Re: [PATCH v8 1/4] md: delete md_redundancy_group when array is becoming inactive

[Xiao Ni <xni@redhat.com>]

On Thu, Oct 30, 2025 at 2:36 PM <linan666@huaweicloud.com> wrote:
>
> From: Li Nan <linan122@huawei.com>
>
> 'md_redundancy_group' are created in md_run() and deleted in del_gendisk(),
> but these are not paired. Writing inactive/active to sysfs array_state can
> trigger md_run() multiple times without del_gendisk(), leading to
> duplicate creation as below:
>
>  sysfs: cannot create duplicate filename '/devices/virtual/block/md0/md/sync_action'
>  Call Trace:
>   dump_stack_lvl+0x9f/0x120
>   dump_stack+0x14/0x20
>   sysfs_warn_dup+0x96/0xc0
>   sysfs_add_file_mode_ns+0x19c/0x1b0
>   internal_create_group+0x213/0x830
>   sysfs_create_group+0x17/0x20
>   md_run+0x856/0xe60
>   ? __x64_sys_openat+0x23/0x30
>   do_md_run+0x26/0x1d0
>   array_state_store+0x559/0x760
>   md_attr_store+0xc9/0x1e0
>   sysfs_kf_write+0x6f/0xa0
>   kernfs_fop_write_iter+0x141/0x2a0
>   vfs_write+0x1fc/0x5a0
>   ksys_write+0x79/0x180
>   __x64_sys_write+0x1d/0x30
>   x64_sys_call+0x2818/0x2880
>   do_syscall_64+0xa9/0x580
>   entry_SYSCALL_64_after_hwframe+0x4b/0x53
>  md: cannot register extra attributes for md0
>
> Creation of it depends on 'pers', its lifecycle cannot be aligned with
> gendisk. So fix this issue by triggering 'md_redundancy_group' deletion
> when the array is becoming inactive.
>
> Fixes: 790abe4d77af ("md: remove/add redundancy group only in level change")
> Signed-off-by: Li Nan <linan122@huawei.com>
> ---
>  drivers/md/md.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index fa13eb02874e..f6fd55a1637b 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -6878,6 +6878,10 @@ static int do_md_stop(struct mddev *mddev, int mode)
>                 if (!md_is_rdwr(mddev))
>                         set_disk_ro(disk, 0);
>
> +               if (mode == 2 && mddev->pers->sync_request &&
> +                   mddev->to_remove == NULL)
> +                       mddev->to_remove = &md_redundancy_group;
> +
>                 __md_stop_writes(mddev);
>                 __md_stop(mddev);
>
> --
> 2.39.2
>

Looks good to me.
Reviewed-by: Xiao Ni <xni@redhat.com>