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From: Paolo Valente <paolo.valente@linaro.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org,
	ulf.hansson@linaro.org, linus.walleij@linaro.org,
	broonie@kernel.org, bfq-iosched@googlegroups.com,
	oleksandr@natalenko.name, mancha@tower-research.com,
	Paolo Valente <paolo.valente@linaro.org>
Subject: [PATCH BUGFIX IMPROVEMENT 03/14] block, bfq: make sure queue budgets are not below service received
Date: Tue, 29 Jan 2019 12:06:27 +0100	[thread overview]
Message-ID: <20190129110638.12652-4-paolo.valente@linaro.org> (raw)
In-Reply-To: <20190129110638.12652-1-paolo.valente@linaro.org>

With some unlucky sequences of events, the function
bfq_updated_next_req updates the current budget of a bfq_queue to a
lower value than the service received by the queue using such a
budget. Unfortunately, if this happens, then the return value of the
function bfq_bfqq_budget_left becomes inconsistent.  This commit
solves this problem by lower-bounding the budget computed in
bfq_updated_next_req to the service currently charged to the queue.

Signed-off-by: Paolo Valente <paolo.valente@linaro.org>
---
 block/bfq-iosched.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 9ea2c4f42501..b0e8006475be 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -907,8 +907,10 @@ static void bfq_updated_next_req(struct bfq_data *bfqd,
 		 */
 		return;
 
-	new_budget = max_t(unsigned long, bfqq->max_budget,
-			   bfq_serv_to_charge(next_rq, bfqq));
+	new_budget = max_t(unsigned long,
+			   max_t(unsigned long, bfqq->max_budget,
+				 bfq_serv_to_charge(next_rq, bfqq)),
+			   entity->service);
 	if (entity->budget != new_budget) {
 		entity->budget = new_budget;
 		bfq_log_bfqq(bfqd, bfqq, "updated next rq: new budget %lu",
-- 
2.20.1


  parent reply	other threads:[~2019-01-29 11:08 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-29 11:06 [PATCH BUGFIX IMPROVEMENT 00/14] batch of patches for next linux release Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 01/14] block, bfq: do not consider interactive queues in srt filtering Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 02/14] block, bfq: avoid selecting a queue w/o budget Paolo Valente
2019-01-29 11:06 ` Paolo Valente [this message]
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 04/14] block, bfq: remove case of redirected bic from insert_request Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 05/14] block, bfq: consider also ioprio classes in symmetry detection Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 06/14] block, bfq: split function bfq_better_to_idle Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 07/14] block, bfq: do not plug I/O of in-service queue when harmful Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 08/14] block, bfq: unconditionally plug I/O in asymmetric scenarios Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 09/14] block, bfq: fix sequential rq detection in rate estimation Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 10/14] block, bfq: fix queue removal from weights tree Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 11/14] block, bfq: reduce threshold for detecting command queueing Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 12/14] block, bfq: port commit "cfq-iosched: improve hw_tag detection" Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 13/14] block, bfq: do not overcharge writes in asymmetric scenarios Paolo Valente
2019-01-29 11:06 ` [PATCH BUGFIX IMPROVEMENT 14/14] block, bfq: fix in-service-queue check for queue merging Paolo Valente
2019-01-31 19:50 ` [PATCH BUGFIX IMPROVEMENT 00/14] batch of patches for next linux release Jens Axboe

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