On Jan 06, 2025 / 14:47, Damien Le Moal wrote:

On 12/25/24 7:09 PM, Shin'ichiro Kawasaki wrote:

quoted

The current null_blk implementation checks if any bad blocks exist in
the target blocks of each IO. If so, the IO fails and data is not
transferred for all of the IO target blocks. However, when real storage
devices have bad blocks, the devices may transfer data partially up to
the first bad blocks. Especially, when the IO is a write operation, such
partial IO leaves partially written data on the device.

To simulate such partial IO using null_blk, perform the data transfer
from the IO start block to the block just before the first bad block.
Introduce __null_handle_rq() to support partial data transfer. Modify
null_handle_badblocks() to calculate the size of the partial data
transfer and call __null_handle_rq().

We should have an option to control this behavior to be able to mimic actual
devices. E.g. SAS devices may do partial data transfers before hitting a bad
block, but ATA devices will not (it is always all or nothing with ATA). The
current default corresponds to an ATA drive behavior and this change allows
emulating a SAS drive behavior. So let's control this with an option.

Thanks. Will do so in v3.