block: add blk_alloc_disk and blk_cleanup_disk APIs

Add two new APIs to allocate and free a gendisk including the
request_queue for use with BIO based drivers.  This is to avoid
boilerplate code in drivers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20210521055116.1053587-6-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/genhd.c

@@ -1293,6 +1293,25 @@ struct gendisk *__alloc_disk_node(int minors, int node_id)
 }
 EXPORT_SYMBOL(__alloc_disk_node);
 
+struct gendisk *__blk_alloc_disk(int node)
+{
+	struct request_queue *q;
+	struct gendisk *disk;
+
+	q = blk_alloc_queue(node);
+	if (!q)
+		return NULL;
+
+	disk = __alloc_disk_node(0, node);
+	if (!disk) {
+		blk_cleanup_queue(q);
+		return NULL;
+	}
+	disk->queue = q;
+	return disk;
+}
+EXPORT_SYMBOL(__blk_alloc_disk);
+
 /**
  * put_disk - decrements the gendisk refcount
  * @disk: the struct gendisk to decrement the refcount for
@@ -1310,6 +1329,22 @@ void put_disk(struct gendisk *disk)
 }
 EXPORT_SYMBOL(put_disk);
 
+/**
+ * blk_cleanup_disk - shutdown a gendisk allocated by blk_alloc_disk
+ * @disk: gendisk to shutdown
+ *
+ * Mark the queue hanging off @disk DYING, drain all pending requests, then mark
+ * the queue DEAD, destroy and put it and the gendisk structure.
+ *
+ * Context: can sleep
+ */
+void blk_cleanup_disk(struct gendisk *disk)
+{
+	blk_cleanup_queue(disk->queue);
+	put_disk(disk);
+}
+EXPORT_SYMBOL(blk_cleanup_disk);
+
 static void set_disk_ro_uevent(struct gendisk *gd, int ro)
 {
 	char event[] = "DISK_RO=1";

include/linux/genhd.h

@@ -278,6 +278,28 @@ extern void put_disk(struct gendisk *disk);
 
 #define alloc_disk(minors) alloc_disk_node(minors, NUMA_NO_NODE)
 
+/**
+ * blk_alloc_disk - allocate a gendisk structure
+ * @node_id: numa node to allocate on
+ *
+ * Allocate and pre-initialize a gendisk structure for use with BIO based
+ * drivers.
+ *
+ * Context: can sleep
+ */
+#define blk_alloc_disk(node_id)						\
+({									\
+	struct gendisk *__disk = __blk_alloc_disk(node_id);		\
+	static struct lock_class_key __key;				\
+									\
+	if (__disk)							\
+		lockdep_init_map(&__disk->lockdep_map,			\
+			"(bio completion)", &__key, 0);			\
+	__disk;								\
+})
+struct gendisk *__blk_alloc_disk(int node);
+void blk_cleanup_disk(struct gendisk *disk);
+
 int __register_blkdev(unsigned int major, const char *name,
 		void (*probe)(dev_t devt));
 #define register_blkdev(major, name) \