linux-kernel - regression: LTP isofs testcase failure - bisection fingers "loop: make autoclear operation asynchronous"

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Date:   Mon, 17 Jan 2022 16:34:02 +0100
From:   Mike Galbraith <efault@....de>
To:     lkml <linux-kernel@...r.kernel.org>
Cc:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Subject: regression: LTP isofs testcase failure  - bisection fingers "loop:
 make autoclear operation asynchronous"

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 <penguin-kernel@...ove.sakura.ne.jp>
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 <syzbot+643e4ce4b6ad1347d372@...kaller.appspotmail.com>
    Suggested-by: Christoph Hellwig <hch@...radead.org>
    Cc: Jan Kara <jack@...e.cz>
    Tested-by: syzbot+643e4ce4b6ad1347d372@...kaller.appspotmail.com
    Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
    Reviewed-by: Christoph Hellwig <hch@....de>
    Link: https://lore.kernel.org/r/1ed7df28-ebd6-71fb-70e5-1c2972e05ddb@i-love.sakura.ne.jp
    Signed-off-by: Jens Axboe <axboe@...nel.dk>

 drivers/block/loop.c | 65 +++++++++++++++++++++++++++++-----------------------
 drivers/block/loop.h |  1 +
 2 files changed, 37 insertions(+), 29 deletions(-)


View attachment "isofs.txt" of type "text/plain" (41639 bytes)