[PATCH 3.8 021/124] slub: Fix calculation of cpu slabs

[Kamal Mostafa]

3.8.13.18 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Li Zefan <lizefan at huawei.com>

commit 8afb1474db4701d1ab80cd8251137a3260e6913e upstream.

  /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.

Acked-by: Christoph Lameter <cl at linux.com>
Reviewed-by: Wanpeng Li <liwanp at linux.vnet.ibm.com>
Signed-off-by: Li Zefan <lizefan at huawei.com>
Signed-off-by: Pekka Enberg <penberg at kernel.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 mm/slub.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/mm/slub.c b/mm/slub.c
index ba2ca53..90fcd67 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -4423,7 +4423,13 @@ 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;
 			}
-- 
1.8.3.2