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

[Lorenzo Stoakes <ljs@kernel.org>]

On Thu, Jul 02, 2026 at 12:09:17AM +0800, Lance Yang wrote:
>
> 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 :)

Thanks you're right, will fix!

Again I swear I ran claude on all of this so it's failing me here :)

>
> 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
> >
> >