ia64/linux-2.6.18-xen.hg

view fs/fs-writeback.c @ 452:c7ed6fe5dca0

kexec: dont initialise regions in reserve_memory()

There is no need to initialise efi_memmap_res and boot_param_res in
reserve_memory() for the initial xen domain as it is done in
machine_kexec_setup_resources() using values from the kexec hypercall.

Signed-off-by: Simon Horman <horms@verge.net.au>
author Keir Fraser <keir.fraser@citrix.com>
date Thu Feb 28 10:55:18 2008 +0000 (2008-02-28)
parents 831230e53067
children
line source
1 /*
2 * fs/fs-writeback.c
3 *
4 * Copyright (C) 2002, Linus Torvalds.
5 *
6 * Contains all the functions related to writing back and waiting
7 * upon dirty inodes against superblocks, and writing back dirty
8 * pages against inodes. ie: data writeback. Writeout of the
9 * inode itself is not handled here.
10 *
11 * 10Apr2002 akpm@zip.com.au
12 * Split out of fs/inode.c
13 * Additions for address_space-based writeback
14 */
16 #include <linux/kernel.h>
17 #include <linux/spinlock.h>
18 #include <linux/sched.h>
19 #include <linux/fs.h>
20 #include <linux/mm.h>
21 #include <linux/writeback.h>
22 #include <linux/blkdev.h>
23 #include <linux/backing-dev.h>
24 #include <linux/buffer_head.h>
26 extern struct super_block *blockdev_superblock;
28 /**
29 * __mark_inode_dirty - internal function
30 * @inode: inode to mark
31 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
32 * Mark an inode as dirty. Callers should use mark_inode_dirty or
33 * mark_inode_dirty_sync.
34 *
35 * Put the inode on the super block's dirty list.
36 *
37 * CAREFUL! We mark it dirty unconditionally, but move it onto the
38 * dirty list only if it is hashed or if it refers to a blockdev.
39 * If it was not hashed, it will never be added to the dirty list
40 * even if it is later hashed, as it will have been marked dirty already.
41 *
42 * In short, make sure you hash any inodes _before_ you start marking
43 * them dirty.
44 *
45 * This function *must* be atomic for the I_DIRTY_PAGES case -
46 * set_page_dirty() is called under spinlock in several places.
47 *
48 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
49 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
50 * the kernel-internal blockdev inode represents the dirtying time of the
51 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
52 * page->mapping->host, so the page-dirtying time is recorded in the internal
53 * blockdev inode.
54 */
55 void __mark_inode_dirty(struct inode *inode, int flags)
56 {
57 struct super_block *sb = inode->i_sb;
59 /*
60 * Don't do this for I_DIRTY_PAGES - that doesn't actually
61 * dirty the inode itself
62 */
63 if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
64 if (sb->s_op->dirty_inode)
65 sb->s_op->dirty_inode(inode);
66 }
68 /*
69 * make sure that changes are seen by all cpus before we test i_state
70 * -- mikulas
71 */
72 smp_mb();
74 /* avoid the locking if we can */
75 if ((inode->i_state & flags) == flags)
76 return;
78 if (unlikely(block_dump)) {
79 struct dentry *dentry = NULL;
80 const char *name = "?";
82 if (!list_empty(&inode->i_dentry)) {
83 dentry = list_entry(inode->i_dentry.next,
84 struct dentry, d_alias);
85 if (dentry && dentry->d_name.name)
86 name = (const char *) dentry->d_name.name;
87 }
89 if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev"))
90 printk(KERN_DEBUG
91 "%s(%d): dirtied inode %lu (%s) on %s\n",
92 current->comm, current->pid, inode->i_ino,
93 name, inode->i_sb->s_id);
94 }
96 spin_lock(&inode_lock);
97 if ((inode->i_state & flags) != flags) {
98 const int was_dirty = inode->i_state & I_DIRTY;
100 inode->i_state |= flags;
102 /*
103 * If the inode is locked, just update its dirty state.
104 * The unlocker will place the inode on the appropriate
105 * superblock list, based upon its state.
106 */
107 if (inode->i_state & I_LOCK)
108 goto out;
110 /*
111 * Only add valid (hashed) inodes to the superblock's
112 * dirty list. Add blockdev inodes as well.
113 */
114 if (!S_ISBLK(inode->i_mode)) {
115 if (hlist_unhashed(&inode->i_hash))
116 goto out;
117 }
118 if (inode->i_state & (I_FREEING|I_CLEAR))
119 goto out;
121 /*
122 * If the inode was already on s_dirty or s_io, don't
123 * reposition it (that would break s_dirty time-ordering).
124 */
125 if (!was_dirty) {
126 inode->dirtied_when = jiffies;
127 list_move(&inode->i_list, &sb->s_dirty);
128 }
129 }
130 out:
131 spin_unlock(&inode_lock);
132 }
134 EXPORT_SYMBOL(__mark_inode_dirty);
136 static int write_inode(struct inode *inode, int sync)
137 {
138 if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode))
139 return inode->i_sb->s_op->write_inode(inode, sync);
140 return 0;
141 }
143 /*
144 * Write a single inode's dirty pages and inode data out to disk.
145 * If `wait' is set, wait on the writeout.
146 *
147 * The whole writeout design is quite complex and fragile. We want to avoid
148 * starvation of particular inodes when others are being redirtied, prevent
149 * livelocks, etc.
150 *
151 * Called under inode_lock.
152 */
153 static int
154 __sync_single_inode(struct inode *inode, struct writeback_control *wbc)
155 {
156 unsigned dirty;
157 struct address_space *mapping = inode->i_mapping;
158 struct super_block *sb = inode->i_sb;
159 int wait = wbc->sync_mode == WB_SYNC_ALL;
160 int ret;
162 BUG_ON(inode->i_state & I_LOCK);
164 /* Set I_LOCK, reset I_DIRTY */
165 dirty = inode->i_state & I_DIRTY;
166 inode->i_state |= I_LOCK;
167 inode->i_state &= ~I_DIRTY;
169 spin_unlock(&inode_lock);
171 ret = do_writepages(mapping, wbc);
173 /* Don't write the inode if only I_DIRTY_PAGES was set */
174 if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
175 int err = write_inode(inode, wait);
176 if (ret == 0)
177 ret = err;
178 }
180 if (wait) {
181 int err = filemap_fdatawait(mapping);
182 if (ret == 0)
183 ret = err;
184 }
186 spin_lock(&inode_lock);
187 inode->i_state &= ~I_LOCK;
188 if (!(inode->i_state & I_FREEING)) {
189 if (!(inode->i_state & I_DIRTY) &&
190 mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
191 /*
192 * We didn't write back all the pages. nfs_writepages()
193 * sometimes bales out without doing anything. Redirty
194 * the inode. It is still on sb->s_io.
195 */
196 if (wbc->for_kupdate) {
197 /*
198 * For the kupdate function we leave the inode
199 * at the head of sb_dirty so it will get more
200 * writeout as soon as the queue becomes
201 * uncongested.
202 */
203 inode->i_state |= I_DIRTY_PAGES;
204 list_move_tail(&inode->i_list, &sb->s_dirty);
205 } else {
206 /*
207 * Otherwise fully redirty the inode so that
208 * other inodes on this superblock will get some
209 * writeout. Otherwise heavy writing to one
210 * file would indefinitely suspend writeout of
211 * all the other files.
212 */
213 inode->i_state |= I_DIRTY_PAGES;
214 inode->dirtied_when = jiffies;
215 list_move(&inode->i_list, &sb->s_dirty);
216 }
217 } else if (inode->i_state & I_DIRTY) {
218 /*
219 * Someone redirtied the inode while were writing back
220 * the pages.
221 */
222 list_move(&inode->i_list, &sb->s_dirty);
223 } else if (atomic_read(&inode->i_count)) {
224 /*
225 * The inode is clean, inuse
226 */
227 list_move(&inode->i_list, &inode_in_use);
228 } else {
229 /*
230 * The inode is clean, unused
231 */
232 list_move(&inode->i_list, &inode_unused);
233 }
234 }
235 wake_up_inode(inode);
236 return ret;
237 }
239 /*
240 * Write out an inode's dirty pages. Called under inode_lock. Either the
241 * caller has ref on the inode (either via __iget or via syscall against an fd)
242 * or the inode has I_WILL_FREE set (via generic_forget_inode)
243 */
244 static int
245 __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
246 {
247 wait_queue_head_t *wqh;
249 if (!atomic_read(&inode->i_count))
250 WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
251 else
252 WARN_ON(inode->i_state & I_WILL_FREE);
254 if ((wbc->sync_mode != WB_SYNC_ALL) && (inode->i_state & I_LOCK)) {
255 list_move(&inode->i_list, &inode->i_sb->s_dirty);
256 return 0;
257 }
259 /*
260 * It's a data-integrity sync. We must wait.
261 */
262 if (inode->i_state & I_LOCK) {
263 DEFINE_WAIT_BIT(wq, &inode->i_state, __I_LOCK);
265 wqh = bit_waitqueue(&inode->i_state, __I_LOCK);
266 do {
267 spin_unlock(&inode_lock);
268 __wait_on_bit(wqh, &wq, inode_wait,
269 TASK_UNINTERRUPTIBLE);
270 spin_lock(&inode_lock);
271 } while (inode->i_state & I_LOCK);
272 }
273 return __sync_single_inode(inode, wbc);
274 }
276 /*
277 * Write out a superblock's list of dirty inodes. A wait will be performed
278 * upon no inodes, all inodes or the final one, depending upon sync_mode.
279 *
280 * If older_than_this is non-NULL, then only write out inodes which
281 * had their first dirtying at a time earlier than *older_than_this.
282 *
283 * If we're a pdlfush thread, then implement pdflush collision avoidance
284 * against the entire list.
285 *
286 * WB_SYNC_HOLD is a hack for sys_sync(): reattach the inode to sb->s_dirty so
287 * that it can be located for waiting on in __writeback_single_inode().
288 *
289 * Called under inode_lock.
290 *
291 * If `bdi' is non-zero then we're being asked to writeback a specific queue.
292 * This function assumes that the blockdev superblock's inodes are backed by
293 * a variety of queues, so all inodes are searched. For other superblocks,
294 * assume that all inodes are backed by the same queue.
295 *
296 * FIXME: this linear search could get expensive with many fileystems. But
297 * how to fix? We need to go from an address_space to all inodes which share
298 * a queue with that address_space. (Easy: have a global "dirty superblocks"
299 * list).
300 *
301 * The inodes to be written are parked on sb->s_io. They are moved back onto
302 * sb->s_dirty as they are selected for writing. This way, none can be missed
303 * on the writer throttling path, and we get decent balancing between many
304 * throttled threads: we don't want them all piling up on __wait_on_inode.
305 */
306 static void
307 sync_sb_inodes(struct super_block *sb, struct writeback_control *wbc)
308 {
309 const unsigned long start = jiffies; /* livelock avoidance */
311 if (!wbc->for_kupdate || list_empty(&sb->s_io))
312 list_splice_init(&sb->s_dirty, &sb->s_io);
314 while (!list_empty(&sb->s_io)) {
315 struct inode *inode = list_entry(sb->s_io.prev,
316 struct inode, i_list);
317 struct address_space *mapping = inode->i_mapping;
318 struct backing_dev_info *bdi = mapping->backing_dev_info;
319 long pages_skipped;
321 if (!bdi_cap_writeback_dirty(bdi)) {
322 list_move(&inode->i_list, &sb->s_dirty);
323 if (sb == blockdev_superblock) {
324 /*
325 * Dirty memory-backed blockdev: the ramdisk
326 * driver does this. Skip just this inode
327 */
328 continue;
329 }
330 /*
331 * Dirty memory-backed inode against a filesystem other
332 * than the kernel-internal bdev filesystem. Skip the
333 * entire superblock.
334 */
335 break;
336 }
338 if (wbc->nonblocking && bdi_write_congested(bdi)) {
339 wbc->encountered_congestion = 1;
340 if (sb != blockdev_superblock)
341 break; /* Skip a congested fs */
342 list_move(&inode->i_list, &sb->s_dirty);
343 continue; /* Skip a congested blockdev */
344 }
346 if (wbc->bdi && bdi != wbc->bdi) {
347 if (sb != blockdev_superblock)
348 break; /* fs has the wrong queue */
349 list_move(&inode->i_list, &sb->s_dirty);
350 continue; /* blockdev has wrong queue */
351 }
353 /* Was this inode dirtied after sync_sb_inodes was called? */
354 if (time_after(inode->dirtied_when, start))
355 break;
357 /* Was this inode dirtied too recently? */
358 if (wbc->older_than_this && time_after(inode->dirtied_when,
359 *wbc->older_than_this))
360 break;
362 /* Is another pdflush already flushing this queue? */
363 if (current_is_pdflush() && !writeback_acquire(bdi))
364 break;
366 BUG_ON(inode->i_state & I_FREEING);
367 __iget(inode);
368 pages_skipped = wbc->pages_skipped;
369 __writeback_single_inode(inode, wbc);
370 if (wbc->sync_mode == WB_SYNC_HOLD) {
371 inode->dirtied_when = jiffies;
372 list_move(&inode->i_list, &sb->s_dirty);
373 }
374 if (current_is_pdflush())
375 writeback_release(bdi);
376 if (wbc->pages_skipped != pages_skipped) {
377 /*
378 * writeback is not making progress due to locked
379 * buffers. Skip this inode for now.
380 */
381 list_move(&inode->i_list, &sb->s_dirty);
382 }
383 spin_unlock(&inode_lock);
384 iput(inode);
385 cond_resched();
386 spin_lock(&inode_lock);
387 if (wbc->nr_to_write <= 0)
388 break;
389 }
390 return; /* Leave any unwritten inodes on s_io */
391 }
393 /*
394 * Start writeback of dirty pagecache data against all unlocked inodes.
395 *
396 * Note:
397 * We don't need to grab a reference to superblock here. If it has non-empty
398 * ->s_dirty it's hadn't been killed yet and kill_super() won't proceed
399 * past sync_inodes_sb() until both the ->s_dirty and ->s_io lists are
400 * empty. Since __sync_single_inode() regains inode_lock before it finally moves
401 * inode from superblock lists we are OK.
402 *
403 * If `older_than_this' is non-zero then only flush inodes which have a
404 * flushtime older than *older_than_this.
405 *
406 * If `bdi' is non-zero then we will scan the first inode against each
407 * superblock until we find the matching ones. One group will be the dirty
408 * inodes against a filesystem. Then when we hit the dummy blockdev superblock,
409 * sync_sb_inodes will seekout the blockdev which matches `bdi'. Maybe not
410 * super-efficient but we're about to do a ton of I/O...
411 */
412 void
413 writeback_inodes(struct writeback_control *wbc)
414 {
415 struct super_block *sb;
417 might_sleep();
418 spin_lock(&sb_lock);
419 restart:
420 sb = sb_entry(super_blocks.prev);
421 for (; sb != sb_entry(&super_blocks); sb = sb_entry(sb->s_list.prev)) {
422 if (!list_empty(&sb->s_dirty) || !list_empty(&sb->s_io)) {
423 /* we're making our own get_super here */
424 sb->s_count++;
425 spin_unlock(&sb_lock);
426 /*
427 * If we can't get the readlock, there's no sense in
428 * waiting around, most of the time the FS is going to
429 * be unmounted by the time it is released.
430 */
431 if (down_read_trylock(&sb->s_umount)) {
432 if (sb->s_root) {
433 spin_lock(&inode_lock);
434 sync_sb_inodes(sb, wbc);
435 spin_unlock(&inode_lock);
436 }
437 up_read(&sb->s_umount);
438 }
439 spin_lock(&sb_lock);
440 if (__put_super_and_need_restart(sb))
441 goto restart;
442 }
443 if (wbc->nr_to_write <= 0)
444 break;
445 }
446 spin_unlock(&sb_lock);
447 }
449 /*
450 * writeback and wait upon the filesystem's dirty inodes. The caller will
451 * do this in two passes - one to write, and one to wait. WB_SYNC_HOLD is
452 * used to park the written inodes on sb->s_dirty for the wait pass.
453 *
454 * A finite limit is set on the number of pages which will be written.
455 * To prevent infinite livelock of sys_sync().
456 *
457 * We add in the number of potentially dirty inodes, because each inode write
458 * can dirty pagecache in the underlying blockdev.
459 */
460 void sync_inodes_sb(struct super_block *sb, int wait)
461 {
462 struct writeback_control wbc = {
463 .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_HOLD,
464 .range_start = 0,
465 .range_end = LLONG_MAX,
466 };
467 unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
468 unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
470 wbc.nr_to_write = nr_dirty + nr_unstable +
471 (inodes_stat.nr_inodes - inodes_stat.nr_unused) +
472 nr_dirty + nr_unstable;
473 wbc.nr_to_write += wbc.nr_to_write / 2; /* Bit more for luck */
474 spin_lock(&inode_lock);
475 sync_sb_inodes(sb, &wbc);
476 spin_unlock(&inode_lock);
477 }
479 /*
480 * Rather lame livelock avoidance.
481 */
482 static void set_sb_syncing(int val)
483 {
484 struct super_block *sb;
485 spin_lock(&sb_lock);
486 sb = sb_entry(super_blocks.prev);
487 for (; sb != sb_entry(&super_blocks); sb = sb_entry(sb->s_list.prev)) {
488 sb->s_syncing = val;
489 }
490 spin_unlock(&sb_lock);
491 }
493 /**
494 * sync_inodes - writes all inodes to disk
495 * @wait: wait for completion
496 *
497 * sync_inodes() goes through each super block's dirty inode list, writes the
498 * inodes out, waits on the writeout and puts the inodes back on the normal
499 * list.
500 *
501 * This is for sys_sync(). fsync_dev() uses the same algorithm. The subtle
502 * part of the sync functions is that the blockdev "superblock" is processed
503 * last. This is because the write_inode() function of a typical fs will
504 * perform no I/O, but will mark buffers in the blockdev mapping as dirty.
505 * What we want to do is to perform all that dirtying first, and then write
506 * back all those inode blocks via the blockdev mapping in one sweep. So the
507 * additional (somewhat redundant) sync_blockdev() calls here are to make
508 * sure that really happens. Because if we call sync_inodes_sb(wait=1) with
509 * outstanding dirty inodes, the writeback goes block-at-a-time within the
510 * filesystem's write_inode(). This is extremely slow.
511 */
512 static void __sync_inodes(int wait)
513 {
514 struct super_block *sb;
516 spin_lock(&sb_lock);
517 restart:
518 list_for_each_entry(sb, &super_blocks, s_list) {
519 if (sb->s_syncing)
520 continue;
521 sb->s_syncing = 1;
522 sb->s_count++;
523 spin_unlock(&sb_lock);
524 down_read(&sb->s_umount);
525 if (sb->s_root) {
526 sync_inodes_sb(sb, wait);
527 sync_blockdev(sb->s_bdev);
528 }
529 up_read(&sb->s_umount);
530 spin_lock(&sb_lock);
531 if (__put_super_and_need_restart(sb))
532 goto restart;
533 }
534 spin_unlock(&sb_lock);
535 }
537 void sync_inodes(int wait)
538 {
539 set_sb_syncing(0);
540 __sync_inodes(0);
542 if (wait) {
543 set_sb_syncing(0);
544 __sync_inodes(1);
545 }
546 }
548 /**
549 * write_inode_now - write an inode to disk
550 * @inode: inode to write to disk
551 * @sync: whether the write should be synchronous or not
552 *
553 * This function commits an inode to disk immediately if it is dirty. This is
554 * primarily needed by knfsd.
555 *
556 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
557 */
558 int write_inode_now(struct inode *inode, int sync)
559 {
560 int ret;
561 struct writeback_control wbc = {
562 .nr_to_write = LONG_MAX,
563 .sync_mode = WB_SYNC_ALL,
564 .range_start = 0,
565 .range_end = LLONG_MAX,
566 };
568 if (!mapping_cap_writeback_dirty(inode->i_mapping))
569 wbc.nr_to_write = 0;
571 might_sleep();
572 spin_lock(&inode_lock);
573 ret = __writeback_single_inode(inode, &wbc);
574 spin_unlock(&inode_lock);
575 if (sync)
576 wait_on_inode(inode);
577 return ret;
578 }
579 EXPORT_SYMBOL(write_inode_now);
581 /**
582 * sync_inode - write an inode and its pages to disk.
583 * @inode: the inode to sync
584 * @wbc: controls the writeback mode
585 *
586 * sync_inode() will write an inode and its pages to disk. It will also
587 * correctly update the inode on its superblock's dirty inode lists and will
588 * update inode->i_state.
589 *
590 * The caller must have a ref on the inode.
591 */
592 int sync_inode(struct inode *inode, struct writeback_control *wbc)
593 {
594 int ret;
596 spin_lock(&inode_lock);
597 ret = __writeback_single_inode(inode, wbc);
598 spin_unlock(&inode_lock);
599 return ret;
600 }
601 EXPORT_SYMBOL(sync_inode);
603 /**
604 * generic_osync_inode - flush all dirty data for a given inode to disk
605 * @inode: inode to write
606 * @mapping: the address_space that should be flushed
607 * @what: what to write and wait upon
608 *
609 * This can be called by file_write functions for files which have the
610 * O_SYNC flag set, to flush dirty writes to disk.
611 *
612 * @what is a bitmask, specifying which part of the inode's data should be
613 * written and waited upon.
614 *
615 * OSYNC_DATA: i_mapping's dirty data
616 * OSYNC_METADATA: the buffers at i_mapping->private_list
617 * OSYNC_INODE: the inode itself
618 */
620 int generic_osync_inode(struct inode *inode, struct address_space *mapping, int what)
621 {
622 int err = 0;
623 int need_write_inode_now = 0;
624 int err2;
626 if (what & OSYNC_DATA)
627 err = filemap_fdatawrite(mapping);
628 if (what & (OSYNC_METADATA|OSYNC_DATA)) {
629 err2 = sync_mapping_buffers(mapping);
630 if (!err)
631 err = err2;
632 }
633 if (what & OSYNC_DATA) {
634 err2 = filemap_fdatawait(mapping);
635 if (!err)
636 err = err2;
637 }
639 spin_lock(&inode_lock);
640 if ((inode->i_state & I_DIRTY) &&
641 ((what & OSYNC_INODE) || (inode->i_state & I_DIRTY_DATASYNC)))
642 need_write_inode_now = 1;
643 spin_unlock(&inode_lock);
645 if (need_write_inode_now) {
646 err2 = write_inode_now(inode, 1);
647 if (!err)
648 err = err2;
649 }
650 else
651 wait_on_inode(inode);
653 return err;
654 }
656 EXPORT_SYMBOL(generic_osync_inode);
658 /**
659 * writeback_acquire: attempt to get exclusive writeback access to a device
660 * @bdi: the device's backing_dev_info structure
661 *
662 * It is a waste of resources to have more than one pdflush thread blocked on
663 * a single request queue. Exclusion at the request_queue level is obtained
664 * via a flag in the request_queue's backing_dev_info.state.
665 *
666 * Non-request_queue-backed address_spaces will share default_backing_dev_info,
667 * unless they implement their own. Which is somewhat inefficient, as this
668 * may prevent concurrent writeback against multiple devices.
669 */
670 int writeback_acquire(struct backing_dev_info *bdi)
671 {
672 return !test_and_set_bit(BDI_pdflush, &bdi->state);
673 }
675 /**
676 * writeback_in_progress: determine whether there is writeback in progress
677 * @bdi: the device's backing_dev_info structure.
678 *
679 * Determine whether there is writeback in progress against a backing device.
680 */
681 int writeback_in_progress(struct backing_dev_info *bdi)
682 {
683 return test_bit(BDI_pdflush, &bdi->state);
684 }
686 /**
687 * writeback_release: relinquish exclusive writeback access against a device.
688 * @bdi: the device's backing_dev_info structure
689 */
690 void writeback_release(struct backing_dev_info *bdi)
691 {
692 BUG_ON(!writeback_in_progress(bdi));
693 clear_bit(BDI_pdflush, &bdi->state);
694 }