On Tue, 2017-11-07 at 15:06 -0700, Jens Axboe wrote: > Just to keep everyone in the loop, this bug is not new to > for-4.15/block, nor is it new to the current 4.41-rc or 4.13. So it's > probably different to what Bart is hitting, but it's a bug none the > less... Hello Jens, There are several reasons why I think that patch "blk-mq: don't handle TAG_SHARED in restart" really should be reverted: * That patch is based on the assumption that only the SCSI driver uses shared tags. That assumption is not correct. null_blk and nvme also use shared tags. * As my tests have shown, the algorithm for restarting queues based on the SCSI starved list is flawed. So using that mechanism instead of the blk-mq shared queue restarting algorithm is wrong. * We are close to the merge window. It is too late for trying to fix the "blk-mq: don't handle TAG_SHARED in restart" patch. My proposal is to make sure that what will be sent to Linus during the v4.15 merge window works reliably. That means using the v4.13/v4.14 algorithm for queue restarting which is an algorithm that is trusted by the community. If Roman Penyaev's patch could get applied that would be even better. Bart.
