Re: [PATCH v2] nvme: scan sequentially only when list scan unsupported

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

在 2022/11/8 10:30, Guixin Liu 写道:
> nvme_ctrl_limited_cns check in nvme_scan_ns_list can be removed.
>
Sorry, my bad, already removed.
> Best regards.
>
> Guixin Liu
>
>
> 在 2022/11/8 03:54, Uday Shankar 写道:
>> Currently, if nvme_scan_ns_list fails, nvme_scan_work will fall back to
>> a sequential scan. nvme_scan_ns_list can fail for a variety of reasons,
>> e.g. transient transport issue. And the resulting sequential scan can be
>> extremely expensive on controllers reporting an NN value close to the
>> maximum allowed (>4 billion). Avoid sequential scans wherever possible
>> by only falling back to them if nvme_scan_ns_list fails due to
>> controller non-support of Identify NS List. This breaks (noncompliant)
>> devices that claim to support version NVME_VS(1, 1, 0) or later, but
>> don't support Identify NS List. Such devices can be made to work again
>> using the existing NVME_QUIRK_IDENTIFY_CNS.
>>
>> Signed-off-by: Uday Shankar <ushankar@purestorage.com>
>> ---
>> Changes from v1:
>> - Move limited_cns check from nvme_scan_ns_list to nvme_scan_work
>> - Move note about devices that may break with this change into commit
>>    message
>>
>>   drivers/nvme/host/core.c | 7 +++----
>>   1 file changed, 3 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
>> index 0090dc0b3ae6..5abd8d4c6d9b 100644
>> --- a/drivers/nvme/host/core.c
>> +++ b/drivers/nvme/host/core.c
>> @@ -4425,9 +4425,6 @@ static int nvme_scan_ns_list(struct nvme_ctrl 
>> *ctrl)
>>       u32 prev = 0;
>>       int ret = 0, i;
>>   -    if (nvme_ctrl_limited_cns(ctrl))
>> -        return -EOPNOTSUPP;
>> -
>>       ns_list = kzalloc(NVME_IDENTIFY_DATA_SIZE, GFP_KERNEL);
>>       if (!ns_list)
>>           return -ENOMEM;
>> @@ -4535,8 +4532,10 @@ static void nvme_scan_work(struct work_struct 
>> *work)
>>       }
>>         mutex_lock(&ctrl->scan_lock);
>> -    if (nvme_scan_ns_list(ctrl) != 0)
>> +    if (nvme_ctrl_limited_cns(ctrl))
>>           nvme_scan_ns_sequential(ctrl);
>> +    else
>> +        nvme_scan_ns_list(ctrl);
>>       mutex_unlock(&ctrl->scan_lock);
>>   }
>>
>> base-commit: d30a909f9bb5283e701a5fdfffac763ef57a3e7c