@@ -977,12 +977,16 @@ static __always_inline bool folio_test_##fname(const struct folio *folio) \
} \
static __always_inline void __folio_set_##fname(struct folio *folio) \
{ \
+ if (folio_test_##fname(folio)) \
+ return; \
VM_BUG_ON_FOLIO(data_race(folio->page.page_type) != UINT_MAX, \
folio); \
folio->page.page_type = (unsigned int)PGTY_##lname << 24; \
} \
static __always_inline void __folio_clear_##fname(struct folio *folio) \
{ \
+ if (folio->page.page_type == UINT_MAX) \
+ return; \
VM_BUG_ON_FOLIO(!folio_test_##fname(folio), folio); \
folio->page.page_type = UINT_MAX; \
}
@@ -995,11 +999,15 @@ static __always_inline int Page##uname(const struct page *page) \
} \
static __always_inline void __SetPage##uname(struct page *page) \
{ \
+ if (Page##uname(page)) \
+ return; \
VM_BUG_ON_PAGE(data_race(page->page_type) != UINT_MAX, page); \
page->page_type = (unsigned int)PGTY_##lname << 24; \
} \
static __always_inline void __ClearPage##uname(struct page *page) \
{ \
+ if (page->page_type == UINT_MAX) \
+ return; \
VM_BUG_ON_PAGE(!Page##uname(page), page); \
page->page_type = UINT_MAX; \
}
Some page flags (page->flags) were converted to page types (page->page_types). A recent example is PG_hugetlb. From the exclusive writer's perspective, e.g., a thread doing __folio_set_hugetlb(), there is a difference between the page flag and type APIs: the former allows the same non-atomic operation to be repeated whereas the latter does not. For example, calling __folio_set_hugetlb() twice triggers VM_BUG_ON_FOLIO(), since the second call expects the type (PG_hugetlb) not to be set previously. Using add_hugetlb_folio() as an example, it calls __folio_set_hugetlb() in the following error-handling path. And when that happens, it triggers the aforementioned VM_BUG_ON_FOLIO(). if (folio_test_hugetlb(folio)) { rc = hugetlb_vmemmap_restore_folio(h, folio); if (rc) { spin_lock_irq(&hugetlb_lock); add_hugetlb_folio(h, folio, false); ... It is possible to make hugeTLB comply with the new requirements from the page type API. However, a straightforward fix would be to just allow the same page type to be set or cleared again inside the API, to avoid any changes to its callers. Fixes: d99e3140a4d3 ("mm: turn folio_test_hugetlb into a PageType") Signed-off-by: Yu Zhao <yuzhao@google.com> Cc: <stable@vger.kernel.org> --- include/linux/page-flags.h | 8 ++++++++ 1 file changed, 8 insertions(+)