block: add a blk_steal_bios helper

This helpers allows to bounce steal the uncompleted bios from a request so
that they can be reissued on another path.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-core.c b/block/blk-core.c
index 96aaa3a419a374242c9658d081da08e3122dba2b..68cfe6780a9b7329ce5b95a3c7d5e8b4c64c7abe 100644 (file)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2769,6 +2769,27 @@ struct request *blk_fetch_request(struct request_queue *q)
 }
 EXPORT_SYMBOL(blk_fetch_request);
 
+/*
+ * Steal bios from a request and add them to a bio list.
+ * The request must not have been partially completed before.
+ */
+void blk_steal_bios(struct bio_list *list, struct request *rq)
+{
+       if (rq->bio) {
+               if (list->tail)
+                       list->tail->bi_next = rq->bio;
+               else
+                       list->head = rq->bio;
+               list->tail = rq->biotail;
+
+               rq->bio = NULL;
+               rq->biotail = NULL;
+       }
+
+       rq->__data_len = 0;
+}
+EXPORT_SYMBOL_GPL(blk_steal_bios);
+
 /**
  * blk_update_request - Special helper function for request stacking drivers
  * @req:      the request being processed

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index eda3d25c0f68927ac72042c7e32a84e983be985f..fddda6a1f9b587925f11c2492db3e246b56a6a6b 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -1094,6 +1094,8 @@ extern struct request *blk_peek_request(struct request_queue *q);
 extern void blk_start_request(struct request *rq);
 extern struct request *blk_fetch_request(struct request_queue *q);
 
+void blk_steal_bios(struct bio_list *list, struct request *rq);
+
 /*
  * Request completion related functions.
  *