Re: [PATCH] memory-hotplug: Clear pgdat which is allocated by bootmem in try_offline_node()

[Yasuaki Ishimatsu]

(2014/10/22 1:56), Toshi Kani wrote:
> On Mon, 2014-10-20 at 19:05 +0900, Yasuaki Ishimatsu wrote:
>   :
> > When hot removing memory, pgdat is set to 0 in try_offline_node().
> > But if the pgdat is allocated by bootmem allocator, the clearing
> > step is skipped. And when hot adding the same memory, the uninitialized
> > pgdat is reused. But free_area_init_node() chacks wether pgdat is set

> s/chacks/checks

I'll update it.

> > to zero. As a result, free_area_init_node() hits WARN_ON().
> >
> > This patch clears pgdat which is allocated by bootmem allocator
> > in try_offline_node().
> >
> > Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
> > CC: Zhang Zhen <zhenzhang.zhang@xxxxxxxxxx>
> > CC: Wang Nan <wangnan0@xxxxxxxxxx>
> > CC: Tang Chen <tangchen@xxxxxxxxxxxxxx>
> > CC: Toshi Kani <toshi.kani@xxxxxx>
> > CC: Dave Hansen <dave.hansen@xxxxxxxxx>
> > CC: David Rientjes <rientjes@xxxxxxxxxx>
> >
> > ---
> >   mm/memory_hotplug.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> > index 29d8693..7649f7c 100644
> > --- a/mm/memory_hotplug.c
> > +++ b/mm/memory_hotplug.c
> > @@ -1943,7 +1943,7 @@ void try_offline_node(int nid)
> >
> >   	if (!PageSlab(pgdat_page) && !PageCompound(pgdat_page))
> >   		/* node data is allocated from boot memory */
> > -		return;
> > +		goto out;

> Do we still need this if-statement?  That is, do we have to skip the
> for-loop below even though it checks with is_vmalloc_addr()?

You are right. The if-statement is not necessary. So the issue can be
fixed by just removing the if-statement.

I'll post updated patch soon.

Thanks,
Yasuaki Ishimatsu

> Thanks,
> -Toshi
>
>
> >   	/* free waittable in each zone */
> >   	for (i = 0; i < MAX_NR_ZONES; i++) {
> > @@ -1957,6 +1957,7 @@ void try_offline_node(int nid)
> >   			vfree(zone->wait_table);
> >   	}
> >
> > +out:
> >   	/*
> >   	 * Since there is no way to guarentee the address of pgdat/zone is not
> >   	 * on stack of any kernel threads or used by other kernel objects


--
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/