On 4/26/21 6:45 PM, Ming Lei wrote:
> diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
> index 100fa44d52a6..773aea4db90c 100644
> --- a/block/blk-mq-tag.c
> +++ b/block/blk-mq-tag.c
> @@ -284,8 +284,11 @@ static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data)
> if ((iter_data->flags & BT_TAG_ITER_STARTED) &&
> !blk_mq_request_started(rq))
> ret = true;
> - else
> + else {
> + rq->rq_flags |= RQF_ITERATING;
> ret = iter_data->fn(rq, iter_data->data, reserved);
> + rq->rq_flags &= ~RQF_ITERATING;
> + }
> if (!iter_static_rqs)
> blk_mq_put_rq_ref(rq);
> return ret;
All existing rq->rq_flags modifications are serialized. The above change
adds code that may change rq_flags concurrently with regular request
processing. I think that counts as a race condition. Additionally, the
RQF_ITERATING flag won't be set correctly in the (unlikely) case that
two concurrent bt_tags_iter() calls examine the same request at the same
time.
Thanks,
Bart.
