On Tue, Jan 25, 2022 at 04:54:43PM +0800, Ming Lei wrote: > > So what is the advantage of trying to remove the freeze from where > > it belongs (common unregister code) while keeping it where it is a bandaid > > (driver specific unregister code)? > > freeze in common unregister code is actually not good, because it provide > nothing for bio based driver, so we can't move blk-cgroup shutdown into > del_gendisk. Also we can't move elevator shutdown to del_gendisk for > similar reason. > > Secondly freeze is pretty slow in percpu mode, so why slow down removing every > disk just for scsi's bandaid? I'd frame this differently: - del_gendisk is the right place to freeze the queue, as that is where the gendisk is unregistered and all fs I/O needs to stop. If we don't get all aspects right we need to fix. As mentioned I'm already looking into keeping a reference for the bio life time for bio based drivers. - SCSI is the only driver that ever submits passthrough I/O without the gendisk. So doing an additional freeze during request_queue teardown is only needed for SCSI and we can eventually remove that for everyone else. And most of your series already does really good work towards that goal! > > > Thanks, > Ming ---end quoted text---
