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heartbeat.c

/* -*- 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 "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);

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

unsigned int o2hb_dead_threshold = O2HB_DEFAULT_DEAD_THRESHOLD;

/* 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);
      }
}

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;

      /* 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;

      /* 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;

      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 void o2hb_write_timeout(struct work_struct *work)
{
      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)); 
      o2quo_disk_timeout();
}

static void o2hb_arm_write_timeout(struct o2hb_region *reg)
{
      mlog(0, "Queue write timeout for %u ms\n", O2HB_MAX_WRITE_TIMEOUT_MS);

      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(&reg->hr_write_timeout_work);
      flush_scheduled_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)
{
      struct address_space *mapping = reg->hr_bdev->bd_inode->i_mapping;

      blk_run_address_space(mapping);
      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;
}

/* We want to make sure that nobody is heartbeating on top of us --
 * this will help detect an invalid configuration. */
static int o2hb_check_last_timestamp(struct o2hb_region *reg)
{
      int node_num, ret;
      struct o2hb_disk_slot *slot;
      struct o2hb_disk_heartbeat_block *hb_block;

      node_num = o2nm_this_node();

      ret = 1;
      slot = &reg->hr_slots[node_num];
      /* Don't check on our 1st timestamp */
      if (slot->ds_last_time) {
            hb_block = slot->ds_raw_block;

            if (le64_to_cpu(hb_block->hb_seq) != slot->ds_last_time)
                  ret = 0;
      }

      return ret;
}

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);

      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 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;

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

      /* Is this correct? Do we assume that the node doesn't exist
       * if we're not configured for him? */
      node = o2nm_get_node_by_num(slot->ds_node_num);
      if (!node)
            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);

            /* first on the list generates a callback */
            if (list_empty(&o2hb_live_slots[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);

            /* 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])) {
                  clear_bit(slot->ds_node_num, o2hb_live_node_bitmap);

                  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);

      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, change = 0;
      unsigned long configured_nodes[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);
            return ret;
      }

      highest_node = o2hb_highest_node(configured_nodes, O2NM_MAX_NODES);
      if (highest_node >= O2NM_MAX_NODES) {
            mlog(ML_NOTICE, "ocfs2_heartbeat: no configured nodes found!\n");
            return -EINVAL;
      }

      /* 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);
            return ret;
      }

      /* 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. */
      if (!o2hb_check_last_timestamp(reg))
            mlog(ML_ERROR, "Device \"%s\": another node is heartbeating "
                 "in our slot!\n", reg->hr_dev_name);

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

      /* And fire off the write. Note that we don't wait on this I/O
       * until later. */
      ret = o2hb_issue_node_write(reg, &write_wc);
      if (ret < 0) {
            mlog_errno(ret);
            return ret;
      }

      i = -1;
      while((i = find_next_bit(configured_nodes, O2NM_MAX_NODES, i + 1)) < O2NM_MAX_NODES) {

            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);
            return write_wc.wc_error;
      }

      o2hb_arm_write_timeout(reg);

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

      return 0;
}

/* 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);

      while (!kthread_should_stop() && !reg->hr_unclean_stop) {
            /* We track the time spent inside
             * o2hb_do_disk_heartbeat so that we avoid more then
             * 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);

            i = 0;
            do {
                  ret = o2hb_do_disk_heartbeat(reg);
            } while (ret && ++i < 2);

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

            mlog(0, "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 (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.
       *
       * XXX: Should we skip this on unclean_stop? */
      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);
      }

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

      return 0;
}

void 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));
}

/* 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);

      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);

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

      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;

      mlog_entry_void();

      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:
      mlog_exit(ret);
      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 file *filp = NULL;
      struct inode *inode = NULL;
      ssize_t ret = -EINVAL;

      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;

      filp = fget(fd);
      if (filp == NULL)
            goto out;

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

      inode = igrab(filp->f_mapping->host);
      if (inode == NULL)
            goto out;

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

      reg->hr_bdev = I_BDEV(filp->f_mapping->host);
      ret = blkdev_get(reg->hr_bdev, FMODE_WRITE | FMODE_READ, 0);
      if (ret) {
            reg->hr_bdev = NULL;
            goto out;
      }
      inode = NULL;

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

      sectsize = bdev_hardsect_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 out;
      }

      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 out;
      }

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

      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.
       */
      atomic_set(&reg->hr_steady_iterations, O2HB_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 out;
      }

      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) {
            /* We got interrupted (hello ptrace!).  Clean up */
            spin_lock(&o2hb_live_lock);
            hb_task = reg->hr_task;
            reg->hr_task = NULL;
            spin_unlock(&o2hb_live_lock);

            if (hb_task)
                  kthread_stop(hb_task);
            goto out;
      }

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

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

out:
      if (filp)
            fput(filp);
      if (inode)
            iput(inode);
      if (ret < 0) {
            if (reg->hr_bdev) {
                  blkdev_put(reg->hr_bdev);
                  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 struct config_item *o2hb_heartbeat_group_make_item(struct config_group *group,
                                            const char *name)
{
      struct o2hb_region *reg = NULL;
      struct config_item *ret = NULL;

      reg = kzalloc(sizeof(struct o2hb_region), GFP_KERNEL);
      if (reg == NULL)
            goto out; /* ENOMEM */

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

      ret = &reg->hr_item;

      spin_lock(&o2hb_live_lock);
      list_add_tail(&reg->hr_all_item, &o2hb_all_regions);
      spin_unlock(&o2hb_live_lock);
out:
      if (ret == NULL)
            kfree(reg);

      return 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);

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

      if (hb_task)
            kthread_stop(hb_task);

      /*
       * 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) {
            atomic_set(&reg->hr_steady_iterations, 0);
            wake_up(&o2hb_steady_queue);
      }

      config_item_put(item);
}

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 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 configfs_attribute *o2hb_heartbeat_group_attrs[] = {
      &o2hb_heartbeat_group_attr_threshold.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 issueing */

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);

static struct o2hb_region *o2hb_find_region(const char *region_uuid)
{
      struct o2hb_region *p, *reg = NULL;

      assert_spin_locked(&o2hb_live_lock);

      list_for_each_entry(p, &o2hb_all_regions, hr_all_item) {
            if (!strcmp(region_uuid, config_item_name(&p->hr_item))) {
                  reg = p;
                  break;
            }
      }

      return reg;
}

static int o2hb_region_get(const char *region_uuid)
{
      int ret = 0;
      struct o2hb_region *reg;

      spin_lock(&o2hb_live_lock);

      reg = o2hb_find_region(region_uuid);
      if (!reg)
            ret = -ENOENT;
      spin_unlock(&o2hb_live_lock);

      if (ret)
            goto out;

      ret = o2nm_depend_this_node();
      if (ret)
            goto out;

      ret = o2nm_depend_item(&reg->hr_item);
      if (ret)
            o2nm_undepend_this_node();

out:
      return ret;
}

static void o2hb_region_put(const char *region_uuid)
{
      struct o2hb_region *reg;

      spin_lock(&o2hb_live_lock);

      reg = o2hb_find_region(region_uuid);

      spin_unlock(&o2hb_live_lock);

      if (reg) {
            o2nm_undepend_item(&reg->hr_item);
            o2nm_undepend_this_node();
      }
}

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_get(region_uuid);
            if (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_HEARTBEAT, "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_HEARTBEAT, "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_put(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);

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