Btrfs: do not delete a subvolume which is in a R/O subvolume

Step to reproduce:
 # mkfs.btrfs <disk>
 # mount <disk> <mnt>
 # btrfs sub create <mnt>/subv0
 # btrfs sub snap <mnt> <mnt>/subv0/snap0
 # change <mnt>/subv0 from R/W to R/O
 # btrfs sub del <mnt>/subv0/snap0

We deleted the snapshot successfully. I think we should not be able to delete
the snapshot since the parent subvolume is R/O.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index dd8e3448fe8fafaebc315df5032d897be975c3fb..5a72896bd76995917fc2040cd0d8225daa6569a2 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2095,13 +2095,13 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file,
                err = inode_permission(inode, MAY_WRITE | MAY_EXEC);
                if (err)
                        goto out_dput;
-
-               /* check if subvolume may be deleted by a non-root user */
-               err = btrfs_may_delete(dir, dentry, 1);
-               if (err)
-                       goto out_dput;
        }
 
+       /* check if subvolume may be deleted by a user */
+       err = btrfs_may_delete(dir, dentry, 1);
+       if (err)
+               goto out_dput;
+
        if (btrfs_ino(inode) != BTRFS_FIRST_FREE_OBJECTID) {
                err = -EINVAL;
                goto out_dput;