From: Jens Axboe <axboe@kernel.dk>
Date: Wed, 9 May 2018 19:28:50 +0000 (-0600)
Subject: blk-mq: don't call into depth limiting for reserved tags
X-Git-Tag: for-4.18/block-20180603~131
X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=17a511993225ff7c1e2af182c0720bb4d31c7d3a;p=linux-block.git

blk-mq: don't call into depth limiting for reserved tags

It's not useful, they are internal and/or error handling recovery
commands.

Acked-by: Paolo Valente <paolo.valente@linaro.org>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 4e9d83594cca..64630caaf27e 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -360,9 +360,11 @@ static struct request *blk_mq_get_request(struct request_queue *q,
 
 		/*
 		 * Flush requests are special and go directly to the
-		 * dispatch list.
+		 * dispatch list. Don't include reserved tags in the
+		 * limiting, as it isn't useful.
 		 */
-		if (!op_is_flush(op) && e->type->ops.mq.limit_depth)
+		if (!op_is_flush(op) && e->type->ops.mq.limit_depth &&
+		    !(data->flags & BLK_MQ_REQ_RESERVED))
 			e->type->ops.mq.limit_depth(op, data);
 	}