From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.bootlin.com ([62.4.15.54]:38561 "EHLO mail.bootlin.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727799AbeIJRrM (ORCPT ); Mon, 10 Sep 2018 13:47:12 -0400 Date: Mon, 10 Sep 2018 14:53:12 +0200 From: Boris Brezillon To: Miquel Raynal , Brian Norris Cc: Richard Weinberger , David Woodhouse , Marek Vasut , =?UTF-8?B?UmFmYcWCIE1pxYJlY2tp?= , linux-mtd@lists.infradead.org, stable@vger.kernel.org Subject: Re: [PATCH] mtd: partitions: fix of_node_get/put balance in parser Message-ID: <20180910145312.3b9ae4ad@bbrezillon> In-Reply-To: <20180907163824.6cec1a43@xps13> References: <20180907143554.13496-1-miquel.raynal@bootlin.com> <20180907163824.6cec1a43@xps13> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: stable-owner@vger.kernel.org List-ID: Hi Miquel, On Fri, 7 Sep 2018 16:38:24 +0200 Miquel Raynal wrote: > Hello, > > I forgot to add Rafal which I know worked a lot on the parsers. > > Miquel Raynal 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. That's probably something we should patch at some point, but that implies patching all mtd_get_of_node() users at the same time, so let's keep that for later. BTW, if mtd_get_of_node() was actually retaining a reference, you would miss an of_node_put() in the !mtd_is_partition(master) case. > > 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()). I don't get your point. Are you saying other places in the code are doing the wrong thing? Should we fix them too? > > > > 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 > > > > 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 You can drop the above line since this patch is fixing a bug introduced in 4.19-rc1. > > Signed-off-by: Miquel Raynal > > --- > > 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) The patch itself looks correct, but I'd like some clarification about the commit message before applying it. Thanks, Boris -- Boris Brezillon, Bootlin Embedded Linux and Kernel engineering https://bootlin.com