Re: [PATCH v2] mm: fix the memory leak after collapsing the huge page fails (fwd)

[Julia Lawall <julia.lawall@lip6.fr>]

On Wed, 10 May 2017, Vlastimil Babka wrote:

> On 05/10/2017 08:25 AM, Julia Lawall wrote:
> >
> >
> > On Wed, 10 May 2017, zhong jiang wrote:
> >
> >> On 2017/5/9 23:43, Julia Lawall wrote:
> >>> Hello,
> >>>
> >>> I don't know if there is a bug here, but it could e worth checking on.  If
> >>> the loop on line 1481 is executed, page will not be NULL at the out label
> >>> on line 1560.  Instead it will have a dummy value.  Perhaps the value of
> >>> result keeps the if at the out label from being taken.
> >>>
> >>> julia
> >>   Hi, Julia
> >>
> >>    it has no memory leak.  so my initial thought is not correct. but I do not know you mean.
> >>    The page is local variable.  it aybe a  dummy value. but it should not cause any issue.
> >>    is it right? or I miss something.
> >
> > I had first been thinking that the if branch was referencing page.  In
> > that case, if page were a dummy value, then there could be a problem.  But
> > now I see that the branch does not refer to page.  So the question is
> > just, if the loop on lines 1481-1491 is executed, is it correct to execute
> > the code put_page(new_page)?  Or will result be SCAN_SUCCEEDED in that
> > case?
>
> That loop is under "if (result == SCAN_SUCCEED)", so yeah. It also ends
> with "*hpage = NULL;", so the put_page(hpage) in khugepaged_do_scan()
> won't apply. I see no problem besides the very non-obvious code :/

OK, thanks for the clarification.

julia

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