blk-mq: ensure mq_ops ->poll() is entered at least once

Right now we immediately bail if need_resched() is true, but
we need to do at least one loop in case we have entries waiting.
So just invert the need_resched() check, putting it at the
bottom of the loop.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-mq.c b/block/blk-mq.c
index c2751f0a3ccc0f777fff08e473a52ac0f93348f6..ba3c7b6476b77a2ed5da1666bfe15c706712038d 100644 (file)
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3375,7 +3375,7 @@ static int blk_mq_poll(struct request_queue *q, blk_qc_t cookie, bool spin)
        hctx->poll_considered++;
 
        state = current->state;
-       while (!need_resched()) {
+       do {
                int ret;
 
                hctx->poll_invoked++;
@@ -3395,7 +3395,7 @@ static int blk_mq_poll(struct request_queue *q, blk_qc_t cookie, bool spin)
                if (ret < 0 || !spin)
                        break;
                cpu_relax();
-       }
+       } while (!need_resched());
 
        __set_current_state(TASK_RUNNING);
        return 0;