syncthing/lib/fs/basicfs_copy_range_ioctl.go
2020-08-19 07:56:35 +02:00

94 lines
2.1 KiB
Go

// Copyright (C) 2019 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.
// +build linux,!ppc,!ppc64,!ppc64le
package fs
import (
"io"
"syscall"
"unsafe"
)
func init() {
registerCopyRangeImplementation(CopyRangeMethodIoctl, copyRangeImplementationForBasicFile(copyRangeIoctl))
}
const FICLONE = 0x40049409
const FICLONERANGE = 0x4020940d
/*
http://man7.org/linux/man-pages/man2/ioctl_ficlonerange.2.html
struct file_clone_range {
__s64 src_fd;
__u64 src_offset;
__u64 src_length;
__u64 dest_offset;
};
*/
type fileCloneRange struct {
srcFd int64
srcOffset uint64
srcLength uint64
dstOffset uint64
}
func copyRangeIoctl(src, dst basicFile, srcOffset, dstOffset, size int64) error {
fi, err := src.Stat()
if err != nil {
return err
}
if srcOffset+size > fi.Size() {
return io.ErrUnexpectedEOF
}
// https://www.man7.org/linux/man-pages/man2/ioctl_ficlonerange.2.html
// If src_length is zero, the ioctl reflinks to the end of the source file.
if srcOffset+size == fi.Size() {
size = 0
}
if srcOffset == 0 && dstOffset == 0 && size == 0 {
// Optimization for whole file copies.
var errNo syscall.Errno
_, err := withFileDescriptors(src, dst, func(srcFd, dstFd uintptr) (int, error) {
_, _, errNo = syscall.Syscall(syscall.SYS_IOCTL, dstFd, FICLONE, srcFd)
return 0, nil
})
// Failure in withFileDescriptors
if err != nil {
return err
}
if errNo != 0 {
return errNo
}
return nil
}
var errNo syscall.Errno
_, err = withFileDescriptors(src, dst, func(srcFd, dstFd uintptr) (int, error) {
params := fileCloneRange{
srcFd: int64(srcFd),
srcOffset: uint64(srcOffset),
srcLength: uint64(size),
dstOffset: uint64(dstOffset),
}
_, _, errNo = syscall.Syscall(syscall.SYS_IOCTL, dstFd, FICLONERANGE, uintptr(unsafe.Pointer(&params)))
return 0, nil
})
// Failure in withFileDescriptors
if err != nil {
return err
}
if errNo != 0 {
return errNo
}
return nil
}