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block_disk_store.go
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block_disk_store.go
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// Copyright 2016 Keybase Inc. All rights reserved.
// Use of this source code is governed by a BSD
// license that can be found in the LICENSE file.
package libkbfs
import (
"context"
"path/filepath"
"strings"
"sync"
"github.com/keybase/client/go/kbfs/ioutil"
"github.com/keybase/client/go/kbfs/kbfsblock"
"github.com/keybase/client/go/kbfs/kbfscodec"
"github.com/keybase/client/go/kbfs/kbfscrypto"
"github.com/keybase/go-codec/codec"
"github.com/pkg/errors"
)
// blockDiskStore stores block data in flat files on disk.
//
// The directory layout looks like:
//
// dir/0100/0...01/data
// dir/0100/0...01/id
// dir/0100/0...01/ksh
// dir/0100/0...01/refs
// ...
// dir/01cc/5...55/id
// dir/01cc/5...55/refs
// ...
// dir/01dd/6...66/data
// dir/01dd/6...66/id
// dir/01dd/6...66/ksh
// ...
// dir/01ff/f...ff/data
// dir/01ff/f...ff/id
// dir/01ff/f...ff/ksh
// dir/01ff/f...ff/refs
//
// Each block has its own subdirectory with its ID truncated to 17
// bytes (34 characters) as a name. The block subdirectories are
// splayed over (# of possible hash types) * 256 subdirectories -- one
// byte for the hash type (currently only one) plus the first byte of
// the hash data -- using the first four characters of the name to
// keep the number of directories in dir itself to a manageable
// number, similar to git.
//
// Each block directory has the following files:
//
// - id: The full block ID in binary format. Always present.
// - data: The raw block data that should hash to the block ID.
// May be missing.
// - ksh: The raw data for the associated key server half.
// May be missing, but should be present when data is.
// - refs: The list of references to the block, along with other
// block-specific info, encoded as a serialized
// blockJournalInfo. May be missing. TODO: rename this to
// something more generic if we ever upgrade the journal
// version.
//
// Future versions of the disk store might add more files to this
// directory; if any code is written to move blocks around, it should
// be careful to preserve any unknown files in a block directory.
//
// The maximum number of characters added to the root dir by a block
// disk store is 44:
//
// /01ff/f...(30 characters total)...ff/data
//
// blockDiskStore is goroutine-safe on a per-operation, per-block ID
// basis, so any code that uses it can make concurrent calls.
// However, it's likely that much of the time, the caller will require
// consistency across multiple calls (i.e., one call to
// `getDataSize()`, followed by a call to `remove()`), so higher-level
// locking is also recommended. For performance reasons though, it's
// recommended that the `put()` method can be called concurrently, as
// needed.
type blockDiskStore struct {
codec kbfscodec.Codec
dir string
lock sync.Mutex
puts map[kbfsblock.ID]<-chan struct{}
}
// filesPerBlockMax is an upper bound for the number of files
// (including directories) to store one block: 4 for the regular
// files, 2 for the (splayed) directories, and 1 for the journal
// entry.
const filesPerBlockMax = 7
// makeBlockDiskStore returns a new blockDiskStore for the given
// directory.
func makeBlockDiskStore(codec kbfscodec.Codec, dir string) *blockDiskStore {
return &blockDiskStore{
codec: codec,
dir: dir,
puts: make(map[kbfsblock.ID]<-chan struct{}),
}
}
// The functions below are for building various paths.
func (s *blockDiskStore) blockPath(id kbfsblock.ID) string {
// Truncate to 34 characters, which corresponds to 16 random
// bytes (since the first byte is a hash type) or 128 random
// bits, which means that the expected number of blocks
// generated before getting a path collision is 2^64 (see
// https://en.wikipedia.org/wiki/Birthday_problem#Cast_as_a_collision_problem
// ).
idStr := id.String()
return filepath.Join(s.dir, idStr[:4], idStr[4:34])
}
func (s *blockDiskStore) dataPath(id kbfsblock.ID) string {
return filepath.Join(s.blockPath(id), "data")
}
const idFilename = "id"
func (s *blockDiskStore) idPath(id kbfsblock.ID) string {
return filepath.Join(s.blockPath(id), idFilename)
}
func (s *blockDiskStore) keyServerHalfPath(id kbfsblock.ID) string {
return filepath.Join(s.blockPath(id), "ksh")
}
func (s *blockDiskStore) infoPath(id kbfsblock.ID) string {
// TODO: change the file name to "info" the next we change the
// journal layout.
return filepath.Join(s.blockPath(id), "refs")
}
// makeDir makes the directory for the given block ID and writes the
// ID file, if necessary.
func (s *blockDiskStore) makeDir(id kbfsblock.ID) error {
err := ioutil.MkdirAll(s.blockPath(id), 0700)
if err != nil {
return err
}
// TODO: Only write if the file doesn't exist.
return ioutil.WriteFile(s.idPath(id), []byte(id.String()), 0600)
}
// blockJournalInfo contains info about a particular block in the
// journal, such as the set of references to it.
type blockJournalInfo struct {
Refs blockRefMap
Flushed bool `codec:"f,omitempty"`
codec.UnknownFieldSetHandler
}
// TODO: Add caching for refs
func (s *blockDiskStore) startOpOrWait(id kbfsblock.ID) (
closeCh chan<- struct{}, waitCh <-chan struct{}) {
s.lock.Lock()
defer s.lock.Unlock()
waitCh = s.puts[id]
if waitCh == nil {
// If this caller is getting exclusive access to this `id`,
// make a channel, store it as receive-only in `puts`, and
// return it as send-only to the caller, to ensure that only
// this caller can finish the exclusive access.
ch := make(chan struct{})
s.puts[id] = ch
closeCh = ch
}
return closeCh, waitCh
}
func (s *blockDiskStore) finishOp(id kbfsblock.ID, closeCh chan<- struct{}) {
s.lock.Lock()
defer s.lock.Unlock()
delete(s.puts, id)
close(closeCh)
}
func (s *blockDiskStore) exclusify(ctx context.Context, id kbfsblock.ID) (
cleanupFn func(), err error) {
// Get a guarantee that we're acting exclusively on this
// particular block ID.
for {
// Repeatedly request exclusive access until until we don't
// get a non-nil channel to wait on.
closeCh, waitCh := s.startOpOrWait(id)
if waitCh == nil {
// If there's nothing to wait on, then we have exclusive
// access, so return.
return func() { s.finishOp(id, closeCh) }, nil
}
select {
case <-waitCh:
case <-ctx.Done():
return nil, errors.WithStack(ctx.Err())
}
}
}
// getRefInfo returns the references for the given ID. exclusify must
// have been called by the caller.
func (s *blockDiskStore) getInfo(id kbfsblock.ID) (blockJournalInfo, error) {
var info blockJournalInfo
err := kbfscodec.DeserializeFromFile(s.codec, s.infoPath(id), &info)
if !ioutil.IsNotExist(err) && err != nil {
return blockJournalInfo{}, err
}
if info.Refs == nil {
info.Refs = make(blockRefMap)
}
return info, nil
}
// putRefInfo stores the given references for the given ID. exclusify
// must have been called by the caller.
func (s *blockDiskStore) putInfo(
id kbfsblock.ID, info blockJournalInfo) error {
return kbfscodec.SerializeToFile(s.codec, info, s.infoPath(id))
}
// addRefs adds references for the given contexts to the given ID, all
// with the same status and tag. `exclusify` must be called by the
// caller.
func (s *blockDiskStore) addRefsExclusive(
id kbfsblock.ID, contexts []kbfsblock.Context, status blockRefStatus,
tag string) error {
info, err := s.getInfo(id)
if err != nil {
return err
}
if len(info.Refs) > 0 {
// Check existing contexts, if any.
for _, context := range contexts {
_, _, err := info.Refs.checkExists(context)
if err != nil {
return err
}
}
}
for _, context := range contexts {
err = info.Refs.put(context, status, tag)
if err != nil {
return err
}
}
return s.putInfo(id, info)
}
// getData returns the data and server half for the given ID, if
// present. `exclusify` must be called by the caller.
func (s *blockDiskStore) getDataExclusive(id kbfsblock.ID) (
[]byte, kbfscrypto.BlockCryptKeyServerHalf, error) {
data, err := ioutil.ReadFile(s.dataPath(id))
if ioutil.IsNotExist(err) {
return nil, kbfscrypto.BlockCryptKeyServerHalf{},
blockNonExistentError{id}
} else if err != nil {
return nil, kbfscrypto.BlockCryptKeyServerHalf{}, err
}
keyServerHalfPath := s.keyServerHalfPath(id)
buf, err := ioutil.ReadFile(keyServerHalfPath)
if ioutil.IsNotExist(err) {
return nil, kbfscrypto.BlockCryptKeyServerHalf{},
blockNonExistentError{id}
} else if err != nil {
return nil, kbfscrypto.BlockCryptKeyServerHalf{}, err
}
// Check integrity.
err = kbfsblock.VerifyID(data, id)
if err != nil {
return nil, kbfscrypto.BlockCryptKeyServerHalf{}, err
}
var serverHalf kbfscrypto.BlockCryptKeyServerHalf
err = serverHalf.UnmarshalBinary(buf)
if err != nil {
return nil, kbfscrypto.BlockCryptKeyServerHalf{}, err
}
return data, serverHalf, nil
}
// getData returns the data and server half for the given ID, if
// present.
func (s *blockDiskStore) getData(ctx context.Context, id kbfsblock.ID) (
[]byte, kbfscrypto.BlockCryptKeyServerHalf, error) {
cleanup, err := s.exclusify(ctx, id)
if err != nil {
return nil, kbfscrypto.BlockCryptKeyServerHalf{}, err
}
defer cleanup()
return s.getDataExclusive(id)
}
// All functions below are public functions.
func (s *blockDiskStore) hasAnyRefExclusive(
id kbfsblock.ID) (bool, error) {
info, err := s.getInfo(id)
if err != nil {
return false, err
}
return len(info.Refs) > 0, nil
}
func (s *blockDiskStore) hasAnyRef(
ctx context.Context, id kbfsblock.ID) (bool, error) {
cleanup, err := s.exclusify(ctx, id)
if err != nil {
return false, err
}
defer cleanup()
return s.hasAnyRefExclusive(id)
}
func (s *blockDiskStore) hasNonArchivedRef(
ctx context.Context, id kbfsblock.ID) (bool, error) {
cleanup, err := s.exclusify(ctx, id)
if err != nil {
return false, err
}
defer cleanup()
info, err := s.getInfo(id)
if err != nil {
return false, err
}
return info.Refs.hasNonArchivedRef(), nil
}
func (s *blockDiskStore) getLiveCount(
ctx context.Context, id kbfsblock.ID) (int, error) {
cleanup, err := s.exclusify(ctx, id)
if err != nil {
return 0, err
}
defer cleanup()
info, err := s.getInfo(id)
if err != nil {
return 0, err
}
return info.Refs.getLiveCount(), nil
}
func (s *blockDiskStore) hasContextExclusive(
id kbfsblock.ID, context kbfsblock.Context) (
bool, blockRefStatus, error) {
info, err := s.getInfo(id)
if err != nil {
return false, unknownBlockRef, err
}
return info.Refs.checkExists(context)
}
func (s *blockDiskStore) hasContext(
ctx context.Context, id kbfsblock.ID, context kbfsblock.Context) (
bool, blockRefStatus, error) {
cleanup, err := s.exclusify(ctx, id)
if err != nil {
return false, unknownBlockRef, err
}
defer cleanup()
return s.hasContextExclusive(id, context)
}
func (s *blockDiskStore) hasDataExclusive(id kbfsblock.ID) (bool, error) {
_, err := ioutil.Stat(s.dataPath(id))
if ioutil.IsNotExist(err) {
return false, nil
} else if err != nil {
return false, err
}
return true, nil
}
func (s *blockDiskStore) hasData(
ctx context.Context, id kbfsblock.ID) (bool, error) {
cleanup, err := s.exclusify(ctx, id)
if err != nil {
return false, err
}
defer cleanup()
_, err = ioutil.Stat(s.dataPath(id))
if ioutil.IsNotExist(err) {
return false, nil
} else if err != nil {
return false, err
}
return true, nil
}
func (s *blockDiskStore) isUnflushed(
ctx context.Context, id kbfsblock.ID) (bool, error) {
cleanup, err := s.exclusify(ctx, id)
if err != nil {
return false, err
}
defer cleanup()
ok, err := s.hasDataExclusive(id)
if err != nil {
return false, err
}
if !ok {
return false, nil
}
// The data is there; has it been flushed?
info, err := s.getInfo(id)
if err != nil {
return false, err
}
return !info.Flushed, nil
}
func (s *blockDiskStore) markFlushed(
ctx context.Context, id kbfsblock.ID) error {
cleanup, err := s.exclusify(ctx, id)
if err != nil {
return err
}
defer cleanup()
info, err := s.getInfo(id)
if err != nil {
return err
}
info.Flushed = true
return s.putInfo(id, info)
}
func (s *blockDiskStore) getDataSize(
ctx context.Context, id kbfsblock.ID) (int64, error) {
cleanup, err := s.exclusify(ctx, id)
if err != nil {
return 0, err
}
defer cleanup()
fi, err := ioutil.Stat(s.dataPath(id))
if ioutil.IsNotExist(err) {
return 0, nil
} else if err != nil {
return 0, err
}
return fi.Size(), nil
}
func (s *blockDiskStore) getDataWithContextExclusive(
id kbfsblock.ID, context kbfsblock.Context) (
[]byte, kbfscrypto.BlockCryptKeyServerHalf, error) {
hasContext, _, err := s.hasContextExclusive(id, context)
if err != nil {
return nil, kbfscrypto.BlockCryptKeyServerHalf{}, err
}
if !hasContext {
return nil, kbfscrypto.BlockCryptKeyServerHalf{},
blockNonExistentError{id}
}
return s.getDataExclusive(id)
}
func (s *blockDiskStore) getDataWithContext(
ctx context.Context, id kbfsblock.ID, context kbfsblock.Context) (
[]byte, kbfscrypto.BlockCryptKeyServerHalf, error) {
cleanup, err := s.exclusify(ctx, id)
if err != nil {
return nil, kbfscrypto.BlockCryptKeyServerHalf{}, err
}
defer cleanup()
return s.getDataWithContextExclusive(id, context)
}
func (s *blockDiskStore) getAllRefsForTest() (map[kbfsblock.ID]blockRefMap, error) {
res := make(map[kbfsblock.ID]blockRefMap)
fileInfos, err := ioutil.ReadDir(s.dir)
if ioutil.IsNotExist(err) {
return res, nil
} else if err != nil {
return nil, err
}
for _, fi := range fileInfos {
name := fi.Name()
if !fi.IsDir() {
return nil, errors.Errorf("Unexpected non-dir %q", name)
}
subFileInfos, err := ioutil.ReadDir(filepath.Join(s.dir, name))
if err != nil {
return nil, err
}
for _, sfi := range subFileInfos {
subName := sfi.Name()
if !sfi.IsDir() {
return nil, errors.Errorf("Unexpected non-dir %q",
subName)
}
idPath := filepath.Join(
s.dir, name, subName, idFilename)
idBytes, err := ioutil.ReadFile(idPath)
if err != nil {
return nil, err
}
id, err := kbfsblock.IDFromString(string(idBytes))
if err != nil {
return nil, errors.WithStack(err)
}
if !strings.HasPrefix(id.String(), name+subName) {
return nil, errors.Errorf(
"%q unexpectedly not a prefix of %q",
name+subName, id.String())
}
info, err := s.getInfo(id)
if err != nil {
return nil, err
}
if len(info.Refs) > 0 {
res[id] = info.Refs
}
}
}
return res, nil
}
// put puts the given data for the block, which may already exist, and
// adds a reference for the given context. If isRegularPut is true,
// additional validity checks are performed. If err is nil, putData
// indicates whether the data didn't already exist and was put; if
// false, it means that the data already exists, but this might have
// added a new ref.
//
// For performance reasons, this method can be called concurrently by
// many goroutines for different blocks.
//
// Note that the block won't be get-able until `addReference`
// explicitly adds a tag for it.
func (s *blockDiskStore) put(
ctx context.Context, isRegularPut bool, id kbfsblock.ID,
context kbfsblock.Context, buf []byte,
serverHalf kbfscrypto.BlockCryptKeyServerHalf) (
putData bool, err error) {
cleanup, err := s.exclusify(ctx, id)
if err != nil {
return false, err
}
defer cleanup()
err = validateBlockPut(isRegularPut, id, context, buf)
if err != nil {
return false, err
}
// Check the data and retrieve the server half, if they exist.
_, existingServerHalf, err := s.getDataWithContextExclusive(id, context)
var exists bool
switch err.(type) {
case blockNonExistentError:
exists = false
case nil:
exists = true
default:
return false, err
}
if exists {
// If the entry already exists, everything should be
// the same, except for possibly additional
// references.
// We checked that both buf and the existing data hash
// to id, so no need to check that they're both equal.
if isRegularPut && existingServerHalf != serverHalf {
return false, errors.Errorf(
"key server half mismatch: expected %s, got %s",
existingServerHalf, serverHalf)
}
} else {
err = s.makeDir(id)
if err != nil {
return false, err
}
err = ioutil.WriteFile(s.dataPath(id), buf, 0600)
if err != nil {
return false, err
}
// TODO: Add integrity-checking for key server half?
data, err := serverHalf.MarshalBinary()
if err != nil {
return false, err
}
err = ioutil.WriteFile(s.keyServerHalfPath(id), data, 0600)
if err != nil {
return false, err
}
}
return !exists, nil
}
func (s *blockDiskStore) addReference(
ctx context.Context, id kbfsblock.ID, context kbfsblock.Context,
tag string) error {
cleanup, err := s.exclusify(ctx, id)
if err != nil {
return err
}
defer cleanup()
err = s.makeDir(id)
if err != nil {
return err
}
return s.addRefsExclusive(
id, []kbfsblock.Context{context}, liveBlockRef, tag)
}
func (s *blockDiskStore) archiveReference(
ctx context.Context, id kbfsblock.ID, idContexts []kbfsblock.Context,
tag string) error {
cleanup, err := s.exclusify(ctx, id)
if err != nil {
return err
}
defer cleanup()
err = s.makeDir(id)
if err != nil {
return err
}
return s.addRefsExclusive(id, idContexts, archivedBlockRef, tag)
}
func (s *blockDiskStore) archiveReferences(
ctx context.Context, contexts kbfsblock.ContextMap, tag string) error {
for id, idContexts := range contexts {
err := s.archiveReference(ctx, id, idContexts, tag)
if err != nil {
return err
}
}
return nil
}
// removeReferences removes references for the given contexts from
// their respective IDs. If tag is non-empty, then a reference will be
// removed only if its most recent tag (passed in to addRefs) matches
// the given one.
func (s *blockDiskStore) removeReferences(
ctx context.Context, id kbfsblock.ID, contexts []kbfsblock.Context,
tag string) (liveCount int, err error) {
cleanup, err := s.exclusify(ctx, id)
if err != nil {
return 0, err
}
defer cleanup()
info, err := s.getInfo(id)
if err != nil {
return 0, err
}
if len(info.Refs) == 0 {
return 0, nil
}
for _, context := range contexts {
err := info.Refs.remove(context, tag)
if err != nil {
return 0, err
}
if len(info.Refs) == 0 {
break
}
}
err = s.putInfo(id, info)
if err != nil {
return 0, err
}
return len(info.Refs), nil
}
// remove removes any existing data for the given ID, which must not
// have any references left.
func (s *blockDiskStore) remove(ctx context.Context, id kbfsblock.ID) error {
cleanup, err := s.exclusify(ctx, id)
if err != nil {
return err
}
defer cleanup()
hasAnyRef, err := s.hasAnyRefExclusive(id)
if err != nil {
return err
}
if hasAnyRef {
return errors.Errorf(
"Trying to remove data for referenced block %s", id)
}
path := s.blockPath(id)
err = ioutil.RemoveAll(path)
if err != nil {
return err
}
// Remove the parent (splayed) directory if it exists and is
// empty.
err = ioutil.Remove(filepath.Dir(path))
if ioutil.IsNotExist(err) || ioutil.IsExist(err) {
err = nil
}
return err
}
func (s *blockDiskStore) clear() error {
return ioutil.RemoveAll(s.dir)
}