Re: [PATCH 6/9] block: add a mark_dead holder operation

[Jan Kara <jack@suse.cz>]

On Fri 05-05-23 13:51:29, Christoph Hellwig wrote:
> Add a mark_dead method to blk_holder_ops that is called from blk_mark_disk_dead
> to notify the holder that the block device it is using has been marked dead.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

One question below:

> ---
>  block/genhd.c          | 24 ++++++++++++++++++++++++
>  include/linux/blkdev.h |  1 +
>  2 files changed, 25 insertions(+)
> 
> diff --git a/block/genhd.c b/block/genhd.c
> index d1c673b967c254..af97a4ef1e926c 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -575,6 +575,28 @@ int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
>  }
>  EXPORT_SYMBOL(device_add_disk);
>  
> +static void blk_report_disk_dead(struct gendisk *disk)
> +{
> +	struct block_device *bdev;
> +	unsigned long idx;
> +
> +	rcu_read_lock();
> +	xa_for_each(&disk->part_tbl, idx, bdev) {
> +		if (!kobject_get_unless_zero(&bdev->bd_device.kobj))
> +			continue;
> +		rcu_read_unlock();
> +
> +		mutex_lock(&bdev->bd_holder_lock);
> +		if (bdev->bd_holder_ops && bdev->bd_holder_ops->mark_dead)
> +			bdev->bd_holder_ops->mark_dead(bdev);
> +		mutex_unlock(&bdev->bd_holder_lock);
> +
> +		put_device(&bdev->bd_device);
> +		rcu_read_lock();
> +	}
> +	rcu_read_unlock();
> +}
> +
>  /**
>   * blk_mark_disk_dead - mark a disk as dead
>   * @disk: disk to mark as dead
> @@ -602,6 +624,8 @@ void blk_mark_disk_dead(struct gendisk *disk)
>  	 * Prevent new I/O from crossing bio_queue_enter().
>  	 */
>  	blk_queue_start_drain(disk->queue);
> +
> +	blk_report_disk_dead(disk);

Hum, but this gets called from del_gendisk() after blk_drop_partitions()
happens. So how is this going to be able to iterate anything?

								Honza

-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR