devices: fix name handlingdev-dct-devs3

- Fix cases where incorrect device paths were left
  on the dev->aliases list.  Leaving incorrect paths
  on dev->aliases could result in using the wrong device.

- Fix a widespread incorrect assumption that dev_name()
  always returns a valid path (or NULL).  dev_name()
  returns "[unknown]" when there are no paths to a
  device, and is mainly meant to be used in messages.

- Check for valid dev paths in cases that want to use
  the from dev_name() for things other than a message.

15 files changed, 251 insertions, 168 deletions

diff --git a/lib/activate/dev_manager.c b/lib/activate/dev_manager.c
index 63bfd9b74..2cae3bed1 100644
--- a/lib/activate/dev_manager.c
+++ b/lib/activate/dev_manager.c
@@ -2947,6 +2947,10 @@ int add_areas_line(struct dev_manager *dm, struct lv_segment *seg,
 
 	/* FIXME Avoid repeating identical stat in dm_tree_node_add_target_area */
 	for (s = start_area; s < areas; s++) {
+
+		/* FIXME: dev_name() does not return NULL!  It needs to check if dm_list_empty(&dev->aliases)
+		   but this knot of logic is too complex to pull apart without careful deconstruction. */
+
 		if ((seg_type(seg, s) == AREA_PV &&
 		     (!seg_pvseg(seg, s) || !seg_pv(seg, s) || !seg_dev(seg, s) ||
 		       !(name = dev_name(seg_dev(seg, s))) || !*name ||
@@ -2965,7 +2969,10 @@ int add_areas_line(struct dev_manager *dm, struct lv_segment *seg,
 				return_0;
 			num_error_areas++;
 		} else if (seg_type(seg, s) == AREA_PV) {
-			if (!dm_tree_node_add_target_area(node, dev_name(seg_dev(seg, s)), NULL,
+			struct device *dev = seg_dev(seg, s);
+			name = dm_list_empty(&dev->aliases) ? NULL : dev_name(dev);
+
+			if (!dm_tree_node_add_target_area(node, name, NULL,
 				    (seg_pv(seg, s)->pe_start + (extent_size * seg_pe(seg, s)))))
 				return_0;
 			num_existing_areas++;
diff --git a/lib/device/dev-cache.c b/lib/device/dev-cache.c
index d3fae4948..8db28bd84 100644
--- a/lib/device/dev-cache.c
+++ b/lib/device/dev-cache.c
@@ -351,7 +351,7 @@ static int _add_alias(struct device *dev, const char *path, enum add_hash hash)
 			goto out;
 		}
 
-	if (!(path = dm_pool_strdup(_cache.mem, path)) ||
+	if (!(path = _strdup(path)) ||
 	    !(sl = _zalloc(sizeof(*sl)))) {
 		log_error("Failed to add allias to dev cache.");
 		return 0;
@@ -1162,6 +1162,17 @@ static int _insert(const char *path, const struct stat *info,
 	return 1;
 }
 
+static void _drop_all_aliases(struct device *dev)
+{
+	struct dm_str_list *strl, *strl2;
+
+	dm_list_iterate_items_safe(strl, strl2, &dev->aliases) {
+		log_debug("Drop alias for %d:%d %s.", (int)MAJOR(dev->dev), (int)MINOR(dev->dev), strl->str);
+		dm_hash_remove(_cache.names, strl->str);
+		dm_list_del(&strl->list);
+	}
+}
+
 void dev_cache_scan(struct cmd_context *cmd)
 {
 	log_debug_devs("Creating list of system devices.");
@@ -1371,59 +1382,6 @@ int dev_cache_add_dir(const char *path)
 	return 1;
 }
 
-/* Check cached device name is still valid before returning it */
-/* This should be a rare occurrence */
-/* set quiet if the cache is expected to be out-of-date */
-/* FIXME Make rest of code pass/cache struct device instead of dev_name */
-const char *dev_name_confirmed(struct device *dev, int quiet)
-{
-	struct stat buf;
-	const char *name;
-	int r;
-
-	if ((dev->flags & DEV_REGULAR))
-		return dev_name(dev);
-
-	while ((r = stat(name = dm_list_item(dev->aliases.n,
-					  struct dm_str_list)->str, &buf)) ||
-	       (buf.st_rdev != dev->dev)) {
-		if (r < 0) {
-			if (quiet)
-				log_sys_debug("stat", name);
-			else
-				log_sys_error("stat", name);
-		}
-		if (quiet)
-			log_debug_devs("Path %s no longer valid for device(%d,%d)",
-				       name, (int) MAJOR(dev->dev),
-				       (int) MINOR(dev->dev));
-		else
-			log_warn("Path %s no longer valid for device(%d,%d)",
-				 name, (int) MAJOR(dev->dev),
-				 (int) MINOR(dev->dev));
-
-		/* Remove the incorrect hash entry */
-		dm_hash_remove(_cache.names, name);
-
-		/* Leave list alone if there isn't an alternative name */
-		/* so dev_name will always find something to return. */
-		/* Otherwise add the name to the correct device. */
-		if (dm_list_size(&dev->aliases) > 1) {
-			dm_list_del(dev->aliases.n);
-			if (!r)
-				_insert(name, &buf, 0, obtain_device_list_from_udev());
-			continue;
-		}
-
-		/* Scanning issues this inappropriately sometimes. */
-		log_debug_devs("Aborting - please provide new pathname for what "
-			       "used to be %s", name);
-		return NULL;
-	}
-
-	return dev_name(dev);
-}
-
 struct device *dev_hash_get(const char *name)
 {
 	return (struct device *) dm_hash_lookup(_cache.names, name);
@@ -1452,26 +1410,23 @@ static void _remove_alias(struct device *dev, const char *name)
  * deactivated LV.  Those old paths are all invalid and are dropped here.
  */
 
-static void _verify_aliases(struct device *dev, const char *newname)
+static void _verify_aliases(struct device *dev)
 {
 	struct dm_str_list *strl, *strl2;
 	struct stat st;
 
 	dm_list_iterate_items_safe(strl, strl2, &dev->aliases) {
-		/* newname was just stat'd and added by caller */
-		if (newname && !strcmp(strl->str, newname))
-			continue;
-
 		if (stat(strl->str, &st) || (st.st_rdev != dev->dev)) {
-			log_debug("Drop invalid path %s for %d:%d (new path %s).",
-				  strl->str, (int)MAJOR(dev->dev), (int)MINOR(dev->dev), newname ?: "");
+			log_debug("Drop alias for %d:%d invalid path %s %d:%d.",
+				  (int)MAJOR(dev->dev), (int)MINOR(dev->dev), strl->str,
+				  (int)MAJOR(st.st_rdev), (int)MINOR(st.st_rdev));
 			dm_hash_remove(_cache.names, strl->str);
 			dm_list_del(&strl->list);
 		}
 	}
 }
 
-struct device *dev_cache_get(struct cmd_context *cmd, const char *name, struct dev_filter *f)
+static struct device *_dev_cache_get(struct cmd_context *cmd, const char *name, struct dev_filter *f, int existing)
 {
 	struct device *dev = (struct device *) dm_hash_lookup(_cache.names, name);
 	struct stat st;
@@ -1485,13 +1440,18 @@ struct device *dev_cache_get(struct cmd_context *cmd, const char *name, struct d
 	if (dev && (dev->flags & DEV_REGULAR))
 		return dev;
 
+	if (dev && dm_list_empty(&dev->aliases)) {
+		/* shouldn't happen */
+		log_warn("Ignoring dev with no valid paths for %s.", name);
+		return NULL;
+	}
+
 	/*
-	 * The requested path is invalid, remove any dev-cache
-	 * info for it.
+	 * The requested path is invalid, remove any dev-cache info for it.
 	 */
 	if (stat(name, &st)) {
 		if (dev) {
-			log_print("Device path %s is invalid for %d:%d %s.",
+			log_debug("Device path %s is invalid for %d:%d %s.",
 				  name, (int)MAJOR(dev->dev), (int)MINOR(dev->dev), dev_name(dev));
 
 			dm_hash_remove(_cache.names, name);
@@ -1499,11 +1459,17 @@ struct device *dev_cache_get(struct cmd_context *cmd, const char *name, struct d
 			_remove_alias(dev, name);
 
 			/* Remove any other names in dev->aliases that are incorrect. */
-			_verify_aliases(dev, NULL);
+			_verify_aliases(dev);
 		}
 		return NULL;
 	}
 
+	if (dev && dm_list_empty(&dev->aliases)) {
+		/* shouldn't happen */
+		log_warn("Ignoring dev with no valid paths for %s.", name);
+		return NULL;
+	}
+
 	if (!S_ISBLK(st.st_mode)) {
 		log_debug("Not a block device %s.", name);
 		return NULL;
@@ -1514,26 +1480,110 @@ struct device *dev_cache_get(struct cmd_context *cmd, const char *name, struct d
 	 * Remove incorrect info and then add new dev-cache entry.
 	 */
 	if (dev && (st.st_rdev != dev->dev)) {
-		log_debug("Device path %s does not match %d:%d %s.",
-			  name, (int)MAJOR(dev->dev), (int)MINOR(dev->dev), dev_name(dev));
+		struct device *dev_by_devt = (struct device *) btree_lookup(_cache.devices, (uint32_t) st.st_rdev);
+
+		/*
+		 * lvm commands create this condition when they
+		 * activate/deactivate LVs combined with creating new LVs.
+		 * The command does not purge dev structs when deactivating
+		 * an LV (which it probably should do), but the better
+		 * approach would be not using dev-cache at all for LVs.
+		 */
+
+		log_debug("Dropping aliases for device entry %d:%d %s for new device %d:%d %s.",
+			  (int)MAJOR(dev->dev), (int)MINOR(dev->dev), dev_name(dev),
+			  (int)MAJOR(st.st_rdev), (int)MINOR(st.st_rdev), name);
+
+		_drop_all_aliases(dev);
 
-		dm_hash_remove(_cache.names, name);
+		if (dev_by_devt) {
+			log_debug("Dropping aliases for device entry %d:%d %s for new device %d:%d %s.",
+				   (int)MAJOR(dev_by_devt->dev), (int)MINOR(dev_by_devt->dev), dev_name(dev_by_devt),
+				   (int)MAJOR(st.st_rdev), (int)MINOR(st.st_rdev), name);
+
+			_drop_all_aliases(dev_by_devt);
+		}
+
+#if 0
+		/*
+		 * I think only lvm's own dm devs should be added here, so use
+		 * a warning to look for any other unknown cases.
+		 */
+		if (MAJOR(st.st_rdev) != cmd->dev_types->device_mapper_major) {
+			log_warn("WARNING: new device appeared %d:%d %s",
+				  (int)MAJOR(st.st_rdev), (int)(MINOR(st.st_rdev)), name);
+		}
+#endif
+
+		if (!_insert_dev(name, st.st_rdev))
+			return_NULL;
+
+		/* Get the struct dev that was just added. */
+		dev = (struct device *) dm_hash_lookup(_cache.names, name);
 
-		_remove_alias(dev, name);
+		if (!dev) {
+			log_error("Failed to get device %s", name);
+			return NULL;
+		}
 
-		/* Remove any other names in dev->aliases that are incorrect. */
-		_verify_aliases(dev, NULL);
+		goto out;
+	}
 
-		/* Add new dev-cache entry next. */
-		dev = NULL;
+	if (dev && dm_list_empty(&dev->aliases)) {
+		/* shouldn't happen */
+		log_warn("Ignoring dev with no valid paths for %s.", name);
+		return NULL;
 	}
 
+	if (!dev && existing)
+		return_NULL;
+
 	/*
-	 * Either add a new struct dev for st_rdev and name,
-	 * or add name as a new alias for an existing struct dev
-	 * for st_rdev.
+	 * This case should never be hit for a PV. It should only
+	 * happen when the command is opening a new LV it has created.
+	 * Add an arg to all callers indicating when the arg should be
+	 * new (for an LV) and not existing.
+	 * FIXME: fix this further by not using dev-cache struct devs
+	 * at all for new dm devs (LVs) that lvm uses.  Make the
+	 * dev-cache contain only devs for PVs.
+	 * Places to fix that use a dev for LVs include:
+	 * . lv_resize opening lv to discard
+	 * . wipe_lv opening lv to zero it
+	 * . _extend_sanlock_lv opening lv to extend it
+	 * . _write_log_header opening lv to write header
+	 * Also, io to LVs should not go through bcache.
+	 * bcache should contain only labels and metadata
+	 * scanned from PVs.
 	 */
 	if (!dev) {
+		/*
+		 * This case should only be used for new devices created by this
+		 * command (opening LVs it's created), so if a dev exists for the
+		 * dev_t referenced by the name, then drop all aliases for before
+		 * _insert_dev adds the new name.  lvm commands actually hit this
+		 * fairly often when it uses some LV, deactivates the LV, then
+		 * creates some new LV which ends up with the same major:minor.
+		 * Without dropping the aliases, it's plausible that lvm commands
+		 * could end up using the wrong dm device.
+		 */
+		struct device *dev_by_devt = (struct device *) btree_lookup(_cache.devices, (uint32_t) st.st_rdev);
+		if (dev_by_devt) {
+			log_debug("Dropping aliases for %d:%d before adding new path %s.",
+				  (int)MAJOR(st.st_rdev), (int)(MINOR(st.st_rdev)), name);
+			_drop_all_aliases(dev_by_devt);
+		}
+
+#if 0
+		/*
+		 * I think only lvm's own dm devs should be added here, so use
+		 * a warning to look for any other unknown cases.
+		 */
+		if (MAJOR(st.st_rdev) != cmd->dev_types->device_mapper_major) {
+			log_warn("WARNING: new device appeared %d:%d %s",
+				  (int)MAJOR(st.st_rdev), (int)(MINOR(st.st_rdev)), name);
+		}
+#endif
+
 		if (!_insert_dev(name, st.st_rdev))
 			return_NULL;
 
@@ -1544,10 +1594,9 @@ struct device *dev_cache_get(struct cmd_context *cmd, const char *name, struct d
 			log_error("Failed to get device %s", name);
 			return NULL;
 		}
-
-		_verify_aliases(dev, name);
 	}
 
+ out:
 	/*
 	 * The caller passed a filter if they only want the dev if it
 	 * passes filters.
@@ -1577,63 +1626,23 @@ struct device *dev_cache_get(struct cmd_context *cmd, const char *name, struct d
 	return dev;
 }
 
-struct device *dev_cache_get_by_devt(struct cmd_context *cmd, dev_t dev, struct dev_filter *f, int *filtered)
+struct device *dev_cache_get_existing(struct cmd_context *cmd, const char *name, struct dev_filter *f)
 {
-	char path[PATH_MAX];
-	const char *sysfs_dir;
-	struct stat info;
-	struct device *d = (struct device *) btree_lookup(_cache.devices, (uint32_t) dev);
-	int ret;
-
-	if (filtered)
-		*filtered = 0;
-
-	if (!d) {
-		sysfs_dir = dm_sysfs_dir();
-		if (sysfs_dir && *sysfs_dir) {
-			/* First check if dev is sysfs to avoid useless scan */
-			if (dm_snprintf(path, sizeof(path), "%sdev/block/%d:%d",
-					sysfs_dir, (int)MAJOR(dev), (int)MINOR(dev)) < 0) {
-				log_error("dm_snprintf partition failed.");
-				return NULL;
-			}
-
-			if (lstat(path, &info)) {
-				log_debug("No sysfs entry for %d:%d errno %d at %s.",
-					  (int)MAJOR(dev), (int)MINOR(dev), errno, path);
-				return NULL;
-			}
-		}
-
-		log_debug_devs("Device num not found in dev_cache repeat dev_cache_scan for %d:%d",
-				(int)MAJOR(dev), (int)MINOR(dev));
-		dev_cache_scan(cmd);
-		d = (struct device *) btree_lookup(_cache.devices, (uint32_t) dev);
-
-		if (!d)
-			return NULL;
-	}
-
-	if (d->flags & DEV_REGULAR)
-		return d;
-
-	if (!f)
-		return d;
-
-	ret = f->passes_filter(cmd, f, d, NULL);
-
-	if (ret == -EAGAIN) {
-		log_debug_devs("get device by number defer filter %s", dev_name(d));
-		d->flags |= DEV_FILTER_AFTER_SCAN;
-		ret = 1;
-	}
+	return _dev_cache_get(cmd, name, f, 1);
+}
 
-	if (ret)
-		return d;
+struct device *dev_cache_get(struct cmd_context *cmd, const char *name, struct dev_filter *f)
+{
+	return _dev_cache_get(cmd, name, f, 0);
+}
 
-	if (filtered)
-		*filtered = 1;
+struct device *dev_cache_get_by_devt(struct cmd_context *cmd, dev_t devt)
+{
+	struct device *dev = (struct device *) btree_lookup(_cache.devices, (uint32_t) devt);
 
+	if (dev)
+		return dev;
+	log_debug_devs("No devno %d:%d in dev cache.", (int)MAJOR(devt), (int)MINOR(devt));
 	return NULL;
 }
 
@@ -1703,8 +1712,10 @@ int dev_fd(struct device *dev)
 
 const char *dev_name(const struct device *dev)
 {
-	return (dev && dev->aliases.n) ? dm_list_item(dev->aliases.n, struct dm_str_list)->str :
-	    unknown_device_name();
+	if (dev && dev->aliases.n && !dm_list_empty(&dev->aliases))
+		return dm_list_item(dev->aliases.n, struct dm_str_list)->str;
+	else
+		return unknown_device_name();
 }
 
 bool dev_cache_has_md_with_end_superblock(struct dev_types *dt)
diff --git a/lib/device/dev-cache.h b/lib/device/dev-cache.h
index 449bfeb75..622335982 100644
--- a/lib/device/dev-cache.h
+++ b/lib/device/dev-cache.h
@@ -53,8 +53,8 @@ int dev_cache_has_scanned(void);
 
 int dev_cache_add_dir(const char *path);
 struct device *dev_cache_get(struct cmd_context *cmd, const char *name, struct dev_filter *f);
-
-struct device *dev_cache_get_by_devt(struct cmd_context *cmd, dev_t device, struct dev_filter *f, int *filtered);
+struct device *dev_cache_get_existing(struct cmd_context *cmd, const char *name, struct dev_filter *f);
+struct device *dev_cache_get_by_devt(struct cmd_context *cmd, dev_t devt);
 
 struct device *dev_hash_get(const char *name);
 
diff --git a/lib/device/dev-io.c b/lib/device/dev-io.c
index b4f1930b1..811ad8978 100644
--- a/lib/device/dev-io.c
+++ b/lib/device/dev-io.c
@@ -58,6 +58,9 @@ static int _dev_get_size_file(struct device *dev, uint64_t *size)
 	const char *name = dev_name(dev);
 	struct stat info;
 
+	if (dm_list_empty(&dev->aliases))
+		return_0;
+
 	if (dev->size_seqno == _dev_size_seqno) {
 		log_very_verbose("%s: using cached size %" PRIu64 " sectors",
 				 name, dev->size);
@@ -87,7 +90,7 @@ static int _dev_get_size_dev(struct device *dev, uint64_t *size)
 	int do_close = 0;
 
 	if (dm_list_empty(&dev->aliases))
-		return 0;
+		return_0;
 
 	if (dev->size_seqno == _dev_size_seqno) {
 		log_very_verbose("%s: using cached size %" PRIu64 " sectors",
@@ -305,6 +308,13 @@ int dev_open_flags(struct device *dev, int flags, int direct, int quiet)
 	if ((flags & O_EXCL))
 		need_excl = 1;
 
+	if (dm_list_empty(&dev->aliases)) {
+		/* shouldn't happen */
+		log_print("Cannot open device %d:%d with no valid paths.", (int)MAJOR(dev->dev), (int)MINOR(dev->dev));
+		return 0;
+	}
+	name = dev_name(dev);
+
 	if (dev->fd >= 0) {
 		if (((dev->flags & DEV_OPENED_RW) || !need_rw) &&
 		    ((dev->flags & DEV_OPENED_EXCL) || !need_excl)) {
@@ -314,7 +324,7 @@ int dev_open_flags(struct device *dev, int flags, int direct, int quiet)
 
 		if (dev->open_count && !need_excl)
 			log_debug_devs("%s: Already opened read-only. Upgrading "
-				       "to read-write.", dev_name(dev));
+				       "to read-write.", name);
 
 		/* dev_close_immediate will decrement this */
 		dev->open_count++;
@@ -327,11 +337,7 @@ int dev_open_flags(struct device *dev, int flags, int direct, int quiet)
 
 	if (critical_section())
 		/* FIXME Make this log_error */
-		log_verbose("dev_open(%s) called while suspended",
-			    dev_name(dev));
-
-	if (!(name = dev_name_confirmed(dev, quiet)))
-		return_0;
+		log_verbose("dev_open(%s) called while suspended", name);
 
 #ifdef O_DIRECT_SUPPORT
 	if (direct) {
@@ -372,9 +378,9 @@ int dev_open_flags(struct device *dev, int flags, int direct, int quiet)
 		}
 #endif
 		if (quiet)
-			log_sys_debug("open", name);
+			log_debug("Failed to open device path %s (%d).", name, errno);
 		else
-			log_sys_error("open", name);
+			log_error("Failed to open device path %s (%d).", name, errno);
 
 		dev->flags |= DEV_OPEN_FAILURE;
 		return 0;
@@ -415,10 +421,12 @@ int dev_open_flags(struct device *dev, int flags, int direct, int quiet)
 	if ((flags & O_CREAT) && !(flags & O_TRUNC))
 		dev->end = lseek(dev->fd, (off_t) 0, SEEK_END);
 
-	log_debug_devs("Opened %s %s%s%s", dev_name(dev),
-		       dev->flags & DEV_OPENED_RW ? "RW" : "RO",
-		       dev->flags & DEV_OPENED_EXCL ? " O_EXCL" : "",
-		       dev->flags & DEV_O_DIRECT ? " O_DIRECT" : "");
+	if (!quiet) {
+		log_debug_devs("Opened %s %s%s%s", name,
+				dev->flags & DEV_OPENED_RW ? "RW" : "RO",
+				dev->flags & DEV_OPENED_EXCL ? " O_EXCL" : "",
+				dev->flags & DEV_O_DIRECT ? " O_DIRECT" : "");
+	}
 
 	dev->flags &= ~DEV_OPEN_FAILURE;
 	return 1;
diff --git a/lib/device/dev-type.c b/lib/device/dev-type.c
index 0e77a009d..c67a86fa3 100644
--- a/lib/device/dev-type.c
+++ b/lib/device/dev-type.c
@@ -966,6 +966,9 @@ static int _wipe_known_signatures_with_blkid(struct device *dev, const char *nam
 
 	/* TODO: Should we check for valid dev - _dev_is_valid(dev)? */
 
+	if (dm_list_empty(&dev->aliases))
+		goto_out;
+
 	if (!(probe = blkid_new_probe_from_filename(dev_name(dev)))) {
 		log_error("Failed to create a new blkid probe for device %s.", dev_name(dev));
 		goto out;
diff --git a/lib/device/device.h b/lib/device/device.h
index 8c3a8c30e..572994bb9 100644
--- a/lib/device/device.h
+++ b/lib/device/device.h
@@ -204,9 +204,6 @@ struct device *dev_create_file(const char *filename, struct device *dev,
 			       struct dm_str_list *alias, int use_malloc);
 void dev_destroy_file(struct device *dev);
 
-/* Return a valid device name from the alias list; NULL otherwise */
-const char *dev_name_confirmed(struct device *dev, int quiet);
-
 int dev_mpath_init(const char *config_wwids_file);
 void dev_mpath_exit(void);
 
diff --git a/lib/device/device_id.c b/lib/device/device_id.c
index 003f10a96..7ce955b11 100644
--- a/lib/device/device_id.c
+++ b/lib/device/device_id.c
@@ -347,6 +347,8 @@ const char *device_id_system_read(struct cmd_context *cmd, struct device *dev, u
 	}
 
 	else if (idtype == DEV_ID_TYPE_DEVNAME) {
+		if (dm_list_empty(&dev->aliases))
+			goto_bad;
 		if (!(idname = strdup(dev_name(dev))))
 			goto_bad;
 		return idname;
@@ -955,6 +957,10 @@ int device_id_add(struct cmd_context *cmd, struct device *dev, const char *pvid_
 	if (!dev_get_partition_number(dev, &part))
 		return_0;
 
+	/* Ensure valid dev_name(dev) below. */
+	if (dm_list_empty(&dev->aliases))
+		return_0;
+
 	/*
 	 * When enable_devices_file=0 and pending_devices_file=1 we let
 	 * pvcreate/vgcreate add new du's to cmd->use_devices.  These du's may
@@ -1577,7 +1583,7 @@ void device_ids_match_device_list(struct cmd_context *cmd)
 	dm_list_iterate_items(du, &cmd->use_devices) {
 		if (du->dev)
 			continue;
-		if (!(du->dev = dev_cache_get(cmd, du->devname, NULL))) {
+		if (!(du->dev = dev_cache_get_existing(cmd, du->devname, NULL))) {
 			log_warn("Device not found for %s.", du->devname);
 		} else {
 			/* Should we set dev->id?  Which idtype?  Use --deviceidtype? */
@@ -1625,7 +1631,7 @@ void device_ids_match(struct cmd_context *cmd)
 		 * the du/dev pairs in preparation for using the filters.
 		 */
 		if (du->devname &&
-		    (dev = dev_cache_get(cmd, du->devname, NULL))) {
+		    (dev = dev_cache_get_existing(cmd, du->devname, NULL))) {
 			/* On successful match, du, dev, and id are linked. */
 			if (_match_du_to_dev(cmd, du, dev))
 				continue;
@@ -1842,6 +1848,9 @@ void device_ids_validate(struct cmd_context *cmd, struct dm_list *scanned_devs,
 		if (dev->flags & DEV_SCAN_NOT_READ)
 			continue;
 
+		if (dm_list_empty(&dev->aliases))
+			continue;
+
 		if (!cmd->filter->passes_filter(cmd, cmd->filter, dev, "persistent")) {
 			log_warn("Devices file %s is excluded by filter: %s.",
 				 dev_name(dev), dev_filtered_reason(dev));
@@ -2225,14 +2234,14 @@ void device_ids_find_renamed_devs(struct cmd_context *cmd, struct dm_list *dev_l
 	dm_list_iterate_items(dil, &search_pvids) {
 		char *dup_devname1, *dup_devname2, *dup_devname3;
 
-		if (!dil->dev) {
+		if (!dil->dev || dm_list_empty(&dil->dev->aliases)) {
 			not_found++;
 			continue;
 		}
-		found++;
 
 		dev = dil->dev;
 		devname = dev_name(dev);
+		found++;
 
 		if (!(du = get_du_for_pvid(cmd, dil->pvid))) {
 			/* shouldn't happen */
diff --git a/lib/label/hints.c b/lib/label/hints.c
index 35ae7f5cc..edce6f517 100644
--- a/lib/label/hints.c
+++ b/lib/label/hints.c
@@ -500,6 +500,8 @@ int validate_hints(struct cmd_context *cmd, struct dm_list *hints)
 	if (!(iter = dev_iter_create(NULL, 0)))
 		return 0;
 	while ((dev = dev_iter_get(cmd, iter))) {
+		if (dm_list_empty(&dev->aliases))
+			continue;
 		if (!(hint = _find_hint_name(hints, dev_name(dev))))
 			continue;
 
diff --git a/lib/label/label.c b/lib/label/label.c
index fe2bc8fec..ffb393891 100644
--- a/lib/label/label.c
+++ b/lib/label/label.c
@@ -1130,11 +1130,12 @@ int label_scan_vg_online(struct cmd_context *cmd, const char *vgname,
 	 * sure to find the device.
 	 */
 	if (try_dev_scan) {
+		log_debug("Repeat dev cache scan to translate devnos.");
 		dev_cache_scan(cmd);
 		dm_list_iterate_items(po, &pvs_online) {
 			if (po->dev)
 				continue;
-			if (!(po->dev = dev_cache_get_by_devt(cmd, po->devno, NULL, NULL))) {
+			if (!(po->dev = dev_cache_get_by_devt(cmd, po->devno))) {
 				log_error("No device found for %d:%d PVID %s",
 					  (int)MAJOR(po->devno), (int)MINOR(po->devno), po->pvid);
 				goto bad;
@@ -1722,7 +1723,7 @@ void label_scan_invalidate_lv(struct cmd_context *cmd, struct logical_volume *lv
 	if (lv_info(cmd, lv, 0, &lvinfo, 0, 0) && lvinfo.exists) {
 		/* FIXME: Still unclear what is it supposed to find */
 		devt = MKDEV(lvinfo.major, lvinfo.minor);
-		if ((dev = dev_cache_get_by_devt(cmd, devt, NULL, NULL)))
+		if ((dev = dev_cache_get_by_devt(cmd, devt)))
 			label_scan_invalidate(dev);
 	}
 }
@@ -1736,13 +1737,19 @@ void label_scan_invalidate_lvs(struct cmd_context *cmd, struct dm_list *lvs)
 	struct lv_list *lvl;
 	dev_t devt;
 
+	/*
+	 * FIXME: this is all unnecessary unless there are PVs stacked on LVs,
+	 * so we can skip all of this if scan_lvs=0.
+	 */
+	log_debug("invalidating devs for any pvs on lvs");
+
 	if (get_device_list(NULL, &devs, &devs_features)) {
 		if (devs_features & DM_DEVICE_LIST_HAS_UUID) {
 			dm_list_iterate_items(dm_dev, devs)
 				if (dm_dev->uuid &&
 				    strncmp(dm_dev->uuid, UUID_PREFIX, sizeof(UUID_PREFIX) - 1) == 0) {
 					devt = MKDEV(dm_dev->major, dm_dev->minor);
-					if ((dev = dev_cache_get_by_devt(cmd, devt, NULL, NULL)))
+					if ((dev = dev_cache_get_by_devt(cmd, devt)))
 						label_scan_invalidate(dev);
 				}
 			/* ATM no further caching for any lvconvert command
@@ -1879,10 +1886,24 @@ int label_scan_open_rw(struct device *dev)
 
 int label_scan_reopen_rw(struct device *dev)
 {
+	const char *name;
 	int flags = 0;
 	int prev_fd = dev->bcache_fd;
 	int fd;
 
+	if (dm_list_empty(&dev->aliases)) {
+		log_error("Cannot reopen rw device %d:%d with no valid paths di %d fd %d.",
+			  (int)MAJOR(dev->dev), (int)MINOR(dev->dev), dev->bcache_di, dev->bcache_fd);
+		return 0;
+	}
+
+	name = dev_name(dev);
+	if (!name || name[0] != '/') {
+		log_error("Cannot reopen rw device %d:%d with no valid name di %d fd %d.",
+			  (int)MAJOR(dev->dev), (int)MINOR(dev->dev), dev->bcache_di, dev->bcache_fd);
+		return 0;
+	}
+
 	if (!(dev->flags & DEV_IN_BCACHE)) {
 		if ((dev->bcache_fd != -1) || (dev->bcache_di != -1)) {
 			/* shouldn't happen */
@@ -1912,7 +1933,7 @@ int label_scan_reopen_rw(struct device *dev)
 	flags |= O_NOATIME;
 	flags |= O_RDWR;
 
-	fd = open(dev_name(dev), flags, 0777);
+	fd = open(name, flags, 0777);
 	if (fd < 0) {
 		log_error("Failed to open rw %s errno %d di %d fd %d.",
 			  dev_name(dev), errno, dev->bcache_di, dev->bcache_fd);
diff --git a/lib/locking/lvmlockd.c b/lib/locking/lvmlockd.c
index b598df3d6..60c80f1b1 100644
--- a/lib/locking/lvmlockd.c
+++ b/lib/locking/lvmlockd.c
@@ -272,6 +272,8 @@ static void _lockd_retrive_vg_pv_list(struct volume_group *vg,
 
 	i = 0;
 	dm_list_iterate_items(pvl, &vg->pvs) {
+		if (!pvl->pv->dev || dm_list_empty(&pvl->pv->dev->aliases))
+			continue;
 		lock_pvs->path[i] = strdup(pv_dev_name(pvl->pv));
 		if (!lock_pvs->path[i]) {
 			log_error("Fail to allocate PV path for VG %s", vg->name);
@@ -341,6 +343,8 @@ static void _lockd_retrive_lv_pv_list(struct volume_group *vg,
 
 	dm_list_iterate_items(pvl, &vg->pvs) {
 		if (lv_is_on_pv(lv, pvl->pv)) {
+			if (!pvl->pv->dev || dm_list_empty(&pvl->pv->dev->aliases))
+				continue;
 			lock_pvs->path[i] = strdup(pv_dev_name(pvl->pv));
 			if (!lock_pvs->path[i]) {
 				log_error("Fail to allocate PV path for LV %s/%s",
diff --git a/lib/metadata/mirror.c b/lib/metadata/mirror.c
index e2bf191a1..46da57948 100644
--- a/lib/metadata/mirror.c
+++ b/lib/metadata/mirror.c
@@ -1231,14 +1231,23 @@ int remove_mirrors_from_segments(struct logical_volume *lv,
 const char *get_pvmove_pvname_from_lv_mirr(const struct logical_volume *lv_mirr)
 {
 	struct lv_segment *seg;
+	struct device *dev;
 
 	dm_list_iterate_items(seg, &lv_mirr->segments) {
 		if (!seg_is_mirrored(seg))
 			continue;
-		if (seg_type(seg, 0) == AREA_PV)
-			return dev_name(seg_dev(seg, 0));
-		if (seg_type(seg, 0) == AREA_LV)
-			return dev_name(seg_dev(first_seg(seg_lv(seg, 0)), 0));
+		if (seg_type(seg, 0) == AREA_PV) {
+			dev = seg_dev(seg, 0);
+			if (!dev || dm_list_empty(&dev->aliases))
+				return NULL;
+			return dev_name(dev);
+		}
+		if (seg_type(seg, 0) == AREA_LV) {
+			dev = seg_dev(first_seg(seg_lv(seg, 0)), 0);
+			if (!dev || dm_list_empty(&dev->aliases))
+				return NULL;
+			return dev_name(dev);
+		}
 	}
 
 	return NULL;
diff --git a/lib/metadata/pv_list.c b/lib/metadata/pv_list.c
index 813e8e525..fc3667db0 100644
--- a/lib/metadata/pv_list.c
+++ b/lib/metadata/pv_list.c
@@ -152,6 +152,11 @@ static int _create_pv_entry(struct dm_pool *mem, struct pv_list *pvl,
 	struct pv_list *new_pvl = NULL, *pvl2;
 	struct dm_list *pe_ranges;
 
+	if (!pvl->pv->dev || dm_list_empty(&pvl->pv->dev->aliases)) {
+		log_error("Failed to create PV entry for missing device.");
+		return 0;
+	}
+
 	pvname = pv_dev_name(pvl->pv);
 	if (allocatable_only && !(pvl->pv->status & ALLOCATABLE_PV)) {
 		log_warn("WARNING: Physical volume %s not allocatable.", pvname);
diff --git a/lib/metadata/vg.c b/lib/metadata/vg.c
index 85482552a..adc954bab 100644
--- a/lib/metadata/vg.c
+++ b/lib/metadata/vg.c
@@ -679,6 +679,11 @@ int vgreduce_single(struct cmd_context *cmd, struct volume_group *vg,
 		return r;
 	}
 
+	if (!pv->dev || dm_list_empty(&pv->dev->aliases)) {
+		log_error("No device found for PV.");
+		return r;
+	}
+
 	log_debug("vgreduce_single VG %s PV %s", vg->name, pv_dev_name(pv));
 
 	if (pv_pe_alloc_count(pv)) {
diff --git a/test/shell/losetup-partscan.sh b/test/shell/losetup-partscan.sh
index 99f552ad1..670568945 100644
--- a/test/shell/losetup-partscan.sh
+++ b/test/shell/losetup-partscan.sh
@@ -33,6 +33,8 @@ aux udev_wait
 ls -la "${LOOP}"*
 test -e "${LOOP}p1"
 
+aux lvmconf 'devices/scan = "/dev"'
+
 aux extend_filter "a|$LOOP|"
 aux extend_devices "$LOOP"
 
diff --git a/tools/toollib.c b/tools/toollib.c
index b08c044fa..897adec34 100644
--- a/tools/toollib.c
+++ b/tools/toollib.c
@@ -1488,7 +1488,7 @@ int process_each_label(struct cmd_context *cmd, int argc, char **argv,
 				goto out;
 			}
 
-			if (!(dev = dev_cache_get(cmd, argv[opt], cmd->filter))) {
+			if (!(dev = dev_cache_get_existing(cmd, argv[opt], cmd->filter))) {
 				log_error("Failed to find device "
 					  "\"%s\".", argv[opt]);
 				ret_max = ECMD_FAILED;
@@ -3925,7 +3925,7 @@ static int _get_arg_devices(struct cmd_context *cmd,
 			return ECMD_FAILED;
 		}
 
-		if (!(dil->dev = dev_cache_get(cmd, sl->str, cmd->filter))) {
+		if (!(dil->dev = dev_cache_get_existing(cmd, sl->str, cmd->filter))) {
 			log_error("Cannot use %s: %s", sl->str, devname_error_reason(sl->str));
 			ret_max = EINIT_FAILED;
 		} else {
@@ -5261,7 +5261,7 @@ int pvcreate_each_device(struct cmd_context *cmd,
 		struct device *dev;
 
 		/* No filter used here */
-		if (!(dev = dev_cache_get(cmd, pd->name, NULL))) {
+		if (!(dev = dev_cache_get_existing(cmd, pd->name, NULL))) {
 			log_error("No device found for %s.", pd->name);
 			dm_list_del(&pd->list);
 			dm_list_add(&pp->arg_fail, &pd->list);