mm/mmap/vma_merge: rename adj_next to adj_start

The variable 'adj_next' holds the value by which we adjust vm_start of a
vma in variable 'adjust', that's either 'next' or 'mid', so the current
name is inaccurate.  Rename it to 'adj_start'.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Vlastimil Babka <[email protected]>
Reviewed-by: Liam R. Howlett <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

mm/mmap.c

@@ -904,7 +904,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
 	bool vma_expanded = false;
 	struct vma_prepare vp;
 	unsigned long vma_end = end;
-	long adj_next = 0;
+	long adj_start = 0;
 	unsigned long vma_start = addr;
 
 	validate_mm(mm);
@@ -973,15 +973,15 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
 				remove = mid;
 			} else {			/* case 5 */
 				adjust = mid;
-				adj_next = (end - mid->vm_start);
+				adj_start = (end - mid->vm_start);
 			}
 		}
 	} else if (merge_next) {
 		res = next;
 		if (prev && addr < prev->vm_end) {	/* case 4 */
 			vma_end = addr;
 			adjust = next;
-			adj_next = -(prev->vm_end - addr);
+			adj_start = -(prev->vm_end - addr);
 			err = dup_anon_vma(next, prev);
 		} else {
 			vma = next;			/* case 3 */
@@ -1004,7 +1004,7 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
 	if (vma_iter_prealloc(vmi))
 		return NULL;
 
-	vma_adjust_trans_huge(vma, vma_start, vma_end, adj_next);
+	vma_adjust_trans_huge(vma, vma_start, vma_end, adj_start);
 	init_multi_vma_prep(&vp, vma, adjust, remove, remove2);
 	VM_WARN_ON(vp.anon_vma && adjust && adjust->anon_vma &&
 		   vp.anon_vma != adjust->anon_vma);
@@ -1020,10 +1020,10 @@ struct vm_area_struct *vma_merge(struct vma_iterator *vmi, struct mm_struct *mm,
 	if (vma_expanded)
 		vma_iter_store(vmi, vma);
 
-	if (adj_next) {
-		adjust->vm_start += adj_next;
-		adjust->vm_pgoff += adj_next >> PAGE_SHIFT;
-		if (adj_next < 0) {
+	if (adj_start) {
+		adjust->vm_start += adj_start;
+		adjust->vm_pgoff += adj_start >> PAGE_SHIFT;
+		if (adj_start < 0) {
 			WARN_ON(vma_expanded);
 			vma_iter_store(vmi, next);
 		}