SLUB: Define functions for cpu slab handling instead of using PageActive

Use inline functions to access the per cpu bit.  Intoduce the notion of
"freezing" a slab to make things more understandable.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/slub.c b/mm/slub.c
index 022c1b4d74d4dfbf23350eeedaeacdffe95d33bb..ce96d485a88f9883a01f506f41154c58e4561cef 100644 (file)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -78,10 +78,18 @@
  *
  * Overloading of page flags that are otherwise used for LRU management.
  *
- * PageActive          The slab is used as a cpu cache. Allocations
- *                     may be performed from the slab. The slab is not
- *                     on any slab list and cannot be moved onto one.
- *                     The cpu slab may be equipped with an additioanl
+ * PageActive          The slab is frozen and exempt from list processing.
+ *                     This means that the slab is dedicated to a purpose
+ *                     such as satisfying allocations for a specific
+ *                     processor. Objects may be freed in the slab while
+ *                     it is frozen but slab_free will then skip the usual
+ *                     list operations. It is up to the processor holding
+ *                     the slab to integrate the slab into the slab lists
+ *                     when the slab is no longer needed.
+ *
+ *                     One use of this flag is to mark slabs that are
+ *                     used for allocations. Then such a slab becomes a cpu
+ *                     slab. The cpu slab may be equipped with an additional
  *                     lockless_freelist that allows lockless access to
  *                     free objects in addition to the regular freelist
  *                     that requires the slab lock.
@@ -91,6 +99,21 @@
  *                     the fast path and disables lockless freelists.
  */
 
+static inline int SlabFrozen(struct page *page)
+{
+       return PageActive(page);
+}
+
+static inline void SetSlabFrozen(struct page *page)
+{
+       SetPageActive(page);
+}
+
+static inline void ClearSlabFrozen(struct page *page)
+{
+       ClearPageActive(page);
+}
+
 static inline int SlabDebug(struct page *page)
 {
 #ifdef CONFIG_SLUB_DEBUG
@@ -1135,11 +1158,12 @@ static void remove_partial(struct kmem_cache *s,
  *
  * Must hold list_lock.
  */
-static int lock_and_del_slab(struct kmem_cache_node *n, struct page *page)
+static inline int lock_and_freeze_slab(struct kmem_cache_node *n, struct page *page)
 {
        if (slab_trylock(page)) {
                list_del(&page->lru);
                n->nr_partial--;
+               SetSlabFrozen(page);
                return 1;
        }
        return 0;
@@ -1163,7 +1187,7 @@ static struct page *get_partial_node(struct kmem_cache_node *n)
 
        spin_lock(&n->list_lock);
        list_for_each_entry(page, &n->partial, lru)
-               if (lock_and_del_slab(n, page))
+               if (lock_and_freeze_slab(n, page))
                        goto out;
        page = NULL;
 out:
@@ -1242,10 +1266,11 @@ static struct page *get_partial(struct kmem_cache *s, gfp_t flags, int node)
  *
  * On exit the slab lock will have been dropped.
  */
-static void putback_slab(struct kmem_cache *s, struct page *page)
+static void unfreeze_slab(struct kmem_cache *s, struct page *page)
 {
        struct kmem_cache_node *n = get_node(s, page_to_nid(page));
 
+       ClearSlabFrozen(page);
        if (page->inuse) {
 
                if (page->freelist)
@@ -1296,9 +1321,7 @@ static void deactivate_slab(struct kmem_cache *s, struct page *page, int cpu)
                page->inuse--;
        }
        s->cpu_slab[cpu] = NULL;
-       ClearPageActive(page);
-
-       putback_slab(s, page);
+       unfreeze_slab(s, page);
 }
 
 static void flush_slab(struct kmem_cache *s, struct page *page, int cpu)
@@ -1389,9 +1412,7 @@ another_slab:
 new_slab:
        page = get_partial(s, gfpflags, node);
        if (page) {
-have_slab:
                s->cpu_slab[cpu] = page;
-               SetPageActive(page);
                goto load_freelist;
        }
 
@@ -1421,7 +1442,9 @@ have_slab:
                        flush_slab(s, s->cpu_slab[cpu], cpu);
                }
                slab_lock(page);
-               goto have_slab;
+               SetSlabFrozen(page);
+               s->cpu_slab[cpu] = page;
+               goto load_freelist;
        }
        return NULL;
 debug:
@@ -1508,11 +1531,7 @@ checks_ok:
        page->freelist = object;
        page->inuse--;
 
-       if (unlikely(PageActive(page)))
-               /*
-                * Cpu slabs are never on partial lists and are
-                * never freed.
-                */
+       if (unlikely(SlabFrozen(page)))
                goto out_unlock;
 
        if (unlikely(!page->inuse))
@@ -1544,7 +1563,7 @@ slab_empty:
 debug:
        if (!free_object_checks(s, page, x))
                goto out_unlock;
-       if (!PageActive(page) && !page->freelist)
+       if (!SlabFrozen(page) && !page->freelist)
                remove_full(s, page);
        if (s->flags & SLAB_STORE_USER)
                set_track(s, x, TRACK_FREE, addr);