From: Yu Kuai <yukuai3@xxxxxxxxxx>
Original state:
Process 1 Process 2 Process 3 Process 4
(BIC1) (BIC2) (BIC3) (BIC4)
Λ | | |
\--------------\ \-------------\ \-------------\|
V V V
bfqq1--------->bfqq2---------->bfqq3----------->bfqq4
ref 0 1 2 4
After commit 0e456dba86c7 ("block, bfq: choose the last bfqq from merge
chain in bfq_setup_cooperator()"), if P1 issues a new IO:
Without the patch:
Process 1 Process 2 Process 3 Process 4
(BIC1) (BIC2) (BIC3) (BIC4)
Λ | | |
\------------------------------\ \-------------\|
V V
bfqq1--------->bfqq2---------->bfqq3----------->bfqq4
ref 0 0 2 4
bfqq3 will be used to handle IO from P1, this is not expected, IO
should be redirected to bfqq4;
With the patch:
-------------------------------------------
| |
Process 1 Process 2 Process 3 | Process 4
(BIC1) (BIC2) (BIC3) | (BIC4)
| | | |
\-------------\ \-------------\|
V V
bfqq1--------->bfqq2---------->bfqq3----------->bfqq4
ref 0 0 2 4
IO is redirected to bfqq4, however, procress reference of bfqq3 is still
2, while there is only P2 using it.
Fix the problem by calling bfq_merge_bfqqs() for each bfqq in the merge
chain. Also change bfqq_merge_bfqqs() to return new_bfqq to simplify
code.
Fixes: 0e456dba86c7 ("block, bfq: choose the last bfqq from merge chain in bfq_setup_cooperator()")
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
---
block/bfq-iosched.c | 37 +++++++++++++++++--------------------
1 file changed, 17 insertions(+), 20 deletions(-)
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index d5d39974c674..f4192d5411d2 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -3129,10 +3129,12 @@ void bfq_release_process_ref(struct bfq_data *bfqd, struct bfq_queue *bfqq)
bfq_put_queue(bfqq);
}
-static void
-bfq_merge_bfqqs(struct bfq_data *bfqd, struct bfq_io_cq *bic,
- struct bfq_queue *bfqq, struct bfq_queue *new_bfqq)
+static struct bfq_queue *bfq_merge_bfqqs(struct bfq_data *bfqd,
+ struct bfq_io_cq *bic,
+ struct bfq_queue *bfqq)
{
+ struct bfq_queue *new_bfqq = bfqq->new_bfqq;
+
bfq_log_bfqq(bfqd, bfqq, "merging with queue %lu",
(unsigned long)new_bfqq->pid);
/* Save weight raising and idle window of the merged queues */
@@ -3226,6 +3228,8 @@ bfq_merge_bfqqs(struct bfq_data *bfqd, struct bfq_io_cq *bic,
bfq_reassign_last_bfqq(bfqq, new_bfqq);
bfq_release_process_ref(bfqd, bfqq);
+
+ return new_bfqq;
}
static bool bfq_allow_bio_merge(struct request_queue *q, struct request *rq,
@@ -3261,14 +3265,8 @@ static bool bfq_allow_bio_merge(struct request_queue *q, struct request *rq,
* fulfilled, i.e., bic can be redirected to new_bfqq
* and bfqq can be put.
*/
- bfq_merge_bfqqs(bfqd, bfqd->bio_bic, bfqq,
- new_bfqq);
- /*
- * If we get here, bio will be queued into new_queue,
- * so use new_bfqq to decide whether bio and rq can be
- * merged.
- */
- bfqq = new_bfqq;
+ while (bfqq != new_bfqq)
+ bfqq = bfq_merge_bfqqs(bfqd, bfqd->bio_bic, bfqq);
/*
* Change also bqfd->bio_bfqq, as
@@ -5705,9 +5703,7 @@ bfq_do_early_stable_merge(struct bfq_data *bfqd, struct bfq_queue *bfqq,
* state before killing it.
*/
bfqq->bic = bic;
- bfq_merge_bfqqs(bfqd, bic, bfqq, new_bfqq);
-
- return new_bfqq;
+ return bfq_merge_bfqqs(bfqd, bic, bfqq);
}
/*
@@ -6162,6 +6158,7 @@ static bool __bfq_insert_request(struct bfq_data *bfqd, struct request *rq)
bool waiting, idle_timer_disabled = false;
if (new_bfqq) {
+ struct bfq_queue *old_bfqq = bfqq;
/*
* Release the request's reference to the old bfqq
* and make sure one is taken to the shared queue.
@@ -6178,18 +6175,18 @@ static bool __bfq_insert_request(struct bfq_data *bfqd, struct request *rq)
* new_bfqq.
*/
if (bic_to_bfqq(RQ_BIC(rq), true,
- bfq_actuator_index(bfqd, rq->bio)) == bfqq)
- bfq_merge_bfqqs(bfqd, RQ_BIC(rq),
- bfqq, new_bfqq);
+ bfq_actuator_index(bfqd, rq->bio)) == bfqq) {
+ while (bfqq != new_bfqq)
+ bfqq = bfq_merge_bfqqs(bfqd, RQ_BIC(rq), bfqq);
+ }
- bfq_clear_bfqq_just_created(bfqq);
+ bfq_clear_bfqq_just_created(old_bfqq);
/*
* rq is about to be enqueued into new_bfqq,
* release rq reference on bfqq
*/
- bfq_put_queue(bfqq);
+ bfq_put_queue(old_bfqq);
rq->elv.priv[1] = new_bfqq;
- bfqq = new_bfqq;
}
bfq_update_io_thinktime(bfqd, bfqq);
--
2.39.2
