[PATCH] mm, slab: clean up slab->obj_exts always

[Zhenhua Huang]

When memory allocation profiling is disabled at runtime or due to an
error, shutdown_mem_profiling() is called: slab->obj_exts which
previously allocated remains.
It won't be cleared by unaccount_slab() because of
mem_alloc_profiling_enabled() not true. It's incorrect, slab->obj_exts
should always be cleaned up in unaccount_slab() to avoid following error:

[...]BUG: Bad page state in process...
..
[...]page dumped because: page still charged to cgroup

Fixes: 21c690a349baa ("mm: introduce slabobj_ext to support slab object extensions")
Signed-off-by: Zhenhua Huang <quic_zhenhuah@xxxxxxxxxxx>
---
 mm/slub.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/mm/slub.c b/mm/slub.c
index dac149df1be1..b42ce3a88806 100644
--- a/mm/slub.c
+++ b/mm/slub.c
@@ -2023,7 +2023,7 @@ int alloc_slab_obj_exts(struct slab *slab, struct kmem_cache *s,
 	return 0;
 }
 
-/* Should be called only if mem_alloc_profiling_enabled() */
+/* Should be called if slab_obj_exts(slab) */
 static noinline void free_slab_obj_exts(struct slab *slab)
 {
 	struct slabobj_ext *obj_exts;
@@ -2592,7 +2592,11 @@ static __always_inline void account_slab(struct slab *slab, int order,
 static __always_inline void unaccount_slab(struct slab *slab, int order,
 					   struct kmem_cache *s)
 {
-	if (memcg_kmem_online() || need_slab_obj_ext())
+	/*
+	 * The slab object extensions should now be freed regardless of
+	 * whether mem_alloc_profiling_enabled() or not now.
+	 */
+	if (memcg_kmem_online() || slab_obj_exts(slab))
 		free_slab_obj_exts(slab);
 
 	mod_node_page_state(slab_pgdat(slab), cache_vmstat_idx(s),
-- 
2.25.1