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X-CSE-ConnectionGUID: 4fJjBk0bTvWB/eMmMjOyow== X-CSE-MsgGUID: e3i5n/wNSRWu8YU9pBcJEA== X-IronPort-AV: E=McAfee;i="6800,10657,11910"; a="77968082" X-IronPort-AV: E=Sophos;i="6.27,111,1787036400"; d="scan'208";a="77968082" Received: from fmviesa013.fm.intel.com ([10.60.135.153]) by fmvoesa110.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 20 Sep 2026 01:46:28 -0700 X-CSE-ConnectionGUID: IQ8rWYG7SHOHwwNte+lCjQ== X-CSE-MsgGUID: 4/rIdET0QGuGZFjtqW9S+Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.27,111,1787036400"; d="scan'208";a="3543410" Received: from spr10.sh.intel.com (HELO localhost) ([10.239.23.75]) by fmviesa013.fm.intel.com with ESMTP; 20 Sep 2026 01:46:25 -0700 From: Yuan Liu To: David Hildenbrand , Oscar Salvador , Mike Rapoport , Wei Yang Cc: linux-mm@kvack.org, Nanhai Zou , Chen Zhang , Yuan Liu , Jason Zeng , Chen Yu , Pan Deng , Tianyou Li , linux-kernel@vger.kernel.org Subject: [PATCH v10 1/2] mm/memory_hotplug: make shrink_zone_span() more robust Date: Sun, 20 Sep 2026 04:49:45 -0400 Message-ID: <20260920084946.3266279-2-yuan1.liu@intel.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260920084946.3266279-1-yuan1.liu@intel.com> References: <20260920084946.3266279-1-yuan1.liu@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 33285C0003 X-Stat-Signature: 84ufj16b7emrizt5rhwjqyk171cqd1sp X-HE-Tag: 1789893989-689361 X-HE-Meta: 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 NiWpjLJP 2MinUNY1p5dYzbTzm0CUKujyBmea00ZaqEY71pNL/bEL1WBZ0w+OmxpzMTTgZRapeCRnKD38sj6c0a0dP5r8hxRo8GBkTWNh14EGQsGP04a8xq9wO9y7nu0X7lcjUYU44dLbuAhRVjySEMG8dgS0iLmr1mnOV5KAAJb+yryqonx2h3rFOv6H5Hp+lWd+nKlEwJqmyc0n2VKXziGNBiXio0w3T4wlLHuPPMXvn5fzl8H+v/+QFmc3QI4eI5yt5fqcGc0koxETFVz1AU7rcL5imAuPQtFTLgosjlxiqsJLcVgdz7cV617DeR44maQFQh1Mc6/RTgzYG1hghvaz2AgsssrLiI+MH9/nK4WxK Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: From: "David Hildenbrand (Arm)" Let's make shrink_zone_span() more robust by checking in find_smallest_section_pfn() / find_biggest_section_pfn() that the start or end PFN of the subsection is within the zone. While at it, clean up the function by factoring the core check out into subsection_overlaps_zone(). There likely is no need to check the nid first. We require SPARSEMEM_VMEMMAP_ENABLE, where pfn_to_page() is cheap, and pfn_to_nid() on CONFIG_NUMA would call pfn_to_page() either way. So let's just drop that for now. Signed-off-by: David Hildenbrand (Arm) Tested-by: Yuan Liu Reviewed-by: Wei Yang Signed-off-by: Yuan Liu --- mm/memory_hotplug.c | 59 ++++++++++++++++++--------------------------- 1 file changed, 24 insertions(+), 35 deletions(-) diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 226ab9cb078a..9f19876ec3ec 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -425,49 +425,39 @@ int __add_pages(int nid, unsigned long pfn, unsigned long nr_pages, return err; } -/* find the smallest valid pfn in the range [start_pfn, end_pfn) */ -static unsigned long find_smallest_section_pfn(int nid, struct zone *zone, - unsigned long start_pfn, - unsigned long end_pfn) +static bool subsection_overlaps_zone(unsigned long pfn, struct zone *zone) { - for (; start_pfn < end_pfn; start_pfn += PAGES_PER_SUBSECTION) { - if (unlikely(!pfn_to_online_page(start_pfn))) - continue; + const unsigned long start_pfn = ALIGN_DOWN(pfn, PAGES_PER_SUBSECTION); + const unsigned long end_pfn = start_pfn + PAGES_PER_SUBSECTION - 1; - if (unlikely(pfn_to_nid(start_pfn) != nid)) - continue; + /* All pages in a subsection are either online or offline. */ + if (unlikely(!pfn_to_online_page(start_pfn))) + return false; - if (zone != page_zone(pfn_to_page(start_pfn))) - continue; + /* Checking start+end is sufficient. */ + return zone == page_zone(pfn_to_page(start_pfn)) || + zone == page_zone(pfn_to_page(end_pfn)); +} - return start_pfn; +/* find the smallest valid pfn in the range [start_pfn, end_pfn) */ +static unsigned long find_smallest_section_pfn(struct zone *zone, + unsigned long start_pfn, unsigned long end_pfn) +{ + for (; start_pfn < end_pfn; start_pfn += PAGES_PER_SUBSECTION) { + if (subsection_overlaps_zone(start_pfn, zone)) + return start_pfn; } - return 0; } /* find the biggest valid pfn in the range [start_pfn, end_pfn). */ -static unsigned long find_biggest_section_pfn(int nid, struct zone *zone, - unsigned long start_pfn, - unsigned long end_pfn) +static unsigned long find_biggest_section_pfn(struct zone *zone, + unsigned long start_pfn, unsigned long end_pfn) { - unsigned long pfn; - - /* pfn is the end pfn of a memory section. */ - pfn = end_pfn - 1; - for (; pfn >= start_pfn; pfn -= PAGES_PER_SUBSECTION) { - if (unlikely(!pfn_to_online_page(pfn))) - continue; - - if (unlikely(pfn_to_nid(pfn) != nid)) - continue; - - if (zone != page_zone(pfn_to_page(pfn))) - continue; - - return pfn; + for (; end_pfn > start_pfn; end_pfn -= PAGES_PER_SUBSECTION) { + if (subsection_overlaps_zone(end_pfn - 1, zone)) + return end_pfn - 1; } - return 0; } @@ -475,7 +465,6 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn, unsigned long end_pfn) { unsigned long pfn; - int nid = zone_to_nid(zone); if (zone->zone_start_pfn == start_pfn) { /* @@ -484,7 +473,7 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn, * In this case, we find second smallest valid mem_section * for shrinking zone. */ - pfn = find_smallest_section_pfn(nid, zone, end_pfn, + pfn = find_smallest_section_pfn(zone, end_pfn, zone_end_pfn(zone)); if (pfn) { zone->spanned_pages = zone_end_pfn(zone) - pfn; @@ -500,7 +489,7 @@ static void shrink_zone_span(struct zone *zone, unsigned long start_pfn, * In this case, we find second biggest valid mem_section for * shrinking zone. */ - pfn = find_biggest_section_pfn(nid, zone, zone->zone_start_pfn, + pfn = find_biggest_section_pfn(zone, zone->zone_start_pfn, start_pfn); if (pfn) zone->spanned_pages = pfn - zone->zone_start_pfn + 1; -- 2.47.3