Commit 4ea425b6 authored by Jan Kara's avatar Jan Kara Committed by Al Viro

vfs: Avoid unnecessary WB_SYNC_NONE writeback during sys_sync and reorder sync passes

wakeup_flusher_threads(0) will queue work doing complete writeback for each
flusher thread. Thus there is not much point in submitting another work doing
full inode WB_SYNC_NONE writeback by writeback_inodes_sb().

After this change it does not make sense to call nonblocking ->sync_fs and
block device flush before calling sync_inodes_sb() because
wakeup_flusher_threads() is completely asynchronous and thus these functions
would be called in parallel with inode writeback running which will effectively
void any work they do. So we move sync_inodes_sb() call before these two
functions.
Signed-off-by: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent d0e91b13
...@@ -73,12 +73,6 @@ static void sync_inodes_one_sb(struct super_block *sb, void *arg) ...@@ -73,12 +73,6 @@ static void sync_inodes_one_sb(struct super_block *sb, void *arg)
sync_inodes_sb(sb); sync_inodes_sb(sb);
} }
static void writeback_inodes_one_sb(struct super_block *sb, void *arg)
{
if (!(sb->s_flags & MS_RDONLY))
writeback_inodes_sb(sb, WB_REASON_SYNC);
}
static void sync_fs_one_sb(struct super_block *sb, void *arg) static void sync_fs_one_sb(struct super_block *sb, void *arg)
{ {
if (!(sb->s_flags & MS_RDONLY) && sb->s_op->sync_fs) if (!(sb->s_flags & MS_RDONLY) && sb->s_op->sync_fs)
...@@ -96,17 +90,22 @@ static void fdatawait_one_bdev(struct block_device *bdev, void *arg) ...@@ -96,17 +90,22 @@ static void fdatawait_one_bdev(struct block_device *bdev, void *arg)
} }
/* /*
* sync everything. Start out by waking pdflush, because that writes back * Sync everything. We start by waking flusher threads so that most of
* all queues in parallel. * writeback runs on all devices in parallel. Then we sync all inodes reliably
* which effectively also waits for all flusher threads to finish doing
* writeback. At this point all data is on disk so metadata should be stable
* and we tell filesystems to sync their metadata via ->sync_fs() calls.
* Finally, we writeout all block devices because some filesystems (e.g. ext2)
* just write metadata (such as inodes or bitmaps) to block device page cache
* and do not sync it on their own in ->sync_fs().
*/ */
SYSCALL_DEFINE0(sync) SYSCALL_DEFINE0(sync)
{ {
int nowait = 0, wait = 1; int nowait = 0, wait = 1;
wakeup_flusher_threads(0, WB_REASON_SYNC); wakeup_flusher_threads(0, WB_REASON_SYNC);
iterate_supers(writeback_inodes_one_sb, NULL);
iterate_supers(sync_fs_one_sb, &nowait);
iterate_supers(sync_inodes_one_sb, NULL); iterate_supers(sync_inodes_one_sb, NULL);
iterate_supers(sync_fs_one_sb, &nowait);
iterate_supers(sync_fs_one_sb, &wait); iterate_supers(sync_fs_one_sb, &wait);
iterate_bdevs(fdatawrite_one_bdev, NULL); iterate_bdevs(fdatawrite_one_bdev, NULL);
iterate_bdevs(fdatawait_one_bdev, NULL); iterate_bdevs(fdatawait_one_bdev, NULL);
......
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