/* Page cache parameters for non-mmap() pages */
  int nCacheMax;                  /* Configured cache size (in pages) */
  int nCacheAlloc;                /* Current cache size (in pages) */
  Page *pLruFirst;                /* Head of the LRU list */
  Page *pLruLast;                 /* Tail of the LRU list */
  int nHash;                      /* Number of hash slots in hash table */
  Page **apHash;                  /* nHash Hash slots */

  /* Both types of pages */
  Page *pWaiting;                 /* b-tree pages waiting to be written */

  /* Statistics */
  int nOut;                       /* Number of outstanding pages */
  int nWrite;                     /* Total number of pages written */
  int nRead;                      /* Total number of pages read */
};
................................................................................

  iHash = fsHashKey(pFS->nHash, pPg->iPg);
  for(pp=&pFS->apHash[iHash]; *pp!=pPg; pp=&(*pp)->pHashNext);
  *pp = pPg->pHashNext;
  pPg->pHashNext = 0;
}








/*
** Purge the cache of all non-mmap pages with nRef==0.
*/
void lsmFsPurgeCache(FileSystem *pFS){
  Page *pPg;

  pPg = pFS->pLruFirst;
  while( pPg ){
    Page *pNext = pPg->pLruNext;
    assert( pPg->flags & PAGE_FREE );
    fsPageRemoveFromHash(pFS, pPg);
    lsmFree(pFS->pEnv, pPg->aData);
    lsmFree(pFS->pEnv, pPg);
    pPg = pNext;
    pFS->nCacheAlloc--;
  }
  pFS->pLruFirst = 0;
  pFS->pLruLast = 0;

  assert( pFS->nCacheAlloc<=pFS->nOut && pFS->nCacheAlloc>=0 );
}

................................................................................
  if( pPage ){
    pPage->flags = PAGE_FREE;
  }
  *ppOut = pPage;
  return rc;
}

static void fsPageBufferFree(Page *pPg){
  assert( pPg->pLruNext==0 );
  assert( pPg->pLruPrev==0 );
  assert( pPg->pFS->pLruFirst!=pPg );
  assert( pPg->pFS->pLruLast!=pPg );

  lsmFree(pPg->pFS->pEnv, pPg->aData);
  lsmFree(pPg->pFS->pEnv, pPg);
}

static void fsGrowMapping(
  FileSystem *pFS,
  i64 iSz,
  int *pRc
){
  /* This function won't work with compressed databases yet. */
  assert( pFS->pCompress==0 );

  /* Page cache parameters for non-mmap() pages */
  int nCacheMax;                  /* Configured cache size (in pages) */
  int nCacheAlloc;                /* Current cache size (in pages) */
  Page *pLruFirst;                /* Head of the LRU list */
  Page *pLruLast;                 /* Tail of the LRU list */
  int nHash;                      /* Number of hash slots in hash table */
  Page **apHash;                  /* nHash Hash slots */


  Page *pWaiting;                 /* b-tree pages waiting to be written */

  /* Statistics */
  int nOut;                       /* Number of outstanding pages */
  int nWrite;                     /* Total number of pages written */
  int nRead;                      /* Total number of pages read */
};
................................................................................

  iHash = fsHashKey(pFS->nHash, pPg->iPg);
  for(pp=&pFS->apHash[iHash]; *pp!=pPg; pp=&(*pp)->pHashNext);
  *pp = pPg->pHashNext;
  pPg->pHashNext = 0;
}

static void fsPageBufferFree(Page *pPg){
  pPg->pFS->nCacheAlloc--;
  lsmFree(pPg->pFS->pEnv, pPg->aData);
  lsmFree(pPg->pFS->pEnv, pPg);
}


/*
** Purge the cache of all non-mmap pages with nRef==0.
*/
void lsmFsPurgeCache(FileSystem *pFS){
  Page *pPg;

  pPg = pFS->pLruFirst;
  while( pPg ){
    Page *pNext = pPg->pLruNext;
    assert( pPg->flags & PAGE_FREE );
    fsPageRemoveFromHash(pFS, pPg);
    fsPageBufferFree(pPg);

    pPg = pNext;

  }
  pFS->pLruFirst = 0;
  pFS->pLruLast = 0;

  assert( pFS->nCacheAlloc<=pFS->nOut && pFS->nCacheAlloc>=0 );
}

................................................................................
  if( pPage ){
    pPage->flags = PAGE_FREE;
  }
  *ppOut = pPage;
  return rc;
}











static void fsGrowMapping(
  FileSystem *pFS,
  i64 iSz,
  int *pRc
){
  /* This function won't work with compressed databases yet. */
  assert( pFS->pCompress==0 );

  lsm_i64 *pnOut
){
  off_t iSz;
  int prc;
  PosixFile *p = (PosixFile *)pFile;
  struct stat buf;






  if( p->pMap ){
    munmap(p->pMap, p->nMap);
    *ppOut = p->pMap = 0;
    *pnOut = p->nMap = 0;
  }

  if( iMin>=0 ){
    memset(&buf, 0, sizeof(buf));
    prc = fstat(p->fd, &buf);
    if( prc!=0 ) return LSM_IOERR_BKPT;
    iSz = buf.st_size;
    if( iSz<iMin ){
      iSz = ((iMin + (2<<20) - 1) / (2<<20)) * (2<<20);
      prc = ftruncate(p->fd, iSz);
      if( prc!=0 ) return LSM_IOERR_BKPT;
    }

    p->pMap = mmap(0, iSz, PROT_READ|PROT_WRITE, MAP_SHARED, p->fd, 0);
    p->nMap = iSz;
  }

  lsm_i64 *pnOut
){
  off_t iSz;
  int prc;
  PosixFile *p = (PosixFile *)pFile;
  struct stat buf;

  /* If the file is between 0 and 2MB in size, extend it in chunks of 256K.
  ** Thereafter, in chunks of 1MB at a time.  */
  const int aIncrSz[] = {256*1024, 1024*1024};
  int nIncrSz = aIncrSz[iMin>(2*1024*1024)];

  if( p->pMap ){
    munmap(p->pMap, p->nMap);
    *ppOut = p->pMap = 0;
    *pnOut = p->nMap = 0;
  }

  if( iMin>=0 ){
    memset(&buf, 0, sizeof(buf));
    prc = fstat(p->fd, &buf);
    if( prc!=0 ) return LSM_IOERR_BKPT;
    iSz = buf.st_size;
    if( iSz<iMin ){
      iSz = ((iMin + nIncrSz-1) / nIncrSz) * nIncrSz;
      prc = ftruncate(p->fd, iSz);
      if( prc!=0 ) return LSM_IOERR_BKPT;
    }

    p->pMap = mmap(0, iSz, PROT_READ|PROT_WRITE, MAP_SHARED, p->fd, 0);
    p->nMap = iSz;
  }