zhack: Add repair label option

In case if all label checksums will be invalid on any vdev, the pool
will become unimportable. The zhack with newly added cli options could
be used to restore label checksums and make pool importable again.

Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Fedor Uporov <[email protected]>
Closes #2510
Closes #12686 

1 files changed, 170 insertions, 1 deletions

diff --git a/cmd/zhack/zhack.c b/cmd/zhack/zhack.c
index b27423f53..bae242712 100644
--- a/cmd/zhack/zhack.c
+++ b/cmd/zhack/zhack.c
@@ -33,6 +33,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <ctype.h>
+#include <sys/stat.h>
 #include <sys/zfs_context.h>
 #include <sys/spa.h>
 #include <sys/spa_impl.h>
@@ -41,6 +42,7 @@
 #include <sys/zfs_znode.h>
 #include <sys/dsl_synctask.h>
 #include <sys/vdev.h>
+#include <sys/vdev_impl.h>
 #include <sys/fs/zfs.h>
 #include <sys/dmu_objset.h>
 #include <sys/dsl_pool.h>
@@ -76,7 +78,12 @@ usage(void)
 	    "        -d decrease instead of increase the refcount\n"
 	    "        -m add the feature to the label if increasing refcount\n"
 	    "\n"
-	    "    <feature> : should be a feature guid\n");
+	    "    <feature> : should be a feature guid\n"
+	    "\n"
+	    "    label repair <device>\n"
+	    "        repair corrupted label checksums\n"
+	    "\n"
+	    "    <device> : path to vdev\n");
 	exit(1);
 }
 
@@ -471,6 +478,166 @@ zhack_do_feature(int argc, char **argv)
 	return (0);
 }
 
+static int
+zhack_repair_label_cksum(int argc, char **argv)
+{
+	zio_checksum_info_t *ci = &zio_checksum_table[ZIO_CHECKSUM_LABEL];
+	const char *cfg_keys[] = { ZPOOL_CONFIG_VERSION,
+	    ZPOOL_CONFIG_POOL_STATE, ZPOOL_CONFIG_GUID };
+	boolean_t labels_repaired[VDEV_LABELS];
+	boolean_t repaired = B_FALSE;
+	vdev_label_t labels[VDEV_LABELS];
+	struct stat st;
+	int fd;
+
+	bzero(labels_repaired, sizeof (labels_repaired));
+	bzero(labels, sizeof (labels));
+
+	abd_init();
+
+	argc -= 1;
+	argv += 1;
+
+	if (argc < 1) {
+		(void) fprintf(stderr, "error: missing device\n");
+		usage();
+	}
+
+	if ((fd = open(argv[0], O_RDWR)) == -1)
+		fatal(NULL, FTAG, "cannot open '%s': %s", argv[0],
+		    strerror(errno));
+
+	if (stat(argv[0], &st) != 0)
+		fatal(NULL, FTAG, "cannot stat '%s': %s", argv[0],
+		    strerror(errno));
+
+	for (int l = 0; l < VDEV_LABELS; l++) {
+		uint64_t label_offset, offset;
+		zio_cksum_t expected_cksum;
+		zio_cksum_t actual_cksum;
+		zio_cksum_t verifier;
+		zio_eck_t *eck;
+		nvlist_t *cfg;
+		int byteswap;
+		uint64_t val;
+		ssize_t err;
+
+		vdev_label_t *vl = &labels[l];
+
+		label_offset = vdev_label_offset(st.st_size, l, 0);
+		err = pread64(fd, vl, sizeof (vdev_label_t), label_offset);
+		if (err == -1) {
+			(void) fprintf(stderr, "error: cannot read "
+			    "label %d: %s\n", l, strerror(errno));
+			continue;
+		} else if (err != sizeof (vdev_label_t)) {
+			(void) fprintf(stderr, "error: bad label %d read size "
+			    "\n", l);
+			continue;
+		}
+
+		err = nvlist_unpack(vl->vl_vdev_phys.vp_nvlist,
+		    VDEV_PHYS_SIZE - sizeof (zio_eck_t), &cfg, 0);
+		if (err) {
+			(void) fprintf(stderr, "error: cannot unpack nvlist "
+			    "label %d\n", l);
+			continue;
+		}
+
+		for (int i = 0; i < ARRAY_SIZE(cfg_keys); i++) {
+			err = nvlist_lookup_uint64(cfg, cfg_keys[i], &val);
+			if (err) {
+				(void) fprintf(stderr, "error: label %d: "
+				    "cannot find nvlist key %s\n",
+				    l, cfg_keys[i]);
+				continue;
+			}
+		}
+
+		void *data = (char *)vl + offsetof(vdev_label_t, vl_vdev_phys);
+		eck = (zio_eck_t *)((char *)(data) + VDEV_PHYS_SIZE) - 1;
+
+		offset = label_offset + offsetof(vdev_label_t, vl_vdev_phys);
+		ZIO_SET_CHECKSUM(&verifier, offset, 0, 0, 0);
+
+		byteswap = (eck->zec_magic == BSWAP_64(ZEC_MAGIC));
+		if (byteswap)
+			byteswap_uint64_array(&verifier, sizeof (zio_cksum_t));
+
+		expected_cksum = eck->zec_cksum;
+		eck->zec_cksum = verifier;
+
+		abd_t *abd = abd_get_from_buf(data, VDEV_PHYS_SIZE);
+		ci->ci_func[byteswap](abd, VDEV_PHYS_SIZE, NULL, &actual_cksum);
+		abd_free(abd);
+
+		if (byteswap)
+			byteswap_uint64_array(&expected_cksum,
+			    sizeof (zio_cksum_t));
+
+		if (ZIO_CHECKSUM_EQUAL(actual_cksum, expected_cksum))
+			continue;
+
+		eck->zec_cksum = actual_cksum;
+
+		err = pwrite64(fd, data, VDEV_PHYS_SIZE, offset);
+		if (err == -1) {
+			(void) fprintf(stderr, "error: cannot write "
+			    "label %d: %s\n", l, strerror(errno));
+			continue;
+		} else if (err != VDEV_PHYS_SIZE) {
+			(void) fprintf(stderr, "error: bad write size "
+			    "label %d\n", l);
+			continue;
+		}
+
+		fsync(fd);
+
+		labels_repaired[l] = B_TRUE;
+	}
+
+	close(fd);
+
+	abd_fini();
+
+	for (int l = 0; l < VDEV_LABELS; l++) {
+		(void) printf("label %d: %s\n", l,
+		    labels_repaired[l] ? "repaired" : "skipped");
+		repaired |= labels_repaired[l];
+	}
+
+	if (repaired)
+		return (0);
+
+	return (1);
+}
+
+static int
+zhack_do_label(int argc, char **argv)
+{
+	char *subcommand;
+	int err;
+
+	argc--;
+	argv++;
+	if (argc == 0) {
+		(void) fprintf(stderr,
+		    "error: no label operation specified\n");
+		usage();
+	}
+
+	subcommand = argv[0];
+	if (strcmp(subcommand, "repair") == 0) {
+		err = zhack_repair_label_cksum(argc, argv);
+	} else {
+		(void) fprintf(stderr, "error: unknown subcommand: %s\n",
+		    subcommand);
+		usage();
+	}
+
+	return (err);
+}
+
 #define	MAX_NUM_PATHS 1024
 
 int
@@ -516,6 +683,8 @@ main(int argc, char **argv)
 
 	if (strcmp(subcommand, "feature") == 0) {
 		rv = zhack_do_feature(argc, argv);
+	} else if (strcmp(subcommand, "label") == 0) {
+		return (zhack_do_label(argc, argv));
 	} else {
 		(void) fprintf(stderr, "error: unknown subcommand: %s\n",
 		    subcommand);