diff options
Diffstat (limited to 'block')
| -rw-r--r-- | block/blk-mq.c | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c index 7df9dbfab022..baebd6c8210e 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -523,6 +523,15 @@ void blk_mq_start_request(struct request *rq) } EXPORT_SYMBOL(blk_mq_start_request); +/* + * When we reach here because queue is busy, REQ_ATOM_COMPLETE + * flag isn't set yet, so there may be race with timeout hanlder, + * but given rq->deadline is just set in .queue_rq() under + * this situation, the race won't be possible in reality because + * rq->timeout should be set as big enough to cover the window + * between blk_mq_start_request() called from .queue_rq() and + * clearing REQ_ATOM_STARTED here. + */ static void __blk_mq_requeue_request(struct request *rq) { struct request_queue *q = rq->q; @@ -696,6 +705,19 @@ static void blk_mq_check_expired(struct blk_mq_hw_ctx *hctx, if (!test_bit(REQ_ATOM_STARTED, &rq->atomic_flags)) return; + /* + * The rq being checked may have been freed and reallocated + * out already here, we avoid this race by checking rq->deadline + * and REQ_ATOM_COMPLETE flag together: + * + * - if rq->deadline is observed as new value because of + * reusing, the rq won't be timed out because of timing. + * - if rq->deadline is observed as previous value, + * REQ_ATOM_COMPLETE flag won't be cleared in reuse path + * because we put a barrier between setting rq->deadline + * and clearing the flag in blk_mq_start_request(), so + * this rq won't be timed out too. + */ if (time_after_eq(jiffies, rq->deadline)) { if (!blk_mark_rq_complete(rq)) blk_mq_rq_timed_out(rq, reserved); |