Commit 5a473e83 authored by Jens Axboe's avatar Jens Axboe
Browse files

block: provide plug based way of signaling forced no-wait semantics 



Provide a way for the caller to specify that IO should be marked
with REQ_NOWAIT to avoid blocking on allocation.

Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 2e0464d4

block/blk-core.c

+6 −0
Original line number Diff line number Diff line
@@ -958,6 +958,7 @@ generic_make_request_checks(struct bio *bio) 
	struct request_queue *q;

	int nr_sectors = bio_sectors(bio);

	blk_status_t status = BLK_STS_IOERR;

	struct blk_plug *plug;

	char b[BDEVNAME_SIZE];



	might_sleep();
@@ -971,6 +972,10 @@ generic_make_request_checks(struct bio *bio) 
		goto end_io;

	}



	plug = blk_mq_plug(q, bio);

	if (plug && plug->nowait)

		bio->bi_opf |= REQ_NOWAIT;



	/*

	 * For a REQ_NOWAIT based request, return -EOPNOTSUPP

	 * if queue is not a request based queue.
@@ -1800,6 +1805,7 @@ void blk_start_plug(struct blk_plug *plug) 
	INIT_LIST_HEAD(&plug->cb_list);

	plug->rq_count = 0;

	plug->multiple_queues = false;

	plug->nowait = false;



	/*

	 * Store ordering should not be needed here, since a potential

include/linux/blkdev.h

+1 −0
Original line number Diff line number Diff line
@@ -1189,6 +1189,7 @@ struct blk_plug { 
	struct list_head cb_list; /* md requires an unplug callback */

	unsigned short rq_count;

	bool multiple_queues;

	bool nowait;

};

#define BLK_MAX_REQUEST_COUNT 16

#define BLK_PLUG_FLUSH_SIZE (128 * 1024)