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

[Ming Lei]

On Fri, Jun 16, 2023 at 07:48:00AM +0200, Christoph Hellwig wrote:
> On Thu, Jun 15, 2023 at 11:43:51PM +0800, Ming Lei wrote:
> > On Thu, Jun 15, 2023 at 09:16:27AM -0600, Keith Busch wrote:
> > > On Thu, Jun 15, 2023 at 10:32:33PM +0800, Ming Lei wrote:
> > > > NVMe calls freeze/unfreeze in different contexts, and controller removal
> > > > may break in-progress error recovery, then leave queues in frozen state.
> > > > So cause IO hang in del_gendisk() because pending writeback IOs are
> > > > still waited in bio_queue_enter().
> > > 
> > > Shouldn't those writebacks be unblocked by the existing check in
> > > bio_queue_enter, test_bit(GD_DEAD, &disk->state))? Or are we missing a
> > > disk state update or wakeup on this condition?
> > 
> > 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().

Thanks,
Ming