ovl: properly implement sync_filesystem()
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>
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 6792bb7..346f668 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -160,6 +160,25 @@
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 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,