@@ -6165,11 +6165,13 @@ static void bfq_completed_request(struct bfq_queue *bfqq, struct bfq_data *bfqd)
* of other queues. But a false waker will unjustly steal
* bandwidth to its supposedly woken queue. So considering
* also shared queues in the waking mechanism may cause more
- * control troubles than throughput benefits. Then do not set
- * last_completed_rq_bfqq to bfqq if bfqq is a shared queue.
+ * control troubles than throughput benefits. Then reset
+ * last_completed_rq_bfqq if bfqq is a shared queue.
*/
if (!bfq_bfqq_coop(bfqq))
bfqd->last_completed_rq_bfqq = bfqq;
+ else
+ bfqd->last_completed_rq_bfqq = NULL;
/*
* If we are waiting to discover whether the request pattern
Commit 85686d0dc194 ("block, bfq: keep shared queues out of the waker mechanism") leaves shared bfq_queues out of the waker-detection mechanism. It attains this goal by not updating the pointer last_completed_rq_bfqq, if the last request completed belongs to a shared bfq_queue (so that the pointer will not point to the shared bfq_queue). Yet this has a side effect: the pointer last_completed_rq_bfqq keeps pointing, deceptively, to a bfq_queue that actually is not the last one to have had a request completed. As a consequence, such a bfq_queue may deceptively be considered as a waker of some bfq_queue, even of some shared bfq_queue. To address this issue, reset last_completed_rq_bfqq if the last request completed belongs to a shared queue. Fixes: 85686d0dc194 ("block, bfq: keep shared queues out of the waker mechanism") Signed-off-by: Paolo Valente <paolo.valente@linaro.org> --- block/bfq-iosched.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)