From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Subject: fork: use VMA iterator

The VMA iterator is faster than the linked list and removing the linked
list will shrink the vm_area_struct.

Link: https://lkml.kernel.org/r/20220426150616.3937571-51-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>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 kernel/fork.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/kernel/fork.c~fork-use-vma-iterator
+++ a/kernel/fork.c
@@ -1286,13 +1286,16 @@ int replace_mm_exe_file(struct mm_struct
 	/* Forbid mm->exe_file change if old file still mapped. */
 	old_exe_file = get_mm_exe_file(mm);
 	if (old_exe_file) {
+		VMA_ITERATOR(vmi, mm, 0);
 		mmap_read_lock(mm);
-		for (vma = mm->mmap; vma && !ret; vma = vma->vm_next) {
+		for_each_vma(vmi, vma) {
 			if (!vma->vm_file)
 				continue;
 			if (path_equal(&vma->vm_file->f_path,
-				       &old_exe_file->f_path))
+				       &old_exe_file->f_path)) {
 				ret = -EBUSY;
+				break;
+			}
 		}
 		mmap_read_unlock(mm);
 		fput(old_exe_file);
_