| Message ID | 20221128154434.4177442-9-linan122@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | iocost bugfix | expand |
On Mon, Nov 28, 2022 at 11:44:34PM +0800, Li Nan wrote:
> Fix problem by moving rq_qos_exit() to disk_release().
No, that now means it is removed to later. You need to add proper
synchronization.
Hi, 在 2022/11/29 22:25, Christoph Hellwig 写道: > On Mon, Nov 28, 2022 at 11:44:34PM +0800, Li Nan wrote: >> Fix problem by moving rq_qos_exit() to disk_release(). > > No, that now means it is removed to later. You need to add proper > synchronization. > . > Can you explain a bit more? Maybe I'm being noob, here disk is about to be freed, and I can think of any contention. Thanks, Kuai
On Wed, Nov 30, 2022 at 09:32:58AM +0800, Yu Kuai wrote: > > No, that now means it is removed to later. You need to add proper > > synchronization. > > . > > > > Can you explain a bit more? Maybe I'm being noob, here disk is about to > be freed, and I can think of any contention. Right now we need synchronization with e.g. open_mutex and a check for a dead disk, which I suggst to add insted of creating a lifetime imbalance.
diff --git a/block/genhd.c b/block/genhd.c index dcf200bcbd3e..c264da49eaaa 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -656,7 +656,6 @@ void del_gendisk(struct gendisk *disk) elevator_exit(q); mutex_unlock(&q->sysfs_lock); } - rq_qos_exit(q); blk_mq_unquiesce_queue(q); /* @@ -1168,6 +1167,7 @@ static void disk_release(struct device *dev) !test_bit(GD_ADDED, &disk->state)) blk_mq_exit_queue(disk->queue); + rq_qos_exit(q); blkcg_exit_disk(disk); bioset_exit(&disk->bio_split);
Remove block device when iocost is initializing may cause null-pointer dereference: CPU1 CPU2 ioc_qos_write blkcg_conf_open_bdev blkdev_get_no_open kobject_get_unless_zero blk_iocost_init rq_qos_add del_gendisk rq_qos_exit q->rq_qos = rqos->next //iocost is removed from q->roqs blkcg_activate_policy pd_init_fn ioc_pd_init ioc = q_to_ioc(blkg->q) //cant find iocost and return null Fix problem by moving rq_qos_exit() to disk_release(). ioc_qos_write() get bd_device.kobj in blkcg_conf_open_bdev(), so disk_release will not be actived until iocost initialization is complited. Signed-off-by: Li Nan <linan122@huawei.com> --- block/genhd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)