linux-kernel - Re: [PATCH] vfs: automount should ignore LOOKUP

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Date:	Thu, 8 Sep 2011 10:42:28 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	Ian Kent <raven@...maw.net>, David Howells <dhowells@...hat.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Leonardo Chiquitto <leonardo.lists@...il.com>,
	Al Viro <viro@...iv.linux.org.uk>, autofs@...ux.kernel.org
Subject: Re: [PATCH] vfs: automount should ignore LOOKUP_FOLLOW

On Thu, Sep 8, 2011 at 6:38 AM, Miklos Szeredi <miklos@...redi.hu> wrote:
>
> Yes, 2.6.38 and later kernels do trigger on stat(2) but not on lstat(2).
>
> My question is this:  does this behavior improve anything compared to
> kernels before 2.6.38?  Because I don't see that it does, in fact it's
> just causing regressions.
>
> You say it's a step in the right direction but I don't see why.  Either
> we want stat *and* lstat to both be correct and trigger the automount or
> we are satisfied with the incorrect but well established practice of not
> triggering on (l)stat.
>
> The middle ground makes no sense IMO, there's nothing gained by the
> differentiated behavior based on LOOKUP_FOLLOW.
>
> Can you explain why it's better if stat() tiggers automounts and gives a
> correct result but lstat() doesn't?

I have to say that this is a very cogent question.

The one thing I've not seen in the thread yet is a description of the
failure. What does the regression look like? Just "very slow 'ls' with
some versions of 'ls'" or what?

I'm inclined to apply the patch as a regression fix, but I'll let this
thread try to convince me for another day..

                         Linus
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