Re: [PATCH] mm, vmalloc: fix vmalloc users tracking properly

[Geert Uytterhoeven]

Hi Michal,

On Tue, May 9, 2017 at 4:41 PM, Michal Hocko <mhocko@xxxxxxxxxx> wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
>
> 1f5307b1e094 ("mm, vmalloc: properly track vmalloc users") has pulled
> asm/pgtable.h include dependency to linux/vmalloc.h and that turned out
> to be a bad idea for some architectures. E.g. m68k fails with
>    In file included from arch/m68k/include/asm/pgtable_mm.h:145:0,
>                     from arch/m68k/include/asm/pgtable.h:4,
>                     from include/linux/vmalloc.h:9,
>                     from arch/m68k/kernel/module.c:9:
>    arch/m68k/include/asm/mcf_pgtable.h: In function 'nocache_page':
>>> arch/m68k/include/asm/mcf_pgtable.h:339:43: error: 'init_mm' undeclared (first use in this function)
>     #define pgd_offset_k(address) pgd_offset(&init_mm, address)
>
> as spotted by kernel build bot. nios2 fails for other reason
> In file included from ./include/asm-generic/io.h:767:0,
>                  from ./arch/nios2/include/asm/io.h:61,
>                  from ./include/linux/io.h:25,
>                  from ./arch/nios2/include/asm/pgtable.h:18,
>                  from ./include/linux/mm.h:70,
>                  from ./include/linux/pid_namespace.h:6,
>                  from ./include/linux/ptrace.h:9,
>                  from ./arch/nios2/include/uapi/asm/elf.h:23,
>                  from ./arch/nios2/include/asm/elf.h:22,
>                  from ./include/linux/elf.h:4,
>                  from ./include/linux/module.h:15,
>                  from init/main.c:16:
> ./include/linux/vmalloc.h: In function '__vmalloc_node_flags':
> ./include/linux/vmalloc.h:99:40: error: 'PAGE_KERNEL' undeclared (first use in this function); did you mean 'GFP_KERNEL'?
>
> which is due to the newly added #include <asm/pgtable.h>, which on nios2
> includes <linux/io.h> and thus <asm/io.h> and <asm-generic/io.h> which
> again includes <linux/vmalloc.h>.
>
> Tweaking that around just turns out a bigger headache than
> necessary. This patch reverts 1f5307b1e094 and reimplements the original
> fix in a different way. __vmalloc_node_flags can stay static inline
> which will cover vmalloc* functions. We only have one external user
> (kvmalloc_node) and we can export __vmalloc_node_flags_caller and
> provide the caller directly. This is much simpler and it doesn't really
> need any games with header files.
>
> Fixes: 1f5307b1e094 ("mm, vmalloc: properly track vmalloc users")
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>

FWIW, this did fix the following build failure on m68k in linus/master
(commit 2868b2513aa732a9 ("Merge tag 'linux-kselftest-4.12-rc1' of
git://git.kernel.org/pub/scm/linux/kernel/git/shuah/linux-kselftest"):

    In file included from arch/m68k/include/asm/pgtable_mm.h:148,
                     from arch/m68k/include/asm/pgtable.h:5,
                     from include/linux/vmalloc.h:10,
                     from arch/m68k/kernel/module.c:10:
    arch/m68k/include/asm/motorola_pgtable.h: In function âpgd_offsetâ:
    arch/m68k/include/asm/motorola_pgtable.h:198: error: dereferencing
pointer to incomplete type
    scripts/Makefile.build:294: recipe for target
'arch/m68k/kernel/module.o' failed

but given the complaints from 0day on this and future versions, I think it's
better not to provide a Tested-by yet.

Gr{oetje,eeting}s,

                        Geert

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

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