From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Snitzer Subject: Re: [RFC 1/2] block: implement an unprep function corresponding directly to prep Date: Wed, 30 Jun 2010 23:47:31 -0400 Message-ID: <20100701034731.GA9499@redhat.com> References: <1277917264.2839.153.camel@mulgrave.site> <20100701104653O.fujita.tomonori@lab.ntt.co.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from mx1.redhat.com ([209.132.183.28]:28784 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752755Ab0GADrv (ORCPT ); Wed, 30 Jun 2010 23:47:51 -0400 Content-Disposition: inline In-Reply-To: <20100701104653O.fujita.tomonori@lab.ntt.co.jp> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: FUJITA Tomonori Cc: James.Bottomley@suse.de, hch@lst.de, axboe@kernel.dk, linux-scsi@vger.kernel.org, dm-devel@redhat.com Hi, On Wed, Jun 30 2010 at 9:47pm -0400, FUJITA Tomonori wrote: > On Wed, 30 Jun 2010 12:01:04 -0500 > James Bottomley wrote: > > > So this is more directly what I'm thinking. It gives us an exactly > > correct place to hang the discard allocation in SCSI. The next patch > > shows a potential implementation in sd. > > Yeah, making the prep_rq_fn API symmetrical makes sense lots. > > > > I think it should avoid all the leaks people have been seeing trying to > > move the discard allocation/free into scsi. I also think it should > > facilitate sending discard through SCSI as a REQ_TYPE_FS. > > I think so. If I can figure out why qemu scsi driver is broken, the > job is done. When I combine this patch 1/2 and patch 2/2 with Christoph's discard payload rework (a1d949f5f448) already staged in for-2.6.36 I'm finding that: sd_unprep_fn's __free_page causes the system to hard hang/crash. I need to get serial connected and/or kdump configured to see if I can catch what is happening. But if I comment out sd_unprep_fn's __free_page() from James' patch 2/2 I don't see a crash. Seems some other code is altering the request before James' new sd_unprep_fn hhook? Are James' patches meant to be dependent on your REQ_TYPE_FS conversion work? I wouldn't think so.. but I haven't traced the call chains close enough to know. > I'll see how this patchset works and update my FS discard patchset on > the top of this. I look forward to your results! Thanks, Mike