heartbeat.c

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/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * Copyright (C) 2004, 2005 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; either
 * version 2 of the License, or (at your option) any later version.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/jiffies.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/delay.h>
#include <linux/file.h>
#include <linux/kthread.h>
#include <linux/configfs.h>
#include <linux/random.h>
#include <linux/crc32.h>
#include <linux/time.h>
#include <linux/debugfs.h>
#include <linux/slab.h>

#include "heartbeat.h"
#include "tcp.h"
#include "nodemanager.h"
#include "quorum.h"

#include "masklog.h"


/*
 * The first heartbeat pass had one global thread that would serialize all hb
 * callback calls.  This global serializing sem should only be removed once
 * we've made sure that all callees can deal with being called concurrently
 * from multiple hb region threads.
 */
static DECLARE_RWSEM(o2hb_callback_sem);

/*
 * multiple hb threads are watching multiple regions.  A node is live
 * whenever any of the threads sees activity from the node in its region.
 */
static DEFINE_SPINLOCK(o2hb_live_lock);
static struct list_head o2hb_live_slots[O2NM_MAX_NODES];
static unsigned long o2hb_live_node_bitmap[BITS_TO_LONGS(O2NM_MAX_NODES)];
static LIST_HEAD(o2hb_node_events);
static DECLARE_WAIT_QUEUE_HEAD(o2hb_steady_queue);

/*
 * In global heartbeat, we maintain a series of region bitmaps.
 *  - o2hb_region_bitmap allows us to limit the region number to max region.
 *  - o2hb_live_region_bitmap tracks live regions (seen steady iterations).
 *  - o2hb_quorum_region_bitmap tracks live regions that have seen all nodes
 *      heartbeat on it.
 *  - o2hb_failed_region_bitmap tracks the regions that have seen io timeouts.
 */
static unsigned long o2hb_region_bitmap[BITS_TO_LONGS(O2NM_MAX_REGIONS)];
static unsigned long o2hb_live_region_bitmap[BITS_TO_LONGS(O2NM_MAX_REGIONS)];
static unsigned long o2hb_quorum_region_bitmap[BITS_TO_LONGS(O2NM_MAX_REGIONS)];
static unsigned long o2hb_failed_region_bitmap[BITS_TO_LONGS(O2NM_MAX_REGIONS)];

#define O2HB_DB_TYPE_LIVENODES      0
#define O2HB_DB_TYPE_LIVEREGIONS    1
#define O2HB_DB_TYPE_QUORUMREGIONS  2
#define O2HB_DB_TYPE_FAILEDREGIONS  3
#define O2HB_DB_TYPE_REGION_LIVENODES   4
#define O2HB_DB_TYPE_REGION_NUMBER  5
#define O2HB_DB_TYPE_REGION_ELAPSED_TIME    6
#define O2HB_DB_TYPE_REGION_PINNED  7
struct o2hb_debug_buf {
    int db_type;
    int db_size;
    int db_len;
    void *db_data;
};

static struct o2hb_debug_buf *o2hb_db_livenodes;
static struct o2hb_debug_buf *o2hb_db_liveregions;
static struct o2hb_debug_buf *o2hb_db_quorumregions;
static struct o2hb_debug_buf *o2hb_db_failedregions;

#define O2HB_DEBUG_DIR          "o2hb"
#define O2HB_DEBUG_LIVENODES        "livenodes"
#define O2HB_DEBUG_LIVEREGIONS      "live_regions"
#define O2HB_DEBUG_QUORUMREGIONS    "quorum_regions"
#define O2HB_DEBUG_FAILEDREGIONS    "failed_regions"
#define O2HB_DEBUG_REGION_NUMBER    "num"
#define O2HB_DEBUG_REGION_ELAPSED_TIME  "elapsed_time_in_ms"
#define O2HB_DEBUG_REGION_PINNED    "pinned"

static struct dentry *o2hb_debug_dir;
static struct dentry *o2hb_debug_livenodes;
static struct dentry *o2hb_debug_liveregions;
static struct dentry *o2hb_debug_quorumregions;
static struct dentry *o2hb_debug_failedregions;

static LIST_HEAD(o2hb_all_regions);

static struct o2hb_callback {
    struct list_head list;
} o2hb_callbacks[O2HB_NUM_CB];

static struct o2hb_callback *hbcall_from_type(enum o2hb_callback_type type);

#define O2HB_DEFAULT_BLOCK_BITS       9

enum o2hb_heartbeat_modes {
    O2HB_HEARTBEAT_LOCAL        = 0,
    O2HB_HEARTBEAT_GLOBAL,
    O2HB_HEARTBEAT_NUM_MODES,
};

char *o2hb_heartbeat_mode_desc[O2HB_HEARTBEAT_NUM_MODES] = {
        "local",    /* O2HB_HEARTBEAT_LOCAL */
        "global",   /* O2HB_HEARTBEAT_GLOBAL */
};

unsigned int o2hb_dead_threshold = O2HB_DEFAULT_DEAD_THRESHOLD;
unsigned int o2hb_heartbeat_mode = O2HB_HEARTBEAT_LOCAL;

/*
 * o2hb_dependent_users tracks the number of registered callbacks that depend
 * on heartbeat. o2net and o2dlm are two entities that register this callback.
 * However only o2dlm depends on the heartbeat. It does not want the heartbeat
 * to stop while a dlm domain is still active.
 */
unsigned int o2hb_dependent_users;

/*
 * In global heartbeat mode, all regions are pinned if there are one or more
 * dependent users and the quorum region count is <= O2HB_PIN_CUT_OFF. All
 * regions are unpinned if the region count exceeds the cut off or the number
 * of dependent users falls to zero.
 */
#define O2HB_PIN_CUT_OFF        3

/*
 * In local heartbeat mode, we assume the dlm domain name to be the same as
 * region uuid. This is true for domains created for the file system but not
 * necessarily true for userdlm domains. This is a known limitation.
 *
 * In global heartbeat mode, we pin/unpin all o2hb regions. This solution
 * works for both file system and userdlm domains.
 */
static int o2hb_region_pin(const char *region_uuid);
static void o2hb_region_unpin(const char *region_uuid);

/* Only sets a new threshold if there are no active regions.
 *
 * No locking or otherwise interesting code is required for reading
 * o2hb_dead_threshold as it can't change once regions are active and
 * it's not interesting to anyone until then anyway. */
static void o2hb_dead_threshold_set(unsigned int threshold)
{
    if (threshold > O2HB_MIN_DEAD_THRESHOLD) {
        spin_lock(&o2hb_live_lock);
        if (list_empty(&o2hb_all_regions))
            o2hb_dead_threshold = threshold;
        spin_unlock(&o2hb_live_lock);
    }
}

static int o2hb_global_hearbeat_mode_set(unsigned int hb_mode)
{
    int ret = -1;

    if (hb_mode < O2HB_HEARTBEAT_NUM_MODES) {
        spin_lock(&o2hb_live_lock);
        if (list_empty(&o2hb_all_regions)) {
            o2hb_heartbeat_mode = hb_mode;
            ret = 0;
        }
        spin_unlock(&o2hb_live_lock);
    }

    return ret;
}

struct o2hb_node_event {
    struct list_head        hn_item;
    enum o2hb_callback_type hn_event_type;
    struct o2nm_node        *hn_node;
    int                     hn_node_num;
};

struct o2hb_disk_slot {
    struct o2hb_disk_heartbeat_block *ds_raw_block;
    u8          ds_node_num;
    u64         ds_last_time;
    u64         ds_last_generation;
    u16         ds_equal_samples;
    u16         ds_changed_samples;
    struct list_head    ds_live_item;
};

/* each thread owns a region.. when we're asked to tear down the region
 * we ask the thread to stop, who cleans up the region */
struct o2hb_region {
    struct config_item  hr_item;

    struct list_head    hr_all_item;
    unsigned        hr_unclean_stop:1,
                hr_aborted_start:1,
                hr_item_pinned:1,
                hr_item_dropped:1;

    /* protected by the hr_callback_sem */
    struct task_struct  *hr_task;

    unsigned int        hr_blocks;
    unsigned long long  hr_start_block;

    unsigned int        hr_block_bits;
    unsigned int        hr_block_bytes;

    unsigned int        hr_slots_per_page;
    unsigned int        hr_num_pages;

    struct page             **hr_slot_data;
    struct block_device *hr_bdev;
    struct o2hb_disk_slot   *hr_slots;

    /* live node map of this region */
    unsigned long       hr_live_node_bitmap[BITS_TO_LONGS(O2NM_MAX_NODES)];
    unsigned int        hr_region_num;

    struct dentry       *hr_debug_dir;
    struct dentry       *hr_debug_livenodes;
    struct dentry       *hr_debug_regnum;
    struct dentry       *hr_debug_elapsed_time;
    struct dentry       *hr_debug_pinned;
    struct o2hb_debug_buf   *hr_db_livenodes;
    struct o2hb_debug_buf   *hr_db_regnum;
    struct o2hb_debug_buf   *hr_db_elapsed_time;
    struct o2hb_debug_buf   *hr_db_pinned;

    /* let the person setting up hb wait for it to return until it
     * has reached a 'steady' state.  This will be fixed when we have
     * a more complete api that doesn't lead to this sort of fragility. */
    atomic_t        hr_steady_iterations;

    /* terminate o2hb thread if it does not reach steady state
     * (hr_steady_iterations == 0) within hr_unsteady_iterations */
    atomic_t        hr_unsteady_iterations;

    char            hr_dev_name[BDEVNAME_SIZE];

    unsigned int        hr_timeout_ms;

    /* randomized as the region goes up and down so that a node
     * recognizes a node going up and down in one iteration */
    u64         hr_generation;

    struct delayed_work hr_write_timeout_work;
    unsigned long       hr_last_timeout_start;

    /* Used during o2hb_check_slot to hold a copy of the block
     * being checked because we temporarily have to zero out the
     * crc field. */
    struct o2hb_disk_heartbeat_block *hr_tmp_block;
};

struct o2hb_bio_wait_ctxt {
    atomic_t          wc_num_reqs;
    struct completion wc_io_complete;
    int               wc_error;
};

static int o2hb_pop_count(void *map, int count)
{
    int i = -1, pop = 0;

    while ((i = find_next_bit(map, count, i + 1)) < count)
        pop++;
    return pop;
}

static void o2hb_write_timeout(struct work_struct *work)
{
    int failed, quorum;
    unsigned long flags;
    struct o2hb_region *reg =
        container_of(work, struct o2hb_region,
                 hr_write_timeout_work.work);

    mlog(ML_ERROR, "Heartbeat write timeout to device %s after %u "
         "milliseconds\n", reg->hr_dev_name,
         jiffies_to_msecs(jiffies - reg->hr_last_timeout_start));

    if (o2hb_global_heartbeat_active()) {
        spin_lock_irqsave(&o2hb_live_lock, flags);
        if (test_bit(reg->hr_region_num, o2hb_quorum_region_bitmap))
            set_bit(reg->hr_region_num, o2hb_failed_region_bitmap);
        failed = o2hb_pop_count(&o2hb_failed_region_bitmap,
                    O2NM_MAX_REGIONS);
        quorum = o2hb_pop_count(&o2hb_quorum_region_bitmap,
                    O2NM_MAX_REGIONS);
        spin_unlock_irqrestore(&o2hb_live_lock, flags);

        mlog(ML_HEARTBEAT, "Number of regions %d, failed regions %d\n",
             quorum, failed);

        /*
         * Fence if the number of failed regions >= half the number
         * of  quorum regions
         */
        if ((failed << 1) < quorum)
            return;
    }

    o2quo_disk_timeout();
}

static void o2hb_arm_write_timeout(struct o2hb_region *reg)
{
    /* Arm writeout only after thread reaches steady state */
    if (atomic_read(&reg->hr_steady_iterations) != 0)
        return;

    mlog(ML_HEARTBEAT, "Queue write timeout for %u ms\n",
         O2HB_MAX_WRITE_TIMEOUT_MS);

    if (o2hb_global_heartbeat_active()) {
        spin_lock(&o2hb_live_lock);
        clear_bit(reg->hr_region_num, o2hb_failed_region_bitmap);
        spin_unlock(&o2hb_live_lock);
    }
    cancel_delayed_work(&reg->hr_write_timeout_work);
    reg->hr_last_timeout_start = jiffies;
    schedule_delayed_work(&reg->hr_write_timeout_work,
                  msecs_to_jiffies(O2HB_MAX_WRITE_TIMEOUT_MS));
}

static void o2hb_disarm_write_timeout(struct o2hb_region *reg)
{
    cancel_delayed_work_sync(&reg->hr_write_timeout_work);
}

static inline void o2hb_bio_wait_init(struct o2hb_bio_wait_ctxt *wc)
{
    atomic_set(&wc->wc_num_reqs, 1);
    init_completion(&wc->wc_io_complete);
    wc->wc_error = 0;
}

/* Used in error paths too */
static inline void o2hb_bio_wait_dec(struct o2hb_bio_wait_ctxt *wc,
                     unsigned int num)
{
    /* sadly atomic_sub_and_test() isn't available on all platforms.  The
     * good news is that the fast path only completes one at a time */
    while(num--) {
        if (atomic_dec_and_test(&wc->wc_num_reqs)) {
            BUG_ON(num > 0);
            complete(&wc->wc_io_complete);
        }
    }
}

static void o2hb_wait_on_io(struct o2hb_region *reg,
                struct o2hb_bio_wait_ctxt *wc)
{
    o2hb_bio_wait_dec(wc, 1);
    wait_for_completion(&wc->wc_io_complete);
}

static void o2hb_bio_end_io(struct bio *bio,
               int error)
{
    struct o2hb_bio_wait_ctxt *wc = bio->bi_private;

    if (error) {
        mlog(ML_ERROR, "IO Error %d\n", error);
        wc->wc_error = error;
    }

    o2hb_bio_wait_dec(wc, 1);
    bio_put(bio);
}

/* Setup a Bio to cover I/O against num_slots slots starting at
 * start_slot. */
static struct bio *o2hb_setup_one_bio(struct o2hb_region *reg,
                      struct o2hb_bio_wait_ctxt *wc,
                      unsigned int *current_slot,
                      unsigned int max_slots)
{
    int len, current_page;
    unsigned int vec_len, vec_start;
    unsigned int bits = reg->hr_block_bits;
    unsigned int spp = reg->hr_slots_per_page;
    unsigned int cs = *current_slot;
    struct bio *bio;
    struct page *page;

    /* Testing has shown this allocation to take long enough under
     * GFP_KERNEL that the local node can get fenced. It would be
     * nicest if we could pre-allocate these bios and avoid this
     * all together. */
    bio = bio_alloc(GFP_ATOMIC, 16);
    if (!bio) {
        mlog(ML_ERROR, "Could not alloc slots BIO!\n");
        bio = ERR_PTR(-ENOMEM);
        goto bail;
    }

    /* Must put everything in 512 byte sectors for the bio... */
    bio->bi_sector = (reg->hr_start_block + cs) << (bits - 9);
    bio->bi_bdev = reg->hr_bdev;
    bio->bi_private = wc;
    bio->bi_end_io = o2hb_bio_end_io;

    vec_start = (cs << bits) % PAGE_CACHE_SIZE;
    while(cs < max_slots) {
        current_page = cs / spp;
        page = reg->hr_slot_data[current_page];

        vec_len = min(PAGE_CACHE_SIZE - vec_start,
                  (max_slots-cs) * (PAGE_CACHE_SIZE/spp) );

        mlog(ML_HB_BIO, "page %d, vec_len = %u, vec_start = %u\n",
             current_page, vec_len, vec_start);

        len = bio_add_page(bio, page, vec_len, vec_start);
        if (len != vec_len) break;

        cs += vec_len / (PAGE_CACHE_SIZE/spp);
        vec_start = 0;
    }

bail:
    *current_slot = cs;
    return bio;
}

static int o2hb_read_slots(struct o2hb_region *reg,
               unsigned int max_slots)
{
    unsigned int current_slot=0;
    int status;
    struct o2hb_bio_wait_ctxt wc;
    struct bio *bio;

    o2hb_bio_wait_init(&wc);

    while(current_slot < max_slots) {
        bio = o2hb_setup_one_bio(reg, &wc, &current_slot, max_slots);
        if (IS_ERR(bio)) {
            status = PTR_ERR(bio);
            mlog_errno(status);
            goto bail_and_wait;
        }

        atomic_inc(&wc.wc_num_reqs);
        submit_bio(READ, bio);
    }

    status = 0;

bail_and_wait:
    o2hb_wait_on_io(reg, &wc);
    if (wc.wc_error && !status)
        status = wc.wc_error;

    return status;
}

static int o2hb_issue_node_write(struct o2hb_region *reg,
                 struct o2hb_bio_wait_ctxt *write_wc)
{
    int status;
    unsigned int slot;
    struct bio *bio;

    o2hb_bio_wait_init(write_wc);

    slot = o2nm_this_node();

    bio = o2hb_setup_one_bio(reg, write_wc, &slot, slot+1);
    if (IS_ERR(bio)) {
        status = PTR_ERR(bio);
        mlog_errno(status);
        goto bail;
    }

    atomic_inc(&write_wc->wc_num_reqs);
    submit_bio(WRITE, bio);

    status = 0;
bail:
    return status;
}

static u32 o2hb_compute_block_crc_le(struct o2hb_region *reg,
                     struct o2hb_disk_heartbeat_block *hb_block)
{
    __le32 old_cksum;
    u32 ret;

    /* We want to compute the block crc with a 0 value in the
     * hb_cksum field. Save it off here and replace after the
     * crc. */
    old_cksum = hb_block->hb_cksum;
    hb_block->hb_cksum = 0;

    ret = crc32_le(0, (unsigned char *) hb_block, reg->hr_block_bytes);

    hb_block->hb_cksum = old_cksum;

    return ret;
}

static void o2hb_dump_slot(struct o2hb_disk_heartbeat_block *hb_block)
{
    mlog(ML_ERROR, "Dump slot information: seq = 0x%llx, node = %u, "
         "cksum = 0x%x, generation 0x%llx\n",
         (long long)le64_to_cpu(hb_block->hb_seq),
         hb_block->hb_node, le32_to_cpu(hb_block->hb_cksum),
         (long long)le64_to_cpu(hb_block->hb_generation));
}

static int o2hb_verify_crc(struct o2hb_region *reg,
               struct o2hb_disk_heartbeat_block *hb_block)
{
    u32 read, computed;

    read = le32_to_cpu(hb_block->hb_cksum);
    computed = o2hb_compute_block_crc_le(reg, hb_block);

    return read == computed;
}

/*
 * Compare the slot data with what we wrote in the last iteration.
 * If the match fails, print an appropriate error message. This is to
 * detect errors like... another node hearting on the same slot,
 * flaky device that is losing writes, etc.
 * Returns 1 if check succeeds, 0 otherwise.
 */
static int o2hb_check_own_slot(struct o2hb_region *reg)
{
    struct o2hb_disk_slot *slot;
    struct o2hb_disk_heartbeat_block *hb_block;
    char *errstr;

    slot = &reg->hr_slots[o2nm_this_node()];
    /* Don't check on our 1st timestamp */
    if (!slot->ds_last_time)
        return 0;

    hb_block = slot->ds_raw_block;
    if (le64_to_cpu(hb_block->hb_seq) == slot->ds_last_time &&
        le64_to_cpu(hb_block->hb_generation) == slot->ds_last_generation &&
        hb_block->hb_node == slot->ds_node_num)
        return 1;

#define ERRSTR1     "Another node is heartbeating on device"
#define ERRSTR2     "Heartbeat generation mismatch on device"
#define ERRSTR3     "Heartbeat sequence mismatch on device"

    if (hb_block->hb_node != slot->ds_node_num)
        errstr = ERRSTR1;
    else if (le64_to_cpu(hb_block->hb_generation) !=
         slot->ds_last_generation)
        errstr = ERRSTR2;
    else
        errstr = ERRSTR3;

    mlog(ML_ERROR, "%s (%s): expected(%u:0x%llx, 0x%llx), "
         "ondisk(%u:0x%llx, 0x%llx)\n", errstr, reg->hr_dev_name,
         slot->ds_node_num, (unsigned long long)slot->ds_last_generation,
         (unsigned long long)slot->ds_last_time, hb_block->hb_node,
         (unsigned long long)le64_to_cpu(hb_block->hb_generation),
         (unsigned long long)le64_to_cpu(hb_block->hb_seq));

    return 0;
}

static inline void o2hb_prepare_block(struct o2hb_region *reg,
                      u64 generation)
{
    int node_num;
    u64 cputime;
    struct o2hb_disk_slot *slot;
    struct o2hb_disk_heartbeat_block *hb_block;

    node_num = o2nm_this_node();
    slot = &reg->hr_slots[node_num];

    hb_block = (struct o2hb_disk_heartbeat_block *)slot->ds_raw_block;
    memset(hb_block, 0, reg->hr_block_bytes);
    /* TODO: time stuff */
    cputime = CURRENT_TIME.tv_sec;
    if (!cputime)
        cputime = 1;

    hb_block->hb_seq = cpu_to_le64(cputime);
    hb_block->hb_node = node_num;
    hb_block->hb_generation = cpu_to_le64(generation);
    hb_block->hb_dead_ms = cpu_to_le32(o2hb_dead_threshold * O2HB_REGION_TIMEOUT_MS);

    /* This step must always happen last! */
    hb_block->hb_cksum = cpu_to_le32(o2hb_compute_block_crc_le(reg,
                                   hb_block));

    mlog(ML_HB_BIO, "our node generation = 0x%llx, cksum = 0x%x\n",
         (long long)generation,
         le32_to_cpu(hb_block->hb_cksum));
}

static void o2hb_fire_callbacks(struct o2hb_callback *hbcall,
                struct o2nm_node *node,
                int idx)
{
    struct list_head *iter;
    struct o2hb_callback_func *f;

    list_for_each(iter, &hbcall->list) {
        f = list_entry(iter, struct o2hb_callback_func, hc_item);
        mlog(ML_HEARTBEAT, "calling funcs %p\n", f);
        (f->hc_func)(node, idx, f->hc_data);
    }
}

/* Will run the list in order until we process the passed event */
static void o2hb_run_event_list(struct o2hb_node_event *queued_event)
{
    int empty;
    struct o2hb_callback *hbcall;
    struct o2hb_node_event *event;

    spin_lock(&o2hb_live_lock);
    empty = list_empty(&queued_event->hn_item);
    spin_unlock(&o2hb_live_lock);
    if (empty)
        return;

    /* Holding callback sem assures we don't alter the callback
     * lists when doing this, and serializes ourselves with other
     * processes wanting callbacks. */
    down_write(&o2hb_callback_sem);

    spin_lock(&o2hb_live_lock);
    while (!list_empty(&o2hb_node_events)
           && !list_empty(&queued_event->hn_item)) {
        event = list_entry(o2hb_node_events.next,
                   struct o2hb_node_event,
                   hn_item);
        list_del_init(&event->hn_item);
        spin_unlock(&o2hb_live_lock);

        mlog(ML_HEARTBEAT, "Node %s event for %d\n",
             event->hn_event_type == O2HB_NODE_UP_CB ? "UP" : "DOWN",
             event->hn_node_num);

        hbcall = hbcall_from_type(event->hn_event_type);

        /* We should *never* have gotten on to the list with a
         * bad type... This isn't something that we should try
         * to recover from. */
        BUG_ON(IS_ERR(hbcall));

        o2hb_fire_callbacks(hbcall, event->hn_node, event->hn_node_num);

        spin_lock(&o2hb_live_lock);
    }
    spin_unlock(&o2hb_live_lock);

    up_write(&o2hb_callback_sem);
}

static void o2hb_queue_node_event(struct o2hb_node_event *event,
                  enum o2hb_callback_type type,
                  struct o2nm_node *node,
                  int node_num)
{
    assert_spin_locked(&o2hb_live_lock);

    BUG_ON((!node) && (type != O2HB_NODE_DOWN_CB));

    event->hn_event_type = type;
    event->hn_node = node;
    event->hn_node_num = node_num;

    mlog(ML_HEARTBEAT, "Queue node %s event for node %d\n",
         type == O2HB_NODE_UP_CB ? "UP" : "DOWN", node_num);

    list_add_tail(&event->hn_item, &o2hb_node_events);
}

static void o2hb_shutdown_slot(struct o2hb_disk_slot *slot)
{
    struct o2hb_node_event event =
        { .hn_item = LIST_HEAD_INIT(event.hn_item), };
    struct o2nm_node *node;

    node = o2nm_get_node_by_num(slot->ds_node_num);
    if (!node)
        return;

    spin_lock(&o2hb_live_lock);
    if (!list_empty(&slot->ds_live_item)) {
        mlog(ML_HEARTBEAT, "Shutdown, node %d leaves region\n",
             slot->ds_node_num);

        list_del_init(&slot->ds_live_item);

        if (list_empty(&o2hb_live_slots[slot->ds_node_num])) {
            clear_bit(slot->ds_node_num, o2hb_live_node_bitmap);

            o2hb_queue_node_event(&event, O2HB_NODE_DOWN_CB, node,
                          slot->ds_node_num);
        }
    }
    spin_unlock(&o2hb_live_lock);

    o2hb_run_event_list(&event);

    o2nm_node_put(node);
}

static void o2hb_set_quorum_device(struct o2hb_region *reg)
{
    if (!o2hb_global_heartbeat_active())
        return;

    /* Prevent race with o2hb_heartbeat_group_drop_item() */
    if (kthread_should_stop())
        return;

    /* Tag region as quorum only after thread reaches steady state */
    if (atomic_read(&reg->hr_steady_iterations) != 0)
        return;

    spin_lock(&o2hb_live_lock);

    if (test_bit(reg->hr_region_num, o2hb_quorum_region_bitmap))
        goto unlock;

    /*
     * A region can be added to the quorum only when it sees all
     * live nodes heartbeat on it. In other words, the region has been
     * added to all nodes.
     */
    if (memcmp(reg->hr_live_node_bitmap, o2hb_live_node_bitmap,
           sizeof(o2hb_live_node_bitmap)))
        goto unlock;

    printk(KERN_NOTICE "o2hb: Region %s (%s) is now a quorum device\n",
           config_item_name(&reg->hr_item), reg->hr_dev_name);

    set_bit(reg->hr_region_num, o2hb_quorum_region_bitmap);

    /*
     * If global heartbeat active, unpin all regions if the
     * region count > CUT_OFF
     */
    if (o2hb_pop_count(&o2hb_quorum_region_bitmap,
               O2NM_MAX_REGIONS) > O2HB_PIN_CUT_OFF)
        o2hb_region_unpin(NULL);
unlock:
    spin_unlock(&o2hb_live_lock);
}

static int o2hb_check_slot(struct o2hb_region *reg,
               struct o2hb_disk_slot *slot)
{
    int changed = 0, gen_changed = 0;
    struct o2hb_node_event event =
        { .hn_item = LIST_HEAD_INIT(event.hn_item), };
    struct o2nm_node *node;
    struct o2hb_disk_heartbeat_block *hb_block = reg->hr_tmp_block;
    u64 cputime;
    unsigned int dead_ms = o2hb_dead_threshold * O2HB_REGION_TIMEOUT_MS;
    unsigned int slot_dead_ms;
    int tmp;

    memcpy(hb_block, slot->ds_raw_block, reg->hr_block_bytes);

    /*
     * If a node is no longer configured but is still in the livemap, we
     * may need to clear that bit from the livemap.
     */
    node = o2nm_get_node_by_num(slot->ds_node_num);
    if (!node) {
        spin_lock(&o2hb_live_lock);
        tmp = test_bit(slot->ds_node_num, o2hb_live_node_bitmap);
        spin_unlock(&o2hb_live_lock);
        if (!tmp)
            return 0;
    }

    if (!o2hb_verify_crc(reg, hb_block)) {
        /* all paths from here will drop o2hb_live_lock for
         * us. */
        spin_lock(&o2hb_live_lock);

        /* Don't print an error on the console in this case -
         * a freshly formatted heartbeat area will not have a
         * crc set on it. */
        if (list_empty(&slot->ds_live_item))
            goto out;

        /* The node is live but pushed out a bad crc. We
         * consider it a transient miss but don't populate any
         * other values as they may be junk. */
        mlog(ML_ERROR, "Node %d has written a bad crc to %s\n",
             slot->ds_node_num, reg->hr_dev_name);
        o2hb_dump_slot(hb_block);

        slot->ds_equal_samples++;
        goto fire_callbacks;
    }

    /* we don't care if these wrap.. the state transitions below
     * clear at the right places */
    cputime = le64_to_cpu(hb_block->hb_seq);
    if (slot->ds_last_time != cputime)
        slot->ds_changed_samples++;
    else
        slot->ds_equal_samples++;
    slot->ds_last_time = cputime;

    /* The node changed heartbeat generations. We assume this to
     * mean it dropped off but came back before we timed out. We
     * want to consider it down for the time being but don't want
     * to lose any changed_samples state we might build up to
     * considering it live again. */
    if (slot->ds_last_generation != le64_to_cpu(hb_block->hb_generation)) {
        gen_changed = 1;
        slot->ds_equal_samples = 0;
        mlog(ML_HEARTBEAT, "Node %d changed generation (0x%llx "
             "to 0x%llx)\n", slot->ds_node_num,
             (long long)slot->ds_last_generation,
             (long long)le64_to_cpu(hb_block->hb_generation));
    }

    slot->ds_last_generation = le64_to_cpu(hb_block->hb_generation);

    mlog(ML_HEARTBEAT, "Slot %d gen 0x%llx cksum 0x%x "
         "seq %llu last %llu changed %u equal %u\n",
         slot->ds_node_num, (long long)slot->ds_last_generation,
         le32_to_cpu(hb_block->hb_cksum),
         (unsigned long long)le64_to_cpu(hb_block->hb_seq),
         (unsigned long long)slot->ds_last_time, slot->ds_changed_samples,
         slot->ds_equal_samples);

    spin_lock(&o2hb_live_lock);

fire_callbacks:
    /* dead nodes only come to life after some number of
     * changes at any time during their dead time */
    if (list_empty(&slot->ds_live_item) &&
        slot->ds_changed_samples >= O2HB_LIVE_THRESHOLD) {
        mlog(ML_HEARTBEAT, "Node %d (id 0x%llx) joined my region\n",
             slot->ds_node_num, (long long)slot->ds_last_generation);

        set_bit(slot->ds_node_num, reg->hr_live_node_bitmap);

        /* first on the list generates a callback */
        if (list_empty(&o2hb_live_slots[slot->ds_node_num])) {
            mlog(ML_HEARTBEAT, "o2hb: Add node %d to live nodes "
                 "bitmap\n", slot->ds_node_num);
            set_bit(slot->ds_node_num, o2hb_live_node_bitmap);

            o2hb_queue_node_event(&event, O2HB_NODE_UP_CB, node,
                          slot->ds_node_num);

            changed = 1;
        }

        list_add_tail(&slot->ds_live_item,
                  &o2hb_live_slots[slot->ds_node_num]);

        slot->ds_equal_samples = 0;

        /* We want to be sure that all nodes agree on the
         * number of milliseconds before a node will be
         * considered dead. The self-fencing timeout is
         * computed from this value, and a discrepancy might
         * result in heartbeat calling a node dead when it
         * hasn't self-fenced yet. */
        slot_dead_ms = le32_to_cpu(hb_block->hb_dead_ms);
        if (slot_dead_ms && slot_dead_ms != dead_ms) {
            /* TODO: Perhaps we can fail the region here. */
            mlog(ML_ERROR, "Node %d on device %s has a dead count "
                 "of %u ms, but our count is %u ms.\n"
                 "Please double check your configuration values "
                 "for 'O2CB_HEARTBEAT_THRESHOLD'\n",
                 slot->ds_node_num, reg->hr_dev_name, slot_dead_ms,
                 dead_ms);
        }
        goto out;
    }

    /* if the list is dead, we're done.. */
    if (list_empty(&slot->ds_live_item))
        goto out;

    /* live nodes only go dead after enough consequtive missed
     * samples..  reset the missed counter whenever we see
     * activity */
    if (slot->ds_equal_samples >= o2hb_dead_threshold || gen_changed) {
        mlog(ML_HEARTBEAT, "Node %d left my region\n",
             slot->ds_node_num);

        clear_bit(slot->ds_node_num, reg->hr_live_node_bitmap);

        /* last off the live_slot generates a callback */
        list_del_init(&slot->ds_live_item);
        if (list_empty(&o2hb_live_slots[slot->ds_node_num])) {
            mlog(ML_HEARTBEAT, "o2hb: Remove node %d from live "
                 "nodes bitmap\n", slot->ds_node_num);
            clear_bit(slot->ds_node_num, o2hb_live_node_bitmap);

            /* node can be null */
            o2hb_queue_node_event(&event, O2HB_NODE_DOWN_CB,
                          node, slot->ds_node_num);

            changed = 1;
        }

        /* We don't clear this because the node is still
         * actually writing new blocks. */
        if (!gen_changed)
            slot->ds_changed_samples = 0;
        goto out;
    }
    if (slot->ds_changed_samples) {
        slot->ds_changed_samples = 0;
        slot->ds_equal_samples = 0;
    }
out:
    spin_unlock(&o2hb_live_lock);

    o2hb_run_event_list(&event);

    if (node)
        o2nm_node_put(node);
    return changed;
}

/* This could be faster if we just implmented a find_last_bit, but I
 * don't think the circumstances warrant it. */
static int o2hb_highest_node(unsigned long *nodes,
                 int numbits)
{
    int highest, node;

    highest = numbits;
    node = -1;
    while ((node = find_next_bit(nodes, numbits, node + 1)) != -1) {
        if (node >= numbits)
            break;

        highest = node;
    }

    return highest;
}

static int o2hb_do_disk_heartbeat(struct o2hb_region *reg)
{
    int i, ret, highest_node;
    int membership_change = 0, own_slot_ok = 0;
    unsigned long configured_nodes[BITS_TO_LONGS(O2NM_MAX_NODES)];
    unsigned long live_node_bitmap[BITS_TO_LONGS(O2NM_MAX_NODES)];
    struct o2hb_bio_wait_ctxt write_wc;

    ret = o2nm_configured_node_map(configured_nodes,
                       sizeof(configured_nodes));
    if (ret) {
        mlog_errno(ret);
        goto bail;
    }

    /*
     * If a node is not configured but is in the livemap, we still need
     * to read the slot so as to be able to remove it from the livemap.
     */
    o2hb_fill_node_map(live_node_bitmap, sizeof(live_node_bitmap));
    i = -1;
    while ((i = find_next_bit(live_node_bitmap,
                  O2NM_MAX_NODES, i + 1)) < O2NM_MAX_NODES) {
        set_bit(i, configured_nodes);
    }

    highest_node = o2hb_highest_node(configured_nodes, O2NM_MAX_NODES);
    if (highest_node >= O2NM_MAX_NODES) {
        mlog(ML_NOTICE, "o2hb: No configured nodes found!\n");
        ret = -EINVAL;
        goto bail;
    }

    /* No sense in reading the slots of nodes that don't exist
     * yet. Of course, if the node definitions have holes in them
     * then we're reading an empty slot anyway... Consider this
     * best-effort. */
    ret = o2hb_read_slots(reg, highest_node + 1);
    if (ret < 0) {
        mlog_errno(ret);
        goto bail;
    }

    /* With an up to date view of the slots, we can check that no
     * other node has been improperly configured to heartbeat in
     * our slot. */
    own_slot_ok = o2hb_check_own_slot(reg);

    /* fill in the proper info for our next heartbeat */
    o2hb_prepare_block(reg, reg->hr_generation);

    ret = o2hb_issue_node_write(reg, &write_wc);
    if (ret < 0) {
        mlog_errno(ret);
        goto bail;
    }

    i = -1;
    while((i = find_next_bit(configured_nodes,
                 O2NM_MAX_NODES, i + 1)) < O2NM_MAX_NODES) {
        membership_change |= o2hb_check_slot(reg, &reg->hr_slots[i]);
    }

    /*
     * We have to be sure we've advertised ourselves on disk
     * before we can go to steady state.  This ensures that
     * people we find in our steady state have seen us.
     */
    o2hb_wait_on_io(reg, &write_wc);
    if (write_wc.wc_error) {
        /* Do not re-arm the write timeout on I/O error - we
         * can't be sure that the new block ever made it to
         * disk */
        mlog(ML_ERROR, "Write error %d on device \"%s\"\n",
             write_wc.wc_error, reg->hr_dev_name);
        ret = write_wc.wc_error;
        goto bail;
    }

    /* Skip disarming the timeout if own slot has stale/bad data */
    if (own_slot_ok) {
        o2hb_set_quorum_device(reg);
        o2hb_arm_write_timeout(reg);
    }

bail:
    /* let the person who launched us know when things are steady */
    if (atomic_read(&reg->hr_steady_iterations) != 0) {
        if (!ret && own_slot_ok && !membership_change) {
            if (atomic_dec_and_test(&reg->hr_steady_iterations))
                wake_up(&o2hb_steady_queue);
        }
    }

    if (atomic_read(&reg->hr_steady_iterations) != 0) {
        if (atomic_dec_and_test(&reg->hr_unsteady_iterations)) {
            printk(KERN_NOTICE "o2hb: Unable to stabilize "
                   "heartbeart on region %s (%s)\n",
                   config_item_name(&reg->hr_item),
                   reg->hr_dev_name);
            atomic_set(&reg->hr_steady_iterations, 0);
            reg->hr_aborted_start = 1;
            wake_up(&o2hb_steady_queue);
            ret = -EIO;
        }
    }

    return ret;
}

/* Subtract b from a, storing the result in a. a *must* have a larger
 * value than b. */
static void o2hb_tv_subtract(struct timeval *a,
                 struct timeval *b)
{
    /* just return 0 when a is after b */
    if (a->tv_sec < b->tv_sec ||
        (a->tv_sec == b->tv_sec && a->tv_usec < b->tv_usec)) {
        a->tv_sec = 0;
        a->tv_usec = 0;
        return;
    }

    a->tv_sec -= b->tv_sec;
    a->tv_usec -= b->tv_usec;
    while ( a->tv_usec < 0 ) {
        a->tv_sec--;
        a->tv_usec += 1000000;
    }
}

static unsigned int o2hb_elapsed_msecs(struct timeval *start,
                       struct timeval *end)
{
    struct timeval res = *end;

    o2hb_tv_subtract(&res, start);

    return res.tv_sec * 1000 + res.tv_usec / 1000;
}

/*
 * we ride the region ref that the region dir holds.  before the region
 * dir is removed and drops it ref it will wait to tear down this
 * thread.
 */
static int o2hb_thread(void *data)
{
    int i, ret;
    struct o2hb_region *reg = data;
    struct o2hb_bio_wait_ctxt write_wc;
    struct timeval before_hb, after_hb;
    unsigned int elapsed_msec;

    mlog(ML_HEARTBEAT|ML_KTHREAD, "hb thread running\n");

    set_user_nice(current, -20);

    /* Pin node */
    o2nm_depend_this_node();

    while (!kthread_should_stop() &&
           !reg->hr_unclean_stop && !reg->hr_aborted_start) {
        /* We track the time spent inside
         * o2hb_do_disk_heartbeat so that we avoid more than
         * hr_timeout_ms between disk writes. On busy systems
         * this should result in a heartbeat which is less
         * likely to time itself out. */
        do_gettimeofday(&before_hb);

        ret = o2hb_do_disk_heartbeat(reg);

        do_gettimeofday(&after_hb);
        elapsed_msec = o2hb_elapsed_msecs(&before_hb, &after_hb);

        mlog(ML_HEARTBEAT,
             "start = %lu.%lu, end = %lu.%lu, msec = %u\n",
             before_hb.tv_sec, (unsigned long) before_hb.tv_usec,
             after_hb.tv_sec, (unsigned long) after_hb.tv_usec,
             elapsed_msec);

        if (!kthread_should_stop() &&
            elapsed_msec < reg->hr_timeout_ms) {
            /* the kthread api has blocked signals for us so no
             * need to record the return value. */
            msleep_interruptible(reg->hr_timeout_ms - elapsed_msec);
        }
    }

    o2hb_disarm_write_timeout(reg);

    /* unclean stop is only used in very bad situation */
    for(i = 0; !reg->hr_unclean_stop && i < reg->hr_blocks; i++)
        o2hb_shutdown_slot(&reg->hr_slots[i]);

    /* Explicit down notification - avoid forcing the other nodes
     * to timeout on this region when we could just as easily
     * write a clear generation - thus indicating to them that
     * this node has left this region.
     */
    if (!reg->hr_unclean_stop && !reg->hr_aborted_start) {
        o2hb_prepare_block(reg, 0);
        ret = o2hb_issue_node_write(reg, &write_wc);
        if (ret == 0)
            o2hb_wait_on_io(reg, &write_wc);
        else
            mlog_errno(ret);
    }

    /* Unpin node */
    o2nm_undepend_this_node();

    mlog(ML_HEARTBEAT|ML_KTHREAD, "o2hb thread exiting\n");

    return 0;
}

#ifdef CONFIG_DEBUG_FS
static int o2hb_debug_open(struct inode *inode, struct file *file)
{
    struct o2hb_debug_buf *db = inode->i_private;
    struct o2hb_region *reg;
    unsigned long map[BITS_TO_LONGS(O2NM_MAX_NODES)];
    unsigned long lts;
    char *buf = NULL;
    int i = -1;
    int out = 0;

    /* max_nodes should be the largest bitmap we pass here */
    BUG_ON(sizeof(map) < db->db_size);

    buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
    if (!buf)
        goto bail;

    switch (db->db_type) {
    case O2HB_DB_TYPE_LIVENODES:
    case O2HB_DB_TYPE_LIVEREGIONS:
    case O2HB_DB_TYPE_QUORUMREGIONS:
    case O2HB_DB_TYPE_FAILEDREGIONS:
        spin_lock(&o2hb_live_lock);
        memcpy(map, db->db_data, db->db_size);
        spin_unlock(&o2hb_live_lock);
        break;

    case O2HB_DB_TYPE_REGION_LIVENODES:
        spin_lock(&o2hb_live_lock);
        reg = (struct o2hb_region *)db->db_data;
        memcpy(map, reg->hr_live_node_bitmap, db->db_size);
        spin_unlock(&o2hb_live_lock);
        break;

    case O2HB_DB_TYPE_REGION_NUMBER:
        reg = (struct o2hb_region *)db->db_data;
        out += snprintf(buf + out, PAGE_SIZE - out, "%d\n",
                reg->hr_region_num);
        goto done;

    case O2HB_DB_TYPE_REGION_ELAPSED_TIME:
        reg = (struct o2hb_region *)db->db_data;
        lts = reg->hr_last_timeout_start;
        /* If 0, it has never been set before */
        if (lts)
            lts = jiffies_to_msecs(jiffies - lts);
        out += snprintf(buf + out, PAGE_SIZE - out, "%lu\n", lts);
        goto done;

    case O2HB_DB_TYPE_REGION_PINNED:
        reg = (struct o2hb_region *)db->db_data;
        out += snprintf(buf + out, PAGE_SIZE - out, "%u\n",
                !!reg->hr_item_pinned);
        goto done;

    default:
        goto done;
    }

    while ((i = find_next_bit(map, db->db_len, i + 1)) < db->db_len)
        out += snprintf(buf + out, PAGE_SIZE - out, "%d ", i);
    out += snprintf(buf + out, PAGE_SIZE - out, "\n");

done:
    i_size_write(inode, out);

    file->private_data = buf;

    return 0;
bail:
    return -ENOMEM;
}

static int o2hb_debug_release(struct inode *inode, struct file *file)
{
    kfree(file->private_data);
    return 0;
}

static ssize_t o2hb_debug_read(struct file *file, char __user *buf,
                 size_t nbytes, loff_t *ppos)
{
    return simple_read_from_buffer(buf, nbytes, ppos, file->private_data,
                       i_size_read(file->f_mapping->host));
}
#else
static int o2hb_debug_open(struct inode *inode, struct file *file)
{
    return 0;
}
static int o2hb_debug_release(struct inode *inode, struct file *file)
{
    return 0;
}
static ssize_t o2hb_debug_read(struct file *file, char __user *buf,
                   size_t nbytes, loff_t *ppos)
{
    return 0;
}
#endif  /* CONFIG_DEBUG_FS */

static const struct file_operations o2hb_debug_fops = {
    .open =     o2hb_debug_open,
    .release =  o2hb_debug_release,
    .read =     o2hb_debug_read,
    .llseek =   generic_file_llseek,
};

void o2hb_exit(void)
{
    kfree(o2hb_db_livenodes);
    kfree(o2hb_db_liveregions);
    kfree(o2hb_db_quorumregions);
    kfree(o2hb_db_failedregions);
    debugfs_remove(o2hb_debug_failedregions);
    debugfs_remove(o2hb_debug_quorumregions);
    debugfs_remove(o2hb_debug_liveregions);
    debugfs_remove(o2hb_debug_livenodes);
    debugfs_remove(o2hb_debug_dir);
}

static struct dentry *o2hb_debug_create(const char *name, struct dentry *dir,
                    struct o2hb_debug_buf **db, int db_len,
                    int type, int size, int len, void *data)
{
    *db = kmalloc(db_len, GFP_KERNEL);
    if (!*db)
        return NULL;

    (*db)->db_type = type;
    (*db)->db_size = size;
    (*db)->db_len = len;
    (*db)->db_data = data;

    return debugfs_create_file(name, S_IFREG|S_IRUSR, dir, *db,
                   &o2hb_debug_fops);
}

static int o2hb_debug_init(void)
{
    int ret = -ENOMEM;

    o2hb_debug_dir = debugfs_create_dir(O2HB_DEBUG_DIR, NULL);
    if (!o2hb_debug_dir) {
        mlog_errno(ret);
        goto bail;
    }

    o2hb_debug_livenodes = o2hb_debug_create(O2HB_DEBUG_LIVENODES,
                         o2hb_debug_dir,
                         &o2hb_db_livenodes,
                         sizeof(*o2hb_db_livenodes),
                         O2HB_DB_TYPE_LIVENODES,
                         sizeof(o2hb_live_node_bitmap),
                         O2NM_MAX_NODES,
                         o2hb_live_node_bitmap);
    if (!o2hb_debug_livenodes) {
        mlog_errno(ret);
        goto bail;
    }

    o2hb_debug_liveregions = o2hb_debug_create(O2HB_DEBUG_LIVEREGIONS,
                           o2hb_debug_dir,
                           &o2hb_db_liveregions,
                           sizeof(*o2hb_db_liveregions),
                           O2HB_DB_TYPE_LIVEREGIONS,
                           sizeof(o2hb_live_region_bitmap),
                           O2NM_MAX_REGIONS,
                           o2hb_live_region_bitmap);
    if (!o2hb_debug_liveregions) {
        mlog_errno(ret);
        goto bail;
    }

    o2hb_debug_quorumregions =
            o2hb_debug_create(O2HB_DEBUG_QUORUMREGIONS,
                      o2hb_debug_dir,
                      &o2hb_db_quorumregions,
                      sizeof(*o2hb_db_quorumregions),
                      O2HB_DB_TYPE_QUORUMREGIONS,
                      sizeof(o2hb_quorum_region_bitmap),
                      O2NM_MAX_REGIONS,
                      o2hb_quorum_region_bitmap);
    if (!o2hb_debug_quorumregions) {
        mlog_errno(ret);
        goto bail;
    }

    o2hb_debug_failedregions =
            o2hb_debug_create(O2HB_DEBUG_FAILEDREGIONS,
                      o2hb_debug_dir,
                      &o2hb_db_failedregions,
                      sizeof(*o2hb_db_failedregions),
                      O2HB_DB_TYPE_FAILEDREGIONS,
                      sizeof(o2hb_failed_region_bitmap),
                      O2NM_MAX_REGIONS,
                      o2hb_failed_region_bitmap);
    if (!o2hb_debug_failedregions) {
        mlog_errno(ret);
        goto bail;
    }

    ret = 0;
bail:
    if (ret)
        o2hb_exit();

    return ret;
}

int o2hb_init(void)
{
    int i;

    for (i = 0; i < ARRAY_SIZE(o2hb_callbacks); i++)
        INIT_LIST_HEAD(&o2hb_callbacks[i].list);

    for (i = 0; i < ARRAY_SIZE(o2hb_live_slots); i++)
        INIT_LIST_HEAD(&o2hb_live_slots[i]);

    INIT_LIST_HEAD(&o2hb_node_events);

    memset(o2hb_live_node_bitmap, 0, sizeof(o2hb_live_node_bitmap));
    memset(o2hb_region_bitmap, 0, sizeof(o2hb_region_bitmap));
    memset(o2hb_live_region_bitmap, 0, sizeof(o2hb_live_region_bitmap));
    memset(o2hb_quorum_region_bitmap, 0, sizeof(o2hb_quorum_region_bitmap));
    memset(o2hb_failed_region_bitmap, 0, sizeof(o2hb_failed_region_bitmap));

    o2hb_dependent_users = 0;

    return o2hb_debug_init();
}

/* if we're already in a callback then we're already serialized by the sem */
static void o2hb_fill_node_map_from_callback(unsigned long *map,
                         unsigned bytes)
{
    BUG_ON(bytes < (BITS_TO_LONGS(O2NM_MAX_NODES) * sizeof(unsigned long)));

    memcpy(map, &o2hb_live_node_bitmap, bytes);
}

/*
 * get a map of all nodes that are heartbeating in any regions
 */
void o2hb_fill_node_map(unsigned long *map, unsigned bytes)
{
    /* callers want to serialize this map and callbacks so that they
     * can trust that they don't miss nodes coming to the party */
    down_read(&o2hb_callback_sem);
    spin_lock(&o2hb_live_lock);
    o2hb_fill_node_map_from_callback(map, bytes);
    spin_unlock(&o2hb_live_lock);
    up_read(&o2hb_callback_sem);
}
EXPORT_SYMBOL_GPL(o2hb_fill_node_map);

/*
 * heartbeat configfs bits.  The heartbeat set is a default set under
 * the cluster set in nodemanager.c.
 */

static struct o2hb_region *to_o2hb_region(struct config_item *item)
{
    return item ? container_of(item, struct o2hb_region, hr_item) : NULL;
}

/* drop_item only drops its ref after killing the thread, nothing should
 * be using the region anymore.  this has to clean up any state that
 * attributes might have built up. */
static void o2hb_region_release(struct config_item *item)
{
    int i;
    struct page *page;
    struct o2hb_region *reg = to_o2hb_region(item);

    mlog(ML_HEARTBEAT, "hb region release (%s)\n", reg->hr_dev_name);

    if (reg->hr_tmp_block)
        kfree(reg->hr_tmp_block);

    if (reg->hr_slot_data) {
        for (i = 0; i < reg->hr_num_pages; i++) {
            page = reg->hr_slot_data[i];
            if (page)
                __free_page(page);
        }
        kfree(reg->hr_slot_data);
    }

    if (reg->hr_bdev)
        blkdev_put(reg->hr_bdev, FMODE_READ|FMODE_WRITE);

    if (reg->hr_slots)
        kfree(reg->hr_slots);

    kfree(reg->hr_db_regnum);
    kfree(reg->hr_db_livenodes);
    debugfs_remove(reg->hr_debug_livenodes);
    debugfs_remove(reg->hr_debug_regnum);
    debugfs_remove(reg->hr_debug_elapsed_time);
    debugfs_remove(reg->hr_debug_pinned);
    debugfs_remove(reg->hr_debug_dir);

    spin_lock(&o2hb_live_lock);
    list_del(&reg->hr_all_item);
    spin_unlock(&o2hb_live_lock);

    kfree(reg);
}

static int o2hb_read_block_input(struct o2hb_region *reg,
                 const char *page,
                 size_t count,
                 unsigned long *ret_bytes,
                 unsigned int *ret_bits)
{
    unsigned long bytes;
    char *p = (char *)page;

    bytes = simple_strtoul(p, &p, 0);
    if (!p || (*p && (*p != '\n')))
        return -EINVAL;

    /* Heartbeat and fs min / max block sizes are the same. */
    if (bytes > 4096 || bytes < 512)
        return -ERANGE;
    if (hweight16(bytes) != 1)
        return -EINVAL;

    if (ret_bytes)
        *ret_bytes = bytes;
    if (ret_bits)
        *ret_bits = ffs(bytes) - 1;

    return 0;
}

static ssize_t o2hb_region_block_bytes_read(struct o2hb_region *reg,
                        char *page)
{
    return sprintf(page, "%u\n", reg->hr_block_bytes);
}

static ssize_t o2hb_region_block_bytes_write(struct o2hb_region *reg,
                         const char *page,
                         size_t count)
{
    int status;
    unsigned long block_bytes;
    unsigned int block_bits;

    if (reg->hr_bdev)
        return -EINVAL;

    status = o2hb_read_block_input(reg, page, count,
                       &block_bytes, &block_bits);
    if (status)
        return status;

    reg->hr_block_bytes = (unsigned int)block_bytes;
    reg->hr_block_bits = block_bits;

    return count;
}

static ssize_t o2hb_region_start_block_read(struct o2hb_region *reg,
                        char *page)
{
    return sprintf(page, "%llu\n", reg->hr_start_block);
}

static ssize_t o2hb_region_start_block_write(struct o2hb_region *reg,
                         const char *page,
                         size_t count)
{
    unsigned long long tmp;
    char *p = (char *)page;

    if (reg->hr_bdev)
        return -EINVAL;

    tmp = simple_strtoull(p, &p, 0);
    if (!p || (*p && (*p != '\n')))
        return -EINVAL;

    reg->hr_start_block = tmp;

    return count;
}

static ssize_t o2hb_region_blocks_read(struct o2hb_region *reg,
                       char *page)
{
    return sprintf(page, "%d\n", reg->hr_blocks);
}

static ssize_t o2hb_region_blocks_write(struct o2hb_region *reg,
                    const char *page,
                    size_t count)
{
    unsigned long tmp;
    char *p = (char *)page;

    if (reg->hr_bdev)
        return -EINVAL;

    tmp = simple_strtoul(p, &p, 0);
    if (!p || (*p && (*p != '\n')))
        return -EINVAL;

    if (tmp > O2NM_MAX_NODES || tmp == 0)
        return -ERANGE;

    reg->hr_blocks = (unsigned int)tmp;

    return count;
}

static ssize_t o2hb_region_dev_read(struct o2hb_region *reg,
                    char *page)
{
    unsigned int ret = 0;

    if (reg->hr_bdev)
        ret = sprintf(page, "%s\n", reg->hr_dev_name);

    return ret;
}

static void o2hb_init_region_params(struct o2hb_region *reg)
{
    reg->hr_slots_per_page = PAGE_CACHE_SIZE >> reg->hr_block_bits;
    reg->hr_timeout_ms = O2HB_REGION_TIMEOUT_MS;

    mlog(ML_HEARTBEAT, "hr_start_block = %llu, hr_blocks = %u\n",
         reg->hr_start_block, reg->hr_blocks);
    mlog(ML_HEARTBEAT, "hr_block_bytes = %u, hr_block_bits = %u\n",
         reg->hr_block_bytes, reg->hr_block_bits);
    mlog(ML_HEARTBEAT, "hr_timeout_ms = %u\n", reg->hr_timeout_ms);
    mlog(ML_HEARTBEAT, "dead threshold = %u\n", o2hb_dead_threshold);
}

static int o2hb_map_slot_data(struct o2hb_region *reg)
{
    int i, j;
    unsigned int last_slot;
    unsigned int spp = reg->hr_slots_per_page;
    struct page *page;
    char *raw;
    struct o2hb_disk_slot *slot;

    reg->hr_tmp_block = kmalloc(reg->hr_block_bytes, GFP_KERNEL);
    if (reg->hr_tmp_block == NULL) {
        mlog_errno(-ENOMEM);
        return -ENOMEM;
    }

    reg->hr_slots = kcalloc(reg->hr_blocks,
                sizeof(struct o2hb_disk_slot), GFP_KERNEL);
    if (reg->hr_slots == NULL) {
        mlog_errno(-ENOMEM);
        return -ENOMEM;
    }

    for(i = 0; i < reg->hr_blocks; i++) {
        slot = &reg->hr_slots[i];
        slot->ds_node_num = i;
        INIT_LIST_HEAD(&slot->ds_live_item);
        slot->ds_raw_block = NULL;
    }

    reg->hr_num_pages = (reg->hr_blocks + spp - 1) / spp;
    mlog(ML_HEARTBEAT, "Going to require %u pages to cover %u blocks "
               "at %u blocks per page\n",
         reg->hr_num_pages, reg->hr_blocks, spp);

    reg->hr_slot_data = kcalloc(reg->hr_num_pages, sizeof(struct page *),
                    GFP_KERNEL);
    if (!reg->hr_slot_data) {
        mlog_errno(-ENOMEM);
        return -ENOMEM;
    }

    for(i = 0; i < reg->hr_num_pages; i++) {
        page = alloc_page(GFP_KERNEL);
        if (!page) {
            mlog_errno(-ENOMEM);
            return -ENOMEM;
        }

        reg->hr_slot_data[i] = page;

        last_slot = i * spp;
        raw = page_address(page);
        for (j = 0;
             (j < spp) && ((j + last_slot) < reg->hr_blocks);
             j++) {
            BUG_ON((j + last_slot) >= reg->hr_blocks);

            slot = &reg->hr_slots[j + last_slot];
            slot->ds_raw_block =
                (struct o2hb_disk_heartbeat_block *) raw;

            raw += reg->hr_block_bytes;
        }
    }

    return 0;
}

/* Read in all the slots available and populate the tracking
 * structures so that we can start with a baseline idea of what's
 * there. */
static int o2hb_populate_slot_data(struct o2hb_region *reg)
{
    int ret, i;
    struct o2hb_disk_slot *slot;
    struct o2hb_disk_heartbeat_block *hb_block;

    ret = o2hb_read_slots(reg, reg->hr_blocks);
    if (ret) {
        mlog_errno(ret);
        goto out;
    }

    /* We only want to get an idea of the values initially in each
     * slot, so we do no verification - o2hb_check_slot will
     * actually determine if each configured slot is valid and
     * whether any values have changed. */
    for(i = 0; i < reg->hr_blocks; i++) {
        slot = &reg->hr_slots[i];
        hb_block = (struct o2hb_disk_heartbeat_block *) slot->ds_raw_block;

        /* Only fill the values that o2hb_check_slot uses to
         * determine changing slots */
        slot->ds_last_time = le64_to_cpu(hb_block->hb_seq);
        slot->ds_last_generation = le64_to_cpu(hb_block->hb_generation);
    }

out:
    return ret;
}

/* this is acting as commit; we set up all of hr_bdev and hr_task or nothing */
static ssize_t o2hb_region_dev_write(struct o2hb_region *reg,
                     const char *page,
                     size_t count)
{
    struct task_struct *hb_task;
    long fd;
    int sectsize;
    char *p = (char *)page;
    struct fd f;
    struct inode *inode;
    ssize_t ret = -EINVAL;
    int live_threshold;

    if (reg->hr_bdev)
        goto out;

    /* We can't heartbeat without having had our node number
     * configured yet. */
    if (o2nm_this_node() == O2NM_MAX_NODES)
        goto out;

    fd = simple_strtol(p, &p, 0);
    if (!p || (*p && (*p != '\n')))
        goto out;

    if (fd < 0 || fd >= INT_MAX)
        goto out;

    f = fdget(fd);
    if (f.file == NULL)
        goto out;

    if (reg->hr_blocks == 0 || reg->hr_start_block == 0 ||
        reg->hr_block_bytes == 0)
        goto out2;

    inode = igrab(f.file->f_mapping->host);
    if (inode == NULL)
        goto out2;

    if (!S_ISBLK(inode->i_mode))
        goto out3;

    reg->hr_bdev = I_BDEV(f.file->f_mapping->host);
    ret = blkdev_get(reg->hr_bdev, FMODE_WRITE | FMODE_READ, NULL);
    if (ret) {
        reg->hr_bdev = NULL;
        goto out3;
    }
    inode = NULL;

    bdevname(reg->hr_bdev, reg->hr_dev_name);

    sectsize = bdev_logical_block_size(reg->hr_bdev);
    if (sectsize != reg->hr_block_bytes) {
        mlog(ML_ERROR,
             "blocksize %u incorrect for device, expected %d",
             reg->hr_block_bytes, sectsize);
        ret = -EINVAL;
        goto out3;
    }

    o2hb_init_region_params(reg);

    /* Generation of zero is invalid */
    do {
        get_random_bytes(&reg->hr_generation,
                 sizeof(reg->hr_generation));
    } while (reg->hr_generation == 0);

    ret = o2hb_map_slot_data(reg);
    if (ret) {
        mlog_errno(ret);
        goto out3;
    }

    ret = o2hb_populate_slot_data(reg);
    if (ret) {
        mlog_errno(ret);
        goto out3;
    }

    INIT_DELAYED_WORK(&reg->hr_write_timeout_work, o2hb_write_timeout);

    /*
     * A node is considered live after it has beat LIVE_THRESHOLD
     * times.  We're not steady until we've given them a chance
     * _after_ our first read.
     * The default threshold is bare minimum so as to limit the delay
     * during mounts. For global heartbeat, the threshold doubled for the
     * first region.
     */
    live_threshold = O2HB_LIVE_THRESHOLD;
    if (o2hb_global_heartbeat_active()) {
        spin_lock(&o2hb_live_lock);
        if (o2hb_pop_count(&o2hb_region_bitmap, O2NM_MAX_REGIONS) == 1)
            live_threshold <<= 1;
        spin_unlock(&o2hb_live_lock);
    }
    ++live_threshold;
    atomic_set(&reg->hr_steady_iterations, live_threshold);
    /* unsteady_iterations is double the steady_iterations */
    atomic_set(&reg->hr_unsteady_iterations, (live_threshold << 1));

    hb_task = kthread_run(o2hb_thread, reg, "o2hb-%s",
                  reg->hr_item.ci_name);
    if (IS_ERR(hb_task)) {
        ret = PTR_ERR(hb_task);
        mlog_errno(ret);
        goto out3;
    }

    spin_lock(&o2hb_live_lock);
    reg->hr_task = hb_task;
    spin_unlock(&o2hb_live_lock);

    ret = wait_event_interruptible(o2hb_steady_queue,
                atomic_read(&reg->hr_steady_iterations) == 0);
    if (ret) {
        atomic_set(&reg->hr_steady_iterations, 0);
        reg->hr_aborted_start = 1;
    }

    if (reg->hr_aborted_start) {
        ret = -EIO;
        goto out3;
    }

    /* Ok, we were woken.  Make sure it wasn't by drop_item() */
    spin_lock(&o2hb_live_lock);
    hb_task = reg->hr_task;
    if (o2hb_global_heartbeat_active())
        set_bit(reg->hr_region_num, o2hb_live_region_bitmap);
    spin_unlock(&o2hb_live_lock);

    if (hb_task)
        ret = count;
    else
        ret = -EIO;

    if (hb_task && o2hb_global_heartbeat_active())
        printk(KERN_NOTICE "o2hb: Heartbeat started on region %s (%s)\n",
               config_item_name(&reg->hr_item), reg->hr_dev_name);

out3:
    iput(inode);
out2:
    fdput(f);
out:
    if (ret < 0) {
        if (reg->hr_bdev) {
            blkdev_put(reg->hr_bdev, FMODE_READ|FMODE_WRITE);
            reg->hr_bdev = NULL;
        }
    }
    return ret;
}

static ssize_t o2hb_region_pid_read(struct o2hb_region *reg,
                                      char *page)
{
    pid_t pid = 0;

    spin_lock(&o2hb_live_lock);
    if (reg->hr_task)
        pid = task_pid_nr(reg->hr_task);
    spin_unlock(&o2hb_live_lock);

    if (!pid)
        return 0;

    return sprintf(page, "%u\n", pid);
}

struct o2hb_region_attribute {
    struct configfs_attribute attr;
    ssize_t (*show)(struct o2hb_region *, char *);
    ssize_t (*store)(struct o2hb_region *, const char *, size_t);
};

static struct o2hb_region_attribute o2hb_region_attr_block_bytes = {
    .attr   = { .ca_owner = THIS_MODULE,
            .ca_name = "block_bytes",
            .ca_mode = S_IRUGO | S_IWUSR },
    .show   = o2hb_region_block_bytes_read,
    .store  = o2hb_region_block_bytes_write,
};

static struct o2hb_region_attribute o2hb_region_attr_start_block = {
    .attr   = { .ca_owner = THIS_MODULE,
            .ca_name = "start_block",
            .ca_mode = S_IRUGO | S_IWUSR },
    .show   = o2hb_region_start_block_read,
    .store  = o2hb_region_start_block_write,
};

static struct o2hb_region_attribute o2hb_region_attr_blocks = {
    .attr   = { .ca_owner = THIS_MODULE,
            .ca_name = "blocks",
            .ca_mode = S_IRUGO | S_IWUSR },
    .show   = o2hb_region_blocks_read,
    .store  = o2hb_region_blocks_write,
};

static struct o2hb_region_attribute o2hb_region_attr_dev = {
    .attr   = { .ca_owner = THIS_MODULE,
            .ca_name = "dev",
            .ca_mode = S_IRUGO | S_IWUSR },
    .show   = o2hb_region_dev_read,
    .store  = o2hb_region_dev_write,
};

static struct o2hb_region_attribute o2hb_region_attr_pid = {
       .attr   = { .ca_owner = THIS_MODULE,
                   .ca_name = "pid",
                   .ca_mode = S_IRUGO | S_IRUSR },
       .show   = o2hb_region_pid_read,
};

static struct configfs_attribute *o2hb_region_attrs[] = {
    &o2hb_region_attr_block_bytes.attr,
    &o2hb_region_attr_start_block.attr,
    &o2hb_region_attr_blocks.attr,
    &o2hb_region_attr_dev.attr,
    &o2hb_region_attr_pid.attr,
    NULL,
};

static ssize_t o2hb_region_show(struct config_item *item,
                struct configfs_attribute *attr,
                char *page)
{
    struct o2hb_region *reg = to_o2hb_region(item);
    struct o2hb_region_attribute *o2hb_region_attr =
        container_of(attr, struct o2hb_region_attribute, attr);
    ssize_t ret = 0;

    if (o2hb_region_attr->show)
        ret = o2hb_region_attr->show(reg, page);
    return ret;
}

static ssize_t o2hb_region_store(struct config_item *item,
                 struct configfs_attribute *attr,
                 const char *page, size_t count)
{
    struct o2hb_region *reg = to_o2hb_region(item);
    struct o2hb_region_attribute *o2hb_region_attr =
        container_of(attr, struct o2hb_region_attribute, attr);
    ssize_t ret = -EINVAL;

    if (o2hb_region_attr->store)
        ret = o2hb_region_attr->store(reg, page, count);
    return ret;
}

static struct configfs_item_operations o2hb_region_item_ops = {
    .release        = o2hb_region_release,
    .show_attribute     = o2hb_region_show,
    .store_attribute    = o2hb_region_store,
};

static struct config_item_type o2hb_region_type = {
    .ct_item_ops    = &o2hb_region_item_ops,
    .ct_attrs   = o2hb_region_attrs,
    .ct_owner   = THIS_MODULE,
};

/* heartbeat set */

struct o2hb_heartbeat_group {
    struct config_group hs_group;
    /* some stuff? */
};

static struct o2hb_heartbeat_group *to_o2hb_heartbeat_group(struct config_group *group)
{
    return group ?
        container_of(group, struct o2hb_heartbeat_group, hs_group)
        : NULL;
}

static int o2hb_debug_region_init(struct o2hb_region *reg, struct dentry *dir)
{
    int ret = -ENOMEM;

    reg->hr_debug_dir =
        debugfs_create_dir(config_item_name(&reg->hr_item), dir);
    if (!reg->hr_debug_dir) {
        mlog_errno(ret);
        goto bail;
    }

    reg->hr_debug_livenodes =
            o2hb_debug_create(O2HB_DEBUG_LIVENODES,
                      reg->hr_debug_dir,
                      &(reg->hr_db_livenodes),
                      sizeof(*(reg->hr_db_livenodes)),
                      O2HB_DB_TYPE_REGION_LIVENODES,
                      sizeof(reg->hr_live_node_bitmap),
                      O2NM_MAX_NODES, reg);
    if (!reg->hr_debug_livenodes) {
        mlog_errno(ret);
        goto bail;
    }

    reg->hr_debug_regnum =
            o2hb_debug_create(O2HB_DEBUG_REGION_NUMBER,
                      reg->hr_debug_dir,
                      &(reg->hr_db_regnum),
                      sizeof(*(reg->hr_db_regnum)),
                      O2HB_DB_TYPE_REGION_NUMBER,
                      0, O2NM_MAX_NODES, reg);
    if (!reg->hr_debug_regnum) {
        mlog_errno(ret);
        goto bail;
    }

    reg->hr_debug_elapsed_time =
            o2hb_debug_create(O2HB_DEBUG_REGION_ELAPSED_TIME,
                      reg->hr_debug_dir,
                      &(reg->hr_db_elapsed_time),
                      sizeof(*(reg->hr_db_elapsed_time)),
                      O2HB_DB_TYPE_REGION_ELAPSED_TIME,
                      0, 0, reg);
    if (!reg->hr_debug_elapsed_time) {
        mlog_errno(ret);
        goto bail;
    }

    reg->hr_debug_pinned =
            o2hb_debug_create(O2HB_DEBUG_REGION_PINNED,
                      reg->hr_debug_dir,
                      &(reg->hr_db_pinned),
                      sizeof(*(reg->hr_db_pinned)),
                      O2HB_DB_TYPE_REGION_PINNED,
                      0, 0, reg);
    if (!reg->hr_debug_pinned) {
        mlog_errno(ret);
        goto bail;
    }

    ret = 0;
bail:
    return ret;
}

static struct config_item *o2hb_heartbeat_group_make_item(struct config_group *group,
                              const char *name)
{
    struct o2hb_region *reg = NULL;
    int ret;

    reg = kzalloc(sizeof(struct o2hb_region), GFP_KERNEL);
    if (reg == NULL)
        return ERR_PTR(-ENOMEM);

    if (strlen(name) > O2HB_MAX_REGION_NAME_LEN) {
        ret = -ENAMETOOLONG;
        goto free;
    }

    spin_lock(&o2hb_live_lock);
    reg->hr_region_num = 0;
    if (o2hb_global_heartbeat_active()) {
        reg->hr_region_num = find_first_zero_bit(o2hb_region_bitmap,
                             O2NM_MAX_REGIONS);
        if (reg->hr_region_num >= O2NM_MAX_REGIONS) {
            spin_unlock(&o2hb_live_lock);
            ret = -EFBIG;
            goto free;
        }
        set_bit(reg->hr_region_num, o2hb_region_bitmap);
    }
    list_add_tail(&reg->hr_all_item, &o2hb_all_regions);
    spin_unlock(&o2hb_live_lock);

    config_item_init_type_name(&reg->hr_item, name, &o2hb_region_type);

    ret = o2hb_debug_region_init(reg, o2hb_debug_dir);
    if (ret) {
        config_item_put(&reg->hr_item);
        goto free;
    }

    return &reg->hr_item;
free:
    kfree(reg);
    return ERR_PTR(ret);
}

static void o2hb_heartbeat_group_drop_item(struct config_group *group,
                       struct config_item *item)
{
    struct task_struct *hb_task;
    struct o2hb_region *reg = to_o2hb_region(item);
    int quorum_region = 0;

    /* stop the thread when the user removes the region dir */
    spin_lock(&o2hb_live_lock);
    hb_task = reg->hr_task;
    reg->hr_task = NULL;
    reg->hr_item_dropped = 1;
    spin_unlock(&o2hb_live_lock);

    if (hb_task)
        kthread_stop(hb_task);

    if (o2hb_global_heartbeat_active()) {
        spin_lock(&o2hb_live_lock);
        clear_bit(reg->hr_region_num, o2hb_region_bitmap);
        clear_bit(reg->hr_region_num, o2hb_live_region_bitmap);
        if (test_bit(reg->hr_region_num, o2hb_quorum_region_bitmap))
            quorum_region = 1;
        clear_bit(reg->hr_region_num, o2hb_quorum_region_bitmap);
        spin_unlock(&o2hb_live_lock);
        printk(KERN_NOTICE "o2hb: Heartbeat %s on region %s (%s)\n",
               ((atomic_read(&reg->hr_steady_iterations) == 0) ?
            "stopped" : "start aborted"), config_item_name(item),
               reg->hr_dev_name);
    }

    /*
     * If we're racing a dev_write(), we need to wake them.  They will
     * check reg->hr_task
     */
    if (atomic_read(&reg->hr_steady_iterations) != 0) {
        reg->hr_aborted_start = 1;
        atomic_set(&reg->hr_steady_iterations, 0);
        wake_up(&o2hb_steady_queue);
    }

    config_item_put(item);

    if (!o2hb_global_heartbeat_active() || !quorum_region)
        return;

    /*
     * If global heartbeat active and there are dependent users,
     * pin all regions if quorum region count <= CUT_OFF
     */
    spin_lock(&o2hb_live_lock);

    if (!o2hb_dependent_users)
        goto unlock;

    if (o2hb_pop_count(&o2hb_quorum_region_bitmap,
               O2NM_MAX_REGIONS) <= O2HB_PIN_CUT_OFF)
        o2hb_region_pin(NULL);

unlock:
    spin_unlock(&o2hb_live_lock);
}

struct o2hb_heartbeat_group_attribute {
    struct configfs_attribute attr;
    ssize_t (*show)(struct o2hb_heartbeat_group *, char *);
    ssize_t (*store)(struct o2hb_heartbeat_group *, const char *, size_t);
};

static ssize_t o2hb_heartbeat_group_show(struct config_item *item,
                     struct configfs_attribute *attr,
                     char *page)
{
    struct o2hb_heartbeat_group *reg = to_o2hb_heartbeat_group(to_config_group(item));
    struct o2hb_heartbeat_group_attribute *o2hb_heartbeat_group_attr =
        container_of(attr, struct o2hb_heartbeat_group_attribute, attr);
    ssize_t ret = 0;

    if (o2hb_heartbeat_group_attr->show)
        ret = o2hb_heartbeat_group_attr->show(reg, page);
    return ret;
}

static ssize_t o2hb_heartbeat_group_store(struct config_item *item,
                      struct configfs_attribute *attr,
                      const char *page, size_t count)
{
    struct o2hb_heartbeat_group *reg = to_o2hb_heartbeat_group(to_config_group(item));
    struct o2hb_heartbeat_group_attribute *o2hb_heartbeat_group_attr =
        container_of(attr, struct o2hb_heartbeat_group_attribute, attr);
    ssize_t ret = -EINVAL;

    if (o2hb_heartbeat_group_attr->store)
        ret = o2hb_heartbeat_group_attr->store(reg, page, count);
    return ret;
}

static ssize_t o2hb_heartbeat_group_threshold_show(struct o2hb_heartbeat_group *group,
                             char *page)
{
    return sprintf(page, "%u\n", o2hb_dead_threshold);
}

static ssize_t o2hb_heartbeat_group_threshold_store(struct o2hb_heartbeat_group *group,
                            const char *page,
                            size_t count)
{
    unsigned long tmp;
    char *p = (char *)page;

    tmp = simple_strtoul(p, &p, 10);
    if (!p || (*p && (*p != '\n')))
                return -EINVAL;

    /* this will validate ranges for us. */
    o2hb_dead_threshold_set((unsigned int) tmp);

    return count;
}

static
ssize_t o2hb_heartbeat_group_mode_show(struct o2hb_heartbeat_group *group,
                       char *page)
{
    return sprintf(page, "%s\n",
               o2hb_heartbeat_mode_desc[o2hb_heartbeat_mode]);
}

static
ssize_t o2hb_heartbeat_group_mode_store(struct o2hb_heartbeat_group *group,
                    const char *page, size_t count)
{
    unsigned int i;
    int ret;
    size_t len;

    len = (page[count - 1] == '\n') ? count - 1 : count;
    if (!len)
        return -EINVAL;

    for (i = 0; i < O2HB_HEARTBEAT_NUM_MODES; ++i) {
        if (strnicmp(page, o2hb_heartbeat_mode_desc[i], len))
            continue;

        ret = o2hb_global_hearbeat_mode_set(i);
        if (!ret)
            printk(KERN_NOTICE "o2hb: Heartbeat mode set to %s\n",
                   o2hb_heartbeat_mode_desc[i]);
        return count;
    }

    return -EINVAL;

}

static struct o2hb_heartbeat_group_attribute o2hb_heartbeat_group_attr_threshold = {
    .attr   = { .ca_owner = THIS_MODULE,
            .ca_name = "dead_threshold",
            .ca_mode = S_IRUGO | S_IWUSR },
    .show   = o2hb_heartbeat_group_threshold_show,
    .store  = o2hb_heartbeat_group_threshold_store,
};

static struct o2hb_heartbeat_group_attribute o2hb_heartbeat_group_attr_mode = {
    .attr   = { .ca_owner = THIS_MODULE,
        .ca_name = "mode",
        .ca_mode = S_IRUGO | S_IWUSR },
    .show   = o2hb_heartbeat_group_mode_show,
    .store  = o2hb_heartbeat_group_mode_store,
};

static struct configfs_attribute *o2hb_heartbeat_group_attrs[] = {
    &o2hb_heartbeat_group_attr_threshold.attr,
    &o2hb_heartbeat_group_attr_mode.attr,
    NULL,
};

static struct configfs_item_operations o2hb_hearbeat_group_item_ops = {
    .show_attribute     = o2hb_heartbeat_group_show,
    .store_attribute    = o2hb_heartbeat_group_store,
};

static struct configfs_group_operations o2hb_heartbeat_group_group_ops = {
    .make_item  = o2hb_heartbeat_group_make_item,
    .drop_item  = o2hb_heartbeat_group_drop_item,
};

static struct config_item_type o2hb_heartbeat_group_type = {
    .ct_group_ops   = &o2hb_heartbeat_group_group_ops,
    .ct_item_ops    = &o2hb_hearbeat_group_item_ops,
    .ct_attrs   = o2hb_heartbeat_group_attrs,
    .ct_owner   = THIS_MODULE,
};

/* this is just here to avoid touching group in heartbeat.h which the
 * entire damn world #includes */
struct config_group *o2hb_alloc_hb_set(void)
{
    struct o2hb_heartbeat_group *hs = NULL;
    struct config_group *ret = NULL;

    hs = kzalloc(sizeof(struct o2hb_heartbeat_group), GFP_KERNEL);
    if (hs == NULL)
        goto out;

    config_group_init_type_name(&hs->hs_group, "heartbeat",
                    &o2hb_heartbeat_group_type);

    ret = &hs->hs_group;
out:
    if (ret == NULL)
        kfree(hs);
    return ret;
}

void o2hb_free_hb_set(struct config_group *group)
{
    struct o2hb_heartbeat_group *hs = to_o2hb_heartbeat_group(group);
    kfree(hs);
}

/* hb callback registration and issuing */

static struct o2hb_callback *hbcall_from_type(enum o2hb_callback_type type)
{
    if (type == O2HB_NUM_CB)
        return ERR_PTR(-EINVAL);

    return &o2hb_callbacks[type];
}

void o2hb_setup_callback(struct o2hb_callback_func *hc,
             enum o2hb_callback_type type,
             o2hb_cb_func *func,
             void *data,
             int priority)
{
    INIT_LIST_HEAD(&hc->hc_item);
    hc->hc_func = func;
    hc->hc_data = data;
    hc->hc_priority = priority;
    hc->hc_type = type;
    hc->hc_magic = O2HB_CB_MAGIC;
}
EXPORT_SYMBOL_GPL(o2hb_setup_callback);

/*
 * In local heartbeat mode, region_uuid passed matches the dlm domain name.
 * In global heartbeat mode, region_uuid passed is NULL.
 *
 * In local, we only pin the matching region. In global we pin all the active
 * regions.
 */
static int o2hb_region_pin(const char *region_uuid)
{
    int ret = 0, found = 0;
    struct o2hb_region *reg;
    char *uuid;

    assert_spin_locked(&o2hb_live_lock);

    list_for_each_entry(reg, &o2hb_all_regions, hr_all_item) {
        uuid = config_item_name(&reg->hr_item);

        /* local heartbeat */
        if (region_uuid) {
            if (strcmp(region_uuid, uuid))
                continue;
            found = 1;
        }

        if (reg->hr_item_pinned || reg->hr_item_dropped)
            goto skip_pin;

        /* Ignore ENOENT only for local hb (userdlm domain) */
        ret = o2nm_depend_item(&reg->hr_item);
        if (!ret) {
            mlog(ML_CLUSTER, "Pin region %s\n", uuid);
            reg->hr_item_pinned = 1;
        } else {
            if (ret == -ENOENT && found)
                ret = 0;
            else {
                mlog(ML_ERROR, "Pin region %s fails with %d\n",
                     uuid, ret);
                break;
            }
        }
skip_pin:
        if (found)
            break;
    }

    return ret;
}

/*
 * In local heartbeat mode, region_uuid passed matches the dlm domain name.
 * In global heartbeat mode, region_uuid passed is NULL.
 *
 * In local, we only unpin the matching region. In global we unpin all the
 * active regions.
 */
static void o2hb_region_unpin(const char *region_uuid)
{
    struct o2hb_region *reg;
    char *uuid;
    int found = 0;

    assert_spin_locked(&o2hb_live_lock);

    list_for_each_entry(reg, &o2hb_all_regions, hr_all_item) {
        uuid = config_item_name(&reg->hr_item);
        if (region_uuid) {
            if (strcmp(region_uuid, uuid))
                continue;
            found = 1;
        }

        if (reg->hr_item_pinned) {
            mlog(ML_CLUSTER, "Unpin region %s\n", uuid);
            o2nm_undepend_item(&reg->hr_item);
            reg->hr_item_pinned = 0;
        }
        if (found)
            break;
    }
}

static int o2hb_region_inc_user(const char *region_uuid)
{
    int ret = 0;

    spin_lock(&o2hb_live_lock);

    /* local heartbeat */
    if (!o2hb_global_heartbeat_active()) {
        ret = o2hb_region_pin(region_uuid);
        goto unlock;
    }

    /*
     * if global heartbeat active and this is the first dependent user,
     * pin all regions if quorum region count <= CUT_OFF
     */
    o2hb_dependent_users++;
    if (o2hb_dependent_users > 1)
        goto unlock;

    if (o2hb_pop_count(&o2hb_quorum_region_bitmap,
               O2NM_MAX_REGIONS) <= O2HB_PIN_CUT_OFF)
        ret = o2hb_region_pin(NULL);

unlock:
    spin_unlock(&o2hb_live_lock);
    return ret;
}

void o2hb_region_dec_user(const char *region_uuid)
{
    spin_lock(&o2hb_live_lock);

    /* local heartbeat */
    if (!o2hb_global_heartbeat_active()) {
        o2hb_region_unpin(region_uuid);
        goto unlock;
    }

    /*
     * if global heartbeat active and there are no dependent users,
     * unpin all quorum regions
     */
    o2hb_dependent_users--;
    if (!o2hb_dependent_users)
        o2hb_region_unpin(NULL);

unlock:
    spin_unlock(&o2hb_live_lock);
}

int o2hb_register_callback(const char *region_uuid,
               struct o2hb_callback_func *hc)
{
    struct o2hb_callback_func *tmp;
    struct list_head *iter;
    struct o2hb_callback *hbcall;
    int ret;

    BUG_ON(hc->hc_magic != O2HB_CB_MAGIC);
    BUG_ON(!list_empty(&hc->hc_item));

    hbcall = hbcall_from_type(hc->hc_type);
    if (IS_ERR(hbcall)) {
        ret = PTR_ERR(hbcall);
        goto out;
    }

    if (region_uuid) {
        ret = o2hb_region_inc_user(region_uuid);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
    }

    down_write(&o2hb_callback_sem);

    list_for_each(iter, &hbcall->list) {
        tmp = list_entry(iter, struct o2hb_callback_func, hc_item);
        if (hc->hc_priority < tmp->hc_priority) {
            list_add_tail(&hc->hc_item, iter);
            break;
        }
    }
    if (list_empty(&hc->hc_item))
        list_add_tail(&hc->hc_item, &hbcall->list);

    up_write(&o2hb_callback_sem);
    ret = 0;
out:
    mlog(ML_CLUSTER, "returning %d on behalf of %p for funcs %p\n",
         ret, __builtin_return_address(0), hc);
    return ret;
}
EXPORT_SYMBOL_GPL(o2hb_register_callback);

void o2hb_unregister_callback(const char *region_uuid,
                  struct o2hb_callback_func *hc)
{
    BUG_ON(hc->hc_magic != O2HB_CB_MAGIC);

    mlog(ML_CLUSTER, "on behalf of %p for funcs %p\n",
         __builtin_return_address(0), hc);

    /* XXX Can this happen _with_ a region reference? */
    if (list_empty(&hc->hc_item))
        return;

    if (region_uuid)
        o2hb_region_dec_user(region_uuid);

    down_write(&o2hb_callback_sem);

    list_del_init(&hc->hc_item);

    up_write(&o2hb_callback_sem);
}
EXPORT_SYMBOL_GPL(o2hb_unregister_callback);

int o2hb_check_node_heartbeating(u8 node_num)
{
    unsigned long testing_map[BITS_TO_LONGS(O2NM_MAX_NODES)];

    o2hb_fill_node_map(testing_map, sizeof(testing_map));
    if (!test_bit(node_num, testing_map)) {
        mlog(ML_HEARTBEAT,
             "node (%u) does not have heartbeating enabled.\n",
             node_num);
        return 0;
    }

    return 1;
}
EXPORT_SYMBOL_GPL(o2hb_check_node_heartbeating);

int o2hb_check_node_heartbeating_from_callback(u8 node_num)
{
    unsigned long testing_map[BITS_TO_LONGS(O2NM_MAX_NODES)];

    o2hb_fill_node_map_from_callback(testing_map, sizeof(testing_map));
    if (!test_bit(node_num, testing_map)) {
        mlog(ML_HEARTBEAT,
             "node (%u) does not have heartbeating enabled.\n",
             node_num);
        return 0;
    }

    return 1;
}
EXPORT_SYMBOL_GPL(o2hb_check_node_heartbeating_from_callback);

/* Makes sure our local node is configured with a node number, and is
 * heartbeating. */
int o2hb_check_local_node_heartbeating(void)
{
    u8 node_num;

    /* if this node was set then we have networking */
    node_num = o2nm_this_node();
    if (node_num == O2NM_MAX_NODES) {
        mlog(ML_HEARTBEAT, "this node has not been configured.\n");
        return 0;
    }

    return o2hb_check_node_heartbeating(node_num);
}
EXPORT_SYMBOL_GPL(o2hb_check_local_node_heartbeating);

/*
 * this is just a hack until we get the plumbing which flips file systems
 * read only and drops the hb ref instead of killing the node dead.
 */
void o2hb_stop_all_regions(void)
{
    struct o2hb_region *reg;

    mlog(ML_ERROR, "stopping heartbeat on all active regions.\n");

    spin_lock(&o2hb_live_lock);

    list_for_each_entry(reg, &o2hb_all_regions, hr_all_item)
        reg->hr_unclean_stop = 1;

    spin_unlock(&o2hb_live_lock);
}
EXPORT_SYMBOL_GPL(o2hb_stop_all_regions);

int o2hb_get_all_regions(char *region_uuids, u8 max_regions)
{
    struct o2hb_region *reg;
    int numregs = 0;
    char *p;

    spin_lock(&o2hb_live_lock);

    p = region_uuids;
    list_for_each_entry(reg, &o2hb_all_regions, hr_all_item) {
        mlog(0, "Region: %s\n", config_item_name(&reg->hr_item));
        if (numregs < max_regions) {
            memcpy(p, config_item_name(&reg->hr_item),
                   O2HB_MAX_REGION_NAME_LEN);
            p += O2HB_MAX_REGION_NAME_LEN;
        }
        numregs++;
    }

    spin_unlock(&o2hb_live_lock);

    return numregs;
}
EXPORT_SYMBOL_GPL(o2hb_get_all_regions);

int o2hb_global_heartbeat_active(void)
{
    return (o2hb_heartbeat_mode == O2HB_HEARTBEAT_GLOBAL);
}
EXPORT_SYMBOL(o2hb_global_heartbeat_active);