RE: [PATCH] pstore: Solve lockdep warning by moving inode locks

[Lofstedt, Marta]

> -----Original Message-----
> From: Chris Wilson [mailto:chris@xxxxxxxxxxxxxxxxxx]
> Sent: Friday, April 28, 2017 10:53 AM
> To: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx; Anton Vorontsov <anton@xxxxxxxxxx>;
> Colin Cross <ccross@xxxxxxxxxxx>; Luck, Tony <tony.luck@xxxxxxxxx>;
> Lofstedt, Marta <marta.lofstedt@xxxxxxxxx>; Namhyung Kim
> <namhyung@xxxxxxxxxx>
> Subject: Re: [PATCH] pstore: Solve lockdep warning by moving inode locks
> 
> On Thu, Apr 27, 2017 at 04:20:37PM -0700, Kees Cook wrote:
> > Lockdep complains about a possible deadlock between mount and unlink
> > (which is technically impossible), but fixing this improves possible
> > future multiple-backend support, and keeps locking in the right order.
> 
> I have merged your for-next/pstore branch (which included this patch, so I
> hope I chose correctly ;) into our CI. That should exercise it on the machines
> that we originally found the lockdep splat.
> 
> Thanks,
> -Chris
> 

Chris, I tested this on drm-tip after you merged for-next/pstore. 
EFI_VARS_PSTORE is enabled. 
I deliberately cause kernel panic and reboot, but unfortunately that kernel doesn't reboot properly. On display I see a bunch of:
"Cleaning orphaned inode ...", but then kernel boot  is stuck. 
I run this on a BDW NUCi5, which I have been using successfully with pstore-efi for weeks. 
Fortunately I had some other pstore enabled kernels, so if I clean out /sys/fs/pstore/* with one of them I can boot above kernel again.

BR,
Marta

> --
> Chris Wilson, Intel Open Source Technology Centre