[PATCH v2 2/3] mm/memory: remove the mkwrite argument from __vm_insert_mixed()

[Sang-Heon Jeon]

__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.

Signed-off-by: Sang-Heon Jeon <ekffu200098@xxxxxxxxx>
---
 mm/memory.c | 57 +++++++++++++++++------------------------------------
 1 file changed, 18 insertions(+), 39 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 4b2e4be28031..6c1d38eba7b2 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2453,7 +2453,14 @@ static int insert_page_into_pte_locked(struct vm_area_struct *vma, pte_t *pte,
 		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;
@@ -2858,7 +2865,7 @@ int vm_map_pages_zero(struct vm_area_struct *vma, struct page **pages,
 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;
@@ -2868,38 +2875,12 @@ static vm_fault_t insert_pfn(struct vm_area_struct *vma, unsigned long addr,
 	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? */
 
@@ -2967,7 +2948,7 @@ vm_fault_t vmf_insert_pfn_prot(struct vm_area_struct *vma, unsigned long addr,
 
 	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);
 
@@ -2998,11 +2979,9 @@ vm_fault_t vmf_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
 }
 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)
@@ -3013,12 +2992,12 @@ static bool vm_mixed_ok(struct vm_area_struct *vma, unsigned long pfn,
 }
 
 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)
@@ -3045,9 +3024,9 @@ static vm_fault_t __vm_insert_mixed(struct vm_area_struct *vma,
 		 * 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)
@@ -3086,7 +3065,7 @@ EXPORT_SYMBOL_GPL(vmf_insert_page_mkwrite);
 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);
 
-- 
2.43.0