From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mta0.migadu.com (out-234.mta0.migadu.com [91.218.175.234])
	(using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits))
	(No client certificate requested)
	by smtp.subspace.kernel.org (Postfix) with ESMTPS id 82F052F746D
	for <linux-kernel@vger.kernel.org>; Sat, 15 Aug 2026 14:12:22 +0000 (UTC)
Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.234
ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116;
	t=1786803145; cv=none; b=LbDypkw1k5ZpozU55B6OuWoklNwVko2bj+g9AqerF+tK3xgLY3zfN3xQeIQ3wqit2z6JHtmvMhxJ9tg+NyjxAR4JeRykCKosfxDkMP968++KfLbzlMBGHf8Eay8trSPSwJQq2PiHee+3Xn3lqz5mB0y3FxMW0qiFvVsdk7kxoTk=
ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org;
	s=arc-20240116; t=1786803145; c=relaxed/simple;
	bh=2pSAzOc521eM8MMUWAwepyHjyA8he2kR0aSHgrLA2RE=;
	h=Mime-Version:Content-Type:Date:Message-Id:From:To:Cc:Subject:
	 References:In-Reply-To; b=byTJx6ZWZsLVp34bJLaytITY0WNLBYXTceT63Tzwk8zNdPR9JBptsZOox/2DjmSgI3AQL6gyA2/uQZjOztGXgb1lsFhJk8PuizFqxguvXoV3jnJBneKgvA20OL85H0NVcD+0LCONXN9jJIxljMWhEA6XwWejrG6f6Eu+PhSnVWg=
ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=oO35hbFo; arc=none smtp.client-ip=91.218.175.234
Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev
Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev
Authentication-Results: smtp.subspace.kernel.org;
	dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="oO35hbFo"
X-Envelope-To: linux-kernel@vger.kernel.org
DKIM-Signature: a=rsa-sha256; bh=2pSAzOc521eM8MMUWAwepyHjyA8he2kR0aSHgrLA2RE=;
 c=simple/simple; d=linux.dev;
 h=from:to:subject:date:message-id:mime-version:content-type; s=key1;
 t=1786803140; v=1; x=1787407940;
 b=oO35hbFo/ErXscONn67gzt+dz8S+Psv+RpqJZGNn252F6lCKhshBp1ye+FTKxUzgB/E0kwdd
 jkyAzjwEUHgv6IfnaYEWUChFVbSEEZv98n8Y65oGRaldyMH1nS7sxERdHJTsnucuxdL0QGYxuzM
 i+PBfzpHud/h24leU6Cm/lT0=
X-Envelope-To: linux-kernel@vger.kernel.org
Received: from localhost (77.97.51.77)
	by smtp.migadu.com with ESMTPS id 685b1f35c1f5c486;
	Sat, 15 Aug 2026 14:12:10 +0000
X-Migadu-Flow: FLOW_OUT
Precedence: bulk
X-Mailing-List: linux-kernel@vger.kernel.org
List-Id: <linux-kernel.vger.kernel.org>
List-Subscribe: <mailto:linux-kernel+subscribe@vger.kernel.org>
List-Unsubscribe: <mailto:linux-kernel+unsubscribe@vger.kernel.org>
Mime-Version: 1.0
Content-Transfer-Encoding: quoted-printable
Content-Type: text/plain; charset=UTF-8
Date: Sat, 15 Aug 2026 15:12:09 +0100
Message-Id: <DKPKUHN1WU1B.1C1L6KZF8NEDX@linux.dev>
From: "Brendan Jackman" <brendan.jackman@linux.dev>
To: "Vlastimil Babka (SUSE)" <vbabka@kernel.org>, "Borislav Petkov"
 <bp@alien8.de>, "Dave Hansen" <dave.hansen@linux.intel.com>, "Peter
 Zijlstra" <peterz@infradead.org>, "Andrew Morton"
 <akpm@linux-foundation.org>, "David Hildenbrand" <david@kernel.org>, "Mike
 Rapoport" <rppt@kernel.org>, "Wei Xu" <weixugc@google.com>, "Johannes
 Weiner" <hannes@cmpxchg.org>, "Zi Yan" <ziy@nvidia.com>, "Lorenzo Stoakes"
 <ljs@kernel.org>
Cc: <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>, <x86@kernel.org>,
 "Sumit Garg" <sumit.garg@oss.qualcomm.com>, "Will Deacon"
 <will@kernel.org>, <rientjes@google.com>, <patrick.roy@linux.dev>,
 "Itazuri, Takahiro" <itazur@amazon.co.uk>, "Andy Lutomirski"
 <luto@kernel.org>, "David Kaplan" <david.kaplan@amd.com>, "Thomas Gleixner"
 <tglx@kernel.org>, "Yosry Ahmed" <yosry@kernel.org>, "Patrick Bellasi"
 <derkling@google.com>, "Reiji Watanabe" <reijiw@google.com>, "Sean
 Christopherson" <seanjc@google.com>
Subject: Re: [PATCH v3 21/26] mm/page_alloc: implement FREETYPE_UNMAPPED
 allocations
X-Mailer: aerc 0.21.0
References: <20260726-page_alloc-unmapped-v3-0-6f5729aa9832@google.com>
 <20260726-page_alloc-unmapped-v3-21-6f5729aa9832@google.com>
 <f29c4d91-5a6b-4949-8051-debe8c6fbffd@kernel.org>
In-Reply-To: <f29c4d91-5a6b-4949-8051-debe8c6fbffd@kernel.org>

On Mon Aug 3, 2026 at 10:18 AM BST, Vlastimil Babka (SUSE) wrote:
>> +/*
>> + * Can pages of these two freetypes be combined into a single higher-or=
der free
>> + * page?
>> + */
>> +static inline bool can_merge_freetypes(freetype_t a, freetype_t b)
>> +{
>> +	if (freetypes_equal(a, b))
>> +		return true;
>> +
>> +	if (!migratetype_is_mergeable(free_to_migratetype(a)) ||
>> +	    !migratetype_is_mergeable(free_to_migratetype(b)))
>> +		return false;
>> +
>> +	/*
>> +	 * Mustn't "just" merge pages with different freetype flags, changing
>> +	 * those requires updating pagetables.
>> +	 */
>> +	return freetype_flags(a) =3D=3D freetype_flags(b);
>> +}
>> +
>>  /*
>>   * Freeing function for a buddy system allocator.
>>   *
>> @@ -1069,9 +1090,7 @@ static inline void __free_one_page(struct page *pa=
ge,
>>  			buddy_ft =3D get_pfnblock_freetype(buddy, buddy_pfn);
>>  			buddy_mt =3D free_to_migratetype(buddy_ft);
>
> There's a comment above this that should probably be moved to
> can_merge_freetypes() as well?

True, thanks.