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>

1 files changed, 9 insertions, 8 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index f5c1c150d9f3..afbf3ac2079d 100644
--- 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;
 }