From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751426Ab0FWCiR (ORCPT ); Tue, 22 Jun 2010 22:38:17 -0400 Received: from out2.smtp.messagingengine.com ([66.111.4.26]:33521 "EHLO out2.smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751006Ab0FWCiQ (ORCPT ); Tue, 22 Jun 2010 22:38:16 -0400 X-Sasl-enc: DivD/VWS9qaWdidaBNViEYFfD3gSVIP5bbGDctzdSJAE 1277260684 Subject: Re: [autofs] [PATCH 04/38] autofs4: Save autofs trigger's vfsmount in super block info From: Ian Kent To: "J. R. Okajima" Cc: Miklos Szeredi , viro@zeniv.linux.org.uk, vaurora@redhat.com, autofs@linux.kernel.org, linux-kernel@vger.kernel.org, hch@infradead.org, linux-fsdevel@vger.kernel.org, jblunck@suse.de In-Reply-To: <9219.1277258833@jrobl> References: <1276627208-17242-1-git-send-email-vaurora@redhat.com> <1276627208-17242-5-git-send-email-vaurora@redhat.com> <1276661043.2339.35.camel@localhost> <1277091579.3827.9.camel@localhost> <1277181999.2829.2.camel@localhost> <26799.1277185756@jrobl> <1277256214.2848.17.camel@localhost> <9219.1277258833@jrobl> Content-Type: text/plain; charset="UTF-8" Date: Wed, 23 Jun 2010 10:37:58 +0800 Message-ID: <1277260678.2848.19.camel@localhost> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 (2.28.3-1.fc12) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2010-06-23 at 11:07 +0900, J. R. Okajima wrote: > Ian Kent: > > I may be missing something about this, but why is it safe to use > > iterate_mounts(), since it doesn't take the vfsmount_lock when > > traversing the list of mounts? > > The sample code was not correct. > We need to acquire vfsmount_lock or down_read(namespace_sem). > > Or it may be better to extract the body of iterate_mounts() and create a > new function __iterate_mounts() such like that. > > __iterate_mounts() > { > /* equiv to the current iterate_mounts */ > } > > iterate_mount() > { > down_read(namespace_sem); > or spin_lock(&vfsmount_lock); > > __iterate_mount(); > > spin_unlock(&vfsmount_lock); > or up_read(namespace_sem); > } Yep, thought so. That's a useful enough function to warrant that IMHO. I'll continue checking its usages before I do it though. Ian