Re: [PATCH 12/15] writeback: remove writeback_control.more_io

[Hugh Dickins]

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
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