Commit:     436c6541b13a73790646eb11429bdc8ee50eec41
Parent:     ff7283fa3a66823933991ad55a558a3a01d5ab27
Author:     Hugh Dickins <[EMAIL PROTECTED]>
AuthorDate: Thu Feb 7 00:14:12 2008 -0800
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Thu Feb 7 08:42:20 2008 -0800

    memcgroup: fix zone isolation OOM
    mem_cgroup_charge_common shows a tendency to OOM without good reason, when
    a memhog goes well beyond its rss limit but with plenty of swap available.
    Seen on x86 but not on PowerPC; seen when the next patch omits swapcache
    from memcgroup, but we presume it can happen without.
    mem_cgroup_isolate_pages is not quite satisfying reclaim's criteria for OOM
    avoidance.  Already it has to scan beyond the nr_to_scan limit when it
    finds a !LRU page or an active page when handling inactive or an inactive
    page when handling active.  It needs to do exactly the same when it finds a
    page from the wrong zone (the x86 tests had two zones, the PowerPC tests
    had only one).
    Don't increment scan and then decrement it in these cases, just move the
    incrementation down.  Fix recent off-by-one when checking against
    nr_to_scan.  Cut out "Check if the meta page went away from under us",
    presumably left over from early debugging: no amount of such checks could
    save us if this list really were being updated without locking.
    This change does make the unlimited scan while holding two spinlocks
    even worse - bad for latency and bad for containment; but that's a
    separate issue which is better left to be fixed a little later.
    Signed-off-by: Hugh Dickins <[EMAIL PROTECTED]>
    Cc: Pavel Emelianov <[EMAIL PROTECTED]>
    Acked-by: Balbir Singh <[EMAIL PROTECTED]>
    Cc: Paul Menage <[EMAIL PROTECTED]>
    Cc: Peter Zijlstra <[EMAIL PROTECTED]>
    Cc: "Eric W. Biederman" <[EMAIL PROTECTED]>
    Cc: Nick Piggin <[EMAIL PROTECTED]>
    Cc: Kirill Korotaev <[EMAIL PROTECTED]>
    Cc: Herbert Poetzl <[EMAIL PROTECTED]>
    Cc: David Rientjes <[EMAIL PROTECTED]>
    Cc: Vaidyanathan Srinivasan <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
 mm/memcontrol.c |   17 ++++-------------
 1 files changed, 4 insertions(+), 13 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index e8493fb..9793873 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -260,24 +260,20 @@ unsigned long mem_cgroup_isolate_pages(unsigned long 
        scan = 0;
        list_for_each_entry_safe_reverse(pc, tmp, src, lru) {
-               if (scan++ > nr_to_scan)
+               if (scan >= nr_to_scan)
                page = pc->page;
-               if (unlikely(!PageLRU(page))) {
-                       scan--;
+               if (unlikely(!PageLRU(page)))
-               }
                if (PageActive(page) && !active) {
                        __mem_cgroup_move_lists(pc, true);
-                       scan--;
                if (!PageActive(page) && active) {
                        __mem_cgroup_move_lists(pc, false);
-                       scan--;
@@ -288,13 +284,8 @@ unsigned long mem_cgroup_isolate_pages(unsigned long 
                if (page_zone(page) != z)
-               /*
-                * Check if the meta page went away from under us
-                */
-               if (!list_empty(&pc->lru))
-                       list_move(&pc->lru, &pc_list);
-               else
-                       continue;
+               scan++;
+               list_move(&pc->lru, &pc_list);
                if (__isolate_lru_page(page, mode) == 0) {
                        list_move(&page->lru, dst);
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