Btrfs: do not overwrite error return value in the balance ioctl

If the call to btrfs_balance() failed we would overwrite the error
returned to user space with -EFAULT if the call to copy_to_user() failed
as well. Fix that by calling copy_to_user() only if btrfs_balance()
returned success or was canceled.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index b07b19a..c21cc40 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4781,7 +4781,7 @@ do_balance:
        ret = btrfs_balance(fs_info, bctl, bargs);
        bctl = NULL;
 
-       if (arg) {
+       if ((ret == 0 || ret == -ECANCELED) && arg) {
                if (copy_to_user(arg, bargs, sizeof(*bargs)))
                        ret = -EFAULT;
        }