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authorPravin B Shelar2012-06-20 12:52:56 -0700
committerLinus Torvalds2012-06-20 14:39:35 -0700
commitabca7c4965845924f65d40e0aa1092bdd895e314 (patch)
tree18d908b58243b6f46cadfa4515d6370299c88d3f
parent485802a6c524e62b5924849dd727ddbb1497cc71 (diff)
mm: fix slab->page _count corruption when using slub
On arches that do not support this_cpu_cmpxchg_double() slab_lock is used to do atomic cmpxchg() on double word which contains page->_count. The page count can be changed from get_page() or put_page() without taking slab_lock. That corrupts page counter. Fix it by moving page->_count out of cmpxchg_double data. So that slub does no change it while updating slub meta-data in struct page. [akpm@linux-foundation.org: use standard comment layout, tweak comment text] Reported-by: Amey Bhide <abhide@nicira.com> Signed-off-by: Pravin B Shelar <pshelar@nicira.com> Acked-by: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@cs.helsinki.fi> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--include/linux/mm_types.h10
1 files changed, 10 insertions, 0 deletions
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index dad95bdd06d7..704a626d94a0 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -57,8 +57,18 @@ struct page {
};
union {
+#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \
+ defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
/* Used for cmpxchg_double in slub */
unsigned long counters;
+#else
+ /*
+ * Keep _count separate from slub cmpxchg_double data.
+ * As the rest of the double word is protected by
+ * slab_lock but _count is not.
+ */
+ unsigned counters;
+#endif
struct {