Re: [PATCH v2] ovl: introduce new "index=nouuid" option for inodes index feature

[Pavel Tikhomirov]

On 9/23/20 7:36 PM, Amir Goldstein wrote:
> > > @@ -414,7 +415,7 @@ static int ovl_check_origin(struct ovl_fs *ofs, struct dentry *upperdentry,
> > >    * Return 0 on match, -ESTALE on mismatch, < 0 on error.
> > >    */
> > >   static int ovl_verify_fh(struct dentry *dentry, const char *name,
> > > -                        const struct ovl_fh *fh)
> > > +                        const struct ovl_fh *fh, bool nouuid)
> > >   {
> > >          struct ovl_fh *ofh = ovl_get_fh(dentry, name);
> > >          int err = 0;
> > > @@ -425,8 +426,14 @@ static int ovl_verify_fh(struct dentry *dentry, const char *name,
> > >          if (IS_ERR(ofh))
> > >                  return PTR_ERR(ofh);
> > >
> > > -       if (fh->fb.len != ofh->fb.len || memcmp(&fh->fb, &ofh->fb, fh->fb.len))
> > > +       if (fh->fb.len != ofh->fb.len) {
> > >                  err = -ESTALE;
> > > +       } else {
> > > +               if (nouuid && !uuid_equal(&fh->fb.uuid, &ofh->fb.uuid))
> > > +                       ofh->fb.uuid = fh->fb.uuid;
> > > +               if (memcmp(&fh->fb, &ofh->fb, fh->fb.len))
> > > +                       err = -ESTALE;
> > > +       }
>
> On second thought I am wondering if we should do that differently.
> If users want to work with index=nouuid, they need to work with it from day 1.
> index=nouuid should export null uuid in NFS handles and write null uuid
> in trusted.overlay.origin xattr.
>
> So in ovl_encode_real_fh() you set null uuid and
> instead of relaxing uuid_equal() in ovl_decode_real_fh()
> you change it to uuid_is_null().
>
> Do you have a problem with that for Virtuozzo use case?

Actually we've enabled index=on by default in kernel config in Virtuozzo 
only in the new update which is not yet released. So probably we can 
switch to index=nouuid with null uuid in fh.

> Thanks,
> Amir.

--
Best regards, Tikhomirov Pavel
Software Developer, Virtuozzo.