Re: [Qemu-devel] [PATCH 22/23] userfaultfd: avoid mmap_sem read recursion in mcopy_atomic

[Andrew Morton]

There's a more serious failure with i386 allmodconfig:

fs/userfaultfd.c:145:2: note: in expansion of macro 'BUILD_BUG_ON'
  BUILD_BUG_ON(sizeof(struct uffd_msg) != 32);

I'm surprised the feature is even reachable on i386 builds?