linux-kernel - [PATCH 14/35] mm, dmem: dmem-pmd vs thp-pmd

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Message-Id: <ba67a6820a16327db236bd2217344a01b24645a2.1602093760.git.yuleixzhang@tencent.com>
Date:   Thu,  8 Oct 2020 15:54:04 +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 14/35] mm, dmem: dmem-pmd vs thp-pmd

From: Yulei Zhang <yuleixzhang@...cent.com>

A dmem huge page is ultimately not a transparent huge page. As we
decided to use pmd_special() to distinguish dmem-pmd from thp-pmd,
we should make some slightly different semantics between pmd_special()
and pmd_trans_huge(), just as pmd_devmap() in upstream. This distinction
is especially important in some mm-core paths such as zap_pmd_range().

Explicitly mark the pmd_trans_huge() helpers that dmem needs by adding
pmd_special() checks. This method could be reused in many mm-core paths.

Signed-off-by: Chen Zhuo <sagazchen@...cent.com>
Signed-off-by: Yulei Zhang <yuleixzhang@...cent.com>
---
 arch/x86/include/asm/pgtable.h | 10 +++++++++-
 include/linux/pgtable.h        |  5 +++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index ea4554a728bc..e29601cad384 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -260,7 +260,7 @@ static inline int pmd_large(pmd_t pte)
 /* NOTE: when predicate huge page, consider also pmd_devmap, or use pmd_large */
 static inline int pmd_trans_huge(pmd_t pmd)
 {
-	return (pmd_val(pmd) & (_PAGE_PSE|_PAGE_DEVMAP)) == _PAGE_PSE;
+	return (pmd_val(pmd) & (_PAGE_PSE|_PAGE_DEVMAP|_PAGE_DMEM)) == _PAGE_PSE;
 }
 
 #ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
@@ -276,6 +276,14 @@ static inline int has_transparent_hugepage(void)
 	return boot_cpu_has(X86_FEATURE_PSE);
 }
 
+#ifdef CONFIG_ARCH_HAS_PTE_DMEM
+static inline int pmd_special(pmd_t pmd)
+{
+	return (pmd_val(pmd) & (_PAGE_SPECIAL | _PAGE_DMEM)) ==
+		(_PAGE_SPECIAL | _PAGE_DMEM);
+}
+#endif
+
 #ifdef CONFIG_ARCH_HAS_PTE_DEVMAP
 static inline int pmd_devmap(pmd_t pmd)
 {
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 45d4c4a3e519..1fe8546c0a7c 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -1134,6 +1134,11 @@ static inline pmd_t pmd_mkdmem(pmd_t pmd)
 {
 	return pmd;
 }
+
+static inline int pmd_special(pmd_t pmd)
+{
+	return 0;
+}
 #endif
 
 #ifndef pmd_read_atomic
-- 
2.28.0