diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c
index fe742567a7dd..377dc9b0a6e6 100644
--- a/fs/xfs/libxfs/xfs_btree.c
+++ b/fs/xfs/libxfs/xfs_btree.c
@@ -491,6 +491,8 @@ xfs_btree_del_cursor(
 	if (cur->bc_flags & XFS_BTREE_IN_MEMORY) {
 		if (cur->bc_mem.pag)
 			xfs_perag_put(cur->bc_mem.pag);
+		if (cur->bc_mem.rtg)
+			xfs_rtgroup_put(cur->bc_mem.rtg);
 	}
 	kmem_cache_free(cur->bc_cache, cur);
 }
diff --git a/fs/xfs/libxfs/xfs_btree.h b/fs/xfs/libxfs/xfs_btree.h
index 5a733767649b..20342ed62bf4 100644
--- a/fs/xfs/libxfs/xfs_btree.h
+++ b/fs/xfs/libxfs/xfs_btree.h
@@ -266,6 +266,7 @@ struct xfs_btree_cur_mem {
 	struct xfbtree			*xfbtree;
 	struct xfs_buf			*head_bp;
 	struct xfs_perag		*pag;
+	struct xfs_rtgroup		*rtg;
 };
 
 struct xfs_btree_level {
diff --git a/fs/xfs/libxfs/xfs_rmap.c b/fs/xfs/libxfs/xfs_rmap.c
index 9c678e9fded5..06840fc31f02 100644
--- a/fs/xfs/libxfs/xfs_rmap.c
+++ b/fs/xfs/libxfs/xfs_rmap.c
@@ -328,8 +328,12 @@ xfs_rmap_check_irec(
 	struct xfs_btree_cur		*cur,
 	const struct xfs_rmap_irec	*irec)
 {
-	if (cur->bc_btnum == XFS_BTNUM_RTRMAP)
+	if (cur->bc_btnum == XFS_BTNUM_RTRMAP) {
+		if (cur->bc_flags & XFS_BTREE_IN_MEMORY)
+			return xfs_rmap_check_rtgroup_irec(cur->bc_mem.rtg,
+					irec);
 		return xfs_rmap_check_rtgroup_irec(cur->bc_ino.rtg, irec);
+	}
 
 	if (cur->bc_flags & XFS_BTREE_IN_MEMORY)
 		return xfs_rmap_check_perag_irec(cur->bc_mem.pag, irec);
diff --git a/fs/xfs/libxfs/xfs_rtrmap_btree.c b/fs/xfs/libxfs/xfs_rtrmap_btree.c
index 418173f6f3ca..878bfeed411f 100644
--- a/fs/xfs/libxfs/xfs_rtrmap_btree.c
+++ b/fs/xfs/libxfs/xfs_rtrmap_btree.c
@@ -29,6 +29,9 @@
 #include "xfs_bmap.h"
 #include "xfs_imeta.h"
 #include "xfs_health.h"
+#include "scrub/xfile.h"
+#include "scrub/xfbtree.h"
+#include "xfs_btree_mem.h"
 
 static struct kmem_cache	*xfs_rtrmapbt_cur_cache;
 
@@ -557,6 +560,125 @@ xfs_rtrmapbt_stage_cursor(
 	return cur;
 }
 
+#ifdef CONFIG_XFS_IN_MEMORY_BTREE
+/*
+ * Validate an in-memory realtime rmap btree block.  Callers are allowed to
+ * generate an in-memory btree even if the ondisk feature is not enabled.
+ */
+static xfs_failaddr_t
+xfs_rtrmapbt_mem_verify(
+	struct xfs_buf		*bp)
+{
+	struct xfs_mount	*mp = bp->b_mount;
+	struct xfs_btree_block	*block = XFS_BUF_TO_BLOCK(bp);
+	xfs_failaddr_t		fa;
+	unsigned int		level;
+
+	if (!xfs_verify_magic(bp, block->bb_magic))
+		return __this_address;
+
+	fa = xfs_btree_lblock_v5hdr_verify(bp, XFS_RMAP_OWN_UNKNOWN);
+	if (fa)
+		return fa;
+
+	level = be16_to_cpu(block->bb_level);
+	if (xfs_has_rmapbt(mp)) {
+		if (level >= mp->m_rtrmap_maxlevels)
+			return __this_address;
+	} else {
+		if (level >= xfs_rtrmapbt_maxlevels_ondisk())
+			return __this_address;
+	}
+
+	return xfbtree_lblock_verify(bp,
+			xfs_rtrmapbt_maxrecs(mp, xfo_to_b(1), level == 0));
+}
+
+static void
+xfs_rtrmapbt_mem_rw_verify(
+	struct xfs_buf	*bp)
+{
+	xfs_failaddr_t	fa = xfs_rtrmapbt_mem_verify(bp);
+
+	if (fa)
+		xfs_verifier_error(bp, -EFSCORRUPTED, fa);
+}
+
+/* skip crc checks on in-memory btrees to save time */
+static const struct xfs_buf_ops xfs_rtrmapbt_mem_buf_ops = {
+	.name			= "xfs_rtrmapbt_mem",
+	.magic			= { 0, cpu_to_be32(XFS_RTRMAP_CRC_MAGIC) },
+	.verify_read		= xfs_rtrmapbt_mem_rw_verify,
+	.verify_write		= xfs_rtrmapbt_mem_rw_verify,
+	.verify_struct		= xfs_rtrmapbt_mem_verify,
+};
+
+static const struct xfs_btree_ops xfs_rtrmapbt_mem_ops = {
+	.rec_len		= sizeof(struct xfs_rmap_rec),
+	.key_len		= 2 * sizeof(struct xfs_rmap_key),
+	.geom_flags		= XFS_BTREE_CRC_BLOCKS | XFS_BTREE_OVERLAPPING |
+				  XFS_BTREE_LONG_PTRS | XFS_BTREE_IN_MEMORY,
+
+	.dup_cursor		= xfbtree_dup_cursor,
+	.set_root		= xfbtree_set_root,
+	.alloc_block		= xfbtree_alloc_block,
+	.free_block		= xfbtree_free_block,
+	.get_minrecs		= xfbtree_get_minrecs,
+	.get_maxrecs		= xfbtree_get_maxrecs,
+	.init_key_from_rec	= xfs_rtrmapbt_init_key_from_rec,
+	.init_high_key_from_rec	= xfs_rtrmapbt_init_high_key_from_rec,
+	.init_rec_from_cur	= xfs_rtrmapbt_init_rec_from_cur,
+	.init_ptr_from_cur	= xfbtree_init_ptr_from_cur,
+	.key_diff		= xfs_rtrmapbt_key_diff,
+	.buf_ops		= &xfs_rtrmapbt_mem_buf_ops,
+	.diff_two_keys		= xfs_rtrmapbt_diff_two_keys,
+	.keys_inorder		= xfs_rtrmapbt_keys_inorder,
+	.recs_inorder		= xfs_rtrmapbt_recs_inorder,
+	.keys_contiguous	= xfs_rtrmapbt_keys_contiguous,
+};
+
+/* Create a cursor for an in-memory btree. */
+struct xfs_btree_cur *
+xfs_rtrmapbt_mem_cursor(
+	struct xfs_rtgroup	*rtg,
+	struct xfs_trans	*tp,
+	struct xfs_buf		*head_bp,
+	struct xfbtree		*xfbtree)
+{
+	struct xfs_btree_cur	*cur;
+	struct xfs_mount	*mp = rtg->rtg_mount;
+
+	/* Overlapping btree; 2 keys per pointer. */
+	cur = xfs_btree_alloc_cursor(mp, tp, XFS_BTNUM_RTRMAP,
+			&xfs_rtrmapbt_mem_ops, mp->m_rtrmap_maxlevels,
+			xfs_rtrmapbt_cur_cache);
+	cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_rmap_2);
+	cur->bc_mem.xfbtree = xfbtree;
+	cur->bc_mem.head_bp = head_bp;
+	cur->bc_nlevels = xfs_btree_mem_head_nlevels(head_bp);
+
+	cur->bc_mem.rtg = xfs_rtgroup_bump(rtg);
+	return cur;
+}
+
+int
+xfs_rtrmapbt_mem_create(
+	struct xfs_mount	*mp,
+	xfs_rgnumber_t		rgno,
+	struct xfs_buftarg	*target,
+	struct xfbtree		**xfbtreep)
+{
+	struct xfbtree_config	cfg = {
+		.btree_ops	= &xfs_rtrmapbt_mem_ops,
+		.target		= target,
+		.flags		= XFBTREE_DIRECT_MAP,
+		.owner		= rgno,
+	};
+
+	return xfbtree_create(mp, &cfg, xfbtreep);
+}
+#endif /* CONFIG_XFS_IN_MEMORY_BTREE */
+
 /*
  * Install a new rt reverse mapping btree root.  Caller is responsible for
  * invalidating and freeing the old btree blocks.
diff --git a/fs/xfs/libxfs/xfs_rtrmap_btree.h b/fs/xfs/libxfs/xfs_rtrmap_btree.h
index 1f0a6f9620e8..ff60a2ca945f 100644
--- a/fs/xfs/libxfs/xfs_rtrmap_btree.h
+++ b/fs/xfs/libxfs/xfs_rtrmap_btree.h
@@ -206,4 +206,13 @@ int xfs_rtrmapbt_create(struct xfs_trans **tpp, struct xfs_imeta_path *path,
 unsigned long long xfs_rtrmapbt_calc_size(struct xfs_mount *mp,
 		unsigned long long len);
 
+#ifdef CONFIG_XFS_IN_MEMORY_BTREE
+struct xfbtree;
+struct xfs_btree_cur *xfs_rtrmapbt_mem_cursor(struct xfs_rtgroup *rtg,
+		struct xfs_trans *tp, struct xfs_buf *mhead_bp,
+		struct xfbtree *xfbtree);
+int xfs_rtrmapbt_mem_create(struct xfs_mount *mp, xfs_rgnumber_t rgno,
+		struct xfs_buftarg *target, struct xfbtree **xfbtreep);
+#endif /* CONFIG_XFS_IN_MEMORY_BTREE */
+
 #endif	/* __XFS_RTRMAP_BTREE_H__ */
diff --git a/fs/xfs/scrub/rtrmap_repair.c b/fs/xfs/scrub/rtrmap_repair.c
index d856a4e46d6f..5775efa67de6 100644
--- a/fs/xfs/scrub/rtrmap_repair.c
+++ b/fs/xfs/scrub/rtrmap_repair.c
@@ -12,6 +12,7 @@
 #include "xfs_defer.h"
 #include "xfs_btree.h"
 #include "xfs_btree_staging.h"
+#include "xfs_btree_mem.h"
 #include "xfs_bit.h"
 #include "xfs_log_format.h"
 #include "xfs_trans.h"
@@ -40,6 +41,7 @@
 #include "scrub/iscan.h"
 #include "scrub/newbt.h"
 #include "scrub/reap.h"
+#include "scrub/xfbtree.h"
 
 /*
  * Realtime Reverse Mapping Btree Repair
@@ -68,28 +70,16 @@ int
 xrep_setup_rtrmapbt(
 	struct xfs_scrub	*sc)
 {
-	/* For now this is a placeholder until we land other pieces. */
-	return 0;
+	return xrep_setup_buftarg(sc, "rtrmapbt repair");
 }
 
-/*
- * Packed rmap record.  The UNWRITTEN flags are hidden in the upper bits of
- * offset, just like the on-disk record.
- */
-struct xrep_rtrmap_extent {
-	xfs_rgblock_t	startblock;
-	xfs_extlen_t	blockcount;
-	uint64_t	owner;
-	uint64_t	offset;
-} __packed;
-
 /* Context for collecting rmaps */
 struct xrep_rtrmap {
 	/* new rtrmapbt information */
 	struct xrep_newbt	new_btree;
 
 	/* rmap records generated from primary metadata */
-	struct xfarray		*rtrmap_records;
+	struct xfbtree		*rtrmap_btree;
 
 	struct xfs_scrub	*sc;
 
@@ -99,8 +89,11 @@ struct xrep_rtrmap {
 	/* inode scan cursor */
 	struct xchk_iscan	iscan;
 
-	/* get_records()'s position in the free space record array. */
-	xfarray_idx_t		array_cur;
+	/* in-memory btree cursor for the ->get_blocks walk */
+	struct xfs_btree_cur	*mcur;
+
+	/* Number of records we're staging in the new btree. */
+	uint64_t		nr_records;
 };
 
 /* Make sure there's nothing funny about this mapping. */
@@ -130,11 +123,6 @@ xrep_rtrmap_stash(
 	uint64_t		offset,
 	unsigned int		flags)
 {
-	struct xrep_rtrmap_extent	rre = {
-		.startblock	= startblock,
-		.blockcount	= blockcount,
-		.owner		= owner,
-	};
 	struct xfs_rmap_irec	rmap = {
 		.rm_startblock	= startblock,
 		.rm_blockcount	= blockcount,
@@ -143,6 +131,8 @@ xrep_rtrmap_stash(
 		.rm_flags	= flags,
 	};
 	struct xfs_scrub	*sc = rr->sc;
+	struct xfs_btree_cur	*mcur;
+	struct xfs_buf		*mhead_bp;
 	int			error = 0;
 
 	if (xchk_should_terminate(sc, &error))
@@ -150,8 +140,23 @@ xrep_rtrmap_stash(
 
 	trace_xrep_rtrmap_found(sc->mp, &rmap);
 
-	rre.offset = xfs_rmap_irec_offset_pack(&rmap);
-	return xfarray_append(rr->rtrmap_records, &rre);
+	/* Add entry to in-memory btree. */
+	error = xfbtree_head_read_buf(rr->rtrmap_btree, sc->tp, &mhead_bp);
+	if (error)
+		return error;
+
+	mcur = xfs_rtrmapbt_mem_cursor(sc->sr.rtg, sc->tp, mhead_bp,
+			rr->rtrmap_btree);
+	error = xfs_rmap_map_raw(mcur, &rmap);
+	xfs_btree_del_cursor(mcur, error);
+	if (error)
+		goto out_cancel;
+
+	return xfbtree_trans_commit(rr->rtrmap_btree, sc->tp);
+
+out_cancel:
+	xfbtree_trans_cancel(rr->rtrmap_btree, sc->tp);
+	return error;
 }
 
 /* Finding all file and bmbt extents. */
@@ -395,6 +400,24 @@ xrep_rtrmap_scan_ag(
 	return error;
 }
 
+/* Count and check all collected records. */
+STATIC int
+xrep_rtrmap_check_record(
+	struct xfs_btree_cur		*cur,
+	const struct xfs_rmap_irec	*rec,
+	void				*priv)
+{
+	struct xrep_rtrmap		*rr = priv;
+	int				error;
+
+	error = xrep_rtrmap_check_mapping(rr->sc, rec);
+	if (error)
+		return error;
+
+	rr->nr_records++;
+	return 0;
+}
+
 STATIC int
 xrep_rtrmap_find_super_rmaps(
 	struct xrep_rtrmap	*rr)
@@ -414,6 +437,8 @@ xrep_rtrmap_find_rmaps(
 	struct xfs_scrub	*sc = rr->sc;
 	struct xfs_perag	*pag;
 	struct xfs_inode	*ip;
+	struct xfs_buf		*mhead_bp;
+	struct xfs_btree_cur	*mcur;
 	xfs_agnumber_t		agno;
 	int			error;
 
@@ -476,7 +501,25 @@ xrep_rtrmap_find_rmaps(
 		}
 	}
 
-	return 0;
+	/*
+	 * Now that we have everything locked again, we need to count the
+	 * number of rmap records stashed in the btree.  This should reflect
+	 * all actively-owned rt files in the filesystem.  At the same time,
+	 * check all our records before we start building a new btree, which
+	 * requires the rtbitmap lock.
+	 */
+	error = xfbtree_head_read_buf(rr->rtrmap_btree, NULL, &mhead_bp);
+	if (error)
+		return error;
+
+	mcur = xfs_rtrmapbt_mem_cursor(rr->sc->sr.rtg, NULL, mhead_bp,
+			rr->rtrmap_btree);
+	rr->nr_records = 0;
+	error = xfs_rmap_query_all(mcur, xrep_rtrmap_check_record, rr);
+	xfs_btree_del_cursor(mcur, error);
+	xfs_buf_relse(mhead_bp);
+
+	return error;
 }
 
 /* Building the new rtrmap btree. */
@@ -490,29 +533,25 @@ xrep_rtrmap_get_records(
 	unsigned int			nr_wanted,
 	void				*priv)
 {
-	struct xrep_rtrmap_extent	rec;
-	struct xfs_rmap_irec		*irec = &cur->bc_rec.r;
 	struct xrep_rtrmap		*rr = priv;
 	union xfs_btree_rec		*block_rec;
 	unsigned int			loaded;
 	int				error;
 
 	for (loaded = 0; loaded < nr_wanted; loaded++, idx++) {
-		error = xfarray_load_next(rr->rtrmap_records, &rr->array_cur,
-				&rec);
+		int			stat = 0;
+
+		error = xfs_btree_increment(rr->mcur, 0, &stat);
 		if (error)
 			return error;
-
-		irec->rm_startblock = rec.startblock;
-		irec->rm_blockcount = rec.blockcount;
-		irec->rm_owner = rec.owner;
-
-		if (xfs_rmap_irec_offset_unpack(rec.offset, irec) != NULL)
+		if (!stat)
 			return -EFSCORRUPTED;
 
-		error = xrep_rtrmap_check_mapping(rr->sc, irec);
+		error = xfs_rmap_get_rec(rr->mcur, &cur->bc_rec.r, &stat);
 		if (error)
 			return error;
+		if (!stat)
+			return -EFSCORRUPTED;
 
 		block_rec = xfs_btree_rec_addr(cur, idx, block);
 		cur->bc_ops->init_rec_from_cur(cur, block_rec);
@@ -558,7 +597,7 @@ xrep_rtrmap_build_new_tree(
 	struct xfs_scrub	*sc = rr->sc;
 	struct xfs_rtgroup	*rtg = sc->sr.rtg;
 	struct xfs_btree_cur	*rmap_cur;
-	uint64_t		nr_records;
+	struct xfs_buf		*mhead_bp;
 	int			error;
 
 	/*
@@ -579,11 +618,9 @@ xrep_rtrmap_build_new_tree(
 	rmap_cur = xfs_rtrmapbt_stage_cursor(sc->mp, rtg, rtg->rtg_rmapip,
 			&rr->new_btree.ifake);
 
-	nr_records = xfarray_length(rr->rtrmap_records);
-
 	/* Compute how many blocks we'll need for the rmaps collected. */
 	error = xfs_btree_bload_compute_geometry(rmap_cur,
-			&rr->new_btree.bload, nr_records);
+			&rr->new_btree.bload, rr->nr_records);
 	if (error)
 		goto err_cur;
 
@@ -609,12 +646,25 @@ xrep_rtrmap_build_new_tree(
 	if (error)
 		goto err_cur;
 
+	/*
+	 * Create a cursor to the in-memory btree so that we can bulk load the
+	 * new btree.
+	 */
+	error = xfbtree_head_read_buf(rr->rtrmap_btree, NULL, &mhead_bp);
+	if (error)
+		goto err_cur;
+
+	rr->mcur = xfs_rtrmapbt_mem_cursor(sc->sr.rtg, NULL, mhead_bp,
+			rr->rtrmap_btree);
+	error = xfs_btree_goto_left_edge(rr->mcur);
+	if (error)
+		goto err_mcur;
+
 	/* Add all observed rmap records. */
 	rr->new_btree.ifake.if_fork->if_format = XFS_DINODE_FMT_RMAP;
-	rr->array_cur = XFARRAY_CURSOR_INIT;
 	error = xfs_btree_bload(rmap_cur, &rr->new_btree.bload, rr);
 	if (error)
-		goto err_cur;
+		goto err_mcur;
 
 	/*
 	 * Install the new rtrmap btree in the inode.  After this point the old
@@ -624,6 +674,15 @@ xrep_rtrmap_build_new_tree(
 	xfs_rtrmapbt_commit_staged_btree(rmap_cur, sc->tp);
 	xrep_inode_set_nblocks(rr->sc, rr->new_btree.ifake.if_blocks);
 	xfs_btree_del_cursor(rmap_cur, 0);
+	xfs_btree_del_cursor(rr->mcur, 0);
+	rr->mcur = NULL;
+	xfs_buf_relse(mhead_bp);
+
+	/*
+	 * Now that we've written the new btree to disk, we don't need to keep
+	 * updating the in-memory btree.  Abort the scan to stop live updates.
+	 */
+	xchk_iscan_abort(&rr->iscan);
 
 	/* Dispose of any unused blocks and the accounting information. */
 	error = xrep_newbt_commit(&rr->new_btree);
@@ -632,6 +691,9 @@ xrep_rtrmap_build_new_tree(
 
 	return xrep_roll_trans(sc);
 
+err_mcur:
+	xfs_btree_del_cursor(rr->mcur, error);
+	xfs_buf_relse(mhead_bp);
 err_cur:
 	xfs_btree_del_cursor(rmap_cur, error);
 	xrep_newbt_cancel(&rr->new_btree);
@@ -689,8 +751,8 @@ xrep_rtrmapbt(
 	xfsb_bitmap_init(&rr->old_rtrmapbt_blocks);
 
 	/* Set up some storage */
-	error = xfarray_create(sc->mp, "rtrmap records", 0,
-			sizeof(struct xrep_rtrmap_extent), &rr->rtrmap_records);
+	error = xfs_rtrmapbt_mem_create(sc->mp, sc->sr.rtg->rtg_rgno,
+			sc->xfile_buftarg, &rr->rtrmap_btree);
 	if (error)
 		goto out_bitmap;
 
@@ -714,7 +776,7 @@ xrep_rtrmapbt(
 
 out_records:
 	xchk_iscan_finish(&rr->iscan);
-	xfarray_destroy(rr->rtrmap_records);
+	xfbtree_destroy(rr->rtrmap_btree);
 out_bitmap:
 	xfsb_bitmap_destroy(&rr->old_rtrmapbt_blocks);
 	kfree(rr);
diff --git a/fs/xfs/scrub/xfbtree.c b/fs/xfs/scrub/xfbtree.c
index 55d530213d40..d803bb1d151a 100644
--- a/fs/xfs/scrub/xfbtree.c
+++ b/fs/xfs/scrub/xfbtree.c
@@ -17,6 +17,7 @@
 #include "xfs_error.h"
 #include "xfs_btree_mem.h"
 #include "xfs_ag.h"
+#include "xfs_rtgroup.h"
 #include "scrub/scrub.h"
 #include "scrub/xfile.h"
 #include "scrub/xfbtree.h"
@@ -267,6 +268,8 @@ xfbtree_dup_cursor(
 
 	if (cur->bc_mem.pag)
 		ncur->bc_mem.pag = xfs_perag_bump(cur->bc_mem.pag);
+	if (cur->bc_mem.rtg)
+		ncur->bc_mem.rtg = xfs_rtgroup_bump(cur->bc_mem.rtg);
 
 	return ncur;
 }
