linux-kernel - Re: [PATCH 7/7] writeback: splice dirty inode entries to default bdi on bdi

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Message-ID: <20090914105600.GB14984@kernel.dk>
Date:	Mon, 14 Sep 2009 12:56:00 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Cc:	chris.mason@...cle.com, hch@...radead.org, tytso@....edu,
	akpm@...ux-foundation.org, jack@...e.cz, trond.myklebust@....uio.no
Subject: Re: [PATCH 7/7] writeback: splice dirty inode entries to default
	bdi on bdi_destroy()

On Mon, Sep 14 2009, Jens Axboe wrote:
> We cannot safely ensure that the inodes are all gone at this point
> in time, and we must not destroy this bdi with inodes having off it.
> So just splice our entries to the default bdi since that one will
> always persist.
> 
> Signed-off-by: Jens Axboe <jens.axboe@...cle.com>
> ---
>  mm/backing-dev.c |   12 +++++++++++-
>  1 files changed, 11 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/backing-dev.c b/mm/backing-dev.c
> index fd93566..27f82dc 100644
> --- a/mm/backing-dev.c
> +++ b/mm/backing-dev.c
> @@ -668,7 +668,17 @@ void bdi_destroy(struct backing_dev_info *bdi)
>  {
>  	int i;
>  
> -	WARN_ON(bdi_has_dirty_io(bdi));
> +	/*
> +	 * Splice our entries to the default_backing_dev_info, if this
> +	 * bdi disappears
> +	 */
> +	if (bdi_has_dirty_io(bdi)) {
> +		struct bdi_writeback *dst = &default_backing_dev_info.wb;
> +
> +		list_splice(&bdi->wb.b_dirty, &dst->b_dirty);
> +		list_splice(&bdi->wb.b_io, &dst->b_io);
> +		list_splice(&bdi->wb.b_more_io, &dst->b_more_io);
> +	}

This needs locking, of course...

-- 
Jens Axboe

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