in ext3_writepage(). Make them |
2914 | * freeable here, so the page does not leak. |
2915 | */ |
2916 | do_invalidatepage(page, 0, PAGE_CACHE_SIZE); |
2917 | unlock_page(page); |
2918 | return 0; /* don't care */ |
2919 | } |
2920 | |
2921 | /* |
2922 | * The page straddles i_size. It must be zeroed out on each and every |
2923 | * writepage invocation because it may be mmapped. "A file is mapped |
2924 | * in multiples of the page size. For a file that is not a multiple of |
2925 | * the page size, the remaining memory is zeroed when mapped, and |
2926 | * writes to that region are not written out to the file." |
2927 | */ |
2928 | zero_user_segment(page, offset, PAGE_CACHE_SIZE); |
2929 | return __block_write_full_page(inode, page, get_block, wbc, |
2930 | end_buffer_async_write); |
2931 | } |
2932 | EXPORT_SYMBOL(block_write_full_page); |
2933 | |
2934 | sector_t generic_block_bmap(struct address_space *mapping, sector_t block, |
2935 | get_block_t *get_block) |
2936 | { |
2937 | struct buffer_head tmp; |
2938 | struct inode *inode = mapping->host; |
2939 | tmp.b_state = 0; |
2940 | tmp.b_blocknr = 0; |
2941 | tmp.b_size = 1 << inode->i_blkbits; |
2942 | get_block(inode, block, &tmp, 0); |
2943 | return tmp.b_blocknr; |
2944 | } |
2945 | EXPORT_SYMBOL(generic_block_bmap); |
2946 | |
2947 | static void end_bio_bh_io_sync(struct bio *bio, int err) |
2948 | { |
2949 | struct buffer_head *bh = bio->bi_private; |
2950 | |
2951 | if (err == -EOPNOTSUPP) { |
2952 | set_bit(BIO_EOPNOTSUPP, &bio->bi_flags); |
2953 | } |
2954 | |
2955 | if (unlikely (test_bit(BIO_QUIET,&bio->bi_flags))) |
2956 | set_bit(BH_Quiet, &bh->b_state); |
2957 | |
2958 | bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags)); |
2959 | bio_put(bio); |
2960 | } |
2961 | |
2962 | /* |
2963 | * This allows us to do IO even on the odd last sectors |
2964 | * of a device, even if the bh block size is some multiple |
2965 | * of the physical sector size. |
2966 | * |
2967 | * We'll just truncate the bio to the size of the device, |
2968 | * and clear the end of the buffer head manually. |
2969 | * |
2970 | * Truly out-of-range accesses will turn into actual IO |
2971 | * errors, this only handles the "we need to be able to |
2972 | * do IO at the final sector" case. |
2973 | */ |
2974 | static void guard_bh_eod(int rw, struct bio *bio, struct buffer_head *bh) |
2975 | { |
2976 | sector_t maxsector; |
2977 | unsigned bytes; |
2978 | |
2979 | maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9; |
2980 | if (!maxsector) |
2981 | return; |
2982 | |
2983 | /* |
2984 | * If the *whole* IO is past the end of the device, |
2985 | * let it through, and the IO layer will turn it into |
2986 | * an EIO. |
2987 | */ |
2988 | if (unlikely(bio->bi_iter.bi_sector >= maxsector)) |
2989 | return; |
2990 | |
2991 | maxsector -= bio->bi_iter.bi_sector; |
2992 | bytes = bio->bi_iter.bi_size; |
2993 | if (likely((bytes >> 9) <= maxsector)) |
2994 | return; |
2995 | |
2996 | /* Uhhuh. We've got a bh that straddles the device size! */ |
2997 | bytes = maxsector << 9; |
2998 | |
2999 | /* Truncate the bio.. */ |
3000 | bio->bi_iter.bi_size = bytes; |
3001 | bio->bi_io_vec[0].bv_len = bytes; |
3002 | |
3003 | /* ..and clear the end of the buffer for reads */ |
3004 | if ((rw & RW_MASK) == READ) { |
3005 | void *kaddr = kmap_atomic(bh->b_page); |
3006 | memset(kaddr + bh_offset(bh) + bytes, 0, bh->b_size - bytes); |
3007 | kunmap_atomic(kaddr); |
3008 | flush_dcache_page(bh->b_page); |
3009 | } |
3010 | } |
3011 | |
3012 | int _submit_bh(int rw, struct buffer_head *bh, unsigned long bio_flags) |
3013 | { |
3014 | struct bio *bio; |
3015 | int ret = 0; |
3016 | |
3017 | BUG_ON(!buffer_locked(bh)); |
3018 | BUG_ON(!buffer_mapped(bh)); |
3019 | BUG_ON(!bh->b_end_io); |
3020 | BUG_ON(buffer_delay(bh)); |
3021 | BUG_ON(buffer_unwritten(bh)); |
3022 | |
3023 | /* |
3024 | * Only clear out a write error when rewriting |
3025 | */ |
3026 | if (test_set_buffer_req(bh) && (rw & WRITE)) |
3027 | clear_buffer_write_io_error(bh); |
3028 | |
3029 | /* |
3030 | * from here on down, it's all bio -- do the initial mapping, |
3031 | * submit_bio -> generic_make_request may further map this bio around |
3032 | */ |
3033 | bio = bio_alloc(GFP_NOIO, 1); |
3034 | |
3035 | bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9); |
3036 | bio->bi_bdev = bh->b_bdev; |
3037 | bio->bi_io_vec[0].bv_page = bh->b_page; |
3038 | bio->bi_io_vec[0].bv_len = bh->b_size; |
3039 | bio->bi_io_vec[0].bv_offset = bh_offset(bh); |
3040 | |
3041 | bio->bi_vcnt = 1; |
3042 | bio->bi_iter.bi_size = bh->b_size; |
3043 | |
3044 | bio->bi_end_io = end_bio_bh_io_sync; |
3045 | bio->bi_private = bh; |
3046 | bio->bi_flags |= bio_flags; |
3047 | |
3048 | /* Take care of bh's that straddle the end of the device */ |
3049 | guard_bh_eod(rw, bio, bh); |
3050 | |
3051 | if (buffer_meta(bh)) |
3052 | rw |= REQ_META; |
3053 | if (buffer_prio(bh)) |
3054 | rw |= REQ_PRIO; |
3055 | |
3056 | bio_get(bio); |
3057 | submit_bio(rw, bio); |
3058 | |
3059 | if (bio_flagged(bio, BIO_EOPNOTSUPP)) |
3060 | ret = -EOPNOTSUPP; |
3061 | |
3062 | bio_put(bio); |
3063 | return ret; |
3064 | } |
3065 | EXPORT_SYMBOL_GPL(_submit_bh); |
3066 | |
3067 | int submit_bh(int rw, struct buffer_head *bh) |
3068 | { |
3069 | return _submit_bh(rw, bh, 0); |
3070 | } |
3071 | EXPORT_SYMBOL(submit_bh); |
3072 | |
3073 | /** |
3074 | * ll_rw_block: low-level access to block devices (DEPRECATED) |
3075 | * @rw: whether to %READ or %WRITE or maybe %READA (readahead) |
3076 | * @nr: number of &struct buffer_heads in the array |
3077 | * @bhs: array of pointers to &struct buffer_head |
3078 | * |
3079 | * ll_rw_block() takes an array of pointers to &struct buffer_heads, and |
3080 | * requests an I/O operation on them, either a %READ or a %WRITE. The third |
3081 | * %READA option is described in the documentation for generic_make_request() |
3082 | * which ll_rw_block() calls. |
3083 | * |
3084 | * This function drops any buffer that it cannot get a lock on (with the |
3085 | * BH_Lock state bit), any buffer that appears to be clean when doing a write |
3086 | * request, and any buffer that appears to be up-to-date when doing read |
3087 | * request. Further it marks as clean buffers that are processed for |
3088 | * writing (the buffer cache won't assume that they are actually clean |
3089 | * until the buffer gets unlocked). |
3090 | * |
3091 | * ll_rw_block sets b_end_io to simple completion handler that marks |
3092 | * the buffer up-to-date (if appropriate), unlocks the buffer and wakes |
3093 | * any waiters. |
3094 | * |
3095 | * All of the buffers must be for the same device, and must also be a |
3096 | * multiple of the current approved size for the device. |
3097 | */ |
3098 | void ll_rw_block(int rw, int nr, struct buffer_head *bhs[]) |
3099 | { |
3100 | int i; |
3101 | |
3102 | for (i = 0; i < nr; i++) { |
3103 | struct buffer_head *bh = bhs[i]; |
3104 | |
3105 | if (!trylock_buffer(bh)) |
3106 | continue; |
3107 | if (rw == WRITE) { |
3108 | if (test_clear_buffer_dirty(bh)) { |
3109 | bh->b_end_io = end_buffer_write_sync; |
3110 | get_bh(bh); |
3111 | submit_bh(WRITE, bh); |
3112 | continue; |
3113 | } |
3114 | } else { |
3115 | if (!buffer_uptodate(bh)) { |
3116 | bh->b_end_io = end_buffer_read_sync; |
3117 | get_bh(bh); |
3118 | submit_bh(rw, bh); |
3119 | continue; |
3120 | } |
3121 | } |
3122 | unlock_buffer(bh); |
3123 | } |
3124 | } |
3125 | EXPORT_SYMBOL(ll_rw_block); |
3126 | |
3127 | void write_dirty_buffer(struct buffer_head *bh, int rw) |
3128 | { |
3129 | lock_buffer(bh); |
3130 | if (!test_clear_buffer_dirty(bh)) { |
3131 | unlock_buffer(bh); |
3132 | return; |
3133 | } |
3134 | bh->b_end_io = end_buffer_write_sync; |
3135 | get_bh(bh); |
3136 | submit_bh(rw, bh); |
3137 | } |
3138 | EXPORT_SYMBOL(write_dirty_buffer); |
3139 | |
3140 | /* |
3141 | * For a data-integrity writeout, we need to wait upon any in-progress I/O |
3142 | * and then start new I/O and then wait upon it. The caller must have a ref on |
3143 | * the buffer_head. |
3144 | */ |
3145 | int __sync_dirty_buffer(struct buffer_head *bh, int rw) |
3146 | { |
3147 | int ret = 0; |
3148 | |
3149 | WARN_ON(atomic_read(&bh->b_count) < 1); |
3150 | lock_buffer(bh); |
3151 | if (test_clear_buffer_dirty(bh)) { |
3152 | get_bh(bh); |
3153 | bh->b_end_io = end_buffer_write_sync; |
3154 | ret = submit_bh(rw, bh); |
3155 | wait_on_buffer(bh); |
3156 | if (!ret && !buffer_uptodate(bh)) |
3157 | ret = -EIO; |
3158 | } else { |
3159 | unlock_buffer(bh); |
3160 | } |
3161 | return ret; |
3162 | } |
3163 | EXPORT_SYMBOL(__sync_dirty_buffer); |
3164 | |
3165 | int sync_dirty_buffer(struct buffer_head *bh) |
3166 | { |
3167 | return __sync_dirty_buffer(bh, WRITE_SYNC); |
3168 | } |
3169 | EXPORT_SYMBOL(sync_dirty_buffer); |
3170 | |
3171 | /* |
3172 | * try_to_free_buffers() checks if all the buffers on this particular page |
3173 | * are unused, and releases them if so. |
3174 | * |
3175 | * Exclusion against try_to_free_buffers may be obtained by either |
3176 | * locking the page or by holding its mapping's private_lock. |
3177 | * |
3178 | * If the page is dirty but all the buffers are clean then we need to |
3179 | * be sure to mark the page clean as well. This is because the page |
3180 | * may be against a block device, and a later reattachment of buffers |
3181 | * to a dirty page will set *all* buffers dirty. Which would corrupt |
3182 | * filesystem data on the same device. |
3183 | * |
3184 | * The same applies to regular filesystem pages: if all the buffers are |
3185 | * clean then we set the page clean and proceed. To do that, we require |
3186 | * total exclusion from __set_page_dirty_buffers(). That is obtained with |
3187 | * private_lock. |
3188 | * |
3189 | * try_to_free_buffers() is non-blocking. |
3190 | */ |
3191 | static inline int buffer_busy(struct buffer_head *bh) |
3192 | { |
3193 | return atomic_read(&bh->b_count) | |
3194 | (bh->b_state & ((1 << BH_Dirty) | (1 << BH_Lock))); |
3195 | } |
3196 | |
3197 | static int |
3198 | drop_buffers(struct page *page, struct buffer_head **buffers_to_free) |
3199 | { |
3200 | struct buffer_head *head = page_buffers(page); |
3201 | struct buffer_head *bh; |
3202 | |
3203 | bh = head; |
3204 | do { |
3205 | if (buffer_write_io_error(bh) && page->mapping) |
3206 | set_bit(AS_EIO, &page->mapping->flags); |
3207 | if (buffer_busy(bh)) |
3208 | goto failed; |
3209 | bh = bh->b_this_page; |
3210 | } while (bh != head); |
3211 | |
3212 | do { |
3213 | struct buffer_head *next = bh->b_this_page; |
3214 | |
3215 | if (bh->b_assoc_map) |
3216 | __remove_assoc_queue(bh); |
3217 | bh = next; |
3218 | } while (bh != head); |
3219 | *buffers_to_free = head; |
3220 | __clear_page_buffers(page); |
3221 | return 1; |
3222 | failed: |
3223 | return 0; |
3224 | } |
3225 | |
3226 | int try_to_free_buffers(struct page *page) |
3227 | { |
3228 | struct address_space * const mapping = page->mapping; |
3229 | struct buffer_head *buffers_to_free = NULL; |
3230 | int ret = 0; |
3231 | |
3232 | BUG_ON(!PageLocked(page)); |
3233 | if (PageWriteback(page)) |
3234 | return 0; |
3235 | |
3236 | if (mapping == NULL) { /* can this still happen? */ |
3237 | ret = drop_buffers(page, &buffers_to_free); |
3238 | goto out; |
3239 | } |
3240 | |
3241 | spin_lock(&mapping->private_lock); |
3242 | ret = drop_buffers(page, &buffers_to_free); |
3243 | |
3244 | /* |
3245 | * If the filesystem writes its buffers by hand (eg ext3) |
3246 | * then we can have clean buffers against a dirty page. We |
3247 | * clean the page here; otherwise the VM will never notice |
3248 | * that the filesystem did any IO at all. |
3249 | * |
3250 | * Also, during truncate, discard_buffer will have marked all |
3251 | * the page's buffers clean. We discover that here and clean |
3252 | * the page also. |
3253 | * |
3254 | * private_lock must be held over this entire operation in order |
3255 | * to synchronise against __set_page_dirty_buffers and prevent the |
3256 | * dirty bit from being lost. |
3257 | */ |
3258 | if (ret) |
3259 | cancel_dirty_page(page, PAGE_CACHE_SIZE); |
3260 | spin_unlock(&mapping->private_lock); |
3261 | out: |
3262 | if (buffers_to_free) { |
3263 | struct buffer_head *bh = buffers_to_free; |
3264 | |
3265 | do { |
3266 | struct buffer_head *next = bh->b_this_page; |
3267 | free_buffer_head(bh); |
3268 | bh = next; |
3269 | } while (bh != buffers_to_free); |
3270 | } |
3271 | return ret; |
3272 | } |
3273 | EXPORT_SYMBOL(try_to_free_buffers); |
3274 | |
3275 | /* |
3276 | * There are no bdflush tunables left. But distributions are |
3277 | * still running obsolete flush daemons, so we terminate them here. |
3278 | * |
3279 | * Use of bdflush() is deprecated and will be removed in a future kernel. |
3280 | * The `flush-X' kernel threads fully replace bdflush daemons and this call. |
3281 | */ |
3282 | SYSCALL_DEFINE2(bdflush, int, func, long, data) |
3283 | { |
3284 | static int msg_count; |
3285 | |
3286 | if (!capable(CAP_SYS_ADMIN)) |
3287 | return -EPERM; |
3288 | |
3289 | if (msg_count < 5) { |
3290 | msg_count++; |
3291 | printk(KERN_INFO |
3292 | "warning: process `%s' used the obsolete bdflush" |
3293 | " system call\n", current->comm); |
3294 | printk(KERN_INFO "Fix your initscripts?\n"); |
3295 | } |
3296 | |
3297 | if (func == 1) |
3298 | do_exit(0); |
3299 | return 0; |
3300 | } |
3301 | |
3302 | /* |
3303 | * Buffer-head allocation |
3304 | */ |
3305 | static struct kmem_cache *bh_cachep __read_mostly; |
3306 | |
3307 | /* |
3308 | * Once the number of bh's in the machine exceeds this level, we start |
3309 | * stripping them in writeback. |
3310 | */ |
3311 | static unsigned long max_buffer_heads; |
3312 | |
3313 | int buffer_heads_over_limit; |
3314 | |
3315 | struct bh_accounting { |
3316 | int nr; /* Number of live bh's */ |
3317 | int ratelimit; /* Limit cacheline bouncing */ |
3318 | }; |
3319 | |
3320 | static DEFINE_PER_CPU(struct bh_accounting, bh_accounting) = {0, 0}; |
3321 | |
3322 | static void recalc_bh_state(void) |
3323 | { |
3324 | int i; |
3325 | int tot = 0; |
3326 | |
3327 | if (__this_cpu_inc_return(bh_accounting.ratelimit) - 1 < 4096) |
3328 | return; |
3329 | __this_cpu_write(bh_accounting.ratelimit, 0); |
3330 | for_each_online_cpu(i) |
3331 | tot += per_cpu(bh_accounting, i).nr; |
3332 | buffer_heads_over_limit = (tot > max_buffer_heads); |
3333 | } |
3334 | |
3335 | struct buffer_head *alloc_buffer_head(gfp_t gfp_flags) |
3336 | { |
3337 | struct buffer_head *ret = kmem_cache_zalloc(bh_cachep, gfp_flags); |
3338 | if (ret) { |
3339 | INIT_LIST_HEAD(&ret->b_assoc_buffers); |
3340 | preempt_disable(); |
3341 | __this_cpu_inc(bh_accounting.nr); |
3342 | recalc_bh_state(); |
3343 | preempt_enable(); |
3344 | } |
3345 | return ret; |
3346 | } |
3347 | EXPORT_SYMBOL(alloc_buffer_head); |
3348 | |
3349 | void free_buffer_head(struct buffer_head *bh) |
3350 | { |
3351 | BUG_ON(!list_empty(&bh->b_assoc_buffers)); |
3352 | kmem_cache_free(bh_cachep, bh); |
3353 | preempt_disable(); |
3354 | __this_cpu_dec(bh_accounting.nr); |
3355 | recalc_bh_state(); |
3356 | preempt_enable(); |
3357 | } |
3358 | EXPORT_SYMBOL(free_buffer_head); |
3359 | |
3360 | static void buffer_exit_cpu(int cpu) |
3361 | { |
3362 | int i; |
3363 | struct bh_lru *b = &per_cpu(bh_lrus, cpu); |
3364 | |
3365 | for (i = 0; i < BH_LRU_SIZE; i++) { |
3366 | brelse(b->bhs[i]); |
3367 | b->bhs[i] = NULL; |
3368 | } |
3369 | this_cpu_add(bh_accounting.nr, per_cpu(bh_accounting, cpu).nr); |
3370 | per_cpu(bh_accounting, cpu).nr = 0; |
3371 | } |
3372 | |
3373 | static int buffer_cpu_notify(struct notifier_block *self, |
3374 | unsigned long action, void *hcpu) |
3375 | { |
3376 | if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) |
3377 | buffer_exit_cpu((unsigned long)hcpu); |
3378 | return NOTIFY_OK; |
3379 | } |
3380 | |
3381 | /** |
3382 | * bh_uptodate_or_lock - Test whether the buffer is uptodate |
3383 | * @bh: struct buffer_head |
3384 | * |
3385 | * Return true if the buffer is up-to-date and false, |
3386 | * with the buffer locked, if not. |
3387 | */ |
3388 | int bh_uptodate_or_lock(struct buffer_head *bh) |
3389 | { |
3390 | if (!buffer_uptodate(bh)) { |
3391 | lock_buffer(bh); |
3392 | if (!buffer_uptodate(bh)) |
3393 | return 0; |
3394 | unlock_buffer(bh); |
3395 | } |
3396 | return 1; |
3397 | } |
3398 | EXPORT_SYMBOL(bh_uptodate_or_lock); |
3399 | |
3400 | /** |
3401 | * bh_submit_read - Submit a locked buffer for reading |
3402 | * @bh: struct buffer_head |
3403 | * |
3404 | * Returns zero on success and -EIO on error. |
3405 | */ |
3406 | int bh_submit_read(struct buffer_head *bh) |
3407 | { |
3408 | BUG_ON(!buffer_locked(bh)); |
3409 | |
3410 | if (buffer_uptodate(bh)) { |
3411 | unlock_buffer(bh); |
3412 | return 0; |
3413 | } |
3414 | |
3415 | get_bh(bh); |
3416 | bh->b_end_io = end_buffer_read_sync; |
3417 | submit_bh(READ, bh); |
3418 | wait_on_buffer(bh); |
3419 | if (buffer_uptodate(bh)) |
3420 | return 0; |
3421 | return -EIO; |
3422 | } |
3423 | EXPORT_SYMBOL(bh_submit_read); |
3424 | |
3425 | void __init buffer_init(void) |
3426 | { |
3427 | unsigned long nrpages; |
3428 | |
3429 | bh_cachep = kmem_cache_create("buffer_head", |
3430 | sizeof(struct buffer_head), 0, |
3431 | (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC| |
3432 | SLAB_MEM_SPREAD), |
3433 | NULL); |
3434 | |
3435 | /* |
3436 | * Limit the bh occupancy to 10% of ZONE_NORMAL |
3437 | */ |
3438 | nrpages = (nr_free_buffer_pages() * 10) / 100; |
3439 | max_buffer_heads = nrpages * (PAGE_SIZE / sizeof(struct buffer_head)); |
3440 | hotcpu_notifier(buffer_cpu_notify, 0); |
3441 | } |
3442 |
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