1 files changed, 883 insertions, 0 deletions

diff --git a/fs/ocfs2/stack_user.c b/fs/ocfs2/stack_user.c
new file mode 100644
index 000000000000..7428663f9cbb
--- /dev/null
+++ b/fs/ocfs2/stack_user.c
@@ -0,0 +1,883 @@
+/* -*- mode: c; c-basic-offset: 8; -*-
+ * vim: noexpandtab sw=8 ts=8 sts=0:
+ *
+ * stack_user.c
+ *
+ * Code which interfaces ocfs2 with fs/dlm and a userspace stack.
+ *
+ * Copyright (C) 2007 Oracle.  All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public
+ * License as published by the Free Software Foundation, version 2.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include <linux/module.h>
+#include <linux/fs.h>
+#include <linux/miscdevice.h>
+#include <linux/mutex.h>
+#include <linux/reboot.h>
+#include <asm/uaccess.h>
+
+#include "ocfs2.h"  /* For struct ocfs2_lock_res */
+#include "stackglue.h"
+
+
+/*
+ * The control protocol starts with a handshake.  Until the handshake
+ * is complete, the control device will fail all write(2)s.
+ *
+ * The handshake is simple.  First, the client reads until EOF.  Each line
+ * of output is a supported protocol tag.  All protocol tags are a single
+ * character followed by a two hex digit version number.  Currently the
+ * only things supported is T01, for "Text-base version 0x01".  Next, the
+ * client writes the version they would like to use, including the newline.
+ * Thus, the protocol tag is 'T01\n'.  If the version tag written is
+ * unknown, -EINVAL is returned.  Once the negotiation is complete, the
+ * client can start sending messages.
+ *
+ * The T01 protocol has three messages.  First is the "SETN" message.
+ * It has the following syntax:
+ *
+ *  SETN<space><8-char-hex-nodenum><newline>
+ *
+ * This is 14 characters.
+ *
+ * The "SETN" message must be the first message following the protocol.
+ * It tells ocfs2_control the local node number.
+ *
+ * Next comes the "SETV" message.  It has the following syntax:
+ *
+ *  SETV<space><2-char-hex-major><space><2-char-hex-minor><newline>
+ *
+ * This is 11 characters.
+ *
+ * The "SETV" message sets the filesystem locking protocol version as
+ * negotiated by the client.  The client negotiates based on the maximum
+ * version advertised in /sys/fs/ocfs2/max_locking_protocol.  The major
+ * number from the "SETV" message must match
+ * user_stack.sp_proto->lp_max_version.pv_major, and the minor number
+ * must be less than or equal to ...->lp_max_version.pv_minor.
+ *
+ * Once this information has been set, mounts will be allowed.  From this
+ * point on, the "DOWN" message can be sent for node down notification.
+ * It has the following syntax:
+ *
+ *  DOWN<space><32-char-cap-hex-uuid><space><8-char-hex-nodenum><newline>
+ *
+ * eg:
+ *
+ *  DOWN 632A924FDD844190BDA93C0DF6B94899 00000001\n
+ *
+ * This is 47 characters.
+ */
+
+/*
+ * Whether or not the client has done the handshake.
+ * For now, we have just one protocol version.
+ */
+#define OCFS2_CONTROL_PROTO			"T01\n"
+#define OCFS2_CONTROL_PROTO_LEN			4
+
+/* Handshake states */
+#define OCFS2_CONTROL_HANDSHAKE_INVALID		(0)
+#define OCFS2_CONTROL_HANDSHAKE_READ		(1)
+#define OCFS2_CONTROL_HANDSHAKE_PROTOCOL	(2)
+#define OCFS2_CONTROL_HANDSHAKE_VALID		(3)
+
+/* Messages */
+#define OCFS2_CONTROL_MESSAGE_OP_LEN		4
+#define OCFS2_CONTROL_MESSAGE_SETNODE_OP	"SETN"
+#define OCFS2_CONTROL_MESSAGE_SETNODE_TOTAL_LEN	14
+#define OCFS2_CONTROL_MESSAGE_SETVERSION_OP	"SETV"
+#define OCFS2_CONTROL_MESSAGE_SETVERSION_TOTAL_LEN	11
+#define OCFS2_CONTROL_MESSAGE_DOWN_OP		"DOWN"
+#define OCFS2_CONTROL_MESSAGE_DOWN_TOTAL_LEN	47
+#define OCFS2_TEXT_UUID_LEN			32
+#define OCFS2_CONTROL_MESSAGE_VERNUM_LEN	2
+#define OCFS2_CONTROL_MESSAGE_NODENUM_LEN	8
+
+/*
+ * ocfs2_live_connection is refcounted because the filesystem and
+ * miscdevice sides can detach in different order.  Let's just be safe.
+ */
+struct ocfs2_live_connection {
+	struct list_head		oc_list;
+	struct ocfs2_cluster_connection	*oc_conn;
+};
+
+struct ocfs2_control_private {
+	struct list_head op_list;
+	int op_state;
+	int op_this_node;
+	struct ocfs2_protocol_version op_proto;
+};
+
+/* SETN<space><8-char-hex-nodenum><newline> */
+struct ocfs2_control_message_setn {
+	char	tag[OCFS2_CONTROL_MESSAGE_OP_LEN];
+	char	space;
+	char	nodestr[OCFS2_CONTROL_MESSAGE_NODENUM_LEN];
+	char	newline;
+};
+
+/* SETV<space><2-char-hex-major><space><2-char-hex-minor><newline> */
+struct ocfs2_control_message_setv {
+	char	tag[OCFS2_CONTROL_MESSAGE_OP_LEN];
+	char	space1;
+	char	major[OCFS2_CONTROL_MESSAGE_VERNUM_LEN];
+	char	space2;
+	char	minor[OCFS2_CONTROL_MESSAGE_VERNUM_LEN];
+	char	newline;
+};
+
+/* DOWN<space><32-char-cap-hex-uuid><space><8-char-hex-nodenum><newline> */
+struct ocfs2_control_message_down {
+	char	tag[OCFS2_CONTROL_MESSAGE_OP_LEN];
+	char	space1;
+	char	uuid[OCFS2_TEXT_UUID_LEN];
+	char	space2;
+	char	nodestr[OCFS2_CONTROL_MESSAGE_NODENUM_LEN];
+	char	newline;
+};
+
+union ocfs2_control_message {
+	char					tag[OCFS2_CONTROL_MESSAGE_OP_LEN];
+	struct ocfs2_control_message_setn	u_setn;
+	struct ocfs2_control_message_setv	u_setv;
+	struct ocfs2_control_message_down	u_down;
+};
+
+static struct ocfs2_stack_plugin user_stack;
+
+static atomic_t ocfs2_control_opened;
+static int ocfs2_control_this_node = -1;
+static struct ocfs2_protocol_version running_proto;
+
+static LIST_HEAD(ocfs2_live_connection_list);
+static LIST_HEAD(ocfs2_control_private_list);
+static DEFINE_MUTEX(ocfs2_control_lock);
+
+static inline void ocfs2_control_set_handshake_state(struct file *file,
+						     int state)
+{
+	struct ocfs2_control_private *p = file->private_data;
+	p->op_state = state;
+}
+
+static inline int ocfs2_control_get_handshake_state(struct file *file)
+{
+	struct ocfs2_control_private *p = file->private_data;
+	return p->op_state;
+}
+
+static struct ocfs2_live_connection *ocfs2_connection_find(const char *name)
+{
+	size_t len = strlen(name);
+	struct ocfs2_live_connection *c;
+
+	BUG_ON(!mutex_is_locked(&ocfs2_control_lock));
+
+	list_for_each_entry(c, &ocfs2_live_connection_list, oc_list) {
+		if ((c->oc_conn->cc_namelen == len) &&
+		    !strncmp(c->oc_conn->cc_name, name, len))
+			return c;
+	}
+
+	return c;
+}
+
+/*
+ * ocfs2_live_connection structures are created underneath the ocfs2
+ * mount path.  Since the VFS prevents multiple calls to
+ * fill_super(), we can't get dupes here.
+ */
+static int ocfs2_live_connection_new(struct ocfs2_cluster_connection *conn,
+				     struct ocfs2_live_connection **c_ret)
+{
+	int rc = 0;
+	struct ocfs2_live_connection *c;
+
+	c = kzalloc(sizeof(struct ocfs2_live_connection), GFP_KERNEL);
+	if (!c)
+		return -ENOMEM;
+
+	mutex_lock(&ocfs2_control_lock);
+	c->oc_conn = conn;
+
+	if (atomic_read(&ocfs2_control_opened))
+		list_add(&c->oc_list, &ocfs2_live_connection_list);
+	else {
+		printk(KERN_ERR
+		       "ocfs2: Userspace control daemon is not present\n");
+		rc = -ESRCH;
+	}
+
+	mutex_unlock(&ocfs2_control_lock);
+
+	if (!rc)
+		*c_ret = c;
+	else
+		kfree(c);
+
+	return rc;
+}
+
+/*
+ * This function disconnects the cluster connection from ocfs2_control.
+ * Afterwards, userspace can't affect the cluster connection.
+ */
+static void ocfs2_live_connection_drop(struct ocfs2_live_connection *c)
+{
+	mutex_lock(&ocfs2_control_lock);
+	list_del_init(&c->oc_list);
+	c->oc_conn = NULL;
+	mutex_unlock(&ocfs2_control_lock);
+
+	kfree(c);
+}
+
+static int ocfs2_control_cfu(void *target, size_t target_len,
+			     const char __user *buf, size_t count)
+{
+	/* The T01 expects write(2) calls to have exactly one command */
+	if ((count != target_len) ||
+	    (count > sizeof(union ocfs2_control_message)))
+		return -EINVAL;
+
+	if (copy_from_user(target, buf, target_len))
+		return -EFAULT;
+
+	return 0;
+}
+
+static ssize_t ocfs2_control_validate_protocol(struct file *file,
+					       const char __user *buf,
+					       size_t count)
+{
+	ssize_t ret;
+	char kbuf[OCFS2_CONTROL_PROTO_LEN];
+
+	ret = ocfs2_control_cfu(kbuf, OCFS2_CONTROL_PROTO_LEN,
+				buf, count);
+	if (ret)
+		return ret;
+
+	if (strncmp(kbuf, OCFS2_CONTROL_PROTO, OCFS2_CONTROL_PROTO_LEN))
+		return -EINVAL;
+
+	ocfs2_control_set_handshake_state(file,
+					  OCFS2_CONTROL_HANDSHAKE_PROTOCOL);
+
+	return count;
+}
+
+static void ocfs2_control_send_down(const char *uuid,
+				    int nodenum)
+{
+	struct ocfs2_live_connection *c;
+
+	mutex_lock(&ocfs2_control_lock);
+
+	c = ocfs2_connection_find(uuid);
+	if (c) {
+		BUG_ON(c->oc_conn == NULL);
+		c->oc_conn->cc_recovery_handler(nodenum,
+						c->oc_conn->cc_recovery_data);
+	}
+
+	mutex_unlock(&ocfs2_control_lock);
+}
+
+/*
+ * Called whenever configuration elements are sent to /dev/ocfs2_control.
+ * If all configuration elements are present, try to set the global
+ * values.  If there is a problem, return an error.  Skip any missing
+ * elements, and only bump ocfs2_control_opened when we have all elements
+ * and are successful.
+ */
+static int ocfs2_control_install_private(struct file *file)
+{
+	int rc = 0;
+	int set_p = 1;
+	struct ocfs2_control_private *p = file->private_data;
+
+	BUG_ON(p->op_state != OCFS2_CONTROL_HANDSHAKE_PROTOCOL);
+
+	mutex_lock(&ocfs2_control_lock);
+
+	if (p->op_this_node < 0) {
+		set_p = 0;
+	} else if ((ocfs2_control_this_node >= 0) &&
+		   (ocfs2_control_this_node != p->op_this_node)) {
+		rc = -EINVAL;
+		goto out_unlock;
+	}
+
+	if (!p->op_proto.pv_major) {
+		set_p = 0;
+	} else if (!list_empty(&ocfs2_live_connection_list) &&
+		   ((running_proto.pv_major != p->op_proto.pv_major) ||
+		    (running_proto.pv_minor != p->op_proto.pv_minor))) {
+		rc = -EINVAL;
+		goto out_unlock;
+	}
+
+	if (set_p) {
+		ocfs2_control_this_node = p->op_this_node;
+		running_proto.pv_major = p->op_proto.pv_major;
+		running_proto.pv_minor = p->op_proto.pv_minor;
+	}
+
+out_unlock:
+	mutex_unlock(&ocfs2_control_lock);
+
+	if (!rc && set_p) {
+		/* We set the global values successfully */
+		atomic_inc(&ocfs2_control_opened);
+		ocfs2_control_set_handshake_state(file,
+					OCFS2_CONTROL_HANDSHAKE_VALID);
+	}
+
+	return rc;
+}
+
+static int ocfs2_control_get_this_node(void)
+{
+	int rc;
+
+	mutex_lock(&ocfs2_control_lock);
+	if (ocfs2_control_this_node < 0)
+		rc = -EINVAL;
+	else
+		rc = ocfs2_control_this_node;
+	mutex_unlock(&ocfs2_control_lock);
+
+	return rc;
+}
+
+static int ocfs2_control_do_setnode_msg(struct file *file,
+					struct ocfs2_control_message_setn *msg)
+{
+	long nodenum;
+	char *ptr = NULL;
+	struct ocfs2_control_private *p = file->private_data;
+
+	if (ocfs2_control_get_handshake_state(file) !=
+	    OCFS2_CONTROL_HANDSHAKE_PROTOCOL)
+		return -EINVAL;
+
+	if (strncmp(msg->tag, OCFS2_CONTROL_MESSAGE_SETNODE_OP,
+		    OCFS2_CONTROL_MESSAGE_OP_LEN))
+		return -EINVAL;
+
+	if ((msg->space != ' ') || (msg->newline != '\n'))
+		return -EINVAL;
+	msg->space = msg->newline = '\0';
+
+	nodenum = simple_strtol(msg->nodestr, &ptr, 16);
+	if (!ptr || *ptr)
+		return -EINVAL;
+
+	if ((nodenum == LONG_MIN) || (nodenum == LONG_MAX) ||
+	    (nodenum > INT_MAX) || (nodenum < 0))
+		return -ERANGE;
+	p->op_this_node = nodenum;
+
+	return ocfs2_control_install_private(file);
+}
+
+static int ocfs2_control_do_setversion_msg(struct file *file,
+					   struct ocfs2_control_message_setv *msg)
+ {
+	long major, minor;
+	char *ptr = NULL;
+	struct ocfs2_control_private *p = file->private_data;
+	struct ocfs2_protocol_version *max =
+		&user_stack.sp_proto->lp_max_version;
+
+	if (ocfs2_control_get_handshake_state(file) !=
+	    OCFS2_CONTROL_HANDSHAKE_PROTOCOL)
+		return -EINVAL;
+
+	if (strncmp(msg->tag, OCFS2_CONTROL_MESSAGE_SETVERSION_OP,
+		    OCFS2_CONTROL_MESSAGE_OP_LEN))
+		return -EINVAL;
+
+	if ((msg->space1 != ' ') || (msg->space2 != ' ') ||
+	    (msg->newline != '\n'))
+		return -EINVAL;
+	msg->space1 = msg->space2 = msg->newline = '\0';
+
+	major = simple_strtol(msg->major, &ptr, 16);
+	if (!ptr || *ptr)
+		return -EINVAL;
+	minor = simple_strtol(msg->minor, &ptr, 16);
+	if (!ptr || *ptr)
+		return -EINVAL;
+
+	/*
+	 * The major must be between 1 and 255, inclusive.  The minor
+	 * must be between 0 and 255, inclusive.  The version passed in
+	 * must be within the maximum version supported by the filesystem.
+	 */
+	if ((major == LONG_MIN) || (major == LONG_MAX) ||
+	    (major > (u8)-1) || (major < 1))
+		return -ERANGE;
+	if ((minor == LONG_MIN) || (minor == LONG_MAX) ||
+	    (minor > (u8)-1) || (minor < 0))
+		return -ERANGE;
+	if ((major != max->pv_major) ||
+	    (minor > max->pv_minor))
+		return -EINVAL;
+
+	p->op_proto.pv_major = major;
+	p->op_proto.pv_minor = minor;
+
+	return ocfs2_control_install_private(file);
+}
+
+static int ocfs2_control_do_down_msg(struct file *file,
+				     struct ocfs2_control_message_down *msg)
+{
+	long nodenum;
+	char *p = NULL;
+
+	if (ocfs2_control_get_handshake_state(file) !=
+	    OCFS2_CONTROL_HANDSHAKE_VALID)
+		return -EINVAL;
+
+	if (strncmp(msg->tag, OCFS2_CONTROL_MESSAGE_DOWN_OP,
+		    OCFS2_CONTROL_MESSAGE_OP_LEN))
+		return -EINVAL;
+
+	if ((msg->space1 != ' ') || (msg->space2 != ' ') ||
+	    (msg->newline != '\n'))
+		return -EINVAL;
+	msg->space1 = msg->space2 = msg->newline = '\0';
+
+	nodenum = simple_strtol(msg->nodestr, &p, 16);
+	if (!p || *p)
+		return -EINVAL;
+
+	if ((nodenum == LONG_MIN) || (nodenum == LONG_MAX) ||
+	    (nodenum > INT_MAX) || (nodenum < 0))
+		return -ERANGE;
+
+	ocfs2_control_send_down(msg->uuid, nodenum);
+
+	return 0;
+}
+
+static ssize_t ocfs2_control_message(struct file *file,
+				     const char __user *buf,
+				     size_t count)
+{
+	ssize_t ret;
+	union ocfs2_control_message msg;
+
+	/* Try to catch padding issues */
+	WARN_ON(offsetof(struct ocfs2_control_message_down, uuid) !=
+		(sizeof(msg.u_down.tag) + sizeof(msg.u_down.space1)));
+
+	memset(&msg, 0, sizeof(union ocfs2_control_message));
+	ret = ocfs2_control_cfu(&msg, count, buf, count);
+	if (ret)
+		goto out;
+
+	if ((count == OCFS2_CONTROL_MESSAGE_SETNODE_TOTAL_LEN) &&
+	    !strncmp(msg.tag, OCFS2_CONTROL_MESSAGE_SETNODE_OP,
+		     OCFS2_CONTROL_MESSAGE_OP_LEN))
+		ret = ocfs2_control_do_setnode_msg(file, &msg.u_setn);
+	else if ((count == OCFS2_CONTROL_MESSAGE_SETVERSION_TOTAL_LEN) &&
+		 !strncmp(msg.tag, OCFS2_CONTROL_MESSAGE_SETVERSION_OP,
+			  OCFS2_CONTROL_MESSAGE_OP_LEN))
+		ret = ocfs2_control_do_setversion_msg(file, &msg.u_setv);
+	else if ((count == OCFS2_CONTROL_MESSAGE_DOWN_TOTAL_LEN) &&
+		 !strncmp(msg.tag, OCFS2_CONTROL_MESSAGE_DOWN_OP,
+			  OCFS2_CONTROL_MESSAGE_OP_LEN))
+		ret = ocfs2_control_do_down_msg(file, &msg.u_down);
+	else
+		ret = -EINVAL;
+
+out:
+	return ret ? ret : count;
+}
+
+static ssize_t ocfs2_control_write(struct file *file,
+				   const char __user *buf,
+				   size_t count,
+				   loff_t *ppos)
+{
+	ssize_t ret;
+
+	switch (ocfs2_control_get_handshake_state(file)) {
+		case OCFS2_CONTROL_HANDSHAKE_INVALID:
+			ret = -EINVAL;
+			break;
+
+		case OCFS2_CONTROL_HANDSHAKE_READ:
+			ret = ocfs2_control_validate_protocol(file, buf,
+							      count);
+			break;
+
+		case OCFS2_CONTROL_HANDSHAKE_PROTOCOL:
+		case OCFS2_CONTROL_HANDSHAKE_VALID:
+			ret = ocfs2_control_message(file, buf, count);
+			break;
+
+		default:
+			BUG();
+			ret = -EIO;
+			break;
+	}
+
+	return ret;
+}
+
+/*
+ * This is a naive version.  If we ever have a new protocol, we'll expand
+ * it.  Probably using seq_file.
+ */
+static ssize_t ocfs2_control_read(struct file *file,
+				  char __user *buf,
+				  size_t count,
+				  loff_t *ppos)
+{
+	char *proto_string = OCFS2_CONTROL_PROTO;
+	size_t to_write = 0;
+
+	if (*ppos >= OCFS2_CONTROL_PROTO_LEN)
+		return 0;
+
+	to_write = OCFS2_CONTROL_PROTO_LEN - *ppos;
+	if (to_write > count)
+		to_write = count;
+	if (copy_to_user(buf, proto_string + *ppos, to_write))
+		return -EFAULT;
+
+	*ppos += to_write;
+
+	/* Have we read the whole protocol list? */
+	if (*ppos >= OCFS2_CONTROL_PROTO_LEN)
+		ocfs2_control_set_handshake_state(file,
+						  OCFS2_CONTROL_HANDSHAKE_READ);
+
+	return to_write;
+}
+
+static int ocfs2_control_release(struct inode *inode, struct file *file)
+{
+	struct ocfs2_control_private *p = file->private_data;
+
+	mutex_lock(&ocfs2_control_lock);
+
+	if (ocfs2_control_get_handshake_state(file) !=
+	    OCFS2_CONTROL_HANDSHAKE_VALID)
+		goto out;
+
+	if (atomic_dec_and_test(&ocfs2_control_opened)) {
+		if (!list_empty(&ocfs2_live_connection_list)) {
+			/* XXX: Do bad things! */
+			printk(KERN_ERR
+			       "ocfs2: Unexpected release of ocfs2_control!\n"
+			       "       Loss of cluster connection requires "
+			       "an emergency restart!\n");
+			emergency_restart();
+		}
+		/*
+		 * Last valid close clears the node number and resets
+		 * the locking protocol version
+		 */
+		ocfs2_control_this_node = -1;
+		running_proto.pv_major = 0;
+		running_proto.pv_major = 0;
+	}
+
+out:
+	list_del_init(&p->op_list);
+	file->private_data = NULL;
+
+	mutex_unlock(&ocfs2_control_lock);
+
+	kfree(p);
+
+	return 0;
+}
+
+static int ocfs2_control_open(struct inode *inode, struct file *file)
+{
+	struct ocfs2_control_private *p;
+
+	p = kzalloc(sizeof(struct ocfs2_control_private), GFP_KERNEL);
+	if (!p)
+		return -ENOMEM;
+	p->op_this_node = -1;
+
+	mutex_lock(&ocfs2_control_lock);
+	file->private_data = p;
+	list_add(&p->op_list, &ocfs2_control_private_list);
+	mutex_unlock(&ocfs2_control_lock);
+
+	return 0;
+}
+
+static const struct file_operations ocfs2_control_fops = {
+	.open    = ocfs2_control_open,
+	.release = ocfs2_control_release,
+	.read    = ocfs2_control_read,
+	.write   = ocfs2_control_write,
+	.owner   = THIS_MODULE,
+};
+
+struct miscdevice ocfs2_control_device = {
+	.minor		= MISC_DYNAMIC_MINOR,
+	.name		= "ocfs2_control",
+	.fops		= &ocfs2_control_fops,
+};
+
+static int ocfs2_control_init(void)
+{
+	int rc;
+
+	atomic_set(&ocfs2_control_opened, 0);
+
+	rc = misc_register(&ocfs2_control_device);
+	if (rc)
+		printk(KERN_ERR
+		       "ocfs2: Unable to register ocfs2_control device "
+		       "(errno %d)\n",
+		       -rc);
+
+	return rc;
+}
+
+static void ocfs2_control_exit(void)
+{
+	int rc;
+
+	rc = misc_deregister(&ocfs2_control_device);
+	if (rc)
+		printk(KERN_ERR
+		       "ocfs2: Unable to deregister ocfs2_control device "
+		       "(errno %d)\n",
+		       -rc);
+}
+
+static struct dlm_lksb *fsdlm_astarg_to_lksb(void *astarg)
+{
+	struct ocfs2_lock_res *res = astarg;
+	return &res->l_lksb.lksb_fsdlm;
+}
+
+static void fsdlm_lock_ast_wrapper(void *astarg)
+{
+	struct dlm_lksb *lksb = fsdlm_astarg_to_lksb(astarg);
+	int status = lksb->sb_status;
+
+	BUG_ON(user_stack.sp_proto == NULL);
+
+	/*
+	 * For now we're punting on the issue of other non-standard errors
+	 * where we can't tell if the unlock_ast or lock_ast should be called.
+	 * The main "other error" that's possible is EINVAL which means the
+	 * function was called with invalid args, which shouldn't be possible
+	 * since the caller here is under our control.  Other non-standard
+	 * errors probably fall into the same category, or otherwise are fatal
+	 * which means we can't carry on anyway.
+	 */
+
+	if (status == -DLM_EUNLOCK || status == -DLM_ECANCEL)
+		user_stack.sp_proto->lp_unlock_ast(astarg, 0);
+	else
+		user_stack.sp_proto->lp_lock_ast(astarg);
+}
+
+static void fsdlm_blocking_ast_wrapper(void *astarg, int level)
+{
+	BUG_ON(user_stack.sp_proto == NULL);
+
+	user_stack.sp_proto->lp_blocking_ast(astarg, level);
+}
+
+static int user_dlm_lock(struct ocfs2_cluster_connection *conn,
+			 int mode,
+			 union ocfs2_dlm_lksb *lksb,
+			 u32 flags,
+			 void *name,
+			 unsigned int namelen,
+			 void *astarg)
+{
+	int ret;
+
+	if (!lksb->lksb_fsdlm.sb_lvbptr)
+		lksb->lksb_fsdlm.sb_lvbptr = (char *)lksb +
+					     sizeof(struct dlm_lksb);
+
+	ret = dlm_lock(conn->cc_lockspace, mode, &lksb->lksb_fsdlm,
+		       flags|DLM_LKF_NODLCKWT, name, namelen, 0,
+		       fsdlm_lock_ast_wrapper, astarg,
+		       fsdlm_blocking_ast_wrapper);
+	return ret;
+}
+
+static int user_dlm_unlock(struct ocfs2_cluster_connection *conn,
+			   union ocfs2_dlm_lksb *lksb,
+			   u32 flags,
+			   void *astarg)
+{
+	int ret;
+
+	ret = dlm_unlock(conn->cc_lockspace, lksb->lksb_fsdlm.sb_lkid,
+			 flags, &lksb->lksb_fsdlm, astarg);
+	return ret;
+}
+
+static int user_dlm_lock_status(union ocfs2_dlm_lksb *lksb)
+{
+	return lksb->lksb_fsdlm.sb_status;
+}
+
+static void *user_dlm_lvb(union ocfs2_dlm_lksb *lksb)
+{
+	return (void *)(lksb->lksb_fsdlm.sb_lvbptr);
+}
+
+static void user_dlm_dump_lksb(union ocfs2_dlm_lksb *lksb)
+{
+}
+
+/*
+ * Compare a requested locking protocol version against the current one.
+ *
+ * If the major numbers are different, they are incompatible.
+ * If the current minor is greater than the request, they are incompatible.
+ * If the current minor is less than or equal to the request, they are
+ * compatible, and the requester should run at the current minor version.
+ */
+static int fs_protocol_compare(struct ocfs2_protocol_version *existing,
+			       struct ocfs2_protocol_version *request)
+{
+	if (existing->pv_major != request->pv_major)
+		return 1;
+
+	if (existing->pv_minor > request->pv_minor)
+		return 1;
+
+	if (existing->pv_minor < request->pv_minor)
+		request->pv_minor = existing->pv_minor;
+
+	return 0;
+}
+
+static int user_cluster_connect(struct ocfs2_cluster_connection *conn)
+{
+	dlm_lockspace_t *fsdlm;
+	struct ocfs2_live_connection *control;
+	int rc = 0;
+
+	BUG_ON(conn == NULL);
+
+	rc = ocfs2_live_connection_new(conn, &control);
+	if (rc)
+		goto out;
+
+	/*
+	 * running_proto must have been set before we allowed any mounts
+	 * to proceed.
+	 */
+	if (fs_protocol_compare(&running_proto, &conn->cc_version)) {
+		printk(KERN_ERR
+		       "Unable to mount with fs locking protocol version "
+		       "%u.%u because the userspace control daemon has "
+		       "negotiated %u.%u\n",
+		       conn->cc_version.pv_major, conn->cc_version.pv_minor,
+		       running_proto.pv_major, running_proto.pv_minor);
+		rc = -EPROTO;
+		ocfs2_live_connection_drop(control);
+		goto out;
+	}
+
+	rc = dlm_new_lockspace(conn->cc_name, strlen(conn->cc_name),
+			       &fsdlm, DLM_LSFL_FS, DLM_LVB_LEN);
+	if (rc) {
+		ocfs2_live_connection_drop(control);
+		goto out;
+	}
+
+	conn->cc_private = control;
+	conn->cc_lockspace = fsdlm;
+out:
+	return rc;
+}
+
+static int user_cluster_disconnect(struct ocfs2_cluster_connection *conn,
+				   int hangup_pending)
+{
+	dlm_release_lockspace(conn->cc_lockspace, 2);
+	conn->cc_lockspace = NULL;
+	ocfs2_live_connection_drop(conn->cc_private);
+	conn->cc_private = NULL;
+	return 0;
+}
+
+static int user_cluster_this_node(unsigned int *this_node)
+{
+	int rc;
+
+	rc = ocfs2_control_get_this_node();
+	if (rc < 0)
+		return rc;
+
+	*this_node = rc;
+	return 0;
+}
+
+static struct ocfs2_stack_operations user_stack_ops = {
+	.connect	= user_cluster_connect,
+	.disconnect	= user_cluster_disconnect,
+	.this_node	= user_cluster_this_node,
+	.dlm_lock	= user_dlm_lock,
+	.dlm_unlock	= user_dlm_unlock,
+	.lock_status	= user_dlm_lock_status,
+	.lock_lvb	= user_dlm_lvb,
+	.dump_lksb	= user_dlm_dump_lksb,
+};
+
+static struct ocfs2_stack_plugin user_stack = {
+	.sp_name	= "user",
+	.sp_ops		= &user_stack_ops,
+	.sp_owner	= THIS_MODULE,
+};
+
+
+static int __init user_stack_init(void)
+{
+	int rc;
+
+	rc = ocfs2_control_init();
+	if (!rc) {
+		rc = ocfs2_stack_glue_register(&user_stack);
+		if (rc)
+			ocfs2_control_exit();
+	}
+
+	return rc;
+}
+
+static void __exit user_stack_exit(void)
+{
+	ocfs2_stack_glue_unregister(&user_stack);
+	ocfs2_control_exit();
+}
+
+MODULE_AUTHOR("Oracle");
+MODULE_DESCRIPTION("ocfs2 driver for userspace cluster stacks");
+MODULE_LICENSE("GPL");
+module_init(user_stack_init);
+module_exit(user_stack_exit);