cae4683971
This is believed to address issue #4337 where stale information for debug locks in shown.
289 lines
8.4 KiB
Go
289 lines
8.4 KiB
Go
/*
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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 cmd
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import (
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"errors"
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pathutil "path"
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"sync"
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"github.com/minio/dsync"
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)
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// Global name space lock.
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var globalNSMutex *nsLockMap
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// RWLocker - locker interface extends sync.Locker
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// to introduce RLock, RUnlock.
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type RWLocker interface {
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sync.Locker
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RLock()
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RUnlock()
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}
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// Initialize distributed locking only in case of distributed setup.
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// Returns if the setup is distributed or not on success.
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func initDsyncNodes() error {
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cred := serverConfig.GetCredential()
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// Initialize rpc lock client information only if this instance is a distributed setup.
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clnts := make([]dsync.NetLocker, len(globalEndpoints))
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myNode := -1
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for index, endpoint := range globalEndpoints {
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clnts[index] = newLockRPCClient(authConfig{
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accessKey: cred.AccessKey,
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secretKey: cred.SecretKey,
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serverAddr: endpoint.Host,
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secureConn: globalIsSSL,
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serviceEndpoint: pathutil.Join(minioReservedBucketPath, lockServicePath, endpoint.Path),
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serviceName: lockServiceName,
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})
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if endpoint.IsLocal && myNode == -1 {
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myNode = index
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}
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}
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return dsync.Init(clnts, myNode)
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}
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// initNSLock - initialize name space lock map.
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func initNSLock(isDistXL bool) {
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globalNSMutex = &nsLockMap{
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isDistXL: isDistXL,
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lockMap: make(map[nsParam]*nsLock),
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counters: &lockStat{},
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}
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// Initialize nsLockMap with entry for instrumentation information.
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// Entries of <volume,path> -> stateInfo of locks
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globalNSMutex.debugLockMap = make(map[nsParam]*debugLockInfoPerVolumePath)
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}
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// nsParam - carries name space resource.
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type nsParam struct {
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volume string
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path string
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}
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// nsLock - provides primitives for locking critical namespace regions.
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type nsLock struct {
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RWLocker
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ref uint
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}
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// nsLockMap - namespace lock map, provides primitives to Lock,
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// Unlock, RLock and RUnlock.
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type nsLockMap struct {
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// Lock counter used for lock debugging.
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counters *lockStat
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debugLockMap map[nsParam]*debugLockInfoPerVolumePath // Info for instrumentation on locks.
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// Indicates if namespace is part of a distributed setup.
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isDistXL bool
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lockMap map[nsParam]*nsLock
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lockMapMutex sync.Mutex
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}
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// Lock the namespace resource.
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func (n *nsLockMap) lock(volume, path string, lockSource, opsID string, readLock bool) {
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var nsLk *nsLock
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n.lockMapMutex.Lock()
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param := nsParam{volume, path}
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nsLk, found := n.lockMap[param]
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if !found {
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nsLk = &nsLock{
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RWLocker: func() RWLocker {
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if n.isDistXL {
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return dsync.NewDRWMutex(pathJoin(volume, path))
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}
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return &sync.RWMutex{}
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}(),
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ref: 0,
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}
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n.lockMap[param] = nsLk
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}
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nsLk.ref++ // Update ref count here to avoid multiple races.
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// Change the state of the lock to be blocked for the given
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// pair of <volume, path> and <OperationID> till the lock
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// unblocks. The lock for accessing `globalNSMutex` is held inside
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// the function itself.
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if err := n.statusNoneToBlocked(param, lockSource, opsID, readLock); err != nil {
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errorIf(err, "Failed to set lock state to blocked")
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}
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// Unlock map before Locking NS which might block.
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n.lockMapMutex.Unlock()
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// Locking here can block.
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if readLock {
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nsLk.RLock()
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} else {
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nsLk.Lock()
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}
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// Changing the status of the operation from blocked to
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// running. change the state of the lock to be running (from
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// blocked) for the given pair of <volume, path> and <OperationID>.
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if err := n.statusBlockedToRunning(param, lockSource, opsID, readLock); err != nil {
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errorIf(err, "Failed to set the lock state to running")
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}
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}
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// Unlock the namespace resource.
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func (n *nsLockMap) unlock(volume, path, opsID string, readLock bool) {
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// nsLk.Unlock() will not block, hence locking the map for the
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// entire function is fine.
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n.lockMapMutex.Lock()
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defer n.lockMapMutex.Unlock()
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param := nsParam{volume, path}
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if nsLk, found := n.lockMap[param]; found {
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if readLock {
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nsLk.RUnlock()
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} else {
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nsLk.Unlock()
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}
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if nsLk.ref == 0 {
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errorIf(errors.New("Namespace reference count cannot be 0"),
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"Invalid reference count detected")
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}
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if nsLk.ref != 0 {
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nsLk.ref--
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// delete the lock state entry for given operation ID.
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err := n.deleteLockInfoEntryForOps(param, opsID)
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if err != nil {
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errorIf(err, "Failed to delete lock info entry")
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}
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}
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if nsLk.ref == 0 {
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// Remove from the map if there are no more references.
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delete(n.lockMap, param)
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// delete the lock state entry for given
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// <volume, path> pair.
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err := n.deleteLockInfoEntryForVolumePath(param)
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if err != nil {
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errorIf(err, "Failed to delete lock info entry")
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}
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}
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}
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}
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// Lock - locks the given resource for writes, using a previously
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// allocated name space lock or initializing a new one.
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func (n *nsLockMap) Lock(volume, path, opsID string) {
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readLock := false // This is a write lock.
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lockSource := getSource() // Useful for debugging
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n.lock(volume, path, lockSource, opsID, readLock)
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}
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// Unlock - unlocks any previously acquired write locks.
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func (n *nsLockMap) Unlock(volume, path, opsID string) {
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readLock := false
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n.unlock(volume, path, opsID, readLock)
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}
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// RLock - locks any previously acquired read locks.
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func (n *nsLockMap) RLock(volume, path, opsID string) {
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readLock := true
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lockSource := getSource() // Useful for debugging
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n.lock(volume, path, lockSource, opsID, readLock)
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}
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// RUnlock - unlocks any previously acquired read locks.
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func (n *nsLockMap) RUnlock(volume, path, opsID string) {
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readLock := true
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n.unlock(volume, path, opsID, readLock)
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}
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// ForceUnlock - forcefully unlock a lock based on name.
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func (n *nsLockMap) ForceUnlock(volume, path string) {
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n.lockMapMutex.Lock()
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defer n.lockMapMutex.Unlock()
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// Clarification on operation:
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// - In case of FS or XL we call ForceUnlock on the local globalNSMutex
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// (since there is only a single server) which will cause the 'stuck'
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// mutex to be removed from the map. Existing operations for this
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// will continue to be blocked (and timeout). New operations on this
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// resource will use a new mutex and proceed normally.
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//
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// - In case of Distributed setup (using dsync), there is no need to call
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// ForceUnlock on the server where the lock was acquired and is presumably
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// 'stuck'. Instead dsync.ForceUnlock() will release the underlying locks
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// that participated in granting the lock. Any pending dsync locks that
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// are blocking can now proceed as normal and any new locks will also
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// participate normally.
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if n.isDistXL { // For distributed mode, broadcast ForceUnlock message.
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dsync.NewDRWMutex(pathJoin(volume, path)).ForceUnlock()
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}
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param := nsParam{volume, path}
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if _, found := n.lockMap[param]; found {
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// Remove lock from the map.
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delete(n.lockMap, param)
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}
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// delete the lock state entry for given
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// <volume, path> pair. Ignore error as there
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// is no way to report it back
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n.deleteLockInfoEntryForVolumePath(param)
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}
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// lockInstance - frontend/top-level interface for namespace locks.
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type lockInstance struct {
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ns *nsLockMap
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volume, path, opsID string
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}
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// NewNSLock - returns a lock instance for a given volume and
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// path. The returned lockInstance object encapsulates the nsLockMap,
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// volume, path and operation ID.
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func (n *nsLockMap) NewNSLock(volume, path string) RWLocker {
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return &lockInstance{n, volume, path, getOpsID()}
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}
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// Lock - block until write lock is taken.
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func (li *lockInstance) Lock() {
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lockSource := getSource()
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readLock := false
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li.ns.lock(li.volume, li.path, lockSource, li.opsID, readLock)
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}
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// Unlock - block until write lock is released.
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func (li *lockInstance) Unlock() {
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readLock := false
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li.ns.unlock(li.volume, li.path, li.opsID, readLock)
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}
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// RLock - block until read lock is taken.
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func (li *lockInstance) RLock() {
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lockSource := getSource()
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readLock := true
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li.ns.lock(li.volume, li.path, lockSource, li.opsID, readLock)
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}
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// RUnlock - block until read lock is released.
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func (li *lockInstance) RUnlock() {
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readLock := true
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li.ns.unlock(li.volume, li.path, li.opsID, readLock)
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}
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