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Message-ID: <20170501145258.GI2649@x1>
Date: Mon, 1 May 2017 22:52:58 +0800
From: Baoquan He <bhe@...hat.com>
To: Dan Williams <dan.j.williams@...el.com>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
Kees Cook <keescook@...omium.org>,
Thomas Garnier <thgarnie@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Yasuaki Ishimatsu <yasu.isimatu@...il.com>,
Jinbum Park <jinb.park7@...il.com>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Yinghai Lu <yinghai@...nel.org>, Dave Young <dyoung@...hat.com>
Subject: Re: [PATCH] x86/mm: Fix incorrect for loop count calculation in
sync_global_pgds
On 05/01/17 at 07:40am, Dan Williams wrote:
> On Mon, May 1, 2017 at 4:41 AM, Baoquan He <bhe@...hat.com> wrote:
> > arch/x86/mm/init_64.c | 6 ++++--
> > 1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> > index 15173d3..dbf4f00 100644
> > --- a/arch/x86/mm/init_64.c
> > +++ b/arch/x86/mm/init_64.c
> > @@ -94,12 +94,14 @@ __setup("noexec32=", nonx32_setup);
> > */
> > void sync_global_pgds(unsigned long start, unsigned long end)
> > {
> > - unsigned long address;
> > + unsigned long address, address_next;
> >
> > - for (address = start; address <= end; address += PGDIR_SIZE) {
> > + for (address = start; address <= end; address = address_next) {
> > const pgd_t *pgd_ref = pgd_offset_k(address);
> > struct page *page;
> >
> > + address_next = (address & PGDIR_MASK) + PGDIR_SIZE;
> > +
>
> Let's change this to put the next address calculation in the for loop
> directly and use the ALIGN macro. Something like:
>
> for (address = start; address <= end; address = ALIGN(address + 1, PGDIR_SIZE))
Hi Dan,
Good idea!
Do you think below change is OK for you? Taking out the initialization
can make the for loop line be shorter than 80 char.
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 15173d3..0840311 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -94,12 +94,14 @@ __setup("noexec32=", nonx32_setup);
*/
void sync_global_pgds(unsigned long start, unsigned long end)
{
- unsigned long address;
+ unsigned long address = start;
- for (address = start; address <= end; address += PGDIR_SIZE) {
+ for (; address <= end; address = ALIGN(address + 1, PGDIR_SIZE))
{
const pgd_t *pgd_ref = pgd_offset_k(address);
struct page *page;
+ address_next = (address & PGDIR_MASK) + PGDIR_SIZE;
+
if (pgd_none(*pgd_ref))
continue;
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