diff options
| author | Kinsey Ho <kinseyho@google.com> | 2024-09-05 00:30:52 +0000 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2024-09-09 16:39:16 -0700 |
| commit | 3d150e31a1f62f0b39bdd8b968f563f8f3915d7a (patch) | |
| tree | ea316a3a723c1b8edf17eb250c805620a56a6142 /mm/memcontrol.c | |
| parent | 4a2698b0133b5c477515ccbedff169fec722d0e7 (diff) | |
mm: increment gen # before restarting traversal
The generation number in struct mem_cgroup_reclaim_iter should be
incremented on every round-trip. Currently, it is possible for a
concurrent reclaimer to jump in at the end of the hierarchy, causing a
traversal restart (resetting the iteration position) without incrementing
the generation number.
By resetting the position without incrementing the generation, it's
possible for another ongoing mem_cgroup_iter() thread to walk the tree
twice.
Move the traversal restart such that the generation number is
incremented before the restart.
Link: https://lkml.kernel.org/r/20240905003058.1859929-4-kinseyho@google.com
Signed-off-by: Kinsey Ho <kinseyho@google.com>
Reviewed-by: T.J. Mercier <tjmercier@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Tejun Heo <tj@kernel.org>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Zefan Li <lizefan.x@bytedance.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/memcontrol.c')
| -rw-r--r-- | mm/memcontrol.c | 22 |
1 files changed, 12 insertions, 10 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 8f6cf651cc79..38e3251ed482 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -997,7 +997,7 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root, root = root_mem_cgroup; rcu_read_lock(); - +restart: if (reclaim) { struct mem_cgroup_per_node *mz; @@ -1024,14 +1024,6 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root, for (;;) { css = css_next_descendant_pre(css, &root->css); if (!css) { - /* - * Reclaimers share the hierarchy walk, and a - * new one might jump in right at the end of - * the hierarchy - make sure they see at least - * one group and restart from the beginning. - */ - if (!prev) - continue; break; } @@ -1054,8 +1046,18 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root, */ (void)cmpxchg(&iter->position, pos, memcg); - if (!memcg) + if (!memcg) { iter->generation++; + + /* + * Reclaimers share the hierarchy walk, and a + * new one might jump in right at the end of + * the hierarchy - make sure they see at least + * one group and restart from the beginning. + */ + if (!prev) + goto restart; + } } out_unlock: |