Re: blkfront: barrier: empty write op failed

Luca Lesinigo
Thu, 01 Dec 2011 09:28:00 -0000

After upgrading domU from linux-3.0.4 to 3.0.11I still get these nasty messages
from dmesg when mounting the EXT3 filesystem during boot:
	blkfront: barrier: empty write xvda1 op failed
	blkfront: xvda1: barrier or flush: disabled
	EXT3-fs (xvda1): using internal journal

this 64bit domU is running under Xen-4.1.1 with a 2.6.38 kernel
(gentoo''s xen-sources which basically is a backport of XenLinux
patches).

The system appears to keep working correctly anyway but I suspect it slows down
a little too much under heavy I/O (for example, copying many gigabytes from an
ext3 to another).

Working with raw blocks (eg. swap volumes, or running dd over a not-mounted ext3
volume) does not trigger that message, running a single mkfs.ext3 or mkfs.ext4
does make it appear. I usually have cleancache enabled over tmem, disabling it
doesn''t seem to make any difference.

Ubuntu domUs using their stock 2.6.24-??-xen kernel seem to be immune.

Is this something I should be worried about? What would you suggest to try to
correct it? (eg. is it something related to domU kernel, dom0 kernel,
hypervisor, domU config, whatever?)


thanks.