[PATCH 14/51] libxfs: fix min freelist length calculation

[Darrick J. Wong]

If rmapbt is disabled, it is incorrect to require 1 extra AGFL block
for the rmapbt (due to the + 1); the entire clause needs to be gated
on the feature flag.

This causes serious problems if formatting a v4 filesystem because the
extra AGFL block causes the root inode not to be where xfs_repair
expects it.  In turn, xfs_repair reports major FS damage when
everything is fine.

Signed-off-by: Darrick J. Wong <darrick.wong at oracle.com>
---
 libxfs/xfs_alloc.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)


diff --git a/libxfs/xfs_alloc.c b/libxfs/xfs_alloc.c
index 1a69bdc..40cb20a 100644
--- a/libxfs/xfs_alloc.c
+++ b/libxfs/xfs_alloc.c
@@ -1964,8 +1964,10 @@ xfs_alloc_min_freelist(
 	min_free += min_t(unsigned int, pag->pagf_levels[XFS_BTNUM_CNTi] + 1,
 				       mp->m_ag_maxlevels);
 	/* space needed reverse mapping used space btree */
-	min_free += min_t(unsigned int, pag->pagf_levels[XFS_BTNUM_RMAPi] + 1,
-				       mp->m_ag_maxlevels);
+	if (xfs_sb_version_hasrmapbt(&mp->m_sb))
+		min_free += min_t(unsigned int,
+				  pag->pagf_levels[XFS_BTNUM_RMAPi] + 1,
+				  mp->m_ag_maxlevels);
 
 	return min_free;
 }