linux-kernel - [RFC PATCH 1/4] userfaultfd: move vma_can

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Message-ID: <20251117114631.2029447-2-rppt@kernel.org>
Date: Mon, 17 Nov 2025 13:46:28 +0200
From: Mike Rapoport <rppt@...nel.org>
To: linux-mm@...ck.org
Cc: Andrea Arcangeli <aarcange@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Baolin Wang <baolin.wang@...ux.alibaba.com>,
	David Hildenbrand <david@...hat.com>,
	Hugh Dickins <hughd@...gle.com>,
	"Liam R. Howlett" <Liam.Howlett@...cle.com>,
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Michal Hocko <mhocko@...e.com>,
	Mike Rapoport <rppt@...nel.org>,
	Nikita Kalyazin <kalyazin@...zon.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Peter Xu <peterx@...hat.com>,
	Sean Christopherson <seanjc@...gle.com>,
	Shuah Khan <shuah@...nel.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org,
	linux-kselftest@...r.kernel.org
Subject: [RFC PATCH 1/4] userfaultfd: move vma_can_userfault out of line

From: "Mike Rapoport (Microsoft)" <rppt@...nel.org>

vma_can_userfault() has grown pretty big and it's not called on
performance critical path.

Move it out of line.

No functional changes.

Signed-off-by: Mike Rapoport (Microsoft) <rppt@...nel.org>
---
 include/linux/userfaultfd_k.h | 36 ++---------------------------------
 mm/userfaultfd.c              | 34 +++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 34 deletions(-)

diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index c0e716aec26a..e4f43e7b063f 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -208,40 +208,8 @@ static inline bool userfaultfd_armed(struct vm_area_struct *vma)
 	return vma->vm_flags & __VM_UFFD_FLAGS;
 }
 
-static inline bool vma_can_userfault(struct vm_area_struct *vma,
-				     vm_flags_t vm_flags,
-				     bool wp_async)
-{
-	vm_flags &= __VM_UFFD_FLAGS;
-
-	if (vma->vm_flags & VM_DROPPABLE)
-		return false;
-
-	if ((vm_flags & VM_UFFD_MINOR) &&
-	    (!is_vm_hugetlb_page(vma) && !vma_is_shmem(vma)))
-		return false;
-
-	/*
-	 * If wp async enabled, and WP is the only mode enabled, allow any
-	 * memory type.
-	 */
-	if (wp_async && (vm_flags == VM_UFFD_WP))
-		return true;
-
-#ifndef CONFIG_PTE_MARKER_UFFD_WP
-	/*
-	 * If user requested uffd-wp but not enabled pte markers for
-	 * uffd-wp, then shmem & hugetlbfs are not supported but only
-	 * anonymous.
-	 */
-	if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))
-		return false;
-#endif
-
-	/* By default, allow any of anon|shmem|hugetlb */
-	return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
-	    vma_is_shmem(vma);
-}
+bool vma_can_userfault(struct vm_area_struct *vma, vm_flags_t vm_flags,
+		       bool wp_async);
 
 static inline bool vma_has_uffd_without_event_remap(struct vm_area_struct *vma)
 {
diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index af61b95c89e4..8dc964389b0d 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -1977,6 +1977,40 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start,
 	return moved ? moved : err;
 }
 
+bool vma_can_userfault(struct vm_area_struct *vma, vm_flags_t vm_flags,
+		       bool wp_async)
+{
+	vm_flags &= __VM_UFFD_FLAGS;
+
+	if (vma->vm_flags & VM_DROPPABLE)
+		return false;
+
+	if ((vm_flags & VM_UFFD_MINOR) &&
+	    (!is_vm_hugetlb_page(vma) && !vma_is_shmem(vma)))
+		return false;
+
+	/*
+	 * If wp async enabled, and WP is the only mode enabled, allow any
+	 * memory type.
+	 */
+	if (wp_async && (vm_flags == VM_UFFD_WP))
+		return true;
+
+#ifndef CONFIG_PTE_MARKER_UFFD_WP
+	/*
+	 * If user requested uffd-wp but not enabled pte markers for
+	 * uffd-wp, then shmem & hugetlbfs are not supported but only
+	 * anonymous.
+	 */
+	if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))
+		return false;
+#endif
+
+	/* By default, allow any of anon|shmem|hugetlb */
+	return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
+	    vma_is_shmem(vma);
+}
+
 static void userfaultfd_set_vm_flags(struct vm_area_struct *vma,
 				     vm_flags_t vm_flags)
 {
-- 
2.50.1