dm table: allow upgrade from bio-based to specialized bio-based variant

In practice this is really only meaningful in the context of the DM
multipath target (which uses dm_table_set_type() to set the type of
device DM should create via its "queue_mode" option).

So this change allows a DM multipath device with "queue_mode bio" to be
upgraded from DM_TYPE_BIO_BASED to DM_TYPE_NVME_BIO_BASED -- iff the
underlying device(s) are NVMe.

DM_TYPE_NVME_BIO_BASED is just a DM core implementation detail that
allows for NVMe-specific optimizations (e.g. use direct_make_request
instead of generic_make_request).  If in the future there is no benefit
or need to distinguish NVMe vs not: then it will be removed.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 30b3294a8778e3339cb70ce2645f3b81d4000563..7eb3e2a3c07d5a607669d36aa0a462bfd175d9b3 100644 (file)
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -942,17 +942,12 @@ static int dm_table_determine_type(struct dm_table *t)
 
        if (t->type != DM_TYPE_NONE) {
                /* target already set the table's type */
-               if (t->type == DM_TYPE_BIO_BASED)
-                       return 0;
-               else if (t->type == DM_TYPE_NVME_BIO_BASED) {
-                       if (!dm_table_does_not_support_partial_completion(t)) {
-                               DMERR("nvme bio-based is only possible with devices"
-                                     " that don't support partial completion");
-                               return -EINVAL;
-                       }
-                       /* Fallthru, also verify all devices are blk-mq */
+               if (t->type == DM_TYPE_BIO_BASED) {
+                       /* possibly upgrade to a variant of bio-based */
+                       goto verify_bio_based;
                }
                BUG_ON(t->type == DM_TYPE_DAX_BIO_BASED);
+               BUG_ON(t->type == DM_TYPE_NVME_BIO_BASED);
                goto verify_rq_based;
        }
 
@@ -985,6 +980,7 @@ static int dm_table_determine_type(struct dm_table *t)
        }
 
        if (bio_based) {
+verify_bio_based:
                /* We must use this table as bio-based */
                t->type = DM_TYPE_BIO_BASED;
                if (dm_table_supports_dax(t) ||