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Date: Fri, 7 Sep 2018 16:38:24 +0200
From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Boris Brezillon <boris.brezillon@bootlin.com>,
        Richard Weinberger <richard@nod.at>,
        David Woodhouse <dwmw2@infradead.org>,
        Brian Norris <computersforpeace@gmail.com>,
        Marek Vasut <marek.vasut@gmail.com>
Cc: linux-mtd@lists.infradead.org, stable@vger.kernel.org,
        =?UTF-8?B?UmFm?= =?UTF-8?B?YcWCIE1pxYJlY2tp?= <zajec5@gmail.com>
Subject: Re: [PATCH] mtd: partitions: fix of_node_get/put balance in parser
Message-ID: <20180907163824.6cec1a43@xps13>
In-Reply-To: <20180907143554.13496-1-miquel.raynal@bootlin.com>
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Hello,

I forgot to add Rafal which I know worked a lot on the parsers.

Miquel Raynal <miquel.raynal@bootlin.com> wrote on Fri,  7 Sep 2018
16:35:54 +0200:

> While at first mtd_part_of_parse() would just call
> of_get_chil_by_name(), it has been edited to first try to get the OF
> node thanks to mtd_get_of_node() and fallback on
> of_get_child_by_name().
> 
> A of_node_put() was a bit below in the code, to balance the
> of_get_child_by_name(). However, despite its name, mtd_get_of_node()
> does not take a reference on the OF node. It is a simple helper hiding
> some pointer logic to retrieve the OF node related to an MTD
> device. People often used it this way:
> 
>     of_node_put(mtd_get_of_node(<mtd>)).
> 
> The direct effect of such unbalanced reference counting is visible by
> rmmod'ing any module that would have added MTD partitions:
> 
>     OF: ERROR: Bad of_node_put() on <of_path_to_partition>
> 
> As it seems normal to get a reference on the OF node during the
> of_property_for_each_string() that follows, add a call to
> of_node_get() when relevant.
> 
> Fixes: 76a832254ab0 ("mtd: partitions: use DT info for parsing partitions with "compatible" prop")
> Cc: stable@vger.kernel.org
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> ---
>  drivers/mtd/mtdpart.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
> index 52e2cb35fc79..99c460facd5e 100644
> --- a/drivers/mtd/mtdpart.c
> +++ b/drivers/mtd/mtdpart.c
> @@ -873,8 +873,11 @@ static int mtd_part_of_parse(struct mtd_info *master,
>  	int ret, err = 0;
>  
>  	np = mtd_get_of_node(master);
> -	if (!mtd_is_partition(master))
> +	if (mtd_is_partition(master))
> +		of_node_get(np);
> +	else
>  		np = of_get_child_by_name(np, "partitions");
> +
>  	of_property_for_each_string(np, "compatible", prop, compat) {
>  		parser = mtd_part_get_compatible_parser(compat);
>  		if (!parser)