Skip sync of mirror extension if mirror has LV_NOTSYNCED set

Index: LVM2/lib/metadata/lv_manip.c
===================================================================
@@ -2599,13 +2599,45 @@ int lv_extend(struct logical_volume *lv,
 			return 0;
 		}
 
-		r = _lv_extend_layered_lv(ah, lv, extents, 0,
-					  stripes, stripe_size);
+		if (!(r = _lv_extend_layered_lv(ah, lv, extents, 0,
+						stripes, stripe_size)))
+			goto_out;
 
-		if (r && segtype_is_thin_pool(segtype))
+		if (segtype_is_thin_pool(segtype))
 			r = lv_add_segment(ah, ah->area_count, 1, first_seg(lv)->pool_metadata_lv,
 					   get_segtype_from_string(lv->vg->cmd, "striped"), 0, 0, 0);
+
+		/*
+		 * If we are expanding an existing mirror, we can skip the
+		 * resync of the extension if the LV is currently in-sync
+		 * and the LV has the LV_NOTSYNCED flag set.
+		 */
+		if ((lv->le_count != extents) &&
+		    segtype_is_mirrored(segtype) &&
+		    (lv->status & LV_NOTSYNCED)) {
+			percent_t sync_percent;
+
+			log_verbose("%s/%s created or extended with '--nosync'",
+				    lv->vg->name, lv->name);
+			if (!lv_mirror_percent(lv->vg->cmd, lv, 0,
+					      &sync_percent, NULL)) {
+				log_error("Failed to get sync percent for %s/%s:"
+					  " Forcing resync of extended portion",
+					  lv->vg->name, lv->name);
+			} else if (sync_percent == PERCENT_100) {
+				log_verbose("Skipping initial resync for "
+					    "extended portion of %s/%s",
+					    lv->vg->name, lv->name);
+				init_mirror_in_sync(1);
+			} else {
+				log_verbose("%s/%s is not currently in-sync: "
+					  " Forcing resync of extended portion",
+					  lv->vg->name, lv->name);
+			}
+		}
 	}
+
+out:
 	alloc_destroy(ah);
 	return r;
 }

Index: LVM2/tools/commands.h
===================================================================
@@ -265,6 +265,7 @@ xx(lvextend,
    "\t{-l|--extents [+]LogicalExtentsNumber[%{VG|LV|PVS|FREE|ORIGIN}] |\n"
    "\t -L|--size [+]LogicalVolumeSize[bBsSkKmMgGtTpPeE]}\n"
    "\t[-m|--mirrors Mirrors]\n"
+   "\t[--nosync]\n"
    "\t[--use-policies]\n"
    "\t[-n|--nofsck]\n"
    "\t[--noudevsync]\n"

@@ -276,7 +277,7 @@ xx(lvextend,
    "\tLogicalVolume[Path] [ PhysicalVolumePath... ]\n",
 
    alloc_ARG, autobackup_ARG, extents_ARG, force_ARG, mirrors_ARG,
-   nofsck_ARG, noudevsync_ARG, resizefs_ARG, size_ARG, stripes_ARG,
+   nofsck_ARG, nosync_ARG, noudevsync_ARG, resizefs_ARG, size_ARG, stripes_ARG,
    stripesize_ARG, test_ARG, type_ARG, use_policies_ARG)
 
 xx(lvmchange,

Index: LVM2/tools/lvresize.c
===================================================================
@@ -504,6 +504,13 @@ static int _lvresize(struct cmd_context 
 
 	/* If extending, find mirrors of last segment */
 	if ((lp->extents > lv->le_count)) {
+		/*
+		 * Has the user specified that they would like the additional
+		 * extents of a mirror not to have an initial sync?
+		 */
+		if (seg_is_mirrored(first_seg(lv)) && arg_count(cmd, nosync_ARG))
+			lv->status |= LV_NOTSYNCED;
+
 		dm_list_iterate_back_items(mirr_seg, &lv->segments) {
 			if (seg_is_mirrored(mirr_seg))
 				seg_mirrors = lv_mirror_count(mirr_seg->lv);