From: Li Zhijian <lizhijian@xxxxxxxxxxxxxx>
commit 4b42fb213678d2b6a9eeea92a9be200f23e49583 upstream.
Previously, we noticed the one rpma example was failed[1] since commit
36f30e486dce ("IB/core: Improve ODP to use hmm_range_fault()"), where it
will use ODP feature to do RDMA WRITE between fsdax files.
After digging into the code, we found hmm_vma_handle_pte() will still
return EFAULT even though all the its requesting flags has been
fulfilled. That's because a DAX page will be marked as (_PAGE_SPECIAL |
PAGE_DEVMAP) by pte_mkdevmap().
Link: https://github.com/pmem/rpma/issues/1142 [1]
Link: https://lkml.kernel.org/r/20210830094232.203029-1-lizhijian@xxxxxxxxxxxxxx
Fixes: 405506274922 ("mm/hmm: add missing call to hmm_pte_need_fault in HMM_PFN_SPECIAL handling")
Signed-off-by: Li Zhijian <lizhijian@xxxxxxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
mm/hmm.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -291,10 +291,13 @@ static int hmm_vma_handle_pte(struct mm_
goto fault;
/*
+ * Bypass devmap pte such as DAX page when all pfn requested
+ * flags(pfn_req_flags) are fulfilled.
* Since each architecture defines a struct page for the zero page, just
* fall through and treat it like a normal page.
*/
- if (pte_special(pte) && !is_zero_pfn(pte_pfn(pte))) {
+ if (pte_special(pte) && !pte_devmap(pte) &&
+ !is_zero_pfn(pte_pfn(pte))) {
if (hmm_pte_need_fault(hmm_vma_walk, pfn_req_flags, 0)) {
pte_unmap(ptep);
return -EFAULT;
