SUNRPC: handle RPC client pipefs dentries by network namespace aware routines

v2:
1) "Over-put" of PipeFS mount point fixed. Fix is ugly, but allows to bisect
the patch set. And it will be removed later in the series.

This patch makes RPC clients PipeFs dentries allocations in it's owner network
namespace context.
RPC client pipefs dentries creation logic has been changed:
1) Pipefs dentries creation by sb was moved to separated function, which will
be used for handling PipeFS mount notification.
2) Initial value of RPC client PipeFS dir dentry is set no NULL now.

RPC client pipefs dentries cleanup logic has been changed:
1) Cleanup is done now in separated rpc_remove_pipedir() function, which takes
care about pipefs superblock locking.

Also this patch removes slashes from cb_program.pipe_dir_name and from
NFS_PIPE_DIRNAME to make rpc_d_lookup_sb() work. This doesn't affect
vfs_path_lookup() results in nfs4blocklayout_init() since this slash is cutted
off anyway in link_path_walk().

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfsd/nfs4callback.c

@@ -622,7 +622,7 @@ static struct rpc_program cb_program = {
 	.nrvers			= ARRAY_SIZE(nfs_cb_version),
 	.version		= nfs_cb_version,
 	.stats			= &cb_stats,
-	.pipe_dir_name		= "/nfsd4_cb",
+	.pipe_dir_name		= "nfsd4_cb",
 };
 
 static int max_cb_time(void)

include/linux/nfs.h

@@ -29,7 +29,7 @@
 #define NFS_MNT_VERSION		1
 #define NFS_MNT3_VERSION	3
 
-#define NFS_PIPE_DIRNAME "/nfs"
+#define NFS_PIPE_DIRNAME "nfs"
 
 /*
  * NFS stats. The good thing with these values is that NFSv3 errors are

net/sunrpc/clnt.c

@@ -93,52 +93,89 @@ static void rpc_unregister_client(struct rpc_clnt *clnt)
 	spin_unlock(&rpc_client_lock);
 }
 
-static int
-rpc_setup_pipedir(struct rpc_clnt *clnt, char *dir_name)
+static void __rpc_clnt_remove_pipedir(struct rpc_clnt *clnt)
+{
+	if (clnt->cl_path.dentry)
+		rpc_remove_client_dir(clnt->cl_path.dentry);
+	clnt->cl_path.dentry = NULL;
+}
+
+static void rpc_clnt_remove_pipedir(struct rpc_clnt *clnt)
+{
+	struct super_block *pipefs_sb;
+	int put_mnt = 0;
+
+	pipefs_sb = rpc_get_sb_net(clnt->cl_xprt->xprt_net);
+	if (pipefs_sb) {
+		if (clnt->cl_path.dentry)
+			put_mnt = 1;
+		__rpc_clnt_remove_pipedir(clnt);
+		rpc_put_sb_net(clnt->cl_xprt->xprt_net);
+	}
+	if (put_mnt)
+		rpc_put_mount();
+}
+
+static struct dentry *rpc_setup_pipedir_sb(struct super_block *sb,
+				    struct rpc_clnt *clnt, char *dir_name)
 {
 	static uint32_t clntid;
-	struct path path, dir;
 	char name[15];
 	struct qstr q = {
 		.name = name,
 	};
+	struct dentry *dir, *dentry;
 	int error;
 
+	dir = rpc_d_lookup_sb(sb, dir_name);
+	if (dir == NULL)
+		return dir;
+	for (;;) {
+		q.len = snprintf(name, sizeof(name), "clnt%x", (unsigned int)clntid++);
+		name[sizeof(name) - 1] = '\0';
+		q.hash = full_name_hash(q.name, q.len);
+		dentry = rpc_create_client_dir(dir, &q, clnt);
+		if (!IS_ERR(dentry))
+			break;
+		error = PTR_ERR(dentry);
+		if (error != -EEXIST) {
+			printk(KERN_INFO "RPC: Couldn't create pipefs entry"
+					" %s/%s, error %d\n",
+					dir_name, name, error);
+			break;
+		}
+	}
+	dput(dir);
+	return dentry;
+}
+
+static int
+rpc_setup_pipedir(struct rpc_clnt *clnt, char *dir_name)
+{
+	struct super_block *pipefs_sb;
+	struct path path;
+
 	clnt->cl_path.mnt = ERR_PTR(-ENOENT);
-	clnt->cl_path.dentry = ERR_PTR(-ENOENT);
+	clnt->cl_path.dentry = NULL;
 	if (dir_name == NULL)
 		return 0;
 
 	path.mnt = rpc_get_mount();
 	if (IS_ERR(path.mnt))
 		return PTR_ERR(path.mnt);
-	error = vfs_path_lookup(path.mnt->mnt_root, path.mnt, dir_name, 0, &dir);
-	if (error)
-		goto err;
-
-	for (;;) {
-		q.len = snprintf(name, sizeof(name), "clnt%x", (unsigned int)clntid++);
-		name[sizeof(name) - 1] = '\0';
-		q.hash = full_name_hash(q.name, q.len);
-		path.dentry = rpc_create_client_dir(dir.dentry, &q, clnt);
-		if (!IS_ERR(path.dentry))
-			break;
-		error = PTR_ERR(path.dentry);
-		if (error != -EEXIST) {
-			printk(KERN_INFO "RPC: Couldn't create pipefs entry"
-					" %s/%s, error %d\n",
-					dir_name, name, error);
-			goto err_path_put;
-		}
+	pipefs_sb = rpc_get_sb_net(clnt->cl_xprt->xprt_net);
+	if (!pipefs_sb) {
+		rpc_put_mount();
+		return -ENOENT;
+	}
+	path.dentry = rpc_setup_pipedir_sb(pipefs_sb, clnt, dir_name);
+	rpc_put_sb_net(clnt->cl_xprt->xprt_net);
+	if (IS_ERR(path.dentry)) {
+		rpc_put_mount();
+		return PTR_ERR(path.dentry);
 	}
-	path_put(&dir);
 	clnt->cl_path = path;
 	return 0;
-err_path_put:
-	path_put(&dir);
-err:
-	rpc_put_mount();
-	return error;
 }
 
 static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, struct rpc_xprt *xprt)
@@ -246,10 +283,7 @@ static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, stru
 	return clnt;
 
 out_no_auth:
-	if (!IS_ERR(clnt->cl_path.dentry)) {
-		rpc_remove_client_dir(clnt->cl_path.dentry);
-		rpc_put_mount();
-	}
+	rpc_clnt_remove_pipedir(clnt);
 out_no_path:
 	kfree(clnt->cl_principal);
 out_no_principal:
@@ -474,10 +508,7 @@ rpc_free_client(struct rpc_clnt *clnt)
 {
 	dprintk("RPC:       destroying %s client for %s\n",
 			clnt->cl_protname, clnt->cl_server);
-	if (!IS_ERR(clnt->cl_path.dentry)) {
-		rpc_remove_client_dir(clnt->cl_path.dentry);
-		rpc_put_mount();
-	}
+	rpc_clnt_remove_pipedir(clnt);
 	if (clnt->cl_parent != clnt) {
 		rpc_release_client(clnt->cl_parent);
 		goto out_free;