block: missing bio_put following submit_bio_wait

submit_bio_wait() gives the caller an opportunity to examine
struct bio and so expects the caller to issue the put_bio()

This fixes a memory leak reported by a few people in 4.7-rc2
kmemleak report after 9082e87bfbf8 ("block: remove struct bio_batch")

Signed-off-by: Shaun Tancheff <shaun.tancheff@seagate.com>
Tested-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Larry Finger@lwfinger.net
Tested-by: David Drysdale <drysdale@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

block/blk-lib.c

@@ -113,6 +113,7 @@ int blkdev_issue_discard(struct block_device *bdev, sector_t sector,
 		ret = submit_bio_wait(type, bio);
 		if (ret == -EOPNOTSUPP)
 			ret = 0;
+		bio_put(bio);
 	}
 	blk_finish_plug(&plug);
 
@@ -165,8 +166,10 @@ int blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
 		}
 	}
 
-	if (bio)
+	if (bio) {
 		ret = submit_bio_wait(REQ_WRITE | REQ_WRITE_SAME, bio);
+		bio_put(bio);
+	}
 	return ret != -EOPNOTSUPP ? ret : 0;
 }
 EXPORT_SYMBOL(blkdev_issue_write_same);
@@ -206,8 +209,11 @@ static int __blkdev_issue_zeroout(struct block_device *bdev, sector_t sector,
 		}
 	}
 
-	if (bio)
-		return submit_bio_wait(WRITE, bio);
+	if (bio) {
+		ret = submit_bio_wait(WRITE, bio);
+		bio_put(bio);
+		return ret;
+	}
 	return 0;
 }