Re: [RFC PATCH V3 1/1] block: reject I/O for same fd if block size changed

[Christoph Hellwig]

On Mon, Jan 04, 2021 at 10:06:59PM +0900, Minwoo Im wrote:
> +     if (q->backing_dev_info && q->backing_dev_info->owner &&
> +                     limits->logical_block_size != size) {
> +             bdev = blkdev_get_no_open(q->backing_dev_info->owner->devt);
> +             bdev->bd_disk->flags |= GENHD_FL_BLOCK_SIZE_CHANGED;
> +             blkdev_put_no_open(bdev);
> +     }

We really need the backpointer from the queue to the gendisk I've wanted
to add for a while.  Can we at least restrict this to a live gendisk?

Also I think the size change flag should go into the ->state field and
use the atomic bitops helpers to avoid concurrency problems.