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

[Stefan Priebe - Profihost AG <s.priebe@profihost.ag>]

Am 28.11.2017 um 17:05 schrieb Michael Lyle:
> I don't know.  I don't maintain your userland nor do I know the possible
> implications in your environment.

nobody asked for this - but bcache provides bcache-tools and upstream
udev rules and those don't work in this case. To i consider this an
upstream bug. Not a bug in my envorinment or in my distribution.

I can fix this myself - i just had the hope to get it fixed upstream so
others don't fall into the same issue.

Greets,
Stefan

> Mike
> 
> On Tue, Nov 28, 2017 at 1:36 AM, Stefan Priebe - Profihost AG
> <s.priebe@profihost.ag <mailto:s.priebe@profihost.ag>> wrote:
> 
>     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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> 
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