page-writeback.c 23.2 KB
Newer Older
L
Linus Torvalds 已提交
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48
/*
 * mm/page-writeback.c.
 *
 * Copyright (C) 2002, Linus Torvalds.
 *
 * Contains functions related to writing back dirty pages at the
 * address_space level.
 *
 * 10Apr2002	akpm@zip.com.au
 *		Initial version
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/spinlock.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/swap.h>
#include <linux/slab.h>
#include <linux/pagemap.h>
#include <linux/writeback.h>
#include <linux/init.h>
#include <linux/backing-dev.h>
#include <linux/blkdev.h>
#include <linux/mpage.h>
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/smp.h>
#include <linux/sysctl.h>
#include <linux/cpu.h>
#include <linux/syscalls.h>

/*
 * The maximum number of pages to writeout in a single bdflush/kupdate
 * operation.  We do this so we don't hold I_LOCK against an inode for
 * enormous amounts of time, which would block a userspace task which has
 * been forced to throttle against that inode.  Also, the code reevaluates
 * the dirty each time it has written this many pages.
 */
#define MAX_WRITEBACK_PAGES	1024

/*
 * After a CPU has dirtied this many pages, balance_dirty_pages_ratelimited
 * will look to see if it needs to force writeback or throttling.
 */
static long ratelimit_pages = 32;

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 */
L
Linus Torvalds 已提交
50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74

/*
 * When balance_dirty_pages decides that the caller needs to perform some
 * non-background writeback, this is how many pages it will attempt to write.
 * It should be somewhat larger than RATELIMIT_PAGES to ensure that reasonably
 * large amounts of I/O are submitted.
 */
static inline long sync_writeback_pages(void)
{
	return ratelimit_pages + ratelimit_pages / 2;
}

/* The following parameters are exported via /proc/sys/vm */

/*
 * Start background writeback (via pdflush) at this percentage
 */
int dirty_background_ratio = 10;

/*
 * The generator of dirty data starts writeback at this percentage
 */
int vm_dirty_ratio = 40;

/*
75
 * The interval between `kupdate'-style writebacks, in jiffies
L
Linus Torvalds 已提交
76
 */
77
int dirty_writeback_interval = 5 * HZ;
L
Linus Torvalds 已提交
78 79

/*
80
 * The longest number of jiffies for which data is allowed to remain dirty
L
Linus Torvalds 已提交
81
 */
82
int dirty_expire_interval = 30 * HZ;
L
Linus Torvalds 已提交
83 84 85 86 87 88 89

/*
 * Flag that makes the machine dump writes/reads and block dirtyings.
 */
int block_dump;

/*
90 91
 * Flag that puts the machine in "laptop mode". Doubles as a timeout in jiffies:
 * a full sync is triggered after this time elapses without any disk activity.
L
Linus Torvalds 已提交
92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113
 */
int laptop_mode;

EXPORT_SYMBOL(laptop_mode);

/* End of sysctl-exported parameters */


static void background_writeout(unsigned long _min_pages);

struct writeback_state
{
	unsigned long nr_dirty;
	unsigned long nr_unstable;
	unsigned long nr_mapped;
	unsigned long nr_writeback;
};

static void get_writeback_state(struct writeback_state *wbs)
{
	wbs->nr_dirty = read_page_state(nr_dirty);
	wbs->nr_unstable = read_page_state(nr_unstable);
114 115
	wbs->nr_mapped = global_page_state(NR_FILE_MAPPED) +
				global_page_state(NR_ANON_PAGES);
L
Linus Torvalds 已提交
116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207
	wbs->nr_writeback = read_page_state(nr_writeback);
}

/*
 * Work out the current dirty-memory clamping and background writeout
 * thresholds.
 *
 * The main aim here is to lower them aggressively if there is a lot of mapped
 * memory around.  To avoid stressing page reclaim with lots of unreclaimable
 * pages.  It is better to clamp down on writers than to start swapping, and
 * performing lots of scanning.
 *
 * We only allow 1/2 of the currently-unmapped memory to be dirtied.
 *
 * We don't permit the clamping level to fall below 5% - that is getting rather
 * excessive.
 *
 * We make sure that the background writeout level is below the adjusted
 * clamping level.
 */
static void
get_dirty_limits(struct writeback_state *wbs, long *pbackground, long *pdirty,
		struct address_space *mapping)
{
	int background_ratio;		/* Percentages */
	int dirty_ratio;
	int unmapped_ratio;
	long background;
	long dirty;
	unsigned long available_memory = total_pages;
	struct task_struct *tsk;

	get_writeback_state(wbs);

#ifdef CONFIG_HIGHMEM
	/*
	 * If this mapping can only allocate from low memory,
	 * we exclude high memory from our count.
	 */
	if (mapping && !(mapping_gfp_mask(mapping) & __GFP_HIGHMEM))
		available_memory -= totalhigh_pages;
#endif


	unmapped_ratio = 100 - (wbs->nr_mapped * 100) / total_pages;

	dirty_ratio = vm_dirty_ratio;
	if (dirty_ratio > unmapped_ratio / 2)
		dirty_ratio = unmapped_ratio / 2;

	if (dirty_ratio < 5)
		dirty_ratio = 5;

	background_ratio = dirty_background_ratio;
	if (background_ratio >= dirty_ratio)
		background_ratio = dirty_ratio / 2;

	background = (background_ratio * available_memory) / 100;
	dirty = (dirty_ratio * available_memory) / 100;
	tsk = current;
	if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
		background += background / 4;
		dirty += dirty / 4;
	}
	*pbackground = background;
	*pdirty = dirty;
}

/*
 * balance_dirty_pages() must be called by processes which are generating dirty
 * data.  It looks at the number of dirty pages in the machine and will force
 * the caller to perform writeback if the system is over `vm_dirty_ratio'.
 * If we're over `background_thresh' then pdflush is woken to perform some
 * writeout.
 */
static void balance_dirty_pages(struct address_space *mapping)
{
	struct writeback_state wbs;
	long nr_reclaimable;
	long background_thresh;
	long dirty_thresh;
	unsigned long pages_written = 0;
	unsigned long write_chunk = sync_writeback_pages();

	struct backing_dev_info *bdi = mapping->backing_dev_info;

	for (;;) {
		struct writeback_control wbc = {
			.bdi		= bdi,
			.sync_mode	= WB_SYNC_NONE,
			.older_than_this = NULL,
			.nr_to_write	= write_chunk,
208
			.range_cyclic	= 1,
L
Linus Torvalds 已提交
209 210 211 212 213 214 215 216
		};

		get_dirty_limits(&wbs, &background_thresh,
					&dirty_thresh, mapping);
		nr_reclaimable = wbs.nr_dirty + wbs.nr_unstable;
		if (nr_reclaimable + wbs.nr_writeback <= dirty_thresh)
			break;

217 218
		if (!dirty_exceeded)
			dirty_exceeded = 1;
L
Linus Torvalds 已提交
219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239

		/* Note: nr_reclaimable denotes nr_dirty + nr_unstable.
		 * Unstable writes are a feature of certain networked
		 * filesystems (i.e. NFS) in which data may have been
		 * written to the server's write cache, but has not yet
		 * been flushed to permanent storage.
		 */
		if (nr_reclaimable) {
			writeback_inodes(&wbc);
			get_dirty_limits(&wbs, &background_thresh,
					&dirty_thresh, mapping);
			nr_reclaimable = wbs.nr_dirty + wbs.nr_unstable;
			if (nr_reclaimable + wbs.nr_writeback <= dirty_thresh)
				break;
			pages_written += write_chunk - wbc.nr_to_write;
			if (pages_written >= write_chunk)
				break;		/* We've done our duty */
		}
		blk_congestion_wait(WRITE, HZ/10);
	}

240
	if (nr_reclaimable + wbs.nr_writeback <= dirty_thresh && dirty_exceeded)
L
Linus Torvalds 已提交
241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259
		dirty_exceeded = 0;

	if (writeback_in_progress(bdi))
		return;		/* pdflush is already working this queue */

	/*
	 * In laptop mode, we wait until hitting the higher threshold before
	 * starting background writeout, and then write out all the way down
	 * to the lower threshold.  So slow writers cause minimal disk activity.
	 *
	 * In normal mode, we start background writeout at the lower
	 * background_thresh, to keep the amount of dirty memory low.
	 */
	if ((laptop_mode && pages_written) ||
	     (!laptop_mode && (nr_reclaimable > background_thresh)))
		pdflush_operation(background_writeout, 0);
}

/**
260
 * balance_dirty_pages_ratelimited_nr - balance dirty memory state
261
 * @mapping: address_space which was dirtied
262
 * @nr_pages_dirtied: number of pages which the caller has just dirtied
L
Linus Torvalds 已提交
263 264 265 266 267 268 269 270 271 272
 *
 * Processes which are dirtying memory should call in here once for each page
 * which was newly dirtied.  The function will periodically check the system's
 * dirty state and will initiate writeback if needed.
 *
 * On really big machines, get_writeback_state is expensive, so try to avoid
 * calling it too often (ratelimiting).  But once we're over the dirty memory
 * limit we decrease the ratelimiting by a lot, to prevent individual processes
 * from overshooting the limit by (ratelimit_pages) each.
 */
273 274
void balance_dirty_pages_ratelimited_nr(struct address_space *mapping,
					unsigned long nr_pages_dirtied)
L
Linus Torvalds 已提交
275
{
276 277 278
	static DEFINE_PER_CPU(unsigned long, ratelimits) = 0;
	unsigned long ratelimit;
	unsigned long *p;
L
Linus Torvalds 已提交
279 280 281 282 283 284 285 286 287

	ratelimit = ratelimit_pages;
	if (dirty_exceeded)
		ratelimit = 8;

	/*
	 * Check the rate limiting. Also, we do not want to throttle real-time
	 * tasks in balance_dirty_pages(). Period.
	 */
288 289 290 291 292 293
	preempt_disable();
	p =  &__get_cpu_var(ratelimits);
	*p += nr_pages_dirtied;
	if (unlikely(*p >= ratelimit)) {
		*p = 0;
		preempt_enable();
L
Linus Torvalds 已提交
294 295 296
		balance_dirty_pages(mapping);
		return;
	}
297
	preempt_enable();
L
Linus Torvalds 已提交
298
}
299
EXPORT_SYMBOL(balance_dirty_pages_ratelimited_nr);
L
Linus Torvalds 已提交
300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335

void throttle_vm_writeout(void)
{
	struct writeback_state wbs;
	long background_thresh;
	long dirty_thresh;

        for ( ; ; ) {
		get_dirty_limits(&wbs, &background_thresh, &dirty_thresh, NULL);

                /*
                 * Boost the allowable dirty threshold a bit for page
                 * allocators so they don't get DoS'ed by heavy writers
                 */
                dirty_thresh += dirty_thresh / 10;      /* wheeee... */

                if (wbs.nr_unstable + wbs.nr_writeback <= dirty_thresh)
                        break;
                blk_congestion_wait(WRITE, HZ/10);
        }
}


/*
 * writeback at least _min_pages, and keep writing until the amount of dirty
 * memory is less than the background threshold, or until we're all clean.
 */
static void background_writeout(unsigned long _min_pages)
{
	long min_pages = _min_pages;
	struct writeback_control wbc = {
		.bdi		= NULL,
		.sync_mode	= WB_SYNC_NONE,
		.older_than_this = NULL,
		.nr_to_write	= 0,
		.nonblocking	= 1,
336
		.range_cyclic	= 1,
L
Linus Torvalds 已提交
337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366
	};

	for ( ; ; ) {
		struct writeback_state wbs;
		long background_thresh;
		long dirty_thresh;

		get_dirty_limits(&wbs, &background_thresh, &dirty_thresh, NULL);
		if (wbs.nr_dirty + wbs.nr_unstable < background_thresh
				&& min_pages <= 0)
			break;
		wbc.encountered_congestion = 0;
		wbc.nr_to_write = MAX_WRITEBACK_PAGES;
		wbc.pages_skipped = 0;
		writeback_inodes(&wbc);
		min_pages -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
		if (wbc.nr_to_write > 0 || wbc.pages_skipped > 0) {
			/* Wrote less than expected */
			blk_congestion_wait(WRITE, HZ/10);
			if (!wbc.encountered_congestion)
				break;
		}
	}
}

/*
 * Start writeback of `nr_pages' pages.  If `nr_pages' is zero, write back
 * the whole world.  Returns 0 if a pdflush thread was dispatched.  Returns
 * -1 if all pdflush threads were busy.
 */
367
int wakeup_pdflush(long nr_pages)
L
Linus Torvalds 已提交
368 369 370 371 372 373 374 375 376 377 378 379 380
{
	if (nr_pages == 0) {
		struct writeback_state wbs;

		get_writeback_state(&wbs);
		nr_pages = wbs.nr_dirty + wbs.nr_unstable;
	}
	return pdflush_operation(background_writeout, nr_pages);
}

static void wb_timer_fn(unsigned long unused);
static void laptop_timer_fn(unsigned long unused);

381 382
static DEFINE_TIMER(wb_timer, wb_timer_fn, 0, 0);
static DEFINE_TIMER(laptop_mode_wb_timer, laptop_timer_fn, 0, 0);
L
Linus Torvalds 已提交
383 384 385 386 387 388 389 390 391

/*
 * Periodic writeback of "old" data.
 *
 * Define "old": the first time one of an inode's pages is dirtied, we mark the
 * dirtying-time in the inode's address_space.  So this periodic writeback code
 * just walks the superblock inode list, writing back any inodes which are
 * older than a specific point in time.
 *
392 393
 * Try to run once per dirty_writeback_interval.  But if a writeback event
 * takes longer than a dirty_writeback_interval interval, then leave a
L
Linus Torvalds 已提交
394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412
 * one-second gap.
 *
 * older_than_this takes precedence over nr_to_write.  So we'll only write back
 * all dirty pages if they are all attached to "old" mappings.
 */
static void wb_kupdate(unsigned long arg)
{
	unsigned long oldest_jif;
	unsigned long start_jif;
	unsigned long next_jif;
	long nr_to_write;
	struct writeback_state wbs;
	struct writeback_control wbc = {
		.bdi		= NULL,
		.sync_mode	= WB_SYNC_NONE,
		.older_than_this = &oldest_jif,
		.nr_to_write	= 0,
		.nonblocking	= 1,
		.for_kupdate	= 1,
413
		.range_cyclic	= 1,
L
Linus Torvalds 已提交
414 415 416 417 418
	};

	sync_supers();

	get_writeback_state(&wbs);
419
	oldest_jif = jiffies - dirty_expire_interval;
L
Linus Torvalds 已提交
420
	start_jif = jiffies;
421
	next_jif = start_jif + dirty_writeback_interval;
L
Linus Torvalds 已提交
422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437
	nr_to_write = wbs.nr_dirty + wbs.nr_unstable +
			(inodes_stat.nr_inodes - inodes_stat.nr_unused);
	while (nr_to_write > 0) {
		wbc.encountered_congestion = 0;
		wbc.nr_to_write = MAX_WRITEBACK_PAGES;
		writeback_inodes(&wbc);
		if (wbc.nr_to_write > 0) {
			if (wbc.encountered_congestion)
				blk_congestion_wait(WRITE, HZ/10);
			else
				break;	/* All the old data is written */
		}
		nr_to_write -= MAX_WRITEBACK_PAGES - wbc.nr_to_write;
	}
	if (time_before(next_jif, jiffies + HZ))
		next_jif = jiffies + HZ;
438
	if (dirty_writeback_interval)
L
Linus Torvalds 已提交
439 440 441 442 443 444 445 446 447
		mod_timer(&wb_timer, next_jif);
}

/*
 * sysctl handler for /proc/sys/vm/dirty_writeback_centisecs
 */
int dirty_writeback_centisecs_handler(ctl_table *table, int write,
		struct file *file, void __user *buffer, size_t *length, loff_t *ppos)
{
448 449
	proc_dointvec_userhz_jiffies(table, write, file, buffer, length, ppos);
	if (dirty_writeback_interval) {
L
Linus Torvalds 已提交
450
		mod_timer(&wb_timer,
451 452
			jiffies + dirty_writeback_interval);
		} else {
L
Linus Torvalds 已提交
453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480
		del_timer(&wb_timer);
	}
	return 0;
}

static void wb_timer_fn(unsigned long unused)
{
	if (pdflush_operation(wb_kupdate, 0) < 0)
		mod_timer(&wb_timer, jiffies + HZ); /* delay 1 second */
}

static void laptop_flush(unsigned long unused)
{
	sys_sync();
}

static void laptop_timer_fn(unsigned long unused)
{
	pdflush_operation(laptop_flush, 0);
}

/*
 * We've spun up the disk and we're in laptop mode: schedule writeback
 * of all dirty data a few seconds from now.  If the flush is already scheduled
 * then push it back - the user is still using the disk.
 */
void laptop_io_completion(void)
{
481
	mod_timer(&laptop_mode_wb_timer, jiffies + laptop_mode);
L
Linus Torvalds 已提交
482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519
}

/*
 * We're in laptop mode and we've just synced. The sync's writes will have
 * caused another writeback to be scheduled by laptop_io_completion.
 * Nothing needs to be written back anymore, so we unschedule the writeback.
 */
void laptop_sync_completion(void)
{
	del_timer(&laptop_mode_wb_timer);
}

/*
 * If ratelimit_pages is too high then we can get into dirty-data overload
 * if a large number of processes all perform writes at the same time.
 * If it is too low then SMP machines will call the (expensive)
 * get_writeback_state too often.
 *
 * Here we set ratelimit_pages to a level which ensures that when all CPUs are
 * dirtying in parallel, we cannot go more than 3% (1/32) over the dirty memory
 * thresholds before writeback cuts in.
 *
 * But the limit should not be set too high.  Because it also controls the
 * amount of memory which the balance_dirty_pages() caller has to write back.
 * If this is too large then the caller will block on the IO queue all the
 * time.  So limit it to four megabytes - the balance_dirty_pages() caller
 * will write six megabyte chunks, max.
 */

static void set_ratelimit(void)
{
	ratelimit_pages = total_pages / (num_online_cpus() * 32);
	if (ratelimit_pages < 16)
		ratelimit_pages = 16;
	if (ratelimit_pages * PAGE_CACHE_SIZE > 4096 * 1024)
		ratelimit_pages = (4096 * 1024) / PAGE_CACHE_SIZE;
}

520
static int __cpuinit
L
Linus Torvalds 已提交
521 522 523 524 525 526
ratelimit_handler(struct notifier_block *self, unsigned long u, void *v)
{
	set_ratelimit();
	return 0;
}

527
static struct notifier_block __cpuinitdata ratelimit_nb = {
L
Linus Torvalds 已提交
528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556
	.notifier_call	= ratelimit_handler,
	.next		= NULL,
};

/*
 * If the machine has a large highmem:lowmem ratio then scale back the default
 * dirty memory thresholds: allowing too much dirty highmem pins an excessive
 * number of buffer_heads.
 */
void __init page_writeback_init(void)
{
	long buffer_pages = nr_free_buffer_pages();
	long correction;

	total_pages = nr_free_pagecache_pages();

	correction = (100 * 4 * buffer_pages) / total_pages;

	if (correction < 100) {
		dirty_background_ratio *= correction;
		dirty_background_ratio /= 100;
		vm_dirty_ratio *= correction;
		vm_dirty_ratio /= 100;

		if (dirty_background_ratio <= 0)
			dirty_background_ratio = 1;
		if (vm_dirty_ratio <= 0)
			vm_dirty_ratio = 1;
	}
557
	mod_timer(&wb_timer, jiffies + dirty_writeback_interval);
L
Linus Torvalds 已提交
558 559 560 561 562 563
	set_ratelimit();
	register_cpu_notifier(&ratelimit_nb);
}

int do_writepages(struct address_space *mapping, struct writeback_control *wbc)
{
564 565
	int ret;

L
Linus Torvalds 已提交
566 567
	if (wbc->nr_to_write <= 0)
		return 0;
568
	wbc->for_writepages = 1;
L
Linus Torvalds 已提交
569
	if (mapping->a_ops->writepages)
570 571 572 573 574
		ret =  mapping->a_ops->writepages(mapping, wbc);
	else
		ret = generic_writepages(mapping, wbc);
	wbc->for_writepages = 0;
	return ret;
L
Linus Torvalds 已提交
575 576 577 578 579
}

/**
 * write_one_page - write out a single page and optionally wait on I/O
 *
580 581
 * @page: the page to write
 * @wait: if true, wait on writeout
L
Linus Torvalds 已提交
582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654
 *
 * The page must be locked by the caller and will be unlocked upon return.
 *
 * write_one_page() returns a negative error code if I/O failed.
 */
int write_one_page(struct page *page, int wait)
{
	struct address_space *mapping = page->mapping;
	int ret = 0;
	struct writeback_control wbc = {
		.sync_mode = WB_SYNC_ALL,
		.nr_to_write = 1,
	};

	BUG_ON(!PageLocked(page));

	if (wait)
		wait_on_page_writeback(page);

	if (clear_page_dirty_for_io(page)) {
		page_cache_get(page);
		ret = mapping->a_ops->writepage(page, &wbc);
		if (ret == 0 && wait) {
			wait_on_page_writeback(page);
			if (PageError(page))
				ret = -EIO;
		}
		page_cache_release(page);
	} else {
		unlock_page(page);
	}
	return ret;
}
EXPORT_SYMBOL(write_one_page);

/*
 * For address_spaces which do not use buffers.  Just tag the page as dirty in
 * its radix tree.
 *
 * This is also used when a single buffer is being dirtied: we want to set the
 * page dirty in that case, but not all the buffers.  This is a "bottom-up"
 * dirtying, whereas __set_page_dirty_buffers() is a "top-down" dirtying.
 *
 * Most callers have locked the page, which pins the address_space in memory.
 * But zap_pte_range() does not lock the page, however in that case the
 * mapping is pinned by the vma's ->vm_file reference.
 *
 * We take care to handle the case where the page was truncated from the
 * mapping by re-checking page_mapping() insode tree_lock.
 */
int __set_page_dirty_nobuffers(struct page *page)
{
	if (!TestSetPageDirty(page)) {
		struct address_space *mapping = page_mapping(page);
		struct address_space *mapping2;

		if (mapping) {
			write_lock_irq(&mapping->tree_lock);
			mapping2 = page_mapping(page);
			if (mapping2) { /* Race with truncate? */
				BUG_ON(mapping2 != mapping);
				if (mapping_cap_account_dirty(mapping))
					inc_page_state(nr_dirty);
				radix_tree_tag_set(&mapping->page_tree,
					page_index(page), PAGECACHE_TAG_DIRTY);
			}
			write_unlock_irq(&mapping->tree_lock);
			if (mapping->host) {
				/* !PageAnon && !swapper_space */
				__mark_inode_dirty(mapping->host,
							I_DIRTY_PAGES);
			}
		}
655
		return 1;
L
Linus Torvalds 已提交
656
	}
657
	return 0;
L
Linus Torvalds 已提交
658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686
}
EXPORT_SYMBOL(__set_page_dirty_nobuffers);

/*
 * When a writepage implementation decides that it doesn't want to write this
 * page for some reason, it should redirty the locked page via
 * redirty_page_for_writepage() and it should then unlock the page and return 0
 */
int redirty_page_for_writepage(struct writeback_control *wbc, struct page *page)
{
	wbc->pages_skipped++;
	return __set_page_dirty_nobuffers(page);
}
EXPORT_SYMBOL(redirty_page_for_writepage);

/*
 * If the mapping doesn't provide a set_page_dirty a_op, then
 * just fall through and assume that it wants buffer_heads.
 */
int fastcall set_page_dirty(struct page *page)
{
	struct address_space *mapping = page_mapping(page);

	if (likely(mapping)) {
		int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
		if (spd)
			return (*spd)(page);
		return __set_page_dirty_buffers(page);
	}
687 688 689 690
	if (!PageDirty(page)) {
		if (!TestSetPageDirty(page))
			return 1;
	}
L
Linus Torvalds 已提交
691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770
	return 0;
}
EXPORT_SYMBOL(set_page_dirty);

/*
 * set_page_dirty() is racy if the caller has no reference against
 * page->mapping->host, and if the page is unlocked.  This is because another
 * CPU could truncate the page off the mapping and then free the mapping.
 *
 * Usually, the page _is_ locked, or the caller is a user-space process which
 * holds a reference on the inode by having an open file.
 *
 * In other cases, the page should be locked before running set_page_dirty().
 */
int set_page_dirty_lock(struct page *page)
{
	int ret;

	lock_page(page);
	ret = set_page_dirty(page);
	unlock_page(page);
	return ret;
}
EXPORT_SYMBOL(set_page_dirty_lock);

/*
 * Clear a page's dirty flag, while caring for dirty memory accounting. 
 * Returns true if the page was previously dirty.
 */
int test_clear_page_dirty(struct page *page)
{
	struct address_space *mapping = page_mapping(page);
	unsigned long flags;

	if (mapping) {
		write_lock_irqsave(&mapping->tree_lock, flags);
		if (TestClearPageDirty(page)) {
			radix_tree_tag_clear(&mapping->page_tree,
						page_index(page),
						PAGECACHE_TAG_DIRTY);
			write_unlock_irqrestore(&mapping->tree_lock, flags);
			if (mapping_cap_account_dirty(mapping))
				dec_page_state(nr_dirty);
			return 1;
		}
		write_unlock_irqrestore(&mapping->tree_lock, flags);
		return 0;
	}
	return TestClearPageDirty(page);
}
EXPORT_SYMBOL(test_clear_page_dirty);

/*
 * Clear a page's dirty flag, while caring for dirty memory accounting.
 * Returns true if the page was previously dirty.
 *
 * This is for preparing to put the page under writeout.  We leave the page
 * tagged as dirty in the radix tree so that a concurrent write-for-sync
 * can discover it via a PAGECACHE_TAG_DIRTY walk.  The ->writepage
 * implementation will run either set_page_writeback() or set_page_dirty(),
 * at which stage we bring the page's dirty flag and radix-tree dirty tag
 * back into sync.
 *
 * This incoherency between the page's dirty flag and radix-tree tag is
 * unfortunate, but it only exists while the page is locked.
 */
int clear_page_dirty_for_io(struct page *page)
{
	struct address_space *mapping = page_mapping(page);

	if (mapping) {
		if (TestClearPageDirty(page)) {
			if (mapping_cap_account_dirty(mapping))
				dec_page_state(nr_dirty);
			return 1;
		}
		return 0;
	}
	return TestClearPageDirty(page);
}
771
EXPORT_SYMBOL(clear_page_dirty_for_io);
L
Linus Torvalds 已提交
772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835

int test_clear_page_writeback(struct page *page)
{
	struct address_space *mapping = page_mapping(page);
	int ret;

	if (mapping) {
		unsigned long flags;

		write_lock_irqsave(&mapping->tree_lock, flags);
		ret = TestClearPageWriteback(page);
		if (ret)
			radix_tree_tag_clear(&mapping->page_tree,
						page_index(page),
						PAGECACHE_TAG_WRITEBACK);
		write_unlock_irqrestore(&mapping->tree_lock, flags);
	} else {
		ret = TestClearPageWriteback(page);
	}
	return ret;
}

int test_set_page_writeback(struct page *page)
{
	struct address_space *mapping = page_mapping(page);
	int ret;

	if (mapping) {
		unsigned long flags;

		write_lock_irqsave(&mapping->tree_lock, flags);
		ret = TestSetPageWriteback(page);
		if (!ret)
			radix_tree_tag_set(&mapping->page_tree,
						page_index(page),
						PAGECACHE_TAG_WRITEBACK);
		if (!PageDirty(page))
			radix_tree_tag_clear(&mapping->page_tree,
						page_index(page),
						PAGECACHE_TAG_DIRTY);
		write_unlock_irqrestore(&mapping->tree_lock, flags);
	} else {
		ret = TestSetPageWriteback(page);
	}
	return ret;

}
EXPORT_SYMBOL(test_set_page_writeback);

/*
 * Return true if any of the pages in the mapping are marged with the
 * passed tag.
 */
int mapping_tagged(struct address_space *mapping, int tag)
{
	unsigned long flags;
	int ret;

	read_lock_irqsave(&mapping->tree_lock, flags);
	ret = radix_tree_tagged(&mapping->page_tree, tag);
	read_unlock_irqrestore(&mapping->tree_lock, flags);
	return ret;
}
EXPORT_SYMBOL(mapping_tagged);