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Message-ID: <ZR674ase11YwjvsG@kernel.org> Date: Thu, 5 Oct 2023 15:36:33 +0200 From: Simon Horman <horms@...nel.org> To: Köry Maincent <kory.maincent@...tlin.com> 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 On Thu, Oct 05, 2023 at 10:03:49AM +0200, Köry Maincent wrote: > 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. If you only need the value, then I don' think you need to x2 the allocation. But I could be wrong.
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