diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index 6f54f639913fc81333ff21eed7f21ec7911d03ba..e18f3c089eeae680217ebeff710b6146ab60ea0f 100644
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -2983,6 +2983,7 @@ xfs_alloc_read_agf(
 	struct xfs_agf		*agf;		/* ag freelist header */
 	struct xfs_perag	*pag;		/* per allocation group data */
 	int			error;
+	int			allocbt_blks;
 
 	trace_xfs_alloc_read_agf(mp, agno);
 
@@ -3013,6 +3014,19 @@ xfs_alloc_read_agf(
 		pag->pagf_refcount_level = be32_to_cpu(agf->agf_refcount_level);
 		pag->pagf_init = 1;
 		pag->pagf_agflreset = xfs_agfl_needs_reset(mp, agf);
+
+		/*
+		 * Update the in-core allocbt counter. Filter out the rmapbt
+		 * subset of the btreeblks counter because the rmapbt is managed
+		 * by perag reservation. Subtract one for the rmapbt root block
+		 * because the rmap counter includes it while the btreeblks
+		 * counter only tracks non-root blocks.
+		 */
+		allocbt_blks = pag->pagf_btreeblks;
+		if (xfs_sb_version_hasrmapbt(&mp->m_sb))
+			allocbt_blks -= be32_to_cpu(agf->agf_rmap_blocks) - 1;
+		if (allocbt_blks > 0)
+			atomic64_add(allocbt_blks, &mp->m_allocbt_blks);
 	}
 #ifdef DEBUG
 	else if (!XFS_FORCED_SHUTDOWN(mp)) {
diff --git a/fs/xfs/libxfs/xfs_alloc_btree.c b/fs/xfs/libxfs/xfs_alloc_btree.c
index dbe302d1cb8de526dc09eb2356683b0a470d0242..a43e4c50e69b7ba9bd828e742125c2b75f4334d3 100644
--- a/fs/xfs/libxfs/xfs_alloc_btree.c
+++ b/fs/xfs/libxfs/xfs_alloc_btree.c
@@ -71,6 +71,7 @@ xfs_allocbt_alloc_block(
 		return 0;
 	}
 
+	atomic64_inc(&cur->bc_mp->m_allocbt_blks);
 	xfs_extent_busy_reuse(cur->bc_mp, cur->bc_ag.agno, bno, 1, false);
 
 	new->s = cpu_to_be32(bno);
@@ -94,6 +95,7 @@ xfs_allocbt_free_block(
 	if (error)
 		return error;
 
+	atomic64_dec(&cur->bc_mp->m_allocbt_blks);
 	xfs_extent_busy_insert(cur->bc_tp, be32_to_cpu(agf->agf_seqno), bno, 1,
 			      XFS_EXTENT_BUSY_SKIP_DISCARD);
 	return 0;
diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
index 91a66b7b88151f1e825f98e9569248257a1208f4..80ec62ba6bd899cf38d0bafc0bfd44fd99b85e9d 100644
--- a/fs/xfs/xfs_mount.h
+++ b/fs/xfs/xfs_mount.h
@@ -187,6 +187,12 @@ typedef struct xfs_mount {
 	 * extents or anything related to the rt device.
 	 */
 	struct percpu_counter	m_delalloc_blks;
+	/*
+	 * Global count of allocation btree blocks in use across all AGs. Only
+	 * used when perag reservation is enabled. Helps prevent block
+	 * reservation from attempting to reserve allocation btree blocks.
+	 */
+	atomic64_t		m_allocbt_blks;
 
 	struct radix_tree_root	m_perag_tree;	/* per-ag accounting info */
 	spinlock_t		m_perag_lock;	/* lock for m_perag_tree */