[v3 PATCH 03/11] mm: vmscan: use shrinker_rwsem to protect shrinker_maps allocation
From: Yang Shi <hidden>
Date: 2021-01-05 23:00:13
Also in:
linux-fsdevel, lkml
Subsystem:
memory management, memory management - mglru (multi-gen lru), memory management - reclaim, the rest · Maintainers:
Andrew Morton, Johannes Weiner, Linus Torvalds
Since memcg_shrinker_map_size just can be changd under holding shrinker_rwsem exclusively, the read side can be protected by holding read lock, so it sounds superfluous to have a dedicated mutex. This should not exacerbate the contention to shrinker_rwsem since just one read side critical section is added. Signed-off-by: Yang Shi <redacted> --- mm/vmscan.c | 16 ++++++---------- 1 file changed, 6 insertions(+), 10 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9db7b4d6d0ae..ddb9f972f856 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c@@ -187,7 +187,6 @@ static DECLARE_RWSEM(shrinker_rwsem); #ifdef CONFIG_MEMCG static int memcg_shrinker_map_size; -static DEFINE_MUTEX(memcg_shrinker_map_mutex); static void memcg_free_shrinker_map_rcu(struct rcu_head *head) {
@@ -200,8 +199,6 @@ static int memcg_expand_one_shrinker_map(struct mem_cgroup *memcg, struct memcg_shrinker_map *new, *old; int nid; - lockdep_assert_held(&memcg_shrinker_map_mutex); - for_each_node(nid) { old = rcu_dereference_protected( mem_cgroup_nodeinfo(memcg, nid)->shrinker_map, true);
@@ -250,7 +247,7 @@ int memcg_alloc_shrinker_maps(struct mem_cgroup *memcg) if (mem_cgroup_is_root(memcg)) return 0; - mutex_lock(&memcg_shrinker_map_mutex); + down_read(&shrinker_rwsem); size = memcg_shrinker_map_size; for_each_node(nid) { map = kvzalloc(sizeof(*map) + size, GFP_KERNEL);
@@ -261,7 +258,7 @@ int memcg_alloc_shrinker_maps(struct mem_cgroup *memcg) } rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_map, map); } - mutex_unlock(&memcg_shrinker_map_mutex); + up_read(&shrinker_rwsem); return ret; }
@@ -276,9 +273,8 @@ static int memcg_expand_shrinker_maps(int new_id) if (size <= old_size) return 0; - mutex_lock(&memcg_shrinker_map_mutex); if (!root_mem_cgroup) - goto unlock; + goto out; memcg = mem_cgroup_iter(NULL, NULL, NULL); do {
@@ -287,13 +283,13 @@ static int memcg_expand_shrinker_maps(int new_id) ret = memcg_expand_one_shrinker_map(memcg, size, old_size); if (ret) { mem_cgroup_iter_break(NULL, memcg); - goto unlock; + goto out; } } while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL); -unlock: +out: if (!ret) memcg_shrinker_map_size = size; - mutex_unlock(&memcg_shrinker_map_mutex); + return ret; }
--
2.26.2