block: release q->elevator_lock in ioc_qos_write

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>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20250319105518.468941-2-nilay@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index 38e7bf3c3b4f352d4694b36f132ff97078b0b7b7..56e6fb51316d99f19c59ef0a48e362cfa8d12f0e 100644 (file)
--- 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);