From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 726D2C3A59C for ; Fri, 16 Aug 2019 10:45:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4CDF3206C2 for ; Fri, 16 Aug 2019 10:45:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727233AbfHPKpt (ORCPT ); Fri, 16 Aug 2019 06:45:49 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:41996 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727039AbfHPKpt (ORCPT ); Fri, 16 Aug 2019 06:45:49 -0400 Received: from [5.158.153.52] (helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1hyZjs-0007t3-3s; Fri, 16 Aug 2019 12:45:44 +0200 Date: Fri, 16 Aug 2019 12:45:39 +0200 (CEST) From: Thomas Gleixner To: Arul Jeniston cc: viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, arul_mc@dell.com Subject: Re: [PATCH] FS: timerfd: Fix unexpected return value of timerfd_read function. In-Reply-To: Message-ID: References: <20190816083246.169312-1-arul.jeniston@gmail.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Arul, On Fri, 16 Aug 2019, Arul Jeniston wrote: > Subject: [PATCH] FS: timerfd: Fix unexpected return value of timerfd_read function. The prefix is not 'FS: timerfd:' 1) The usual prefix for fs/* is: 'fs:' but... 2) git log fs/timerfd.c gives you a pretty good hint for the proper prefix. Look at the commits which actually do functional changes to that file, not at those which do (sub)system wide cleanups/adjustments. Also 'timerfd_read function' can be written as 'timerfd_read()' which spares the redundant function and clearly marks it as function via the brackets. > 'hrtimer_forward_now()' returns zero due to bigger backward time drift. > This causes timerfd_read to return 0. As per man page, read on timerfd > is not expected to return 0. > This problem is well explained in https://lkml.org/lkml/2019/7/31/442 1) The explanation needs to be in the changelog itself. Links can point to discussions, bug-reports which have supplementary information. 2) Please do not use lkml.org links. Again: Please read and follow Documentation/process/submitting-patches.rst > . This patch fixes this problem. > Signed-off-by: Arul Jeniston Missing empty line before Signed-off-by. Please use git-log to see how changelogs are properly formatted. Also: 'This patch fixes this problem' is not helpful at all. Again see the document I already pointed you to. > --- > fs/timerfd.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/fs/timerfd.c b/fs/timerfd.c > index 6a6fc8aa1de7..f5094e070e9a 100644 > --- a/fs/timerfd.c > +++ b/fs/timerfd.c > @@ -284,8 +284,16 @@ static ssize_t timerfd_read(struct file *file, > char __user *buf, size_t count, > &ctx->t.alarm, ctx->tintv) - 1; > alarm_restart(&ctx->t.alarm); > } else { > - ticks += hrtimer_forward_now(&ctx->t.tmr, > - ctx->tintv) - 1; > + u64 nooftimeo = hrtimer_forward_now(&ctx->t.tmr, > + ctx->tintv); nooftimeo is pretty non-intuitive. The function documentation of hrtimer_forward_now() says: Returns the number of overruns. So the obvious variable name is overruns, right? > + /* > + * ticks shouldn't become zero at this point. > + * Ignore if hrtimer_forward_now returns 0 > + * due to larger backward time drift. Again. This explanation does not make any sense at all. Time does not go backwards, except if it is CLOCK_REALTIME which can be set backwards via clock_settime() or settimeofday(). > + */ > + if (likely(nooftimeo)) { > + ticks += nooftimeo - 1; > + } Again: Pointless brackets. If you disagree with my review comment, then tell me in a reply. If not, then fix it. If you decide to ignore my comments, then don't wonder if I ignore your patches. Thanks, tglx