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 and end PFNs of the subsection are 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 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 7ac19fab2263..cd82e79f0782 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -422,49 +422,39 @@ 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; } @@ -472,7 +462,6 @@ 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) { /* @@ -481,7 +470,7 @@ 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; @@ -497,7 +486,7 @@ 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