linux-kernel - Re: [PATCH v2] x86/mm: Fix incorrect for loop count calculation in sync_global

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Date:   Mon, 1 May 2017 15:08:00 -0700
From:   Yinghai Lu <yinghai@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Baoquan He <bhe@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        "the arch/x86 maintainers" <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>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Young <dyoung@...hat.com>
Subject: Re: [PATCH v2] x86/mm: Fix incorrect for loop count calculation in sync_global_pgds

On Mon, May 1, 2017 at 12:32 PM, Ingo Molnar <mingo@...nel.org> wrote:
>
> * Baoquan He <bhe@...hat.com> wrote:
>
>>  arch/x86/mm/init_64.c | 4 +++-
>>  1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
>> index 15173d3..dfa9edb 100644
>> --- a/arch/x86/mm/init_64.c
>> +++ b/arch/x86/mm/init_64.c
>> @@ -96,7 +96,9 @@ void sync_global_pgds(unsigned long start, unsigned long end)
>>  {
>>       unsigned long address;
>>
>> -     for (address = start; address <= end; address += PGDIR_SIZE) {
>> +     for (address = start; address <= end;
>> +          address = ALIGN(address + 1, PGDIR_SIZE)) {
>> +
>>               const pgd_t *pgd_ref = pgd_offset_k(address);
>>               struct page *page;
>
> This patch does not apply cleanly to tip:master.
>
> You can avoid the col80 problems by renaming 'address' to the canonical 'addr'
> name, the loop will become:
>
>         for (addr = start; addr <= end; addr = ALIGN(addr + 1, PGDIR_SIZE)) {
>
> ... which fits into 80 cols.

would be more readable to make sync_global_pgds() loop is more like that in
kernel_physical_mapping_init() ?

        vaddr_start = vaddr;

        for (; vaddr < vaddr_end; vaddr = vaddr_next) {
...
                vaddr_next = (vaddr & PGDIR_MASK) + PGDIR_SIZE;

Yinghai