On 10/13/2017 02:00 PM, Michal Hocko wrote: > From: Michal Hocko <[email protected]> > > Michael has noticed that the memory offline tries to migrate kernel code > pages when doing > echo 0 > /sys/devices/system/memory/memory0/online > > The current implementation will fail the operation after several failed > page migration attempts but we shouldn't even attempt to migrate > that memory and fail right away because this memory is clearly not > migrateable. This will become a real problem when we drop the retry loop > counter resp. timeout. > > The real problem is in has_unmovable_pages in fact. We should fail if > there are any non migrateable pages in the area. In orther to guarantee > that remove the migrate type checks because MIGRATE_MOVABLE is not > guaranteed to contain only migrateable pages. It is merely a heuristic. > Similarly MIGRATE_CMA does guarantee that the page allocator doesn't > allocate any non-migrateable pages from the block but CMA allocations > themselves are unlikely to migrateable. Therefore remove both checks. > > Reported-by: Michael Ellerman <[email protected]> > Signed-off-by: Michal Hocko <[email protected]>
Acked-by: Vlastimil Babka <[email protected]> > --- > mm/page_alloc.c | 3 --- > 1 file changed, 3 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 3badcedf96a7..ad0294ab3e4f 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -7355,9 +7355,6 @@ bool has_unmovable_pages(struct zone *zone, struct page > *page, int count, > */ > if (zone_idx(zone) == ZONE_MOVABLE) > return false; > - mt = get_pageblock_migratetype(page); > - if (mt == MIGRATE_MOVABLE || is_migrate_cma(mt)) > - return false; > > pfn = page_to_pfn(page); > for (found = 0, iter = 0; iter < pageblock_nr_pages; iter++) { >
