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Subject: [PATCH 18/23] uts: Free uts namespace one RCU grace period after
 final counter put
From:   Kirill Tkhai <ktkhai@virtuozzo.com>
To:     viro@zeniv.linux.org.uk, adobriyan@gmail.com, davem@davemloft.net,
        ebiederm@xmission.com, akpm@linux-foundation.org,
        christian.brauner@ubuntu.com, areber@redhat.com, serge@hallyn.com,
        linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        ktkhai@virtuozzo.com
Date:   Thu, 30 Jul 2020 15:00:57 +0300
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This is needed to link uts_ns into ns_idr in next patch.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
---
 include/linux/utsname.h |    1 +
 kernel/utsname.c        |   10 +++++++++-
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/include/linux/utsname.h b/include/linux/utsname.h
index 2b1737c9b244..b783d0fe6ca4 100644
--- a/include/linux/utsname.h
+++ b/include/linux/utsname.h
@@ -25,6 +25,7 @@ struct uts_namespace {
 	struct user_namespace *user_ns;
 	struct ucounts *ucounts;
 	struct ns_common ns;
+	struct rcu_head rcu;
 } __randomize_layout;
 extern struct uts_namespace init_uts_ns;
 
diff --git a/kernel/utsname.c b/kernel/utsname.c
index b1ac3ca870f2..aebf4df5f592 100644
--- a/kernel/utsname.c
+++ b/kernel/utsname.c
@@ -103,12 +103,20 @@ struct uts_namespace *copy_utsname(unsigned long flags,
 	return new_ns;
 }
 
+static void free_uts_ns_rcu(struct rcu_head *head)
+{
+	struct uts_namespace *ns;
+
+	ns = container_of(head, struct uts_namespace, rcu);
+	kmem_cache_free(uts_ns_cache, ns);
+}
+
 void free_uts_ns(struct uts_namespace *ns)
 {
 	dec_uts_namespaces(ns->ucounts);
 	put_user_ns(ns->user_ns);
 	ns_free_inum(&ns->ns);
-	kmem_cache_free(uts_ns_cache, ns);
+	call_rcu(&ns->rcu, free_uts_ns_rcu);
 }
 
 static inline struct uts_namespace *to_uts_ns(struct ns_common *ns)