unexpected soft update inconsistency - cannot fix

Tue Jan 10 22:21:14 UTC 2012

> To: Kirk McKusick <mckusick at mckusick.com>
> cc: fs at freebsd.org
> Subject: Re: unexpected soft update inconsistency - cannot fix 
> From: "Julian H. Stacey" <jhs at berklix.com>
> Date: Tue, 10 Jan 2012 22:46:57 +0100
> 
> Hi Kirk 
> cc fs@
> 
> Thanks ! Meantime I'd been looking & made notes below.
> I don't understand how the above  "mv Makefile,v Makefile,v.sav"
> would create a new slot ? wouldnt' it just call rename(2) ?
> So there'd still be no slot to re-label as ".." to point at parent inode ?

The rename will have to create a new slot for "Makefile,v.sav"
which will be at the end of the directory (as that is the only
place where there is enough space for it). That will leave
slot 0 with a reclen of 40. With a reclen of 40, there will
be enough space following the "." entry (which is using the
first 12) that fsck will be able to fit the ".." entry into
the unused space immediately following the "." entry where
it belongs.

> Wouldn't it be better to call fsdb + "ln 79302719 .." as below ?

If you do that the ".." entry will be placed at the end of the 
directory where it does not belong. Fsck will still bitch and
will still be unable to fix it.

> Also as notes below show inode of parent can be deduced,
> wouldn't it be good if such functionality were built into fsck or fsdb code
> (or pro tem added as an example to man fsdb ?)

The path is calculated by getting the inode associated with
".." in the current inode. You then read the ".." inode and
find the name associated with the current inode in it. You
repeat this process level by level until you reach the root of
the filesystem (inode 2) at which point you have the full path.
If the only information you have is the contents of an inode that
is missing its ".." entry you cannot figure out its parent or its
path. At the point in fsck where this error occurs you do not
know what the namespace looks like, you have only a subset of
the inodes. So there is no way to figure out the path.

	---------
	fsdb -r /dev/ad4s4g
		** /dev/ad4s4g (NO WRITE)
		Examining file system `/dev/ad4s4g'
		Last Mounted on 
		current inode: directory
		I=2 MODE=40755 SIZE=512
		OWNER=root GRP=wheel LINKCNT=9 FLAGS=0 BLKCNT=4 GEN=359f3dd1
	fsdb (inum: 2)> inode 825575
		current inode: directory
		I=825575 MODE=40755 SIZE=512
		OWNER=mailnull GRP=mailnull LINKCNT=2 FLAGS=0 BLKCNT=4 GEN=29c28025
	fsdb (inum: 825575)> ls
		slot 0 ino 825575 reclen 20: directory, `.'
		slot 1 ino 825580 reclen 20: regular, `Makefile,v'
		slot 2 ino 825581 reclen 20: regular, `distinfo,v'
		slot 3 ino 825582 reclen 20: regular, `pkg-descr,v'
		slot 4 ino 825583 reclen 432: regular, `pkg-plist,v'
	fsdb (inum: 825575)> print
		current inode: directory
		I=825575 MODE=40755 SIZE=512
		OWNER=mailnull GRP=mailnull LINKCNT=2 FLAGS=0 BLKCNT=4 GEN=29c28025
	# LINKCNT=2 seems wrong, comparing with a goo directory,
	# I think should be 4 without the ".." & 5 with "..".

The ./ftp/.backup/pri/FreeBSD/development/FreeBSD-CVS/ports/net/ \
keepalived/Attic directory contains no directories, so with a ".."
entry it should have a link count of 2.

	fsdb (inum: 825575)> uplink
		fsdb: `uplink' requires write access
		fsdb: rval was 1
		fsdb (inum: 825575)> 
	To Do Later With Fsdb ( without -r )
		uplink
		uplink
		ln 79302719 ..

	mount /usr1 ; mount | grep /usr1
		/dev/ad4s4g on /usr1 (ufs, local, read-only)
	cd /usr1 ; find -x . -inum 825575
		./ftp/.backup/pri/FreeBSD/development/FreeBSD-CVS/\
		ports/net/keepalived/Attic
	cd ftp/.backup/pri/FreeBSD/development/FreeBSD-CVS/ports/net/keepalived
	ls -lai
		total 50
		79302719 drwxr-xr-x     3 mailnull  mailnull    512 Dec 29 20:09 ./
		73700289 drwxr-xr-x  2109 mailnull  mailnull  43520 Dec 29 20:08 ../
		  825575 drwxr-xr-x     2 mailnull  mailnull    512 Dec 29 22:12 Attic/
		79302722 drwxr-xr-x     3 mailnull  mailnull    512 Dec 29 22:12 files/

	fsdb (inum: 825575)> inode 79302719
		current inode: directory
		I=79302719 MODE=40755 SIZE=512
		OWNER=mailnull GRP=mailnull LINKCNT=3 FLAGS=0 BLKCNT=4 GEN=293a450d
	fsdb (inum: 79302719)> ls
		slot 0 ino 79302719 reclen 12: directory, `.'
		slot 1 ino 73700289 reclen 12: directory, `..'
		slot 2 ino 79302722 reclen 16: directory, `files'
		slot 3 ino 825575 reclen 472: directory, `Attic'
	---------

Cheers,
Julian
-- 
Julian Stacey, BSD Unix Linux C Sys Eng Consultants Munich http://berklix.com
 Reply below not above, cumulative like a play script, & indent with "> ".
 Format: Plain text. Not HTML, multipart/alternative, base64, quoted-printable.

So, to refine my earlier suggestion:

cd /usr1/./ftp/.backup/pri/FreeBSD/development/FreeBSD-CVS/ports/net/\
keepalived/Attic
ls -fa
mv Makefile,v Makefile,v.sav
ls -fa
cd /
umount /dev/ad4s4g
fsck /dev/ad4s4g
mount /usr1
cd /usr1/./ftp/.backup/pri/FreeBSD/development/FreeBSD-CVS/ports/net/\
keepalived/Attic
ls -fa
mv Makefile,v.sav Makefile,v
ls -fa

You can use `ls -fa' to see the order of everything in the directory.

	Kirk McKusick