From: Yang Shi shy828301@gmail.com
mainline inclusion from mainline-v5.13-rc1 commit 468ab8437a97a953895856c3709e48b3067da13c category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I48N0H CVE: NA
-------------------------------------------------
The shrinker_info is dereferenced in a couple of places via rcu_dereference_protected with different calling conventions, for example, using mem_cgroup_nodeinfo helper or dereferencing memcg->nodeinfo[nid]->shrinker_info. And the later patch will add more dereference places.
So extract the dereference into a helper to make the code more readable. No functional change.
[akpm@linux-foundation.org: retain rcu_dereference_protected() in free_shrinker_info(), per Hugh]
Link: https://lkml.kernel.org/r/20210311190845.9708-8-shy828301@gmail.com Signed-off-by: Yang Shi shy828301@gmail.com Acked-by: Roman Gushchin guro@fb.com Acked-by: Kirill Tkhai ktkhai@virtuozzo.com Acked-by: Vlastimil Babka vbabka@suse.cz Reviewed-by: Shakeel Butt shakeelb@google.com Cc: Dave Chinner david@fromorbit.com Cc: Johannes Weiner hannes@cmpxchg.org Cc: Michal Hocko mhocko@suse.com Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Chen Wandun chenwandun@huawei.com Reviewed-by: Tong Tiangen tongtiangen@huawei.com Signed-off-by: Zheng Zengkai zhengzengkai@huawei.com --- mm/vmscan.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c index 0e3eae08894c..47826e61f9d8 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -195,6 +195,13 @@ static inline int shrinker_map_size(int nr_items) return (DIV_ROUND_UP(nr_items, BITS_PER_LONG) * sizeof(unsigned long)); }
+static struct shrinker_info *shrinker_info_protected(struct mem_cgroup *memcg, + int nid) +{ + return rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info, + lockdep_is_held(&shrinker_rwsem)); +} + static int expand_one_shrinker_info(struct mem_cgroup *memcg, int size, int old_size) { @@ -204,7 +211,7 @@ static int expand_one_shrinker_info(struct mem_cgroup *memcg,
for_each_node(nid) { pn = memcg->nodeinfo[nid]; - old = rcu_dereference_protected(pn->shrinker_info, true); + old = shrinker_info_protected(memcg, nid); /* Not yet online memcg */ if (!old) return 0; @@ -677,8 +684,7 @@ static unsigned long shrink_slab_memcg(gfp_t gfp_mask, int nid, if (!down_read_trylock(&shrinker_rwsem)) return 0;
- info = rcu_dereference_protected(memcg->nodeinfo[nid]->shrinker_info, - true); + info = shrinker_info_protected(memcg, nid); if (unlikely(!info)) goto unlock;