blk-mq: allow drivers to hook into I/O completion

Split out the bottom half of blk_mq_end_io so that drivers can perform
work when they know a request has been completed, but before it has been
freed.  This also obsoletes blk_mq_end_io_partial as drivers can now
pass any value to blk_update_request directly.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

block/blk-mq.c

@@ -294,20 +294,24 @@ void blk_mq_clone_flush_request(struct request *flush_rq,
 		hctx->cmd_size);
 }
 
-bool blk_mq_end_io_partial(struct request *rq, int error, unsigned int nr_bytes)
+inline void __blk_mq_end_io(struct request *rq, int error)
 {
-	if (blk_update_request(rq, error, blk_rq_bytes(rq)))
-		return true;
-
 	blk_account_io_done(rq);
 
 	if (rq->end_io)
 		rq->end_io(rq, error);
 	else
 		blk_mq_free_request(rq);
-	return false;
 }
-EXPORT_SYMBOL(blk_mq_end_io_partial);
+EXPORT_SYMBOL(__blk_mq_end_io);
+
+void blk_mq_end_io(struct request *rq, int error)
+{
+	if (blk_update_request(rq, error, blk_rq_bytes(rq)))
+		BUG();
+	__blk_mq_end_io(rq, error);
+}
+EXPORT_SYMBOL(blk_mq_end_io);
 
 static void __blk_mq_complete_request_remote(void *data)
 {

include/linux/blk-mq.h

@@ -149,13 +149,8 @@ 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_tag_set *, unsigned int);
 void blk_mq_free_single_hw_queue(struct blk_mq_hw_ctx *, unsigned int);
 
-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_end_io(struct request *rq, int error);
+void __blk_mq_end_io(struct request *rq, int error);
 
 void blk_mq_complete_request(struct request *rq);