On Sun, Dec 3, 2017 at 10:11 PM, Geert Uytterhoeven
<geert@xxxxxxxxxxxxxx> wrote:
> With gcc 4.1.2:
>
> mm/memory.o: In function `wp_huge_pmd':
> memory.c:(.text+0x9b4): undefined reference to `do_huge_pmd_wp_page'
>
> Interestingly, wp_huge_pmd() is emitted in the assembler output, but
> never called.
>
> Apparently replacing the call to pmd_write() in __handle_mm_fault() by a
> call to the more complex pmd_access_permitted() reduced the ability of
> the compiler to remove unused code.
An alternative would be to start using #ifdefs and dummies for the
!CONFIG_TRANSPARENT_HUGEPAGE case, instead of relying on the varying degree
of ability of the various compiler versions to do dead code analysis and
elimination.
> Fix this by marking wp_huge_pmd() inline, like was done in commit
> 91a90140f9987101 ("mm/memory.c: mark create_huge_pmd() inline to prevent
> build failure") for a similar problem.
>
> Fixes: c7da82b894e9eef6 ("mm: replace pmd_write with pmd_access_permitted in fault + gup paths")
> Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> ---
> mm/memory.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 5eb3d2524bdc2823..f4d52847ca07a414 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3831,7 +3831,7 @@ static inline int create_huge_pmd(struct vm_fault *vmf)
> return VM_FAULT_FALLBACK;
> }
>
> -static int wp_huge_pmd(struct vm_fault *vmf, pmd_t orig_pmd)
> +static inline int wp_huge_pmd(struct vm_fault *vmf, pmd_t orig_pmd)
> {
> if (vma_is_anonymous(vmf->vma))
> return do_huge_pmd_wp_page(vmf, orig_pmd);
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
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