[PATCH v4 3/4] mm/gup: remove gup_fast_pgd_leaf() and clean up the relevant codes

Baoquan He
2025-04-10T03:57:45Z

In the current kernel, only pud huge page is supported in some
architectures. P4d and pgd huge pages haven't been supported yet.
And in mm/gup.c, there's no pgd huge page handling in the
follow_page_mask() code path. Hence it doesn't make sense to only
have gup_fast_pgd_leaf() in gup_fast code path.

Here remove gup_fast_pgd_leaf() and clean up the relevant codes.

Signed-off-by: Baoquan He <bhe@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Acked-by: David Hildenbrand <david@redhat.com>
---
mm/gup.c | 49 +++----------------------------------------------
1 file changed, 3 insertions(+), 46 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index eb668da933e1..77a5bc622567 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -3172,46 +3172,6 @@ static int gup_fast_pud_leaf(pud_t orig, pud_t *pudp, unsigned long addr,
return 1;
}

-static int gup_fast_pgd_leaf(pgd_t orig, pgd_t *pgdp, unsigned long addr,
- unsigned long end, unsigned int flags, struct page **pages,
- int *nr)
-{
- int refs;
- struct page *page;
- struct folio *folio;
-
- if (!pgd_access_permitted(orig, flags & FOLL_WRITE))
- return 0;
-
- BUILD_BUG_ON(pgd_devmap(orig));
-
- page = pgd_page(orig);
- refs = record_subpages(page, PGDIR_SIZE, addr, end, pages + *nr);
-
- folio = try_grab_folio_fast(page, refs, flags);
- if (!folio)
- return 0;
-
- if (unlikely(pgd_val(orig) != pgd_val(*pgdp))) {
- gup_put_folio(folio, refs, flags);
- return 0;
- }
-
- if (!pgd_write(orig) && gup_must_unshare(NULL, flags, &folio->page)) {
- gup_put_folio(folio, refs, flags);
- return 0;
- }
-
- if (!gup_fast_folio_allowed(folio, flags)) {
- gup_put_folio(folio, refs, flags);
- return 0;
- }
-
- *nr += refs;
- folio_set_referenced(folio);
- return 1;
-}
-
static int gup_fast_pmd_range(pud_t *pudp, pud_t pud, unsigned long addr,
unsigned long end, unsigned int flags, struct page **pages,
int *nr)
@@ -3306,12 +3266,9 @@ static void gup_fast_pgd_range(unsigned long addr, unsigned long end,
next = pgd_addr_end(addr, end);
if (pgd_none(pgd))
return;
- if (unlikely(pgd_leaf(pgd))) {
- if (!gup_fast_pgd_leaf(pgd, pgdp, addr, next, flags,
- pages, nr))
- return;
- } else if (!gup_fast_p4d_range(pgdp, pgd, addr, next, flags,
- pages, nr))
+ BUILD_BUG_ON(pgd_leaf(pgd));
+ if (!gup_fast_p4d_range(pgdp, pgd, addr, next, flags,
+ pages, nr))
return;
} while (pgdp++, addr = next, addr != end);
}
--
2.41.0