From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: To: "hch\@infradead.org" Cc: "Martin K. Petersen" , KY Srinivasan , James Bottomley , "linux-kernel\@vger.kernel.org" , "devel\@linuxdriverproject.org" , "apw\@canonical.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 From: "Martin K. Petersen" 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> Date: Wed, 16 Jul 2014 13:47:35 -0400 In-Reply-To: <20140716173827.GB20528@infradead.org> (hch@infradead.org's message of "Wed, 16 Jul 2014 10:38:27 -0700") Message-ID: MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: >>>>> "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. -- Martin K. Petersen Oracle Linux Engineering