linux-kernel - [PATCH 2/5] blk-mq: bitmap tag: remove barrier in bt_clear

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Message-Id: <1399741312-10453-3-git-send-email-tom.leiming@gmail.com>
Date:	Sun, 11 May 2014 01:01:49 +0800
From:	Ming Lei <tom.leiming@...il.com>
To:	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org
Cc:	Ming Lei <tom.leiming@...il.com>
Subject: [PATCH 2/5] blk-mq: bitmap tag: remove barrier in bt_clear_tag()

The barrier isn't necessary because both atomic_dec_and_test()
and wake_up() implicate one barrier.

Signed-off-by: Ming Lei <tom.leiming@...il.com>
---
 block/blk-mq-tag.c |    1 -
 1 file changed, 1 deletion(-)

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index b8b968d..777aad7 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -243,7 +243,6 @@ static void bt_clear_tag(struct blk_mq_bitmap_tags *bt, unsigned int tag)
 
 	bs = bt_wake_ptr(bt);
 	if (bs && atomic_dec_and_test(&bs->wait_cnt)) {
-		smp_mb__after_clear_bit();
 		atomic_set(&bs->wait_cnt, BT_WAIT_BATCH);
 		bt_index_inc(&bt->wake_index);
 		wake_up(&bs->wait);
-- 
1.7.9.5

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