Re: [Bug] Reproducible data corruption on i5-3340M: Please revert 53a59fc67!

[Michal Hocko <mhocko@suse.cz>]

On Thu 15-08-13 16:53:32, Michal Hocko wrote:
> On Thu 15-08-13 16:46:00, Michal Hocko wrote:
> > On Thu 15-08-13 15:40:31, Michal Hocko wrote:
> > > On Thu 15-08-13 05:02:31, Linus Torvalds wrote:
> > > > On Thu, Aug 15, 2013 at 2:25 AM, Ben Tebulin <tebulin@googlemail.com> wrote:
> > > > >
> > > > > I just cherry-picked e6c495a96ce0 into 3.9.11 and 3.7.10.
> > > > > Unfortunately this does _not resolve_ my issue (too good to be true) :-(
> > > > 
> > > > Ho humm. I've found at least one other bug, but that one only affects
> > > > hugepages. Do you perhaps have transparent hugepages enabled? But even
> > > > then it looks quite unlikely.
> > > 
> > > __unmap_hugepage_range is hugetlb not THP if you had that one in mind.
> > > And yes, it doesn't set the range which sounds buggy.
> > 
> > Or, did you mean tlb_remove_page called from zap_huge_pmd? That one
> > should be safe as tlb_remove_pmd_tlb_entry sets need_flush and that
> > means that the full range is flushed.
> 
> Dohh... But we need need_flush_all and that is not set here. So this
> really looks buggy.

This is a really dumb attempt to fix this but maybe it is worth trying
to confirm we are really seeing this problem. It still flushes too much
potentially but I am not sure how to find out the proper start...
Will think about it more.
---
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index a92012a..a16f452 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1381,7 +1381,11 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 			VM_BUG_ON(!PageHead(page));
 			tlb->mm->nr_ptes--;
 			spin_unlock(&tlb->mm->page_table_lock);
-			tlb_remove_page(tlb, page);
+			if (!__tlb_remove_page(tlb, page)) {
+				tlb->start = 0;
+				tlb->end = addr + HPAGE_SIZE;
+				tlb_flush_mmu(tlb);
+			}
 		}
 		pte_free(tlb->mm, pgtable);
 		ret = 1;
-- 
Michal Hocko
SUSE Labs

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