FREESPACE
if( ((statfsb.f_bavail*statfsb.f_bsize)/512) < FREESPACE )
if( ustatb.f_tfree < FREESPACE )
key_move_bytes = MIN(FREESPACE(pagep), key_size);
MIN(FREESPACE(pagep) - key_move_bytes, val_size);
FREESPACE(cursorp->pagep) > item_info->seek_size)
#define PAIRFITS(P,K,D) ((PAIRSIZE((K),(D))) <= FREESPACE((P)))
#define BIGPAIRFITS(P) ((FREESPACE((P)) >= PAIR_OVERHEAD))