kernel 2.6.15.5 and fs/nfs errors

["Bernd Prager" <bernd@prager.ws>]

I tried to compile the new kernel.
"make-kpkg clean; make-kpkg kernel_image" generates:

  CC [M]  fs/nfs/direct.o
fs/nfs/direct.c: In function 'nfs_get_user_pages':
fs/nfs/direct.c:110: warning: implicit declaration of function
'nfs_free_user_pages'
fs/nfs/direct.c: At top level:
fs/nfs/direct.c:127: warning: conflicting types for 'nfs_free_user_pages'
fs/nfs/direct.c:127: error: static declaration of 'nfs_free_user_pages'
follows non-static declaration
fs/nfs/direct.c:110: error: previous implicit declaration of
'nfs_free_user_pages' was here

Anybody similar experiences?
Is this a kernel bug?

-- Bernd