blk-mq: allow blk_mq_init_commands() to return failure

If drivers do dynamic allocation in the hardware command init
path, then we need to be able to handle and return failures.

And if they do allocations or mappings in the init command path,
then we need a cleanup function to free up that space at exit
time. So add blk_mq_free_commands() as the cleanup function.

This is required for the mtip32xx driver conversion to blk-mq.
Signed-off-by: Jens Axboe <axboe@fb.com>

block/blk-mq.c

@@ -1058,8 +1058,46 @@ static void blk_mq_hctx_notify(void *data, unsigned long action,
 	blk_mq_put_ctx(ctx);
 }
 
-static void blk_mq_init_hw_commands(struct blk_mq_hw_ctx *hctx,
-				    void (*init)(void *, struct blk_mq_hw_ctx *,
+static int blk_mq_init_hw_commands(struct blk_mq_hw_ctx *hctx,
+				   int (*init)(void *, struct blk_mq_hw_ctx *,
+					struct request *, unsigned int),
+				   void *data)
+{
+	unsigned int i;
+	int ret = 0;
+
+	for (i = 0; i < hctx->queue_depth; i++) {
+		struct request *rq = hctx->rqs[i];
+
+		ret = init(data, hctx, rq, i);
+		if (ret)
+			break;
+	}
+
+	return ret;
+}
+
+int blk_mq_init_commands(struct request_queue *q,
+			 int (*init)(void *, struct blk_mq_hw_ctx *,
+					struct request *, unsigned int),
+			 void *data)
+{
+	struct blk_mq_hw_ctx *hctx;
+	unsigned int i;
+	int ret = 0;
+
+	queue_for_each_hw_ctx(q, hctx, i) {
+		ret = blk_mq_init_hw_commands(hctx, init, data);
+		if (ret)
+			break;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(blk_mq_init_commands);
+
+static void blk_mq_free_hw_commands(struct blk_mq_hw_ctx *hctx,
+				    void (*free)(void *, struct blk_mq_hw_ctx *,
 					struct request *, unsigned int),
 				    void *data)
 {
@@ -1068,12 +1106,12 @@ static void blk_mq_init_hw_commands(struct blk_mq_hw_ctx *hctx,
 	for (i = 0; i < hctx->queue_depth; i++) {
 		struct request *rq = hctx->rqs[i];
 
-		init(data, hctx, rq, i);
+		free(data, hctx, rq, i);
 	}
 }
 
-void blk_mq_init_commands(struct request_queue *q,
-			  void (*init)(void *, struct blk_mq_hw_ctx *,
+void blk_mq_free_commands(struct request_queue *q,
+			  void (*free)(void *, struct blk_mq_hw_ctx *,
 					struct request *, unsigned int),
 			  void *data)
 {
@@ -1081,9 +1119,9 @@ void blk_mq_init_commands(struct request_queue *q,
 	unsigned int i;
 
 	queue_for_each_hw_ctx(q, hctx, i)
-		blk_mq_init_hw_commands(hctx, init, data);
+		blk_mq_free_hw_commands(hctx, free, data);
 }
-EXPORT_SYMBOL(blk_mq_init_commands);
+EXPORT_SYMBOL(blk_mq_free_commands);
 
 static void blk_mq_free_rq_map(struct blk_mq_hw_ctx *hctx)
 {

drivers/block/virtio_blk.c

@@ -490,13 +490,14 @@ static struct blk_mq_reg virtio_mq_reg = {
 	.flags		= BLK_MQ_F_SHOULD_MERGE,
 };
 
-static void virtblk_init_vbr(void *data, struct blk_mq_hw_ctx *hctx,
+static int virtblk_init_vbr(void *data, struct blk_mq_hw_ctx *hctx,
 			     struct request *rq, unsigned int nr)
 {
 	struct virtio_blk *vblk = data;
 	struct virtblk_req *vbr = rq->special;
 
 	sg_init_table(vbr->sg, vblk->sg_elems);
+	return 0;
 }
 
 static int virtblk_probe(struct virtio_device *vdev)

include/linux/blk-mq.h

@@ -117,7 +117,8 @@ enum {
 struct request_queue *blk_mq_init_queue(struct blk_mq_reg *, void *);
 int blk_mq_register_disk(struct gendisk *);
 void blk_mq_unregister_disk(struct gendisk *);
-void blk_mq_init_commands(struct request_queue *, void (*init)(void *data, struct blk_mq_hw_ctx *, struct request *, unsigned int), void *data);
+int blk_mq_init_commands(struct request_queue *, int (*init)(void *data, struct blk_mq_hw_ctx *, struct request *, unsigned int), void *data);
+void blk_mq_free_commands(struct request_queue *, void (*free)(void *data, struct blk_mq_hw_ctx *, struct request *, unsigned int), void *data);
 
 void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule);