[PATCH v2 1/3] mm/memory: move pte_install_uffd_wp_if_needed() into memory.c

[Dev Jain]

pte_install_uffd_wp_if_needed() has grown too large for mm_inline.h.
Move it to memory.c.

This helper is only used inside mm/, so declare it in mm/internal.h
instead of a public header.

While at it, convert the comment to kerneldoc and rename the local
arguments from pte/pteval to ptep/pte so the pointer and PTE value are
easier to distinguish.

Signed-off-by: Dev Jain <dev.jain@xxxxxxx>
---
 include/linux/mm_inline.h | 53 ----------------------------------
 mm/internal.h             |  3 ++
 mm/memory.c               | 60 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 63 insertions(+), 53 deletions(-)

diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
index b5c4dc0f3fe32..621c8653d8f7e 100644
--- a/include/linux/mm_inline.h
+++ b/include/linux/mm_inline.h
@@ -566,59 +566,6 @@ static inline pte_marker copy_pte_marker(
 	return dstm;
 }
 
-/*
- * If this pte is wr-protected by uffd-wp in any form, arm the special pte to
- * replace a none pte.  NOTE!  This should only be called when *pte is already
- * cleared so we will never accidentally replace something valuable.  Meanwhile
- * none pte also means we are not demoting the pte so tlb flushed is not needed.
- * E.g., when pte cleared the caller should have taken care of the tlb flush.
- *
- * Must be called with pgtable lock held so that no thread will see the none
- * pte, and if they see it, they'll fault and serialize at the pgtable lock.
- *
- * Returns true if an uffd-wp pte was installed, false otherwise.
- */
-static inline bool
-pte_install_uffd_wp_if_needed(struct vm_area_struct *vma, unsigned long addr,
-			      pte_t *pte, pte_t pteval)
-{
-	bool arm_uffd_pte = false;
-
-	if (!uffd_supports_wp_marker())
-		return false;
-
-	/* The current status of the pte should be "cleared" before calling */
-	WARN_ON_ONCE(!pte_none(ptep_get(pte)));
-
-	/*
-	 * NOTE: userfaultfd_wp_unpopulated() doesn't need this whole
-	 * thing, because when zapping either it means it's dropping the
-	 * page, or in TTU where the present pte will be quickly replaced
-	 * with a swap pte.  There's no way of leaking the bit.
-	 */
-	if (vma_is_anonymous(vma) || !userfaultfd_wp(vma))
-		return false;
-
-	/* A uffd-wp wr-protected normal pte */
-	if (unlikely(pte_present(pteval) && pte_uffd(pteval)))
-		arm_uffd_pte = true;
-
-	/*
-	 * A uffd-wp wr-protected swap pte.  Note: this should even cover an
-	 * existing pte marker with uffd-wp bit set.
-	 */
-	if (unlikely(pte_swp_uffd_any(pteval)))
-		arm_uffd_pte = true;
-
-	if (unlikely(arm_uffd_pte)) {
-		set_pte_at(vma->vm_mm, addr, pte,
-			   make_pte_marker(PTE_MARKER_UFFD_WP));
-		return true;
-	}
-
-	return false;
-}
-
 static inline bool vma_has_recency(const struct vm_area_struct *vma)
 {
 	if (vma->vm_flags & (VM_SEQ_READ | VM_RAND_READ))
diff --git a/mm/internal.h b/mm/internal.h
index f26423de4ca28..b6a3589a61c1a 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -276,6 +276,9 @@ void unmap_vmas(struct mmu_gather *tlb, struct unmap_desc *unmap);
 
 #ifdef CONFIG_MMU
 
+bool pte_install_uffd_wp_if_needed(struct vm_area_struct *vma,
+		unsigned long addr, pte_t *ptep, pte_t pte);
+
 static inline void get_anon_vma(struct anon_vma *anon_vma)
 {
 	atomic_inc(&anon_vma->refcount);
diff --git a/mm/memory.c b/mm/memory.c
index d5e87624f6920..6c0c4c774674a 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1675,6 +1675,66 @@ static inline bool zap_drop_markers(struct zap_details *details)
 	return details->zap_flags & ZAP_FLAG_DROP_MARKER;
 }
 
+/**
+ * pte_install_uffd_wp_if_needed - install uffd-wp marker after clearing a PTE
+ * @vma: The VMA the page is mapped into.
+ * @addr: Address the page is mapped at.
+ * @ptep: Page table pointer for this entry.
+ * @pte: Old value of the entry pointed to by @ptep.
+ *
+ * If the PTE was write-protected by uffd-wp in any form, arm a special PTE
+ * to replace a none PTE. NOTE! This should only be called when the PTE is
+ * already cleared so we will never accidentally replace something valuable.
+ * Meanwhile none PTEs also mean we are not demoting the PTE so a TLB flush is
+ * not needed. E.g., when the PTE was cleared, the caller should have taken care
+ * of the TLB flush.
+ *
+ * Must be called with the page table lock held so that no thread will see the
+ * none PTE, and if they see it, they'll fault and serialize at the page table
+ * lock.
+ *
+ * Returns true if an uffd-wp PTE was installed, false otherwise.
+ */
+bool pte_install_uffd_wp_if_needed(struct vm_area_struct *vma,
+		unsigned long addr, pte_t *ptep, pte_t pte)
+{
+	bool arm_uffd_pte = false;
+
+	if (!uffd_supports_wp_marker())
+		return false;
+
+	/* The current status of the pte should be "cleared" before calling */
+	WARN_ON_ONCE(!pte_none(ptep_get(ptep)));
+
+	/*
+	 * NOTE: userfaultfd_wp_unpopulated() doesn't need this whole
+	 * thing, because when zapping either it means it's dropping the
+	 * page, or in TTU where the present pte will be quickly replaced
+	 * with a swap pte.  There's no way of leaking the bit.
+	 */
+	if (vma_is_anonymous(vma) || !userfaultfd_wp(vma))
+		return false;
+
+	/* A uffd-wp wr-protected normal pte */
+	if (unlikely(pte_present(pte) && pte_uffd(pte)))
+		arm_uffd_pte = true;
+
+	/*
+	 * A uffd-wp wr-protected swap pte.  Note: this should even cover an
+	 * existing pte marker with uffd-wp bit set.
+	 */
+	if (unlikely(pte_swp_uffd_any(pte)))
+		arm_uffd_pte = true;
+
+	if (unlikely(arm_uffd_pte)) {
+		set_pte_at(vma->vm_mm, addr, ptep,
+			   make_pte_marker(PTE_MARKER_UFFD_WP));
+		return true;
+	}
+
+	return false;
+}
+
 /*
  * This function makes sure that we'll replace the none pte with an uffd-wp
  * swap special pte marker when necessary. Must be with the pgtable lock held.
-- 
2.43.0