From: Mel Gorman Date: Fri, 7 Sep 2012 00:17:44 +0000 (+1000) Subject: slab: do ClearSlabPfmemalloc() for all pages of slab X-Git-Tag: next-20120907~1^2~241 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=fdad9a64954270e1e2915122e7fd916038f131da;p=karo-tx-linux.git slab: do ClearSlabPfmemalloc() for all pages of slab Right now, we call ClearSlabPfmemalloc() for first page of slab when we clear SlabPfmemalloc flag. This is fine for most swap-over-network use cases as it is expected that order-0 pages are in use. Unfortunately it is possible that that __ac_put_obj() checks SlabPfmemalloc on a tail page and while this is harmless, it is sloppy. This patch ensures that the head page is always used. This problem was originally identified by Joonsoo Kim. [js1304@gmail.com: Original implementation and problem identification] Signed-off-by: Mel Gorman Cc: David Miller Cc: Chuck Lever Cc: Joonsoo Kim Cc: David Rientjes Cc: Pekka Enberg Signed-off-by: Andrew Morton --- diff --git a/mm/slab.c b/mm/slab.c index c86b06d942d8..a32609d3f72e 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -993,7 +993,7 @@ static void *__ac_get_obj(struct kmem_cache *cachep, struct array_cache *ac, l3 = cachep->nodelists[numa_mem_id()]; if (!list_empty(&l3->slabs_free) && force_refill) { struct slab *slabp = virt_to_slab(objp); - ClearPageSlabPfmemalloc(virt_to_page(slabp->s_mem)); + ClearPageSlabPfmemalloc(virt_to_head_page(slabp->s_mem)); clear_obj_pfmemalloc(&objp); recheck_pfmemalloc_active(cachep, ac); return objp; @@ -1025,7 +1025,7 @@ static void *__ac_put_obj(struct kmem_cache *cachep, struct array_cache *ac, { if (unlikely(pfmemalloc_active)) { /* Some pfmemalloc slabs exist, check if this is one */ - struct page *page = virt_to_page(objp); + struct page *page = virt_to_head_page(objp); if (PageSlabPfmemalloc(page)) set_obj_pfmemalloc(&objp); }