ceremonyclient/pebble/vfs/file_lock_unix.go

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2024-01-03 07:31:42 +00:00
// Copyright 2014 The LevelDB-Go and Pebble Authors. All rights reserved. Use
// of this source code is governed by a BSD-style license that can be found in
// the LICENSE file.
//go:build darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris
// +build darwin dragonfly freebsd linux netbsd openbsd solaris
package vfs
import (
"io"
"os"
"sync"
"github.com/cockroachdb/errors"
"golang.org/x/sys/unix"
)
var lockedFiles struct {
mu struct {
sync.Mutex
files map[string]bool
}
}
// lockCloser hides all of an os.File's methods, except for Close.
type lockCloser struct {
name string
f *os.File
}
func (l lockCloser) Close() error {
lockedFiles.mu.Lock()
defer lockedFiles.mu.Unlock()
if !lockedFiles.mu.files[l.name] {
panic(errors.Errorf("lock file %q is not locked", l.name))
}
delete(lockedFiles.mu.files, l.name)
return l.f.Close()
}
func (defaultFS) Lock(name string) (io.Closer, error) {
lockedFiles.mu.Lock()
defer lockedFiles.mu.Unlock()
if lockedFiles.mu.files == nil {
lockedFiles.mu.files = map[string]bool{}
}
if lockedFiles.mu.files[name] {
return nil, errors.New("lock held by current process")
}
f, err := os.Create(name)
if err != nil {
return nil, err
}
spec := unix.Flock_t{
Type: unix.F_WRLCK,
Whence: io.SeekStart,
Start: 0,
Len: 0, // 0 means to lock the entire file.
Pid: int32(os.Getpid()),
}
if err := unix.FcntlFlock(f.Fd(), unix.F_SETLK, &spec); err != nil {
f.Close()
return nil, err
}
lockedFiles.mu.files[name] = true
return lockCloser{name, f}, nil
}