Re: [PATCH] scsi: sd_zbc: Disable zoned block devices with scsi-mq

[Bart Van Assche <Bart.VanAssche@wdc.com>]

On Thu, 2017-08-17 at 21:19 +0900, 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.

Hello Damien,

Another possible approach is to fix the ipr driver and to resubmit the
"scsi-mq: Always unprepare before requeuing a request" and "scsi: sd_zbc:
Write unlock zone from sd_uninit_cmnd()" patches.

Bart.