Re: [PATCH v2 05/17] mm/frame-vector: Use FOLL_LONGTERM

On 10/9/20 12:59 AM, Daniel Vetter wrote: ...

@@ -48,40 +47,25 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,

start = untagged_addr(start);

• mmap_read_lock(mm);
• locked = 1;
• vma = find_vma_intersection(mm, start, start + 1);
• if (!vma) {

• ret = -EFAULT;
  

• goto out;
  

• }
• /*

• * While get_vaddr_frames() could be used for transient (kernel
  

• * controlled lifetime) pinning of memory pages all current
  

• * users establish long term (userspace controlled lifetime)
  

• * page pinning. Treat get_vaddr_frames() like
  

• * get_user_pages_longterm() and disallow it for filesystem-dax
  

• * mappings.
  

• */
  

• if (vma_is_fsdax(vma)) {

• ret = -EOPNOTSUPP;
  

• goto out;
  

• }
• if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) {

• ret = pin_user_pages_fast(start, nr_frames,

• 		  FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM,
  

• 		  (struct page **)(vec->ptrs));
  

• if (ret > 0) {

None of the callers that we have today will accept anything less than ret == nr_frames. And the whole partially pinned region idea turns out to be just not useful for almost everyone, from what I recall of the gup/pup call sites. So I wonder if we should just have get_vaddr_frames do the cleanup here and return -EFAULT, if ret != nr_frames ?

thanks,