Re: [PATCH] blk: fix a wrong accounting of hd_struct->in_flight

Jens Axboe
2010-10-14T12:44:39Z

On 2010-10-14 08:07, KOSAKI Motohiro wrote:
>> @@ -1268,7 +1270,17 @@ static int __make_request(struct request
>> * not touch req->buffer either...
>> */
>> req->buffer = bio_data(bio);
>> + src_part = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req));
>> req->__sector = bio->bi_sector;
>> + dst_part = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req));
>
> I think this is wrong. disk_map_sector_rcu() require
> rcu read lock held (see function comment). all other call site take
> part_stat_lock() before disk_map_sector_rcu() call.

It's called under the queue lock with irqs disabled, which implies a
rcu critical section.

--
Jens Axboe