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

["Guilherme G. Piccoli" <gpiccoli@canonical.com>]

On 21/08/2019 13:14, Song Liu wrote:
> [...] 
> 
> What do you mean by "not clear MD_BROKEN"? Do you mean we need to restart
> the array? 
> 
> IOW, the following won't work:
> 
>   mdadm --fail /dev/md0 /dev/sdx
>   mdadm --remove /dev/md0 /dev/sdx
>   mdadm --add /dev/md0 /dev/sdx
>   
> And we need the following instead:
> 
>   mdadm --fail /dev/md0 /dev/sdx
>   mdadm --remove /dev/md0 /dev/sdx
>   mdadm --stop /dev/md0 /dev/sdx
>   mdadm --add /dev/md0 /dev/sdx
>   mdadm --run /dev/md0 /dev/sdx
> 
> Thanks,
> Song
> 

Song, I've tried the first procedure (without the --stop) and failed to
make it work on linear/raid0 arrays, even trying in vanilla kernel.
What I could do is:

1) Mount an array and while writing, remove a member (nvme1n1 in my
case); "mdadm --detail md0" will either show 'clean' state or 'broken'
if we have my patch;

2) Unmount the array and run: "mdadm -If nvme1n1 --path
pci-0000:00:08.0-nvme-1"
This will result: "mdadm: set device faulty failed for nvme1n1:  Device
or resource busy"
Despite the error, md0 device is gone.

3) echo 1 > /sys/bus/pci/rescan [nvme1 device is back]

4) mdadm -A --scan [md0 is back, with both devices and 'clean' state]

So, either if we "--stop" or if we incremental fail a member of the
array, when it's back the state will be 'clean' and not 'broken'.
Hence, I don't see a point in clearing the MD_BROKEN flag for
raid0/linear arrays, nor I see where we could do it.

And thanks for the link for your tree, I'll certainly rebase my patch
against that.
Cheers,


Guilherme