ksm: unmerge is an origin of OOMs

Just as the swapoff system call allocates many pages of RAM to various
processes, perhaps triggering OOM, so "echo 2 >/sys/kernel/mm/ksm/run"
(unmerge) is liable to allocate many pages of RAM to various processes,
perhaps triggering OOM; and each is normally run from a modest admin
process (swapoff or shell), easily repeated until it succeeds.

So treat unmerge_and_remove_all_rmap_items() in the same way that we treat
try_to_unuse(): generalize PF_SWAPOFF to PF_OOM_ORIGIN, and bracket both
with that, to ask the OOM killer to kill them first, to prevent them from
spawning more and more OOM kills.

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
Acked-by: Izik Eidus <ieidus@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index a7b2460e922b..da4c342f2641 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -79,7 +79,7 @@ unsigned long badness(struct task_struct *p, unsigned long uptime)
         /*
          * swapoff can easily use up all memory, so kill those first.
          */
-        if (p->flags & PF_SWAPOFF)
+        if (p->flags & PF_OOM_ORIGIN)
                 return ULONG_MAX;
 
         /*