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
