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Subject: Re: [PATCH] mm: get rid of odd jump label in find_mergeable_anon_vma
To:     linmiaohe <linmiaohe@huawei.com>, akpm@linux-foundation.org,
        richardw.yang@linux.intel.com, sfr@canb.auug.org.au,
        rppt@linux.ibm.com, jannh@google.com, steve.capper@arm.com,
        catalin.marinas@arm.com, aarcange@redhat.com,
        chenjianhong2@huawei.com, walken@google.com,
        dave.hansen@linux.intel.com, tiny.windzz@gmail.com
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org
References: <1573799768-15650-1-git-send-email-linmiaohe@huawei.com>
From:   David Hildenbrand <david@redhat.com>
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Message-ID: <5277de34-ecb3-831e-c697-1fd3f66b45ba@redhat.com>
Date:   Fri, 15 Nov 2019 13:58:02 +0100
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On 15.11.19 07:36, linmiaohe wrote:
> From: Miaohe Lin <linmiaohe@huawei.com>

I'm pro removing unnecessary jump labels.

Subject: "mm: get rid of jump labels in find_mergeable_anon_vma()"

>=20
> The odd jump label try_prev and none is not really need

s/odd jump label/jump labels/

s/is/are/

> in func find_mergeable_anon_vma, eliminate them to
> improve readability.
>=20
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> ---
>  mm/mmap.c | 18 +++++++-----------
>  1 file changed, 7 insertions(+), 11 deletions(-)
>=20
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 4d4db76a07da..ab980d468a10 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1276,25 +1276,21 @@ static struct anon_vma *reusable_anon_vma(struct =
vm_area_struct *old, struct vm_
>   */
>  struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
>  {
> -=09struct anon_vma *anon_vma;
> +=09struct anon_vma *anon_vma =3D NULL;
>  =09struct vm_area_struct *near;
> =20
>  =09near =3D vma->vm_next;
> -=09if (!near)
> -=09=09goto try_prev;
> -
> -=09anon_vma =3D reusable_anon_vma(near, vma, near);
> +=09if (near)
> +=09=09anon_vma =3D reusable_anon_vma(near, vma, near);>  =09if (anon_vma=
)
>  =09=09return anon_vma;

Let me suggest the following instead:

/* Try next first */
near =3D vma->vm_next;
if (near) {
=09anon_vma =3D reusable_anon_vma(near, vma, near);
=09if (anon_vma)
=09=09return anon_vma;
}
/* Try prev next */
near =3D vma->vm_prev;
if (near) {
=09anon_vma =3D reusable_anon_vma(near, vma, near);
=09if (anon_vma)
=09=09return anon_vma;
}

> -try_prev:
> -=09near =3D vma->vm_prev;
> -=09if (!near)
> -=09=09goto none;
> =20
> -=09anon_vma =3D reusable_anon_vma(near, near, vma);
> +=09near =3D vma->vm_prev;
> +=09if (near)
> +=09=09anon_vma =3D reusable_anon_vma(near, near, vma);
>  =09if (anon_vma)
>  =09=09return anon_vma;
> -none:
> +
>  =09/*
>  =09 * There's no absolute need to look only at touching neighbours:
>  =09 * we could search further afield for "compatible" anon_vmas.
>=20


--=20

Thanks,

David / dhildenb