[PATCH 21/48] xfs: compute maximum AG btree height for critical reservation calculation

["Darrick J. Wong" <djwong@xxxxxxxxxx>]

From: Darrick J. Wong <djwong@xxxxxxxxxx>

Source kernel commit: b74e15d720d0764345934ebb599a99a077c52533

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@xxxxxxxxxx>
Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>
Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
---
 include/xfs_mount.h  |    1 +
 libxfs/init.c        |   14 ++++++++++++++
 libxfs/xfs_ag_resv.c |    3 ++-
 3 files changed, 17 insertions(+), 1 deletion(-)


diff --git a/include/xfs_mount.h b/include/xfs_mount.h
index 308ceff0..bd464fbb 100644
--- a/include/xfs_mount.h
+++ b/include/xfs_mount.h
@@ -75,6 +75,7 @@ typedef struct xfs_mount {
 	uint			m_bm_maxlevels[2]; /* XFS_BM_MAXLEVELS */
 	uint			m_rmap_maxlevels; /* max rmap btree levels */
 	uint			m_refc_maxlevels; /* max refc btree levels */
+	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 */
diff --git a/libxfs/init.c b/libxfs/init.c
index f59444ab..12e25379 100644
--- a/libxfs/init.c
+++ b/libxfs/init.c
@@ -703,6 +703,18 @@ libxfs_buftarg_init(
 	mp->m_rtdev_targp = libxfs_buftarg_alloc(mp, rtdev, rfail);
 }
 
+/* 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);
+}
+
 /*
  * Mount structure initialization, provides a filled-in xfs_mount_t
  * such that the numerous XFS_* macros can be used.  If dev is zero,
@@ -754,6 +766,8 @@ libxfs_mount(
 	xfs_rmapbt_compute_maxlevels(mp);
 	xfs_refcountbt_compute_maxlevels(mp);
 
+	xfs_agbtree_compute_maxlevels(mp);
+
 	/*
 	 * Check that the data (and log if separate) are an ok size.
 	 */
diff --git a/libxfs/xfs_ag_resv.c b/libxfs/xfs_ag_resv.c
index b1392cda..546f34e8 100644
--- a/libxfs/xfs_ag_resv.c
+++ b/libxfs/xfs_ag_resv.c
@@ -90,7 +90,8 @@ 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);
 }