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Re: [PATCH 3/6] mm/page_owner: copy last_migrate_reason in copy_page_owner()

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On Tue, May 10, 2016 at 05:13:12PM +0200, Vlastimil Babka wrote:
> On 05/03/2016 07:23 AM, js1304@gmail.com wrote:
> >From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> >
> >Currently, copy_page_owner() doesn't copy all the owner information.
> >It skips last_migrate_reason because copy_page_owner() is used for
> >migration and it will be properly set soon. But, following patch
> >will use copy_page_owner() and this skip will cause the problem that
> >allocated page has uninitialied last_migrate_reason. To prevent it,
> >this patch also copy last_migrate_reason in copy_page_owner().
> 
> Hmm it's a corner case, but if the "new" page was dumped e.g. due to
> a bug during the migration, is the copied migrate reason from the
> "old" page actually meaningful? I'd say it might be misleading and
> it's simpler to just make sure it's initialized to -1.

Hmm... if it is the case, other fields are also misleading. I think
that we can tolerate this corner case and keeping function semantic as
function name suggests is better practice.

Thanks.

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[PATCH 0/6] mm/page_owner: use tackdepot to store stacktrace js1304@gmail.com - 2016-05-03 07:30 +0200
  [PATCH 5/6] tools/vm/page_owner: increase temporary buffer size js1304@gmail.com - 2016-05-03 07:30 +0200
  [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace js1304@gmail.com - 2016-05-03 07:30 +0200
    Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Michal Hocko <mhocko@kernel.org> - 2016-05-03 11:00 +0200
      Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-05-04 04:20 +0200
        Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-05-04 04:40 +0200
          Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Michal Hocko <mhocko@kernel.org> - 2016-05-04 11:30 +0200
            Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Joonsoo Kim <js1304@gmail.com> - 2016-05-04 17:40 +0200
        Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Michal Hocko <mhocko@kernel.org> - 2016-05-04 11:30 +0200
          Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Joonsoo Kim <js1304@gmail.com> - 2016-05-04 17:40 +0200
            Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Joonsoo Kim <js1304@gmail.com> - 2016-05-04 17:50 +0200
              Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Michal Hocko <mhocko@kernel.org> - 2016-05-04 21:50 +0200
            Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Michal Hocko <mhocko@kernel.org> - 2016-05-04 21:50 +0200
              Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Joonsoo Kim <js1304@gmail.com> - 2016-05-10 09:10 +0200
                Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Michal Hocko <mhocko@kernel.org> - 2016-05-10 11:00 +0200
    Re: [PATCH 6/6] mm/page_owner: use stackdepot to store stacktrace Vlastimil Babka <vbabka@suse.cz> - 2016-05-12 14:00 +0200
  [PATCH 3/6] mm/page_owner: copy last_migrate_reason in copy_page_owner() js1304@gmail.com - 2016-05-03 07:30 +0200
    Re: [PATCH 3/6] mm/page_owner: copy last_migrate_reason in  copy_page_owner() Vlastimil Babka <vbabka@suse.cz> - 2016-05-10 17:20 +0200
      Re: [PATCH 3/6] mm/page_owner: copy last_migrate_reason in  copy_page_owner() Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-05-12 05:00 +0200
        Re: [PATCH 3/6] mm/page_owner: copy last_migrate_reason in  copy_page_owner() Vlastimil Babka <vbabka@suse.cz> - 2016-05-12 08:50 +0200
  [PATCH 4/6] mm/page_owner: introduce split_page_owner and replace manual handling js1304@gmail.com - 2016-05-03 07:30 +0200
    Re: [PATCH 4/6] mm/page_owner: introduce split_page_owner and replace  manual handling Vlastimil Babka <vbabka@suse.cz> - 2016-05-10 17:20 +0200
  [PATCH 2/6] mm/page_owner: initialize page owner without holding the zone lock js1304@gmail.com - 2016-05-03 07:30 +0200
    Re: [PATCH 2/6] mm/page_owner: initialize page owner without holding  the zone lock Vlastimil Babka <vbabka@suse.cz> - 2016-05-10 17:10 +0200
  [PATCH 1/6] mm/compaction: split freepages without holding the zone lock js1304@gmail.com - 2016-05-03 07:30 +0200
    Re: [PATCH 1/6] mm/compaction: split freepages without holding the  zone lock Vlastimil Babka <vbabka@suse.cz> - 2016-05-10 17:00 +0200
      Re: [PATCH 1/6] mm/compaction: split freepages without holding the  zone lock Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-05-12 05:00 +0200

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