maybe a amt deletion bug?

gistfile1.txt

package main

import (
	"bytes"
	"context"
	"log"
	"math/rand"

	"github.com/filecoin-project/go-address"
	"github.com/filecoin-project/go-amt-ipld"
	cid "github.com/ipfs/go-cid"
	hamt "github.com/ipfs/go-hamt-ipld"
	cbor "github.com/ipfs/go-ipld-cbor"
	cbg "github.com/whyrusleeping/cbor-gen"

	"github.com/filecoin-project/lotus/api"
	"github.com/filecoin-project/lotus/api/client"
	"github.com/filecoin-project/lotus/chain/actors"
	"github.com/filecoin-project/lotus/chain/vm"
)

var _ amt.Blocks = (*mockStore)(nil)

type mockStore struct {
	local  *hamt.CborIpldStore
	remote api.FullNode
}

func (ms *mockStore) Get(c cid.Cid, v cbg.CBORUnmarshaler) error {
	err := ms.local.Get(context.Background(), c, v)
	if err == nil {
		return nil
	}

	b, err := ms.remote.ChainReadObj(context.Background(), c)
	if err != nil {
		return err
	}

	return v.UnmarshalCBOR(bytes.NewReader(b))
}

func (ms *mockStore) Put(v cbg.CBORMarshaler) (cid.Cid, error) {
	return ms.local.Put(context.Background(), v)
}

func main() {
	// use endpoint of any online lotus instance here
	cli, closer, err := client.NewFullNodeRPC("ws://127.0.0.1:1234/rpc/v0", nil)
	if err != nil {
		log.Fatalln(err)
	}

	defer closer()

	// chose any miner actor address, here we use t01475
	actorAddr, _ := address.NewIDAddress(1475)

	actor, err := cli.StateGetActor(context.Background(), actorAddr, nil)
	if err != nil {
		log.Fatalln("get actor", err)
	}

	log.Printf("actor: %v", actor)

	obj, err := cli.ChainReadObj(context.Background(), actor.Head)
	if err != nil {
		log.Fatalln("chain read obj", err)
	}

	state, err := vm.DumpActorState(actor.Code, obj)
	if err != nil {
		log.Fatalln("dump actor state", err)
	}

	minerState := state.(actors.StorageMinerActorState)
	blockstore := &mockStore{
		local:  hamt.NewCborStore(),
		remote: cli,
	}

	provSets, err := cli.StateMinerProvingSet(context.Background(), actorAddr, nil)
	if err != nil {
		log.Fatalln("proving set", err)
	}

	sids := make([]uint64, 0, len(provSets))
	for _, ps := range provSets {
		sids = append(sids, ps.SectorID)
	}

	log.Println("on chain proving set count", len(sids))

	log.Println("sectors state cid", minerState.Sectors)
	root, err := amt.LoadAMT(blockstore, minerState.Sectors)
	if err != nil {
		log.Fatalln("load root", err)
	}

	choices := make([]uint64, len(sids))
	copy(choices, sids)

	try := len(sids) / 20
	log.Println("expected to delete", try, "items")
	deleted := 0
	for ti := 0; ti < try; ti++ {
		ci := rand.Intn(len(choices))
		if err := root.Delete(choices[ci]); err != nil {
			log.Println("fail to delete", choices[ci], err)
		} else {
			deleted++
		}

		choices[ci], choices[len(choices)-1] = choices[len(choices)-1], choices[ci]
		choices = choices[:len(choices)-1]
	}

	log.Println("choises left", len(choices))
	log.Println("we actually did", deleted, "deletions")

	ncid, err := root.Flush()
	if err != nil {
		log.Fatalln("root flush", err)
	}

	log.Println("new root cid", ncid)

	newRoot, err := amt.LoadAMT(blockstore, ncid)
	if err != nil {
		log.Fatalln("load new amt root", err)
	}

	// use https://github.com/filecoin-project/lotus/blob/master/chain/stmgr/utils.go#L289-L313
	ssids := make([]uint64, 0, len(sids))
	if err := newRoot.ForEach(func(i uint64, v *cbg.Deferred) error {
		var comms [][]byte
		if err := cbor.DecodeInto(v.Raw, &comms); err != nil {
			return err
		}
		ssids = append(ssids, i)
		return nil

	}); err != nil {
		log.Fatalln("decode into new set of sids")
	}

	log.Println("new state count", len(ssids))
}

2020/01/16 18:23:50 actor: &{bafkqac3gnfwc6mjpnvuw4zls bafy2bzacecs6yfgjmmuwilshzavxddy5vvs6jvju5wfsb5j2fgqrs5sweurza 0 1456417521132327522}
2020/01/16 18:23:50 on chain proving set count 1226
2020/01/16 18:23:50 sectors state cid bafy2bzacea4zmb6d5pk3sbekdymsmupshdhg2xjw4lvisykeajyr5ohwlr4oo
2020/01/16 18:23:50 expected to delete 61 items
2020/01/16 18:23:55 choises left 1165
2020/01/16 18:23:55 we actually did 61 deletions
2020/01/16 18:23:55 new root cid bafy2bzacecjgpybk37omxpwc64guzkth2ljowyhkv3tk57eckptwtju7juke4
2020/01/16 18:24:29 new state count 1194