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KCSAN complains about possible data races: while we check for a page_type -- for example for sanity checks -- we might concurrently modify the mapcount that overlays page_type. Let's use READ_ONCE to avoid load tearing (shouldn't make a difference) and to make KCSAN happy. Likely, we might also want to use WRITE_ONCE for the writer side of page_type, if KCSAN ever complains about that. But we'll not mess with that for now. Note: nothing should really be broken besides wrong KCSAN complaints. The sanity check that triggers this was added in commit68f0320824("mm/rmap: convert folio_add_file_rmap_range() into folio_add_file_rmap_[pte|ptes|pmd]()"). Even before that similar races likely where possible, ever since we added page_type in commit6e292b9be7("mm: split page_type out from _mapcount"). Link: https://lkml.kernel.org/r/20240531125616.2850153-1-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Reported-by: kernel test robot <oliver.sang@intel.com> Closes: https://lore.kernel.org/oe-lkp/202405281431.c46a3be9-lkp@intel.com Reviewed-by: Oscar Salvador <osalvador@suse.de> Reviewed-by: Miaohe Lin <linmiaohe@huawei.com> Cc: Matthew Wilcox <willy@infradead.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>