bcachefs: Proper refcounting for journal_keys

The btree iterator code overlays keys from the journal until journal
replay is finished; since we're now starting copygc/rebalance etc.
before replay is finished, this is multithreaded access and thus needs
refcounting.

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

Author: Kent Overstreet

fs/bcachefs/bcachefs.h

@@ -638,6 +638,8 @@ struct journal_keys {
 	size_t			gap;
 	size_t			nr;
 	size_t			size;
+	atomic_t		ref;
+	bool			initial_ref_held;
 };
 
 struct btree_trans_buf {

fs/bcachefs/btree_iter.c

@@ -2981,7 +2981,8 @@ struct btree_trans *__bch2_trans_get(struct bch_fs *c, unsigned fn_idx)
 	trans->fn_idx		= fn_idx;
 	trans->locking_wait.task = current;
 	trans->journal_replay_not_finished =
-		!test_bit(JOURNAL_REPLAY_DONE, &c->journal.flags);
+		unlikely(!test_bit(JOURNAL_REPLAY_DONE, &c->journal.flags)) &&
+		atomic_inc_not_zero(&c->journal_keys.ref);
 	closure_init_stack(&trans->ref);
 
 	s = btree_trans_stats(trans);
@@ -3098,6 +3099,9 @@ void bch2_trans_put(struct btree_trans *trans)
 			kfree(trans->fs_usage_deltas);
 	}
 
+	if (unlikely(trans->journal_replay_not_finished))
+		bch2_journal_keys_put(c);
+
 	if (trans->mem_bytes == BTREE_TRANS_MEM_MAX)
 		mempool_free(trans->mem, &c->btree_trans_mem_pool);
 	else

fs/bcachefs/btree_journal_iter.c

@@ -80,6 +80,8 @@ struct bkey_i *bch2_journal_keys_peek_upto(struct bch_fs *c, enum btree_id btree
 	struct journal_keys *keys = &c->journal_keys;
 	unsigned iters = 0;
 	struct journal_key *k;
+
+	BUG_ON(*idx > keys->nr);
 search:
 	if (!*idx)
 		*idx = __bch2_journal_key_search(keys, btree_id, level, pos);
@@ -189,10 +191,12 @@ int bch2_journal_key_insert_take(struct bch_fs *c, enum btree_id id,
 		/* Since @keys was full, there was no gap: */
 		memcpy(new_keys.d, keys->d, sizeof(keys->d[0]) * keys->nr);
 		kvfree(keys->d);
-		*keys = new_keys;
+		keys->d		= new_keys.d;
+		keys->nr	= new_keys.nr;
+		keys->size	= new_keys.size;
 
 		/* And now the gap is at the end: */
-		keys->gap = keys->nr;
+		keys->gap	= keys->nr;
 	}
 
 	journal_iters_move_gap(c, keys->gap, idx);
@@ -415,10 +419,16 @@ static int journal_sort_key_cmp(const void *_l, const void *_r)
 		cmp_int(l->journal_offset, r->journal_offset);
 }
 
-void bch2_journal_keys_free(struct journal_keys *keys)
+void bch2_journal_keys_put(struct bch_fs *c)
 {
+	struct journal_keys *keys = &c->journal_keys;
 	struct journal_key *i;
 
+	BUG_ON(atomic_read(&keys->ref) <= 0);
+
+	if (!atomic_dec_and_test(&keys->ref))
+		return;
+
 	move_gap(keys->d, keys->nr, keys->size, keys->gap, keys->nr);
 	keys->gap = keys->nr;
 
@@ -429,6 +439,8 @@ void bch2_journal_keys_free(struct journal_keys *keys)
 	kvfree(keys->d);
 	keys->d = NULL;
 	keys->nr = keys->gap = keys->size = 0;
+
+	bch2_journal_entries_free(c);
 }
 
 static void __journal_keys_sort(struct journal_keys *keys)

fs/bcachefs/btree_journal_iter.h

@@ -49,7 +49,15 @@ void bch2_btree_and_journal_iter_init_node_iter(struct btree_and_journal_iter *,
 						struct bch_fs *,
 						struct btree *);
 
-void bch2_journal_keys_free(struct journal_keys *);
+void bch2_journal_keys_put(struct bch_fs *);
+
+static inline void bch2_journal_keys_put_initial(struct bch_fs *c)
+{
+	if (c->journal_keys.initial_ref_held)
+		bch2_journal_keys_put(c);
+	c->journal_keys.initial_ref_held = false;
+}
+
 void bch2_journal_entries_free(struct bch_fs *);
 
 int bch2_journal_keys_sort(struct bch_fs *);

fs/bcachefs/recovery.c

@@ -167,6 +167,8 @@ static int bch2_journal_replay(struct bch_fs *c)
 			goto err;
 	}
 
+	BUG_ON(!atomic_read(&keys->ref));
+
 	for (i = 0; i < keys->nr; i++) {
 		k = keys_sorted[i];
 
@@ -188,6 +190,9 @@ static int bch2_journal_replay(struct bch_fs *c)
 		}
 	}
 
+	if (!c->opts.keep_journal)
+		bch2_journal_keys_put_initial(c);
+
 	replay_now_at(j, j->replay_journal_seq_end);
 	j->replay_journal_seq = 0;
 
@@ -909,10 +914,8 @@ int bch2_fs_recovery(struct bch_fs *c)
 	bch2_flush_fsck_errs(c);
 
 	if (!c->opts.keep_journal &&
-	    test_bit(JOURNAL_REPLAY_DONE, &c->journal.flags)) {
-		bch2_journal_keys_free(&c->journal_keys);
-		bch2_journal_entries_free(c);
-	}
+	    test_bit(JOURNAL_REPLAY_DONE, &c->journal.flags))
+		bch2_journal_keys_put_initial(c);
 	kfree(clean);
 
 	if (!ret && test_bit(BCH_FS_NEED_DELETE_DEAD_SNAPSHOTS, &c->flags)) {

fs/bcachefs/super.c

@@ -508,8 +508,8 @@ static void __bch2_fs_free(struct bch_fs *c)
 	bch2_io_clock_exit(&c->io_clock[WRITE]);
 	bch2_io_clock_exit(&c->io_clock[READ]);
 	bch2_fs_compress_exit(c);
-	bch2_journal_keys_free(&c->journal_keys);
-	bch2_journal_entries_free(c);
+	bch2_journal_keys_put_initial(c);
+	BUG_ON(atomic_read(&c->journal_keys.ref));
 	bch2_fs_btree_write_buffer_exit(c);
 	percpu_free_rwsem(&c->mark_lock);
 	free_percpu(c->online_reserved);
@@ -706,6 +706,8 @@ static struct bch_fs *bch2_fs_alloc(struct bch_sb *sb, struct bch_opts opts)
 
 	init_rwsem(&c->gc_lock);
 	mutex_init(&c->gc_gens_lock);
+	atomic_set(&c->journal_keys.ref, 1);
+	c->journal_keys.initial_ref_held = true;
 
 	for (i = 0; i < BCH_TIME_STAT_NR; i++)
 		bch2_time_stats_init(&c->times[i]);