On 2021/5/12 9:35, Leizhen (ThunderTown) wrote:
>
>
> On 2021/5/12 3:56, Jason Gunthorpe wrote:
>> On Mon, May 10, 2021 at 05:08:40PM +0800, Zhen Lei wrote:
>>> The statement of the last "if (xxx)" branch is the same as the "else"
>>> branch. Delete it to simplify code.
>>>
>>> No functional change.
>>>
>>> Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
>>> ---
>>> drivers/infiniband/core/cm.c | 4 ----
>>> 1 file changed, 4 deletions(-)
>>>
>>> diff --git a/drivers/infiniband/core/cm.c b/drivers/infiniband/core/cm.c
>>> index 0ead0d223154011..510beb25f5b8a0b 100644
>>> --- a/drivers/infiniband/core/cm.c
>>> +++ b/drivers/infiniband/core/cm.c
>>> @@ -668,8 +668,6 @@ static struct cm_id_private *cm_insert_listen(struct cm_id_private *cm_id_priv,
>>> link = &(*link)->rb_right;
>>> else if (be64_lt(service_id, cur_cm_id_priv->id.service_id))
>>> link = &(*link)->rb_left;
>>> - else if (be64_gt(service_id, cur_cm_id_priv->id.service_id))
>>> - link = &(*link)->rb_right;
>>> else
>>> link = &(*link)->rb_right;
>>> }
>>> @@ -700,8 +698,6 @@ static struct cm_id_private *cm_find_listen(struct ib_device *device,
>>> node = node->rb_right;
>>> else if (be64_lt(service_id, cm_id_priv->id.service_id))
>>> node = node->rb_left;
>>> - else if (be64_gt(service_id, cm_id_priv->id.service_id))
>>> - node = node->rb_right;
>>> else
>>> node = node->rb_right;
>>> }
>>
>> I don't like this, if you want to reorganize this function then it
>> should be written in the normal pattern for this kind of comparision
>>
>> if (a < b)
>> ..
>> else if (a > b)
>> ..
>> else // a == b
>> ..
>>
>> You can see the a==b clause written explicitly above this if ladder:
>>
>> if ((cur_cm_id_priv->id.service_mask & service_id) ==
>> (service_mask & cur_cm_id_priv->id.service_id) &&
>> (cm_id_priv->id.device == cur_cm_id_priv->id.device)) {
>
> Right，So we'd better rewrite it with this set of judgments. This is because
> the judgment of (a < b) and (a > b) is performed N times before the judgment
> of (a == b) is performed. Therefore, the above modification you mentioned can
> improve the search performance.
This modification may have to be patched separately. Combined with one patch, the description is unclear.
>
>>
>> Which is why the trailing else is just unexectuable code.
>>
>> Jason
>>
>> .
>>
