From 23f88c1d165563c9432314f92a9e7b8b6e17c7a2 Mon Sep 17 00:00:00 2001 From: Kent Overstreet Date: Wed, 4 Dec 2024 20:43:01 -0500 Subject: [PATCH] bcachefs: Don't call bch2_btree_interior_update_will_free_node() until after update succeeds Originally, btree splits always succeeded once we got to the point of recursing to the btree_insert_node() call. But that changed when we switched to not taking intent locks all the way up to the root, and that introduced a bug, because bch2_btree_interior_update_will_free_node() cancels paending writes and reparents a node that's going to be made visible on disk by another btree update to the current btree update. This was discovered in recent backpointers work, because bch2_btree_interior_update_will_free_node() also clears the will_make_reachable flag, causing backpointer target lookup to spuriously thing it had found a dangling backpointer (when the backpointer just hadn't been created yet by btree_update_nodes_written()). Signed-off-by: Kent Overstreet --- fs/bcachefs/btree_update_interior.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/fs/bcachefs/btree_update_interior.c b/fs/bcachefs/btree_update_interior.c index f2a1d5d3d8d5..7d9dab95bdcf 100644 --- a/fs/bcachefs/btree_update_interior.c +++ b/fs/bcachefs/btree_update_interior.c @@ -1607,8 +1607,6 @@ static int btree_split(struct btree_update *as, struct btree_trans *trans, if (ret) return ret; - bch2_btree_interior_update_will_free_node(as, b); - if (b->nr.live_u64s > BTREE_SPLIT_THRESHOLD(c)) { struct btree *n[2]; @@ -1707,6 +1705,8 @@ static int btree_split(struct btree_update *as, struct btree_trans *trans, if (ret) goto err; + bch2_btree_interior_update_will_free_node(as, b); + if (n3) { bch2_btree_update_get_open_buckets(as, n3); bch2_btree_node_write(c, n3, SIX_LOCK_intent, 0); @@ -2063,9 +2063,6 @@ int __bch2_foreground_maybe_merge(struct btree_trans *trans, trace_and_count(c, btree_node_merge, trans, b); - bch2_btree_interior_update_will_free_node(as, b); - bch2_btree_interior_update_will_free_node(as, m); - n = bch2_btree_node_alloc(as, trans, b->c.level); SET_BTREE_NODE_SEQ(n->data, @@ -2101,6 +2098,9 @@ int __bch2_foreground_maybe_merge(struct btree_trans *trans, if (ret) goto err_free_update; + bch2_btree_interior_update_will_free_node(as, b); + bch2_btree_interior_update_will_free_node(as, m); + bch2_trans_verify_paths(trans); bch2_btree_update_get_open_buckets(as, n); @@ -2155,8 +2155,6 @@ int bch2_btree_node_rewrite(struct btree_trans *trans, if (ret) goto out; - bch2_btree_interior_update_will_free_node(as, b); - n = bch2_btree_node_alloc_replacement(as, trans, b); bch2_btree_build_aux_trees(n); @@ -2180,6 +2178,8 @@ int bch2_btree_node_rewrite(struct btree_trans *trans, if (ret) goto err; + bch2_btree_interior_update_will_free_node(as, b); + bch2_btree_update_get_open_buckets(as, n); bch2_btree_node_write(c, n, SIX_LOCK_intent, 0); -- 2.50.1