Illumos 4891 - want zdb option to dump all metadata

4891 want zdb option to dump all metadata
Reviewed by: Sonu Pillai <sonu.pillai@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: Dan McDonald <danmcd@omniti.com>
Reviewed by: Richard Lowe <richlowe@richlowe.net>
Approved by: Garrett D'Amore <garrett@damore.org>

We'd like a way for zdb to dump metadata in a machine-readable
format, so that we can bring that back from a customer site for
in-house diagnosis.  Think of it as a crash dump for zpools,
which can be used for post-mortem analysis of a malfunctioning
pool

References:
  https://www.illumos.org/issues/4891
  https://github.com/illumos/illumos-gate/commit/df15e41

Porting notes:
- [cmd/zdb/zdb.c]
  - a5778ea zdb: Introduce -V for verbatim import
  - In main() getopt 'opt' variable removed and the code was
    brought back in line with illumos.
- [lib/libzpool/kernel.c]
  - 1e33ac1 Fix Solaris thread dependency by using pthreads
  - f0e324f Update utsname support
  - 4d58b69 Fix vn_open/vn_rdwr error handling
  - In vn_open() allocate 'dumppath' on heap instead of stack
  - Properly handle 'dump_fd == -1' error path
  - Free 'realpath' after added vn_dumpdir_code block

Ported-by: kernelOfTruth kerneloftruth@gmail.com
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

cmd/zdb/zdb.c

@@ -118,7 +118,7 @@ usage(void)
 {
 	(void) fprintf(stderr,
 	    "Usage: %s [-CumMdibcsDvhLXFPA] [-t txg] [-e [-p path...]] "
-	    "[-U config] [-I inflight I/Os] poolname [object...]\n"
+	    "[-U config] [-I inflight I/Os] [-x dumpdir] poolname [object...]\n"
 	    "       %s [-divPA] [-e -p path...] [-U config] dataset "
 	    "[object...]\n"
 	    "       %s -mM [-LXFPA] [-t txg] [-e [-p path...]] [-U config] "
@@ -157,7 +157,7 @@ usage(void)
 	(void) fprintf(stderr, "        -R read and display block from a "
 	    "device\n\n");
 	(void) fprintf(stderr, "    Below options are intended for use "
-	    "with other options (except -l):\n");
+	    "with other options:\n");
 	(void) fprintf(stderr, "        -A ignore assertions (-A), enable "
 	    "panic recovery (-AA) or both (-AAA)\n");
 	(void) fprintf(stderr, "        -F attempt automatic rewind within "
@@ -170,12 +170,14 @@ usage(void)
 	    "has altroot/not in a cachefile\n");
 	(void) fprintf(stderr, "        -p <path> -- use one or more with "
 	    "-e to specify path to vdev dir\n");
+	(void) fprintf(stderr, "        -x <dumpdir> -- "
+	    "dump all read blocks into specified directory\n");
 	(void) fprintf(stderr, "        -P print numbers in parseable form\n");
 	(void) fprintf(stderr, "        -t <txg> -- highest txg to use when "
 	    "searching for uberblocks\n");
 	(void) fprintf(stderr, "        -I <number of inflight I/Os> -- "
-	    "specify the maximum number of checksumming I/Os "
-	    "[default is 200]\n");
+	    "specify the maximum number of "
+	    "checksumming I/Os [default is 200]\n");
 	(void) fprintf(stderr, "Specify an option more than once (e.g. -bb) "
 	    "to make only that option verbose\n");
 	(void) fprintf(stderr, "Default is to dump everything non-verbosely\n");
@@ -3626,7 +3628,6 @@ main(int argc, char **argv)
 	int flags = ZFS_IMPORT_MISSING_LOG;
 	int rewind = ZPOOL_NEVER_REWIND;
 	char *spa_config_path_env;
-	const char *opts = "bcdhilmMI:suCDRSAFLXevp:t:U:PV";
 	boolean_t target_is_spa = B_TRUE;
 
 	(void) setrlimit(RLIMIT_NOFILE, &rl);
@@ -3643,7 +3644,8 @@ main(int argc, char **argv)
 	if (spa_config_path_env != NULL)
 		spa_config_path = spa_config_path_env;
 
-	while ((c = getopt(argc, argv, opts)) != -1) {
+	while ((c = getopt(argc, argv,
+	    "bcdhilmMI:suCDRSAFLXx:evp:t:U:PV")) != -1) {
 		switch (c) {
 		case 'b':
 		case 'c':
@@ -3697,6 +3699,9 @@ main(int argc, char **argv)
 			}
 			searchdirs[nsearch++] = optarg;
 			break;
+		case 'x':
+			vn_dumpdir = optarg;
+			break;
 		case 't':
 			max_txg = strtoull(optarg, NULL, 0);
 			if (max_txg < TXG_INITIAL) {