storagefsm: Fix race spawning more than one new sector at once

extern/storage-sealing/input.go

@@ -27,6 +27,10 @@ func (m *Sealing) handleWaitDeals(ctx statemachine.Context, sector SectorInfo) e
 
 	m.inputLk.Lock()
 
+	if m.creating != nil && *m.creating == sector.SectorNumber {
+		m.creating = nil
+	}
+
 	sid := m.minerSectorID(sector.SectorNumber)
 
 	if len(m.assignedPieces[sid]) > 0 {
@@ -390,6 +394,10 @@ func (m *Sealing) updateInput(ctx context.Context, sp abi.RegisteredSealProof) e
 }
 
 func (m *Sealing) tryCreateDealSector(ctx context.Context, sp abi.RegisteredSealProof) error {
+	if m.creating != nil {
+		return nil // new sector is being created right now
+	}
+
 	cfg, err := m.getConfig()
 	if err != nil {
 		return xerrors.Errorf("getting storage config: %w", err)
@@ -408,6 +416,8 @@ func (m *Sealing) tryCreateDealSector(ctx context.Context, sp abi.RegisteredSeal
 		return err
 	}
 
+	m.creating = &sid
+
 	log.Infow("Creating sector", "number", sid, "type", "deal", "proofType", sp)
 	return m.sectors.Send(uint64(sid), SectorStart{
 		ID:         sid,

extern/storage-sealing/sealing.go

@@ -93,6 +93,7 @@ type Sealing struct {
 	sectorTimers   map[abi.SectorID]*time.Timer
 	pendingPieces  map[cid.Cid]*pendingPiece
 	assignedPieces map[abi.SectorID][]cid.Cid
+	creating       *abi.SectorNumber // used to prevent a race where we could create a new sector more than once
 
 	upgradeLk sync.Mutex
 	toUpgrade map[abi.SectorNumber]struct{}