From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from lamorak.hansenpartnership.com (lamorak.hansenpartnership.com [198.37.111.173]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 00EF62FBE17 for ; Tue, 18 Nov 2025 20:21:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.37.111.173 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763497274; cv=none; b=o+z0jM8e1o6uZUvQdewlP8H6PrgJ0haDTB+JNCxFmM7oJNmFLe1/9y/ZcZA4SzfseP+CoNmS4nig9aTxEI4CeDCt431GAEhz2eRh03DI2jhzBBlJ6dn3TfEu3OPuoFHIn9fJzb4eLoFBevWt9UWspJJjhesxGgSTxul0Y8Kq2VM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763497274; c=relaxed/simple; bh=22Lgc338WllBx937LED3MLuw/SMV+4EM81Gcyxrv534=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; 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<20251118141720.11c8d4d6@gandalf.local.home> References: <58fd478f408a34b578ee8d949c5c4b4da4d4f41d.camel@HansenPartnership.com> <20251118141720.11c8d4d6@gandalf.local.home> Autocrypt: addr=James.Bottomley@HansenPartnership.com; prefer-encrypt=mutual; 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 8mT2Eh9SkH+YVOmaKsajgZgrBxA7fWmGoxXswEVxJIFj3vW7yNc0C5HaUdYa5iGOMs4kg2ht4s7yy7NRQuh7BifWjo6BQ6k4S1H+6axZucxhSV1L6zN9d+lr3Xo/vy1unzA== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.3 Precedence: bulk X-Mailing-List: ksummit@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Tue, 2025-11-18 at 14:17 -0500, Steven Rostedt wrote: > On Tue, 18 Nov 2025 10:38:20 -0800 > Linus Torvalds wrote: >=20 > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 struct x509_parse_context *c= tx __free(kfree) =3D NULL; > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 ... other code ... > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 ctx =3D kzalloc(sizeof(struc= t x509_parse_context), > > GFP_KERNEL); > >=20 > > where you have now split up the whole "this is allocated by > > kmalloc, and free'd by kfree" into two different sections that are > > not next to each other. Yes, I get that; effectively you're declaring an unindented variable scope. However, there will be cases where you want an explicit free (so not a __free variable) and under the rule you propose that should be allowable as tastefully done. I've also got to say that the NULL initialization above should be unnecessary given we can compile time detect if there's potential exit uninitialized, but I can see that simply declaring where allocated would avoid having to move the allocation if you did want to introduce an exit above it in new code. > I've been doing the above, and was even going to recommend it to > James. But if it is preferred to declare the __free() variables where > they are allocated, I'd be much happier. >=20 > I think the code could also be better optimized? I haven't run an > objcopy to confirm but now early exits do not require calling the > __free() function on NULL pointers. Yes, I can confirm that (at least from reading the docs not actually from disassembling the code). >=20 > Most of my code allocates near the top where I don't find this a > problem, but I do have a few places of: >=20 > struct foo *var __free(kfree) =3D NULL; >=20 > if (ret < 0) > return -ERROR; >=20 > [ several more error exits ] >=20 > var =3D kmalloc(..); Agree: moving the declaration avoids the unnecessary check on exit (although I'd also presume a good compiler can optimize this away). There is one last case that hasn't been discussed, which is where you deliberately introduce an extra scope block for the free and allocation, so in your example above it would look like if (ret < ) return -ERROR [ several more error exits ] { struct foo *var __free(kfree) =3D kmalloc(...) [...] } I think adding an explicit scope block with no other purpose than to define the use range of a variable can be beneficial ... with the obvious caveat that doing it too often causes too much indentation. It can also help with the entangled lock and free described in the cleanup.h documentation if the block is paired with a scoped guard. Regards, James