Re: [PATCH 1/2] xfs: only update mount/resv fields on success in __xfs_ag_resv_init

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

On Tue, Jan 24, 2017 at 09:16:19PM +0100, Christoph Hellwig wrote:
> Try to reserve the blocks first and only then update the fields in
> or hanging off the mount structure.  This way we can call __xfs_ag_resv_init
> again after a previous failure.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Looks ok to me,
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> ---
>  fs/xfs/libxfs/xfs_ag_resv.c | 23 ++++++++++++++---------
>  1 file changed, 14 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/xfs/libxfs/xfs_ag_resv.c b/fs/xfs/libxfs/xfs_ag_resv.c
> index d346d42..94234bf 100644
> --- a/fs/xfs/libxfs/xfs_ag_resv.c
> +++ b/fs/xfs/libxfs/xfs_ag_resv.c
> @@ -200,22 +200,27 @@ __xfs_ag_resv_init(
>  	struct xfs_mount		*mp = pag->pag_mount;
>  	struct xfs_ag_resv		*resv;
>  	int				error;
> +	xfs_extlen_t			reserved;
>  
> -	resv = xfs_perag_resv(pag, type);
>  	if (used > ask)
>  		ask = used;
> -	resv->ar_asked = ask;
> -	resv->ar_reserved = resv->ar_orig_reserved = ask - used;
> -	mp->m_ag_max_usable -= ask;
> +	reserved = ask - used;
>  
> -	trace_xfs_ag_resv_init(pag, type, ask);
> -
> -	error = xfs_mod_fdblocks(mp, -(int64_t)resv->ar_reserved, true);
> -	if (error)
> +	error = xfs_mod_fdblocks(mp, -(int64_t)reserved, true);
> +	if (error) {
>  		trace_xfs_ag_resv_init_error(pag->pag_mount, pag->pag_agno,
>  				error, _RET_IP_);
> +		return error;
> +	}
>  
> -	return error;
> +	mp->m_ag_max_usable -= ask;
> +
> +	resv = xfs_perag_resv(pag, type);
> +	resv->ar_asked = ask;
> +	resv->ar_reserved = resv->ar_orig_reserved = reserved;
> +
> +	trace_xfs_ag_resv_init(pag, type, ask);
> +	return 0;
>  }
>  
>  /* Create a per-AG block reservation. */
> -- 
> 2.1.4
>