kernel/fork: convert forking to using the vmi iterator

Avoid using the maple tree interface directly.  This gains type safety.

Link: https://lkml.kernel.org/r/20230120162650.984577-10-Liam.Howlett@oracle.comSigned-off-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

kernel/fork.c

@@ -585,8 +585,8 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
 	int retval;
 	unsigned long charge = 0;
 	LIST_HEAD(uf);
-	MA_STATE(old_mas, &oldmm->mm_mt, 0, 0);
-	MA_STATE(mas, &mm->mm_mt, 0, 0);
+	VMA_ITERATOR(old_vmi, oldmm, 0);
+	VMA_ITERATOR(vmi, mm, 0);
 
 	uprobe_start_dup_mmap();
 	if (mmap_write_lock_killable(oldmm)) {
@@ -613,11 +613,11 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
 		goto out;
 	khugepaged_fork(mm, oldmm);
 
-	retval = mas_expected_entries(&mas, oldmm->map_count);
+	retval = vma_iter_bulk_alloc(&vmi, oldmm->map_count);
 	if (retval)
 		goto out;
 
-	mas_for_each(&old_mas, mpnt, ULONG_MAX) {
+	for_each_vma(old_vmi, mpnt) {
 		struct file *file;
 
 		if (mpnt->vm_flags & VM_DONTCOPY) {
@@ -683,11 +683,8 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
 			hugetlb_dup_vma_private(tmp);
 
 		/* Link the vma into the MT */
-		mas.index = tmp->vm_start;
-		mas.last = tmp->vm_end - 1;
-		mas_store(&mas, tmp);
-		if (mas_is_err(&mas))
-			goto fail_nomem_mas_store;
+		if (vma_iter_bulk_store(&vmi, tmp))
+			goto fail_nomem_vmi_store;
 
 		mm->map_count++;
 		if (!(tmp->vm_flags & VM_WIPEONFORK))
@@ -702,7 +699,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
 	/* a new mm has just been created */
 	retval = arch_dup_mmap(oldmm, mm);
 loop_out:
-	mas_destroy(&mas);
+	vma_iter_free(&vmi);
 out:
 	mmap_write_unlock(mm);
 	flush_tlb_mm(oldmm);
@@ -712,7 +709,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
 	uprobe_end_dup_mmap();
 	return retval;
 
-fail_nomem_mas_store:
+fail_nomem_vmi_store:
 	unlink_anon_vmas(tmp);
 fail_nomem_anon_vma_fork:
 	mpol_put(vma_policy(tmp));