bcachefs: btree node scan: fall back to comparing by journal seq

highly damaged filesystems, or filesystems that have been damaged and
repair and damaged again, may have sequence numbers we can't fully trust
- which in itself is something we need to debug.

Add a journal_seq fallback so that repair doesn't get stuck.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_io.c

@@ -1006,6 +1006,7 @@ int bch2_btree_node_read_done(struct bch_fs *c, struct bch_dev *ca,
 		BTREE_PTR_RANGE_UPDATED(&bkey_i_to_btree_ptr_v2(&b->key)->v);
 	unsigned u64s;
 	unsigned ptr_written = btree_ptr_sectors_written(bkey_i_to_s_c(&b->key));
+	u64 max_journal_seq = 0;
 	struct printbuf buf = PRINTBUF;
 	int ret = 0, retry_read = 0, write = READ;
 	u64 start_time = local_clock();
@@ -1181,6 +1182,8 @@ int bch2_btree_node_read_done(struct bch_fs *c, struct bch_dev *ca,
 		sort_iter_add(iter,
 			      vstruct_idx(i, 0),
 			      vstruct_last(i));
+
+		max_journal_seq = max(max_journal_seq, le64_to_cpu(i->journal_seq));
 	}
 
 	if (ptr_written) {
@@ -1217,6 +1220,7 @@ int bch2_btree_node_read_done(struct bch_fs *c, struct bch_dev *ca,
 	swap(sorted, b->data);
 	set_btree_bset(b, b->set, &b->data->keys);
 	b->nsets = 1;
+	b->data->keys.journal_seq = cpu_to_le64(max_journal_seq);
 
 	BUG_ON(b->nr.live_u64s != u64s);
 

fs/bcachefs/btree_node_scan.c

@@ -22,7 +22,9 @@ struct find_btree_nodes_worker {
 
 static void found_btree_node_to_text(struct printbuf *out, struct bch_fs *c, const struct found_btree_node *n)
 {
-	prt_printf(out, "%s l=%u seq=%u cookie=%llx ", bch2_btree_id_str(n->btree_id), n->level, n->seq, n->cookie);
+	prt_printf(out, "%s l=%u seq=%u journal_seq=%llu cookie=%llx ",
+		   bch2_btree_id_str(n->btree_id), n->level, n->seq,
+		   n->journal_seq, n->cookie);
 	bch2_bpos_to_text(out, n->min_key);
 	prt_str(out, "-");
 	bch2_bpos_to_text(out, n->max_key);
@@ -63,19 +65,37 @@ static void found_btree_node_to_key(struct bkey_i *k, const struct found_btree_n
 	memcpy(bp->v.start, f->ptrs, sizeof(struct bch_extent_ptr) * f->nr_ptrs);
 }
 
+static inline u64 bkey_journal_seq(struct bkey_s_c k)
+{
+	switch (k.k->type) {
+	case KEY_TYPE_inode_v3:
+		return le64_to_cpu(bkey_s_c_to_inode_v3(k).v->bi_journal_seq);
+	default:
+		return 0;
+	}
+}
+
 static bool found_btree_node_is_readable(struct btree_trans *trans,
 					 struct found_btree_node *f)
 {
-	struct { __BKEY_PADDED(k, BKEY_BTREE_PTR_VAL_U64s_MAX); } k;
+	struct { __BKEY_PADDED(k, BKEY_BTREE_PTR_VAL_U64s_MAX); } tmp;
 
-	found_btree_node_to_key(&k.k, f);
+	found_btree_node_to_key(&tmp.k, f);
 
-	struct btree *b = bch2_btree_node_get_noiter(trans, &k.k, f->btree_id, f->level, false);
+	struct btree *b = bch2_btree_node_get_noiter(trans, &tmp.k, f->btree_id, f->level, false);
 	bool ret = !IS_ERR_OR_NULL(b);
 	if (!ret)
 		return ret;
 
 	f->sectors_written = b->written;
+	f->journal_seq = le64_to_cpu(b->data->keys.journal_seq);
+
+	struct bkey_s_c k;
+	struct bkey unpacked;
+	struct btree_node_iter iter;
+	for_each_btree_node_key_unpack(b, k, &iter, &unpacked)
+		f->journal_seq = max(f->journal_seq, bkey_journal_seq(k));
+
 	six_unlock_read(&b->c.lock);
 
 	/*
@@ -84,7 +104,7 @@ static bool found_btree_node_is_readable(struct btree_trans *trans,
 	 * this node
 	 */
 	if (b != btree_node_root(trans->c, b))
-		bch2_btree_node_evict(trans, &k.k);
+		bch2_btree_node_evict(trans, &tmp.k);
 	return ret;
 }
 
@@ -105,7 +125,8 @@ static int found_btree_node_cmp_cookie(const void *_l, const void *_r)
 static int found_btree_node_cmp_time(const struct found_btree_node *l,
 				     const struct found_btree_node *r)
 {
-	return cmp_int(l->seq, r->seq);
+	return  cmp_int(l->seq, r->seq) ?:
+		cmp_int(l->journal_seq, r->journal_seq);
 }
 
 static int found_btree_node_cmp_pos(const void *_l, const void *_r)
@@ -309,15 +330,15 @@ static int handle_overwrites(struct bch_fs *c,
 		} else if (n->level) {
 			n->overwritten = true;
 		} else {
-			struct printbuf buf = PRINTBUF;
-
-			prt_str(&buf, "overlapping btree nodes with same seq! halting\n  ");
-			found_btree_node_to_text(&buf, c, start);
-			prt_str(&buf, "\n  ");
-			found_btree_node_to_text(&buf, c, n);
-			bch_err(c, "%s", buf.buf);
-			printbuf_exit(&buf);
-			return -BCH_ERR_fsck_repair_unimplemented;
+			if (bpos_cmp(start->max_key, n->max_key) >= 0)
+				n->overwritten = true;
+			else {
+				n->range_updated = true;
+				n->min_key = bpos_successor(start->max_key);
+				n->range_updated = true;
+				bubble_up(n, end);
+				goto again;
+			}
 		}
 	}
 

fs/bcachefs/btree_node_scan_types.h

@@ -11,6 +11,7 @@ struct found_btree_node {
 	u8			level;
 	unsigned		sectors_written;
 	u32			seq;
+	u64			journal_seq;
 	u64			cookie;
 
 	struct bpos		min_key;