[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>

fs/jffs2/scan.c

@@ -139,6 +139,8 @@ int jffs2_scan_medium(struct jffs2_sb_info *c)
 	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);