Date: Fri, 10 Jan 2003 20:58:21 +1100 (EST) From: Bruce Evans <bde@zeta.org.au> To: Marcel Moolenaar <marcel@xcllnt.net> Cc: current@FreeBSD.ORG, <gordon@FreeBSD.ORG> Subject: Re: Superblock layout hosed on LP64 systems [was: Re: HEADS UP: VFS changes breaks GPT] Message-ID: <20030110204529.W20087-100000@gamplex.bde.org> In-Reply-To: <20030109232943.GA1189@athlon.pn.xcllnt.net>
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> 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 majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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