static inline bool is_flush_request(struct request *rq,
		struct blk_flush_queue *fq, unsigned int tag)
{
	return ((rq->cmd_flags & REQ_FLUSH_SEQ) &&
			fq->flush_rq->tag == tag);
}
The program contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently.