From 6b09b4d33bd964f49d07d3cabfb4204d58cf9811 Mon Sep 17 00:00:00 2001 From: Jeffle Xu Date: Mon, 22 Feb 2021 14:54:52 +0800 Subject: [PATCH] block: fix potential IO hang when turning off io_poll 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 Signed-off-by: Jens Axboe --- block/blk-sysfs.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index ae39c7f3d83d..0f4f0c8a7825 100644 --- a/block/blk-sysfs.c +++ b/block/blk-sysfs.c @@ -434,10 +434,13 @@ static ssize_t queue_poll_store(struct request_queue *q, const char *page, if (ret < 0) return ret; - if (poll_on) + 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; }