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>

1 files changed, 7 insertions, 1 deletions

diff --git a/mm/slub.c b/mm/slub.c
index 545a170ebf9f..89490d9d91e0 100644
--- 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;
                         }