BUG at IP: blk_mq_get_request+0x23e/0x390 on 4.16.0-rc7

[Sagi Grimberg]

>> diff --git a/block/blk-mq.c b/block/blk-mq.c
>> index 75336848f7a7..81ced3096433 100644
>> --- a/block/blk-mq.c
>> +++ b/block/blk-mq.c
>> @@ -444,6 +444,10 @@ struct request *blk_mq_alloc_request_hctx(struct
>> request_queue *q,
>>                  return ERR_PTR(-EXDEV);
>>          }
>>          cpu = cpumask_first_and(alloc_data.hctx->cpumask, cpu_online_mask);
>> +       if (cpu >= nr_cpu_ids) {
>> +               pr_warn("no online cpu for hctx %d\n", hctx_idx);
>> +               cpu = cpumask_first(alloc_data.hctx->cpumask);
>> +       }
> 
> We may do this way for the special case, but it is ugly, IMO.

Christoph?