From: Muchun Song <songmuchun@xxxxxxxxxxxxx> Subject: mm: fix missing cache flush for all tail pages of compound page The D-cache maintenance inside move_to_new_page() only consider one page, there is still D-cache maintenance issue for tail pages of compound page (e.g. THP or HugeTLB). THP migration is only enabled on x86_64, ARM64 and powerpc, while powerpc and arm64 need to maintain the consistency between I-Cache and D-Cache, which depends on flush_dcache_page() to maintain the consistency between I-Cache and D-Cache. But there is no issues on arm64 and powerpc since they already considers the compound page cache flushing in their icache flush function. HugeTLB migration is enabled on arm, arm64, mips, parisc, powerpc, riscv, s390 and sh, while arm has handled the compound page cache flush in flush_dcache_page(), but most others do not. In theory, the issue exists on many architectures. Fix this by not using flush_dcache_folio() since it is not backportable. Link: https://lkml.kernel.org/r/20220210123058.79206-3-songmuchun@xxxxxxxxxxxxx Fixes: 290408d4a250 ("hugetlb: hugepage migration core") Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx> Reviewed-by: Zi Yan <ziy@xxxxxxxxxx> Cc: Axel Rasmussen <axelrasmussen@xxxxxxxxxx> Cc: David Rientjes <rientjes@xxxxxxxxxx> Cc: Fam Zheng <fam.zheng@xxxxxxxxxxxxx> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Lars Persson <lars.persson@xxxxxxxx> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Cc: Peter Xu <peterx@xxxxxxxxxx> Cc: Xiongchun Duan <duanxiongchun@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/migrate.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) --- a/mm/migrate.c~mm-fix-missing-cache-flush-for-all-tail-pages-of-compound-page +++ a/mm/migrate.c @@ -916,9 +916,12 @@ static int move_to_new_page(struct page if (!PageMappingFlags(page)) page->mapping = NULL; - if (likely(!is_zone_device_page(newpage))) - flush_dcache_page(newpage); + if (likely(!is_zone_device_page(newpage))) { + int i, nr = compound_nr(newpage); + for (i = 0; i < nr; i++) + flush_dcache_page(newpage + i); + } } out: return rc; _
