Merge pull request #3273 from ipfs/fix/pin-fail

fix bug in pinsets and add a stress test for the scenario

Author: whyrusleeping

pin/set.go

@@ -2,15 +2,14 @@ package pin
 
 import (
 	"bytes"
+	"context"
 	"crypto/rand"
 	"encoding/binary"
 	"errors"
 	"fmt"
 	"hash/fnv"
 	"sort"
-	"unsafe"
 
-	"context"
 	"github.com/ipfs/go-ipfs/merkledag"
 	"github.com/ipfs/go-ipfs/pin/internal/pb"
 	"gx/ipfs/QmYEoKZXHoAToWfhGF3vryhMn3WWhE1o2MasQ8uzY5iDi9/go-key"
@@ -19,8 +18,11 @@ import (
 )
 
 const (
+	// defaultFanout specifies the default number of fan-out links per layer
 	defaultFanout = 256
-	maxItems      = 8192
+
+	// maxItems is the maximum number of items that will fit in a single bucket
+	maxItems = 8192
 )
 
 func randomSeed() (uint32, error) {
@@ -40,36 +42,12 @@ func hash(seed uint32, c *cid.Cid) uint32 {
 	return h.Sum32()
 }
 
-type itemIterator func() (c *cid.Cid, data []byte, ok bool)
+type itemIterator func() (c *cid.Cid, ok bool)
 
 type keyObserver func(*cid.Cid)
 
-// refcount is the marshaled format of refcounts. It may change
-// between versions; this is valid for version 1. Changing it may
-// become desirable if there are many links with refcount > 255.
-//
-// There are two guarantees that need to be preserved, if this is
-// changed:
-//
-//     - the marshaled format is of fixed size, matching
-//       unsafe.Sizeof(refcount(0))
-//     - methods of refcount handle endianness, and may
-//       in later versions need encoding/binary.
-type refcount uint8
-
-func (r refcount) Bytes() []byte {
-	return []byte{byte(r)}
-}
-
-// readRefcount returns the idx'th refcount in []byte, which is
-// assumed to be a sequence of refcount.Bytes results.
-func (r *refcount) ReadFromIdx(buf []byte, idx int) {
-	*r = refcount(buf[idx])
-}
-
 type sortByHash struct {
 	links []*merkledag.Link
-	data  []byte
 }
 
 func (s sortByHash) Len() int {
@@ -82,27 +60,22 @@ func (s sortByHash) Less(a, b int) bool {
 
 func (s sortByHash) Swap(a, b int) {
 	s.links[a], s.links[b] = s.links[b], s.links[a]
-	if len(s.data) != 0 {
-		const n = int(unsafe.Sizeof(refcount(0)))
-		tmp := make([]byte, n)
-		copy(tmp, s.data[a*n:a*n+n])
-		copy(s.data[a*n:a*n+n], s.data[b*n:b*n+n])
-		copy(s.data[b*n:b*n+n], tmp)
-	}
 }
 
 func storeItems(ctx context.Context, dag merkledag.DAGService, estimatedLen uint64, iter itemIterator, internalKeys keyObserver) (*merkledag.Node, error) {
 	seed, err := randomSeed()
 	if err != nil {
 		return nil, err
 	}
-	n := &merkledag.Node{
-		Links: make([]*merkledag.Link, 0, defaultFanout+maxItems),
-	}
+
+	n := &merkledag.Node{Links: make([]*merkledag.Link, 0, defaultFanout+maxItems)}
 	for i := 0; i < defaultFanout; i++ {
 		n.Links = append(n.Links, &merkledag.Link{Hash: emptyKey.Hash()})
 	}
+
+	// add emptyKey to our set of internal pinset objects
 	internalKeys(emptyKey)
+
 	hdr := &pb.Set{
 		Version: proto.Uint32(1),
 		Fanout:  proto.Uint32(defaultFanout),
@@ -111,122 +84,138 @@ func storeItems(ctx context.Context, dag merkledag.DAGService, estimatedLen uint
 	if err := writeHdr(n, hdr); err != nil {
 		return nil, err
 	}
-	hdrLen := len(n.Data())
 
 	if estimatedLen < maxItems {
 		// it'll probably fit
 		for i := 0; i < maxItems; i++ {
-			k, data, ok := iter()
+			k, ok := iter()
 			if !ok {
 				// all done
 				break
 			}
 			n.Links = append(n.Links, &merkledag.Link{Hash: k.Hash()})
-			n.SetData(append(n.Data(), data...))
 		}
 		// sort by hash, also swap item Data
 		s := sortByHash{
 			links: n.Links[defaultFanout:],
-			data:  n.Data()[hdrLen:],
 		}
 		sort.Stable(s)
 	}
 
-	// wasteful but simple
-	type item struct {
-		c    *cid.Cid
-		data []byte
-	}
-	hashed := make(map[uint32][]item)
+	hashed := make([][]*cid.Cid, defaultFanout)
 	for {
-		k, data, ok := iter()
+		// This loop essentially enumerates every single item in the set
+		// and maps them all into a set of buckets. Each bucket will be recursively
+		// turned into its own sub-set, and so on down the chain. Each sub-set
+		// gets added to the dagservice, and put into its place in a set nodes
+		// links array.
+		//
+		// Previously, the bucket was selected by taking an int32 from the hash of
+		// the input key + seed. This was erroneous as we would later be assigning
+		// the created sub-sets into an array of length 256 by the modulus of the
+		// int32 hash value with 256. This resulted in overwriting existing sub-sets
+		// and losing pins. The fix (a few lines down from this comment), is to
+		// map the hash value down to the 8 bit keyspace here while creating the
+		// buckets. This way, we avoid any overlapping later on.
+		k, ok := iter()
 		if !ok {
 			break
 		}
-		h := hash(seed, k)
-		hashed[h] = append(hashed[h], item{k, data})
+		h := hash(seed, k) % defaultFanout
+		hashed[h] = append(hashed[h], k)
 	}
+
 	for h, items := range hashed {
-		childIter := func() (c *cid.Cid, data []byte, ok bool) {
-			if len(items) == 0 {
-				return nil, nil, false
-			}
-			first := items[0]
-			items = items[1:]
-			return first.c, first.data, true
+		if len(items) == 0 {
+			// recursion base case
+			continue
 		}
+
+		childIter := getCidListIterator(items)
+
+		// recursively create a pinset from the items for this bucket index
 		child, err := storeItems(ctx, dag, uint64(len(items)), childIter, internalKeys)
 		if err != nil {
 			return nil, err
 		}
+
 		size, err := child.Size()
 		if err != nil {
 			return nil, err
 		}
+
 		childKey, err := dag.Add(child)
 		if err != nil {
 			return nil, err
 		}
+
 		internalKeys(childKey)
-		l := &merkledag.Link{
-			Name: "",
+
+		// overwrite the 'empty key' in the existing links array
+		n.Links[h] = &merkledag.Link{
 			Hash: childKey.Hash(),
 			Size: size,
 		}
-		n.Links[int(h%defaultFanout)] = l
 	}
 	return n, nil
 }
 
-func readHdr(n *merkledag.Node) (*pb.Set, []byte, error) {
+func readHdr(n *merkledag.Node) (*pb.Set, error) {
 	hdrLenRaw, consumed := binary.Uvarint(n.Data())
 	if consumed <= 0 {
-		return nil, nil, errors.New("invalid Set header length")
+		return nil, errors.New("invalid Set header length")
 	}
-	buf := n.Data()[consumed:]
-	if hdrLenRaw > uint64(len(buf)) {
-		return nil, nil, errors.New("impossibly large Set header length")
+
+	pbdata := n.Data()[consumed:]
+	if hdrLenRaw > uint64(len(pbdata)) {
+		return nil, errors.New("impossibly large Set header length")
 	}
 	// as hdrLenRaw was <= an int, we now know it fits in an int
 	hdrLen := int(hdrLenRaw)
 	var hdr pb.Set
-	if err := proto.Unmarshal(buf[:hdrLen], &hdr); err != nil {
-		return nil, nil, err
+	if err := proto.Unmarshal(pbdata[:hdrLen], &hdr); err != nil {
+		return nil, err
 	}
-	buf = buf[hdrLen:]
 
 	if v := hdr.GetVersion(); v != 1 {
-		return nil, nil, fmt.Errorf("unsupported Set version: %d", v)
+		return nil, fmt.Errorf("unsupported Set version: %d", v)
 	}
 	if uint64(hdr.GetFanout()) > uint64(len(n.Links)) {
-		return nil, nil, errors.New("impossibly large Fanout")
+		return nil, errors.New("impossibly large Fanout")
 	}
-	return &hdr, buf, nil
+	return &hdr, nil
 }
 
 func writeHdr(n *merkledag.Node, hdr *pb.Set) error {
 	hdrData, err := proto.Marshal(hdr)
 	if err != nil {
 		return err
 	}
-	n.SetData(make([]byte, binary.MaxVarintLen64, binary.MaxVarintLen64+len(hdrData)))
-	written := binary.PutUvarint(n.Data(), uint64(len(hdrData)))
-	n.SetData(n.Data()[:written])
-	n.SetData(append(n.Data(), hdrData...))
+
+	// make enough space for the length prefix and the marshalled header data
+	data := make([]byte, binary.MaxVarintLen64, binary.MaxVarintLen64+len(hdrData))
+
+	// write the uvarint length of the header data
+	uvarlen := binary.PutUvarint(data, uint64(len(hdrData)))
+
+	// append the actual protobuf data *after* the length value we wrote
+	data = append(data[:uvarlen], hdrData...)
+
+	n.SetData(data)
 	return nil
 }
 
-type walkerFunc func(buf []byte, idx int, link *merkledag.Link) error
+type walkerFunc func(idx int, link *merkledag.Link) error
 
 func walkItems(ctx context.Context, dag merkledag.DAGService, n *merkledag.Node, fn walkerFunc, children keyObserver) error {
-	hdr, buf, err := readHdr(n)
+	hdr, err := readHdr(n)
 	if err != nil {
 		return err
 	}
 	// readHdr guarantees fanout is a safe value
 	fanout := hdr.GetFanout()
 	for i, l := range n.Links[fanout:] {
-		if err := fn(buf, i, l); err != nil {
+		if err := fn(i, l); err != nil {
 			return err
 		}
 	}
@@ -262,7 +251,7 @@ func loadSet(ctx context.Context, dag merkledag.DAGService, root *merkledag.Node
 	}
 
 	var res []*cid.Cid
-	walk := func(buf []byte, idx int, link *merkledag.Link) error {
+	walk := func(idx int, link *merkledag.Link) error {
 		res = append(res, cid.NewCidV0(link.Hash))
 		return nil
 	}
@@ -272,40 +261,21 @@ func loadSet(ctx context.Context, dag merkledag.DAGService, root *merkledag.Node
 	return res, nil
 }
 
-func loadMultiset(ctx context.Context, dag merkledag.DAGService, root *merkledag.Node, name string, internalKeys keyObserver) (map[key.Key]uint64, error) {
-	l, err := root.GetNodeLink(name)
-	if err != nil {
-		return nil, fmt.Errorf("Failed to get link %s: %v", name, err)
-	}
-	c := cid.NewCidV0(l.Hash)
-	internalKeys(c)
-	n, err := l.GetNode(ctx, dag)
-	if err != nil {
-		return nil, fmt.Errorf("Failed to get node from link %s: %v", name, err)
-	}
-
-	refcounts := make(map[key.Key]uint64)
-	walk := func(buf []byte, idx int, link *merkledag.Link) error {
-		var r refcount
-		r.ReadFromIdx(buf, idx)
-		refcounts[key.Key(link.Hash)] += uint64(r)
-		return nil
-	}
-	if err := walkItems(ctx, dag, n, walk, internalKeys); err != nil {
-		return nil, err
-	}
-	return refcounts, nil
-}
-
-func storeSet(ctx context.Context, dag merkledag.DAGService, cids []*cid.Cid, internalKeys keyObserver) (*merkledag.Node, error) {
-	iter := func() (c *cid.Cid, data []byte, ok bool) {
+func getCidListIterator(cids []*cid.Cid) itemIterator {
+	return func() (c *cid.Cid, ok bool) {
 		if len(cids) == 0 {
-			return nil, nil, false
+			return nil, false
 		}
+
 		first := cids[0]
 		cids = cids[1:]
-		return first, nil, true
+		return first, true
 	}
+}
+
+func storeSet(ctx context.Context, dag merkledag.DAGService, cids []*cid.Cid, internalKeys keyObserver) (*merkledag.Node, error) {
+	iter := getCidListIterator(cids)
+
 	n, err := storeItems(ctx, dag, uint64(len(cids)), iter, internalKeys)
 	if err != nil {
 		return nil, err