On Thu, 2018-12-06 at 22:17 -0700, Jens Axboe wrote: > Instead of making special cases for what we can direct issue, and now > having to deal with DM solving the livelock while still retaining a BUSY > condition feedback loop, always just add a request that has been through > ->queue_rq() to the hardware queue dispatch list. These are safe to use > as no merging can take place there. Additionally, if requests do have > prepped data from drivers, we aren't dependent on them not sharing space > in the request structure to safely add them to the IO scheduler lists.
How about making blk_mq_sched_insert_request() complain if a request is passed to it in which the RQF_DONTPREP flag has been set to avoid that this problem is reintroduced in the future? Otherwise this patch looks fine to me. Bart.
