diff --git a/fs/xfs/xfs_fsmap.c b/fs/xfs/xfs_fsmap.c
index 3665638..6d053cf 100644
--- a/fs/xfs/xfs_fsmap.c
+++ b/fs/xfs/xfs_fsmap.c
@@ -39,6 +39,7 @@
 #include "xfs_fsmap.h"
 #include "xfs_refcount.h"
 #include "xfs_refcount_btree.h"
+#include "xfs_alloc_btree.h"
 
 /* Convert an xfs_fsmap to an fsmap. */
 void
@@ -125,6 +126,7 @@ xfs_fsmap_owner_from_rmap(
 	case XFS_RMAP_OWN_INODES:
 	case XFS_RMAP_OWN_REFC:
 	case XFS_RMAP_OWN_COW:
+	case XFS_RMAP_OWN_NULL:	/* "free" */
 		fmr->fmr_owner = rm->rm_owner;
 		return 0;
 	default:
@@ -396,6 +398,31 @@ xfs_getfsmap_rtdev_helper(
 	return xfs_getfsmap_helper(mp, info, rec, rec_daddr);
 }
 
+/* Transform a bnobt irec into a fsmap */
+STATIC int
+xfs_getfsmap_datadev_bnobt_helper(
+	struct xfs_btree_cur		*cur,
+	struct xfs_alloc_rec_incore	*rec,
+	void				*priv)
+{
+	struct xfs_mount		*mp = cur->bc_mp;
+	struct xfs_getfsmap_info	*info = priv;
+	struct xfs_rmap_irec		irec;
+	xfs_fsblock_t			fsb;
+	xfs_daddr_t			rec_daddr;
+
+	fsb = XFS_AGB_TO_FSB(mp, cur->bc_private.a.agno, rec->ar_startblock);
+	rec_daddr = XFS_FSB_TO_DADDR(mp, fsb);
+
+	irec.rm_startblock = rec->ar_startblock;
+	irec.rm_blockcount = rec->ar_blockcount;
+	irec.rm_owner = XFS_RMAP_OWN_NULL;	/* "free" */
+	irec.rm_offset = 0;
+	irec.rm_flags = 0;
+
+	return xfs_getfsmap_helper(mp, info, &irec, rec_daddr);
+}
+
 /* Set rmap flags based on the getfsmap flags */
 static void
 xfs_getfsmap_set_irec_flags(
@@ -583,6 +610,125 @@ xfs_getfsmap_datadev(
 	return error;
 }
 
+/* Execute a getfsmap query against the regular data device's bnobt. */
+STATIC int
+xfs_getfsmap_datadev_bnobt(
+	struct xfs_trans		*tp,
+	struct xfs_fsmap		*keys,
+	struct xfs_getfsmap_info	*info)
+{
+	struct xfs_mount		*mp = tp->t_mountp;
+	struct xfs_btree_cur		*bt_cur = NULL;
+	struct xfs_fsmap		*dkey_low;
+	struct xfs_fsmap		*dkey_high;
+	struct xfs_alloc_rec_incore	alow;
+	struct xfs_alloc_rec_incore	ahigh;
+	xfs_fsblock_t			start_fsb;
+	xfs_fsblock_t			end_fsb;
+	xfs_agnumber_t			start_ag;
+	xfs_agnumber_t			end_ag;
+	xfs_daddr_t			eofs;
+	int				error = 0;
+
+	dkey_low = keys;
+	dkey_high = keys + 1;
+	eofs = XFS_FSB_TO_BB(mp, mp->m_sb.sb_dblocks);
+	if (dkey_low->fmr_physical >= eofs)
+		return 0;
+	if (dkey_high->fmr_physical >= eofs)
+		dkey_high->fmr_physical = eofs - 1;
+	start_fsb = XFS_DADDR_TO_FSB(mp, dkey_low->fmr_physical);
+	end_fsb = XFS_DADDR_TO_FSB(mp, dkey_high->fmr_physical);
+
+	/* Set up search keys */
+	info->low.rm_startblock = XFS_FSB_TO_AGBNO(mp, start_fsb);
+	info->low.rm_offset = XFS_BB_TO_FSBT(mp, dkey_low->fmr_offset);
+	error = xfs_fsmap_owner_to_rmap(dkey_low, &info->low);
+	if (error)
+		return error;
+	info->low.rm_blockcount = 0;
+	xfs_getfsmap_set_irec_flags(&info->low, dkey_low);
+
+	info->high.rm_startblock = -1U;
+	info->high.rm_owner = ULLONG_MAX;
+	info->high.rm_offset = ULLONG_MAX;
+	info->high.rm_blockcount = 0;
+	info->high.rm_flags = XFS_RMAP_KEY_FLAGS | XFS_RMAP_REC_FLAGS;
+
+	info->missing_owner = FMR_OWN_UNKNOWN;
+
+	start_ag = XFS_FSB_TO_AGNO(mp, start_fsb);
+	end_ag = XFS_FSB_TO_AGNO(mp, end_fsb);
+
+	/* Query each AG */
+	for (info->agno = start_ag; info->agno <= end_ag; info->agno++) {
+		if (info->agno == end_ag) {
+			info->high.rm_startblock = XFS_FSB_TO_AGBNO(mp,
+					end_fsb);
+			info->high.rm_offset = XFS_BB_TO_FSBT(mp,
+					dkey_high->fmr_offset);
+			error = xfs_fsmap_owner_to_rmap(dkey_high, &info->high);
+			if (error)
+				goto err;
+			xfs_getfsmap_set_irec_flags(&info->high, dkey_high);
+		}
+
+		if (bt_cur) {
+			xfs_btree_del_cursor(bt_cur, XFS_BTREE_NOERROR);
+			bt_cur = NULL;
+			info->agf_bp = NULL;
+		}
+
+		error = xfs_alloc_read_agf(mp, tp, info->agno, 0,
+				&info->agf_bp);
+		if (error)
+			goto err;
+
+		trace_xfs_fsmap_low_key(mp, info->dev, info->agno,
+				info->low.rm_startblock,
+				info->low.rm_blockcount,
+				info->low.rm_owner,
+				info->low.rm_offset);
+
+		trace_xfs_fsmap_high_key(mp, info->dev, info->agno,
+				info->high.rm_startblock,
+				info->high.rm_blockcount,
+				info->high.rm_owner,
+				info->high.rm_offset);
+
+		bt_cur = xfs_allocbt_init_cursor(mp, tp, info->agf_bp,
+				info->agno, XFS_BTNUM_BNO);
+		alow.ar_startblock = info->low.rm_startblock;
+		ahigh.ar_startblock = info->high.rm_startblock;
+		error = xfs_alloc_query_range(bt_cur, &alow, &ahigh,
+				xfs_getfsmap_datadev_bnobt_helper, info);
+		if (error)
+			goto err;
+
+		if (info->agno == start_ag) {
+			info->low.rm_startblock = 0;
+			info->low.rm_owner = 0;
+			info->low.rm_offset = 0;
+			info->low.rm_flags = 0;
+		}
+	}
+
+	/* Report any free space at the end of the AG */
+	info->last = true;
+	error = xfs_getfsmap_datadev_bnobt_helper(bt_cur, &ahigh, info);
+	if (error)
+		goto err;
+
+err:
+	if (bt_cur)
+		xfs_btree_del_cursor(bt_cur, error < 0 ? XFS_BTREE_ERROR :
+							 XFS_BTREE_NOERROR);
+	if (info->agf_bp)
+		info->agf_bp = NULL;
+
+	return error;
+}
+
 /* Do we recognize the device? */
 STATIC bool
 xfs_getfsmap_is_valid_device(
@@ -651,8 +797,6 @@ xfs_getfsmap(
 	int				i;
 	int				error = 0;
 
-	if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
-		return -EOPNOTSUPP;
 	if (head->fmh_iflags & ~FMH_IF_VALID)
 		return -EINVAL;
 	rkey_low = head->fmh_keys;
@@ -666,7 +810,10 @@ xfs_getfsmap(
 	/* Set up our device handlers. */
 	memset(handlers, 0, sizeof(handlers));
 	handlers[0].dev = new_encode_dev(mp->m_ddev_targp->bt_dev);
-	handlers[0].fn = xfs_getfsmap_datadev;
+	if (xfs_sb_version_hasrmapbt(&mp->m_sb))
+		handlers[0].fn = xfs_getfsmap_datadev;
+	else
+		handlers[0].fn = xfs_getfsmap_datadev_bnobt;
 	if (mp->m_logdev_targp != mp->m_ddev_targp) {
 		handlers[1].dev = new_encode_dev(mp->m_logdev_targp->bt_dev);
 		handlers[1].fn = xfs_getfsmap_logdev;
