Re: [QUESTION] problem about origin xattr

[Vivek Goyal <vgoyal@redhat.com>]

On Thu, Feb 01, 2018 at 01:26:58AM +0200, Amir Goldstein wrote:

[..]
> >> >> > ORIGIN vs REDIRECT seems to be the only major sticking point w.r.t
> >> >> > these patches at this point of time. As long as you and miklos agree
> >> >> > on that semantics, things will be fine.
> >> >>
> >> >> I think there are many problems with using ORIGIN for data.
> >> >>
> >> >> I also think it should not be difficult to generalize the REDIRECT
> >> >> code from directory to regular file.  It should just be adding more
> >> >> conditions to create and handle redirects, no?  The actual code is
> >> >> already there, because we do it for directories.
> >> >
> >> > I guess so. We already are doing it for directories so we should be
> >> > able to extend it for regular files too. I don't know enough to be
> >> > able to say what affect this will have on performance.
> >> >
> >> >>
> >> >> So what's the issue with lowerstack[0]?  Can't we just use the same
> >> >> object for both purposes (i.e. the one found by going down the stack,
> >> >> just like for directories)?
> >> >
> >> > I think we should be able to. But then it seems to make ORIGIN redundant.
> >> > Because currently we are using ORIGIN to retrieve lowerstack[0]. And if
> >> > we change that, that means I will have to rip out ORIGIN logic altogether.
> >> > Its a relatively bigger change. So wanted to figure out is that what
> >> > we are looking for.
> >>
> >> Don't rip out ORIGIN logic, just disable it when we find METACOPY.
> >>
> >> So logic should be:
> >>
> >>  - check METACOPY xattr, if exists continue to lower layers just like
> >> non-opaque directory
> >>  - otherwise use ORIGIN xattr, just like we used to
> 
> Careful there, when following metacopy by path, you also need to apply
> ovl_verify_lower() logic for indexed files, i.e. all files with nfs_export
> and lower hardlinks with index=on. same as I did for merge dir lookup
> with nfs_export.

Hmm..., so for metacopy files, if ORIGIN fh does not match the lower found
in lowerstack[0] what do we do. Return -ESTALE?

Vivek