mm/memory: move pte_install_uffd_wp_if_needed() into memory.c

Patch series "Batch unmap of uffd-wp file folios", v2.

Currently, batched unmapping is supported if:

1) folio is a file folio, not belonging to uffd-wp VMA
2) folio is anonymous and not swapbacked (lazyfree), not belonging to
   uffd-wp VMA

So the cases which are not supported are

1) folio belonging to uffd-wp VMA
2) folio is anonymous and swapbacked

It is easy to see that this adds a lot of cognitive load while reading
try_to_unmap_one - we need to remember throughout whether nr_pages == 1 or
> 1.

The uffd-wp handling in try_to_unmap_one is regarding preserving the
uffd-wp state for file folios via pte_install_uffd_wp_if_needed (for anon
folio, we handle that while constructing the swap pte).

Stop special casing on uffd-wp VMAs by simply adding batching support to
pte_install_uffd_wp_if_needed.


This patch (of 3):

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.

Link: https://lore.kernel.org/20260720065508.2695106-1-dev.jain@arm.com
Link: https://lore.kernel.org/20260720065508.2695106-2-dev.jain@arm.com
Signed-off-by: Dev Jain <dev.jain@arm.com>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Harry Yoo <harry@kernel.org>
Cc: Jann Horn <jannh@google.com>
Cc: Kairui Song <kasong@tencent.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 0 insertions, 53 deletions

diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
index b5c4dc0f3fe3..621c8653d8f7 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))