linux-kernel - [PATCH 02/20] block, bfq: Update bfqd->max

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Message-ID: <20221101093417.10540-3-shikemeng@huawei.com>
Date:   Tue, 1 Nov 2022 17:33:59 +0800
From:   Kemeng Shi <shikemeng@...wei.com>
To:     <paolo.valente@...aro.org>, <axboe@...nel.dk>
CC:     <linux-block@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <shikemeng@...wei.com>
Subject: [PATCH 02/20] block, bfq: Update bfqd->max_budget with bfqd->lock held

bfq_max_budget and bfq_user_max_budget maybe be in inconsisten state if
bfq_max_budget configuration and bfq_max_budget auto-update happen
concurrently.
Example sequence:
config                          auto-update
bfqd->bfq_max_budget =
  __data
                                if (bfqd->bfq_user_max_budget == 0)
                                  bfqd->bfq_max_budget =
                                    bfq_calc_max_budget(bfqd);
bfqd->bfq_user_max_budget =
  __data;

bfq_max_budget is only update in update_thr_responsiveness_params and
configuration code. As update_thr_responsiveness_params is always called
under bfqd->lock, fix this by holding lock in configuration code.

Signed-off-by: Kemeng Shi <shikemeng@...wei.com>
---
 block/bfq-iosched.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 25a88ffd997e..13370c41ad36 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -7328,6 +7328,7 @@ static ssize_t bfq_max_budget_store(struct elevator_queue *e,
 	if (ret)
 		return ret;
 
+	spin_lock_irq(&bfqd->lock);
 	if (__data == 0)
 		bfqd->bfq_max_budget = bfq_calc_max_budget(bfqd);
 	else {
@@ -7337,6 +7338,7 @@ static ssize_t bfq_max_budget_store(struct elevator_queue *e,
 	}
 
 	bfqd->bfq_user_max_budget = __data;
+	spin_unlock_irq(&bfqd->lock);
 
 	return count;
 }
@@ -7362,8 +7364,11 @@ static ssize_t bfq_timeout_sync_store(struct elevator_queue *e,
 		__data = INT_MAX;
 
 	bfqd->bfq_timeout = msecs_to_jiffies(__data);
+
+	spin_lock_irq(&bfqd->lock);
 	if (bfqd->bfq_user_max_budget == 0)
 		bfqd->bfq_max_budget = bfq_calc_max_budget(bfqd);
+	spin_unlock_irq(&bfqd->lock);
 
 	return count;
 }
-- 
2.30.0