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

[Vincent Bernat <bernat@luffy.cx>]

 ❦ 17 août 2015 16:11 +0200, Dominique Martinet <dominique.martinet@cea.fr> :

>> 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.

Hi Dominique!

Did you get any feedback on this? The problem is unfortunately still
present in 4.3-rc3.
-- 
Let the machine do the dirty work.
            - The Elements of Programming Style (Kernighan & Plauger)