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

Stefan Priebe - Profihost AG
2017-11-28T19:32:27Z

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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