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From: Peter Xu <peterx@redhat.com>
To: kbuild-all@lists.01.org
Subject: Re: [aa:mapcount_deshare 20/27] mm/gup.c:2756:3: error: implicit declaration of function 'mm_set_has_pinned_flag'
Date: Tue, 11 May 2021 10:36:36 -0400
Message-ID: <YJqWdPZEro8Thkcr@t490s>
In-Reply-To: <YJqTa+FXy2g/kvEU@t490s>
List-Id: <oe-kbuild-all.lists.linux.dev>

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On Tue, May 11, 2021 at 10:23:39AM -0400, Peter Xu wrote:
> On Tue, May 11, 2021 at 08:31:23AM -0400, Andrea Arcangeli wrote:
> > Hello,
> > =

> > thanks to the report.
> > =

> > Peter, this isn't immediately clear to me, is it perhaps something
> > related to clang?
> > =

> > This is commit 8dec302e87453234fc7ac1cf4d09e4d577a06cf3
> =

> Andrea,
> =

> I guess it's probably a NOMMU arm config so the helper got opted out as I
> errornously put it into a CONFIG_MMU block without noticing..
> =

> So we may need to squash below into that commit.
> =

> I really should think of something to avoid such errors in the future, as=
 this
> is the 2nd time happening at least this year..  Probably I should always =
start
> adding helpers at the beginning of files so I won't overlook any macros..
> =

> Thanks,
> =

> ----8<----
> diff --git a/mm/gup.c b/mm/gup.c
> index bb130723a6717..0223644d0c61a 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -392,6 +392,17 @@ void unpin_user_pages(struct page **pages, unsigned =
long npages)
>  }
>  EXPORT_SYMBOL(unpin_user_pages);
>  =

> +/*
> + * Set the MMF_HAS_PINNED if not set yet; after set it'll be there for t=
he mm's
> + * lifecycle.  Avoid setting the bit unless necessary, or it might cause=
 write
> + * cache bouncing on large SMP machines for concurrent pinned gups.
> + */
> +static inline void mm_set_has_pinned_flag(unsigned long *mm_flags)
> +{
> +       if (!test_bit(MMF_HAS_PINNED, mm_flags))
> +               set_bit(MMF_HAS_PINNED, mm_flags);
> +}
> +
>  #ifdef CONFIG_MMU
>  static struct page *no_page_table(struct vm_area_struct *vma,
>                 unsigned int flags)
> @@ -1270,17 +1281,6 @@ int fixup_user_fault(struct mm_struct *mm,
>  }
>  EXPORT_SYMBOL_GPL(fixup_user_fault);
>  =

> -/*
> - * Set the MMF_HAS_PINNED if not set yet; after set it'll be there for t=
he mm's
> - * lifecycle.  Avoid setting the bit unless necessary, or it might cause=
 write
> - * cache bouncing on large SMP machines for concurrent pinned gups.
> - */
> -static inline void mm_set_has_pinned_flag(unsigned long *mm_flags)
> -{
> -       if (!test_bit(MMF_HAS_PINNED, mm_flags))
> -               set_bit(MMF_HAS_PINNED, mm_flags);
> -}
> -
>  /*
>   * Please note that this function, unlike __get_user_pages will not
>   * return 0 for nr_pages > 0 without FOLL_NOWAIT
> ----8<----

Btw, there's also a space issue with the patch (we need to reindent
mm_set_has_pinned_flag so to use tabs rather than spaces), otherwise checkp=
atch
seems to complain.  Sorry about both issues!

-- =

Peter Xu

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