slub: Fix calculation of cpu slabs

  /sys/kernel/slab/:t-0000048 # cat cpu_slabs
  231 N0=16 N1=215
  /sys/kernel/slab/:t-0000048 # cat slabs
  145 N0=36 N1=109

See, the number of slabs is smaller than that of cpu slabs.

The bug was introduced by commit 49e2258586b423684f03c278149ab46d8f8b6700
("slub: per cpu cache for partial pages").

We should use page->pages instead of page->pobjects when calculating
the number of cpu partial slabs. This also fixes the mapping of slabs
and nodes.

As there's no variable storing the number of total/active objects in
cpu partial slabs, and we don't have user interfaces requiring those
statistics, I just add WARN_ON for those cases.

Cc: <stable@vger.kernel.org> # 3.2+
Acked-by: Christoph Lameter <cl@linux.com>
Reviewed-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Pekka Enberg <penberg@kernel.org>

diff --git a/mm/slub.c b/mm/slub.c
index 545a170ebf9f66cf0e3716c9cd6f4cb7eef0eda6..89490d9d91e0579dbca3ba938fdf07586227c42f 100644 (file)
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4299,7 +4299,13 @@ static ssize_t show_slab_objects(struct kmem_cache *s,
 
                        page = ACCESS_ONCE(c->partial);
                        if (page) {
-                               x = page->pobjects;
+                               node = page_to_nid(page);
+                               if (flags & SO_TOTAL)
+                                       WARN_ON_ONCE(1);
+                               else if (flags & SO_OBJECTS)
+                                       WARN_ON_ONCE(1);
+                               else
+                                       x = page->pages;
                                total += x;
                                nodes[node] += x;
                        }