From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mike Snitzer <snitzer@redhat.com>
Subject: Re: [PATCH 4/5] block: make blkdev_get/put() handle
	exclusive access
Date: Thu, 4 Nov 2010 11:04:00 -0400
Message-ID: <20101104150400.GA32504@redhat.com>
References: <1288628129-12811-1-git-send-email-tj@kernel.org>
	<1288628129-12811-5-git-send-email-tj@kernel.org>
	<20101103161059.GA13621@infradead.org>
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To: device-mapper development <dm-devel@redhat.com>
Cc: jack@suse.cz, leochen@broadcom.com, heiko.carstens@de.ibm.com, adilger.kernel@dilger.ca, konishi.ryusuke@lab.ntt.co.jp, shaggy@linux.vnet.ibm.com, drbd-dev@lists.linbit.com, joel.becker@oracle.com, hch@infradead.org, aelder@sgi.com, mfasheh@suse.com, joern@logfs.org, reiserfs-devel@vger.kernel.org, schwidefsky@de.ibm.com, viro@zeniv.linux.org.uk, swhiteho@redhat.com, chris.mason@oracle.com, axboe@kernel.dk, tytso@mit.edu, sbranden@broadcom.com, petero2@telia.com, linux-kernel@vger.kernel.org, Tejun Heo <tj@kernel.org>, akpm@linux-foundation.org

On Wed, Nov 03 2010 at 12:10pm -0400,
Christoph Hellwig <hch@infradead.org> wrote:

> On Mon, Nov 01, 2010 at 05:15:28PM +0100, Tejun Heo wrote:
> > * blkdev_get() is extended to include exclusive access management.
> >   @holder argument is added and, if is @FMODE_EXCL specified, it will
> >   gain exclusive access atomically w.r.t. other exclusive accesses.
> > 
> > * blkdev_put() is similarly extended.  It now takes @mode argument and
> >   if @FMODE_EXCL is set, it releases an exclusive access.  Also, when
> >   the last exclusive claim is released, the holder/slave symlinks are
> >   removed automatically.
> 
> Could we get rid of FMODE_EXCL and just make a non-NULL holder field
> mean to open it exlusively (and pass a holder to the blkdev_put to
> release it)?

I agree that the need for a FMODE_EXCL flag is awkward.  Christoph's
proposed change should clean things up nicely.

Other than that, for the DM bits:

Acked-by: Mike Snitzer <snitzer@redhat.com>