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 <Zij97qGQY1MRrEb8@fedora>
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From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: Wed, 24 Apr 2024 15:09:13 +0200
Message-ID: <CAMuHMdVrx8M62ETfuX44UZ_y8ab-JwTNA28V6WObg_kFXP+HyA@mail.gmail.com>
Subject: Re: [PATCH] block: allow device to have both virt_boundary_mask and
 max segment size
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org, 
	janpieter.sollie@edpnet.be, Christoph Hellwig <hch@lst.de>, Mike Snitzer <snitzer@kernel.org>, 
	dm-devel@lists.linux.dev, Song Liu <song@kernel.org>, linux-raid@vger.kernel.org, 
	linux-renesas-soc@vger.kernel.org, linux-kernel@vger.kernel.org
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Hi Ming,

On Wed, Apr 24, 2024 at 2:41=E2=80=AFPM Ming Lei <ming.lei@redhat.com> wrot=
e:
> 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 a=
nd
> > > another one with max segment size, the stacking device have both limi=
ts
> > > 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=3D218687
> > > Reported-by: janpieter.sollie@edpnet.be
> > > Fixes: d690cb8ae14b ("block: add an API to atomically update queue li=
mits")
> > > Link: https://lore.kernel.org/linux-block/ZfGl8HzUpiOxCLm3@fedora/
> > > Cc: Christoph Hellwig <hch@lst.de>
> > > Cc: Mike Snitzer <snitzer@kernel.org>
> > > Cc: dm-devel@lists.linux.dev
> > > Cc: Song Liu <song@kernel.org>
> > > Cc: linux-raid@vger.kernel.org
> > > Signed-off-by: Ming Lei <ming.lei@redhat.com>
> >
> > 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=3Dy and IOMMU support enabled, this causes=
 a
> > warning on R-Car Gen3/Gen4 platforms:
> >
> >     DMA-API: renesas_sdhi_internal_dmac ee160000.mmc: mapping sg segmen=
t longer than device claims to support [len=3D86016] [max=3D65536]
> >     WARNING: CPU: 1 PID: 281 at kernel/dma/debug.c:1178 debug_dma_map_s=
g+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 t=
wo
>          * correctly.
>          */
> -       if (!lim->virt_boundary_mask) {
> +       if (lim->virt_boundary_mask) {
> +               if (!lim->max_segment_size)
> +                       lim->max_segment_size =3D UINT_MAX;
> +       } else {
>                 /*
>                  * The maximum segment size has an odd historic 64k defau=
lt that
>                  * drivers probably should override.  Just like the I/O s=
ize we

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

Gr{oetje,eeting}s,

                        Geert

--=20
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k=
org

In personal conversations with technical people, I call myself a hacker. Bu=
t
when I'm talking to journalists I just say "programmer" or something like t=
hat.
                                -- Linus Torvalds