Add ability to scrub from last scrubbed txg

Some users might want to scrub only new data because they would like
to know if the new write wasn't corrupted.  This PR adds possibility
scrub only newly written data.

This introduces new `last_scrubbed_txg` property, indicating the
transaction group (TXG) up to which the most recent scrub operation
has checked and repaired the dataset, so users can run scrub only
from the last saved point. We use a scn_max_txg and scn_min_txg
which are already built into scrub, to accomplish that.

Reviewed-by: Allan Jude <[email protected]>
Reviewed-by: Alexander Motin <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Mariusz Zaborski <[email protected]>
Sponsored-By: Wasabi Technology, Inc.
Sponsored-By: Klara Inc.
Closes openzfs#16301

Author: oshogbo

cmd/zpool/zpool_main.c

@@ -8458,6 +8458,18 @@ zpool_do_scrub(int argc, char **argv)
 		(void) fprintf(stderr, gettext("invalid option "
 		    "combination: -e and -C are mutually exclusive\n"));
 		usage(B_FALSE);
+	} else if (is_pause && is_txg_continue) {
+		(void) fprintf(stderr, gettext("invalid option "
+		    "combination :-p and -C are mutually exclusive\n"));
+		usage(B_FALSE);
+	} else if (is_stop && is_txg_continue) {
+		(void) fprintf(stderr, gettext("invalid option "
+		    "combination :-s and -C are mutually exclusive\n"));
+		usage(B_FALSE);
+	} else if (is_error_scrub && is_txg_continue) {
+		(void) fprintf(stderr, gettext("invalid option "
+		    "combination :-e and -C are mutually exclusive\n"));
+		usage(B_FALSE);
 	} else {
 		if (is_error_scrub)
 			cb.cb_type = POOL_SCAN_ERRORSCRUB;