On Tue, 19 Jan 2016, Kirill A. Shutemov wrote:
> > A newly added tracepoint in the hugepage code uses a variable in the
> > error handling that is not initialized at that point:
> >
> > include/trace/events/huge_memory.h:81:230: error: 'isolated' may be used uninitialized in this function [-Werror=maybe-uninitialized]
> >
> > The result is relatively harmless, as the trace data will in rare
> > cases contain incorrect data.
> >
> > This works around the problem by adding an explicit initialization.
> >
> > Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> > Fixes: 7d2eba0557c1 ("mm: add tracepoint for scanning pages")
>
> There's the same patch in mm tree, but it got lost on the way to Linus'
> tree:
>
> https://ozlabs.org/~akpm/mmots/broken-out/mm-make-optimistic-check-for-swapin-readahead-fix.patch
>
> Andrew?
>
Looks like the patch got the wrong title,
mm-make-optimistic-check-for-swapin-readahead-fix.patch, since the subject
is "khugepaged: avoid usage of uninitialized variable 'isolated'".
Anyway, feel free to add
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
to either patch.
> >
> > diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> > index b2db98136af9..bb3b763b1829 100644
> > --- a/mm/huge_memory.c
> > +++ b/mm/huge_memory.c
> > @@ -2320,7 +2320,7 @@ static void collapse_huge_page(struct mm_struct *mm,
> > pgtable_t pgtable;
> > struct page *new_page;
> > spinlock_t *pmd_ptl, *pte_ptl;
> > - int isolated, result = 0;
> > + int isolated = 0, result = 0;
> > unsigned long hstart, hend;
> > struct mem_cgroup *memcg;
> > unsigned long mmun_start; /* For mmu_notifiers */
> >
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