linux-kernel - Re: [PATCH -next] libnvdimm/region: Fix build error

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Date:   Tue, 31 Mar 2020 02:46:52 -0700
From:   Dan Williams <dan.j.williams@...el.com>
To:     YueHaibing <yuehaibing@...wei.com>
Cc:     Vishal L Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        "Weiny, Ira" <ira.weiny@...el.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        jmoyer <jmoyer@...hat.com>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next] libnvdimm/region: Fix build error

On Mon, Mar 30, 2020 at 7:23 AM YueHaibing <yuehaibing@...wei.com> wrote:
>
> On CONFIG_PPC32=y build fails:
>
> drivers/nvdimm/region_devs.c:1034:14: note: in expansion of macro ‘do_div’
>   remainder = do_div(per_mapping, mappings);
>               ^~~~~~
> In file included from ./arch/powerpc/include/generated/asm/div64.h:1:0,
>                  from ./include/linux/kernel.h:18,
>                  from ./include/asm-generic/bug.h:19,
>                  from ./arch/powerpc/include/asm/bug.h:109,
>                  from ./include/linux/bug.h:5,
>                  from ./include/linux/scatterlist.h:7,
>                  from drivers/nvdimm/region_devs.c:5:
> ./include/asm-generic/div64.h:243:22: error: passing argument 1 of ‘__div64_32’ from incompatible pointer type [-Werror=incompatible-pointer-types]
>    __rem = __div64_32(&(n), __base); \
>
> Use div_u64 instead of do_div to fix this.
>
> Fixes: 2522afb86a8c ("libnvdimm/region: Introduce an 'align' attribute")
> Signed-off-by: YueHaibing <yuehaibing@...wei.com>
> ---
>  drivers/nvdimm/region_devs.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
> index bf239e783940..2291f0649d27 100644
> --- a/drivers/nvdimm/region_devs.c
> +++ b/drivers/nvdimm/region_devs.c
> @@ -564,7 +564,7 @@ static ssize_t align_store(struct device *dev,
>          * space for the namespace.
>          */
>         dpa = val;
> -       remainder = do_div(dpa, nd_region->ndr_mappings);
> +       remainder = div_u64(dpa, nd_region->ndr_mappings);

This is not an equivalent conversion.

    dpa = div_u64_rem(val, nd_region->ndr_mappings, &remainder);

>         if (!is_power_of_2(dpa) || dpa < PAGE_SIZE
>                         || val > region_size(nd_region) || remainder)
>                 return -EINVAL;
> @@ -1031,7 +1031,7 @@ static unsigned long default_align(struct nd_region *nd_region)
>
>         mappings = max_t(u16, 1, nd_region->ndr_mappings);
>         per_mapping = align;
> -       remainder = do_div(per_mapping, mappings);
> +       remainder = div_u64(per_mapping, mappings);

Same problem here.