Re: [PATCH v7 1/4] mm/rmap: remove duplicated exit code in pagewalk loop

[Barry Song]

On Tue, Jun 11, 2024 at 12:02 AM Lance Yang <ioworker0@xxxxxxxxx> wrote:
>
> Introduce the labels walk_done and walk_done_err as exit points to
> eliminate duplicated exit code in the pagewalk loop.
>
> Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>
> Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
> Signed-off-by: Lance Yang <ioworker0@xxxxxxxxx>

I don't think "return false" necessarily indicates an error, so
"walk_done_err" doesn't seem like an appropriate name.
However, this is a minor issue.

Reviewed-by: Barry Song <baohua@xxxxxxxxxx>

> ---
>  mm/rmap.c | 40 +++++++++++++++-------------------------
>  1 file changed, 15 insertions(+), 25 deletions(-)
>
> diff --git a/mm/rmap.c b/mm/rmap.c
> index e8fc5ecb59b2..ddffa30c79fb 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1679,9 +1679,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
>                         /* Restore the mlock which got missed */
>                         if (!folio_test_large(folio))
>                                 mlock_vma_folio(folio, vma);
> -                       page_vma_mapped_walk_done(&pvmw);
> -                       ret = false;
> -                       break;
> +                       goto walk_done_err;
>                 }
>
>                 pfn = pte_pfn(ptep_get(pvmw.pte));
> @@ -1719,11 +1717,8 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
>                          */
>                         if (!anon) {
>                                 VM_BUG_ON(!(flags & TTU_RMAP_LOCKED));
> -                               if (!hugetlb_vma_trylock_write(vma)) {
> -                                       page_vma_mapped_walk_done(&pvmw);
> -                                       ret = false;
> -                                       break;
> -                               }
> +                               if (!hugetlb_vma_trylock_write(vma))
> +                                       goto walk_done_err;
>                                 if (huge_pmd_unshare(mm, vma, address, pvmw.pte)) {
>                                         hugetlb_vma_unlock_write(vma);
>                                         flush_tlb_range(vma,
> @@ -1738,8 +1733,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
>                                          * actual page and drop map count
>                                          * to zero.
>                                          */
> -                                       page_vma_mapped_walk_done(&pvmw);
> -                                       break;
> +                                       goto walk_done;
>                                 }
>                                 hugetlb_vma_unlock_write(vma);
>                         }
> @@ -1811,9 +1805,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
>                         if (unlikely(folio_test_swapbacked(folio) !=
>                                         folio_test_swapcache(folio))) {
>                                 WARN_ON_ONCE(1);
> -                               ret = false;
> -                               page_vma_mapped_walk_done(&pvmw);
> -                               break;
> +                               goto walk_done_err;
>                         }
>
>                         /* MADV_FREE page check */
> @@ -1852,23 +1844,17 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
>                                  */
>                                 set_pte_at(mm, address, pvmw.pte, pteval);
>                                 folio_set_swapbacked(folio);
> -                               ret = false;
> -                               page_vma_mapped_walk_done(&pvmw);
> -                               break;
> +                               goto walk_done_err;
>                         }
>
>                         if (swap_duplicate(entry) < 0) {
>                                 set_pte_at(mm, address, pvmw.pte, pteval);
> -                               ret = false;
> -                               page_vma_mapped_walk_done(&pvmw);
> -                               break;
> +                               goto walk_done_err;
>                         }
>                         if (arch_unmap_one(mm, vma, address, pteval) < 0) {
>                                 swap_free(entry);
>                                 set_pte_at(mm, address, pvmw.pte, pteval);
> -                               ret = false;
> -                               page_vma_mapped_walk_done(&pvmw);
> -                               break;
> +                               goto walk_done_err;
>                         }
>
>                         /* See folio_try_share_anon_rmap(): clear PTE first. */
> @@ -1876,9 +1862,7 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
>                             folio_try_share_anon_rmap_pte(folio, subpage)) {
>                                 swap_free(entry);
>                                 set_pte_at(mm, address, pvmw.pte, pteval);
> -                               ret = false;
> -                               page_vma_mapped_walk_done(&pvmw);
> -                               break;
> +                               goto walk_done_err;
>                         }
>                         if (list_empty(&mm->mmlist)) {
>                                 spin_lock(&mmlist_lock);
> @@ -1918,6 +1902,12 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
>                 if (vma->vm_flags & VM_LOCKED)
>                         mlock_drain_local();
>                 folio_put(folio);
> +               continue;
> +walk_done_err:
> +               ret = false;
> +walk_done:
> +               page_vma_mapped_walk_done(&pvmw);
> +               break;
>         }
>
>         mmu_notifier_invalidate_range_end(&range);
> --
> 2.33.1
>