Subject: linux-next: manual merge of the v4l-dvb-next tree with Linus' tree

From: Stephen Rothwell <[email-masked]>
Date: Wed, 7 Dec 2022 09:23:53 +1100

Hi all,

Today's linux-next merge of the v4l-dvb-next tree got a conflict in:

  drivers/media/common/videobuf2/frame_vector.c

between commit:

  6647e76ab623 ("v4l2: don't fall back to follow_pfn() if pin_user_pages_fast() fails")

from Linus' tree and commit:

  e2fc6edd37ba ("media: videobuf2: revert "get_userptr: buffers are always writable"")

from the v4l-dvb-next tree.

I fixed it up (see below) and can carry the fix as necessary. This
is now fixed as far as linux-next is concerned, but any non trivial
conflicts should be mentioned to your upstream maintainer when your tree
is submitted for merging.  You may also want to consider cooperating
with the maintainer of the conflicting tree to minimise any particularly
complex conflicts.

-- 
Cheers,
Stephen Rothwell

diff --cc drivers/media/common/videobuf2/frame_vector.c
index 144027035892,aad72640f055..000000000000
--- a/drivers/media/common/videobuf2/frame_vector.c
+++ b/drivers/media/common/videobuf2/frame_vector.c
@@@ -32,10 -33,15 +33,11 @@@
   *
   * This function takes care of grabbing mmap_lock as necessary.
   */
- int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
+ int get_vaddr_frames(unsigned long start, unsigned int nr_frames, bool write,
  		     struct frame_vector *vec)
  {
 -	struct mm_struct *mm = current->mm;
 -	struct vm_area_struct *vma;
 -	int ret_pin_user_pages_fast = 0;
 -	int ret = 0;
 -	int err;
 +	int ret;
+ 	unsigned int gup_flags = FOLL_FORCE | FOLL_LONGTERM;
  
  	if (nr_frames == 0)
  		return 0;
@@@ -45,20 -51,62 +47,22 @@@
  
  	start = untagged_addr(start);
  
- 	ret = pin_user_pages_fast(start, nr_frames,
- 				  FOLL_FORCE | FOLL_WRITE | FOLL_LONGTERM,
+ 	if (write)
+ 		gup_flags |= FOLL_WRITE;
+ 
+ 	ret = pin_user_pages_fast(start, nr_frames, gup_flags,
  				  (struct page **)(vec->ptrs));
 -	if (ret > 0) {
 -		vec->got_ref = true;
 -		vec->is_pfns = false;
 -		goto out_unlocked;
 -	}
 -	ret_pin_user_pages_fast = ret;
 +	vec->got_ref = true;
 +	vec->is_pfns = false;
 +	vec->nr_frames = ret;
  
 -	mmap_read_lock(mm);
 -	vec->got_ref = false;
 -	vec->is_pfns = true;
 -	ret = 0;
 -	do {
 -		unsigned long *nums = frame_vector_pfns(vec);
 +	if (likely(ret > 0))
 +		return ret;
  
 -		vma = vma_lookup(mm, start);
 -		if (!vma)
 -			break;
 -
 -		while (ret < nr_frames && start + PAGE_SIZE <= vma->vm_end) {
 -			err = follow_pfn(vma, start, &nums[ret]);
 -			if (err) {
 -				if (ret)
 -					goto out;
 -				// If follow_pfn() returns -EINVAL, then this
 -				// is not an IO mapping or a raw PFN mapping.
 -				// In that case, return the original error from
 -				// pin_user_pages_fast(). Otherwise this
 -				// function would return -EINVAL when
 -				// pin_user_pages_fast() returned -ENOMEM,
 -				// which makes debugging hard.
 -				if (err == -EINVAL && ret_pin_user_pages_fast)
 -					ret = ret_pin_user_pages_fast;
 -				else
 -					ret = err;
 -				goto out;
 -			}
 -			start += PAGE_SIZE;
 -			ret++;
 -		}
 -		/* Bail out if VMA doesn't completely cover the tail page. */
 -		if (start < vma->vm_end)
 -			break;
 -	} while (ret < nr_frames);
 -out:
 -	mmap_read_unlock(mm);
 -out_unlocked:
 -	if (!ret)
 -		ret = -EFAULT;
 -	if (ret > 0)
 -		vec->nr_frames = ret;
 -	return ret;
 +	/* This used to (racily) return non-refcounted pfns. Let people know */
 +	WARN_ONCE(1, "get_vaddr_frames() cannot follow VM_IO mapping");
 +	vec->nr_frames = 0;
 +	return ret ? ret : -EFAULT;
  }
  EXPORT_SYMBOL(get_vaddr_frames);