linux-kernel - Re: [RFC 1/2] lib/vsprintf: Add support for pte

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Message-ID: <aFQP8LzVMctf6XH5@casper.infradead.org>
Date: Thu, 19 Jun 2025 14:26:08 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Anshuman Khandual <anshuman.khandual@....com>
Cc: linux-mm@...ck.org, Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Sergey Senozhatsky <senozhatsky@...omium.org>,
	Petr Mladek <pmladek@...e.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Jonathan Corbet <corbet@....net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Hildenbrand <david@...hat.com>, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org
Subject: Re: [RFC 1/2] lib/vsprintf: Add support for pte_t

On Wed, Jun 18, 2025 at 09:42:34AM +0530, Anshuman Khandual wrote:
> +++ b/mm/memory.c
> @@ -522,9 +522,8 @@ static void print_bad_pte(struct vm_area_struct *vma, unsigned long addr,
>  	mapping = vma->vm_file ? vma->vm_file->f_mapping : NULL;
>  	index = linear_page_index(vma, addr);
>  
> -	pr_alert("BUG: Bad page map in process %s  pte:%08llx pmd:%08llx\n",
> -		 current->comm,
> -		 (long long)pte_val(pte), (long long)pmd_val(*pmd));
> +	pr_alert("BUG: Bad page map in process %s  pte:%ppte pmd:%ppte\n",
> +		 current->comm, &pte, pmd);

Unfortunately, the one example you've converted shows why this is a bad
idea.  You're passing a pmd_t pointer to a function which is assuming a
pte_t pointer.  And a pmd_t and a pte_t are sometimes different sizes!
(eg sometimes one is 64 bit and the other 32 bit).

So no, NACK.