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    • Jianchao Wang's avatar
      blk-mq: fallback to previous nr_hw_queues when updating fails · e01ad46d
      Jianchao Wang authored
      
      
      When we try to increate the nr_hw_queues, we may fail due to
      shortage of memory or other reason, then blk_mq_realloc_hw_ctxs stops
      and some entries in q->queue_hw_ctx are left with NULL. However,
      because queue map has been updated with new nr_hw_queues, some cpus
      have been mapped to hw queue which just encounters allocation failure,
      thus blk_mq_map_queue could return NULL. This will cause panic in
      following blk_mq_map_swqueue.
      
      To fix it, when increase nr_hw_queues fails, fallback to previous
      nr_hw_queues and post warning. At the same time, driver's .map_queues
      usually use completion irq affinity to map hw and cpu, fallback
      nr_hw_queues will cause lack of some cpu's map to hw, so use default
      blk_mq_map_queues to do that.
      
      Reported-by: default avatar <syzbot+83e8cbe702263932d9d4@syzkaller.appspotmail.com>
      Signed-off-by: default avatarJianchao Wang <jianchao.w.wang@oracle.com>
      Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
      e01ad46d