Openmoko Bug #1998: "Unable to mount root fs on unknown-block(179, 2)" after hard shutdown

Openmoko Public Trac bugs at
Sun Sep 14 10:24:01 CEST 2008

#1998: "Unable to mount root fs on unknown-block(179,2)" after hard shutdown
    Reporter:  denver   |        Owner:  openmoko-devel
        Type:  defect   |       Status:  new           
    Priority:  normal   |    Milestone:  Om2008.8      
   Component:  unknown  |      Version:  Om2008.8      
    Severity:  normal   |   Resolution:                
    Keywords:           |    Blockedby:                
Reproducible:           |     Blocking:                

Comment(by andy):

          * Check feature flags regardless of the revision level, since we
          * previously didn't change the revision level when setting the
          * so there is a chance incompat flags are set on a rev 0
         features = EXT2_HAS_INCOMPAT_FEATURE(sb,
         if (features) {
                 printk("EXT2-fs: %s: couldn't mount because of "
                        "unsupported optional features (%x).\n",
                        sb->s_id, le32_to_cpu(features));
                 goto failed_mount;


 Don't really know what it means, but I never saw it myself and Google is
 pretty quiet about it, usually a sign it is the outcome of somthing funny.

 Note the desktop box is doing a mount from userspace, so it's quite
 possible it can try multiple times or take corrective action if it sees
 insanity: we are having one go entirely from kernel so we might be a
 little more fragile.

 Check we are not somehow mixing up rootfstype= between ext2 and ext3, on
 kernel commandline or in /etc/fstab in the root filesystem for example.

 Another angle, IIRC Debian for example has initscript to remount the
 rootfs rw, it is happy to have ro rootfs initially.  I noticed in the ext2
 code there are different rules for what it doesn't like if you mount ro.
 So you might mask this behaviour if you add "ro" to your kernel
 commandline to get the rootfs mounted read only initially.

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