bcachefs: growable btree_paths

XXX: we're allocating memory with btree locks held - bad

We need to plumb through an error path so we can do
allocate_dropping_locks() - but we're merging this now because it fixes
a transaction path overflow caused by indirect extent fragmentation, and
the resize path is rare.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_iter.c

@@ -1209,7 +1209,6 @@ static btree_path_idx_t btree_path_clone(struct btree_trans *trans, btree_path_i
 					 bool intent)
 {
 	btree_path_idx_t new = btree_path_alloc(trans, src);
-
 	btree_path_copy(trans, trans->paths + new, trans->paths + src);
 	__btree_path_get(trans->paths + new, intent);
 	return new;
@@ -1515,7 +1514,47 @@ int __bch2_btree_trans_too_many_iters(struct btree_trans *trans)
 static noinline void btree_path_overflow(struct btree_trans *trans)
 {
 	bch2_dump_trans_paths_updates(trans);
-	panic("trans path overflow\n");
+	bch_err(trans->c, "trans path overflow");
+}
+
+static noinline void btree_paths_realloc(struct btree_trans *trans)
+{
+	unsigned nr = trans->nr_paths * 2;
+
+	void *p = kzalloc(BITS_TO_LONGS(nr) * sizeof(unsigned long) +
+			  sizeof(struct btree_trans_paths) +
+			  nr * sizeof(struct btree_path) +
+			  nr * sizeof(btree_path_idx_t) + 8 +
+			  nr * sizeof(struct btree_insert_entry), GFP_KERNEL|__GFP_NOFAIL);
+
+	unsigned long *paths_allocated = p;
+	memcpy(paths_allocated, trans->paths_allocated, BITS_TO_LONGS(trans->nr_paths) * sizeof(unsigned long));
+	p += BITS_TO_LONGS(nr) * sizeof(unsigned long);
+
+	p += sizeof(struct btree_trans_paths);
+	struct btree_path *paths = p;
+	*trans_paths_nr(paths) = nr;
+	memcpy(paths, trans->paths, trans->nr_paths * sizeof(struct btree_path));
+	p += nr * sizeof(struct btree_path);
+
+	btree_path_idx_t *sorted = p;
+	memcpy(sorted, trans->sorted, trans->nr_sorted * sizeof(btree_path_idx_t));
+	p += nr * sizeof(btree_path_idx_t) + 8;
+
+	struct btree_insert_entry *updates = p;
+	memcpy(updates, trans->updates, trans->nr_paths * sizeof(struct btree_insert_entry));
+
+	unsigned long *old = trans->paths_allocated;
+
+	rcu_assign_pointer(trans->paths_allocated,	paths_allocated);
+	rcu_assign_pointer(trans->paths,		paths);
+	rcu_assign_pointer(trans->sorted,		sorted);
+	rcu_assign_pointer(trans->updates,		updates);
+
+	trans->nr_paths		= nr;
+
+	if (old != trans->_paths_allocated)
+		kfree_rcu_mightsleep(old);
 }
 
 static inline btree_path_idx_t btree_path_alloc(struct btree_trans *trans,
@@ -1523,8 +1562,14 @@ static inline btree_path_idx_t btree_path_alloc(struct btree_trans *trans,
 {
 	btree_path_idx_t idx = find_first_zero_bit(trans->paths_allocated, trans->nr_paths);
 
-	if (unlikely(idx == trans->nr_paths))
+	if (unlikely(idx == trans->nr_paths)) {
+		if (trans->nr_paths == BTREE_ITER_MAX) {
 			btree_path_overflow(trans);
+			return 0;
+		}
+
+		btree_paths_realloc(trans);
+	}
 
 	/*
 	 * Do this before marking the new path as allocated, since it won't be
@@ -2607,21 +2652,18 @@ void __bch2_btree_trans_sort_paths(struct btree_trans *trans)
 static inline void btree_path_list_remove(struct btree_trans *trans,
 					  struct btree_path *path)
 {
-	unsigned i;
-
 	EBUG_ON(path->sorted_idx >= trans->nr_sorted);
 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
 	trans->nr_sorted--;
 	memmove_u64s_down_small(trans->sorted + path->sorted_idx,
 				trans->sorted + path->sorted_idx + 1,
-				DIV_ROUND_UP(trans->nr_sorted - path->sorted_idx, 8));
+				DIV_ROUND_UP(trans->nr_sorted - path->sorted_idx,
+					     sizeof(u64) / sizeof(btree_path_idx_t)));
 #else
 	array_remove_item(trans->sorted, trans->nr_sorted, path->sorted_idx);
 #endif
-	for (i = path->sorted_idx; i < trans->nr_sorted; i++)
+	for (unsigned i = path->sorted_idx; i < trans->nr_sorted; i++)
 		trans->paths[trans->sorted[i]].sorted_idx = i;
-
-	path->sorted_idx = U8_MAX;
 }
 
 static inline void btree_path_list_add(struct btree_trans *trans,
@@ -2629,21 +2671,21 @@ static inline void btree_path_list_add(struct btree_trans *trans,
 				       btree_path_idx_t path_idx)
 {
 	struct btree_path *path = trans->paths + path_idx;
-	unsigned i;
 
 	path->sorted_idx = pos ? trans->paths[pos].sorted_idx + 1 : trans->nr_sorted;
 
 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
 	memmove_u64s_up_small(trans->sorted + path->sorted_idx + 1,
 			      trans->sorted + path->sorted_idx,
-			      DIV_ROUND_UP(trans->nr_sorted - path->sorted_idx, 8));
+			      DIV_ROUND_UP(trans->nr_sorted - path->sorted_idx,
+					   sizeof(u64) / sizeof(btree_path_idx_t)));
 	trans->nr_sorted++;
 	trans->sorted[path->sorted_idx] = path_idx;
 #else
 	array_insert_item(trans->sorted, trans->nr_sorted, path->sorted_idx, path_idx);
 #endif
 
-	for (i = path->sorted_idx; i < trans->nr_sorted; i++)
+	for (unsigned i = path->sorted_idx; i < trans->nr_sorted; i++)
 		trans->paths[trans->sorted[i]].sorted_idx = i;
 
 	btree_trans_verify_sorted_refs(trans);
@@ -2939,7 +2981,7 @@ struct btree_trans *__bch2_trans_get(struct bch_fs *c, unsigned fn_idx)
 	trans->paths		= trans->_paths;
 	trans->updates		= trans->_updates;
 
-	*trans_paths_nr(trans->paths) = BTREE_ITER_MAX;
+	*trans_paths_nr(trans->paths) = BTREE_ITER_INITIAL;
 
 	trans->paths_allocated[0] = 1;
 
@@ -3020,6 +3062,13 @@ void bch2_trans_put(struct btree_trans *trans)
 	if (unlikely(trans->journal_replay_not_finished))
 		bch2_journal_keys_put(c);
 
+	unsigned long *paths_allocated = trans->paths_allocated;
+	trans->paths_allocated	= NULL;
+	trans->paths		= NULL;
+
+	if (paths_allocated != trans->_paths_allocated)
+		kfree_rcu_mightsleep(paths_allocated);
+
 	if (trans->mem_bytes == BTREE_TRANS_MEM_MAX)
 		mempool_free(trans->mem, &c->btree_trans_mem_pool);
 	else

fs/bcachefs/btree_iter.h

@@ -642,7 +642,7 @@ int __bch2_btree_trans_too_many_iters(struct btree_trans *);
 
 static inline int btree_trans_too_many_iters(struct btree_trans *trans)
 {
-	if (bitmap_weight(trans->paths_allocated, trans->nr_paths) > BTREE_ITER_MAX - 8)
+	if (bitmap_weight(trans->paths_allocated, trans->nr_paths) > BTREE_ITER_INITIAL - 8)
 		return __bch2_btree_trans_too_many_iters(trans);
 
 	return 0;

fs/bcachefs/btree_types.h

@@ -358,7 +358,8 @@ struct btree_insert_entry {
 	unsigned long		ip_allocated;
 };
 
-#define BTREE_ITER_MAX		64
+#define BTREE_ITER_INITIAL		64
+#define BTREE_ITER_MAX			(1U << 10)
 
 struct btree_trans_commit_hook;
 typedef int (btree_trans_commit_hook_fn)(struct btree_trans *, struct btree_trans_commit_hook *);
@@ -382,7 +383,7 @@ struct btree_trans {
 
 	unsigned long		*paths_allocated;
 	struct btree_path	*paths;
-	u8			*sorted;
+	btree_path_idx_t	*sorted;
 	struct btree_insert_entry *updates;
 
 	void			*mem;
@@ -438,11 +439,11 @@ struct btree_trans {
 	struct list_head	list;
 	struct closure		ref;
 
-	unsigned long		_paths_allocated[BITS_TO_LONGS(BTREE_ITER_MAX)];
+	unsigned long		_paths_allocated[BITS_TO_LONGS(BTREE_ITER_INITIAL)];
 	struct btree_trans_paths trans_paths;
-	struct btree_path	_paths[BTREE_ITER_MAX];
-	u8			_sorted[BTREE_ITER_MAX + 8];
-	struct btree_insert_entry _updates[BTREE_ITER_MAX];
+	struct btree_path	_paths[BTREE_ITER_INITIAL];
+	btree_path_idx_t	_sorted[BTREE_ITER_INITIAL + 4];
+	struct btree_insert_entry _updates[BTREE_ITER_INITIAL];
 };
 
 static inline struct btree_path *btree_iter_path(struct btree_trans *trans, struct btree_iter *iter)

fs/bcachefs/extent_update.c

@@ -100,7 +100,7 @@ static int count_iters_for_insert(struct btree_trans *trans,
 	return ret2 ?: ret;
 }
 
-#define EXTENT_ITERS_MAX	(BTREE_ITER_MAX / 3)
+#define EXTENT_ITERS_MAX	(BTREE_ITER_INITIAL / 3)
 
 int bch2_extent_atomic_end(struct btree_trans *trans,
 			   struct btree_iter *iter,