> Ok, after digging a bit I noticed that the super block layout
> has changed in a way that makes it incompatible with previous
> super blocks. It appears to be the alignment of fs_uuid on
> revision 1.36 of sys/ufs/ffs/fs.h.
The trick of biting of bits of a char array to make non-char fields
often causes alignment problems and binary compatibility problems (see
mount.h...). I think one of the spare integer fields (if any),
preferably an int64_t field, should be used for fs_swuid. It's not
clear that there are any -- I think ones like:
int64_t fs_sparecon64[17]; /* old rotation block list head */
aren't actually spare since they are clobbered by old versions of fsck.
> The following patch fixes the problem (and fixes the misuse of
> uuid for something that is not universally unique):
>
> Index: fs.h
> ===================================================================
> RCS file: /home/ncvs/src/sys/ufs/ffs/fs.h,v
> retrieving revision 1.36
> diff -u -r1.36 fs.h
> --- fs.h 8 Jan 2003 22:53:54 -0000 1.36
> +++ fs.h 9 Jan 2003 23:23:28 -0000
> ...
> @@ -311,7 +311,8 @@
> int8_t fs_old_flags; /* old FS_ flags */
> u_char fs_fsmnt[MAXMNTLEN]; /* name mounted on */
> u_char fs_volname[MAXVOLLEN]; /* volume name */
> - u_int64_t fs_uuid; /* system-wide unique uid */
> + u_int64_t fs_swuid; /* system-wide unique id */
This change has rotted in the committed version. The comment still
says "uid" and doesn't say "unique", but the id is even less of a user
id than it is universally unique. The "u" in "fs_swuid" is confusing
too. I suppose it's too late to remove the "u"s from "uuid" so that
it doesn't look like "uid" :-).
Bruce
To Unsubscribe: send mail to [EMAIL PROTECTED]
with "unsubscribe freebsd-current" in the body of the message
