bcachefs: Add a mechanism for running callbacks at trans commit time

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

fs/bcachefs/btree_iter.c

@@ -2144,6 +2144,7 @@ void bch2_trans_reset(struct btree_trans *trans, unsigned flags)
 	trans->nr_updates2		= 0;
 	trans->mem_top			= 0;
 
+	trans->hooks			= NULL;
 	trans->extra_journal_entries	= NULL;
 	trans->extra_journal_entry_u64s	= 0;
 

fs/bcachefs/btree_types.h

@@ -343,6 +343,14 @@ struct btree_insert_entry {
 #define BTREE_ITER_MAX		32
 #endif
 
+struct btree_trans_commit_hook;
+typedef int (btree_trans_commit_hook_fn)(struct btree_trans *, struct btree_trans_commit_hook *);
+
+struct btree_trans_commit_hook {
+	btree_trans_commit_hook_fn	*fn;
+	struct btree_trans_commit_hook	*next;
+};
+
 #define BTREE_TRANS_MEM_MAX	(1U << 14)
 
 struct btree_trans {
@@ -379,6 +387,7 @@ struct btree_trans {
 	struct btree_insert_entry *updates2;
 
 	/* update path: */
+	struct btree_trans_commit_hook *hooks;
 	struct jset_entry	*extra_journal_entries;
 	unsigned		extra_journal_entry_u64s;
 	struct journal_entry_pin *journal_pin;

fs/bcachefs/btree_update.h

@@ -77,6 +77,8 @@ int bch2_btree_node_update_key(struct bch_fs *, struct btree_iter *,
 
 int bch2_trans_update(struct btree_trans *, struct btree_iter *,
 		      struct bkey_i *, enum btree_trigger_flags);
+void bch2_trans_commit_hook(struct btree_trans *,
+			    struct btree_trans_commit_hook *);
 int __bch2_trans_commit(struct btree_trans *);
 
 /**

fs/bcachefs/btree_update_leaf.c

@@ -369,6 +369,7 @@ bch2_trans_commit_write_locked(struct btree_trans *trans,
 	struct bch_fs *c = trans->c;
 	struct bch_fs_usage_online *fs_usage = NULL;
 	struct btree_insert_entry *i;
+	struct btree_trans_commit_hook *h;
 	unsigned u64s = 0;
 	bool marking = false;
 	int ret;
@@ -386,6 +387,14 @@ bch2_trans_commit_write_locked(struct btree_trans *trans,
 
 	prefetch(&trans->c->journal.flags);
 
+	h = trans->hooks;
+	while (h) {
+		ret = h->fn(trans, h);
+		if (ret)
+			return ret;
+		h = h->next;
+	}
+
 	trans_for_each_update2(trans, i) {
 		/* Multiple inserts might go to same leaf: */
 		if (!same_leaf_as_prev(trans, i))
@@ -1057,6 +1066,13 @@ int bch2_trans_update(struct btree_trans *trans, struct btree_iter *iter,
 	return 0;
 }
 
+void bch2_trans_commit_hook(struct btree_trans *trans,
+			    struct btree_trans_commit_hook *h)
+{
+	h->next = trans->hooks;
+	trans->hooks = h;
+}
+
 int __bch2_btree_insert(struct btree_trans *trans,
 			enum btree_id id, struct bkey_i *k)
 {