On 2/22/21 2:54 PM, Jeffle Xu wrote:
> QUEUE_FLAG_POLL flag will be cleared when turning off 'io_poll', while
> at that moment there may be IOs stuck in hw queue uncompleted. The
> following polling routine won't help reap these IOs, since blk_poll()
> will return immediately because of cleared QUEUE_FLAG_POLL flag. Thus
> these IOs will hang until they finnaly time out. The hang out can be
> observed by 'fio --engine=io_uring iodepth=1', while turning off
> 'io_poll' at the same time.
>
> To fix this, freeze and flush the request queue first when turning off
> 'io_poll'.
>
> Signed-off-by: Jeffle Xu <jefflexu@xxxxxxxxxxxxxxxxx>
> ---
> block/blk-sysfs.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
> index b513f1683af0..10d74741c002 100644
> --- a/block/blk-sysfs.c
> +++ b/block/blk-sysfs.c
> @@ -430,8 +430,11 @@ static ssize_t queue_poll_store(struct request_queue *q, const char *page,
>
> if (poll_on)
> blk_queue_flag_set(QUEUE_FLAG_POLL, q);
> - else
> + else {
> + blk_mq_freeze_queue(q);
> blk_queue_flag_clear(QUEUE_FLAG_POLL, q);
> + blk_mq_unfreeze_queue(q);
> + }
>
> return ret;
> }
>
Better to place brace to 'if' as well.
Thanks,
Joseph
