On 3/7/23 07:56, Qi Zheng wrote:
> For now, reparent_shrinker_deferred() is the only holder
> of read lock of shrinker_rwsem. And it already holds the
> global cgroup_mutex, so it will not be called in parallel.
>
> Therefore, in order to convert shrinker_rwsem to shrinker_mutex
> later, here we change to hold the write lock of shrinker_rwsem
> to reparent.
>
> Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
> ---
> mm/vmscan.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 9a5a3da5c8b5..7aaf6f94ac1b 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -451,7 +451,7 @@ void reparent_shrinker_deferred(struct mem_cgroup *memcg)
> parent = root_mem_cgroup;
>
> /* Prevent from concurrent shrinker_info expand */
> - down_read(&shrinker_rwsem);
> + down_write(&shrinker_rwsem);
> for_each_node(nid) {
> child_info = shrinker_info_protected(memcg, nid);
> parent_info = shrinker_info_protected(parent, nid);
> @@ -460,7 +460,7 @@ void reparent_shrinker_deferred(struct mem_cgroup *memcg)
> atomic_long_add(nr, &parent_info->nr_deferred[i]);
> }
> }
> - up_read(&shrinker_rwsem);
> + up_write(&shrinker_rwsem);
> }
>
> static bool cgroup_reclaim(struct scan_control *sc)
