| Message ID | 20211214133103.551813-1-qiulaibin@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3,-next] block/wbt: fix negative inflight counter when remove scsi device | expand |
Looks good,
Reviewed-by: Christoph Hellwig <hch@lst.de>
On Tue, Dec 14, 2021 at 09:31:03PM +0800, Laibin Qiu wrote: > Now that we disable wbt by set WBT_STATE_OFF_DEFAULT in > wbt_disable_default() when switch elevator to bfq. And when > we remove scsi device, wbt will be enabled by wbt_enable_default. > If it become false positive between wbt_wait() and wbt_track() > when submit write request. > > The following is the scenario that triggered the problem. > > T1 T2 T3 > elevator_switch_mq > bfq_init_queue > wbt_disable_default <= Set > rwb->enable_state (OFF) > Submit_bio > blk_mq_make_request > rq_qos_throttle > <= rwb->enable_state (OFF) > scsi_remove_device > sd_remove > del_gendisk > blk_unregister_queue > elv_unregister_queue > wbt_enable_default > <= Set rwb->enable_state (ON) > q_qos_track > <= rwb->enable_state (ON) > ^^^^^^ this request will mark WBT_TRACKED without inflight add and will > lead to drop rqw->inflight to -1 in wbt_done() which will trigger IO hung. > > Fix this by move wbt_enable_default() from elv_unregister to > bfq_exit_queue(). Only re-enable wbt when bfq exit. > Fixes: 76a8040817b4b ("blk-wbt: make sure throttle is enabled properly") > Signed-off-by: Laibin Qiu <qiulaibin@huawei.com> > --- > block/bfq-iosched.c | 4 ++++ > block/elevator.c | 2 -- > 2 files changed, 4 insertions(+), 2 deletions(-) > > diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c > index 0c612a911696..8b7524450835 100644 > --- a/block/bfq-iosched.c > +++ b/block/bfq-iosched.c > @@ -6996,6 +6996,7 @@ static void bfq_exit_queue(struct elevator_queue *e) > { > struct bfq_data *bfqd = e->elevator_data; > struct bfq_queue *bfqq, *n; > + struct request_queue *q = bfqd->queue; > > hrtimer_cancel(&bfqd->idle_slice_timer); > > @@ -7019,6 +7020,9 @@ static void bfq_exit_queue(struct elevator_queue *e) > #endif > > kfree(bfqd); > + > + /* Re-enable throttling in case elevator disabled it */ Of course, bfq has disabled it, so the above comment is useless, otherwise looks fine: Reviewed-by: Ming Lei <ming.lei@rehdat.com> Thanks, Ming
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c index 0c612a911696..8b7524450835 100644 --- a/block/bfq-iosched.c +++ b/block/bfq-iosched.c @@ -6996,6 +6996,7 @@ static void bfq_exit_queue(struct elevator_queue *e) { struct bfq_data *bfqd = e->elevator_data; struct bfq_queue *bfqq, *n; + struct request_queue *q = bfqd->queue; hrtimer_cancel(&bfqd->idle_slice_timer); @@ -7019,6 +7020,9 @@ static void bfq_exit_queue(struct elevator_queue *e) #endif kfree(bfqd); + + /* Re-enable throttling in case elevator disabled it */ + wbt_enable_default(q); } static void bfq_init_root_group(struct bfq_group *root_group, diff --git a/block/elevator.c b/block/elevator.c index ec98aed39c4f..482df2a350fc 100644 --- a/block/elevator.c +++ b/block/elevator.c @@ -525,8 +525,6 @@ void elv_unregister_queue(struct request_queue *q) kobject_del(&e->kobj); e->registered = 0; - /* Re-enable throttling in case elevator disabled it */ - wbt_enable_default(q); } }
Now that we disable wbt by set WBT_STATE_OFF_DEFAULT in wbt_disable_default() when switch elevator to bfq. And when we remove scsi device, wbt will be enabled by wbt_enable_default. If it become false positive between wbt_wait() and wbt_track() when submit write request. The following is the scenario that triggered the problem. T1 T2 T3 elevator_switch_mq bfq_init_queue wbt_disable_default <= Set rwb->enable_state (OFF) Submit_bio blk_mq_make_request rq_qos_throttle <= rwb->enable_state (OFF) scsi_remove_device sd_remove del_gendisk blk_unregister_queue elv_unregister_queue wbt_enable_default <= Set rwb->enable_state (ON) q_qos_track <= rwb->enable_state (ON) ^^^^^^ this request will mark WBT_TRACKED without inflight add and will lead to drop rqw->inflight to -1 in wbt_done() which will trigger IO hung. Fix this by move wbt_enable_default() from elv_unregister to bfq_exit_queue(). Only re-enable wbt when bfq exit. Fixes: 76a8040817b4b ("blk-wbt: make sure throttle is enabled properly") Signed-off-by: Laibin Qiu <qiulaibin@huawei.com> --- block/bfq-iosched.c | 4 ++++ block/elevator.c | 2 -- 2 files changed, 4 insertions(+), 2 deletions(-)