linux-kernel - [PATCH 1/2] x86,mem-hotplug: pass sync_global_pgds() a correct argument in remove

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Date:	Wed, 18 Jun 2014 15:37:18 +0900
From:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To:	<akpm@...ux-foundation.org>, <tglx@...utronix.de>,
	<mingo@...hat.com>, <hpa@...or.com>
CC:	<tangchen@...fujitsu.com>, <toshi.kani@...com>,
	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>,
	<x86@...nel.org>, <guz.fnst@...fujitsu.com>,
	<zhangyanfei@...fujitsu.com>
Subject: [PATCH 1/2] x86,mem-hotplug: pass sync_global_pgds() a correct argument
 in remove_pagetable()

remove_pagetable() gets start argument and passes the argument to
sync_global_pgds(). In this case, the argument must not be modified.
If the argument is modified and passed to sync_global_pgds(),
sync_global_pgds() does not correctly synchronize PGD to PGD entries
of all processes MM since synchronized range of memory [start, end]
is wrong.

Unfortunately the start argument is modified in remove_pagetable().
So this patch fixes the issue.

Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>

---
 arch/x86/mm/init_64.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index df1a992..a5b245d 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -975,19 +975,20 @@ static void __meminit
 remove_pagetable(unsigned long start, unsigned long end, bool direct)
 {
 	unsigned long next;
+	unsigned long addr;
 	pgd_t *pgd;
 	pud_t *pud;
 	bool pgd_changed = false;

-	for (; start < end; start = next) {
-		next = pgd_addr_end(start, end);
+	for (addr = start; addr < end; addr = next) {
+		next = pgd_addr_end(addr, end);

-		pgd = pgd_offset_k(start);
+		pgd = pgd_offset_k(addr);
 		if (!pgd_present(*pgd))
 			continue;

 		pud = (pud_t *)pgd_page_vaddr(*pgd);
-		remove_pud_table(pud, start, next, direct);
+		remove_pud_table(pud, addr, next, direct);
 		if (free_pud_table(pud, pgd))
 			pgd_changed = true;
 	}

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