afs_prepare_write() should not mark a page up to date if it only partially
fills it in, in expectation of the caller filling in the rest prior to calling
commit_write().  commit_write(), however, should mark the page up to date.
Signed-off-by: NDavid Howells <dhowells@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>