Re: [PATCH V2 7/8] nvme: use blk_mq_queue_tag_inflight_iter

["jianchao.wang" <jianchao.w.wang@oracle.com>]

Hi Keith

On 3/27/19 10:33 AM, Keith Busch wrote:
> On Wed, Mar 27, 2019 at 10:27:57AM +0800, jianchao.wang wrote:
>> As the comment above, the stable request maybe something that has been freed due to following case,
>> 1. a hctx->fq.flush_rq of dead request_queue that shares the same tagset
>> 2. a removed io scheduler's sched request
>> and this freed request could be allocated by others which may change the field of request->state.
> 
> You're not explaing how that request->state is changed. I understand the
> request can be reallocated, but what is changing its state?
> 

Sorry for my bad description, and lead to the misunderstand.
The _free_ below means,

1. a hctx->fq.flush_rq of dead request_queue that shares the same tagset
   The whole request_queue is cleaned up and freed, so the hctx->fq.flush is freed back to a slab

2. a removed io scheduler's sched request
   The io scheduled is detached and all of the structures are freed, including the pages where sched
   requests locates.

So the pointers in tags->rqs[] may point to memory that is not used as a blk layer request.


Thanks
Jianchao