From mboxrd@z Thu Jan 1 00:00:00 1970 From: Theodore Ts'o Subject: Re: [PATCH] ext4: take i_mutex in ext4_symlink to eliminate a warning from ext4_truncate Date: Wed, 27 Mar 2013 11:12:48 -0400 Message-ID: <20130327151248.GE14900@thunk.org> References: <1364390347-4360-1-git-send-email-wenqing.lz@taobao.com> <20130327134110.GI5861@thunk.org> <20130327140250.GA4316@gmail.com> <20130327135155.GK5861@thunk.org> <20130327150735.GA4395@gmail.com> <20130327151922.GA4487@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: linux-ext4@vger.kernel.org, Zheng Liu Return-path: Received: from li9-11.members.linode.com ([67.18.176.11]:56404 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751950Ab3C0PMt (ORCPT ); Wed, 27 Mar 2013 11:12:49 -0400 Content-Disposition: inline In-Reply-To: <20130327151922.GA4487@gmail.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Wed, Mar 27, 2013 at 11:19:22PM +0800, Zheng Liu wrote: > > > Otherwise, couldn't we end up with problems where a failed write calls > > > ext4_truncate() without i_data_sem(), and that races with something > > > else --- say, a punch or truncate call to that same inode? > > Let me think about it. I need to take a close look at it. Note that I'm not so concerned when we are creating symlink --- you are quite right in pointing out in that case the inode isn't in the namespace yet, so that prevents races --- but also what might happen in an ENOSPC write(2) failure racing against a punch/truncate call. But again, this is why I added the warning --- it was to find these edge cases that we might not have considered. :-) - Ted