Re: [PATCH] loop: drop loop_ctl_mutex around del_gendisk() in loop_remove()

[Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>]

Found that commit 990e78116d38059c ("block: loop: fix deadlock between open and remove") went to 5.13-rc6.

#syz fix: block: loop: fix deadlock between open and remove

Now syzbot is reporting

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(nbd_index_mutex);
                               lock(&bdev->bd_mutex);
                               lock(nbd_index_mutex);
  lock(&bdev->bd_mutex);

at https://syzkaller.appspot.com/text?tag=CrashReport&x=11b8a5bbd00000 .