Re: [PATCH] scsi: ufs: mark HPB support as BROKEN

Jens Axboe
2021-10-26T17:25:38Z

On 10/26/21 11:19 AM, James Bottomley wrote:
> On Tue, 2021-10-26 at 09:36 -0700, Bart Van Assche wrote:
>> On 10/26/21 12:12 AM, Christoph Hellwig wrote:
>>> The HPB support added this merge window is fundanetally flawed as
>>> it
>> ^^^^^^^^^^^^
>> fundanetally ->
>> fundamentally
>>
>> Since the implementation can be reworked not to use
>> blk_insert_cloned_request() I'm not sure using the word
>> "fundamentally" is appropriate.
>
> I'm not so sure about that. The READ BUFFER implementation runs from a
> work queue and looks fine. The WRITE BUFFER implementation is trying
> to spawn a second command to precede the queued command which is a
> fundamental problem for the block API. It's not clear to me that the
> WRITE BUFFER can be fixed because of the tying to the sent command ...
> but like I said, the standard is proprietary so I can't look at it to
> see if there are alternative ways of achieving the same effect.

Is there a model in which this can actually work? If not, or if we
aren't sure, I think we'd be better off just reverting the parts
involved with that block layer misuse. Simply marking it broken is a
half measure that doesn't really solve anything (except send a message).

IMHO, it should be reverted and the clone usage we currently export be
moved into dm for now. That'll prevent further abuse of this in the
future.

--
Jens Axboe