Ensure that all ongoing dm_mq_queue_rq() and dm_mq_requeue_request() calls have stopped before setting the "queue stopped" flag. This allows to remove the "queue stopped" test from dm_mq_queue_rq() and dm_mq_requeue_request(). This patch fixes a race condition because dm_mq_queue_rq() is called without holding the queue lock and hence BLK_MQ_S_STOPPED can be set at any time while dm_mq_queue_rq() is in progress.
Signed-off-by: Bart Van Assche <[email protected]> Cc: Mike Snitzer <[email protected]> --- drivers/md/dm-rq.c | 14 +++----------- 1 file changed, 3 insertions(+), 11 deletions(-) diff --git a/drivers/md/dm-rq.c b/drivers/md/dm-rq.c index 182b679..1b7a65e 100644 --- a/drivers/md/dm-rq.c +++ b/drivers/md/dm-rq.c @@ -116,9 +116,12 @@ static void dm_mq_stop_queue(struct request_queue *q) queue_flag_set(QUEUE_FLAG_STOPPED, q); spin_unlock_irqrestore(q->queue_lock, flags); + /* Wait until dm_mq_queue_rq() has finished. */ + blk_quiesce_queue(q); /* Avoid that requeuing could restart the queue. */ blk_mq_cancel_requeue_work(q); blk_mq_stop_hw_queues(q); + blk_resume_queue(q); } void dm_stop_queue(struct request_queue *q) @@ -901,17 +904,6 @@ static int dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx, dm_put_live_table(md, srcu_idx); } - /* - * On suspend dm_stop_queue() handles stopping the blk-mq - * request_queue BUT: even though the hw_queues are marked - * BLK_MQ_S_STOPPED at that point there is still a race that - * is allowing block/blk-mq.c to call ->queue_rq against a - * hctx that it really shouldn't. The following check guards - * against this rarity (albeit _not_ race-free). - */ - if (unlikely(test_bit(BLK_MQ_S_STOPPED, &hctx->state))) - return BLK_MQ_RQ_QUEUE_BUSY; - if (ti->type->busy && ti->type->busy(ti)) return BLK_MQ_RQ_QUEUE_BUSY; -- 2.10.0 -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
