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blk-mq: bitmap tag: use clear_bit_unlock in bt_clear_tag()

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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@gmail.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Ming Lei 2014-05-11 01:01:48 +08:00 committed by Jens Axboe
parent 59d13bf5f5
commit 0289b2e110
1 changed files with 5 additions and 1 deletions
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6
block/blk-mq-tag.c
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@ -236,7 +236,11 @@ static void bt_clear_tag(struct blk_mq_bitmap_tags *bt, unsigned int tag)
const int index = TAG_TO_INDEX(bt, tag);
struct bt_wait_state *bs;
clear_bit(TAG_TO_BIT(bt, 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(bt, tag), &bt->map[index].word);
bs = bt_wake_ptr(bt);
if (bs && atomic_dec_and_test(&bs->wait_cnt)) {