From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:45807 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751186AbcEIORU (ORCPT ); Mon, 9 May 2016 10:17:20 -0400 Subject: Re: [PATCH 3.16 106/217] sd: disable discard_zeroes_data for UNMAP To: Rafael David Tinoco , Ben Hutchings References: <1461859893.1169.49.camel@decadent.org.uk> Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, akpm@linux-foundation.org, "Martin K. Petersen" , Christoph Hellwig From: Paolo Bonzini Message-ID: <57309BEB.2010900@redhat.com> Date: Mon, 9 May 2016 16:17:15 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: stable-owner@vger.kernel.org List-ID: On 29/04/2016 06:00, Rafael David Tinoco wrote: > Actually, It was an objection. > > Knowing that WRITESAME(16), used as the discard mechanism, can cause > storage servers to misbehave (like QEMU's SCSI WRITESAME > implementation, workaround-ed by commit e461338b6cd4) and those > storage servers can't rely on LBPRZ flag to opt out from WRITESAME as > discard mechanism (like QEMU does) since it is out of spec... I think e461338b6cd4 is a perfectly fine change---independent of whether it's a workaround for QEMU---and should be backported to stable kernels too. Is there a reason to use WRITE SAME if LBPRZ=0? You risk doing a real write which breaks thin provisioning and will probably take a huge time too. Paolo