[RFC PATCHv5 2/7] nvme-multipath: add support for adaptive I/O policy

[Nilay Shroff]

On 7/31/26 8:18 AM, Guixin Liu wrote:
> 
> 
> 在 2026/7/30 20:01, Nilay Shroff 写道:
>> On 7/29/26 1:25 PM, Guixin Liu wrote:
>>> Hi,
>>>    Raise some comments to see if we can keep moving this
>>> feature forward.
>>>    Once this feature is merged, I'll be able to build the
>>> service-time I/O policy on top of it.
>>>
>> Thanks for the review! BTW we alreday have patch revision v6
>> upstream now. You may find it here (in case you missed it):
>> https://lore.kernel.org/all/20260520182112.863076-1-nilay@linux.ibm.com/
>>
> Sorry, I miss that.
>>>
>>> +static bool nvme_mpath_enable_adaptive_path_policy(struct nvme_ns *ns)
>>> +{
>>> +    struct nvme_ns_head *head = ns->head;
>>> +
>>> +    if (!head->disk || head->subsys->iopolicy != NVME_IOPOLICY_ADAPTIVE)
>>> +        return false;
>>> +
>>> +    if (test_and_set_bit(NVME_NS_PATH_STAT, &ns->flags))
>>> +        return false;
>>> +
>>> +    blk_queue_flag_set(QUEUE_FLAG_SAME_FORCE, ns->queue);
>>> +    blk_stat_enable_accounting(ns->queue);
>>> +    return true;
>>> +}
>>> +
>>> +static bool nvme_mpath_disable_adaptive_path_policy(struct nvme_ns *ns)
>>> +{
>>> +
>>> +    if (!test_and_clear_bit(NVME_NS_PATH_STAT, &ns->flags))
>>> +        return false;
>>> +
>>> +    blk_stat_disable_accounting(ns->queue);
>>> +    blk_queue_flag_clear(QUEUE_FLAG_SAME_FORCE, ns->queue);
>>> +    nvme_mpath_reset_adaptive_path_stat(ns);
>>> The adp_path still hold the ns's pointer, should clear too,
>>> otherwise, we will access a freed ns.
> Is this correct?
> 
Yes correct but this has been already addressed in the latest
revision. Please review nvme_disable_ns_latency_sampling().

Thanks,
--Nilay