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Date: Tue, 12 Jul 2011 22:49:56 -0700 (PDT)
From: Hugh Dickins <hughd@google.com>
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To: Hugh Dickins <hughd@google.com>
cc: Wu Fengguang <fengguang.wu@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>, Jan Kara <jack@suse.cz>,
        Mel Gorman <mel@csn.ul.ie>, Dave Chinner <david@fromorbit.com>,
        Christoph Hellwig <hch@infradead.org>,
        Christoph Lameter <cl@linux.com>, Pekka Enberg <penberg@kernel.org>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 12/15] writeback: remove writeback_control.more_io
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On Tue, 12 Jul 2011, Hugh Dickins wrote:
> On Mon, 11 Jul 2011, Wu Fengguang wrote:
> > 
> > It's relatively easy to confirm, by reusing the below trace event to
> > show the inode (together with its state) being requeued.
> > 
> > If this is the root cause, it may equally be fixed by
> > 
> > -			requeue_io(inode, wb);
> > +			redirty_tail(inode, wb);
> > 
> > which would be useful in case the bug is so deadly that it's no longer
> > possible to do tracing.
> 
> I checked again this morning that I could reproduce it on two machines,
> one went in a few minutes, the other within the hour.  Then I made that
> patch changing the requeue_io to redirty_tail, and left home with them
> running the test with the new kernel: we'll see at the end of the day
> how they fared.

I think that fixes it.  The x86_64 is still running with that, but the
ppc64 gave up fairly early, hitting freeze in __slab_free() instead.

I've now, I believe, reconstituted what ChristophL intended from the
mm_types.h struct page patch he posted (which applied neither to mmotm,
nor to Pekka's for-next, so far as I could tell: maybe cl did some
intermediate tidying of some of the random indentation).  So now
testing that with redirty_tail on ppc64: will report in 9 hours.

Hugh