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From:   Suren Baghdasaryan <surenb@google.com>
Date:   Wed, 15 Jul 2020 19:49:52 -0700
Message-ID: <CAJuCfpFFCtmbvjLWDLZ9_bpNq-iT2+1cfdkpEcGV5tFCnbd+5g@mail.gmail.com>
Subject: Re: possible deadlock in shmem_fallocate (4)
To:     Michal Hocko <mhocko@kernel.org>
Cc:     Todd Kjos <tkjos@google.com>, Hridya Valsaraju <hridya@google.com>,
        Hillf Danton <hdanton@sina.com>,
        Eric Biggers <ebiggers@kernel.org>,
        syzbot <syzbot+7a0d9d0b26efefe61780@syzkaller.appspotmail.com>,
        Andrew Morton <akpm@linux-foundation.org>,
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        Christian Brauner <christian@brauner.io>,
        "open list:ANDROID DRIVERS" <devel@driverdev.osuosl.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Hugh Dickins <hughd@google.com>,
        "Joel Fernandes (Google)" <joel@joelfernandes.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux-MM <linux-mm@kvack.org>, Martijn Coenen <maco@android.com>,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        Todd Kjos <tkjos@android.com>,
        Markus Elfring <Markus.Elfring@web.de>
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On Tue, Jul 14, 2020 at 11:36 PM Michal Hocko <mhocko@kernel.org> wrote:
>
> On Tue 14-07-20 10:32:20, Suren Baghdasaryan wrote:
> [...]
> > I'm not sure how we can annotate the fact that the inode_lock in
> > generic_file_write_iter and in shmem_fallocate always operate on
> > different inodes. Ideas?
>
> I believe that the standard way is to use lockdep_set_class on your
> backing inode. But asking lockdep experts would be better than relying
> on my vague recollection

Thanks Michal! I think https://lkml.org/lkml/2020/7/15/1390 should fix
it, however I was unable to reproduce the lockdep warning to confirm
that this warning gets fixed by the patch.

>
> --
> Michal Hocko
> SUSE Labs