From 1841027c7de47527ed819a935b7aa340b9171eb5 Mon Sep 17 00:00:00 2001
From: Kent Overstreet <kent.overstreet@linux.dev>
Date: Thu, 4 Jul 2024 21:02:16 -0400
Subject: [PATCH] bcachefs: bch2_gc_btree() should not use btree_root_lock
btree_root_lock is for the root keys in btree_root, not the pointers to
the nodes themselves; this fixes a lock ordering issue between
btree_root_lock and btree node locks.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
---
fs/bcachefs/btree_gc.c | 30 ++++++++++++++++++++++--------
1 file changed, 22 insertions(+), 8 deletions(-)
diff --git a/fs/bcachefs/btree_gc.c b/fs/bcachefs/btree_gc.c
index 7c72a9e6f511a..a0deb8266011d 100644
--- a/fs/bcachefs/btree_gc.c
+++ b/fs/bcachefs/btree_gc.c
@@ -641,16 +641,30 @@ static int bch2_gc_btree(struct btree_trans *trans, enum btree_id btree, bool in
target_depth = 0;
/* root */
- mutex_lock(&c->btree_root_lock);
- struct btree *b = bch2_btree_id_root(c, btree)->b;
- if (!btree_node_fake(b)) {
+ do {
+retry_root:
+ bch2_trans_begin(trans);
+
+ struct btree_iter iter;
+ bch2_trans_node_iter_init(trans, &iter, btree, POS_MIN,
+ 0, bch2_btree_id_root(c, btree)->b->c.level, 0);
+ struct btree *b = bch2_btree_iter_peek_node(&iter);
+ ret = PTR_ERR_OR_ZERO(b);
+ if (ret)
+ goto err_root;
+
+ if (b != btree_node_root(c, b)) {
+ bch2_trans_iter_exit(trans, &iter);
+ goto retry_root;
+ }
+
gc_pos_set(c, gc_pos_btree(btree, b->c.level + 1, SPOS_MAX));
- ret = lockrestart_do(trans,
- bch2_gc_mark_key(trans, b->c.btree_id, b->c.level + 1,
- NULL, NULL, bkey_i_to_s_c(&b->key), initial));
+ struct bkey_s_c k = bkey_i_to_s_c(&b->key);
+ ret = bch2_gc_mark_key(trans, btree, b->c.level + 1, NULL, NULL, k, initial);
level = b->c.level;
- }
- mutex_unlock(&c->btree_root_lock);
+err_root:
+ bch2_trans_iter_exit(trans, &iter);
+ } while (bch2_err_matches(ret, BCH_ERR_transaction_restart));
if (ret)
return ret;
--
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