slab: correct pfmemalloc check

We checked pfmemalloc by slab unit, not page unit. You can see this
in is_slab_pfmemalloc(). So other pages don't need to be set/cleared
pfmemalloc.

And, therefore we should check pfmemalloc in page flag of first page,
but current implementation don't do that. virt_to_head_page(obj) just
return 'struct page' of that object, not one of first page, since the SLAB
don't use __GFP_COMP when CONFIG_MMU. To get 'struct page' of first page,
we first get a slab and try to get it via virt_to_head_page(slab->s_mem).

Acked-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Pekka Enberg <penberg@iki.fi>

diff --git a/mm/slab.c b/mm/slab.c
index 2580db0..0b4ddaf 100644 (file)
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -930,7 +930,8 @@ 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_head_page(objp);
+               struct slab *slabp = virt_to_slab(objp);
+               struct page *page = virt_to_head_page(slabp->s_mem);
                if (PageSlabPfmemalloc(page))
                        set_obj_pfmemalloc(&objp);
        }
@@ -1776,7 +1777,7 @@ static void *kmem_getpages(struct kmem_cache *cachep, gfp_t flags, int nodeid)
                __SetPageSlab(page + i);
 
                if (page->pfmemalloc)
-                       SetPageSlabPfmemalloc(page + i);
+                       SetPageSlabPfmemalloc(page);
        }
        memcg_bind_pages(cachep, cachep->gfporder);
 
@@ -1809,9 +1810,10 @@ static void kmem_freepages(struct kmem_cache *cachep, void *addr)
        else
                sub_zone_page_state(page_zone(page),
                                NR_SLAB_UNRECLAIMABLE, nr_freed);
+
+       __ClearPageSlabPfmemalloc(page);
        while (i--) {
                BUG_ON(!PageSlab(page));
-               __ClearPageSlabPfmemalloc(page);
                __ClearPageSlab(page);
                page++;
        }