277 lines
7 KiB
Go
277 lines
7 KiB
Go
/*
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* MinIO Cloud Storage, (C) 2016, 2017, 2018, 2019 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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"context"
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"errors"
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pathutil "path"
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"runtime"
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"sort"
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"strings"
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"sync"
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"fmt"
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"time"
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"github.com/minio/lsync"
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"github.com/minio/minio/cmd/logger"
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"github.com/minio/minio/pkg/dsync"
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)
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// local lock servers
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var globalLockServers = make(map[Endpoint]*localLocker)
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// RWLocker - locker interface to introduce GetRLock, RUnlock.
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type RWLocker interface {
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GetLock(timeout *dynamicTimeout) (timedOutErr error)
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Unlock()
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GetRLock(timeout *dynamicTimeout) (timedOutErr error)
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RUnlock()
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}
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// newNSLock - return a new name space lock map.
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func newNSLock(isDistXL bool) *nsLockMap {
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nsMutex := nsLockMap{
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isDistXL: isDistXL,
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}
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if isDistXL {
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return &nsMutex
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}
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nsMutex.lockMap = make(map[string]*nsLock)
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return &nsMutex
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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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*lsync.LRWMutex
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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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// Indicates if namespace is part of a distributed setup.
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isDistXL bool
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lockMap map[string]*nsLock
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lockMapMutex sync.RWMutex
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}
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// Lock the namespace resource.
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func (n *nsLockMap) lock(ctx context.Context, volume string, path string, lockSource, opsID string, readLock bool, timeout time.Duration) (locked bool) {
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var nsLk *nsLock
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resource := pathJoin(volume, path)
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n.lockMapMutex.Lock()
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nsLk, found := n.lockMap[resource]
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if !found {
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nsLk = &nsLock{
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LRWMutex: lsync.NewLRWMutex(ctx),
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ref: 1,
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}
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n.lockMap[resource] = nsLk
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} else {
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// Update ref count here to avoid multiple races.
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nsLk.ref++
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}
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n.lockMapMutex.Unlock()
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// Locking here will block (until timeout).
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if readLock {
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locked = nsLk.GetRLock(opsID, lockSource, timeout)
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} else {
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locked = nsLk.GetLock(opsID, lockSource, timeout)
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}
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if !locked { // We failed to get the lock
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// Decrement ref count since we failed to get the lock
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n.lockMapMutex.Lock()
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nsLk.ref--
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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, resource)
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}
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n.lockMapMutex.Unlock()
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}
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return
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}
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// Unlock the namespace resource.
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func (n *nsLockMap) unlock(volume string, path string, readLock bool) {
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resource := pathJoin(volume, path)
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n.lockMapMutex.RLock()
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nsLk, found := n.lockMap[resource]
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n.lockMapMutex.RUnlock()
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if !found {
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return
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}
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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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n.lockMapMutex.Lock()
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if nsLk.ref == 0 {
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logger.LogIf(GlobalContext, errors.New("Namespace reference count cannot be 0"))
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} else {
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nsLk.ref--
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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, resource)
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}
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}
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n.lockMapMutex.Unlock()
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}
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// dsync's distributed lock instance.
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type distLockInstance struct {
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rwMutex *dsync.DRWMutex
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opsID string
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}
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// Lock - block until write lock is taken or timeout has occurred.
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func (di *distLockInstance) GetLock(timeout *dynamicTimeout) (timedOutErr error) {
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lockSource := getSource()
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start := UTCNow()
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if !di.rwMutex.GetLock(di.opsID, lockSource, timeout.Timeout()) {
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timeout.LogFailure()
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return OperationTimedOut{}
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}
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timeout.LogSuccess(UTCNow().Sub(start))
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return nil
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}
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// Unlock - block until write lock is released.
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func (di *distLockInstance) Unlock() {
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di.rwMutex.Unlock()
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}
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// RLock - block until read lock is taken or timeout has occurred.
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func (di *distLockInstance) GetRLock(timeout *dynamicTimeout) (timedOutErr error) {
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lockSource := getSource()
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start := UTCNow()
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if !di.rwMutex.GetRLock(di.opsID, lockSource, timeout.Timeout()) {
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timeout.LogFailure()
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return OperationTimedOut{}
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}
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timeout.LogSuccess(UTCNow().Sub(start))
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return nil
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}
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// RUnlock - block until read lock is released.
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func (di *distLockInstance) RUnlock() {
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di.rwMutex.RUnlock()
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}
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// localLockInstance - frontend/top-level interface for namespace locks.
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type localLockInstance struct {
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ctx context.Context
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ns *nsLockMap
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volume string
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paths []string
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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(ctx context.Context, lockersFn func() []dsync.NetLocker, volume string, paths ...string) RWLocker {
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opsID := mustGetUUID()
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if n.isDistXL {
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drwmutex := dsync.NewDRWMutex(ctx, &dsync.Dsync{
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GetLockersFn: lockersFn,
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}, pathsJoinPrefix(volume, paths...)...)
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return &distLockInstance{drwmutex, opsID}
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}
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sort.Strings(paths)
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return &localLockInstance{ctx, n, volume, paths, opsID}
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}
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// Lock - block until write lock is taken or timeout has occurred.
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func (li *localLockInstance) GetLock(timeout *dynamicTimeout) (timedOutErr error) {
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lockSource := getSource()
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start := UTCNow()
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readLock := false
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var success []int
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for i, path := range li.paths {
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if !li.ns.lock(li.ctx, li.volume, path, lockSource, li.opsID, readLock, timeout.Timeout()) {
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timeout.LogFailure()
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for _, sint := range success {
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li.ns.unlock(li.volume, li.paths[sint], readLock)
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}
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return OperationTimedOut{}
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}
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success = append(success, i)
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}
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timeout.LogSuccess(UTCNow().Sub(start))
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return
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}
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// Unlock - block until write lock is released.
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func (li *localLockInstance) Unlock() {
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readLock := false
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for _, path := range li.paths {
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li.ns.unlock(li.volume, path, readLock)
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}
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}
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// RLock - block until read lock is taken or timeout has occurred.
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func (li *localLockInstance) GetRLock(timeout *dynamicTimeout) (timedOutErr error) {
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lockSource := getSource()
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start := UTCNow()
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readLock := true
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var success []int
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for i, path := range li.paths {
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if !li.ns.lock(li.ctx, li.volume, path, lockSource, li.opsID, readLock, timeout.Timeout()) {
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timeout.LogFailure()
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for _, sint := range success {
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li.ns.unlock(li.volume, li.paths[sint], readLock)
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}
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return OperationTimedOut{}
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}
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success = append(success, i)
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}
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timeout.LogSuccess(UTCNow().Sub(start))
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return
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}
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// RUnlock - block until read lock is released.
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func (li *localLockInstance) RUnlock() {
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readLock := true
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for _, path := range li.paths {
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li.ns.unlock(li.volume, path, readLock)
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}
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}
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func getSource() string {
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var funcName string
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pc, filename, lineNum, ok := runtime.Caller(2)
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if ok {
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filename = pathutil.Base(filename)
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funcName = strings.TrimPrefix(runtime.FuncForPC(pc).Name(),
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"github.com/minio/minio/cmd.")
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} else {
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filename = "<unknown>"
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lineNum = 0
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}
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return fmt.Sprintf("[%s:%d:%s()]", filename, lineNum, funcName)
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}
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