Re: [PATCH 12/13] mm/mprotect: convert mprotect code to use vma_flags_t

[Lance Yang <lance.yang@linux.dev>]

On Mon, Jun 29, 2026 at 08:25:35PM +0100, Lorenzo Stoakes wrote:
>Replace use of the legacy vm_flags_t flags with vma_flags_t values
>throughout the mprotect logic.
>
>Note that we retain the legacy vm_flags_t bit shifting code in
>do_mprotect_key(), deferring a vma_flags_t approach to this for the time
>being.
>
>Additionally update comments to reflect the changes to be consistent.
>
>No functional change intended.
>
>Signed-off-by: Lorenzo Stoakes <ljs@kernel.org>
>---
> mm/mprotect.c | 16 ++++++++--------
> 1 file changed, 8 insertions(+), 8 deletions(-)
>
>diff --git a/mm/mprotect.c b/mm/mprotect.c
>index 9cbf932b028c..c9504b2a2525 100644
>--- a/mm/mprotect.c
>+++ b/mm/mprotect.c
>@@ -40,7 +40,7 @@
> 
> static bool maybe_change_pte_writable(struct vm_area_struct *vma, pte_t pte)
> {
>-	if (WARN_ON_ONCE(!(vma->vm_flags & VM_WRITE)))
>+	if (WARN_ON_ONCE(!vma_test(vma, VMA_WRITE_BIT)))
> 		return false;
> 
> 	/* Don't touch entries that are not even readable. */
>@@ -97,7 +97,7 @@ static bool can_change_shared_pte_writable(struct vm_area_struct *vma,
> bool can_change_pte_writable(struct vm_area_struct *vma, unsigned long addr,
> 			     pte_t pte)
> {
>-	if (!(vma->vm_flags & VM_SHARED))
>+	if (!vma_test(vma, VMA_SHARED_BIT))
> 		return can_change_private_pte_writable(vma, addr, pte);
> 
> 	return can_change_shared_pte_writable(vma, pte);
>@@ -194,7 +194,7 @@ static __always_inline void set_write_prot_commit_flush_ptes(struct vm_area_stru
> {
> 	bool set_write;
> 
>-	if (vma->vm_flags & VM_SHARED) {
>+	if (vma_test(vma, VMA_SHARED_BIT)) {
> 		set_write = can_change_shared_pte_writable(vma, ptent);
> 		prot_commit_flush_ptes(vma, addr, ptep, oldpte, ptent, nr_ptes,
> 				       /* idx = */ 0, set_write, tlb);
>@@ -811,8 +811,8 @@ mprotect_fixup(struct vma_iterator *vmi, struct mmu_gather *tlb,
> 		vm_unacct_memory(nrpages);
> 
> 	/*
>-	 * Private VM_LOCKED VMA becoming writable: trigger COW to avoid major
>-	 * fault on access.
>+	 * Private VMA_LOCKED_BIT VMA becoming writable: trigger COW to avoid
>+	 * major fault on access.
> 	 */
> 	if (vma_flags_test(&new_vma_flags, VMA_WRITE_BIT) &&
> 	    vma_flags_test(&old_vma_flags, VMA_LOCKED_BIT) &&
>@@ -886,7 +886,7 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
> 			goto out;
> 		start = vma->vm_start;
> 		error = -EINVAL;
>-		if (!(vma->vm_flags & VM_GROWSDOWN))
>+		if (!vma_test(vma, VMA_GROWSDOWN_BIT))
> 			goto out;
> 	} else {
> 		if (vma->vm_start > start)
>@@ -894,7 +894,7 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
> 		if (unlikely(grows & PROT_GROWSUP)) {
> 			end = vma->vm_end;
> 			error = -EINVAL;
>-			if (!(vma->vm_flags & VM_GROWSUP))
>+			if (!vma_test(vma, VMA_GROWSUP_BIT))

IIUC, should this be

if (!vma_test_single_mask(vma, VMA_GROWSUP))

instead?

#elif defined(CONFIG_PARISC)
#define VM_GROWSUP	INIT_VM_FLAG(GROWSUP)
...
#ifndef VM_GROWSUP
#define VM_GROWSUP	VM_NONE
...

VM_GROWSUP is only defined as GROWSUP on parisc and becomes VM_NONE
elsewhere. But VMA_GROWSUP_BIT is the raw ARCH_1 bit, which is also used
for other arch-specific VMA flags:

	DECLARE_VMA_BIT_ALIAS(SAO, ARCH_1),		/* Strong Access Ordering (powerpc) */
	DECLARE_VMA_BIT_ALIAS(GROWSUP, ARCH_1),		/* parisc */
	DECLARE_VMA_BIT_ALIAS(SPARC_ADI, ARCH_1),	/* sparc64 */
	DECLARE_VMA_BIT_ALIAS(ARM64_BTI, ARCH_1),	/* arm64 */
	DECLARE_VMA_BIT_ALIAS(ARCH_CLEAR, ARCH_1),	/* sparc64, arm64 */
	DECLARE_VMA_BIT_ALIAS(MAPPED_COPY, ARCH_1),	/* !CONFIG_MMU */

Other vma_test() changes look fine to me: just fixed INIT_VM_FLAG()
masks matching their VMA_*_BIT :)

Cheers, Lance

> 				goto out;
> 		}
> 	}
>@@ -918,7 +918,7 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
> 		}
> 
> 		/* Does the application expect PROT_READ to imply PROT_EXEC */
>-		if (rier && (vma->vm_flags & VM_MAYEXEC))
>+		if (rier && vma_test(vma, VMA_MAYEXEC_BIT))
> 			prot |= PROT_EXEC;
> 
> 		/*
>-- 
>2.54.0
>
>