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vfs: Make sys_sync() use fsync_super() (version 4)

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It is unnecessarily fragile to have two places (fsync_super() and do_sync())
doing data integrity sync of the filesystem. Alter __fsync_super() to
accommodate needs of both callers and use it. So after this patch
__fsync_super() is the only place where we gather all the calls needed to
properly send all data on a filesystem to disk.

Nice bonus is that we get a complete livelock avoidance and write_supers()
is now only used for periodic writeback of superblocks.

sync_blockdevs() introduced a couple of patches ago is gone now.

[build fixes folded]

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Jan Kara
2009-04-27 16:43:51 +02:00
committed by Al Viro
parent 429479f031
commit 5cee5815d1
7 changed files with 52 additions and 136 deletions
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49
fs/fs-writeback.c
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@@ -678,55 +678,6 @@ void sync_inodes_sb(struct super_block *sb, int wait)
sync_sb_inodes(sb, &wbc);
}
/**
* sync_inodes - writes all inodes to disk
* @wait: wait for completion
*
* sync_inodes() goes through each super block's dirty inode list, writes the
* inodes out, waits on the writeout and puts the inodes back on the normal
* list.
*
* This is for sys_sync(). fsync_dev() uses the same algorithm. The subtle
* part of the sync functions is that the blockdev "superblock" is processed
* last. This is because the write_inode() function of a typical fs will
* perform no I/O, but will mark buffers in the blockdev mapping as dirty.
* What we want to do is to perform all that dirtying first, and then write
* back all those inode blocks via the blockdev mapping in one sweep. So the
* additional (somewhat redundant) sync_blockdev() calls here are to make
* sure that really happens. Because if we call sync_inodes_sb(wait=1) with
* outstanding dirty inodes, the writeback goes block-at-a-time within the
* filesystem's write_inode(). This is extremely slow.
*/
static void __sync_inodes(int wait)
{
struct super_block *sb;
spin_lock(&sb_lock);
restart:
list_for_each_entry(sb, &super_blocks, s_list) {
sb->s_count++;
spin_unlock(&sb_lock);
down_read(&sb->s_umount);
if (sb->s_root) {
sync_inodes_sb(sb, wait);
sync_blockdev(sb->s_bdev);
}
up_read(&sb->s_umount);
spin_lock(&sb_lock);
if (__put_super_and_need_restart(sb))
goto restart;
}
spin_unlock(&sb_lock);
}
void sync_inodes(int wait)
{
__sync_inodes(0);
if (wait)
__sync_inodes(1);
}
/**
* write_inode_now - write an inode to disk
* @inode: inode to write to disk