anon_inodes: move allocation of anon_inode into ->mount()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/anon_inodes.c

@@ -39,19 +39,6 @@ static const struct dentry_operations anon_inodefs_dentry_operations = {
 	.d_dname	= anon_inodefs_dname,
 };
 
-static struct dentry *anon_inodefs_mount(struct file_system_type *fs_type,
-				int flags, const char *dev_name, void *data)
-{
-	return mount_pseudo(fs_type, "anon_inode:", NULL,
-			&anon_inodefs_dentry_operations, ANON_INODE_FS_MAGIC);
-}
-
-static struct file_system_type anon_inode_fs_type = {
-	.name		= "anon_inodefs",
-	.mount		= anon_inodefs_mount,
-	.kill_sb	= kill_anon_super,
-};
-
 /*
  * nop .set_page_dirty method so that people can use .page_mkwrite on
  * anon inodes.
@@ -65,6 +52,62 @@ static const struct address_space_operations anon_aops = {
 	.set_page_dirty = anon_set_page_dirty,
 };
 
+/*
+ * A single inode exists for all anon_inode files. Contrary to pipes,
+ * anon_inode inodes have no associated per-instance data, so we need
+ * only allocate one of them.
+ */
+static struct inode *anon_inode_mkinode(struct super_block *s)
+{
+	struct inode *inode = new_inode_pseudo(s);
+
+	if (!inode)
+		return ERR_PTR(-ENOMEM);
+
+	inode->i_ino = get_next_ino();
+	inode->i_fop = &anon_inode_fops;
+
+	inode->i_mapping->a_ops = &anon_aops;
+
+	/*
+	 * Mark the inode dirty from the very beginning,
+	 * that way it will never be moved to the dirty
+	 * list because mark_inode_dirty() will think
+	 * that it already _is_ on the dirty list.
+	 */
+	inode->i_state = I_DIRTY;
+	inode->i_mode = S_IRUSR | S_IWUSR;
+	inode->i_uid = current_fsuid();
+	inode->i_gid = current_fsgid();
+	inode->i_flags |= S_PRIVATE;
+	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
+	return inode;
+}
+
+static struct dentry *anon_inodefs_mount(struct file_system_type *fs_type,
+				int flags, const char *dev_name, void *data)
+{
+	struct dentry *root;
+	root = mount_pseudo(fs_type, "anon_inode:", NULL,
+			&anon_inodefs_dentry_operations, ANON_INODE_FS_MAGIC);
+	if (!IS_ERR(root)) {
+		struct super_block *s = root->d_sb;
+		anon_inode_inode = anon_inode_mkinode(s);
+		if (IS_ERR(anon_inode_inode)) {
+			dput(root);
+			deactivate_locked_super(s);
+			root = ERR_CAST(anon_inode_inode);
+		}
+	}
+	return root;
+}
+
+static struct file_system_type anon_inode_fs_type = {
+	.name		= "anon_inodefs",
+	.mount		= anon_inodefs_mount,
+	.kill_sb	= kill_anon_super,
+};
+
 /**
  * anon_inode_getfile - creates a new file instance by hooking it up to an
  *                      anonymous inode, and a dentry that describe the "class"
@@ -180,38 +223,6 @@ err_put_unused_fd:
 }
 EXPORT_SYMBOL_GPL(anon_inode_getfd);
 
-/*
- * A single inode exists for all anon_inode files. Contrary to pipes,
- * anon_inode inodes have no associated per-instance data, so we need
- * only allocate one of them.
- */
-static struct inode *anon_inode_mkinode(void)
-{
-	struct inode *inode = new_inode_pseudo(anon_inode_mnt->mnt_sb);
-
-	if (!inode)
-		return ERR_PTR(-ENOMEM);
-
-	inode->i_ino = get_next_ino();
-	inode->i_fop = &anon_inode_fops;
-
-	inode->i_mapping->a_ops = &anon_aops;
-
-	/*
-	 * Mark the inode dirty from the very beginning,
-	 * that way it will never be moved to the dirty
-	 * list because mark_inode_dirty() will think
-	 * that it already _is_ on the dirty list.
-	 */
-	inode->i_state = I_DIRTY;
-	inode->i_mode = S_IRUSR | S_IWUSR;
-	inode->i_uid = current_fsuid();
-	inode->i_gid = current_fsgid();
-	inode->i_flags |= S_PRIVATE;
-	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
-	return inode;
-}
-
 static int __init anon_inode_init(void)
 {
 	int error;
@@ -224,16 +235,8 @@ static int __init anon_inode_init(void)
 		error = PTR_ERR(anon_inode_mnt);
 		goto err_unregister_filesystem;
 	}
-	anon_inode_inode = anon_inode_mkinode();
-	if (IS_ERR(anon_inode_inode)) {
-		error = PTR_ERR(anon_inode_inode);
-		goto err_mntput;
-	}
-
 	return 0;
 
-err_mntput:
-	kern_unmount(anon_inode_mnt);
 err_unregister_filesystem:
 	unregister_filesystem(&anon_inode_fs_type);
 err_exit: