Messages in this thread | | | Date | Fri, 19 Jul 2013 10:08:03 +0800 | Subject | Re: hugepage related lockdep trace. | From | Hillf Danton <> |
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On Fri, Jul 19, 2013 at 1:42 AM, Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> wrote: > Minchan Kim <minchan@kernel.org> writes: >> IMHO, it's a false positive because i_mmap_mutex was held by kswapd >> while one in the middle of fault path could be never on kswapd context. >> >> It seems lockdep for reclaim-over-fs isn't enough smart to identify >> between background and direct reclaim. >> >> Wait for other's opinion. > > Is that reasoning correct ?. We may not deadlock because hugetlb pages > cannot be reclaimed. So the fault path in hugetlb won't end up > reclaiming pages from same inode. But the report is correct right ? > > > Looking at the hugetlb code we have in huge_pmd_share > > out: > pte = (pte_t *)pmd_alloc(mm, pud, addr); > mutex_unlock(&mapping->i_mmap_mutex); > return pte; > > I guess we should move that pmd_alloc outside i_mmap_mutex. Otherwise > that pmd_alloc can result in a reclaim which can call shrink_page_list ? > Hm, can huge pages be reclaimed, say by kswapd currently?
> Something like ? > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 83aff0a..2cb1be3 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -3266,8 +3266,8 @@ pte_t *huge_pmd_share(struct mm_struct *mm, unsigned long addr, pud_t *pud) > put_page(virt_to_page(spte)); > spin_unlock(&mm->page_table_lock); > out: > - pte = (pte_t *)pmd_alloc(mm, pud, addr); > mutex_unlock(&mapping->i_mmap_mutex); > + pte = (pte_t *)pmd_alloc(mm, pud, addr); > return pte; > } >
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