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 <snitzer@xxxxxxxxxx>
Reviewed-by: Ming Lei <ming.lei@xxxxxxxxxx>
---
block/blk-sysfs.c | 5 +++++
block/genhd.c | 20 +++++++++++++++++---
include/linux/genhd.h | 5 +++++
3 files changed, 27 insertions(+), 3 deletions(-)
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 9272452ff456..4a6a40ffd78e 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -921,6 +921,7 @@ int blk_register_queue(struct gendisk *disk)
mutex_unlock(&q->sysfs_lock);
return ret;
}
+EXPORT_SYMBOL_GPL(blk_register_queue);
void blk_unregister_queue(struct gendisk *disk)
{
@@ -929,6 +930,10 @@ void blk_unregister_queue(struct gendisk *disk)
if (WARN_ON(!q))
return;
+ /* Return early if disk->queue was never registered. */
+ if (!test_bit(QUEUE_FLAG_REGISTERED, &q->queue_flags))
+ return;
+
/*
* Protect against the 'queue' kobj being accessed
* while/after it is removed.
diff --git a/block/genhd.c b/block/genhd.c
index 00620e01e043..d4aaf0cae9ad 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -629,7 +629,7 @@ static void register_disk(struct device *parent, struct gendisk *disk)
}
/**
- * device_add_disk - add partitioning information to kernel list
+ * device_add_disk_no_queue_reg - add partitioning information to kernel list
* @parent: parent device for the disk
* @disk: per-device partitioning information
*
@@ -638,7 +638,7 @@ static void register_disk(struct device *parent, struct gendisk *disk)
*
* FIXME: error handling
*/
-void device_add_disk(struct device *parent, struct gendisk *disk)
+void device_add_disk_no_queue_reg(struct device *parent, struct gendisk *disk)
{
dev_t devt;
int retval;
@@ -682,7 +682,6 @@ void device_add_disk(struct device *parent, struct gendisk *disk)
exact_match, exact_lock, disk);
}
register_disk(parent, disk);
- blk_register_queue(disk);
/*
* Take an extra ref on queue which will be put on disk_release()
@@ -693,6 +692,21 @@ void device_add_disk(struct device *parent, struct gendisk *disk)
disk_add_events(disk);
blk_integrity_add(disk);
}
+EXPORT_SYMBOL(device_add_disk_no_queue_reg);
+
+/**
+ * device_add_disk - add disk information to kernel list
+ * @parent: parent device for the disk
+ * @disk: per-device disk information
+ *
+ * Adds partitioning information and also registers the
+ * associated request_queue to @disk.
+ */
+void device_add_disk(struct device *parent, struct gendisk *disk)
+{
+ device_add_disk_no_queue_reg(parent, disk);
+ blk_register_queue(disk);
+}
EXPORT_SYMBOL(device_add_disk);
void del_gendisk(struct gendisk *disk)
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 5144ebe046c9..5e3531027b51 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -395,6 +395,11 @@ static inline void add_disk(struct gendisk *disk)
{
device_add_disk(NULL, disk);
}
+extern void device_add_disk_no_queue_reg(struct device *parent, struct gendisk *disk);
+static inline void add_disk_no_queue_reg(struct gendisk *disk)
+{
+ device_add_disk_no_queue_reg(NULL, disk);
+}
extern void del_gendisk(struct gendisk *gp);
extern struct gendisk *get_gendisk(dev_t dev, int *partno);
--
2.15.0
--
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