On Wed, Sep 4, 2024 at 4:55 PM Xiao Ni <xni@xxxxxxxxxx> wrote:
>
> Reshape needs to specify a backup file when it can't update data offset
> of member disks. For this situation, first, it starts reshape and then
> it kicks off mdadm-grow-continue service which does backup job and
> monitors the reshape process. The service is a new process, so it needs
> to read superblock from member disks to get information.
>
> But in the first step, it doesn't update new level in superblock. So
> in the second step, the new level that systemd service reads from
> superblock is wrong. It can't change to the right new level after reshape
> finishes. This interface is used to update new level during reshape
> progress.
>
> Reproduce steps:
> mdadm -CR /dev/md0 -l6 -n4 /dev/loop[0-3]
> mdadm --wait /dev/md0
> mdadm /dev/md0 --grow -l5 --backup=backup
> cat /proc/mdstat
> Personalities : [raid6] [raid5] [raid4] [raid0] [raid1] [raid10]
> md0 : active raid6 loop3[3] loop2[2] loop1[1] loop0[0]
>
> Test case 07changelevels from mdadm regression tests can trigger this
> problem.
>
> Signed-off-by: Xiao Ni <xni@xxxxxxxxxx>
> ---
> V3: explain more about the root cause
> V2: add detail about test information
> drivers/md/md.c | 29 +++++++++++++++++++++++++++++
> 1 file changed, 29 insertions(+)
>
> diff --git a/drivers/md/md.c b/drivers/md/md.c
> index d3a837506a36..3c354e7a7825 100644
> --- a/drivers/md/md.c
> +++ b/drivers/md/md.c
> @@ -4141,6 +4141,34 @@ level_store(struct mddev *mddev, const char *buf, size_t len)
> static struct md_sysfs_entry md_level =
> __ATTR(level, S_IRUGO|S_IWUSR, level_show, level_store);
>
> +static ssize_t
> +new_level_show(struct mddev *mddev, char *page)
> +{
> + return sprintf(page, "%d\n", mddev->new_level);
> +}
> +
> +static ssize_t
> +new_level_store(struct mddev *mddev, const char *buf, size_t len)
> +{
> + unsigned int n;
> + int err;
> +
> + err = kstrtouint(buf, 10, &n);
> + if (err < 0)
> + return err;
> + err = mddev_lock(mddev);
> + if (err)
> + return err;
> +
> + mddev->new_level = n;
> + md_update_sb(mddev, 1);
> +
> + mddev_unlock(mddev);
> + return len;
> +}
> +static struct md_sysfs_entry md_new_level =
> +__ATTR(new_level, 0664, new_level_show, new_level_store);
Actually, since we can read and write "new_level", please describe how
it will be used (read and write).
Thanks,
Song
