AFS: Fix afs_prepare_write()

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: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/afs/write.c

@@ -206,7 +206,6 @@ int afs_prepare_write(struct file *file, struct page *page,
 			_leave(" = %d [prep]", ret);
 			return ret;
 		}
-		SetPageUptodate(page);
 	}
 
 try_again:
@@ -311,8 +310,8 @@ int afs_commit_write(struct file *file, struct page *page,
 		spin_unlock(&vnode->writeback_lock);
 	}
 
+	SetPageUptodate(page);
 	set_page_dirty(page);
-
 	if (PageDirty(page))
 		_debug("dirtied");