+ mm-memory-remove-the-mkwrite-argument-from-__vm_insert_mixed.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/memory: remove the mkwrite argument from __vm_insert_mixed()
has been added to the -mm mm-new branch.  Its filename is
     mm-memory-remove-the-mkwrite-argument-from-__vm_insert_mixed.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-memory-remove-the-mkwrite-argument-from-__vm_insert_mixed.patch

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

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: Sang-Heon Jeon <ekffu200098@gmail.com>
Subject: mm/memory: remove the mkwrite argument from __vm_insert_mixed()
Date: Sat, 03 Oct 2026 01:05:33 +0900

__vm_insert_mixed() is only called from vmf_insert_mixed() with
mkwrite == false, so mkwrite is also always false in vm_mixed_ok()
and insert_pfn().

So remove the argument and the unreachable code in insert_pfn().

No functional change.

Link: https://lore.kernel.org/20261002160535.661399-3-ekffu200098@gmail.com
Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jose A. Perez de Azpillaga <azpijr@gmail.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: SJ Park <sj@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
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: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
---

 mm/memory.c |   57 +++++++++++++++-----------------------------------
 1 file changed, 18 insertions(+), 39 deletions(-)

--- a/mm/memory.c~mm-memory-remove-the-mkwrite-argument-from-__vm_insert_mixed
+++ a/mm/memory.c
@@ -2459,7 +2459,14 @@ static int insert_page_into_pte_locked(s
 		if (!mkwrite)
 			return -EBUSY;
 
-		/* see insert_pfn(). */
+		/*
+		 * For read faults on private mappings the PFN passed in may
+		 * not match the PFN we have mapped if the mapped PFN is a
+		 * writeable COW page.  In the mkwrite case we are creating a
+		 * writable PTE for a shared mapping and we expect the PFNs to
+		 * match. If they don't match, we are likely racing with block
+		 * allocation and mapping invalidation.
+		 */
 		if (pte_pfn(pteval) != page_to_pfn(page)) {
 			WARN_ON_ONCE(!is_zero_pfn(pte_pfn(pteval)));
 			return -EFAULT;
@@ -2864,7 +2871,7 @@ int vm_map_pages_zero(struct vm_area_str
 EXPORT_SYMBOL(vm_map_pages_zero);
 
 static vm_fault_t insert_pfn(struct vm_area_struct *vma, unsigned long addr,
-			unsigned long pfn, pgprot_t prot, bool mkwrite)
+			unsigned long pfn, pgprot_t prot)
 {
 	struct mm_struct *mm = vma->vm_mm;
 	pte_t *pte, entry;
@@ -2874,38 +2881,12 @@ static vm_fault_t insert_pfn(struct vm_a
 	if (!pte)
 		return VM_FAULT_OOM;
 	entry = ptep_get(pte);
-	if (!pte_none(entry)) {
-		if (mkwrite) {
-			/*
-			 * For read faults on private mappings the PFN passed
-			 * in may not match the PFN we have mapped if the
-			 * mapped PFN is a writeable COW page.  In the mkwrite
-			 * case we are creating a writable PTE for a shared
-			 * mapping and we expect the PFNs to match. If they
-			 * don't match, we are likely racing with block
-			 * allocation and mapping invalidation so just skip the
-			 * update.
-			 */
-			if (pte_pfn(entry) != pfn) {
-				WARN_ON_ONCE(!is_zero_pfn(pte_pfn(entry)));
-				goto out_unlock;
-			}
-			entry = pte_mkyoung(entry);
-			entry = maybe_mkwrite(pte_mkdirty(entry), vma);
-			if (ptep_set_access_flags(vma, addr, pte, entry, 1))
-				update_mmu_cache(vma, addr, pte);
-		}
+	if (!pte_none(entry))
 		goto out_unlock;
-	}
 
 	/* Ok, finally just insert the thing.. */
 	entry = pte_mkspecial(pfn_pte(pfn, prot));
 
-	if (mkwrite) {
-		entry = pte_mkyoung(entry);
-		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
-	}
-
 	set_pte_at(mm, addr, pte, entry);
 	update_mmu_cache(vma, addr, pte); /* XXX: why not for insert_page? */
 
@@ -2973,7 +2954,7 @@ vm_fault_t vmf_insert_pfn_prot(struct vm
 
 	pfnmap_setup_cachemode_pfn(pfn, &pgprot);
 
-	return insert_pfn(vma, addr, pfn, pgprot, false);
+	return insert_pfn(vma, addr, pfn, pgprot);
 }
 EXPORT_SYMBOL(vmf_insert_pfn_prot);
 
@@ -3004,11 +2985,9 @@ vm_fault_t vmf_insert_pfn(struct vm_area
 }
 EXPORT_SYMBOL(vmf_insert_pfn);
 
-static bool vm_mixed_ok(struct vm_area_struct *vma, unsigned long pfn,
-			bool mkwrite)
+static bool vm_mixed_ok(struct vm_area_struct *vma, unsigned long pfn)
 {
-	if (unlikely(is_zero_pfn(pfn)) &&
-	    (mkwrite || !vm_mixed_zeropage_allowed(vma)))
+	if (unlikely(is_zero_pfn(pfn)) && !vm_mixed_zeropage_allowed(vma))
 		return false;
 	/* these checks mirror the abort conditions in vm_normal_page */
 	if (vma->vm_flags & VM_MIXEDMAP)
@@ -3019,12 +2998,12 @@ static bool vm_mixed_ok(struct vm_area_s
 }
 
 static vm_fault_t __vm_insert_mixed(struct vm_area_struct *vma,
-		unsigned long addr, unsigned long pfn, bool mkwrite)
+		unsigned long addr, unsigned long pfn)
 {
 	pgprot_t pgprot = vma->vm_page_prot;
 	int err;
 
-	if (!vm_mixed_ok(vma, pfn, mkwrite))
+	if (!vm_mixed_ok(vma, pfn))
 		return VM_FAULT_SIGBUS;
 
 	if (addr < vma->vm_start || addr >= vma->vm_end)
@@ -3051,9 +3030,9 @@ static vm_fault_t __vm_insert_mixed(stru
 		 * result in pfn_t_has_page() == false.
 		 */
 		page = pfn_to_page(pfn);
-		err = insert_page(vma, addr, page, pgprot, mkwrite);
+		err = insert_page(vma, addr, page, pgprot, false);
 	} else {
-		return insert_pfn(vma, addr, pfn, pgprot, mkwrite);
+		return insert_pfn(vma, addr, pfn, pgprot);
 	}
 
 	if (err == -ENOMEM)
@@ -3092,7 +3071,7 @@ EXPORT_SYMBOL_GPL(vmf_insert_page_mkwrit
 vm_fault_t vmf_insert_mixed(struct vm_area_struct *vma, unsigned long addr,
 		unsigned long pfn)
 {
-	return __vm_insert_mixed(vma, addr, pfn, false);
+	return __vm_insert_mixed(vma, addr, pfn);
 }
 EXPORT_SYMBOL(vmf_insert_mixed);
 
_

Patches currently in -mm which might be from ekffu200098@gmail.com are

mm-memory-remove-unused-vmf_insert_mixed_mkwrite.patch
mm-memory-remove-the-mkwrite-argument-from-__vm_insert_mixed.patch
mm-memory-merge-__vm_insert_mixed-into-vmf_insert_mixed.patch