mfs: clean flag

. also implement now-possible fsck -p option
    	. allows unconditional fsck -p invocation at startup,
    	  only checking each filesystem if not marked clean
    	. mounting unclean is allowed but is forced readonly
    	. updating the superblock while mounted is now not
    	  allowed by mfs - must be done (e.g. by fsck.mfs)
    	  on an unmounted fs
	. clean flag is unset by mfs on mounting, and set by
	  mfs on clean unmounting (if clean flag was set at
	  mount time)

Signed-off-by: Ben Gras <ben@minix3.org>

drivers/ramdisk/Makefile

@@ -3,7 +3,7 @@
 .include <bsd.own.mk>
 
 PROGRAMS= at_wini bios_wini cdprobe dev2name floppy loadramdisk mount \
-	pci procfs sh service sysenv mfs
+	pci procfs sh service sysenv mfs fsck.mfs
 SCRIPTS=newroot
 
 .if ${MKSMALL} != "yes"
@@ -43,6 +43,11 @@ bintoc:	bintoc.c
 
 image:	proto.gen mtab rc $(EXTRA)
 	mkfs.mfs image proto.gen || { rm -f image; false; }
+	if fsck.mfs -s image | grep -q CLEAN;	\
+	then	: ;	\
+	else	echo "CLEAN sanity check of image failed."	;	\
+		echo "(Perhaps install current mkfs and fsck.)" ;	\
+	fi
 
 ahci: ../ahci/ahci
 	install ${STRIPFLAG} ../$@/$@ $@
@@ -104,6 +109,12 @@ mount:  ../../commands/mount/mount
 ../../commands/mount/mount:
 	$(MAKE) -C ../../commands/mount
 
+fsck.mfs:  ../../commands/fsck.mfs/fsck.mfs
+	install ${STRIPFLAG} ../../commands/$@/$@ $@
+
+../../commands/fsck.mfs/fsck.mfs:
+	$(MAKE) -C ../../commands/fsck.mfs
+
 newroot:  ../../commands/newroot/newroot.sh
 	install ${STRIPFLAG} ../../commands/$@/$@.sh $@