Revert "block, dm: don't copy bios for request clones"

This reverts commit 5f1b670d0bef508a5554d92525f5f6d00d640b38.

Justification for revert as reported in this dm-devel post:
https://www.redhat.com/archives/dm-devel/2015-June/msg00160.html

this change should not be pushed to mainline yet.

Firstly, Christoph has a newer version of the patch that fixes silent
data corruption problem:
  https://www.redhat.com/archives/dm-devel/2015-May/msg00229.html

And the new version still depends on LLDDs to always complete requests
to the end when error happens, while block API doesn't enforce such a
requirement. If the assumption is ever broken, the inconsistency between
request and bio (e.g. rq->__sector and rq->bio) will cause silent data
corruption:
  https://www.redhat.com/archives/dm-devel/2015-June/msg00022.html

Reported-by: Junichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 9 insertions, 16 deletions

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index a5f94125ad01..16ba55ad7089 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -942,28 +942,21 @@ static int dm_table_alloc_md_mempools(struct dm_table *t, struct mapped_device *
 {
 	unsigned type = dm_table_get_type(t);
 	unsigned per_bio_data_size = 0;
+	struct dm_target *tgt;
 	unsigned i;
 
-	switch (type) {
-	case DM_TYPE_BIO_BASED:
-		for (i = 0; i < t->num_targets; i++) {
-			struct dm_target *tgt = t->targets + i;
-
-			per_bio_data_size = max(per_bio_data_size,
-						tgt->per_bio_data_size);
-		}
-		t->mempools = dm_alloc_bio_mempools(t->integrity_supported,
-						    per_bio_data_size);
-		break;
-	case DM_TYPE_REQUEST_BASED:
-	case DM_TYPE_MQ_REQUEST_BASED:
-		t->mempools = dm_alloc_rq_mempools(md, type);
-		break;
-	default:
+	if (unlikely(type == DM_TYPE_NONE)) {
 		DMWARN("no table type is set, can't allocate mempools");
 		return -EINVAL;
 	}
 
+	if (type == DM_TYPE_BIO_BASED)
+		for (i = 0; i < t->num_targets; i++) {
+			tgt = t->targets + i;
+			per_bio_data_size = max(per_bio_data_size, tgt->per_bio_data_size);
+		}
+
+	t->mempools = dm_alloc_md_mempools(md, type, t->integrity_supported, per_bio_data_size);
 	if (!t->mempools)
 		return -ENOMEM;