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.
Please briefly describe how the user space (mdadm or something else)
will use the new API to fix this issue.
No need to resend the patch. You can just reply here.
Thanks,
Song
>
> 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);
> +
> static ssize_t
> layout_show(struct mddev *mddev, char *page)
> {
> @@ -5666,6 +5694,7 @@ __ATTR(serialize_policy, S_IRUGO | S_IWUSR, serialize_policy_show,
>
> static struct attribute *md_default_attrs[] = {
> &md_level.attr,
> + &md_new_level.attr,
> &md_layout.attr,
> &md_raid_disks.attr,
> &md_uuid.attr,
> --
> 2.32.0 (Apple Git-132)
>
