[PATCH] slab: page mapping cleanup

Clean up slab allocator page mapping a bit.  The memory allocated for a
slab is physically contiguous so it is okay to assume struct pages are too
so kill the long-standing comment.  Furthermore, rename set_slab_attr to
slab_map_pages and add a comment explaining why its needed.

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 16 insertions, 11 deletions

diff --git a/mm/slab.c b/mm/slab.c
index bf05ea900ce8..a94cf0fea8a2 100644
--- a/mm/slab.c
+++ b/mm/slab.c
@@ -2499,23 +2499,28 @@ static void slab_put_obj(struct kmem_cache *cachep, struct slab *slabp,
         slabp->inuse--;
 }
 
-static void set_slab_attr(struct kmem_cache *cachep, struct slab *slabp,
-                        void *objp)
+/*
+ * Map pages beginning at addr to the given cache and slab. This is required
+ * for the slab allocator to be able to lookup the cache and slab of a
+ * virtual address for kfree, ksize, kmem_ptr_validate, and slab debugging.
+ */
+static void slab_map_pages(struct kmem_cache *cache, struct slab *slab,
+                           void *addr)
 {
-        int i;
+        int nr_pages;
         struct page *page;
 
-        /* Nasty!!!!!! I hope this is OK. */
-        page = virt_to_page(objp);
+        page = virt_to_page(addr);
 
-        i = 1;
+        nr_pages = 1;
         if (likely(!PageCompound(page)))
-                i <<= cachep->gfporder;
+                nr_pages <<= cache->gfporder;
+
         do {
-                page_set_cache(page, cachep);
-                page_set_slab(page, slabp);
+                page_set_cache(page, cache);
+                page_set_slab(page, slab);
                 page++;
-        } while (--i);
+        } while (--nr_pages);
 }
 
 /*
@@ -2587,7 +2592,7 @@ static int cache_grow(struct kmem_cache *cachep, gfp_t flags, int nodeid)
                 goto opps1;
 
         slabp->nodeid = nodeid;
-        set_slab_attr(cachep, slabp, objp);
+        slab_map_pages(cachep, slabp, objp);
 
         cache_init_objs(cachep, slabp, ctor_flags);