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SubjectRe: [PATCH v4] mm: get rid of odd jump labels in find_mergeable_anon_vma()
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On 18.11.19 13:24, linmiaohe wrote:
> From: Miaohe Lin <linmiaohe@huawei.com>
>
> The jump labels try_prev and none are not really needed
> in find_mergeable_anon_vma(), eliminate them to improve
> readability.
>
> Reviewed-by: David Hildenbrand <david@redhat.com>
> Reviewed-by: John Hubbard <jhubbard@nvidia.com>
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> ---
> -v2:
> Fix commit descriptions and further simplify the code
> as suggested by David Hildenbrand and John Hubbard.
> -v3:
> Rewrite patch version info. Don't show this in commit log.
> -v4:
> Get rid of var near completely as well.
> ---
> mm/mmap.c | 36 ++++++++++++++++--------------------
> 1 file changed, 16 insertions(+), 20 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 91d5e097a4ed..4d93bda30eac 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1273,26 +1273,22 @@ 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)
> {
> - struct anon_vma *anon_vma;
> - struct vm_area_struct *near;
> -
> - near = vma->vm_next;
> - if (!near)
> - goto try_prev;
> -
> - anon_vma = reusable_anon_vma(near, vma, near);
> - if (anon_vma)
> - return anon_vma;
> -try_prev:
> - near = vma->vm_prev;
> - if (!near)
> - goto none;
> -
> - anon_vma = reusable_anon_vma(near, near, vma);
> - if (anon_vma)
> - return anon_vma;
> -none:
> + struct anon_vma *anon_vma = NULL;
> +
> + /* Try next first. */
> + if (vma->vm_next) {
> + anon_vma = reusable_anon_vma(vma->vm_next, vma, vma->vm_next);
> + if (anon_vma)
> + return anon_vma;
> + }
> +
> + /* Try prev next. */
> + if (vma->vm_prev)
> + anon_vma = reusable_anon_vma(vma->vm_prev, vma->vm_prev, vma);
> +
> /*
> + * We might reach here with anon_vma == NULL if we can't find
> + * any reusable anon_vma.
> * There's no absolute need to look only at touching neighbours:
> * we could search further afield for "compatible" anon_vmas.
> * But it would probably just be a waste of time searching,
> @@ -1300,7 +1296,7 @@ struct anon_vma *find_mergeable_anon_vma(struct vm_area_struct *vma)
> * We're trying to allow mprotect remerging later on,
> * not trying to minimize memory used for anon_vmas.
> */
> - return NULL;
> + return anon_vma;
> }
>
> /*
>

Looks much better, thanks!

Reviewed-by: David Hildenbrand <david@redhat.com>

--

Thanks,

David / dhildenb

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