dm: add 'use_blk_mq' module param and expose in per-device ro sysfs attr

Request-based DM's blk-mq support defaults to off; but a user can easily
change the default using the dm_mod.use_blk_mq module/boot option.

Also, you can check what mode a given request-based DM device is using
with: cat /sys/block/dm-X/dm/use_blk_mq

This change enabled further cleanup and reduced work (e.g. the
md->io_pool and md->rq_pool isn't created if using blk-mq).

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

1 files changed, 3 insertions, 3 deletions

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 66600cab9fa5..8d025f33de92 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -940,7 +940,7 @@ bool dm_table_mq_request_based(struct dm_table *t)
         return dm_table_get_type(t) == DM_TYPE_MQ_REQUEST_BASED;
 }
 
-static int dm_table_alloc_md_mempools(struct dm_table *t)
+static int dm_table_alloc_md_mempools(struct dm_table *t, struct mapped_device *md)
 {
         unsigned type = dm_table_get_type(t);
         unsigned per_bio_data_size = 0;
@@ -958,7 +958,7 @@ static int dm_table_alloc_md_mempools(struct dm_table *t)
                         per_bio_data_size = max(per_bio_data_size, tgt->per_bio_data_size);
                 }
 
-        t->mempools = dm_alloc_md_mempools(type, t->integrity_supported, per_bio_data_size);
+        t->mempools = dm_alloc_md_mempools(md, type, t->integrity_supported, per_bio_data_size);
         if (!t->mempools)
                 return -ENOMEM;
 
@@ -1128,7 +1128,7 @@ int dm_table_complete(struct dm_table *t)
                 return r;
         }
 
-        r = dm_table_alloc_md_mempools(t);
+        r = dm_table_alloc_md_mempools(t, t->md);
         if (r)
                 DMERR("unable to allocate mempools");