md: fix problems with RAID6 calculations for DDF.

Signed-off-by: NeilBrown <neilb@suse.de>

1 files changed, 13 insertions, 7 deletions

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 25c3c29134d1..d4ce51b4d41b 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -158,11 +158,14 @@ static int raid6_idx_to_slot(int idx, struct stripe_head *sh,
 {
         int slot;
 
+        if (sh->ddf_layout)
+                slot = (*count)++;
         if (idx == sh->pd_idx)
                 return syndrome_disks;
         if (idx == sh->qd_idx)
                 return syndrome_disks + 1;
-        slot = (*count)++;
+        if (!sh->ddf_layout)
+                slot = (*count)++;
         return slot;
 }
 
@@ -727,9 +730,8 @@ static int set_syndrome_sources(struct page **srcs, struct stripe_head *sh)
                 srcs[slot] = sh->dev[i].page;
                 i = raid6_next_disk(i, disks);
         } while (i != d0_idx);
-        BUG_ON(count != syndrome_disks);
 
-        return count;
+        return syndrome_disks;
 }
 
 static struct dma_async_tx_descriptor *
@@ -828,7 +830,6 @@ ops_run_compute6_2(struct stripe_head *sh, struct raid5_percpu *percpu)
                         failb = slot;
                 i = raid6_next_disk(i, disks);
         } while (i != d0_idx);
-        BUG_ON(count != syndrome_disks);
 
         BUG_ON(faila == failb);
         if (failb < faila)
@@ -845,7 +846,7 @@ ops_run_compute6_2(struct stripe_head *sh, struct raid5_percpu *percpu)
                         init_async_submit(&submit, ASYNC_TX_FENCE, NULL,
                                           ops_complete_compute, sh,
                                           to_addr_conv(sh, percpu));
-                        return async_gen_syndrome(blocks, 0, count+2,
+                        return async_gen_syndrome(blocks, 0, syndrome_disks+2,
                                                   STRIPE_SIZE, &submit);
                 } else {
                         struct page *dest;
@@ -1935,10 +1936,15 @@ static sector_t compute_blocknr(struct stripe_head *sh, int i, int previous)
                 case ALGORITHM_PARITY_N:
                         break;
                 case ALGORITHM_ROTATING_N_CONTINUE:
+                        /* Like left_symmetric, but P is before Q */
                         if (sh->pd_idx == 0)
                                 i--;    /* P D D D Q */
-                        else if (i > sh->pd_idx)
-                                i -= 2; /* D D Q P D */
+                        else {
+                                /* D D Q P D */
+                                if (i < sh->pd_idx)
+                                        i += raid_disks;
+                                i -= (sh->pd_idx + 1);
+                        }
                         break;
                 case ALGORITHM_LEFT_ASYMMETRIC_6:
                 case ALGORITHM_RIGHT_ASYMMETRIC_6: