From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 50FE02D130C for ; Fri, 20 Feb 2026 10:43:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771584195; cv=none; b=KS8lyncpsi9V83Vg0ewpTjgDfPv/KXwxHj1hl2SW7/QAHPH+GJexZSddPg/CTwvrVggYqDHemISM0l4VM9m6OENlNzR6Tt7VnFfBQ3H868myYwXtUTGS//Ueiilu88DJ3QgpVjqO2OwaVxu8oay5ZAfiAya0J1zoSc23CB7v1Bw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771584195; c=relaxed/simple; bh=Yvu77UXexzu7sZa0hKrXXXI2ScqTjgPRW4bmvkkBJQQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Q67V1ryBVS1js6DLEkMoyzGvDbZu/4bB9xa/+KXcCJRrvuUUAzpHvFfRLQKqMHEI7IWR4MemEzft15EF3d/HCOWuMgyE7K85FaIIh6Gv4/ghO/jV0CHIzW3m7vGnwr0fRvv9VqndBO4J4EnH3z3go1bC2FPzPSCNzdsJMfbIdpE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=h4Rdg48R; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="h4Rdg48R" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C728BC116D0; Fri, 20 Feb 2026 10:43:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771584195; bh=Yvu77UXexzu7sZa0hKrXXXI2ScqTjgPRW4bmvkkBJQQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=h4Rdg48RMBdTsnXg19agUNta0otbn50YtUgDABQpHPFM2VJDqCrGZiYR05kFA6H8R vUjP0E67Jt5n/RKkfwG8ypfiGduTgpnus1XeBgjOXpHhyyzNcQEf5QXJN3y8bkJUtj E2279EUMv99nJtCLRuGwPwivk8uyyLKM3VhRkz11OXAhlFYWkcmsu0CSUmPQG1Ht66 yu7qlHs+e75gj7+AeSlAogxzfhLJhQzzEb1M5eLQmnRF9JhhAC1djj0a7jhhAiuh9j C8/+zAl7YyDw4XT8rEZ/egq4W7ei38WDxn1uTLL6RvglLCPRcB6zH/w03VXpliGhhE ucFk7lxuD2udA== Message-ID: <8bb7d240-31fb-4cb9-a3f6-ac81b8b9beae@kernel.org> Date: Fri, 20 Feb 2026 11:42:59 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mm-unstable v1 2/5] mm: introduce is_pmd_order helper To: Dev Jain , Nico Pache , linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: aarcange@redhat.com, akpm@linux-foundation.org, anshuman.khandual@arm.com, apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, byungchul@sk.com, catalin.marinas@arm.com, cl@gentwo.org, corbet@lwn.net, dave.hansen@linux.intel.com, gourry@gourry.net, hannes@cmpxchg.org, hughd@google.com, jackmanb@google.com, jack@suse.cz, jannh@google.com, jglisse@google.com, joshua.hahnjy@gmail.com, kas@kernel.org, lance.yang@linux.dev, Liam.Howlett@oracle.com, lorenzo.stoakes@oracle.com, mathieu.desnoyers@efficios.com, matthew.brost@intel.com, mhiramat@kernel.org, mhocko@suse.com, peterx@redhat.com, pfalcato@suse.de, rakie.kim@sk.com, raquini@redhat.com, rdunlap@infradead.org, richard.weiyang@gmail.com, rientjes@google.com, rostedt@goodmis.org, rppt@kernel.org, ryan.roberts@arm.com, shivankg@amd.com, sunnanyong@huawei.com, surenb@google.com, thomas.hellstrom@linux.intel.com, tiwai@suse.de, usamaarif642@gmail.com, vbabka@suse.cz, vishal.moola@gmail.com, wangkefeng.wang@huawei.com, will@kernel.org, willy@infradead.org, yang@os.amperecomputing.com, ying.huang@linux.alibaba.com, ziy@nvidia.com, zokeefe@google.com References: <20260212021835.17755-1-npache@redhat.com> <20260212021835.17755-3-npache@redhat.com> <784588bc-2071-4418-825b-9072cc3659e2@arm.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2/20/26 11:38, Dev Jain wrote: > > On 12/02/26 7:48 am, Nico Pache wrote: >> In order to add mTHP support to khugepaged, we will often be checking if a >> given order is (or is not) a PMD order. Some places in the kernel already >> use this check, so lets create a simple helper function to keep the code >> clean and readable. >> >> Reviewed-by: Lorenzo Stoakes >> Suggested-by: Lorenzo Stoakes >> Signed-off-by: Nico Pache >> >> arches# pick b3ace8be204f # mm/khugepaged: rename hpage_collapse_* to collapse_* >> --- > > Thanks, this is useful. > > In drivers/dax/device.c and fs/dax.c, we have order == PMD_ORDER check, > not HPAGE_PMD_ORDER. Therefore, > > 1) Do we have a bug here, in that these codepaths are fault > handlers, therefore should be using HPAGE_PMD_ORDER since the > definition of this macro zeroes out on !CONFIG_PGTABLE_HAS_HUGE_LEAVES? > > 2) If the distinction between HPAGE_PMD_ORDER and PMD_ORDER is real, > then the helper should be named is_hpage_pmd_order? HPAGE_PMD_ORDER is weird a stupid legacy leftover IIUC, The only thing it checks is that you are not using HPAGE_PMD_ORDER in code that might be compiled without THP support: #ifdef CONFIG_PGTABLE_HAS_HUGE_LEAVES #define HPAGE_PMD_SHIFT PMD_SHIFT ... #else #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; }) ... -- Cheers, David