bcachefs: Check btree topology at startup

When initial btree gc was changed to overlay journal keys as it walks
the btree, it also stopped checking btree topology.

Previously, checking btree topology was a fairly complicated affair -
but it's much easier now that btree_ptr_v2 has min_key in the pointer.

This rewrites the old range_checks code and uses it in both runtime and
initial gc.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_gc.c

@@ -49,64 +49,42 @@ static inline void gc_pos_set(struct bch_fs *c, struct gc_pos new_pos)
 	__gc_pos_set(c, new_pos);
 }
 
-/* range_checks - for validating min/max pos of each btree node: */
-
-struct range_checks {
-	struct range_level {
-		struct bpos	min;
-		struct bpos	max;
-	}			l[BTREE_MAX_DEPTH];
-	unsigned		depth;
-};
-
-static void btree_node_range_checks_init(struct range_checks *r, unsigned depth)
+static int bch2_gc_check_topology(struct bch_fs *c,
+				  struct bkey_s_c k,
+				  struct bpos *expected_start,
+				  struct bpos expected_end,
+				  bool is_last)
 {
-	unsigned i;
-
-	for (i = 0; i < BTREE_MAX_DEPTH; i++)
-		r->l[i].min = r->l[i].max = POS_MIN;
-	r->depth = depth;
-}
-
-static void btree_node_range_checks(struct bch_fs *c, struct btree *b,
-				    struct range_checks *r)
-{
-	struct range_level *l = &r->l[b->c.level];
-
-	struct bpos expected_min = bkey_cmp(l->min, l->max)
-		? bkey_successor(l->max)
-		: l->max;
-
-	bch2_fs_inconsistent_on(bkey_cmp(b->data->min_key, expected_min), c,
-		"btree node has incorrect min key: %llu:%llu != %llu:%llu",
-		b->data->min_key.inode,
-		b->data->min_key.offset,
-		expected_min.inode,
-		expected_min.offset);
-
-	l->max = b->data->max_key;
-
-	if (b->c.level > r->depth) {
-		l = &r->l[b->c.level - 1];
+	int ret = 0;
 
-		bch2_fs_inconsistent_on(bkey_cmp(b->data->min_key, l->min), c,
-			"btree node min doesn't match min of child nodes: %llu:%llu != %llu:%llu",
-			b->data->min_key.inode,
-			b->data->min_key.offset,
-			l->min.inode,
-			l->min.offset);
+	if (k.k->type == KEY_TYPE_btree_ptr_v2) {
+		struct bkey_s_c_btree_ptr_v2 bp = bkey_s_c_to_btree_ptr_v2(k);
 
-		bch2_fs_inconsistent_on(bkey_cmp(b->data->max_key, l->max), c,
-			"btree node max doesn't match max of child nodes: %llu:%llu != %llu:%llu",
-			b->data->max_key.inode,
-			b->data->max_key.offset,
-			l->max.inode,
-			l->max.offset);
+		if (fsck_err_on(bkey_cmp(*expected_start, bp.v->min_key), c,
+				"btree node with incorrect min_key: got %llu:%llu, should be %llu:%llu",
+				bp.v->min_key.inode,
+				bp.v->min_key.offset,
+				expected_start->inode,
+				expected_start->offset)) {
+			BUG();
+		}
+	}
 
-		if (bkey_cmp(b->data->max_key, POS_MAX))
-			l->min = l->max =
-				bkey_successor(b->data->max_key);
+	*expected_start = bkey_cmp(k.k->p, POS_MAX)
+		? bkey_successor(k.k->p)
+		: k.k->p;
+
+	if (fsck_err_on(is_last &&
+			bkey_cmp(k.k->p, expected_end), c,
+			"btree node with incorrect max_key: got %llu:%llu, should be %llu:%llu",
+			k.k->p.inode,
+			k.k->p.offset,
+			expected_end.inode,
+			expected_end.offset)) {
+		BUG();
 	}
+fsck_err:
+	return ret;
 }
 
 /* marking of btree keys/nodes: */
@@ -188,6 +166,7 @@ static int bch2_gc_mark_key(struct bch_fs *c, struct bkey_s_c k,
 static int btree_gc_mark_node(struct bch_fs *c, struct btree *b, u8 *max_stale,
 			      bool initial)
 {
+	struct bpos next_node_start = b->data->min_key;
 	struct btree_node_iter iter;
 	struct bkey unpacked;
 	struct bkey_s_c k;
@@ -198,13 +177,25 @@ static int btree_gc_mark_node(struct bch_fs *c, struct btree *b, u8 *max_stale,
 	if (!btree_node_type_needs_gc(btree_node_type(b)))
 		return 0;
 
-	for_each_btree_node_key_unpack(b, k, &iter,
-				       &unpacked) {
+	bch2_btree_node_iter_init_from_start(&iter, b);
+
+	while ((k = bch2_btree_node_iter_peek_unpack(&iter, b, &unpacked)).k) {
 		bch2_bkey_debugcheck(c, b, k);
 
 		ret = bch2_gc_mark_key(c, k, max_stale, initial);
 		if (ret)
 			break;
+
+		bch2_btree_node_iter_advance(&iter, b);
+
+		if (b->c.level) {
+			ret = bch2_gc_check_topology(c, k,
+					&next_node_start,
+					b->data->max_key,
+					bch2_btree_node_iter_end(&iter));
+			if (ret)
+				break;
+		}
 	}
 
 	return ret;
@@ -216,7 +207,6 @@ static int bch2_gc_btree(struct bch_fs *c, enum btree_id btree_id,
 	struct btree_trans trans;
 	struct btree_iter *iter;
 	struct btree *b;
-	struct range_checks r;
 	unsigned depth = metadata_only			? 1
 		: expensive_debug_checks(c)		? 0
 		: !btree_node_type_needs_gc(btree_id)	? 1
@@ -228,12 +218,8 @@ static int bch2_gc_btree(struct bch_fs *c, enum btree_id btree_id,
 
 	gc_pos_set(c, gc_pos_btree(btree_id, POS_MIN, 0));
 
-	btree_node_range_checks_init(&r, depth);
-
 	__for_each_btree_node(&trans, iter, btree_id, POS_MIN,
 			      0, depth, BTREE_ITER_PREFETCH, b) {
-		btree_node_range_checks(c, b, &r);
-
 		bch2_verify_btree_nr_keys(b);
 
 		gc_pos_set(c, gc_pos_btree_node(b));
@@ -275,11 +261,12 @@ static int bch2_gc_btree(struct bch_fs *c, enum btree_id btree_id,
 }
 
 static int bch2_gc_btree_init_recurse(struct bch_fs *c, struct btree *b,
-					 struct journal_keys *journal_keys,
-					 unsigned target_depth)
+				      struct journal_keys *journal_keys,
+				      unsigned target_depth)
 {
 	struct btree_and_journal_iter iter;
 	struct bkey_s_c k;
+	struct bpos next_node_start = b->data->min_key;
 	u8 max_stale = 0;
 	int ret = 0;
 
@@ -288,28 +275,46 @@ static int bch2_gc_btree_init_recurse(struct bch_fs *c, struct btree *b,
 	while ((k = bch2_btree_and_journal_iter_peek(&iter)).k) {
 		bch2_bkey_debugcheck(c, b, k);
 
+		BUG_ON(bkey_cmp(k.k->p, b->data->min_key) < 0);
+		BUG_ON(bkey_cmp(k.k->p, b->data->max_key) > 0);
+
 		ret = bch2_gc_mark_key(c, k, &max_stale, true);
 		if (ret)
 			break;
 
-		if (b->c.level > target_depth) {
+		if (b->c.level) {
 			struct btree *child;
 			BKEY_PADDED(k) tmp;
 
 			bkey_reassemble(&tmp.k, k);
+			k = bkey_i_to_s_c(&tmp.k);
+
+			bch2_btree_and_journal_iter_advance(&iter);
 
-			child = bch2_btree_node_get_noiter(c, &tmp.k,
-						b->c.btree_id, b->c.level - 1);
-			ret = PTR_ERR_OR_ZERO(child);
+			ret = bch2_gc_check_topology(c, k,
+					&next_node_start,
+					b->data->max_key,
+					!bch2_btree_and_journal_iter_peek(&iter).k);
 			if (ret)
 				break;
 
-			bch2_gc_btree_init_recurse(c, child,
-					journal_keys, target_depth);
-			six_unlock_read(&child->c.lock);
-		}
+			if (b->c.level > target_depth) {
+				child = bch2_btree_node_get_noiter(c, &tmp.k,
+							b->c.btree_id, b->c.level - 1);
+				ret = PTR_ERR_OR_ZERO(child);
+				if (ret)
+					break;
 
-		bch2_btree_and_journal_iter_advance(&iter);
+				ret = bch2_gc_btree_init_recurse(c, child,
+						journal_keys, target_depth);
+				six_unlock_read(&child->c.lock);
+
+				if (ret)
+					break;
+			}
+		} else {
+			bch2_btree_and_journal_iter_advance(&iter);
+		}
 	}
 
 	return ret;
@@ -334,6 +339,20 @@ static int bch2_gc_btree_init(struct bch_fs *c,
 		return 0;
 
 	six_lock_read(&b->c.lock, NULL, NULL);
+	if (fsck_err_on(bkey_cmp(b->data->min_key, POS_MIN), c,
+			"btree root with incorrect min_key: %llu:%llu",
+			b->data->min_key.inode,
+			b->data->min_key.offset)) {
+		BUG();
+	}
+
+	if (fsck_err_on(bkey_cmp(b->data->max_key, POS_MAX), c,
+			"btree root with incorrect min_key: %llu:%llu",
+			b->data->max_key.inode,
+			b->data->max_key.offset)) {
+		BUG();
+	}
+
 	if (b->c.level >= target_depth)
 		ret = bch2_gc_btree_init_recurse(c, b,
 					journal_keys, target_depth);
@@ -341,6 +360,7 @@ static int bch2_gc_btree_init(struct bch_fs *c,
 	if (!ret)
 		ret = bch2_gc_mark_key(c, bkey_i_to_s_c(&b->key),
 				       &max_stale, true);
+fsck_err:
 	six_unlock_read(&b->c.lock);
 
 	return ret;