Commit a327c341 authored by Ming Lei's avatar Ming Lei Committed by Jens Axboe
Browse files

blk-mq: fix passthrough plugging 



First we can't add request into plug list in blk_mq_request_bypass_insert
which may be called when flushing plug list, so nested plug is caused.

Second if polled passthrough request is inserted via blk_execute_rq(),
it can't be added to plug list too since io polling needs the request
to be issued to driver.

Fixes the two by moving plugging into blk_execute_rq_no_wait().

Cc: Christoph Hellwig <hch@lst.de>
Fixes: 1c2d2fff ("block: wire-up support for passthrough plugging")
Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20220512140010.1458645-1-ming.lei@redhat.com


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent f569add4

block/blk-mq.c

+63 −51
Original line number Diff line number Diff line
@@ -1169,6 +1169,62 @@ static void blk_end_sync_rq(struct request *rq, blk_status_t error) 
	complete(waiting);

}



/*

 * Allow 2x BLK_MAX_REQUEST_COUNT requests on plug queue for multiple

 * queues. This is important for md arrays to benefit from merging

 * requests.

 */

static inline unsigned short blk_plug_max_rq_count(struct blk_plug *plug)

{

	if (plug->multiple_queues)

		return BLK_MAX_REQUEST_COUNT * 2;

	return BLK_MAX_REQUEST_COUNT;

}



static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)

{

	struct request *last = rq_list_peek(&plug->mq_list);



	if (!plug->rq_count) {

		trace_block_plug(rq->q);

	} else if (plug->rq_count >= blk_plug_max_rq_count(plug) ||

		   (!blk_queue_nomerges(rq->q) &&

		    blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) {

		blk_mq_flush_plug_list(plug, false);

		trace_block_plug(rq->q);

	}



	if (!plug->multiple_queues && last && last->q != rq->q)

		plug->multiple_queues = true;

	if (!plug->has_elevator && (rq->rq_flags & RQF_ELV))

		plug->has_elevator = true;

	rq->rq_next = NULL;

	rq_list_add(&plug->mq_list, rq);

	plug->rq_count++;

}



static void __blk_execute_rq_nowait(struct request *rq, bool at_head,

		rq_end_io_fn *done, bool use_plug)

{

	WARN_ON(irqs_disabled());

	WARN_ON(!blk_rq_is_passthrough(rq));



	rq->end_io = done;



	blk_account_io_start(rq);



	if (use_plug && current->plug) {

		blk_add_rq_to_plug(current->plug, rq);

		return;

	}

	/*

	 * don't check dying flag for MQ because the request won't

	 * be reused after dying flag is set

	 */

	blk_mq_sched_insert_request(rq, at_head, true, false);

}





/**

 * blk_execute_rq_nowait - insert a request to I/O scheduler for execution

 * @rq:		request to insert
@@ -1184,18 +1240,8 @@ static void blk_end_sync_rq(struct request *rq, blk_status_t error) 
 */

void blk_execute_rq_nowait(struct request *rq, bool at_head, rq_end_io_fn *done)

{

	WARN_ON(irqs_disabled());

	WARN_ON(!blk_rq_is_passthrough(rq));



	rq->end_io = done;

	__blk_execute_rq_nowait(rq, at_head, done, true);



	blk_account_io_start(rq);



	/*

	 * don't check dying flag for MQ because the request won't

	 * be reused after dying flag is set

	 */

	blk_mq_sched_insert_request(rq, at_head, true, false);

}

EXPORT_SYMBOL_GPL(blk_execute_rq_nowait);
@@ -1233,8 +1279,13 @@ blk_status_t blk_execute_rq(struct request *rq, bool at_head) 
	DECLARE_COMPLETION_ONSTACK(wait);

	unsigned long hang_check;



	/*

	 * iopoll requires request to be submitted to driver, so can't

	 * use plug

	 */

	rq->end_io_data = &wait;

	blk_execute_rq_nowait(rq, at_head, blk_end_sync_rq);

	__blk_execute_rq_nowait(rq, at_head, blk_end_sync_rq,

			!blk_rq_is_poll(rq));



	/* Prevent hang_check timer from firing at us during very long I/O */

	hang_check = sysctl_hung_task_timeout_secs;
@@ -2340,40 +2391,6 @@ void __blk_mq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, 
	blk_mq_hctx_mark_pending(hctx, ctx);

}



/*

 * Allow 2x BLK_MAX_REQUEST_COUNT requests on plug queue for multiple

 * queues. This is important for md arrays to benefit from merging

 * requests.

 */

static inline unsigned short blk_plug_max_rq_count(struct blk_plug *plug)

{

	if (plug->multiple_queues)

		return BLK_MAX_REQUEST_COUNT * 2;

	return BLK_MAX_REQUEST_COUNT;

}



static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)

{

	struct request *last = rq_list_peek(&plug->mq_list);



	if (!plug->rq_count) {

		trace_block_plug(rq->q);

	} else if (plug->rq_count >= blk_plug_max_rq_count(plug) ||

		   (!blk_queue_nomerges(rq->q) &&

		    blk_rq_bytes(last) >= BLK_PLUG_FLUSH_SIZE)) {

		blk_mq_flush_plug_list(plug, false);

		trace_block_plug(rq->q);

	}



	if (!plug->multiple_queues && last && last->q != rq->q)

		plug->multiple_queues = true;

	if (!plug->has_elevator && (rq->rq_flags & RQF_ELV))

		plug->has_elevator = true;

	rq->rq_next = NULL;

	rq_list_add(&plug->mq_list, rq);

	plug->rq_count++;

}



/**

 * blk_mq_request_bypass_insert - Insert a request at dispatch list.

 * @rq: Pointer to request to be inserted.
@@ -2387,12 +2404,7 @@ void blk_mq_request_bypass_insert(struct request *rq, bool at_head, 
				  bool run_queue)

{

	struct blk_mq_hw_ctx *hctx = rq->mq_hctx;

	struct blk_plug *plug = current->plug;



	if (plug) {

		blk_add_rq_to_plug(plug, rq);

		return;

	}

	spin_lock(&hctx->lock);

	if (at_head)

		list_add(&rq->queuelist, &hctx->dispatch);