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server.go
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server.go
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// Copyright 2016 the Go-FUSE Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package fuse
import (
"fmt"
"log"
"math"
"os"
"path/filepath"
"runtime"
"strings"
"sync"
"syscall"
"time"
"unsafe"
)
const (
// The kernel caps writes at 128k.
MAX_KERNEL_WRITE = 128 * 1024
minMaxReaders = 2
maxMaxReaders = 16
)
// Server contains the logic for reading from the FUSE device and
// translating it to RawFileSystem interface calls.
type Server struct {
// Empty if unmounted.
mountPoint string
fileSystem RawFileSystem
// writeMu serializes close and notify writes
writeMu sync.Mutex
// I/O with kernel and daemon.
mountFd int
latencies LatencyMap
opts *MountOptions
// maxReaders is the maximum number of goroutines reading requests
maxReaders int
// Pools for []byte
buffers bufferPool
// Pool for request structs.
reqPool sync.Pool
// Pool for raw requests data
readPool sync.Pool
reqMu sync.Mutex
reqReaders int
reqInflight []*request
kernelSettings InitIn
// in-flight notify-retrieve queries
retrieveMu sync.Mutex
retrieveNext uint64
retrieveTab map[uint64]*retrieveCacheRequest // notifyUnique -> retrieve request
singleReader bool
canSplice bool
loops sync.WaitGroup
ready chan error
// for implementing single threaded processing.
requestProcessingMu sync.Mutex
}
// SetDebug is deprecated. Use MountOptions.Debug instead.
func (ms *Server) SetDebug(dbg bool) {
// This will typically trigger the race detector.
ms.opts.Debug = dbg
}
// KernelSettings returns the Init message from the kernel, so
// filesystems can adapt to availability of features of the kernel
// driver. The message should not be altered.
func (ms *Server) KernelSettings() *InitIn {
ms.reqMu.Lock()
s := ms.kernelSettings
ms.reqMu.Unlock()
return &s
}
const _MAX_NAME_LEN = 20
// This type may be provided for recording latencies of each FUSE
// operation.
type LatencyMap interface {
Add(name string, dt time.Duration)
}
// RecordLatencies switches on collection of timing for each request
// coming from the kernel.P assing a nil argument switches off the
func (ms *Server) RecordLatencies(l LatencyMap) {
ms.latencies = l
}
// Unmount calls fusermount -u on the mount. This has the effect of
// shutting down the filesystem. After the Server is unmounted, it
// should be discarded.
func (ms *Server) Unmount() (err error) {
if ms.mountPoint == "" {
return nil
}
delay := time.Duration(0)
for try := 0; try < 5; try++ {
err = unmount(ms.mountPoint, ms.opts)
if err == nil {
break
}
// Sleep for a bit. This is not pretty, but there is
// no way we can be certain that the kernel thinks all
// open files have already been closed.
delay = 2*delay + 5*time.Millisecond
time.Sleep(delay)
}
if err != nil {
return
}
// Wait for event loops to exit.
ms.loops.Wait()
ms.mountPoint = ""
return err
}
// NewServer creates a server and attaches it to the given directory.
func NewServer(fs RawFileSystem, mountPoint string, opts *MountOptions) (*Server, error) {
if opts == nil {
opts = &MountOptions{
MaxBackground: _DEFAULT_BACKGROUND_TASKS,
}
}
o := *opts
if o.MaxWrite < 0 {
o.MaxWrite = 0
}
if o.MaxWrite == 0 {
o.MaxWrite = 1 << 16
}
if o.MaxWrite > MAX_KERNEL_WRITE {
o.MaxWrite = MAX_KERNEL_WRITE
}
if o.Name == "" {
name := fs.String()
l := len(name)
if l > _MAX_NAME_LEN {
l = _MAX_NAME_LEN
}
o.Name = strings.Replace(name[:l], ",", ";", -1)
}
for _, s := range o.optionsStrings() {
if strings.Contains(s, ",") {
return nil, fmt.Errorf("found ',' in option string %q", s)
}
}
maxReaders := runtime.GOMAXPROCS(0)
if maxReaders < minMaxReaders {
maxReaders = minMaxReaders
} else if maxReaders > maxMaxReaders {
maxReaders = maxMaxReaders
}
ms := &Server{
fileSystem: fs,
opts: &o,
maxReaders: maxReaders,
retrieveTab: make(map[uint64]*retrieveCacheRequest),
// OSX has races when multiple routines read from the
// FUSE device: on unmount, sometime some reads do not
// error-out, meaning that unmount will hang.
singleReader: runtime.GOOS == "darwin",
ready: make(chan error, 1),
}
ms.reqPool.New = func() interface{} {
return &request{
cancel: make(chan struct{}),
}
}
ms.readPool.New = func() interface{} {
buf := make([]byte, o.MaxWrite+int(maxInputSize)+logicalBlockSize)
buf = alignSlice(buf, unsafe.Sizeof(WriteIn{}), logicalBlockSize, uintptr(o.MaxWrite)+maxInputSize)
return buf
}
mountPoint = filepath.Clean(mountPoint)
if !filepath.IsAbs(mountPoint) {
cwd, err := os.Getwd()
if err != nil {
return nil, err
}
mountPoint = filepath.Clean(filepath.Join(cwd, mountPoint))
}
fd, err := mount(mountPoint, &o, ms.ready)
if err != nil {
return nil, err
}
ms.mountPoint = mountPoint
ms.mountFd = fd
if code := ms.handleInit(); !code.Ok() {
syscall.Close(fd)
// TODO - unmount as well?
return nil, fmt.Errorf("init: %s", code)
}
// This prepares for Serve being called somewhere, either
// synchronously or asynchronously.
ms.loops.Add(1)
return ms, nil
}
func (o *MountOptions) optionsStrings() []string {
var r []string
r = append(r, o.Options...)
if o.AllowOther {
r = append(r, "allow_other")
}
if o.FsName != "" {
r = append(r, "fsname="+o.FsName)
}
if o.Name != "" {
r = append(r, "subtype="+o.Name)
}
return r
}
// DebugData returns internal status information for debugging
// purposes.
func (ms *Server) DebugData() string {
var r int
ms.reqMu.Lock()
r = ms.reqReaders
ms.reqMu.Unlock()
return fmt.Sprintf("readers: %d", r)
}
// handleEINTR retries the given function until it doesn't return syscall.EINTR.
// This is similar to the HANDLE_EINTR() macro from Chromium ( see
// https://code.google.com/p/chromium/codesearch#chromium/src/base/posix/eintr_wrapper.h
// ) and the TEMP_FAILURE_RETRY() from glibc (see
// https://www.gnu.org/software/libc/manual/html_node/Interrupted-Primitives.html
// ).
//
// Don't use handleEINTR() with syscall.Close(); see
// https://code.google.com/p/chromium/issues/detail?id=269623 .
func handleEINTR(fn func() error) (err error) {
for {
err = fn()
if err != syscall.EINTR {
break
}
}
return
}
// Returns a new request, or error. In case exitIdle is given, returns
// nil, OK if we have too many readers already.
func (ms *Server) readRequest(exitIdle bool) (req *request, code Status) {
req = ms.reqPool.Get().(*request)
dest := ms.readPool.Get().([]byte)
ms.reqMu.Lock()
if ms.reqReaders > ms.maxReaders {
ms.reqMu.Unlock()
return nil, OK
}
ms.reqReaders++
ms.reqMu.Unlock()
var n int
err := handleEINTR(func() error {
var err error
n, err = syscall.Read(ms.mountFd, dest)
return err
})
if err != nil {
code = ToStatus(err)
ms.reqPool.Put(req)
ms.reqMu.Lock()
ms.reqReaders--
ms.reqMu.Unlock()
return nil, code
}
if ms.latencies != nil {
req.startTime = time.Now()
}
gobbled := req.setInput(dest[:n])
ms.reqMu.Lock()
defer ms.reqMu.Unlock()
// Must parse request.Unique under lock
if status := req.parseHeader(); !status.Ok() {
return nil, status
}
req.inflightIndex = len(ms.reqInflight)
ms.reqInflight = append(ms.reqInflight, req)
if !gobbled {
ms.readPool.Put(dest)
dest = nil
}
ms.reqReaders--
if !ms.singleReader && ms.reqReaders <= 0 {
ms.loops.Add(1)
go ms.loop(true)
}
return req, OK
}
// returnRequest returns a request to the pool of unused requests.
func (ms *Server) returnRequest(req *request) {
ms.reqMu.Lock()
this := req.inflightIndex
last := len(ms.reqInflight) - 1
if last != this {
ms.reqInflight[this] = ms.reqInflight[last]
ms.reqInflight[this].inflightIndex = this
}
ms.reqInflight = ms.reqInflight[:last]
interrupted := req.interrupted
ms.reqMu.Unlock()
ms.recordStats(req)
if interrupted {
// Don't reposses data, because someone might still
// be looking at it
return
}
if req.bufferPoolOutputBuf != nil {
ms.buffers.FreeBuffer(req.bufferPoolOutputBuf)
req.bufferPoolOutputBuf = nil
}
req.clear()
if p := req.bufferPoolInputBuf; p != nil {
req.bufferPoolInputBuf = nil
ms.readPool.Put(p)
}
ms.reqPool.Put(req)
}
func (ms *Server) recordStats(req *request) {
if ms.latencies != nil {
dt := time.Now().Sub(req.startTime)
opname := operationName(req.inHeader.Opcode)
ms.latencies.Add(opname, dt)
}
}
// Serve initiates the FUSE loop. Normally, callers should run Serve()
// and wait for it to exit, but tests will want to run this in a
// goroutine.
//
// Each filesystem operation executes in a separate goroutine.
func (ms *Server) Serve() {
ms.loop(false)
ms.loops.Wait()
ms.writeMu.Lock()
syscall.Close(ms.mountFd)
ms.writeMu.Unlock()
// shutdown in-flight cache retrieves.
//
// It is possible that umount comes in the middle - after retrieve
// request was sent to kernel, but corresponding kernel reply has not
// yet been read. We unblock all such readers and wake them up with ENODEV.
ms.retrieveMu.Lock()
rtab := ms.retrieveTab
// retrieve attempts might be erroneously tried even after close
// we have to keep retrieveTab !nil not to panic.
ms.retrieveTab = make(map[uint64]*retrieveCacheRequest)
ms.retrieveMu.Unlock()
for _, reading := range rtab {
reading.n = 0
reading.st = ENODEV
close(reading.ready)
}
}
// Wait waits for the serve loop to exit. This should only be called
// after Serve has been called, or it will hang indefinitely.
func (ms *Server) Wait() {
ms.loops.Wait()
}
func (ms *Server) handleInit() Status {
// The first request should be INIT; read it synchronously,
// and don't spawn new readers.
orig := ms.singleReader
ms.singleReader = true
req, errNo := ms.readRequest(false)
ms.singleReader = orig
if errNo != OK || req == nil {
return errNo
}
if code := ms.handleRequest(req); !code.Ok() {
return code
}
// INIT is handled. Init the file system, but don't accept
// incoming requests, so the file system can setup itself.
ms.fileSystem.Init(ms)
return OK
}
func (ms *Server) loop(exitIdle bool) {
defer ms.loops.Done()
exit:
for {
req, errNo := ms.readRequest(exitIdle)
switch errNo {
case OK:
if req == nil {
break exit
}
case ENOENT:
continue
case ENODEV:
// unmount
if ms.opts.Debug {
log.Printf("received ENODEV (unmount request), thread exiting")
}
break exit
default: // some other error?
log.Printf("Failed to read from fuse conn: %v", errNo)
break exit
}
if ms.singleReader {
go ms.handleRequest(req)
} else {
ms.handleRequest(req)
}
}
}
func (ms *Server) handleRequest(req *request) Status {
if ms.opts.SingleThreaded {
ms.requestProcessingMu.Lock()
defer ms.requestProcessingMu.Unlock()
}
req.parse()
if req.handler == nil {
req.status = ENOSYS
}
if req.status.Ok() && ms.opts.Debug {
log.Println(req.InputDebug())
}
if req.inHeader.NodeId == pollHackInode ||
req.inHeader.NodeId == FUSE_ROOT_ID && len(req.filenames) > 0 && req.filenames[0] == pollHackName {
doPollHackLookup(ms, req)
} else if req.status.Ok() && req.handler.Func == nil {
log.Printf("Unimplemented opcode %v", operationName(req.inHeader.Opcode))
req.status = ENOSYS
} else if req.status.Ok() {
req.handler.Func(ms, req)
}
errNo := ms.write(req)
if errNo != 0 {
log.Printf("writer: Write/Writev failed, err: %v. opcode: %v",
errNo, operationName(req.inHeader.Opcode))
}
ms.returnRequest(req)
return Status(errNo)
}
// alignSlice ensures that the byte at alignedByte is aligned with the
// given logical block size. The input slice should be at least (size
// + blockSize)
func alignSlice(buf []byte, alignedByte, blockSize, size uintptr) []byte {
misaligned := uintptr(unsafe.Pointer(&buf[alignedByte])) & (blockSize - 1)
buf = buf[blockSize-misaligned:]
return buf[:size]
}
func (ms *Server) allocOut(req *request, size uint32) []byte {
if cap(req.bufferPoolOutputBuf) >= int(size) {
req.bufferPoolOutputBuf = req.bufferPoolOutputBuf[:size]
return req.bufferPoolOutputBuf
}
if req.bufferPoolOutputBuf != nil {
ms.buffers.FreeBuffer(req.bufferPoolOutputBuf)
req.bufferPoolOutputBuf = nil
}
// As this allocated a multiple of the page size, very likely
// this is aligned to logicalBlockSize too, which is smaller.
req.bufferPoolOutputBuf = ms.buffers.AllocBuffer(size)
return req.bufferPoolOutputBuf
}
func (ms *Server) write(req *request) Status {
// Forget/NotifyReply do not wait for reply from filesystem server.
switch req.inHeader.Opcode {
case _OP_FORGET, _OP_BATCH_FORGET, _OP_NOTIFY_REPLY:
return OK
case _OP_INTERRUPT:
if req.status.Ok() {
return OK
}
}
header := req.serializeHeader(req.flatDataSize())
if ms.opts.Debug {
log.Println(req.OutputDebug())
}
if header == nil {
return OK
}
s := ms.systemWrite(req, header)
return s
}
// InodeNotify invalidates the information associated with the inode
// (ie. data cache, attributes, etc.)
func (ms *Server) InodeNotify(node uint64, off int64, length int64) Status {
if !ms.kernelSettings.SupportsNotify(NOTIFY_INVAL_INODE) {
return ENOSYS
}
req := request{
inHeader: &InHeader{
Opcode: _OP_NOTIFY_INVAL_INODE,
},
handler: operationHandlers[_OP_NOTIFY_INVAL_INODE],
status: NOTIFY_INVAL_INODE,
}
entry := (*NotifyInvalInodeOut)(req.outData())
entry.Ino = node
entry.Off = off
entry.Length = length
// Protect against concurrent close.
ms.writeMu.Lock()
result := ms.write(&req)
ms.writeMu.Unlock()
if ms.opts.Debug {
log.Println("Response: INODE_NOTIFY", result)
}
return result
}
// InodeNotifyStoreCache tells kernel to store data into inode's cache.
//
// This call is similar to InodeNotify, but instead of only invalidating a data
// region, it gives updated data directly to the kernel.
func (ms *Server) InodeNotifyStoreCache(node uint64, offset int64, data []byte) Status {
if !ms.kernelSettings.SupportsNotify(NOTIFY_STORE_CACHE) {
return ENOSYS
}
for len(data) > 0 {
size := len(data)
if size > math.MaxInt32 {
// NotifyStoreOut has only uint32 for size.
// we check for max(int32), not max(uint32), because on 32-bit
// platforms int has only 31-bit for positive range.
size = math.MaxInt32
}
st := ms.inodeNotifyStoreCache32(node, offset, data[:size])
if st != OK {
return st
}
data = data[size:]
offset += int64(size)
}
return OK
}
// inodeNotifyStoreCache32 is internal worker for InodeNotifyStoreCache which
// handles data chunks not larger than 2GB.
func (ms *Server) inodeNotifyStoreCache32(node uint64, offset int64, data []byte) Status {
req := request{
inHeader: &InHeader{
Opcode: _OP_NOTIFY_STORE_CACHE,
},
handler: operationHandlers[_OP_NOTIFY_STORE_CACHE],
status: NOTIFY_STORE_CACHE,
}
store := (*NotifyStoreOut)(req.outData())
store.Nodeid = node
store.Offset = uint64(offset) // NOTE not int64, as it is e.g. in NotifyInvalInodeOut
store.Size = uint32(len(data))
req.flatData = data
// Protect against concurrent close.
ms.writeMu.Lock()
result := ms.write(&req)
ms.writeMu.Unlock()
if ms.opts.Debug {
log.Printf("Response: INODE_NOTIFY_STORE_CACHE: %v", result)
}
return result
}
// InodeRetrieveCache retrieves data from kernel's inode cache.
//
// InodeRetrieveCache asks kernel to return data from its cache for inode at
// [offset:offset+len(dest)) and waits for corresponding reply. If kernel cache
// has fewer consecutive data starting at offset, that fewer amount is returned.
// In particular if inode data at offset is not cached (0, OK) is returned.
//
// The kernel returns ENOENT if it does not currently have entry for this inode
// in its dentry cache.
func (ms *Server) InodeRetrieveCache(node uint64, offset int64, dest []byte) (n int, st Status) {
// the kernel won't send us in one go more then what we negotiated as MaxWrite.
// retrieve the data in chunks.
// TODO spawn some number of readahead retrievers in parallel.
ntotal := 0
for {
chunkSize := len(dest)
if chunkSize > ms.opts.MaxWrite {
chunkSize = ms.opts.MaxWrite
}
n, st = ms.inodeRetrieveCache1(node, offset, dest[:chunkSize])
if st != OK || n == 0 {
break
}
ntotal += n
offset += int64(n)
dest = dest[n:]
}
// if we could retrieve at least something - it is ok.
// if ntotal=0 - st will be st returned from first inodeRetrieveCache1.
if ntotal > 0 {
st = OK
}
return ntotal, st
}
// inodeRetrieveCache1 is internal worker for InodeRetrieveCache which
// actually talks to kernel and retrieves chunks not larger than ms.opts.MaxWrite.
func (ms *Server) inodeRetrieveCache1(node uint64, offset int64, dest []byte) (n int, st Status) {
if !ms.kernelSettings.SupportsNotify(NOTIFY_RETRIEVE_CACHE) {
return 0, ENOSYS
}
req := request{
inHeader: &InHeader{
Opcode: _OP_NOTIFY_RETRIEVE_CACHE,
},
handler: operationHandlers[_OP_NOTIFY_RETRIEVE_CACHE],
status: NOTIFY_RETRIEVE_CACHE,
}
// retrieve up to 2GB not to overflow uint32 size in NotifyRetrieveOut.
// see InodeNotifyStoreCache in similar place for why it is only 2GB, not 4GB.
//
// ( InodeRetrieveCache calls us with chunks not larger than
// ms.opts.MaxWrite, but MaxWrite is int, so let's be extra cautious )
size := len(dest)
if size > math.MaxInt32 {
size = math.MaxInt32
}
dest = dest[:size]
q := (*NotifyRetrieveOut)(req.outData())
q.Nodeid = node
q.Offset = uint64(offset) // not int64, as it is e.g. in NotifyInvalInodeOut
q.Size = uint32(len(dest))
reading := &retrieveCacheRequest{
nodeid: q.Nodeid,
offset: q.Offset,
dest: dest,
ready: make(chan struct{}),
}
ms.retrieveMu.Lock()
q.NotifyUnique = ms.retrieveNext
ms.retrieveNext++
ms.retrieveTab[q.NotifyUnique] = reading
ms.retrieveMu.Unlock()
// Protect against concurrent close.
ms.writeMu.Lock()
result := ms.write(&req)
ms.writeMu.Unlock()
if ms.opts.Debug {
log.Printf("Response: NOTIFY_RETRIEVE_CACHE: %v", result)
}
if result != OK {
ms.retrieveMu.Lock()
r := ms.retrieveTab[q.NotifyUnique]
if r == reading {
delete(ms.retrieveTab, q.NotifyUnique)
} else if r == nil {
// ok - might be dequeued by umount
} else {
// although very unlikely, it is possible that kernel sends
// unexpected NotifyReply with our notifyUnique, then
// retrieveNext wraps, makes full cycle, and another
// retrieve request is made with the same notifyUnique.
log.Printf("W: INODE_RETRIEVE_CACHE: request with notifyUnique=%d mutated", q.NotifyUnique)
}
ms.retrieveMu.Unlock()
return 0, result
}
// NotifyRetrieveOut sent to the kernel successfully. Now the kernel
// have to return data in a separate write-style NotifyReply request.
// Wait for the result.
<-reading.ready
return reading.n, reading.st
}
// retrieveCacheRequest represents in-flight cache retrieve request.
type retrieveCacheRequest struct {
nodeid uint64
offset uint64
dest []byte
// reply status
n int
st Status
ready chan struct{}
}
// DeleteNotify notifies the kernel that an entry is removed from a
// directory. In many cases, this is equivalent to EntryNotify,
// except when the directory is in use, eg. as working directory of
// some process. You should not hold any FUSE filesystem locks, as that
// can lead to deadlock.
func (ms *Server) DeleteNotify(parent uint64, child uint64, name string) Status {
if ms.kernelSettings.Minor < 18 {
return ms.EntryNotify(parent, name)
}
req := request{
inHeader: &InHeader{
Opcode: _OP_NOTIFY_DELETE,
},
handler: operationHandlers[_OP_NOTIFY_DELETE],
status: NOTIFY_DELETE,
}
entry := (*NotifyInvalDeleteOut)(req.outData())
entry.Parent = parent
entry.Child = child
entry.NameLen = uint32(len(name))
// Many versions of FUSE generate stacktraces if the
// terminating null byte is missing.
nameBytes := make([]byte, len(name)+1)
copy(nameBytes, name)
nameBytes[len(nameBytes)-1] = '\000'
req.flatData = nameBytes
// Protect against concurrent close.
ms.writeMu.Lock()
result := ms.write(&req)
ms.writeMu.Unlock()
if ms.opts.Debug {
log.Printf("Response: DELETE_NOTIFY: %v", result)
}
return result
}
// EntryNotify should be used if the existence status of an entry
// within a directory changes. You should not hold any FUSE filesystem
// locks, as that can lead to deadlock.
func (ms *Server) EntryNotify(parent uint64, name string) Status {
if !ms.kernelSettings.SupportsNotify(NOTIFY_INVAL_ENTRY) {
return ENOSYS
}
req := request{
inHeader: &InHeader{
Opcode: _OP_NOTIFY_INVAL_ENTRY,
},
handler: operationHandlers[_OP_NOTIFY_INVAL_ENTRY],
status: NOTIFY_INVAL_ENTRY,
}
entry := (*NotifyInvalEntryOut)(req.outData())
entry.Parent = parent
entry.NameLen = uint32(len(name))
// Many versions of FUSE generate stacktraces if the
// terminating null byte is missing.
nameBytes := make([]byte, len(name)+1)
copy(nameBytes, name)
nameBytes[len(nameBytes)-1] = '\000'
req.flatData = nameBytes
// Protect against concurrent close.
ms.writeMu.Lock()
result := ms.write(&req)
ms.writeMu.Unlock()
if ms.opts.Debug {
log.Printf("Response: ENTRY_NOTIFY: %v", result)
}
return result
}
// SupportsVersion returns true if the kernel supports the given
// protocol version or newer.
func (in *InitIn) SupportsVersion(maj, min uint32) bool {
return in.Major > maj || (in.Major == maj && in.Minor >= min)
}
// SupportsNotify returns whether a certain notification type is
// supported. Pass any of the NOTIFY_* types as argument.
func (in *InitIn) SupportsNotify(notifyType int) bool {
switch notifyType {
case NOTIFY_INVAL_ENTRY:
return in.SupportsVersion(7, 12)
case NOTIFY_INVAL_INODE:
return in.SupportsVersion(7, 12)
case NOTIFY_STORE_CACHE, NOTIFY_RETRIEVE_CACHE:
return in.SupportsVersion(7, 15)
case NOTIFY_DELETE:
return in.SupportsVersion(7, 18)
}
return false
}
// WaitMount waits for the first request to be served. Use this to
// avoid racing between accessing the (empty or not yet mounted)
// mountpoint, and the OS trying to setup the user-space mount.
func (ms *Server) WaitMount() error {
err := <-ms.ready
if err != nil {
return err
}
return pollHack(ms.mountPoint)
}