[PATCH] RPC,NFS: new rpc_pipefs patch

 Currently rpc_mkdir/rpc_rmdir and rpc_mkpipe/mk_unlink have an API that's
 a little unfortunate.  They take a path relative to the rpc_pipefs root and
 thus need to perform a full lookup.  If you look at debugfs or usbfs they
 always store the dentry for directories they created and thus can pass in
 a dentry + single pathname component pair into their equivalents of the
 above functions.

 And in fact rpc_pipefs actually stores a dentry for all but one component so
 this change not only simplifies the core rpc_pipe code but also the callers.

 Unfortuntately this code path is only used by the NFS4 idmapper and
 AUTH_GSSAPI for which I don't have a test enviroment.  Could someone give
 it a spin?  It's the last bit needed before we can rework the
 lookup_hash API

 Signed-off-by: Christoph Hellwig <hch@lst.de>
 Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/idmap.c

@@ -66,7 +66,6 @@ struct idmap_hashtable {
 };
 
 struct idmap {
-	char                  idmap_path[48];
 	struct dentry        *idmap_dentry;
 	wait_queue_head_t     idmap_wq;
 	struct idmap_msg      idmap_im;
@@ -102,11 +101,8 @@ nfs_idmap_new(struct nfs4_client *clp)
 
 	memset(idmap, 0, sizeof(*idmap));
 
-	snprintf(idmap->idmap_path, sizeof(idmap->idmap_path),
-	    "%s/idmap", clp->cl_rpcclient->cl_pathname);
-
-        idmap->idmap_dentry = rpc_mkpipe(idmap->idmap_path,
-	    idmap, &idmap_upcall_ops, 0);
+	idmap->idmap_dentry = rpc_mkpipe(clp->cl_rpcclient->cl_dentry,
+			"idmap", idmap, &idmap_upcall_ops, 0);
         if (IS_ERR(idmap->idmap_dentry)) {
 		kfree(idmap);
 		return;
@@ -128,7 +124,7 @@ nfs_idmap_delete(struct nfs4_client *clp)
 
 	if (!idmap)
 		return;
-	rpc_unlink(idmap->idmap_path);
+	rpc_unlink(idmap->idmap_dentry);
 	clp->cl_idmap = NULL;
 	kfree(idmap);
 }

include/linux/sunrpc/clnt.h

@@ -59,7 +59,7 @@ struct rpc_clnt {
 
 	int			cl_nodelen;	/* nodename length */
 	char 			cl_nodename[UNX_MAXNODENAME];
-	char			cl_pathname[30];/* Path in rpc_pipe_fs */
+	struct dentry *		__cl_parent_dentry;
 	struct dentry *		cl_dentry;	/* inode */
 	struct rpc_clnt *	cl_parent;	/* Points to parent of clones */
 	struct rpc_rtt		cl_rtt_default;

include/linux/sunrpc/rpc_pipe_fs.h

@@ -41,10 +41,11 @@ RPC_I(struct inode *inode)
 
 extern int rpc_queue_upcall(struct inode *, struct rpc_pipe_msg *);
 
-extern struct dentry *rpc_mkdir(char *, struct rpc_clnt *);
-extern int rpc_rmdir(char *);
-extern struct dentry *rpc_mkpipe(char *, void *, struct rpc_pipe_ops *, int flags);
-extern int rpc_unlink(char *);
+extern struct dentry *rpc_mkdir(struct dentry *, char *, struct rpc_clnt *);
+extern void rpc_rmdir(struct dentry *);
+extern struct dentry *rpc_mkpipe(struct dentry *, char *, void *,
+		struct rpc_pipe_ops *, int flags);
+extern void rpc_unlink(struct dentry *);
 
 #endif
 #endif

net/sunrpc/auth_gss/auth_gss.c

@@ -87,7 +87,6 @@ struct gss_auth {
 	struct list_head upcalls;
 	struct rpc_clnt *client;
 	struct dentry *dentry;
-	char path[48];
 	spinlock_t lock;
 };
 
@@ -690,10 +689,8 @@ gss_create(struct rpc_clnt *clnt, rpc_authflavor_t flavor)
 	if (err)
 		goto err_put_mech;
 
-	snprintf(gss_auth->path, sizeof(gss_auth->path), "%s/%s",
-			clnt->cl_pathname,
-			gss_auth->mech->gm_name);
-	gss_auth->dentry = rpc_mkpipe(gss_auth->path, clnt, &gss_upcall_ops, RPC_PIPE_WAIT_FOR_OPEN);
+	gss_auth->dentry = rpc_mkpipe(clnt->cl_dentry, gss_auth->mech->gm_name,
+			clnt, &gss_upcall_ops, RPC_PIPE_WAIT_FOR_OPEN);
 	if (IS_ERR(gss_auth->dentry)) {
 		err = PTR_ERR(gss_auth->dentry);
 		goto err_put_mech;
@@ -718,7 +715,7 @@ gss_destroy(struct rpc_auth *auth)
 		auth, auth->au_flavor);
 
 	gss_auth = container_of(auth, struct gss_auth, rpc_auth);
-	rpc_unlink(gss_auth->path);
+	rpc_unlink(gss_auth->dentry);
 	gss_mech_put(gss_auth->mech);
 
 	rpcauth_free_credcache(auth);

net/sunrpc/clnt.c

@@ -67,26 +67,42 @@ static u32 *	call_verify(struct rpc_task *task);
 static int
 rpc_setup_pipedir(struct rpc_clnt *clnt, char *dir_name)
 {
-	static uint32_t clntid;
+	static unsigned int clntid;
+	char name[128];
 	int error;
 
 	if (dir_name == NULL)
 		return 0;
-	for (;;) {
-		snprintf(clnt->cl_pathname, sizeof(clnt->cl_pathname),
-				"%s/clnt%x", dir_name,
-				(unsigned int)clntid++);
-		clnt->cl_pathname[sizeof(clnt->cl_pathname) - 1] = '\0';
-		clnt->cl_dentry = rpc_mkdir(clnt->cl_pathname, clnt);
-		if (!IS_ERR(clnt->cl_dentry))
-			return 0;
+
+ retry_parent:
+	clnt->__cl_parent_dentry = rpc_mkdir(NULL, dir_name, NULL);
+	if (IS_ERR(clnt->__cl_parent_dentry)) {
+		error = PTR_ERR(clnt->__cl_parent_dentry);
+		if (error == -EEXIST)
+			goto retry_parent; /* XXX(hch): WTF? */
+
+		printk(KERN_INFO "RPC: Couldn't create pipefs entry %s, error %d\n",
+				dir_name, error);
+		return error;
+	}
+
+
+ retry_child:
+	snprintf(name, sizeof(name), "clnt%x", clntid++);
+	name[sizeof(name) - 1] = '\0';
+
+	clnt->cl_dentry = rpc_mkdir(clnt->__cl_parent_dentry, name, clnt);
+	if (IS_ERR(clnt->cl_dentry)) {
 		error = PTR_ERR(clnt->cl_dentry);
-		if (error != -EEXIST) {
-			printk(KERN_INFO "RPC: Couldn't create pipefs entry %s, error %d\n",
-					clnt->cl_pathname, error);
-			return error;
-		}
+		if (error == -EEXIST)
+			goto retry_child;
+		printk(KERN_INFO "RPC: Couldn't create pipefs entry %s, error %d\n",
+				name, error);
+		rpc_rmdir(clnt->__cl_parent_dentry);
+		return error;
 	}
+
+	return 0;
 }
 
 /*
@@ -174,7 +190,8 @@ rpc_new_client(struct rpc_xprt *xprt, char *servname,
 	return clnt;
 
 out_no_auth:
-	rpc_rmdir(clnt->cl_pathname);
+	rpc_rmdir(clnt->cl_dentry);
+	rpc_rmdir(clnt->__cl_parent_dentry);
 out_no_path:
 	if (clnt->cl_server != clnt->cl_inline_name)
 		kfree(clnt->cl_server);
@@ -302,8 +319,10 @@ rpc_destroy_client(struct rpc_clnt *clnt)
 		rpc_destroy_client(clnt->cl_parent);
 		goto out_free;
 	}
-	if (clnt->cl_pathname[0])
-		rpc_rmdir(clnt->cl_pathname);
+	if (clnt->cl_dentry)
+		rpc_rmdir(clnt->cl_dentry);
+	if (clnt->__cl_parent_dentry)
+		rpc_rmdir(clnt->__cl_parent_dentry);
 	if (clnt->cl_xprt) {
 		xprt_destroy(clnt->cl_xprt);
 		clnt->cl_xprt = NULL;