dm table: train hybrid target type detection to select blk-mq if appropriate

Otherwise replacing the multipath target with the error target fails:
  device-mapper: ioctl: can't change device type after initial table load.

The error target was mistakenly considered to be target type
DM_TYPE_REQUEST_BASED rather than DM_TYPE_MQ_REQUEST_BASED even if the
target it was to replace was of type DM_TYPE_MQ_REQUEST_BASED.

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

2 files changed, 22 insertions, 16 deletions

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 2d7e373955f3..14954d844668 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -831,7 +831,7 @@ static int dm_table_set_type(struct dm_table *t)
         struct dm_target *tgt;
         struct dm_dev_internal *dd;
         struct list_head *devices;
-        unsigned live_md_type;
+        unsigned live_md_type = dm_get_md_type(t->md);
 
         for (i = 0; i < t->num_targets; i++) {
                 tgt = t->targets + i;
@@ -855,8 +855,8 @@ static int dm_table_set_type(struct dm_table *t)
                  * Determine the type from the live device.
                  * Default to bio-based if device is new.
                  */
-                live_md_type = dm_get_md_type(t->md);
-                if (live_md_type == DM_TYPE_REQUEST_BASED)
+                if (live_md_type == DM_TYPE_REQUEST_BASED ||
+                    live_md_type == DM_TYPE_MQ_REQUEST_BASED)
                         request_based = 1;
                 else
                         bio_based = 1;
@@ -870,6 +870,17 @@ static int dm_table_set_type(struct dm_table *t)
 
         BUG_ON(!request_based); /* No targets in this table */
 
+        /*
+         * Request-based dm supports only tables that have a single target now.
+         * To support multiple targets, request splitting support is needed,
+         * and that needs lots of changes in the block-layer.
+         * (e.g. request completion process for partial completion.)
+         */
+        if (t->num_targets > 1) {
+                DMWARN("Request-based dm doesn't support multiple targets yet");
+                return -EINVAL;
+        }
+
         /* Non-request-stackable devices can't be used for request-based dm */
         devices = dm_table_get_devices(t);
         list_for_each_entry(dd, devices, list) {
@@ -893,20 +904,14 @@ static int dm_table_set_type(struct dm_table *t)
                                       " are blk-mq request-stackable");
                                 return -EINVAL;
                         }
-        }
+                t->type = DM_TYPE_MQ_REQUEST_BASED;
 
-        /*
-         * Request-based dm supports only tables that have a single target now.
-         * To support multiple targets, request splitting support is needed,
-         * and that needs lots of changes in the block-layer.
-         * (e.g. request completion process for partial completion.)
-         */
-        if (t->num_targets > 1) {
-                DMWARN("Request-based dm doesn't support multiple targets yet");
-                return -EINVAL;
-        }
+        } else if (hybrid && list_empty(devices) && live_md_type != DM_TYPE_NONE) {
+                /* inherit live MD type */
+                t->type = live_md_type;
 
-        t->type = !use_blk_mq ? DM_TYPE_REQUEST_BASED : DM_TYPE_MQ_REQUEST_BASED;
+        } else
+                t->type = DM_TYPE_REQUEST_BASED;
 
         return 0;
 }
diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index 84d79784b866..59f53e79db82 100644
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -101,7 +101,8 @@ int dm_setup_md_queue(struct mapped_device *md);
 /*
  * To check whether the target type is request-based or not (bio-based).
  */
-#define dm_target_request_based(t) ((t)->type->map_rq != NULL)
+#define dm_target_request_based(t) (((t)->type->map_rq != NULL) || \
+                                    ((t)->type->clone_and_map_rq != NULL))
 
 /*
  * To check whether the target type is a hybrid (capable of being