DDF: Don't fail compare_super_ddf due to re-configure changes.

It is possible that one device has seem some reconfig but the other
hasn't.  In that case  they are still the "same" DDF, even though
one might be older.  Such age will be detected by 'seq' differences.

If A is new and B is old, then it is import that
  mdadm -I B
  mdadm -I A

doesn't get confused because A has the same uuid as B, but compare_super fails.

So: if the seq numbers are different, then just accept as two
different superblocks.
If they are the same, then look to copy data from new to old.

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

1 files changed, 11 insertions, 33 deletions

diff --git a/super-ddf.c b/super-ddf.c
index 8530e98c..37ef665a 100644
--- a/super-ddf.c
+++ b/super-ddf.c
@@ -3946,47 +3946,25 @@ static int compare_super_ddf(struct supertype *st, struct supertype *tst)
 	if (memcmp(first->anchor.guid, second->anchor.guid, DDF_GUID_LEN) != 0)
 		return 2;
 
-	if (first->max_part != second->max_part ||
-	    !be16_eq(first->phys->used_pdes, second->phys->used_pdes) ||
-	    !be16_eq(first->virt->populated_vdes,
-		     second->virt->populated_vdes)) {
-		dprintf("%s: PD/VD number mismatch\n", __func__);
-		return 3;
-	}
-
-	max_pds = be16_to_cpu(first->phys->used_pdes);
-	for (dl2 = second->dlist; dl2; dl2 = dl2->next) {
-		for (pd = 0; pd < max_pds; pd++)
-			if (be32_eq(first->phys->entries[pd].refnum,
-				    dl2->disk.refnum))
-				break;
-		if (pd == max_pds) {
-			dprintf("%s: no match for disk %08x\n", __func__,
-				be32_to_cpu(dl2->disk.refnum));
-			return 3;
-		}
-	}
+	/* It is only OK to compare info in the anchor.  Anything else
+	 * could be changing due to a reconfig so must be ignored.
+	 * guid really should be enough anyway.
+	 */
 
-	max_vds = be16_to_cpu(first->active->max_vd_entries);
-	for (vl2 = second->conflist; vl2; vl2 = vl2->next) {
-		if (!be32_eq(vl2->conf.magic, DDF_VD_CONF_MAGIC))
-			continue;
-		for (vd = 0; vd < max_vds; vd++)
-			if (!memcmp(first->virt->entries[vd].guid,
-				    vl2->conf.guid, DDF_GUID_LEN))
-				break;
-		if (vd == max_vds) {
-			dprintf("%s: no match for VD config\n", __func__);
-			return 3;
-		}
+	if (!be32_eq(first->active->seq, second->active->seq)) {
+		dprintf("%s: sequence number mismatch %u<->%u\n", __func__,
+			be32_to_cpu(first->active->seq),
+			be32_to_cpu(second->active->seq));
+		return 0;
 	}
-	/* FIXME should I look at anything else? */
 
 	/*
 	 * At this point we are fairly sure that the meta data matches.
 	 * But the new disk may contain additional local data.
 	 * Add it to the super block.
 	 */
+	max_vds = be16_to_cpu(first->active->max_vd_entries);
+	max_pds = be16_to_cpu(first->phys->used_pdes);
 	for (vl2 = second->conflist; vl2; vl2 = vl2->next) {
 		for (vl1 = first->conflist; vl1; vl1 = vl1->next)
 			if (!memcmp(vl1->conf.guid, vl2->conf.guid,