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 <hch@xxxxxx>
Reviewed-by: Sagi Grimberg <sagi@xxxxxxxxxxx>
Reviewed-by: Javier González <javier@xxxxxxxxxxxx>
Reviewed-by: Hannes Reinecke <hare@xxxxxxxx>
---
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 14f7674fa0b1..b8c80f39f5fe 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2241,6 +2241,40 @@ 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
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 02fa42d24b52..780f01db5899 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -936,6 +936,7 @@ 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 *);
--
2.14.2
