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SubjectRe: [v7 PATCH 06/12] mm: vmscan: add shrinker_info_protected() helper
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On 09.02.2021 20:46, Yang Shi wrote:
> 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>

Acked-by: Kirill Tkhai <ktkhai@virtuozzo.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;
>
>

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