From c43332fe028c252a2a28e46be70a530f64fc3c9d Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Wed, 8 Feb 2023 07:35:14 +0100 Subject: blk-cgroup: delay calling blkcg_exit_disk until disk_release MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit While del_gendisk ensures there is no outstanding I/O on the queue, it can't prevent block layer users from building new I/O. This leads to a NULL ->root_blkg reference in bio_associate_blkg when allocating a new bio on a shut down file system. Delay freeing the blk-cgroup subsystems from del_gendisk until disk_release to make sure the blkg and throttle information is still avaŃ–lable for bio submitters, even if those bios will immediately fail. This now can cause a case where disk_release is called on a disk that hasn't been added. That's mostly harmless, except for a case in blk_throttl_exit that now needs to check for a NULL ->td pointer. Fixes: 178fa7d49815 ("blk-cgroup: delay blk-cgroup initialization until add_disk") Reported-by: Ming Lei Signed-off-by: Christoph Hellwig Reviewed-by: Ming Lei Link: https://lore.kernel.org/r/20230208063514.171485-1-hch@lst.de Signed-off-by: Jens Axboe --- block/blk-throttle.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'block/blk-throttle.c') diff --git a/block/blk-throttle.c b/block/blk-throttle.c index 902203bdddb4..e7bd7050d684 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -2411,7 +2411,8 @@ void blk_throtl_exit(struct gendisk *disk) { struct request_queue *q = disk->queue; - BUG_ON(!q->td); + if (!q->td) + return; del_timer_sync(&q->td->service_queue.pending_timer); throtl_shutdown_wq(q); blkcg_deactivate_policy(disk, &blkcg_policy_throtl); -- cgit v1.2.3