Re: [V9fs-developer] 9p/overlayfs: read error when reading an empty file

[Dominique Martinet <dominique.martinet@cea.fr>]

Vincent Bernat wrote on Sat, Aug 15, 2015 at 03:18:56PM +0200:
> For this bug, I was able to bisect to this commit:
> 
> 4bacc9c9234c7c8eec44f5ed4e960d9f96fa0f01 is the first bad commit
> commit 4bacc9c9234c7c8eec44f5ed4e960d9f96fa0f01
> Author: David Howells <dhowells@redhat.com>
> Date:   Thu Jun 18 14:32:31 2015 +0100
> 
>     overlayfs: Make f_path always point to the overlay and f_inode to the underlay
> 
> In fact, any file reading of files present in the lower layer will lead
> to this. No need to try to switch root or anything complex.

Hmm, that is going to be annoying to fix, since we use
file->f_path.dentry to get a new fid to the same file (clone), and
current code pretty much depends on that...

I guess it used to work because file->f_op, file->f_inode and
file->f_path used to all be from the same layer, which isn't the case
anymore.


Does any overlayfs person reading this know if it's still possible to
get the right dentry at this point?
I'm sure the object exists somewhere in memory, but it could be annoying
to find.

Thanks,
-- 
Dominique