Add state fork logic

Signed-off-by: Jakub Sztandera <kubuxu@protocol.ai>

chain/stmgr/forks.go

@@ -2,6 +2,7 @@ package stmgr
 
 import (
 	"context"
+	"math/big"
 
 	amt "github.com/filecoin-project/go-amt-ipld/v2"
 	"github.com/filecoin-project/lotus/build"
@@ -35,12 +36,69 @@ func (sm *StateManager) handleStateForks(ctx context.Context, pstate cid.Cid, he
 			if err != nil {
 				return cid.Undef, xerrors.Errorf("booty bay bug fix failed: %w", err)
 			}
+		case build.ForkMissingSnowballs:
+			log.Warnw("Adding more snow to the world", "height", i)
+			pstate, err = fixTooFewSnowballs(ctx, sm, pstate)
+			if err != nil {
+				return cid.Undef, xerrors.Errorf("booty bay bug fix failed: %w", err)
+			}
 		}
 	}
 
 	return pstate, nil
 }
 
+func fixTooFewSnowballs(ctx context.Context, sm *StateManager, pstate cid.Cid) (cid.Cid, error) {
+	cst := hamt.CSTFromBstore(sm.cs.Blockstore())
+	st, err := state.LoadStateTree(cst, pstate)
+	if err != nil {
+		return cid.Undef, err
+	}
+
+	spa, err := st.GetActor(actors.StoragePowerAddress)
+	if err != nil {
+		return cid.Undef, xerrors.Errorf("failed to get storage power actor: %w", err)
+	}
+
+	var spast actors.StoragePowerState
+	if err := cst.Get(ctx, spa.Head, &spast); err != nil {
+		return cid.Undef, err
+	}
+
+	miners, err := actors.MinerSetList(ctx, cst, spast.Miners)
+	if err != nil {
+		return cid.Undef, err
+	}
+
+	sum := new(big.Int)
+	for _, m := range miners {
+		mact, err := st.GetActor(m)
+		if err != nil {
+			return cid.Undef, xerrors.Errorf("getting miner actor to fix: %w", err)
+		}
+
+		var mstate actors.StorageMinerActorState
+		if err := cst.Get(ctx, mact.Head, &mstate); err != nil {
+			return cid.Undef, xerrors.Errorf("failed to load miner actor state: %w", err)
+		}
+
+		if mstate.SlashedAt != 0 {
+			continue
+		}
+		sum = sum.Add(sum, mstate.Power.Int)
+	}
+
+	spast.TotalStorage.Int = sum
+	nspahead, err := cst.Put(ctx, spast)
+	if err != nil {
+		return cid.Undef, err
+	}
+
+	spa.Head = nspahead
+
+	return st.Flush(ctx)
+}
+
 /*
 1) Iterate through each miner in the chain:
 	1.1) Fixup their sector set and proving set