[v4,0/7] Improve libata support for FUA

Message

Damien Le Moal Oct. 31, 2022, 2:26 a.m. UTC

(Resending with updated cover letter)

These patches cleanup and improve libata support for the FUA feature of
ATA devices.

The first patch modifies the block layer to prevent the use of REQ_FUA
with read requests. This is necessary as FUA is not supported with ATA
devices when NCQ is not enabled (device queue depth set to 1) and that
unlike for write requests, the flush machinery cannot enforce access to
the media for FUA read commands.

Patch 2 and 3 are libata cleanup preparatory patches. Patch 4 cleans up
the detection for FUA support. Patch 5 fixes building a taskfile for FUA
write requests. Patch 6 prevents the use of FUA with known bad drives.

Finally, patch 7 enables FUA support by default in libata.

Changes from v3:
- Added patch 1 to prevent any block device user from issuing a
  REQ_FUA read.
- Changed patch 5 to remove the check for REQ_FUA read and also remove 
  support for ATA_CMD_WRITE_MULTI_FUA_EXT as this command is obsolete
  in recent ACS specifications.

Changes from v2:
 - Added patch 1 and 2 as preparatory patches
 - Added patch 4 to fix FUA writes handling for the non-ncq case. Note
   that it is possible that the drives blacklisted in patch 5 are
   actually OK since the code back in 2012 had the issue with the wrong
   use of LBA 28 commands for FUA writes.

Changes from v1:
 - Removed Maciej's patch 2. Instead, blacklist drives which are known
   to have a buggy FUA support.

Damien Le Moal (7):
  block: Prevent the use of REQ_FUA with read operations
  ata: libata: Introduce ata_ncq_supported()
  ata: libata: Rename and cleanup ata_rwcmd_protocol()
  ata: libata: cleanup fua support detection
  ata: libata: Fix FUA handling in ata_build_rw_tf()
  ata: libata: blacklist FUA support for known buggy drives
  ata: libata: Enable fua support by default

 .../admin-guide/kernel-parameters.txt         |  3 +
 block/blk-flush.c                             | 12 +++
 drivers/ata/libata-core.c                     | 77 ++++++++++++++-----
 drivers/ata/libata-scsi.c                     | 30 +-------
 include/linux/libata.h                        | 34 +++++---
 5 files changed, 100 insertions(+), 56 deletions(-)