The padding field in the structure was previously reserved to
maintain a stable interface for potential new fields, ensuring
compatibility with user-space shared data structures.
However,it was accidentally removed by tiantao in a prior commit,
which may lead to incompatibility between user space and the kernel.

This patch reinstates the padding to restore the original structure
layout and preserve compatibility.

Fixes: 8ddde07a3d28 ("dma-mapping: benchmark: extract a common header file for map_benchmark definition")
Cc: stable@vger.kernel.org
Signed-off-by: Qinxin Xia <xiaqinxin@huawei.com>
---
 include/linux/map_benchmark.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/linux/map_benchmark.h b/include/linux/map_benchmark.h
index 62674c83bde4..2ac2fe52f248 100644
--- a/include/linux/map_benchmark.h
+++ b/include/linux/map_benchmark.h
@@ -27,5 +27,6 @@ struct map_benchmark {
 	__u32 dma_dir; /* DMA data direction */
 	__u32 dma_trans_ns; /* time for DMA transmission in ns */
 	__u32 granule;  /* how many PAGE_SIZE will do map/unmap once a time */
+	__u8 expansion[76];     /* For future use */
 };
 #endif /* _KERNEL_DMA_BENCHMARK_H */
-- 
2.33.0

On Fri, May 9, 2025 at 2:02 PM Qinxin Xia <xiaqinxin@huawei.com> wrote:
>
> The padding field in the structure was previously reserved to
> maintain a stable interface for potential new fields, ensuring
> compatibility with user-space shared data structures.
> However,it was accidentally removed by tiantao in a prior commit,
> which may lead to incompatibility between user space and the kernel.
>
> This patch reinstates the padding to restore the original structure
> layout and preserve compatibility.
>
> Fixes: 8ddde07a3d28 ("dma-mapping: benchmark: extract a common header file for map_benchmark definition")
> Cc: stable@vger.kernel.org
> Signed-off-by: Qinxin Xia <xiaqinxin@huawei.com>

+Marek, +Robin

Acked-by: Barry Song <baohua@kernel.org>

> ---
>  include/linux/map_benchmark.h | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/include/linux/map_benchmark.h b/include/linux/map_benchmark.h
> index 62674c83bde4..2ac2fe52f248 100644
> --- a/include/linux/map_benchmark.h
> +++ b/include/linux/map_benchmark.h
> @@ -27,5 +27,6 @@ struct map_benchmark {
>         __u32 dma_dir; /* DMA data direction */
>         __u32 dma_trans_ns; /* time for DMA transmission in ns */
>         __u32 granule;  /* how many PAGE_SIZE will do map/unmap once a time */
> +       __u8 expansion[76];     /* For future use */
>  };
>  #endif /* _KERNEL_DMA_BENCHMARK_H */
> --
> 2.33.0
>

Thanks
Barry

On 2025/5/9 11:31:09, Barry Song <21cnbao@gmail.com> wrote:
> On Fri, May 9, 2025 at 2:02 PM Qinxin Xia <xiaqinxin@huawei.com> wrote:
>> The padding field in the structure was previously reserved to
>> maintain a stable interface for potential new fields, ensuring
>> compatibility with user-space shared data structures.
>> However,it was accidentally removed by tiantao in a prior commit,
>> which may lead to incompatibility between user space and the kernel.
>>
>> This patch reinstates the padding to restore the original structure
>> layout and preserve compatibility.
>>
>> Fixes: 8ddde07a3d28 ("dma-mapping: benchmark: extract a common header file for map_benchmark definition")
>> Cc: stable@vger.kernel.org
>> Signed-off-by: Qinxin Xia <xiaqinxin@huawei.com>
> +Marek, +Robin
>
> Acked-by: Barry Song <baohua@kernel.org>
OK!
>> ---
>>   include/linux/map_benchmark.h | 1 +
>>   1 file changed, 1 insertion(+)
>>
>> diff --git a/include/linux/map_benchmark.h b/include/linux/map_benchmark.h
>> index 62674c83bde4..2ac2fe52f248 100644
>> --- a/include/linux/map_benchmark.h
>> +++ b/include/linux/map_benchmark.h
>> @@ -27,5 +27,6 @@ struct map_benchmark {
>>          __u32 dma_dir; /* DMA data direction */
>>          __u32 dma_trans_ns; /* time for DMA transmission in ns */
>>          __u32 granule;  /* how many PAGE_SIZE will do map/unmap once a time */
>> +       __u8 expansion[76];     /* For future use */
>>   };
>>   #endif /* _KERNEL_DMA_BENCHMARK_H */
>> --
>> 2.33.0
>>
> Thanks
> Barry

Thanks

Qinxin