linux-kernel - Re: bio linked list corruption.

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Message-ID: <20161020225028.czodw54tjbiwwv3o@codemonkey.org.uk>
Date:   Thu, 20 Oct 2016 18:50:28 -0400
From:   Dave Jones <davej@...emonkey.org.uk>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Chris Mason <clm@...com>, Jens Axboe <axboe@...com>,
        Al Viro <viro@...iv.linux.org.uk>, Josef Bacik <jbacik@...com>,
        David Sterba <dsterba@...e.com>,
        linux-btrfs <linux-btrfs@...r.kernel.org>,
        Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: bio linked list corruption.

On Tue, Oct 18, 2016 at 06:05:57PM -0700, Andy Lutomirski wrote:

 > One possible debugging approach would be to change:
 > 
 > #define NR_CACHED_STACKS 2
 > 
 > to
 > 
 > #define NR_CACHED_STACKS 0
 > 
 > in kernel/fork.c and to set CONFIG_DEBUG_PAGEALLOC=y.  The latter will 
 > force an immediate TLB flush after vfree.

I can give that idea some runtime, but it sounds like this a case where
we're trying to prove a negative, and that'll just run and run ? In which case I
might do this when I'm travelling on Sunday.

 > Also, CONFIG_DEBUG_VIRTUAL=y can be quite helpful for debugging stack 
 > issues.  I'm tempted to do something equivalent to hardwiring that 
 > option on for a while if CONFIG_VMAP_STACK=y.

This one I had on. Nothing interesting jumped out.

	Dave