md: fix some bugs with growing raid5/raid6 arrays.

The recent changed to raid5 to allow offload of parity calculation etc
introduced some bugs in the code for growing (i.e.  adding a disk to) raid5
and raid6.  This fixes them
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/md/raid5.c

@@ -2541,7 +2541,7 @@ static void handle_stripe_expansion(raid5_conf_t *conf, struct stripe_head *sh,
 	struct dma_async_tx_descriptor *tx = NULL;
 	clear_bit(STRIPE_EXPAND_SOURCE, &sh->state);
 	for (i = 0; i < sh->disks; i++)
-		if (i != sh->pd_idx && (r6s && i != r6s->qd_idx)) {
+		if (i != sh->pd_idx && (!r6s || i != r6s->qd_idx)) {
 			int dd_idx, pd_idx, j;
 			struct stripe_head *sh2;
 
@@ -2574,7 +2574,8 @@ static void handle_stripe_expansion(raid5_conf_t *conf, struct stripe_head *sh,
 			set_bit(R5_UPTODATE, &sh2->dev[dd_idx].flags);
 			for (j = 0; j < conf->raid_disks; j++)
 				if (j != sh2->pd_idx &&
-				    (r6s && j != r6s->qd_idx) &&
+				    (!r6s || j != raid6_next_disk(sh2->pd_idx,
+								 sh2->disks)) &&
 				    !test_bit(R5_Expanded, &sh2->dev[j].flags))
 					break;
 			if (j == conf->raid_disks) {
@@ -2583,12 +2584,12 @@ static void handle_stripe_expansion(raid5_conf_t *conf, struct stripe_head *sh,
 			}
 			release_stripe(sh2);
 
+		}
 	/* done submitting copies, wait for them to complete */
-			if (i + 1 >= sh->disks) {
+	if (tx) {
 		async_tx_ack(tx);
 		dma_wait_for_async_tx(tx);
 	}
-		}
 }
 
 /*
@@ -2855,7 +2856,7 @@ static void handle_stripe5(struct stripe_head *sh)
 		sh->disks = conf->raid_disks;
 		sh->pd_idx = stripe_to_pdidx(sh->sector, conf,
 			conf->raid_disks);
-		s.locked += handle_write_operations5(sh, 0, 1);
+		s.locked += handle_write_operations5(sh, 1, 1);
 	} else if (s.expanded &&
 		!test_bit(STRIPE_OP_POSTXOR, &sh->ops.pending)) {
 		clear_bit(STRIPE_EXPAND_READY, &sh->state);