/*

 * 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/referenceBlock.h#1 $

 */

#ifndef REFERENCE_BLOCK_H

#define REFERENCE_BLOCK_H

#include "constants.h"

#include "journalPoint.h"

#include "types.h"

#include "waitQueue.h"

/**

 * A type representing a reference count.

 **/

typedef uint8_t ReferenceCount;

/**

 * Special ReferenceCount values.

 **/

enum {

  EMPTY_REFERENCE_COUNT       = 0,

  MAXIMUM_REFERENCE_COUNT     = 254,

  PROVISIONAL_REFERENCE_COUNT = 255,

};

enum {

  COUNTS_PER_SECTOR = ((VDO_SECTOR_SIZE - sizeof(PackedJournalPoint))

                       / sizeof(ReferenceCount)),

  COUNTS_PER_BLOCK  = COUNTS_PER_SECTOR * SECTORS_PER_BLOCK,

};

/**

 * The format of a ReferenceSector on disk.

 **/

typedef struct {

  PackedJournalPoint commitPoint;

  ReferenceCount     counts[COUNTS_PER_SECTOR];

} __attribute__((packed)) PackedReferenceSector;

typedef struct {

  PackedReferenceSector sectors[SECTORS_PER_BLOCK];

} PackedReferenceBlock;

/*

 * ReferenceBlock structure

 *

 * Blocks are used as a proxy, permitting saves of partial refcounts.

 **/

typedef struct {

  /** This block waits on the refCounts to tell it to write */

  Waiter          waiter;

  /** The parent RefCount structure */

  RefCounts      *refCounts;

  /** The number of references in this block that represent allocations */

  BlockSize       allocatedCount;

  /** The slab journal block on which this block must hold a lock */

  SequenceNumber  slabJournalLock;

  /**

   * The slab journal block which should be released when this block

   * is committed

   **/

  SequenceNumber  slabJournalLockToRelease;

  /** The point up to which each sector is accurate on disk */

  JournalPoint    commitPoints[SECTORS_PER_BLOCK];

  /** Whether this block has been modified since it was written to disk */

  bool            isDirty;

  /** Whether this block is currently writing */

  bool            isWriting;

} ReferenceBlock;

#endif // REFERENCE_BLOCK_H