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From:   Axel Rasmussen <axelrasmussen@google.com>
Date:   Tue, 16 Mar 2021 09:16:57 -0700
Message-ID: <CAJHvVcgBrpg0pq4b4Lisc4Qsx4W_y=0_piEvO6AJV_Q2+o4ArQ@mail.gmail.com>
Subject: Re: [PATCH v2] mm/shmem: Enclose shmem_mcopy_atomic_pte() with 'CONFIG_USERFAULTFD'
To:     SeongJae Park <sjpark@amazon.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Hugh Dickins <hughd@google.com>, amit@kernel.org,
        Linux MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        SeongJae Park <sjpark@amazon.de>
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Sorry for the build failure! I sent a new version of my patch with
this same fix on the 10th
(https://lore.kernel.org/patchwork/patch/1392464/), and I believe
Andrew has already included it in his tree.

On Tue, Mar 16, 2021 at 8:40 AM SeongJae Park <sjpark@amazon.com> wrote:
>
> From: SeongJae Park <sjpark@amazon.de>
>
> Commit 49eeab03fa0a ("userfaultfd: support minor fault handling for
> shmem") introduced shmem_mcopy_atomic_pte().  The function is declared
> in 'userfaultfd_k.h' when 'CONFIG_USERFAULTFD' is defined, and defined
> as 'BUG()' if the config is unset.  However, the definition of the
> function in 'shmem.c' is not protected by the '#ifdef' macro.  As a
> result, the build fails when the config is not set.  This commit fixes
> the problem.
>
> Fixes: 49eeab03fa0a ("userfaultfd: support minor fault handling for shmem")
> Signed-off-by: SeongJae Park <sjpark@amazon.de>
> ---
>
> Changes from v1
> - Remove unnecessary internal code review URL
>
> ---
>  mm/shmem.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 547df2b766f7..c0d3abefeb3f 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2359,6 +2359,7 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode
>         return inode;
>  }
>
> +#ifdef CONFIG_USERFAULTFD
>  int shmem_mcopy_atomic_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd,
>                            struct vm_area_struct *dst_vma,
>                            unsigned long dst_addr, unsigned long src_addr,
> @@ -2492,6 +2493,7 @@ int shmem_mcopy_atomic_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd,
>         shmem_inode_unacct_blocks(inode, 1);
>         goto out;
>  }
> +#endif
>
>  #ifdef CONFIG_TMPFS
>  static const struct inode_operations shmem_symlink_inode_operations;
> --
> 2.17.1
>
>
>
>
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>