7277 zdb should be able to print zfs_dbgmsg's

Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Igor Kozhukhov <ikozhukhov@gmail.com>
Approved by: Dan McDonald <danmcd@omniti.com>

usr/src/cmd/zdb/zdb.c

@@ -21,7 +21,7 @@
 
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2011, 2015 by Delphix. All rights reserved.
+ * Copyright (c) 2011, 2016 by Delphix. All rights reserved.
  * Copyright (c) 2014 Integros [integros.com]
  */
 
@@ -117,7 +117,7 @@ static void
 usage(void)
 {
 	(void) fprintf(stderr,
-	    "Usage: %s [-CumMdibcsDvhLXFPA] [-t txg] [-e [-p path...]] "
+	    "Usage: %s [-CumMdibcsDvhLXFPAG] [-t txg] [-e [-p path...]] "
 	    "[-U config] [-I inflight I/Os] [-x dumpdir] poolname [object...]\n"
 	    "       %s [-divPA] [-e -p path...] [-U config] dataset "
 	    "[object...]\n"
@@ -178,12 +178,23 @@ usage(void)
 	(void) fprintf(stderr, "        -I <number of inflight I/Os> -- "
 	    "specify the maximum number of "
 	    "checksumming I/Os [default is 200]\n");
+	(void) fprintf(stderr, "        -G dump zfs_dbgmsg buffer before "
+	    "exiting\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");
 	exit(1);
 }
 
+static void
+dump_debug_buffer()
+{
+	if (dump_opt['G']) {
+		(void) printf("\n");
+		zfs_dbgmsg_print("zdb");
+	}
+}
+
 /*
  * Called for usage errors that are discovered after a call to spa_open(),
  * dmu_bonus_hold(), or pool_match().  abort() is called for other errors.
@@ -200,6 +211,8 @@ fatal(const char *fmt, ...)
 	va_end(ap);
 	(void) fprintf(stderr, "\n");
 
+	dump_debug_buffer();
+
 	exit(1);
 }
 
@@ -3079,8 +3092,10 @@ dump_zpool(spa_t *spa)
 	if (dump_opt['h'])
 		dump_history(spa);
 
-	if (rc != 0)
+	if (rc != 0) {
+		dump_debug_buffer();
 		exit(rc);
+	}
 }
 
 #define	ZDB_FLAG_CHECKSUM	0x0001
@@ -3550,7 +3565,7 @@ main(int argc, char **argv)
 		spa_config_path = spa_config_path_env;
 
 	while ((c = getopt(argc, argv,
-	    "bcdhilmMI:suCDRSAFLXx:evp:t:U:P")) != -1) {
+	    "bcdhilmMI:suCDRSAFLXx:evp:t:U:PG")) != -1) {
 		switch (c) {
 		case 'b':
 		case 'c':
@@ -3566,6 +3581,7 @@ main(int argc, char **argv)
 		case 'M':
 		case 'R':
 		case 'S':
+		case 'G':
 			dump_opt[c]++;
 			dump_all = 0;
 			break;
@@ -3800,6 +3816,8 @@ main(int argc, char **argv)
 	fuid_table_destroy();
 	sa_loaded = B_FALSE;
 
+	dump_debug_buffer();
+
 	libzfs_fini(g_zfs);
 	kernel_fini();
 

usr/src/man/man1m/zdb.1m

@@ -11,15 +11,15 @@
 .\"
 .\"
 .\" Copyright 2012, Richard Lowe.
-.\" Copyright (c) 2012, 2014 by Delphix. All rights reserved.
+.\" Copyright (c) 2012, 2016 by Delphix. All rights reserved.
 .\"
-.TH "ZDB" "1M" "March 6, 2014" "" ""
+.TH "ZDB" "1M" "Feb 4, 2016" "" ""
 
 .SH "NAME"
 \fBzdb\fR - Display zpool debugging and consistency information
 
 .SH "SYNOPSIS"
-\fBzdb\fR [-CumdibcsDvhLMXFPA] [-e [-p \fIpath\fR...]] [-t \fItxg\fR]
+\fBzdb\fR [-CumdibcsDvhLMXFPAG] [-e [-p \fIpath\fR...]] [-t \fItxg\fR]
     [-U \fIcache\fR] [-I \fIinflight I/Os\fR] [-x \fIdumpdir\fR]
     [\fIpoolname\fR [\fIobject\fR ...]]
 
@@ -397,6 +397,17 @@ Attempt to make an unreadable pool readable by trying progressively older
 transactions.
 .RE
 
+.sp
+.ne 2
+.na
+\fB-G\fR
+.ad
+.sp .6
+.RS 4n
+Dump the contents of the zfs_dbgmsg buffer before exiting zdb. zfs_dbgmsg is
+a buffer used by ZFS to dump advanced debug information.
+.RE
+
 .sp
 .ne 2
 .na