scan = ptr + offsetof(struct trx_header, flag_version);
trx->crc32 = crc32buf(scan, trx->len - (scan - ptr));
msync(ptr, sizeof(struct trx_header), MS_SYNC|MS_INVALIDATE);
scan = ptr + offsetof(struct trx_header, flag_version);
trx->crc32 = crc32buf(scan, trx->len - (scan - ptr));
msync(ptr, sizeof(struct trx_header), MS_SYNC|MS_INVALIDATE);