From d7b236e10cedd95373a79fd53b7e9c105bea4f08 Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Wed, 15 Nov 2017 17:33:22 -0800 Subject: [PATCH] mm: drop migrate type checks from has_unmovable_pages 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. [akpm@linux-foundation.org: remove unused local `mt'] Link: http://lkml.kernel.org/r/20171013120013.698-1-mhocko@kernel.org Signed-off-by: Michal Hocko Reported-by: Michael Ellerman Tested-by: Michael Ellerman Acked-by: Vlastimil Babka Tested-by: Tony Lindgren Tested-by: Ran Wang Cc: Igor Mammedov Cc: KAMEZAWA Hiroyuki Cc: Reza Arbab Cc: Vitaly Kuznetsov Cc: Xishi Qiu Cc: Yasuaki Ishimatsu Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 4 ---- 1 file changed, 4 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 77e4d3c..e6d4234 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7356,7 +7356,6 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, bool skip_hwpoisoned_pages) { unsigned long pfn, iter, found; - int mt; /* * For avoiding noise data, lru_add_drain_all() should be called @@ -7364,9 +7363,6 @@ 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++) { -- 2.7.4