memstick/mspro_block: simplify refcounting

Implement the ->free_disk method to free the msb_data structure only once
the last gendisk reference goes away instead of keeping a local
refcount.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220215094514.3828912-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Author: Christoph Hellwig

drivers/memstick/core/mspro_block.c

@@ -133,7 +133,6 @@ struct mspro_devinfo {
 
 struct mspro_block_data {
 	struct memstick_dev   *card;
-	unsigned int          usage_count;
 	unsigned int          caps;
 	struct gendisk        *disk;
 	struct request_queue  *queue;
@@ -178,48 +177,16 @@ static int mspro_block_complete_req(struct memstick_dev *card, int error);
 
 /*** Block device ***/
 
-static int mspro_block_bd_open(struct block_device *bdev, fmode_t mode)
-{
-	struct gendisk *disk = bdev->bd_disk;
-	struct mspro_block_data *msb = disk->private_data;
-	int rc = -ENXIO;
-
-	mutex_lock(&mspro_block_disk_lock);
-
-	if (msb && msb->card)
-		msb->usage_count++;
-
-	mutex_unlock(&mspro_block_disk_lock);
-
-	return rc;
-}
-
-
-static void mspro_block_disk_release(struct gendisk *disk)
+static void mspro_block_bd_free_disk(struct gendisk *disk)
 {
 	struct mspro_block_data *msb = disk->private_data;
 	int disk_id = MINOR(disk_devt(disk)) >> MSPRO_BLOCK_PART_SHIFT;
 
 	mutex_lock(&mspro_block_disk_lock);
-
-	if (msb) {
-		if (msb->usage_count)
-			msb->usage_count--;
-
-		if (!msb->usage_count) {
-			kfree(msb);
-			disk->private_data = NULL;
-			idr_remove(&mspro_block_disk_idr, disk_id);
-			put_disk(disk);
-		}
-	}
-
+	idr_remove(&mspro_block_disk_idr, disk_id);
 	mutex_unlock(&mspro_block_disk_lock);
-}
 
-static void mspro_block_bd_release(struct gendisk *disk, fmode_t mode)
-{
-	mspro_block_disk_release(disk);
+	kfree(msb);
 }
 
 static int mspro_block_bd_getgeo(struct block_device *bdev,
@@ -235,10 +202,9 @@ static int mspro_block_bd_getgeo(struct block_device *bdev,
 }
 
 static const struct block_device_operations ms_block_bdops = {
-	.open    = mspro_block_bd_open,
-	.release = mspro_block_bd_release,
-	.getgeo  = mspro_block_bd_getgeo,
-	.owner   = THIS_MODULE
+	.owner		= THIS_MODULE,
+	.getgeo		= mspro_block_bd_getgeo,
+	.free_disk	= mspro_block_bd_free_disk,
 };
 
 /*** Information ***/
@@ -1221,7 +1187,6 @@ static int mspro_block_init_disk(struct memstick_dev *card)
 	msb->disk->first_minor = disk_id << MSPRO_BLOCK_PART_SHIFT;
 	msb->disk->minors = 1 << MSPRO_BLOCK_PART_SHIFT;
 	msb->disk->fops = &ms_block_bdops;
-	msb->usage_count = 1;
 	msb->disk->private_data = msb;
 
 	sprintf(msb->disk->disk_name, "mspblk%d", disk_id);
@@ -1339,7 +1304,7 @@ static void mspro_block_remove(struct memstick_dev *card)
 	mspro_block_data_clear(msb);
 	mutex_unlock(&mspro_block_disk_lock);
 
-	mspro_block_disk_release(msb->disk);
+	put_disk(msb->disk);
 	memstick_set_drvdata(card, NULL);
 }