Greetings, LTP's isofs testcase began failing this cycle, and bisected as below, which a revert then confirmed. Full testcase output attached. 322c4293ecc58110227b49d7e47ae37b9b03566f is the first bad commit commit 322c4293ecc58110227b49d7e47ae37b9b03566f Author: Tetsuo Handa Date: Mon Dec 13 21:55:27 2021 +0900 loop: make autoclear operation asynchronous syzbot is reporting circular locking problem at __loop_clr_fd() [1], for commit 87579e9b7d8dc36e ("loop: use worker per cgroup instead of kworker") is calling destroy_workqueue() with disk->open_mutex held. This circular dependency cannot be broken unless we call __loop_clr_fd() without holding disk->open_mutex. Therefore, defer __loop_clr_fd() from lo_release() to a WQ context. Link: https://syzkaller.appspot.com/bug?extid=643e4ce4b6ad1347d372 [1] Reported-by: syzbot Suggested-by: Christoph Hellwig Cc: Jan Kara Tested-by: syzbot+643e4ce4b6ad1347d372@syzkaller.appspotmail.com Signed-off-by: Tetsuo Handa Reviewed-by: Christoph Hellwig Link: https://lore.kernel.org/r/1ed7df28-ebd6-71fb-70e5-1c2972e05ddb@i-love.sakura.ne.jp Signed-off-by: Jens Axboe drivers/block/loop.c | 65 +++++++++++++++++++++++++++++----------------------- drivers/block/loop.h | 1 + 2 files changed, 37 insertions(+), 29 deletions(-)