linux-kernel - Re: [PATCH 3/3] f2fs: prevent waiter encountering incorrect discard states

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Date:   Mon, 27 Mar 2017 16:56:08 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <yuchao0@...wei.com>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, chao@...nel.org
Subject: Re: [PATCH 3/3] f2fs: prevent waiter encountering incorrect discard
 states

On 03/27, Chao Yu wrote:
> In f2fs_submit_discard_endio, we will wake up waiter before setting
> discard command states, so waiter may use incorrect states. Change
> the order between complete() and states setting to fix this issue.
> 
> Signed-off-by: Chao Yu <yuchao0@...wei.com>
> ---
>  fs/f2fs/segment.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 57a81f9c8c14..9f9542c9fe47 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -717,9 +717,9 @@ static void f2fs_submit_discard_endio(struct bio *bio)
>  {
>  	struct discard_cmd *dc = (struct discard_cmd *)bio->bi_private;
>  
> -	complete(&dc->wait);
>  	dc->error = bio->bi_error;
>  	dc->state = D_DONE;
> +	complete(&dc->wait);

If we set D_DONE first, the object can be released by __remove_discard_cmd()?

Thanks,

>  	bio_put(bio);
>  }
>  
> -- 
> 2.8.2.295.g3f1c1d0