s390: remove vma linked list walks

Use the VMA iterator instead.

Link: https://lkml.kernel.org/r/20220906194824.2110408-35-Liam.Howlett@oracle.com
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>
Tested-by: Yu Zhao <yuzhao@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arch/s390/kernel/vdso.c

@@ -69,10 +69,11 @@ static struct page *find_timens_vvar_page(struct vm_area_struct *vma)
 int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
 {
 	struct mm_struct *mm = task->mm;
+	VMA_ITERATOR(vmi, mm, 0);
 	struct vm_area_struct *vma;
 
 	mmap_read_lock(mm);
-	for (vma = mm->mmap; vma; vma = vma->vm_next) {
+	for_each_vma(vmi, vma) {
 		unsigned long size = vma->vm_end - vma->vm_start;
 
 		if (!vma_is_special_mapping(vma, &vvar_mapping))

arch/s390/mm/gmap.c

@@ -2515,8 +2515,9 @@ static const struct mm_walk_ops thp_split_walk_ops = {
 static inline void thp_split_mm(struct mm_struct *mm)
 {
 	struct vm_area_struct *vma;
+	VMA_ITERATOR(vmi, mm, 0);
 
-	for (vma = mm->mmap; vma != NULL; vma = vma->vm_next) {
+	for_each_vma(vmi, vma) {
 		vma->vm_flags &= ~VM_HUGEPAGE;
 		vma->vm_flags |= VM_NOHUGEPAGE;
 		walk_page_vma(vma, &thp_split_walk_ops, NULL);
@@ -2584,8 +2585,9 @@ int gmap_mark_unmergeable(void)
 	struct mm_struct *mm = current->mm;
 	struct vm_area_struct *vma;
 	int ret;
+	VMA_ITERATOR(vmi, mm, 0);
 
-	for (vma = mm->mmap; vma; vma = vma->vm_next) {
+	for_each_vma(vmi, vma) {
 		ret = ksm_madvise(vma, vma->vm_start, vma->vm_end,
 				  MADV_UNMERGEABLE, &vma->vm_flags);
 		if (ret)