After discussing the issue on linux-nvme, the bug was located in
xen/biomerge.c. It can be fixed in 4.9.30 as well as 4.13RC1 using the
patch from Roger Pau Monne below.
---
drivers/xen/biomerge.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/xen/biomerge.c b/drivers/xen/biomerge.c
index 4da69dbf7dca..1bdd02a6d6ac 100644
--- a/drivers/xen/biomerge.c
+++ b/drivers/xen/biomerge.c
@@ -10,8 +10,7 @@ bool xen_biovec_phys_mergeable(const struct bio_vec *vec1,
unsigned long bfn1 = pfn_to_bfn(page_to_pfn(vec1->bv_page));
unsigned long bfn2 = pfn_to_bfn(page_to_pfn(vec2->bv_page));
- return __BIOVEC_PHYS_MERGEABLE(vec1, vec2) &&
- ((bfn1 == bfn2) || ((bfn1+1) == bfn2));
+ return bfn1 + PFN_DOWN(vec1->bv_offset + vec1->bv_len) == bfn2;
#else
/*
* XXX: Add support for merging bio_vec when using different page
