From: Ming Lei <ming.lei@redhat.com> mainline inclusion from mainline-v5.14-rc7 commit c797b40ccc340b8a66f7a7842aecc90bf749f087 category: bugfix bugzilla: 34280, https://gitee.com/openeuler/kernel/issues/I4AKY4 CVE: NA ----------------------------------------------- Inside blk_mq_queue_tag_busy_iter() we already grabbed request's refcount before calling ->fn(), so needn't to grab it one more time in blk_mq_check_expired(). Meantime remove extra request expire check in blk_mq_check_expired(). Cc: Keith Busch <kbusch@kernel.org> Signed-off-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: John Garry <john.garry@huawei.com> Link: https://lore.kernel.org/r/20210811155202.629575-1-ming.lei@redhat.com Signed-off-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Yu Kuai <yukuai3@huawei.com> Reviewed-by: Hou Tao <houtao1@huawei.com> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> --- block/blk-mq.c | 30 +++++------------------------- 1 file changed, 5 insertions(+), 25 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index 62cd94ef443ec..c60c936705c3c 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -871,34 +871,14 @@ static void blk_mq_check_expired(struct blk_mq_hw_ctx *hctx, unsigned long *next = priv; /* - * Just do a quick check if it is expired before locking the request in - * so we're not unnecessarilly synchronizing across CPUs. - */ - if (!blk_mq_req_expired(rq, next)) - return; - - /* - * We have reason to believe the request may be expired. Take a - * reference on the request to lock this request lifetime into its - * currently allocated context to prevent it from being reallocated in - * the event the completion by-passes this timeout handler. - * - * If the reference was already released, then the driver beat the - * timeout handler to posting a natural completion. - */ - if (!refcount_inc_not_zero(&rq->ref)) - return; - - /* - * The request is now locked and cannot be reallocated underneath the - * timeout handler's processing. Re-verify this exact request is truly - * expired; if it is not expired, then the request was completed and - * reallocated as a new request. + * blk_mq_queue_tag_busy_iter() has locked the request, so it cannot + * be reallocated underneath the timeout handler's processing, then + * the expire check is reliable. If the request is not expired, then + * it was completed and reallocated as a new request after returning + * from blk_mq_check_expired(). */ if (blk_mq_req_expired(rq, next)) blk_mq_rq_timed_out(rq, reserved); - - blk_mq_put_rq_ref(rq, hctx); } static void blk_mq_timeout_work(struct work_struct *work) -- 2.25.1