Re: [PATCH 03/15] blk-cgroup: delay blk-cgroup initialization until add_disk

[Andreas Herrmann <aherrmann-l3A5Bk7waGM@public.gmane.org>]

On Tue, Jan 17, 2023 at 09:12:45AM +0100, Christoph Hellwig wrote:
> There is no need to initialize the group code before the disk is marked
> live.  Moving the cgroup initialization earlier will help to have a
> fully initialized struct device in the gendisk for the cgroup code to
> use in the future.  Similarly tear the cgroup information down in
> del_gendisk to be symmetric and because none of the cgroup tracking is
> needed once non-passthrough I/O stops.
> 
> Signed-off-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
> ---
>  block/genhd.c | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)

Looks good to me. Feel free to add
Reviewed-by: Andreas Herrmann <aherrmann-l3A5Bk7waGM@public.gmane.org>

> diff --git a/block/genhd.c b/block/genhd.c
> index 23cf83b3331cde..705dec0800d62e 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -466,10 +466,14 @@ int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
>  	 */
>  	pm_runtime_set_memalloc_noio(ddev, true);
>  
> -	ret = blk_integrity_add(disk);
> +	ret = blkcg_init_disk(disk);
>  	if (ret)
>  		goto out_del_block_link;
>  
> +	ret = blk_integrity_add(disk);
> +	if (ret)
> +		goto out_blkcg_exit;
> +
>  	disk->part0->bd_holder_dir =
>  		kobject_create_and_add("holders", &ddev->kobj);
>  	if (!disk->part0->bd_holder_dir) {
> @@ -534,6 +538,8 @@ int __must_check device_add_disk(struct device *parent, struct gendisk *disk,
>  	kobject_put(disk->part0->bd_holder_dir);
>  out_del_integrity:
>  	blk_integrity_del(disk);
> +out_blkcg_exit:
> +	blkcg_exit_disk(disk);
>  out_del_block_link:
>  	if (!sysfs_deprecated)
>  		sysfs_remove_link(block_depr, dev_name(ddev));
> @@ -662,6 +668,8 @@ void del_gendisk(struct gendisk *disk)
>  	rq_qos_exit(q);
>  	blk_mq_unquiesce_queue(q);
>  
> +	blkcg_exit_disk(disk);
> +
>  	/*
>  	 * If the disk does not own the queue, allow using passthrough requests
>  	 * again.  Else leave the queue frozen to fail all I/O.
> @@ -1171,8 +1179,6 @@ static void disk_release(struct device *dev)
>  	    !test_bit(GD_ADDED, &disk->state))
>  		blk_mq_exit_queue(disk->queue);
>  
> -	blkcg_exit_disk(disk);
> -
>  	bioset_exit(&disk->bio_split);
>  
>  	disk_release_events(disk);
> @@ -1385,9 +1391,6 @@ struct gendisk *__alloc_disk_node(struct request_queue *q, int node_id,
>  	if (xa_insert(&disk->part_tbl, 0, disk->part0, GFP_KERNEL))
>  		goto out_destroy_part_tbl;
>  
> -	if (blkcg_init_disk(disk))
> -		goto out_erase_part0;
> -
>  	rand_initialize_disk(disk);
>  	disk_to_dev(disk)->class = &block_class;
>  	disk_to_dev(disk)->type = &disk_type;
> @@ -1400,8 +1403,6 @@ struct gendisk *__alloc_disk_node(struct request_queue *q, int node_id,
>  #endif
>  	return disk;
>  
> -out_erase_part0:
> -	xa_erase(&disk->part_tbl, 0);
>  out_destroy_part_tbl:
>  	xa_destroy(&disk->part_tbl);
>  	disk->part0->bd_disk = NULL;
> -- 
> 2.39.0
> 

-- 
Regards,
Andreas

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