dm raid: clarify and fix recovery

Add function rs_setup_recovery() to allow for defined setup of RAID set
recovery in the constructor.

Will be called with dev_sectors={0, rdev->sectors, MaxSectors} to
recover a new or enforced sync, grown or not to be synhronized RAID set
respectively.

Prevents recovery on raid0, which doesn't support it.

Enforces recovery on raid6 to ensure properly defined Syndromes
mandatory for that MD personality are being created.

Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-raid.c

@@ -349,6 +349,12 @@ static bool rs_is_raid10(struct raid_set *rs)
 	return rs->md.level == 10;
 }
 
+/* Return true, if raid set in @rs is level 6 */
+static bool rs_is_raid6(struct raid_set *rs)
+{
+	return rs->md.level == 6;
+}
+
 /* Return true, if raid set in @rs is level 4, 5 or 6 */
 static bool rs_is_raid456(struct raid_set *rs)
 {
@@ -681,7 +687,7 @@ static struct raid_set *raid_set_alloc(struct dm_target *ti, struct raid_type *r
 	rs->md.layout = raid_type->algorithm;
 	rs->md.new_layout = rs->md.layout;
 	rs->md.delta_disks = 0;
-	rs->md.recovery_cp = rs_is_raid0(rs) ? MaxSector : 0;
+	rs->md.recovery_cp = MaxSector;
 
 	for (i = 0; i < raid_devs; i++)
 		md_rdev_init(&rs->dev[i].rdev);
@@ -1090,7 +1096,6 @@ static int parse_raid_params(struct raid_set *rs, struct dm_arg_set *as,
 				rs->ti->error = "Only one 'nosync' argument allowed";
 				return -EINVAL;
 			}
-			rs->md.recovery_cp = MaxSector;
 			continue;
 		}
 		if (!strcasecmp(key, dm_raid_arg_name_by_flag(CTR_FLAG_SYNC))) {
@@ -1098,7 +1103,6 @@ static int parse_raid_params(struct raid_set *rs, struct dm_arg_set *as,
 				rs->ti->error = "Only one 'sync' argument allowed";
 				return -EINVAL;
 			}
-			rs->md.recovery_cp = 0;
 			continue;
 		}
 		if (!strcasecmp(key, dm_raid_arg_name_by_flag(CTR_FLAG_RAID10_USE_NEAR_SETS))) {
@@ -1412,7 +1416,6 @@ static int rs_set_dev_and_array_sectors(struct raid_set *rs, bool use_mddev)
 	struct mddev *mddev = &rs->md;
 	struct md_rdev *rdev;
 	sector_t array_sectors = rs->ti->len, dev_sectors = rs->ti->len;
-	sector_t cur_dev_sectors = rs->dev[0].rdev.sectors;
 
 	if (use_mddev) {
 		delta_disks = mddev->delta_disks;
@@ -1453,15 +1456,50 @@ static int rs_set_dev_and_array_sectors(struct raid_set *rs, bool use_mddev)
 	mddev->array_sectors = array_sectors;
 	mddev->dev_sectors = dev_sectors;
 
-	if (!rs_is_raid0(rs) && dev_sectors > cur_dev_sectors)
-		mddev->recovery_cp = dev_sectors;
-
 	return 0;
 bad:
 	rs->ti->error = "Target length not divisible by number of data devices";
 	return EINVAL;
 }
 
+/* Setup recovery on @rs */
+static void __rs_setup_recovery(struct raid_set *rs, sector_t dev_sectors)
+{
+	/* raid0 does not recover */
+	if (rs_is_raid0(rs))
+		rs->md.recovery_cp = MaxSector;
+	/*
+	 * A raid6 set has to be recovered either
+	 * completely or for the grown part to
+	 * ensure proper parity and Q-Syndrome
+	 */
+	else if (rs_is_raid6(rs))
+		rs->md.recovery_cp = dev_sectors;
+	/*
+	 * Other raid set types may skip recovery
+	 * depending on the 'nosync' flag.
+	 */
+	else
+		rs->md.recovery_cp = test_bit(__CTR_FLAG_NOSYNC, &rs->ctr_flags)
+				     ? MaxSector : dev_sectors;
+}
+
+/* Setup recovery on @rs based on raid type, device size and 'nosync' flag */
+static void rs_setup_recovery(struct raid_set *rs, sector_t dev_sectors)
+{
+	if (!dev_sectors)
+		/* New raid set or 'sync' flag provided */
+		__rs_setup_recovery(rs, 0);
+	else if (dev_sectors == MaxSector)
+		/* Prevent recovery */
+		__rs_setup_recovery(rs, MaxSector);
+	else if (rs->dev[0].rdev.sectors < dev_sectors)
+		/* Grown raid set */
+		__rs_setup_recovery(rs, rs->dev[0].rdev.sectors);
+	else
+		__rs_setup_recovery(rs, MaxSector);
+}
+
 static void do_table_event(struct work_struct *ws)
 {
 	struct raid_set *rs = container_of(ws, struct raid_set, md.event_work);
@@ -2086,7 +2124,6 @@ static int super_init_validation(struct raid_set *rs, struct md_rdev *rdev)
 		if (new_devs == rs->raid_disks) {
 			DMINFO("Superblocks created for new raid set");
 			set_bit(MD_ARRAY_FIRST_USE, &mddev->flags);
-			mddev->recovery_cp = 0;
 		} else if (new_devs != rebuilds &&
 			   new_devs != rs->delta_disks) {
 			DMERR("New device injected into existing raid set without "
@@ -2633,6 +2670,7 @@ static int raid_ctr(struct dm_target *ti, unsigned argc, char **argv)
 	int r;
 	struct raid_type *rt;
 	unsigned num_raid_params, num_raid_devs;
+	sector_t calculated_dev_sectors;
 	struct raid_set *rs = NULL;
 	const char *arg;
 	struct rs_layout rs_layout;
@@ -2689,6 +2727,8 @@ static int raid_ctr(struct dm_target *ti, unsigned argc, char **argv)
 	if (r)
 		return r;
 
+	calculated_dev_sectors = rs->dev[0].rdev.sectors;
+
 	/*
 	 * Backup any new raid set level, layout, ...
 	 * requested to be able to compare to superblock
@@ -2700,6 +2740,8 @@ static int raid_ctr(struct dm_target *ti, unsigned argc, char **argv)
 	if (r)
 		goto bad;
 
+	rs_setup_recovery(rs, calculated_dev_sectors);
+
 	INIT_WORK(&rs->md.event_work, do_table_event);
 	ti->private = rs;
 	ti->num_flush_bios = 1;
@@ -2786,8 +2828,12 @@ static int raid_ctr(struct dm_target *ti, unsigned argc, char **argv)
 			set_bit(MD_ARRAY_FIRST_USE, &rs->md.flags);
 
 		rs_set_cur(rs);
-	} else
+		rs_setup_recovery(rs, MaxSector);
+	} else {
 		rs_set_cur(rs);
+		rs_setup_recovery(rs, test_bit(__CTR_FLAG_SYNC, &rs->ctr_flags) ?
+				      0 : calculated_dev_sectors);
+	}
 
 	/* If constructor requested it, change data and new_data offsets */
 	r = rs_adjust_data_offsets(rs);