Implemented zpool scrub pause/resume

Currently, there is no way to pause a scrub. Pausing may
be useful when the pool is busy with other I/O to preserve
bandwidth.

This patch adds the ability to pause and resume scrubbing.
This is achieved by maintaining a persistent on-disk scrub state.
While the state is 'paused' we do not scrub any more blocks.
We do however perform regular scan housekeeping such as
freeing async destroyed and deadlist blocks while paused.

Reviewed by: Matthew Ahrens <[email protected]>
Reviewed by: Thomas Caputi <[email protected]>
Reviewed-by: Serapheim Dimitropoulos <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Alek Pinchuk <[email protected]>
Closes #6167

1 files changed, 45 insertions, 15 deletions

diff --git a/cmd/zpool/zpool_main.c b/cmd/zpool/zpool_main.c
index 2a68fe66f..14181b083 100644
--- a/cmd/zpool/zpool_main.c
+++ b/cmd/zpool/zpool_main.c
@@ -342,7 +342,7 @@ get_usage(zpool_help_t idx)
 	case HELP_REOPEN:
 		return (gettext("\treopen <pool>\n"));
 	case HELP_SCRUB:
-		return (gettext("\tscrub [-s] <pool> ...\n"));
+		return (gettext("\tscrub [-s | -p] <pool> ...\n"));
 	case HELP_STATUS:
 		return (gettext("\tstatus [-c [script1,script2,...]] [-gLPvxD]"
 		    "[-T d|u] [pool] ... [interval [count]]\n"));
@@ -5759,6 +5759,7 @@ typedef struct scrub_cbdata {
 	int	cb_type;
 	int	cb_argc;
 	char	**cb_argv;
+	pool_scrub_cmd_t cb_scrub_cmd;
 } scrub_cbdata_t;
 
 int
@@ -5776,15 +5777,16 @@ scrub_callback(zpool_handle_t *zhp, void *data)
 		return (1);
 	}
 
-	err = zpool_scan(zhp, cb->cb_type);
+	err = zpool_scan(zhp, cb->cb_type, cb->cb_scrub_cmd);
 
 	return (err != 0);
 }
 
 /*
- * zpool scrub [-s] <pool> ...
+ * zpool scrub [-s | -p] <pool> ...
  *
  *	-s	Stop.  Stops any in-progress scrub.
+ *	-p	Pause. Pause in-progress scrub.
  */
 int
 zpool_do_scrub(int argc, char **argv)
@@ -5793,13 +5795,17 @@ zpool_do_scrub(int argc, char **argv)
 	scrub_cbdata_t cb;
 
 	cb.cb_type = POOL_SCAN_SCRUB;
+	cb.cb_scrub_cmd = POOL_SCRUB_NORMAL;
 
 	/* check options */
-	while ((c = getopt(argc, argv, "s")) != -1) {
+	while ((c = getopt(argc, argv, "sp")) != -1) {
 		switch (c) {
 		case 's':
 			cb.cb_type = POOL_SCAN_NONE;
 			break;
+		case 'p':
+			cb.cb_scrub_cmd = POOL_SCRUB_PAUSE;
+			break;
 		case '?':
 			(void) fprintf(stderr, gettext("invalid option '%c'\n"),
 			    optopt);
@@ -5807,6 +5813,13 @@ zpool_do_scrub(int argc, char **argv)
 		}
 	}
 
+	if (cb.cb_type == POOL_SCAN_NONE &&
+	    cb.cb_scrub_cmd == POOL_SCRUB_PAUSE) {
+		(void) fprintf(stderr, gettext("invalid option combination: "
+		    "-s and -p are mutually exclusive\n"));
+		usage(B_FALSE);
+	}
+
 	cb.cb_argc = argc;
 	cb.cb_argv = argv;
 	argc -= optind;
@@ -5826,7 +5839,7 @@ zpool_do_scrub(int argc, char **argv)
 void
 print_scan_status(pool_scan_stat_t *ps)
 {
-	time_t start, end;
+	time_t start, end, pause;
 	uint64_t elapsed, mins_left, hours_left;
 	uint64_t pass_exam, examined, total;
 	uint_t rate;
@@ -5844,6 +5857,7 @@ print_scan_status(pool_scan_stat_t *ps)
 
 	start = ps->pss_start_time;
 	end = ps->pss_end_time;
+	pause = ps->pss_pass_scrub_pause;
 	zfs_nicebytes(ps->pss_processed, processed_buf, sizeof (processed_buf));
 
 	assert(ps->pss_func == POOL_SCAN_SCRUB ||
@@ -5886,8 +5900,17 @@ print_scan_status(pool_scan_stat_t *ps)
 	 * Scan is in progress.
 	 */
 	if (ps->pss_func == POOL_SCAN_SCRUB) {
-		(void) printf(gettext("scrub in progress since %s"),
-		    ctime(&start));
+		if (pause == 0) {
+			(void) printf(gettext("scrub in progress since %s"),
+			    ctime(&start));
+		} else {
+			char buf[32];
+			struct tm *p = localtime(&pause);
+			(void) strftime(buf, sizeof (buf), "%a %b %e %T %Y", p);
+			(void) printf(gettext("scrub paused since %s\n"), buf);
+			(void) printf(gettext("\tscrub started on   %s"),
+			    ctime(&start));
+		}
 	} else if (ps->pss_func == POOL_SCAN_RESILVER) {
 		(void) printf(gettext("resilver in progress since %s"),
 		    ctime(&start));
@@ -5899,6 +5922,7 @@ print_scan_status(pool_scan_stat_t *ps)
 
 	/* elapsed time for this pass */
 	elapsed = time(NULL) - ps->pss_pass_start;
+	elapsed -= ps->pss_pass_scrub_spent_paused;
 	elapsed = elapsed ? elapsed : 1;
 	pass_exam = ps->pss_pass_exam ? ps->pss_pass_exam : 1;
 	rate = pass_exam / elapsed;
@@ -5908,19 +5932,25 @@ print_scan_status(pool_scan_stat_t *ps)
 
 	zfs_nicebytes(examined, examined_buf, sizeof (examined_buf));
 	zfs_nicebytes(total, total_buf, sizeof (total_buf));
-	zfs_nicebytes(rate, rate_buf, sizeof (rate_buf));
 
 	/*
 	 * do not print estimated time if hours_left is more than 30 days
+	 * or we have a paused scrub
 	 */
-	(void) printf(gettext("\t%s scanned out of %s at %s/s"),
-	    examined_buf, total_buf, rate_buf);
-	if (hours_left < (30 * 24)) {
-		(void) printf(gettext(", %lluh%um to go\n"),
-		    (u_longlong_t)hours_left, (uint_t)(mins_left % 60));
+	if (pause == 0) {
+		zfs_nicebytes(rate, rate_buf, sizeof (rate_buf));
+		(void) printf(gettext("\t%s scanned out of %s at %s/s"),
+		    examined_buf, total_buf, rate_buf);
+		if (hours_left < (30 * 24)) {
+			(void) printf(gettext(", %lluh%um to go\n"),
+			    (u_longlong_t)hours_left, (uint_t)(mins_left % 60));
+		} else {
+			(void) printf(gettext(
+			    ", (scan is slow, no estimated time)\n"));
+		}
 	} else {
-		(void) printf(gettext(
-		    ", (scan is slow, no estimated time)\n"));
+		(void) printf(gettext("\t%s scanned out of %s\n"),
+		    examined_buf, total_buf);
 	}
 
 	if (ps->pss_func == POOL_SCAN_RESILVER) {