On Tue, Sep 18, 2012 at 10:49:20AM +0200, Richard Neuboeck wrote: > Hi XFS gurus, > > I've a XFS related problem that boggles my find and I couldn't find a > solution yet. > > I've got a virtual machine (huddle) that gets a ~66TB logical volume > from the host handed as (virtio) block device (/dev/vdb). For ease of > maintenance I didn't partition the device but formatted it directly with > xfs. The system at the time of formatting was Ubuntu Lucid 64bit. virtio configuration? (i.e. cache=none?) > A few days ago I upgraded the virtual machine to Ubuntu LTS 'precise', > Kernel 3.2, and got the following error while trying to mount the device: Upgraded from what? > root@huddle:~# mount /dev/vdb /mnt/storage > mount: /dev/vdb: can't read superblock > > dmesg shows some more info: > root@huddle:~# dmesg | tail > [ 672.774206] end_request: I/O error, dev vdb, sector 0 > [ 672.774393] XFS (vdb): SB buffer read failed > > At first I thought the block device had some error and checked the > virtual machine configuration and host system. > > From the host system (Ubuntu lucid 64bit, Kernel 2.6) I can still mount > the xfs formatted device without problems. I also ran xfs_repair -n that > didn't show any problem. So the filesystem is accesible via direct IO from the host. What's the xfs_info output once it is mounted? > I tried to hand the virual machine a different ext4 formated block > device (also without partition and preformatted). This didn't yield any > mount problems. > > The Ubuntu 'precise' machine has an older kernel (2.6.32-42) too. > Booting this kernel the xfs formatted block device gets mounted without > error. The newer kernel has a different buffer cache implementation, so sector sized IO (such as superblocks) is cached and issued differently. > The curious part is that it is still possible to mount the volume under > Kernel 3.2 without error using the loop option: > > root@huddle:~# mount -v -t xfs -o loop /dev/vdb /mnt/storage/ Turns all IO into pagecache based IO, so 4k aligned. Will avoid any sector size mismatch issues. > Trying xfs_repair also brings up the I/O Error unless I use it with the > -f option under Kernel 3.2. -f can turn direct IO into buffered IO is there is a sector size mismatch between the filesystem and the underlying storage. > Obviously the problem is Kernel 3.2 related. I'm not sure if I'm at the > right place in the XFS Mailinglist but thought it would make a good > starting point since I couldn't find anything related in bugzilla or the > web in general and the problem didn't show up using ext4 (so may not be > a generic kernel problem). Sounds like a sector size based problem to me - direct Io does sector aligned and sized IO, buffered IO does page sized IO. So my initial thought is that you've got a 512 byte sector filesystem on a 4k sector device.... > Running any kernel, blkid still identifies the device correctly as xfs > volume: > root@huddle:~# blkid /dev/vdb > /dev/vdb: UUID="5adcd575-d3f2-48c3-81de-104f125b275e" TYPE="xfs" Buffered IO, again. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
