Update and fix monitoring of thin pool devices

Code adds better support for monitoring of thin pool devices.
update_pool_lv uses DMEVENTD_MONITOR_IGNORE to not manipulate with monitoring.
vgchange & lvchange are checking real thin pool device for existance
as we are using   _tpool  real device and visible LV pool device might not
be even active (_tpool is activated implicitely for any thin volume).
monitor_dev_for_events is another _lv_postorder like code it might be worth
to think about reusing it here - for now update the code to properly
monitory thin volume deps.
For unmonitoring add extra code to check the usage of thin pool - in case it's in use
unmonitoring of thin volume is skipped.

3 files changed, 36 insertions, 0 deletions

diff --git a/lib/activate/activate.c b/lib/activate/activate.c
index e6b40ba5..d2cc5bfb 100644
--- a/lib/activate/activate.c
+++ b/lib/activate/activate.c
@@ -1221,6 +1221,8 @@ int monitor_dev_for_events(struct cmd_context *cmd, struct logical_volume *lv,
 	int (*monitor_fn) (struct lv_segment *s, int e);
 	uint32_t s;
 	static const struct lv_activate_opts zlaopts = { 0 };
+	static const struct lv_activate_opts thinopts = { .skip_in_use = 1 };
+	struct lvinfo info;
 
 	if (!laopts)
 		laopts = &zlaopts;
@@ -1236,6 +1238,19 @@ int monitor_dev_for_events(struct cmd_context *cmd, struct logical_volume *lv,
 		return 1;
 
 	/*
+	 * Allow to unmonitor thin pool via explicit pool unmonitor
+	 * or unmonitor before the last thin pool user deactivation
+	 * Skip unmonitor, if invoked via unmonitor of thin volume
+	 * and there is another thin pool user (open_count > 1)
+	 */
+	if (laopts->skip_in_use && lv_info(lv->vg->cmd, lv, 1, &info, 1, 0) &&
+	    (info.open_count != 1)) {
+		log_debug("Skipping unmonitor of opened %s (open:%d)",
+			  lv->name, info.open_count);
+		return 1;
+	}
+
+	/*
 	 * In case of a snapshot device, we monitor lv->snapshot->lv,
 	 * not the actual LV itself.
 	 */
@@ -1279,6 +1294,21 @@ int monitor_dev_for_events(struct cmd_context *cmd, struct logical_volume *lv,
 			}
 		}
 
+		/*
+		 * If requested unmonitoring of thin volume, request test
+		 * if there is no other thin pool user
+		 *
+		 * FIXME: code here looks like _lv_postorder()
+		 */
+		if (seg->pool_lv &&
+		    !monitor_dev_for_events(cmd, seg->pool_lv,
+					    (!monitor) ? &thinopts : NULL, monitor))
+			r = 0;
+
+		if (seg->metadata_lv &&
+		    !monitor_dev_for_events(cmd, seg->metadata_lv, NULL, monitor))
+			r = 0;
+
 		if (!seg_monitored(seg) || (seg->status & PVMOVE))
 			continue;
 
diff --git a/lib/activate/activate.h b/lib/activate/activate.h
index ccea9919..2b90a7b8 100644
--- a/lib/activate/activate.h
+++ b/lib/activate/activate.h
@@ -36,6 +36,7 @@ struct lv_activate_opts {
 	int no_merging;
 	int real_pool;
 	int is_activate;
+	int skip_in_use;
 	unsigned revert;
 	unsigned read_only;
 };
diff --git a/lib/metadata/thin_manip.c b/lib/metadata/thin_manip.c
index 0c00e7a6..ae8d509e 100644
--- a/lib/metadata/thin_manip.c
+++ b/lib/metadata/thin_manip.c
@@ -388,6 +388,8 @@ int extend_pool(struct logical_volume *pool_lv, const struct segment_type *segty
 
 int update_pool_lv(struct logical_volume *lv, int activate)
 {
+	int monitored;
+
 	if (!lv_is_thin_pool(lv)) {
 		log_error(INTERNAL_ERROR "Updated LV %s is not pool.", lv->name);
 		return 0;
@@ -399,10 +401,13 @@ int update_pool_lv(struct logical_volume *lv, int activate)
 	if (activate) {
 		/* If the pool is not active, do activate deactivate */
 		if (!lv_is_active(lv)) {
+			monitored = dmeventd_monitor_mode();
+			init_dmeventd_monitor(DMEVENTD_MONITOR_IGNORE);
 			if (!activate_lv_excl(lv->vg->cmd, lv))
 				return_0;
 			if (!deactivate_lv(lv->vg->cmd, lv))
 				return_0;
+			init_dmeventd_monitor(monitored);
 		}
 		/*
 		 * Resume active pool to send thin messages.