[RFC 10/23] xen/biomerge: WORKAROUND always says the biovec are not mergeable

When Linux is using 64K page granularity, every page will be slipt in
multiple non-contiguous 4K MFN.

I'm not sure how to handle efficiently the check to know whether we can
merge 2 biovec with a such case. So for now, always says that biovec are
not mergeable.

Signed-off-by: Julien Grall <redacted>
Cc: Konrad Rzeszutek Wilk <redacted>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: David Vrabel <redacted>
---
  drivers/xen/biomerge.c | 3 +++
  1 file changed, 3 insertions(+)

diff --git a/drivers/xen/biomerge.c b/drivers/xen/biomerge.c
index 0edb91c..20387c2 100644
--- a/drivers/xen/biomerge.c
+++ b/drivers/xen/biomerge.c

@@ -9,6 +9,9 @@ bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
  	unsigned long mfn1 = pfn_to_mfn(page_to_pfn(vec1->bv_page));
  	unsigned long mfn2 = pfn_to_mfn(page_to_pfn(vec2->bv_page));
  
+	/* TODO: Implement it correctly */
+	return 0;
+
  	return __BIOVEC_PHYS_MERGEABLE(vec1, vec2) &&
  		((mfn1 == mfn2) || ((mfn1+1) == mfn2));
  }