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>
diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 63e05e3..109f9dc 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -196,6 +196,17 @@
If unsure, say N.
+config DM_MQ_DEFAULT
+ bool "request-based DM: use blk-mq I/O path by default"
+ depends on BLK_DEV_DM
+ ---help---
+ This option enables the blk-mq based I/O path for request-based
+ DM devices by default. With the option the dm_mod.use_blk_mq
+ module/boot option defaults to Y, without it to N, but it can
+ still be overriden either way.
+
+ If unsure say N.
+
config DM_DEBUG
bool "Device mapper debugging support"
depends on BLK_DEV_DM