[PATCH v2 19/37] mm/gup: remove record_subpages()

David Hildenbrand
2025-09-01T15:40:44Z

We can just cleanup the code by calculating the #refs earlier,
so we can just inline what remains of record_subpages().

Calculate the number of references/pages ahead of times, and record them
only once all our tests passed.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
mm/gup.c | 25 ++++++++-----------------
1 file changed, 8 insertions(+), 17 deletions(-)

diff --git a/mm/gup.c b/mm/gup.c
index c10cd969c1a3b..f0f4d1a68e094 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -484,19 +484,6 @@ static inline void mm_set_has_pinned_flag(struct mm_struct *mm)
#ifdef CONFIG_MMU

#ifdef CONFIG_HAVE_GUP_FAST
-static int record_subpages(struct page *page, unsigned long sz,
- unsigned long addr, unsigned long end,
- struct page **pages)
-{
- int nr;
-
- page += (addr & (sz - 1)) >> PAGE_SHIFT;
- for (nr = 0; addr != end; nr++, addr += PAGE_SIZE)
- pages[nr] = page++;
-
- return nr;
-}
-
/**
* try_grab_folio_fast() - Attempt to get or pin a folio in fast path.
* @page: pointer to page to be grabbed
@@ -2967,8 +2954,8 @@ static int gup_fast_pmd_leaf(pmd_t orig, pmd_t *pmdp, unsigned long addr,
if (pmd_special(orig))
return 0;

- page = pmd_page(orig);
- refs = record_subpages(page, PMD_SIZE, addr, end, pages + *nr);
+ refs = (end - addr) >> PAGE_SHIFT;
+ page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);

folio = try_grab_folio_fast(page, refs, flags);
if (!folio)
@@ -2989,6 +2976,8 @@ static int gup_fast_pmd_leaf(pmd_t orig, pmd_t *pmdp, unsigned long addr,
}

*nr += refs;
+ for (; refs; refs--)
+ *(pages++) = page++;
folio_set_referenced(folio);
return 1;
}
@@ -3007,8 +2996,8 @@ static int gup_fast_pud_leaf(pud_t orig, pud_t *pudp, unsigned long addr,
if (pud_special(orig))
return 0;

- page = pud_page(orig);
- refs = record_subpages(page, PUD_SIZE, addr, end, pages + *nr);
+ refs = (end - addr) >> PAGE_SHIFT;
+ page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);

folio = try_grab_folio_fast(page, refs, flags);
if (!folio)
@@ -3030,6 +3019,8 @@ static int gup_fast_pud_leaf(pud_t orig, pud_t *pudp, unsigned long addr,
}

*nr += refs;
+ for (; refs; refs--)
+ *(pages++) = page++;
folio_set_referenced(folio);
return 1;
}
--
2.50.1