On 2022/9/19 20:39, Ming Lei wrote: > On Mon, Sep 19, 2022 at 05:12:21PM +0800, Ziyang Zhang wrote: >> On 2022/9/19 11:55, Ming Lei wrote: >>> On Tue, Sep 13, 2022 at 12:17:04PM +0800, ZiyangZhang wrote: >>>> With recovery feature enabled, in ublk_queue_rq or task work >>>> (in exit_task_work or fallback wq), we requeue rqs instead of >>>> ending(aborting) them. Besides, No matter recovery feature is enabled >>>> or disabled, we schedule monitor_work immediately. >>>> >>>> Signed-off-by: ZiyangZhang <ZiyangZhang@xxxxxxxxxxxxxxxxx> >>>> --- >>>> drivers/block/ublk_drv.c | 34 ++++++++++++++++++++++++++++++++-- >>>> 1 file changed, 32 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c >>>> index 23337bd7c105..b067f33a1913 100644 >>>> --- a/drivers/block/ublk_drv.c >>>> +++ b/drivers/block/ublk_drv.c >>>> @@ -682,6 +682,21 @@ static void ubq_complete_io_cmd(struct ublk_io *io, int res) >>>> >>>> #define UBLK_REQUEUE_DELAY_MS 3 >>>> >>>> +static inline void __ublk_abort_rq_in_task_work(struct ublk_queue *ubq, >>>> + struct request *rq) >>>> +{ >>>> + pr_devel("%s: %s q_id %d tag %d io_flags %x.\n", __func__, >>>> + (ublk_queue_can_use_recovery(ubq)) ? "requeue" : "abort", >>>> + ubq->q_id, rq->tag, ubq->ios[rq->tag].flags); >>>> + /* We cannot process this rq so just requeue it. */ >>>> + if (ublk_queue_can_use_recovery(ubq)) { >>>> + blk_mq_requeue_request(rq, false); >>>> + blk_mq_delay_kick_requeue_list(rq->q, UBLK_REQUEUE_DELAY_MS); >>> >>> Here you needn't to kick requeue list since we know it can't make >>> progress. And you can do that once before deleting gendisk >>> or the queue is recovered. >> >> No, kicking rq here is necessary. >> >> Consider USER_RECOVERY is enabled and everything goes well. >> User sends STOP_DEV, and we have kicked requeue list in >> ublk_stop_dev() and are going to call del_gendisk(). >> However, a crash happens now. Then rqs may be still requeued >> by ublk_queue_rq() because ublk_queue_rq() sees a dying >> ubq_daemon. So del_gendisk() will hang because there are >> rqs leaving in requeue list and no one kicks them. > > Why can't you kick requeue list before calling del_gendisk(). Yes, we can kick requeue list once before calling del_gendisk(). But a crash may happen just after kicking but before del_gendisk(). So some rqs may be requeued at this moment. But we have already kicked the requeue list! Then del_gendisk() will hang, right? > >> >> BTW, kicking requeue list after requeue rqs is really harmless >> since we schedule quiesce_work immediately after finding a >> dying ubq_daemon. So few rqs have chance to be re-dispatched. > > Do you think it makes sense to kick requeue list when the queue > can't handle any request? I know it does not make sense while ubq_daemon is dying, but it is good for handling the situation I discribed before. Regards, Zhang.