[0/3] Make target send correct io limits

Message

Anastasia Kovaleva June 30, 2022, 12:22 p.m. UTC

Currently iblock always reports MAXIMUM TRANSFER LENGTH in 512b units
regardless of the LU block size.

Target block size:
  target:~ # fdisk -l /dev/nullb0
  Disk /dev/nullb0: 250 GiB, 268435456000 bytes, 65536000 sectors
  Units: sectors of 1 * 4096 = 4096 bytes
  Sector size (logical/physical): 4096 bytes / 4096 bytes
  I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Initiator block size:
  initiator:~ # fdisk -l /dev/sdc
  Disk /dev/sdc: 250 GiB, 268435456000 bytes, 65536000 sectors
  Disk model: nullb0
  Units: sectors of 1 * 4096 = 4096 bytes
  Sector size (logical/physical): 4096 bytes / 4096 bytes
  I/O size (minimum/optimal): 4096 bytes / 131072 bytes

target max transfer length limit:
  target:~ # cat /sys/block/nullb0/queue/max_hw_sectors_kb
  128

So the maximum transfer length should be 128 * 1024 / 4096 = 32 blocks
But the target sends MTL in 512b units, so the initiators see 256 blocks
instead.

  initiator:~ # sg_inq -p 0xb0 /dev/sdc
  VPD INQUIRY: Block limits page (SBC)
    Maximum compare and write length: 1 blocks
    Optimal transfer length granularity: 1 blocks
    Maximum transfer length: 256 blocks
    Optimal transfer length: 32 blocks
    Maximum prefetch transfer length: 0 blocks [ignored]

This happens because MAXIMUM TRANSFER LENGTH field in VPD Block Limits
page is derived from dev->dev_attrib.hw_max_sectors which happens to be
in 512b units for iblock. This patch series fixes this issue and removes
some special-casing for other backstores.

Anastasia Kovaleva (3):
  target: core: Send mtl in blocks
  target: core: make hw_max_sectors store the sectors amount in blocks
  target: core: Change the way target_xcopy_do_work sets restiction on
    max io

 drivers/target/target_core_configfs.c |  2 -
 drivers/target/target_core_file.c     |  1 -
 drivers/target/target_core_iblock.c   |  3 +-
 drivers/target/target_core_spc.c      |  7 ++-
 drivers/target/target_core_xcopy.c    | 68 ++++++++++++++-------------
 drivers/target/target_core_xcopy.h    |  2 +-
 include/target/target_core_base.h     |  1 -
 7 files changed, 45 insertions(+), 39 deletions(-)