On Wed, Sep 07, 2022 at 02:39:02PM +0200, David Hildenbrand wrote:
> On 07.09.22 14:11, Naoya Horiguchi wrote:
...
> > ---
> > From 8a5c284df732943065d23838090d15c94cd10395 Mon Sep 17 00:00:00 2001
> > From: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
> > Date: Wed, 7 Sep 2022 20:58:44 +0900
> > Subject: [PATCH] mm/huge_memory: use pfn_to_online_page() in
> > split_huge_pages_all()
> >
> > NULL pointer dereference is triggered when calling thp split via debugfs
> > on the system with offlined memory blocks. With debug option enabled,
> > the following kernel messages are printed out:
> >
> > page:00000000467f4890 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x121c000
> > flags: 0x17fffc00000000(node=0|zone=2|lastcpupid=0x1ffff)
> > raw: 0017fffc00000000 0000000000000000 dead000000000122 0000000000000000
> > raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
> > page dumped because: unmovable page
> > page:000000007d7ab72e is uninitialized and poisoned
> > page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
> > ------------[ cut here ]------------
> > kernel BUG at include/linux/mm.h:1248!
> > invalid opcode: 0000 [#1] PREEMPT SMP PTI
> > CPU: 16 PID: 20964 Comm: bash Tainted: G I 6.0.0-rc3-foll-numa+ #41
> > ...
> > RIP: 0010:split_huge_pages_write+0xcf4/0xe30
> >
> > This shows that page_to_nid() in page_zone() is unexpectedly called for an
> > offlined memmap.
> >
> > Use pfn_to_online_page() to get struct page in PFN walker.
> >
> > Fixes: 49071d436b51 ("thp: add debugfs handle to split all huge pages")
> > Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
>
> Feel free to use
>
> Co-developed-by: David Hildenbrand <david@xxxxxxxxxx>
> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Sure, I'll add these.
> instead
>
> > Signed-off-by: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
> > Cc: <stable@xxxxxxxxxxxxxxx>
> > ---
> > mm/huge_memory.c | 7 ++-----
> > 1 file changed, 2 insertions(+), 5 deletions(-)
> >
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index 5fa2ba86dae4..03149a8f46f9 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -2894,11 +2894,8 @@ static void split_huge_pages_all(void)
> > max_zone_pfn = zone_end_pfn(zone);
> > for (pfn = zone->zone_start_pfn; pfn < max_zone_pfn; pfn++) {
> > int nr_pages;
>
> Add an empty line here please, while at it.
Added it.
> > - if (!pfn_valid(pfn))
> > - continue;
> > -
> > - page = pfn_to_page(pfn);
> > - if (!get_page_unless_zero(page))
> > + page = pfn_to_online_page(pfn);
> > + if (!page || !get_page_unless_zero(page))
> > continue;
> > if (zone != page_zone(page))
>
> Can you send the patch "officially" as well? Thanks
Yes, I'll send this later in the normal patch submission manner.
Thanks,
Naoya Horiguchi
