userfaultfd: fix return error if mmap_changing is non-zero in MOVE ioctl

To be consistent with other uffd ioctl's returning EAGAIN when
mmap_changing is detected, we should change UFFDIO_MOVE to do the same.

Link: https://lkml.kernel.org/r/20240117223922.1445327-1-lokeshgidra@google.comSigned-off-by: Lokesh Gidra <lokeshgidra@google.com>
Acked-by: Suren Baghdasaryan <surenb@google.com>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Nicolas Geoffray <ngeoffray@google.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

fs/userfaultfd.c

@@ -2047,7 +2047,7 @@ static int userfaultfd_move(struct userfaultfd_ctx *ctx,
 			ret = move_pages(ctx, mm, uffdio_move.dst, uffdio_move.src,
 					 uffdio_move.len, uffdio_move.mode);
 		else
-			ret = -EINVAL;
+			ret = -EAGAIN;
 
 		mmap_read_unlock(mm);
 		mmput(mm);