Re: [PATCH] scsi: ufs: Fix proper API to send HPB pre-request

[Bart Van Assche]

On 10/28/21 8:27 AM, Christoph Hellwig wrote:
> On Thu, Oct 28, 2021 at 10:28:01AM -0400, James Bottomley wrote:
> > If the block people are happy with this, then I'm OK with it, but it
> > doesn't look like you've solved the fanout deadlock problem because
> > this new mechanism is still going to allocate a new tag.
>
> Yes, same problem as before.

Hi Christoph,

I spent some time looking around for other examples of allocating and
inserting a request from inside block layer callbacks. I only found one
such example, namely in the NVMe core. nvme_timeout() calls
nvme_alloc_request() and blk_execute_rq_nowait(). The difference between
what the UFS HPB code is doing and what nvme_timeout() does doesn't seem
that big to me. For clarity, I don't like the UFS HPB protocol nor how
support for that protocol has been implemented. However, I don't see how
the UFS HPB implementation would complicate maintenance of the block
layer core. Am I perhaps missing something?

Thanks,

Bart.