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Date:   Thu, 5 Oct 2023 10:03:49 +0200
From:   =?UTF-8?B?S8O2cnk=?= Maincent <kory.maincent@bootlin.com>
To:     Simon Horman <horms@kernel.org>
Cc:     Michal Kubecek <mkubecek@suse.cz>,
        "David S. Miller" <davem@davemloft.net>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Maxime Chevallier <maxime.chevallier@bootlin.com>,
        stable@vger.kernel.org, thomas.petazzoni@bootlin.com,
        Eric Dumazet <edumazet@google.com>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>
Subject: Re: [PATCH net 1/1] ethtool: Fix mod state of verbose no_mask
 bitset
Message-ID: <20231005100349.113f3bf1@kmaincent-XPS-13-7390>
In-Reply-To: <ZR1HYg2ElUjy2aud@kernel.org>
References: <20231003085653.3104411-1-kory.maincent@bootlin.com>
        <ZR1HYg2ElUjy2aud@kernel.org>
Organization: bootlin
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Hello Simon,

Thank for your review.

On Wed, 4 Oct 2023 13:07:14 +0200
Simon Horman <horms@kernel.org> wrote:

> On Tue, Oct 03, 2023 at 10:56:52AM +0200, K=C3=B6ry Maincent wrote:
> > From: Kory Maincent <kory.maincent@bootlin.com>
>
> > @@ -448,8 +450,11 @@ ethnl_update_bitset32_verbose(u32 *bitmap, unsigned
> > int nbits, }
> > =20
> >  	no_mask =3D tb[ETHTOOL_A_BITSET_NOMASK];
> > -	if (no_mask)
> > -		ethnl_bitmap32_clear(bitmap, 0, nbits, mod);
> > +	if (no_mask) {
> > +		tmp =3D kcalloc(nbits, sizeof(u32), GFP_KERNEL);
> > +		memcpy(tmp, bitmap, nbits); =20
>=20
> Hi K=C3=B6ry,
>=20
> I'm no expert on etnhl bitmaps. But the above doesn't seem correct to me.
> Given that sizeof(u32) =3D=3D 4:
>=20
> * The allocation is for nbits * 4 bytes
> * The copy is for its for nbits bytes
> * I believe that bitmap contains space for the value followed by a mask.
>   So it seems to me the size of bitmap, in words, is
>   DIV_ROUND_UP(nbits, 32) * 2
>   And in bytes: DIV_ROUND_UP(nbits, 32) * 16
>   But perhaps only half is needed if only the value part of tmp is used.
>=20
> If I'm on the right track here I'd suggest helpers might be in order.

You are right I should use the same alloc as ethnl_update_bitset with tmp
instead of bitmap32:

        u32 small_bitmap32[ETHNL_SMALL_BITMAP_WORDS];                     =
=20
        u32 *bitmap32 =3D small_bitmap32;=20
        if (nbits > ETHNL_SMALL_BITMAP_BITS) {                            =
=20
                unsigned int dst_words =3D DIV_ROUND_UP(nbits, 32);        =
 =20
                                                                          =
=20
                bitmap32 =3D kmalloc_array(dst_words, sizeof(u32), GFP_KERN=
EL);
                if (!bitmap32)                                            =
=20
                        return -ENOMEM;                                   =
=20
        }  =20

But I am still wondering if it needs to be double as you said for the size =
of
the value followed by the mask. Not sure about it, as ethnl_update_bitset d=
oes
not do it.=20

Regards,