From d8478ed6f131b6cfa93a22aa3bb3ace3f1dd3ae7 Mon Sep 17 00:00:00 2001
From: Zach Brown <zab@versity.com>
Date: Fri, 18 Dec 2020 09:24:27 -0800
Subject: [PATCH] Add scoutfs_btree_rebalance()

Add a btree call to just dirty to a leaf block, joining and splitting
along the way so that the blocks in the path satisfy the balance
constraints.

Signed-off-by: Zach Brown <zab@versity.com>
---
 kmod/src/btree.c | 24 ++++++++++++++++++++++++
 kmod/src/btree.h |  5 +++++
 2 files changed, 29 insertions(+)

diff --git a/kmod/src/btree.c b/kmod/src/btree.c
index 03ad5b96..f2e16924 100644
--- a/kmod/src/btree.c
+++ b/kmod/src/btree.c
@@ -1868,6 +1868,30 @@ int scoutfs_btree_set_parent(struct super_block *sb,
 			  key, 0, NULL, NULL, par_root);
 }
 
+/*
+ * Descend to the leaf, making sure that all the blocks conform to the
+ * balance constraints.  Blocks below the low threshold will be joined.
+ * This is called to split blocks that were too large for insertions,
+ * but those insertions were in a distant context and we don't bother
+ * communicating the val_len back here.  We just try to insert a max
+ * value.
+ *
+ * This always dirties all the way to the leaf.  It could be made more
+ * efficient with more btree walk flags to walk and check for blocks
+ * that need balancing, and then walks that don't dirty unless they need
+ * to join/split.
+ */
+int scoutfs_btree_rebalance(struct super_block *sb,
+			    struct scoutfs_alloc *alloc,
+			    struct scoutfs_block_writer *wri,
+			    struct scoutfs_btree_root *root,
+			    struct scoutfs_key *key)
+{
+	return btree_walk(sb, alloc, wri, root,
+			  BTW_DIRTY | BTW_INSERT | BTW_DELETE,
+			  key, SCOUTFS_BTREE_MAX_VAL_LEN, NULL, NULL, NULL);
+}
+
 struct merge_pos {
 	struct rb_node node;
 	struct scoutfs_btree_root *root;
diff --git a/kmod/src/btree.h b/kmod/src/btree.h
index 02228290..63447669 100644
--- a/kmod/src/btree.h
+++ b/kmod/src/btree.h
@@ -97,6 +97,11 @@ int scoutfs_btree_set_parent(struct super_block *sb,
 			     struct scoutfs_btree_root *root,
 			     struct scoutfs_key *key,
 			     struct scoutfs_btree_root *par_root);
+int scoutfs_btree_rebalance(struct super_block *sb,
+			    struct scoutfs_alloc *alloc,
+			    struct scoutfs_block_writer *wri,
+			    struct scoutfs_btree_root *root,
+			    struct scoutfs_key *key);
 
 /* merge input is a list of roots */
 struct scoutfs_btree_root_head {