From: Ming Lei <ming.lei@canonical.com>
Date: Tue, 24 Nov 2015 02:35:31 +0000 (+0800)
Subject: blk-merge: warn if figured out segment number is bigger than nr_phys_segments
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=12e57f59ca3344a588531f68eeede45666e8a6e0;p=linux-beck.git

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

We had seen lots of reports of this kind issue, so add one
warnning in blk-merge, then it can be triggered easily and
avoid to depend on warning/bug from drivers.

Signed-off-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
---

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 50793cdc5331..41a55ba0d78e 100644
--- 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);