Bug 436493

I have a fedora 9 alpha xen machine (updated by updating the packages from
Fedora 8 xen) which I am trying to boot from the 2.6.25-0.0.rc4.fc9xen xen
kernel. However it frequently doesn't boot, with the boot messages finishing up
Loading xenblk module
blkfront: xvda: barriers enabled
 xvda: xvda1 xvda2 xvda3 xvda4 < xvda5 xvda6 >
Trying to resume from /sys/block/hda//hda3
Unable to access resume device (/sys/block/hda//hda3)
Creating root device.
Mounting root filesystem.
mount: could not find filesystem '/dev/root'
Setting up other filesystems.
Setting up new root fs
setuproot: moving /dev failed: No such file or directory
no fstab.sys, mounting internal defaults
setuproot: error mounting /proc: No such file or directory
setuproot: error mounting /sys: No such file or directory
Mount failed for selinuxfs on /selinux:  No such file or directory
Switching to new root and running init.
unmounting old /dev
unmounting old /proc
unmounting old /sys
switchroot: mount failed: No such file or directory
Booting has failed.

This is from a fedora 7 xen host machine running xen-3.1.2-2.fc7 and
kernel-xen-2.6.21-7.fc7. When trying to debug this I built a new initrd
replacing /sys/block/hda//hda3 with /sys/block/xvda//xvda3 and on unsuccessful
boots get something like
Loading xenblk module
blkfront: xvda: barriers enabled
 xvda: xvda1 xvda2 xvda3 xvda4 < xvda5Trying to resume from /sys/block/xvda//xvda3
Unable to access resume device (/sys/block/xvda//xvda3)
Creating root device.
...
Booting has failed.
 xvda6 >

and for a successful boot I get
Loading xenblk module
blkfront: xvda: barriers enabled
 xvda: xvda1 xvda2 xvda3 xvda4 < xvda5 xvda6 >
Trying to resume from /sys/block/xvda//xvda3
Creating root device.
Mounting root filesystem.
kjournald starting.  Commit interval 5 seconds
...

which suggests to me that the disks aren't accessible, or maybe haven't finished
being mounted for some boots, since when it fails it can't access
/sys/block/xvda//xvda3 but it can when it succeeds.