[dm-devel] block: Fix a WRITE SAME BUG_ON

[zhangxiaoxu (A)]

Any progress about the problme?
Should we disable the write same when stack the different LBA disks?

On 2/2/2019 12:18 AM, Christoph Hellwig wrote:
> On Fri, Feb 01, 2019 at 05:03:40PM +0100, Heinz Mauelshagen wrote:
>> On 2/1/19 3:09 PM, John Dorminy wrote:
>>> I didn't know such a thing existed... does it work on any block
>>> device? Where do I read more about this?
>>
>>
>> Use sg_write_same(8) from package sg3_utils.
>>
>> For instance 'sg_write_same --in=foobarfile --lba=0 --num=20000
>> --xferlen=512 /dev/sdwhatever'
>>
>> will read the pattern to write same from file 'foobarfile' with length
>> explicitely set to 512 bytes
>> (rather than derived from foobarfile's size) and write it 20000 times
>> starting at LBA 0 to /dev/sdwhatever.
> 
> Yeah.  Note that this will only work on SCSI disks (and maybe ATA
> for a very specific corner case).  But for actual devices and not
> remappers the same is true of REQ_OP_WRITE_SAME.
> 
> .
>