[RFC V2 20/37] mm: support dmem huge pmd for vmf_insert_pfn_pmd()

[yulei . kernel]

From: Yulei Zhang <yuleixzh...@tencent.com>

Since vmf_insert_pfn_pmd will BUG_ON non-pmd-devmap, we make pfn dmem pass
the check.

Dmem huge pmd will be marked with _PAGE_SPECIAL and _PAGE_DMEM, so that
follow_pfn() could recognize it.

Signed-off-by: Chen Zhuo <sagazc...@tencent.com>
Signed-off-by: Yulei Zhang <yuleixzh...@tencent.com>
---
 mm/huge_memory.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 2a818ec..6e52d57 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -781,6 +781,8 @@ static void insert_pfn_pmd(struct vm_area_struct *vma, 
unsigned long addr,
        entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
        if (pfn_t_devmap(pfn))
                entry = pmd_mkdevmap(entry);
+       else if (pfn_t_dmem(pfn))
+               entry = pmd_mkdmem(entry);
        if (write) {
                entry = pmd_mkyoung(pmd_mkdirty(entry));
                entry = maybe_pmd_mkwrite(entry, vma);
@@ -827,7 +829,7 @@ vm_fault_t vmf_insert_pfn_pmd_prot(struct vm_fault *vmf, 
pfn_t pfn,
         * can't support a 'special' bit.
         */
        BUG_ON(!(vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) &&
-                       !pfn_t_devmap(pfn));
+                       !pfn_t_devmap(pfn) && !pfn_t_dmem(pfn));
        BUG_ON((vma->vm_flags & (VM_PFNMAP|VM_MIXEDMAP)) ==
                                                (VM_PFNMAP|VM_MIXEDMAP));
        BUG_ON((vma->vm_flags & VM_PFNMAP) && is_cow_mapping(vma->vm_flags));
-- 
1.8.3.1