From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Snitzer Subject: Re: [PATCH, RFC] block: don't allocate a payload for discard request Date: Sat, 19 Jun 2010 00:25:34 -0400 Message-ID: <20100619042534.GA16217@redhat.com> References: <20100618145942.GA1148@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20100618145942.GA1148@lst.de> Sender: linux-kernel-owner@vger.kernel.org To: Christoph Hellwig Cc: axboe@kernel.dk, martin.petersen@oracle.com, James.Bottomley@suse.de, linux-kernel@vger.kernel.org, dm-devel@redhat.com List-Id: dm-devel.ids On Fri, Jun 18 2010 at 10:59am -0400, Christoph Hellwig wrote: > > Allocating a fixed payload for discard requests always was a horrible hack, > and it's not coming to byte us when adding support for discard in DM/MD. > > So change the code to leave the allocation of a payload to the lowlevel > driver. Unfortunately that means we'll need another hack, which allows > us to update the various block layer length fields indicating that we > have a payload. Instead of hiding this in sd.c, which we already partially > do for UNMAP support add a documented helper in the core block layer for it. > > Signed-off-by: Christoph Hellwig Acked-by: Mike Snitzer I've built on your patch to successfully implement discard support for DM (this includes splitting discards that span targets; only the linear and striped DM targets are supported so far). The patchset is still a work in progress but is available here (against 2.6.34 at the moment): http://people.redhat.com/msnitzer/patches/dm-discard/latest/