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>

diff --git a/Documentation/device-mapper/dm-raid.txt b/Documentation/device-mapper/dm-raid.txt
index 1c184495716697610d4bb41e1dde3ab60dce9e51..728c38c242d631b88117958360c6f8441a72be4b 100644 (file)
--- 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 10635e965fecfe3d6ea1b736e2310efe8b5f890f..4e79ebaab3c1d11502c9fc94bfa9199e64dce827 100644 (file)
--- 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,