You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
128 lines
3.0 KiB
128 lines
3.0 KiB
/*
|
|
* Minio Cloud Storage, (C) 2016 Minio, Inc.
|
|
*
|
|
* 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 main
|
|
|
|
import (
|
|
"errors"
|
|
"sync"
|
|
)
|
|
|
|
// nsParam - carries name space resource.
|
|
type nsParam struct {
|
|
volume string
|
|
path string
|
|
}
|
|
|
|
// nsLock - provides primitives for locking critical namespace regions.
|
|
type nsLock struct {
|
|
*sync.RWMutex
|
|
ref uint
|
|
}
|
|
|
|
// nsLockMap - namespace lock map, provides primitives to Lock,
|
|
// Unlock, RLock and RUnlock.
|
|
type nsLockMap struct {
|
|
lockMap map[nsParam]*nsLock
|
|
mutex *sync.Mutex
|
|
}
|
|
|
|
// Global name space lock.
|
|
var nsMutex *nsLockMap
|
|
|
|
// initNSLock - initialize name space lock map.
|
|
func initNSLock() {
|
|
nsMutex = &nsLockMap{
|
|
lockMap: make(map[nsParam]*nsLock),
|
|
mutex: &sync.Mutex{},
|
|
}
|
|
}
|
|
|
|
// Lock the namespace resource.
|
|
func (n *nsLockMap) lock(volume, path string, readLock bool) {
|
|
n.mutex.Lock()
|
|
|
|
param := nsParam{volume, path}
|
|
nsLk, found := n.lockMap[param]
|
|
if !found {
|
|
nsLk = &nsLock{
|
|
RWMutex: &sync.RWMutex{},
|
|
ref: 0,
|
|
}
|
|
n.lockMap[param] = nsLk
|
|
}
|
|
nsLk.ref++ // Update ref count here to avoid multiple races.
|
|
// Unlock map before Locking NS which might block.
|
|
n.mutex.Unlock()
|
|
|
|
// Locking here can block.
|
|
if readLock {
|
|
nsLk.RLock()
|
|
} else {
|
|
nsLk.Lock()
|
|
}
|
|
}
|
|
|
|
// Unlock the namespace resource.
|
|
func (n *nsLockMap) unlock(volume, path string, readLock bool) {
|
|
// nsLk.Unlock() will not block, hence locking the map for the entire function is fine.
|
|
n.mutex.Lock()
|
|
defer n.mutex.Unlock()
|
|
|
|
param := nsParam{volume, path}
|
|
if nsLk, found := n.lockMap[param]; found {
|
|
if readLock {
|
|
nsLk.RUnlock()
|
|
} else {
|
|
nsLk.Unlock()
|
|
}
|
|
if nsLk.ref == 0 {
|
|
errorIf(errors.New("Namespace reference count cannot be 0."), "Invalid reference count detected.")
|
|
}
|
|
if nsLk.ref != 0 {
|
|
nsLk.ref--
|
|
}
|
|
if nsLk.ref == 0 {
|
|
// Remove from the map if there are no more references.
|
|
delete(n.lockMap, param)
|
|
}
|
|
}
|
|
}
|
|
|
|
// Lock - locks the given resource for writes, using a previously
|
|
// allocated name space lock or initializing a new one.
|
|
func (n *nsLockMap) Lock(volume, path string) {
|
|
readLock := false
|
|
n.lock(volume, path, readLock)
|
|
}
|
|
|
|
// Unlock - unlocks any previously acquired write locks.
|
|
func (n *nsLockMap) Unlock(volume, path string) {
|
|
readLock := false
|
|
n.unlock(volume, path, readLock)
|
|
}
|
|
|
|
// RLock - locks any previously acquired read locks.
|
|
func (n *nsLockMap) RLock(volume, path string) {
|
|
readLock := true
|
|
n.lock(volume, path, readLock)
|
|
}
|
|
|
|
// RUnlock - unlocks any previously acquired read locks.
|
|
func (n *nsLockMap) RUnlock(volume, path string) {
|
|
readLock := true
|
|
n.unlock(volume, path, readLock)
|
|
}
|
|
|