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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 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 X-Stat-Signature: 6npicdmhf9rtchjitpdq543p4umf7a61 X-Rspamd-Server: rspam11 X-Rspam-User: X-Rspamd-Queue-Id: 824BC180002 X-HE-Tag: 1771584196-569289 X-HE-Meta: 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 32OIjbe8 t1m5OCwraBt67YkOwyl2snbAp1Zi0TfbRGAvMFFbgjHNBVsgSq57onrHkUmkVdH8eSTk52WEwpaMPqIVQ7lcAEN3UJ/Mo2Vt7fCWQ9bOt7US56l0zhTsiJ33YONhkxsqdXPa+xwYz4dGIfbYlLc47KJOOJjGYTlOCvmS9O8bsBceTpv08Rtp37uD94WHyZ6BGbC2LXCGihtls1yk3OkIuWH5EB7+2NaDHfLJi4u1DfMLKMegYdgBQ2GVyycH07M0EmH71hojdsfkjoDV3R1oC0dZnQzdK9T58eG1Ak4wxySWcTOtzrf1ZV2sFX/QxWbLp5pSyygjN0sL420MXfpxliyCQFpr1BjCMDZW/HErGqDFiip+iI+1cozkiwq6x0CVXBIs4WGguwlftU86WOR/S7cFNv9pp6tMnzggT8XLXenjFxzk= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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