text: /* -*- 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 <linux/bitmap.h>
  #include <linux/ktime.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_heartbeat_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,
  				hr_node_deleted: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 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 = bitmap_weight(o2hb_failed_region_bitmap,
  					O2NM_MAX_REGIONS);
  		quorum = bitmap_weight(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)
  {
  	struct o2hb_bio_wait_ctxt *wc = bio->bi_private;
  
  	if (bio->bi_error) {
  		mlog(ML_ERROR, "IO Error %d\n", bio->bi_error);
  		wc->wc_error = bio->bi_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_iter.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_SYNC, 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 o2hb_callback_func *f;
  
  	list_for_each_entry(f, &hbcall->list, 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)
  {
  	struct o2hb_callback *hbcall;
  	struct o2hb_node_event *event;
  
  	/* 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;
  	int queued = 0;
  
  	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);
  			queued = 1;
  		}
  	}
  	spin_unlock(&o2hb_live_lock);
  
  	if (queued)
  		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 (bitmap_weight(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;
  	int queued = 0;
  
  	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;
  			queued = 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;
  			queued = 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);
  
  	if (queued)
  		o2hb_run_event_list(&event);
  
  	if (node)
  		o2nm_node_put(node);
  	return changed;
  }
  
  static int o2hb_highest_node(unsigned long *nodes, int numbits)
  {
  	return find_last_bit(nodes, numbits);
  }
  
  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;
  }
  
  /*
   * 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;
  	ktime_t before_hb, after_hb;
  	unsigned int elapsed_msec;
  
  	mlog(ML_HEARTBEAT|ML_KTHREAD, "hb thread running\n");
  
  	set_user_nice(current, MIN_NICE);
  
  	/* Pin node */
  	ret = o2nm_depend_this_node();
  	if (ret) {
  		mlog(ML_ERROR, "Node has been deleted, ret = %d\n", ret);
  		reg->hr_node_deleted = 1;
  		wake_up(&o2hb_steady_queue);
  		return 0;
  	}
  
  	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. */
  		before_hb = ktime_get_real();
  
  		ret = o2hb_do_disk_heartbeat(reg);
  
  		after_hb = ktime_get_real();
  
  		elapsed_msec = (unsigned int)
  				ktime_ms_delta(after_hb, before_hb);
  
  		mlog(ML_HEARTBEAT,
  		     "start = %lld, end = %lld, msec = %u, ret = %d\n",
  		     before_hb.tv64, after_hb.tv64, elapsed_msec, ret);
  
  		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);
  
  	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);
  
  	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_show(struct config_item *item,
  					    char *page)
  {
  	return sprintf(page, "%u\n", to_o2hb_region(item)->hr_block_bytes);
  }
  
  static ssize_t o2hb_region_block_bytes_store(struct config_item *item,
  					     const char *page,
  					     size_t count)
  {
  	struct o2hb_region *reg = to_o2hb_region(item);
  	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_show(struct config_item *item,
  					    char *page)
  {
  	return sprintf(page, "%llu\n", to_o2hb_region(item)->hr_start_block);
  }
  
  static ssize_t o2hb_region_start_block_store(struct config_item *item,
  					     const char *page,
  					     size_t count)
  {
  	struct o2hb_region *reg = to_o2hb_region(item);
  	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_show(struct config_item *item, char *page)
  {
  	return sprintf(page, "%d\n", to_o2hb_region(item)->hr_blocks);
  }
  
  static ssize_t o2hb_region_blocks_store(struct config_item *item,
  					const char *page,
  					size_t count)
  {
  	struct o2hb_region *reg = to_o2hb_region(item);
  	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_show(struct config_item *item, char *page)
  {
  	unsigned int ret = 0;
  
  	if (to_o2hb_region(item)->hr_bdev)
  		ret = sprintf(page, "%s\n", to_o2hb_region(item)->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)
  		return -ENOMEM;
  
  	reg->hr_slots = kcalloc(reg->hr_blocks,
  				sizeof(struct o2hb_disk_slot), GFP_KERNEL);
  	if (reg->hr_slots == NULL)
  		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)
  		return -ENOMEM;
  
  	for(i = 0; i < reg->hr_num_pages; i++) {
  		page = alloc_page(GFP_KERNEL);
  		if (!page)
  			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)
  		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_store(struct config_item *item,
  				     const char *page,
  				     size_t count)
  {
  	struct o2hb_region *reg = to_o2hb_region(item);
  	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 (bitmap_weight(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 ||
  				reg->hr_node_deleted);
  	if (ret) {
  		atomic_set(&reg->hr_steady_iterations, 0);
  		reg->hr_aborted_start = 1;
  	}
  
  	if (reg->hr_aborted_start) {
  		ret = -EIO;
  		goto out3;
  	}
  
  	if (reg->hr_node_deleted) {
  		ret = -EINVAL;
  		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_show(struct config_item *item, char *page)
  {
  	struct o2hb_region *reg = to_o2hb_region(item);
  	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);
  }
  
  CONFIGFS_ATTR(o2hb_region_, block_bytes);
  CONFIGFS_ATTR(o2hb_region_, start_block);
  CONFIGFS_ATTR(o2hb_region_, blocks);
  CONFIGFS_ATTR(o2hb_region_, dev);
  CONFIGFS_ATTR_RO(o2hb_region_, pid);
  
  static struct configfs_attribute *o2hb_region_attrs[] = {
  	&o2hb_region_attr_block_bytes,
  	&o2hb_region_attr_start_block,
  	&o2hb_region_attr_blocks,
  	&o2hb_region_attr_dev,
  	&o2hb_region_attr_pid,
  	NULL,
  };
  
  static struct configfs_item_operations o2hb_region_item_ops = {
  	.release		= o2hb_region_release,
  };
  
  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 (bitmap_weight(o2hb_quorum_region_bitmap,
  			   O2NM_MAX_REGIONS) <= O2HB_PIN_CUT_OFF)
  		o2hb_region_pin(NULL);
  
  unlock:
  	spin_unlock(&o2hb_live_lock);
  }
  
  static ssize_t o2hb_heartbeat_group_dead_threshold_show(struct config_item *item,
  		char *page)
  {
  	return sprintf(page, "%u\n", o2hb_dead_threshold);
  }
  
  static ssize_t o2hb_heartbeat_group_dead_threshold_store(struct config_item *item,
  		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 config_item *item,
  		char *page)
  {
  	return sprintf(page, "%s\n",
  		       o2hb_heartbeat_mode_desc[o2hb_heartbeat_mode]);
  }
  
  static ssize_t o2hb_heartbeat_group_mode_store(struct config_item *item,
  		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 (strncasecmp(page, o2hb_heartbeat_mode_desc[i], len))
  			continue;
  
  		ret = o2hb_global_heartbeat_mode_set(i);
  		if (!ret)
  			printk(KERN_NOTICE "o2hb: Heartbeat mode set to %s\n",
  			       o2hb_heartbeat_mode_desc[i]);
  		return count;
  	}
  
  	return -EINVAL;
  
  }
  
  CONFIGFS_ATTR(o2hb_heartbeat_group_, dead_threshold);
  CONFIGFS_ATTR(o2hb_heartbeat_group_, mode);
  
  static struct configfs_attribute *o2hb_heartbeat_group_attrs[] = {
  	&o2hb_heartbeat_group_attr_dead_threshold,
  	&o2hb_heartbeat_group_attr_mode,
  	NULL,
  };
  
  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_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) {
  		if (reg->hr_item_dropped)
  			continue;
  
  		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) {
  		if (reg->hr_item_dropped)
  			continue;
  
  		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 (bitmap_weight(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 *f;
  	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_entry(f, &hbcall->list, hc_item) {
  		if (hc->hc_priority < f->hc_priority) {
  			list_add_tail(&hc->hc_item, &f->hc_item);
  			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_no_sem(u8 node_num)
  {
  	unsigned long testing_map[BITS_TO_LONGS(O2NM_MAX_NODES)];
  	unsigned long flags;
  
  	spin_lock_irqsave(&o2hb_live_lock, flags);
  	o2hb_fill_node_map_from_callback(testing_map, sizeof(testing_map));
  	spin_unlock_irqrestore(&o2hb_live_lock, flags);
  	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_no_sem);
  
  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) {
  		if (reg->hr_item_dropped)
  			continue;
  
  		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);
  