linux-kernel - [PATCH, RFC 08/10] x86, thp: remove remove infrastructure for handling splitting PMDs

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Message-Id: <1402329861-7037-9-git-send-email-kirill.shutemov@linux.intel.com>
Date:	Mon,  9 Jun 2014 19:04:19 +0300
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>
Cc:	Dave Hansen <dave.hansen@...el.com>,
	Hugh Dickins <hughd@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Rik van Riel <riel@...hat.com>,
	Vlastimil Babka <vbabka@...e.cz>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCH, RFC 08/10] x86, thp: remove remove infrastructure for handling splitting PMDs

With new refcounting we don't need to mark PMDs splitting. Let's drop
code to handle this.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 arch/x86/include/asm/pgtable.h       |  9 ---------
 arch/x86/include/asm/pgtable_types.h |  2 --
 arch/x86/mm/gup.c                    | 13 +------------
 arch/x86/mm/pgtable.c                | 14 --------------
 4 files changed, 1 insertion(+), 37 deletions(-)

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 0ec056012618..1c60bfca6b65 100644
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -158,11 +158,6 @@ static inline int pmd_large(pmd_t pte)
 }
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
-static inline int pmd_trans_splitting(pmd_t pmd)
-{
-	return pmd_val(pmd) & _PAGE_SPLITTING;
-}
-
 static inline int pmd_trans_huge(pmd_t pmd)
 {
 	return pmd_val(pmd) & _PAGE_PSE;
@@ -799,10 +794,6 @@ extern int pmdp_clear_flush_young(struct vm_area_struct *vma,
 				  unsigned long address, pmd_t *pmdp);
 
 
-#define __HAVE_ARCH_PMDP_SPLITTING_FLUSH
-extern void pmdp_splitting_flush(struct vm_area_struct *vma,
-				 unsigned long addr, pmd_t *pmdp);
-
 #define __HAVE_ARCH_PMD_WRITE
 static inline int pmd_write(pmd_t pmd)
 {
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index f216963760e5..7d8066d1d9c0 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -22,7 +22,6 @@
 #define _PAGE_BIT_PAT_LARGE	12	/* On 2MB or 1GB pages */
 #define _PAGE_BIT_SPECIAL	_PAGE_BIT_SOFTW1
 #define _PAGE_BIT_CPA_TEST	_PAGE_BIT_SOFTW1
-#define _PAGE_BIT_SPLITTING	_PAGE_BIT_SOFTW2 /* only valid on a PSE pmd */
 #define _PAGE_BIT_IOMAP		_PAGE_BIT_SOFTW2 /* flag used to indicate IO mapping */
 #define _PAGE_BIT_HIDDEN	_PAGE_BIT_SOFTW3 /* hidden by kmemcheck */
 #define _PAGE_BIT_SOFT_DIRTY	_PAGE_BIT_SOFTW3 /* software dirty tracking */
@@ -57,7 +56,6 @@
 #define _PAGE_PAT_LARGE (_AT(pteval_t, 1) << _PAGE_BIT_PAT_LARGE)
 #define _PAGE_SPECIAL	(_AT(pteval_t, 1) << _PAGE_BIT_SPECIAL)
 #define _PAGE_CPA_TEST	(_AT(pteval_t, 1) << _PAGE_BIT_CPA_TEST)
-#define _PAGE_SPLITTING	(_AT(pteval_t, 1) << _PAGE_BIT_SPLITTING)
 #define __HAVE_ARCH_PTE_SPECIAL
 
 #ifdef CONFIG_KMEMCHECK
diff --git a/arch/x86/mm/gup.c b/arch/x86/mm/gup.c
index 754bca23ec1b..b65b3fc4494a 100644
--- a/arch/x86/mm/gup.c
+++ b/arch/x86/mm/gup.c
@@ -157,18 +157,7 @@ static int gup_pmd_range(pud_t pud, unsigned long addr, unsigned long end,
 		pmd_t pmd = *pmdp;
 
 		next = pmd_addr_end(addr, end);
-		/*
-		 * The pmd_trans_splitting() check below explains why
-		 * pmdp_splitting_flush has to flush the tlb, to stop
-		 * this gup-fast code from running while we set the
-		 * splitting bit in the pmd. Returning zero will take
-		 * the slow path that will call wait_split_huge_page()
-		 * if the pmd is still in splitting state. gup-fast
-		 * can't because it has irq disabled and
-		 * wait_split_huge_page() would never return as the
-		 * tlb flush IPI wouldn't run.
-		 */
-		if (pmd_none(pmd) || pmd_trans_splitting(pmd))
+		if (pmd_none(pmd))
 			return 0;
 		if (unlikely(pmd_large(pmd))) {
 			/*
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 6fb6927f9e76..336847f5719e 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -429,20 +429,6 @@ int pmdp_clear_flush_young(struct vm_area_struct *vma,
 
 	return young;
 }
-
-void pmdp_splitting_flush(struct vm_area_struct *vma,
-			  unsigned long address, pmd_t *pmdp)
-{
-	int set;
-	VM_BUG_ON(address & ~HPAGE_PMD_MASK);
-	set = !test_and_set_bit(_PAGE_BIT_SPLITTING,
-				(unsigned long *)pmdp);
-	if (set) {
-		pmd_update(vma->vm_mm, address, pmdp);
-		/* need tlb flush only to serialize against gup-fast */
-		flush_tlb_range(vma, address, address + HPAGE_PMD_SIZE);
-	}
-}
 #endif
 
 /**
-- 
2.0.0.rc4

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