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authorLaibin Qiu <qiulaibin@huawei.com>2022-01-22 12:10:45 +0100
committerJens Axboe <axboe@kernel.dk>2022-02-17 15:54:03 +0100
commite92bc4cd34de2ce454bdea8cd198b8067ee4e123 (patch)
tree7429e849741ebcbb669e0543385c0ec9bb69a189
parentblock: fix surprise removal for drivers calling blk_set_queue_dying (diff)
downloadlinux-e92bc4cd34de2ce454bdea8cd198b8067ee4e123.tar.xz
linux-e92bc4cd34de2ce454bdea8cd198b8067ee4e123.zip
block/wbt: fix negative inflight counter when remove scsi device
Now that we disable wbt by set WBT_STATE_OFF_DEFAULT in wbt_disable_default() when switch elevator to bfq. And when we remove scsi device, wbt will be enabled by wbt_enable_default. If it become false positive between wbt_wait() and wbt_track() when submit write request. The following is the scenario that triggered the problem. T1 T2 T3 elevator_switch_mq bfq_init_queue wbt_disable_default <= Set rwb->enable_state (OFF) Submit_bio blk_mq_make_request rq_qos_throttle <= rwb->enable_state (OFF) scsi_remove_device sd_remove del_gendisk blk_unregister_queue elv_unregister_queue wbt_enable_default <= Set rwb->enable_state (ON) q_qos_track <= rwb->enable_state (ON) ^^^^^^ this request will mark WBT_TRACKED without inflight add and will lead to drop rqw->inflight to -1 in wbt_done() which will trigger IO hung. Fix this by move wbt_enable_default() from elv_unregister to bfq_exit_queue(). Only re-enable wbt when bfq exit. Fixes: 76a8040817b4b ("blk-wbt: make sure throttle is enabled properly") Remove oneline stale comment, and kill one oneshot local variable. Signed-off-by: Ming Lei <ming.lei@rehdat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/linux-block/20211214133103.551813-1-qiulaibin@huawei.com/ Signed-off-by: Laibin Qiu <qiulaibin@huawei.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--block/bfq-iosched.c2
-rw-r--r--block/elevator.c2
2 files changed, 2 insertions, 2 deletions
diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 0c612a911696..36a66e97e3c2 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -7018,6 +7018,8 @@ static void bfq_exit_queue(struct elevator_queue *e)
spin_unlock_irq(&bfqd->lock);
#endif
+ wbt_enable_default(bfqd->queue);
+
kfree(bfqd);
}
diff --git a/block/elevator.c b/block/elevator.c
index ec98aed39c4f..482df2a350fc 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -525,8 +525,6 @@ void elv_unregister_queue(struct request_queue *q)
kobject_del(&e->kobj);
e->registered = 0;
- /* Re-enable throttling in case elevator disabled it */
- wbt_enable_default(q);
}
}