bcachefs: better error message in check_snapshot_tree()

If we find a snapshot node and it didn't match the snapshot tree, we
should print it.

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

diff --git a/fs/bcachefs/snapshot.c b/fs/bcachefs/snapshot.c
index feaf2aa0d9002a74562383a8e2e8edf641265c03..34e01bd8127f955d1c5a9c1afd13a66d22b8311f 100644 (file)
--- a/fs/bcachefs/snapshot.c
+++ b/fs/bcachefs/snapshot.c
@@ -506,7 +506,6 @@ static int bch2_snapshot_tree_master_subvol(struct btree_trans *trans,
                        break;
                }
        }
-
        bch2_trans_iter_exit(trans, &iter);
 
        if (!ret && !found) {
@@ -536,6 +535,7 @@ static int check_snapshot_tree(struct btree_trans *trans,
        struct bch_snapshot s;
        struct bch_subvolume subvol;
        struct printbuf buf = PRINTBUF;
+       struct btree_iter snapshot_iter = {};
        u32 root_id;
        int ret;
 
@@ -545,16 +545,27 @@ static int check_snapshot_tree(struct btree_trans *trans,
        st = bkey_s_c_to_snapshot_tree(k);
        root_id = le32_to_cpu(st.v->root_snapshot);
 
-       ret = bch2_snapshot_lookup(trans, root_id, &s);
+       struct bkey_s_c_snapshot snapshot_k =
+               bch2_bkey_get_iter_typed(trans, &snapshot_iter, BTREE_ID_snapshots,
+                                        POS(0, root_id), 0, snapshot);
+       ret = bkey_err(snapshot_k);
        if (ret && !bch2_err_matches(ret, ENOENT))
                goto err;
 
+       if (!ret)
+               bkey_val_copy(&s, snapshot_k);
+
        if (fsck_err_on(ret ||
                        root_id != bch2_snapshot_root(c, root_id) ||
                        st.k->p.offset != le32_to_cpu(s.tree),
                        trans, snapshot_tree_to_missing_snapshot,
                        "snapshot tree points to missing/incorrect snapshot:\n  %s",
-                       (bch2_bkey_val_to_text(&buf, c, st.s_c), buf.buf))) {
+                       (bch2_bkey_val_to_text(&buf, c, st.s_c),
+                        prt_newline(&buf),
+                        ret
+                        ? prt_printf(&buf, "(%s)", bch2_err_str(ret))
+                        : bch2_bkey_val_to_text(&buf, c, snapshot_k.s_c),
+                        buf.buf))) {
                ret = bch2_btree_delete_at(trans, iter, 0);
                goto err;
        }
@@ -605,6 +616,7 @@ static int check_snapshot_tree(struct btree_trans *trans,
        }
 err:
 fsck_err:
+       bch2_trans_iter_exit(trans, &snapshot_iter);
        printbuf_exit(&buf);
        return ret;
 }