On Fri, Mar 09, 2012 at 01:37:32PM -0800, Hugh Dickins wrote:
> Respectfully revert commit e6ca7b89dc76 "memcg: fix mapcount check
> in move charge code for anonymous page" for the 3.3 release, so that
> it behaves exactly like releases 2.6.35 through 3.2 in this respect.
>
> Horiguchi-san's commit is correct in itself, 1 makes much more sense
> than 2 in that check; but it does not go far enough - swapcount
> should be considered too - if we really want such a check at all.
Agreed. We should rethink whole design rather than detail.
> We appear to have reached agreement now, and expect that 3.4 will
> remove the mapcount check, but had better not make 3.3 different.
>
> Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Reviewed-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
> ---
>
> mm/memcontrol.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- 3.3-rc6+/mm/memcontrol.c 2012-03-05 22:03:45.940000832 -0800
> +++ linux/mm/memcontrol.c 2012-03-09 13:06:41.716250093 -0800
> @@ -5075,7 +5075,7 @@ static struct page *mc_handle_present_pt
> return NULL;
> if (PageAnon(page)) {
> /* we don't move shared anon */
> - if (!move_anon() || page_mapcount(page) > 1)
> + if (!move_anon() || page_mapcount(page) > 2)
> return NULL;
> } else if (!move_file())
> /* we ignore mapcount for file pages */
>
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