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Message-Id: <1399741312-10453-2-git-send-email-tom.leiming@gmail.com>
Date: Sun, 11 May 2014 01:01:48 +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 1/5] blk-mq: bitmap tag: use clear_bit_unlock in bt_clear_tag()
The unlock memory barrier need to order access to req in free
path and clearing tag bit, otherwise either request free path
may see a allocated request, or initialized request in allocate
path might be modified by the ongoing free path.
Signed-off-by: Ming Lei <tom.leiming@...il.com>
---
block/blk-mq-tag.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index 8dc933b..b8b968d 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -235,7 +235,11 @@ static void bt_clear_tag(struct blk_mq_bitmap_tags *bt, unsigned int tag)
const int index = TAG_TO_INDEX(tag);
struct bt_wait_state *bs;
- clear_bit(TAG_TO_BIT(tag), &bt->map[index].word);
+ /*
+ * The unlock memory barrier need to order access to req in free
+ * path and clearing tag bit
+ */
+ clear_bit_unlock(TAG_TO_BIT(tag), &bt->map[index].word);
bs = bt_wake_ptr(bt);
if (bs && atomic_dec_and_test(&bs->wait_cnt)) {
--
1.7.9.5
--
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