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Subject[PATCH 3.8 021/124] slub: Fix calculation of cpu slabs
Date
3.8.13.18 -stable review patch.  If anyone has any objections, please let me know.

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

From: Li Zefan <lizefan@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@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>
Signed-off-by: Kamal Mostafa <kamal@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


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