Fix 'zpool import' blkid device names

When importing a pool using the blkid cache only the device
node path was added to the list of known paths for a device.
This results in 'zpool import' always using the sdX names
in preference to the 'path' name stored in the label.

To fix the issue the blkid import path has been updated to
add both the 'path', 'devid', and 'devname' names from the
label to the known paths.  A sanity check is done to ensure
these paths do refer to the same device identified by blkid.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tony Hutter <hutter2@llnl.gov>
Closes openzfs#4523
Closes openzfs#3043

lib/libzfs/libzfs_import.c

@@ -97,6 +97,8 @@ typedef struct pool_list {
 	name_entry_t		*names;
 } pool_list_t;
 
+#define	DEV_BYID_PATH	"/dev/disk/by-id/"
+
 static char *
 get_devid(const char *path)
 {
@@ -162,7 +164,6 @@ fix_paths(nvlist_t *nv, name_entry_t *names)
 	best = NULL;
 	for (ne = names; ne != NULL; ne = ne->ne_next) {
 		if (ne->ne_guid == guid) {
-
 			if (path == NULL) {
 				best = ne;
 				break;
@@ -352,6 +353,116 @@ add_config(libzfs_handle_t *hdl, pool_list_t *pl, const char *path,
 	return (0);
 }
 
+static int
+add_path(libzfs_handle_t *hdl, pool_list_t *pools, uint64_t pool_guid,
+    uint64_t vdev_guid, const char *path, int order)
+{
+	nvlist_t *label;
+	uint64_t guid;
+	int error, fd, num_labels;
+
+	fd = open64(path, O_RDONLY);
+	if (fd < 0)
+		return (errno);
+
+	error = zpool_read_label(fd, &label, &num_labels);
+	close(fd);
+
+	if (error || label == NULL)
+		return (ENOENT);
+
+	error = nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_GUID, &guid);
+	if (error || guid != pool_guid) {
+		nvlist_free(label);
+		return (EINVAL);
+	}
+
+	error = nvlist_lookup_uint64(label, ZPOOL_CONFIG_GUID, &guid);
+	if (error || guid != vdev_guid) {
+		nvlist_free(label);
+		return (EINVAL);
+	}
+
+	error = add_config(hdl, pools, path, order, num_labels, label);
+
+	return (error);
+}
+
+static int
+add_configs_from_label_impl(libzfs_handle_t *hdl, pool_list_t *pools,
+    nvlist_t *nvroot, uint64_t pool_guid, uint64_t vdev_guid)
+{
+	char udevpath[MAXPATHLEN];
+	char *path;
+	nvlist_t **child;
+	uint_t c, children;
+	uint64_t guid;
+	int error;
+
+	if (nvlist_lookup_nvlist_array(nvroot, ZPOOL_CONFIG_CHILDREN,
+	    &child, &children) == 0) {
+		for (c = 0; c < children; c++) {
+			error  = add_configs_from_label_impl(hdl, pools,
+			    child[c], pool_guid, vdev_guid);
+			if (error)
+				return (error);
+		}
+		return (0);
+	}
+
+	if (nvroot == NULL)
+		return (0);
+
+	error = nvlist_lookup_uint64(nvroot, ZPOOL_CONFIG_GUID, &guid);
+	if ((error != 0) || (guid != vdev_guid))
+		return (0);
+
+	error = nvlist_lookup_string(nvroot, ZPOOL_CONFIG_PATH, &path);
+	if (error == 0)
+		(void) add_path(hdl, pools, pool_guid, vdev_guid, path, 0);
+
+	error = nvlist_lookup_string(nvroot, ZPOOL_CONFIG_DEVID, &path);
+	if (error == 0) {
+		sprintf(udevpath, "%s%s", DEV_BYID_PATH, path);
+		(void) add_path(hdl, pools, pool_guid, vdev_guid, udevpath, 1);
+	}
+
+	return (0);
+}
+
+/*
+ * Given a disk label call add_config() for all known paths to the device
+ * as described by the label itself.  The paths are added in the following
+ * priority order: 'path', 'devid', 'devnode'.  As these alternate paths are
+ * added the labels are verified to make sure they refer to the same device.
+ */
+static int
+add_configs_from_label(libzfs_handle_t *hdl, pool_list_t *pools,
+    char *devname, int num_labels, nvlist_t *label)
+{
+	nvlist_t *nvroot;
+	uint64_t pool_guid;
+	uint64_t vdev_guid;
+	int error;
+
+	if (nvlist_lookup_nvlist(label, ZPOOL_CONFIG_VDEV_TREE, &nvroot) ||
+	    nvlist_lookup_uint64(label, ZPOOL_CONFIG_POOL_GUID, &pool_guid) ||
+	    nvlist_lookup_uint64(label, ZPOOL_CONFIG_GUID, &vdev_guid))
+		return (ENOENT);
+
+	/* Allow devlinks to stabilize so all paths are available. */
+	zpool_label_disk_wait(devname, DISK_LABEL_WAIT);
+
+	/* Add alternate paths as described by the label vdev_tree. */
+	(void) add_configs_from_label_impl(hdl, pools, nvroot,
+	    pool_guid, vdev_guid);
+
+	/* Add the device node /dev/sdX path as a last resort. */
+	error = add_config(hdl, pools, devname, 100, num_labels, label);
+
+	return (error);
+}
+
 /*
  * Returns true if the named pool matches the given GUID.
  */
@@ -975,9 +1086,7 @@ zpool_find_import_blkid(libzfs_handle_t *hdl, pool_list_t *pools)
 	blkid_cache cache;
 	blkid_dev_iterate iter;
 	blkid_dev dev;
-	const char *devname;
-	nvlist_t *config;
-	int fd, err, num_labels;
+	int err;
 
 	err = blkid_get_cache(&cache, NULL);
 	if (err != 0) {
@@ -1008,25 +1117,23 @@ zpool_find_import_blkid(libzfs_handle_t *hdl, pool_list_t *pools)
 	}
 
 	while (blkid_dev_next(iter, &dev) == 0) {
-		devname = blkid_dev_devname(dev);
+		nvlist_t *label;
+		char *devname;
+		int fd, num_labels;
+
+		devname = (char *) blkid_dev_devname(dev);
 		if ((fd = open64(devname, O_RDONLY)) < 0)
 			continue;
 
-		err = zpool_read_label(fd, &config, &num_labels);
+		err = zpool_read_label(fd, &label, &num_labels);
 		(void) close(fd);
 
-		if (err != 0) {
-			(void) no_memory(hdl);
-			goto err_blkid3;
-		}
+		if (err || label == NULL)
+			continue;
 
-		if (config != NULL) {
-			err = add_config(hdl, pools, devname, 0,
-			    num_labels, config);
-			if (err != 0)
-				goto err_blkid3;
-		}
+		add_configs_from_label(hdl, pools, devname, num_labels, label);
 	}
+	err = 0;
 
 err_blkid3:
 	blkid_dev_iterate_end(iter);