[PATCH 1/6] mm/gup: move gup_can_follow_protnone() to gup.c

gup_can_follow_protnone() is defined in include/linux/mm.h but only used
by mm/gup.c.

First, there is no reason to have it in already gigantic header.

Next, the upcoming refactoring of userfaultfd flags will make
gup_can_follow_protnone() depend on userfaultfd_k.h which would cause a
cyclic header dependency.

Move gup_can_follow_protnone() to mm/gup.c.

No functional change.

Assisted-by: copilot:claude-opus-5
Signed-off-by: Mike Rapoport (Microsoft) <[email protected]>
---
 include/linux/mm.h | 38 --------------------------------------
 mm/gup.c           | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 38 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 0829e0d3b2d1..4daf9cd6ae8e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -4860,44 +4860,6 @@ static inline int vm_fault_to_errno(vm_fault_t vm_fault, int foll_flags)
 	return 0;
 }
 
-/*
- * Indicates whether GUP can follow a PROT_NONE mapped page, or whether
- * a (NUMA hinting or userfaultfd RWP) fault is required.
- */
-static inline bool gup_can_follow_protnone(const struct vm_area_struct *vma,
-					   unsigned int flags)
-{
-	/*
-	 * VM_UFFD_RWP uses protnone as an access-tracking marker, not for
-	 * NUMA hinting. GUP must always take a fault so the access is
-	 * delivered to userfaultfd, regardless of FOLL_HONOR_NUMA_FAULT.
-	 *
-	 * Only do so while the VMA is accessible. If it has been made
-	 * inaccessible (e.g. mprotect(PROT_NONE)), fall through to the guard
-	 * below: forcing a fault there would loop, as handle_mm_fault() makes
-	 * no progress on protnone in an inaccessible VMA, and the access is
-	 * denied regardless of RWP anyway.
-	 */
-	if (vma_test_single_mask(vma, VMA_UFFD_RWP) && vma_is_accessible(vma))
-		return false;
-
-	/*
-	 * If callers don't want to honor NUMA hinting faults, no need to
-	 * determine if we would actually have to trigger a NUMA hinting fault.
-	 */
-	if (!(flags & FOLL_HONOR_NUMA_FAULT))
-		return true;
-
-	/*
-	 * NUMA hinting faults don't apply in inaccessible (PROT_NONE) VMAs.
-	 *
-	 * Requiring a fault here even for inaccessible VMAs would mean that
-	 * FOLL_FORCE cannot make any progress, because handle_mm_fault()
-	 * refuses to process NUMA hinting faults in inaccessible VMAs.
-	 */
-	return !vma_is_accessible(vma);
-}
-
 typedef int (*pte_fn_t)(pte_t *pte, unsigned long addr, void *data);
 extern int apply_to_page_range(struct mm_struct *mm, unsigned long address,
 			       unsigned long size, pte_fn_t fn, void *data);
diff --git a/mm/gup.c b/mm/gup.c
index eb898ea1ee22..500e2aa99e48 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -633,6 +633,44 @@ static struct page *no_page_table(struct vm_area_struct *vma,
 	return NULL;
 }
 
+/*
+ * Indicates whether GUP can follow a PROT_NONE mapped page, or whether
+ * a (NUMA hinting or userfaultfd RWP) fault is required.
+ */
+static inline bool gup_can_follow_protnone(const struct vm_area_struct *vma,
+					   unsigned int flags)
+{
+	/*
+	 * VM_UFFD_RWP uses protnone as an access-tracking marker, not for
+	 * NUMA hinting. GUP must always take a fault so the access is
+	 * delivered to userfaultfd, regardless of FOLL_HONOR_NUMA_FAULT.
+	 *
+	 * Only do so while the VMA is accessible. If it has been made
+	 * inaccessible (e.g. mprotect(PROT_NONE)), fall through to the guard
+	 * below: forcing a fault there would loop, as handle_mm_fault() makes
+	 * no progress on protnone in an inaccessible VMA, and the access is
+	 * denied regardless of RWP anyway.
+	 */
+	if (vma_test_single_mask(vma, VMA_UFFD_RWP) && vma_is_accessible(vma))
+		return false;
+
+	/*
+	 * If callers don't want to honor NUMA hinting faults, no need to
+	 * determine if we would actually have to trigger a NUMA hinting fault.
+	 */
+	if (!(flags & FOLL_HONOR_NUMA_FAULT))
+		return true;
+
+	/*
+	 * NUMA hinting faults don't apply in inaccessible (PROT_NONE) VMAs.
+	 *
+	 * Requiring a fault here even for inaccessible VMAs would mean that
+	 * FOLL_FORCE cannot make any progress, because handle_mm_fault()
+	 * refuses to process NUMA hinting faults in inaccessible VMAs.
+	 */
+	return !vma_is_accessible(vma);
+}
+
 #ifdef CONFIG_PGTABLE_HAS_HUGE_LEAVES
 /* FOLL_FORCE can write to even unwritable PUDs in COW mappings. */
 static inline bool can_follow_write_pud(pud_t pud, struct page *page,

-- 
2.53.0