[PATCH 1/4] blk-mq: add API of blk_mq_unfreeze_queue_force

[Sagi Grimberg]

>>>> GD_DEAD is only set if the device is really dead, then all pending IO
>>>> will be failed.
>>>
>>> del_gendisk also sets GD_DEAD early on.
>>
>> No.
>>
>> The hang happens in fsync_bdev() of del_gendisk(), and there are IOs pending on
>> bio_queue_enter().
> 
> IFF we know we can't do I/O by the time del_gendisk is called, we
> need to call mark_disk_dead first and not paper over the problem.
> 
> An API that force unfreezes is just broken and will leaves us with
> freezecount mismatches.

I absolutely agree here.