linux-kernel - Re: [PATCH] autofs4 - detect invalid direct mount requests

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Date:	Fri, 20 Jun 2008 21:12:12 +0800
From:	Ian Kent <raven@...maw.net>
To:	Jeff Moyer <jmoyer@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Kernel Mailing List <linux-kernel@...r.kernel.org>,
	autofs mailing list <autofs@...ux.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH] autofs4 - detect invalid direct mount requests

On Fri, 2008-06-20 at 09:00 -0400, Jeff Moyer wrote:
> Ian Kent <raven@...maw.net> writes:
> 
> > autofs v5 dierct and offset mounts within an autofs filesystem are
> > triggered by existing autofs triger mounts so the mount point dentry
> > must be positive. If the mount point dentry is negative then the
> > trigger doesn't exist so we can return fail immediately.
> 
> What are the conditions that lead us here in that case?

v5 doesn't need to get those dir/otherdir messages that we can't avoid
for v4.

Basically, attempts to access a non-existent directory in multi-mount
tree leads to a negative dentry being sent to the wait queue, but v5
direct and offset mounts must always have an existing (non-negative
dentry) directory upon which to mount. This is only relevant for
multi-mounts that don't have an explicit multi-mount root so that the
lookups occur within the autofs file system.

Sorry, I still can't think of a way to avoid this for v4.

Ian

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