On Fri, 2021-04-30 at 16:15 -0400, Mike Snitzer wrote:

If calling sg_io() is an issue then how does Martin's latest
patchset,
that exports and calls sg_io direct from DM, work!?

It works by doing sg_io on the _path_ devices. There's no difference
wrt to the current code in this respect. My code just retries on a
different path when one fails.

Hannes' original idea had passed the _dm_ device directly to
scsi_cmd_blk_ioctl().

Martin