Re: [PATCH] block: tolerate 0 byte discard_granularity in __blkdev_issue_discard()

[Johannes Thumshirn]

On 04/08/2020 16:34, Coly Li wrote:
> On 2020/8/4 22:31, Johannes Thumshirn wrote:
>> On 04/08/2020 16:23, Coly Li wrote:
>>> This is the procedure to reproduce the panic,
>>>   # modprobe scsi_debug delay=0 dev_size_mb=2048 max_queue=1
>>>   # losetup -f /dev/nvme0n1 --direct-io=on
>>>   # blkdiscard /dev/loop0 -o 0 -l 0x200
>>
>> losetup -f /dev/sdX isn't it?
>>
> 
> In my case, I use a NVMe SSD as the backing device of the loop device.
> Because I don't have a scsi lun.
> 
> And loading scsi_debug module seems necessary, otherwise the discard
> process just hang and I cannot see the kernel panic (I don't know why yet).

OK, now that's highly interesting. Does it also happen if you back loop with
a file? loop_config_discard() has different cases for the different backing devices/files. S