linux-kernel - [PATCH 18/20] xfs: use RCU to free 'struct xfs

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Message-ID: <20150323023740.8161.39099.stgit@notabene.brown>
Date:	Mon, 23 Mar 2015 13:37:40 +1100
From:	NeilBrown <neilb@...e.de>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 18/20] xfs: use RCU to free 'struct xfs_mount'.

In order for ->follow_link to be safe in RCU-walk, any
data structures accessed need to be freed after
an RCU grace period.

'struct xfs_mount' is not currently guaranteed to be delayed
sufficiently, so use kfree_rcu() to free it.

Signed-off-by: NeilBrown <neilb@...e.de>
---
 fs/xfs/xfs_mount.h |    2 ++
 fs/xfs/xfs_super.c |    2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 0d8abd6364d9..6a1094e493e9 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -185,6 +185,8 @@ typedef struct xfs_mount {
 	 * to various other kinds of pain inflicted on the pNFS server.
 	 */
 	__uint32_t		m_generation;
+
+	struct rcu_head		m_rcu;
 } xfs_mount_t;

 /*
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index 8fcc4ccc5c79..3827be14383c 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1047,7 +1047,7 @@ xfs_fs_put_super(
 	xfs_destroy_mount_workqueues(mp);
 	xfs_close_devices(mp);
 	xfs_free_fsname(mp);
-	kfree(mp);
+	kfree_rcu(mp, m_rcu);
 }

 STATIC int

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