Commit c43332fe authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

blk-cgroup: delay calling blkcg_exit_disk until disk_release 



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 avaіlable 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: 178fa7d4 ("blk-cgroup: delay blk-cgroup initialization until add_disk")
Reported-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20230208063514.171485-1-hch@lst.de


Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent a872818f

block/blk-throttle.c

+2 −1
Original line number Diff line number Diff line
@@ -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);

block/genhd.c

+2 −2
Original line number Diff line number Diff line
@@ -668,8 +668,6 @@ void del_gendisk(struct gendisk *disk) 
	rq_qos_exit(q);

	blk_mq_unquiesce_queue(q);



	blkcg_exit_disk(disk);



	/*

	 * If the disk does not own the queue, allow using passthrough requests

	 * again.  Else leave the queue frozen to fail all I/O.
@@ -1166,6 +1164,8 @@ static void disk_release(struct device *dev) 
	might_sleep();

	WARN_ON_ONCE(disk_live(disk));



	blkcg_exit_disk(disk);



	/*

	 * To undo the all initialization from blk_mq_init_allocated_queue in

	 * case of a probe failure where add_disk is never called we have to