exfat: call sync_filesystem for read-only remount

We need to commit dirty metadata and pages to disk
before remounting exfat as read-only.

This fixes a failure in xfstests generic/452

generic/452 does the following:
cp something <exfat>/
mount -o remount,ro <exfat>

the <exfat>/something is corrupted. because while
exfat is remounted as read-only, exfat doesn't
have a chance to commit metadata and
vfs invalidates page caches in a block device.

Signed-off-by: Hyunchul Lee <hyc.lee@gmail.com>
Acked-by: Sungjong Seo <sj1557.seo@samsung.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>

diff --git a/fs/exfat/super.c b/fs/exfat/super.c
index e650e65536f848c544b731f273b5f8839298e850..253a92460d5222f4f3aa75e52fc0b3eab084bc06 100644 (file)
--- a/fs/exfat/super.c
+++ b/fs/exfat/super.c
@@ -693,10 +693,20 @@ static void exfat_free(struct fs_context *fc)
        }
 }
 
+static int exfat_reconfigure(struct fs_context *fc)
+{
+       fc->sb_flags |= SB_NODIRATIME;
+
+       /* volume flag will be updated in exfat_sync_fs */
+       sync_filesystem(fc->root->d_sb);
+       return 0;
+}
+
 static const struct fs_context_operations exfat_context_ops = {
        .parse_param    = exfat_parse_param,
        .get_tree       = exfat_get_tree,
        .free           = exfat_free,
+       .reconfigure    = exfat_reconfigure,
 };
 
 static int exfat_init_fs_context(struct fs_context *fc)