md: replace last_sync_action with new enum type

The only difference is that "none" is removed and initial
last_sync_action will be idle.

On the one hand, this value is introduced by commit c4a39551
("MD: Remember the last sync operation that was performed"), and the
usage described in commit message is not affected. On the other hand,
last_sync_action is not used in mdadm or mdmon, and none of the tests
that I can find.
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20240611132251.1967786-10-yukuai1@huaweicloud.com

drivers/md/dm-raid.c

@@ -3542,7 +3542,7 @@ static void raid_status(struct dm_target *ti, status_type_t type,
 		recovery = rs->md.recovery;
 		state = decipher_sync_action(mddev, recovery);
 		progress = rs_get_progress(rs, recovery, state, resync_max_sectors);
-		resync_mismatches = (mddev->last_sync_action && !strcasecmp(mddev->last_sync_action, "check")) ?
+		resync_mismatches = mddev->last_sync_action == ACTION_CHECK ?
 				    atomic64_read(&mddev->resync_mismatches) : 0;
 
 		/* HM FIXME: do we want another state char for raid0? It shows 'D'/'A'/'-' now */

drivers/md/md.c

@@ -768,7 +768,7 @@ int mddev_init(struct mddev *mddev)
 	init_waitqueue_head(&mddev->recovery_wait);
 	mddev->reshape_position = MaxSector;
 	mddev->reshape_backwards = 0;
-	mddev->last_sync_action = "none";
+	mddev->last_sync_action = ACTION_IDLE;
 	mddev->resync_min = 0;
 	mddev->resync_max = MaxSector;
 	mddev->level = LEVEL_NONE;
@@ -5149,7 +5149,8 @@ __ATTR_PREALLOC(sync_action, S_IRUGO|S_IWUSR, action_show, action_store);
 static ssize_t
 last_sync_action_show(struct mddev *mddev, char *page)
 {
-	return sprintf(page, "%s\n", mddev->last_sync_action);
+	return sprintf(page, "%s\n",
+		       md_sync_action_name(mddev->last_sync_action));
 }
 
 static struct md_sysfs_entry md_last_scan_mode = __ATTR_RO(last_sync_action);
@@ -8963,7 +8964,7 @@ void md_do_sync(struct md_thread *thread)
 
 	action = md_sync_action(mddev);
 	desc = md_sync_action_name(action);
-	mddev->last_sync_action = desc;
+	mddev->last_sync_action = action;
 
 	/*
 	 * Before starting a resync we must have set curr_resync to

drivers/md/md.h

@@ -426,13 +426,12 @@ struct mddev {
 	struct md_thread __rcu		*thread;	/* management thread */
 	struct md_thread __rcu		*sync_thread;	/* doing resync or reconstruct */
 
-	/* 'last_sync_action' is initialized to "none".  It is set when a
-	 * sync operation (i.e "data-check", "requested-resync", "resync",
-	 * "recovery", or "reshape") is started.  It holds this value even
+	/*
+	 * Set when a sync operation is started. It holds this value even
 	 * when the sync thread is "frozen" (interrupted) or "idle" (stopped
 	 * or finished). It is overwritten when a new sync operation is begun.
 	 */
-	const char			*last_sync_action;
+	enum sync_action		last_sync_action;
 	sector_t			curr_resync;	/* last block scheduled */
 	/* As resync requests can complete out of order, we cannot easily track
 	 * how much resync has been completed.  So we occasionally pause until