Re: [PATCH 2/2] x86,mem-hotplug: modify PGD entry when removing memory

[Yasuaki Ishimatsu]

(2014/06/25 0:12), Toshi Kani wrote:
> On Tue, 2014-06-24 at 09:31 +0900, Yasuaki Ishimatsu wrote:
> > (2014/06/21 3:30), Toshi Kani wrote:
> > > On Wed, 2014-06-18 at 15:38 +0900, Yasuaki Ishimatsu wrote:
> > >    :
> > > > @@ -186,7 +186,12 @@ void sync_global_pgds(unsigned long start, unsigned long end)
> > > >    		const pgd_t *pgd_ref = pgd_offset_k(address);
> > > >    		struct page *page;
> > > >
> > > > -		if (pgd_none(*pgd_ref))
> > > > +		/*
> > > > +		 * When it is called after memory hot remove, pgd_none()
> > > > +		 * returns true. In this case (removed == 1), we must clear
> > > > +		 * the PGD entries in the local PGD level page.
> > > > +		 */
> > > > +		if (pgd_none(*pgd_ref) && !removed)
> > > >    			continue;
> > > >
> > > >    		spin_lock(&pgd_lock);
> > > > @@ -199,12 +204,18 @@ void sync_global_pgds(unsigned long start, unsigned long end)
> > > >    			pgt_lock = &pgd_page_get_mm(page)->page_table_lock;
> > > >    			spin_lock(pgt_lock);
> > > >
> > > > -			if (pgd_none(*pgd))
> > > > -				set_pgd(pgd, *pgd_ref);
> > > > -			else
> >
> > > > +			if (!pgd_none(*pgd_ref) && !pgd_none(*pgd))
> > > >    				BUG_ON(pgd_page_vaddr(*pgd)
> > > >    				       != pgd_page_vaddr(*pgd_ref));
> > > >
> > > > +			if (removed) {
> > >
> > > Shouldn't this condition be "else if"?
> >
> > The first if sentence checks whether PGDs hit to BUG_ON. And the second
> > if sentence checks whether the function was called after hot-removing memory.
> > I think that the first if sentence and the second if sentence check different
> > things. So I think the condition should be "if" sentence.
>
> When the 1st if sentence is true, you have no additional operation and
> the 2nd if sentence is redundant. But I agree that the two ifs can be
> logically separated. So:

> Acked-by: Toshi Kani <toshi.kani@xxxxxx>

Thank you for your review.

Thanks,
Yasuaki Ishimatsu

> Thanks,
> -Toshi


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/