On Thu, May 20, 2021 at 5:57 PM Ming Lei <ming.lei@xxxxxxxxxx> wrote: > > On Fri, May 21, 2021 at 12:33:53AM +0200, Jan Kara wrote: > > Lockdep complains about lock inversion between ioc->lock and bfqd->lock: > > > > bfqd -> ioc: > > put_io_context+0x33/0x90 -> ioc->lock grabbed > > blk_mq_free_request+0x51/0x140 > > blk_put_request+0xe/0x10 > > blk_attempt_req_merge+0x1d/0x30 > > elv_attempt_insert_merge+0x56/0xa0 > > blk_mq_sched_try_insert_merge+0x4b/0x60 > > bfq_insert_requests+0x9e/0x18c0 -> bfqd->lock grabbed > > We could move blk_put_request() into scheduler code, then the lock > inversion is avoided. So far only mq-deadline and bfq calls into > blk_mq_sched_try_insert_merge(), and this change should be small. We'd potentially be putting multiple requests if we keep the recursive merge. Could we move backmerge loop to the schedulers, perhaps? > > > Thanks, > Ming >
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