136 lines
3.5 KiB
Go
136 lines
3.5 KiB
Go
// Copyright 2019 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package gofer
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import (
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"syscall"
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"gvisor.dev/gvisor/pkg/context"
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"gvisor.dev/gvisor/pkg/p9"
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"gvisor.dev/gvisor/pkg/safemem"
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)
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// handle represents a remote "open file descriptor", consisting of an opened
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// fid (p9.File) and optionally a host file descriptor.
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type handle struct {
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file p9file
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fd int32 // -1 if unavailable
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}
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// Preconditions: read || write.
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func openHandle(ctx context.Context, file p9file, read, write, trunc bool) (handle, error) {
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_, newfile, err := file.walk(ctx, nil)
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if err != nil {
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return handle{fd: -1}, err
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}
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var flags p9.OpenFlags
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switch {
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case read && !write:
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flags = p9.ReadOnly
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case !read && write:
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flags = p9.WriteOnly
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case read && write:
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flags = p9.ReadWrite
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}
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if trunc {
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flags |= p9.OpenTruncate
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}
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fdobj, _, _, err := newfile.open(ctx, flags)
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if err != nil {
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newfile.close(ctx)
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return handle{fd: -1}, err
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}
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fd := int32(-1)
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if fdobj != nil {
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fd = int32(fdobj.Release())
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}
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return handle{
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file: newfile,
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fd: fd,
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}, nil
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}
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func (h *handle) close(ctx context.Context) {
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h.file.close(ctx)
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h.file = p9file{}
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if h.fd >= 0 {
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syscall.Close(int(h.fd))
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h.fd = -1
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}
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}
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func (h *handle) readToBlocksAt(ctx context.Context, dsts safemem.BlockSeq, offset uint64) (uint64, error) {
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if dsts.IsEmpty() {
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return 0, nil
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}
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if h.fd >= 0 {
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ctx.UninterruptibleSleepStart(false)
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n, err := hostPreadv(h.fd, dsts, int64(offset))
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ctx.UninterruptibleSleepFinish(false)
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return n, err
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}
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if dsts.NumBlocks() == 1 && !dsts.Head().NeedSafecopy() {
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n, err := h.file.readAt(ctx, dsts.Head().ToSlice(), offset)
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return uint64(n), err
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}
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// Buffer the read since p9.File.ReadAt() takes []byte.
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buf := make([]byte, dsts.NumBytes())
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n, err := h.file.readAt(ctx, buf, offset)
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if n == 0 {
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return 0, err
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}
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if cp, cperr := safemem.CopySeq(dsts, safemem.BlockSeqOf(safemem.BlockFromSafeSlice(buf[:n]))); cperr != nil {
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return cp, cperr
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}
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return uint64(n), err
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}
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func (h *handle) writeFromBlocksAt(ctx context.Context, srcs safemem.BlockSeq, offset uint64) (uint64, error) {
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if srcs.IsEmpty() {
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return 0, nil
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}
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if h.fd >= 0 {
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ctx.UninterruptibleSleepStart(false)
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n, err := hostPwritev(h.fd, srcs, int64(offset))
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ctx.UninterruptibleSleepFinish(false)
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return n, err
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}
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if srcs.NumBlocks() == 1 && !srcs.Head().NeedSafecopy() {
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n, err := h.file.writeAt(ctx, srcs.Head().ToSlice(), offset)
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return uint64(n), err
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}
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// Buffer the write since p9.File.WriteAt() takes []byte.
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buf := make([]byte, srcs.NumBytes())
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cp, cperr := safemem.CopySeq(safemem.BlockSeqOf(safemem.BlockFromSafeSlice(buf)), srcs)
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if cp == 0 {
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return 0, cperr
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}
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n, err := h.file.writeAt(ctx, buf[:cp], offset)
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if err != nil {
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return uint64(n), err
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}
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return cp, cperr
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}
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func (h *handle) sync(ctx context.Context) error {
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if h.fd >= 0 {
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ctx.UninterruptibleSleepStart(false)
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err := syscall.Fsync(int(h.fd))
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ctx.UninterruptibleSleepFinish(false)
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return err
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}
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return h.file.fsync(ctx)
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}
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