+ userfaultfd-move-vma_can_userfault-out-of-line.patch added to mm-unstable branch

Andrew Morton
2026-04-02T04:36:48Z

The patch titled
Subject: userfaultfd: move vma_can_userfault out of line
has been added to the -mm mm-unstable branch. Its filename is
userfaultfd-move-vma_can_userfault-out-of-line.patch

This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/userfaultfd-move-vma_can_userfault-out-of-line.patch

This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
Subject: userfaultfd: move vma_can_userfault out of line
Date: Thu, 2 Apr 2026 07:11:47 +0300

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

Move it out of line.

No functional changes.

Link: https://lkml.kernel.org/r/20260402041156.1377214-7-rppt@kernel.org
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reviewed-by: David Hildenbrand (Red Hat) <david@kernel.org>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andrei Vagin <avagin@google.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Harry Yoo <harry.yoo@oracle.com>
Cc: Harry Yoo (Oracle) <harry@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nikita Kalyazin <kalyazin@amazon.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

include/linux/userfaultfd_k.h | 35 +-------------------------------
mm/userfaultfd.c | 33 ++++++++++++++++++++++++++++++
2 files changed, 35 insertions(+), 33 deletions(-)

--- a/include/linux/userfaultfd_k.h~userfaultfd-move-vma_can_userfault-out-of-line
+++ a/include/linux/userfaultfd_k.h
@@ -211,39 +211,8 @@ static inline bool userfaultfd_armed(str
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;
-
- /*
- * If user requested uffd-wp but not enabled pte markers for
- * uffd-wp, then shmem & hugetlbfs are not supported but only
- * anonymous.
- */
- if (!uffd_supports_wp_marker() && (vm_flags & VM_UFFD_WP) &&
- !vma_is_anonymous(vma))
- return false;
-
- /* 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)
{
--- a/mm/userfaultfd.c~userfaultfd-move-vma_can_userfault-out-of-line
+++ a/mm/userfaultfd.c
@@ -2018,6 +2018,39 @@ out:
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;
+
+ /*
+ * If user requested uffd-wp but not enabled pte markers for
+ * uffd-wp, then shmem & hugetlbfs are not supported but only
+ * anonymous.
+ */
+ if (!uffd_supports_wp_marker() && (vm_flags & VM_UFFD_WP) &&
+ !vma_is_anonymous(vma))
+ return false;
+
+ /* 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)
{
_

Patches currently in -mm which might be from rppt@kernel.org are

userfaultfd-introduce-mfill_copy_folio_locked-helper.patch
userfaultfd-introduce-struct-mfill_state.patch
userfaultfd-introduce-mfill_establish_pmd-helper.patch
userfaultfd-introduce-mfill_get_vma-and-mfill_put_vma.patch
userfaultfd-retry-copying-with-locks-dropped-in-mfill_atomic_pte_copy.patch
userfaultfd-move-vma_can_userfault-out-of-line.patch
userfaultfd-introduce-vm_uffd_ops.patch
shmem-userfaultfd-use-a-vma-callback-to-handle-uffdio_continue.patch
userfaultfd-introduce-vm_uffd_ops-alloc_folio.patch
shmem-userfaultfd-implement-shmem-uffd-operations-using-vm_uffd_ops.patch
userfaultfd-mfill_atomic-remove-retry-logic.patch