cache: implement better revert path

When cache creation fails on table reload path, implemen more
advanced revert solution, that tries to restore state of LVM
metadata into is look before actual caching started.

WHATS_NEW

@@ -1,5 +1,6 @@
 Version 2.03.14 - 
 ==================================
+  Enhance recover path on cache creation failure.
   Filter out unsupported MQ/SMQ cache policy setting.
   Fix memleak in mpath filter.
   Support newer location for VDO statistics.

lib/metadata/lv_manip.c

@@ -8789,9 +8789,35 @@ static struct logical_volume *_lv_create_an_lv(struct volume_group *vg,
 			return_NULL; /* revert? */
 
 		if (!lv_update_and_reload(lv)) {
-			/* FIXME Do a better revert */
-			log_error("Aborting. Manual intervention required.");
-			return NULL; /* FIXME: revert */
+			char name[NAME_LEN];
+
+			log_debug("Reverting created caching layer.");
+
+			tmp_lv = seg_lv(first_seg(lv), 0); /* tmp corigin */
+			pool_lv = first_seg(lv)->pool_lv;
+
+			if (!detach_pool_lv(first_seg(lv)))
+				return_NULL;
+			if (!remove_layer_from_lv(lv, tmp_lv))
+				return_NULL;
+			if (!lv_remove(tmp_lv))
+				return_NULL;
+
+			/* Either we need to preserve existing LV and remove created cache pool LV.
+			   Or we need to preserve existing cache pool LV and remove created new LV. */
+			if (origin_lv)
+				lv = pool_lv; // created cache pool to be reverted as new LV
+			else {
+				/* Cut off suffix _cpool from preserved existing cache pool */
+				if (!drop_lvname_suffix(name, pool_lv->name, "cpool")) {
+					/* likely older instance of metadata */
+					log_debug("LV %s has no suffix for cachepool (skipping rename).",
+						  display_lvname(pool_lv));
+				} else if (!lv_uniq_rename_update(cmd, pool_lv, name, 0))
+					return_NULL;
+			}
+
+			goto deactivate_and_revert_new_lv;
 		}
 	} else if (lp->snapshot) {
 		/* Deactivate zeroed COW, avoid any race usage */