linux-kernel - Re: [PATCH v2 2/5] iommu/mediatek: Add error path for loop of mm_dts

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Message-ID: <a53c4a4d9922c9a3fc774976494dea6da1bd8daa.camel@mediatek.com>
Date:   Thu, 23 Jun 2022 09:54:44 +0800
From:   Yong Wu <yong.wu@...iatek.com>
To:     Robin Murphy <robin.murphy@....com>
CC:     Joerg Roedel <joro@...tes.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Will Deacon <will@...nel.org>,
        <iommu@...ts.linux-foundation.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        <mingyuan.ma@...iatek.com>, <yf.wang@...iatek.com>,
        <libo.kang@...iatek.com>, <chengci.xu@...iatek.com>,
        <youlin.pei@...iatek.com>, <anan.sun@...iatek.com>,
        <xueqi.zhang@...iatek.com>, Guenter Roeck <groeck@...omium.org>,
        "Dan Carpenter" <dan.carpenter@...cle.com>
Subject: Re: [PATCH v2 2/5] iommu/mediatek: Add error path for loop of
 mm_dts_parse

On Thu, 2022-06-16 at 11:31 +0100, Robin Murphy wrote:
> On 2022-06-16 11:08, Yong Wu wrote:
> > On Thu, 2022-06-16 at 09:59 +0100, Robin Murphy wrote:
> > > On 2022-06-16 06:42, Yong Wu wrote:
> > > > The mtk_iommu_mm_dts_parse will parse the smi larbs nodes. if
> > > > the
> > > > i+1
> > > > larb is parsed fail(return -EINVAL), we should of_node_put for
> > > > the
> > > > 0..i
> > > > larbs. In the fail path, one of_node_put matches with
> > > > of_parse_phandle in
> > > > it.
> > > > 
> > > > Fixes: d2e9a1102cfc ("iommu/mediatek: Contain MM IOMMU flow
> > > > with
> > > > the MM TYPE")
> > > > Signed-off-by: Yong Wu <yong.wu@...iatek.com>
> > > > ---
> > > >    drivers/iommu/mtk_iommu.c | 21 ++++++++++++++++-----
> > > >    1 file changed, 16 insertions(+), 5 deletions(-)

[snip..]

> > > > +err_larbnode_put:
> > > > +	while (i--) {
> > > > +		larbnode = of_parse_phandle(dev->of_node,
> > > > "mediatek,larbs", i);
> > > > +		if (larbnode &&
> > > > of_device_is_available(larbnode)) {
> > > > +			of_node_put(larbnode);
> > > > +			of_node_put(larbnode);
> > > > +		}
> > > 
> > > This looks a bit awkward - could we not just iterate through
> > > data->larb_imu and put dev->of_node for each valid dev?
> > 
> > It should work. Thanks very much.
> > 
> > > 
> > > Also, of_find_device_by_node() takes a reference on the struct
> > > device
> > > itself, so strictly we should be doing put_device() on those as
> > > well
> > > if we're bailing out.
> > 
> > Thanks for this hint. A new reference for me. I will add it.
> 
> In fact, thinking about it some more we may as well do the
> of_node_put() 
> unconditionally immediately after the of_find_device_by_node() call, 

of_node_put is called in component_release_of in the normal case, thus
we shouldn't call of_node_put unconditionally. Right?

(Sorry for reply late)

> so 
> then it's *only* the device references we'd need to worry about
> cleaning 
> up in the failure path.
> 
> Robin.