linux-kernel - Re: bio linked list corruption.

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Message-ID: <20161020230341.jsxpia2sy53xn5l5@codemonkey.org.uk>
Date:   Thu, 20 Oct 2016 19:03:41 -0400
From:   Dave Jones <davej@...emonkey.org.uk>
To:     Andy Lutomirski <luto@...capital.net>
Cc:     Andy Lutomirski <luto@...nel.org>,
        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 Thu, Oct 20, 2016 at 04:01:12PM -0700, Andy Lutomirski wrote:
 > On Thu, Oct 20, 2016 at 3:50 PM, Dave Jones <davej@...emonkey.org.uk> wrote:
 > > 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.
 > 
 > The idea is that the stack will be free and unmapped immediately upon
 > process exit if configured like this so that bogus stack accesses (by
 > the CPU, not DMA) would OOPS immediately.

oh, misparsed. ok, I can definitely get behind that idea then.
I'll do that next.

	Dave