RE: [PATCH] [v2] nvme: use correct upper limit for tag in nvme_handle_cqe()

From: Tianxianting
Date: Fri Sep 18 2020 - 23:16:06 EST

Hi Keith,
Thanks a lot for your comments,
I will try to figure out a safe fix for this issue, then for you review:)

-----Original Message-----
From: Keith Busch [mailto:kbusch@xxxxxxxxxx]
Sent: Saturday, September 19, 2020 3:21 AM
To: tianxianting (RD) <tian.xianting@xxxxxxx>
Cc: axboe@xxxxxx; hch@xxxxxx; sagi@xxxxxxxxxxx; linux-nvme@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
Subject: Re: [PATCH] [v2] nvme: use correct upper limit for tag in nvme_handle_cqe()

On Fri, Sep 18, 2020 at 06:44:20PM +0800, Xianting Tian wrote:
> @@ -940,7 +940,9 @@ static inline void nvme_handle_cqe(struct nvme_queue *nvmeq, u16 idx)
> struct nvme_completion *cqe = &nvmeq->cqes[idx];
> struct request *req;
> - if (unlikely(cqe->command_id >= nvmeq->q_depth)) {
> + if (unlikely(cqe->command_id >=
> + nvmeq->qid ? nvmeq->dev->tagset.queue_depth :
> + nvmeq->dev->admin_tagset.queue_depth)) {

Both of these values are set before blk_mq_alloc_tag_set(), so you still have a race. The interrupt handler probably just shouldn't be registered with the queue before the tagset is initialized since there can't be any work for the handler to do before that happens anyway.

The controller is definitely broken, though, and will lead to unavoidable corruption if it's really behaving this way.