[Mesa-dev] [PATCH] tests/cache_test: allow crossing mount points

[Juan A. Suarez Romero]

On Tue, 2017-03-28 at 17:50 +0200, Nicolai Hähnle wrote:
>  The crossing happens because I'm running it inside a docker container,
> > which uses internally an overlayfs. This means that some of those
> > subdirectories can be in one mountpoint and others in other mountpoint.
> >   This seems to be how nftw() call handles this overlayfs.
> 
> I still don't quite get it. My understanding is that overlayfs allows 
> you to merge two directory trees, e.g. for setups where you have a 
> read-only base, and a writable "overlay" which gets used during some 
> operation and then thrown away.
> 
> If ntfw fails to remove some files, then which ones are in the overlay 
> and which ones in the "underlay"?
> 
> Or... oh wait. Here's what the kernel docs say:
> 
>     This approach is 'hybrid' because the objects that appear in the
>     filesystem do not all appear to belong to that filesystem.  In many
>     cases an object accessed in the union will be indistinguishable
>     from accessing the corresponding object from the original filesystem.
>     This is most obvious from the 'st_dev' field returned by stat(2).
> 
> So it seems the issue is that the directories themselves are considered 
> to belong to the overlayfs itself, while the created files of the cache 
> belong to the "overlay" (temporary) filesystem? That's annoying, but 
> there's nothing we can do about it. The patch is:
> 


Yeah, seems so. It's a nasty bug, but as nftw() is only used in the
test, I think it is safe to remove the flag.

Thanks for reviewing it!

> Reviewed-by: Nicolai Hähnle <nicolai.haehnle at amd.com>