[PATCH v14 00/19] Improve write performance for zoned UFS devices​

Bart Van Assche
2023-10-23T21:56:49Z

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 the block layer patches of this series for the next merge window.

Thank you,

Bart.

Changes compared to v13:
- Reworked patch "block: Preserve the order of requeued zoned writes".
- Addressed a performance concern by removing the eh_needs_prepare_resubmit
SCSI driver callback and by introducing the SCSI host template flag
.needs_prepare_resubmit instead.
- Added a patch that adds a 'host' argument to scsi_eh_flush_done_q().
- Made the code in unit tests less repetitive.

Changes compared to v12:
- Added two new patches: "block: Preserve the order of requeued zoned writes"
and "scsi: sd: Add a unit test for sd_cmp_sector()"
- Restricted the number of zoned write retries. To my surprise I had to add
"&& scmd->retries <= scmd->allowed" in the SCSI error handler to limit the
number of retries.
- In patch "scsi: ufs: Inform the block layer about write ordering", only set
ELEVATOR_F_ZBD_SEQ_WRITE for zoned block devices.

Changes compared to v11:
- Fixed a NULL pointer dereference that happened when booting from an ATA
device by adding an scmd->device != NULL check in scsi_needs_preparation().
- Updated Reviewed-by tags.

Changes compared to v10:
- Dropped the UFS MediaTek and HiSilicon patches because these are not correct
and because it is safe to drop these patches.
- Updated Acked-by / Reviewed-by tags.

Changes compared to v9:
- Introduced an additional scsi_driver callback: .eh_needs_prepare_resubmit().
- Renamed the scsi_debug kernel module parameter 'no_zone_write_lock' into
'preserves_write_order'.
- Fixed an out-of-bounds access in the unit scsi_call_prepare_resubmit() unit
test.
- Wrapped ufshcd_auto_hibern8_update() calls in UFS host drivers with
WARN_ON_ONCE() such that a kernel stack appears in case an error code is
returned.
- Elaborated a comment in the UFSHCI driver.

Changes compared to v8:
- Fixed handling of 'driver_preserves_write_order' and 'use_zone_write_lock'
in blk_stack_limits().
- Added a comment in disk_set_zoned().
- Modified blk_req_needs_zone_write_lock() such that it returns false if
q->limits.use_zone_write_lock is false.
- Modified disk_clear_zone_settings() such that it clears
q->limits.use_zone_write_lock.
- Left out one change from the mq-deadline patch that became superfluous due to
the blk_req_needs_zone_write_lock() change.
- Modified scsi_call_prepare_resubmit() such that it only calls list_sort() if
zoned writes have to be resubmitted for which zone write locking is disabled.
- Added an additional unit test for scsi_call_prepare_resubmit().
- Modified the sorting code in the sd driver such that only those SCSI commands
are sorted for which write locking is disabled.
- Modified sd_zbc.c such that ELEVATOR_F_ZBD_SEQ_WRITE is only set if the
write order is not preserved.
- Included three patches for UFS host drivers that rework code that wrote
directly to the auto-hibernation controller register.
- Modified the UFS driver such that enabling auto-hibernation is not allowed
if a zoned logical unit is present and if the controller operates in legacy
mode.
- Also in the UFS driver, simplified ufshcd_auto_hibern8_update().

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 (19):
block: Introduce more member variables related to zone write locking
block: Only use write locking if necessary
block: Preserve the order of requeued zoned writes
block/mq-deadline: Only use zone locking if necessary
scsi: Add an argument to scsi_eh_flush_done_q()
scsi: core: Introduce a mechanism for reordering requests in the error
handler
scsi: core: Add unit tests for scsi_call_prepare_resubmit()
scsi: sd: Sort commands by LBA before resubmitting
scsi: sd: Add a unit test for sd_cmp_sector()
scsi: core: Retry unaligned zoned writes
scsi: sd_zbc: Only require an I/O scheduler if needed
scsi: scsi_debug: Add the preserves_write_order module parameter
scsi: scsi_debug: Support injecting unaligned write errors
scsi: ufs: hisi: Rework the code that disables auto-hibernation
scsi: ufs: Rename ufshcd_auto_hibern8_enable() and make it static
scsi: ufs: Change the return type of ufshcd_auto_hibern8_update()
scsi: ufs: Simplify ufshcd_auto_hibern8_update()
scsi: ufs: Forbid auto-hibernation without I/O scheduler
scsi: ufs: Inform the block layer about write ordering

block/blk-mq.c | 6 +-
block/blk-settings.c | 15 ++
block/blk-zoned.c | 10 +-
block/mq-deadline.c | 11 +-
drivers/ata/libata-eh.c | 2 +-
drivers/scsi/Kconfig | 2 +
drivers/scsi/Kconfig.kunit | 9 ++
drivers/scsi/Makefile | 2 +
drivers/scsi/Makefile.kunit | 2 +
drivers/scsi/libsas/sas_scsi_host.c | 2 +-
drivers/scsi/scsi_debug.c | 21 ++-
drivers/scsi/scsi_error.c | 75 ++++++++-
drivers/scsi/scsi_error_test.c | 227 ++++++++++++++++++++++++++++
drivers/scsi/scsi_lib.c | 1 +
drivers/scsi/scsi_priv.h | 2 +
drivers/scsi/sd.c | 43 ++++++
drivers/scsi/sd.h | 2 +
drivers/scsi/sd_test.c | 86 +++++++++++
drivers/scsi/sd_zbc.c | 4 +-
drivers/ufs/core/ufs-sysfs.c | 2 +-
drivers/ufs/core/ufshcd-priv.h | 1 -
drivers/ufs/core/ufshcd.c | 119 ++++++++++++---
drivers/ufs/host/ufs-hisi.c | 5 +-
include/linux/blkdev.h | 10 ++
include/scsi/scsi.h | 1 +
include/scsi/scsi_driver.h | 1 +
include/scsi/scsi_eh.h | 3 +-
include/scsi/scsi_host.h | 6 +
include/ufs/ufshcd.h | 3 +-
29 files changed, 627 insertions(+), 46 deletions(-)
create mode 100644 drivers/scsi/Kconfig.kunit
create mode 100644 drivers/scsi/Makefile.kunit
create mode 100644 drivers/scsi/scsi_error_test.c
create mode 100644 drivers/scsi/sd_test.c