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

Anastasia Kovaleva
2022-10-14T11:46:17Z

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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(-)

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2.30.2