Re: [PATCH] xfsprogs: fix geometry calls on older kernels for 5.2.1

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Tue, Aug 20, 2019 at 03:47:29PM -0500, Eric Sandeen wrote:
> I didn't think 5.2.0 through; the udpate of the geometry ioctl means
> that the tools won't work on older kernels that don't support the
> v5 ioctls, since I failed to merge Darrick's wrappers.
> 
> As a very quick one-off I'd like to merge this to just revert every
> geometry call back to the original ioctl, so it keeps working on
> older kernels and I'll release 5.2.1.  This hack can go away when
> Darrick's wrappers get merged.
> 
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>

For the four line code fix,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

> ---
> 
> I'm a little concerned that 3rd party existing code which worked fine
> before will now get the new XFS_IOC_FSGEOMETRY definition if they get
> rebuilt, and suddenly stop working on older kernels. Am I overreacting
> or misunderstanding our compatibility goals?

As for this question ^^^ ... <URRRK>.

I thought the overall strategy was to get everything in xfsprogs using
libfrog wrappers that would degrade gracefully on old kernels.

For xfsdump/restore, I think we should just merge it into xfsprogs and
then it can use our wrappers.

For everything else... I thought the story was that you shouldn't really
be using xfs ioctls unless you're keeping up with upstream.

<shrug> Feel free to differ, that's just a braindump of my shattered
mind. :P

--D

> diff --git a/libxfs/xfs_fs.h b/libxfs/xfs_fs.h
> index f1158a79..253b706c 100644
> --- a/libxfs/xfs_fs.h
> +++ b/libxfs/xfs_fs.h
> @@ -720,7 +720,10 @@ struct xfs_scrub_metadata {
>  #define XFS_IOC_ATTRMULTI_BY_HANDLE  _IOW ('X', 123, struct xfs_fsop_attrmulti_handlereq)
>  #define XFS_IOC_FSGEOMETRY_V4	     _IOR ('X', 124, struct xfs_fsop_geom_v4)
>  #define XFS_IOC_GOINGDOWN	     _IOR ('X', 125, uint32_t)
> -#define XFS_IOC_FSGEOMETRY	     _IOR ('X', 126, struct xfs_fsop_geom)
> +/* For backwards compatibility in 5.2.1, just for now */
> +/* #define XFS_IOC_FSGEOMETRY	     _IOR ('X', 126, struct xfs_fsop_geom_v5) */
> +#define XFS_IOC_FSGEOMETRY XFS_IOC_FSGEOMETRY_V4
> +
>  /*	XFS_IOC_GETFSUUID ---------- deprecated 140	 */
>  
>  /* reflink ioctls; these MUST match the btrfs ioctl definitions */
>