linux-kernel - [PATCH v4 7/8] mm: vmscan: remove shrinker_rwsem from synchronize

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Message-Id: <20230307065605.58209-8-zhengqi.arch@bytedance.com>
Date:   Tue,  7 Mar 2023 14:56:04 +0800
From:   Qi Zheng <zhengqi.arch@...edance.com>
To:     akpm@...ux-foundation.org, tkhai@...ru, hannes@...xchg.org,
        shakeelb@...gle.com, mhocko@...nel.org, roman.gushchin@...ux.dev,
        muchun.song@...ux.dev, david@...hat.com, shy828301@...il.com,
        rppt@...nel.org
Cc:     sultan@...neltoast.com, dave@...olabs.net,
        penguin-kernel@...ove.SAKURA.ne.jp, paulmck@...nel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Qi Zheng <zhengqi.arch@...edance.com>
Subject: [PATCH v4 7/8] mm: vmscan: remove shrinker_rwsem from synchronize_shrinkers()

Now there are no readers of shrinker_rwsem, so
synchronize_shrinkers() does not need to hold the
writer of shrinker_rwsem to wait for all running
shinkers to complete, synchronize_srcu() is enough.

Signed-off-by: Qi Zheng <zhengqi.arch@...edance.com>
---
 mm/vmscan.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 7aaf6f94ac1b..ac7ab4aa344f 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -796,15 +796,11 @@ EXPORT_SYMBOL(unregister_shrinker);
 /**
  * synchronize_shrinkers - Wait for all running shrinkers to complete.
  *
- * This is equivalent to calling unregister_shrink() and register_shrinker(),
- * but atomically and with less overhead. This is useful to guarantee that all
- * shrinker invocations have seen an update, before freeing memory, similar to
- * rcu.
+ * This is useful to guarantee that all shrinker invocations have seen an
+ * update, before freeing memory.
  */
 void synchronize_shrinkers(void)
 {
-	down_write(&shrinker_rwsem);
-	up_write(&shrinker_rwsem);
 	atomic_inc(&shrinker_srcu_generation);
 	synchronize_srcu(&shrinker_srcu);
 }
-- 
2.20.1