/* -*- 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_protocol_version locking_max_version;

  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\"
  ",
  		       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
  ",

  		       plugin_name);

  	} else if (rc == -EBUSY) {
  		printk(KERN_ERR

  		       "ocfs2: A different cluster stack is in use
  ");

  	}
  
  	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_max_proto = locking_max_version;

  		list_add(&plugin->sp_list, &ocfs2_stack_list);
  		printk(KERN_INFO "ocfs2: Registered cluster interface %s
  ",
  		       plugin->sp_name);
  		rc = 0;
  	} else {
  		printk(KERN_ERR "ocfs2: Stack \"%s\" already registered
  ",
  		       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
  ",
  		       plugin->sp_name);
  	} else {
  		printk(KERN_ERR "Stack \"%s\" is not registered
  ",
  		       plugin->sp_name);
  	}
  	spin_unlock(&ocfs2_stack_lock);
  }
  EXPORT_SYMBOL_GPL(ocfs2_stack_glue_unregister);

  void ocfs2_stack_glue_set_max_proto_version(struct ocfs2_protocol_version *max_proto)

  {
  	struct ocfs2_stack_plugin *p;

  	spin_lock(&ocfs2_stack_lock);

  	if (memcmp(max_proto, &locking_max_version,
  		   sizeof(struct ocfs2_protocol_version))) {
  		BUG_ON(locking_max_version.pv_major != 0);

  		locking_max_version = *max_proto;
  		list_for_each_entry(p, &ocfs2_stack_list, sp_list) {
  			p->sp_max_proto = locking_max_version;
  		}

  	}

  	spin_unlock(&ocfs2_stack_lock);
  }

  EXPORT_SYMBOL_GPL(ocfs2_stack_glue_set_max_proto_version);

  /*

   * The ocfs2_dlm_lock() and ocfs2_dlm_unlock() functions take no argument
   * for the ast and bast functions.  They will pass the lksb to the ast
   * and bast.  The caller can wrap the lksb with their own structure to
   * get more information.

   */

  int ocfs2_dlm_lock(struct ocfs2_cluster_connection *conn,
  		   int mode,

  		   struct ocfs2_dlm_lksb *lksb,

  		   u32 flags,
  		   void *name,

  		   unsigned int namelen)

  {

  	if (!lksb->lksb_conn)
  		lksb->lksb_conn = conn;
  	else
  		BUG_ON(lksb->lksb_conn != conn);

  	return active_stack->sp_ops->dlm_lock(conn, mode, lksb, flags,

  					      name, namelen);

  }

  EXPORT_SYMBOL_GPL(ocfs2_dlm_lock);

  int ocfs2_dlm_unlock(struct ocfs2_cluster_connection *conn,

  		     struct ocfs2_dlm_lksb *lksb,

  		     u32 flags)

  {

  	BUG_ON(lksb->lksb_conn == NULL);

  	return active_stack->sp_ops->dlm_unlock(conn, lksb, flags);

  }

  EXPORT_SYMBOL_GPL(ocfs2_dlm_unlock);

  int ocfs2_dlm_lock_status(struct ocfs2_dlm_lksb *lksb)

  {

  	return active_stack->sp_ops->lock_status(lksb);

  }

  EXPORT_SYMBOL_GPL(ocfs2_dlm_lock_status);

  int ocfs2_dlm_lvb_valid(struct ocfs2_dlm_lksb *lksb)

  {
  	return active_stack->sp_ops->lvb_valid(lksb);
  }
  EXPORT_SYMBOL_GPL(ocfs2_dlm_lvb_valid);

  void *ocfs2_dlm_lvb(struct ocfs2_dlm_lksb *lksb)

  {

  	return active_stack->sp_ops->lock_lvb(lksb);

  }

  EXPORT_SYMBOL_GPL(ocfs2_dlm_lvb);

  void ocfs2_dlm_dump_lksb(struct 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,

  			  struct ocfs2_locking_protocol *lproto,

  			  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;
  	}

  	if (memcmp(&lproto->lp_max_version, &locking_max_version,
  		   sizeof(struct ocfs2_protocol_version))) {
  		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;

  	new_conn->cc_proto = lproto;

  	/* 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);

  /* The caller will ensure all nodes have the same cluster stack */
  int ocfs2_cluster_connect_agnostic(const char *group,
  				   int grouplen,
  				   struct ocfs2_locking_protocol *lproto,
  				   void (*recovery_handler)(int node_num,
  							    void *recovery_data),
  				   void *recovery_data,
  				   struct ocfs2_cluster_connection **conn)
  {
  	char *stack_name = NULL;
  
  	if (cluster_stack_name[0])
  		stack_name = cluster_stack_name;
  	return ocfs2_cluster_connect(stack_name, group, grouplen, lproto,
  				     recovery_handler, recovery_data, conn);
  }
  EXPORT_SYMBOL_GPL(ocfs2_cluster_connect_agnostic);

  /* 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\"
  ",
  		       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 (locking_max_version.pv_major)

  		ret = snprintf(buf, PAGE_SIZE, "%u.%u
  ",

  			       locking_max_version.pv_major,
  			       locking_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
  ",
  			       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
  ",
  			       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
  ", 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] == '
  ')
  		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[] = {
  	{

  		.procname	= "hb_ctl_path",
  		.data		= ocfs2_hb_ctl_path,
  		.maxlen		= OCFS2_MAX_HB_CTL_PATH,
  		.mode		= 0644,

  		.proc_handler	= proc_dostring,

  	},

  	{ }

  };
  
  static ctl_table ocfs2_mod_table[] = {
  	{

  		.procname	= "nm",
  		.data		= NULL,
  		.maxlen		= 0,
  		.mode		= 0555,
  		.child		= ocfs2_nm_table
  	},

  	{ }

  };
  
  static ctl_table ocfs2_kern_table[] = {
  	{

  		.procname	= "ocfs2",
  		.data		= NULL,
  		.maxlen		= 0,
  		.mode		= 0555,
  		.child		= ocfs2_mod_table
  	},

  	{ }

  };
  
  static ctl_table ocfs2_root_table[] = {
  	{

  		.procname	= "fs",
  		.data		= NULL,
  		.maxlen		= 0,
  		.mode		= 0555,
  		.child		= ocfs2_kern_table
  	},

  	{ }

  };
  
  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
  ");
  		return -ENOMEM; /* or something. */
  	}

  	return ocfs2_sysfs_init();

  }

  static void __exit ocfs2_stack_glue_exit(void)
  {

  	memset(&locking_max_version, 0,
  	       sizeof(struct ocfs2_protocol_version));
  	locking_max_version.pv_major = 0;
  	locking_max_version.pv_minor = 0;

  	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);