Re: [KJ PATCH] Replacing memset(<addr>,0,PAGE_SIZE) with clear_page() in kernel/kexec.c

[ebiederm@xmission.com (Eric W. Biederman)]

"Satyam Sharma" <satyam.sharma@gmail.com> writes:

> On 5/8/07, Pekka Enberg <penberg@cs.helsinki.fi> wrote:
>> Shani Moideen wrote:
>> > >                 ptr = kmap(page);
>> > > -               memset(ptr, 0, PAGE_SIZE);
>> > > +               clear_page(ptr);
>>
>> On 5/8/07, Michael Tokarev <mjt@tls.msk.ru> wrote:
>> > I wonder if it's worth to invent kzmap() or something like that... ;)
>>
>> I am counting 59 kmap + memset pairs in the kernel, so perhaps it is
>> worth it to reduce kernel text size.
>
> Stuff of the sort already exists. Look for clear_highpage(),
> clear_user_highpage() and memclear_highpage_flush (recently renamed to
> zero_user_page, see -mm). But they all use kmap_atomic() -- kmap()
> variants would have to be added. Also, they're all inlines, so I'm not
> sure you'd be able to cut down text size, but still getting rid of
> open-coding is always good.

In this instance a clear_page variant should be ok.  The combined
variants are likely not because I use the mapping after it is cleared.

Eric



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