Re: [PATCH] nfsd: allow SCSI layout support without Block layout

From: Dave Chinner <david@fromorbit.com>
To: "J. Bruce Fields" <bfields@fieldses.org>
Cc: Benjamin Coddington <bcodding@redhat.com>,
	Christoph Hellwig <hch@lst.de>,
	xfs@oss.sgi.com
Subject: Re: [PATCH] nfsd: allow SCSI layout support without Block layout
Date: Thu, 7 Jul 2016 08:16:48 +1000	[thread overview]
Message-ID: <20160706221648.GE12670@dastard> (raw)
In-Reply-To: <20160706124326.GA18856@fieldses.org>

On Wed, Jul 06, 2016 at 08:43:26AM -0400, J. Bruce Fields wrote:
> On Wed, Jul 06, 2016 at 05:58:09AM -0400, Benjamin Coddington wrote:
> > On 6 Jul 2016, at 5:19, Dave Chinner wrote:
> > 
> > >On Tue, Jul 05, 2016 at 09:48:47PM -0400, Benjamin Coddington wrote:
> > >>We shouldn't have to configure both NFSD_BLOCKLAYOUT and
> > >>NFSD_SCSILAYOUT if
> > >>all we want are SCSI layouts on the server, so define the xfs export
> > >>operations for either configuration.
> > >>
> > >>Signed-off-by: Benjamin Coddington <bcodding@redhat.com>
> > >
> > >I don't really like exploding config option dependencies into
> > >subsystems that aren't actually related to the config options.
> > >It's confusing enough laready that we've got XFS code dependent on
> > >PNFSD config options without adding more to it. Instead, I'd
> > >suggest this should be resolved in the kconfig files. i.e. make
> > >CONFIG_NFSD_SCSILAYOUT=y select CONFIG_NFSD_BLOCKLAYOUT to resolve
> > >the config dependency at config time.
> > 
> > But the point is to leave CONFIG_NFSD_BLOCKLAYOUT undefined
> > otherwise knfsd
> > will advertise block layouts to clients -- which we don't want.

Pnfsd layout is determined at compile time?  That's seems less than
useful to me for distros wanting to support for multiple layout
types in the one kernel. i.e. Shouldn't the layout to be advertised
be something like a per-export configuration option rather than
determined at compile time define?

> > Would a third define specific for xfs_export_operations that gets
> > set in kconfig files work for you?  Something like XFS_PNFS_EXPORT_OPS.
>
> That makes sense to me....

Sounds good, but I'd drop the "XFS_" prefix because when multiple
filesytems end up supporting it, we don't want to have to select
every single one of them from the PNFSD config options...

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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