[dm-devel] [PATCH v2 1/2] md raid0/linear: Introduce new array state 'broken'

[Song Liu]

On Fri, Aug 16, 2019 at 6:41 AM Guilherme G. Piccoli
<gpiccoli at canonical.com> wrote:
>
> Currently if md raid0/linear array gets one or more members removed while
> being mounted, kernel keeps showing state 'clean' in the 'array_state'
> sysfs attribute. Despite udev signaling the member device is gone, 'mdadm'
> cannot issue the STOP_ARRAY ioctl successfully, given the array is mounted.
>
> Nothing else hints that something is wrong (except that the removed devices
> don't show properly in the output of 'mdadm detail' command). There is no
> other property to be checked, and if user is not performing reads/writes
> to the array, even kernel log is quiet and doesn't give a clue about the
> missing member.
>
> This patch changes this behavior; when 'array_state' is read we introduce
> a non-expensive check (only for raid0/md-linear) that relies in the
> comparison of the total number of disks when array was assembled with
> gendisk flags of those devices to validate if all members are available
> and functional. A new array state 'broken' was added: it mimics the state
> 'clean' in every aspect, being useful only to distinguish if such array
> has some member missing. Also, we show a rate-limited warning in kernel
> log in such case.
>
> This patch has no proper functional change other than adding the
> 'clean'-like state; it was tested with ext4 and xfs filesystems. It
> requires a 'mdadm' counterpart to handle the 'broken' state.
>
> Cc: NeilBrown <neilb at suse.com>
> Cc: Song Liu <songliubraving at fb.com>
> Signed-off-by: Guilherme G. Piccoli <gpiccoli at canonical.com>

If we merge this with the MD_BROKEN patch, would the code look simpler?

Thanks,
Song