[PATCH v8 0/9] Improve performance for zoned UFS devices

[Bart Van Assche <bvanassche@acm.org>]

Hi Jens,

This patch series improves small write IOPS by a factor of four (+300%) for
zoned UFS devices on my test setup with an UFSHCI 3.0 controller. Please
consider this patch series for the next merge window.

Thank you,

Bart.

Changes compared to v7:
 - Split the queue_limits member variable `use_zone_write_lock' into two member
   variables: `use_zone_write_lock' (set by disk_set_zoned()) and
   `driver_preserves_write_order' (set by the block driver or SCSI LLD). This
   should clear up the confusion about the purpose of this variable.
 - Moved the code for sorting SCSI commands by LBA from the SCSI error handler
   into the SCSI disk (sd) driver as requested by Christoph.
   
Changes compared to v6:
 - Removed QUEUE_FLAG_NO_ZONE_WRITE_LOCK and instead introduced a flag in
   the request queue limits data structure.

Changes compared to v5:
 - Renamed scsi_cmp_lba() into scsi_cmp_sector().
 - Improved several source code comments.

Changes compared to v4:
 - Dropped the patch that introduces the REQ_NO_ZONE_WRITE_LOCK flag.
 - Dropped the null_blk patch and added two scsi_debug patches instead.
 - Dropped the f2fs patch.
 - Split the patch for the UFS driver into two patches.
 - Modified several patch descriptions and source code comments.
 - Renamed dd_use_write_locking() into dd_use_zone_write_locking().
 - Moved the list_sort() call from scsi_unjam_host() into scsi_eh_flush_done_q()
   such that sorting happens just before reinserting.
 - Removed the scsi_cmd_retry_allowed() call from scsi_check_sense() to make
   sure that the retry counter is adjusted once per retry instead of twice.

Changes compared to v3:
 - Restored the patch that introduces QUEUE_FLAG_NO_ZONE_WRITE_LOCK. That patch
   had accidentally been left out from v2.
 - In patch "block: Introduce the flag REQ_NO_ZONE_WRITE_LOCK", improved the
   patch description and added the function blk_no_zone_write_lock().
 - In patch "block/mq-deadline: Only use zone locking if necessary", moved the
   blk_queue_is_zoned() call into dd_use_write_locking().
 - In patch "fs/f2fs: Disable zone write locking", set REQ_NO_ZONE_WRITE_LOCK
   from inside __bio_alloc() instead of in f2fs_submit_write_bio().

Changes compared to v2:
 - Renamed the request queue flag for disabling zone write locking.
 - Introduced a new request flag for disabling zone write locking.
 - Modified the mq-deadline scheduler such that zone write locking is only
   disabled if both flags are set.
 - Added an F2FS patch that sets the request flag for disabling zone write
   locking.
 - Only disable zone write locking in the UFS driver if auto-hibernation is
   disabled.

Changes compared to v1:
 - Left out the patches that are already upstream.
 - Switched the approach in patch "scsi: Retry unaligned zoned writes" from
   retrying immediately to sending unaligned write commands to the SCSI error
   handler.

Bart Van Assche (9):
  block: Introduce more member variables related to zone write locking
  block/mq-deadline: Only use zone locking if necessary
  scsi: core: Call .eh_prepare_resubmit() before resubmitting
  scsi: sd: Sort commands by LBA before resubmitting
  scsi: core: Retry unaligned zoned writes
  scsi: scsi_debug: Support disabling zone write locking
  scsi: scsi_debug: Support injecting unaligned write errors
  scsi: ufs: Split an if-condition
  scsi: ufs: Inform the block layer about write ordering

 block/blk-settings.c           |  7 +++
 block/mq-deadline.c            | 14 +++---
 drivers/scsi/Kconfig           |  2 +
 drivers/scsi/Kconfig.kunit     |  4 ++
 drivers/scsi/Makefile          |  2 +
 drivers/scsi/Makefile.kunit    |  1 +
 drivers/scsi/scsi_debug.c      | 20 +++++++-
 drivers/scsi/scsi_error.c      | 59 ++++++++++++++++++++++
 drivers/scsi/scsi_error_test.c | 92 ++++++++++++++++++++++++++++++++++
 drivers/scsi/scsi_lib.c        |  1 +
 drivers/scsi/scsi_priv.h       |  1 +
 drivers/scsi/sd.c              | 25 +++++++++
 drivers/ufs/core/ufshcd.c      | 40 +++++++++++++--
 include/linux/blkdev.h         | 10 ++++
 include/scsi/scsi.h            |  1 +
 include/scsi/scsi_driver.h     |  1 +
 16 files changed, 270 insertions(+), 10 deletions(-)
 create mode 100644 drivers/scsi/Kconfig.kunit
 create mode 100644 drivers/scsi/Makefile.kunit
 create mode 100644 drivers/scsi/scsi_error_test.c