stackglue.c

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/* -*- 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\"\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_max_proto = locking_max_version;
        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_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\"\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 (locking_max_version.pv_major)
        ret = snprintf(buf, PAGE_SIZE, "%u.%u\n",
                   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\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[] = {
    {
        .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\n");
        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);