Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/nab/target...

[linux-btrfs-devel.git] / fs / ocfs2 / stack_user.c

/* -*- 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/slab.h>
#include <linux/reboot.h>
#include <asm/uaccess.h>

#include "stackglue.h"

#include <linux/dlm_plock.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
 * ocfs2_user_plugin.sp_max_proto.pv_major, and the minor number
 * must be less than or equal to ...sp_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 ocfs2_user_plugin;

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 NULL;
}

/*
 * 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 =
                &ocfs2_user_plugin.sp_max_proto;

        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)
{
        ssize_t ret;

        ret = simple_read_from_buffer(buf, count, ppos,
                        OCFS2_CONTROL_PROTO, OCFS2_CONTROL_PROTO_LEN);

        /* Have we read the whole protocol list? */
        if (ret > 0 && *ppos >= OCFS2_CONTROL_PROTO_LEN)
                ocfs2_control_set_handshake_state(file,
                                                  OCFS2_CONTROL_HANDSHAKE_READ);

        return ret;
}

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,
        .llseek  = default_llseek,
};

static 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 void fsdlm_lock_ast_wrapper(void *astarg)
{
        struct ocfs2_dlm_lksb *lksb = astarg;
        int status = lksb->lksb_fsdlm.sb_status;

        /*
         * 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)
                lksb->lksb_conn->cc_proto->lp_unlock_ast(lksb, 0);
        else
                lksb->lksb_conn->cc_proto->lp_lock_ast(lksb);
}

static void fsdlm_blocking_ast_wrapper(void *astarg, int level)
{
        struct ocfs2_dlm_lksb *lksb = astarg;

        lksb->lksb_conn->cc_proto->lp_blocking_ast(lksb, level);
}

static int user_dlm_lock(struct ocfs2_cluster_connection *conn,
                         int mode,
                         struct ocfs2_dlm_lksb *lksb,
                         u32 flags,
                         void *name,
                         unsigned int namelen)
{
        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, lksb,
                       fsdlm_blocking_ast_wrapper);
        return ret;
}

static int user_dlm_unlock(struct ocfs2_cluster_connection *conn,
                           struct ocfs2_dlm_lksb *lksb,
                           u32 flags)
{
        int ret;

        ret = dlm_unlock(conn->cc_lockspace, lksb->lksb_fsdlm.sb_lkid,
                         flags, &lksb->lksb_fsdlm, lksb);
        return ret;
}

static int user_dlm_lock_status(struct ocfs2_dlm_lksb *lksb)
{
        return lksb->lksb_fsdlm.sb_status;
}

static int user_dlm_lvb_valid(struct ocfs2_dlm_lksb *lksb)
{
        int invalid = lksb->lksb_fsdlm.sb_flags & DLM_SBF_VALNOTVALID;

        return !invalid;
}

static void *user_dlm_lvb(struct ocfs2_dlm_lksb *lksb)
{
        if (!lksb->lksb_fsdlm.sb_lvbptr)
                lksb->lksb_fsdlm.sb_lvbptr = (char *)lksb +
                                             sizeof(struct dlm_lksb);
        return (void *)(lksb->lksb_fsdlm.sb_lvbptr);
}

static void user_dlm_dump_lksb(struct ocfs2_dlm_lksb *lksb)
{
}

static int user_plock(struct ocfs2_cluster_connection *conn,
                      u64 ino,
                      struct file *file,
                      int cmd,
                      struct file_lock *fl)
{
        /*
         * This more or less just demuxes the plock request into any
         * one of three dlm calls.
         *
         * Internally, fs/dlm will pass these to a misc device, which
         * a userspace daemon will read and write to.
         *
         * For now, cancel requests (which happen internally only),
         * are turned into unlocks. Most of this function taken from
         * gfs2_lock.
         */

        if (cmd == F_CANCELLK) {
                cmd = F_SETLK;
                fl->fl_type = F_UNLCK;
        }

        if (IS_GETLK(cmd))
                return dlm_posix_get(conn->cc_lockspace, ino, file, fl);
        else if (fl->fl_type == F_UNLCK)
                return dlm_posix_unlock(conn->cc_lockspace, ino, file, fl);
        else
                return dlm_posix_lock(conn->cc_lockspace, ino, file, cmd, fl);
}

/*
 * 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 *uninitialized_var(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)
{
        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 ocfs2_user_plugin_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,
        .lvb_valid      = user_dlm_lvb_valid,
        .lock_lvb       = user_dlm_lvb,
        .plock          = user_plock,
        .dump_lksb      = user_dlm_dump_lksb,
};

static struct ocfs2_stack_plugin ocfs2_user_plugin = {
        .sp_name        = "user",
        .sp_ops         = &ocfs2_user_plugin_ops,
        .sp_owner       = THIS_MODULE,
};


static int __init ocfs2_user_plugin_init(void)
{
        int rc;

        rc = ocfs2_control_init();
        if (!rc) {
                rc = ocfs2_stack_glue_register(&ocfs2_user_plugin);
                if (rc)
                        ocfs2_control_exit();
        }

        return rc;
}

static void __exit ocfs2_user_plugin_exit(void)
{
        ocfs2_stack_glue_unregister(&ocfs2_user_plugin);
        ocfs2_control_exit();
}

MODULE_AUTHOR("Oracle");
MODULE_DESCRIPTION("ocfs2 driver for userspace cluster stacks");
MODULE_LICENSE("GPL");
module_init(ocfs2_user_plugin_init);
module_exit(ocfs2_user_plugin_exit);