Re: [PATCH 2/3] mm/rmap: could be partially_mapped only after no entire map

[Lorenzo Stoakes <lorenzo.stoakes@oracle.com>]

On Fri, Aug 15, 2025 at 08:49:42AM +0000, Wei Yang wrote:
> If it is not the last entire map, we are sure the folio is not partially
> mapped.
>
> Move the check when there is no entire map.
>

This one I don't like, you're having to sit and think about why it is that
this would be the case, vs. just unconditionally doing it.

Again, as mentioned on previous series, just because we could do something
doesn't mean we should, unless there's statistically reliable perf data on
something real-world indicating we _must_, code clarity absolutely beats
everything else on importance.

So yeah, sorry but no to this patch, please resend with just the two
reviewed (unless David radically disagrees with me :)

> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
> Cc: David Hildenbrand <david@redhat.com>
> Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> Cc: Rik van Riel <riel@surriel.com>
> Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Harry Yoo <harry.yoo@oracle.com>
> ---
>  mm/rmap.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/rmap.c b/mm/rmap.c
> index a927437a56c2..645d924bfc7d 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1757,9 +1757,9 @@ static __always_inline void __folio_remove_rmap(struct folio *folio,
>  				/* An add of ENTIRELY_MAPPED raced ahead */
>  				nr = 0;
>  			}
> -		}
>
> -		partially_mapped = nr && nr < nr_pmdmapped;
> +			partially_mapped = nr && nr < nr_pmdmapped;
> +		}
>  		break;
>  	default:
>  		BUILD_BUG();
> --
> 2.34.1
>
>