mm/rmap: not necessary to mask off FOLIO_PAGES_MAPPED

At this point, we are in an if branch conditional on (nr <
ENTIRELY_MAPPED), and FOLIO_PAGES_MAPPED is equal to (ENTIRELY_MAPPED -
1).  This means the upper bits are already cleared.

It is not necessary to mask it off.

Link: https://lkml.kernel.org/r/20250817032647.29147-2-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: David Hildenbrand <david@redhat.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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/rmap.c b/mm/rmap.c
index 4c00348c35fce8581bd128de23762165a50cdc1d..2f8e7ce03685b315c122f9557ee138c7f30d1247 100644 (file)
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1748,7 +1748,7 @@ static __always_inline void __folio_remove_rmap(struct folio *folio,
                                nr_pages = folio_large_nr_pages(folio);
                                if (level == PGTABLE_LEVEL_PMD)
                                        nr_pmdmapped = nr_pages;
-                               nr = nr_pages - (nr & FOLIO_PAGES_MAPPED);
+                               nr = nr_pages - nr;
                                /* Raced ahead of another remove and an add? */
                                if (unlikely(nr < 0))
                                        nr = 0;