[PATCH v3 0/4] Initial support for multi-actuator HDDs

[Damien Le Moal <damien.lemoal@wdc.com>]

Single LUN multi-actuator hard-disks are cappable to seek and execute
multiple commands in parallel. This capability is exposed to the host
using the Concurrent Positioning Ranges VPD page (SCSI) and Log (ATA).
Each positioning range describes the contiguous set of LBAs that an
actuator serves.

This series adds support the scsi disk driver to retreive this
information and advertize it to user space through sysfs. libata is also
modified to handle ATA drives.

The first patch adds the block layer plumbing to expose concurrent
sector ranges of the device through sysfs as a sub-directory of the
device sysfs queue directory. Patch 2 and 3 add support to sd and
libata. Finally patch 4 documents the sysfs queue attributed changes.

This series does not attempt in any way to optimize accesses to
multi-actuator devices (e.g. block IO scheduler or filesystems). This
initial support only exposes the actuators information to user space
through sysfs.

Changes from v2:
* Update patch 1 to fix a compilation warning for a potential NULL
  pointer dereference of the cr argument of blk_queue_set_cranges().
  Warning reported by the kernel test robot <lkp@intel.com>).

Changes from v1:
* Moved libata-scsi hunk from patch 1 to patch 3 where it belongs
* Fixed unintialized variable in patch 2
  Reported-by: kernel test robot <lkp@intel.com>
  Reported-by: Dan Carpenter <dan.carpenter@oracle.com
* Changed patch 3 adding struct ata_cpr_log to contain both the number
  of concurrent ranges and the array of concurrent ranges.
* Added a note in the documentation (patch 4) about the unit used for
  the concurrent ranges attributes.

Damien Le Moal (4):
  block: Add concurrent positioning ranges support
  scsi: sd: add concurrent positioning ranges support
  libata: support concurrent positioning ranges log
  doc: document sysfs queue/cranges attributes

 Documentation/block/queue-sysfs.rst |  30 ++-
 block/Makefile                      |   2 +-
 block/blk-cranges.c                 | 295 ++++++++++++++++++++++++++++
 block/blk-sysfs.c                   |  13 ++
 block/blk.h                         |   3 +
 drivers/ata/libata-core.c           |  52 +++++
 drivers/ata/libata-scsi.c           |  48 ++++-
 drivers/scsi/sd.c                   |  81 ++++++++
 drivers/scsi/sd.h                   |   1 +
 include/linux/ata.h                 |   1 +
 include/linux/blkdev.h              |  29 +++
 include/linux/libata.h              |  15 ++
 12 files changed, 559 insertions(+), 11 deletions(-)
 create mode 100644 block/blk-cranges.c

-- 
2.31.1