On Thu, Mar 09, 2023 at 12:12:49PM +0100, Vlastimil Babka wrote:
> In the merging preparation part of vma_merge(), some vma pointer
> variables are assigned for later execution of the merge, but also read
> from in the block itself. The code is easier follow and check against
> the cases diagram in the comment if the code reads only from the
> "primary" vma variables prev, mid, next instead. No functional change.
>
> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>
> ---
> mm/mmap.c | 14 +++++++-------
> 1 file changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 740b54be3ed4..0a8b052e3022 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -950,16 +950,16 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
> is_mergeable_anon_vma(prev->anon_vma, next->anon_vma, NULL)) {
> remove = mid; /* case 1 */
> vma_end = next->vm_end;
> - err = dup_anon_vma(res, remove);
> + err = dup_anon_vma(prev, mid);
> if (mid != next) { /* case 6 */
> remove2 = next;
> - if (!remove->anon_vma)
> - err = dup_anon_vma(res, remove2);
> + if (!mid->anon_vma)
> + err = dup_anon_vma(prev, next);
> }
> } else if (merge_prev) {
> err = 0; /* case 2 */
> if (mid && end > mid->vm_start) {
> - err = dup_anon_vma(res, mid);
> + err = dup_anon_vma(prev, mid);
> if (end == mid->vm_end) { /* case 7 */
> remove = mid;
> } else { /* case 5 */
> @@ -972,8 +972,8 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
> if (prev && addr < prev->vm_end) { /* case 4 */
> vma_end = addr;
> adjust = mid;
> - adj_next = -(vma->vm_end - addr);
> - err = dup_anon_vma(adjust, prev);
> + adj_next = -(prev->vm_end - addr);
> + err = dup_anon_vma(mid, prev);
> } else {
> vma = next; /* case 3 */
> vma_start = addr;
> @@ -982,7 +982,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
> err = 0;
> if (mid != next) { /* case 8 */
> remove = mid;
> - err = dup_anon_vma(res, remove);
> + err = dup_anon_vma(next, mid);
> }
> }
> }
> --
> 2.39.2
>
Big improvement in readability already here.
Reviewed-by: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
