new wrapper: alloc_file_pseudo()

takes inode, vfsmount, name, O_... flags and file_operations and
either returns a new struct file (in which case inode reference we
held is consumed) or returns ERR_PTR(), in which case no refcounts
are altered.

converted aio_private_file() and sock_alloc_file() to it

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/net/socket.c b/net/socket.c
index 2cdbe8f..4cf3568 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -391,33 +391,15 @@ static struct file_system_type sock_fs_type = {
 
 struct file *sock_alloc_file(struct socket *sock, int flags, const char *dname)
 {
-	struct qstr name = { .name = "" };
-	struct path path;
 	struct file *file;
 
-	if (dname) {
-		name.name = dname;
-		name.len = strlen(name.name);
-	} else if (sock->sk) {
-		name.name = sock->sk->sk_prot_creator->name;
-		name.len = strlen(name.name);
-	}
-	path.dentry = d_alloc_pseudo(sock_mnt->mnt_sb, &name);
-	if (unlikely(!path.dentry)) {
-		sock_release(sock);
-		return ERR_PTR(-ENOMEM);
-	}
-	path.mnt = mntget(sock_mnt);
+	if (!dname)
+		dname = sock->sk ? sock->sk->sk_prot_creator->name : "";
 
-	d_instantiate(path.dentry, SOCK_INODE(sock));
-
-	file = alloc_file(&path, O_RDWR | (flags & O_NONBLOCK),
-		  &socket_file_ops);
+	file = alloc_file_pseudo(SOCK_INODE(sock), sock_mnt, dname,
+				O_RDWR | (flags & O_NONBLOCK),
+				&socket_file_ops);
 	if (IS_ERR(file)) {
-		/* drop dentry, keep inode for a bit */
-		ihold(d_inode(path.dentry));
-		path_put(&path);
-		/* ... and now kill it properly */
 		sock_release(sock);
 		return file;
 	}