[PATCH 09/12] multipathd: merge uevents before proccessing

[tang.junhui@zte.com.cn]

From: tang.junhui <tang.junhui@zte.com.cn>

These uevents are going to be merged:
1) uevents come from paths and
2) uevents type is same and
3) uevents type is addition or deletion and
4) uevents wwid is same.

Change-Id: I05ee057391c092aa0c5f989b7a4f9cb550bb4d98
Signed-off-by: tang.junhui <tang.junhui@zte.com.cn>
---
 libmultipath/uevent.c | 125 +++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 114 insertions(+), 11 deletions(-)

diff --git a/libmultipath/uevent.c b/libmultipath/uevent.c
index b0b05e9..114068c 100644
--- a/libmultipath/uevent.c
+++ b/libmultipath/uevent.c
@@ -85,6 +85,20 @@ struct uevent * alloc_uevent (void)
 	return uev;
 }
 
+void
+uevq_cleanup(struct list_head *tmpq)
+{
+	struct uevent *uev, *tmp;
+
+	list_for_each_entry_safe(uev, tmp, tmpq, node) {
+		list_del_init(&uev->node);
+
+		if (uev->udev)
+			udev_device_unref(uev->udev);
+		FREE(uev);
+	}
+}
+
 bool
 uevent_can_discard(char *devpath, char *kernel)
 {
@@ -125,6 +139,103 @@ uevent_can_discard(char *devpath, char *kernel)
 	return false;
 }
 
+bool
+merge_need_stop(struct uevent *earlier, struct uevent *later)
+{
+	/*
+	 * dm uevent do not try to merge with left uevents
+	 */
+	if (!strncmp(later->kernel, "dm-", 3))
+		return true;
+
+	/*
+	 * we can not make a jugement without wwid,
+	 * so it is sensible to stop merging
+	 */
+	if (!earlier->wwid || !later->wwid)
+		return true;
+	/*
+	 * uevents merging stoped
+	 * when we meet an opposite action uevent from the same LUN to AVOID
+	 * "add path1 |remove path1 |add path2 |remove path2 |add path3"
+	 * to merge as "remove path1, path2" and "add path1, path2, path3"
+	 * OR
+	 * "remove path1 |add path1 |remove path2 |add path2 |remove path3"
+	 * to merge as "add path1, path2" and "remove path1, path2, path3"
+	 * SO
+	 * when we meet a non-change uevent from the same LUN
+	 * with the same wwid and different action
+	 * it would be better to stop merging.
+	 */
+	if (!strcmp(earlier->wwid, later->wwid) &&
+	    strcmp(earlier->action, later->action) &&
+	    strcmp(earlier->action, "change") &&
+	    strcmp(later->action, "change"))
+		return true;
+
+	return false;
+}
+
+bool
+uevent_can_merge(struct uevent *earlier, struct uevent *later)
+{
+	/* merge paths uevents
+	 * whose wwids exsit and are same
+	 * and actions are same,
+	 * and actions are addition or deletion
+	 */
+	if (earlier->wwid && later->wwid &&
+	    !strcmp(earlier->wwid, later->wwid) &&
+	    !strcmp(earlier->action, later->action) &&
+	    strncmp(earlier->action, "change", 6) &&
+	    strncmp(earlier->kernel, "dm-", 3)) {
+		return true;
+	}
+
+	return false;
+}
+
+void
+uevent_merge(struct uevent *later, struct list_head *tmpq)
+{
+	struct uevent *earlier, *temp;
+	/*
+	 * compare the uevent with earlier uevents
+	 */
+	list_for_some_entry_reverse(earlier, &later->node, tmpq, node) {
+next_earlier_node:
+		if (merge_need_stop(earlier, later))
+			break;
+		/*
+		 * try to merge earlier uevents to the later uevent
+		 */
+		if (uevent_can_merge(earlier, later)) {
+			condlog(3, "merged uevent: %s-%s-%s with uevent: %s-%s-%s",
+				earlier->action, earlier->kernel, earlier->wwid,
+				later->action, later->kernel, later->wwid);
+			temp = earlier;
+
+			earlier = list_entry(earlier->node.prev, typeof(struct uevent), node);
+			list_move(&temp->node, &later->merge_node);
+
+			if (earlier ==  list_entry(tmpq, typeof(struct uevent), node))
+				break;
+			else
+				goto next_earlier_node;
+		}
+	}
+}
+
+void
+merge_uevq(struct list_head *tmpq)
+{
+	struct uevent *later;
+
+	list_for_each_entry_reverse(later, tmpq, node) {
+		uevent_merge(later, tmpq);
+	}
+}
+
 void
 service_uevq(struct list_head *tmpq)
 {
@@ -136,6 +247,8 @@ service_uevq(struct list_head *tmpq)
 		if (my_uev_trigger && my_uev_trigger(uev, my_trigger_data))
 			condlog(0, "uevent trigger error");
 
+		uevq_cleanup(&uev->merge_node);
+
 		if (uev->udev)
 			udev_device_unref(uev->udev);
 		FREE(uev);
@@ -150,17 +263,6 @@ static void uevent_cleanup(void *arg)
 	udev_unref(udev);
 }
 
-void
-uevq_cleanup(struct list_head *tmpq)
-{
-	struct uevent *uev, *tmp;
-
-	list_for_each_entry_safe(uev, tmp, tmpq, node) {
-		list_del_init(&uev->node);
-		FREE(uev);
-	}
-}
-
 /*
  * Service the uevent queue.
  */
@@ -189,6 +291,7 @@ int uevent_dispatch(int (*uev_trigger)(struct uevent *, void * trigger_data),
 		pthread_mutex_unlock(uevq_lockp);
 		if (!my_uev_trigger)
 			break;
+		merge_uevq(&uevq_tmp);
 		service_uevq(&uevq_tmp);
 	}
 	condlog(3, "Terminating uev service queue");
-- 
2.8.1.windows.1