From 89cc04ae0d68f7e8d7b2aeb28958b00b5ca2459a Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <djwong@kernel.org>
Date: Tue, 15 Oct 2024 12:44:34 -0700
Subject: [PATCH] xfs: add metadata reservations for realtime rmap btrees

Reserve some free blocks so that we will always have enough free blocks
in the data volume to handle expansion of the realtime rmap btree.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
---
 libxfs/xfs_metafile.c     |  6 +++++-
 libxfs/xfs_rtrmap_btree.c | 41 +++++++++++++++++++++++++++++++++++++++
 libxfs/xfs_rtrmap_btree.h |  2 ++
 3 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/libxfs/xfs_metafile.c b/libxfs/xfs_metafile.c
index 435b8f8bf..ce0e61f02 100644
--- a/libxfs/xfs_metafile.c
+++ b/libxfs/xfs_metafile.c
@@ -202,7 +202,11 @@ void
 xfs_metafile_resv_free(
 	struct xfs_inode	*ip)
 {
-	if (!ip)
+	/*
+	 * We can end up here for the rt bitmap/summary inodes that don't have
+	 * reservations.  Just exist early in that case.
+	 */
+	if (!ip || !ip->i_delayed_blks)
 		return;
 
 	ASSERT(xfs_is_metadir_inode(ip));
diff --git a/libxfs/xfs_rtrmap_btree.c b/libxfs/xfs_rtrmap_btree.c
index 6e780f1bd..93ab59ff0 100644
--- a/libxfs/xfs_rtrmap_btree.c
+++ b/libxfs/xfs_rtrmap_btree.c
@@ -539,3 +539,44 @@ xfs_rtrmapbt_compute_maxlevels(
 	/* Add one level to handle the inode root level. */
 	mp->m_rtrmap_maxlevels = min(d_maxlevels, r_maxlevels) + 1;
 }
+
+/* Calculate the rtrmap btree size for some records. */
+static unsigned long long
+xfs_rtrmapbt_calc_size(
+	struct xfs_mount	*mp,
+	unsigned long long	len)
+{
+	return xfs_btree_calc_size(mp->m_rtrmap_mnr, len);
+}
+
+/*
+ * Calculate the maximum rmap btree size.
+ */
+static unsigned long long
+xfs_rtrmapbt_max_size(
+	struct xfs_mount	*mp,
+	xfs_rtblock_t		rtblocks)
+{
+	/* Bail out if we're uninitialized, which can happen in mkfs. */
+	if (mp->m_rtrmap_mxr[0] == 0)
+		return 0;
+
+	return xfs_rtrmapbt_calc_size(mp, rtblocks);
+}
+
+/*
+ * Figure out how many blocks to reserve and how many are used by this btree.
+ */
+xfs_filblks_t
+xfs_rtrmapbt_calc_reserves(
+	struct xfs_mount	*mp)
+{
+	uint32_t		blocks = mp->m_groups[XG_TYPE_RTG].blocks;
+
+	if (!xfs_has_rtrmapbt(mp))
+		return 0;
+
+	/* 1/64th (~1.5%) of the space, and enough for 1 record per block. */
+	return max_t(xfs_filblks_t, blocks >> 6,
+			xfs_rtrmapbt_max_size(mp, blocks));
+}
diff --git a/libxfs/xfs_rtrmap_btree.h b/libxfs/xfs_rtrmap_btree.h
index 63aabae2e..ad5cb1078 100644
--- a/libxfs/xfs_rtrmap_btree.h
+++ b/libxfs/xfs_rtrmap_btree.h
@@ -79,4 +79,6 @@ unsigned int xfs_rtrmapbt_maxlevels_ondisk(void);
 int __init xfs_rtrmapbt_init_cur_cache(void);
 void xfs_rtrmapbt_destroy_cur_cache(void);
 
+xfs_filblks_t xfs_rtrmapbt_calc_reserves(struct xfs_mount *mp);
+
 #endif	/* __XFS_RTRMAP_BTREE_H__ */
-- 
2.50.1