block: WARN in __blk_put_request() for potential bio leak

Put a WARN_ON in __blk_put_request if it is about to
leak bio(s). This is a serious bug that can happen in error
handling code paths.

For this to work I have fixed a couple of places in block/ where
request->bio != NULL ownership was not honored. And a small cleanup
at sg_io() while at it.

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 5a244f05360f..e39cb24b7679 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -403,6 +403,8 @@ static int attempt_merge(struct request_queue *q, struct request *req,
         if (blk_rq_cpu_valid(next))
                 req->cpu = next->cpu;
 
+        /* owner-ship of bio passed from next to req */
+        next->bio = NULL;
         __blk_put_request(q, next);
         return 1;
 }