Re: [PATCH 04/11] blk-mq: Facilitate a shared sbitmap per tagset

[John Garry <john.garry@huawei.com>]

On 03/12/2019 15:02, Hannes Reinecke wrote:
>>> +     */
>> If you don't have a shared sched bitmap - which I didn't think we needed
>> - then all we need is a simple sbitmap_queue_resize(&tagset->__bitmap_tags)
>>
>> Otherwise it's horrible to resize shared sched bitmaps...
>>
> Resizing shared sched bitmaps is done in patch 6/11.
> General idea is to move the scheduler bitmap into the request queue
> (well, actually the elevator), as this gives us a per-request_queue
> bitmap. Which is actually what we want here, as the scheduler will need
> to look at all requests, hence needing to access to the same bitmap.
> And it also gives us an easy way of resizing the sched tag bitmap, as
> then we can resize the bitmap on a per-queue basis, and leave the
> underlying tagset bitmap untouched.

OK, but I am just concerned if that is really required in this series 
and whether it is just another obstacle to getting it accepted.

Thanks,
John

> 
> [ .. ]
>>> diff --git a/block/blk-mq.h b/block/blk-mq.h
>>> index 78d38b5f2793..4c1ea206d3f4 100644
>>> --- a/block/blk-mq.h
>>> +++ b/block/blk-mq.h