Btrfs: reorder locks and sanity checks in btrfs_ioctl_defrag

Operation-specific check (whether subvol is readonly or not) should go
after the mutual exclusiveness check.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index f5c1c15..afbf3ac 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -2186,19 +2186,20 @@ static int btrfs_ioctl_defrag(struct file *file, void __user *argp)
        struct btrfs_ioctl_defrag_range_args *range;
        int ret;
 
-       if (btrfs_root_readonly(root))
-               return -EROFS;
+       ret = mnt_want_write_file(file);
+       if (ret)
+               return ret;
 
        if (atomic_xchg(&root->fs_info->mutually_exclusive_operation_running,
                        1)) {
                pr_info("btrfs: dev add/delete/balance/replace/resize operation in progress\n");
+               mnt_drop_write_file(file);
                return -EINVAL;
        }
-       ret = mnt_want_write_file(file);
-       if (ret) {
-               atomic_set(&root->fs_info->mutually_exclusive_operation_running,
-                          0);
-               return ret;
+
+       if (btrfs_root_readonly(root)) {
+               ret = -EROFS;
+               goto out;
        }
 
        switch (inode->i_mode & S_IFMT) {
@@ -2250,8 +2251,8 @@ static int btrfs_ioctl_defrag(struct file *file, void __user *argp)
                ret = -EINVAL;
        }
 out:
-       mnt_drop_write_file(file);
        atomic_set(&root->fs_info->mutually_exclusive_operation_running, 0);
+       mnt_drop_write_file(file);
        return ret;
 }