bcachefs: tighten up reserve sizes

3 files changed, 24 insertions, 22 deletions

diff --git a/fs/bcachefs/bcachefs.h b/fs/bcachefs/bcachefs.h
index 6beff8810c09..4702b016945e 100644
--- a/fs/bcachefs/bcachefs.h
+++ b/fs/bcachefs/bcachefs.h
@@ -302,21 +302,14 @@ enum bch_time_stats {
 #include "rebalance_types.h"
 #include "super_types.h"
 
-/*
- * Number of nodes we might have to allocate in a worst case btree split
- * operation - we split all the way up to the root, then allocate a new root.
- */
-#define btree_reserve_required_nodes(depth)	(((depth) + 1) * 2 + 1)
-
 /* Number of nodes btree coalesce will try to coalesce at once */
 #define GC_MERGE_NODES		4U
 
 /* Maximum number of nodes we might need to allocate atomically: */
-#define BTREE_RESERVE_MAX						\
-	(btree_reserve_required_nodes(BTREE_MAX_DEPTH) + GC_MERGE_NODES)
+#define BTREE_RESERVE_MAX	(BTREE_MAX_DEPTH + (BTREE_MAX_DEPTH - 1))
 
 /* Size of the freelist we allocate btree nodes from: */
-#define BTREE_NODE_RESERVE		(BTREE_RESERVE_MAX * 4)
+#define BTREE_NODE_RESERVE	(BTREE_RESERVE_MAX * 4)
 
 struct btree;
 
diff --git a/fs/bcachefs/btree_update_interior.c b/fs/bcachefs/btree_update_interior.c
index c3ecc1e96726..817c3dee553e 100644
--- a/fs/bcachefs/btree_update_interior.c
+++ b/fs/bcachefs/btree_update_interior.c
@@ -1704,10 +1704,10 @@ retry:
 	}
 
 	as = bch2_btree_update_start(c, iter->btree_id,
-				     btree_update_reserve_required(c, b),
-				     BTREE_INSERT_NOFAIL|
-				     BTREE_INSERT_USE_RESERVE,
-				     &cl);
+			 btree_update_reserve_required(c, parent) + 1,
+			 BTREE_INSERT_NOFAIL|
+			 BTREE_INSERT_USE_RESERVE,
+			 &cl);
 	if (IS_ERR(as)) {
 		ret = PTR_ERR(as);
 		goto out_unlock;
@@ -1778,8 +1778,10 @@ static int __btree_node_rewrite(struct bch_fs *c, struct btree_iter *iter,
 	struct btree_update *as;
 
 	as = bch2_btree_update_start(c, iter->btree_id,
-				     btree_update_reserve_required(c, b),
-				     flags, cl);
+		(parent
+		 ? btree_update_reserve_required(c, parent)
+		 : 0) + 1,
+		flags, cl);
 	if (IS_ERR(as)) {
 		trace_btree_gc_rewrite_node_fail(c, b);
 		return PTR_ERR(as);
@@ -1966,6 +1968,7 @@ static void __bch2_btree_node_update_key(struct bch_fs *c,
 int bch2_btree_node_update_key(struct bch_fs *c, struct btree_iter *iter,
 			       struct btree *b, struct bkey_i_extent *new_key)
 {
+	struct btree *parent = btree_node_parent(iter, b);
 	struct btree_update *as = NULL;
 	struct btree *new_hash = NULL;
 	struct closure cl;
@@ -2003,11 +2006,12 @@ int bch2_btree_node_update_key(struct bch_fs *c, struct btree_iter *iter,
 	}
 
 	as = bch2_btree_update_start(c, iter->btree_id,
-				     btree_update_reserve_required(c, b),
-				     BTREE_INSERT_NOFAIL|
-				     BTREE_INSERT_USE_RESERVE|
-				     BTREE_INSERT_USE_ALLOC_RESERVE,
-				     &cl);
+		parent ? btree_update_reserve_required(c, parent) : 0,
+		BTREE_INSERT_NOFAIL|
+		BTREE_INSERT_USE_RESERVE|
+		BTREE_INSERT_USE_ALLOC_RESERVE,
+		&cl);
+
 	if (IS_ERR(as)) {
 		ret = PTR_ERR(as);
 		if (ret == -EAGAIN)
diff --git a/fs/bcachefs/btree_update_interior.h b/fs/bcachefs/btree_update_interior.h
index 25bfc7ab9ee0..abf14e4c41dc 100644
--- a/fs/bcachefs/btree_update_interior.h
+++ b/fs/bcachefs/btree_update_interior.h
@@ -183,9 +183,14 @@ void bch2_btree_root_alloc(struct bch_fs *, enum btree_id);
 static inline unsigned btree_update_reserve_required(struct bch_fs *c,
 						     struct btree *b)
 {
-	unsigned depth = btree_node_root(c, b)->level - b->level;
+	unsigned depth = btree_node_root(c, b)->level - b->level + 1;
 
-	return btree_reserve_required_nodes(depth);
+	/*
+	 * Number of nodes we might have to allocate in a worst case btree
+	 * split operation - we split all the way up to the root, then allocate
+	 * a new root.
+	 */
+	return depth * 2 + 1;
 }
 
 static inline void btree_node_reset_sib_u64s(struct btree *b)