linux-kernel - [PATCH v2 3/7] mm, slab: move kfence_shutdown_cache() outside slab

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Message-Id: <20240807-b4-slab-kfree_rcu-destroy-v2-3-ea79102f428c@suse.cz>
Date: Wed, 07 Aug 2024 12:31:16 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: "Paul E. McKenney" <paulmck@...nel.org>, 
 Joel Fernandes <joel@...lfernandes.org>, 
 Josh Triplett <josh@...htriplett.org>, Boqun Feng <boqun.feng@...il.com>, 
 Christoph Lameter <cl@...ux.com>, David Rientjes <rientjes@...gle.com>
Cc: Steven Rostedt <rostedt@...dmis.org>, 
 Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, 
 Lai Jiangshan <jiangshanlai@...il.com>, Zqiang <qiang.zhang1211@...il.com>, 
 Julia Lawall <Julia.Lawall@...ia.fr>, Jakub Kicinski <kuba@...nel.org>, 
 "Jason A. Donenfeld" <Jason@...c4.com>, 
 "Uladzislau Rezki (Sony)" <urezki@...il.com>, 
 Andrew Morton <akpm@...ux-foundation.org>, 
 Roman Gushchin <roman.gushchin@...ux.dev>, 
 Hyeonggon Yoo <42.hyeyoo@...il.com>, linux-mm@...ck.org, 
 linux-kernel@...r.kernel.org, rcu@...r.kernel.org, 
 Alexander Potapenko <glider@...gle.com>, Marco Elver <elver@...gle.com>, 
 Dmitry Vyukov <dvyukov@...gle.com>, kasan-dev@...glegroups.com, 
 Jann Horn <jannh@...gle.com>, Mateusz Guzik <mjguzik@...il.com>, 
 Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH v2 3/7] mm, slab: move kfence_shutdown_cache() outside
 slab_mutex

kfence_shutdown_cache() is called under slab_mutex when the cache is
destroyed synchronously, and outside slab_mutex during the delayed
destruction of SLAB_TYPESAFE_BY_RCU caches.

It seems it should always be safe to call it outside of slab_mutex so we
can just move the call to kmem_cache_release(), which is called outside.

Signed-off-by: Vlastimil Babka <vbabka@...e.cz>
---
 mm/slab_common.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/mm/slab_common.c b/mm/slab_common.c
index db61df3b4282..a079b8540334 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -492,6 +492,7 @@ EXPORT_SYMBOL(kmem_buckets_create);
  */
 static void kmem_cache_release(struct kmem_cache *s)
 {
+	kfence_shutdown_cache(s);
 	if (__is_defined(SLAB_SUPPORTS_SYSFS) && slab_state >= FULL)
 		sysfs_slab_release(s);
 	else
@@ -521,10 +522,8 @@ static void slab_caches_to_rcu_destroy_workfn(struct work_struct *work)

 	rcu_barrier();

-	list_for_each_entry_safe(s, s2, &to_destroy, list) {
-		kfence_shutdown_cache(s);
+	list_for_each_entry_safe(s, s2, &to_destroy, list)
 		kmem_cache_release(s);
-	}
 }

 void slab_kmem_cache_release(struct kmem_cache *s)
@@ -563,9 +562,6 @@ void kmem_cache_destroy(struct kmem_cache *s)

 	list_del(&s->list);

-	if (!err && !rcu_set)
-		kfence_shutdown_cache(s);
-
 	mutex_unlock(&slab_mutex);
 	cpus_read_unlock();

-- 
2.46.0