linux-kernel - [PATCH 4/9] vmalloc: use plain pte

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Message-Id: <6b78f2a4c559d86e940c8f6cd82b2a027caa0b09.1292450600.git.jeremy.fitzhardinge@citrix.com>
Date:	Wed, 15 Dec 2010 14:19:50 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Haavard Skinnemoen <hskinnemoen@...el.com>,
	Linux-MM <linux-mm@...ck.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Nick Piggin <npiggin@...nel.dk>,
	Xen-devel <xen-devel@...ts.xensource.com>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Subject: [PATCH 4/9] vmalloc: use plain pte_clear() for unmaps

From: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>

ptep_get_and_clear() is potentially moderately expensive (at least
an atomic operation, or potentially a trap-and-fault when virtualized)
so use a plain pte_clear().

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
---
 mm/vmalloc.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index e95980a..67ce748 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -39,8 +39,9 @@ static void vunmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end)
 
 	pte = pte_offset_kernel(pmd, addr);
 	do {
-		pte_t ptent = ptep_get_and_clear(&init_mm, addr, pte);
+		pte_t ptent = *pte;
 		WARN_ON(!pte_none(ptent) && !pte_present(ptent));
+		pte_clear(&init_mm, addr, pte);
 	} while (pte++, addr += PAGE_SIZE, addr != end);
 }
 
-- 
1.7.3.3

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