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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/p9"
"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
// fid (p9.File) and optionally a host file descriptor.
//
// These are explicitly not savable.
type handle struct {
file p9file
fd int32 // -1 if unavailable
}
// Preconditions: read || write.
func openHandle(ctx context.Context, file p9file, read, write, trunc bool) (handle, error) {
_, newfile, err := file.walk(ctx, nil)
if err != nil {
return handle{fd: -1}, err
}
var flags p9.OpenFlags
switch {
case read && !write:
flags = p9.ReadOnly
case !read && write:
flags = p9.WriteOnly
case read && write:
flags = p9.ReadWrite
}
if trunc {
flags |= p9.OpenTruncate
}
fdobj, _, _, err := newfile.open(ctx, flags)
if err != nil {
newfile.close(ctx)
return handle{fd: -1}, err
}
fd := int32(-1)
if fdobj != nil {
fd = int32(fdobj.Release())
}
return handle{
file: newfile,
fd: fd,
}, nil
}
func (h *handle) isOpen() bool {
return !h.file.isNil()
}
func (h *handle) close(ctx context.Context) {
h.file.close(ctx)
h.file = p9file{}
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
}
if dsts.NumBlocks() == 1 && !dsts.Head().NeedSafecopy() {
n, err := h.file.readAt(ctx, dsts.Head().ToSlice(), offset)
return uint64(n), err
}
// Buffer the read since p9.File.ReadAt() takes []byte.
buf := make([]byte, dsts.NumBytes())
n, err := h.file.readAt(ctx, buf, offset)
if n == 0 {
return 0, err
}
if cp, cperr := safemem.CopySeq(dsts, safemem.BlockSeqOf(safemem.BlockFromSafeSlice(buf[:n]))); cperr != nil {
return cp, cperr
}
return uint64(n), err
}
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
}
if srcs.NumBlocks() == 1 && !srcs.Head().NeedSafecopy() {
n, err := h.file.writeAt(ctx, srcs.Head().ToSlice(), offset)
return uint64(n), err
}
// Buffer the write since p9.File.WriteAt() takes []byte.
buf := make([]byte, srcs.NumBytes())
cp, cperr := safemem.CopySeq(safemem.BlockSeqOf(safemem.BlockFromSafeSlice(buf)), srcs)
if cp == 0 {
return 0, cperr
}
n, err := h.file.writeAt(ctx, buf[:cp], offset)
// err takes precedence over cperr.
if err != nil {
return uint64(n), err
}
return uint64(n), cperr
}
type handleReadWriter struct {
ctx context.Context
h *handle
off uint64
}
var handleReadWriterPool = sync.Pool{
New: func() interface{} {
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)
}
// 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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