[PATCH 8/9] block: hold a request_queue reference for the lifetime of struct gendisk

[Christoph Hellwig]

Acquire the queue ref dropped in disk_release in __blk_alloc_disk so any
allocate gendisk always has a queue reference.

Signed-off-by: Christoph Hellwig <hch at lst.de>
---
 block/genhd.c         | 19 +++++++------------
 include/linux/genhd.h |  1 -
 2 files changed, 7 insertions(+), 13 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index f18122ee2778..6294517cebe6 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -551,15 +551,6 @@ void device_add_disk(struct device *parent, struct gendisk *disk,
 	register_disk(parent, disk, groups);
 	blk_register_queue(disk);
 
-	/*
-	 * Take an extra ref on queue which will be put on disk_release()
-	 * so that it sticks around as long as @disk is there.
-	 */
-	if (blk_get_queue(disk->queue))
-		set_bit(GD_QUEUE_REF, &disk->state);
-	else
-		WARN_ON_ONCE(1);
-
 	disk_add_events(disk);
 	blk_integrity_add(disk);
 }
@@ -1087,8 +1078,7 @@ static void disk_release(struct device *dev)
 	disk_release_events(disk);
 	kfree(disk->random);
 	xa_destroy(&disk->part_tbl);
-	if (test_bit(GD_QUEUE_REF, &disk->state) && disk->queue)
-		blk_put_queue(disk->queue);
+	blk_put_queue(disk->queue);
 	iput(disk->part0->bd_inode);	/* frees the disk */
 }
 
@@ -1259,9 +1249,12 @@ struct gendisk *__alloc_disk_node(struct request_queue *q, int node_id,
 {
 	struct gendisk *disk;
 
+	if (!blk_get_queue(q))
+		return NULL;
+
 	disk = kzalloc_node(sizeof(struct gendisk), GFP_KERNEL, node_id);
 	if (!disk)
-		return NULL;
+		goto out_put_queue;
 
 	disk->bdi = bdi_alloc(node_id);
 	if (!disk->bdi)
@@ -1296,6 +1289,8 @@ struct gendisk *__alloc_disk_node(struct request_queue *q, int node_id,
 	bdi_put(disk->bdi);
 out_free_disk:
 	kfree(disk);
+out_put_queue:
+	blk_put_queue(q);
 	return NULL;
 }
 EXPORT_SYMBOL(__alloc_disk_node);
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 13e90e6231d8..55acefdd8a20 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -149,7 +149,6 @@ struct gendisk {
 	unsigned long state;
 #define GD_NEED_PART_SCAN		0
 #define GD_READ_ONLY			1
-#define GD_QUEUE_REF			2
 
 	struct mutex open_mutex;	/* open/close mutex */
 	unsigned open_partitions;	/* number of open partitions */
-- 
2.30.2