Re: [PATCH] be2net: Fix some u16 fields appropriately
From: 严海双
Date: Mon Aug 28 2017 - 21:05:09 EST
> On 2017年8月29日, at 上午7:19, David Miller <davem@xxxxxxxxxxxxx> wrote:
>
> From: Haishuang Yan <yanhaishuang@xxxxxxxxxxxxxxxxxxxx>
> Date: Sun, 27 Aug 2017 15:24:45 +0800
>
>> In be_tx_compl_process, frag_index declared as u32, so it's better to
>> declare last_index as u32 also.
>>
>> CC: Ajit Khaparde <ajit.khaparde@xxxxxxxxxxxx>
>> Fixes: b0fd2eb28bd4 ("be2net: Declare some u16 fields as u32 to improve
>> performance")
>> Signed-off-by: Haishuang Yan <yanhaishuang@xxxxxxxxxxxxxxxxxxxx>
>
> That is not a legitimate reason for making this change.
>
>> @@ -255,7 +255,7 @@ struct be_tx_stats {
>> /* Structure to hold some data of interest obtained from a TX CQE */
>> struct be_tx_compl_info {
>> u8 status; /* Completion status */
>> - u16 end_index; /* Completed TXQ Index */
>> + u32 end_index; /* Completed TXQ Index */
>> };
>>
>> struct be_tx_obj {
>
> The ->end_index comes solely from:
>
> txcp->end_index = GET_TX_COMPL_BITS(wrb_index, compl);
>
> Which is precisely a 16-bit value.
>
> I'm not applying this, sorry.
>
Hi David,
The GET_TX_COMPL_BITS comes from amap_get which also returns a 32-bit value:
6 static inline u32 amap_get(void *ptr, u32 dw_offset, u32 mask, u32 offset)
5 {
4 u32 *dw = (u32 *) ptr;
3 return mask & (*(dw + dw_offset) >> offset);
2 }
1
869 #define AMAP_GET_BITS(_struct, field, ptr) \
1 amap_get(ptr, \
2 offsetof(_struct, field)/32, \
3 amap_mask(sizeof(((_struct *)0)->field)), \
4 AMAP_BIT_OFFSET(_struct, field))