Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1588805

Re: [PATCH V5 2/6] mm: don't assume anonymous pages have SwapBacked flag

Show all headers | View raw

On Mon 27-02-17 08:10:24, Shaohua Li wrote:
> On Mon, Feb 27, 2017 at 03:35:34PM +0100, Michal Hocko wrote:
> > On Fri 24-02-17 13:31:45, Shaohua Li wrote:
> > > There are a few places the code assumes anonymous pages should have
> > > SwapBacked flag set. MADV_FREE pages are anonymous pages but we are
> > > going to add them to LRU_INACTIVE_FILE list and clear SwapBacked flag
> > > for them. The assumption doesn't hold any more, so fix them.
> > > 
> > > Cc: Michal Hocko <mhocko@suse.com>
> > > Cc: Minchan Kim <minchan@kernel.org>
> > > Cc: Hugh Dickins <hughd@google.com>
> > > Cc: Rik van Riel <riel@redhat.com>
> > > Cc: Mel Gorman <mgorman@techsingularity.net>
> > > Cc: Andrew Morton <akpm@linux-foundation.org>
> > > Acked-by: Johannes Weiner <hannes@cmpxchg.org>
> > > Signed-off-by: Shaohua Li <shli@fb.com>

Anyway, feel free to add
Acked-by: Michal Hocko <mhocko@suse.com>

> > 
> > Looks good to me.
> > [...]
> > > index 96eb85c..c621088 100644
> > > --- a/mm/rmap.c
> > > +++ b/mm/rmap.c
> > > @@ -1416,7 +1416,8 @@ static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma,
> > >  			 * Store the swap location in the pte.
> > >  			 * See handle_pte_fault() ...
> > >  			 */
> > > -			VM_BUG_ON_PAGE(!PageSwapCache(page), page);
> > > +			VM_BUG_ON_PAGE(!PageSwapCache(page) && PageSwapBacked(page),
> > > +				page);
> > 
> > just this part makes me scratch my head. I really do not understand what
> > kind of problem it tries to prevent from, maybe I am missing something
> > obvoious...
> 
> Just check a page which isn't lazyfree but wrongly enters here without swap
> entry. Or maybe you suggest we delete this statement?

Ohh, I figured out when seeing later patch in the series, I then wanted
to get back to this one but forgot... This on its own didn't really tell
me much. Maybe a comment would be helpful or even drop the VM_BUG_ON
altogether.
-- 
Michal Hocko
SUSE Labs

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

[PATCH V5 0/6] mm: fix some MADV_FREE issues Shaohua Li <shli@fb.com> - 2017-02-24 22:40 +0100
  [PATCH V5 6/6] proc: show MADV_FREE pages info in smaps Shaohua Li <shli@fb.com> - 2017-02-24 22:40 +0100
    Re: [PATCH V5 6/6] proc: show MADV_FREE pages info in smaps Michal Hocko <mhocko@kernel.org> - 2017-02-27 16:10 +0100
    Re: [PATCH V5 6/6] proc: show MADV_FREE pages info in smaps "Hillf Danton" <hillf.zj@alibaba-inc.com> - 2017-02-28 04:30 +0100
  [PATCH V5 4/6] mm: reclaim MADV_FREE pages Shaohua Li <shli@fb.com> - 2017-02-24 22:40 +0100
    Re: [PATCH V5 4/6] mm: reclaim MADV_FREE pages Minchan Kim <minchan@kernel.org> - 2017-02-27 07:50 +0100
      Re: [PATCH V5 4/6] mm: reclaim MADV_FREE pages Michal Hocko <mhocko@kernel.org> - 2017-02-27 17:40 +0100
      Re: [PATCH V5 4/6] mm: reclaim MADV_FREE pages Minchan Kim <minchan@kernel.org> - 2017-02-28 06:50 +0100
    Re: [PATCH V5 4/6] mm: reclaim MADV_FREE pages Michal Hocko <mhocko@kernel.org> - 2017-02-27 16:30 +0100
    Re: [PATCH V5 4/6] mm: reclaim MADV_FREE pages Johannes Weiner <hannes@cmpxchg.org> - 2017-02-27 18:30 +0100
    Re: [PATCH V5 4/6] mm: reclaim MADV_FREE pages "Hillf Danton" <hillf.zj@alibaba-inc.com> - 2017-02-28 04:30 +0100
  [PATCH V5 1/6] mm: delete unnecessary TTU_* flags Shaohua Li <shli@fb.com> - 2017-02-24 22:40 +0100
    Re: [PATCH V5 1/6] mm: delete unnecessary TTU_* flags Michal Hocko <mhocko@kernel.org> - 2017-02-27 16:10 +0100
  [PATCH V5 2/6] mm: don't assume anonymous pages have SwapBacked flag Shaohua Li <shli@fb.com> - 2017-02-24 22:40 +0100
    Re: [PATCH V5 2/6] mm: don't assume anonymous pages have SwapBacked flag "Hillf Danton" <hillf.zj@alibaba-inc.com> - 2017-02-27 08:00 +0100
    Re: [PATCH V5 2/6] mm: don't assume anonymous pages have SwapBacked  flag Michal Hocko <mhocko@kernel.org> - 2017-02-27 16:00 +0100
      Re: [PATCH V5 2/6] mm: don't assume anonymous pages have SwapBacked  flag Michal Hocko <mhocko@kernel.org> - 2017-02-27 17:50 +0100

csiph-web