[RFC PATCH v2 8/8] ovl: implement containerized syncfs for overlayfs

[Chengguang Xu <cgxu519@mykernel.net>]

Now overlayfs can only sync dirty inode during
syncfs, so remove unnecessary sync_filesystem()
on upper file system.

Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
---
 fs/overlayfs/super.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 1d04117fb6ad..df33e8c8f1d0 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -271,8 +271,7 @@ static int ovl_sync_fs(struct super_block *sb, int wait)
 	 * Not called for sync(2) call or an emergency sync (SB_I_SKIP_SYNC).
 	 * All the super blocks will be iterated, including upper_sb.
 	 *
-	 * If this is a syncfs(2) call, then we do need to call
-	 * sync_filesystem() on upper_sb, but enough if we do it when being
+	 * If this is a syncfs(2) call, it will be enough we do it when being
 	 * called with wait == 1.
 	 */
 	if (!wait)
@@ -281,7 +280,10 @@ static int ovl_sync_fs(struct super_block *sb, int wait)
 	upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
 
 	down_read(&upper_sb->s_umount);
-	ret = sync_filesystem(upper_sb);
+	if (upper_sb->s_op->sync_fs)
+		ret = upper_sb->s_op->sync_fs(upper_sb, wait);
+	if (!ret)
+		ret = sync_blockdev(upper_sb->s_bdev);
 	up_read(&upper_sb->s_umount);
 
 	return ret;
-- 
2.26.2