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

["Darrick J. Wong" <darrick.wong@xxxxxxxxxx>]

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@xxxxxxxxxx>
---
 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;
 }