blk-mq: support partial I/O completions

Add a new blk_mq_end_io_partial function to partially complete requests
as needed by the SCSI layer.  We do this by reusing blk_update_request
to advance the bio instead of having a simplified version of it in
the blk-mq code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index ff28fe37ddda..2ff2e8d982be 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -133,7 +133,13 @@ struct blk_mq_hw_ctx *blk_mq_map_queue(struct request_queue *, const int ctx_ind
 struct blk_mq_hw_ctx *blk_mq_alloc_single_hw_queue(struct blk_mq_reg *, unsigned int);
 void blk_mq_free_single_hw_queue(struct blk_mq_hw_ctx *, unsigned int);
 
-void blk_mq_end_io(struct request *rq, int error);
+bool blk_mq_end_io_partial(struct request *rq, int error,
+                unsigned int nr_bytes);
+static inline void blk_mq_end_io(struct request *rq, int error)
+{
+        bool done = !blk_mq_end_io_partial(rq, error, blk_rq_bytes(rq));
+        BUG_ON(!done);
+}
 
 void blk_mq_complete_request(struct request *rq);