13013 Port OpenZFS zpool label clear improvements

13012 zpool_read_label semantics should match OpenZFS
Portions contributed by: Jason King <jason.king@joyent.com>
Reviewed by: Matt Ahrens <mahrens@delphix.com>
Reviewed by: Tim Chase <tim@chase2k.com>
Reviewed by: Tony Hutter <hutter2@llnl.gov>
Reviewed by: Andy Fiddaman <andy@omniosce.org>
Reviewed by: Toomas Soome <tsoome@me.com>
Approved by: Dan McDonald <danmcd@joyent.com>

2 files changed, 51 insertions, 9 deletions

diff --git a/usr/src/lib/libzfs/common/libzfs_import.c b/usr/src/lib/libzfs/common/libzfs_import.c
index 706f08e6ec..dc15aca0c0 100644
--- a/usr/src/lib/libzfs/common/libzfs_import.c
+++ b/usr/src/lib/libzfs/common/libzfs_import.c
@@ -169,23 +169,66 @@ zpool_clear_label(int fd)
 	int l;
 	vdev_label_t *label;
 	uint64_t size;
+	int labels_cleared = 0;
 
 	if (fstat64(fd, &statbuf) == -1)
 		return (0);
+
 	size = P2ALIGN_TYPED(statbuf.st_size, sizeof (vdev_label_t), uint64_t);
 
 	if ((label = calloc(sizeof (vdev_label_t), 1)) == NULL)
 		return (-1);
 
 	for (l = 0; l < VDEV_LABELS; l++) {
-		if (pwrite64(fd, label, sizeof (vdev_label_t),
+		uint64_t state, guid;
+		nvlist_t *config;
+
+		if (pread64(fd, label, sizeof (vdev_label_t),
 		    label_offset(size, l)) != sizeof (vdev_label_t)) {
-			free(label);
-			return (-1);
+			continue;
+		}
+
+		if (nvlist_unpack(label->vl_vdev_phys.vp_nvlist,
+		    sizeof (label->vl_vdev_phys.vp_nvlist), &config, 0) != 0) {
+			continue;
+		}
+
+		/* Skip labels which do not have a valid guid. */
+		if (nvlist_lookup_uint64(config, ZPOOL_CONFIG_GUID,
+		    &guid) != 0 || guid == 0) {
+			nvlist_free(config);
+			continue;
+		}
+
+		/* Skip labels which are not in a known valid state. */
+		if (nvlist_lookup_uint64(config, ZPOOL_CONFIG_POOL_STATE,
+		    &state) != 0 || state > POOL_STATE_L2CACHE) {
+			nvlist_free(config);
+			continue;
+		}
+
+		nvlist_free(config);
+
+		/*
+		 * A valid label was found, overwrite this label's nvlist
+		 * and uberblocks with zeros on disk.  This is done to prevent
+		 * system utilities, like blkid, from incorrectly detecting a
+		 * partial label.  The leading pad space is left untouched.
+		 */
+		memset(label, 0, sizeof (vdev_label_t));
+		size_t label_size = sizeof (vdev_label_t) - (2 * VDEV_PAD_SIZE);
+
+		if (pwrite64(fd, label, label_size, label_offset(size, l) +
+		    (2 * VDEV_PAD_SIZE)) == label_size) {
+			labels_cleared++;
 		}
 	}
 
 	free(label);
+
+	if (labels_cleared == 0)
+		return (-1);
+
 	return (0);
 }
 
diff --git a/usr/src/lib/libzutil/common/zutil_import.c b/usr/src/lib/libzutil/common/zutil_import.c
index 961247c5c0..b4e6ccc0ca 100644
--- a/usr/src/lib/libzutil/common/zutil_import.c
+++ b/usr/src/lib/libzutil/common/zutil_import.c
@@ -25,6 +25,7 @@
  * Copyright (c) 2012, 2018 by Delphix. All rights reserved.
  * Copyright 2015 RackTop Systems.
  * Copyright (c) 2016, Intel Corporation.
+ * Copyright 2020 Joyent, Inc.
  */
 
 /*
@@ -913,8 +914,11 @@ zpool_read_label(int fd, nvlist_t **config, int *num_labels)
 
 	*config = NULL;
 
+	if (num_labels != NULL)
+		*num_labels = 0;
+
 	if (fstat64(fd, &statbuf) == -1)
-		return (-1);
+		return (0);
 	size = P2ALIGN_TYPED(statbuf.st_size, sizeof (vdev_label_t), uint64_t);
 
 	if ((label = malloc(sizeof (vdev_label_t))) == NULL)
@@ -968,11 +972,6 @@ zpool_read_label(int fd, nvlist_t **config, int *num_labels)
 	free(label);
 	*config = expected_config;
 
-	if (count == 0) {
-		errno = ENOENT;
-		return (-1);
-	}
-
 	return (0);
 }