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

[Song Liu <songliubraving@fb.com>]

> On Aug 21, 2019, at 12:10 PM, Guilherme G. Piccoli <gpiccoli@canonical.com> wrote:
> 
> 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.

I think this makes sense. Please send the patch and we can discuss
further while looking at the code. 

Thanks,
Song