From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754726AbZHTOmq (ORCPT ); Thu, 20 Aug 2009 10:42:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754540AbZHTOmp (ORCPT ); Thu, 20 Aug 2009 10:42:45 -0400 Received: from cantor.suse.de ([195.135.220.2]:34162 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754418AbZHTOmo (ORCPT ); Thu, 20 Aug 2009 10:42:44 -0400 Subject: Re: [PATCH, RFC] xfs: batched discard support From: James Bottomley To: Mark Lord Cc: Ric Wheeler , Ingo Molnar , Christoph Hellwig , Peter Zijlstra , Paul Mackerras , Linus Torvalds , xfs@oss.sgi.com, linux-fsdevel@vger.kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, jens.axboe@oracle.com, IDE/ATA development list , Neil Brown In-Reply-To: <4A8D5FDB.7080505@rtr.ca> References: <20090816004705.GA7347@infradead.org> <20090819203916.GA25296@elte.hu> <4A8CA956.2060406@rtr.ca> <4A8D5442.1000302@redhat.com> <4A8D5FDB.7080505@rtr.ca> Content-Type: text/plain Date: Thu, 20 Aug 2009 08:42:36 -0600 Message-Id: <1250779356.5533.15.camel@mulgrave.site> Mime-Version: 1.0 X-Mailer: Evolution 2.24.1.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2009-08-20 at 10:38 -0400, Mark Lord wrote: > Would it still be okay to do the TRIMs when the entire parity stripe > (across all members) is being discarded? (As opposed to just partial > data there being dropped) Not really. The problem is that array verification is done at the block level not the fs level (although, I suppose, we could change that). So a fully discarded stripe still has to verify OK (as in what's read for the parity must match what's read for the data). All of this is the reason for the TPRZ bit for SCSI UNMAP ... and why WRITE_SAME is also under consideration for discards in T10. James