Commit c76f48eb5c ("block: take bd_mutex around delete_partitions in
del_gendisk") adds disk->part0->bd_mutex in del_gendisk(), this way
causes the following AB/BA deadlock between removing loop and opening
loop:
1) loop_control_ioctl(LOOP_CTL_REMOVE)
-> mutex_lock(&loop_ctl_mutex)
-> del_gendisk
-> mutex_lock(&disk->part0->bd_mutex)
2) blkdev_get_by_dev
-> mutex_lock(&disk->part0->bd_mutex)
-> lo_open
-> mutex_lock(&loop_ctl_mutex)
Add a new Lo_deleting state to remove the need for clearing
->private_data and thus holding loop_ctl_mutex in the ioctl
LOOP_CTL_REMOVE path.
Based on an analysis and earlier patch from
Ming Lei <ming.lei@redhat.com>.
Reported-by: Colin Ian King <colin.king@canonical.com>
Fixes: c76f48eb5c ("block: take bd_mutex around delete_partitions in del_gendisk")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20210605140950.5800-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
990e78116d