changes as per review

extern/storage-sealing/input.go

@@ -313,15 +313,35 @@ func (m *Sealing) SectorAddPieceToAny(ctx context.Context, size abi.UnpaddedPiec
 	m.inputLk.Lock()
 	if pp, exist := m.pendingPieces[proposalCID(deal)]; exist {
 		m.inputLk.Unlock()
-		select {
-		case <-pp.doneCh:
-			res := pp.resp
+
+		// we already have a pre-existing add piece call for this deal, let's wait for it to finish and see if it's successful
+		for {
+			res, err := waitAddPieceResp(ctx, pp)
+			if err != nil {
+				return api.SectorOffset{}, err
+			}
+			//  there was an error waiting for a pre-existing add piece call, let's retry
+			if res.err != nil {
+				m.inputLk.Lock()
+				pp = m.addPendingPiece(ctx, size, data, deal, sp)
+				m.inputLk.Unlock()
+				continue
+			}
+			// all good, return the response
 			return api.SectorOffset{Sector: res.sn, Offset: res.offset.Padded()}, res.err
-		case <-ctx.Done():
-			return api.SectorOffset{}, ctx.Err()
 		}
 	}
 
+	pp := m.addPendingPiece(ctx, size, data, deal, sp)
+	m.inputLk.Unlock()
+	res, err := waitAddPieceResp(ctx, pp)
+	if err != nil {
+		return api.SectorOffset{}, err
+	}
+	return api.SectorOffset{Sector: res.sn, Offset: res.offset.Padded()}, res.err
+}
+
+func (m *Sealing) addPendingPiece(ctx context.Context, size abi.UnpaddedPieceSize, data storage.Data, deal api.PieceDealInfo, sp abi.RegisteredSealProof) *pendingPiece {
 	doneCh := make(chan struct{})
 	pp := &pendingPiece{
 		doneCh:   doneCh,
@@ -337,18 +357,21 @@ func (m *Sealing) SectorAddPieceToAny(ctx context.Context, size abi.UnpaddedPiec
 
 	m.pendingPieces[proposalCID(deal)] = pp
 	go func() {
-		defer m.inputLk.Unlock()
 		if err := m.updateInput(ctx, sp); err != nil {
 			log.Errorf("%+v", err)
 		}
 	}()
 
+	return pp
+}
+
+func waitAddPieceResp(ctx context.Context, pp *pendingPiece) (*pieceAcceptResp, error) {
 	select {
-	case <-doneCh:
+	case <-pp.doneCh:
 		res := pp.resp
-		return api.SectorOffset{Sector: res.sn, Offset: res.offset.Padded()}, res.err
+		return res, nil
 	case <-ctx.Done():
-		return api.SectorOffset{}, ctx.Err()
+		return nil, ctx.Err()
 	}
 }