Re: [PATCH] btrfs: ioctl: reorder exclusive op check in RM_DEV

[Filipe Manana <fdmanana@gmail.com>]

On Wed, May 4, 2016 at 10:32 AM, David Sterba <dsterba@suse.com> wrote:
> From: David Sterba <dsterba@suse.cz>
>
> Move the op exclusivity check before the other code (same as in
> ADD_DEV).
>
> Signed-off-by: David Sterba <dsterba@suse.com>
> ---
>  fs/btrfs/ioctl.c | 23 +++++++++++------------
>  1 file changed, 11 insertions(+), 12 deletions(-)
>
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index e3239272fa61..45beb6dd8417 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -2680,32 +2680,31 @@ static long btrfs_ioctl_rm_dev(struct file *file, void __user *arg)
>         if (ret)
>                 return ret;
>
> +       if (atomic_xchg(&root->fs_info->mutually_exclusive_operation_running,
> +                       1)) {
> +               ret = BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS;
> +               goto out_drop_write;
> +       }
> +
>         vol_args = memdup_user(arg, sizeof(*vol_args));
>         if (IS_ERR(vol_args)) {
>                 ret = PTR_ERR(vol_args);
> -               goto err_drop;
> +               goto out_drop_write;

goto out, otherwise
root->fs_info->mutually_exclusive_operation_running remains with value
1 forever...

>         }
>
>         vol_args->name[BTRFS_PATH_NAME_MAX] = '\0';
> -
> -       if (atomic_xchg(&root->fs_info->mutually_exclusive_operation_running,
> -                       1)) {
> -               ret = BTRFS_ERROR_DEV_EXCL_RUN_IN_PROGRESS;
> -               goto out;
> -       }
> -
>         mutex_lock(&root->fs_info->volume_mutex);
>         ret = btrfs_rm_device(root, vol_args->name);
>         mutex_unlock(&root->fs_info->volume_mutex);
> -       atomic_set(&root->fs_info->mutually_exclusive_operation_running, 0);
>
>         if (!ret)
>                 btrfs_info(root->fs_info, "disk deleted %s",vol_args->name);
> -
> -out:
>         kfree(vol_args);
> -err_drop:
> +out:
> +       atomic_set(&root->fs_info->mutually_exclusive_operation_running, 0);
> +out_drop_write:
>         mnt_drop_write_file(file);
> +
>         return ret;
>  }
>
> --
> 2.7.1
>
> --
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-- 
Filipe David Manana,

"Reasonable men adapt themselves to the world.
 Unreasonable men adapt the world to themselves.
 That's why all progress depends on unreasonable men."