/*
* Copyright (c) 2020 Red Hat, Inc.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*
* $Id: //eng/vdo-releases/aluminum/src/c++/vdo/base/pbnLock.h#3 $
*/
#ifndef PBN_LOCK_H
#define PBN_LOCK_H
#include "atomic.h"
#include "types.h"
/**
* The type of a PBN lock.
**/
typedef enum {
VIO_READ_LOCK = 0,
VIO_WRITE_LOCK,
VIO_COMPRESSED_WRITE_LOCK,
VIO_BLOCK_MAP_WRITE_LOCK,
} PBNLockType;
typedef struct pbnLockImplementation PBNLockImplementation;
/**
* A PBN lock.
**/
struct pbnLock {
/** The implementation of the lock */
const PBNLockImplementation *implementation;
/** The number of VIOs holding or sharing this lock */
VIOCount holderCount;
/**
* The number of compressed block writers holding a share of this lock while
* they are acquiring a reference to the PBN.
**/
uint8_t fragmentLocks;
/**
* Whether the locked PBN has been provisionally referenced on behalf of the
* lock holder.
**/
bool hasProvisionalReference;
/**
* For read locks, the number of references that were known to be available
* on the locked block at the time the lock was acquired.
**/
uint8_t incrementLimit;
/**
* For read locks, the number of DataVIOs that have tried to claim one of
* the available increments during the lifetime of the lock. Each claim will
* first increment this counter, so it can exceed the increment limit.
**/
Atomic32 incrementsClaimed;
};
/**
* Initialize a PBNLock.
*
* @param lock The lock to initialize
* @param type The type of the lock
**/
void initializePBNLock(PBNLock *lock, PBNLockType type);
/**
* Check whether a PBNLock is a read lock.
*
* @param lock The lock to check
*
* @return <code>true</code> if the lock is a read lock
**/
bool isPBNReadLock(const PBNLock *lock)
__attribute__((warn_unused_result));
/**
* Downgrade a PBN write lock to a PBN read lock. The lock holder count is
* cleared and the caller is responsible for setting the new count.
*
* @param lock The PBN write lock to downgrade
**/
void downgradePBNWriteLock(PBNLock *lock);
/**
* Try to claim one of the available reference count increments on a read
* lock. Claims may be attempted from any thread. A claim is only valid until
* the PBN lock is released.
*
* @param lock The PBN read lock from which to claim an increment
*
* @return <code>true</code> if the claim succeeded, guaranteeing one
* increment can be made without overflowing the PBN's reference count
**/
bool claimPBNLockIncrement(PBNLock *lock)
__attribute__((warn_unused_result));
/**
* Check whether a PBN lock has a provisional reference.
*
* @param lock The PBN lock
**/
static inline bool hasProvisionalReference(PBNLock *lock)
{
return ((lock != NULL) && lock->hasProvisionalReference);
}
/**
* Inform a PBN lock that it is responsible for a provisional reference.
*
* @param lock The PBN lock
**/
void assignProvisionalReference(PBNLock *lock);
/**
* Inform a PBN lock that it is no longer responsible for a provisional
* reference.
*
* @param lock The PBN lock
**/
void unassignProvisionalReference(PBNLock *lock);
/**
* If the lock is responsible for a provisional reference, release that
* reference. This method is called when the lock is released.
*
* @param lock The lock
* @param lockedPBN The PBN covered by the lock
* @param allocator The block allocator from which to release the reference
**/
void releaseProvisionalReference(PBNLock *lock,
PhysicalBlockNumber lockedPBN,
BlockAllocator *allocator);
#endif /* PBN_LOCK_H */