[v2,0/3] Make target send correct io limits

Message

Anastasia Kovaleva Oct. 14, 2022, noon 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.

The last time this patch set was sent, a kernel bot found some issues
with building a kernel for i586 and m68k using a cross-compiler. I tried
to reproduce this issues locally but didn't succeed. Even with given
configs all things are built correctly without errors. For m68k I used
m68k-linux-gnu-gcc version 11.2.0, for i586 I used
i586-unknown-linux-gnu-gcc version 8.3.0. It would be great if you could
share the kernel bot's cross-compilers.

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   |  4 +-
 drivers/target/target_core_spc.c      |  6 +-
 drivers/target/target_core_xcopy.c    | 96 ++++++++++++++-------------
 drivers/target/target_core_xcopy.h    |  2 +-
 include/target/target_core_base.h     |  1 -
 7 files changed, 59 insertions(+), 53 deletions(-)