Re: Dirty pages underflow on 3.14.23

From: Mikulas Patocka
Date: Tue Jan 06 2015 - 12:55:09 EST




On Tue, 6 Jan 2015, Johannes Weiner wrote:

> > The bug probably happened during git pull or apt-get update, though one
> > can't be sure that these commands caused it.
> >
> > I see that 3.14.24 containes some fix for underflow (commit
> > 6619741f17f541113a02c30f22a9ca22e32c9546, upstream commit
> > abe5f972912d086c080be4bde67750630b6fb38b), but it doesn't seem that that
> > commit fixes this condition. If you have a commit that could fix this, say
> > it.
>
> That's an unrelated counter, but there is a known dirty underflow
> problem that was addressed in 87a7e00b206a ("mm: protect
> set_page_dirty() from ongoing truncation"). It should make it into
> the stable kernels in the near future. Can you reproduce this issue?
>
> Thanks,
> Johannes

I can't reprodce it. It happened just once.

That patch is supposed to fix an occasional underflow by a single page -
while my meminfo showed underflow by 22952KiB (5738 pages).

Mikulas
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