Re: [PATCH 4/7] writeback: use RCU to protect bdi_list

From: Minchan Kim <minchan.kim@gmail.com>
To: Jens Axboe <jens.axboe@oracle.com>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	chris.mason@oracle.com, hch@infradead.org, tytso@mit.edu,
	akpm@linux-foundation.org, jack@suse.cz,
	trond.myklebust@fys.uio.no
Subject: Re: [PATCH 4/7] writeback: use RCU to protect bdi_list
Date: Mon, 14 Sep 2009 20:10:02 +0900	[thread overview]
Message-ID: <20090914201002.0ca94166.minchan.kim@barrios-desktop> (raw)
In-Reply-To: <1252920994-11141-5-git-send-email-jens.axboe@oracle.com>

On Mon, 14 Sep 2009 11:36:31 +0200
Jens Axboe <jens.axboe@oracle.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@oracle.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