On Fri, Jul 28, 2017 at 9:17 AM, Bart Van Assche [off-list ref] wrote:

On Mon, 2017-04-17 at 12:09 -0700, Dan Williams wrote:

quoted

diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index b7767da50c26..1de8372d9459 100644
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig

@@ -200,6 +200,7 @@ config BLK_DEV_DM_BUILTIN
 config BLK_DEV_DM
      tristate "Device mapper support"
      select BLK_DEV_DM_BUILTIN
+     select DAX
      ---help---
        Device-mapper is a low level volume manager.  It works by allowing
        people to specify mappings for ranges of logical sectors.  Various

(replying to an e-mail of three months ago)

Hello Dan,

While building a v4.12 kernel I noticed that enabling device mapper support
now unconditionally enables DAX. I think there are plenty of systems that use
dm but do not need DAX. Have you considered to rework this such that instead
of dm selecting DAX that DAX support is only enabled in dm if CONFIG_DAX is
enabled?

I'd rather flip this around and add a CONFIG_DM_DAX that gates whether
DM enables / links to the DAX core. I'll take a look at a patch.