[JFFS2] Reschedule in loops

Make JFFS2 nicer and teach it to call cond_resched() in loops
which may be quite large.

Signed-off-by: Artem Bityutskiy <dedekind@infradead.org>
diff --git a/fs/jffs2/scan.c b/fs/jffs2/scan.c
index a167e1c..3af746e 100644
--- a/fs/jffs2/scan.c
+++ b/fs/jffs2/scan.c
@@ -139,6 +139,8 @@
 	for (i=0; i<c->nr_blocks; i++) {
 		struct jffs2_eraseblock *jeb = &c->blocks[i];
 
+		cond_resched();
+
 		/* reset summary info for next eraseblock scan */
 		jffs2_sum_reset_collected(s);