From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ewan Milne Subject: Re: [PATCH v2] sg: add SG_FLAG_Q_AT_TAIL flag Date: Wed, 11 Jun 2014 10:54:27 -0400 Message-ID: <1402498467.3820.96.camel@localhost.localdomain> References: <538F3416.5090306@interlog.com> Reply-To: emilne@redhat.com Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from mx1.redhat.com ([209.132.183.28]:22706 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932468AbaFKPkr (ORCPT ); Wed, 11 Jun 2014 11:40:47 -0400 In-Reply-To: <538F3416.5090306@interlog.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: dgilbert@interlog.com Cc: SCSI development list , Christoph Hellwig , James Bottomley , openosd@gmail.com On Wed, 2014-06-04 at 10:58 -0400, Douglas Gilbert wrote: > When the SG_IO ioctl was copied into the block layer and > later into the bsg driver, subtle differences emerged. > > One difference is the way injected commands are queued through > the block layer (i.e. this is not SCSI device queueing nor SATA > NCQ). Summarizing: > - SG_IO in the block layer: blk_exec*(at_head=false) > - sg SG_IO: at_head=true > - bsg SG_IO: at_head=true > > Some time ago Boaz Harrosh introduced a sg v4 flag called > BSG_FLAG_Q_AT_TAIL to override the bsg driver default. > This patch does the equivalent for the sg driver. > > > ChangeLog: > Introduce SG_FLAG_Q_AT_TAIL flag to cause commands > to be injected into the block layer with > at_head=false. > > Changes since v1: > Make guard condition (only take sg v3 interface or later > invocations) clearer. > > Signed-off-by: Douglas Gilbert Looks good. Reviewed-by: Ewan D. Milne