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

Jan Kara
2023-05-08T13:01:50Z

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