diff options
| -rw-r--r-- | include/linux/mm.h | 13 |
1 files changed, 11 insertions, 2 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 7ff6e2410aa3..3adc37cebe6f 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -719,11 +719,20 @@ int vma_is_stack_for_current(struct vm_area_struct *vma); struct mmu_gather; struct inode; +/* + * compound_order() can be called without holding a reference, which means + * that niceties like page_folio() don't work. These callers should be + * prepared to handle wild return values. For example, PG_head may be + * set before _folio_order is initialised, or this may be a tail page. + * See compaction.c for some good examples. + */ static inline unsigned int compound_order(struct page *page) { - if (!PageHead(page)) + struct folio *folio = (struct folio *)page; + + if (!test_bit(PG_head, &folio->flags)) return 0; - return page[1].compound_order; + return folio->_folio_order; } /** |