Initial commit

Proof-of-concept implementation. Bugs will occur.

vendor/github.com/hanwen/go-fuse/v2/splice/copy.go

@@ -0,0 +1,72 @@
+//go:build linux
+
+// 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 splice
+
+import (
+	"io"
+	"os"
+)
+
+func SpliceCopy(dst *os.File, src *os.File, p *Pair) (int64, error) {
+	total := int64(0)
+
+	for {
+		n, err := p.LoadFrom(src.Fd(), p.size)
+		if err != nil {
+			return total, err
+		}
+		if n == 0 {
+			break
+		}
+		m, err := p.WriteTo(dst.Fd(), n)
+		total += int64(m)
+		if err != nil {
+			return total, err
+		}
+		if m < n {
+			return total, err
+		}
+		if int(n) < p.size {
+			break
+		}
+	}
+
+	return total, nil
+}
+
+// Argument ordering follows io.Copy.
+func CopyFile(dstName string, srcName string, mode int) error {
+	src, err := os.Open(srcName)
+	if err != nil {
+		return err
+	}
+	defer src.Close()
+
+	dst, err := os.OpenFile(dstName, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, os.FileMode(mode))
+	if err != nil {
+		return err
+	}
+	defer dst.Close()
+
+	return CopyFds(dst, src)
+}
+
+func CopyFds(dst *os.File, src *os.File) (err error) {
+	p, err := splicePool.get()
+	if p != nil {
+		p.Grow(256 * 1024)
+		_, err := SpliceCopy(dst, src, p)
+		splicePool.done(p)
+		return err
+	} else {
+		_, err = io.Copy(dst, src)
+	}
+	if err == io.EOF {
+		err = nil
+	}
+	return err
+}

vendor/github.com/hanwen/go-fuse/v2/splice/pair.go

@@ -0,0 +1,70 @@
+//go:build linux
+
+// 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 splice
+
+import (
+	"fmt"
+	"syscall"
+)
+
+type Pair struct {
+	r, w int
+	size int
+}
+
+func (p *Pair) MaxGrow() {
+	for p.Grow(2*p.size) == nil {
+	}
+}
+
+func (p *Pair) Grow(n int) error {
+	if n <= p.size {
+		return nil
+	}
+	if !resizable {
+		return fmt.Errorf("splice: want %d bytes, but not resizable", n)
+	}
+	if n > maxPipeSize {
+		return fmt.Errorf("splice: want %d bytes, max pipe size %d", n, maxPipeSize)
+	}
+
+	newsize, errNo := fcntl(uintptr(p.r), F_SETPIPE_SZ, n)
+	if errNo != 0 {
+		return fmt.Errorf("splice: fcntl returned %v", errNo)
+	}
+	p.size = newsize
+	return nil
+}
+
+func (p *Pair) Cap() int {
+	return p.size
+}
+
+func (p *Pair) Close() error {
+	err1 := syscall.Close(p.r)
+	err2 := syscall.Close(p.w)
+	if err1 != nil {
+		return err1
+	}
+	return err2
+}
+
+func (p *Pair) Read(d []byte) (n int, err error) {
+	return syscall.Read(p.r, d)
+}
+
+func (p *Pair) Write(d []byte) (n int, err error) {
+	return syscall.Write(p.w, d)
+}
+
+func (p *Pair) ReadFd() uintptr {
+	return uintptr(p.r)
+}
+
+func (p *Pair) WriteFd() uintptr {
+	return uintptr(p.w)
+}

vendor/github.com/hanwen/go-fuse/v2/splice/pair_linux.go

@@ -0,0 +1,54 @@
+// 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 splice
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"syscall"
+)
+
+func (p *Pair) LoadFromAt(fd uintptr, sz int, off int64) (int, error) {
+	n, err := syscall.Splice(int(fd), &off, p.w, nil, sz, 0)
+	return int(n), err
+}
+
+func (p *Pair) LoadFrom(fd uintptr, sz int) (int, error) {
+	if sz > p.size {
+		return 0, fmt.Errorf("LoadFrom: not enough space %d, %d",
+			sz, p.size)
+	}
+
+	n, err := syscall.Splice(int(fd), nil, p.w, nil, sz, 0)
+	if err != nil {
+		err = os.NewSyscallError("Splice load from", err)
+	}
+	return int(n), err
+}
+
+func (p *Pair) WriteTo(fd uintptr, n int) (int, error) {
+	m, err := syscall.Splice(p.r, nil, int(fd), nil, int(n), 0)
+	if err != nil {
+		err = os.NewSyscallError("Splice write", err)
+	}
+	return int(m), err
+}
+
+const _SPLICE_F_NONBLOCK = 0x2
+
+func (p *Pair) discard() {
+	_, err := syscall.Splice(p.r, nil, devNullFD(), nil, int(p.size), _SPLICE_F_NONBLOCK)
+	if err == syscall.EAGAIN {
+		// all good.
+	} else if err != nil {
+		errR := syscall.Close(p.r)
+		errW := syscall.Close(p.w)
+
+		// This can happen if something closed our fd
+		// inadvertently (eg. double close)
+		log.Panicf("splicing into /dev/null: %v (close R %d '%v', close W %d '%v')", err, p.r, errR, p.w, errW)
+	}
+}

vendor/github.com/hanwen/go-fuse/v2/splice/pool.go

@@ -0,0 +1,107 @@
+//go:build linux
+
+// 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 splice
+
+import (
+	"sync"
+)
+
+var splicePool *pairPool
+
+type pairPool struct {
+	sync.Mutex
+	unused    []*Pair
+	usedCount int
+}
+
+func ClearSplicePool() {
+	splicePool.clear()
+}
+
+func Get() (*Pair, error) {
+	return splicePool.get()
+}
+
+func Total() int {
+	return splicePool.total()
+}
+
+func Used() int {
+	return splicePool.used()
+}
+
+// Done returns the pipe pair to pool.
+func Done(p *Pair) {
+	splicePool.done(p)
+}
+
+// Closes and discards pipe pair.
+func Drop(p *Pair) {
+	splicePool.drop(p)
+}
+
+func newSplicePairPool() *pairPool {
+	return &pairPool{}
+}
+
+func (pp *pairPool) clear() {
+	pp.Lock()
+	for _, p := range pp.unused {
+		p.Close()
+	}
+	pp.unused = pp.unused[:0]
+	pp.Unlock()
+}
+
+func (pp *pairPool) used() (n int) {
+	pp.Lock()
+	n = pp.usedCount
+	pp.Unlock()
+
+	return n
+}
+
+func (pp *pairPool) total() int {
+	pp.Lock()
+	n := pp.usedCount + len(pp.unused)
+	pp.Unlock()
+	return n
+}
+
+func (pp *pairPool) drop(p *Pair) {
+	p.Close()
+	pp.Lock()
+	pp.usedCount--
+	pp.Unlock()
+}
+
+func (pp *pairPool) get() (p *Pair, err error) {
+	pp.Lock()
+	defer pp.Unlock()
+
+	pp.usedCount++
+	l := len(pp.unused)
+	if l > 0 {
+		p := pp.unused[l-1]
+		pp.unused = pp.unused[:l-1]
+		return p, nil
+	}
+
+	return newSplicePair()
+}
+
+func (pp *pairPool) done(p *Pair) {
+	p.discard()
+	pp.Lock()
+	pp.usedCount--
+	pp.unused = append(pp.unused, p)
+	pp.Unlock()
+}
+
+func init() {
+	splicePool = newSplicePairPool()
+}

vendor/github.com/hanwen/go-fuse/v2/splice/splice.go

@@ -0,0 +1,106 @@
+//go:build linux
+
+// 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 splice
+
+// Routines for efficient file to file copying.
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"sync"
+	"syscall"
+)
+
+var maxPipeSize int
+var resizable bool
+
+func Resizable() bool {
+	return resizable
+}
+
+func MaxPipeSize() int {
+	return maxPipeSize
+}
+
+// From manpage on ubuntu Lucid:
+//
+// Since Linux 2.6.11, the pipe capacity is 65536 bytes.
+const DefaultPipeSize = 16 * 4096
+
+var (
+	devNullFDOnce  sync.Once
+	devNullFDValue int
+)
+
+func init() {
+	content, err := os.ReadFile("/proc/sys/fs/pipe-max-size")
+	if err != nil {
+		maxPipeSize = DefaultPipeSize
+	} else {
+		fmt.Sscan(string(content), &maxPipeSize)
+	}
+
+	r, w, err := os.Pipe()
+	if err != nil {
+		log.Panicf("cannot create pipe: %v", err)
+	}
+	sz, errNo := fcntl(r.Fd(), F_GETPIPE_SZ, 0)
+	resizable = (errNo == 0)
+	_, errNo = fcntl(r.Fd(), F_SETPIPE_SZ, 2*sz)
+	resizable = resizable && (errNo == 0)
+	r.Close()
+	w.Close()
+}
+
+// We empty pipes by splicing to /dev/null.
+func devNullFD() int {
+	devNullFDOnce.Do(func() {
+		fd, err := syscall.Open("/dev/null", os.O_WRONLY, 0)
+		if err != nil {
+			panic(fmt.Sprintf("failed to open /dev/null: %s", err))
+		}
+		devNullFDValue = fd
+	})
+	return devNullFDValue
+}
+
+// copy & paste from syscall.
+func fcntl(fd uintptr, cmd int, arg int) (val int, errno syscall.Errno) {
+	r0, _, e1 := syscall.Syscall(syscall.SYS_FCNTL, fd, uintptr(cmd), uintptr(arg))
+	val = int(r0)
+	errno = syscall.Errno(e1)
+	return
+}
+
+const F_SETPIPE_SZ = 1031
+const F_GETPIPE_SZ = 1032
+
+func osPipe() (int, int, error) {
+	var fds [2]int
+	err := syscall.Pipe2(fds[:], syscall.O_NONBLOCK)
+	return fds[0], fds[1], err
+}
+
+func newSplicePair() (p *Pair, err error) {
+	p = &Pair{}
+	p.r, p.w, err = osPipe()
+	if err != nil {
+		return nil, err
+	}
+	var errNo syscall.Errno
+	p.size, errNo = fcntl(uintptr(p.r), F_GETPIPE_SZ, 0)
+	if err == syscall.EINVAL {
+		p.size = DefaultPipeSize
+		return p, nil
+	}
+	if errNo != 0 {
+		p.Close()
+		return nil, fmt.Errorf("fcntl getsize: %v", errNo)
+	}
+	return p, nil
+}