Let's simplify the calculation a bit further to make it easier to get,
reusing vma_last_pgoff() which we move from interval_tree.c to mm.h.

Signed-off-by: David Hildenbrand (Arm) <david@kernel.org>
---
 include/linux/mm.h |  5 +++++
 mm/interval_tree.c |  5 -----
 mm/memory.c        | 12 +++++-------
 3 files changed, 10 insertions(+), 12 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index a8138ff7d1fa..d3ef586ee1c0 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -4000,6 +4000,11 @@ static inline unsigned long vma_pages(const struct vm_area_struct *vma)
 	return (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
 }
 
+static inline unsigned long vma_last_pgoff(struct vm_area_struct *vma)
+{
+	return vma->vm_pgoff + vma_pages(vma) - 1;
+}
+
 static inline unsigned long vma_desc_size(const struct vm_area_desc *desc)
 {
 	return desc->end - desc->start;
diff --git a/mm/interval_tree.c b/mm/interval_tree.c
index 32e390c42c53..32bcfbfcf15f 100644
--- a/mm/interval_tree.c
+++ b/mm/interval_tree.c
@@ -15,11 +15,6 @@ static inline unsigned long vma_start_pgoff(struct vm_area_struct *v)
 	return v->vm_pgoff;
 }
 
-static inline unsigned long vma_last_pgoff(struct vm_area_struct *v)
-{
-	return v->vm_pgoff + vma_pages(v) - 1;
-}
-
 INTERVAL_TREE_DEFINE(struct vm_area_struct, shared.rb,
 		     unsigned long, shared.rb_subtree_last,
 		     vma_start_pgoff, vma_last_pgoff, /* empty */, vma_interval_tree)
diff --git a/mm/memory.c b/mm/memory.c
index 5c47309331f5..e4154f03feac 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4227,17 +4227,15 @@ static inline void unmap_mapping_range_tree(struct rb_root_cached *root,
 					    struct zap_details *details)
 {
 	struct vm_area_struct *vma;
-	pgoff_t vba, vea, zba, zea;
 	unsigned long start, size;
 	struct mmu_gather tlb;
 
 	vma_interval_tree_foreach(vma, root, first_index, last_index) {
-		vba = vma->vm_pgoff;
-		vea = vba + vma_pages(vma) - 1;
-		zba = max(first_index, vba);
-		zea = min(last_index, vea);
-		start = ((zba - vba) << PAGE_SHIFT) + vma->vm_start;
-		size = (zea - zba + 1) << PAGE_SHIFT;
+		const pgoff_t start_idx = max(first_index, vma->vm_pgoff);
+		const pgoff_t end_idx = min(last_index, vma_last_pgoff(vma)) + 1;
+
+		start = vma->vm_start + ((start_idx - vma->vm_pgoff) << PAGE_SHIFT);
+		size = (end_idx - start_idx) << PAGE_SHIFT;
 
 		tlb_gather_mmu(&tlb, vma->vm_mm);
 		zap_page_range_single_batched(&tlb, vma, start, size, details);
-- 
2.43.0