[PATCH 0/5] Recover from persistent UNIT ATTENTION conditions

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

Hi Martin,

Some SCSI targets do not clear a power-on or reset UNIT ATTENTION
condition for all commands. BIWIN BWU2A05* UFS devices, for example,
keep reporting UNIT ATTENTION for WRITE commands while TEST UNIT READY,
READ and SYNCHRONIZE CACHE clear the condition. Today such WRITE
commands are retried until the command runtime limit is exceeded. A
quirk has been proposed for these devices [1]. This patch series instead
makes the SCSI core recover from persistent UNIT ATTENTION conditions,
so that no per-device quirk list has to be maintained:
- Patches 1 and 2 prepare the SCSI error handler for the changes in
  the later patches.
- Patch 3 makes the SCSI error handler send TEST UNIT READY to clear
  UNIT ATTENTION conditions before it falls back to resetting the
  device.
- Patch 4 makes scsi_decide_disposition() invoke the error handler if
  a command receives the same UNIT ATTENTION repeatedly. The behavior
  of the exported scsi_check_sense() function, used by libata, is not
  changed.
- Patch 5 limits the number of retries in scsi_io_completion_action()
  of commands that keep receiving UNIT ATTENTION.

Please consider this patch series for the next merge window.

[1] https://lore.kernel.org/linux-scsi/20261028-biwin-tua-quirk-v1-1-767a12c9b9cc@flipper.net/

Thanks,

Bart.

Bart Van Assche (5):
  scsi: core: Introduce scsi_cmd_needs_stu()
  scsi: core: Simplify scsi_eh_ready_devs()
  scsi: core: Clear UNIT ATTENTION conditions with TEST UNIT READY
  scsi: core: Escalate persistent UNIT ATTENTION conditions
  scsi: core: Limit retries of commands that receive UNIT ATTENTION

 drivers/scsi/scsi_error.c | 255 +++++++++++++++++++++++++++++++++++---
 drivers/scsi/scsi_lib.c   |   5 +
 include/scsi/scsi_cmnd.h  |   7 ++
 3 files changed, 249 insertions(+), 18 deletions(-)