From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751681AbbBLXby (ORCPT ); Thu, 12 Feb 2015 18:31:54 -0500 Received: from smtp.infotech.no ([82.134.31.41]:33081 "EHLO smtp.infotech.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751536AbbBLXbx (ORCPT ); Thu, 12 Feb 2015 18:31:53 -0500 Message-ID: <54DD37D9.9050202@interlog.com> Date: Thu, 12 Feb 2015 18:31:37 -0500 From: Douglas Gilbert Reply-To: dgilbert@interlog.com User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 MIME-Version: 1.0 To: Tony Battersby , linux-scsi@vger.kernel.org, "James E.J. Bottomley" CC: linux-kernel@vger.kernel.org Subject: Re: [PATCH] [SCSI] sg: fix read() error reporting References: <54DB8406.4020804@cybernetics.com> <54DB953C.1090104@interlog.com> <54DB9BD7.7090605@cybernetics.com> In-Reply-To: <54DB9BD7.7090605@cybernetics.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 15-02-11 01:13 PM, Tony Battersby wrote: > On 02/11/2015 12:45 PM, Douglas Gilbert wrote: >> On 15-02-11 11:32 AM, Tony Battersby wrote: >>> Fix SCSI generic read() incorrectly returning success after detecting an >>> error. >>> >>> Cc: >>> Signed-off-by: Tony Battersby >>> --- >>> >>> For inclusion in kernel 3.20. >>> >>> --- linux-3.19.0/drivers/scsi/sg.c.orig 2015-02-08 21:54:22.000000000 -0500 >>> +++ linux-3.19.0/drivers/scsi/sg.c 2015-02-10 09:26:09.000000000 -0500 >>> @@ -546,7 +546,7 @@ static ssize_t >>> sg_new_read(Sg_fd * sfp, char __user *buf, size_t count, Sg_request * srp) >>> { >>> sg_io_hdr_t *hp = &srp->header; >>> - int err = 0; >>> + int err = 0, err2; >>> int len; >>> >>> if (count < SZ_SG_IO_HDR) { >>> @@ -575,8 +575,8 @@ sg_new_read(Sg_fd * sfp, char __user *bu >>> goto err_out; >>> } >>> err_out: >>> - err = sg_finish_rem_req(srp); >>> - return (0 == err) ? count : err; >>> + err2 = sg_finish_rem_req(srp); >>> + return err ? : err2 ? : count; >> Tony, >> Your point is well made. >> >> I just don't like that last line, using a gcc extension that >> hasn't even made it into C11 (or C++11). Wouldn't: >> return err ? err : (err2 ? err2 : count); >> >> be a bit better? I think the following snippet makes the intent >> clear but would it generate any more code: >> if (err || err2) An improvement on the above line would be: if (unlikely(err || err2)) >> return err ? err : err2; >> else >> return count; >> Another approach is to return the good path prior to the err_out label. This would require two calls to sg_finish_rem_req(). However Tony's clean-up is sufficient. > I checked before submitting, and the foo ? : bar construct is already > used at least 455 times in the kernel, so it is nothing new. > > find linux-3.19 -type f -name "*.[ch]" | xargs grep '\? :' | wc -l > 455 > > But you are probably right; I think that with such small variable names > your version is more readable due to the nesting. Updated patch below. > > --- > > Fix SCSI generic read() incorrectly returning success after detecting an > error. > > Cc: > Signed-off-by: Tony Battersby Acked-by: Douglas Gilbert > --- > > --- linux-3.19.0/drivers/scsi/sg.c.orig 2015-02-08 21:54:22.000000000 -0500 > +++ linux-3.19.0/drivers/scsi/sg.c 2015-02-11 13:02:56.000000000 -0500 > @@ -546,7 +546,7 @@ static ssize_t > sg_new_read(Sg_fd * sfp, char __user *buf, size_t count, Sg_request * srp) > { > sg_io_hdr_t *hp = &srp->header; > - int err = 0; > + int err = 0, err2; > int len; > > if (count < SZ_SG_IO_HDR) { > @@ -575,8 +575,8 @@ sg_new_read(Sg_fd * sfp, char __user *bu > goto err_out; > } > err_out: > - err = sg_finish_rem_req(srp); > - return (0 == err) ? count : err; > + err2 = sg_finish_rem_req(srp); > + return err ? err : (err2 ? err2 : count); > } > > static ssize_t > > --