As ->vm_private_data is used as a cursor for swapout of VM_NONLINEAR vmas,
the check for NULL ->vm_private_data or VM_RESERVED is too strict, and
should allow VM_NONLINEAR vmas with non-NULL ->vm_private_data.

This fixes an issue on 2.6.7-mm5 where system calls to remap_file_pages()
spuriously failed while under memory pressure.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>