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274 lines
8.7 KiB
274 lines
8.7 KiB
/*
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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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"fmt"
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pathutil "path"
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"runtime"
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"strconv"
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"strings"
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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 nsMutex *nsLockMap
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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(disks []string, port int) error {
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serverPort := strconv.Itoa(port)
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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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var clnts []dsync.RPC
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for _, disk := range disks {
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if idx := strings.LastIndex(disk, ":"); idx != -1 {
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clnts = append(clnts, newAuthClient(&authConfig{
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accessKey: cred.AccessKeyID,
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secretKey: cred.SecretAccessKey,
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// Construct a new dsync server addr.
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address: disk[:idx] + ":" + serverPort,
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// Construct a new rpc path for the disk.
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path: pathutil.Join(lockRPCPath, disk[idx+1:]),
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loginMethod: "Dsync.LoginHandler",
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}))
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}
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}
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return dsync.SetNodesWithClients(clnts)
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}
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// initNSLock - initialize name space lock map.
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func initNSLock(isDist bool) {
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nsMutex = &nsLockMap{
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isDist: isDist,
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lockMap: make(map[nsParam]*nsLock),
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}
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if globalDebugLock {
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// lock Debugging enabed, initialize nsLockMap with entry for debugging information.
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// entries of <volume,path> -> stateInfo of locks, for instrumentation purpose.
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nsMutex.debugLockMap = make(map[nsParam]*debugLockInfoPerVolumePath)
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}
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}
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func (n *nsLockMap) initLockInfoForVolumePath(param nsParam) {
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n.debugLockMap[param] = newDebugLockInfoPerVolumePath()
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}
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// RWLocker - interface that any read-write locking library should implement.
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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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// 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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writer RWLocker
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readerArray []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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globalLockCounter int64 //total locks held.
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blockedCounter int64 // total operations blocked waiting for locks.
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runningLockCounter int64 // total locks held but not released yet.
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debugLockMap map[nsParam]*debugLockInfoPerVolumePath // info for instrumentation on locks.
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isDist bool // indicates whether the locking service is part of a distributed setup or not.
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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, lockOrigin, 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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writer: func() RWLocker {
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if n.isDist {
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return dsync.NewDRWMutex(pathutil.Join(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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rwlock := nsLk.writer
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if readLock && n.isDist {
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rwlock = dsync.NewDRWMutex(pathutil.Join(volume, path))
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}
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if globalDebugLock {
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// change the state of the lock to be blocked for the given pair of <volume, path> and <OperationID> till the lock unblocks.
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// The lock for accessing `nsMutex` is held inside the function itself.
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err := n.statusNoneToBlocked(param, lockOrigin, opsID, readLock)
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if err != nil {
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errorIf(err, "Failed to set lock state to blocked.")
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}
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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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rwlock.RLock()
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if n.isDist {
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// Only add (for reader case) to array after RLock() succeeds
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// (so that we know for sure that element in [0] can be RUnlocked())
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n.lockMapMutex.Lock()
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if len(nsLk.readerArray) == 0 {
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nsLk.readerArray = []RWLocker{rwlock}
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} else {
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nsLk.readerArray = append(nsLk.readerArray, rwlock)
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}
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n.lockMapMutex.Unlock()
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}
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} else {
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rwlock.Lock()
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}
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// check if lock debugging enabled.
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if globalDebugLock {
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// Changing the status of the operation from blocked to running.
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// change the state of the lock to be running (from blocked) for the given pair of <volume, path> and <OperationID>.
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err := n.statusBlockedToRunning(param, lockOrigin, opsID, readLock)
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if 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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}
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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 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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if n.isDist {
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if len(nsLk.readerArray) == 0 {
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errorIf(errors.New("Length of reader lock array cannot be 0."), "Invalid reader lock array length detected.")
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}
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// Release first lock first (FIFO)
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nsLk.readerArray[0].RUnlock()
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// And discard first element
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nsLk.readerArray = nsLk.readerArray[1:]
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} else {
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nsLk.writer.RUnlock()
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}
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} else {
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nsLk.writer.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."), "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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// locking debug enabled, delete the lock state entry for given operation ID.
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if globalDebugLock {
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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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}
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if nsLk.ref == 0 {
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if len(nsLk.readerArray) != 0 && n.isDist {
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errorIf(errors.New("Length of reader lock array should be 0 upon deleting map entry."), "Invalid reader lock array length detected.")
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}
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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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// locking debug enabled, delete the lock state entry for given <volume, path> pair.
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if globalDebugLock {
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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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}
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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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var lockOrigin string
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// lock debugging enabled. The caller information of the lock held has be obtained here before calling any other function.
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if globalDebugLock {
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// fetching the package, function name and the line number of the caller from the runtime.
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// here is an example https://play.golang.org/p/perrmNRI9_ .
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pc, fn, line, success := runtime.Caller(1)
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if !success {
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errorIf(errors.New("Couldn't get caller info."), "Fetching caller info form runtime failed.")
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}
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lockOrigin = fmt.Sprintf("[lock held] in %s[%s:%d]", runtime.FuncForPC(pc).Name(), fn, line)
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}
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readLock := false
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n.lock(volume, path, lockOrigin, 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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var lockOrigin string
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readLock := true
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// lock debugging enabled. The caller information of the lock held has be obtained here before calling any other function.
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if globalDebugLock {
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// fetching the package, function name and the line number of the caller from the runtime.
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// here is an example https://play.golang.org/p/perrmNRI9_ .
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pc, fn, line, success := runtime.Caller(1)
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if !success {
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errorIf(errors.New("Couldn't get caller info."), "Fetching caller info form runtime failed.")
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}
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lockOrigin = fmt.Sprintf("[lock held] in %s[%s:%d]", runtime.FuncForPC(pc).Name(), fn, line)
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}
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n.lock(volume, path, lockOrigin, 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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