/*

 * 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/vioPool.h#4 $

 */

#ifndef VIO_POOL_H

#define VIO_POOL_H

#include "permassert.h"

#include "completion.h"

#include "types.h"

#include "waitQueue.h"

/**

 * A VIOPool is a collection of preallocated VIOs used to write arbitrary

 * metadata blocks.

 **/

/**

 * An VIOPoolEntry is the pair of VIO and buffer whether in use or not.

 **/

typedef struct {

  RingNode  node;

  VIO      *vio;

  void     *buffer;

  void     *parent;

  void     *context;

} VIOPoolEntry;

/**

 * A function which constructs a VIO for a pool.

 *

 * @param [in]  layer   The physical layer in which the VIO will operate

 * @param [in]  parent  The parent of the VIO

 * @param [in]  buffer  The data buffer for the VIO

 * @param [out] vioPtr  A pointer to hold the new VIO

 **/

typedef int VIOConstructor(PhysicalLayer  *layer,

                           void           *parent,

                           void           *buffer,

                           VIO           **vioPtr);

/**

 * Create a new VIO pool.

 *

 * @param [in]  layer           the physical layer to write to and read from

 * @param [in]  poolSize        the number of VIOs in the pool

 * @param [in]  threadID        the ID of the thread using this pool

 * @param [in]  vioConstructor  the constructor for VIOs in the pool

 * @param [in]  context         the context that each entry will have

 * @param [out] poolPtr         the resulting pool

 *

 * @return a success or error code

 **/

int makeVIOPool(PhysicalLayer   *layer,

                size_t           poolSize,

                ThreadID         threadID,

                VIOConstructor  *vioConstructor,

                void            *context,

                VIOPool        **poolPtr)

  __attribute__((warn_unused_result));

/**

 * Destroy a VIO pool

 *

 * @param poolPtr  the pointer holding the pool, which will be nulled out

 **/

void freeVIOPool(VIOPool **poolPtr);

/**

 * Check whether an VIO pool has outstanding entries.

 *

 * @return true if the pool is busy

 **/

bool isVIOPoolBusy(VIOPool *pool)

  __attribute__((warn_unused_result));

/**

 * Acquire a VIO and buffer from the pool (asynchronous).

 *

 * @param pool    the VIO pool

 * @param waiter  object that is requesting a VIO

 *

 * @return VDO_SUCCESS or an error

 **/

int acquireVIOFromPool(VIOPool *pool, Waiter *waiter);

/**

 * Return a VIO and its buffer to the pool.

 *

 * @param pool   the VIO pool

 * @param entry  a VIO pool entry

 **/

void returnVIOToPool(VIOPool *pool, VIOPoolEntry *entry);

/**

 * Convert a RingNode to the VIOPoolEntry that contains it.

 *

 * @param node  The RingNode to convert

 *

 * @return The VIOPoolEntry wrapping the RingNode

 **/

static inline VIOPoolEntry *asVIOPoolEntry(RingNode *node)

{

  STATIC_ASSERT(offsetof(VIOPoolEntry, node) == 0);

  return (VIOPoolEntry *) node;

}

/**

 * Return the outage count of an VIO pool.

 *

 * @param pool  The pool

 *

 * @return the number of times an acquisition request had to wait

 **/

uint64_t getVIOPoolOutageCount(VIOPool *pool)

  __attribute__((warn_unused_result));

#endif // VIO_POOL_H