Re: Can't reshape raid0 to raid10

[Xiao Ni <xni@redhat.com>]

----- Original Message -----
> From: "Xiao Ni" <xni@redhat.com>
> To: linux-raid@vger.kernel.org
> Sent: Tuesday, December 30, 2014 11:13:41 AM
> Subject: Can't reshape raid0 to raid10
> 
> Hi Neil
> 
>    When I try to reshape a raid0 to raid10, it'll fail like this:
> 
> [root@dhcp-12-133 mdadm-3.3.2]# lsblk
> NAME                    MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
> sda                       8:0    0 111.8G  0 disk
> ├─sda1                    8:1    0  1000M  0 part /boot
> ├─sda2                    8:2    0  29.3G  0 part /
> ├─sda3                    8:3    0   512M  0 part [SWAP]
> ├─sda4                    8:4    0     1K  0 part
> ├─sda5                    8:5    0   102M  0 part
> └─sda6                    8:6    0  10.1G  0 part
>   └─VolGroup00-LogVol00 254:0    0   9.9G  0 lvm
> sdb                       8:16   0 111.8G  0 disk
> ├─sdb1                    8:17   0     2G  0 part
> └─sdb2                    8:18   0    10G  0 part
> sdc                       8:32   0 186.3G  0 disk
> ├─sdc1                    8:33   0     2G  0 part
> └─sdc2                    8:34   0    10G  0 part
> sdd                       8:48   0 111.8G  0 disk
> ├─sdd1                    8:49   0     2G  0 part
> └─sdd2                    8:50   0    10G  0 part
> [root@dhcp-12-133 mdadm-3.3.2]# mdadm -CR /dev/md0 -l0 -n3 /dev/sdb1
> /dev/sdc1 /dev/sdd1
> mdadm: Defaulting to version 1.2 metadata
> mdadm: array /dev/md0 started.
> [root@dhcp-12-133 mdadm-3.3.2]# mdadm --grow /dev/md0 -l10 -a /dev/sdb2
> /dev/sdc2 /dev/sdd2
> mdadm: level of /dev/md0 changed to raid10
> mdadm: add new device failed for /dev/sdb2 as 6: No space left on device
> 
>    
>    But if I reshape the raid0 to raid5, reshape raid5 to raid0, then reshape
>    raid0 to raid10 use
> the same command it'll succeed.
> 
> [root@dhcp-12-133 mdadm-3.3.2]# mdadm -CR /dev/md0 -l0 -n3 /dev/sdb1
> /dev/sdc1 /dev/sdd1
> [root@dhcp-12-133 mdadm-3.3.2]# mdadm --grow /dev/md0 -l5
> [root@dhcp-12-133 mdadm-3.3.2]# cat /proc/mdstat
> Personalities : [raid6] [raid5] [raid4] [raid0] [raid10]
> md0 : active raid5 sdd1[2] sdc1[1] sdb1[0]
>       6285312 blocks super 1.2 level 5, 512k chunk, algorithm 2 [4/3] [UUU_]
>       
> unused devices: <none>
> 
> [root@dhcp-12-133 mdadm-3.3.2]# mdadm --grow /dev/md0 -l0
> [root@dhcp-12-133 mdadm-3.3.2]# cat /proc/mdstat
> Personalities : [raid6] [raid5] [raid4] [raid0] [raid10]
> md0 : active raid0 sdd1[2] sdc1[1] sdb1[0]
>       6285312 blocks super 1.2 512k chunks
>       
> unused devices: <none>
> [root@dhcp-12-133 mdadm-3.3.2]# mdadm --grow /dev/md0 -l10 -a /dev/sdb2
> /dev/sdc2 /dev/sdd2
> mdadm: level of /dev/md0 changed to raid10
> mdadm: added /dev/sdb2
> mdadm: added /dev/sdc2
> mdadm: added /dev/sdd2
> 
>     So I guess it's the problem add the disk to raid10 after the reshaping.
>     In the function
> super_1_validate, it'll set the  mddev->dev_sectors using the superblock read
> from disks.
> If it's raid0, the le64_to_cpu(sb-size) is 0. So when add disk to raid10
> bind_rdev_to_array
> return -ENOSPC.
> 
>     When create raid0, it doesn't write give the value to s->size. So the
>     sb-size is 0.
> I modify the code about Create.c. I'm not sure whether it's right to do so.
> But it can resolve
> the problem.
> 
> diff --git a/Create.c b/Create.c
> index 330c5b4..f3135c5 100644
> --- a/Create.c
> +++ b/Create.c
> @@ -489,7 +489,7 @@ int Create(struct supertype *st, char *mddev,
>                         pr_err("no size and no drives given - aborting
>                         create.\n");
>                         return 1;
>                 }
> -               if (s->level > 0 || s->level == LEVEL_MULTIPATH
> +               if (s->level >= 0 || s->level == LEVEL_MULTIPATH
>                     || s->level == LEVEL_FAULTY
>                     || st->ss->external ) {
>                         /* size is meaningful */
> 

Hi Neil

   Any update for this? 

Best Regards
Xiao
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