DM RAID: Add rebuild capability for RAID10

DM RAID:  Add code to validate replacement slots for RAID10 arrays

RAID10 can handle 'copies - 1' failures for each mirror group.  This code
ensures the user has provided a valid array - one whose devices specified for
rebuild do not exceed the amount of redundancy available.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.de>

2 files changed, 42 insertions, 1 deletions

diff --git a/Documentation/device-mapper/dm-raid.txt b/Documentation/device-mapper/dm-raid.txt
index 1c184495716..728c38c242d 100644
--- a/Documentation/device-mapper/dm-raid.txt
+++ b/Documentation/device-mapper/dm-raid.txt
@@ -132,3 +132,12 @@ Here we can see the RAID type is raid4, there are 5 devices - all of
 which are 'A'live, and the array is 2/490221568 complete with recovery.
 Faulty or missing devices are marked 'D'.  Devices that are out-of-sync
 are marked 'a'.
+
+
+Version History
+---------------
+1.0.0   Initial version.  Support for RAID 4/5/6
+1.1.0   Added support for RAID 1
+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
diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
index 10635e965fe..4e79ebaab3c 100644
--- a/drivers/md/dm-raid.c
+++ b/drivers/md/dm-raid.c
@@ -349,6 +349,7 @@ static int validate_region_size(struct raid_set *rs, unsigned long region_size)
 static int validate_rebuild_devices(struct raid_set *rs)
 {
         unsigned i, rebuild_cnt = 0;
+        unsigned rebuilds_per_group, copies, d;
 
         if (!(rs->print_flags & DMPF_REBUILD))
                 return 0;
@@ -369,6 +370,37 @@ static int validate_rebuild_devices(struct raid_set *rs)
                         goto too_many;
                 break;
         case 10:
+                copies = raid10_md_layout_to_copies(rs->md.layout);
+                if (rebuild_cnt < copies)
+                        break;
+
+                /*
+                 * It is possible to have a higher rebuild count for RAID10,
+                 * as long as the failed devices occur in different mirror
+                 * groups (i.e. different stripes).
+                 *
+                 * Right now, we only allow for "near" copies.  When other
+                 * formats are added, we will have to check those too.
+                 *
+                 * When checking "near" format, make sure no adjacent devices
+                 * have failed beyond what can be handled.  In addition to the
+                 * simple case where the number of devices is a multiple of the
+                 * number of copies, we must also handle cases where the number
+                 * of devices is not a multiple of the number of copies.
+                 * E.g.    dev1 dev2 dev3 dev4 dev5
+                 *          A    A    B    B    C
+                 *          C    D    D    E    E
+                 */
+                rebuilds_per_group = 0;
+                for (i = 0; i < rs->md.raid_disks * copies; i++) {
+                        d = i % rs->md.raid_disks;
+                        if (!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);
@@ -1385,7 +1417,7 @@ static void raid_resume(struct dm_target *ti)
 
 static struct target_type raid_target = {
         .name = "raid",
-        .version = {1, 3, 0},
+        .version = {1, 3, 1},
         .module = THIS_MODULE,
         .ctr = raid_ctr,
         .dtr = raid_dtr,