linux-kernel - [PATCH] null_blk: fix race and oops at removing device with bandwidth limit

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Date:   Mon, 01 Apr 2019 11:30:23 +0300
From:   Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To:     linux-block@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
        linux-kernel@...r.kernel.org
Cc:     Shaohua Li <shli@...com>
Subject: [PATCH] null_blk: fix race and oops at removing device with
 bandwidth limit

Function null_del_dev should disable throttling before canceling timer,
otherwise timer could be restarted by null_handle_cmd().

Remove bump of cur_bytes - without NULLB_DEV_FL_THROTTLED it has no effect.

Fixes: eff2c4f10873 ("nullb: bandwidth control")
Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
---
 drivers/block/null_blk_main.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/null_blk_main.c b/drivers/block/null_blk_main.c
index 417a9f15c116..757b58e0fec7 100644
--- a/drivers/block/null_blk_main.c
+++ b/drivers/block/null_blk_main.c
@@ -1383,8 +1383,8 @@ static void null_del_dev(struct nullb *nullb)
 	del_gendisk(nullb->disk);
 
 	if (test_bit(NULLB_DEV_FL_THROTTLED, &nullb->dev->flags)) {
+		clear_bit(NULLB_DEV_FL_THROTTLED, &nullb->dev->flags);
 		hrtimer_cancel(&nullb->bw_timer);
-		atomic_long_set(&nullb->cur_bytes, LONG_MAX);
 		null_restart_queue_async(nullb);
 	}