Re: [PATCH 0/3] Fixes for vfs-scale and vfs-automount

[Ian Kent <raven@themaw.net>]

On Thu, 2011-02-24 at 05:47 +0000, Al Viro wrote:
> On Thu, Feb 24, 2011 at 03:58:37AM +0000, Al Viro wrote:
> > On Thu, Feb 24, 2011 at 11:28:57AM +0800, Ian Kent wrote:
> > 
> > > Ha, I haven't even turned on my Ultrsparc 2 in months, it's only got an
> > > old version of Solaris on it now anyway, ;)
> > 
> > U60, with lenny (and mainline kernel) on it.  Probably ought to upgrade
> > to squeeze one of those days...  It works, all right, but it's only 2-way,
> > so reproducing would probably be harder.  Plus the fun of building the tests
> > themselves on somewhat different userland...
> > 
> > Anyway, I wonder why you care about __d_lookup_rcu() and ->d_inode stability;
> > d_mountpoint() _is_ stable at that point (we hold vfsmount_lock) and you
> > don't seem to look at ->d_inode at all in RCU case.  Note that ->d_automount()
> > is never called in RCU case at all; nor is ->lookup() and friends, so you
> > really only have ->d_manage() to cope with, what with autofs4 having no
> > ->d_revalidate() anymore.
> 
> FWIW, can we _ever_ get to __do_follow_link() with link->mnt != nd->path.mnt?
> It's probably not what's happening here, or we would've stepped on another
> BUG_ON(), but still it might be worth checking...
> 
> AFAICS, if we ever get there that way, we are fscked, so the check before
> mntget() ought to replaced with BUG_ON(link->mnt != nd->path.mnt)...

Yeah, don't think autofs can go their with no ->follow_link() defined.
I've largely ignored that code to date.