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

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

On Mon, Jun 29, 2026 at 08:25:36PM +0100, Lorenzo Stoakes wrote:
>Replace use of the legacy vm_flags_t flags with vma_flags_t values
>throughout the mremap logic.
>
>Additionally update comments to reflect the changes to be consistent.
>
>No functional change intended.
>
>Signed-off-by: Lorenzo Stoakes <ljs@kernel.org>
>---

The vm_flags_set() cases below spell out vma_start_write(), but the
vm_flags_clear() cases don't?

Thanks, Lance

> mm/mremap.c | 38 ++++++++++++++++++++------------------
> 1 file changed, 20 insertions(+), 18 deletions(-)
>
>diff --git a/mm/mremap.c b/mm/mremap.c
>index 079a0ba0c4a7..0ea43302b7ed 100644
>--- a/mm/mremap.c
>+++ b/mm/mremap.c
>@@ -68,7 +68,7 @@ struct vma_remap_struct {
> 	bool populate_expand;		/* mlock()'d expanded, must populate. */
> 	enum mremap_type remap_type;	/* expand, shrink, etc. */
> 	bool mmap_locked;		/* Is mm currently write-locked? */
>-	unsigned long charged;		/* If VM_ACCOUNT, # pages to account. */
>+	unsigned long charged;		/* If VMA_ACCOUNT_BIT, # pgs to account */
> 	bool vmi_needs_invalidate;	/* Is the VMA iterator invalidated? */
> };
> 
>@@ -954,7 +954,7 @@ static unsigned long vrm_set_new_addr(struct vma_remap_struct *vrm)
> 
> 	if (vrm->flags & MREMAP_FIXED)
> 		map_flags |= MAP_FIXED;
>-	if (vma->vm_flags & VM_MAYSHARE)
>+	if (vma_test(vma, VMA_MAYSHARE_BIT))
> 		map_flags |= MAP_SHARED;
> 
> 	res = get_unmapped_area(vma->vm_file, new_addr, vrm->new_len, pgoff,
>@@ -976,7 +976,7 @@ static bool vrm_calc_charge(struct vma_remap_struct *vrm)
> {
> 	unsigned long charged;
> 
>-	if (!(vrm->vma->vm_flags & VM_ACCOUNT))
>+	if (!vma_test(vrm->vma, VMA_ACCOUNT_BIT))
> 		return true;
> 
> 	/*
>@@ -1003,7 +1003,7 @@ static bool vrm_calc_charge(struct vma_remap_struct *vrm)
>  */
> static void vrm_uncharge(struct vma_remap_struct *vrm)
> {
>-	if (!(vrm->vma->vm_flags & VM_ACCOUNT))
>+	if (!vma_test(vrm->vma, VMA_ACCOUNT_BIT))
> 		return;
> 
> 	vm_unacct_memory(vrm->charged);
>@@ -1023,7 +1023,7 @@ static void vrm_stat_account(struct vma_remap_struct *vrm,
> 	struct vm_area_struct *vma = vrm->vma;
> 
> 	vm_stat_account(mm, vma->vm_flags, pages);
>-	if (vma->vm_flags & VM_LOCKED)
>+	if (vma_test(vma, VMA_LOCKED_BIT))
> 		mm->locked_vm += pages;
> }
> 
>@@ -1167,7 +1167,7 @@ static void unmap_source_vma(struct vma_remap_struct *vrm)
> 	 * arose, in which case we _do_ wish to unmap the _new_ VMA, which means
> 	 * we actually _do_ want it be unaccounted.
> 	 */
>-	bool accountable_move = (vma->vm_flags & VM_ACCOUNT) &&
>+	bool accountable_move = vma_test(vma, VMA_ACCOUNT_BIT) &&
> 		!(vrm->flags & MREMAP_DONTUNMAP);
> 
> 	/*
>@@ -1186,7 +1186,7 @@ static void unmap_source_vma(struct vma_remap_struct *vrm)
> 	 * portions of the original VMA that remain.
> 	 */
> 	if (accountable_move) {
>-		vm_flags_clear(vma, VM_ACCOUNT);
>+		vma_clear_flags(vma, VMA_ACCOUNT_BIT);
> 		/* We are about to split vma, so store the start/end. */
> 		vm_start = vma->vm_start;
> 		vm_end = vma->vm_end;
>@@ -1211,8 +1211,8 @@ static void unmap_source_vma(struct vma_remap_struct *vrm)
> 	 * |             |
> 	 * |-------------|
> 	 *
>-	 * Having cleared VM_ACCOUNT from the whole VMA, after we unmap above
>-	 * we'll end up with:
>+	 * Having cleared VMA_ACCOUNT_BIT from the whole VMA, after we unmap
>+	 * above we'll end up with:
> 	 *
> 	 *    addr  end
> 	 *     |     |
>@@ -1232,13 +1232,15 @@ static void unmap_source_vma(struct vma_remap_struct *vrm)
> 		if (vm_start < addr) {
> 			struct vm_area_struct *prev = vma_prev(&vmi);
> 
>-			vm_flags_set(prev, VM_ACCOUNT); /* Acquires VMA lock. */
>+			vma_start_write(prev);
>+			vma_set_flags(prev, VMA_ACCOUNT_BIT);
> 		}
> 
> 		if (vm_end > end) {
> 			struct vm_area_struct *next = vma_next(&vmi);
> 
>-			vm_flags_set(next, VM_ACCOUNT); /* Acquires VMA lock. */
>+			vma_start_write(next);
>+			vma_set_flags(next, VMA_ACCOUNT_BIT);
> 		}
> 	}
> }
>@@ -1321,8 +1323,8 @@ static void dontunmap_complete(struct vma_remap_struct *vrm,
> 	unsigned long old_start = vrm->vma->vm_start;
> 	unsigned long old_end = vrm->vma->vm_end;
> 
>-	/* We always clear VM_LOCKED[ONFAULT] on the old VMA. */
>-	vm_flags_clear(vrm->vma, VM_LOCKED_MASK);
>+	/* We always clear VMA_LOCKED[ONFAULT]_BIT on the old VMA. */
>+	vma_clear_flags_mask(vrm->vma, VMA_LOCKED_MASK);
> 
> 	/*
> 	 * anon_vma links of the old vma is no longer needed after its page
>@@ -1758,14 +1760,14 @@ static int check_prep_vma(struct vma_remap_struct *vrm)
> 	 * based on the original.  There are no known use cases for this
> 	 * behavior.  As a result, fail such attempts.
> 	 */
>-	if (!old_len && !(vma->vm_flags & (VM_SHARED | VM_MAYSHARE))) {
>+	if (!old_len && !vma_test_any(vma, VMA_SHARED_BIT, VMA_MAYSHARE_BIT)) {
> 		pr_warn_once("%s (%d): attempted to duplicate a private mapping with mremap.  This is not supported.\n",
> 			     current->comm, current->pid);
> 		return -EINVAL;
> 	}
> 
> 	if ((vrm->flags & MREMAP_DONTUNMAP) &&
>-			(vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP)))
>+	    vma_test_any(vma, VMA_DONTEXPAND_BIT, VMA_PFNMAP_BIT))
> 		return -EINVAL;
> 
> 	/*
>@@ -1795,7 +1797,7 @@ static int check_prep_vma(struct vma_remap_struct *vrm)
> 		return 0;
> 
> 	/* We are expanding and the VMA is mlock()'d so we need to populate. */
>-	if (vma->vm_flags & VM_LOCKED)
>+	if (vma_test(vma, VMA_LOCKED_BIT))
> 		vrm->populate_expand = true;
> 
> 	/* Need to be careful about a growing mapping */
>@@ -1803,10 +1805,10 @@ static int check_prep_vma(struct vma_remap_struct *vrm)
> 	if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
> 		return -EINVAL;
> 
>-	if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
>+	if (vma_test_any(vma, VMA_DONTEXPAND_BIT, VMA_PFNMAP_BIT))
> 		return -EFAULT;
> 
>-	if (!mlock_future_ok(mm, vma->vm_flags & VM_LOCKED, vrm->delta))
>+	if (!mlock_future_ok(mm, vma_test(vma, VMA_LOCKED_BIT), vrm->delta))
> 		return -EAGAIN;
> 
> 	if (!may_expand_vm(mm, &vma->flags, vrm->delta >> PAGE_SHIFT))
>-- 
>2.54.0
>
>