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

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Message-ID: <20110908215425.GW2203@ZenIV.linux.org.uk>
Date:	Thu, 8 Sep 2011 22:54:25 +0100
From:	Al Viro <viro@...IV.linux.org.uk>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
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 08, 2011 at 01:19:49PM -0700, Linus Torvalds wrote:

> >> 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.

Yes.  Again, IIRC that's what SunOS implementation had been doing all along;
I think the reason was that stat()+open()+fstat() getting different results
for stat and fstat would spook quite a few programs, but I could be easily
wrong on that.

I've no strong preferences for or against that change; to be honest, the set
of situations when automount triggers always left an impression of voodoo
balancing between usability (== not triggering it too much, lest we end up
with stuck boxen and unhappy admins) and not breaking expectations of userland
(e.g. stat/open/fstat issue)...
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