/*

 * 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.c#5 $

 */

#include "vioPool.h"

#include "logger.h"

#include "memoryAlloc.h"

#include "permassert.h"

#include "constants.h"

#include "vio.h"

#include "types.h"

/**

 * An VIOPool is a collection of preallocated VIOs.

 **/

struct vioPool {

  /** The number of objects managed by the pool */

  size_t         size;

  /** The list of objects which are available */

  RingNode       available;

  /** The queue of requestors waiting for objects from the pool */

  WaitQueue      waiting;

  /** The number of objects currently in use */

  size_t         busyCount;

  /** The list of objects which are in use */

  RingNode       busy;

  /** The number of requests when no object was available */

  uint64_t       outageCount;

  /** The ID of the thread on which this pool may be used */

  ThreadID       threadID;

  /** The buffer backing the pool's VIOs */

  char          *buffer;

  /** The pool entries */

  VIOPoolEntry   entries[];

};

/**********************************************************************/

int makeVIOPool(PhysicalLayer   *layer,

                size_t           poolSize,

                ThreadID         threadID,

                VIOConstructor  *vioConstructor,

                void            *context,

                VIOPool        **poolPtr)

{

  VIOPool *pool;

  int result = ALLOCATE_EXTENDED(VIOPool, poolSize, VIOPoolEntry, __func__,

                                 &pool);

  if (result != VDO_SUCCESS) {

    return result;

  }

  pool->threadID = threadID;

  initializeRing(&pool->available);

  initializeRing(&pool->busy);

  result = ALLOCATE(poolSize * VDO_BLOCK_SIZE, char, "VIO pool buffer",

                    &pool->buffer);

  if (result != VDO_SUCCESS) {

    freeVIOPool(&pool);

    return result;

  }

  char *ptr = pool->buffer;

  for (size_t i = 0; i < poolSize; i++) {

    VIOPoolEntry *entry = &pool->entries[i];

    entry->buffer       = ptr;

    entry->context      = context;

    result = vioConstructor(layer, entry, ptr, &entry->vio);

    if (result != VDO_SUCCESS) {

      freeVIOPool(&pool);

      return result;

    }

    ptr += VDO_BLOCK_SIZE;

    initializeRing(&entry->node);

    pushRingNode(&pool->available, &entry->node);

    pool->size++;

  }

  *poolPtr = pool;

  return VDO_SUCCESS;

}

/**********************************************************************/

void freeVIOPool(VIOPool **poolPtr)

{

  if (*poolPtr == NULL) {

    return;

  }

  // Remove all available entries from the object pool.

  VIOPool *pool = *poolPtr;

  ASSERT_LOG_ONLY(!hasWaiters(&pool->waiting),

                  "VIO pool must not have any waiters when being freed");

  ASSERT_LOG_ONLY((pool->busyCount == 0),

                  "VIO pool must not have %zu busy entries when being freed",

                  pool->busyCount);

  ASSERT_LOG_ONLY(isRingEmpty(&pool->busy),

                  "VIO pool must not have busy entries when being freed");

  VIOPoolEntry *entry;

  while ((entry = asVIOPoolEntry(chopRingNode(&pool->available))) != NULL) {

    freeVIO(&entry->vio);

  }

  // Make sure every VIOPoolEntry has been removed.

  for (size_t i = 0; i < pool->size; i++) {

    VIOPoolEntry *entry = &pool->entries[i];

    ASSERT_LOG_ONLY(isRingEmpty(&entry->node), "VIO Pool entry still in use:"

                    " VIO is in use for physical block %" PRIu64

                    " for operation %u",

                    entry->vio->physical,

                    entry->vio->operation);

  }

  FREE(pool->buffer);

  FREE(pool);

  *poolPtr = NULL;

}

/**********************************************************************/

bool isVIOPoolBusy(VIOPool *pool)

{

  return (pool->busyCount != 0);

}

/**********************************************************************/

int acquireVIOFromPool(VIOPool *pool, Waiter *waiter)

{

  ASSERT_LOG_ONLY((pool->threadID == getCallbackThreadID()),

                  "acquire from active VIOPool called from correct thread");

  if (isRingEmpty(&pool->available)) {

    pool->outageCount++;

    return enqueueWaiter(&pool->waiting, waiter);

  }

  pool->busyCount++;

  RingNode *entry = chopRingNode(&pool->available);

  pushRingNode(&pool->busy, entry);

  (*waiter->callback)(waiter, entry);

  return VDO_SUCCESS;

}

/**********************************************************************/

void returnVIOToPool(VIOPool *pool, VIOPoolEntry *entry)

{

  ASSERT_LOG_ONLY((pool->threadID == getCallbackThreadID()),

                  "vio pool entry returned on same thread as it was acquired");

  entry->vio->completion.errorHandler = NULL;

  if (hasWaiters(&pool->waiting)) {

    notifyNextWaiter(&pool->waiting, NULL, entry);

    return;

  }

  pushRingNode(&pool->available, &entry->node);

  --pool->busyCount;

}

/**********************************************************************/

uint64_t getVIOPoolOutageCount(VIOPool *pool)

{

  return pool->outageCount;

}