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From: Miklos Szeredi <miklos@szeredi.hu>
To: Amir Goldstein <amir73il@gmail.com>
Cc: syzbot+3ef5c0d1a5cb0b21e6be@syzkaller.appspotmail.com,
	linux-kernel <linux-kernel@vger.kernel.org>,
	overlayfs <linux-unionfs@vger.kernel.org>,
	syzkaller-bugs@googlegroups.com
Subject: Re: possible deadlock in ovl_copy_up_start
Date: Thu, 18 Oct 2018 10:41:17 +0200	[thread overview]
Message-ID: <CAJfpegsDfJMsT8OJVYuUFpNz94ex0fm5Z-e2Gp=cUgXsb_L-Jg@mail.gmail.com> (raw)
In-Reply-To: <CAOQ4uxjY1LpVKv1id6W-1nHaKC=RbG8HUkTvgGTdGo8MKwzSTw@mail.gmail.com>

On Thu, Oct 18, 2018 at 8:26 AM, Amir Goldstein <amir73il@gmail.com> wrote:

> Can someone tell me what the expected behavior of a nested
> mutex_lock_interruptible(&lock); ?
>
> Why does the reproducer only warn and not really deadlock.
> It is because that is considered the lesser evil?
> and obviously, then inner unlock releases the outer lock?

No, it's not the same lock, just the same lock class (first one is
OVL_I(d_inode(old))->lock, the other is
OVL_I(d_inode(new->d_parent)))->lock).

So we could possibly get away with annotating with
mutex_lock_nested().  Is this the only place that ovl_i_lock is
nested?

Thanks,
Miklos

  reply	other threads:[~2018-10-18  8:41 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-18  4:47 possible deadlock in ovl_copy_up_start syzbot
2018-10-18  6:26 ` Amir Goldstein
2018-10-18  8:41   ` Miklos Szeredi [this message]
2018-10-18 10:40     ` Amir Goldstein

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