zram: cleanup backing_dev_store

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

drivers/block/zram/zram_drv.c

@@ -491,9 +491,10 @@ static ssize_t backing_dev_store(struct device *dev,
 		goto out;
 	}
 
-	bdev = bdgrab(I_BDEV(inode));
-	err = blkdev_get(bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL, zram);
-	if (err < 0) {
+	bdev = blkdev_get_by_dev(inode->i_rdev,
+			FMODE_READ | FMODE_WRITE | FMODE_EXCL, zram);
+	if (IS_ERR(bdev)) {
+		err = PTR_ERR(bdev);
 		bdev = NULL;
 		goto out;
 	}