Re: [Linux-nvdimm] [PATCH 1/3 v6] mm(v4.1): New pfn_mkwrite same as page_mkwrite for VM_PFNMAP

On Tue, Apr 07, 2015 at 03:57:32PM +0300, Boaz Harrosh wrote: > +/* > + * Handle write page faults for VM_MIXEDMAP or VM_PFNMAP for a VM_SHARED > + * mapping > + */ > +static int wp_pfn_shared(struct mm_struct *mm, > + struct vm_area_struct *vma, unsigned long address, > + pte_t *page_table, spinlock_t *ptl, pte_t orig_pte, > + pmd_t *pmd) > +{ > + if (vma->vm_ops && vma->vm_ops->pfn_mkwrite) { > + struct vm_fault vmf = { > + .page = NULL, > + .pgoff = linear_page_index(vma, address), > + .virtual_address = (void __user *)(address & PAGE_MASK), > + .flags = FAULT_FLAG_WRITE | FAULT_FLAG_MKWRITE, > + }; > + int ret; > + > + pte_unmap_unlock(page_table, ptl); > + ret = vma->vm_ops->pfn_mkwrite(vma, &vmf); > + if (ret & VM_FAULT_ERROR) > + return ret; > + page_table = pte_offset_map_lock(mm, pmd, address, &ptl); > + /* Did pfn_mkwrite already fixed up the pte */

> + if (!pte_same(*page_table, orig_pte)) { > + pte_unmap_unlock(page_table, ptl); > + return ret; This should be "return 0;", shouldn't it? VM_FAULT_NOPAGE would imply you've installed new pte, but you did not.