linux-kernel - Re: [PATCH] bcache: prevent crash on changing writeback

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Message-ID: <CACHGV4J8pQM7pt+0NXJL60OJHxMUQu2S9U_DnKFh0BW0=1XpuA@mail.gmail.com>
Date:	Tue, 19 Aug 2014 11:03:11 -0700
From:	Slava Pestov <sp@...era.io>
To:	Stefan Bader <stefan.bader@...onical.com>
Cc:	linux-kernel@...r.kernel.org, linux-bcache@...r.kernel.org,
	Kent Overstreet <kmo@...erainc.com>
Subject: Re: [PATCH] bcache: prevent crash on changing writeback_running

Thanks, this is now in our development branch.

On Tue, Aug 19, 2014 at 6:01 AM, Stefan Bader
<stefan.bader@...onical.com> wrote:
> commit a664d0f05a2ec02c8f042db536d84d15d6e19e81
>     bcache: fix crash on shutdown in passthrough mode
>
> added a safeguard in the shutdown case. At least while not being
> attached it is also possible to trigger a kernel bug by writing into
> writeback_running. This change  adds the same check before trying to
> wake up the thread for that case.
>
> Signed-off-by: Stefan Bader <stefan.bader@...onical.com>
> ---
>  drivers/md/bcache/writeback.h | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/md/bcache/writeback.h b/drivers/md/bcache/writeback.h
> index 0a9dab1..073a042 100644
> --- a/drivers/md/bcache/writeback.h
> +++ b/drivers/md/bcache/writeback.h
> @@ -63,7 +63,8 @@ static inline bool should_writeback(struct cached_dev *dc, struct bio *bio,
>
>  static inline void bch_writeback_queue(struct cached_dev *dc)
>  {
> -       wake_up_process(dc->writeback_thread);
> +       if (!IS_ERR_OR_NULL(dc->writeback_thread))
> +               wake_up_process(dc->writeback_thread);
>  }
>
>  static inline void bch_writeback_add(struct cached_dev *dc)
> --
> 1.9.1
>
> --
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