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

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Message-ID: <CA5F6A4B62957246A9595641974606435968466A@IRSMSX106.ger.corp.intel.com>
Date:   Fri, 28 Apr 2017 09:00:32 +0000
From:   "Lofstedt, Marta" <marta.lofstedt@...el.com>
To:     Chris Wilson <chris@...is-wilson.co.uk>,
        Kees Cook <keescook@...omium.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Anton Vorontsov" <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        "Luck, Tony" <tony.luck@...el.com>,
        Namhyung Kim <namhyung@...nel.org>
Subject: RE: [PATCH] pstore: Solve lockdep warning by moving inode locks



> -----Original Message-----
> From: Chris Wilson [mailto:chris@...is-wilson.co.uk]
> Sent: Friday, April 28, 2017 10:53 AM
> To: Kees Cook <keescook@...omium.org>
> Cc: linux-kernel@...r.kernel.org; Anton Vorontsov <anton@...msg.org>;
> Colin Cross <ccross@...roid.com>; Luck, Tony <tony.luck@...el.com>;
> Lofstedt, Marta <marta.lofstedt@...el.com>; Namhyung Kim
> <namhyung@...nel.org>
> 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