On Wed, Feb 01, 2023 at 02:41:06PM +0100, Christoph Hellwig wrote:
> There is no need to initialize the cgroup 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@xxxxxx>
> Reviewed-by: Andreas Herrmann <aherrmann@xxxxxxx>
> ---
> block/genhd.c | 17 +++++++++--------
> 1 file changed, 9 insertions(+), 8 deletions(-)
>
> 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);
This patch causes kernel panic:
[ 581.975121] bio_associate_blkg+0x28/0x60
[ 581.975798] bio_init+0x6d/0xc0
[ 581.976364] blkdev_issue_flush+0x21/0x40
[ 581.977021] ? _raw_write_unlock+0x12/0x30
[ 581.977686] ? jbd2_journal_start_commit+0x4b/0x80
[ 581.978418] ext4_sync_fs+0x1c6/0x1d0
[ 581.979062] sync_filesystem+0x77/0x90
[ 581.979883] generic_shutdown_super+0x22/0x130
[ 581.980773] kill_block_super+0x21/0x50
[ 581.981622] deactivate_locked_super+0x2c/0xa0
[ 581.982306] cleanup_mnt+0xbd/0x150
because disk->root_blkg is freed & set as NULL in del_gendisk().
by the following script:
modprobe -r scsi_debug
modprobe scsi_debug dev_size_mb=1024
mkfs.xfs -f /dev/sdc #suppose sdc is the scsi debug disk
mount /dev/sdc /mnt
echo 1 > /sys/block/sdc/device/delete
sleep 1
umount /mnt
Thanks,
Ming
