mm/mremap: avoid unneeded do_munmap call

When old_len == new_len, do_munmap will return -EINVAL due to len == 0.
This errno will be simply ignored because of old_len != new_len check.  So
it is unnecessary to call do_munmap when old_len == new_len because
nothing is actually done.

Link: https://lkml.kernel.org/r/20220401081023.37080-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/mremap.c b/mm/mremap.c
index f2a53d5..98f50e6 100644 (file)
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -820,9 +820,9 @@ static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
                        goto out;
        }
 
-       if (old_len >= new_len) {
+       if (old_len > new_len) {
                ret = do_munmap(mm, addr+new_len, old_len - new_len, uf_unmap);
-               if (ret && old_len != new_len)
+               if (ret)
                        goto out;
                old_len = new_len;
        }