slab: use __GFP_COMP flag for allocating slab pages

If we use 'struct page' of first page as 'struct slab', there is no
advantage not to use __GFP_COMP. So use __GFP_COMP flag for all the cases.

Acked-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Christoph Lameter <cl@linux.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 f9e676e..75c6082 100644 (file)
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -1718,15 +1718,6 @@ static struct page *kmem_getpages(struct kmem_cache *cachep, gfp_t flags,
 {
        struct page *page;
        int nr_pages;
-       int i;
-
-#ifndef CONFIG_MMU
-       /*
-        * Nommu uses slab's for process anonymous memory allocations, and thus
-        * requires __GFP_COMP to properly refcount higher order allocations
-        */
-       flags |= __GFP_COMP;
-#endif
 
        flags |= cachep->allocflags;
        if (cachep->flags & SLAB_RECLAIM_ACCOUNT)
@@ -1750,12 +1741,9 @@ static struct page *kmem_getpages(struct kmem_cache *cachep, gfp_t flags,
        else
                add_zone_page_state(page_zone(page),
                        NR_SLAB_UNRECLAIMABLE, nr_pages);
-       for (i = 0; i < nr_pages; i++) {
-               __SetPageSlab(page + i);
-
-               if (page->pfmemalloc)
-                       SetPageSlabPfmemalloc(page);
-       }
+       __SetPageSlab(page);
+       if (page->pfmemalloc)
+               SetPageSlabPfmemalloc(page);
        memcg_bind_pages(cachep, cachep->gfporder);
 
        if (kmemcheck_enabled && !(cachep->flags & SLAB_NOTRACK)) {
@@ -1775,8 +1763,7 @@ static struct page *kmem_getpages(struct kmem_cache *cachep, gfp_t flags,
  */
 static void kmem_freepages(struct kmem_cache *cachep, struct page *page)
 {
-       unsigned long i = (1 << cachep->gfporder);
-       const unsigned long nr_freed = i;
+       const unsigned long nr_freed = (1 << cachep->gfporder);
 
        kmemcheck_free_shadow(page, cachep->gfporder);
 
@@ -1787,12 +1774,9 @@ static void kmem_freepages(struct kmem_cache *cachep, struct page *page)
                sub_zone_page_state(page_zone(page),
                                NR_SLAB_UNRECLAIMABLE, nr_freed);
 
+       BUG_ON(!PageSlab(page));
        __ClearPageSlabPfmemalloc(page);
-       while (i--) {
-               BUG_ON(!PageSlab(page));
-               __ClearPageSlab(page);
-               page++;
-       }
+       __ClearPageSlab(page);
 
        memcg_release_pages(cachep, cachep->gfporder);
        if (current->reclaim_state)
@@ -2362,7 +2346,7 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags)
        cachep->colour = left_over / cachep->colour_off;
        cachep->slab_size = slab_size;
        cachep->flags = flags;
-       cachep->allocflags = 0;
+       cachep->allocflags = __GFP_COMP;
        if (CONFIG_ZONE_DMA_FLAG && (flags & SLAB_CACHE_DMA))
                cachep->allocflags |= GFP_DMA;
        cachep->size = size;
@@ -2729,17 +2713,8 @@ static void slab_put_obj(struct kmem_cache *cachep, struct slab *slabp,
 static void slab_map_pages(struct kmem_cache *cache, struct slab *slab,
                           struct page *page)
 {
-       int nr_pages;
-
-       nr_pages = 1;
-       if (likely(!PageCompound(page)))
-               nr_pages <<= cache->gfporder;
-
-       do {
-               page->slab_cache = cache;
-               page->slab_page = slab;
-               page++;
-       } while (--nr_pages);
+       page->slab_cache = cache;
+       page->slab_page = slab;
 }
 
 /*