[PATCH 1/2] block: add initial kdoc over the request_queue

[Luis Chamberlain <mcgrof@kernel.org>]

We start off with an initial description of the request_queue data
structure, followed by describing the purpose of the debugfs_mutex
debugfs_dir, and blk_trace.

Suggested-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
---
 include/linux/blkdev.h | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 70461b347169..ea319c2b0593 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -394,6 +394,26 @@ static inline int blkdev_zone_mgmt_ioctl(struct block_device *bdev,
 
 #endif /* CONFIG_BLK_DEV_ZONED */
 
+/**
+ * struct request_queue - block device driver request queue
+ * @debugfs_mutex: used to protect access to the @debugfs_dir
+ * @blk_trace: used by blktrace to keep track of setup / tracing
+ * @debugfs_dir: directory created to place debugfs information. This is always
+ *	created for make_request and request-based block drivers upon
+ *	initialization. blktrace requires for this directory to be created,
+ *	and so it will be created on demand if its block driver type does not
+ *	create it opon initialization.
+ *
+ * The request_queue is used to manage incoming block layer device driver
+ * requests. We have three main type of block driver types which end up making
+ * use of the request_queue:
+ *
+ *   o make_request block drivers (multiqueue)
+ *   o request-based block drivers
+ *   o custom solutions such as scsi-generic
+ *
+ * All partitions share the same request_queue data structure.
+ */
 struct request_queue {
 	struct request		*last_merge;
 	struct elevator_queue	*elevator;
-- 
2.26.2