staging/lustre/llite: clip page correctly for vvp_io_commit_sync

The original code was wrong which clipped page incorrectly for
partial pages started with zero.
Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Reviewed-on: http://review.whamcloud.com/8531
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-4201Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: wangdi <di.wang@intel.com>
Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/llite/vvp_io.c

@@ -595,15 +595,17 @@ static int vvp_io_commit_sync(const struct lu_env *env, struct cl_io *io,
 	if (plist->pl_nr == 0)
 		return 0;
 
-	if (from != 0) {
+	if (from > 0 || to != PAGE_SIZE) {
 		page = cl_page_list_first(plist);
-		cl_page_clip(env, page, from,
-			     plist->pl_nr == 1 ? to : PAGE_SIZE);
-	}
-	if (to != PAGE_SIZE && plist->pl_nr > 1) {
+		if (plist->pl_nr == 1) {
+			cl_page_clip(env, page, from, to);
+		} else if (from > 0) {
+			cl_page_clip(env, page, from, PAGE_SIZE);
+		} else {
 		page = cl_page_list_last(plist);
 		cl_page_clip(env, page, 0, to);
 	}
+	}
 
 	cl_2queue_init(queue);
 	cl_page_list_splice(plist, &queue->c2_qin);