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[2003:d8:2f14:2400:afc:9797:137c:a25b]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-46e2a9af775sm26973055e9.7.2025.09.24.03.40.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 24 Sep 2025 03:40:51 -0700 (PDT) Message-ID: Date: Wed, 24 Sep 2025 12:40:49 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mm-new 1/1] mm/khugepaged: abort collapse scan on non-swap entries To: Kiryl Shutsemau Cc: Lance Yang , akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, dev.jain@arm.com, hughd@google.com, ioworker0@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, mpenttil@redhat.com, npache@redhat.com, ryan.roberts@arm.com, ziy@nvidia.com, richard.weiyang@gmail.com References: <20250924100207.28332-1-lance.yang@linux.dev> <1282de5a-3dce-443d-91d1-111103140973@redhat.com> <2i5t62obfweid2zrt33vo3boviw4okha4d3gglw76eqv43ofky@pdv3evw5yjmh> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: 8qqjsj8xzxybiuzufho4yc73o3zm55jn X-Rspam-User: X-Rspamd-Queue-Id: 39D834000C X-Rspamd-Server: rspam10 X-HE-Tag: 1758710455-475293 X-HE-Meta: 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 FxUHW9TC 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 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 24.09.25 12:17, Kiryl Shutsemau wrote: > On Wed, Sep 24, 2025 at 12:10:47PM +0200, David Hildenbrand wrote: >> On 24.09.25 12:02, Lance Yang wrote: >>> From: Lance Yang >>> >>> The existing check in hpage_collapse_scan_pmd() is specific to uffd-wp >>> markers. Other special markers (e.g., GUARD, POISONED) would not be caught >>> early, leading to failures deeper in the swap-in logic. >>> >>> hpage_collapse_scan_pmd() >>> `- collapse_huge_page() >>> `- __collapse_huge_page_swapin() -> fails! >>> >>> As David suggested[1], this patch skips any such non-swap entries early. >>> If a special marker is found, the scan is aborted immediately with the >>> SCAN_PTE_NON_PRESENT result, as Lorenzo suggested[2], avoiding wasted >>> work. >> >> Note that I suggested to skip all non-present entries except swap entries, >> which includes migration entries, hwpoisoned entries etc. > > Hm. So swap in is fine, but wait for migration to complete is not? If so we'd have to add the logic to actually wait for migration entries, and not count them towards max swap entries. But that's a different discussion and could be added on top of cleanly handling all non-swap entries. -- Cheers David / dhildenb