linux-kernel - [PATCH v2 02/12] NFS: callback service creation function introduced

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Date:	Tue, 22 May 2012 11:36:02 +0400
From:	Stanislav Kinsbursky <skinsbursky@...allels.com>
To:	bfields@...ldses.org
Cc:	linux-nfs@...r.kernel.org, Trond.Myklebust@...app.com,
	linux-kernel@...r.kernel.org, devel@...nvz.org
Subject: [PATCH v2 02/12] NFS: callback service creation function introduced

This function creates service if it's not exist, or increase usage counter of
the existent, and returns pointer to it.
Usage counter will be droppepd by svc_destroy() later in nfs_callback_up().

Signed-off-by: Stanislav Kinsbursky <skinsbursky@...allels.com>
---
 fs/nfs/callback.c |   55 +++++++++++++++++++++++++++++++++++++++++++----------
 1 files changed, 45 insertions(+), 10 deletions(-)

diff --git a/fs/nfs/callback.c b/fs/nfs/callback.c
index f3d7ee2..b34ccc6 100644
--- a/fs/nfs/callback.c
+++ b/fs/nfs/callback.c
@@ -242,12 +242,46 @@ static inline void nfs_callback_bc_serv(u32 minorversion, struct rpc_xprt *xprt,
 }
 #endif /* CONFIG_NFS_V4_1 */
 
+static struct svc_serv *nfs_callback_create_svc(int minorversion)
+{
+	struct nfs_callback_data *cb_info = &nfs_callback_info[minorversion];
+	struct svc_serv *serv;
+
+	/*
+	 * Check whether we're already up and running.
+	 */
+	if (cb_info->task) {
+		/*
+		 * Note: increase service usage, because later in case of error
+		 * svc_destroy() will be called.
+		 */
+		svc_get(cb_info->serv);
+		return cb_info->serv;
+	}
+
+	/*
+	 * Sanity check: if there's no task,
+	 * we should be the first user ...
+	 */
+	if (cb_info->users)
+		printk(KERN_WARNING "nfs_callback_up: no kthread, %d users??\n",
+			cb_info->users);
+
+	serv = svc_create(&nfs4_callback_program, NFS4_CALLBACK_BUFSIZE, NULL);
+	if (!serv) {
+		printk(KERN_ERR "lockd_up: create service failed\n");
+		return ERR_PTR(-ENOMEM);
+	}
+	dprintk("nfs_callback_up: service created\n");
+	return serv;
+}
+
 /*
  * Bring up the callback thread if it is not already up.
  */
 int nfs_callback_up(u32 minorversion, struct rpc_xprt *xprt)
 {
-	struct svc_serv *serv = NULL;
+	struct svc_serv *serv;
 	struct svc_rqst *rqstp;
 	int (*callback_svc)(void *vrqstp);
 	struct nfs_callback_data *cb_info = &nfs_callback_info[minorversion];
@@ -257,15 +291,17 @@ int nfs_callback_up(u32 minorversion, struct rpc_xprt *xprt)
 	struct net *net = current->nsproxy->net_ns;
 
 	mutex_lock(&nfs_callback_mutex);
+
+	serv = nfs_callback_create_svc(minorversion);
+	if (IS_ERR(serv)) {
+		ret = PTR_ERR(serv);
+		goto err_create;
+	}
+
 	if (cb_info->users++ || cb_info->task != NULL) {
 		nfs_callback_bc_serv(minorversion, xprt, cb_info);
 		goto out;
 	}
-	serv = svc_create(&nfs4_callback_program, NFS4_CALLBACK_BUFSIZE, NULL);
-	if (!serv) {
-		ret = -ENOMEM;
-		goto out_err;
-	}
 
 	ret = svc_bind(serv, net);
 	if (ret < 0) {
@@ -306,16 +342,15 @@ out:
 	 * on both success and failure so that the refcount is 1 when the
 	 * thread exits.
 	 */
-	if (serv)
-		svc_destroy(serv);
+	svc_destroy(serv);
+err_create:
 	mutex_unlock(&nfs_callback_mutex);
 	return ret;
 out_err:
 	dprintk("NFS: Couldn't create callback socket or server thread; "
 		"err = %d\n", ret);
 	cb_info->users--;
-	if (serv)
-		svc_shutdown_net(serv, net);
+	svc_shutdown_net(serv, net);
 	goto out;
 }
 

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