diff options
| author | David Hildenbrand <david@redhat.com> | 2024-05-31 14:56:16 +0200 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2024-07-03 19:30:20 -0700 |
| commit | dc9e6f7053dd540db2c9fba30c31a07de5edab01 (patch) | |
| tree | 0129be2587070ace09ff4a661d58488de431d80c /include/linux/page-flags.h | |
| parent | 2f9f0854360f0ed0f530dbc4566b052a4a7f3637 (diff) | |
mm: read page_type using READ_ONCE
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 commit 68f0320824fa
("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 commit
6e292b9be7f4 ("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>
Diffstat (limited to 'include/linux/page-flags.h')
| -rw-r--r-- | include/linux/page-flags.h | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h index 1d441908b726..5769fe6e4950 100644 --- a/include/linux/page-flags.h +++ b/include/linux/page-flags.h @@ -955,9 +955,9 @@ enum pagetype { }; #define PageType(page, flag) \ - ((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE) + ((READ_ONCE(page->page_type) & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE) #define folio_test_type(folio, flag) \ - ((folio->page.page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE) + ((READ_ONCE(folio->page.page_type) & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE) static inline int page_type_has_type(unsigned int page_type) { @@ -966,7 +966,7 @@ static inline int page_type_has_type(unsigned int page_type) static inline int page_has_type(const struct page *page) { - return page_type_has_type(page->page_type); + return page_type_has_type(READ_ONCE(page->page_type)); } #define FOLIO_TYPE_OPS(lname, fname) \ |