On Fri, Oct 04, 2024 at 01:21:27PM +0900, Sergey Senozhatsky wrote:
> Dunno. Is something like this completely silly?
__blk_mark_disk_dead got moved into the lock by: 7e04da2dc701
("block: fix deadlock between sd_remove & sd_release"), which has a trace
that looks very similar to the one your reported.
And that commit also points out something I missed - we do not set
QUEUE_FLAG_DYING here because the gendisk does not own the queue for
SCSI. Because of that allocating the request in sd/sr will not fail, and
it will deadlock.
So I think the short term fix is to also fail passthrough request here -
either by clearing and resurrecting QUEUE_FLAG_DYING or by also checking
q->disk for GD_DEAD if it exists. Both of these are a bit ugly because
they will fail passthrough through /dev/sg during the removal which is
unexpected (although probably not happening for usual workloads).
The proper fix would be to split the freezing mechanism for file system
vs passthrough I/O, but that's going to be a huge change.
