vfs_rootmount() failed

[Hiten Pandya]

As a side note, this failure is similar to one which was reported by 
someone on the #dragonflybsd IRC channel, except his root partition was 
sitting at /dev/ad3s1a (or /dev/ad1s3a, not sure).

	-Hiten
	hmp at xxxxxxxxxxxxx
Hiroki Sato wrote:

Hi,

 I upgraded my box to a kernel as of 05/29 but it fails to boot at
 the point of mounting the root filesystem.  Another kernel as of
 05/19 could boot successfully, but the following warning was displayed
 (the root filesystem is /dev/ad4s1a):
 | ad4: 58644MB <IC35L060AVER07-0> [119150/16/63] at ata2-master UDMA66
 | WARNING: "ad" is usurping "ad"'s cdevsw[]
 With the 05/29 kernel, the following message appears and the boot
 fails:
 | Mounting root from ufs:/dev/ad4s1a
 | no such device 'ad'
 | setrootbyname failed
 | ffs_mountroot: can't find rootvp
 | Root mount failed: 6
 I have confirmed that at the stage in getdiskbyname()@sys/kern/vfs_conf.c
 the kernel did not know the ad device.  This loop in the function
 |351          for (cd = 0; cd < NUMCDEVSW; cd++) {
 |352                  dev = udev2dev(makeudev(cd, 0), 0);
 |353                  if (dev_is_good(dev) && dev_dname(dev) &&
 |354                      strcmp(dev_dname(dev), name) == 0) {
 |355                          goto gotit;
 |356                  }
 |357          }
 did not match the name "ad" (acd was found, BTW).  Is this
 a side-effect of the recent cdevsw related changes?
 The box has two on-board ATA controllers and a Promise ATA card,
 but all hard drives are connected to the Promise card.  If I am missing
 something or another information is needed, please let me know.