Unsatisfied with my previous conclusion, I looked at this again, and came
up with the following patch.

===================================================================
RCS file: /b/source/CVS/src/sys/arch/i386/boot/sys.c,v
retrieving revision 1.10
diff -c -2 -r1.10 sys.c
*** 1.10	1994/07/21 19:05:31
--- sys.c	1994/07/21 20:24:41
***************
*** 205,208 ****
--- 205,217 ----
  	devread();
  
+ 	/*
+ 	 * Deal with old file system format.  This is borrowed from
+ 	 * ffs_oldfscompat() in ufs/ffs/ffs_vfsops.c.
+ 	 */
+ 	if (fs->fs_inodefmt < FS_44INODEFMT) {			/* XXX */
+ 		fs->fs_qbmask = ~fs->fs_bmask;			/* XXX */
+ 		fs->fs_qfmask = ~fs->fs_fmask;			/* XXX */
+ 	}							/* XXX */
+ 
  	/***********************************************\
  	* Find the actual FILE on the mounted device	*


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