From: Jens Axboe <axboe@kernel.dk>
Date: Wed, 14 Nov 2018 04:32:10 +0000 (-0700)
Subject: blk-mq: ensure mq_ops ->poll() is entered at least once
X-Git-Tag: v5.0-rc1~52^2~196
X-Git-Url: http://git.osdn.net/view?a=commitdiff_plain;h=aa61bec30eca11816789dc25c2090366b0ccfaf8;p=uclinux-h8%2Flinux.git

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 c2751f0a3ccc..ba3c7b6476b7 100644
--- 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;