zram: cleanup reset_store

Use a local variable for the gendisk instead of the part0 block_device,
as the gendisk is what this function actually operates on.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220330052917.2566582-3-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/zram/zram_drv.c

@@ -1786,7 +1786,7 @@ static ssize_t reset_store(struct device *dev,
 	int ret;
 	unsigned short do_reset;
 	struct zram *zram;
-	struct block_device *bdev;
+	struct gendisk *disk;
 
 	ret = kstrtou16(buf, 10, &do_reset);
 	if (ret)
@@ -1796,26 +1796,26 @@ static ssize_t reset_store(struct device *dev,
 		return -EINVAL;
 
 	zram = dev_to_zram(dev);
-	bdev = zram->disk->part0;
+	disk = zram->disk;
 
-	mutex_lock(&bdev->bd_disk->open_mutex);
+	mutex_lock(&disk->open_mutex);
 	/* Do not reset an active device or claimed device */
-	if (bdev->bd_openers || zram->claim) {
-		mutex_unlock(&bdev->bd_disk->open_mutex);
+	if (disk->part0->bd_openers || zram->claim) {
+		mutex_unlock(&disk->open_mutex);
 		return -EBUSY;
 	}
 
 	/* From now on, anyone can't open /dev/zram[0-9] */
 	zram->claim = true;
-	mutex_unlock(&bdev->bd_disk->open_mutex);
+	mutex_unlock(&disk->open_mutex);
 
 	/* Make sure all the pending I/O are finished */
-	sync_blockdev(bdev);
+	sync_blockdev(disk->part0);
 	zram_reset_device(zram);
 
-	mutex_lock(&bdev->bd_disk->open_mutex);
+	mutex_lock(&disk->open_mutex);
 	zram->claim = false;
-	mutex_unlock(&bdev->bd_disk->open_mutex);
+	mutex_unlock(&disk->open_mutex);
 
 	return len;
 }