From d0e853f3600cd2a3f7c4a067dc38155c77c51df9 Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <darrick.wong@oracle.com>
Date: Mon, 3 Oct 2016 09:11:24 -0700
Subject: xfs: reserve AG space for the refcount btree root

Reduce the max AG usable space size so that we always have space for
the refcount btree root.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c
index be7e3fc..effb64c 100644
--- a/fs/xfs/libxfs/xfs_alloc.c
+++ b/fs/xfs/libxfs/xfs_alloc.c
@@ -128,6 +128,8 @@ xfs_alloc_ag_max_usable(
 		blocks++;		/* finobt root block */
 	if (xfs_sb_version_hasrmapbt(&mp->m_sb))
 		blocks++; 		/* rmap root block */
+	if (xfs_sb_version_hasreflink(&mp->m_sb))
+		blocks++;		/* refcount root block */
 
 	return mp->m_sb.sb_agblocks - blocks;
 }
-- 
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