[PATCH 5/5] virtio_blk: simplify refcounting

Christoph Hellwig
2022-02-15T09:45:42Z

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

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
---
drivers/block/virtio_blk.c | 66 ++++++++------------------------------
1 file changed, 14 insertions(+), 52 deletions(-)

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index c443cd64fc9b4..5c636ca7f1a7f 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -69,13 +69,6 @@ struct virtio_blk {
/* Process context for config space updates */
struct work_struct config_work;

- /*
- * Tracks references from block_device_operations open/release and
- * virtio_driver probe/remove so this object can be freed once no
- * longer in use.
- */
- refcount_t refs;
-
/* What host tells us, plus 2 for header & tailer. */
unsigned int sg_elems;

@@ -391,43 +384,6 @@ static int virtblk_get_id(struct gendisk *disk, char *id_str)
return err;
}

-static void virtblk_get(struct virtio_blk *vblk)
-{
- refcount_inc(&vblk->refs);
-}
-
-static void virtblk_put(struct virtio_blk *vblk)
-{
- if (refcount_dec_and_test(&vblk->refs)) {
- ida_simple_remove(&vd_index_ida, vblk->index);
- mutex_destroy(&vblk->vdev_mutex);
- kfree(vblk);
- }
-}
-
-static int virtblk_open(struct block_device *bd, fmode_t mode)
-{
- struct virtio_blk *vblk = bd->bd_disk->private_data;
- int ret = 0;
-
- mutex_lock(&vblk->vdev_mutex);
-
- if (vblk->vdev)
- virtblk_get(vblk);
- else
- ret = -ENXIO;
-
- mutex_unlock(&vblk->vdev_mutex);
- return ret;
-}
-
-static void virtblk_release(struct gendisk *disk, fmode_t mode)
-{
- struct virtio_blk *vblk = disk->private_data;
-
- virtblk_put(vblk);
-}
-
/* We provide getgeo only to please some old bootloader/partitioning tools */
static int virtblk_getgeo(struct block_device *bd, struct hd_geometry *geo)
{
@@ -460,11 +416,19 @@ static int virtblk_getgeo(struct block_device *bd, struct hd_geometry *geo)
return ret;
}

+static void virtblk_free_disk(struct gendisk *disk)
+{
+ struct virtio_blk *vblk = disk->private_data;
+
+ ida_simple_remove(&vd_index_ida, vblk->index);
+ mutex_destroy(&vblk->vdev_mutex);
+ kfree(vblk);
+}
+
static const struct block_device_operations virtblk_fops = {
- .owner = THIS_MODULE,
- .open = virtblk_open,
- .release = virtblk_release,
- .getgeo = virtblk_getgeo,
+ .owner = THIS_MODULE,
+ .getgeo = virtblk_getgeo,
+ .free_disk = virtblk_free_disk,
};

static int index_to_minor(int index)
@@ -791,8 +755,6 @@ static int virtblk_probe(struct virtio_device *vdev)
goto out_free_index;
}

- /* This reference is dropped in virtblk_remove(). */
- refcount_set(&vblk->refs, 1);
mutex_init(&vblk->vdev_mutex);

vblk->vdev = vdev;
@@ -970,7 +932,7 @@ static void virtblk_remove(struct virtio_device *vdev)
flush_work(&vblk->config_work);

del_gendisk(vblk->disk);
- blk_cleanup_disk(vblk->disk);
+ blk_cleanup_queue(vblk->disk->queue);
blk_mq_free_tag_set(&vblk->tag_set);

mutex_lock(&vblk->vdev_mutex);
@@ -986,7 +948,7 @@ static void virtblk_remove(struct virtio_device *vdev)

mutex_unlock(&vblk->vdev_mutex);

- virtblk_put(vblk);
+ put_disk(vblk->disk);
}

#ifdef CONFIG_PM_SLEEP
--
2.30.2