101 lines
2.6 KiB
Go
101 lines
2.6 KiB
Go
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// +build !windows,!plan9,!solaris
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/*
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* MinIO Cloud Storage, (C) 2016 MinIO, Inc.
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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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*/
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package lock
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import (
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"os"
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"syscall"
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)
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// Internal function implements support for both
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// blocking and non blocking lock type.
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func lockedOpenFile(path string, flag int, perm os.FileMode, lockType int) (*LockedFile, error) {
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switch flag {
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case syscall.O_RDONLY:
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lockType |= syscall.LOCK_SH
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case syscall.O_WRONLY:
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fallthrough
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case syscall.O_RDWR:
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fallthrough
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case syscall.O_WRONLY | syscall.O_CREAT:
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fallthrough
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case syscall.O_RDWR | syscall.O_CREAT:
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lockType |= syscall.LOCK_EX
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default:
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return nil, &os.PathError{
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Op: "open",
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Path: path,
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Err: syscall.EINVAL,
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}
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}
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f, err := os.OpenFile(path, flag|syscall.O_SYNC, perm)
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if err != nil {
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return nil, err
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}
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if err = syscall.Flock(int(f.Fd()), lockType); err != nil {
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f.Close()
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if err == syscall.EWOULDBLOCK {
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err = ErrAlreadyLocked
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}
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return nil, err
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}
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st, err := os.Stat(path)
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if err != nil {
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f.Close()
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return nil, err
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}
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if st.IsDir() {
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f.Close()
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return nil, &os.PathError{
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Op: "open",
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Path: path,
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Err: syscall.EISDIR,
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}
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}
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return &LockedFile{File: f}, nil
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}
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// TryLockedOpenFile - tries a new write lock, functionality
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// it is similar to LockedOpenFile with with syscall.LOCK_EX
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// mode but along with syscall.LOCK_NB such that the function
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// doesn't wait forever but instead returns if it cannot
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// acquire a write lock.
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func TryLockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
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return lockedOpenFile(path, flag, perm, syscall.LOCK_NB)
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}
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// LockedOpenFile - initializes a new lock and protects
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// the file from concurrent access across mount points.
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// This implementation doesn't support all the open
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// flags and shouldn't be considered as replacement
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// for os.OpenFile().
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func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
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return lockedOpenFile(path, flag, perm, 0)
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}
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// Open - Call os.OpenFile
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func Open(path string, flag int, perm os.FileMode) (*os.File, error) {
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return os.OpenFile(path, flag, perm)
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}
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