1. 20 Jul, 2022 1 commit
    • Jinke Han's avatar
      block: don't allow the same type rq_qos add more than once · 14a6e2eb
      Jinke Han authored
      In our test of iocost, we encountered some list add/del corruptions of
      inner_walk list in ioc_timer_fn.
      
      The reason can be described as follows:
      
      cpu 0					cpu 1
      ioc_qos_write				ioc_qos_write
      
      ioc = q_to_ioc(queue);
      if (!ioc) {
              ioc = kzalloc();
      					ioc = q_to_ioc(queue);
      					if (!ioc) {
      						ioc = kzalloc();
      						...
      						rq_qos_add(q, rqos);
      					}
              ...
              rq_qos_add(q, rqos);
              ...
      }
      
      When the io.cost.qos file is written by two cpus concurrently, rq_qos may
      be added to one disk twice. In that case, there will be two iocs enabled
      and running on one disk. They own different iocgs on their active list. In
      the ioc_timer_fn function, because of the iocgs from two iocs have the
      same root iocg, the root iocg's walk_list may be overwritten by each other
      and this leads to list add/del corruptions in building or destroying the
      inner_walk list.
      
      And so far, the blk-rq-qos framework works in case that one instance for
      one type rq_qos per queue by default. This patch make this explicit and
      also fix the crash above.
      Signed-off-by: default avatarJinke Han <hanjinke.666@bytedance.com>
      Reviewed-by: default avatarMuchun Song <songmuchun@bytedance.com>
      Acked-by: default avatarTejun Heo <tj@kernel.org>
      Cc: <stable@vger.kernel.org>
      Link: https://lore.kernel.org/r/20220720093616.70584-1-hanjinke.666@bytedance.comSigned-off-by: default avatarJens Axboe <axboe@kernel.dk>
      14a6e2eb
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