On Fri, Sep 20, 2019 at 12:12:04AM +0800, Jia He wrote: > @@ -2152,7 +2163,29 @@ static inline void cow_user_page(struct page *dst, > struct page *src, unsigned lo > */ > if (unlikely(!src)) { > void *kaddr = kmap_atomic(dst); > - void __user *uaddr = (void __user *)(va & PAGE_MASK); > + void __user *uaddr = (void __user *)(addr & PAGE_MASK); > + pte_t entry; > + > + /* On architectures with software "accessed" bits, we would > + * take a double page fault, so mark it accessed here. > + */ > + if (arch_faults_on_old_pte() && !pte_young(vmf->orig_pte)) { > + spin_lock(vmf->ptl); > + if (likely(pte_same(*vmf->pte, vmf->orig_pte))) { > + entry = pte_mkyoung(vmf->orig_pte); > + if (ptep_set_access_flags(vma, addr, > + vmf->pte, entry, 0)) > + update_mmu_cache(vma, addr, vmf->pte); > + } else { > + /* Other thread has already handled the fault > + * and we don't need to do anything. If it's > + * not the case, the fault will be triggered > + * again on the same address. > + */ > + return -1; > + } > + spin_unlock(vmf->ptl);
Returning with the spinlock held doesn't normally go very well ;). -- Catalin