Re: [PATCH v2 2/2] xfs: add FS_IOC_GETFSUUID ioctl

["Darrick J. Wong" <djwong@kernel.org>]

On Fri, Nov 18, 2022 at 01:14:08PM -0800, Catherine Hoang wrote:
> Add a new ioctl to retrieve the UUID of a mounted xfs filesystem. This is a
> precursor to adding the SETFSUUID ioctl.
> 
> Signed-off-by: Catherine Hoang <catherine.hoang@oracle.com>
> Reviewed-by: Allison Henderson <allison.henderson@oracle.com>

LGTM,
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
>  fs/xfs/xfs_ioctl.c | 36 ++++++++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
> 
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index 1f783e979629..cf77715afe9e 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -1865,6 +1865,39 @@ xfs_fs_eofblocks_from_user(
>  	return 0;
>  }
>  
> +static int
> +xfs_ioctl_getuuid(
> +	struct xfs_mount	*mp,
> +	struct fsuuid __user	*ufsuuid)
> +{
> +	struct fsuuid		fsuuid;
> +	__u8			uuid[UUID_SIZE];
> +
> +	if (copy_from_user(&fsuuid, ufsuuid, sizeof(fsuuid)))
> +		return -EFAULT;
> +
> +	if (fsuuid.fsu_len == 0) {
> +		fsuuid.fsu_len = UUID_SIZE;
> +		if (copy_to_user(&ufsuuid->fsu_len, &fsuuid.fsu_len,
> +					sizeof(fsuuid.fsu_len)))
> +			return -EFAULT;
> +		return 0;
> +	}
> +
> +	if (fsuuid.fsu_len < UUID_SIZE || fsuuid.fsu_flags != 0)
> +		return -EINVAL;
> +
> +	spin_lock(&mp->m_sb_lock);
> +	memcpy(uuid, &mp->m_sb.sb_uuid, UUID_SIZE);
> +	spin_unlock(&mp->m_sb_lock);
> +
> +	fsuuid.fsu_len = UUID_SIZE;
> +	if (copy_to_user(ufsuuid, &fsuuid, sizeof(fsuuid)) ||
> +	    copy_to_user(&ufsuuid->fsu_uuid[0], uuid, UUID_SIZE))
> +		return -EFAULT;
> +	return 0;
> +}
> +
>  /*
>   * These long-unused ioctls were removed from the official ioctl API in 5.17,
>   * but retain these definitions so that we can log warnings about them.
> @@ -2153,6 +2186,9 @@ xfs_file_ioctl(
>  		return error;
>  	}
>  
> +	case FS_IOC_GETFSUUID:
> +		return xfs_ioctl_getuuid(mp, arg);
> +
>  	default:
>  		return -ENOTTY;
>  	}
> -- 
> 2.25.1
>