Re: nvme-tcp: kernel NULL pointer dereference, address: 0000000000000034

[Sagi Grimberg <sagi@grimberg.me>]

> Could you try this patch with your tcp polling queues enabled?
> 
> ---
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 9e5e0277a4d95..12f7ab369f7ba 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -844,30 +844,12 @@ void submit_bio(struct bio *bio)
>   }
>   EXPORT_SYMBOL(submit_bio);
>   
> -/**
> - * bio_poll - poll for BIO completions
> - * @bio: bio to poll for
> - * @iob: batches of IO
> - * @flags: BLK_POLL_* flags that control the behavior
> - *
> - * Poll for completions on queue associated with the bio. Returns number of
> - * completed entries found.
> - *
> - * Note: the caller must either be the context that submitted @bio, or
> - * be in a RCU critical section to prevent freeing of @bio.
> - */
> -int bio_poll(struct bio *bio, struct io_comp_batch *iob, unsigned int flags)
> +static int blk_poll(struct request_queue *q, struct io_comp_batch *iob,
> +		    struct bio *bio, unsigned int flags)
>   {
>   	blk_qc_t cookie = READ_ONCE(bio->bi_cookie);

You need to pass in the cookie as well.
Probably can pass BLK_QC_T_NONE for blk_rq_poll...