From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754041Ab3L0BJ7 (ORCPT ); Thu, 26 Dec 2013 20:09:59 -0500 Received: from out3-smtp.messagingengine.com ([66.111.4.27]:38058 "EHLO out3-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753920Ab3L0BJ4 (ORCPT ); Thu, 26 Dec 2013 20:09:56 -0500 X-Sasl-enc: z1eRybsuHk3ybnqThCoJ3N5UJ20jhz/bWo0WzMCPerIk 1388106594 Message-ID: <1388106592.2446.25.camel@perseus.fritz.box> Subject: Re: [PATCH] autofs - fix fix symlinks arent checked for expiry From: Ian Kent To: Andrew Morton Cc: linux-fsdevel , autofs mailing list , Kernel Mailing List Date: Fri, 27 Dec 2013 09:09:52 +0800 In-Reply-To: <20131226134253.5f4b2f02a00e11b8de49770e@linux-foundation.org> References: <20131224094459.20051.4889.stgit@perseus.fritz.box> <20131226134253.5f4b2f02a00e11b8de49770e@linux-foundation.org> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.6.4 (3.6.4-3.fc18) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2013-12-26 at 13:42 -0800, Andrew Morton wrote: > On Tue, 24 Dec 2013 17:44:59 +0800 Ian Kent wrote: > > > When following a symlink the last_used counter is unconditionally > > updated causing the expire checks from user space to prevent > > expiry. Opps! > > A bit unclear. You're saying that userspace's act of checking expiry > status will itself disrupt the expiry process? If the user space expire code uses stat(2) instead of lstat(2), yes. It's quite possible this will be the case since it made no difference when not using symlinks in the autofs directory tree. > > Also, it's rather unclear what the userspace impact is here, and how > severe it is. Please always carefully describe the user-visible impact > so that others can decide which kernel version(s) need the patch. The impact of this is that symlinks within an an autofs directory tree don't cause a callback to the daemon so they can be expired (removed in this case). autofs4_oz_mode() is the mechanism that's used to identify the user space process that's managing the automount tree. It's used in a number of places to prevent the process managing the tree from doing things like triggering mounts itself or updating the last_used counter. It's a bit of a puzzle why it worked when I originally tested it. But later when I looked at it to work out why some symlinks weren't expiring it was obvious. Do you want me to re-submit this with an updated description? > > > --- a/fs/autofs4/symlink.c > > +++ b/fs/autofs4/symlink.c > > @@ -14,8 +14,9 @@ > > > > static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd) > > { > > + struct autofs_sb_info *sbi = autofs4_sbi(dentry->d_sb); > > struct autofs_info *ino = autofs4_dentry_ino(dentry); > > - if (ino) > > + if (ino && !autofs4_oz_mode(sbi)) > > ino->last_used = jiffies; > > nd_set_link(nd, dentry->d_inode->i_private); > > return NULL; > > What kernel is this against? 3.13-rc5 is quite different: That's a good question. Which tree should I be basing patches on? As it turns out it is against 3.13-rc5 which was the version the linus tree was at (when I pulled it) prior to mailing the patch. > > static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd) > { > nd_set_link(nd, dentry->d_inode->i_private); > return NULL; > } > Ian