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b=CUNYyx8cfhjh/ngKFyNusCJPTPD77D53HIlqiNow7NmMEDs2H5VvBVmHsIs5q/LR0 bcZjPt8xm/BTSKGHldQTRheQ006nnUjt7hTzvzfzWo/oCmx2cF9wV4kH2DV4fuVRrG Hmzg8QKxSGQ40xLg3O2HDHCMNFascA5AMl4LWF25igFMjWZCV9pPh1hOIBxpB/sGaR 0P4sPHo3eys1QoJE8GsyaIMjgjlhPEvFa3Xf8PodrRaZeQzAbwBf5FHtul70BgIj/y zzKkezo0d09mlIVbgU8EON7IajTYi1wE5omU/4qHOTWdEJl1u3KbsnbDyB5ehMo7pc oF2ygtkUhskGQ== Date: Thu, 22 Jan 2026 13:16:43 +0200 From: Mike Rapoport To: Tianyou Li Cc: David Hildenbrand , Oscar Salvador , Wei Yang , Michal Hocko , 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 Subject: Re: [PATCH v8 1/3] mm/memory hotplug: Fix zone->contiguous always false when hotplug Message-ID: References: <20260120143346.1427837-1-tianyou.li@intel.com> <20260120143346.1427837-2-tianyou.li@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260120143346.1427837-2-tianyou.li@intel.com> X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 9932FA0008 X-Stat-Signature: bcz4wdnnbypw7sr8n8m81r9qnqkqhi4p X-Rspam-User: X-HE-Tag: 1769080613-695754 X-HE-Meta: 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 dvL8QwIS +cR6iNt9e1h5phiDa3jB7DFZAahGzPo0xnB3xLjQdQ9AyT6OBBOyf6xuwbYCZLgSdlRoNlpzU/BlAs0Ne5Z/X0PXP5cclMfl82DnuTmlAi7z0gyqBLs0CJy1T2brLv7ULfDqrjgXVOIX9edbmqq/2WoQtDe9sqeiXfhG1Vv4ib2ZAi3enyVj+lAkH1j/8jRnSWDqWqtHtQqFvk17yJUoK5GHP8r8vxUez5dcooSg2FD7Zl4qaEtj5vCz4FvIB4mIZsqLHHpIuOEnji25drwzjxBFyg3DiXYBYvt/81bTbq555fQaGIpm8/6g5pgfo3Qwa+5jIxCnDKdM8QST14NP1sYTZfBkZjRLw0vo8TUA6Selu0URR616OkyAr8vnXpvef2/tsfcD4midH24kYuSrHVYXBsPXbZlp3uJbQ 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: Hi, On Tue, Jan 20, 2026 at 10:33:44PM +0800, 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. > > 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 stable@ perhaps? > Cc: Michal Hocko > Reviewed-by: Nanhai Zou > Signed-off-by: Yuan Liu > Signed-off-by: Tianyou Li > --- > mm/memory_hotplug.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index a63ec679d861..c8f492b5daf0 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -782,8 +782,6 @@ void move_pfn_range_to_zone(struct zone *zone, unsigned long start_pfn, > memmap_init_range(nr_pages, nid, zone_idx(zone), start_pfn, 0, > MEMINIT_HOTPLUG, altmap, migratetype, > isolate_pageblock); > - > - set_zone_contiguous(zone); move_pfn_range_to_zone() is also called from memremap::pagemap_range(). Shouldn't we add set_zone_contiguous() there as well? > } > > struct auto_movable_stats { > @@ -1205,6 +1203,13 @@ int online_pages(unsigned long pfn, unsigned long nr_pages, > } > > online_pages_range(pfn, nr_pages); > + > + /* > + * Now that the ranges are indicated as online, check whether the whole > + * zone is contiguous. > + */ > + set_zone_contiguous(zone); > + > adjust_present_page_count(pfn_to_page(pfn), group, nr_pages); > > if (node_arg.nid >= 0) > -- > 2.47.1 > -- Sincerely yours, Mike.