Commit 81ada09c authored by Chengming Zhou's avatar Chengming Zhou Committed by Jens Axboe
Browse files

blk-flush: reuse rq queuelist in flush state machine 



Since we don't need to maintain inflight flush_data requests list
anymore, we can reuse rq->queuelist for flush pending list.

Note in mq_flush_data_end_io(), we need to re-initialize rq->queuelist
before reusing it in the state machine when end, since the rq->rq_next
also reuse it, may have corrupted rq->queuelist by the driver.

This patch decrease the size of struct request by 16 bytes.

Signed-off-by: default avatarChengming Zhou <zhouchengming@bytedance.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20230717040058.3993930-5-chengming.zhou@linux.dev


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent b175c867

block/blk-flush.c

+10 −7
Original line number Diff line number Diff line
@@ -183,14 +183,13 @@ static void blk_flush_complete_seq(struct request *rq, 
		/* queue for flush */

		if (list_empty(pending))

			fq->flush_pending_since = jiffies;

		list_move_tail(&rq->flush.list, pending);

		list_move_tail(&rq->queuelist, pending);

		break;



	case REQ_FSEQ_DATA:

		list_del_init(&rq->flush.list);

		fq->flush_data_in_flight++;

		spin_lock(&q->requeue_lock);

		list_add(&rq->queuelist, &q->requeue_list);

		list_move(&rq->queuelist, &q->requeue_list);

		spin_unlock(&q->requeue_lock);

		blk_mq_kick_requeue_list(q);

		break;
@@ -202,7 +201,7 @@ static void blk_flush_complete_seq(struct request *rq, 
		 * flush data request completion path.  Restore @rq for

		 * normal completion and end it.

		 */

		list_del_init(&rq->flush.list);

		list_del_init(&rq->queuelist);

		blk_flush_restore_request(rq);

		blk_mq_end_request(rq, error);

		break;
@@ -258,7 +257,7 @@ static enum rq_end_io_ret flush_end_io(struct request *flush_rq, 
	fq->flush_running_idx ^= 1;



	/* and push the waiting requests to the next stage */

	list_for_each_entry_safe(rq, n, running, flush.list) {

	list_for_each_entry_safe(rq, n, running, queuelist) {

		unsigned int seq = blk_flush_cur_seq(rq);



		BUG_ON(seq != REQ_FSEQ_PREFLUSH && seq != REQ_FSEQ_POSTFLUSH);
@@ -292,7 +291,7 @@ static void blk_kick_flush(struct request_queue *q, struct blk_flush_queue *fq, 
{

	struct list_head *pending = &fq->flush_queue[fq->flush_pending_idx];

	struct request *first_rq =

		list_first_entry(pending, struct request, flush.list);

		list_first_entry(pending, struct request, queuelist);

	struct request *flush_rq = fq->flush_rq;



	/* C1 described at the top of this file */
@@ -376,6 +375,11 @@ static enum rq_end_io_ret mq_flush_data_end_io(struct request *rq, 
	 */

	spin_lock_irqsave(&fq->mq_flush_lock, flags);

	fq->flush_data_in_flight--;

	/*

	 * May have been corrupted by rq->rq_next reuse, we need to

	 * re-initialize rq->queuelist before reusing it here.

	 */

	INIT_LIST_HEAD(&rq->queuelist);

	blk_flush_complete_seq(rq, fq, REQ_FSEQ_DATA, error);

	spin_unlock_irqrestore(&fq->mq_flush_lock, flags);
@@ -386,7 +390,6 @@ static enum rq_end_io_ret mq_flush_data_end_io(struct request *rq, 
static void blk_rq_init_flush(struct request *rq)

{

	rq->flush.seq = 0;

	INIT_LIST_HEAD(&rq->flush.list);

	rq->rq_flags |= RQF_FLUSH_SEQ;

	rq->flush.saved_end_io = rq->end_io; /* Usually NULL */

	rq->end_io = mq_flush_data_end_io;

include/linux/blk-mq.h

+0 −1
Original line number Diff line number Diff line
@@ -178,7 +178,6 @@ struct request { 


	struct {

		unsigned int		seq;

		struct list_head	list;

		rq_end_io_fn		*saved_end_io;

	} flush;