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Commit f421e1d9 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

block: provide a direct_make_request helper 



This helper allows reinserting a bio into a new queue without much
overhead, but requires all queue limits to be the same for the upper
and lower queues, and it does not provide any recursion preventions.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarSagi Grimberg <sagi@grimberg.me>
Reviewed-by: default avatarJavier González <javier@cnexlabs.com>
Reviewed-by: default avatarHannes Reinecke <hare@suse.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 96222bcc

block/blk-core.c

+34 −0
Original line number Diff line number Diff line
@@ -2243,6 +2243,40 @@ blk_qc_t generic_make_request(struct bio *bio) 
}

EXPORT_SYMBOL(generic_make_request);



/**

 * direct_make_request - hand a buffer directly to its device driver for I/O

 * @bio:  The bio describing the location in memory and on the device.

 *

 * This function behaves like generic_make_request(), but does not protect

 * against recursion.  Must only be used if the called driver is known

 * to not call generic_make_request (or direct_make_request) again from

 * its make_request function.  (Calling direct_make_request again from

 * a workqueue is perfectly fine as that doesn't recurse).

 */

blk_qc_t direct_make_request(struct bio *bio)

{

	struct request_queue *q = bio->bi_disk->queue;

	bool nowait = bio->bi_opf & REQ_NOWAIT;

	blk_qc_t ret;



	if (!generic_make_request_checks(bio))

		return BLK_QC_T_NONE;



	if (unlikely(blk_queue_enter(q, nowait))) {

		if (nowait && !blk_queue_dying(q))

			bio->bi_status = BLK_STS_AGAIN;

		else

			bio->bi_status = BLK_STS_IOERR;

		bio_endio(bio);

		return BLK_QC_T_NONE;

	}



	ret = q->make_request_fn(q, bio);

	blk_queue_exit(q);

	return ret;

}

EXPORT_SYMBOL_GPL(direct_make_request);



/**

 * submit_bio - submit a bio to the block device layer for I/O

 * @bio: The &struct bio which describes the I/O

include/linux/blkdev.h

+1 −0
Original line number Diff line number Diff line
@@ -920,6 +920,7 @@ static inline void rq_flush_dcache_pages(struct request *rq) 
extern int blk_register_queue(struct gendisk *disk);

extern void blk_unregister_queue(struct gendisk *disk);

extern blk_qc_t generic_make_request(struct bio *bio);

extern blk_qc_t direct_make_request(struct bio *bio);

extern void blk_rq_init(struct request_queue *q, struct request *rq);

extern void blk_init_request_from_bio(struct request *req, struct bio *bio);

extern void blk_put_request(struct request *);