From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Martin K. Petersen" Subject: Re: [PATCH v5 2/2] Add support for SCT Write Same Date: Wed, 10 Aug 2016 21:33:51 -0400 Message-ID: References: <1470790829-3793-1-git-send-email-shaun@tancheff.com> <1470790829-3793-3-git-send-email-shaun@tancheff.com> Mime-Version: 1.0 Content-Type: text/plain Return-path: Received: from userp1040.oracle.com ([156.151.31.81]:27339 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752234AbcHKBeG (ORCPT ); Wed, 10 Aug 2016 21:34:06 -0400 In-Reply-To: (Shaun Tancheff's message of "Wed, 10 Aug 2016 09:34:53 -0500") Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Shaun Tancheff Cc: Tom Yan , Shaun Tancheff , linux-ide@vger.kernel.org, LKML , Christoph Hellwig , Tejun Heo , Josh Bingaman >>>>> "Shaun" == Shaun Tancheff writes: Shaun, Shaun> You are correct in that we can advertise the larger limit in Shaun> ata_scsi_dev_config() when only SCT write same is supported Shaun> rather than fall back to WS10. I deliberately capped WRITE SAME to 64K blocks unless otherwise reported by the device because: a) Several older drives supported the WRITE SAME(16) command but ignored the upper bytes of the transfer length effectively turning it into a WRITE SAME(10). b) 64K blocks was the sweet spot for older drives as well, a size commonly used by RAID array firmwares that were the only commonplace users of the WRITE SAME family. Shaun> I really am not sure what would be considered the correct Shaun> solution though. I believe that the WRITE SAME defaults are Shaun> currently being chosen around physical limits. Lacking a solid reporting facility in the spec, I suggest you just leave it unset and let the SCSI defaults apply. Shaun> I think we can also bump the command timeout for WRITE SAME? The default WRITE SAME timeout is 120s. -- Martin K. Petersen Oracle Linux Engineering