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// Copyright 2019 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package gofer
import (
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/lisafs"
"gvisor.dev/gvisor/pkg/log"
"gvisor.dev/gvisor/pkg/safemem"
"gvisor.dev/gvisor/pkg/sentry/hostfd"
"gvisor.dev/gvisor/pkg/sync"
)
// handle represents a remote "open file descriptor", consisting of an opened
// lisafs FD and optionally a host file descriptor.
//
// These are explicitly not savable.
type handle struct {
fdLisa lisafs.ClientFD
fd int32 // -1 if unavailable
}
// Preconditions: read || write.
func openHandle(ctx context.Context, fdLisa lisafs.ClientFD, read, write, trunc bool) (handle, error) {
flags := uint32(unix.O_RDONLY)
switch {
case read && write:
flags = unix.O_RDWR
case read:
flags = unix.O_RDONLY
case write:
flags = unix.O_WRONLY
default:
log.Debugf("openHandle called with read = write = false. Falling back to read only FD.")
}
if trunc {
flags |= unix.O_TRUNC
}
openFD, hostFD, err := fdLisa.OpenAt(ctx, flags)
if err != nil {
return handle{fd: -1}, err
}
h := handle{
fdLisa: fdLisa.Client().NewFD(openFD),
fd: int32(hostFD),
}
return h, nil
}
func (h *handle) isOpen() bool {
return h.fdLisa.Ok()
}
func (h *handle) close(ctx context.Context) {
h.fdLisa.Close(ctx, true /* flush */)
if h.fd >= 0 {
unix.Close(int(h.fd))
h.fd = -1
}
}
func (h *handle) readToBlocksAt(ctx context.Context, dsts safemem.BlockSeq, offset uint64) (uint64, error) {
if dsts.IsEmpty() {
return 0, nil
}
if h.fd >= 0 {
ctx.UninterruptibleSleepStart(false)
n, err := hostfd.Preadv2(h.fd, dsts, int64(offset), 0 /* flags */)
ctx.UninterruptibleSleepFinish(false)
return n, err
}
rw := getHandleReadWriter(ctx, h, int64(offset))
defer putHandleReadWriter(rw)
return safemem.FromIOReader{rw}.ReadToBlocks(dsts)
}
func (h *handle) writeFromBlocksAt(ctx context.Context, srcs safemem.BlockSeq, offset uint64) (uint64, error) {
if srcs.IsEmpty() {
return 0, nil
}
if h.fd >= 0 {
ctx.UninterruptibleSleepStart(false)
n, err := hostfd.Pwritev2(h.fd, srcs, int64(offset), 0 /* flags */)
ctx.UninterruptibleSleepFinish(false)
return n, err
}
rw := getHandleReadWriter(ctx, h, int64(offset))
defer putHandleReadWriter(rw)
return safemem.FromIOWriter{rw}.WriteFromBlocks(srcs)
}
type handleReadWriter struct {
ctx context.Context
h *handle
off uint64
}
var handleReadWriterPool = sync.Pool{
New: func() any {
return &handleReadWriter{}
},
}
func getHandleReadWriter(ctx context.Context, h *handle, offset int64) *handleReadWriter {
rw := handleReadWriterPool.Get().(*handleReadWriter)
rw.ctx = ctx
rw.h = h
rw.off = uint64(offset)
return rw
}
func putHandleReadWriter(rw *handleReadWriter) {
rw.ctx = nil
rw.h = nil
handleReadWriterPool.Put(rw)
}
// Read implements io.Reader.Read.
func (rw *handleReadWriter) Read(dst []byte) (int, error) {
n, err := rw.h.fdLisa.Read(rw.ctx, dst, rw.off)
rw.off += n
return int(n), err
}
// Write implements io.Writer.Write.
func (rw *handleReadWriter) Write(src []byte) (int, error) {
n, err := rw.h.fdLisa.Write(rw.ctx, src, rw.off)
rw.off += n
return int(n), err
}
// ReadToBlocks implements safemem.Reader.ReadToBlocks.
func (rw *handleReadWriter) ReadToBlocks(dsts safemem.BlockSeq) (uint64, error) {
n, err := rw.h.readToBlocksAt(rw.ctx, dsts, rw.off)
rw.off += n
return n, err
}
// WriteFromBlocks implements safemem.Writer.WriteFromBlocks.
func (rw *handleReadWriter) WriteFromBlocks(srcs safemem.BlockSeq) (uint64, error) {
n, err := rw.h.writeFromBlocksAt(rw.ctx, srcs, rw.off)
rw.off += n
return n, err
}
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