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ovl: properly implement sync_filesystem()

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overlayfs syncs all inode pages on sync_filesystem(), but it also
needs to call s_op->sync_fs() of upper fs for metadata sync.

This fixes correctness of syncfs(2) as demonstrated by following
xfs specific test:

xfs_sync_stats()
{
	echo $1
	echo -n "xfs_log_force = "
	grep log /proc/fs/xfs/stat  | awk '{ print $5 }'
}

xfs_sync_stats "before touch"
touch x
xfs_sync_stats "after touch"
xfs_io -c syncfs .
xfs_sync_stats "after syncfs"
xfs_io -c fsync x
xfs_sync_stats "after fsync"
xfs_io -c fsync x
xfs_sync_stats "after fsync #2"

When this test is run in overlay mount over xfs, log force
count does not increase with syncfs command.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Amir Goldstein 2017-01-23 14:32:21 +02:00 committed by Miklos Szeredi
parent 01ad3eb8a0
commit e593b2bf51
1 changed files with 20 additions and 0 deletions
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20
fs/overlayfs/super.c
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@ -160,6 +160,25 @@ static void ovl_put_super(struct super_block *sb)
kfree(ufs);
}
static int ovl_sync_fs(struct super_block *sb, int wait)
{
struct ovl_fs *ufs = sb->s_fs_info;
struct super_block *upper_sb;
int ret;
if (!ufs->upper_mnt)
return 0;
upper_sb = ufs->upper_mnt->mnt_sb;
if (!upper_sb->s_op->sync_fs)
return 0;
/* real inodes have already been synced by sync_filesystem(ovl_sb) */
down_read(&upper_sb->s_umount);
ret = upper_sb->s_op->sync_fs(upper_sb, wait);
up_read(&upper_sb->s_umount);
return ret;
}
/**
* ovl_statfs
* @sb: The overlayfs super block
@ -222,6 +241,7 @@ static int ovl_remount(struct super_block *sb, int *flags, char *data)
static const struct super_operations ovl_super_operations = {
.put_super = ovl_put_super,
.sync_fs = ovl_sync_fs,
.statfs = ovl_statfs,
.show_options = ovl_show_options,
.remount_fs = ovl_remount,