Re: Issues with md raid 1 on kernel 6.18 after booting kernel 6.19rc1 once

["Yu Kuai" <yukuai@fnnas.com>]

Hi,

在 2025/12/17 14:58, BugReports 写道:
> Hi,
>
> i hope i am reaching out to the correct mailing list and this is the 
> way to correctly report issues with rc kernels.
>
> I installed kernel 6.19-rc 1 recently (with linux-tkg, but that should 
> not matter).  Booting the 6.19 rc1 kernel worked fine and i could 
> access my md raid 1.
>
> After that i wanted to switch back to kernel 6.18.1 and noticed the 
> following:
>
> - I can not access the raid 1 md anymore as it does not assemble anymore
>
> - The following error message shows up when i try to assemble the raid:
>
> |mdadm: /dev/sdc1 is identified as a member of /dev/md/1, slot 0. 
> mdadm: /dev/sda1 is identified as a member of /dev/md/1, slot 1. 
> mdadm: failed to add /dev/sda1 to /dev/md/1: Invalid argument mdadm: 
> failed to add /dev/sdc1 to /dev/md/1: Invalid argument - The following 
> error shows up in dmesg: ||[Di, 16. Dez 2025, 11:50:38] md: md1 
> stopped. [Di, 16. Dez 2025, 11:50:38] md: sda1 does not have a valid 
> v1.2 superblock, not importing! [Di, 16. Dez 2025, 11:50:38] md: 
> md_import_device returned -22 [Di, 16. Dez 2025, 11:50:38] md: sdc1 
> does not have a valid v1.2 superblock, not importing! [Di, 16. Dez 
> 2025, 11:50:38] md: md_import_device returned -22 [Di, 16. Dez 2025, 
> 11:50:38] md: md1 stopped. - mdadm --examine used with kerne 6.18 
> shows the following : ||cat mdadmin618.txt /dev/sdc1: Magic : a92b4efc 
> Version : 1.2 Feature Map : 0x1 Array UUID : 
> 3b786bf1:559584b0:b9eabbe2:82bdea18 Name : gamebox:1 (local to host 
> gamebox) Creation Time : Tue Nov 26 20:39:09 2024 Raid Level : raid1 
> Raid Devices : 2 Avail Dev Size : 3859879936 sectors (1840.53 GiB 
> 1976.26 GB) Array Size : 1929939968 KiB (1840.53 GiB 1976.26 GB) Data 
> Offset : 264192 sectors Super Offset : 8 sectors Unused Space : 
> before=264112 sectors, after=0 sectors State : clean Device UUID : 
> 9f185862:a11d8deb:db6d708e:a7cc6a91 Internal Bitmap : 8 sectors from 
> superblock Update Time : Mon Dec 15 22:40:46 2025 Bad Block Log : 512 
> entries available at offset 16 sectors Checksum : f11e2fa5 - correct 
> Events : 2618 Device Role : Active device 0 Array State : AA ('A' == 
> active, '.' == missing, 'R' == replacing) /dev/sda1: Magic : a92b4efc 
> Version : 1.2 Feature Map : 0x1 Array UUID : 
> 3b786bf1:559584b0:b9eabbe2:82bdea18 Name : gamebox:1 (local to host 
> gamebox) Creation Time : Tue Nov 26 20:39:09 2024 Raid Level : raid1 
> Raid Devices : 2 Avail Dev Size : 3859879936 sectors (1840.53 GiB 
> 1976.26 GB) Array Size : 1929939968 KiB (1840.53 GiB 1976.26 GB) Data 
> Offset : 264192 sectors Super Offset : 8 sectors Unused Space : 
> before=264112 sectors, after=0 sectors State : clean Device UUID : 
> fc196769:0e25b5af:dfc6cab6:639ac8f9 Internal Bitmap : 8 sectors from 
> superblock Update Time : Mon Dec 15 22:40:46 2025 Bad Block Log : 512 
> entries available at offset 16 sectors Checksum : 4d0d5f31 - correct 
> Events : 2618 Device Role : Active device 1 Array State : AA ('A' == 
> active, '.' == missing, 'R' == replacing)|
> |- Mdadm --detail shows the following in 6.19 rc1 (i am using 6.19 
> output as it does not work anymore in 6.18.1): ||/dev/md1: Version : 
> 1.2 Creation Time : Tue Nov 26 20:39:09 2024 Raid Level : raid1 Array 
> Size : 1929939968 (1840.53 GiB 1976.26 GB) Used Dev Size : 1929939968 
> (1840.53 GiB 1976.26 GB) Raid Devices : 2 Total Devices : 2 
> Persistence : Superblock is persistent Intent Bitmap : Internal Update 
> Time : Tue Dec 16 13:14:10 2025 State : clean Active Devices : 2 
> Working Devices : 2 Failed Devices : 0 Spare Devices : 0 Consistency 
> Policy : bitmap Name : gamebox:1 (local to host gamebox) UUID : 
> 3b786bf1:559584b0:b9eabbe2:82bdea18 Events : 2618 Number Major Minor 
> RaidDevice State 0 8 33 0 active sync /dev/sdc1 1 8 1 1 active sync 
> /dev/sda1|
>
>
> I didn't spot any obvious issue in the mdadm --examine on kernel 6.18 
> pointing to why it thinks this is not a valid 1.2 superblock.
>
> The mdraid still works nicely on kernel 6.19 but i am unable to use it 
> on kernel 6.18 (worked fine before booting 6.19).
>
> Is kernel 6.19 rc1 doing adjustments on the md superblock when the md 
> is used which are not compatible with older kernels (the md was 
> created already in Nov 2024)?

I believe this is because lbs is now stored in metadata of md arrays, while this field is still
not defined in old kernels, see dtails in the following set:

[PATCH v9 0/5] make logical block size configurable - linan666 <https://lore.kernel.org/linux-raid/20251103125757.1405796-1-linan666@huaweicloud.com/>

We'll have to backport following patch into old kernels to make new arrays to assemble in old
kernels.

https://lore.kernel.org/linux-raid/20251103125757.1405796-5-linan666@huaweicloud.com

+CC Nan, would you mind backport above patch into stable kernels?

>
>
> Many thx !
>
>
>
-- 
Thansk,
Kuai