From: Ming Lei Date: Sat, 10 May 2014 17:01:48 +0000 (+0800) Subject: blk-mq: bitmap tag: use clear_bit_unlock in bt_clear_tag() X-Git-Tag: v3.16-rc1~30^2~49^2~41^2~3 X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=0289b2e110b7824b2f76d194ad6f8f0844e270ad;p=linux.git 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 Signed-off-by: Jens Axboe --- diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index 6c78c08865e3..a81b138e89fe 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -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)) {