Re: [PATCH 1/3] libxfs: don't set mp->m_rtdev_targp when no RT devices is provided

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

On Fri, Sep 11, 2026 at 04:45:42PM +0200, Christoph Hellwig wrote:
> The user-space only parts of commit 9840f7e09e2f ("xfs: allow internal
> RT devices for zoned mode") accidentally set m_rtdev_targp to
> m_ddev_targp when not name is set for the RT device, and thus disable
> the check for a non-NULL m_rtdev_targp in rtmount_init.
> 
> This lead to tools working without specifying a RT device when they
> should abort.  For example this can lead to repair trying to read
> and rewrite the rtsb when called without -rc, which will then fail
> in weird ways.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  libxfs/init.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/libxfs/init.c b/libxfs/init.c
> index 5d8b4a153e28..2a46ddf086ed 100644
> --- a/libxfs/init.c
> +++ b/libxfs/init.c
> @@ -573,7 +573,7 @@ libxfs_buftarg_init(
>  	else
>  		mp->m_logdev_targp = libxfs_buftarg_alloc(mp, xi, &xi->log,
>  				lfail);
> -	if (!xi->rt.dev || xi->rt.dev == xi->data.dev)
> +	if (xi->rt.dev == xi->data.dev)
>  		mp->m_rtdev_targp = mp->m_ddev_targp;
>  	else
>  		mp->m_rtdev_targp = libxfs_buftarg_alloc(mp, xi, &xi->rt,

Does this mean that m_rtdev_targp is never NULL, even when we don't
specify or have a rt device attached?  I would have expected this to be:

	if (!xi->rt.dev)
		mp->m_rtdev_targp = NULL;
	else if (xi->rt.dev == xi->data.dev)
		mp->m_rtdev_targp = mp->m_ddev_targp;
	else
		mp->m_rtdev_targp = libxfs_buftarg_alloc(...);

--D

> -- 
> 2.53.0
> 
>