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
Acked-by: Barry Song <baohua@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..48e2ff95332f 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 Tue, Oct 28, 2025 at 8:09 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")

It would be preferable to include the following as well:

Reported-by: Barry Song <baohua@kernel.org>
Closes: https://lore.kernel.org/lkml/CAGsJ_4waiZ2+NBJG+SCnbNk+nQ_ZF13_Q5FHJqZyxyJTcEop2A@mail.gmail.com/

> Cc: stable@vger.kernel.org
> Acked-by: Barry Song <baohua@kernel.org>
> Signed-off-by: Qinxin Xia <xiaqinxin@huawei.com>

Thank you. We also need to include Jonathan’s tag[1]:

Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>

[1] https://lore.kernel.org/lkml/20250616105318.00001132@huawei.com/

I assume Marek can assist with adding those tags when you apply the patch?

Thanks
Barry

On 28.10.2025 20:57, Barry Song wrote:
> On Tue, Oct 28, 2025 at 8:09 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")
> It would be preferable to include the following as well:
>
> Reported-by: Barry Song <baohua@kernel.org>
> Closes: https://lore.kernel.org/lkml/CAGsJ_4waiZ2+NBJG+SCnbNk+nQ_ZF13_Q5FHJqZyxyJTcEop2A@mail.gmail.com/
>
>> Cc: stable@vger.kernel.org
>> Acked-by: Barry Song <baohua@kernel.org>
>> Signed-off-by: Qinxin Xia <xiaqinxin@huawei.com>
> Thank you. We also need to include Jonathan’s tag[1]:
>
> Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
>
> [1] https://lore.kernel.org/lkml/20250616105318.00001132@huawei.com/
>
> I assume Marek can assist with adding those tags when you apply the patch?

Thanks, applied to dma-mapping-fixes 
branch with all the above additional tags.


Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland