From 6623c0fcdffe22db466ec38c5f9f4b3a44c33003 Mon Sep 17 00:00:00 2001 From: Kent Overstreet Date: Fri, 17 Feb 2023 20:51:52 -0500 Subject: [PATCH] bcachefs: Add an assertion for using multiple btree_trans A thread should never be using more than one btree_trans - doing so is an invitation for deadlocks. Signed-off-by: Kent Overstreet --- fs/bcachefs/btree_iter.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/fs/bcachefs/btree_iter.c b/fs/bcachefs/btree_iter.c index 4ac1364acc8bb..5ab22c4c2b2eb 100644 --- a/fs/bcachefs/btree_iter.c +++ b/fs/bcachefs/btree_iter.c @@ -2955,6 +2955,15 @@ void __bch2_trans_init(struct btree_trans *trans, struct bch_fs *c, unsigned fn_ mutex_lock(&c->btree_trans_lock); list_for_each_entry(pos, &c->btree_trans_list, list) { + /* + * We'd much prefer to be stricter here and completely + * disallow multiple btree_trans in the same thread - + * but the data move path calls bch2_write when we + * already have a btree_trans initialized. + */ + BUG_ON(trans->locking_wait.task->pid == pos->locking_wait.task->pid && + bch2_trans_locked(pos)); + if (trans->locking_wait.task->pid < pos->locking_wait.task->pid) { list_add_tail(&trans->list, &pos->list); goto list_add_done; -- 2.30.2