Fix zdb pool/ with -k

When examining the root dataset with zdb -k, we get into a mismatched
state. main() knows we are not examining the whole pool, but it strips
off the trailing slash. import_checkpointed_state() then thinks we are
examining the whole pool, and does not update the target path
appropriately. The fix is to directly inform import_checkpointed_state
that we are examining a filesystem, and not the whole pool.

Sponsored-by: Klara, Inc.
Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Alexander Motin <[email protected]>
Reviewed-by: Rob Norris <[email protected]>
Signed-off-by: Paul Dagnelie <[email protected]>
Co-authored-by: Paul Dagnelie <[email protected]>
Closes #17536

Author: Paul Dagnelie

cmd/zdb/zdb.c

@@ -7706,19 +7706,20 @@ zdb_set_skip_mmp(char *target)
  * applies to the new_path parameter if allocated.
  */
 static char *
-import_checkpointed_state(char *target, nvlist_t *cfg, char **new_path)
+import_checkpointed_state(char *target, nvlist_t *cfg, boolean_t target_is_spa,
+    char **new_path)
 {
 	int error = 0;
 	char *poolname, *bogus_name = NULL;
 	boolean_t freecfg = B_FALSE;
 
 	/* If the target is not a pool, the extract the pool name */
 	char *path_start = strchr(target, '/');
-	if (path_start != NULL) {
+	if (target_is_spa || path_start == NULL) {
+		poolname = target;
+	} else {
 		size_t poolname_len = path_start - target;
 		poolname = strndup(target, poolname_len);
-	} else {
-		poolname = target;
 	}
 
 	if (cfg == NULL) {
@@ -7749,10 +7750,11 @@ import_checkpointed_state(char *target, nvlist_t *cfg, char **new_path)
 		    "with error %d\n", bogus_name, error);
 	}
 
-	if (new_path != NULL && path_start != NULL) {
-		if (asprintf(new_path, "%s%s", bogus_name, path_start) == -1) {
+	if (new_path != NULL && !target_is_spa) {
+		if (asprintf(new_path, "%s%s", bogus_name,
+		    path_start != NULL ? path_start : "") == -1) {
 			free(bogus_name);
-			if (path_start != NULL)
+			if (!target_is_spa && path_start != NULL)
 				free(poolname);
 			return (NULL);
 		}
@@ -7981,7 +7983,7 @@ verify_checkpoint_blocks(spa_t *spa)
 	 * name) so we can do verification on it against the current state
 	 * of the pool.
 	 */
-	checkpoint_pool = import_checkpointed_state(spa->spa_name, NULL,
+	checkpoint_pool = import_checkpointed_state(spa->spa_name, NULL, B_TRUE,
 	    NULL);
 	ASSERT(strcmp(spa->spa_name, checkpoint_pool) != 0);
 
@@ -9705,7 +9707,7 @@ main(int argc, char **argv)
 	char *checkpoint_target = NULL;
 	if (dump_opt['k']) {
 		checkpoint_pool = import_checkpointed_state(target, cfg,
-		    &checkpoint_target);
+		    target_is_spa, &checkpoint_target);
 
 		if (checkpoint_target != NULL)
 			target = checkpoint_target;

tests/zfs-tests/tests/functional/pool_checkpoint/checkpoint_zdb.ksh

@@ -63,13 +63,15 @@ log_must eval "zdb $TESTPOOL | grep -q \"Checkpointed uberblock found\""
 log_mustnot eval "zdb -k $TESTPOOL | grep -q \"Checkpointed uberblock found\""
 log_mustnot eval "zdb $TESTPOOL | grep \"Dataset $FS1\""
 log_must eval "zdb -k $TESTPOOL | grep \"Dataset $CHECKPOINTED_FS1\""
+log_must eval "zdb -k $TESTPOOL/ | grep \"$TESTPOOL$BOGUS_SUFFIX\""
 
 log_must zpool export $TESTPOOL
 
 log_must eval "zdb -e $TESTPOOL | grep \"Checkpointed uberblock found\""
 log_mustnot eval "zdb -k -e $TESTPOOL | grep \"Checkpointed uberblock found\""
 log_mustnot eval "zdb -e $TESTPOOL | grep \"Dataset $FS1\""
 log_must eval "zdb -k -e $TESTPOOL | grep \"Dataset $CHECKPOINTED_FS1\""
+log_must eval "zdb -k -e $TESTPOOL/ | grep \"$TESTPOOL$BOGUS_SUFFIX\""
 
 log_must zpool import $TESTPOOL