RE: [PATCH v2 07/25] pnfsblock: add blocklayout Kconfig option, Makefile, and stubs

From: "Myklebust, Trond" <Trond.Myklebust@netapp.com>
To: "Benny Halevy" <bhalevy@tonian.com>, "Jim Rees" <rees@umich.edu>
Cc: <linux-nfs@vger.kernel.org>, "peter honeyman" <honey@citi.umich.edu>
Subject: RE: [PATCH v2 07/25] pnfsblock: add blocklayout Kconfig option, Makefile, and stubs
Date: Mon, 25 Jul 2011 07:38:12 -0700	[thread overview]
Message-ID: <2E1EB2CF9ED1CB4AA966F0EB76EAB4430A517B56@SACMVEXC2-PRD.hq.netapp.com> (raw)
In-Reply-To: <4E2D7E0D.60808@tonian.com>

> -----Original Message-----
> From: Benny Halevy [mailto:bhalevy@tonian.com]
> Sent: Monday, July 25, 2011 10:31 AM
> To: Jim Rees
> Cc: Myklebust, Trond; linux-nfs@vger.kernel.org; peter honeyman
> Subject: Re: [PATCH v2 07/25] pnfsblock: add blocklayout Kconfig
> option, Makefile, and stubs
> 
> On 2011-07-21 15:34, Jim Rees wrote:
> > From: Fred Isaman <iisaman@citi.umich.edu>
> >
> > Define a configuration variable to enable/disable compilation of the
> > block driver code.
> >
> > Add the minimal structure for a pnfs block layout driver, and empty
> > list-heads that will hold the extent data
> >
> > [pnfsblock: make NFS_V4_1 select PNFS_BLOCK]
> > Signed-off-by: Peng Tao <peng_tao@emc.com>
> > Signed-off-by: Fred Isaman <iisaman@citi.umich.edu>
> > Signed-off-by: Benny Halevy <bhalevy@panasas.com>
> > [pnfs-block: fix CONFIG_PNFS_BLOCK dependencies]
> > Signed-off-by: Benny Halevy <bhalevy@panasas.com>
> > Signed-off-by: Benny Halevy <benny@tonian.com>
> > [pnfsblock: SQUASHME: port block layout code]
> > Signed-off-by: Peng Tao <peng_tao@emc.com>
> > [pnfsblock: SQUASHME: adjust to API change]
> > Signed-off-by: Fred Isaman <iisaman@citi.umich.edu>
> > [pnfs: move pnfs_layout_type inline in nfs_inode]
> > Signed-off-by: Benny Halevy <bhalevy@panasas.com>
> > [blocklayout: encode_layoutcommit implementation]
> > Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
> > Signed-off-by: Benny Halevy <bhalevy@panasas.com>
> > Signed-off-by: Benny Halevy <benny@tonian.com>
> > [pnfsblock: layout alloc and free]
> > Signed-off-by: Fred Isaman <iisaman@citi.umich.edu>
> > [pnfs: move pnfs_layout_type inline in nfs_inode]
> > Signed-off-by: Benny Halevy <bhalevy@panasas.com>
> > Signed-off-by: Benny Halevy <benny@tonian.com>
> > [pnfsblock: define module alias]
> > Signed-off-by: Peng Tao <peng_tao@emc.com>
> > ---
> >  fs/nfs/Kconfig                   |    8 ++-
> >  fs/nfs/Makefile                  |    1 +
> >  fs/nfs/blocklayout/Makefile      |    5 +
> >  fs/nfs/blocklayout/blocklayout.c |  175
> ++++++++++++++++++++++++++++++++++++++
> >  fs/nfs/blocklayout/blocklayout.h |   91 ++++++++++++++++++++
> >  5 files changed, 279 insertions(+), 1 deletions(-)
> >  create mode 100644 fs/nfs/blocklayout/Makefile
> >  create mode 100644 fs/nfs/blocklayout/blocklayout.c
> >  create mode 100644 fs/nfs/blocklayout/blocklayout.h
> >
> > diff --git a/fs/nfs/Kconfig b/fs/nfs/Kconfig
> > index 2cde5d9..be02077 100644
> > --- a/fs/nfs/Kconfig
> > +++ b/fs/nfs/Kconfig
> > @@ -79,15 +79,21 @@ config NFS_V4_1
> >  	depends on NFS_FS && NFS_V4 && EXPERIMENTAL
> >  	select SUNRPC_BACKCHANNEL
> >  	select PNFS_FILE_LAYOUT
> > +	select PNFS_BLOCK
> > +	select MD
> > +	select BLK_DEV_DM
> 
> Why is PNFS_BLOCK enabled automatically in all cases?
> That renders the use of modules for layout drivers totally useless.
> I sort of understand that for PNFS_FILE_LAYOUT (when my
> arm is twisted really hard behind my back :) since it
> is an integral part of RFC5661 but what's the justification
> for PNFS_BLOCK? and why blocks and not objects?

The question is rather why did objects add a selectable compile option?
What is the point of not compiling a given layout driver if all the
dependencies are met?

IOW: The only thing I'd change above is the select MD and select
BLK_DEV_DM: I'd prefer something like

config PNFS_BLOCK
	depends on NFS_V4_1 && MD && BLK_DEV_DM
	default y

Trond