From 17459f120ef9089ff8dc1910fb7cbf9eecdece2a Mon Sep 17 00:00:00 2001 From: Yosry Ahmed Date: Sat, 3 Aug 2024 05:33:06 +0000 Subject: [PATCH] mm: zswap: make the lock critical section obvious in shrink_worker() Move the comments and spin_{lock/unlock}() calls around in shrink_worker() to make it obvious the lock is protecting the loop updating zswap_next_shrink. Link: https://lkml.kernel.org/r/20240803053306.2685541-1-yosryahmed@google.com Signed-off-by: Yosry Ahmed Acked-by: Johannes Weiner Reviewed-by: Chengming Zhou Reviewed-by: Nhat Pham Cc: Takero Funaki Signed-off-by: Andrew Morton --- mm/zswap.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) diff --git a/mm/zswap.c b/mm/zswap.c index d46caa42ed4f..71b75ff1f3fb 100644 --- a/mm/zswap.c +++ b/mm/zswap.c @@ -1348,24 +1348,22 @@ static void shrink_worker(struct work_struct *w) * until the next run of shrink_worker(). */ do { - spin_lock(&zswap_shrink_lock); - /* * Start shrinking from the next memcg after zswap_next_shrink. * When the offline cleaner has already advanced the cursor, * advancing the cursor here overlooks one memcg, but this * should be negligibly rare. + * + * If we get an online memcg, keep the extra reference in case + * the original one obtained by mem_cgroup_iter() is dropped by + * zswap_memcg_offline_cleanup() while we are shrinking the + * memcg. */ + spin_lock(&zswap_shrink_lock); do { memcg = mem_cgroup_iter(NULL, zswap_next_shrink, NULL); zswap_next_shrink = memcg; } while (memcg && !mem_cgroup_tryget_online(memcg)); - /* - * Note that if we got an online memcg, we will keep the extra - * reference in case the original reference obtained by mem_cgroup_iter - * is dropped by the zswap memcg offlining callback, ensuring that the - * memcg is not killed when we are reclaiming. - */ spin_unlock(&zswap_shrink_lock); if (!memcg) { -- 2.50.1