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/[email protected]
Signed-off-by: Lokesh Gidra <[email protected]>
Acked-by: Suren Baghdasaryan <[email protected]>
Acked-by: Mike Rapoport (IBM) <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Axel Rasmussen <[email protected]>
Cc: Brian Geffon <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Jann Horn <[email protected]>
Cc: Kalesh Singh <[email protected]>
Cc: Matthew Wilcox (Oracle) <[email protected]>
Cc: Nicolas Geoffray <[email protected]>
Cc: Peter Xu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: SENSEIIIII

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);