devices: exclude multipath components based on matching wwid

If multipath component devices get through the filter and
cause lvm to see duplicate PVs, then check the wwid of the
devs and drop the component devices as if they had been
filtered.  If a dm mpath device was found among the duplicates
then use that as the PV, otherwise do not use any of the
components as the PV.

"duplicate PVs" associated with multipath configs will no
longer stop commands from working.

1 files changed, 179 insertions, 7 deletions

diff --git a/lib/cache/lvmcache.c b/lib/cache/lvmcache.c
index bee63ebb4..a0811d4ea 100644
--- a/lib/cache/lvmcache.c
+++ b/lib/cache/lvmcache.c
@@ -625,6 +625,102 @@ static void _warn_unused_duplicates(struct cmd_context *cmd)
 	}
 }
 
+static int _all_multipath_components(struct cmd_context *cmd, struct lvmcache_info *info, const char *pvid,
+				     struct dm_list *altdevs, struct device **dev_mpath)
+{
+	struct device_list *devl;
+	struct device *dev_mp = NULL;
+	struct device *dev1 = NULL;
+	struct device *dev;
+	const char *wwid1 = NULL;
+	const char *wwid;
+	int diff_wwid = 0;
+	int same_wwid = 0;
+	int dev_is_mp;
+
+	*dev_mpath = NULL;
+
+	/* This function only makes sense with more than one dev. */
+	if ((info && dm_list_empty(altdevs)) || (!info && (dm_list_size(altdevs) == 1))) {
+		log_debug("Skip multipath component checks with single device for PVID %s", pvid);
+		return 0;
+	}
+
+	log_debug("Checking for multipath components for duplicate PVID %s", pvid);
+
+	if (info) {
+		dev = info->dev;
+		dev_is_mp = (cmd->dev_types->device_mapper_major == MAJOR(dev->dev)) && dev_has_mpath_uuid(cmd, dev, NULL);
+
+		if (dev_is_mp) {
+			if ((wwid1 = dev_mpath_component_wwid(cmd, dev))) {
+				dev_mp = dev;
+				dev1 = dev;
+			}
+		} else {
+			if ((wwid1 = device_id_system_read(cmd, dev, DEV_ID_TYPE_SYS_WWID)))
+				dev1 = dev;
+		}
+	}
+
+	dm_list_iterate_items(devl, altdevs) {
+		dev = devl->dev;
+		dev_is_mp = (cmd->dev_types->device_mapper_major == MAJOR(dev->dev)) && dev_has_mpath_uuid(cmd, dev, NULL);
+
+		if (dev_is_mp)
+			wwid = dev_mpath_component_wwid(cmd, dev);
+		else
+			wwid = device_id_system_read(cmd, dev, DEV_ID_TYPE_SYS_WWID);
+
+		if (!wwid && wwid1) {
+			log_print("Different wwids for duplicate PVs %s %s %s none",
+				  dev_name(dev1), wwid1, dev_name(dev));
+			diff_wwid++;
+			continue;
+		}
+
+		if (!wwid)
+			continue;
+
+		if (!wwid1) {
+			wwid1 = wwid;
+			dev1 = dev;
+			continue;
+		}
+
+		/* Different wwids indicates these are not multipath components. */
+		if (strcmp(wwid1, wwid)) {
+			log_print("Different wwids for duplicate PVs %s %s %s %s",
+				  dev_name(dev1), wwid1, dev_name(dev), wwid);
+			diff_wwid++;
+			continue;
+		}
+
+		/* Different mpath devs with the same wwid shouldn't happen. */
+		if (dev_is_mp && dev_mp) {
+			log_print("Found multiple multipath devices for PVID %s WWID %s: %s %s",
+				   pvid, wwid1, dev_name(dev_mp), dev_name(dev));
+			continue;
+		}
+
+		log_debug("Same wwids for duplicate PVs %s %s", dev_name(dev1), dev_name(dev));
+		same_wwid++;
+
+		/* Save the mpath device so it can be used as the PV. */
+		if (dev_is_mp)
+			dev_mp = dev;
+	}
+
+	if (diff_wwid || !same_wwid)
+		return 0;
+
+	if (dev_mp)
+		log_debug("Found multipath device %s for PVID %s WWID %s.", dev_name(dev_mp), pvid, wwid1);
+
+	*dev_mpath = dev_mp;
+	return 1;
+}
+
 /*
  * If we've found devices with the same PVID, decide which one
  * to use.
@@ -680,6 +776,8 @@ static void _choose_duplicates(struct cmd_context *cmd,
 	struct device_list *devl, *devl_safe, *devl_add, *devl_del;
 	struct lvmcache_info *info;
 	struct device *dev1, *dev2;
+	struct device *dev_mpath;
+	struct device *dev_drop;
 	const char *device_id = NULL, *device_id_type = NULL;
 	const char *idname1 = NULL, *idname2 = NULL;
 	uint32_t dev1_major, dev1_minor, dev2_major, dev2_minor;
@@ -702,6 +800,7 @@ static void _choose_duplicates(struct cmd_context *cmd,
 next:
 	dm_list_init(&altdevs);
 	pvid = NULL;
+	dev_mpath = NULL;
 
 	dm_list_iterate_items_safe(devl, devl_safe, &_initial_duplicates) {
 		if (!pvid) {
@@ -720,23 +819,97 @@ next:
 		return;
 	}
 
+	info = lvmcache_info_from_pvid(pvid, NULL, 0);
+
 	/*
-	 * Get rid of any md components before comparing alternatives.
-	 * (Since an md component can never be used, it's not an
-	 * option to use like other kinds of alternatives.)
+	 * Usually and ideally, components of md and multipath devs should have
+	 * been excluded by filters, and not scanned for a PV.  In some unusual
+	 * cases the components can get through the filters, and a PV can be
+	 * found on them.  Detecting the same PVID on both the component and
+	 * the md/mpath device gives us a last chance to drop the component.
+	 * An md/mpath component device is completely ignored, as if it had
+	 * been filtered, and not kept in the list unused duplicates.
 	 */
 
-	info = lvmcache_info_from_pvid(pvid, NULL, 0);
+	/*
+	 * Get rid of multipath components based on matching wwids.
+	 */
+	if (_all_multipath_components(cmd, info, pvid, &altdevs, &dev_mpath)) {
+		if (info && dev_mpath && (info->dev != dev_mpath)) {
+			/*
+			 * info should be dropped from lvmcache and info->dev
+			 * should be treated as if it had been excluded by a filter.
+			 * dev_mpath should be added to lvmcache by the caller.
+			 */
+			dev_drop = info->dev;
+
+			/* Have caller add dev_mpath to lvmcache. */
+			log_debug("Using multipath device %s for PVID %s.", dev_name(dev_mpath), pvid);
+			if ((devl_add = zalloc(sizeof(*devl_add)))) {
+				devl_add->dev = dev_mpath;
+				dm_list_add(add_cache_devs, &devl_add->list);
+			}
+
+			/* Remove dev_mpath from altdevs. */
+			if ((devl = _get_devl_in_device_list(dev_mpath, &altdevs)))
+				dm_list_del(&devl->list);
+
+			/* Remove info from lvmcache that came from the component dev. */
+			log_debug("Ignoring multipath component %s with PVID %s (dropping info)", dev_name(dev_drop), pvid);
+			lvmcache_del(info);
+			info = NULL;
+
+			/* Make the component dev look like it was filtered. */
+			cmd->filter->wipe(cmd, cmd->filter, dev_drop, NULL);
+			dev_drop->flags &= ~DEV_SCAN_FOUND_LABEL;
+		}
+
+		if (info && !dev_mpath) {
+			/*
+			 * Only mpath component devs were found and no actual
+			 * multipath dev, so drop the component from lvmcache.
+			 */
+			dev_drop = info->dev;
+
+			log_debug("Ignoring multipath component %s with PVID %s (dropping info)", dev_name(dev_drop), pvid);
+			lvmcache_del(info);
+			info = NULL;
+
+			/* Make the component dev look like it was filtered. */
+			cmd->filter->wipe(cmd, cmd->filter, dev_drop, NULL);
+			dev_drop->flags &= ~DEV_SCAN_FOUND_LABEL;
+		}
+
+		dm_list_iterate_items_safe(devl, devl_safe, &altdevs) {
+			/*
+			 * The altdevs are all mpath components that should look
+			 * like they were filtered, they are not in lvmcache.
+			 */
+			dev_drop = devl->dev;
+
+			log_debug("Ignoring multipath component %s with PVID %s (dropping duplicate)", dev_name(dev_drop), pvid);
+			dm_list_del(&devl->list);
+
+			cmd->filter->wipe(cmd, cmd->filter, dev_drop, NULL);
+			dev_drop->flags &= ~DEV_SCAN_FOUND_LABEL;
+		}
+		goto next;
+	}
+
+	/*
+	 * Get rid of any md components.
+	 * FIXME: use a function like _all_multipath_components to pick the actual md device.
+	 */
 	if (info && dev_is_md_component(cmd, info->dev, NULL, 1)) {
 		/* does not go in del_cache_devs which become unused_duplicates */
-		log_debug_cache("PV %s drop MD component from scan selection %s", pvid, dev_name(info->dev));
+		log_debug("Ignoring md component %s with PVID %s (dropping info)", dev_name(info->dev), pvid);
 		lvmcache_del(info);
 		info = NULL;
 	}
 
 	dm_list_iterate_items_safe(devl, devl_safe, &altdevs) {
 		if (dev_is_md_component(cmd, devl->dev, NULL, 1)) {
-			log_debug_cache("PV %s drop MD component from scan duplicates %s", pvid, dev_name(devl->dev));
+			log_debug("Ignoring md component %s with PVID %s (dropping duplicate)", dev_name(devl->dev), pvid);
 			dm_list_del(&devl->list);
 		}
 	}
@@ -744,7 +917,6 @@ next:
 	if (dm_list_empty(&altdevs))
 		goto next;
 
-
 	/*
 	 * Find the device for the pvid that's currently in lvmcache.
 	 */