path: root/block/genhd.c
diff options
authorMike Snitzer <>2018-01-08 22:01:13 -0500
committerJens Axboe <>2018-01-15 08:41:38 -0700
commitfa70d2e2c4a0a54ced98260c6a176cc94c876d27 (patch)
tree76c502acc8e87e03abc499aedd78150ce8703641 /block/genhd.c
parent667257e8b2988c0183ba23e2bcd6900e87961606 (diff)
block: allow gendisk's request_queue registration to be deferred
Since I can remember DM has forced the block layer to allow the allocation and initialization of the request_queue to be distinct operations. Reason for this is block/genhd.c:add_disk() has requires that the request_queue (and associated bdi) be tied to the gendisk before add_disk() is called -- because add_disk() also deals with exposing the request_queue via blk_register_queue(). DM's dynamic creation of arbitrary device types (and associated request_queue types) requires the DM device's gendisk be available so that DM table loads can establish a master/slave relationship with subordinate devices that are referenced by loaded DM tables -- using bd_link_disk_holder(). But until these DM tables, and their associated subordinate devices, are known DM cannot know what type of request_queue it needs -- nor what its queue_limits should be. This chicken and egg scenario has created all manner of problems for DM and, at times, the block layer. Summary of changes: - Add device_add_disk_no_queue_reg() and add_disk_no_queue_reg() variant that drivers may use to add a disk without also calling blk_register_queue(). Driver must call blk_register_queue() once its request_queue is fully initialized. - Return early from blk_unregister_queue() if QUEUE_FLAG_REGISTERED is not set. It won't be set if driver used add_disk_no_queue_reg() but driver encounters an error and must del_gendisk() before calling blk_register_queue(). - Export blk_register_queue(). These changes allow DM to use add_disk_no_queue_reg() to anchor its gendisk as the "master" for master/slave relationships DM must establish with subordinate devices referenced in DM tables that get loaded. Once all "slave" devices for a DM device are known its request_queue can be properly initialized and then advertised via sysfs -- important improvement being that no request_queue resource initialization performed by blk_register_queue() is missed for DM devices anymore. Signed-off-by: Mike Snitzer <> Reviewed-by: Ming Lei <> Signed-off-by: Jens Axboe <>
Diffstat (limited to 'block/genhd.c')
1 files changed, 17 insertions, 3 deletions
diff --git a/block/genhd.c b/block/genhd.c
index 00620e0..88a53c1 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -629,16 +629,18 @@ exit:
- * device_add_disk - add partitioning information to kernel list
+ * __device_add_disk - add disk information to kernel list
* @parent: parent device for the disk
* @disk: per-device partitioning information
+ * @register_queue: register the queue if set to true
* This function registers the partitioning information in @disk
* with the kernel.
* FIXME: error handling
-void device_add_disk(struct device *parent, struct gendisk *disk)
+static void __device_add_disk(struct device *parent, struct gendisk *disk,
+ bool register_queue)
dev_t devt;
int retval;
@@ -682,7 +684,8 @@ void device_add_disk(struct device *parent, struct gendisk *disk)
exact_match, exact_lock, disk);
register_disk(parent, disk);
- blk_register_queue(disk);
+ if (register_queue)
+ blk_register_queue(disk);
* Take an extra ref on queue which will be put on disk_release()
@@ -693,8 +696,19 @@ void device_add_disk(struct device *parent, struct gendisk *disk)
+void device_add_disk(struct device *parent, struct gendisk *disk)
+ __device_add_disk(parent, disk, true);
+void device_add_disk_no_queue_reg(struct device *parent, struct gendisk *disk)
+ __device_add_disk(parent, disk, false);
void del_gendisk(struct gendisk *disk)
struct disk_part_iter piter;