mm, oom: cleanup pagefault oom handler

To lock the entire system from parallel oom killing, it's possible to pass
in a zonelist with all zones rather than using for_each_populated_zone()
for the iteration.  This obsoletes try_set_system_oom() and
clear_system_oom() so that they can be removed.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index fe36205a7f8a17c298111bafcaeb39c47afc75ba..0e30ff7b21c541253eb0f983d8c9a07ca298a70f 100644 (file)
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -591,43 +591,6 @@ void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
        spin_unlock(&zone_scan_lock);
 }
 
-/*
- * Try to acquire the oom killer lock for all system zones.  Returns zero if a
- * parallel oom killing is taking place, otherwise locks all zones and returns
- * non-zero.
- */
-static int try_set_system_oom(void)
-{
-       struct zone *zone;
-       int ret = 1;
-
-       spin_lock(&zone_scan_lock);
-       for_each_populated_zone(zone)
-               if (zone_is_oom_locked(zone)) {
-                       ret = 0;
-                       goto out;
-               }
-       for_each_populated_zone(zone)
-               zone_set_flag(zone, ZONE_OOM_LOCKED);
-out:
-       spin_unlock(&zone_scan_lock);
-       return ret;
-}
-
-/*
- * Clears ZONE_OOM_LOCKED for all system zones so that failed allocation
- * attempts or page faults may now recall the oom killer, if necessary.
- */
-static void clear_system_oom(void)
-{
-       struct zone *zone;
-
-       spin_lock(&zone_scan_lock);
-       for_each_populated_zone(zone)
-               zone_clear_flag(zone, ZONE_OOM_LOCKED);
-       spin_unlock(&zone_scan_lock);
-}
-
 /**
  * out_of_memory - kill the "best" process when we run out of memory
  * @zonelist: zonelist pointer
@@ -708,15 +671,17 @@ out:
 
 /*
  * The pagefault handler calls here because it is out of memory, so kill a
- * memory-hogging task.  If a populated zone has ZONE_OOM_LOCKED set, a parallel
- * oom killing is already in progress so do nothing.  If a task is found with
- * TIF_MEMDIE set, it has been killed so do nothing and allow it to exit.
+ * memory-hogging task.  If any populated zone has ZONE_OOM_LOCKED set, a
+ * parallel oom killing is already in progress so do nothing.
  */
 void pagefault_out_of_memory(void)
 {
-       if (try_set_system_oom()) {
+       struct zonelist *zonelist = node_zonelist(first_online_node,
+                                                 GFP_KERNEL);
+
+       if (try_set_zonelist_oom(zonelist, GFP_KERNEL)) {
                out_of_memory(NULL, 0, 0, NULL, false);
-               clear_system_oom();
+               clear_zonelist_oom(zonelist, GFP_KERNEL);
        }
        schedule_timeout_killable(1);
 }