linux-kernel - Re: [PATCH 1/2] [PATCH] bcache: cached_dev

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Message-ID: <20191206092713.GB7650@infradead.org>
Date:   Fri, 6 Dec 2019 01:27:13 -0800
From:   Christoph Hellwig <hch@...radead.org>
To:     Liang Chen <liangchen.linux@...il.com>
Cc:     colyli@...e.de, kent.overstreet@...il.com,
        linux-kernel@...r.kernel.org, linux-bcache@...r.kernel.org
Subject: Re: [PATCH 1/2] [PATCH] bcache: cached_dev_free needs to put the sb
 page

On Fri, Dec 06, 2019 at 04:55:42PM +0800, Liang Chen wrote:
> Same as cache device, the buffer page needs to be put while
> freeing cached_dev.  Otherwise a page would be leaked every
> time a cached_dev is stopped.
> 
> Signed-off-by: Liang Chen <liangchen.linux@...il.com>
> ---
>  drivers/md/bcache/super.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
> index 77e9869345e7..a573ce1d85aa 100644
> --- a/drivers/md/bcache/super.c
> +++ b/drivers/md/bcache/super.c
> @@ -1275,6 +1275,9 @@ static void cached_dev_free(struct closure *cl)
>  
>  	mutex_unlock(&bch_register_lock);
>  
> +	if (dc->sb_bio.bi_inline_vecs[0].bv_page)
> +		put_page(bio_first_page_all(&dc->sb_bio));

Using bio_first_page_all in the put_page call, but open coding it
for the check looks rather strange.

The cleanest thing here would be to just add a page pointer to the
cached device structure and use that instead of all the indirections.