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

[fdmanana]

From: Filipe Manana <fdman...@suse.com>

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.

Signed-off-by: Filipe Manana <fdman...@suse.com>
---
 fs/btrfs/ioctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index abe45fd97ab5..4ad7288f77d0 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -4707,7 +4707,7 @@ static long btrfs_ioctl_balance(struct file *file, void 
__user *arg)
        ret = btrfs_balance(fs_info, bctl, bargs);
        bctl = NULL;
 
-       if (arg) {
+       if (ret == 0 && arg) {
                if (copy_to_user(arg, bargs, sizeof(*bargs)))
                        ret = -EFAULT;
        }
-- 
2.11.0