bcache: Explicitly track btree node's parent

This is prep work for the reworked btree insertion code.

The way we set b->parent is ugly and hacky... the problem is, when
btree_split() or garbage collection splits or rewrites a btree node, the
parent changes for all its (potentially already cached) children.

I may change this later and add some code to look through the btree node
cache and find all our cached child nodes and change the parent pointer
then...

Signed-off-by: Kent Overstreet <kmo@daterainc.com>

1 files changed, 10 insertions, 4 deletions

diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
index d1734d9d9c7..87299baa8a1 100644
--- a/drivers/md/bcache/btree.c
+++ b/drivers/md/bcache/btree.c
@@ -884,6 +884,7 @@ out:
 
 	lock_set_subclass(&b->lock.dep_map, level + 1, _THIS_IP_);
 	b->level	= level;
+	b->parent	= (void *) ~0UL;
 
 	mca_reinit(b);
 
@@ -1898,7 +1899,7 @@ out:
 
 static int btree_split(struct btree *b, struct btree_op *op)
 {
-	bool split, root = b == b->c->root;
+	bool split;
 	struct btree *n1, *n2 = NULL, *n3 = NULL;
 	uint64_t start_time = local_clock();
 
@@ -1920,7 +1921,7 @@ static int btree_split(struct btree *b, struct btree_op *op)
 		if (IS_ERR(n2))
 			goto err_free1;
 
-		if (root) {
+		if (!b->parent) {
 			n3 = bch_btree_node_alloc(b->c, b->level + 1, &op->cl);
 			if (IS_ERR(n3))
 				goto err_free2;
@@ -1928,7 +1929,8 @@ static int btree_split(struct btree *b, struct btree_op *op)
 
 		bch_btree_insert_keys(n1, op);
 
-		/* Has to be a linear search because we don't have an auxiliary
+		/*
+		 * Has to be a linear search because we don't have an auxiliary
 		 * search tree yet
 		 */
 
@@ -1960,6 +1962,8 @@ static int btree_split(struct btree *b, struct btree_op *op)
 	bch_btree_node_write(n1, &op->cl);
 
 	if (n3) {
+		/* Depth increases, make a new root */
+
 		bkey_copy_key(&n3->key, &MAX_KEY);
 		bch_btree_insert_keys(n3, op);
 		bch_btree_node_write(n3, &op->cl);
@@ -1967,7 +1971,9 @@ static int btree_split(struct btree *b, struct btree_op *op)
 		closure_sync(&op->cl);
 		bch_btree_set_root(n3);
 		rw_unlock(true, n3);
-	} else if (root) {
+	} else if (!b->parent) {
+		/* Root filled up but didn't need to be split */
+
 		op->keys.top = op->keys.bottom;
 		closure_sync(&op->cl);
 		bch_btree_set_root(n1);