----- Original Message -----
> From: "Guoqing Jiang" <gqjiang@xxxxxxxx>
> To: "Gi-Oh Kim" <gi-oh.kim@xxxxxxxxxxxxxxxx>, "Shaohua Li" <shli@xxxxxx>, "NeilBrown" <neilb@xxxxxxx>
> Cc: "Jinpu Wang" <jinpu.wang@xxxxxxxxxxxxxxxx>, linux-raid@xxxxxxxxxxxxxxx
> Sent: Friday, September 21, 2018 11:57:50 AM
> Subject: Re: [RFC] wrong behavior of re-adding a device
>
>
>
> On 9/20/18 9:36 PM, Gi-Oh Kim wrote:
> > On Wed, Sep 19, 2018 at 5:09 PM Gi-Oh Kim <gi-oh.kim@xxxxxxxxxxxxxxxx>
> > wrote:
> >> Hi,
> >>
> >> I found a weird behavior of re-adding a device.
> >> I think it is a kernel bug.
> >> I would appreciate it if somebody can confirm if it is a bug or feature.
> >>
> >> I tested re-adding a device as following.
> >> 1. create md with ram0 and ram1
> >> 2. add ram2
> >> 3. grow raid-device number to 3
> >> 4. remove ram2
> >> 5. grow raid-device number to 2
> >> 6. add ram2
> >> 7. ram0 become faulty and ram2 become active
> >> 8. stop md
> >> 9. assemble md with ram0 and ram1 => fail because ram0 is faulty
Hi Gi
I haven't reproduce your problem. Are there something wrong with the steps?
[root@dell-per230-03 home]# uname -r
4.19.0-rc4
[root@dell-per230-03 home]# modprobe brd rd_nr=4 rd_size=12582912
[root@dell-per230-03 home]# ls /dev/ram*
/dev/ram0 /dev/ram1 /dev/ram2 /dev/ram3
[root@dell-per230-03 home]# mdadm -CR /dev/md0 -l1 -n2 /dev/ram0 /dev/ram1
[root@dell-per230-03 home]# mdadm /dev/md0 -a /dev/ram2
mdadm: added /dev/ram2
[root@dell-per230-03 home]# cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 ram2[2](S) ram1[1] ram0[0]
12573696 blocks super 1.2 [2/2] [UU]
[root@dell-per230-03 home]# mdadm /dev/md0 --grow --raid-device=3
raid_disks for /dev/md0 set to 3
[root@dell-per230-03 home]# cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 ram2[2] ram1[1] ram0[0]
12573696 blocks super 1.2 [3/3] [UUU]
unused devices: <none>
[root@dell-per230-03 home]# mdadm /dev/md0 -f /dev/ram2
mdadm: set /dev/ram2 faulty in /dev/md0
[root@dell-per230-03 home]# mdadm /dev/md0 -r /dev/ram2
mdadm: hot removed /dev/ram2 from /dev/md0
[root@dell-per230-03 home]# cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 ram1[1] ram0[0]
12573696 blocks super 1.2 [3/2] [UU_]
unused devices: <none>
[root@dell-per230-03 home]# mdadm /dev/md0 --grow --raid-devices=2
raid_disks for /dev/md0 set to 2
[root@dell-per230-03 home]# cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 ram1[1] ram0[0]
12573696 blocks super 1.2 [2/2] [UU]
unused devices: <none>
[root@dell-per230-03 home]# mdadm /dev/md0 -a /dev/ram2
mdadm: added /dev/ram2
[root@dell-per230-03 home]# cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 ram2[2](S) ram1[1] ram0[0]
12573696 blocks super 1.2 [2/2] [UU]
unused devices: <none>
Regards
Xiao
