barrier-based sync failed. How bad is it?

[Andrea]

Hi,

I get this error on /var/log/messages

kernel: JBD: barrier-based sync failed on dm-0:8 - disabling barriers

How bad is it? What does it mean?

This is the part of /var/log/messages preceding it, involving ext4

Jul 29 19:54:53 thinkpad kernel: device-mapper: multipath: version 1.0.5 loaded
Jul 29 19:54:53 thinkpad kernel: EXT4 FS on dm-0, internal journal on dm-0:8
Jul 29 19:54:53 thinkpad kernel: kjournald starting.  Commit interval 5 seconds
Jul 29 19:54:53 thinkpad kernel: EXT3 FS on sda3, internal journal
Jul 29 19:54:53 thinkpad kernel: EXT3-fs: mounted filesystem with ordered data mode.
Jul 29 19:54:53 thinkpad kernel: EXT4-fs: barriers enabled
Jul 29 19:54:53 thinkpad kernel: kjournald2 starting: pid 1146, dev dm-1:8, commit interval 5 seconds
Jul 29 19:54:53 thinkpad kernel: EXT4 FS on dm-1, internal journal on dm-1:8
Jul 29 19:54:53 thinkpad kernel: EXT4-fs: delayed allocation enabled
Jul 29 19:54:53 thinkpad kernel: EXT4-fs: file extents enabled
Jul 29 19:54:53 thinkpad kernel: EXT4-fs: mballoc enabled
Jul 29 19:54:53 thinkpad kernel: EXT4-fs: mounted filesystem dm-1 with ordered data mode
Jul 29 19:54:53 thinkpad kernel: swap_cgroup: uses 1024 bytes of vmalloc for pointer array space and 
1048576 bytes to hold mem_cgroup pointers on swap
Jul 29 19:54:53 thinkpad kernel: swap_cgroup can be disabled by noswapaccount boot option.
Jul 29 19:54:53 thinkpad kernel: Adding 1048568k swap on /dev/mapper/VolGroup00-LogVol01. 
Priority:-1 extents:1 across:1048568k

Anybody knows what it means?