Am Dienstag, 16. Oktober 2018, 04:19:51 CEST schrieb Jens Axboe: > On 10/15/18 4:44 PM, Richard Weinberger wrote: > > Am Dienstag, 16. Oktober 2018, 00:04:20 CEST schrieb Jens Axboe: > >> On 10/15/18 3:46 PM, Richard Weinberger wrote: > >>> 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? > >> > >> It is, the problem is that queue_one_vec() doesn't always return an > >> error. The caller is doing a loop per bio, so we can encounter an > >> error, requeue, and then the caller will call us again. We're in > >> an illegal state at that point, and the next requeue will make that > >> obvious since it's already pending. Actually, both the caller and > >> ubd_queue_one_vec() also requeue. So it's a bit of a mess, the below > >> might help. > > > > I agree, the driver *is* a mess. > > Unless someone else volunteers to clean it up, I'll push that task on > > my never ending TODO list. > > I doubt you'll have to fight anyone for that task ;-) > > > Thanks for your hint with the illegal state. > > Now with correct requeuing the driver seems to work fine! > > Write/Flush support also suffered from that but didn't trigger the BUG_ON()... > > OK good, at least we're making progress! Yes. Shall I send a patch with your suggestion or will you? I have one more question, in your first conversion you set queue_depth to 2. How does one know this value? My conversion has 64, which is more or less an educated guess... ;) Thanks, //richard
