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Subject[v7 PATCH 06/12] mm: vmscan: add shrinker_info_protected() helper
Date
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.

Signed-off-by: Yang Shi <shy828301@gmail.com>
---
mm/vmscan.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9436f9246d32..273efbf4d53c 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -190,6 +190,13 @@ static int shrinker_nr_max;
#define NR_MAX_TO_SHR_MAP_SIZE(nr_max) \
(DIV_ROUND_UP(nr_max, 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 void free_shrinker_info_rcu(struct rcu_head *head)
{
kvfree(container_of(head, struct shrinker_info, rcu));
@@ -202,8 +209,7 @@ static int expand_one_shrinker_info(struct mem_cgroup *memcg,
int nid;

for_each_node(nid) {
- old = rcu_dereference_protected(
- mem_cgroup_nodeinfo(memcg, nid)->shrinker_info, true);
+ old = shrinker_info_protected(memcg, nid);
/* Not yet online memcg */
if (!old)
return 0;
@@ -234,7 +240,7 @@ void free_shrinker_info(struct mem_cgroup *memcg)

for_each_node(nid) {
pn = mem_cgroup_nodeinfo(memcg, nid);
- info = rcu_dereference_protected(pn->shrinker_info, true);
+ info = shrinker_info_protected(memcg, nid);
kvfree(info);
rcu_assign_pointer(pn->shrinker_info, NULL);
}
@@ -674,8 +680,7 @@ 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;

--
2.26.2
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