Re: [PATCH] block: allow device to have both virt_boundary_mask and max segment size

[Geert Uytterhoeven]

Hi Ming,

On Wed, Apr 24, 2024 at 2:41 PM Ming Lei <ming.lei@xxxxxxxxxx> wrote:
> On Wed, Apr 24, 2024 at 12:26:26PM +0200, Geert Uytterhoeven wrote:
> > On Sun, 7 Apr 2024, Ming Lei wrote:
> > > When one stacking device is over one device with virt_boundary_mask and
> > > another one with max segment size, the stacking device have both limits
> > > set. This way is allowed before d690cb8ae14b ("block: add an API to
> > > atomically update queue limits").
> > >
> > > Relax the limit so that we won't break such kind of stacking setting.
> > >
> > > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218687
> > > Reported-by: janpieter.sollie@xxxxxxxxx
> > > Fixes: d690cb8ae14b ("block: add an API to atomically update queue limits")
> > > Link: https://lore.kernel.org/linux-block/ZfGl8HzUpiOxCLm3@fedora/
> > > Cc: Christoph Hellwig <hch@xxxxxx>
> > > Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
> > > Cc: dm-devel@xxxxxxxxxxxxxxx
> > > Cc: Song Liu <song@xxxxxxxxxx>
> > > Cc: linux-raid@xxxxxxxxxxxxxxx
> > > Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx>
> >
> > Thanks for your patch, which is now commit b561ea56a26415bf ("block:
> > allow device to have both virt_boundary_mask and max segment size") in
> > v6.9-rc4.
> >
> > With CONFIG_DMA_API_DEBUG_SG=y and IOMMU support enabled, this causes a
> > warning on R-Car Gen3/Gen4 platforms:
> >
> >     DMA-API: renesas_sdhi_internal_dmac ee160000.mmc: mapping sg segment longer than device claims to support [len=86016] [max=65536]
> >     WARNING: CPU: 1 PID: 281 at kernel/dma/debug.c:1178 debug_dma_map_sg+0x2ac/0x330
> >
> > Reverting this commit, or disabling IOMMU support fixes the issue.
>
> Can you test the following patch?
>
>
> diff --git a/block/blk-settings.c b/block/blk-settings.c
> index 8e1d7ed52fef..ebba05a2bc7f 100644
> --- a/block/blk-settings.c
> +++ b/block/blk-settings.c
> @@ -188,7 +188,10 @@ static int blk_validate_limits(struct queue_limits *lim)
>          * bvec and lower layer bio splitting is supposed to handle the two
>          * correctly.
>          */
> -       if (!lim->virt_boundary_mask) {
> +       if (lim->virt_boundary_mask) {
> +               if (!lim->max_segment_size)
> +                       lim->max_segment_size = UINT_MAX;
> +       } else {
>                 /*
>                  * The maximum segment size has an odd historic 64k default that
>                  * drivers probably should override.  Just like the I/O size we

Thanks, that works for me (both with/without IOMMU support)!
Tested-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68korg

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds