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>

1 files changed, 9 insertions, 34 deletions

diff --git a/mm/slab.c b/mm/slab.c
index f9e676edeb0f..75c60821e382 100644
--- 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;
 }
 
 /*