Re: [PATCH v2 09/20] nvme: Add helper to execute Reservation Report

Keith Busch
2022-08-10T03:21:50Z

On Wed, Aug 10, 2022 at 01:45:48AM +0000, Chaitanya Kulkarni wrote:
> On 8/9/22 09:21, Mike Christie wrote:
> > On 8/9/22 9:51 AM, Keith Busch wrote:
> >> On Tue, Aug 09, 2022 at 10:56:55AM +0000, Chaitanya Kulkarni wrote:
> >>> On 8/8/22 17:04, Mike Christie wrote:
> >>>> +
> >>>> + c.common.opcode = nvme_cmd_resv_report;
> >>>> + c.common.cdw10 = cpu_to_le32(nvme_bytes_to_numd(data_len));
> >>>> + c.common.cdw11 = 1;
> >>>> + *eds = true;
> >>>> +
> >>>> +retry:
> >>>> + if (IS_ENABLED(CONFIG_NVME_MULTIPATH) &&
> >>>> + bdev->bd_disk->fops == &nvme_ns_head_ops)
> >>>> + ret = nvme_send_ns_head_pr_command(bdev, &c, data, data_len);
> >>>> + else
> >>>> + ret = nvme_send_ns_pr_command(bdev->bd_disk->private_data, &c,
> >>>> + data, data_len);
> >>>> + if (ret == NVME_SC_HOST_ID_INCONSIST && c.common.cdw11) {
> >>>> + c.common.cdw11 = 0;
> >>>> + *eds = false;
> >>>> + goto retry;
> >>>
> >>> Unconditional retries without any limit can create problems,
> >>> perhaps consider adding some soft limits.
> >>
> >> It's already conditioned on cdw11, which is cleared to 0 on the 2nd try. Not
> >> that that's particularly clear. I'd suggest naming an enum value for it so the
> >> code tells us what the signficance of cdw11 is in this context (it's the
> >> Extended Data Structure control flag).
> >
>
> true, my concern is if controller went bad (not a common case but it is
> H/W afterall) then we should have some soft limit to avoid infinite
> retries.

cdw11 is '0' on the 2nd try, and the 'goto' is conditioned on cdw11 being
non-zero. There's no infinite retry here.