[v5,0/3] scsi/dm: dm_blk_ioctl(): implement failover for SG_IO on dm-multipath

Message

Martin Wilck June 28, 2021, 3:15 p.m. UTC

From: Martin Wilck <[e-mail]>

Hello Mike, hello Martin,

here is v5 of my attempt to add retry logic to SG_IO on dm-multipath
devices.

Christoph's comment on v4 has been received, but as I'm still confused
how to handle the SCSI result / blk_status_t conversion properly, and
waiting for more guidance, I want to fix the nasty bug in v4 first.

Regards
Martin

Changes v4->v5:

 - (2/3) Fixed bug in logical / bitwise and expression
   Reported-by: kernel test robot <[e-mail]>

Changes v3->v4 (thanks to Mike Snitzer):

 - Added an additional helper function sg_io_to_blk_status() to
   scsi_ioctl.c, in order to avoid open-coding handling of the SCSI result
   code in device-mapper.

 - Added a new method dm_sg_io_ioctl_fn() in struct target_type, define
   only by the multipath target. This allows moving the bulk of the new
   code to dm-mpath.c, and avoids the wrong limitation of the code to
   request-based multipath.

Changes v2->v3:

 - un-inlined scsi_result_to_blk_status again, and move the helper
   __scsi_result_to_blk_status to block/scsi_ioctl.c instead
   (Bart v. Assche)
 - open-coded the status/msg/host/driver-byte -> result conversion
   where the standard SCSI helpers aren't usable (Bart v. Assche)
    
Changes v1->v2:

 - applied modifications from Mike Snitzer
 - moved SG_IO dependent code to a separate file, no scsi includes in
   dm.c any more
 - made the new code depend on a configuration option 
 - separated out scsi changes, made scsi_result_to_blk_status()
   inline to avoid dependency of dm_mod from scsi_mod (Paolo Bonzini)

Martin Wilck (3):
  scsi: scsi_ioctl: export __scsi_result_to_blk_status()
  scsi: scsi_ioctl: add sg_io_to_blk_status()
  dm mpath: add CONFIG_DM_MULTIPATH_SG_IO - failover for SG_IO

Martin Wilck (3):
  scsi: scsi_ioctl: export __scsi_result_to_blk_status()
  scsi: scsi_ioctl: add sg_io_to_blk_status()
  dm mpath: add CONFIG_DM_MULTIPATH_SG_IO - failover for SG_IO

 block/scsi_ioctl.c            |  72 ++++++++++++++++++++++-
 drivers/md/Kconfig            |  11 ++++
 drivers/md/dm-core.h          |   5 ++
 drivers/md/dm-mpath.c         | 105 ++++++++++++++++++++++++++++++++++
 drivers/md/dm.c               |  26 ++++++++-
 drivers/scsi/scsi_lib.c       |  24 +-------
 include/linux/blkdev.h        |   4 ++
 include/linux/device-mapper.h |   8 ++-
 8 files changed, 226 insertions(+), 29 deletions(-)