From: David Hildenbrand <david@xxxxxxxxxx> Subject: mm/page_alloc: fix and rework pfn handling in memmap_init_zone() Let's update the pfn manually whenever we continue the loop. This makes the code easier to read but also less error prone (and we can directly fix one issue). When overlap_memmap_init() returns true, pfn is updated to "memblock_region_memory_end_pfn(r)". So it already points at the *next* pfn to process. Incrementing the pfn another time is wrong, we might leave one uninitialized. I spotted this by inspecting the code, so I have no idea if this is relevant in practise (with kernelcore=3Dmirror). Link: http://lkml.kernel.org/r/20200113144035.10848-2-david@xxxxxxxxxx Fixes: a9a9e77fbf27 ("mm: move mirrored memory specific code outside of m= emmap_init_zone") Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Reviewed-by: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx> Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Oscar Salvador <osalvador@xxxxxxx> Cc: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx> Cc: Baoquan He <bhe@xxxxxxxxxx> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxx> Cc: "Jin, Zhi" <zhi.jin@xxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/page_alloc.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) --- a/mm/page_alloc.c~mm-page_alloc-fix-and-rework-pfn-handling-in-memmap_init_zone +++ a/mm/page_alloc.c @@ -5905,18 +5905,20 @@ void __meminit memmap_init_zone(unsigned } #endif - for (pfn = start_pfn; pfn < end_pfn; pfn++) { + for (pfn = start_pfn; pfn < end_pfn; ) { /* * There can be holes in boot-time mem_map[]s handed to this * function. They do not exist on hotplugged memory. */ if (context == MEMMAP_EARLY) { if (!early_pfn_valid(pfn)) { - pfn = next_pfn(pfn) - 1; + pfn = next_pfn(pfn); continue; } - if (!early_pfn_in_nid(pfn, nid)) + if (!early_pfn_in_nid(pfn, nid)) { + pfn++; continue; + } if (overlap_memmap_init(zone, &pfn)) continue; if (defer_init(nid, pfn, end_pfn)) @@ -5944,6 +5946,7 @@ void __meminit memmap_init_zone(unsigned set_pageblock_migratetype(page, MIGRATE_MOVABLE); cond_resched(); } + pfn++; } } _
