diff options
| -rw-r--r-- | mm/huge_memory.c | 37 |
1 files changed, 23 insertions, 14 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 9237976abe72..91ca9b103ee5 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -2202,7 +2202,7 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, { spinlock_t *ptl; struct mmu_notifier_range range; - bool was_locked = false; + bool do_unlock_page = false; pmd_t _pmd; mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma, vma->vm_mm, @@ -2218,7 +2218,6 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, VM_BUG_ON(freeze && !page); if (page) { VM_WARN_ON_ONCE(!PageLocked(page)); - was_locked = true; if (page != pmd_page(*pmd)) goto out; } @@ -2227,19 +2226,29 @@ repeat: if (pmd_trans_huge(*pmd)) { if (!page) { page = pmd_page(*pmd); - if (unlikely(!trylock_page(page))) { - get_page(page); - _pmd = *pmd; - spin_unlock(ptl); - lock_page(page); - spin_lock(ptl); - if (unlikely(!pmd_same(*pmd, _pmd))) { - unlock_page(page); + /* + * An anonymous page must be locked, to ensure that a + * concurrent reuse_swap_page() sees stable mapcount; + * but reuse_swap_page() is not used on shmem or file, + * and page lock must not be taken when zap_pmd_range() + * calls __split_huge_pmd() while i_mmap_lock is held. + */ + if (PageAnon(page)) { + if (unlikely(!trylock_page(page))) { + get_page(page); + _pmd = *pmd; + spin_unlock(ptl); + lock_page(page); + spin_lock(ptl); + if (unlikely(!pmd_same(*pmd, _pmd))) { + unlock_page(page); + put_page(page); + page = NULL; + goto repeat; + } put_page(page); - page = NULL; - goto repeat; } - put_page(page); + do_unlock_page = true; } } if (PageMlocked(page)) @@ -2249,7 +2258,7 @@ repeat: __split_huge_pmd_locked(vma, pmd, range.start, freeze); out: spin_unlock(ptl); - if (!was_locked && page) + if (do_unlock_page) unlock_page(page); /* * No need to double call mmu_notifier->invalidate_range() callback. |