From: Jianpeng Ma <majianpeng@gmail.com>
Date: Wed, 11 Sep 2013 19:21:07 +0000 (-0600)
Subject: block: trace all devices plug operation
X-Git-Tag: firefly_0821_release~176^2~5264^2~6
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=7aef2e780b13973ea60aed8c556107dabde6a495;p=firefly-linux-kernel-4.4.55.git

block: trace all devices plug operation

In func blk_queue_bio, if list of plug is empty,it will call
blk_trace_plug.
If process deal with a single device,it't ok.But if process deal with
multi devices,it only trace the first device.
Using request_count to judge, it can soleve this problem.

In addition, i modify the comment.

Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/block/blk-core.c b/block/blk-core.c
index 93a18d1d3da8..91037f74668e 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1549,11 +1549,9 @@ get_rq:
 	if (plug) {
 		/*
 		 * If this is the first request added after a plug, fire
-		 * of a plug trace. If others have been added before, check
-		 * if we have multiple devices in this plug. If so, make a
-		 * note to sort the list before dispatch.
+		 * of a plug trace.
 		 */
-		if (list_empty(&plug->list))
+		if (!request_count)
 			trace_block_plug(q);
 		else {
 			if (request_count >= BLK_MAX_REQUEST_COUNT) {