MFV r303083: 7164 zdb should be able to open the root dataset

Note: conversion of the manual page change from roff to mdoc is mine.

illumos/illumos-gate@b702644a6eb66615d67b492fd73ecd9efa11fc7d
https://github.com/illumos/illumos-gate/commit/b702644a6eb66615d67b492fd73ecd9efa11fc7d

https://www.illumos.org/issues/7164
  If the pool/dataset command-line argument is specified with a trailing
  slash, for example, "tank/", we should interpret it as the topmost
  dataset (rather than the whole pool)

Reviewed by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Author: Tim Chase <tim@chase2k.com>
PR:		204661
MFC after:	1 week
Relnotes:	yes

2 files changed, 28 insertions, 1 deletions

diff --git a/cddl/contrib/opensolaris/cmd/zdb/zdb.8 b/cddl/contrib/opensolaris/cmd/zdb/zdb.8
index 4ef437e9daa1..6ae25c398f2d 100644
--- a/cddl/contrib/opensolaris/cmd/zdb/zdb.8
+++ b/cddl/contrib/opensolaris/cmd/zdb/zdb.8
@@ -86,6 +86,17 @@ pool, and is inherently unstable.
 The precise output of most invocations is not documented, a knowledge of ZFS
 internals is assumed.
 .Pp
+If the
+.Ar dataset
+argument does not contain any
+.Sy /
+or
+.Sy @
+characters, it is interpreted as a pool name.
+The root dataset can be specified as
+.Pa pool Ns Sy /
+(pool name followed by a slash).
+.Pp
 When operating on an imported and active pool it is possible, though unlikely,
 that zdb may interpret inconsistent pool data and behave erratically.
 .Sh OPTIONS
diff --git a/cddl/contrib/opensolaris/cmd/zdb/zdb.c b/cddl/contrib/opensolaris/cmd/zdb/zdb.c
index 49311364a73c..893e6a268ffe 100644
--- a/cddl/contrib/opensolaris/cmd/zdb/zdb.c
+++ b/cddl/contrib/opensolaris/cmd/zdb/zdb.c
@@ -3559,6 +3559,7 @@ main(int argc, char **argv)
 	uint64_t max_txg = UINT64_MAX;
 	int rewind = ZPOOL_NEVER_REWIND;
 	char *spa_config_path_env;
+	boolean_t target_is_spa = B_TRUE;
 
 	(void) setrlimit(RLIMIT_NOFILE, &rl);
 	(void) enable_extended_FILE_stdio(-1, -1);
@@ -3738,8 +3739,23 @@ main(int argc, char **argv)
 		}
 	}
 
+	if (strpbrk(target, "/@") != NULL) {
+		size_t targetlen;
+
+		target_is_spa = B_FALSE;
+		/*
+		 * Remove any trailing slash.  Later code would get confused
+		 * by it, but we want to allow it so that "pool/" can
+		 * indicate that we want to dump the topmost filesystem,
+		 * rather than the whole pool.
+		 */
+		targetlen = strlen(target);
+		if (targetlen != 0 && target[targetlen - 1] == '/')
+			target[targetlen - 1] = '\0';
+	}
+
 	if (error == 0) {
-		if (strpbrk(target, "/@") == NULL || dump_opt['R']) {
+		if (target_is_spa || dump_opt['R']) {
 			error = spa_open_rewind(target, &spa, FTAG, policy,
 			    NULL);
 			if (error) {