Re: [PATCH v7 09/12] xfs: wire up ->lease_direct()

[Dave Chinner <david@fromorbit.com>]

On Fri, Oct 06, 2017 at 03:36:06PM -0700, Dan Williams wrote:
> A 'lease_direct' lease requires that the vma have a valid MAP_DIRECT
> mapping established. For xfs we establish a new lease and then check if
> the MAP_DIRECT mapping has been broken. We want to be sure that the
> process will receive notification that the MAP_DIRECT mapping is being
> torn down so it knows why other code paths are throwing failures.
> 
> For example in the RDMA/ibverbs case we want ibv_reg_mr() to fail if the
> MAP_DIRECT mapping is invalid or in the process of being invalidated.
> 
> Cc: Jan Kara <jack@suse.cz>
> Cc: Jeff Moyer <jmoyer@redhat.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Dave Chinner <david@fromorbit.com>
> Cc: "Darrick J. Wong" <darrick.wong@oracle.com>
> Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
> Cc: Jeff Layton <jlayton@poochiereds.net>
> Cc: "J. Bruce Fields" <bfields@fieldses.org>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  fs/xfs/xfs_file.c |   28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index e35518600e28..823b65f17429 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -1166,6 +1166,33 @@ xfs_filemap_direct_close(
>  	put_map_direct_vma(vma->vm_private_data);
>  }
>  
> +static struct lease_direct *
> +xfs_filemap_direct_lease(
> +	struct vm_area_struct	*vma,
> +	void			(*break_fn)(void *),
> +	void			*owner)
> +{
> +	struct lease_direct	*ld;
> +
> +	ld = map_direct_lease(vma, break_fn, owner);
> +
> +	if (IS_ERR(ld))
> +		return ld;
> +
> +	/*
> +	 * We now have an established lease while the base MAP_DIRECT
> +	 * lease was not broken. So, we know that the "lease holder" will
> +	 * receive a SIGIO notification when the lease is broken and
> +	 * take any necessary cleanup actions.
> +	 */
> +	if (!is_map_direct_broken(vma->vm_private_data))
> +		return ld;
> +
> +	map_direct_lease_destroy(ld);
> +
> +	return ERR_PTR(-ENXIO);

What's any of this got to do with XFS? Shouldn't it be in generic
code, and called generic_filemap_direct_lease()?

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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