On Mon, 2016-06-20 at 14:00 -0400, Mike Snitzer wrote:

On Mon, Jun 13 2016 at  6:57pm -0400,
Mike Snitzer [off-list ref] wrote:

quoted

On Mon, Jun 13 2016 at  6:21pm -0400,
Toshi Kani [off-list ref] wrote:

quoted

This patch-set adds DAX support to device-mapper dm-linear devices
used by LVM.  It works with LVM commands as follows:
 - Creation of a logical volume with all DAX capable devices (such
   as pmem) sets the logical volume DAX capable as well.
 - Once a logical volume is set to DAX capable, the volume may not
   be extended with non-DAX capable devices.

The direct_access interface is added to dm and dm-linear to map
a request to a target device.

 - Patch 1-2 introduce GENHD_FL_DAX flag to indicate DAX capability.
 - Patch 3-4 add direct_access functions to dm and dm-linear.
 - Patch 5-6 set GENHD_FL_DAX to dm when all targets are DAX capable.

---
Toshi Kani (6):
 1/6 genhd: Add GENHD_FL_DAX to gendisk flags
 2/6 block: Check GENHD_FL_DAX for DAX capability
 3/6 dm: Add dm_blk_direct_access() for mapped device
 4/6 dm-linear: Add linear_direct_access()
 5/6 dm, dm-linear: Add dax_supported to dm_target
 6/6 dm: Enable DAX support for mapper device

Thanks a lot for doing this.  I recently added it to my TODO so your
patches come at a great time.

I'll try to get to reviewing/testing your work by the end of this week.

I rebased your patches on linux-dm.git's 'for-next' (which includes what
I've already staged for the 4.8 merge window).  And I folded/changed
some of the DM patches so that there are only 2 now (1 for DM core and 1
for dm-linear).  Please see the 4 topmost commits in my 'wip' here:

http://git.kernel.org/cgit/linux/kernel/git/snitzer/linux.git/log/?h=wip

Feel free to pick these patches up to use as the basis for continued
work or re-posting of this set.. either that or I could post them as v2
on your behalf.

As for testing, I've verified that basic IO works to a pmem-based DM
linear device and that mixed table types are rejected as expected.

Great! I will send additional patch, add DAX support to dm-stripe, on top of
these once I finish my testing.

Thanks,
-Toshi
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