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Christoph Hellwig authored
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:
Ming Lei <ming.lei@redhat.com> Signed-off-by:
Christoph Hellwig <hch@lst.de> Reviewed-by:
Ming Lei <ming.lei@redhat.com> Link: https://lore.kernel.org/r/20230208063514.171485-1-hch@lst.deSigned-off-by:
Jens Axboe <axboe@kernel.dk>
c43332fe