Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2543 insertions, 0 deletions

diff --git a/fs/ocfs2/cluster/heartbeat.c b/fs/ocfs2/cluster/heartbeat.c
new file mode 100644
index 000000000..b13d344d4
--- /dev/null
+++ b/fs/ocfs2/cluster/heartbeat.c
@@ -0,0 +1,2543 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2004, 2005 Oracle.  All rights reserved.
+ */
+
+#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 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);
+
+enum o2hb_heartbeat_modes {
+	O2HB_HEARTBEAT_LOCAL		= 0,
+	O2HB_HEARTBEAT_GLOBAL,
+	O2HB_HEARTBEAT_NUM_MODES,
+};
+
+static const 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;
+static 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.
+ */
+static 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 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;
+
+	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;
+
+	/* negotiate timer, used to negotiate extending hb timeout. */
+	struct delayed_work	hr_nego_timeout_work;
+	unsigned long		hr_nego_node_bitmap[BITS_TO_LONGS(O2NM_MAX_NODES)];
+
+	/* 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;
+
+	/* Message key for negotiate timeout message. */
+	unsigned int		hr_key;
+	struct list_head	hr_handler_list;
+
+	/* last hb status, 0 for success, other value for error. */
+	int			hr_last_hb_status;
+};
+
+struct o2hb_bio_wait_ctxt {
+	atomic_t          wc_num_reqs;
+	struct completion wc_io_complete;
+	int               wc_error;
+};
+
+#define O2HB_NEGO_TIMEOUT_MS (O2HB_MAX_WRITE_TIMEOUT_MS/2)
+
+enum {
+	O2HB_NEGO_TIMEOUT_MSG = 1,
+	O2HB_NEGO_APPROVE_MSG = 2,
+};
+
+struct o2hb_nego_msg {
+	u8 node_num;
+};
+
+static void o2hb_write_timeout(struct work_struct *work)
+{
+	int failed, quorum;
+	struct o2hb_region *reg =
+		container_of(work, struct o2hb_region,
+			     hr_write_timeout_work.work);
+
+	mlog(ML_ERROR, "Heartbeat write timeout to device %pg after %u "
+	     "milliseconds\n", reg->hr_bdev,
+	     jiffies_to_msecs(jiffies - reg->hr_last_timeout_start));
+
+	if (o2hb_global_heartbeat_active()) {
+		spin_lock(&o2hb_live_lock);
+		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(&o2hb_live_lock);
+
+		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_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);
+	schedule_delayed_work(&reg->hr_write_timeout_work,
+			      msecs_to_jiffies(O2HB_MAX_WRITE_TIMEOUT_MS));
+
+	cancel_delayed_work(&reg->hr_nego_timeout_work);
+	/* negotiate timeout must be less than write timeout. */
+	schedule_delayed_work(&reg->hr_nego_timeout_work,
+			      msecs_to_jiffies(O2HB_NEGO_TIMEOUT_MS));
+	memset(reg->hr_nego_node_bitmap, 0, sizeof(reg->hr_nego_node_bitmap));
+}
+
+static void o2hb_disarm_timeout(struct o2hb_region *reg)
+{
+	cancel_delayed_work_sync(&reg->hr_write_timeout_work);
+	cancel_delayed_work_sync(&reg->hr_nego_timeout_work);
+}
+
+static int o2hb_send_nego_msg(int key, int type, u8 target)
+{
+	struct o2hb_nego_msg msg;
+	int status, ret;
+
+	msg.node_num = o2nm_this_node();
+again:
+	ret = o2net_send_message(type, key, &msg, sizeof(msg),
+			target, &status);
+
+	if (ret == -EAGAIN || ret == -ENOMEM) {
+		msleep(100);
+		goto again;
+	}
+
+	return ret;
+}
+
+static void o2hb_nego_timeout(struct work_struct *work)
+{
+	unsigned long live_node_bitmap[BITS_TO_LONGS(O2NM_MAX_NODES)];
+	int master_node, i, ret;
+	struct o2hb_region *reg;
+
+	reg = container_of(work, struct o2hb_region, hr_nego_timeout_work.work);
+	/* don't negotiate timeout if last hb failed since it is very
+	 * possible io failed. Should let write timeout fence self.
+	 */
+	if (reg->hr_last_hb_status)
+		return;
+
+	o2hb_fill_node_map(live_node_bitmap, sizeof(live_node_bitmap));
+	/* lowest node as master node to make negotiate decision. */
+	master_node = find_first_bit(live_node_bitmap, O2NM_MAX_NODES);
+
+	if (master_node == o2nm_this_node()) {
+		if (!test_bit(master_node, reg->hr_nego_node_bitmap)) {
+			printk(KERN_NOTICE "o2hb: node %d hb write hung for %ds on region %s (%pg).\n",
+				o2nm_this_node(), O2HB_NEGO_TIMEOUT_MS/1000,
+				config_item_name(&reg->hr_item), reg->hr_bdev);
+			set_bit(master_node, reg->hr_nego_node_bitmap);
+		}
+		if (memcmp(reg->hr_nego_node_bitmap, live_node_bitmap,
+				sizeof(reg->hr_nego_node_bitmap))) {
+			/* check negotiate bitmap every second to do timeout
+			 * approve decision.
+			 */
+			schedule_delayed_work(&reg->hr_nego_timeout_work,
+				msecs_to_jiffies(1000));
+
+			return;
+		}
+
+		printk(KERN_NOTICE "o2hb: all nodes hb write hung, maybe region %s (%pg) is down.\n",
+			config_item_name(&reg->hr_item), reg->hr_bdev);
+		/* approve negotiate timeout request. */
+		o2hb_arm_timeout(reg);
+
+		i = -1;
+		while ((i = find_next_bit(live_node_bitmap,
+				O2NM_MAX_NODES, i + 1)) < O2NM_MAX_NODES) {
+			if (i == master_node)
+				continue;
+
+			mlog(ML_HEARTBEAT, "send NEGO_APPROVE msg to node %d\n", i);
+			ret = o2hb_send_nego_msg(reg->hr_key,
+					O2HB_NEGO_APPROVE_MSG, i);
+			if (ret)
+				mlog(ML_ERROR, "send NEGO_APPROVE msg to node %d fail %d\n",
+					i, ret);
+		}
+	} else {
+		/* negotiate timeout with master node. */
+		printk(KERN_NOTICE "o2hb: node %d hb write hung for %ds on region %s (%pg), negotiate timeout with node %d.\n",
+			o2nm_this_node(), O2HB_NEGO_TIMEOUT_MS/1000, config_item_name(&reg->hr_item),
+			reg->hr_bdev, master_node);
+		ret = o2hb_send_nego_msg(reg->hr_key, O2HB_NEGO_TIMEOUT_MSG,
+				master_node);
+		if (ret)
+			mlog(ML_ERROR, "send NEGO_TIMEOUT msg to node %d fail %d\n",
+				master_node, ret);
+	}
+}
+
+static int o2hb_nego_timeout_handler(struct o2net_msg *msg, u32 len, void *data,
+				void **ret_data)
+{
+	struct o2hb_region *reg = data;
+	struct o2hb_nego_msg *nego_msg;
+
+	nego_msg = (struct o2hb_nego_msg *)msg->buf;
+	printk(KERN_NOTICE "o2hb: receive negotiate timeout message from node %d on region %s (%pg).\n",
+		nego_msg->node_num, config_item_name(&reg->hr_item), reg->hr_bdev);
+	if (nego_msg->node_num < O2NM_MAX_NODES)
+		set_bit(nego_msg->node_num, reg->hr_nego_node_bitmap);
+	else
+		mlog(ML_ERROR, "got nego timeout message from bad node.\n");
+
+	return 0;
+}
+
+static int o2hb_nego_approve_handler(struct o2net_msg *msg, u32 len, void *data,
+				void **ret_data)
+{
+	struct o2hb_region *reg = data;
+
+	printk(KERN_NOTICE "o2hb: negotiate timeout approved by master node on region %s (%pg).\n",
+		config_item_name(&reg->hr_item), reg->hr_bdev);
+	o2hb_arm_timeout(reg);
+	return 0;
+}
+
+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_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_status) {
+		mlog(ML_ERROR, "IO Error %d\n", bio->bi_status);
+		wc->wc_error = blk_status_to_errno(bio->bi_status);
+	}
+
+	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, blk_opf_t opf)
+{
+	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(reg->hr_bdev, 16, opf, GFP_ATOMIC);
+	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_private = wc;
+	bio->bi_end_io = o2hb_bio_end_io;
+
+	vec_start = (cs << bits) % PAGE_SIZE;
+	while(cs < max_slots) {
+		current_page = cs / spp;
+		page = reg->hr_slot_data[current_page];
+
+		vec_len = min(PAGE_SIZE - vec_start,
+			      (max_slots-cs) * (PAGE_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_SIZE/spp);
+		vec_start = 0;
+	}
+
+bail:
+	*current_slot = cs;
+	return bio;
+}
+
+static int o2hb_read_slots(struct o2hb_region *reg,
+			   unsigned int begin_slot,
+			   unsigned int max_slots)
+{
+	unsigned int current_slot = begin_slot;
+	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,
+					 REQ_OP_READ);
+		if (IS_ERR(bio)) {
+			status = PTR_ERR(bio);
+			mlog_errno(status);
+			goto bail_and_wait;
+		}
+
+		atomic_inc(&wc.wc_num_reqs);
+		submit_bio(bio);
+	}
+
+	status = 0;
+
+bail_and_wait:
+	o2hb_wait_on_io(&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,
+				 REQ_OP_WRITE | REQ_SYNC);
+	if (IS_ERR(bio)) {
+		status = PTR_ERR(bio);
+		mlog_errno(status);
+		goto bail;
+	}
+
+	atomic_inc(&write_wc->wc_num_reqs);
+	submit_bio(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 (%pg): expected(%u:0x%llx, 0x%llx), "
+	     "ondisk(%u:0x%llx, 0x%llx)\n", errstr, reg->hr_bdev,
+	     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 = ktime_get_real_seconds();
+	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 (%pg) is now a quorum device\n",
+	       config_item_name(&reg->hr_item), reg->hr_bdev);
+
+	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 %pg\n",
+		     slot->ds_node_num, reg->hr_bdev);
+		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 %pg 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_bdev, 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_lowest_node(unsigned long *nodes, int numbits)
+{
+	return find_first_bit(nodes, numbits);
+}
+
+static int o2hb_do_disk_heartbeat(struct o2hb_region *reg)
+{
+	int i, ret, highest_node, lowest_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);
+	lowest_node = o2hb_lowest_node(configured_nodes, O2NM_MAX_NODES);
+	if (highest_node >= O2NM_MAX_NODES || lowest_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, lowest_node, 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(&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 \"%pg\"\n",
+		     write_wc.wc_error, reg->hr_bdev);
+		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_timeout(reg);
+		reg->hr_last_timeout_start = jiffies;
+	}
+
+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 "
+			       "heartbeat on region %s (%pg)\n",
+			       config_item_name(&reg->hr_item),
+			       reg->hr_bdev);
+			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);
+		reg->hr_last_hb_status = ret;
+
+		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, after_hb, 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_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(&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 += scnprintf(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 += scnprintf(buf + out, PAGE_SIZE - out, "%lu\n", lts);
+		goto done;
+
+	case O2HB_DB_TYPE_REGION_PINNED:
+		reg = (struct o2hb_region *)db->db_data;
+		out += scnprintf(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 += scnprintf(buf + out, PAGE_SIZE - out, "%d ", i);
+	out += scnprintf(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)
+{
+	debugfs_remove_recursive(o2hb_debug_dir);
+	kfree(o2hb_db_livenodes);
+	kfree(o2hb_db_liveregions);
+	kfree(o2hb_db_quorumregions);
+	kfree(o2hb_db_failedregions);
+}
+
+static void 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;
+
+	(*db)->db_type = type;
+	(*db)->db_size = size;
+	(*db)->db_len = len;
+	(*db)->db_data = data;
+
+	debugfs_create_file(name, S_IFREG|S_IRUSR, dir, *db, &o2hb_debug_fops);
+}
+
+static void o2hb_debug_init(void)
+{
+	o2hb_debug_dir = debugfs_create_dir(O2HB_DEBUG_DIR, NULL);
+
+	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);
+
+	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);
+
+	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);
+
+	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);
+}
+
+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]);
+
+	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;
+
+	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 (%pg)\n", reg->hr_bdev);
+
+	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);
+
+	debugfs_remove_recursive(reg->hr_debug_dir);
+	kfree(reg->hr_db_livenodes);
+	kfree(reg->hr_db_regnum);
+	kfree(reg->hr_db_elapsed_time);
+	kfree(reg->hr_db_pinned);
+
+	spin_lock(&o2hb_live_lock);
+	list_del(&reg->hr_all_item);
+	spin_unlock(&o2hb_live_lock);
+
+	o2net_unregister_handler_list(&reg->hr_handler_list);
+	kfree(reg);
+}
+
+static int o2hb_read_block_input(struct o2hb_region *reg,
+				 const char *page,
+				 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, &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;
+	ssize_t ret;
+
+	if (reg->hr_bdev)
+		return -EINVAL;
+
+	ret = kstrtoull(p, 0, &tmp);
+	if (ret)
+		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, "%pg\n", to_o2hb_region(item)->hr_bdev);
+
+	return ret;
+}
+
+static void o2hb_init_region_params(struct o2hb_region *reg)
+{
+	reg->hr_slots_per_page = PAGE_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, 0, 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;
+	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;
+
+	if (!S_ISBLK(f.file->f_mapping->host->i_mode))
+		goto out2;
+
+	reg->hr_bdev = blkdev_get_by_dev(f.file->f_mapping->host->i_rdev,
+					 FMODE_WRITE | FMODE_READ, NULL);
+	if (IS_ERR(reg->hr_bdev)) {
+		ret = PTR_ERR(reg->hr_bdev);
+		reg->hr_bdev = NULL;
+		goto out2;
+	}
+
+	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);
+	INIT_DELAYED_WORK(&reg->hr_nego_timeout_work, o2hb_nego_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 triple the steady_iterations */
+	atomic_set(&reg->hr_unsteady_iterations, (live_threshold * 3));
+
+	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 (%pg)\n",
+		       config_item_name(&reg->hr_item), reg->hr_bdev);
+
+out3:
+	if (ret < 0) {
+		blkdev_put(reg->hr_bdev, FMODE_READ | FMODE_WRITE);
+		reg->hr_bdev = NULL;
+	}
+out2:
+	fdput(f);
+out:
+	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 const 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 void o2hb_debug_region_init(struct o2hb_region *reg,
+				   struct dentry *parent)
+{
+	struct dentry *dir;
+
+	dir = debugfs_create_dir(config_item_name(&reg->hr_item), parent);
+	reg->hr_debug_dir = dir;
+
+	o2hb_debug_create(O2HB_DEBUG_LIVENODES, 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);
+
+	o2hb_debug_create(O2HB_DEBUG_REGION_NUMBER, dir, &(reg->hr_db_regnum),
+			  sizeof(*(reg->hr_db_regnum)),
+			  O2HB_DB_TYPE_REGION_NUMBER, 0, O2NM_MAX_NODES, reg);
+
+	o2hb_debug_create(O2HB_DEBUG_REGION_ELAPSED_TIME, dir,
+			  &(reg->hr_db_elapsed_time),
+			  sizeof(*(reg->hr_db_elapsed_time)),
+			  O2HB_DB_TYPE_REGION_ELAPSED_TIME, 0, 0, reg);
+
+	o2hb_debug_create(O2HB_DEBUG_REGION_PINNED, dir, &(reg->hr_db_pinned),
+			  sizeof(*(reg->hr_db_pinned)),
+			  O2HB_DB_TYPE_REGION_PINNED, 0, 0, reg);
+
+}
+
+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);
+
+	/* this is the same way to generate msg key as dlm, for local heartbeat,
+	 * name is also the same, so make initial crc value different to avoid
+	 * message key conflict.
+	 */
+	reg->hr_key = crc32_le(reg->hr_region_num + O2NM_MAX_REGIONS,
+		name, strlen(name));
+	INIT_LIST_HEAD(&reg->hr_handler_list);
+	ret = o2net_register_handler(O2HB_NEGO_TIMEOUT_MSG, reg->hr_key,
+			sizeof(struct o2hb_nego_msg),
+			o2hb_nego_timeout_handler,
+			reg, NULL, &reg->hr_handler_list);
+	if (ret)
+		goto remove_item;
+
+	ret = o2net_register_handler(O2HB_NEGO_APPROVE_MSG, reg->hr_key,
+			sizeof(struct o2hb_nego_msg),
+			o2hb_nego_approve_handler,
+			reg, NULL, &reg->hr_handler_list);
+	if (ret)
+		goto unregister_handler;
+
+	o2hb_debug_region_init(reg, o2hb_debug_dir);
+
+	return &reg->hr_item;
+
+unregister_handler:
+	o2net_unregister_handler_list(&reg->hr_handler_list);
+remove_item:
+	spin_lock(&o2hb_live_lock);
+	list_del(&reg->hr_all_item);
+	if (o2hb_global_heartbeat_active())
+		clear_bit(reg->hr_region_num, o2hb_region_bitmap);
+	spin_unlock(&o2hb_live_lock);
+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 (%pg)\n",
+		       ((atomic_read(&reg->hr_steady_iterations) == 0) ?
+			"stopped" : "start aborted"), config_item_name(item),
+		       reg->hr_bdev);
+	}
+
+	/*
+	 * 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 const 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;
+}
+
+static 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_no_sem(u8 node_num)
+{
+	unsigned long testing_map[BITS_TO_LONGS(O2NM_MAX_NODES)];
+
+	spin_lock(&o2hb_live_lock);
+	o2hb_fill_node_map_from_callback(testing_map, sizeof(testing_map));
+	spin_unlock(&o2hb_live_lock);
+	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);
+
+/*
+ * 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);