From: Muchun Song <songmuchun@bytedance.com>
To: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>,
LKML <linux-kernel@vger.kernel.org>,
Linux Memory Management List <linux-mm@kvack.org>,
Gerald Schaefer <gerald.schaefer@linux.ibm.com>,
Oscar Salvador <osalvador@suse.de>,
Heiko Carstens <hca@linux.ibm.com>,
Sven Schnelle <svens@linux.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [External] Re: [PATCH] hugetlb: fix uninitialized subpool pointer
Date: Wed, 24 Feb 2021 19:10:42 +0800 [thread overview]
Message-ID: <CAMZfGtXBKvz6wg-N5LpwMcensRiiwnKYa5XDnGi2ueBMa0Q+NA@mail.gmail.com> (raw)
In-Reply-To: <YDYfwuSjFsa8iWTT@dhcp22.suse.cz>
On Wed, Feb 24, 2021 at 5:43 PM Michal Hocko <mhocko@suse.com> wrote:
>
> On Tue 23-02-21 13:55:44, Mike Kravetz wrote:
> > Gerald Schaefer reported a panic on s390 in hugepage_subpool_put_pages()
> > with linux-next 5.12.0-20210222.
> > Call trace:
> > hugepage_subpool_put_pages.part.0+0x2c/0x138
> > __free_huge_page+0xce/0x310
> > alloc_pool_huge_page+0x102/0x120
> > set_max_huge_pages+0x13e/0x350
> > hugetlb_sysctl_handler_common+0xd8/0x110
> > hugetlb_sysctl_handler+0x48/0x58
> > proc_sys_call_handler+0x138/0x238
> > new_sync_write+0x10e/0x198
> > vfs_write.part.0+0x12c/0x238
> > ksys_write+0x68/0xf8
> > do_syscall+0x82/0xd0
> > __do_syscall+0xb4/0xc8
> > system_call+0x72/0x98
> >
> > This is a result of the change which moved the hugetlb page subpool
> > pointer from page->private to page[1]->private. When new pages are
> > allocated from the buddy allocator, the private field of the head
> > page will be cleared, but the private field of subpages is not modified.
> > Therefore, old values may remain.
>
> Very interesting. I have expected that the page->private would be in a
> reasonable state when allocated. On the other hand hugetlb doesn't do
> __GFP_COMP so tail pages are not initialized by the allocator.
It seems that the buddy allocator does not initialize the private field
of the tail page even when we specify __GFP_COMP.
>
> > Fix by initializing hugetlb page subpool pointer in prep_new_huge_page().
> >
> > Fixes: f1280272ae4d ("hugetlb: use page.private for hugetlb specific page flags")
>
> This is not a stable sha to refer to as it comes from linux next.
>
> > Reported-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
> > Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
>
> Acked-by: Michal Hocko <mhocko@suse.com>
>
> I think this would be worth a separate patch rather than having it
> folded into the original patch. Thi is really subtle.
>
> > ---
> > mm/hugetlb.c | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > index c232cb67dda2..7ae5c18c98a7 100644
> > --- a/mm/hugetlb.c
> > +++ b/mm/hugetlb.c
> > @@ -1465,6 +1465,7 @@ static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)
> > {
> > INIT_LIST_HEAD(&page->lru);
> > set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
> > + hugetlb_set_page_subpool(page, NULL);
> > set_hugetlb_cgroup(page, NULL);
> > set_hugetlb_cgroup_rsvd(page, NULL);
> > spin_lock(&hugetlb_lock);
> > --
> > 2.29.2
> >
>
> --
> Michal Hocko
> SUSE Labs
next prev parent reply other threads:[~2021-02-24 11:11 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-23 21:55 [PATCH] hugetlb: fix uninitialized subpool pointer Mike Kravetz
2021-02-23 22:45 ` Oscar Salvador
2021-02-23 22:55 ` Mike Kravetz
2021-02-23 22:58 ` Oscar Salvador
2021-02-23 23:21 ` Mike Kravetz
2021-02-24 0:27 ` Mike Kravetz
2021-02-24 3:12 ` [External] " Muchun Song
2021-02-24 9:43 ` Michal Hocko
2021-02-24 11:10 ` Muchun Song [this message]
2021-02-24 11:36 ` [External] " Michal Hocko
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