From: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
To: Jan Kara <jack@suse.cz>, Tejun Heo <tj@kernel.org>
Cc: Dmitry Vyukov <dvyukov@google.com>, Jens Axboe <axboe@kernel.dk>,
syzbot <syzbot+4a7438e774b21ddd8eca@syzkaller.appspotmail.com>,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Dave Chinner <david@fromorbit.com>,
linux-block@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [PATCH] bdi: Fix another oops in wb_workfn()
Date: Wed, 13 Jun 2018 20:51:13 +0900 [thread overview]
Message-ID: <6d3dc916-94fd-3684-7861-6b120e5616ee@i-love.sakura.ne.jp> (raw)
In-Reply-To: <b210e55c-b06a-41ff-8592-0dbe21875779@i-love.sakura.ne.jp>
Tetsuo Handa wrote:
> Or, toggling a dedicated flag using test_and_change_bit():
>
>
> include/linux/backing-dev-defs.h | 1 +
> mm/backing-dev.c | 8 +++++++-
> 2 files changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/include/linux/backing-dev-defs.h b/include/linux/backing-dev-defs.h
> index 0bd432a..93ff83c 100644
> --- a/include/linux/backing-dev-defs.h
> +++ b/include/linux/backing-dev-defs.h
> @@ -26,6 +26,7 @@ enum wb_state {
> WB_writeback_running, /* Writeback is in progress */
> WB_has_dirty_io, /* Dirty inodes on ->b_{dirty|io|more_io} */
> WB_start_all, /* nr_pages == 0 (all) work pending */
> + WB_postpone_kfree, /* cgwb_bdi_unregister() will access later */
> };
>
> enum wb_congested_state {
> diff --git a/mm/backing-dev.c b/mm/backing-dev.c
> index 347cc83..422d7a7 100644
> --- a/mm/backing-dev.c
> +++ b/mm/backing-dev.c
> @@ -516,7 +516,10 @@ static void cgwb_release_workfn(struct work_struct *work)
> fprop_local_destroy_percpu(&wb->memcg_completions);
> percpu_ref_exit(&wb->refcnt);
> wb_exit(wb);
> - kfree_rcu(wb, rcu);
> + spin_lock_irq(&cgwb_lock);
> + if (!test_and_change_bit(WB_postpone_kfree, &wb->state))
> + kfree_rcu(wb, rcu);
> + spin_unlock_irq(&cgwb_lock);
> }
>
> static void cgwb_release(struct percpu_ref *refcnt)
> @@ -721,9 +724,12 @@ static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
> while (!list_empty(&bdi->wb_list)) {
> wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
> bdi_node);
> + set_bit(WB_postpone_kfree, &wb->state);
> spin_unlock_irq(&cgwb_lock);
> wb_shutdown(wb);
> spin_lock_irq(&cgwb_lock);
> + if (!test_and_change_bit(WB_postpone_kfree, &wb->state))
> + kfree_rcu(wb, rcu);
> }
> spin_unlock_irq(&cgwb_lock);
> }
Forgot to include below change, but isn't this approach the simplest?
@@ -370,7 +370,6 @@ static void wb_shutdown(struct bdi_writeback *wb)
set_bit(WB_shutting_down, &wb->state);
spin_unlock_bh(&wb->work_lock);
- cgwb_remove_from_bdi_list(wb);
/*
* Drain work list and shutdown the delayed_work. !WB_registered
* tells wb_workfn() that @wb is dying and its work_list needs to
@@ -379,6 +378,7 @@ static void wb_shutdown(struct bdi_writeback *wb)
mod_delayed_work(bdi_wq, &wb->dwork, 0);
flush_delayed_work(&wb->dwork);
WARN_ON(!list_empty(&wb->work_list));
+ cgwb_remove_from_bdi_list(wb);
/*
* Make sure bit gets cleared after shutdown is finished. Matches with
* the barrier provided by test_and_clear_bit() above.
--
next prev parent reply other threads:[~2018-06-13 11:51 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-26 9:15 general protection fault in wb_workfn (2) syzbot
2018-05-27 0:47 ` Tetsuo Handa
2018-05-27 2:21 ` [PATCH] bdi: Fix another oops in wb_workfn() Tetsuo Handa
2018-05-27 2:36 ` Tejun Heo
2018-05-28 13:35 ` general protection fault in wb_workfn (2) Jan Kara
2018-05-30 16:00 ` Tetsuo Handa
2018-05-31 11:42 ` Jan Kara
2018-05-31 13:19 ` Tetsuo Handa
2018-05-31 13:42 ` Jan Kara
2018-05-31 16:56 ` Jens Axboe
2018-06-05 13:45 ` Tetsuo Handa
2018-06-07 18:46 ` Dmitry Vyukov
2018-06-08 2:31 ` Tetsuo Handa
2018-06-08 14:45 ` Dmitry Vyukov
2018-06-08 15:16 ` Dmitry Vyukov
2018-06-08 16:53 ` Dmitry Vyukov
2018-06-08 17:14 ` Dmitry Vyukov
2018-06-09 5:30 ` Tetsuo Handa
2018-06-09 14:00 ` [PATCH] bdi: Fix another oops in wb_workfn() Tetsuo Handa
2018-06-11 9:12 ` Jan Kara
2018-06-11 16:01 ` Tejun Heo
2018-06-11 16:29 ` Jan Kara
2018-06-11 17:20 ` Tejun Heo
2018-06-12 15:57 ` Jan Kara
2018-06-13 10:43 ` Tetsuo Handa
2018-06-13 11:51 ` Tetsuo Handa [this message]
2018-06-13 14:06 ` Linus Torvalds
2018-06-13 14:46 ` Jan Kara
2018-06-13 14:55 ` Linus Torvalds
2018-06-13 16:20 ` Tetsuo Handa
2018-06-13 16:25 ` Linus Torvalds
2018-06-13 16:45 ` Jan Kara
2018-06-13 21:04 ` Tetsuo Handa
2018-06-14 10:11 ` Jan Kara
2018-06-13 14:33 ` Tejun Heo
2018-06-15 12:06 ` Jan Kara
2018-06-18 12:27 ` Jan Kara
2018-06-01 2:30 ` general protection fault in wb_workfn (2) Dave Chinner
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