virtio_blk: simplify refcounting

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>
Link: https://lore.kernel.org/r/20220215094514.3828912-6-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index c443cd6..5c636ca 100644 (file)
--- 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 @@ out:
        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 @@ out:
        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