Hi Boris,
Boris Brezillon boris.brezillon@bootlin.com wrote on Mon, 10 Sep 2018 14:53:12 +0200:
Hi Miquel,
On Fri, 7 Sep 2018 16:38:24 +0200 Miquel Raynal miquel.raynal@bootlin.com wrote:
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.
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.
I think there is a misunderstanding here: mtd_get_of_node() is not retaining a reference, and I do not think it should! It is by design a helper to shortcut from the MTD device to the related FW node. Maybe calling it differently than "get" would be definitely less prone to errors. Maybe mtd_to_of_node() would be better?
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>)).
I don't get your point. Are you saying other places in the code are doing the wrong thing? Should we fix them too?
No, other places are doing the right thing. I think if the helper was named "mtd_to_of_node()" that would be much clearer for everyone and of_node_get(mtd_to_of_node(mtd)) would be the way to retain a reference on the OF node.
I don't think creating a helper for that would be better because I really prefer seeing the of_node_get() in the code, meaning an of_node_put() will be needed at some point.
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
You can drop the above line since this patch is fixing a bug introduced in 4.19-rc1.
Right!
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)
The patch itself looks correct, but I'd like some clarification about the commit message before applying it.
Thanks,
Boris
Thanks, Miquèl