blk-merge: warn if figured out segment number is bigger than nr_phys_segments

[linux-2.6-block.git] / block / blk-merge.c

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 50793cdc53314d5b0da41639cb804c6029918a81..41a55ba0d78e8a97b5707a9194cce3b6ebd1c811 100644 (file)
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -428,6 +428,12 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq,
        if (sg)
                sg_mark_end(sg);
 
+       /*
+        * Something must have been wrong if the figured number of
+        * segment is bigger than number of req's physical segments
+        */
+       WARN_ON(nsegs > rq->nr_phys_segments);
+
        return nsegs;
 }
 EXPORT_SYMBOL(blk_rq_map_sg);