On Wed, 2018-11-14 at 16:25 +-0800, Ming Lei wrote: +AD4 --- a/drivers/scsi/scsi+AF8-lib.c +AD4 +-+-+- b/drivers/scsi/scsi+AF8-lib.c +AD4 +AEAAQA -697,6 +-697,12 +AEAAQA static bool scsi+AF8-end+AF8-request(struct request +ACo-req, +AD4 blk+AF8-status+AF8-t error, +AD4 +ACo-/ +AD4 scsi+AF8-mq+AF8-uninit+AF8-cmd(cmd)+ADs +AD4 +AD4 +- /+ACo +AD4 +- +ACo queue is still alive, so grab the ref for preventing it +AD4 +- +ACo from being cleaned up during running queue. +AD4 +- +ACo-/ +AD4 +- percpu+AF8-ref+AF8-get(+ACY-q-+AD4-q+AF8-usage+AF8-counter)+ADs +AD4 +- I think the above comment is misleading. In the block layer a queue is called alive if the +ACI-dying+ACI flag has not been set. When the above call to percpu+AF8-ref+AF8-get() occurs it is not guaranteed that that flag has not yet been set. But it is guaranteed that q-+AD4-q+AF8-usage+AF8-counter is not zero. I would prefer if the comment would be modified. What's not clear to me is why this patch only protects the blk-mq path but not the legacy path. Does the legacy path need similar protection? It also triggers a queue run after having finished a request. Otherwise this patch looks fine to me. Bart.
