265 lines
7.3 KiB
Go
265 lines
7.3 KiB
Go
/*
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* MinIO Cloud Storage, (C) 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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"fmt"
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"sync"
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"time"
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"github.com/minio/minio/pkg/dsync"
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)
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// lockRequesterInfo stores various info from the client for each lock that is requested.
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type lockRequesterInfo struct {
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Writer bool // Bool whether write or read lock.
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UID string // UID to uniquely identify request of client.
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Timestamp time.Time // Timestamp set at the time of initialization.
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TimeLastCheck time.Time // Timestamp for last check of validity of lock.
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Source string // Contains line, function and filename reqesting the lock.
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// Owner represents the UUID of the owner who originally requested the lock
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// useful in expiry.
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Owner string
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// Quorum represents the quorum required for this lock to be active.
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Quorum int
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}
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// isWriteLock returns whether the lock is a write or read lock.
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func isWriteLock(lri []lockRequesterInfo) bool {
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return len(lri) == 1 && lri[0].Writer
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}
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// localLocker implements Dsync.NetLocker
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type localLocker struct {
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mutex sync.Mutex
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lockMap map[string][]lockRequesterInfo
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}
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func (l *localLocker) String() string {
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return globalEndpoints.Localhost()
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}
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func (l *localLocker) canTakeUnlock(resources ...string) bool {
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var lkCnt int
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for _, resource := range resources {
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isWriteLockTaken := isWriteLock(l.lockMap[resource])
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if isWriteLockTaken {
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lkCnt++
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}
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}
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return lkCnt == len(resources)
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}
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func (l *localLocker) canTakeLock(resources ...string) bool {
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var noLkCnt int
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for _, resource := range resources {
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_, lockTaken := l.lockMap[resource]
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if !lockTaken {
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noLkCnt++
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}
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}
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return noLkCnt == len(resources)
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}
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func (l *localLocker) Lock(ctx context.Context, args dsync.LockArgs) (reply bool, err error) {
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l.mutex.Lock()
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defer l.mutex.Unlock()
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if !l.canTakeLock(args.Resources...) {
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// Not all locks can be taken on resources,
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// reject it completely.
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return false, nil
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}
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// No locks held on the all resources, so claim write
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// lock on all resources at once.
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for _, resource := range args.Resources {
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l.lockMap[resource] = []lockRequesterInfo{
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{
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Writer: true,
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Source: args.Source,
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Owner: args.Owner,
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UID: args.UID,
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Timestamp: UTCNow(),
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TimeLastCheck: UTCNow(),
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Quorum: args.Quorum,
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},
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}
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}
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return true, nil
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}
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func (l *localLocker) Unlock(args dsync.LockArgs) (reply bool, err error) {
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l.mutex.Lock()
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defer l.mutex.Unlock()
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if !l.canTakeUnlock(args.Resources...) {
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// Unless it is a write lock reject it.
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return reply, fmt.Errorf("Unlock attempted on a read locked entity: %s", args.Resources)
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}
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for _, resource := range args.Resources {
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lri, ok := l.lockMap[resource]
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if ok {
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l.removeEntry(resource, args, &lri)
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}
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}
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return true, nil
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}
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// removeEntry based on the uid of the lock message, removes a single entry from the
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// lockRequesterInfo array or the whole array from the map (in case of a write lock
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// or last read lock)
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func (l *localLocker) removeEntry(name string, args dsync.LockArgs, lri *[]lockRequesterInfo) bool {
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// Find correct entry to remove based on uid.
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for index, entry := range *lri {
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if entry.UID == args.UID && entry.Owner == args.Owner {
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if len(*lri) == 1 {
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// Remove the write lock.
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delete(l.lockMap, name)
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} else {
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// Remove the appropriate read lock.
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*lri = append((*lri)[:index], (*lri)[index+1:]...)
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l.lockMap[name] = *lri
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}
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return true
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}
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}
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// None found return false, perhaps entry removed in previous run.
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return false
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}
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func (l *localLocker) RLock(ctx context.Context, args dsync.LockArgs) (reply bool, err error) {
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l.mutex.Lock()
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defer l.mutex.Unlock()
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lrInfo := lockRequesterInfo{
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Writer: false,
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Source: args.Source,
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Owner: args.Owner,
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UID: args.UID,
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Timestamp: UTCNow(),
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TimeLastCheck: UTCNow(),
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Quorum: args.Quorum,
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}
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resource := args.Resources[0]
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if lri, ok := l.lockMap[resource]; ok {
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if reply = !isWriteLock(lri); reply {
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// Unless there is a write lock
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l.lockMap[resource] = append(l.lockMap[resource], lrInfo)
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}
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} else {
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// No locks held on the given name, so claim (first) read lock
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l.lockMap[resource] = []lockRequesterInfo{lrInfo}
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reply = true
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}
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return reply, nil
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}
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func (l *localLocker) RUnlock(args dsync.LockArgs) (reply bool, err error) {
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l.mutex.Lock()
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defer l.mutex.Unlock()
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var lri []lockRequesterInfo
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resource := args.Resources[0]
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if lri, reply = l.lockMap[resource]; !reply {
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// No lock is held on the given name
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return true, nil
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}
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if reply = !isWriteLock(lri); !reply {
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// A write-lock is held, cannot release a read lock
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return reply, fmt.Errorf("RUnlock attempted on a write locked entity: %s", resource)
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}
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l.removeEntry(resource, args, &lri)
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return reply, nil
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}
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func (l *localLocker) DupLockMap() map[string][]lockRequesterInfo {
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l.mutex.Lock()
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defer l.mutex.Unlock()
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lockCopy := map[string][]lockRequesterInfo{}
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for k, v := range l.lockMap {
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lockCopy[k] = append(lockCopy[k], v...)
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}
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return lockCopy
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}
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func (l *localLocker) Close() error {
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return nil
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}
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// IsOnline - local locker is always online.
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func (l *localLocker) IsOnline() bool {
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return true
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}
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// IsLocal - local locker returns true.
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func (l *localLocker) IsLocal() bool {
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return true
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}
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func (l *localLocker) Expired(ctx context.Context, args dsync.LockArgs) (expired bool, err error) {
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select {
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case <-ctx.Done():
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return false, ctx.Err()
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default:
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l.mutex.Lock()
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defer l.mutex.Unlock()
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// Lock found, proceed to verify if belongs to given uid.
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for _, resource := range args.Resources {
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if lri, ok := l.lockMap[resource]; ok {
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// Check whether uid is still active
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for _, entry := range lri {
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if entry.UID == args.UID && entry.Owner == args.Owner {
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if ep, ok := globalRemoteEndpoints[args.Owner]; ok {
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if err = isServerResolvable(ep); err != nil {
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return true, nil
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}
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}
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return false, nil
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}
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}
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}
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}
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return true, nil
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}
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}
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// Similar to removeEntry but only removes an entry only if the lock entry exists in map.
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// Caller must hold 'l.mutex' lock.
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func (l *localLocker) removeEntryIfExists(nlrip nameLockRequesterInfoPair) {
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l.mutex.Lock()
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defer l.mutex.Unlock()
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// Check if entry is still in map (could have been removed altogether by 'concurrent' (R)Unlock of last entry)
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if lri, ok := l.lockMap[nlrip.name]; ok {
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// Even if the entry exists, it may not be the same entry which was
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// considered as expired, so we simply an attempt to remove it if its
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// not possible there is nothing we need to do.
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l.removeEntry(nlrip.name, dsync.LockArgs{Owner: nlrip.lri.Owner, UID: nlrip.lri.UID}, &lri)
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}
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}
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func newLocker() *localLocker {
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return &localLocker{
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lockMap: make(map[string][]lockRequesterInfo),
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}
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}
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