/*
   * Copyright (C) 2006-2009 Red Hat, Inc.
   *
   * This file is released under the LGPL.
   */
  
  #include <linux/bio.h>
  #include <linux/slab.h>
  #include <linux/dm-dirty-log.h>
  #include <linux/device-mapper.h>
  #include <linux/dm-log-userspace.h>
  #include <linux/module.h>
  #include <linux/workqueue.h>
  
  #include "dm-log-userspace-transfer.h"
  
  #define DM_LOG_USERSPACE_VSN "1.3.0"
  
  struct flush_entry {
  	int type;
  	region_t region;
  	struct list_head list;
  };
  
  /*
   * This limit on the number of mark and clear request is, to a degree,
   * arbitrary.  However, there is some basis for the choice in the limits
   * imposed on the size of data payload by dm-log-userspace-transfer.c:
   * dm_consult_userspace().
   */
  #define MAX_FLUSH_GROUP_COUNT 32
  
  struct log_c {
  	struct dm_target *ti;
  	struct dm_dev *log_dev;
  	uint32_t region_size;
  	region_t region_count;
  	uint64_t luid;
  	char uuid[DM_UUID_LEN];
  
  	char *usr_argv_str;
  	uint32_t usr_argc;
  
  	/*
  	 * in_sync_hint gets set when doing is_remote_recovering.  It
  	 * represents the first region that needs recovery.  IOW, the
  	 * first zero bit of sync_bits.  This can be useful for to limit
  	 * traffic for calls like is_remote_recovering and get_resync_work,
  	 * but be take care in its use for anything else.
  	 */
  	uint64_t in_sync_hint;
  
  	/*
  	 * Mark and clear requests are held until a flush is issued
  	 * so that we can group, and thereby limit, the amount of
  	 * network traffic between kernel and userspace.  The 'flush_lock'
  	 * is used to protect these lists.
  	 */
  	spinlock_t flush_lock;
  	struct list_head mark_list;
  	struct list_head clear_list;
  
  	/*
  	 * Workqueue for flush of clear region requests.
  	 */
  	struct workqueue_struct *dmlog_wq;
  	struct delayed_work flush_log_work;
  	atomic_t sched_flush;
  
  	/*
  	 * Combine userspace flush and mark requests for efficiency.
  	 */
  	uint32_t integrated_flush;
  };
  
  static mempool_t *flush_entry_pool;
  
  static void *flush_entry_alloc(gfp_t gfp_mask, void *pool_data)
  {
  	return kmalloc(sizeof(struct flush_entry), gfp_mask);
  }
  
  static void flush_entry_free(void *element, void *pool_data)
  {
  	kfree(element);
  }
  
  static int userspace_do_request(struct log_c *lc, const char *uuid,
  				int request_type, char *data, size_t data_size,
  				char *rdata, size_t *rdata_size)
  {
  	int r;
  
  	/*
  	 * If the server isn't there, -ESRCH is returned,
  	 * and we must keep trying until the server is
  	 * restored.
  	 */
  retry:
  	r = dm_consult_userspace(uuid, lc->luid, request_type, data,
  				 data_size, rdata, rdata_size);
  
  	if (r != -ESRCH)
  		return r;
  
  	DMERR(" Userspace log server not found.");
  	while (1) {
  		set_current_state(TASK_INTERRUPTIBLE);
  		schedule_timeout(2*HZ);
  		DMWARN("Attempting to contact userspace log server...");
  		r = dm_consult_userspace(uuid, lc->luid, DM_ULOG_CTR,
  					 lc->usr_argv_str,
  					 strlen(lc->usr_argv_str) + 1,
  					 NULL, NULL);
  		if (!r)
  			break;
  	}
  	DMINFO("Reconnected to userspace log server... DM_ULOG_CTR complete");
  	r = dm_consult_userspace(uuid, lc->luid, DM_ULOG_RESUME, NULL,
  				 0, NULL, NULL);
  	if (!r)
  		goto retry;
  
  	DMERR("Error trying to resume userspace log: %d", r);
  
  	return -ESRCH;
  }
  
  static int build_constructor_string(struct dm_target *ti,
  				    unsigned argc, char **argv,
  				    char **ctr_str)
  {
  	int i, str_size;
  	char *str = NULL;
  
  	*ctr_str = NULL;
  
  	/*
  	 * Determine overall size of the string.
  	 */
  	for (i = 0, str_size = 0; i < argc; i++)
  		str_size += strlen(argv[i]) + 1; /* +1 for space between args */
  
  	str_size += 20; /* Max number of chars in a printed u64 number */
  
  	str = kzalloc(str_size, GFP_KERNEL);
  	if (!str) {
  		DMWARN("Unable to allocate memory for constructor string");
  		return -ENOMEM;
  	}
  
  	str_size = sprintf(str, "%llu", (unsigned long long)ti->len);
  	for (i = 0; i < argc; i++)
  		str_size += sprintf(str + str_size, " %s", argv[i]);
  
  	*ctr_str = str;
  	return str_size;
  }
  
  static void do_flush(struct work_struct *work)
  {
  	int r;
  	struct log_c *lc = container_of(work, struct log_c, flush_log_work.work);
  
  	atomic_set(&lc->sched_flush, 0);
  
  	r = userspace_do_request(lc, lc->uuid, DM_ULOG_FLUSH, NULL, 0, NULL, NULL);
  
  	if (r)
  		dm_table_event(lc->ti->table);
  }
  
  /*
   * userspace_ctr
   *
   * argv contains:
   *	<UUID> [integrated_flush] <other args>
   * Where 'other args' are the userspace implementation-specific log
   * arguments.
   *
   * Example:
   *	<UUID> [integrated_flush] clustered-disk <arg count> <log dev>
   *	<region_size> [[no]sync]
   *
   * This module strips off the <UUID> and uses it for identification
   * purposes when communicating with userspace about a log.
   *
   * If integrated_flush is defined, the kernel combines flush
   * and mark requests.
   *
   * The rest of the line, beginning with 'clustered-disk', is passed
   * to the userspace ctr function.
   */
  static int userspace_ctr(struct dm_dirty_log *log, struct dm_target *ti,
  			 unsigned argc, char **argv)
  {
  	int r = 0;
  	int str_size;
  	char *ctr_str = NULL;
  	struct log_c *lc = NULL;
  	uint64_t rdata;
  	size_t rdata_size = sizeof(rdata);
  	char *devices_rdata = NULL;
  	size_t devices_rdata_size = DM_NAME_LEN;
  
  	if (argc < 3) {
  		DMWARN("Too few arguments to userspace dirty log");
  		return -EINVAL;
  	}
  
  	lc = kzalloc(sizeof(*lc), GFP_KERNEL);
  	if (!lc) {
  		DMWARN("Unable to allocate userspace log context.");
  		return -ENOMEM;
  	}
  
  	/* The ptr value is sufficient for local unique id */
  	lc->luid = (unsigned long)lc;
  
  	lc->ti = ti;
  
  	if (strlen(argv[0]) > (DM_UUID_LEN - 1)) {
  		DMWARN("UUID argument too long.");
  		kfree(lc);
  		return -EINVAL;
  	}
  
  	lc->usr_argc = argc;
  
  	strncpy(lc->uuid, argv[0], DM_UUID_LEN);
  	argc--;
  	argv++;
  	spin_lock_init(&lc->flush_lock);
  	INIT_LIST_HEAD(&lc->mark_list);
  	INIT_LIST_HEAD(&lc->clear_list);
  
  	if (!strcasecmp(argv[0], "integrated_flush")) {
  		lc->integrated_flush = 1;
  		argc--;
  		argv++;
  	}
  
  	str_size = build_constructor_string(ti, argc, argv, &ctr_str);
  	if (str_size < 0) {
  		kfree(lc);
  		return str_size;
  	}
  
  	devices_rdata = kzalloc(devices_rdata_size, GFP_KERNEL);
  	if (!devices_rdata) {
  		DMERR("Failed to allocate memory for device information");
  		r = -ENOMEM;
  		goto out;
  	}
  
  	/*
  	 * Send table string and get back any opened device.
  	 */
  	r = dm_consult_userspace(lc->uuid, lc->luid, DM_ULOG_CTR,
  				 ctr_str, str_size,
  				 devices_rdata, &devices_rdata_size);
  
  	if (r < 0) {
  		if (r == -ESRCH)
  			DMERR("Userspace log server not found");
  		else
  			DMERR("Userspace log server failed to create log");
  		goto out;
  	}
  
  	/* Since the region size does not change, get it now */
  	rdata_size = sizeof(rdata);
  	r = dm_consult_userspace(lc->uuid, lc->luid, DM_ULOG_GET_REGION_SIZE,
  				 NULL, 0, (char *)&rdata, &rdata_size);
  
  	if (r) {
  		DMERR("Failed to get region size of dirty log");
  		goto out;
  	}
  
  	lc->region_size = (uint32_t)rdata;
  	lc->region_count = dm_sector_div_up(ti->len, lc->region_size);
  
  	if (devices_rdata_size) {
  		if (devices_rdata[devices_rdata_size - 1] != '\0') {
  			DMERR("DM_ULOG_CTR device return string not properly terminated");
  			r = -EINVAL;
  			goto out;
  		}
  		r = dm_get_device(ti, devices_rdata,
  				  dm_table_get_mode(ti->table), &lc->log_dev);
  		if (r)
  			DMERR("Failed to register %s with device-mapper",
  			      devices_rdata);
  	}
  
  	if (lc->integrated_flush) {
  		lc->dmlog_wq = alloc_workqueue("dmlogd", WQ_MEM_RECLAIM, 0);
  		if (!lc->dmlog_wq) {
  			DMERR("couldn't start dmlogd");
  			r = -ENOMEM;
  			goto out;
  		}
  
  		INIT_DELAYED_WORK(&lc->flush_log_work, do_flush);
  		atomic_set(&lc->sched_flush, 0);
  	}
  
  out:
  	kfree(devices_rdata);
  	if (r) {
  		kfree(lc);
  		kfree(ctr_str);
  	} else {
  		lc->usr_argv_str = ctr_str;
  		log->context = lc;
  	}
  
  	return r;
  }
  
  static void userspace_dtr(struct dm_dirty_log *log)
  {
  	struct log_c *lc = log->context;
  
  	if (lc->integrated_flush) {
  		/* flush workqueue */
  		if (atomic_read(&lc->sched_flush))
  			flush_delayed_work(&lc->flush_log_work);
  
  		destroy_workqueue(lc->dmlog_wq);
  	}
  
  	(void) dm_consult_userspace(lc->uuid, lc->luid, DM_ULOG_DTR,
  				    NULL, 0, NULL, NULL);
  
  	if (lc->log_dev)
  		dm_put_device(lc->ti, lc->log_dev);
  
  	kfree(lc->usr_argv_str);
  	kfree(lc);
  
  	return;
  }
  
  static int userspace_presuspend(struct dm_dirty_log *log)
  {
  	int r;
  	struct log_c *lc = log->context;
  
  	r = dm_consult_userspace(lc->uuid, lc->luid, DM_ULOG_PRESUSPEND,
  				 NULL, 0, NULL, NULL);
  
  	return r;
  }
  
  static int userspace_postsuspend(struct dm_dirty_log *log)
  {
  	int r;
  	struct log_c *lc = log->context;
  
  	/*
  	 * Run planned flush earlier.
  	 */
  	if (lc->integrated_flush && atomic_read(&lc->sched_flush))
  		flush_delayed_work(&lc->flush_log_work);
  
  	r = dm_consult_userspace(lc->uuid, lc->luid, DM_ULOG_POSTSUSPEND,
  				 NULL, 0, NULL, NULL);
  
  	return r;
  }
  
  static int userspace_resume(struct dm_dirty_log *log)
  {
  	int r;
  	struct log_c *lc = log->context;
  
  	lc->in_sync_hint = 0;
  	r = dm_consult_userspace(lc->uuid, lc->luid, DM_ULOG_RESUME,
  				 NULL, 0, NULL, NULL);
  
  	return r;
  }
  
  static uint32_t userspace_get_region_size(struct dm_dirty_log *log)
  {
  	struct log_c *lc = log->context;
  
  	return lc->region_size;
  }
  
  /*
   * userspace_is_clean
   *
   * Check whether a region is clean.  If there is any sort of
   * failure when consulting the server, we return not clean.
   *
   * Returns: 1 if clean, 0 otherwise
   */
  static int userspace_is_clean(struct dm_dirty_log *log, region_t region)
  {
  	int r;
  	uint64_t region64 = (uint64_t)region;
  	int64_t is_clean;
  	size_t rdata_size;
  	struct log_c *lc = log->context;
  
  	rdata_size = sizeof(is_clean);
  	r = userspace_do_request(lc, lc->uuid, DM_ULOG_IS_CLEAN,
  				 (char *)&region64, sizeof(region64),
  				 (char *)&is_clean, &rdata_size);
  
  	return (r) ? 0 : (int)is_clean;
  }
  
  /*
   * userspace_in_sync
   *
   * Check if the region is in-sync.  If there is any sort
   * of failure when consulting the server, we assume that
   * the region is not in sync.
   *
   * If 'can_block' is set, return immediately
   *
   * Returns: 1 if in-sync, 0 if not-in-sync, -EWOULDBLOCK
   */
  static int userspace_in_sync(struct dm_dirty_log *log, region_t region,
  			     int can_block)
  {
  	int r;
  	uint64_t region64 = region;
  	int64_t in_sync;
  	size_t rdata_size;
  	struct log_c *lc = log->context;
  
  	/*
  	 * We can never respond directly - even if in_sync_hint is
  	 * set.  This is because another machine could see a device
  	 * failure and mark the region out-of-sync.  If we don't go
  	 * to userspace to ask, we might think the region is in-sync
  	 * and allow a read to pick up data that is stale.  (This is
  	 * very unlikely if a device actually fails; but it is very
  	 * likely if a connection to one device from one machine fails.)
  	 *
  	 * There still might be a problem if the mirror caches the region
  	 * state as in-sync... but then this call would not be made.  So,
  	 * that is a mirror problem.
  	 */
  	if (!can_block)
  		return -EWOULDBLOCK;
  
  	rdata_size = sizeof(in_sync);
  	r = userspace_do_request(lc, lc->uuid, DM_ULOG_IN_SYNC,
  				 (char *)&region64, sizeof(region64),
  				 (char *)&in_sync, &rdata_size);
  	return (r) ? 0 : (int)in_sync;
  }
  
  static int flush_one_by_one(struct log_c *lc, struct list_head *flush_list)
  {
  	int r = 0;
  	struct flush_entry *fe;
  
  	list_for_each_entry(fe, flush_list, list) {
  		r = userspace_do_request(lc, lc->uuid, fe->type,
  					 (char *)&fe->region,
  					 sizeof(fe->region),
  					 NULL, NULL);
  		if (r)
  			break;
  	}
  
  	return r;
  }
  
  static int flush_by_group(struct log_c *lc, struct list_head *flush_list,
  			  int flush_with_payload)
  {
  	int r = 0;
  	int count;
  	uint32_t type = 0;
  	struct flush_entry *fe, *tmp_fe;
  	LIST_HEAD(tmp_list);
  	uint64_t group[MAX_FLUSH_GROUP_COUNT];
  
  	/*
  	 * Group process the requests
  	 */
  	while (!list_empty(flush_list)) {
  		count = 0;
  
  		list_for_each_entry_safe(fe, tmp_fe, flush_list, list) {
  			group[count] = fe->region;
  			count++;
  
  			list_move(&fe->list, &tmp_list);
  
  			type = fe->type;
  			if (count >= MAX_FLUSH_GROUP_COUNT)
  				break;
  		}
  
  		if (flush_with_payload) {
  			r = userspace_do_request(lc, lc->uuid, DM_ULOG_FLUSH,
  						 (char *)(group),
  						 count * sizeof(uint64_t),
  						 NULL, NULL);
  			/*
  			 * Integrated flush failed.
  			 */
  			if (r)
  				break;
  		} else {
  			r = userspace_do_request(lc, lc->uuid, type,
  						 (char *)(group),
  						 count * sizeof(uint64_t),
  						 NULL, NULL);
  			if (r) {
  				/*
  				 * Group send failed.  Attempt one-by-one.
  				 */
  				list_splice_init(&tmp_list, flush_list);
  				r = flush_one_by_one(lc, flush_list);
  				break;
  			}
  		}
  	}
  
  	/*
  	 * Must collect flush_entrys that were successfully processed
  	 * as a group so that they will be free'd by the caller.
  	 */
  	list_splice_init(&tmp_list, flush_list);
  
  	return r;
  }
  
  /*
   * userspace_flush
   *
   * This function is ok to block.
   * The flush happens in two stages.  First, it sends all
   * clear/mark requests that are on the list.  Then it
   * tells the server to commit them.  This gives the
   * server a chance to optimise the commit, instead of
   * doing it for every request.
   *
   * Additionally, we could implement another thread that
   * sends the requests up to the server - reducing the
   * load on flush.  Then the flush would have less in
   * the list and be responsible for the finishing commit.
   *
   * Returns: 0 on success, < 0 on failure
   */
  static int userspace_flush(struct dm_dirty_log *log)
  {
  	int r = 0;
  	unsigned long flags;
  	struct log_c *lc = log->context;
  	LIST_HEAD(mark_list);
  	LIST_HEAD(clear_list);
  	int mark_list_is_empty;
  	int clear_list_is_empty;
  	struct flush_entry *fe, *tmp_fe;
  
  	spin_lock_irqsave(&lc->flush_lock, flags);
  	list_splice_init(&lc->mark_list, &mark_list);
  	list_splice_init(&lc->clear_list, &clear_list);
  	spin_unlock_irqrestore(&lc->flush_lock, flags);
  
  	mark_list_is_empty = list_empty(&mark_list);
  	clear_list_is_empty = list_empty(&clear_list);
  
  	if (mark_list_is_empty && clear_list_is_empty)
  		return 0;
  
  	r = flush_by_group(lc, &clear_list, 0);
  	if (r)
  		goto out;
  
  	if (!lc->integrated_flush) {
  		r = flush_by_group(lc, &mark_list, 0);
  		if (r)
  			goto out;
  		r = userspace_do_request(lc, lc->uuid, DM_ULOG_FLUSH,
  					 NULL, 0, NULL, NULL);
  		goto out;
  	}
  
  	/*
  	 * Send integrated flush request with mark_list as payload.
  	 */
  	r = flush_by_group(lc, &mark_list, 1);
  	if (r)
  		goto out;
  
  	if (mark_list_is_empty && !atomic_read(&lc->sched_flush)) {
  		/*
  		 * When there are only clear region requests,
  		 * we schedule a flush in the future.
  		 */
  		queue_delayed_work(lc->dmlog_wq, &lc->flush_log_work, 3 * HZ);
  		atomic_set(&lc->sched_flush, 1);
  	} else {
  		/*
  		 * Cancel pending flush because we
  		 * have already flushed in mark_region.
  		 */
  		cancel_delayed_work(&lc->flush_log_work);
  		atomic_set(&lc->sched_flush, 0);
  	}
  
  out:
  	/*
  	 * We can safely remove these entries, even after failure.
  	 * Calling code will receive an error and will know that
  	 * the log facility has failed.
  	 */
  	list_for_each_entry_safe(fe, tmp_fe, &mark_list, list) {
  		list_del(&fe->list);
  		mempool_free(fe, flush_entry_pool);
  	}
  	list_for_each_entry_safe(fe, tmp_fe, &clear_list, list) {
  		list_del(&fe->list);
  		mempool_free(fe, flush_entry_pool);
  	}
  
  	if (r)
  		dm_table_event(lc->ti->table);
  
  	return r;
  }
  
  /*
   * userspace_mark_region
   *
   * This function should avoid blocking unless absolutely required.
   * (Memory allocation is valid for blocking.)
   */
  static void userspace_mark_region(struct dm_dirty_log *log, region_t region)
  {
  	unsigned long flags;
  	struct log_c *lc = log->context;
  	struct flush_entry *fe;
  
  	/* Wait for an allocation, but _never_ fail */
  	fe = mempool_alloc(flush_entry_pool, GFP_NOIO);
  	BUG_ON(!fe);
  
  	spin_lock_irqsave(&lc->flush_lock, flags);
  	fe->type = DM_ULOG_MARK_REGION;
  	fe->region = region;
  	list_add(&fe->list, &lc->mark_list);
  	spin_unlock_irqrestore(&lc->flush_lock, flags);
  
  	return;
  }
  
  /*
   * userspace_clear_region
   *
   * This function must not block.
   * So, the alloc can't block.  In the worst case, it is ok to
   * fail.  It would simply mean we can't clear the region.
   * Does nothing to current sync context, but does mean
   * the region will be re-sync'ed on a reload of the mirror
   * even though it is in-sync.
   */
  static void userspace_clear_region(struct dm_dirty_log *log, region_t region)
  {
  	unsigned long flags;
  	struct log_c *lc = log->context;
  	struct flush_entry *fe;
  
  	/*
  	 * If we fail to allocate, we skip the clearing of
  	 * the region.  This doesn't hurt us in any way, except
  	 * to cause the region to be resync'ed when the
  	 * device is activated next time.
  	 */
  	fe = mempool_alloc(flush_entry_pool, GFP_ATOMIC);
  	if (!fe) {
  		DMERR("Failed to allocate memory to clear region.");
  		return;
  	}
  
  	spin_lock_irqsave(&lc->flush_lock, flags);
  	fe->type = DM_ULOG_CLEAR_REGION;
  	fe->region = region;
  	list_add(&fe->list, &lc->clear_list);
  	spin_unlock_irqrestore(&lc->flush_lock, flags);
  
  	return;
  }
  
  /*
   * userspace_get_resync_work
   *
   * Get a region that needs recovery.  It is valid to return
   * an error for this function.
   *
   * Returns: 1 if region filled, 0 if no work, <0 on error
   */
  static int userspace_get_resync_work(struct dm_dirty_log *log, region_t *region)
  {
  	int r;
  	size_t rdata_size;
  	struct log_c *lc = log->context;
  	struct {
  		int64_t i; /* 64-bit for mix arch compatibility */
  		region_t r;
  	} pkg;
  
  	if (lc->in_sync_hint >= lc->region_count)
  		return 0;
  
  	rdata_size = sizeof(pkg);
  	r = userspace_do_request(lc, lc->uuid, DM_ULOG_GET_RESYNC_WORK,
  				 NULL, 0, (char *)&pkg, &rdata_size);
  
  	*region = pkg.r;
  	return (r) ? r : (int)pkg.i;
  }
  
  /*
   * userspace_set_region_sync
   *
   * Set the sync status of a given region.  This function
   * must not fail.
   */
  static void userspace_set_region_sync(struct dm_dirty_log *log,
  				      region_t region, int in_sync)
  {
  	int r;
  	struct log_c *lc = log->context;
  	struct {
  		region_t r;
  		int64_t i;
  	} pkg;
  
  	pkg.r = region;
  	pkg.i = (int64_t)in_sync;
  
  	r = userspace_do_request(lc, lc->uuid, DM_ULOG_SET_REGION_SYNC,
  				 (char *)&pkg, sizeof(pkg), NULL, NULL);
  
  	/*
  	 * It would be nice to be able to report failures.
  	 * However, it is easy emough to detect and resolve.
  	 */
  	return;
  }
  
  /*
   * userspace_get_sync_count
   *
   * If there is any sort of failure when consulting the server,
   * we assume that the sync count is zero.
   *
   * Returns: sync count on success, 0 on failure
   */
  static region_t userspace_get_sync_count(struct dm_dirty_log *log)
  {
  	int r;
  	size_t rdata_size;
  	uint64_t sync_count;
  	struct log_c *lc = log->context;
  
  	rdata_size = sizeof(sync_count);
  	r = userspace_do_request(lc, lc->uuid, DM_ULOG_GET_SYNC_COUNT,
  				 NULL, 0, (char *)&sync_count, &rdata_size);
  
  	if (r)
  		return 0;
  
  	if (sync_count >= lc->region_count)
  		lc->in_sync_hint = lc->region_count;
  
  	return (region_t)sync_count;
  }
  
  /*
   * userspace_status
   *
   * Returns: amount of space consumed
   */
  static int userspace_status(struct dm_dirty_log *log, status_type_t status_type,
  			    char *result, unsigned maxlen)
  {
  	int r = 0;
  	char *table_args;
  	size_t sz = (size_t)maxlen;
  	struct log_c *lc = log->context;
  
  	switch (status_type) {
  	case STATUSTYPE_INFO:
  		r = userspace_do_request(lc, lc->uuid, DM_ULOG_STATUS_INFO,
  					 NULL, 0, result, &sz);
  
  		if (r) {
  			sz = 0;
  			DMEMIT("%s 1 COM_FAILURE", log->type->name);
  		}
  		break;
  	case STATUSTYPE_TABLE:
  		sz = 0;
  		table_args = strchr(lc->usr_argv_str, ' ');
  		BUG_ON(!table_args); /* There will always be a ' ' */
  		table_args++;
  
  		DMEMIT("%s %u %s ", log->type->name, lc->usr_argc, lc->uuid);
  		if (lc->integrated_flush)
  			DMEMIT("integrated_flush ");
  		DMEMIT("%s ", table_args);
  		break;
  	}
  	return (r) ? 0 : (int)sz;
  }
  
  /*
   * userspace_is_remote_recovering
   *
   * Returns: 1 if region recovering, 0 otherwise
   */
  static int userspace_is_remote_recovering(struct dm_dirty_log *log,
  					  region_t region)
  {
  	int r;
  	uint64_t region64 = region;
  	struct log_c *lc = log->context;
  	static unsigned long long limit;
  	struct {
  		int64_t is_recovering;
  		uint64_t in_sync_hint;
  	} pkg;
  	size_t rdata_size = sizeof(pkg);
  
  	/*
  	 * Once the mirror has been reported to be in-sync,
  	 * it will never again ask for recovery work.  So,
  	 * we can safely say there is not a remote machine
  	 * recovering if the device is in-sync.  (in_sync_hint
  	 * must be reset at resume time.)
  	 */
  	if (region < lc->in_sync_hint)
  		return 0;
  	else if (jiffies < limit)
  		return 1;
  
  	limit = jiffies + (HZ / 4);
  	r = userspace_do_request(lc, lc->uuid, DM_ULOG_IS_REMOTE_RECOVERING,
  				 (char *)&region64, sizeof(region64),
  				 (char *)&pkg, &rdata_size);
  	if (r)
  		return 1;
  
  	lc->in_sync_hint = pkg.in_sync_hint;
  
  	return (int)pkg.is_recovering;
  }
  
  static struct dm_dirty_log_type _userspace_type = {
  	.name = "userspace",
  	.module = THIS_MODULE,
  	.ctr = userspace_ctr,
  	.dtr = userspace_dtr,
  	.presuspend = userspace_presuspend,
  	.postsuspend = userspace_postsuspend,
  	.resume = userspace_resume,
  	.get_region_size = userspace_get_region_size,
  	.is_clean = userspace_is_clean,
  	.in_sync = userspace_in_sync,
  	.flush = userspace_flush,
  	.mark_region = userspace_mark_region,
  	.clear_region = userspace_clear_region,
  	.get_resync_work = userspace_get_resync_work,
  	.set_region_sync = userspace_set_region_sync,
  	.get_sync_count = userspace_get_sync_count,
  	.status = userspace_status,
  	.is_remote_recovering = userspace_is_remote_recovering,
  };
  
  static int __init userspace_dirty_log_init(void)
  {
  	int r = 0;
  
  	flush_entry_pool = mempool_create(100, flush_entry_alloc,
  					  flush_entry_free, NULL);
  
  	if (!flush_entry_pool) {
  		DMWARN("Unable to create flush_entry_pool:  No memory.");
  		return -ENOMEM;
  	}
  
  	r = dm_ulog_tfr_init();
  	if (r) {
  		DMWARN("Unable to initialize userspace log communications");
  		mempool_destroy(flush_entry_pool);
  		return r;
  	}
  
  	r = dm_dirty_log_type_register(&_userspace_type);
  	if (r) {
  		DMWARN("Couldn't register userspace dirty log type");
  		dm_ulog_tfr_exit();
  		mempool_destroy(flush_entry_pool);
  		return r;
  	}
  
  	DMINFO("version " DM_LOG_USERSPACE_VSN " loaded");
  	return 0;
  }
  
  static void __exit userspace_dirty_log_exit(void)
  {
  	dm_dirty_log_type_unregister(&_userspace_type);
  	dm_ulog_tfr_exit();
  	mempool_destroy(flush_entry_pool);
  
  	DMINFO("version " DM_LOG_USERSPACE_VSN " unloaded");
  	return;
  }
  
  module_init(userspace_dirty_log_init);
  module_exit(userspace_dirty_log_exit);
  
  MODULE_DESCRIPTION(DM_NAME " userspace dirty log link");
  MODULE_AUTHOR("Jonathan Brassow <dm-devel@redhat.com>");
  MODULE_LICENSE("GPL");