Re: [PATCH] nvme: fix handling single range discard request

Chaitanya Kulkarni
2023-03-08T05:36:16Z

>>> Was referring to this:
>>> --
>>> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
>>> index 3345f866178e..dbc402587431 100644
>>> --- a/drivers/nvme/host/core.c
>>> +++ b/drivers/nvme/host/core.c
>>> @@ -781,6 +781,7 @@ static blk_status_t nvme_setup_discard(struct
>>> nvme_ns
>>> *ns, struct request *req,
>>>                  range = page_address(ns->ctrl->discard_page);
>>>          }
>>>
>>> +       segments = min(segments, queue_max_discard_segments(req->q));
>>
>> That can't work.
>>
>> In case of queue_max_discard_segments(req->q) == 1, the request still
>> can have more than one bios since the normal merge is taken for discard
>> IOs.
>
> Ah, I see, the bios are contiguous though right?
> We could add a contiguity check in the loop and conditionally
> increment n, but maybe that would probably be more complicated...

It will be great if we can avoid above mentioned complicated pattern...

-ck