diff --git a/fs/xfs/xfs_attr_leaf.c b/fs/xfs/xfs_attr_leaf.c
index aa00162..afdc891 100644
--- a/fs/xfs/xfs_attr_leaf.c
+++ b/fs/xfs/xfs_attr_leaf.c
@@ -155,7 +155,8 @@
 		 * minimum offset only needs to be the space required for 
 		 * the btree root.
 		 */ 
-		if (!dp->i_d.di_forkoff && dp->i_df.if_bytes > mp->m_attroffset)
+		if (!dp->i_d.di_forkoff && dp->i_df.if_bytes >
+		    xfs_default_attroffset(dp))
 			dsize = XFS_BMDR_SPACE_CALC(MINDBTPTRS);
 		break;
 		
diff --git a/fs/xfs/xfs_bmap.c b/fs/xfs/xfs_bmap.c
index 47a87de..3a6ed42 100644
--- a/fs/xfs/xfs_bmap.c
+++ b/fs/xfs/xfs_bmap.c
@@ -3569,6 +3569,27 @@
 }
 
 /*
+ * Calculate the default attribute fork offset for newly created inodes.
+ */
+uint
+xfs_default_attroffset(
+	struct xfs_inode	*ip)
+{
+	struct xfs_mount	*mp = ip->i_mount;
+	uint			offset;
+
+	if (mp->m_sb.sb_inodesize == 256) {
+		offset = XFS_LITINO(mp) -
+				XFS_BMDR_SPACE_CALC(MINABTPTRS);
+	} else {
+		offset = XFS_BMDR_SPACE_CALC(6 * MINABTPTRS);
+	}
+
+	ASSERT(offset < XFS_LITINO(mp));
+	return offset;
+}
+
+/*
  * Helper routine to reset inode di_forkoff field when switching
  * attribute fork from local to extent format - we reset it where
  * possible to make space available for inline data fork extents.
@@ -3580,15 +3601,18 @@
 	int		whichfork)
 {
 	if (whichfork == XFS_ATTR_FORK &&
-	    (ip->i_d.di_format != XFS_DINODE_FMT_DEV) &&
-	    (ip->i_d.di_format != XFS_DINODE_FMT_UUID) &&
-	    (ip->i_d.di_format != XFS_DINODE_FMT_BTREE) &&
-	    ((mp->m_attroffset >> 3) > ip->i_d.di_forkoff)) {
-		ip->i_d.di_forkoff = mp->m_attroffset >> 3;
-		ip->i_df.if_ext_max = XFS_IFORK_DSIZE(ip) /
-					(uint)sizeof(xfs_bmbt_rec_t);
-		ip->i_afp->if_ext_max = XFS_IFORK_ASIZE(ip) /
-					(uint)sizeof(xfs_bmbt_rec_t);
+	    ip->i_d.di_format != XFS_DINODE_FMT_DEV &&
+	    ip->i_d.di_format != XFS_DINODE_FMT_UUID &&
+	    ip->i_d.di_format != XFS_DINODE_FMT_BTREE) {
+		uint	dfl_forkoff = xfs_default_attroffset(ip) >> 3;
+
+		if (dfl_forkoff > ip->i_d.di_forkoff) {
+			ip->i_d.di_forkoff = dfl_forkoff;
+			ip->i_df.if_ext_max =
+				XFS_IFORK_DSIZE(ip) / sizeof(xfs_bmbt_rec_t);
+			ip->i_afp->if_ext_max =
+				XFS_IFORK_ASIZE(ip) / sizeof(xfs_bmbt_rec_t);
+		}
 	}
 }
 
@@ -4057,7 +4081,7 @@
 	case XFS_DINODE_FMT_BTREE:
 		ip->i_d.di_forkoff = xfs_attr_shortform_bytesfit(ip, size);
 		if (!ip->i_d.di_forkoff)
-			ip->i_d.di_forkoff = mp->m_attroffset >> 3;
+			ip->i_d.di_forkoff = xfs_default_attroffset(ip) >> 3;
 		else if (mp->m_flags & XFS_MOUNT_ATTR2)
 			version = 2;
 		break;
@@ -4204,12 +4228,12 @@
 	 * (a signed 16-bit number, xfs_aextnum_t).
 	 *
 	 * Note that we can no longer assume that if we are in ATTR1 that
-	 * the fork offset of all the inodes will be (m_attroffset >> 3)
-	 * because we could have mounted with ATTR2 and then mounted back
-	 * with ATTR1, keeping the di_forkoff's fixed but probably at
-	 * various positions. Therefore, for both ATTR1 and ATTR2
-	 * we have to assume the worst case scenario of a minimum size
-	 * available.
+	 * the fork offset of all the inodes will be
+	 * (xfs_default_attroffset(ip) >> 3) because we could have mounted
+	 * with ATTR2 and then mounted back with ATTR1, keeping the
+	 * di_forkoff's fixed but probably at various positions. Therefore,
+	 * for both ATTR1 and ATTR2 we have to assume the worst case scenario
+	 * of a minimum size available.
 	 */
 	if (whichfork == XFS_DATA_FORK) {
 		maxleafents = MAXEXTNUM;
diff --git a/fs/xfs/xfs_bmap.h b/fs/xfs/xfs_bmap.h
index 589d3da..1b8ff92 100644
--- a/fs/xfs/xfs_bmap.h
+++ b/fs/xfs/xfs_bmap.h
@@ -338,6 +338,10 @@
 	xfs_extnum_t		idx,
 	xfs_extnum_t		num);
 
+uint
+xfs_default_attroffset(
+	struct xfs_inode	*ip);
+
 #ifdef __KERNEL__
 
 /*
diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c
index 1c372f9..92fedfc 100644
--- a/fs/xfs/xfs_mount.c
+++ b/fs/xfs/xfs_mount.c
@@ -256,6 +256,22 @@
 		return XFS_ERROR(ENOSYS);
 	}
 
+	/*
+	 * Currently only very few inode sizes are supported.
+	 */
+	switch (sbp->sb_inodesize) {
+	case 256:
+	case 512:
+	case 1024:
+	case 2048:
+		break;
+	default:
+		xfs_fs_mount_cmn_err(flags,
+			"inode size of %d bytes not supported",
+			sbp->sb_inodesize);
+		return XFS_ERROR(ENOSYS);
+	}
+
 	if (xfs_sb_validate_fsb_count(sbp, sbp->sb_dblocks) ||
 	    xfs_sb_validate_fsb_count(sbp, sbp->sb_rblocks)) {
 		xfs_fs_mount_cmn_err(flags,
@@ -578,27 +594,6 @@
 	mp->m_blockwsize = sbp->sb_blocksize >> XFS_WORDLOG;
 	mp->m_blockwmask = mp->m_blockwsize - 1;
 
-	/*
-	 * Setup for attributes, in case they get created.
-	 * This value is for inodes getting attributes for the first time,
-	 * the per-inode value is for old attribute values.
-	 */
-	ASSERT(sbp->sb_inodesize >= 256 && sbp->sb_inodesize <= 2048);
-	switch (sbp->sb_inodesize) {
-	case 256:
-		mp->m_attroffset = XFS_LITINO(mp) -
-				   XFS_BMDR_SPACE_CALC(MINABTPTRS);
-		break;
-	case 512:
-	case 1024:
-	case 2048:
-		mp->m_attroffset = XFS_BMDR_SPACE_CALC(6 * MINABTPTRS);
-		break;
-	default:
-		ASSERT(0);
-	}
-	ASSERT(mp->m_attroffset < XFS_LITINO(mp));
-
 	mp->m_alloc_mxr[0] = xfs_allocbt_maxrecs(mp, sbp->sb_blocksize, 1);
 	mp->m_alloc_mxr[1] = xfs_allocbt_maxrecs(mp, sbp->sb_blocksize, 0);
 	mp->m_alloc_mnr[0] = mp->m_alloc_mxr[0] / 2;
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 5dbc6f7..7af44ad 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -276,7 +276,6 @@
 	int			m_fixedfsid[2];	/* unchanged for life of FS */
 	uint			m_dmevmask;	/* DMI events for this FS */
 	__uint64_t		m_flags;	/* global mount flags */
-	uint			m_attroffset;	/* inode attribute offset */
 	uint			m_dir_node_ents; /* #entries in a dir danode */
 	uint			m_attr_node_ents; /* #entries in attr danode */
 	int			m_ialloc_inos;	/* inodes in inode allocation */