fs/proc/base: use the vma iterators in place of linked list

Use the vma iterator instead of a for loop across the linked list.  The
link list of vmas will be removed in this patch set.

Link: https://lkml.kernel.org/r/20220906194824.2110408-43-Liam.Howlett@oracle.comSigned-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
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: Davidlohr Bueso <dave@stgolabs.net>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: SeongJae Park <sj@kernel.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/proc/base.c

@@ -2350,6 +2350,7 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
 	GENRADIX(struct map_files_info) fa;
 	struct map_files_info *p;
 	int ret;
+	struct vma_iterator vmi;
 
 	genradix_init(&fa);
 
@@ -2388,7 +2389,9 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
 	 * routine might require mmap_lock taken in might_fault().
 	 */
 
-	for (vma = mm->mmap, pos = 2; vma; vma = vma->vm_next) {
+	pos = 2;
+	vma_iter_init(&vmi, mm, 0);
+	for_each_vma(vmi, vma) {
 		if (!vma->vm_file)
 			continue;
 		if (++pos <= ctx->pos)