This commit adds basic support for the UFS2 filesystem. The UFS2

filesystem expands the inode to 256 bytes to make space for 64-bit
block pointers. It also adds a file-creation time field, an ability
to use jumbo blocks per inode to allow extent like pointer density,
and space for extended attributes (up to twice the filesystem block
size worth of attributes, e.g., on a 16K filesystem, there is space
for 32K of attributes). UFS2 fully supports and runs existing UFS1
filesystems. New filesystems built using newfs can be built in either
UFS1 or UFS2 format using the -O option. In this commit UFS1 is
the default format, so if you want to build UFS2 format filesystems,
you must specify -O 2. This default will be changed to UFS2 when
UFS2 proves itself to be stable. In this commit the boot code for
reading UFS2 filesystems is not compiled (see /sys/boot/common/ufsread.c)
as there is insufficient space in the boot block. Once the size of the
boot block is increased, this code can be defined.

Things to note: the definition of SBSIZE has changed to SBLOCKSIZE.
The header file <ufs/ufs/dinode.h> must be included before
<ufs/ffs/fs.h> so as to get the definitions of ufs2_daddr_t and
ufs_lbn_t.

Still TODO:
Verify that the first level bootstraps work for all the architectures.
Convert the utility ffsinfo to understand UFS2 and test growfs.
Add support for the extended attribute storage. Update soft updates
to ensure integrity of extended attribute storage. Switch the
current extended attribute interfaces to use the extended attribute
storage. Add the extent like functionality (framework is there,
but is currently never used).

Sponsored by: DARPA & NAI Labs.
Reviewed by:	Poul-Henning Kamp <phk@freebsd.org>

1 files changed, 162 insertions, 115 deletions

diff --git a/sys/ufs/ffs/ffs_vfsops.c b/sys/ufs/ffs/ffs_vfsops.c
index ed52815..53a1ea5 100644
--- a/sys/ufs/ffs/ffs_vfsops.c
+++ b/sys/ufs/ffs/ffs_vfsops.c
@@ -39,6 +39,7 @@
 
 #include <sys/param.h>
 #include <sys/systm.h>
+#include <sys/stdint.h>
 #include <sys/namei.h>
 #include <sys/proc.h>
 #include <sys/kernel.h>
@@ -67,8 +68,10 @@
 static MALLOC_DEFINE(M_FFSNODE, "FFS node", "FFS vnode private part");
 
 static int	ffs_sbupdate(struct ufsmount *, int);
-int	ffs_reload(struct mount *,struct ucred *,struct thread *);
-static int	ffs_oldfscompat(struct fs *);
+       int	ffs_reload(struct mount *,struct ucred *,struct thread *);
+static void	ffs_oldfscompat_read(struct fs *, struct ufsmount *,
+		    ufs2_daddr_t);
+static void	ffs_oldfscompat_write(struct fs *, struct ufsmount *);
 static int	ffs_init(struct vfsconf *);
 
 static struct vfsops ufs_vfsops = {
@@ -139,8 +142,8 @@ ffs_mount(mp, path, data, ndp, td)
         struct nameidata	*ndp;	/* mount point credentials*/
         struct thread		*td;	/* process requesting mount*/
 {
-	size_t		size;
-	struct vnode	*devvp;
+	size_t size;
+	struct vnode *devvp;
 	struct ufs_args args;
 	struct ufsmount *ump = 0;
 	struct fs *fs;
@@ -201,8 +204,9 @@ ffs_mount(mp, path, data, ndp, td)
 			}
 			if (fs->fs_pendingblocks != 0 ||
 			    fs->fs_pendinginodes != 0) {
-				printf("%s: update error: blocks %d files %d\n",
-				    fs->fs_fsmnt, fs->fs_pendingblocks,
+				printf("%s: %s: blocks %lld files %d\n",
+				    fs->fs_fsmnt, "update error",
+				    (intmax_t)fs->fs_pendingblocks,
 				    fs->fs_pendinginodes);
 				fs->fs_pendingblocks = 0;
 				fs->fs_pendinginodes = 0;
@@ -384,9 +388,9 @@ ffs_reload(mp, cred, td)
 	struct buf *bp;
 	struct fs *fs, *newfs;
 	dev_t dev;
+	ufs2_daddr_t sblockloc;
 	int i, blks, size, error;
 	int32_t *lp;
-	u_int sectorsize;
 
 	if ((mp->mnt_flag & MNT_RDONLY) == 0)
 		return (EINVAL);
@@ -416,20 +420,18 @@ ffs_reload(mp, cred, td)
 	/*
 	 * Step 2: re-read superblock from disk.
 	 */
-	if (VOP_IOCTL(devvp, DIOCGSECTORSIZE, (caddr_t)&sectorsize,
-	    FREAD, NOCRED, td) != 0)
-		size = DEV_BSIZE;
-	else
-		size = sectorsize;
-	if ((error = bread(devvp, (ufs_daddr_t)(SBOFF/size), SBSIZE, NOCRED,&bp)) != 0)
+	fs = VFSTOUFS(mp)->um_fs;
+	if ((error = bread(devvp, fsbtodb(fs, fs->fs_sblockloc), fs->fs_sbsize,
+	    NOCRED, &bp)) != 0)
 		return (error);
 	newfs = (struct fs *)bp->b_data;
-	if (newfs->fs_magic != FS_MAGIC || newfs->fs_bsize > MAXBSIZE ||
-		newfs->fs_bsize < sizeof(struct fs)) {
+	if ((newfs->fs_magic != FS_UFS1_MAGIC &&
+	     newfs->fs_magic != FS_UFS2_MAGIC) ||
+	    newfs->fs_bsize > MAXBSIZE ||
+	    newfs->fs_bsize < sizeof(struct fs)) {
 			brelse(bp);
 			return (EIO);		/* XXX needs translation */
 	}
-	fs = VFSTOUFS(mp)->um_fs;
 	/*
 	 * Copy pointer fields back into superblock before copying in	XXX
 	 * new superblock. These should really be in the ufsmount.	XXX
@@ -439,20 +441,15 @@ ffs_reload(mp, cred, td)
 	newfs->fs_maxcluster = fs->fs_maxcluster;
 	newfs->fs_contigdirs = fs->fs_contigdirs;
 	newfs->fs_active = fs->fs_active;
+	sblockloc = fs->fs_sblockloc;
 	bcopy(newfs, fs, (u_int)fs->fs_sbsize);
-	if (fs->fs_sbsize < SBSIZE)
-		bp->b_flags |= B_INVAL | B_NOCACHE;
 	brelse(bp);
 	mp->mnt_maxsymlinklen = fs->fs_maxsymlinklen;
-	ffs_oldfscompat(fs);
-	/* An old fsck may have zeroed these fields, so recheck them. */
-	if (fs->fs_avgfilesize <= 0)		/* XXX */
-		fs->fs_avgfilesize = AVFILESIZ;	/* XXX */
-	if (fs->fs_avgfpdir <= 0)		/* XXX */
-		fs->fs_avgfpdir = AFPDIR;	/* XXX */
+	ffs_oldfscompat_read(fs, VFSTOUFS(mp), sblockloc);
 	if (fs->fs_pendingblocks != 0 || fs->fs_pendinginodes != 0) {
-		printf("%s: reload pending error: blocks %d files %d\n",
-		    fs->fs_fsmnt, fs->fs_pendingblocks, fs->fs_pendinginodes);
+		printf("%s: reload pending error: blocks %lld files %d\n",
+		    fs->fs_fsmnt, (intmax_t)fs->fs_pendingblocks,
+		    fs->fs_pendinginodes);
 		fs->fs_pendingblocks = 0;
 		fs->fs_pendinginodes = 0;
 	}
@@ -517,8 +514,7 @@ loop:
 			vput(vp);
 			return (error);
 		}
-		ip->i_din = *((struct dinode *)bp->b_data +
-		    ino_to_fsbo(fs, ip->i_number));
+		ffs_load_inode(bp, ip, NULL, fs, ip->i_number);
 		ip->i_effnlink = ip->i_nlink;
 		brelse(bp);
 		vput(vp);
@@ -528,9 +524,10 @@ loop:
 	return (0);
 }
 
-#include <sys/sysctl.h>
-int bigcgs = 0;
-SYSCTL_INT(_debug, OID_AUTO, bigcgs, CTLFLAG_RW, &bigcgs, 0, "");
+/*
+ * Possible superblock locations ordered from most to least likely.
+ */
+static int sblock_try[] = SBLOCKSEARCH;
 
 /*
  * Common code for mount and mountroot
@@ -547,10 +544,10 @@ ffs_mountfs(devvp, mp, td, malloctype)
 	struct fs *fs;
 	dev_t dev;
 	void *space;
+	ufs2_daddr_t sblockloc;
 	int error, i, blks, size, ronly;
 	int32_t *lp;
 	struct ucred *cred;
-	u_int64_t maxfilesize;					/* XXX */
 	size_t strsize;
 	int ncount;
 	u_int sectorsize;
@@ -617,15 +614,32 @@ ffs_mountfs(devvp, mp, td, malloctype)
 
 	bp = NULL;
 	ump = NULL;
-	if ((error = bread(devvp, SBLOCK, SBSIZE, cred, &bp)) != 0)
-		goto out;
-	fs = (struct fs *)bp->b_data;
-	if (fs->fs_magic != FS_MAGIC || fs->fs_bsize > MAXBSIZE ||
-	    fs->fs_bsize < sizeof(struct fs)) {
+	fs = NULL;
+	sblockloc = 0;
+	/*
+	 * Try reading the superblock in each of its possible locations.
+	 */
+	for (i = 0; sblock_try[i] != -1; i++) {
+		if ((error = bread(devvp, sblock_try[i] / size, SBLOCKSIZE,
+		    cred, &bp)) != 0)
+			goto out;
+		fs = (struct fs *)bp->b_data;
+		sblockloc = numfrags(fs, sblock_try[i]);
+		if ((fs->fs_magic == FS_UFS1_MAGIC ||
+		     (fs->fs_magic == FS_UFS2_MAGIC &&
+		      fs->fs_sblockloc == sblockloc)) &&
+		    fs->fs_bsize <= MAXBSIZE &&
+		    fs->fs_bsize >= sizeof(struct fs))
+			break;
+		brelse(bp);
+		bp = NULL;
+	}
+	if (sblock_try[i] == -1) {
 		error = EINVAL;		/* XXX needs translation */
 		goto out;
 	}
 	fs->fs_fmod = 0;
+	fs->fs_flags &= ~FS_INDEXDIRS;	/* no support for directory indicies */
 	fs->fs_flags &= ~FS_UNCLEAN;
 	if (fs->fs_clean == 0) {
 		fs->fs_flags |= FS_UNCLEAN;
@@ -642,40 +656,45 @@ ffs_mountfs(devvp, mp, td, malloctype)
 			error = EPERM;
 			goto out;
 		}
-		if (fs->fs_pendingblocks != 0 || fs->fs_pendinginodes != 0) {
-			printf("%s: lost blocks %d files %d\n", fs->fs_fsmnt,
-			    fs->fs_pendingblocks, fs->fs_pendinginodes);
+		if ((fs->fs_pendingblocks != 0 || fs->fs_pendinginodes != 0) &&
+		    (mp->mnt_flag & MNT_FORCE)) {
+			printf("%s: lost blocks %lld files %d\n", fs->fs_fsmnt,
+			    (intmax_t)fs->fs_pendingblocks,
+			    fs->fs_pendinginodes);
 			fs->fs_pendingblocks = 0;
 			fs->fs_pendinginodes = 0;
 		}
 	}
 	if (fs->fs_pendingblocks != 0 || fs->fs_pendinginodes != 0) {
-		printf("%s: mount pending error: blocks %d files %d\n",
-		    fs->fs_fsmnt, fs->fs_pendingblocks, fs->fs_pendinginodes);
+		printf("%s: mount pending error: blocks %lld files %d\n",
+		    fs->fs_fsmnt, (intmax_t)fs->fs_pendingblocks,
+		    fs->fs_pendinginodes);
 		fs->fs_pendingblocks = 0;
 		fs->fs_pendinginodes = 0;
 	}
-	/* XXX updating 4.2 FFS superblocks trashes rotational layout tables */
-	if (fs->fs_postblformat == FS_42POSTBLFMT && !ronly) {
-		error = EROFS;          /* needs translation */
-		goto out;
-	}
 	ump = malloc(sizeof *ump, M_UFSMNT, M_WAITOK | M_ZERO);
 	ump->um_malloctype = malloctype;
 	ump->um_fs = malloc((u_long)fs->fs_sbsize, M_UFSMNT,
 	    M_WAITOK);
+	if (fs->fs_magic == FS_UFS1_MAGIC) {
+		ump->um_fstype = UFS1;
+		ump->um_balloc = ffs_balloc_ufs1;
+	} else {
+		ump->um_fstype = UFS2;
+		ump->um_balloc = ffs_balloc_ufs2;
+	}
 	ump->um_blkatoff = ffs_blkatoff;
 	ump->um_truncate = ffs_truncate;
 	ump->um_update = ffs_update;
 	ump->um_valloc = ffs_valloc;
 	ump->um_vfree = ffs_vfree;
-	ump->um_balloc = ffs_balloc;
 	bcopy(bp->b_data, ump->um_fs, (u_int)fs->fs_sbsize);
-	if (fs->fs_sbsize < SBSIZE)
+	if (fs->fs_sbsize < SBLOCKSIZE)
 		bp->b_flags |= B_INVAL | B_NOCACHE;
 	brelse(bp);
 	bp = NULL;
 	fs = ump->um_fs;
+	ffs_oldfscompat_read(fs, ump, sblockloc);
 	fs->fs_ronly = ronly;
 	size = fs->fs_cssize;
 	blks = howmany(size, fs->fs_fsize);
@@ -708,11 +727,6 @@ ffs_mountfs(devvp, mp, td, malloctype)
 	fs->fs_contigdirs = (u_int8_t *)space;
 	bzero(fs->fs_contigdirs, size);
 	fs->fs_active = NULL;
-	/* Compatibility for old filesystems 	   XXX */
-	if (fs->fs_avgfilesize <= 0)		/* XXX */
-		fs->fs_avgfilesize = AVFILESIZ;	/* XXX */
-	if (fs->fs_avgfpdir <= 0)		/* XXX */
-		fs->fs_avgfpdir = AFPDIR;	/* XXX */
 	mp->mnt_data = (qaddr_t)ump;
 	mp->mnt_stat.f_fsid.val[0] = fs->fs_id[0];
 	mp->mnt_stat.f_fsid.val[1] = fs->fs_id[1];
@@ -733,7 +747,6 @@ ffs_mountfs(devvp, mp, td, malloctype)
 	ufs_extattr_uepm_init(&ump->um_extattr);
 #endif
 	devvp->v_rdev->si_mountpoint = mp;
-	ffs_oldfscompat(fs);
 
 	/*
 	 * Set FS local "last mounted on" information (NULL pad)
@@ -753,15 +766,6 @@ ffs_mountfs(devvp, mp, td, malloctype)
 		mp->mnt_time = fs->fs_time;
 	}
 
-	ump->um_savedmaxfilesize = fs->fs_maxfilesize;		/* XXX */
-	maxfilesize = (u_int64_t)0x40000000 * fs->fs_bsize - 1;	/* XXX */
-	if (fs->fs_maxfilesize > maxfilesize)			/* XXX */
-		fs->fs_maxfilesize = maxfilesize;		/* XXX */
-	if (bigcgs) {
-		if (fs->fs_sparecon[0] <= 0)
-			fs->fs_sparecon[0] = fs->fs_cgsize;
-		fs->fs_cgsize = fs->fs_bsize;
-	}
 	if (ronly == 0) {
 		if ((fs->fs_flags & FS_DOSOFTDEP) &&
 		    (error = softdep_mount(devvp, mp, fs, cred)) != 0) {
@@ -808,36 +812,90 @@ out:
 	return (error);
 }
 
+#include <sys/sysctl.h>
+int bigcgs = 0;
+SYSCTL_INT(_debug, OID_AUTO, bigcgs, CTLFLAG_RW, &bigcgs, 0, "");
+
 /*
- * Sanity checks for old filesystems.
+ * Sanity checks for loading old filesystem superblocks.
+ * See ffs_oldfscompat_write below for unwound actions.
  *
- * XXX - goes away some day.
+ * XXX - Parts get retired eventually.
+ * Unfortunately new bits get added.
  */
-static int
-ffs_oldfscompat(fs)
+static void
+ffs_oldfscompat_read(fs, ump, sblockloc)
 	struct fs *fs;
+	struct ufsmount *ump;
+	ufs2_daddr_t sblockloc;
 {
+	off_t maxfilesize;
 
-	fs->fs_npsect = max(fs->fs_npsect, fs->fs_nsect);	/* XXX */
-	fs->fs_interleave = max(fs->fs_interleave, 1);		/* XXX */
-	if (fs->fs_postblformat == FS_42POSTBLFMT)		/* XXX */
-		fs->fs_nrpos = 8;				/* XXX */
-	if (fs->fs_inodefmt < FS_44INODEFMT) {			/* XXX */
-#if 0
-		int i;						/* XXX */
-		u_int64_t sizepb = fs->fs_bsize;		/* XXX */
-								/* XXX */
-		fs->fs_maxfilesize = fs->fs_bsize * NDADDR - 1;	/* XXX */
-		for (i = 0; i < NIADDR; i++) {			/* XXX */
-			sizepb *= NINDIR(fs);			/* XXX */
-			fs->fs_maxfilesize += sizepb;		/* XXX */
-		}						/* XXX */
-#endif
+	/*
+	 * If not yet done, update UFS1 superblock with new wider fields.
+	 */
+	if (fs->fs_magic == FS_UFS1_MAGIC &&
+	    fs->fs_sblockloc != sblockloc) {
+		fs->fs_maxbsize = fs->fs_bsize;
+		fs->fs_sblockloc = sblockloc;
+		fs->fs_time = fs->fs_old_time;
+		fs->fs_size = fs->fs_old_size;
+		fs->fs_dsize = fs->fs_old_dsize;
+		fs->fs_csaddr = fs->fs_old_csaddr;
+		fs->fs_cstotal.cs_ndir = fs->fs_old_cstotal.cs_ndir;
+		fs->fs_cstotal.cs_nbfree = fs->fs_old_cstotal.cs_nbfree;
+		fs->fs_cstotal.cs_nifree = fs->fs_old_cstotal.cs_nifree;
+		fs->fs_cstotal.cs_nffree = fs->fs_old_cstotal.cs_nffree;
+	}
+	if (fs->fs_magic == FS_UFS1_MAGIC &&
+	    fs->fs_old_inodefmt < FS_44INODEFMT) {
 		fs->fs_maxfilesize = (u_quad_t) 1LL << 39;
-		fs->fs_qbmask = ~fs->fs_bmask;			/* XXX */
-		fs->fs_qfmask = ~fs->fs_fmask;			/* XXX */
-	}							/* XXX */
-	return (0);
+		fs->fs_qbmask = ~fs->fs_bmask;
+		fs->fs_qfmask = ~fs->fs_fmask;
+	}
+	ump->um_savedmaxfilesize = fs->fs_maxfilesize;
+	maxfilesize = (u_int64_t)0x40000000 * fs->fs_bsize - 1;
+	if (fs->fs_maxfilesize > maxfilesize)
+		fs->fs_maxfilesize = maxfilesize;
+	/* Compatibility for old filesystems */
+	if (fs->fs_avgfilesize <= 0)
+		fs->fs_avgfilesize = AVFILESIZ;
+	if (fs->fs_avgfpdir <= 0)
+		fs->fs_avgfpdir = AFPDIR;
+	if (bigcgs) {
+		fs->fs_save_cgsize = fs->fs_cgsize;
+		fs->fs_cgsize = fs->fs_bsize;
+	}
+}
+
+/*
+ * Unwinding superblock updates for old filesystems.
+ * See ffs_oldfscompat_read above for details.
+ *
+ * XXX - Parts get retired eventually.
+ * Unfortunately new bits get added.
+ */
+static void
+ffs_oldfscompat_write(fs, ump)
+	struct fs *fs;
+	struct ufsmount *ump;
+{
+
+	/*
+	 * Copy back UFS2 updated fields that UFS1 inspects.
+	 */
+	if (fs->fs_magic == FS_UFS1_MAGIC) {
+		fs->fs_old_time = fs->fs_time;
+		fs->fs_old_cstotal.cs_ndir = fs->fs_cstotal.cs_ndir;
+		fs->fs_old_cstotal.cs_nbfree = fs->fs_cstotal.cs_nbfree;
+		fs->fs_old_cstotal.cs_nifree = fs->fs_cstotal.cs_nifree;
+		fs->fs_old_cstotal.cs_nffree = fs->fs_cstotal.cs_nffree;
+	}
+	fs->fs_maxfilesize = ump->um_savedmaxfilesize;
+	if (bigcgs) {
+		fs->fs_cgsize = fs->fs_save_cgsize;
+		fs->fs_save_cgsize = 0;
+	}
 }
 
 /*
@@ -874,13 +932,10 @@ ffs_unmount(mp, mntflags, td)
 			return (error);
 	}
 	fs = ump->um_fs;
-	if (bigcgs) {
-		fs->fs_cgsize = fs->fs_sparecon[0];
-		fs->fs_sparecon[0] = 0;
-	}
 	if (fs->fs_pendingblocks != 0 || fs->fs_pendinginodes != 0) {
-		printf("%s: unmount pending error: blocks %d files %d\n",
-		    fs->fs_fsmnt, fs->fs_pendingblocks, fs->fs_pendinginodes);
+		printf("%s: unmount pending error: blocks %lld files %d\n",
+		    fs->fs_fsmnt, (intmax_t)fs->fs_pendingblocks,
+		    fs->fs_pendinginodes);
 		fs->fs_pendingblocks = 0;
 		fs->fs_pendinginodes = 0;
 	}
@@ -980,7 +1035,7 @@ ffs_statfs(mp, sbp, td)
 
 	ump = VFSTOUFS(mp);
 	fs = ump->um_fs;
-	if (fs->fs_magic != FS_MAGIC)
+	if (fs->fs_magic != FS_UFS1_MAGIC && fs->fs_magic != FS_UFS2_MAGIC)
 		panic("ffs_statfs");
 	sbp->f_bsize = fs->fs_fsize;
 	sbp->f_iosize = fs->fs_bsize;
@@ -1173,6 +1228,7 @@ ffs_vget(mp, ino, flags, vpp)
 	lockinit(vp->v_vnlock, PINOD, "inode", VLKTIMEOUT, LK_CANRECURSE);
 	vp->v_data = ip;
 	ip->i_vnode = vp;
+	ip->i_ump = ump;
 	ip->i_fs = fs = ump->um_fs;
 	ip->i_dev = dev;
 	ip->i_number = ino;
@@ -1222,7 +1278,7 @@ ffs_vget(mp, ino, flags, vpp)
 		*vpp = NULL;
 		return (error);
 	}
-	ip->i_din = *((struct dinode *)bp->b_data + ino_to_fsbo(fs, ino));
+	ffs_load_inode(bp, ip, ump->um_malloctype, fs, ino);
 	if (DOINGSOFTDEP(vp))
 		softdep_load_inodeblock(ip);
 	else
@@ -1250,16 +1306,19 @@ ffs_vget(mp, ino, flags, vpp)
 	 */
 	if (ip->i_gen == 0) {
 		ip->i_gen = random() / 2 + 1;
-		if ((vp->v_mount->mnt_flag & MNT_RDONLY) == 0)
+		if ((vp->v_mount->mnt_flag & MNT_RDONLY) == 0) {
 			ip->i_flag |= IN_MODIFIED;
+			DIP(ip, i_gen) = ip->i_gen;
+		}
 	}
 	/*
 	 * Ensure that uid and gid are correct. This is a temporary
 	 * fix until fsck has been changed to do the update.
 	 */
-	if (fs->fs_inodefmt < FS_44INODEFMT) {		/* XXX */
-		ip->i_uid = ip->i_din.di_ouid;		/* XXX */
-		ip->i_gid = ip->i_din.di_ogid;		/* XXX */
+	if (fs->fs_magic == FS_UFS1_MAGIC &&		/* XXX */
+	    fs->fs_old_inodefmt < FS_44INODEFMT) {	/* XXX */
+		ip->i_uid = ip->i_din1->di_ouid;	/* XXX */
+		ip->i_gid = ip->i_din1->di_ogid;	/* XXX */
 	}						/* XXX */
 
 	*vpp = vp;
@@ -1333,7 +1392,7 @@ ffs_sbupdate(mp, waitfor)
 	struct ufsmount *mp;
 	int waitfor;
 {
-	struct fs *dfs, *fs = mp->um_fs;
+	struct fs *fs = mp->um_fs;
 	struct buf *bp;
 	int blks;
 	void *space;
@@ -1364,24 +1423,12 @@ ffs_sbupdate(mp, waitfor)
 	 */
 	if (allerror)
 		return (allerror);
-	bp = getblk(mp->um_devvp, SBLOCK, (int)fs->fs_sbsize, 0, 0);
+	bp = getblk(mp->um_devvp, fsbtodb(fs, fs->fs_sblockloc),
+	    (int)fs->fs_sbsize, 0, 0);
 	fs->fs_fmod = 0;
 	fs->fs_time = time_second;
 	bcopy((caddr_t)fs, bp->b_data, (u_int)fs->fs_sbsize);
-	/* Restore compatibility to old filesystems.		   XXX */
-	dfs = (struct fs *)bp->b_data;				/* XXX */
-	if (fs->fs_postblformat == FS_42POSTBLFMT)		/* XXX */
-		dfs->fs_nrpos = -1;				/* XXX */
-	if (fs->fs_inodefmt < FS_44INODEFMT) {			/* XXX */
-		int32_t *lp, tmp;				/* XXX */
-								/* XXX */
-		lp = (int32_t *)&dfs->fs_qbmask;		/* XXX */
-		tmp = lp[4];					/* XXX */
-		for (i = 4; i > 0; i--)				/* XXX */
-			lp[i] = lp[i-1];			/* XXX */
-		lp[0] = tmp;					/* XXX */
-	}							/* XXX */
-	dfs->fs_maxfilesize = mp->um_savedmaxfilesize;		/* XXX */
+	ffs_oldfscompat_write((struct fs *)bp->b_data, mp);
 	if (waitfor != MNT_WAIT)
 		bawrite(bp);
 	else if ((error = bwrite(bp)) != 0)