ia64/linux-2.6.18-xen.hg

view mm/page-writeback.c @ 749:2892ca2b9c17

linux/x86: cleanup IO-APIC code

- get 32-bit code in sync with 64-bit wrt ExtINT pin detection being
unnecessary
- eliminate build warnings resulting from c/s 725

Signed-off-by: Jan Beulich <jbeulich@novell.com>
author Keir Fraser <keir.fraser@citrix.com>
date Fri Nov 28 13:31:21 2008 +0000 (2008-11-28)
parents 831230e53067
children
line source
1 /*
2 * mm/page-writeback.c.
3 *
4 * Copyright (C) 2002, Linus Torvalds.
5 *
6 * Contains functions related to writing back dirty pages at the
7 * address_space level.
8 *
9 * 10Apr2002 akpm@zip.com.au
10 * Initial version
11 */
13 #include <linux/kernel.h>
14 #include <linux/module.h>
15 #include <linux/spinlock.h>
16 #include <linux/fs.h>
17 #include <linux/mm.h>
18 #include <linux/swap.h>
19 #include <linux/slab.h>
20 #include <linux/pagemap.h>
21 #include <linux/writeback.h>
22 #include <linux/init.h>
23 #include <linux/backing-dev.h>
24 #include <linux/blkdev.h>
25 #include <linux/mpage.h>
26 #include <linux/percpu.h>
27 #include <linux/notifier.h>
28 #include <linux/smp.h>
29 #include <linux/sysctl.h>
30 #include <linux/cpu.h>
31 #include <linux/syscalls.h>
33 /*
34 * The maximum number of pages to writeout in a single bdflush/kupdate
35 * operation. We do this so we don't hold I_LOCK against an inode for
36 * enormous amounts of time, which would block a userspace task which has
37 * been forced to throttle against that inode. Also, the code reevaluates
38 * the dirty each time it has written this many pages.
39 */
40 #define MAX_WRITEBACK_PAGES 1024
42 /*
43 * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited
44 * will look to see if it needs to force writeback or throttling.
45 */
46 static long ratelimit_pages = 32;
48 static long total_pages; /* The total number of pages in the machine. */
49 static int dirty_exceeded __cacheline_aligned_in_smp; /* Dirty mem may be over limit */
51 /*
52 * When balance_dirty_pages decides that the caller needs to perform some
53 * non-background writeback, this is how many pages it will attempt to write.
54 * It should be somewhat larger than RATELIMIT_PAGES to ensure that reasonably
55 * large amounts of I/O are submitted.
56 */
57 static inline long sync_writeback_pages(void)
58 {
59 return ratelimit_pages + ratelimit_pages / 2;
60 }
62 /* The following parameters are exported via /proc/sys/vm */
64 /*
65 * Start background writeback (via pdflush) at this percentage
66 */
67 int dirty_background_ratio = 10;
69 /*
70 * The generator of dirty data starts writeback at this percentage
71 */
72 int vm_dirty_ratio = 40;
74 /*
75 * The interval between `kupdate'-style writebacks, in jiffies
76 */
77 int dirty_writeback_interval = 5 * HZ;
79 /*
80 * The longest number of jiffies for which data is allowed to remain dirty
81 */
82 int dirty_expire_interval = 30 * HZ;
84 /*
85 * Flag that makes the machine dump writes/reads and block dirtyings.
86 */
87 int block_dump;
89 /*
90 * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies:
91 * a full sync is triggered after this time elapses without any disk activity.
92 */
93 int laptop_mode;
95 EXPORT_SYMBOL(laptop_mode);
97 /* End of sysctl-exported parameters */
100 static void background_writeout(unsigned long _min_pages);
102 /*
103 * Work out the current dirty-memory clamping and background writeout
104 * thresholds.
105 *
106 * The main aim here is to lower them aggressively if there is a lot of mapped
107 * memory around. To avoid stressing page reclaim with lots of unreclaimable
108 * pages. It is better to clamp down on writers than to start swapping, and
109 * performing lots of scanning.
110 *
111 * We only allow 1/2 of the currently-unmapped memory to be dirtied.
112 *
113 * We don't permit the clamping level to fall below 5% - that is getting rather
114 * excessive.
115 *
116 * We make sure that the background writeout level is below the adjusted
117 * clamping level.
118 */
119 static void
120 get_dirty_limits(long *pbackground, long *pdirty,
121 struct address_space *mapping)
122 {
123 int background_ratio; /* Percentages */
124 int dirty_ratio;
125 int unmapped_ratio;
126 long background;
127 long dirty;
128 unsigned long available_memory = total_pages;
129 struct task_struct *tsk;
131 #ifdef CONFIG_HIGHMEM
132 /*
133 * If this mapping can only allocate from low memory,
134 * we exclude high memory from our count.
135 */
136 if (mapping && !(mapping_gfp_mask(mapping) & __GFP_HIGHMEM))
137 available_memory -= totalhigh_pages;
138 #endif
141 unmapped_ratio = 100 - ((global_page_state(NR_FILE_MAPPED) +
142 global_page_state(NR_ANON_PAGES)) * 100) /
143 total_pages;
145 dirty_ratio = vm_dirty_ratio;
146 if (dirty_ratio > unmapped_ratio / 2)
147 dirty_ratio = unmapped_ratio / 2;
149 if (dirty_ratio < 5)
150 dirty_ratio = 5;
152 background_ratio = dirty_background_ratio;
153 if (background_ratio >= dirty_ratio)
154 background_ratio = dirty_ratio / 2;
156 background = (background_ratio * available_memory) / 100;
157 dirty = (dirty_ratio * available_memory) / 100;
158 tsk = current;
159 if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
160 background += background / 4;
161 dirty += dirty / 4;
162 }
163 *pbackground = background;
164 *pdirty = dirty;
165 }
167 /*
168 * balance_dirty_pages() must be called by processes which are generating dirty
169 * data. It looks at the number of dirty pages in the machine and will force
170 * the caller to perform writeback if the system is over `vm_dirty_ratio'.
171 * If we're over `background_thresh' then pdflush is woken to perform some
172 * writeout.
173 */
174 static void balance_dirty_pages(struct address_space *mapping)
175 {
176 long nr_reclaimable;
177 long background_thresh;
178 long dirty_thresh;
179 unsigned long pages_written = 0;
180 unsigned long write_chunk = sync_writeback_pages();
182 struct backing_dev_info *bdi = mapping->backing_dev_info;
184 for (;;) {
185 struct writeback_control wbc = {
186 .bdi = bdi,
187 .sync_mode = WB_SYNC_NONE,
188 .older_than_this = NULL,
189 .nr_to_write = write_chunk,
190 .range_cyclic = 1,
191 };
193 get_dirty_limits(&background_thresh, &dirty_thresh, mapping);
194 nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
195 global_page_state(NR_UNSTABLE_NFS);
196 if (nr_reclaimable + global_page_state(NR_WRITEBACK) <=
197 dirty_thresh)
198 break;
200 if (!dirty_exceeded)
201 dirty_exceeded = 1;
203 /* Note: nr_reclaimable denotes nr_dirty + nr_unstable.
204 * Unstable writes are a feature of certain networked
205 * filesystems (i.e. NFS) in which data may have been
206 * written to the server's write cache, but has not yet
207 * been flushed to permanent storage.
208 */
209 if (nr_reclaimable) {
210 writeback_inodes(&wbc);
211 get_dirty_limits(&background_thresh,
212 &dirty_thresh, mapping);
213 nr_reclaimable = global_page_state(NR_FILE_DIRTY) +
214 global_page_state(NR_UNSTABLE_NFS);
215 if (nr_reclaimable +
216 global_page_state(NR_WRITEBACK)
217 <= dirty_thresh)
218 break;
219 pages_written += write_chunk - wbc.nr_to_write;
220 if (pages_written >= write_chunk)
221 break; /* We've done our duty */
222 }
223 blk_congestion_wait(WRITE, HZ/10);
224 }
226 if (nr_reclaimable + global_page_state(NR_WRITEBACK)
227 <= dirty_thresh && dirty_exceeded)
228 dirty_exceeded = 0;
230 if (writeback_in_progress(bdi))
231 return; /* pdflush is already working this queue */
233 /*
234 * In laptop mode, we wait until hitting the higher threshold before
235 * starting background writeout, and then write out all the way down
236 * to the lower threshold. So slow writers cause minimal disk activity.
237 *
238 * In normal mode, we start background writeout at the lower
239 * background_thresh, to keep the amount of dirty memory low.
240 */
241 if ((laptop_mode && pages_written) ||
242 (!laptop_mode && (nr_reclaimable > background_thresh)))
243 pdflush_operation(background_writeout, 0);
244 }
246 /**
247 * balance_dirty_pages_ratelimited_nr - balance dirty memory state
248 * @mapping: address_space which was dirtied
249 * @nr_pages_dirtied: number of pages which the caller has just dirtied
250 *
251 * Processes which are dirtying memory should call in here once for each page
252 * which was newly dirtied. The function will periodically check the system's
253 * dirty state and will initiate writeback if needed.
254 *
255 * On really big machines, get_writeback_state is expensive, so try to avoid
256 * calling it too often (ratelimiting). But once we're over the dirty memory
257 * limit we decrease the ratelimiting by a lot, to prevent individual processes
258 * from overshooting the limit by (ratelimit_pages) each.
259 */
260 void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
261 unsigned long nr_pages_dirtied)
262 {
263 static DEFINE_PER_CPU(unsigned long, ratelimits) = 0;
264 unsigned long ratelimit;
265 unsigned long *p;
267 ratelimit = ratelimit_pages;
268 if (dirty_exceeded)
269 ratelimit = 8;
271 /*
272 * Check the rate limiting. Also, we do not want to throttle real-time
273 * tasks in balance_dirty_pages(). Period.
274 */
275 preempt_disable();
276 p = &__get_cpu_var(ratelimits);
277 *p += nr_pages_dirtied;
278 if (unlikely(*p >= ratelimit)) {
279 *p = 0;
280 preempt_enable();
281 balance_dirty_pages(mapping);
282 return;
283 }
284 preempt_enable();
285 }
286 EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr);
288 void throttle_vm_writeout(void)
289 {
290 long background_thresh;
291 long dirty_thresh;
293 for ( ; ; ) {
294 get_dirty_limits(&background_thresh, &dirty_thresh, NULL);
296 /*
297 * Boost the allowable dirty threshold a bit for page
298 * allocators so they don't get DoS'ed by heavy writers
299 */
300 dirty_thresh += dirty_thresh / 10; /* wheeee... */
302 if (global_page_state(NR_UNSTABLE_NFS) +
303 global_page_state(NR_WRITEBACK) <= dirty_thresh)
304 break;
305 blk_congestion_wait(WRITE, HZ/10);
306 }
307 }
310 /*
311 * writeback at least _min_pages, and keep writing until the amount of dirty
312 * memory is less than the background threshold, or until we're all clean.
313 */
314 static void background_writeout(unsigned long _min_pages)
315 {
316 long min_pages = _min_pages;
317 struct writeback_control wbc = {
318 .bdi = NULL,
319 .sync_mode = WB_SYNC_NONE,
320 .older_than_this = NULL,
321 .nr_to_write = 0,
322 .nonblocking = 1,
323 .range_cyclic = 1,
324 };
326 for ( ; ; ) {
327 long background_thresh;
328 long dirty_thresh;
330 get_dirty_limits(&background_thresh, &dirty_thresh, NULL);
331 if (global_page_state(NR_FILE_DIRTY) +
332 global_page_state(NR_UNSTABLE_NFS) < background_thresh
333 && min_pages <= 0)
334 break;
335 wbc.encountered_congestion = 0;
336 wbc.nr_to_write = MAX_WRITEBACK_PAGES;
337 wbc.pages_skipped = 0;
338 writeback_inodes(&wbc);
339 min_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
340 if (wbc.nr_to_write > 0 || wbc.pages_skipped > 0) {
341 /* Wrote less than expected */
342 blk_congestion_wait(WRITE, HZ/10);
343 if (!wbc.encountered_congestion)
344 break;
345 }
346 }
347 }
349 /*
350 * Start writeback of `nr_pages' pages. If `nr_pages' is zero, write back
351 * the whole world. Returns 0 if a pdflush thread was dispatched. Returns
352 * -1 if all pdflush threads were busy.
353 */
354 int wakeup_pdflush(long nr_pages)
355 {
356 if (nr_pages == 0)
357 nr_pages = global_page_state(NR_FILE_DIRTY) +
358 global_page_state(NR_UNSTABLE_NFS);
359 return pdflush_operation(background_writeout, nr_pages);
360 }
362 static void wb_timer_fn(unsigned long unused);
363 static void laptop_timer_fn(unsigned long unused);
365 static DEFINE_TIMER(wb_timer, wb_timer_fn, 0, 0);
366 static DEFINE_TIMER(laptop_mode_wb_timer, laptop_timer_fn, 0, 0);
368 /*
369 * Periodic writeback of "old" data.
370 *
371 * Define "old": the first time one of an inode's pages is dirtied, we mark the
372 * dirtying-time in the inode's address_space. So this periodic writeback code
373 * just walks the superblock inode list, writing back any inodes which are
374 * older than a specific point in time.
375 *
376 * Try to run once per dirty_writeback_interval. But if a writeback event
377 * takes longer than a dirty_writeback_interval interval, then leave a
378 * one-second gap.
379 *
380 * older_than_this takes precedence over nr_to_write. So we'll only write back
381 * all dirty pages if they are all attached to "old" mappings.
382 */
383 static void wb_kupdate(unsigned long arg)
384 {
385 unsigned long oldest_jif;
386 unsigned long start_jif;
387 unsigned long next_jif;
388 long nr_to_write;
389 struct writeback_control wbc = {
390 .bdi = NULL,
391 .sync_mode = WB_SYNC_NONE,
392 .older_than_this = &oldest_jif,
393 .nr_to_write = 0,
394 .nonblocking = 1,
395 .for_kupdate = 1,
396 .range_cyclic = 1,
397 };
399 sync_supers();
401 oldest_jif = jiffies - dirty_expire_interval;
402 start_jif = jiffies;
403 next_jif = start_jif + dirty_writeback_interval;
404 nr_to_write = global_page_state(NR_FILE_DIRTY) +
405 global_page_state(NR_UNSTABLE_NFS) +
406 (inodes_stat.nr_inodes - inodes_stat.nr_unused);
407 while (nr_to_write > 0) {
408 wbc.encountered_congestion = 0;
409 wbc.nr_to_write = MAX_WRITEBACK_PAGES;
410 writeback_inodes(&wbc);
411 if (wbc.nr_to_write > 0) {
412 if (wbc.encountered_congestion)
413 blk_congestion_wait(WRITE, HZ/10);
414 else
415 break; /* All the old data is written */
416 }
417 nr_to_write -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
418 }
419 if (time_before(next_jif, jiffies + HZ))
420 next_jif = jiffies + HZ;
421 if (dirty_writeback_interval)
422 mod_timer(&wb_timer, next_jif);
423 }
425 /*
426 * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs
427 */
428 int dirty_writeback_centisecs_handler(ctl_table *table, int write,
429 struct file *file, void __user *buffer, size_t *length, loff_t *ppos)
430 {
431 proc_dointvec_userhz_jiffies(table, write, file, buffer, length, ppos);
432 if (dirty_writeback_interval) {
433 mod_timer(&wb_timer,
434 jiffies + dirty_writeback_interval);
435 } else {
436 del_timer(&wb_timer);
437 }
438 return 0;
439 }
441 static void wb_timer_fn(unsigned long unused)
442 {
443 if (pdflush_operation(wb_kupdate, 0) < 0)
444 mod_timer(&wb_timer, jiffies + HZ); /* delay 1 second */
445 }
447 static void laptop_flush(unsigned long unused)
448 {
449 sys_sync();
450 }
452 static void laptop_timer_fn(unsigned long unused)
453 {
454 pdflush_operation(laptop_flush, 0);
455 }
457 /*
458 * We've spun up the disk and we're in laptop mode: schedule writeback
459 * of all dirty data a few seconds from now. If the flush is already scheduled
460 * then push it back - the user is still using the disk.
461 */
462 void laptop_io_completion(void)
463 {
464 mod_timer(&laptop_mode_wb_timer, jiffies + laptop_mode);
465 }
467 /*
468 * We're in laptop mode and we've just synced. The sync's writes will have
469 * caused another writeback to be scheduled by laptop_io_completion.
470 * Nothing needs to be written back anymore, so we unschedule the writeback.
471 */
472 void laptop_sync_completion(void)
473 {
474 del_timer(&laptop_mode_wb_timer);
475 }
477 /*
478 * If ratelimit_pages is too high then we can get into dirty-data overload
479 * if a large number of processes all perform writes at the same time.
480 * If it is too low then SMP machines will call the (expensive)
481 * get_writeback_state too often.
482 *
483 * Here we set ratelimit_pages to a level which ensures that when all CPUs are
484 * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory
485 * thresholds before writeback cuts in.
486 *
487 * But the limit should not be set too high. Because it also controls the
488 * amount of memory which the balance_dirty_pages() caller has to write back.
489 * If this is too large then the caller will block on the IO queue all the
490 * time. So limit it to four megabytes - the balance_dirty_pages() caller
491 * will write six megabyte chunks, max.
492 */
494 static void set_ratelimit(void)
495 {
496 ratelimit_pages = total_pages / (num_online_cpus() * 32);
497 if (ratelimit_pages < 16)
498 ratelimit_pages = 16;
499 if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024)
500 ratelimit_pages = (4096 * 1024) / PAGE_CACHE_SIZE;
501 }
503 static int __cpuinit
504 ratelimit_handler(struct notifier_block *self, unsigned long u, void *v)
505 {
506 set_ratelimit();
507 return 0;
508 }
510 static struct notifier_block __cpuinitdata ratelimit_nb = {
511 .notifier_call = ratelimit_handler,
512 .next = NULL,
513 };
515 /*
516 * If the machine has a large highmem:lowmem ratio then scale back the default
517 * dirty memory thresholds: allowing too much dirty highmem pins an excessive
518 * number of buffer_heads.
519 */
520 void __init page_writeback_init(void)
521 {
522 long buffer_pages = nr_free_buffer_pages();
523 long correction;
525 total_pages = nr_free_pagecache_pages();
527 correction = (100 * 4 * buffer_pages) / total_pages;
529 if (correction < 100) {
530 dirty_background_ratio *= correction;
531 dirty_background_ratio /= 100;
532 vm_dirty_ratio *= correction;
533 vm_dirty_ratio /= 100;
535 if (dirty_background_ratio <= 0)
536 dirty_background_ratio = 1;
537 if (vm_dirty_ratio <= 0)
538 vm_dirty_ratio = 1;
539 }
540 mod_timer(&wb_timer, jiffies + dirty_writeback_interval);
541 set_ratelimit();
542 register_cpu_notifier(&ratelimit_nb);
543 }
545 int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
546 {
547 int ret;
549 if (wbc->nr_to_write <= 0)
550 return 0;
551 wbc->for_writepages = 1;
552 if (mapping->a_ops->writepages)
553 ret = mapping->a_ops->writepages(mapping, wbc);
554 else
555 ret = generic_writepages(mapping, wbc);
556 wbc->for_writepages = 0;
557 return ret;
558 }
560 /**
561 * write_one_page - write out a single page and optionally wait on I/O
562 *
563 * @page: the page to write
564 * @wait: if true, wait on writeout
565 *
566 * The page must be locked by the caller and will be unlocked upon return.
567 *
568 * write_one_page() returns a negative error code if I/O failed.
569 */
570 int write_one_page(struct page *page, int wait)
571 {
572 struct address_space *mapping = page->mapping;
573 int ret = 0;
574 struct writeback_control wbc = {
575 .sync_mode = WB_SYNC_ALL,
576 .nr_to_write = 1,
577 };
579 BUG_ON(!PageLocked(page));
581 if (wait)
582 wait_on_page_writeback(page);
584 if (clear_page_dirty_for_io(page)) {
585 page_cache_get(page);
586 ret = mapping->a_ops->writepage(page, &wbc);
587 if (ret == 0 && wait) {
588 wait_on_page_writeback(page);
589 if (PageError(page))
590 ret = -EIO;
591 }
592 page_cache_release(page);
593 } else {
594 unlock_page(page);
595 }
596 return ret;
597 }
598 EXPORT_SYMBOL(write_one_page);
600 /*
601 * For address_spaces which do not use buffers. Just tag the page as dirty in
602 * its radix tree.
603 *
604 * This is also used when a single buffer is being dirtied: we want to set the
605 * page dirty in that case, but not all the buffers. This is a "bottom-up"
606 * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying.
607 *
608 * Most callers have locked the page, which pins the address_space in memory.
609 * But zap_pte_range() does not lock the page, however in that case the
610 * mapping is pinned by the vma's ->vm_file reference.
611 *
612 * We take care to handle the case where the page was truncated from the
613 * mapping by re-checking page_mapping() insode tree_lock.
614 */
615 int __set_page_dirty_nobuffers(struct page *page)
616 {
617 if (!TestSetPageDirty(page)) {
618 struct address_space *mapping = page_mapping(page);
619 struct address_space *mapping2;
621 if (mapping) {
622 write_lock_irq(&mapping->tree_lock);
623 mapping2 = page_mapping(page);
624 if (mapping2) { /* Race with truncate? */
625 BUG_ON(mapping2 != mapping);
626 if (mapping_cap_account_dirty(mapping))
627 __inc_zone_page_state(page,
628 NR_FILE_DIRTY);
629 radix_tree_tag_set(&mapping->page_tree,
630 page_index(page), PAGECACHE_TAG_DIRTY);
631 }
632 write_unlock_irq(&mapping->tree_lock);
633 if (mapping->host) {
634 /* !PageAnon && !swapper_space */
635 __mark_inode_dirty(mapping->host,
636 I_DIRTY_PAGES);
637 }
638 }
639 return 1;
640 }
641 return 0;
642 }
643 EXPORT_SYMBOL(__set_page_dirty_nobuffers);
645 /*
646 * When a writepage implementation decides that it doesn't want to write this
647 * page for some reason, it should redirty the locked page via
648 * redirty_page_for_writepage() and it should then unlock the page and return 0
649 */
650 int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page)
651 {
652 wbc->pages_skipped++;
653 return __set_page_dirty_nobuffers(page);
654 }
655 EXPORT_SYMBOL(redirty_page_for_writepage);
657 /*
658 * If the mapping doesn't provide a set_page_dirty a_op, then
659 * just fall through and assume that it wants buffer_heads.
660 */
661 int fastcall set_page_dirty(struct page *page)
662 {
663 struct address_space *mapping = page_mapping(page);
665 if (likely(mapping)) {
666 int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
667 if (spd)
668 return (*spd)(page);
669 return __set_page_dirty_buffers(page);
670 }
671 if (!PageDirty(page)) {
672 if (!TestSetPageDirty(page))
673 return 1;
674 }
675 return 0;
676 }
677 EXPORT_SYMBOL(set_page_dirty);
679 /*
680 * set_page_dirty() is racy if the caller has no reference against
681 * page->mapping->host, and if the page is unlocked. This is because another
682 * CPU could truncate the page off the mapping and then free the mapping.
683 *
684 * Usually, the page _is_ locked, or the caller is a user-space process which
685 * holds a reference on the inode by having an open file.
686 *
687 * In other cases, the page should be locked before running set_page_dirty().
688 */
689 int set_page_dirty_lock(struct page *page)
690 {
691 int ret;
693 lock_page(page);
694 ret = set_page_dirty(page);
695 unlock_page(page);
696 return ret;
697 }
698 EXPORT_SYMBOL(set_page_dirty_lock);
700 /*
701 * Clear a page's dirty flag, while caring for dirty memory accounting.
702 * Returns true if the page was previously dirty.
703 */
704 int test_clear_page_dirty(struct page *page)
705 {
706 struct address_space *mapping = page_mapping(page);
707 unsigned long flags;
709 if (mapping) {
710 write_lock_irqsave(&mapping->tree_lock, flags);
711 if (TestClearPageDirty(page)) {
712 radix_tree_tag_clear(&mapping->page_tree,
713 page_index(page),
714 PAGECACHE_TAG_DIRTY);
715 if (mapping_cap_account_dirty(mapping))
716 __dec_zone_page_state(page, NR_FILE_DIRTY);
717 write_unlock_irqrestore(&mapping->tree_lock, flags);
718 return 1;
719 }
720 write_unlock_irqrestore(&mapping->tree_lock, flags);
721 return 0;
722 }
723 return TestClearPageDirty(page);
724 }
725 EXPORT_SYMBOL(test_clear_page_dirty);
727 /*
728 * Clear a page's dirty flag, while caring for dirty memory accounting.
729 * Returns true if the page was previously dirty.
730 *
731 * This is for preparing to put the page under writeout. We leave the page
732 * tagged as dirty in the radix tree so that a concurrent write-for-sync
733 * can discover it via a PAGECACHE_TAG_DIRTY walk. The ->writepage
734 * implementation will run either set_page_writeback() or set_page_dirty(),
735 * at which stage we bring the page's dirty flag and radix-tree dirty tag
736 * back into sync.
737 *
738 * This incoherency between the page's dirty flag and radix-tree tag is
739 * unfortunate, but it only exists while the page is locked.
740 */
741 int clear_page_dirty_for_io(struct page *page)
742 {
743 struct address_space *mapping = page_mapping(page);
745 if (mapping) {
746 if (TestClearPageDirty(page)) {
747 if (mapping_cap_account_dirty(mapping))
748 dec_zone_page_state(page, NR_FILE_DIRTY);
749 return 1;
750 }
751 return 0;
752 }
753 return TestClearPageDirty(page);
754 }
755 EXPORT_SYMBOL(clear_page_dirty_for_io);
757 int test_clear_page_writeback(struct page *page)
758 {
759 struct address_space *mapping = page_mapping(page);
760 int ret;
762 if (mapping) {
763 unsigned long flags;
765 write_lock_irqsave(&mapping->tree_lock, flags);
766 ret = TestClearPageWriteback(page);
767 if (ret)
768 radix_tree_tag_clear(&mapping->page_tree,
769 page_index(page),
770 PAGECACHE_TAG_WRITEBACK);
771 write_unlock_irqrestore(&mapping->tree_lock, flags);
772 } else {
773 ret = TestClearPageWriteback(page);
774 }
775 return ret;
776 }
778 int test_set_page_writeback(struct page *page)
779 {
780 struct address_space *mapping = page_mapping(page);
781 int ret;
783 if (mapping) {
784 unsigned long flags;
786 write_lock_irqsave(&mapping->tree_lock, flags);
787 ret = TestSetPageWriteback(page);
788 if (!ret)
789 radix_tree_tag_set(&mapping->page_tree,
790 page_index(page),
791 PAGECACHE_TAG_WRITEBACK);
792 if (!PageDirty(page))
793 radix_tree_tag_clear(&mapping->page_tree,
794 page_index(page),
795 PAGECACHE_TAG_DIRTY);
796 write_unlock_irqrestore(&mapping->tree_lock, flags);
797 } else {
798 ret = TestSetPageWriteback(page);
799 }
800 return ret;
802 }
803 EXPORT_SYMBOL(test_set_page_writeback);
805 /*
806 * Return true if any of the pages in the mapping are marged with the
807 * passed tag.
808 */
809 int mapping_tagged(struct address_space *mapping, int tag)
810 {
811 unsigned long flags;
812 int ret;
814 read_lock_irqsave(&mapping->tree_lock, flags);
815 ret = radix_tree_tagged(&mapping->page_tree, tag);
816 read_unlock_irqrestore(&mapping->tree_lock, flags);
817 return ret;
818 }
819 EXPORT_SYMBOL(mapping_tagged);