Am Montag, 15. Oktober 2018, 22:55:29 CEST schrieb Christoph Hellwig: > On Mon, Oct 15, 2018 at 10:42:47PM +0200, Richard Weinberger wrote: > > > Sadly not. I'm checking now what exactly is broken. > > > > I take this back. Christoph's fixup makes reading work. > > The previous version corrupted my test block device in interesting ways > > and confused all tests. > > But the removal of blk_rq_map_sg() still has issues. > > Now the device blocks endless upon flush. > > I suspect we still need to special case flush. Updated patch below > including your other suggestion:
While playing further with the patch I managed to hit BUG_ON(blk_queued_rq(rq)) in blk_mq_requeue_request(). UML requeues the request in ubd_queue_one_vec() if it was not able to submit the request to the host io-thread. The fd can return -EAGAIN, then UML has to try later. Isn't this allowed in that context? drivers/block/xen-blkfront.c seem to faced the same problem, since it does a list_del_init(&req->queuelist) right before calling blk_mq_requeue_request() o_O. Thanks, //richard
