bcachefs: Check for btree locks held on transaction init

Ideally we would disallow multiple btree_trans being initialized within
the same process - and hopefully we will at some point, the stack usage
is excessive - but for now there are a couple places where we do this:

 - transaction commit error path -> journal reclaim - btree key cache
   flush
 - move data path -> do_pending_writes -> write path -> bucket
   allocation (in the near future when bucket allocation switches to
   using a freespace btree)

In order to avoid deadlocking the first btree_trans must have been
unlocked with bch2_trans_unlock() before using the second btree_trans -
this patch adds an assertion to bch2_trans_init() that verifies that
this has been done when lockdep is enabled.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/bcachefs/btree_iter.c b/fs/bcachefs/btree_iter.c
index 39db0d08063f..565c811703ca 100644
--- a/fs/bcachefs/btree_iter.c
+++ b/fs/bcachefs/btree_iter.c
@@ -3076,6 +3076,8 @@ void __bch2_trans_init(struct btree_trans *trans, struct bch_fs *c,
 		       const char *fn)
 	__acquires(&c->btree_trans_barrier)
 {
+	BUG_ON(lock_class_is_held(&bch2_btree_node_lock_key));
+
 	memset(trans, 0, sizeof(*trans));
 	trans->c		= c;
 	trans->fn		= fn;