Merge tag 'md-3.8-fixes' of git://neil.brown.name/md

Pull dmraid fix from NeilBrown:
 "Just one fix for md in 3.8

  dmraid assess redundancy and replacements slightly inaccurately which
  could lead to some degraded arrays failing to assemble."

* tag 'md-3.8-fixes' of git://neil.brown.name/md:
  DM-RAID: Fix RAID10's check for sufficient redundancy

Documentation/device-mapper/dm-raid.txt

@@ -141,3 +141,4 @@ Version History
 1.2.0	Handle creation of arrays that contain failed devices.
 1.3.0	Added support for RAID 10
 1.3.1	Allow device replacement/rebuild for RAID 10
+1.3.2   Fix/improve redundancy checking for RAID10

drivers/md/dm-raid.c

@@ -340,24 +340,22 @@ static int validate_region_size(struct raid_set *rs, unsigned long region_size)
 }
 
 /*
- * validate_rebuild_devices
+ * validate_raid_redundancy
  * @rs
  *
- * Determine if the devices specified for rebuild can result in a valid
- * usable array that is capable of rebuilding the given devices.
+ * Determine if there are enough devices in the array that haven't
+ * failed (or are being rebuilt) to form a usable array.
  *
  * Returns: 0 on success, -EINVAL on failure.
  */
-static int validate_rebuild_devices(struct raid_set *rs)
+static int validate_raid_redundancy(struct raid_set *rs)
 {
 	unsigned i, rebuild_cnt = 0;
 	unsigned rebuilds_per_group, copies, d;
 
-	if (!(rs->print_flags & DMPF_REBUILD))
-		return 0;
-
 	for (i = 0; i < rs->md.raid_disks; i++)
-		if (!test_bit(In_sync, &rs->dev[i].rdev.flags))
+		if (!test_bit(In_sync, &rs->dev[i].rdev.flags) ||
+		    !rs->dev[i].rdev.sb_page)
 			rebuild_cnt++;
 
 	switch (rs->raid_type->level) {
@@ -393,27 +391,24 @@ static int validate_rebuild_devices(struct raid_set *rs)
 		 *          A    A    B    B    C
 		 *          C    D    D    E    E
 		 */
-		rebuilds_per_group = 0;
 		for (i = 0; i < rs->md.raid_disks * copies; i++) {
+			if (!(i % copies))
+				rebuilds_per_group = 0;
 			d = i % rs->md.raid_disks;
-			if (!test_bit(In_sync, &rs->dev[d].rdev.flags) &&
+			if ((!rs->dev[d].rdev.sb_page ||
+			     !test_bit(In_sync, &rs->dev[d].rdev.flags)) &&
 			    (++rebuilds_per_group >= copies))
 				goto too_many;
-			if (!((i + 1) % copies))
-				rebuilds_per_group = 0;
 		}
 		break;
 	default:
-		DMERR("The rebuild parameter is not supported for %s",
-		      rs->raid_type->name);
-		rs->ti->error = "Rebuild not supported for this RAID type";
+		if (rebuild_cnt)
 			return -EINVAL;
 	}
 
 	return 0;
 
 too_many:
-	rs->ti->error = "Too many rebuild devices specified";
 	return -EINVAL;
 }
 
@@ -664,9 +659,6 @@ static int parse_raid_params(struct raid_set *rs, char **argv,
 	}
 	rs->md.dev_sectors = sectors_per_dev;
 
-	if (validate_rebuild_devices(rs))
-		return -EINVAL;
-
 	/* Assume there are no metadata devices until the drives are parsed */
 	rs->md.persistent = 0;
 	rs->md.external = 1;
@@ -995,28 +987,10 @@ static int super_validate(struct mddev *mddev, struct md_rdev *rdev)
 static int analyse_superblocks(struct dm_target *ti, struct raid_set *rs)
 {
 	int ret;
-	unsigned redundancy = 0;
 	struct raid_dev *dev;
 	struct md_rdev *rdev, *tmp, *freshest;
 	struct mddev *mddev = &rs->md;
 
-	switch (rs->raid_type->level) {
-	case 1:
-		redundancy = rs->md.raid_disks - 1;
-		break;
-	case 4:
-	case 5:
-	case 6:
-		redundancy = rs->raid_type->parity_devs;
-		break;
-	case 10:
-		redundancy = raid10_md_layout_to_copies(mddev->layout) - 1;
-		break;
-	default:
-		ti->error = "Unknown RAID type";
-		return -EINVAL;
-	}
-
 	freshest = NULL;
 	rdev_for_each_safe(rdev, tmp, mddev) {
 		/*
@@ -1045,7 +1019,6 @@ static int analyse_superblocks(struct dm_target *ti, struct raid_set *rs)
 			break;
 		default:
 			dev = container_of(rdev, struct raid_dev, rdev);
-			if (redundancy--) {
 			if (dev->meta_dev)
 				dm_put_device(ti, dev->meta_dev);
 
@@ -1072,17 +1045,17 @@ static int analyse_superblocks(struct dm_target *ti, struct raid_set *rs)
 			rdev->bdev = NULL;
 
 			list_del(&rdev->same_set);
-
-				continue;
-			}
-			ti->error = "Failed to load superblock";
-			return ret;
 		}
 	}
 
 	if (!freshest)
 		return 0;
 
+	if (validate_raid_redundancy(rs)) {
+		rs->ti->error = "Insufficient redundancy to activate array";
+		return -EINVAL;
+	}
+
 	/*
 	 * Validation of the freshest device provides the source of
 	 * validation for the remaining devices.
@@ -1432,7 +1405,7 @@ static void raid_resume(struct dm_target *ti)
 
 static struct target_type raid_target = {
 	.name = "raid",
-	.version = {1, 4, 0},
+	.version = {1, 4, 1},
 	.module = THIS_MODULE,
 	.ctr = raid_ctr,
 	.dtr = raid_dtr,