From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755127Ab2IXHDk (ORCPT ); Mon, 24 Sep 2012 03:03:40 -0400 Received: from e23smtp07.au.ibm.com ([202.81.31.140]:56850 "EHLO e23smtp07.au.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753647Ab2IXHDj (ORCPT ); Mon, 24 Sep 2012 03:03:39 -0400 Message-ID: <1348470210.2475.47.camel@ThinkPad-T420> Subject: Re: [PATCH scsi] Add NULL checking of return value from scsi_cmd_to_driver() From: Li Zhong To: James Bottomley Cc: LKML , linux-scsi@vger.kernel.org, "Paul E. McKenney" Date: Mon, 24 Sep 2012 15:03:30 +0800 In-Reply-To: <1348465493.2467.3.camel@dabdike> References: <1348464626.2475.13.camel@ThinkPad-T420> <1348465493.2467.3.camel@dabdike> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.2.3-0ubuntu6 Content-Transfer-Encoding: 7bit Mime-Version: 1.0 x-cbid: 12092407-0260-0000-0000-000001E35A84 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 2012-09-24 at 09:44 +0400, James Bottomley wrote: > On Mon, 2012-09-24 at 13:30 +0800, Li Zhong wrote: > > Just noticed that after commit 919f797, it is possible that > > scsi_cmd_to_driver() returns NULL. This patch adds the NULL checking for drv > > returned from the above function. > > > > Maybe it is not possible at run time, but from the code itself, we'd better > > have this check? > > There's not much point having a check that never trips, unless it's an > assert, in which case a NULL deref does that. All it does is add > pointless instructions to the critical path. only REQ_TYPE_BLOCK_PC > commands can be submitted without a driver, so the check above would > seem to preclude that. Hi James, Thank you, it sounds reasonable to me. Let's drop it. Thanks, Zhong > James > >