From: Christoph Hellwig <hch@infradead.org>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: syzbot <syzbot+4f1a237abaf14719db49@syzkaller.appspotmail.com>,
axboe@kernel.dk, linux-block@vger.kernel.org,
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
Jan Kara <jack@suse.cz>
Subject: Re: [syzbot] INFO: task can't die in blkdev_common_ioctl
Date: Sun, 3 Apr 2022 21:58:06 -0700 [thread overview]
Message-ID: <Ykp63pk7aSj/bNRT@infradead.org> (raw)
In-Reply-To: <d3213c1a-f82a-02f6-b5b2-0d3242e0242a@I-love.SAKURA.ne.jp>
On Sat, Apr 02, 2022 at 08:26:23PM +0900, Tetsuo Handa wrote:
> > git tree: linux-next
> > console output: https://syzkaller.appspot.com/x/log.txt?x=168d578db00000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=be9183de0824e4d7
> > dashboard link: https://syzkaller.appspot.com/bug?extid=4f1a237abaf14719db49
> > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> >
> > Unfortunately, I don't have any reproducer for this issue yet.
>
> This is a known problem, and Christoph does not like a mitigation patch.
> https://lkml.kernel.org/r/YgoQBTzb3b0l1SzP@infradead.org
And this report shows why: your patch makes the lock acquisition in
blkdev_fallocate killable. Which would not help with this problem at
all, as it does not come through blkdev_fallocate. The problem is that
the loop writing actual zeroes to the disk can take forever, and we
hold the invalidate_lock over that.
next prev parent reply other threads:[~2022-04-04 4:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-02 7:20 [syzbot] INFO: task can't die in blkdev_common_ioctl syzbot
2022-04-02 11:26 ` Tetsuo Handa
2022-04-04 4:58 ` Christoph Hellwig [this message]
2022-04-04 5:12 ` Tetsuo Handa
2022-04-05 6:44 ` Christoph Hellwig
2022-04-05 13:15 ` Tetsuo Handa
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