Re: [PATCH] dma-mapping: direct: fix missing mapping for THRU_HOST_BRIDGE segments

[Pranjal Shrivastava <praan@google.com>]

On Thu, Jun 04, 2026 at 10:18:56AM +0300, Leon Romanovsky wrote:
> On Wed, Jun 03, 2026 at 06:25:22PM +0200, Marek Szyprowski wrote:
> > On 03.06.2026 03:37, lirongqing wrote:
> > > From: Li RongQing <lirongqing@baidu.com>
> > >
> > > In dma_direct_map_sg(), the case PCI_P2PDMA_MAP_THRU_HOST_BRIDGE
> > > incorrectly used 'break' instead of falling through to MAP_NONE.
> > > As a result, segments traversing the host bridge skipped the required
> > > dma_direct_map_phys() call entirely, leaving sg->dma_address
> > > uninitialized and leading to DMA failures. Fix this by using
> > > 'fallthrough;'.
> > >
> > > Fixes: a25e7962db0d79 ("PCI/P2PDMA: Refactor the p2pdma mapping helpers")
> > > Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
> > > Signed-off-by: Li RongQing <lirongqing@baidu.com>
> > 
> > Applied to dma-mapping-fixes, thanks!
> 
> The change looks correct, but it will be better if this change will
> improve d0d08f4bd7f6 ("dma-direct: Fix missing sg_dma_len assignment in
> P2PDMA bus mappings") too.

I was thinking the same and was about to post a fix.

> 
> diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
> index ec887f443741..e98b6547c950 100644
> --- a/kernel/dma/direct.c
> +++ b/kernel/dma/direct.c
> @@ -489,9 +489,8 @@ int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
>                 case PCI_P2PDMA_MAP_BUS_ADDR:
>                         sg->dma_address = pci_p2pdma_bus_addr_map(
>                                 p2pdma_state.mem, sg_phys(sg));
> -                       sg_dma_len(sg) = sg->length;
>                         sg_dma_mark_bus_address(sg);
> -                       continue;
> +                       break;
>                 default:
>                         ret = -EREMOTEIO;
>                         goto out_unmap;
> 
> Thanks
> 

For this fix:
Reviewed-by: Pranjal Shrivastava <praan@google.com>

Thanks,
Praan