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Received: from 30.74.144.131(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0X162pFv_1776301501 cluster:ay36) by smtp.aliyun-inc.com; Thu, 16 Apr 2026 09:05:01 +0800 Message-ID: Date: Thu, 16 Apr 2026 09:05:01 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: shmem: don't set large-order range for internal shmem mount To: "David Hildenbrand (Arm)" , akpm@linux-foundation.org, hughd@google.com Cc: willy@infradead.org, ziy@nvidia.com, ljs@kernel.org, lance.yang@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <2d138a3f-0006-4a01-852a-4570d7ba781d@linux.alibaba.com> <1a3cb6b2-94e0-4268-8cd9-1f9a9deb6c6b@linux.alibaba.com> <875dc63b-0cd2-49e5-8b0d-3fb062789813@kernel.org> From: Baolin Wang In-Reply-To: <875dc63b-0cd2-49e5-8b0d-3fb062789813@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: mmc1r3kruzcs7zea1ta3q6x1nutyzcq6 X-Rspam-User: X-Rspamd-Queue-Id: B96CE1A000D X-Rspamd-Server: rspam05 X-HE-Tag: 1776301505-555269 X-HE-Meta: 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 gVO+tDUA UKREdsUf70165uytctQWVqdA0slTCmmwGoyLtwUaEfNwpbaglufFOz8maak0JD87t/nc5ycMU0JbFE67hpiXLcvnU1yZLQcKwoc6A/TiJYI/xhKhjgGECEl0yqey5B6tpPJI9GBCS1ECGyTgMOCNbyi5pUdk9NSf2jggQ6tJaq5bugf1SEt//gEYzvSdqVVrSPwHfZajDEEYRPrF5oHBzhyd9Givcfj8a1MpfMiwR98AztEpON1xvA1ghmGUc9XXICEDPceJlTjTKv8u6dKK892vWL8SVIxjcg3oxGDytbyTEHqsKDBd8rsRDNBBOiNmy4T6AZEaWchSDRYa1xxZhyHxH0g== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/15/26 10:36 PM, David Hildenbrand (Arm) wrote: > On 4/15/26 12:05, Baolin Wang wrote: >> >> >> On 4/15/26 5:54 PM, David Hildenbrand (Arm) wrote: >>>> >>>> Yes, that makes sense. >>>> >>>> However, it’s also possible that the mapping does not support large >>>> folios, yet anonymous shmem can still allocate large folios via the >>>> sysfs interfaces. That doesn't make sense, right? >>> >>> That's what I am saying: if there could be large folios in there, then >>> let's tell the world. >>> >>> Getting in a scenario where the mapping claims to not support large >>> folios, but then we have large folios in there is inconsistent, not? >>> >>> [...] >>> >>>> >>>> For the current anonymous shmem (tmpfs is already clear, no questions), >>>> I don’t think there will be any "will never have/does never allow" >>>> cases, because it can be changed dynamically via the sysfs interfaces. >>> >>> Right. It's about non-anon shmem with huge=off. >>> >>>> >>>> If we still want that logic, then for anonymous shmem we can treat it as >>>> always "might have large folios". >> >> OK. To resolve the confusion about 1, the logic should be changed as >> follows. Does that make sense to you? >> >> if (sbinfo->huge || (sb->s_flags & SB_KERNMOUNT)) >>     mapping_set_large_folios(inode->i_mapping); > > I think that's better. Thanks for your valuable input. But has Willy says, maybe we can just > unconditionally set it and have it even simpler. However, for tmpfs mounts, we should still respect the 'huge=' mount option. See commit 5a90c155defa ("tmpfs: don't enable large folios if not supported").