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/20220906194824.2110408-50-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>

diff --git a/kernel/fork.c b/kernel/fork.c
index 430f63cd7a37129e086d47086d9cf0bd422a2716..49e4ab6f520887f42df3e921e6a413ec1a648f2c 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1301,13 +1301,16 @@ int replace_mm_exe_file(struct mm_struct *mm, struct file *new_exe_file)
        /* 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);