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/20220504011345.662299-34-Liam.Howlett@oracle.com
Link: https://lkml.kernel.org/r/20220621204632.3370049-50-Liam.Howlett@oracle.com
Link: https://lkml.kernel.org/r/20220720021727.17018-50-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>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hulk Robot <hulkci@huawei.com>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/kernel/fork.c b/kernel/fork.c
index da4d77b81853cbec3b806d2ac7d1390222e70d8a..16b593f6e1030066eb6335432ec98184307904b3 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1299,13 +1299,16 @@ 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);