block: cleanup blkdev_bszset

Use blkdev_get_by_dev instead of bdgrab + blkdev_get.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/ioctl.c

@@ -478,15 +478,14 @@ static int blkdev_bszset(struct block_device *bdev, fmode_t mode,
 	if (get_user(n, argp))
 		return -EFAULT;
 
-	if (!(mode & FMODE_EXCL)) {
-		bdgrab(bdev);
-		if (blkdev_get(bdev, mode | FMODE_EXCL, &bdev) < 0)
-			return -EBUSY;
-	}
+	if (mode & FMODE_EXCL)
+		return set_blocksize(bdev, n);
 
+	if (IS_ERR(blkdev_get_by_dev(bdev->bd_dev, mode | FMODE_EXCL, &bdev)))
+		return -EBUSY;
 	ret = set_blocksize(bdev, n);
-	if (!(mode & FMODE_EXCL))
-		blkdev_put(bdev, mode | FMODE_EXCL);
+	blkdev_put(bdev, mode | FMODE_EXCL);
+
 	return ret;
 }