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

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Message-ID: <CA+55aFzfXOi2xk1JVnTTzQPzoNH+iQkhtpT6cVEz+D7si8MAfw@mail.gmail.com>
Date:	Thu, 8 Sep 2011 13:19:49 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	Miklos Szeredi <miklos@...redi.hu>, 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>,
	autofs@...ux.kernel.org
Subject: Re: [PATCH] vfs: automount should ignore LOOKUP_FOLLOW

On Thu, Sep 8, 2011 at 12:50 PM, Al Viro <viro@...iv.linux.org.uk> wrote:
> On Thu, Sep 08, 2011 at 10:42:28AM -0700, Linus Torvalds wrote:
>
>> > 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..
>
> IIRC, that matches traditional SunOS behaviour and it actually does make
> sense; you want wildcard expansion and ls -l to be doable even when there's
> a stuck NFS server.  IOW, non-triggering lstat(2) is a matter of usability...

non-triggering lstat() isn't the issue, afaik. We never trigger on lstat.

nontriggering *stat()* is the issue. We didn't *use* to trigger on
stat() either. Now in 2.6.38+ we do.

                   Linus
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