small refactor*

server/pkg/go-nfs/helpers/billlyfs.go

@@ -0,0 +1,157 @@
+package helpers
+
+import (
+	"context"
+	"io/fs"
+
+	"git.kmsign.ru/royalcat/tstor/server/pkg/go-nfs"
+	"github.com/go-git/go-billy/v5"
+)
+
+func WrapBillyFS(bf billy.Filesystem) nfs.Filesystem {
+	return &wrapFS{
+		Filesystem: bf,
+	}
+}
+
+type wrapFS struct {
+	billy.Filesystem
+}
+
+var _ nfs.Filesystem = (*wrapFS)(nil)
+
+// Create implements Filesystem.
+// Subtle: this method shadows the method (Filesystem).Create of MemFS.Filesystem.
+func (m *wrapFS) Create(ctx context.Context, filename string) (nfs.File, error) {
+	bf, err := m.Filesystem.Create(filename)
+	if err != nil {
+		return nil, err
+	}
+	return &wrapFile{bf}, nil
+}
+
+// Lstat implements Filesystem.
+// Subtle: this method shadows the method (Filesystem).Lstat of MemFS.Filesystem.
+func (m *wrapFS) Lstat(ctx context.Context, filename string) (fs.FileInfo, error) {
+	return m.Filesystem.Lstat(filename)
+}
+
+// MkdirAll implements Filesystem.
+// Subtle: this method shadows the method (Filesystem).MkdirAll of MemFS.Filesystem.
+func (m *wrapFS) MkdirAll(ctx context.Context, filename string, perm fs.FileMode) error {
+	return m.Filesystem.MkdirAll(filename, perm)
+}
+
+// Open implements Filesystem.
+// Subtle: this method shadows the method (Filesystem).Open of MemFS.Filesystem.
+func (m *wrapFS) Open(ctx context.Context, filename string) (nfs.File, error) {
+	bf, err := m.Filesystem.Open(filename)
+	if err != nil {
+		return nil, err
+	}
+	return WrapFile(bf), nil
+}
+
+// OpenFile implements Filesystem.
+// Subtle: this method shadows the method (Filesystem).OpenFile of MemFS.Filesystem.
+func (m *wrapFS) OpenFile(ctx context.Context, filename string, flag int, perm fs.FileMode) (nfs.File, error) {
+	bf, err := m.Filesystem.OpenFile(filename, flag, perm)
+	if err != nil {
+		return nil, err
+	}
+	return WrapFile(bf), nil
+}
+
+// ReadDir implements Filesystem.
+// Subtle: this method shadows the method (Filesystem).ReadDir of MemFS.Filesystem.
+func (m *wrapFS) ReadDir(ctx context.Context, path string) ([]fs.FileInfo, error) {
+	return m.Filesystem.ReadDir(path)
+}
+
+// Readlink implements Filesystem.
+// Subtle: this method shadows the method (Filesystem).Readlink of MemFS.Filesystem.
+func (m *wrapFS) Readlink(ctx context.Context, link string) (string, error) {
+	return m.Filesystem.Readlink(link)
+}
+
+// Remove implements Filesystem.
+// Subtle: this method shadows the method (Filesystem).Remove of MemFS.Filesystem.
+func (m *wrapFS) Remove(ctx context.Context, filename string) error {
+	return m.Filesystem.Remove(filename)
+}
+
+// Rename implements Filesystem.
+// Subtle: this method shadows the method (Filesystem).Rename of MemFS.Filesystem.
+func (m *wrapFS) Rename(ctx context.Context, oldpath string, newpath string) error {
+	return m.Filesystem.Rename(oldpath, newpath)
+}
+
+// Stat implements Filesystem.
+// Subtle: this method shadows the method (Filesystem).Stat of MemFS.Filesystem.
+func (m *wrapFS) Stat(ctx context.Context, filename string) (fs.FileInfo, error) {
+	return m.Filesystem.Stat(filename)
+}
+
+// Symlink implements Filesystem.
+// Subtle: this method shadows the method (Filesystem).Symlink of MemFS.Filesystem.
+func (m *wrapFS) Symlink(ctx context.Context, target string, link string) error {
+	return m.Filesystem.Symlink(target, link)
+}
+
+func WrapFile(bf billy.File) nfs.File {
+	return &wrapFile{File: bf}
+}
+
+type wrapFile struct {
+	billy.File
+}
+
+var _ nfs.File = (*wrapFile)(nil)
+
+// Close implements File.
+// Subtle: this method shadows the method (File).Close of MemFile.File.
+func (m *wrapFile) Close(ctx context.Context) error {
+	return m.File.Close()
+}
+
+// Lock implements File.
+// Subtle: this method shadows the method (File).Lock of MemFile.File.
+func (m *wrapFile) Lock() error {
+	return m.File.Lock()
+}
+
+// Name implements File.
+// Subtle: this method shadows the method (File).Name of MemFile.File.
+func (m *wrapFile) Name() string {
+	return m.File.Name()
+}
+
+// Truncate implements File.
+// Subtle: this method shadows the method (File).Truncate of memFile.File.
+func (m *wrapFile) Truncate(ctx context.Context, size int64) error {
+	return m.File.Truncate(size)
+}
+
+// Read implements File.
+// Subtle: this method shadows the method (File).Read of MemFile.File.
+func (m *wrapFile) Read(ctx context.Context, p []byte) (n int, err error) {
+	return m.File.Read(p)
+}
+
+// ReadAt implements File.
+// Subtle: this method shadows the method (File).ReadAt of MemFile.File.
+func (m *wrapFile) ReadAt(ctx context.Context, p []byte, off int64) (n int, err error) {
+	return m.File.ReadAt(p, off)
+}
+
+// Unlock implements File.
+// Subtle: this method shadows the method (File).Unlock of MemFile.File.
+func (m *wrapFile) Unlock() error {
+	return m.File.Unlock()
+}
+
+// Write implements File.
+// Subtle: this method shadows the method (File).Write of MemFile.File.
+func (m *wrapFile) Write(ctx context.Context, p []byte) (n int, err error) {
+	return m.File.Write(p)
+}

server/pkg/go-nfs/helpers/cachinghandler.go

@@ -0,0 +1,199 @@
+package helpers
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/binary"
+	"io/fs"
+	"reflect"
+
+	"git.kmsign.ru/royalcat/tstor/server/pkg/go-nfs"
+
+	"github.com/google/uuid"
+	lru "github.com/hashicorp/golang-lru/v2"
+)
+
+// NewCachingHandler wraps a handler to provide a basic to/from-file handle cache.
+func NewCachingHandler(h nfs.Handler, limit int) nfs.Handler {
+	return NewCachingHandlerWithVerifierLimit(h, limit, limit)
+}
+
+// NewCachingHandlerWithVerifierLimit provides a basic to/from-file handle cache that can be tuned with a smaller cache of active directory listings.
+func NewCachingHandlerWithVerifierLimit(h nfs.Handler, limit int, verifierLimit int) nfs.Handler {
+	if limit < 2 || verifierLimit < 2 {
+		nfs.Log.Warnf("Caching handler created with insufficient cache to support directory listing", "size", limit, "verifiers", verifierLimit)
+	}
+	cache, _ := lru.New[uuid.UUID, entry](limit)
+	reverseCache := make(map[string][]uuid.UUID)
+	verifiers, _ := lru.New[uint64, verifier](verifierLimit)
+	return &CachingHandler{
+		Handler:         h,
+		activeHandles:   cache,
+		reverseHandles:  reverseCache,
+		activeVerifiers: verifiers,
+		cacheLimit:      limit,
+	}
+}
+
+// CachingHandler implements to/from handle via an LRU cache.
+type CachingHandler struct {
+	nfs.Handler
+	activeHandles   *lru.Cache[uuid.UUID, entry]
+	reverseHandles  map[string][]uuid.UUID
+	activeVerifiers *lru.Cache[uint64, verifier]
+	cacheLimit      int
+}
+
+type entry struct {
+	f nfs.Filesystem
+	p []string
+}
+
+// ToHandle takes a file and represents it with an opaque handle to reference it.
+// In stateless nfs (when it's serving a unix fs) this can be the device + inode
+// but we can generalize with a stateful local cache of handed out IDs.
+func (c *CachingHandler) ToHandle(ctx context.Context, f nfs.Filesystem, path []string) []byte {
+	joinedPath := f.Join(path...)
+
+	if handle := c.searchReverseCache(f, joinedPath); handle != nil {
+		return handle
+	}
+
+	id := uuid.New()
+
+	newPath := make([]string, len(path))
+
+	copy(newPath, path)
+	evictedKey, evictedPath, ok := c.activeHandles.GetOldest()
+	if evicted := c.activeHandles.Add(id, entry{f, newPath}); evicted && ok {
+		rk := evictedPath.f.Join(evictedPath.p...)
+		c.evictReverseCache(rk, evictedKey)
+	}
+
+	if _, ok := c.reverseHandles[joinedPath]; !ok {
+		c.reverseHandles[joinedPath] = []uuid.UUID{}
+	}
+	c.reverseHandles[joinedPath] = append(c.reverseHandles[joinedPath], id)
+	b, _ := id.MarshalBinary()
+
+	return b
+}
+
+// FromHandle converts from an opaque handle to the file it represents
+func (c *CachingHandler) FromHandle(ctx context.Context, fh []byte) (nfs.Filesystem, []string, error) {
+	id, err := uuid.FromBytes(fh)
+	if err != nil {
+		return nil, []string{}, err
+	}
+
+	if f, ok := c.activeHandles.Get(id); ok {
+		for _, k := range c.activeHandles.Keys() {
+			candidate, _ := c.activeHandles.Peek(k)
+			if hasPrefix(f.p, candidate.p) {
+				_, _ = c.activeHandles.Get(k)
+			}
+		}
+		if ok {
+			newP := make([]string, len(f.p))
+			copy(newP, f.p)
+			return f.f, newP, nil
+		}
+	}
+	return nil, []string{}, &nfs.NFSStatusError{NFSStatus: nfs.NFSStatusStale}
+}
+
+func (c *CachingHandler) searchReverseCache(f nfs.Filesystem, path string) []byte {
+	uuids, exists := c.reverseHandles[path]
+
+	if !exists {
+		return nil
+	}
+
+	for _, id := range uuids {
+		if candidate, ok := c.activeHandles.Get(id); ok {
+			if reflect.DeepEqual(candidate.f, f) {
+				return id[:]
+			}
+		}
+	}
+
+	return nil
+}
+
+func (c *CachingHandler) evictReverseCache(path string, handle uuid.UUID) {
+	uuids, exists := c.reverseHandles[path]
+
+	if !exists {
+		return
+	}
+	for i, u := range uuids {
+		if u == handle {
+			uuids = append(uuids[:i], uuids[i+1:]...)
+			c.reverseHandles[path] = uuids
+			return
+		}
+	}
+}
+
+func (c *CachingHandler) InvalidateHandle(ctx context.Context, fs nfs.Filesystem, handle []byte) error {
+	//Remove from cache
+	id, _ := uuid.FromBytes(handle)
+	entry, ok := c.activeHandles.Get(id)
+	if ok {
+		rk := entry.f.Join(entry.p...)
+		c.evictReverseCache(rk, id)
+	}
+	c.activeHandles.Remove(id)
+	return nil
+}
+
+// HandleLimit exports how many file handles can be safely stored by this cache.
+func (c *CachingHandler) HandleLimit() int {
+	return c.cacheLimit
+}
+
+func hasPrefix(path, prefix []string) bool {
+	if len(prefix) > len(path) {
+		return false
+	}
+	for i, e := range prefix {
+		if path[i] != e {
+			return false
+		}
+	}
+	return true
+}
+
+type verifier struct {
+	path     string
+	contents []fs.FileInfo
+}
+
+func hashPathAndContents(path string, contents []fs.FileInfo) uint64 {
+	//calculate a cookie-verifier.
+	vHash := sha256.New()
+
+	// Add the path to avoid collisions of directories with the same content
+	vHash.Write(binary.BigEndian.AppendUint64([]byte{}, uint64(len(path))))
+	vHash.Write([]byte(path))
+
+	for _, c := range contents {
+		vHash.Write([]byte(c.Name())) // Never fails according to the docs
+	}
+
+	verify := vHash.Sum(nil)[0:8]
+	return binary.BigEndian.Uint64(verify)
+}
+
+func (c *CachingHandler) VerifierFor(path string, contents []fs.FileInfo) uint64 {
+	id := hashPathAndContents(path, contents)
+	c.activeVerifiers.Add(id, verifier{path, contents})
+	return id
+}
+
+func (c *CachingHandler) DataForVerifier(path string, id uint64) []fs.FileInfo {
+	if cache, ok := c.activeVerifiers.Get(id); ok {
+		return cache.contents
+	}
+	return nil
+}

server/pkg/go-nfs/helpers/memfs/memfs.go

@@ -0,0 +1,414 @@
+// Package memfs is a variant of "github.com/go-git/go-billy/v5/memfs" with
+// stable mtimes for items.
+package memfs
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"syscall"
+	"time"
+
+	"github.com/go-git/go-billy/v5"
+	"github.com/go-git/go-billy/v5/helper/chroot"
+	"github.com/go-git/go-billy/v5/util"
+)
+
+const separator = filepath.Separator
+
+// Memory a very convenient filesystem based on memory files
+type Memory struct {
+	s *storage
+}
+
+// New returns a new Memory filesystem.
+func New() billy.Filesystem {
+	fs := &Memory{s: newStorage()}
+	return chroot.New(fs, string(separator))
+}
+
+func (fs *Memory) Create(filename string) (billy.File, error) {
+	return fs.OpenFile(filename, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0666)
+}
+
+func (fs *Memory) Open(filename string) (billy.File, error) {
+	return fs.OpenFile(filename, os.O_RDONLY, 0)
+}
+
+func (fs *Memory) OpenFile(filename string, flag int, perm os.FileMode) (billy.File, error) {
+	f, has := fs.s.Get(filename)
+	if !has {
+		if !isCreate(flag) {
+			return nil, os.ErrNotExist
+		}
+
+		var err error
+		f, err = fs.s.New(filename, perm, flag)
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		if isExclusive(flag) {
+			return nil, os.ErrExist
+		}
+
+		if target, isLink := fs.resolveLink(filename, f); isLink {
+			return fs.OpenFile(target, flag, perm)
+		}
+	}
+
+	if f.mode.IsDir() {
+		return nil, fmt.Errorf("cannot open directory: %s", filename)
+	}
+
+	return f.Duplicate(filename, perm, flag), nil
+}
+
+func (fs *Memory) resolveLink(fullpath string, f *file) (target string, isLink bool) {
+	if !isSymlink(f.mode) {
+		return fullpath, false
+	}
+
+	target = string(f.content.bytes)
+	if !isAbs(target) {
+		target = fs.Join(filepath.Dir(fullpath), target)
+	}
+
+	return target, true
+}
+
+// On Windows OS, IsAbs validates if a path is valid based on if stars with a
+// unit (eg.: `C:\`)  to assert that is absolute, but in this mem implementation
+// any path starting by `separator` is also considered absolute.
+func isAbs(path string) bool {
+	return filepath.IsAbs(path) || strings.HasPrefix(path, string(separator))
+}
+
+func (fs *Memory) Stat(filename string) (os.FileInfo, error) {
+	f, has := fs.s.Get(filename)
+	if !has {
+		return nil, os.ErrNotExist
+	}
+
+	fi, _ := f.Stat()
+
+	var err error
+	if target, isLink := fs.resolveLink(filename, f); isLink {
+		fi, err = fs.Stat(target)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	// the name of the file should always the name of the stated file, so we
+	// overwrite the Stat returned from the storage with it, since the
+	// filename may belong to a link.
+	fi.(*fileInfo).name = filepath.Base(filename)
+	return fi, nil
+}
+
+func (fs *Memory) Lstat(filename string) (os.FileInfo, error) {
+	f, has := fs.s.Get(filename)
+	if !has {
+		return nil, os.ErrNotExist
+	}
+
+	return f.Stat()
+}
+
+type ByName []os.FileInfo
+
+func (a ByName) Len() int           { return len(a) }
+func (a ByName) Less(i, j int) bool { return a[i].Name() < a[j].Name() }
+func (a ByName) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
+
+func (fs *Memory) ReadDir(path string) ([]os.FileInfo, error) {
+	if f, has := fs.s.Get(path); has {
+		if target, isLink := fs.resolveLink(path, f); isLink {
+			return fs.ReadDir(target)
+		}
+	} else {
+		return nil, &os.PathError{Op: "open", Path: path, Err: syscall.ENOENT}
+	}
+
+	var entries []os.FileInfo
+	for _, f := range fs.s.Children(path) {
+		fi, _ := f.Stat()
+		entries = append(entries, fi)
+	}
+
+	sort.Sort(ByName(entries))
+
+	return entries, nil
+}
+
+func (fs *Memory) MkdirAll(path string, perm os.FileMode) error {
+	_, err := fs.s.New(path, perm|os.ModeDir, 0)
+	return err
+}
+
+func (fs *Memory) TempFile(dir, prefix string) (billy.File, error) {
+	return util.TempFile(fs, dir, prefix)
+}
+
+func (fs *Memory) Rename(from, to string) error {
+	return fs.s.Rename(from, to)
+}
+
+func (fs *Memory) Remove(filename string) error {
+	return fs.s.Remove(filename)
+}
+
+func (fs *Memory) Join(elem ...string) string {
+	return filepath.Join(elem...)
+}
+
+func (fs *Memory) Symlink(target, link string) error {
+	_, err := fs.Stat(link)
+	if err == nil {
+		return os.ErrExist
+	}
+
+	if !os.IsNotExist(err) {
+		return err
+	}
+
+	return util.WriteFile(fs, link, []byte(target), 0777|os.ModeSymlink)
+}
+
+func (fs *Memory) Readlink(link string) (string, error) {
+	f, has := fs.s.Get(link)
+	if !has {
+		return "", os.ErrNotExist
+	}
+
+	if !isSymlink(f.mode) {
+		return "", &os.PathError{
+			Op:   "readlink",
+			Path: link,
+			Err:  fmt.Errorf("not a symlink"),
+		}
+	}
+
+	return string(f.content.bytes), nil
+}
+
+// Capabilities implements the Capable interface.
+func (fs *Memory) Capabilities() billy.Capability {
+	return billy.WriteCapability |
+		billy.ReadCapability |
+		billy.ReadAndWriteCapability |
+		billy.SeekCapability |
+		billy.TruncateCapability
+}
+
+type file struct {
+	name     string
+	content  *content
+	position int64
+	flag     int
+	mode     os.FileMode
+	mtime    time.Time
+
+	isClosed bool
+}
+
+func (f *file) Name() string {
+	return f.name
+}
+
+func (f *file) Read(b []byte) (int, error) {
+	n, err := f.ReadAt(b, f.position)
+	f.position += int64(n)
+
+	if err == io.EOF && n != 0 {
+		err = nil
+	}
+
+	return n, err
+}
+
+func (f *file) ReadAt(b []byte, off int64) (int, error) {
+	if f.isClosed {
+		return 0, os.ErrClosed
+	}
+
+	if !isReadAndWrite(f.flag) && !isReadOnly(f.flag) {
+		return 0, errors.New("read not supported")
+	}
+
+	n, err := f.content.ReadAt(b, off)
+
+	return n, err
+}
+
+func (f *file) Seek(offset int64, whence int) (int64, error) {
+	if f.isClosed {
+		return 0, os.ErrClosed
+	}
+
+	switch whence {
+	case io.SeekCurrent:
+		f.position += offset
+	case io.SeekStart:
+		f.position = offset
+	case io.SeekEnd:
+		f.position = int64(f.content.Len()) + offset
+	}
+
+	return f.position, nil
+}
+
+func (f *file) Write(p []byte) (int, error) {
+	return f.WriteAt(p, f.position)
+}
+
+func (f *file) WriteAt(p []byte, off int64) (int, error) {
+	if f.isClosed {
+		return 0, os.ErrClosed
+	}
+
+	if !isReadAndWrite(f.flag) && !isWriteOnly(f.flag) {
+		return 0, errors.New("write not supported")
+	}
+
+	n, err := f.content.WriteAt(p, off)
+	f.position = off + int64(n)
+	f.mtime = time.Now()
+
+	return n, err
+}
+
+func (f *file) Close() error {
+	if f.isClosed {
+		return os.ErrClosed
+	}
+
+	f.isClosed = true
+	return nil
+}
+
+func (f *file) Truncate(size int64) error {
+	if size < int64(len(f.content.bytes)) {
+		f.content.bytes = f.content.bytes[:size]
+	} else if more := int(size) - len(f.content.bytes); more > 0 {
+		f.content.bytes = append(f.content.bytes, make([]byte, more)...)
+	}
+	f.mtime = time.Now()
+
+	return nil
+}
+
+func (f *file) Duplicate(filename string, mode os.FileMode, flag int) billy.File {
+	new := &file{
+		name:    filename,
+		content: f.content,
+		mode:    mode,
+		flag:    flag,
+		mtime:   time.Now(),
+	}
+
+	if isTruncate(flag) {
+		new.content.Truncate()
+	}
+
+	if isAppend(flag) {
+		new.position = int64(new.content.Len())
+	}
+
+	return new
+}
+
+func (f *file) Stat() (os.FileInfo, error) {
+	return &fileInfo{
+		name:  f.Name(),
+		mode:  f.mode,
+		size:  f.content.Len(),
+		mtime: f.mtime,
+	}, nil
+}
+
+// Lock is a no-op in memfs.
+func (f *file) Lock() error {
+	return nil
+}
+
+// Unlock is a no-op in memfs.
+func (f *file) Unlock() error {
+	return nil
+}
+
+type fileInfo struct {
+	name  string
+	size  int
+	mode  os.FileMode
+	mtime time.Time
+}
+
+func (fi *fileInfo) Name() string {
+	return fi.name
+}
+
+func (fi *fileInfo) Size() int64 {
+	return int64(fi.size)
+}
+
+func (fi *fileInfo) Mode() os.FileMode {
+	return fi.mode
+}
+
+func (fi *fileInfo) ModTime() time.Time {
+	return fi.mtime
+}
+
+func (fi *fileInfo) IsDir() bool {
+	return fi.mode.IsDir()
+}
+
+func (*fileInfo) Sys() interface{} {
+	return nil
+}
+
+func (c *content) Truncate() {
+	c.bytes = make([]byte, 0)
+}
+
+func (c *content) Len() int {
+	return len(c.bytes)
+}
+
+func isCreate(flag int) bool {
+	return flag&os.O_CREATE != 0
+}
+
+func isExclusive(flag int) bool {
+	return flag&os.O_EXCL != 0
+}
+
+func isAppend(flag int) bool {
+	return flag&os.O_APPEND != 0
+}
+
+func isTruncate(flag int) bool {
+	return flag&os.O_TRUNC != 0
+}
+
+func isReadAndWrite(flag int) bool {
+	return flag&os.O_RDWR != 0
+}
+
+func isReadOnly(flag int) bool {
+	return flag == os.O_RDONLY
+}
+
+func isWriteOnly(flag int) bool {
+	return flag&os.O_WRONLY != 0
+}
+
+func isSymlink(m os.FileMode) bool {
+	return m&os.ModeSymlink != 0
+}

server/pkg/go-nfs/helpers/memfs/storage.go

@@ -0,0 +1,243 @@
+package memfs
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"time"
+)
+
+type storage struct {
+	files    map[string]*file
+	children map[string]map[string]*file
+}
+
+func newStorage() *storage {
+	return &storage{
+		files:    make(map[string]*file, 0),
+		children: make(map[string]map[string]*file, 0),
+	}
+}
+
+func (s *storage) Has(path string) bool {
+	path = clean(path)
+
+	_, ok := s.files[path]
+	return ok
+}
+
+func (s *storage) New(path string, mode os.FileMode, flag int) (*file, error) {
+	path = clean(path)
+	if s.Has(path) {
+		if !s.MustGet(path).mode.IsDir() {
+			return nil, fmt.Errorf("file already exists %q", path)
+		}
+
+		return nil, nil
+	}
+
+	name := filepath.Base(path)
+
+	f := &file{
+		name:    name,
+		content: &content{name: name},
+		mode:    mode,
+		flag:    flag,
+		mtime:   time.Now(),
+	}
+
+	s.files[path] = f
+	if err := s.createParent(path, mode, f); err != nil {
+		return nil, err
+	}
+	return f, nil
+}
+
+func (s *storage) createParent(path string, mode os.FileMode, f *file) error {
+	base := filepath.Dir(path)
+	base = clean(base)
+	if f.Name() == string(separator) {
+		return nil
+	}
+
+	if _, err := s.New(base, mode.Perm()|os.ModeDir, 0); err != nil {
+		return err
+	}
+
+	if _, ok := s.children[base]; !ok {
+		s.children[base] = make(map[string]*file, 0)
+	}
+
+	s.children[base][f.Name()] = f
+	return nil
+}
+
+func (s *storage) Children(path string) []*file {
+	path = clean(path)
+
+	l := make([]*file, 0)
+	for _, f := range s.children[path] {
+		l = append(l, f)
+	}
+
+	return l
+}
+
+func (s *storage) MustGet(path string) *file {
+	f, ok := s.Get(path)
+	if !ok {
+		panic(fmt.Errorf("couldn't find %q", path))
+	}
+
+	return f
+}
+
+func (s *storage) Get(path string) (*file, bool) {
+	path = clean(path)
+	if !s.Has(path) {
+		return nil, false
+	}
+
+	file, ok := s.files[path]
+	return file, ok
+}
+
+func (s *storage) Rename(from, to string) error {
+	from = clean(from)
+	to = clean(to)
+
+	if !s.Has(from) {
+		return os.ErrNotExist
+	}
+
+	move := [][2]string{{from, to}}
+
+	for pathFrom := range s.files {
+		if pathFrom == from || !strings.HasPrefix(pathFrom, from) {
+			continue
+		}
+
+		rel, _ := filepath.Rel(from, pathFrom)
+		pathTo := filepath.Join(to, rel)
+
+		move = append(move, [2]string{pathFrom, pathTo})
+	}
+
+	for _, ops := range move {
+		from := ops[0]
+		to := ops[1]
+
+		if err := s.move(from, to); err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func (s *storage) move(from, to string) error {
+	s.files[to] = s.files[from]
+	s.files[to].name = filepath.Base(to)
+	s.children[to] = s.children[from]
+
+	defer func() {
+		delete(s.children, from)
+		delete(s.files, from)
+		delete(s.children[filepath.Dir(from)], filepath.Base(from))
+	}()
+
+	return s.createParent(to, 0644, s.files[to])
+}
+
+func (s *storage) Remove(path string) error {
+	path = clean(path)
+
+	f, has := s.Get(path)
+	if !has {
+		return os.ErrNotExist
+	}
+
+	if f.mode.IsDir() && len(s.children[path]) != 0 {
+		return fmt.Errorf("dir: %s contains files", path)
+	}
+
+	base, file := filepath.Split(path)
+	base = filepath.Clean(base)
+
+	delete(s.children[base], file)
+	delete(s.files, path)
+	return nil
+}
+
+func clean(path string) string {
+	return filepath.Clean(filepath.FromSlash(path))
+}
+
+type content struct {
+	name  string
+	bytes []byte
+
+	m sync.RWMutex
+}
+
+func (c *content) WriteAt(p []byte, off int64) (int, error) {
+	if off < 0 {
+		return 0, &os.PathError{
+			Op:   "writeat",
+			Path: c.name,
+			Err:  errors.New("negative offset"),
+		}
+	}
+
+	c.m.Lock()
+	prev := len(c.bytes)
+
+	diff := int(off) - prev
+	if diff > 0 {
+		c.bytes = append(c.bytes, make([]byte, diff)...)
+	}
+
+	c.bytes = append(c.bytes[:off], p...)
+	if len(c.bytes) < prev {
+		c.bytes = c.bytes[:prev]
+	}
+	c.m.Unlock()
+
+	return len(p), nil
+}
+
+func (c *content) ReadAt(b []byte, off int64) (n int, err error) {
+	if off < 0 {
+		return 0, &os.PathError{
+			Op:   "readat",
+			Path: c.name,
+			Err:  errors.New("negative offset"),
+		}
+	}
+
+	c.m.RLock()
+	size := int64(len(c.bytes))
+	if off >= size {
+		c.m.RUnlock()
+		return 0, io.EOF
+	}
+
+	l := int64(len(b))
+	if off+l > size {
+		l = size - off
+	}
+
+	btr := c.bytes[off : off+l]
+	n = copy(b, btr)
+
+	if len(btr) < len(b) {
+		err = io.EOF
+	}
+	c.m.RUnlock()
+
+	return
+}

server/pkg/go-nfs/helpers/nullauthhandler.go

@@ -0,0 +1,59 @@
+package helpers
+
+import (
+	"context"
+	"net"
+
+	"git.kmsign.ru/royalcat/tstor/server/pkg/ctxbilly"
+	nfs "git.kmsign.ru/royalcat/tstor/server/pkg/go-nfs"
+)
+
+// NewNullAuthHandler creates a handler for the provided filesystem
+func NewNullAuthHandler(fs nfs.Filesystem) nfs.Handler {
+	return &NullAuthHandler{fs}
+}
+
+// NullAuthHandler returns a NFS backing that exposes a given file system in response to all mount requests.
+type NullAuthHandler struct {
+	fs nfs.Filesystem
+}
+
+// Mount backs Mount RPC Requests, allowing for access control policies.
+func (h *NullAuthHandler) Mount(ctx context.Context, conn net.Conn, req nfs.MountRequest) (status nfs.MountStatus, hndl nfs.Filesystem, auths []nfs.AuthFlavor) {
+	status = nfs.MountStatusOk
+	hndl = h.fs
+	auths = []nfs.AuthFlavor{nfs.AuthFlavorNull}
+	return
+}
+
+// Change provides an interface for updating file attributes.
+func (h *NullAuthHandler) Change(fs nfs.Filesystem) nfs.Change {
+	if c, ok := h.fs.(ctxbilly.Change); ok {
+		return c
+	}
+	return nil
+}
+
+// FSStat provides information about a filesystem.
+func (h *NullAuthHandler) FSStat(context.Context, nfs.Filesystem, *nfs.FSStat) error {
+	return nil
+}
+
+// ToHandle handled by CachingHandler
+func (h *NullAuthHandler) ToHandle(context.Context, nfs.Filesystem, []string) []byte {
+	return []byte{}
+}
+
+// FromHandle handled by CachingHandler
+func (h *NullAuthHandler) FromHandle(context.Context, []byte) (nfs.Filesystem, []string, error) {
+	return nil, []string{}, nil
+}
+
+func (c *NullAuthHandler) InvalidateHandle(context.Context, nfs.Filesystem, []byte) error {
+	return nil
+}
+
+// HandleLImit handled by cachingHandler
+func (h *NullAuthHandler) HandleLimit() int {
+	return -1
+}