On Tue, Jun 18, 2024 at 8:10 AM David Hildenbrand <david@xxxxxxxxxx> wrote:
>
> Let's simplify and reduce code indentation. In the RMAP_LEVEL_PTE case, we
> already check for nr when computing partially_mapped.
>
> For RMAP_LEVEL_PMD, it's a bit more confusing. Likely, we don't need the
> "nr" check, but we could have "nr < nr_pmdmapped" also if we stumbled
> into the "/* Raced ahead of another remove and an add? */" case. So
> let's simply move the nr check in there.
>
> Note that partially_mapped is always false for small folios.
>
> No functional change intended.
>
> Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Makes sense to me. FWIW:
Reviewed-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
> ---
> mm/rmap.c | 10 ++++------
> 1 file changed, 4 insertions(+), 6 deletions(-)
>
> diff --git a/mm/rmap.c b/mm/rmap.c
> index afec4b6800caf..aa900e46cdf82 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1551,11 +1551,12 @@ static __always_inline void __folio_remove_rmap(struct folio *folio,
> }
> }
>
> - partially_mapped = nr < nr_pmdmapped;
> + partially_mapped = nr && nr < nr_pmdmapped;
> break;
> }
>
> - if (nr) {
> + if (partially_mapped && folio_test_anon(folio) &&
> + list_empty(&folio->_deferred_list))
> /*
> * Queue anon large folio for deferred split if at least one
> * page of the folio is unmapped and at least one page
> @@ -1563,10 +1564,7 @@ static __always_inline void __folio_remove_rmap(struct folio *folio,
> *
> * Check partially_mapped first to ensure it is a large folio.
> */
> - if (folio_test_anon(folio) && partially_mapped &&
> - list_empty(&folio->_deferred_list))
> - deferred_split_folio(folio);
> - }
> + deferred_split_folio(folio);
FWIW, I prefer moving the comment out of the one-line if block as you
originally suggested in [1].
[1]https://lore.kernel.org/lkml/1a408ed1-7e81-457e-a205-db274b4d6b78@xxxxxxxxxx/
> __folio_mod_stat(folio, -nr, -nr_pmdmapped);
>
> /*
> --
> 2.45.2
>
