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

[Yasuaki Ishimatsu]

(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.

Thanks,
Yasuaki Ishimatsu

> Thanks,
> -Toshi
>
> > +				if (pgd_none(*pgd_ref) && !pgd_none(*pgd))
> > +					pgd_clear(pgd);
> > +			} else {
> > +				if (pgd_none(*pgd))
> > +					set_pgd(pgd, *pgd_ref);
> > +			}
> > +
> >   			spin_unlock(pgt_lock);
> >   		}


--
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/