Re: [PATCH v2] fs: try an opportunistic lookup for O_CREAT opens too

[Jeff Layton]

On Wed, 2024-08-14 at 03:40 +0100, Al Viro wrote:
> On Wed, Aug 14, 2024 at 03:18:17AM +0100, Al Viro wrote:
> 
> > That's not the only problem; your "is it negative" test is inherently
> > racy in RCU mode.  IOW, what is positive at the time you get here can
> > bloody well go negative immediately afterwards.  Hit that with
> > O_CREAT and you've got a bogus ENOENT...
> 
> Hmm...  OTOH, in that case you end up in step_into(), which will do the
> right thing...
> 
> 	How well does that series survive NFS client regression tests?
> That's where I'd expect potentially subtle shite, what with short-circuited
> ->d_revalidate() on the final pathwalk step in open()...

Christian took in my v3 patch which is a bit different from this one.
It seems to be doing fine in testing with NFS and otherwise.

I don't think we short-circuit the d_revalidate though, do we? That
version calls lookup_fast on the last component which should
d_revalidate the last dentry before returning it.
-- 
Jeff Layton <jlayton@xxxxxxxxxx>