On Sun, Feb 16, 2014 at 12:00 PM, Hugh Dickins [off-list ref] wrote:

On Sun, 16 Feb 2014, Weijie Yang wrote:

quoted

In putback_inactive_pages() and move_active_pages_to_lru(),
lruvec is already an input parameter and pages are all from this lruvec,
therefore there is no need to call mem_cgroup_page_lruvec() in loop.

Signed-off-by: Weijie Yang <redacted>

Looks plausible but I believe it's incorrect.  The lruvec passed in
is the one we took the pages from, but there's a small but real chance
that the page has become uncharged meanwhile, and should now be put back
on the root_mem_cgroup's lruvec instead of the original memcg's lruvec.

Hi Hugh,

Thanks for your review.
Frankly speaking, I am not very sure about it, that is why I add a RFC tag here.
So,  do we need update the reclaim_stat meanwhile as we change the lruvec?

Regards,

Hugh

quoted

---
 mm/vmscan.c |    3 ---
 1 file changed, 3 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index a9c74b4..4804fdb 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c

@@ -1393,8 +1393,6 @@ putback_inactive_pages(struct lruvec *lruvec, struct list_head *page_list)
                      continue;
              }

-             lruvec = mem_cgroup_page_lruvec(page, zone);
-
              SetPageLRU(page);
              lru = page_lru(page);
              add_page_to_lru_list(page, lruvec, lru);

@@ -1602,7 +1600,6 @@ static void move_active_pages_to_lru(struct lruvec *lruvec,

      while (!list_empty(list)) {
              page = lru_to_page(list);
-             lruvec = mem_cgroup_page_lruvec(page, zone);

              VM_BUG_ON_PAGE(PageLRU(page), page);
              SetPageLRU(page);
--

1.7.10.4


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