From: Wei Yang Date: Wed, 10 Sep 2025 09:22:40 +0000 (+0000) Subject: mm/compaction: fix low_pfn advance on isolating hugetlb X-Git-Tag: v6.18-rc1~130^2~21 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=89e688edcffee7858aa394fd107df98bfd7647a4;p=thirdparty%2Fkernel%2Fstable.git mm/compaction: fix low_pfn advance on isolating hugetlb Commit 56ae0bb349b4 ("mm: compaction: convert to use a folio in isolate_migratepages_block()") converts api from page to folio. But the low_pfn advance for hugetlb page seems wrong when low_pfn doesn't point to head page. Originally, if page is a hugetlb tail page, compound_nr() return 1, which means low_pfn only advance one in next iteration. After the change, low_pfn would advance more than the hugetlb range, since folio_nr_pages() always return total number of the large page. This results in skipping some range to isolate and then to migrate. The worst case for alloc_contig is it does all the isolation and migration, but finally find some range is still not isolated. And then undo all the work and try a new range. Advance low_pfn to the end of hugetlb. Link: https://lkml.kernel.org/r/20250910092240.3981-1-richard.weiyang@gmail.com Fixes: 56ae0bb349b4 ("mm: compaction: convert to use a folio in isolate_migratepages_block()") Signed-off-by: Wei Yang Acked-by: Zi Yan Cc: "Vishal Moola (Oracle)" Cc: Kefeng Wang Cc: Oscar Salvador Cc: Brendan Jackman Cc: Johannes Weiner Cc: Michal Hocko Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Wei Yang Signed-off-by: Andrew Morton --- diff --git a/mm/compaction.c b/mm/compaction.c index bf021b31c7ece..1e8f8eca318c6 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -989,7 +989,7 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, * Hugepage was successfully isolated and placed * on the cc->migratepages list. */ - low_pfn += folio_nr_pages(folio) - 1; + low_pfn += folio_nr_pages(folio) - folio_page_idx(folio, page) - 1; goto isolate_success_no_list; }