From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753941AbeDTAPW (ORCPT ); Thu, 19 Apr 2018 20:15:22 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:55988 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753703AbeDTAPV (ORCPT ); Thu, 19 Apr 2018 20:15:21 -0400 Date: Thu, 19 Apr 2018 17:15:20 -0700 From: Andrew Morton To: Alexey Dobriyan Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH 4/5] proc: simpler iterations for /proc/*/cmdline Message-Id: <20180419171520.444c0e9736b6a020fb6b3b7f@linux-foundation.org> In-Reply-To: <20180221193009.GA28678@avx2> References: <20180221192339.GA28548@avx2> <20180221192605.GB28548@avx2> <20180221192751.GC28548@avx2> <20180221193009.GA28678@avx2> X-Mailer: Sylpheed 3.6.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 21 Feb 2018 22:30:09 +0300 Alexey Dobriyan wrote: > "rv" variable is used both as a counter of bytes transferred and > an error value holder but it can be reduced solely to error values > if original start of userspace buffer is stashed and used at the very > end. > > ... > > --- a/fs/proc/base.c > +++ b/fs/proc/base.c > > ... > > @@ -371,12 +365,16 @@ static ssize_t proc_pid_cmdline_read(struct file *file, char __user *buf, > } > } > > +end: > + free_page((unsigned long)page); > + mmput(mm); > + *pos += buf - buf0; > + return buf - buf0; > + > out_free_page: > free_page((unsigned long)page); > out_mmput: > mmput(mm); > - if (rv > 0) > - *pos += rv; > return rv; > } (scratches head). Why not do this? --- a/fs/proc/base.c~proc-simpler-iterations-for-proc-cmdline-fix +++ a/fs/proc/base.c @@ -363,11 +363,8 @@ static ssize_t proc_pid_cmdline_read(str } end: - free_page((unsigned long)page); - mmput(mm); *pos += buf - buf0; - return buf - buf0; - + rv = buf - buf0; out_free_page: free_page((unsigned long)page); out_mmput: (and maybe rv should be ssize_t)