On 8/18/17 00:01, Bart Van Assche wrote: > 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, Yes, getting back "scsi-mq: Always unprepare before requeuing a request" in would be ideal. Right now, I do not have a clue how to otherwise avoid the deadlock on mq with a solution that fits both sq and mq, that is, one that will not get a NAK from Christoph :) But since we already are at rc5, it is risky to wait for a fix for the PowerPC boot problem that may not come in time. So still trying. Best. -- Damien Le Moal, Western Digital
