linux-kernel - [PATCH v2 1/4] SUNRPC: release per-net clients lock before calling PipeFS dentries creation

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Date:	Mon, 27 Feb 2012 19:50:55 +0400
From:	Stanislav Kinsbursky <skinsbursky@...allels.com>
To:	Trond.Myklebust@...app.com
Cc:	linux-nfs@...r.kernel.org, xemul@...allels.com, neilb@...e.de,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	jbottomley@...allels.com, bfields@...ldses.org,
	davem@...emloft.net, devel@...nvz.org
Subject: [PATCH v2 1/4] SUNRPC: release per-net clients lock before calling
 PipeFS dentries creation

Lockdep is sad otherwise, because inode mutex is taken on PipeFS dentry
creation, which can be called on mount notification, where this per-net client
lock is taken on clients list walk.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@...allels.com>

---
 net/sunrpc/clnt.c |   10 +++++++---
 1 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index bb7ed2f3..ddb5741 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -84,7 +84,7 @@ static void rpc_register_client(struct rpc_clnt *clnt)
 	struct sunrpc_net *sn = net_generic(clnt->cl_xprt->xprt_net, sunrpc_net_id);
 
 	spin_lock(&sn->rpc_client_lock);
-	list_add(&clnt->cl_clients, &sn->all_clients);
+	list_add_tail(&clnt->cl_clients, &sn->all_clients);
 	spin_unlock(&sn->rpc_client_lock);
 }
 
@@ -208,15 +208,19 @@ static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event,
 			    void *ptr)
 {
 	struct super_block *sb = ptr;
-	struct rpc_clnt *clnt;
+	struct rpc_clnt *clnt, *tmp;
 	int error = 0;
 	struct sunrpc_net *sn = net_generic(sb->s_fs_info, sunrpc_net_id);
 
 	spin_lock(&sn->rpc_client_lock);
-	list_for_each_entry(clnt, &sn->all_clients, cl_clients) {
+	list_for_each_entry_safe(clnt, tmp, &sn->all_clients, cl_clients) {
+		atomic_inc(&clnt->cl_count);
+		spin_unlock(&sn->rpc_client_lock);
 		error = __rpc_pipefs_event(clnt, event, sb);
+		rpc_release_client(clnt);
 		if (error)
 			break;
+		spin_lock(&sn->rpc_client_lock);
 	}
 	spin_unlock(&sn->rpc_client_lock);
 	return error;

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