xfs: compute maximum AG btree height for critical reservation calculation

Compute the actual maximum AG btree height for deciding if a per-AG
block reservation is critically low.  This only affects the sanity check
condition, since we /generally/ will trigger on the 10% threshold.  This
is a long-winded way of saying that we're removing one more usage of
XFS_BTREE_MAXLEVELS.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

fs/xfs/libxfs/xfs_ag_resv.c

@@ -91,7 +91,8 @@ xfs_ag_resv_critical(
 	trace_xfs_ag_resv_critical(pag, type, avail);
 
 	/* Critically low if less than 10% or max btree height remains. */
-	return XFS_TEST_ERROR(avail < orig / 10 || avail < XFS_BTREE_MAXLEVELS,
+	return XFS_TEST_ERROR(avail < orig / 10 ||
+			      avail < pag->pag_mount->m_agbtree_maxlevels,
 			pag->pag_mount, XFS_ERRTAG_AG_RESV_CRITICAL);
 }
 

fs/xfs/xfs_mount.c

@@ -567,6 +567,18 @@ xfs_mount_setup_inode_geom(
 	xfs_ialloc_setup_geometry(mp);
 }
 
+/* Compute maximum possible height for per-AG btree types for this fs. */
+static inline void
+xfs_agbtree_compute_maxlevels(
+	struct xfs_mount	*mp)
+{
+	unsigned int		levels;
+
+	levels = max(mp->m_alloc_maxlevels, M_IGEO(mp)->inobt_maxlevels);
+	levels = max(levels, mp->m_rmap_maxlevels);
+	mp->m_agbtree_maxlevels = max(levels, mp->m_refc_maxlevels);
+}
+
 /*
  * This function does the following on an initial mount of a file system:
  *	- reads the superblock from disk and init the mount struct
@@ -638,6 +650,8 @@ xfs_mountfs(
 	xfs_rmapbt_compute_maxlevels(mp);
 	xfs_refcountbt_compute_maxlevels(mp);
 
+	xfs_agbtree_compute_maxlevels(mp);
+
 	/*
 	 * Check if sb_agblocks is aligned at stripe boundary.  If sb_agblocks
 	 * is NOT aligned turn off m_dalign since allocator alignment is within

fs/xfs/xfs_mount.h

@@ -132,6 +132,7 @@ typedef struct xfs_mount {
 	uint			m_bm_maxlevels[2]; /* max bmap btree levels */
 	uint			m_rmap_maxlevels; /* max rmap btree levels */
 	uint			m_refc_maxlevels; /* max refcount btree level */
+	unsigned int		m_agbtree_maxlevels; /* max level of all AG btrees */
 	xfs_extlen_t		m_ag_prealloc_blocks; /* reserved ag blocks */
 	uint			m_alloc_set_aside; /* space we can't use */
 	uint			m_ag_max_usable; /* max space per AG */