Re: [PATCH v9 1/1] nvmet: support reservation feature

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

在 2024/9/24 00:32, Dmitry Bogdanov 写道:
>> 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>
>> ---
>>   drivers/nvme/target/Makefile    |    2 +-
>>   drivers/nvme/target/admin-cmd.c |   24 +-
>>   drivers/nvme/target/configfs.c  |   27 +
>>   drivers/nvme/target/core.c      |   58 +-
>>   drivers/nvme/target/nvmet.h     |   49 ++
>>   drivers/nvme/target/pr.c        | 1214 +++++++++++++++++++++++++++++++
>>   include/linux/nvme.h            |   54 ++
>>   7 files changed, 1419 insertions(+), 9 deletions(-)
>>   create mode 100644 drivers/nvme/target/pr.c
> ...
>> +
>> +static void nvmet_pr_unregister_one(struct nvmet_pr *pr,
>> +                                   struct nvmet_pr_registrant *reg)
>> +{
>> +       struct nvmet_pr_registrant *first_reg;
>> +       struct nvmet_pr_registrant *holder;
>> +       u8 original_rtype;
>> +
>> +       lockdep_assert_held(&pr->pr_lock);
>> +       list_del_rcu(&reg->entry);
>> +
>> +       holder = rcu_dereference_protected(pr->holder,
>> +                       lockdep_is_held(&pr->pr_lock));
>> +       if (reg != holder)
>> +               goto out;
>> +
>> +       original_rtype = holder->rtype;
>> +       if (original_rtype == NVME_PR_WRITE_EXCLUSIVE_ALL_REGS ||
>> +           original_rtype == NVME_PR_EXCLUSIVE_ACCESS_ALL_REGS) {
>> +               first_reg = list_first_or_null_rcu(&pr->registrant_list,
>> +                               struct nvmet_pr_registrant, entry);
>> +               if (first_reg)
>> +                       first_reg->rtype = original_rtype;
>> +               rcu_assign_pointer(pr->holder, first_reg);
>> +       } else {
>> +               rcu_assign_pointer(pr->holder, NULL);
>> +
>> +               if (original_rtype == NVME_PR_WRITE_EXCLUSIVE_REG_ONLY ||
>> +                   original_rtype == NVME_PR_WRITE_EXCLUSIVE_REG_ONLY)
> copy&past error?
> The second check should be against NVME_PR_EXCLUSIVE_ACCESS_REG_ONLY?
Indeed, my mistake, it will be fixed in v10.
>> +                       nvmet_pr_resv_released(pr, &reg->hostid);
>> +       }
>> +out:
>> +       synchronize_rcu();
>> +       kfree(reg);
>> +}
>> +
>> ......
>> +
>> +static u16 nvmet_pr_preempt(struct nvmet_req *req,
>> +                           struct nvmet_pr_registrant *reg,
>> +                           u8 rtype,
>> +                           struct nvmet_pr_acquire_data *d,
>> +                           bool abort)
>> +{
>> +       struct nvmet_ctrl *ctrl = req->sq->ctrl;
>> +       struct nvmet_pr *pr = &req->ns->pr;
>> +       struct nvmet_pr_registrant *holder;
>> +       enum nvme_pr_type original_rtype;
>> +       u64 prkey = le64_to_cpu(d->prkey);
>> +       u16 status;
>> +
>> +       lockdep_assert_held(&pr->pr_lock);
>> +       holder = rcu_dereference_protected(pr->holder,
>> +                       lockdep_is_held(&pr->pr_lock));
>> +       if (!holder)
>> +               return nvmet_pr_unreg_all_host_by_prkey(req, prkey,
>> +                                       &ctrl->hostid, abort);
>> +
>> +       original_rtype = holder->rtype;
>> +       if (original_rtype == NVME_PR_WRITE_EXCLUSIVE_ALL_REGS ||
>> +           original_rtype == NVME_PR_EXCLUSIVE_ACCESS_ALL_REGS) {
>> +               if (!prkey) {
>> +                       nvmet_pr_unreg_all_others(req, &ctrl->hostid, abort);
>> +                       nvmet_pr_set_new_holder(pr, rtype, reg);
> You didnot address the reservation atomicity here. You still remove an
> old holder and then after a some time you set the new holder.
> In this time gap an incomming WRITE command from a non holder will write
> to the media.
Right, I will change it in v10.
>> +                       return NVME_SC_SUCCESS;
>> +               }
>> +               return nvmet_pr_unreg_all_host_by_prkey(req, prkey,
>> +                               &ctrl->hostid, abort);
>> +       }
>> +
>> +       if (holder == reg) {
>> +               status = nvmet_pr_update_reg_attr(pr, holder,
>> +                               nvmet_pr_update_holder_rtype, &rtype);
>> +               if (!status && original_rtype != rtype)
>> +                       nvmet_pr_resv_released(pr, &reg->hostid);
>> +               return status;
>> +       }
>> +
>> +       if (prkey == holder->rkey) {
>> +               status = nvmet_pr_unreg_all_others_by_prkey(req, prkey,
>> +                                       &ctrl->hostid, abort);
> And here too that timegap with released reservation.
I will fix this too, and also the

nvmet_pr_unreg_all_others_by_prkey() does not need a return value,

I remove it.

>> +               if (status)
>> +                       return status;
>> +
>> +               nvmet_pr_set_new_holder(pr, rtype, reg);
>> +               if (original_rtype != rtype)
>> +                       nvmet_pr_resv_released(pr, &reg->hostid);
> This function is(may be) already invoked in nvmet_pr_unregister_one.
>
Not, here the original_rtype is not NVME_PR_WRITE_EXCLUSIVE_REG_ONLY or

NVME_PR_EXCLUSIVE_ACCESS_ALL_REGS, so the nvmet_pr_unregister_one will

not call nvmet_pr_resv_released.

>> +               return status;
>> +       }
>> +
>> +       if (prkey)
>> +               return nvmet_pr_unreg_all_host_by_prkey(req, prkey,
>> +                                       &ctrl->hostid, abort);
>> +       return NVME_SC_INVALID_FIELD | NVME_SC_DNR;
>> +}
>> +
>> +static void nvmet_pr_confirm_ns_pc_ref(struct percpu_ref *ref)
>> +{
>> +       struct nvmet_pr_per_ctrl_ref *pc_ref =
>> +               container_of(ref, struct nvmet_pr_per_ctrl_ref, ref);
>> +
>> +       complete(&pc_ref->confirm_done);
>> +}
>> +
>> +static void nvmet_pr_do_abort(struct nvmet_req *req)
>> +{
>> +       struct nvmet_subsys *subsys = req->sq->ctrl->subsys;
>> +       struct nvmet_pr_per_ctrl_ref *pc_ref;
>> +       struct nvmet_ctrl *ctrl = NULL;
>> +
>> +find_next:
>> +       mutex_lock(&subsys->lock);
>> +       list_for_each_entry(ctrl, &subsys->ctrls, subsys_entry) {
>> +               if (ctrl->pr_abort)
>> +                       goto do_abort;
>> +       }
>> +       mutex_unlock(&subsys->lock);
>> +       return;
>> +
>> +do_abort:
>> +       mutex_unlock(&subsys->lock);
>> +       /*
>> +        * The target dose not support abort, just wait ref to 0.
> typo "dose"->"does"
>
Sure.
>> +        */
>> +       pc_ref = xa_load(&req->ns->pr_per_ctrl_refs, ctrl->cntlid);
>> +       percpu_ref_kill_and_confirm(&pc_ref->ref, nvmet_pr_confirm_ns_pc_ref);
>> +       wait_for_completion(&pc_ref->confirm_done);
>> +       wait_for_completion(&pc_ref->free_done);
>> +       reinit_completion(&pc_ref->confirm_done);
>> +       reinit_completion(&pc_ref->free_done);
>> +       percpu_ref_resurrect(&pc_ref->ref);
>> +
>> +       ctrl->pr_abort = false;
> pr_abort flag is per controller, but this function is per namespace.
> The use case of preempt_and_abort is to preempt reservation of a "zomby" host
> for the all namespaces. It means that preempt_and_abort command will be sent
> for the each namespace and there will be several parallel abort processes for
> the same controllers. And you should not mix them.
>
> May be doing ref_kill instead of setting ctlr->pr_abort=true will more
> accuratelly set the barier for incoming IO. You may use Mark feature in
> XArrays to mark pc_ref to wait the completion for and use xa_for_each_marked
> for going through such pc_refs.

Good idea, thanks very much, will changed in v10.

Best Regards,

Guixin Liu

>> +       nvmet_ctrl_put(ctrl);
>> +       goto find_next;
>> +}
>> +
>> +static u16 __nvmet_execute_pr_acquire(struct nvmet_req *req,
>> +                                     struct nvmet_pr_registrant *reg,
>> +                                     u8 acquire_act,
>> +                                     u8 rtype,
>> +                                     struct nvmet_pr_acquire_data *d)
>> +{
>> +       u16 status;
>> +
>> +       switch (acquire_act) {
>> +       case NVME_PR_ACQUIRE_ACT_ACQUIRE:
>> +               status = nvmet_pr_acquire(req, reg, rtype);
>> +               goto out;
>> +       case NVME_PR_ACQUIRE_ACT_PREEMPT:
>> +               status = nvmet_pr_preempt(req, reg, rtype, d, false);
>> +               goto inc_gen;
>> +       case NVME_PR_ACQUIRE_ACT_PREEMPT_AND_ABORT:
>> +               status = nvmet_pr_preempt(req, reg, rtype, d, true);
>> +               if (!status)
>> +                       nvmet_pr_do_abort(req);
>> +               goto inc_gen;
>> +       default:
>> +               req->error_loc = offsetof(struct nvme_common_command, cdw10);
>> +               status = NVME_SC_INVALID_OPCODE | NVME_SC_DNR;
>> +               goto out;
>> +       }
>> +inc_gen:
>> +       if (!status)
>> +               atomic_inc(&req->ns->pr.generation);
>> +out:
>> +       return status;
>> +}
>> +