Re: ont out of 6 bcache devices does not register automatically

Stefan Priebe - Profihost AG
2017-11-28T09:37:00Z

ping - nobody? Ideas?

Am 23.11.2017 um 08:10 schrieb Stefan Priebe - Profihost AG:
> Hello,
>
> i got it...
>
> first of all the same issue still applies to util-linux v2.31 which is
> the latest upstream version.
>
> # ./blkid --version
> lt-blkid from util-linux 2.31 (libblkid 2.31.0, 19-Oct-2017)
>
> # ./blkid -o udev -p /dev/sdf1
> ID_FS_AMBIVALENT=other:bcache other:xfs_external_log
>
> The issue is somewhat different. The device is used for ceph which
> stores on on that Disk 4MB slices of VM block devices.
>
> So we have:
> bcache => XFS on top => thousands of files containing VM images => XFS
> in those images
>
> So the xfs_external_log superblock which is seen by blkid is in reality
> a superblock of a VM image inside a file which is saved in bcache.
>
> This make even more sense as the system was bootable without any
> problems for the last few years without swapping a disk. But somewhat
> now a VM image file has exactly positioned it's superblock on a position
> blkid expects a superblock.
>
> I see no way to solve it except for changing the udev rules file which
> comes with bcache-tools.
>
> Instead of only checking:
> ENV{ID_FS_TYPE}=="bcache", GOTO="bcache_backing_found"
>
> it also needs to check for:
> ID_FS_AMBIVALENT=other:bcache
>
> Any opinions or suggestions?
>
> Greets,
> Stefan
>
> Am 22.11.2017 um 22:13 schrieb Stefan Priebe - Profihost AG:
>>
>> Am 22.11.2017 um 22:10 schrieb Michael Lyle:
>>> On 11/22/2017 01:07 PM, Stefan Priebe - Profihost AG wrote:
>>>> default debian jessie version:
>>>> # blkid -v
>>>> blkid from util-linux 2.25.2 (libblkid 2.25.0, 24-Oct-2014)
>>>
>>> OK, so it's ancient.
>>>
>>> One other thing that can get you-- if there was ever an xfs or other
>>> filesystem on this disk -without- bcache, then you created bcache & xfs
>>> on it without wipefs... the old superblock can still be hanging around
>>> and not having happened to been rewritten.
>>
>> no there shouldn't eb ever an xfs without it on disk - but i can't
>> guarantee that.
>>
>> To reproduce the isue you need the first 10MB of the disk.
>>
>> See below:
>>
>> Still ok:
>>
>> # dd if=/dev/sdf1 of=/tmp/8k bs=8M count=1
>> 1+0 records in
>> 1+0 records out
>> 8388608 bytes (8,4 MB) copied, 0,01318 s, 636 MB/s
>> # /sbin/blkid -o udev -p /tmp/8k
>> ID_FS_UUID=65811163-4ffc-4823-ad72-bae10ce85b63
>> ID_FS_UUID_ENC=65811163-4ffc-4823-ad72-bae10ce85b63
>> ID_FS_TYPE=bcache
>> ID_FS_USAGE=other
>>
>> not anymore:
>>
>> # dd if=/dev/sdf1 of=/tmp/8k bs=10M count=1
>> 1+0 records in
>> 1+0 records out
>> 10485760 bytes (10 MB) copied, 0,0115798 s, 906 MB/s
>> # /sbin/blkid -o udev -p /tmp/8k
>> ID_FS_AMBIVALENT=other:bcache other:xfs_external_log
>>
>> Stefan
>>
>>>
>>> Mike
>>>
>>>>
>>>>>
>>>>> Mike
>>>>> --
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>>>