Root/fs/fs-writeback.c

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 Andrew Morton
12 * Split out of fs/inode.c
13 * Additions for address_space-based writeback
14 */
15
16#include <linux/kernel.h>
17#include <linux/module.h>
18#include <linux/spinlock.h>
19#include <linux/sched.h>
20#include <linux/fs.h>
21#include <linux/mm.h>
22#include <linux/writeback.h>
23#include <linux/blkdev.h>
24#include <linux/backing-dev.h>
25#include <linux/buffer_head.h>
26#include "internal.h"
27
28
29/**
30 * writeback_acquire - attempt to get exclusive writeback access to a device
31 * @bdi: the device's backing_dev_info structure
32 *
33 * It is a waste of resources to have more than one pdflush thread blocked on
34 * a single request queue. Exclusion at the request_queue level is obtained
35 * via a flag in the request_queue's backing_dev_info.state.
36 *
37 * Non-request_queue-backed address_spaces will share default_backing_dev_info,
38 * unless they implement their own. Which is somewhat inefficient, as this
39 * may prevent concurrent writeback against multiple devices.
40 */
41static int writeback_acquire(struct backing_dev_info *bdi)
42{
43    return !test_and_set_bit(BDI_pdflush, &bdi->state);
44}
45
46/**
47 * writeback_in_progress - determine whether there is writeback in progress
48 * @bdi: the device's backing_dev_info structure.
49 *
50 * Determine whether there is writeback in progress against a backing device.
51 */
52int writeback_in_progress(struct backing_dev_info *bdi)
53{
54    return test_bit(BDI_pdflush, &bdi->state);
55}
56
57/**
58 * writeback_release - relinquish exclusive writeback access against a device.
59 * @bdi: the device's backing_dev_info structure
60 */
61static void writeback_release(struct backing_dev_info *bdi)
62{
63    BUG_ON(!writeback_in_progress(bdi));
64    clear_bit(BDI_pdflush, &bdi->state);
65}
66
67static noinline void block_dump___mark_inode_dirty(struct inode *inode)
68{
69    if (inode->i_ino || strcmp(inode->i_sb->s_id, "bdev")) {
70        struct dentry *dentry;
71        const char *name = "?";
72
73        dentry = d_find_alias(inode);
74        if (dentry) {
75            spin_lock(&dentry->d_lock);
76            name = (const char *) dentry->d_name.name;
77        }
78        printk(KERN_DEBUG
79               "%s(%d): dirtied inode %lu (%s) on %s\n",
80               current->comm, task_pid_nr(current), inode->i_ino,
81               name, inode->i_sb->s_id);
82        if (dentry) {
83            spin_unlock(&dentry->d_lock);
84            dput(dentry);
85        }
86    }
87}
88
89/**
90 * __mark_inode_dirty - internal function
91 * @inode: inode to mark
92 * @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
93 * Mark an inode as dirty. Callers should use mark_inode_dirty or
94 * mark_inode_dirty_sync.
95 *
96 * Put the inode on the super block's dirty list.
97 *
98 * CAREFUL! We mark it dirty unconditionally, but move it onto the
99 * dirty list only if it is hashed or if it refers to a blockdev.
100 * If it was not hashed, it will never be added to the dirty list
101 * even if it is later hashed, as it will have been marked dirty already.
102 *
103 * In short, make sure you hash any inodes _before_ you start marking
104 * them dirty.
105 *
106 * This function *must* be atomic for the I_DIRTY_PAGES case -
107 * set_page_dirty() is called under spinlock in several places.
108 *
109 * Note that for blockdevs, inode->dirtied_when represents the dirtying time of
110 * the block-special inode (/dev/hda1) itself. And the ->dirtied_when field of
111 * the kernel-internal blockdev inode represents the dirtying time of the
112 * blockdev's pages. This is why for I_DIRTY_PAGES we always use
113 * page->mapping->host, so the page-dirtying time is recorded in the internal
114 * blockdev inode.
115 */
116void __mark_inode_dirty(struct inode *inode, int flags)
117{
118    struct super_block *sb = inode->i_sb;
119
120    /*
121     * Don't do this for I_DIRTY_PAGES - that doesn't actually
122     * dirty the inode itself
123     */
124    if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
125        if (sb->s_op->dirty_inode)
126            sb->s_op->dirty_inode(inode);
127    }
128
129    /*
130     * make sure that changes are seen by all cpus before we test i_state
131     * -- mikulas
132     */
133    smp_mb();
134
135    /* avoid the locking if we can */
136    if ((inode->i_state & flags) == flags)
137        return;
138
139    if (unlikely(block_dump))
140        block_dump___mark_inode_dirty(inode);
141
142    spin_lock(&inode_lock);
143    if ((inode->i_state & flags) != flags) {
144        const int was_dirty = inode->i_state & I_DIRTY;
145
146        inode->i_state |= flags;
147
148        /*
149         * If the inode is being synced, just update its dirty state.
150         * The unlocker will place the inode on the appropriate
151         * superblock list, based upon its state.
152         */
153        if (inode->i_state & I_SYNC)
154            goto out;
155
156        /*
157         * Only add valid (hashed) inodes to the superblock's
158         * dirty list. Add blockdev inodes as well.
159         */
160        if (!S_ISBLK(inode->i_mode)) {
161            if (hlist_unhashed(&inode->i_hash))
162                goto out;
163        }
164        if (inode->i_state & (I_FREEING|I_CLEAR))
165            goto out;
166
167        /*
168         * If the inode was already on s_dirty/s_io/s_more_io, don't
169         * reposition it (that would break s_dirty time-ordering).
170         */
171        if (!was_dirty) {
172            inode->dirtied_when = jiffies;
173            list_move(&inode->i_list, &sb->s_dirty);
174        }
175    }
176out:
177    spin_unlock(&inode_lock);
178}
179
180EXPORT_SYMBOL(__mark_inode_dirty);
181
182static int write_inode(struct inode *inode, int sync)
183{
184    if (inode->i_sb->s_op->write_inode && !is_bad_inode(inode))
185        return inode->i_sb->s_op->write_inode(inode, sync);
186    return 0;
187}
188
189/*
190 * Redirty an inode: set its when-it-was dirtied timestamp and move it to the
191 * furthest end of its superblock's dirty-inode list.
192 *
193 * Before stamping the inode's ->dirtied_when, we check to see whether it is
194 * already the most-recently-dirtied inode on the s_dirty list. If that is
195 * the case then the inode must have been redirtied while it was being written
196 * out and we don't reset its dirtied_when.
197 */
198static void redirty_tail(struct inode *inode)
199{
200    struct super_block *sb = inode->i_sb;
201
202    if (!list_empty(&sb->s_dirty)) {
203        struct inode *tail_inode;
204
205        tail_inode = list_entry(sb->s_dirty.next, struct inode, i_list);
206        if (time_before(inode->dirtied_when,
207                tail_inode->dirtied_when))
208            inode->dirtied_when = jiffies;
209    }
210    list_move(&inode->i_list, &sb->s_dirty);
211}
212
213/*
214 * requeue inode for re-scanning after sb->s_io list is exhausted.
215 */
216static void requeue_io(struct inode *inode)
217{
218    list_move(&inode->i_list, &inode->i_sb->s_more_io);
219}
220
221static void inode_sync_complete(struct inode *inode)
222{
223    /*
224     * Prevent speculative execution through spin_unlock(&inode_lock);
225     */
226    smp_mb();
227    wake_up_bit(&inode->i_state, __I_SYNC);
228}
229
230static bool inode_dirtied_after(struct inode *inode, unsigned long t)
231{
232    bool ret = time_after(inode->dirtied_when, t);
233#ifndef CONFIG_64BIT
234    /*
235     * For inodes being constantly redirtied, dirtied_when can get stuck.
236     * It _appears_ to be in the future, but is actually in distant past.
237     * This test is necessary to prevent such wrapped-around relative times
238     * from permanently stopping the whole pdflush writeback.
239     */
240    ret = ret && time_before_eq(inode->dirtied_when, jiffies);
241#endif
242    return ret;
243}
244
245/*
246 * Move expired dirty inodes from @delaying_queue to @dispatch_queue.
247 */
248static void move_expired_inodes(struct list_head *delaying_queue,
249                   struct list_head *dispatch_queue,
250                unsigned long *older_than_this)
251{
252    while (!list_empty(delaying_queue)) {
253        struct inode *inode = list_entry(delaying_queue->prev,
254                        struct inode, i_list);
255        if (older_than_this &&
256            inode_dirtied_after(inode, *older_than_this))
257            break;
258        list_move(&inode->i_list, dispatch_queue);
259    }
260}
261
262/*
263 * Queue all expired dirty inodes for io, eldest first.
264 */
265static void queue_io(struct super_block *sb,
266                unsigned long *older_than_this)
267{
268    list_splice_init(&sb->s_more_io, sb->s_io.prev);
269    move_expired_inodes(&sb->s_dirty, &sb->s_io, older_than_this);
270}
271
272int sb_has_dirty_inodes(struct super_block *sb)
273{
274    return !list_empty(&sb->s_dirty) ||
275           !list_empty(&sb->s_io) ||
276           !list_empty(&sb->s_more_io);
277}
278EXPORT_SYMBOL(sb_has_dirty_inodes);
279
280/*
281 * Wait for writeback on an inode to complete.
282 */
283static void inode_wait_for_writeback(struct inode *inode)
284{
285    DEFINE_WAIT_BIT(wq, &inode->i_state, __I_SYNC);
286    wait_queue_head_t *wqh;
287
288    wqh = bit_waitqueue(&inode->i_state, __I_SYNC);
289    do {
290        spin_unlock(&inode_lock);
291        __wait_on_bit(wqh, &wq, inode_wait, TASK_UNINTERRUPTIBLE);
292        spin_lock(&inode_lock);
293    } while (inode->i_state & I_SYNC);
294}
295
296/*
297 * Write out an inode's dirty pages. Called under inode_lock. Either the
298 * caller has ref on the inode (either via __iget or via syscall against an fd)
299 * or the inode has I_WILL_FREE set (via generic_forget_inode)
300 *
301 * If `wait' is set, wait on the writeout.
302 *
303 * The whole writeout design is quite complex and fragile. We want to avoid
304 * starvation of particular inodes when others are being redirtied, prevent
305 * livelocks, etc.
306 *
307 * Called under inode_lock.
308 */
309static int
310writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
311{
312    struct address_space *mapping = inode->i_mapping;
313    int wait = wbc->sync_mode == WB_SYNC_ALL;
314    unsigned dirty;
315    int ret;
316
317    if (!atomic_read(&inode->i_count))
318        WARN_ON(!(inode->i_state & (I_WILL_FREE|I_FREEING)));
319    else
320        WARN_ON(inode->i_state & I_WILL_FREE);
321
322    if (inode->i_state & I_SYNC) {
323        /*
324         * If this inode is locked for writeback and we are not doing
325         * writeback-for-data-integrity, move it to s_more_io so that
326         * writeback can proceed with the other inodes on s_io.
327         *
328         * We'll have another go at writing back this inode when we
329         * completed a full scan of s_io.
330         */
331        if (!wait) {
332            requeue_io(inode);
333            return 0;
334        }
335
336        /*
337         * It's a data-integrity sync. We must wait.
338         */
339        inode_wait_for_writeback(inode);
340    }
341
342    BUG_ON(inode->i_state & I_SYNC);
343
344    /* Set I_SYNC, reset I_DIRTY */
345    dirty = inode->i_state & I_DIRTY;
346    inode->i_state |= I_SYNC;
347    inode->i_state &= ~I_DIRTY;
348
349    spin_unlock(&inode_lock);
350
351    ret = do_writepages(mapping, wbc);
352
353    /* Don't write the inode if only I_DIRTY_PAGES was set */
354    if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
355        int err = write_inode(inode, wait);
356        if (ret == 0)
357            ret = err;
358    }
359
360    if (wait) {
361        int err = filemap_fdatawait(mapping);
362        if (ret == 0)
363            ret = err;
364    }
365
366    spin_lock(&inode_lock);
367    inode->i_state &= ~I_SYNC;
368    if (!(inode->i_state & (I_FREEING | I_CLEAR))) {
369        if (!(inode->i_state & I_DIRTY) &&
370            mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
371            /*
372             * We didn't write back all the pages. nfs_writepages()
373             * sometimes bales out without doing anything. Redirty
374             * the inode; Move it from s_io onto s_more_io/s_dirty.
375             */
376            /*
377             * akpm: if the caller was the kupdate function we put
378             * this inode at the head of s_dirty so it gets first
379             * consideration. Otherwise, move it to the tail, for
380             * the reasons described there. I'm not really sure
381             * how much sense this makes. Presumably I had a good
382             * reasons for doing it this way, and I'd rather not
383             * muck with it at present.
384             */
385            if (wbc->for_kupdate) {
386                /*
387                 * For the kupdate function we move the inode
388                 * to s_more_io so it will get more writeout as
389                 * soon as the queue becomes uncongested.
390                 */
391                inode->i_state |= I_DIRTY_PAGES;
392                if (wbc->nr_to_write <= 0) {
393                    /*
394                     * slice used up: queue for next turn
395                     */
396                    requeue_io(inode);
397                } else {
398                    /*
399                     * somehow blocked: retry later
400                     */
401                    redirty_tail(inode);
402                }
403            } else {
404                /*
405                 * Otherwise fully redirty the inode so that
406                 * other inodes on this superblock will get some
407                 * writeout. Otherwise heavy writing to one
408                 * file would indefinitely suspend writeout of
409                 * all the other files.
410                 */
411                inode->i_state |= I_DIRTY_PAGES;
412                redirty_tail(inode);
413            }
414        } else if (inode->i_state & I_DIRTY) {
415            /*
416             * Someone redirtied the inode while were writing back
417             * the pages.
418             */
419            redirty_tail(inode);
420        } else if (atomic_read(&inode->i_count)) {
421            /*
422             * The inode is clean, inuse
423             */
424            list_move(&inode->i_list, &inode_in_use);
425        } else {
426            /*
427             * The inode is clean, unused
428             */
429            list_move(&inode->i_list, &inode_unused);
430        }
431    }
432    inode_sync_complete(inode);
433    return ret;
434}
435
436/*
437 * Write out a superblock's list of dirty inodes. A wait will be performed
438 * upon no inodes, all inodes or the final one, depending upon sync_mode.
439 *
440 * If older_than_this is non-NULL, then only write out inodes which
441 * had their first dirtying at a time earlier than *older_than_this.
442 *
443 * If we're a pdflush thread, then implement pdflush collision avoidance
444 * against the entire list.
445 *
446 * If `bdi' is non-zero then we're being asked to writeback a specific queue.
447 * This function assumes that the blockdev superblock's inodes are backed by
448 * a variety of queues, so all inodes are searched. For other superblocks,
449 * assume that all inodes are backed by the same queue.
450 *
451 * FIXME: this linear search could get expensive with many fileystems. But
452 * how to fix? We need to go from an address_space to all inodes which share
453 * a queue with that address_space. (Easy: have a global "dirty superblocks"
454 * list).
455 *
456 * The inodes to be written are parked on sb->s_io. They are moved back onto
457 * sb->s_dirty as they are selected for writing. This way, none can be missed
458 * on the writer throttling path, and we get decent balancing between many
459 * throttled threads: we don't want them all piling up on inode_sync_wait.
460 */
461void generic_sync_sb_inodes(struct super_block *sb,
462                struct writeback_control *wbc)
463{
464    const unsigned long start = jiffies; /* livelock avoidance */
465    int sync = wbc->sync_mode == WB_SYNC_ALL;
466
467    spin_lock(&inode_lock);
468    if (!wbc->for_kupdate || list_empty(&sb->s_io))
469        queue_io(sb, wbc->older_than_this);
470
471    while (!list_empty(&sb->s_io)) {
472        struct inode *inode = list_entry(sb->s_io.prev,
473                        struct inode, i_list);
474        struct address_space *mapping = inode->i_mapping;
475        struct backing_dev_info *bdi = mapping->backing_dev_info;
476        long pages_skipped;
477
478        if (!bdi_cap_writeback_dirty(bdi)) {
479            redirty_tail(inode);
480            if (sb_is_blkdev_sb(sb)) {
481                /*
482                 * Dirty memory-backed blockdev: the ramdisk
483                 * driver does this. Skip just this inode
484                 */
485                continue;
486            }
487            /*
488             * Dirty memory-backed inode against a filesystem other
489             * than the kernel-internal bdev filesystem. Skip the
490             * entire superblock.
491             */
492            break;
493        }
494
495        if (inode->i_state & (I_NEW | I_WILL_FREE)) {
496            requeue_io(inode);
497            continue;
498        }
499
500        if (wbc->nonblocking && bdi_write_congested(bdi)) {
501            wbc->encountered_congestion = 1;
502            if (!sb_is_blkdev_sb(sb))
503                break; /* Skip a congested fs */
504            requeue_io(inode);
505            continue; /* Skip a congested blockdev */
506        }
507
508        if (wbc->bdi && bdi != wbc->bdi) {
509            if (!sb_is_blkdev_sb(sb))
510                break; /* fs has the wrong queue */
511            requeue_io(inode);
512            continue; /* blockdev has wrong queue */
513        }
514
515        /*
516         * Was this inode dirtied after sync_sb_inodes was called?
517         * This keeps sync from extra jobs and livelock.
518         */
519        if (inode_dirtied_after(inode, start))
520            break;
521
522        /* Is another pdflush already flushing this queue? */
523        if (current_is_pdflush() && !writeback_acquire(bdi))
524            break;
525
526        BUG_ON(inode->i_state & (I_FREEING | I_CLEAR));
527        __iget(inode);
528        pages_skipped = wbc->pages_skipped;
529        writeback_single_inode(inode, wbc);
530        if (current_is_pdflush())
531            writeback_release(bdi);
532        if (wbc->pages_skipped != pages_skipped) {
533            /*
534             * writeback is not making progress due to locked
535             * buffers. Skip this inode for now.
536             */
537            redirty_tail(inode);
538        }
539        spin_unlock(&inode_lock);
540        iput(inode);
541        cond_resched();
542        spin_lock(&inode_lock);
543        if (wbc->nr_to_write <= 0) {
544            wbc->more_io = 1;
545            break;
546        }
547        if (!list_empty(&sb->s_more_io))
548            wbc->more_io = 1;
549    }
550
551    if (sync) {
552        struct inode *inode, *old_inode = NULL;
553
554        /*
555         * Data integrity sync. Must wait for all pages under writeback,
556         * because there may have been pages dirtied before our sync
557         * call, but which had writeout started before we write it out.
558         * In which case, the inode may not be on the dirty list, but
559         * we still have to wait for that writeout.
560         */
561        list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
562            struct address_space *mapping;
563
564            if (inode->i_state &
565                    (I_FREEING|I_CLEAR|I_WILL_FREE|I_NEW))
566                continue;
567            mapping = inode->i_mapping;
568            if (mapping->nrpages == 0)
569                continue;
570            __iget(inode);
571            spin_unlock(&inode_lock);
572            /*
573             * We hold a reference to 'inode' so it couldn't have
574             * been removed from s_inodes list while we dropped the
575             * inode_lock. We cannot iput the inode now as we can
576             * be holding the last reference and we cannot iput it
577             * under inode_lock. So we keep the reference and iput
578             * it later.
579             */
580            iput(old_inode);
581            old_inode = inode;
582
583            filemap_fdatawait(mapping);
584
585            cond_resched();
586
587            spin_lock(&inode_lock);
588        }
589        spin_unlock(&inode_lock);
590        iput(old_inode);
591    } else
592        spin_unlock(&inode_lock);
593
594    return; /* Leave any unwritten inodes on s_io */
595}
596EXPORT_SYMBOL_GPL(generic_sync_sb_inodes);
597
598static void sync_sb_inodes(struct super_block *sb,
599                struct writeback_control *wbc)
600{
601    generic_sync_sb_inodes(sb, wbc);
602}
603
604/*
605 * Start writeback of dirty pagecache data against all unlocked inodes.
606 *
607 * Note:
608 * We don't need to grab a reference to superblock here. If it has non-empty
609 * ->s_dirty it's hadn't been killed yet and kill_super() won't proceed
610 * past sync_inodes_sb() until the ->s_dirty/s_io/s_more_io lists are all
611 * empty. Since __sync_single_inode() regains inode_lock before it finally moves
612 * inode from superblock lists we are OK.
613 *
614 * If `older_than_this' is non-zero then only flush inodes which have a
615 * flushtime older than *older_than_this.
616 *
617 * If `bdi' is non-zero then we will scan the first inode against each
618 * superblock until we find the matching ones. One group will be the dirty
619 * inodes against a filesystem. Then when we hit the dummy blockdev superblock,
620 * sync_sb_inodes will seekout the blockdev which matches `bdi'. Maybe not
621 * super-efficient but we're about to do a ton of I/O...
622 */
623void
624writeback_inodes(struct writeback_control *wbc)
625{
626    struct super_block *sb;
627
628    might_sleep();
629    spin_lock(&sb_lock);
630restart:
631    list_for_each_entry_reverse(sb, &super_blocks, s_list) {
632        if (sb_has_dirty_inodes(sb)) {
633            /* we're making our own get_super here */
634            sb->s_count++;
635            spin_unlock(&sb_lock);
636            /*
637             * If we can't get the readlock, there's no sense in
638             * waiting around, most of the time the FS is going to
639             * be unmounted by the time it is released.
640             */
641            if (down_read_trylock(&sb->s_umount)) {
642                if (sb->s_root)
643                    sync_sb_inodes(sb, wbc);
644                up_read(&sb->s_umount);
645            }
646            spin_lock(&sb_lock);
647            if (__put_super_and_need_restart(sb))
648                goto restart;
649        }
650        if (wbc->nr_to_write <= 0)
651            break;
652    }
653    spin_unlock(&sb_lock);
654}
655
656/*
657 * writeback and wait upon the filesystem's dirty inodes. The caller will
658 * do this in two passes - one to write, and one to wait.
659 *
660 * A finite limit is set on the number of pages which will be written.
661 * To prevent infinite livelock of sys_sync().
662 *
663 * We add in the number of potentially dirty inodes, because each inode write
664 * can dirty pagecache in the underlying blockdev.
665 */
666void sync_inodes_sb(struct super_block *sb, int wait)
667{
668    struct writeback_control wbc = {
669        .sync_mode = wait ? WB_SYNC_ALL : WB_SYNC_NONE,
670        .range_start = 0,
671        .range_end = LLONG_MAX,
672    };
673
674    if (!wait) {
675        unsigned long nr_dirty = global_page_state(NR_FILE_DIRTY);
676        unsigned long nr_unstable = global_page_state(NR_UNSTABLE_NFS);
677
678        wbc.nr_to_write = nr_dirty + nr_unstable +
679            (inodes_stat.nr_inodes - inodes_stat.nr_unused);
680    } else
681        wbc.nr_to_write = LONG_MAX; /* doesn't actually matter */
682
683    sync_sb_inodes(sb, &wbc);
684}
685
686/**
687 * write_inode_now - write an inode to disk
688 * @inode: inode to write to disk
689 * @sync: whether the write should be synchronous or not
690 *
691 * This function commits an inode to disk immediately if it is dirty. This is
692 * primarily needed by knfsd.
693 *
694 * The caller must either have a ref on the inode or must have set I_WILL_FREE.
695 */
696int write_inode_now(struct inode *inode, int sync)
697{
698    int ret;
699    struct writeback_control wbc = {
700        .nr_to_write = LONG_MAX,
701        .sync_mode = sync ? WB_SYNC_ALL : WB_SYNC_NONE,
702        .range_start = 0,
703        .range_end = LLONG_MAX,
704    };
705
706    if (!mapping_cap_writeback_dirty(inode->i_mapping))
707        wbc.nr_to_write = 0;
708
709    might_sleep();
710    spin_lock(&inode_lock);
711    ret = writeback_single_inode(inode, &wbc);
712    spin_unlock(&inode_lock);
713    if (sync)
714        inode_sync_wait(inode);
715    return ret;
716}
717EXPORT_SYMBOL(write_inode_now);
718
719/**
720 * sync_inode - write an inode and its pages to disk.
721 * @inode: the inode to sync
722 * @wbc: controls the writeback mode
723 *
724 * sync_inode() will write an inode and its pages to disk. It will also
725 * correctly update the inode on its superblock's dirty inode lists and will
726 * update inode->i_state.
727 *
728 * The caller must have a ref on the inode.
729 */
730int sync_inode(struct inode *inode, struct writeback_control *wbc)
731{
732    int ret;
733
734    spin_lock(&inode_lock);
735    ret = writeback_single_inode(inode, wbc);
736    spin_unlock(&inode_lock);
737    return ret;
738}
739EXPORT_SYMBOL(sync_inode);
740
741/**
742 * generic_osync_inode - flush all dirty data for a given inode to disk
743 * @inode: inode to write
744 * @mapping: the address_space that should be flushed
745 * @what: what to write and wait upon
746 *
747 * This can be called by file_write functions for files which have the
748 * O_SYNC flag set, to flush dirty writes to disk.
749 *
750 * @what is a bitmask, specifying which part of the inode's data should be
751 * written and waited upon.
752 *
753 * OSYNC_DATA: i_mapping's dirty data
754 * OSYNC_METADATA: the buffers at i_mapping->private_list
755 * OSYNC_INODE: the inode itself
756 */
757
758int generic_osync_inode(struct inode *inode, struct address_space *mapping, int what)
759{
760    int err = 0;
761    int need_write_inode_now = 0;
762    int err2;
763
764    if (what & OSYNC_DATA)
765        err = filemap_fdatawrite(mapping);
766    if (what & (OSYNC_METADATA|OSYNC_DATA)) {
767        err2 = sync_mapping_buffers(mapping);
768        if (!err)
769            err = err2;
770    }
771    if (what & OSYNC_DATA) {
772        err2 = filemap_fdatawait(mapping);
773        if (!err)
774            err = err2;
775    }
776
777    spin_lock(&inode_lock);
778    if ((inode->i_state & I_DIRTY) &&
779        ((what & OSYNC_INODE) || (inode->i_state & I_DIRTY_DATASYNC)))
780        need_write_inode_now = 1;
781    spin_unlock(&inode_lock);
782
783    if (need_write_inode_now) {
784        err2 = write_inode_now(inode, 1);
785        if (!err)
786            err = err2;
787    }
788    else
789        inode_sync_wait(inode);
790
791    return err;
792}
793EXPORT_SYMBOL(generic_osync_inode);
794

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