Re: [PATCH v11 1/1] nvmet: support reservation feature

[Guixin Liu <kanie@linux.alibaba.com>]

在 2024/10/7 16:08, Dmitry Bogdanov 写道:
> On Sat, Oct 05, 2024 at 10:26:58PM +0800, Guixin Liu wrote:
>> 在 2024/9/30 20:53, Dmitry Bogdanov 写道:
>>> On Sun, Sep 29, 2024 at 11:14:10AM +0800, Guixin Liu wrote:
>>>> This patch implements the reservation feature, includes:
>>>> 1. reservation register(register, unregister and replace).
>>>> 2. reservation acquire(acquire, preempt, preempt and abort).
>>>> 3. reservation release(release and clear).
>>>> 4. reservation report.
>>>> 5. set feature and get feature of reservation notify mask.
>>>> 6. get log page of reservation event.
>>>>
>>>> And also make reservation configurable, one can set ns to support
>>>> reservation before enable ns. The default of resv_enable is false.
>>>>
>>>> Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
>>>> ---
>>>> +
>>>> +static void nvmet_execute_pr_report(struct nvmet_req *req)
>>>> +{
>>>> +       u32 cdw11 = le32_to_cpu(req->cmd->common.cdw11);
>>>> +       u32 cdw10 = le32_to_cpu(req->cmd->common.cdw10);
>>>> +       u32 num_bytes = 4 * (cdw10 + 1); /* cdw10 is number of dwords */
>>>> +       u8 eds = cdw11 & 1; /* Extended data structure, bit 00 */
>>>> +       struct nvme_registered_ctrl_ext *ctrl_eds;
>>>> +       struct nvme_reservation_status_ext *data;
>>>> +       struct nvmet_pr *pr = &req->ns->pr;
>>>> +       struct nvmet_pr_registrant *holder;
>>>> +       struct nvmet_pr_registrant *reg;
>>>> +       u16 num_ctrls = 0;
>>>> +       u16 status;
>>>> +       u8 rtype;
>>>> +
>>>> +       /* nvmet hostid(uuid_t) is 128 bit. */
>>>> +       if (!eds) {
>>>> +               req->error_loc = offsetof(struct nvme_common_command, cdw11);
>>>> +               status = NVME_SC_HOST_ID_INCONSIST | NVME_SC_DNR;
>>>> +               goto out;
>>>> +       }
>>>> +
>>>> +       if (num_bytes < sizeof(struct nvme_reservation_status_ext)) {
>>>> +               req->error_loc = offsetof(struct nvme_common_command, cdw10);
>>>> +               status = NVME_SC_INVALID_FIELD | NVME_SC_DNR;
>>>> +               goto out;
>>>> +       }
>>>> +
>>>> +       data = kmalloc(num_bytes, GFP_KERNEL);
>>>> +       if (!data) {
>>>> +               status = NVME_SC_INTERNAL;
>>>> +               goto out;
>>>> +       }
>>>> +       memset(data, 0, num_bytes);
>>>> +       data->gen = cpu_to_le32(atomic_read(&pr->generation));
>>>> +       data->ptpls = 0;
>>>> +       ctrl_eds = data->regctl_eds;
>>>> +
>>>> +       rcu_read_lock();
>>>> +       holder = rcu_dereference(pr->holder);
>>>> +       rtype = holder ? holder->rtype : 0;
>>>> +       data->rtype = rtype;
>>>> +
>>>> +       list_for_each_entry_rcu(reg, &pr->registrant_list, entry) {
>>>> +               if ((void *)ctrl_eds >= (void *)(data + num_bytes))
>>>> +                       break;
>>>> +               /*
>>>> +                * Dynamic controller, set cntlid to 0xffff.
>>>> +                */
>>>> +               ctrl_eds->cntlid = 0xffff;
>>>> +               if (rtype == NVME_PR_WRITE_EXCLUSIVE_ALL_REGS ||
>>>> +                   rtype == NVME_PR_EXCLUSIVE_ACCESS_ALL_REGS)
>>>> +                       ctrl_eds->rcsts = 1;
>>>> +               if (holder && uuid_equal(&reg->hostid, &holder->hostid))
>>> is just (reg == holder) not enough here?
>> Yes.
>>>> +                       ctrl_eds->rcsts = 1;
>>>> +               uuid_copy((uuid_t *)&ctrl_eds->hostid, &reg->hostid);
>>>> +               ctrl_eds->rkey = cpu_to_le64(reg->rkey);
>>>> +               ctrl_eds++;
>>>> +               num_ctrls++;
>>>> +       }
>>>> +       rcu_read_unlock();
>>>> +
>>>> +       put_unaligned_le16(num_ctrls, data->regctl);
>>> Here you should report the number of all registered registrants in ns,
>>> not the only reported. It is used by the host to understand that it got
>>> not a full response.
>>> NUMD field (cdw11) is about transfering the response. But the structure itsef in
>>> the reposnse has to be complete.
>> The NVMe spec says that:
>>
>>      "This indicates the number of Registered Controller data structures
>> and/or Registered Controller extended data structures contained in this
>> data structure."
> You read not the latest Spec again. Spec v2.1 has another statement:
>    Number of Registrants (REGSTRNT): This field indicates the number of registrants of the
>    namespace. This indicates the number of Registrant data structures or Registrant Extended data
>    structures contained in this data structure.

Well, still, "contained in this data structure" means that we should 
report how many

registrants we reported.

I do a research on nvme-cli and SPDK:

1. nvme-cli: In json_nvme_resv_report, use reported regctls to traverse 
reported registrants.

2. SPDK: In nvmf_ns_reservation_report, set regctl to the number of 
reported registrants.

Best Regards,

Guixin Liu

>> It means that host use this filed to obtain the reported registrants number.
>>
> Think from the host point of view - how are you going to understand
> how much registrants are there in the namespace?
>
> BR,
>   Dmitry