Re: interesting MD-xfs bug

Dave Chinner
2015-04-09T22:18:56Z

On Thu, Apr 09, 2015 at 05:02:33PM -0400, Joe Landman wrote:
> If I build an MD raid0 with a non power of 2 chunk size, it appears
> that I can mkfs.xfs a file system, but it doesn't show up in blkid
> and is not mountable. Yet, using a power of 2 chunk size, this does
> work correctly. This is kernel 3.18.9.
>
>
> For example, non-power of 2 chunk:
>
> root@unison:~# wipefs -a /dev/sdb
> 4 bytes were erased at offset 0x1000 (linux_raid_member)
> they were: fc 4e 2b a9
> root@unison:~# wipefs -a /dev/sda
> 4 bytes were erased at offset 0x1000 (linux_raid_member)
> they were: fc 4e 2b a9
> root@unison:~# mdadm --create /dev/md20 --level=0 --metadata=1.2
> --chunk=1152 --auto=yes --raid-disks=2 /dev/sd[ab]
> mdadm: array /dev/md20 started.
>
> root@unison:~# mkfs.xfs /dev/md20
> log stripe unit (1179648 bytes) is too large (maximum is 256KiB)
> log stripe unit adjusted to 32KiB
> meta-data=/dev/md20 isize=256 agcount=50,
> agsize=268435296 blks
> = sectsz=512 attr=2, projid32bit=0
> data = bsize=4096 blocks=13164865984, imaxpct=5
> = sunit=288 swidth=576 blks
> naming =version 2 bsize=4096 ascii-ci=0
> log =internal log bsize=4096 blocks=521728, version=2
> = sectsz=512 sunit=8 blks, lazy-count=1
> realtime =none extsz=4096 blocks=0, rtextents=0
>
> root@unison:~# blkid | grep xfs

That looks more like a blkid or udev problem. try using blkid -p so
that it doesn't look up the cache but directly probes devices for
the signatures. strace might tell you a bit more, too. And if the
filesystem mounts, then it definitely isn't an XFS problem ;)