On Thu, May 20, 2021 at 08:29:49PM -0700, Khazhy Kumykov wrote: > 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. Oh, we still can pass a list to hold all requests to be freed, then free them all outside in scheduler code. Thanks, Ming
