From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752070Ab2GUQe5 (ORCPT ); Sat, 21 Jul 2012 12:34:57 -0400 Received: from palinux.external.hp.com ([192.25.206.14]:41135 "EHLO mail.parisc-linux.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751480Ab2GUQez (ORCPT ); Sat, 21 Jul 2012 12:34:55 -0400 Date: Sat, 21 Jul 2012 10:34:53 -0600 From: Matthew Wilcox To: zwu.kernel@gmail.com Cc: viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Zhi Yong Wu Subject: Re: [PATCH] vfs: simply the code logic Message-ID: <20120721163453.GB31693@parisc-linux.org> References: <1342885099-22662-1-git-send-email-zwu.kernel@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1342885099-22662-1-git-send-email-zwu.kernel@gmail.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jul 21, 2012 at 11:38:19PM +0800, zwu.kernel@gmail.com wrote: > if (offset >= 0 && offset <= size) { > - if (offset != file->f_pos) { > - file->f_pos = offset; > - } > - retval = offset; > + retval = file->f_pos = offset; > } But now you're writing to f_pos unconditionally. That may cause cacheline bouncing. NAK. Plus, you're now using a less-well-known feature of C, so while it's fewer lines of code, it's not necessarily a simplification. -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step."