[RFC PATCH v5 10/10] ovl: implement containerized syncfs for overlayfs

[Chengguang Xu <cgxu519@mykernel.net>]

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

Signed-off-by: Chengguang Xu <cgxu519@mykernel.net>
---
 fs/overlayfs/super.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index bf4000eb9be8..ef998ada6cb9 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -15,6 +15,7 @@
 #include <linux/seq_file.h>
 #include <linux/posix_acl_xattr.h>
 #include <linux/exportfs.h>
+#include <linux/writeback.h>
 #include "overlayfs.h"
 
 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
@@ -281,18 +282,15 @@ 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
-	 * called with wait == 1.
 	 */
-	if (!wait)
-		return 0;
 
 	upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
 
 	down_read(&upper_sb->s_umount);
-	ret = sync_filesystem(upper_sb);
+	if (wait)
+		wait_sb_inodes(upper_sb);
+
+	ret = sync_fs_and_blockdev(upper_sb, wait);
 	up_read(&upper_sb->s_umount);
 
 	return ret;
-- 
2.27.0