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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 <jefflexu@linux.alibaba.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
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@ -434,10 +434,13 @@ static ssize_t queue_poll_store(struct request_queue *q, const char *page,
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if (ret < 0)
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if (ret < 0)
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return ret;
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return ret;
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if (poll_on)
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if (poll_on) {
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blk_queue_flag_set(QUEUE_FLAG_POLL, q);
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blk_queue_flag_set(QUEUE_FLAG_POLL, q);
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else
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} else {
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blk_mq_freeze_queue(q);
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blk_queue_flag_clear(QUEUE_FLAG_POLL, q);
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blk_queue_flag_clear(QUEUE_FLAG_POLL, q);
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blk_mq_unfreeze_queue(q);
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}
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return ret;
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return ret;
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}
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}
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