[PATCH] blk-cgroup: fix disk reference leak in blkcg_maybe_throttle_current()

[Jackie Liu <liu.yun@linux.dev>]

From: Jackie Liu <liuyun01@kylinos.cn>

Add the missing put_disk() on the error path in
blkcg_maybe_throttle_current(). When blkcg lookup, blkg lookup, or
blkg_tryget() fails, the function jumps to the out label which only
calls rcu_read_unlock() but does not release the disk reference acquired
by blkcg_schedule_throttle() via get_device(). Since current->throttle_disk
is already set to NULL before the lookup, blkcg_exit() cannot release
this reference either, causing the disk to never be freed.

Restore the reference release that was present as blk_put_queue() in the
original code but was inadvertently dropped during the conversion from
request_queue to gendisk.

Fixes: f05837ed73d0 ("blk-cgroup: store a gendisk to throttle in struct task_struct")
Signed-off-by: Jackie Liu <liuyun01@kylinos.cn>
---
 block/blk-cgroup.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index b70096497d38..c377241ee13c 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -2022,6 +2022,7 @@ void blkcg_maybe_throttle_current(void)
 	return;
 out:
 	rcu_read_unlock();
+	put_disk(disk);
 }
 
 /**
-- 
2.51.1