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Message-ID: <20231005100349.113f3bf1@kmaincent-XPS-13-7390> Date: Thu, 5 Oct 2023 10:03:49 +0200 From: Köry Maincent <kory.maincent@...tlin.com> To: Simon Horman <horms@...nel.org> Cc: Michal Kubecek <mkubecek@...e.cz>, "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, Maxime Chevallier <maxime.chevallier@...tlin.com>, stable@...r.kernel.org, thomas.petazzoni@...tlin.com, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com> Subject: Re: [PATCH net 1/1] ethtool: Fix mod state of verbose no_mask bitset Hello Simon, Thank for your review. On Wed, 4 Oct 2023 13:07:14 +0200 Simon Horman <horms@...nel.org> wrote: > On Tue, Oct 03, 2023 at 10:56:52AM +0200, Köry Maincent wrote: > > From: Kory Maincent <kory.maincent@...tlin.com> > > > @@ -448,8 +450,11 @@ ethnl_update_bitset32_verbose(u32 *bitmap, unsigned > > int nbits, } > > > > no_mask = tb[ETHTOOL_A_BITSET_NOMASK]; > > - if (no_mask) > > - ethnl_bitmap32_clear(bitmap, 0, nbits, mod); > > + if (no_mask) { > > + tmp = kcalloc(nbits, sizeof(u32), GFP_KERNEL); > > + memcpy(tmp, bitmap, nbits); > > Hi Köry, > > I'm no expert on etnhl bitmaps. But the above doesn't seem correct to me. > Given that sizeof(u32) == 4: > > * 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. > > 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]; u32 *bitmap32 = small_bitmap32; if (nbits > ETHNL_SMALL_BITMAP_BITS) { unsigned int dst_words = DIV_ROUND_UP(nbits, 32); bitmap32 = kmalloc_array(dst_words, sizeof(u32), GFP_KERNEL); if (!bitmap32) return -ENOMEM; } 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 does not do it. Regards,
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