linux-kernel - Re: [PATCH 4/7] writeback: use RCU to protect bdi

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Message-Id: <20090914201002.0ca94166.minchan.kim@barrios-desktop>
Date:	Mon, 14 Sep 2009 20:10:02 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Jens Axboe <jens.axboe@...cle.com>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	chris.mason@...cle.com, hch@...radead.org, tytso@....edu,
	akpm@...ux-foundation.org, jack@...e.cz, trond.myklebust@....uio.no
Subject: Re: [PATCH 4/7] writeback: use RCU to protect bdi_list

On Mon, 14 Sep 2009 11:36:31 +0200
Jens Axboe <jens.axboe@...cle.com> wrote:

> Now that bdi_writeback_all() no longer handles integrity writeback,
> it doesn't have to block anymore. This means that we can switch
> bdi_list reader side protection to RCU.
> 
> Signed-off-by: Jens Axboe <jens.axboe@...cle.com>
> ---
>  fs/fs-writeback.c           |    4 +-
>  include/linux/backing-dev.h |    1 +
>  mm/backing-dev.c            |   76 +++++++++++++++++++++++++++++++------------
>  mm/page-writeback.c         |    8 ++--
>  4 files changed, 62 insertions(+), 27 deletions(-)
> 
> diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> index 5d4bd1c..d7592c7 100644
> --- a/fs/fs-writeback.c
> +++ b/fs/fs-writeback.c
> @@ -849,7 +849,7 @@ static void bdi_writeback_all(struct writeback_control *wbc)
>  
>  	WARN_ON(wbc->sync_mode == WB_SYNC_ALL);
>  
> -	spin_lock(&bdi_lock);
> +	rcu_read_lock();
>  
>  	list_for_each_entry(bdi, &bdi_list, bdi_list) {

list_for_each_entry_rcu?

-- 
Kind regards,
Minchan Kim
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