linux-kernel - [PATCH v2 2/4] NFS: release per-net clients lock before calling PipeFS dentries creation

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Message-ID: <20120227155103.7941.17006.stgit@localhost6.localdomain6>
Date:	Mon, 27 Feb 2012 19:51:04 +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 2/4] NFS: 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>

---
 fs/nfs/client.c |    2 +-
 fs/nfs/idmap.c  |    8 ++++++--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 8563585..6aeb6b3 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -538,7 +538,7 @@ nfs_get_client(const struct nfs_client_initdata *cl_init,
 	/* install a new client and return with it unready */
 install_client:
 	clp = new;
-	list_add(&clp->cl_share_link, &nn->nfs_client_list);
+	list_add_tail(&clp->cl_share_link, &nn->nfs_client_list);
 	spin_unlock(&nn->nfs_client_lock);
 
 	error = cl_init->rpc_ops->init_client(clp, timeparms, ip_addr,
diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
index b5c6d8e..8a9e7a4 100644
--- a/fs/nfs/idmap.c
+++ b/fs/nfs/idmap.c
@@ -558,16 +558,20 @@ static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event,
 {
 	struct super_block *sb = ptr;
 	struct nfs_net *nn = net_generic(sb->s_fs_info, nfs_net_id);
-	struct nfs_client *clp;
+	struct nfs_client *clp, *tmp;
 	int error = 0;
 
 	spin_lock(&nn->nfs_client_lock);
-	list_for_each_entry(clp, &nn->nfs_client_list, cl_share_link) {
+	list_for_each_entry_safe(clp, tmp, &nn->nfs_client_list, cl_share_link) {
 		if (clp->rpc_ops != &nfs_v4_clientops)
 			continue;
+		atomic_inc(&clp->cl_count);
+		spin_unlock(&nn->nfs_client_lock);
 		error = __rpc_pipefs_event(clp, event, sb);
+		nfs_put_client(clp);
 		if (error)
 			break;
+		spin_lock(&nn->nfs_client_lock);
 	}
 	spin_unlock(&nn->nfs_client_lock);
 	return error;

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