[Xen-devel] mdadm fails to start raid in pv fc16 DomU on old host

[Virgil <virtualization@xxxxxxxxxxxxxxxx>]

Hi list, I posted this in to the xen list yesterday, however, I thought it may 
be more appropriate here. Let me know if I shouldn't do this.

I'm having a problem with mdraid running in a DomU. The issue is that mdraid 
declares one leg of the raid to have failed (when there's actually nothing 
wrong).

DomU is fc16 - 3.2.2-1.fc16.x86_64
Dom0 is fc14 - 2.6.32.26-174.2.xendom0.fc12.x86_64 (xen 4.0.1-7)

The same DomU running on Dom0 fc16 - 3.2.7-1.fc16.x86_64 (xen 4.1.2-6)  runs 
perfectly.

This appears to be a known issue, however the resolution (which seems to be to 
disable barriers on the fly) doesn't seem to work in this case.

My question is: Is it possible to pass a parameter to the blkfront driver to 
ask it not to enable barrier during initialization? or is there another work 
around?

[    1.033058] blkfront: xvda: barrier: enabled
[    1.099153]  xvda: xvda1 xvda2
[    1.102871] blkfront: xvdb: barrier: enabled
[    1.130876]  xvdb: xvdb1 xvdb2
[    1.292692] md: bind<xvdb1>
[    1.413416] md: bind<xvda1>
[    1.419411] md: raid1 personality registered for level 1
[    1.419836] bio: create slab <bio-1> at 1
[    1.419953] md/raid1:md127: active with 2 out of 2 mirrors
[    1.419992] md127: detected capacity change from 0 to 7516180480
[    1.424562]  md127: unknown partition table
[    1.547284] EXT4-fs (md127): barriers disabled
[    1.553107] EXT4-fs (md127): mounted filesystem with ordered data mode. 
Opts: (null)
[    1.669483] dracut: Checking ext4: /dev/disk/by-label/rootfs
[    1.669592] dracut: issuing e2fsck -a  /dev/disk/by-label/rootfs
[    1.690595] blkfront: barrier: empty write xvdb op failed
[    1.690611] blkfront: xvdb: barrier or flush: disabled
[    1.690628] end_request: I/O error, dev xvdb, sector 14682096
[    1.690638] end_request: I/O error, dev xvdb, sector 14682096
[    1.690646] md: super_written gets error=-5, uptodate=0
[    1.690655] md/raid1:md127: Disk failure on xvdb1, disabling device.
[    1.690657] md/raid1:md127: Operation continuing on 1 devices.
[    1.690677] blkfront: barrier: empty write xvda op failed
[    1.690684] blkfront: xvda: barrier or flush: disabled
[    1.690696] end_request: I/O error, dev xvda, sector 14682096
[    1.690705] end_request: I/O error, dev xvda, sector 14682096
[    1.690713] md: super_written gets error=-5, uptodate=0
[    1.692991] RAID1 conf printout:
[    1.692997]  --- wd:1 rd:2
[    1.693002]  disk 0, wo:0, o:1, dev:xvda1
[    1.693006]  disk 1, wo:1, o:0, dev:xvdb1
[    1.693010] RAID1 conf printout:
[    1.693013]  --- wd:1 rd:2
[    1.693016]  disk 0, wo:0, o:1, dev:xvda1
[    1.702896] dracut: rootfs: clean, 25635/454272 files, 293967/1835005 blocks
[    1.703682] dracut: Remounting /dev/disk/by-label/rootfs with -o ro
[    1.773347] EXT4-fs (md127): barriers disabled
[    1.774552] EXT4-fs (md127): mounted filesystem with ordered data mode. 
Opts: (null)
[    1.797159] dracut: Mounted root filesystem /dev/md127
[    1.937620] dracut: Switching root

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