Messages in this thread | | | Date | Wed, 24 Feb 2021 10:43:30 +0100 | From | Michal Hocko <> | Subject | Re: [PATCH] hugetlb: fix uninitialized subpool pointer |
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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.
> 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
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