/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * stackglue.c
 *
 * Code which implements an OCFS2 specific interface to underlying
 * cluster stacks.
 *
 * Copyright (C) 2007, 2009 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/list.h>
#include <linux/spinlock.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/kmod.h>
#include <linux/fs.h>
#include <linux/kobject.h>
#include <linux/sysfs.h>
#include <linux/sysctl.h>

#include "ocfs2_fs.h"

#include "stackglue.h"

#define OCFS2_STACK_PLUGIN_O2CB         "o2cb"
#define OCFS2_STACK_PLUGIN_USER         "user"
#define OCFS2_MAX_HB_CTL_PATH           256

static struct ocfs2_locking_protocol *lproto;
static DEFINE_SPINLOCK(ocfs2_stack_lock);
static LIST_HEAD(ocfs2_stack_list);
static char cluster_stack_name[OCFS2_STACK_LABEL_LEN + 1];
static char ocfs2_hb_ctl_path[OCFS2_MAX_HB_CTL_PATH] = "/sbin/ocfs2_hb_ctl";

/*
 * The stack currently in use.  If not null, active_stack->sp_count > 0,
 * the module is pinned, and the locking protocol cannot be changed.
 */
static struct ocfs2_stack_plugin *active_stack;

static struct ocfs2_stack_plugin *ocfs2_stack_lookup(const char *name)
{
        struct ocfs2_stack_plugin *p;

        assert_spin_locked(&ocfs2_stack_lock);

        list_for_each_entry(p, &ocfs2_stack_list, sp_list) {
                if (!strcmp(p->sp_name, name))
                        return p;
        }

        return NULL;
}

static int ocfs2_stack_driver_request(const char *stack_name,
                                      const char *plugin_name)
{
        int rc;
        struct ocfs2_stack_plugin *p;

        spin_lock(&ocfs2_stack_lock);

        /*
         * If the stack passed by the filesystem isn't the selected one,
         * we can't continue.
         */
        if (strcmp(stack_name, cluster_stack_name)) {
                rc = -EBUSY;
                goto out;
        }

        if (active_stack) {
                /*
                 * If the active stack isn't the one we want, it cannot
                 * be selected right now.
                 */
                if (!strcmp(active_stack->sp_name, plugin_name))
                        rc = 0;
                else
                        rc = -EBUSY;
                goto out;
        }

        p = ocfs2_stack_lookup(plugin_name);
        if (!p || !try_module_get(p->sp_owner)) {
                rc = -ENOENT;
                goto out;
        }

        active_stack = p;
        rc = 0;

out:
        /* If we found it, pin it */
        if (!rc)
                active_stack->sp_count++;

        spin_unlock(&ocfs2_stack_lock);
        return rc;
}

/*
 * This function looks up the appropriate stack and makes it active.  If
 * there is no stack, it tries to load it.  It will fail if the stack still
 * cannot be found.  It will also fail if a different stack is in use.
 */
static int ocfs2_stack_driver_get(const char *stack_name)
{
        int rc;
        char *plugin_name = OCFS2_STACK_PLUGIN_O2CB;

        /*
         * Classic stack does not pass in a stack name.  This is
         * compatible with older tools as well.
         */
        if (!stack_name || !*stack_name)
                stack_name = OCFS2_STACK_PLUGIN_O2CB;

        if (strlen(stack_name) != OCFS2_STACK_LABEL_LEN) {
                printk(KERN_ERR
                       "ocfs2 passed an invalid cluster stack label: \"%s\"\n",
                       stack_name);
                return -EINVAL;
        }

        /* Anything that isn't the classic stack is a user stack */
        if (strcmp(stack_name, OCFS2_STACK_PLUGIN_O2CB))
                plugin_name = OCFS2_STACK_PLUGIN_USER;

        rc = ocfs2_stack_driver_request(stack_name, plugin_name);
        if (rc == -ENOENT) {
                request_module("ocfs2_stack_%s", plugin_name);
                rc = ocfs2_stack_driver_request(stack_name, plugin_name);
        }

        if (rc == -ENOENT) {
                printk(KERN_ERR
                       "ocfs2: Cluster stack driver \"%s\" cannot be found\n",
                       plugin_name);
        } else if (rc == -EBUSY) {
                printk(KERN_ERR
                       "ocfs2: A different cluster stack is in use\n");
        }

        return rc;
}

static void ocfs2_stack_driver_put(void)
{
        spin_lock(&ocfs2_stack_lock);
        BUG_ON(active_stack == NULL);
        BUG_ON(active_stack->sp_count == 0);

        active_stack->sp_count--;
        if (!active_stack->sp_count) {
                module_put(active_stack->sp_owner);
                active_stack = NULL;
        }
        spin_unlock(&ocfs2_stack_lock);
}

int ocfs2_stack_glue_register(struct ocfs2_stack_plugin *plugin)
{
        int rc;

        spin_lock(&ocfs2_stack_lock);
        if (!ocfs2_stack_lookup(plugin->sp_name)) {
                plugin->sp_count = 0;
                plugin->sp_proto = lproto;
                list_add(&plugin->sp_list, &ocfs2_stack_list);
                printk(KERN_INFO "ocfs2: Registered cluster interface %s\n",
                       plugin->sp_name);
                rc = 0;
        } else {
                printk(KERN_ERR "ocfs2: Stack \"%s\" already registered\n",
                       plugin->sp_name);
                rc = -EEXIST;
        }
        spin_unlock(&ocfs2_stack_lock);

        return rc;
}
EXPORT_SYMBOL_GPL(ocfs2_stack_glue_register);

void ocfs2_stack_glue_unregister(struct ocfs2_stack_plugin *plugin)
{
        struct ocfs2_stack_plugin *p;

        spin_lock(&ocfs2_stack_lock);
        p = ocfs2_stack_lookup(plugin->sp_name);
        if (p) {
                BUG_ON(p != plugin);
                BUG_ON(plugin == active_stack);
                BUG_ON(plugin->sp_count != 0);
                list_del_init(&plugin->sp_list);
                printk(KERN_INFO "ocfs2: Unregistered cluster interface %s\n",
                       plugin->sp_name);
        } else {
                printk(KERN_ERR "Stack \"%s\" is not registered\n",
                       plugin->sp_name);
        }
        spin_unlock(&ocfs2_stack_lock);
}
EXPORT_SYMBOL_GPL(ocfs2_stack_glue_unregister);

void ocfs2_stack_glue_set_locking_protocol(struct ocfs2_locking_protocol *proto)
{
        struct ocfs2_stack_plugin *p;

        BUG_ON(proto == NULL);

        spin_lock(&ocfs2_stack_lock);
        BUG_ON(active_stack != NULL);

        lproto = proto;
        list_for_each_entry(p, &ocfs2_stack_list, sp_list) {
                p->sp_proto = lproto;
        }

        spin_unlock(&ocfs2_stack_lock);
}
EXPORT_SYMBOL_GPL(ocfs2_stack_glue_set_locking_protocol);


/*
 * The ocfs2_dlm_lock() and ocfs2_dlm_unlock() functions take
 * "struct ocfs2_lock_res *astarg" instead of "void *astarg" because the
 * underlying stack plugins need to pilfer the lksb off of the lock_res.
 * If some other structure needs to be passed as an astarg, the plugins
 * will need to be given a different avenue to the lksb.
 */
int ocfs2_dlm_lock(struct ocfs2_cluster_connection *conn,
                   int mode,
                   union ocfs2_dlm_lksb *lksb,
                   u32 flags,
                   void *name,
                   unsigned int namelen,
                   struct ocfs2_lock_res *astarg)
{
        BUG_ON(lproto == NULL);

        return active_stack->sp_ops->dlm_lock(conn, mode, lksb, flags,
                                              name, namelen, astarg);
}
EXPORT_SYMBOL_GPL(ocfs2_dlm_lock);

int ocfs2_dlm_unlock(struct ocfs2_cluster_connection *conn,
                     union ocfs2_dlm_lksb *lksb,
                     u32 flags,
                     struct ocfs2_lock_res *astarg)
{
        BUG_ON(lproto == NULL);

        return active_stack->sp_ops->dlm_unlock(conn, lksb, flags, astarg);
}
EXPORT_SYMBOL_GPL(ocfs2_dlm_unlock);

int ocfs2_dlm_lock_status(union ocfs2_dlm_lksb *lksb)
{
        return active_stack->sp_ops->lock_status(lksb);
}
EXPORT_SYMBOL_GPL(ocfs2_dlm_lock_status);

int ocfs2_dlm_lvb_valid(union ocfs2_dlm_lksb *lksb)
{
        return active_stack->sp_ops->lvb_valid(lksb);
}
EXPORT_SYMBOL_GPL(ocfs2_dlm_lvb_valid);

void *ocfs2_dlm_lvb(union ocfs2_dlm_lksb *lksb)
{
        return active_stack->sp_ops->lock_lvb(lksb);
}
EXPORT_SYMBOL_GPL(ocfs2_dlm_lvb);

void ocfs2_dlm_dump_lksb(union ocfs2_dlm_lksb *lksb)
{
        active_stack->sp_ops->dump_lksb(lksb);
}
EXPORT_SYMBOL_GPL(ocfs2_dlm_dump_lksb);

int ocfs2_stack_supports_plocks(void)
{
        return active_stack && active_stack->sp_ops->plock;
}
EXPORT_SYMBOL_GPL(ocfs2_stack_supports_plocks);

/*
 * ocfs2_plock() can only be safely called if
 * ocfs2_stack_supports_plocks() returned true
 */
int ocfs2_plock(struct ocfs2_cluster_connection *conn, u64 ino,
                struct file *file, int cmd, struct file_lock *fl)
{
        WARN_ON_ONCE(active_stack->sp_ops->plock == NULL);
        if (active_stack->sp_ops->plock)
                return active_stack->sp_ops->plock(conn, ino, file, cmd, fl);
        return -EOPNOTSUPP;
}
EXPORT_SYMBOL_GPL(ocfs2_plock);

int ocfs2_cluster_connect(const char *stack_name,
                          const char *group,
                          int grouplen,
                          void (*recovery_handler)(int node_num,
                                                   void *recovery_data),
                          void *recovery_data,
                          struct ocfs2_cluster_connection **conn)
{
        int rc = 0;
        struct ocfs2_cluster_connection *new_conn;

        BUG_ON(group == NULL);
        BUG_ON(conn == NULL);
        BUG_ON(recovery_handler == NULL);

        if (grouplen > GROUP_NAME_MAX) {
                rc = -EINVAL;
                goto out;
        }

        new_conn = kzalloc(sizeof(struct ocfs2_cluster_connection),
                           GFP_KERNEL);
        if (!new_conn) {
                rc = -ENOMEM;
                goto out;
        }

        memcpy(new_conn->cc_name, group, grouplen);
        new_conn->cc_namelen = grouplen;
        new_conn->cc_recovery_handler = recovery_handler;
        new_conn->cc_recovery_data = recovery_data;

        /* Start the new connection at our maximum compatibility level */
        new_conn->cc_version = lproto->lp_max_version;

        /* This will pin the stack driver if successful */
        rc = ocfs2_stack_driver_get(stack_name);
        if (rc)
                goto out_free;

        rc = active_stack->sp_ops->connect(new_conn);
        if (rc) {
                ocfs2_stack_driver_put();
                goto out_free;
        }

        *conn = new_conn;

out_free:
        if (rc)
                kfree(new_conn);

out:
        return rc;
}
EXPORT_SYMBOL_GPL(ocfs2_cluster_connect);

/* If hangup_pending is 0, the stack driver will be dropped */
int ocfs2_cluster_disconnect(struct ocfs2_cluster_connection *conn,
                             int hangup_pending)
{
        int ret;

        BUG_ON(conn == NULL);

        ret = active_stack->sp_ops->disconnect(conn);

        /* XXX Should we free it anyway? */
        if (!ret) {
                kfree(conn);
                if (!hangup_pending)
                        ocfs2_stack_driver_put();
        }

        return ret;
}
EXPORT_SYMBOL_GPL(ocfs2_cluster_disconnect);

/*
 * Leave the group for this filesystem.  This is executed by a userspace
 * program (stored in ocfs2_hb_ctl_path).
 */
static void ocfs2_leave_group(const char *group)
{
        int ret;
        char *argv[5], *envp[3];

        argv[0] = ocfs2_hb_ctl_path;
        argv[1] = "-K";
        argv[2] = "-u";
        argv[3] = (char *)group;
        argv[4] = NULL;

        /* minimal command environment taken from cpu_run_sbin_hotplug */
        envp[0] = "HOME=/";
        envp[1] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
        envp[2] = NULL;

        ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_PROC);
        if (ret < 0) {
                printk(KERN_ERR
                       "ocfs2: Error %d running user helper "
                       "\"%s %s %s %s\"\n",
                       ret, argv[0], argv[1], argv[2], argv[3]);
        }
}

/*
 * Hangup is a required post-umount.  ocfs2-tools software expects the
 * filesystem to call "ocfs2_hb_ctl" during unmount.  This happens
 * regardless of whether the DLM got started, so we can't do it
 * in ocfs2_cluster_disconnect().  The ocfs2_leave_group() function does
 * the actual work.
 */
void ocfs2_cluster_hangup(const char *group, int grouplen)
{
        BUG_ON(group == NULL);
        BUG_ON(group[grouplen] != '\0');

        ocfs2_leave_group(group);

        /* cluster_disconnect() was called with hangup_pending==1 */
        ocfs2_stack_driver_put();
}
EXPORT_SYMBOL_GPL(ocfs2_cluster_hangup);

int ocfs2_cluster_this_node(unsigned int *node)
{
        return active_stack->sp_ops->this_node(node);
}
EXPORT_SYMBOL_GPL(ocfs2_cluster_this_node);


/*
 * Sysfs bits
 */

static ssize_t ocfs2_max_locking_protocol_show(struct kobject *kobj,
                                               struct kobj_attribute *attr,
                                               char *buf)
{
        ssize_t ret = 0;

        spin_lock(&ocfs2_stack_lock);
        if (lproto)
                ret = snprintf(buf, PAGE_SIZE, "%u.%u\n",
                               lproto->lp_max_version.pv_major,
                               lproto->lp_max_version.pv_minor);
        spin_unlock(&ocfs2_stack_lock);

        return ret;
}

static struct kobj_attribute ocfs2_attr_max_locking_protocol =
        __ATTR(max_locking_protocol, S_IFREG | S_IRUGO,
               ocfs2_max_locking_protocol_show, NULL);

static ssize_t ocfs2_loaded_cluster_plugins_show(struct kobject *kobj,
                                                 struct kobj_attribute *attr,
                                                 char *buf)
{
        ssize_t ret = 0, total = 0, remain = PAGE_SIZE;
        struct ocfs2_stack_plugin *p;

        spin_lock(&ocfs2_stack_lock);
        list_for_each_entry(p, &ocfs2_stack_list, sp_list) {
                ret = snprintf(buf, remain, "%s\n",
                               p->sp_name);
                if (ret < 0) {
                        total = ret;
                        break;
                }
                if (ret == remain) {
                        /* snprintf() didn't fit */
                        total = -E2BIG;
                        break;
                }
                total += ret;
                remain -= ret;
        }
        spin_unlock(&ocfs2_stack_lock);

        return total;
}

static struct kobj_attribute ocfs2_attr_loaded_cluster_plugins =
        __ATTR(loaded_cluster_plugins, S_IFREG | S_IRUGO,
               ocfs2_loaded_cluster_plugins_show, NULL);

static ssize_t ocfs2_active_cluster_plugin_show(struct kobject *kobj,
                                                struct kobj_attribute *attr,
                                                char *buf)
{
        ssize_t ret = 0;

        spin_lock(&ocfs2_stack_lock);
        if (active_stack) {
                ret = snprintf(buf, PAGE_SIZE, "%s\n",
                               active_stack->sp_name);
                if (ret == PAGE_SIZE)
                        ret = -E2BIG;
        }
        spin_unlock(&ocfs2_stack_lock);

        return ret;
}

static struct kobj_attribute ocfs2_attr_active_cluster_plugin =
        __ATTR(active_cluster_plugin, S_IFREG | S_IRUGO,
               ocfs2_active_cluster_plugin_show, NULL);

static ssize_t ocfs2_cluster_stack_show(struct kobject *kobj,
                                        struct kobj_attribute *attr,
                                        char *buf)
{
        ssize_t ret;
        spin_lock(&ocfs2_stack_lock);
        ret = snprintf(buf, PAGE_SIZE, "%s\n", cluster_stack_name);
        spin_unlock(&ocfs2_stack_lock);

        return ret;
}

static ssize_t ocfs2_cluster_stack_store(struct kobject *kobj,
                                         struct kobj_attribute *attr,
                                         const char *buf, size_t count)
{
        size_t len = count;
        ssize_t ret;

        if (len == 0)
                return len;

        if (buf[len - 1] == '\n')
                len--;

        if ((len != OCFS2_STACK_LABEL_LEN) ||
            (strnlen(buf, len) != len))
                return -EINVAL;

        spin_lock(&ocfs2_stack_lock);
        if (active_stack) {
                if (!strncmp(buf, cluster_stack_name, len))
                        ret = count;
                else
                        ret = -EBUSY;
        } else {
                memcpy(cluster_stack_name, buf, len);
                ret = count;
        }
        spin_unlock(&ocfs2_stack_lock);

        return ret;
}


static struct kobj_attribute ocfs2_attr_cluster_stack =
        __ATTR(cluster_stack, S_IFREG | S_IRUGO | S_IWUSR,
               ocfs2_cluster_stack_show,
               ocfs2_cluster_stack_store);

static struct attribute *ocfs2_attrs[] = {
        &ocfs2_attr_max_locking_protocol.attr,
        &ocfs2_attr_loaded_cluster_plugins.attr,
        &ocfs2_attr_active_cluster_plugin.attr,
        &ocfs2_attr_cluster_stack.attr,
        NULL,
};

static struct attribute_group ocfs2_attr_group = {
        .attrs = ocfs2_attrs,
};

static struct kset *ocfs2_kset;

static void ocfs2_sysfs_exit(void)
{
        kset_unregister(ocfs2_kset);
}

static int ocfs2_sysfs_init(void)
{
        int ret;

        ocfs2_kset = kset_create_and_add("ocfs2", NULL, fs_kobj);
        if (!ocfs2_kset)
                return -ENOMEM;

        ret = sysfs_create_group(&ocfs2_kset->kobj, &ocfs2_attr_group);
        if (ret)
                goto error;

        return 0;

error:
        kset_unregister(ocfs2_kset);
        return ret;
}

/*
 * Sysctl bits
 *
 * The sysctl lives at /proc/sys/fs/ocfs2/nm/hb_ctl_path.  The 'nm' doesn't
 * make as much sense in a multiple cluster stack world, but it's safer
 * and easier to preserve the name.
 */

#define FS_OCFS2_NM             1

static ctl_table ocfs2_nm_table[] = {
        {
                .ctl_name       = 1,
                .procname       = "hb_ctl_path",
                .data           = ocfs2_hb_ctl_path,
                .maxlen         = OCFS2_MAX_HB_CTL_PATH,
                .mode           = 0644,
                .proc_handler   = &proc_dostring,
                .strategy       = &sysctl_string,
        },
        { .ctl_name = 0 }
};

static ctl_table ocfs2_mod_table[] = {
        {
                .ctl_name       = FS_OCFS2_NM,
                .procname       = "nm",
                .data           = NULL,
                .maxlen         = 0,
                .mode           = 0555,
                .child          = ocfs2_nm_table
        },
        { .ctl_name = 0}
};

static ctl_table ocfs2_kern_table[] = {
        {
                .ctl_name       = FS_OCFS2,
                .procname       = "ocfs2",
                .data           = NULL,
                .maxlen         = 0,
                .mode           = 0555,
                .child          = ocfs2_mod_table
        },
        { .ctl_name = 0}
};

static ctl_table ocfs2_root_table[] = {
        {
                .ctl_name       = CTL_FS,
                .procname       = "fs",
                .data           = NULL,
                .maxlen         = 0,
                .mode           = 0555,
                .child          = ocfs2_kern_table
        },
        { .ctl_name = 0 }
};

static struct ctl_table_header *ocfs2_table_header = NULL;


/*
 * Initialization
 */

static int __init ocfs2_stack_glue_init(void)
{
        strcpy(cluster_stack_name, OCFS2_STACK_PLUGIN_O2CB);

        ocfs2_table_header = register_sysctl_table(ocfs2_root_table);
        if (!ocfs2_table_header) {
                printk(KERN_ERR
                       "ocfs2 stack glue: unable to register sysctl\n");
                return -ENOMEM; /* or something. */
        }

        return ocfs2_sysfs_init();
}

static void __exit ocfs2_stack_glue_exit(void)
{
        lproto = NULL;
        ocfs2_sysfs_exit();
        if (ocfs2_table_header)
                unregister_sysctl_table(ocfs2_table_header);
}

MODULE_AUTHOR("Oracle");
MODULE_DESCRIPTION("ocfs2 cluter stack glue layer");
MODULE_LICENSE("GPL");
module_init(ocfs2_stack_glue_init);
module_exit(ocfs2_stack_glue_exit);