On Tue, Jan 31, 2017 at 10:25:58AM +0100, Hannes Reinecke wrote:
> Enable lockless command submission for scsi-mq by moving the
> command structure into the payload for struct request.
We support cmd_size for both the mq and !mq code path, so this
could be simplified by always taking your new block-mq path.
> 4 files changed, 427 insertions(+), 57 deletions(-)
The amount of new code scare me. Especially compared to the very
shport changelog.
> diff --git a/drivers/scsi/mpt3sas/mpt3sas_base.c b/drivers/scsi/mpt3sas/mpt3sas_base.c
> index 942fb7e..29e139f 100644
> --- a/drivers/scsi/mpt3sas/mpt3sas_base.c
> +++ b/drivers/scsi/mpt3sas/mpt3sas_base.c
> @@ -867,6 +867,20 @@ struct scsiio_tracker *
> {
> WARN_ON(!smid);
> WARN_ON(smid >= ioc->hi_priority_smid);
> + if (shost_use_blk_mq(ioc->shost)) {
> + u16 hwq = (smid - 1) % ioc->shost->nr_hw_queues;
> + u16 tag = (smid - 1) / ioc->shost->nr_hw_queues;
> + struct blk_mq_tag_set *tagset = &ioc->shost->tag_set;
> + struct request *req;
> +
> + req = blk_mq_tag_to_rq(tagset->tags[hwq], tag);
> + if (req) {
> + struct scsi_cmnd *cmd = blk_mq_rq_to_pdu(req);
> +
> + return scsi_cmd_priv(cmd);
> + } else
> + return NULL;
> + }
This looks like it basically duplicates scsi_host_find_tag().
> + if (shost_use_blk_mq(ioc->shost)) {
> + unsigned int unique_tag = blk_mq_unique_tag(scmd->request);
> + u16 hwq = blk_mq_unique_tag_to_hwq(unique_tag);
> + u16 tag = blk_mq_unique_tag_to_tag(unique_tag);
> + u16 smid = (tag * ioc->shost->nr_hw_queues) + hwq + 1;
> +
> + request = scsi_cmd_priv(scmd);
> + request->scmd = scmd;
no need for a backpointer, blk_mq_rq_from_pdu gets your
back to the request, and scsi_cmd_priv back to driver private data.
> + request->cb_idx = cb_idx;
> + request->msix_io = hwq;
> + request->smid = smid;
why do we need to store the smid?
> @@ -562,12 +642,7 @@ enum block_state {
> _ctl_set_task_mid(struct MPT3SAS_ADAPTER *ioc, struct mpt3_ioctl_command *karg,
I think this function just needs to go away instantly.
Trying to send task management requests from userspace for any
active smid is plain dangerous.
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