On Wed, Jul 20, 2022 at 03:08:45PM +0200, Christoph Hellwig wrote: > On Wed, Jul 20, 2022 at 06:23:22PM +0800, Ming Lei wrote: > > Even though alloc_disk and add_disk is paired here, GD_OWNS_QUEUE still > > can't be set because request queue has to be workable for the new alloc/ > > added disk, just like scsi. > > How so? dm has totally normall disk/request_queue lifetimes. The only > caveat is that the blk-mq bits of the queue are added after the initial > non-mq disk allocation. There is no newly added disk after the disk > and queue are torn down. I meant that request queue is supposed to be low level stuff for implementing disk function, and request queue hasn't to be released and re-allocated after each disk whole lifetime(alloc disk, add disk, del_gendisk, release disk). IMO, the limit is just from GD_OWNS_QUEUE which moves releasing some queue resource into del_gendisk or disk release(as the fixes you posted), and this way is fragile, frankly speaking. In theory, allocating queue and releasing queue should be completely symmetrical, but GD_OWNS_QUEUE does change this way. And GD_OWNS_QUEUE can't be set for SCSI, so the two modes have to be supported by block layer. Thanks, Ming
