Re: [PATCH 2/2] dma-mapping: benchmark: Add padding to ensure uABI remained consistent

[Qinxin Xia]

On 2025/7/24 17:07:08, Barry Song <21cnbao@xxxxxxxxx> wrote:
> On Thu, Jul 24, 2025 at 4:56 PM Qinxin Xia <xiaqinxin@xxxxxxxxxx> 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@xxxxxxxxxxxxxxx
> > Acked-by: Barry Song <baohua@xxxxxxxxxx>
> > Signed-off-by: Qinxin Xia <xiaqinxin@xxxxxxxxxx>
>
> I don’t think these two patches should be part of the same series. This
> one is a bug fix and should be handled separately—ideally picked up on
> its own and backported to stable.
>
> Also, the subject should not say "Add"—it should be "Restore". I assume
> Marek can handle it?
>
> > ---
> >   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

Ok, I will send a new version to fix it.
Thanks