[PATCH 1/2] block: release q->elevator_lock in ioc_qos_write

[Nilay Shroff <nilay@linux.ibm.com>]

The ioc_qos_write method acquires q->elevator_lock to protect
updates to blk-wbt parameters. Once these updates are complete,
the lock should be released before returning from ioc_qos_write.

However, in one code path, the release of q->elevator_lock was
mistakenly omitted, potentially leading to a lock leak. This commit
fixes the issue by ensuring that q->elevator_lock is properly
released in all return paths of ioc_qos_write.

Fixes: 245618f8e45f ("block: protect wbt_lat_usec using q->elevator_lock")
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202503171650.cc082b66-lkp@intel.com
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
---
 block/blk-iocost.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 38e7bf3c3b4f..56e6fb51316d 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -3348,6 +3348,7 @@ static ssize_t ioc_qos_write(struct kernfs_open_file *of, char *input,
 		wbt_enable_default(disk);
 
 	blk_mq_unquiesce_queue(disk->queue);
+	mutex_unlock(&disk->queue->elevator_lock);
 	blk_mq_unfreeze_queue(disk->queue, memflags);
 
 	blkg_conf_exit(&ctx);
-- 
2.47.1