vgchange: allow changing system ID with majority of PVsdev-dct-vgchange-majority

when used with --majoritypvs.  This allows the fail-over
of a VG between systems (by changing the VG system ID)
when a PV is missing.

3 files changed, 26 insertions, 0 deletions

diff --git a/tools/args.h b/tools/args.h
index baae333e1..9ad53cadb 100644
--- a/tools/args.h
+++ b/tools/args.h
@@ -390,6 +390,10 @@ arg(logonly_ARG, '\0', "logonly", 0, 0, 0,
 arg(longhelp_ARG, '\0', "longhelp", 0, 0, 0,
     "Display long help text.\n")
 
+arg(majoritypvs_ARG, '\0', "majoritypvs", 0, 0, 0,
+    "Change the VG system ID if the majority of PVs in the VG\n"
+    "are present (one more than half).\n")
+
 arg(maxrecoveryrate_ARG, '\0', "maxrecoveryrate", sizekb_VAL, 0, 0,
     "Sets the maximum recovery rate for a RAID LV.  The rate value\n"
     "is an amount of data per second for each device in the array.\n"
diff --git a/tools/command-lines.in b/tools/command-lines.in
index b6a03d158..fd69f7420 100644
--- a/tools/command-lines.in
+++ b/tools/command-lines.in
@@ -1766,6 +1766,7 @@ ID: vgchange_refresh
 DESC: Reactivate LVs using the latest metadata.
 
 vgchange --systemid String VG
+OO: --majoritypvs
 ID: vgchange_systemid
 DESC: Change the system ID of a VG.
 
diff --git a/tools/vgchange.c b/tools/vgchange.c
index ea22bada0..3f622fc65 100644
--- a/tools/vgchange.c
+++ b/tools/vgchange.c
@@ -1344,6 +1344,24 @@ static int _vgchange_systemid_single(struct cmd_context *cmd, const char *vg_nam
 			             struct volume_group *vg,
 			             struct processing_handle *handle)
 {
+	if (arg_is_set(cmd, majoritypvs_ARG)) {
+		struct pv_list *pvl;
+		int missing_pvs = 0;
+		int found_pvs = 0;
+
+		dm_list_iterate_items(pvl, &vg->pvs) {
+			if (!pvl->pv->dev)
+				missing_pvs++;
+			else
+				found_pvs++;
+		}
+		if (found_pvs <= missing_pvs) {
+			log_error("Cannot change system ID without the majority of PVs (found %d of %d)",
+				  found_pvs, found_pvs+missing_pvs);
+			return ECMD_FAILED;
+		}
+	}
+
 	if (!_vgchange_system_id(cmd, vg))
 		return_ECMD_FAILED;
 
@@ -1376,6 +1394,9 @@ int vgchange_systemid_cmd(struct cmd_context *cmd, int argc, char **argv)
 		return ECMD_FAILED;
 	}
 
+	if (arg_is_set(cmd, majoritypvs_ARG))
+		cmd->handles_missing_pvs = 1;
+
 	ret = process_each_vg(cmd, argc, argv, NULL, NULL, READ_FOR_UPDATE, 0, handle, &_vgchange_systemid_single);
 
 	destroy_processing_handle(cmd, handle);