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locker.go
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locker.go
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// Copyright (c) 2015-2021, NVIDIA CORPORATION.
// SPDX-License-Identifier: Apache-2.0
package inode
// Lock-related wrappers for inodes
//
// These APIs wrap calls to package DLM, which is a generic locking package.
//
// These wrappers enforce a naming convention for lock IDs.
//
import (
"fmt"
"github.com/swiftstack/ProxyFS/dlm"
)
// MakeLockID creates the ID of an inode used in volume
func (vS *volumeStruct) MakeLockID(inodeNumber InodeNumber) (lockID string, err error) {
myLockID := fmt.Sprintf("vol.%s:ino.%d", vS.volumeName, inodeNumber)
return myLockID, nil
}
// InitInodeLock creates an inode lock. If callerID is non-nil, it is used.
// Otherwise a new callerID is allocated.
func (vS *volumeStruct) InitInodeLock(inodeNumber InodeNumber, callerID dlm.CallerID) (lock *dlm.RWLockStruct, err error) {
lockID, err := vS.MakeLockID(inodeNumber)
if err != nil {
return nil, err
}
if callerID == nil {
callerID = dlm.GenerateCallerID()
}
return &dlm.RWLockStruct{LockID: lockID,
Notify: nil,
LockCallerID: callerID,
}, nil
}
// GetReadLock is a convenience function to create and acquire an inode lock
func (vS *volumeStruct) GetReadLock(inodeNumber InodeNumber, callerID dlm.CallerID) (*dlm.RWLockStruct, error) {
lock, err := vS.InitInodeLock(inodeNumber, callerID)
if err != nil {
return nil, err
}
err = lock.ReadLock()
return lock, err
}
// GetWriteLock is a convenience function to create and acquire an inode lock
func (vS *volumeStruct) GetWriteLock(inodeNumber InodeNumber, callerID dlm.CallerID) (*dlm.RWLockStruct, error) {
lock, err := vS.InitInodeLock(inodeNumber, callerID)
if err != nil {
return nil, err
}
err = lock.WriteLock()
return lock, err
}
// AttemptReadLock is a convenience function to create and try to acquire an inode lock
func (vS *volumeStruct) AttemptReadLock(inodeNumber InodeNumber, callerID dlm.CallerID) (*dlm.RWLockStruct, error) {
lock, err := vS.InitInodeLock(inodeNumber, callerID)
if err != nil {
return nil, err
}
err = lock.TryReadLock()
return lock, err
}
// AttemptWriteLock is a convenience function to create and try to acquire an inode lock
func (vS *volumeStruct) AttemptWriteLock(inodeNumber InodeNumber, callerID dlm.CallerID) (*dlm.RWLockStruct, error) {
lock, err := vS.InitInodeLock(inodeNumber, callerID)
if err != nil {
return nil, err
}
err = lock.TryWriteLock()
return lock, err
}
// EnsureReadLock ensures that a lock of the right type is held by the given callerID. If the lock is not held, it
// acquires it. If the lock is held, it returns nil (so you don't unlock twice; even if that's not crashworthy, you'd
// still release a lock that other code thinks it still holds).
func (vS *volumeStruct) EnsureReadLock(inodeNumber InodeNumber, callerID dlm.CallerID) (*dlm.RWLockStruct, error) {
lock, err := vS.InitInodeLock(inodeNumber, callerID)
if err != nil {
return nil, err
}
if lock.IsReadHeld() {
return nil, nil
}
err = lock.ReadLock()
return lock, err
}
// EnsureWriteLock ensures that a lock of the right type is held by the given callerID. If the lock is not held, it
// acquires it. If the lock is held, it returns nil (so you don't unlock twice; even if that's not crashworthy, you'd
// still release a lock that other code thinks it still holds).
func (vS *volumeStruct) EnsureWriteLock(inodeNumber InodeNumber, callerID dlm.CallerID) (*dlm.RWLockStruct, error) {
lock, err := vS.InitInodeLock(inodeNumber, callerID)
if err != nil {
return nil, err
}
if lock.IsWriteHeld() {
return nil, nil
}
err = lock.WriteLock()
return lock, err
}