slub: get_map() function to establish map of free objects in a slab

The bit map of free objects in a slab page is determined in various functions
if debugging is enabled.

Provide a common function for that purpose.

Signed-off-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

1 files changed, 22 insertions, 12 deletions

diff --git a/mm/slub.c b/mm/slub.c
index 5284fb77967..837f932671a 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -271,10 +271,6 @@ static inline void set_freepointer(struct kmem_cache *s, void *object, void *fp)
         for (__p = (__addr); __p < (__addr) + (__objects) * (__s)->size;\
                         __p += (__s)->size)
 
-/* Scan freelist */
-#define for_each_free_object(__p, __s, __free) \
-        for (__p = (__free); __p; __p = get_freepointer((__s), __p))
-
 /* Determine object index from a given position */
 static inline int slab_index(void *p, struct kmem_cache *s, void *addr)
 {
@@ -330,6 +326,21 @@ static inline int oo_objects(struct kmem_cache_order_objects x)
         return x.x & OO_MASK;
 }
 
+/*
+ * Determine a map of object in use on a page.
+ *
+ * Slab lock or node listlock must be held to guarantee that the page does
+ * not vanish from under us.
+ */
+static void get_map(struct kmem_cache *s, struct page *page, unsigned long *map)
+{
+        void *p;
+        void *addr = page_address(page);
+
+        for (p = page->freelist; p; p = get_freepointer(s, p))
+                set_bit(slab_index(p, s, addr), map);
+}
+
 #ifdef CONFIG_SLUB_DEBUG
 /*
  * Debug settings:
@@ -2673,9 +2684,8 @@ static void list_slab_objects(struct kmem_cache *s, struct page *page,
                 return;
         slab_err(s, page, "%s", text);
         slab_lock(page);
-        for_each_free_object(p, s, page->freelist)
-                set_bit(slab_index(p, s, addr), map);
 
+        get_map(s, page, map);
         for_each_object(p, s, addr, page->objects) {
 
                 if (!test_bit(slab_index(p, s, addr), map)) {
@@ -3610,10 +3620,11 @@ static int validate_slab(struct kmem_cache *s, struct page *page,
         /* Now we know that a valid freelist exists */
         bitmap_zero(map, page->objects);
 
-        for_each_free_object(p, s, page->freelist) {
-                set_bit(slab_index(p, s, addr), map);
-                if (!check_object(s, page, p, SLUB_RED_INACTIVE))
-                        return 0;
+        get_map(s, page, map);
+        for_each_object(p, s, addr, page->objects) {
+                if (test_bit(slab_index(p, s, addr), map))
+                        if (!check_object(s, page, p, SLUB_RED_INACTIVE))
+                                return 0;
         }
 
         for_each_object(p, s, addr, page->objects)
@@ -3821,8 +3832,7 @@ static void process_slab(struct loc_track *t, struct kmem_cache *s,
         void *p;
 
         bitmap_zero(map, page->objects);
-        for_each_free_object(p, s, page->freelist)
-                set_bit(slab_index(p, s, addr), map);
+        get_map(s, page, map);
 
         for_each_object(p, s, addr, page->objects)
                 if (!test_bit(slab_index(p, s, addr), map))