Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934831AbaGPSCS (ORCPT ); Wed, 16 Jul 2014 14:02:18 -0400 Received: from mx2.parallels.com ([199.115.105.18]:43316 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934606AbaGPSCQ convert rfc822-to-8bit (ORCPT ); Wed, 16 Jul 2014 14:02:16 -0400 From: James Bottomley To: "martin.petersen@oracle.com" CC: "linux-kernel@vger.kernel.org" , "hch@infradead.org" , "devel@linuxdriverproject.org" , "apw@canonical.com" , "kys@microsoft.com" , "stable@vger.kernel.org" , "linux-scsi@vger.kernel.org" , "ohering@suse.com" , "jasowang@redhat.com" Subject: Re: [PATCH 4/8] Drivers: scsi: storvsc: Filter WRITE_SAME_16 Thread-Topic: [PATCH 4/8] Drivers: scsi: storvsc: Filter WRITE_SAME_16 Thread-Index: AQHPoR4G2vh72TcerE+9u7O+On3hT5ujc0EA Date: Wed, 16 Jul 2014 18:02:14 +0000 Message-ID: <1405533734.3165.12.camel@dabdike.int.hansenpartnership.com> References: <20140709084300.GD6012@infradead.org> <1404935792.2184.5.camel@dabdike.int.hansenpartnership.com> <2f3ae589e6f149acbe4c5dd79f905971@BY2PR03MB299.namprd03.prod.outlook.com> <1404944843.2184.8.camel@dabdike.int.hansenpartnership.com> <20140711063216.GA20660@infradead.org> <328b7a6174ef4dd8a54a7db5ac959834@BY2PR03MB299.namprd03.prod.outlook.com> <20140716110111.GA7382@infradead.org> <20140716173827.GB20528@infradead.org> In-Reply-To: Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [50.46.103.107] Content-Type: text/plain; charset=US-ASCII Content-ID: Content-Transfer-Encoding: 7BIT MIME-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2014-07-16 at 13:47 -0400, Martin K. Petersen wrote: > >>>>> "Christoph" == hch@infradead org writes: > > Christoph> Oh, we actually have devices that support WRITE SAME with > Christoph> unmap, but not without? That's defintively a little strange. > > Yep :( > > There were several SSDs that did not want to support wearing out flash > by writing gobs of zeroes and only support the UNMAP case. > > Christoph> Yes, and it did this intentionally. I really wouldn't expect > Christoph> devices to support WRITE SAME with UNMAP but blow up on a > Christoph> WRITE SAME without it (and not just simple fail it in an > Christoph> orderly way). > > *sigh* > > Christoph> It definitively seems odd to default to trying WRITE SAME for > Christoph> unmap for a device that explicitly tells us that it doesn't > Christoph> support WRITE SAME. > > Maybe it's just a naming thing. I was really trying to convey > no_req_write_same support, not no_write_same_10_or_16. > > Christoph> Note that I'm not against your patch - I suspect forcing us > Christoph> to read EVPD pages even for devices that claim to be SPC-2 > Christoph> will come in useful in various scenarios. > > I don't have a problem with a BLIST_PREFER_UNMAP flag or something like > that. But BLIST_TRY_VPD_PAGES seems more generally useful and it does > fix the problem at hand. That's why I went that route. Hang on ... unless we apply Christoph or my fix, we'll get the same issue with every raid driver (that's about 10 I think) that set no_write_same when they hit a >2TB RAID volume, so I think we need both fixes. James -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/