linux-kernel - [PATCH 2/2] ipc: get rid of free_ipc

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Date:   Fri, 18 Feb 2022 13:31:14 -0500
From:   Rik van Riel <riel@...riel.com>
To:     linux-kernel@...r.kernel.org
Cc:     kernel-team@...com, linux-fsdevel@...r.kernel.org,
        paulmck@...nel.org, gscrivan@...hat.com, viro@...iv.linux.org.uk,
        Rik van Riel <riel@...riel.com>
Subject: [PATCH 2/2] ipc: get rid of free_ipc_work workqueue

With kern_unmount deferring the freeing of the vfsmount structure
through queue_rcu_work, we no longer need a separate workqueue for
freeing up ipc_namespace structures.

Signed-off-by: Rik van Riel <riel@...riel.com>
---
 include/linux/ipc_namespace.h |  2 --
 ipc/namespace.c               | 21 +--------------------
 2 files changed, 1 insertion(+), 22 deletions(-)

diff --git a/include/linux/ipc_namespace.h b/include/linux/ipc_namespace.h
index b75395ec8d52..5a3debde2f3d 100644
--- a/include/linux/ipc_namespace.h
+++ b/include/linux/ipc_namespace.h
@@ -67,8 +67,6 @@ struct ipc_namespace {
 	struct user_namespace *user_ns;
 	struct ucounts *ucounts;
 
-	struct llist_node mnt_llist;
-
 	struct ns_common ns;
 } __randomize_layout;
 
diff --git a/ipc/namespace.c b/ipc/namespace.c
index ae83f0f2651b..090a08b17710 100644
--- a/ipc/namespace.c
+++ b/ipc/namespace.c
@@ -117,9 +117,6 @@ void free_ipcs(struct ipc_namespace *ns, struct ipc_ids *ids,
 
 static void free_ipc_ns(struct ipc_namespace *ns)
 {
-	/* mq_put_mnt() waits for a grace period as kern_unmount()
-	 * uses synchronize_rcu().
-	 */
 	mq_put_mnt(ns);
 	sem_exit_ns(ns);
 	msg_exit_ns(ns);
@@ -131,21 +128,6 @@ static void free_ipc_ns(struct ipc_namespace *ns)
 	kfree(ns);
 }
 
-static LLIST_HEAD(free_ipc_list);
-static void free_ipc(struct work_struct *unused)
-{
-	struct llist_node *node = llist_del_all(&free_ipc_list);
-	struct ipc_namespace *n, *t;
-
-	llist_for_each_entry_safe(n, t, node, mnt_llist)
-		free_ipc_ns(n);
-}
-
-/*
- * The work queue is used to avoid the cost of synchronize_rcu in kern_unmount.
- */
-static DECLARE_WORK(free_ipc_work, free_ipc);
-
 /*
  * put_ipc_ns - drop a reference to an ipc namespace.
  * @ns: the namespace to put
@@ -168,8 +150,7 @@ void put_ipc_ns(struct ipc_namespace *ns)
 		mq_clear_sbinfo(ns);
 		spin_unlock(&mq_lock);
 
-		if (llist_add(&ns->mnt_llist, &free_ipc_list))
-			schedule_work(&free_ipc_work);
+		free_ipc_ns(ns);
 	}
 }
 
-- 
2.34.1