From: Liam R. Howlett <Liam.Howlett@oracle.com>
Date: Mon, 27 Oct 2025 20:47:36 +0000 (-0400)
Subject: mm/userfaultfd: Move zeropage to global validation for hugetlb
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=2205f1b5e8e23255ddab05ca23a17ec55b70d275;p=users%2Fjedix%2Flinux-maple.git

mm/userfaultfd: Move zeropage to global validation for hugetlb

This is for review reasons, with the goal of showing hugetlb is the same
as everything else in mfill_atomic().

Signed-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
---

diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 47b169d25eb8..94e57865c043 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -575,6 +575,16 @@ uffd_ctx_lock_and_validate_dst(struct userfaultfd_ctx *ctx,
 	if ((flags & MFILL_ATOMIC_WP) && !(dst_vma->vm_flags & VM_UFFD_WP))
 		return -EINVAL;
 
+	/*
+	 * There is no default zero huge page for all huge page sizes as
+	 * supported by hugetlb.  A PMD_SIZE huge pages may exist as used
+	 * by THP.  Since we can not reliably insert a zero page, this
+	 * feature is not supported.
+	 */
+	if (is_vm_hugetlb_page(dst_vma) &&
+	    uffd_flags_mode_is(flags, MFILL_ATOMIC_ZEROPAGE))
+		return -EINVAL;
+
 	uffd_ops = vma_get_uffd_ops(dst_vma);
 	WARN_ON_ONCE(!uffd_ops || !uffd_ops->is_dst_valid);
 	return uffd_ops->is_dst_valid(dst_vma, dst_start, len);
@@ -601,18 +611,6 @@ static __always_inline ssize_t mfill_atomic_hugetlb(struct userfaultfd_ctx *ctx,
 	const struct vm_uffd_ops *uffd_ops;
 	unsigned long increment;
 
-	/*
-	 * There is no default zero huge page for all huge page sizes as
-	 * supported by hugetlb.  A PMD_SIZE huge pages may exist as used
-	 * by THP.  Since we can not reliably insert a zero page, this
-	 * feature is not supported.
-	 */
-	if (uffd_flags_mode_is(flags, MFILL_ATOMIC_ZEROPAGE)) {
-		up_read(&ctx->map_changing_lock);
-		uffd_mfill_unlock(dst_vma);
-		return -EINVAL;
-	}
-
 	src_addr = src_start;
 	dst_addr = dst_start;
 	copied = 0;