mm: mark stable page dirty in KSM

The MADV_FREE patchset changes page reclaim to simply free a clean
anonymous page with no dirty ptes, instead of swapping it out; but
KSM uses clean write-protected ptes to reference the stable ksm page.
So be sure to mark that page dirty, so it's never mistakenly discarded.

[hughd: adjusted comments]
Acked-by: Hugh Dickins <>
Signed-off-by: Minchan Kim <>
1 file changed