Cause zpool scan resume commands to get logged in history

Currently, commands that resume a scrub/errorscrub from a paused state
don't get logged in the pool history. This is because resumes actually
return ECANCELED, instead of 0. This causes the tsd code in the common
ioctl logic to not think the ioctl succeeded, which causes the
log_history ioctl to fail with EPERM. However, for resuming a scrub from
a paused state, ECANCELED is success.

There are two options for how to deal with this. The first is the one
that I implemented here; I can't find a good reason for dmu_scan to
return ECANCELED on resume instead of 0, so let's just not. The only
place we check for the ECANCELED value is in zpool_scan, where we just
convert it back to zero.  However, I am aware that this is changing an
ioctl interface, which I believe is a breaking change. I don't think
it's an important change, but maybe there is someone who relies on it.

The other option that could be implemented is to either allow ECANCELED
specifically from dsl_scan in the common ioctl code, or add a generic
facility to the common ioctl code that allows each command to specify
whether or not success happened, regardless of the return values. I am
open to feedback on which option people think would be better.

Reviewed-by: Rob Norris <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Alexander Motin <[email protected]>
Signed-off-by: Paul Dagnelie <[email protected]>
Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Closes #17301
(cherry picked from commit 086105f)

Author: pcd1193182

lib/libzfs/libzfs_pool.c

@@ -2761,6 +2761,11 @@ zpool_scan(zpool_handle_t *zhp, pool_scan_func_t func, pool_scrub_cmd_t cmd)
 	 * 1. we resumed a paused scrub.
 	 * 2. we resumed a paused error scrub.
 	 * 3. Error scrub is not run because of no error log.
+	 *
+	 * Note that we no longer return ECANCELED in case 1 or 2. However, in
+	 * order to prevent problems where we have a newer userland than
+	 * kernel, we keep this check in place. That prevents erroneous
+	 * failures when an older kernel returns ECANCELED in those cases.
 	 */
 	if (err == ECANCELED && (func == POOL_SCAN_SCRUB ||
 	    func == POOL_SCAN_ERRORSCRUB) && cmd == POOL_SCRUB_NORMAL)

module/zfs/dsl_scan.c

@@ -1021,7 +1021,7 @@ dsl_scan(dsl_pool_t *dp, pool_scan_func_t func, uint64_t txgstart,
 			if (err == 0) {
 				spa_event_notify(spa, NULL, NULL,
 				    ESC_ZFS_ERRORSCRUB_RESUME);
-				return (ECANCELED);
+				return (0);
 			}
 			return (SET_ERROR(err));
 		}
@@ -1037,7 +1037,7 @@ dsl_scan(dsl_pool_t *dp, pool_scan_func_t func, uint64_t txgstart,
 		    POOL_SCRUB_NORMAL);
 		if (err == 0) {
 			spa_event_notify(spa, NULL, NULL, ESC_ZFS_SCRUB_RESUME);
-			return (SET_ERROR(ECANCELED));
+			return (0);
 		}
 		return (SET_ERROR(err));
 	}