From 7055bd5233863e27e3efe6605aa07901cc61b544 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Thu, 2 Nov 2017 21:29:50 +0300 Subject: block: provide a direct_make_request helper MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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: Christoph Hellwig Reviewed-by: Sagi Grimberg Reviewed-by: Javier González Reviewed-by: Hannes Reinecke Signed-off-by: Jens Axboe (cherry picked from commit f421e1d9ade4e1b88183e54425cf50e390d16a7f) --- block/blk-core.c | 34 ++++++++++++++++++++++++++++++++++ include/linux/blkdev.h | 1 + 2 files changed, 35 insertions(+) diff --git a/block/blk-core.c b/block/blk-core.c index 0b14aebfd1a8..468025c9e03f 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -2259,6 +2259,40 @@ out: } 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 diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 4d4af0e94059..ed83e71f0afa 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -954,6 +954,7 @@ do { \ 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 *); -- cgit v1.2.3