From: Wei Yang Subject: mm/memcg: move generation assignment and comparison together For each round-trip, we assign generation on first invocation and compare it on subsequent invocations. Let's move them together to make it more self-explaining. Also this reduce a check on prev. [hannes@cmpxchg.org: better comment to explain reclaim model] Link: https://lkml.kernel.org/r/20220330234719.18340-4-richard.weiyang@gmail.com Signed-off-by: Wei Yang Acked-by: Johannes Weiner Reviewed-by: Roman Gushchin Signed-off-by: Andrew Morton --- mm/memcontrol.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) --- a/mm/memcontrol.c~mm-memcg-move-generation-assignment-and-comparison-together +++ a/mm/memcontrol.c @@ -1022,7 +1022,13 @@ struct mem_cgroup *mem_cgroup_iter(struc mz = root->nodeinfo[reclaim->pgdat->node_id]; iter = &mz->iter; - if (prev && reclaim->generation != iter->generation) + /* + * On start, join the current reclaim iteration cycle. + * Exit when a concurrent walker completes it. + */ + if (!prev) + reclaim->generation = iter->generation; + else if (reclaim->generation != iter->generation) goto out_unlock; while (1) { @@ -1084,8 +1090,6 @@ struct mem_cgroup *mem_cgroup_iter(struc if (!memcg) iter->generation++; - else if (!prev) - reclaim->generation = iter->generation; } out_unlock: _