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locks.go
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locks.go
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// Copyright 2018-2021 CERN
//
// 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.
//
// In applying this license, CERN does not waive the privileges and immunities
// granted to it by virtue of its status as an Intergovernmental Organization
// or submit itself to any jurisdiction.
package node
import (
"context"
"encoding/json"
"io/fs"
"os"
"path/filepath"
"time"
provider "github.com/cs3org/go-cs3apis/cs3/storage/provider/v1beta1"
types "github.com/cs3org/go-cs3apis/cs3/types/v1beta1"
"github.com/cs3org/reva/v2/pkg/appctx"
ctxpkg "github.com/cs3org/reva/v2/pkg/ctx"
"github.com/cs3org/reva/v2/pkg/errtypes"
"github.com/cs3org/reva/v2/pkg/storage/utils/filelocks"
"github.com/cs3org/reva/v2/pkg/utils"
"github.com/pkg/errors"
)
// SetLock sets a lock on the node
func (n *Node) SetLock(ctx context.Context, lock *provider.Lock) error {
lockFilePath := n.LockFilePath()
// ensure parent path exists
if err := os.MkdirAll(filepath.Dir(lockFilePath), 0700); err != nil {
return errors.Wrap(err, "Decomposedfs: error creating parent folder for lock")
}
// get file lock, so that nobody can create the lock in the meantime
fileLock, err := filelocks.AcquireWriteLock(n.InternalPath())
if err != nil {
return err
}
defer func() {
rerr := filelocks.ReleaseLock(fileLock)
// if err is non nil we do not overwrite that
if err == nil {
err = rerr
}
}()
// check if already locked
l, err := n.ReadLock(ctx, true) // we already have a write file lock, so ReadLock() would fail to acquire a read file lock -> skip it
switch err.(type) {
case errtypes.NotFound:
// file not locked, continue
case nil:
if l != nil {
return errtypes.PreconditionFailed("already locked")
}
default:
return errors.Wrap(err, "Decomposedfs: could check if file already is locked")
}
// O_EXCL to make open fail when the file already exists
f, err := os.OpenFile(lockFilePath, os.O_EXCL|os.O_CREATE|os.O_WRONLY, 0600)
if err != nil {
return errors.Wrap(err, "Decomposedfs: could not create lock file")
}
defer f.Close()
if err := json.NewEncoder(f).Encode(lock); err != nil {
return errors.Wrap(err, "Decomposedfs: could not write lock file")
}
return err
}
// ReadLock reads the lock id for a node
func (n Node) ReadLock(ctx context.Context, skipFileLock bool) (*provider.Lock, error) {
// ensure parent path exists
if err := os.MkdirAll(filepath.Dir(n.InternalPath()), 0700); err != nil {
return nil, errors.Wrap(err, "Decomposedfs: error creating parent folder for lock")
}
// the caller of ReadLock already may hold a file lock
if !skipFileLock {
fileLock, err := filelocks.AcquireReadLock(n.InternalPath())
if err != nil {
return nil, err
}
defer func() {
rerr := filelocks.ReleaseLock(fileLock)
// if err is non nil we do not overwrite that
if err == nil {
err = rerr
}
}()
}
f, err := os.Open(n.LockFilePath())
if err != nil {
if errors.Is(err, fs.ErrNotExist) {
return nil, errtypes.NotFound("no lock found")
}
return nil, errors.Wrap(err, "Decomposedfs: could not open lock file")
}
defer f.Close()
lock := &provider.Lock{}
if err := json.NewDecoder(f).Decode(lock); err != nil {
appctx.GetLogger(ctx).Error().Err(err).Msg("Decomposedfs: could not decode lock file, ignoring")
return nil, errors.Wrap(err, "Decomposedfs: could not read lock file")
}
// lock already expired
if lock.Expiration != nil && time.Now().After(time.Unix(int64(lock.Expiration.Seconds), int64(lock.Expiration.Nanos))) {
if err = os.Remove(f.Name()); err != nil {
return nil, errors.Wrap(err, "Decomposedfs: could not remove expired lock file")
}
// we successfully deleted the expired lock
return nil, errtypes.NotFound("no lock found")
}
return lock, nil
}
// RefreshLock refreshes the node's lock
func (n *Node) RefreshLock(ctx context.Context, lock *provider.Lock, existingLockID string) error {
// ensure parent path exists
if err := os.MkdirAll(filepath.Dir(n.InternalPath()), 0700); err != nil {
return errors.Wrap(err, "Decomposedfs: error creating parent folder for lock")
}
fileLock, err := filelocks.AcquireWriteLock(n.InternalPath())
if err != nil {
return err
}
defer func() {
rerr := filelocks.ReleaseLock(fileLock)
// if err is non nil we do not overwrite that
if err == nil {
err = rerr
}
}()
f, err := os.OpenFile(n.LockFilePath(), os.O_RDWR, os.ModeExclusive)
switch {
case errors.Is(err, fs.ErrNotExist):
return errtypes.PreconditionFailed("lock does not exist")
case err != nil:
return errors.Wrap(err, "Decomposedfs: could not open lock file")
}
defer f.Close()
readLock := &provider.Lock{}
if err := json.NewDecoder(f).Decode(readLock); err != nil {
return errors.Wrap(err, "Decomposedfs: could not read lock")
}
// check refresh lockID match
if existingLockID == "" && readLock.LockId != lock.LockId {
return errtypes.Aborted("mismatching lock ID")
}
// check if UnlockAndRelock sends the correct lockID
if existingLockID != "" && readLock.LockId != existingLockID {
return errtypes.Aborted("mismatching existing lock ID")
}
if ok, err := isLockModificationAllowed(ctx, readLock, lock); !ok {
return err
}
// Rewind to the beginning of the file before writing a refreshed lock
_, err = f.Seek(0, 0)
if err != nil {
return errors.Wrap(err, "could not seek to the beginning of the lock file")
}
if err := json.NewEncoder(f).Encode(lock); err != nil {
return errors.Wrap(err, "Decomposedfs: could not write lock file")
}
return err
}
// Unlock unlocks the node
func (n *Node) Unlock(ctx context.Context, lock *provider.Lock) error {
// ensure parent path exists
if err := os.MkdirAll(filepath.Dir(n.InternalPath()), 0700); err != nil {
return errors.Wrap(err, "Decomposedfs: error creating parent folder for lock")
}
fileLock, err := filelocks.AcquireWriteLock(n.InternalPath())
if err != nil {
return err
}
defer func() {
rerr := filelocks.ReleaseLock(fileLock)
// if err is non nil we do not overwrite that
if err == nil {
err = rerr
}
}()
f, err := os.OpenFile(n.LockFilePath(), os.O_RDONLY, os.ModeExclusive)
switch {
case errors.Is(err, fs.ErrNotExist):
return errtypes.Aborted("lock does not exist")
case err != nil:
return errors.Wrap(err, "Decomposedfs: could not open lock file")
}
defer f.Close()
oldLock := &provider.Lock{}
if err := json.NewDecoder(f).Decode(oldLock); err != nil {
return errors.Wrap(err, "Decomposedfs: could not read lock")
}
// check lock
if lock == nil || (oldLock.LockId != lock.LockId) {
return errtypes.Locked(oldLock.LockId)
}
if ok, err := isLockModificationAllowed(ctx, oldLock, lock); !ok {
return err
}
if err = os.Remove(f.Name()); err != nil {
return errors.Wrap(err, "Decomposedfs: could not remove lock file")
}
return err
}
// CheckLock compares the context lock with the node lock
func (n *Node) CheckLock(ctx context.Context) error {
contextLock, _ := ctxpkg.ContextGetLockID(ctx)
diskLock, _ := n.ReadLock(ctx, false)
if diskLock != nil {
switch contextLock {
case "":
return errtypes.Locked(diskLock.LockId) // no lockid in request
case diskLock.LockId:
return nil // ok
default:
return errtypes.Aborted("mismatching lock")
}
}
if contextLock != "" {
return errtypes.Aborted("not locked") // no lock on disk. why is there a lockid in the context
}
return nil // ok
}
func readLocksIntoOpaque(ctx context.Context, n *Node, ri *provider.ResourceInfo) error {
// ensure parent path exists
if err := os.MkdirAll(filepath.Dir(n.InternalPath()), 0700); err != nil {
return errors.Wrap(err, "Decomposedfs: error creating parent folder for lock")
}
fileLock, err := filelocks.AcquireReadLock(n.InternalPath())
if err != nil {
return err
}
defer func() {
rerr := filelocks.ReleaseLock(fileLock)
// if err is non nil we do not overwrite that
if err == nil {
err = rerr
}
}()
f, err := os.Open(n.LockFilePath())
if err != nil {
appctx.GetLogger(ctx).Error().Err(err).Msg("Decomposedfs: could not open lock file")
return err
}
defer f.Close()
lock := &provider.Lock{}
if err := json.NewDecoder(f).Decode(lock); err != nil {
appctx.GetLogger(ctx).Error().Err(err).Msg("Decomposedfs: could not read lock file")
}
// reencode to ensure valid json
var b []byte
if b, err = json.Marshal(lock); err != nil {
appctx.GetLogger(ctx).Error().Err(err).Msg("Decomposedfs: could not marshal locks")
}
if ri.Opaque == nil {
ri.Opaque = &types.Opaque{
Map: map[string]*types.OpaqueEntry{},
}
}
ri.Opaque.Map["lock"] = &types.OpaqueEntry{
Decoder: "json",
Value: b,
}
return err
}
func (n *Node) hasLocks(ctx context.Context) bool {
_, err := os.Stat(n.LockFilePath()) // FIXME better error checking
return err == nil
}
func isLockModificationAllowed(ctx context.Context, oldLock *provider.Lock, newLock *provider.Lock) (bool, error) {
if oldLock.Type == provider.LockType_LOCK_TYPE_SHARED {
return true, nil
}
appNameEquals := oldLock.AppName == newLock.AppName
if !appNameEquals {
return false, errtypes.PermissionDenied("app names of the locks are mismatching")
}
var lockUserEquals, contextUserEquals bool
if oldLock.User == nil && newLock.GetUser() == nil {
// no user lock set
lockUserEquals = true
contextUserEquals = true
} else {
lockUserEquals = utils.UserIDEqual(oldLock.User, newLock.GetUser())
if !lockUserEquals {
return false, errtypes.PermissionDenied("users of the locks are mismatching")
}
u := ctxpkg.ContextMustGetUser(ctx)
contextUserEquals = utils.UserIDEqual(oldLock.User, u.Id)
if !contextUserEquals {
return false, errtypes.PermissionDenied("lock holder and current user are mismatching")
}
}
return appNameEquals && lockUserEquals && contextUserEquals, nil
}