diff options
| -rw-r--r-- | mm/huge_memory.c | 36 |
1 files changed, 15 insertions, 21 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 5a68730eebd6..f0ae8d1d4329 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2356,26 +2356,13 @@ static void __split_huge_page_tail(struct page *head, int tail, struct page *page_tail = head + tail; VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail); - VM_BUG_ON_PAGE(page_ref_count(page_tail) != 0, page_tail); /* - * tail_page->_refcount is zero and not changing from under us. But - * get_page_unless_zero() may be running from under us on the - * tail_page. If we used atomic_set() below instead of atomic_inc() or - * atomic_add(), we would then run atomic_set() concurrently with - * get_page_unless_zero(), and atomic_set() is implemented in C not - * using locked ops. spin_unlock on x86 sometime uses locked ops - * because of PPro errata 66, 92, so unless somebody can guarantee - * atomic_set() here would be safe on all archs (and not only on x86), - * it's safer to use atomic_inc()/atomic_add(). + * Clone page flags before unfreezing refcount. + * + * After successful get_page_unless_zero() might follow flags change, + * for exmaple lock_page() which set PG_waiters. */ - if (PageAnon(head) && !PageSwapCache(head)) { - page_ref_inc(page_tail); - } else { - /* Additional pin to radix tree */ - page_ref_add(page_tail, 2); - } - page_tail->flags &= ~PAGE_FLAGS_CHECK_AT_PREP; page_tail->flags |= (head->flags & ((1L << PG_referenced) | @@ -2388,14 +2375,21 @@ static void __split_huge_page_tail(struct page *head, int tail, (1L << PG_unevictable) | (1L << PG_dirty))); - /* - * After clearing PageTail the gup refcount can be released. - * Page flags also must be visible before we make the page non-compound. - */ + /* Page flags must be visible before we make the page non-compound. */ smp_wmb(); + /* + * Clear PageTail before unfreezing page refcount. + * + * After successful get_page_unless_zero() might follow put_page() + * which needs correct compound_head(). + */ clear_compound_head(page_tail); + /* Finally unfreeze refcount. Additional reference from page cache. */ + page_ref_unfreeze(page_tail, 1 + (!PageAnon(head) || + PageSwapCache(head))); + if (page_is_young(head)) set_page_young(page_tail); if (page_is_idle(head)) |