Re: [PATCH] vfs: automount should ignore LOOKUP_FOLLOW

[Al Viro <viro@ZenIV.linux.org.uk>]

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...