Re: [PATCH 1/9] block: consolidate the shutdown logic in blk_mark_disk_dead and del_gendisk

[Jan Kara <jack@suse.cz>]

On Fri 05-05-23 13:51:24, Christoph Hellwig wrote:
> blk_mark_disk_dead does very similar work a a section of del_gendisk:
> 
>  - set the GD_DEAD flag
>  - set the capacity to zero
>  - start a queue drain
> 
> but del_gendisk also sets QUEUE_FLAG_DYING on the queue if it is owned by
> the disk, sets the capacity to zero before starting the drain, and both
> with sending a uevent and kernel message for this fake capacity change.
> 
> Move the exact logic from the more heavily used del_gendisk into
> blk_mark_disk_dead and then call blk_mark_disk_dead from del_gendisk.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

I'm somewhat wondering about the lost notification from
blk_mark_disk_dead(). E.g. DM uses blk_mark_disk_dead() so if some udev
script depends on the event when DM device gets destroyed, we would break
it?

								Honza

> ---
>  block/genhd.c | 26 ++++++++++++--------------
>  1 file changed, 12 insertions(+), 14 deletions(-)
> 
> diff --git a/block/genhd.c b/block/genhd.c
> index 90c402771bb570..461999e9489937 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -583,13 +583,22 @@ EXPORT_SYMBOL(device_add_disk);
>   */
>  void blk_mark_disk_dead(struct gendisk *disk)
>  {
> +	/*
> +	 * Fail any new I/O.
> +	 */
>  	set_bit(GD_DEAD, &disk->state);
> -	blk_queue_start_drain(disk->queue);
> +	if (test_bit(GD_OWNS_QUEUE, &disk->state))
> +		blk_queue_flag_set(QUEUE_FLAG_DYING, disk->queue);
>  
>  	/*
>  	 * Stop buffered writers from dirtying pages that can't be written out.
>  	 */
> -	set_capacity_and_notify(disk, 0);
> +	set_capacity(disk, 0);
> +
> +	/*
> +	 * Prevent new I/O from crossing bio_queue_enter().
> +	 */
> +	blk_queue_start_drain(disk->queue);
>  }
>  EXPORT_SYMBOL_GPL(blk_mark_disk_dead);
>  
> @@ -632,18 +641,7 @@ void del_gendisk(struct gendisk *disk)
>  	fsync_bdev(disk->part0);
>  	__invalidate_device(disk->part0, true);
>  
> -	/*
> -	 * Fail any new I/O.
> -	 */
> -	set_bit(GD_DEAD, &disk->state);
> -	if (test_bit(GD_OWNS_QUEUE, &disk->state))
> -		blk_queue_flag_set(QUEUE_FLAG_DYING, q);
> -	set_capacity(disk, 0);
> -
> -	/*
> -	 * Prevent new I/O from crossing bio_queue_enter().
> -	 */
> -	blk_queue_start_drain(q);
> +	blk_mark_disk_dead(disk);
>  
>  	if (!(disk->flags & GENHD_FL_HIDDEN)) {
>  		sysfs_remove_link(&disk_to_dev(disk)->kobj, "bdi");
> -- 
> 2.39.2
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR