On 8/17/17 21:19, Damien Le Moal wrote: > > > On 8/17/17 16:59, Christoph Hellwig wrote: >> On Thu, Aug 17, 2017 at 11:45:50AM +0900, Damien Le Moal wrote: >>> blk-mq may not maintain write requests order at dispatch time. So host >>> managed drives will not reliably work. Worse, potential reordering of >>> write requests on requeue may cause the zone write locking code to >>> deadlock command dispatch to the disk. So for now, until the write >>> ordering issue is fixed, do not support zoned block devices with >>> scsi-mq by showing a 0 LBA capacity disk. >> >> NAK. Please fix the issue instead of this. > > I do have a fix ready to send. All the fixes are at blk-mq level and > basically ensure that dispatch from the hctx->dispatch list are in order > for write commands (regular writes, write same and write zeroes). > It is well tested and at least fixes all the problems I have seen with > dm-zoned and f2fs. > > But: > 1) It is not small, so I strongly doubt it is RC material > 2) We need Bart's patch for "always unprepare requests" which was reverted > 3) Bart does not really like the solution I implemented... > > I can still send it if you want to have a look. Or were you thinking of just getting the deadlock fixed without addressing the reordering problem ? In the end, ZBC disks would still not be usable, so to me, disabling them is exactly equivalent... -- Damien Le Moal, Western Digital Research
