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

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Message-ID: <20090914111121.GC14984@kernel.dk>
Date:	Mon, 14 Sep 2009 13:11:21 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Minchan Kim <minchan.kim@...il.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, Sep 14 2009, Minchan Kim wrote:
> 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?

Indeed, pretty silly. Thanks!

-- 
Jens Axboe

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