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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770382861; bh=xmLMB+sdewOcCxQz83Kl8Xqpk9X80TVAUBfSvRJdhE0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=k1TvsrKuDX4ULVsLQHNN3r/U8zVYERr11gg7p18nkto5s8l6xgrLSFvCABym1KroS hSf545ZUDsS066b1eoRVkxNPo/nUhLdax068IyipdGdOYA1qK7o0sa4aiyKHZGLyN8 VpM4K/08ZLkKx94jn2snGBs8p6TTyrI4Tg2v8dwGxrRkPLr6HUMByBgqEgnRhso2Lh zvqVcuvOTtkXZe6QFp1lR/+3ounkJZscyMNEyNwVDhLuIj67yp+r6BVp+7XNjnJOdU VwunTYuNceAdcWO5mtMYEPOwEm89jqsbaAGEuKrDJI+hmYCZKvtUmOnmB24N/3Jp+x W1t9upOlirA9A== Message-ID: <2bf497eb-47b0-4eb9-a66e-607c82c36c20@kernel.org> Date: Fri, 6 Feb 2026 14:00:56 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v9] mm/memory hotplug: Fix zone->contiguous always false when hotplug To: Tianyou Li , Oscar Salvador , Mike Rapoport , Wei Yang , Michal Hocko Cc: linux-mm@kvack.org, Yong Hu , Nanhai Zou , Yuan Liu , Tim Chen , Qiuxu Zhuo , Yu C Chen , Pan Deng , Chen Zhang , linux-kernel@vger.kernel.org References: <20260130160635.2671167-1-tianyou.li@intel.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-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: C1B6A120023 X-Stat-Signature: bc7f9ez66nxtdqas43iik6nxnbzcha44 X-HE-Tag: 1770382862-147491 X-HE-Meta: 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 //uybbbA +pHRV+K2vWuR8Dp2YSKUlWbZZ8B3Xmx40/Z72TSLYiwK7S69BZK/br7g6B35tDvrz1gAUZ8V4fW+NAwNmCqHODZDOUnclVqseKmbTwBApyB1DEcr7omelkL7XVhaOlrBe45NEcfjm9i9SghjxPKfU8ScR2i2dNXJRTloqoUaNuTgToMFShMN33eChzDrJw4DwQcOrzTvK7rwu81QQBwcz7x594n7mM/LzOEw9NOR9TMuN/QPGCNa5xBZgk07adirJlyoPm+b3g/RkLOw1N5uOQ9xCuNvIctyZEskj9ZgmX1/dzvB6GdOWDxt2OdcUW5s6i54GQO0l1E6DV61nsuuamaMqO0WSFLaWp1r//Zza2yJJ4OQnWjcCxdNhG3j3IN+mj60mbE5inUTq4SJh9/Ifkr2/3be6zclyyLqaUwtMncx0mYqNLsNODCawwQ== 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 1/30/26 17:06, Tianyou Li wrote: > From: Yuan Liu > > set_zone_contiguous() uses __pageblock_pfn_to_page() to detect > pageblocks that either do not exist (hole) or that do not belong > to the same zone. > > __pageblock_pfn_to_page(), however, relies on pfn_to_online_page(), > effectively always returning NULL for memory ranges that were not > onlined yet. So when called on a range-to-be-onlined, it indicates > a memory hole to set_zone_contiguous(). > > Consequently, the set_zone_contiguous() call in move_pfn_range_to_zone(), > which happens early during memory onlining, will never detect a > zone as being contiguous. Bad: the fast path relies on the zone > contiguous state may skipped. > > To fix the issue, move the set_zone_contiguous() call to a later > stage in memory onlining, where pfn_to_online_page() will succeed: > after we mark the memory sections to be online. > > Fixes: 2d070eab2e82 ("mm: consider zone which is not fully populated to have holes") > Cc: Michal Hocko > Cc: stable@vger.kernel.org > Reviewed-by: Nanhai Zou > Signed-off-by: Yuan Liu > Signed-off-by: Tianyou Li > I assume this one is to be ignored :) -- Cheers, David