Messages in this thread | | | Date | Tue, 16 Aug 2016 18:20:40 +0800 | From | Xishi Qiu <> | Subject | Re: [PATCH 1/3] mm: fix set pageblock migratetype in deferred struct page init |
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On 2016/8/16 18:12, Vlastimil Babka wrote:
> On 08/16/2016 11:23 AM, Michal Hocko wrote: >> On Tue 16-08-16 16:56:54, Xishi Qiu wrote: >>> On 2016/8/16 16:41, Michal Hocko wrote: >>> >>>> On Thu 04-08-16 19:25:03, Xishi Qiu wrote: >>>>> MAX_ORDER_NR_PAGES is usually 4M, and a pageblock is usually 2M, so we only >>>>> set one pageblock's migratetype in deferred_free_range() if pfn is aligned >>>>> to MAX_ORDER_NR_PAGES. >>>> >>>> Do I read the changelog correctly and the bug causes leaking unmovable >>>> allocations into movable zones? >>> >>> Hi Michal, >>> >>> This bug will cause uninitialized migratetype, you can see from >>> "cat /proc/pagetypeinfo", almost half blocks are Unmovable. >> >> Please add that information to the changelog. Leaking unmovable >> allocations to the movable zones defeats the whole purpose of the >> movable zone so I guess we really want to mark this for stable. > > Note that it's not as severe. Pageblock migratetype is just heuristic against fragmentation. It should not allow unmovable allocations from movable zones (although I can't find what really does govern it). >
Yes, leaking unmovable migratetype to movable zone is fine for mem-offline, we will check every page in offline_pages(). But as I pointed that we missed to free the last block in deferred_init_memmap(), this will lead to mem-offline fail.
Thanks, Xishi Qiu
>> AFAICS it should also note: >> Fixes: ac5d2539b238 ("mm: meminit: reduce number of times pageblocks are set during struct page init") >> and stable 4.2+ > > > > > . >
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