linux-kernel - [PATCH 5/8] mm: make clear_huge_page cache clear only around the fault address

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Date:	Fri, 16 Aug 2013 09:34:01 -0500
From:	Alex Thorlton <athorlton@....com>
To:	linux-kernel@...r.kernel.org
Cc:	Alex Thorlton <athorlton@....com>, Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	"Eric W . Biederman" <ebiederm@...ssion.com>,
	Sedat Dilek <sedat.dilek@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Dave Jones <davej@...hat.com>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	"Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
	David Howells <dhowells@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Al Viro <viro@...iv.linux.org.uk>,
	Oleg Nesterov <oleg@...hat.com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Kees Cook <keescook@...omium.org>, Robin Holt <holt@....com>
Subject: [PATCH 5/8] mm: make clear_huge_page cache clear only around the fault address

---
 mm/memory.c | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/mm/memory.c b/mm/memory.c
index 69a5a38..17d61f0 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4231,18 +4231,35 @@ EXPORT_SYMBOL(might_fault);
 #endif
 
 #if defined(CONFIG_TRANSPARENT_HUGEPAGE) || defined(CONFIG_HUGETLBFS)
+
+#ifndef ARCH_HAS_USER_NOCACHE
+#define ARCH_HAS_USER_NOCACHE 0
+#endif
+
+#if ARCH_HAS_USER_NOCACHE == 0
+#define clear_user_highpage_nocache clear_user_highpage
+#endif
+
 static void clear_gigantic_page(struct page *page,
 				unsigned long addr,
 				unsigned int pages_per_huge_page)
 {
 	int i;
 	struct page *p = page;
+	unsigned long vaddr;
+	unsigned long haddr = addr & HPAGE_PMD_MASK;
+	int target = (addr - haddr) >> PAGE_SHIFT;
 
 	might_sleep();
+	vaddr = haddr;
 	for (i = 0; i < pages_per_huge_page;
 	     i++, p = mem_map_next(p, page, i)) {
 		cond_resched();
-		clear_user_highpage(p, addr + i * PAGE_SIZE);
+		vaddr = haddr + i*PAGE_SIZE;
+		if (!ARCH_HAS_USER_NOCACHE  || i == target)
+			clear_user_highpage(p, vaddr);
+		else
+			clear_user_highpage_nocache(p, vaddr);
 	}
 }
 void clear_huge_page(struct page *page,
@@ -4250,6 +4267,8 @@ void clear_huge_page(struct page *page,
 {
 	int i;
 	unsigned long haddr = addr & HPAGE_PMD_MASK;
+	unsigned long vaddr;
+	int target = (addr - haddr) >> PAGE_SHIFT;
 
 	if (unlikely(pages_per_huge_page > MAX_ORDER_NR_PAGES)) {
 		clear_gigantic_page(page, haddr, pages_per_huge_page);
@@ -4257,9 +4276,14 @@ void clear_huge_page(struct page *page,
 	}
 
 	might_sleep();
+	vaddr = haddr;
 	for (i = 0; i < pages_per_huge_page; i++) {
 		cond_resched();
-		clear_user_highpage(page + i, haddr + i * PAGE_SIZE);
+		vaddr = haddr + i*PAGE_SIZE;
+		if (!ARCH_HAS_USER_NOCACHE || i == target)
+			clear_user_highpage(page + i, vaddr);
+		else
+			clear_user_highpage_nocache(page + i, vaddr);
 	}
 }
 
-- 
1.7.12.4

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