linux-kernel - [PATCH 20/35] mm: support dmem huge pmd for vmf_insert_pfn

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Date:   Thu,  8 Oct 2020 15:54:10 +0800
From:   yulei.kernel@...il.com
To:     akpm@...ux-foundation.org, naoya.horiguchi@....com,
        viro@...iv.linux.org.uk, pbonzini@...hat.com
Cc:     linux-fsdevel@...r.kernel.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, xiaoguangrong.eric@...il.com,
        kernellwp@...il.com, lihaiwei.kernel@...il.com,
        Yulei Zhang <yuleixzhang@...cent.com>,
        Chen Zhuo <sagazchen@...cent.com>
Subject: [PATCH 20/35] mm: support dmem huge pmd for vmf_insert_pfn_pmd()

From: Yulei Zhang <yuleixzhang@...cent.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 <sagazchen@...cent.com>
Signed-off-by: Yulei Zhang <yuleixzhang@...cent.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 73af337b454e..a24601c93713 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));
-- 
2.28.0