linux-kernel - Re: Clarifying confusion of our variable placement rules caused by cleanup.h

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Message-ID: <20251118141720.11c8d4d6@gandalf.local.home>
Date: Tue, 18 Nov 2025 14:17:20 -0500
From: Steven Rostedt <rostedt@...dmis.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Bart Van Assche <bvanassche@....org>, James Bottomley
 <James.Bottomley@...senpartnership.com>, ksummit@...ts.linux.dev, Dan
 Williams <dan.j.williams@...el.com>, linux-kernel
 <linux-kernel@...r.kernel.org>, Dan Carpenter <dan.carpenter@...aro.org>
Subject: Re: Clarifying confusion of our variable placement rules caused by
 cleanup.h

On Tue, 18 Nov 2025 10:38:20 -0800
Linus Torvalds <torvalds@...ux-foundation.org> wrote:

>         struct x509_parse_context *ctx __free(kfree) = NULL;
>         ... other code ...
>         ctx = kzalloc(sizeof(struct x509_parse_context), GFP_KERNEL);
> 
> 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.

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.

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.

Most of my code allocates near the top where I don't find this a problem,
but I do have a few places of:

	struct foo *var __free(kfree) = NULL;

	if (ret < 0)
		return -ERROR;

	[ several more error exits ]

	var = kmalloc(..);

-- Steve