[Devel] [PATCH RHEL7 COMMIT] oom: drop OOM_SCAN_ABORT

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-327.3.1-vz7.10.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-327.3.1.vz7.10.7
------>
commit 6d5743c9c782df30ac7790bd57e1e5eea426611d
Author: Vladimir Davydov <vdavydov at virtuozzo.com>
Date:   Thu Jan 28 20:21:28 2016 +0400

    oom: drop OOM_SCAN_ABORT
    
    Rebase to RHEL 7.2 based kernel:
    https://jira.sw.ru/browse/PSBM-42320
    ===
    From: Vladimir Davydov <vdavydov at parallels.com>
    
    Patchset description: oom enhancements - part 2
    
     - Patches 1-2 prepare memcg for upcoming changes in oom design.
     - Patch 3 reworks oom locking design so that the executioner waits for
       victim to exit. This is necessary to increase oom kill rate, which is
       essential for berserker mode.
     - Patch 4 drops unused OOM_SCAN_ABORT
     - Patch 5 introduces oom timeout.
       https://jira.sw.ru/browse/PSBM-38581
     - Patch 6 makes oom fairer when it comes to selecting a victim among
       different containers.
       https://jira.sw.ru/browse/PSBM-37915
     - Patch 7 prepares oom for introducing berserker mode
     - Patch 8 resurrects oom berserker mode, which is supposed to cope with
       actively forking processes.
       https://jira.sw.ru/browse/PSBM-17930
    
    https://jira.sw.ru/browse/PSBM-26973
    
    Changes in v3:
     - rework oom_trylock (patch 3)
     - select exiting process instead of aborting oom scan so as not to keep
       busy-waiting for an exiting process to exit (patches 3, 4)
     - cleanup oom timeout handling + fix stuck process trace dumped
       multiple times on timeout (patch 5)
     - set max_overdraft to ULONG_MAX on selected processes (patch 6)
     - rework oom berserker process selection logic (patches 7, 8)
    
    Changes in v2:
     - s/time_after/time_after_eq to avoid BUG_ON in oom_trylock (patch 4)
     - propagate victim to the context that initiated oom in oom_unlock
       (patch 6)
     - always set oom_end on releasing oom context (patch 6)
    
    Vladimir Davydov (8):
      memcg: add mem_cgroup_get/put helpers
      memcg: add lock for protecting memcg->oom_notify list
      oom: rework locking design
      oom: introduce oom timeout
      oom: drop OOM_SCAN_ABORT
      oom: rework logic behind memory.oom_guarantee
      oom: pass points and overdraft to oom_kill_process
      oom: resurrect berserker mode
    
    Reviewed-by: Kirill Tkhai <ktkhai at odin.com>
    
    =========================================
    This patch description:
    
    It is not used anymore, neither should it be used with the new locking
    design.
    
    Signed-off-by: Vladimir Davydov <vdavydov at parallels.com>
---
 include/linux/oom.h | 1 -
 mm/memcontrol.c     | 6 ------
 mm/oom_kill.c       | 7 +------
 3 files changed, 1 insertion(+), 13 deletions(-)

diff --git a/include/linux/oom.h b/include/linux/oom.h
index f804551..6d4a94f 100644
--- a/include/linux/oom.h
+++ b/include/linux/oom.h
@@ -27,7 +27,6 @@ enum oom_constraint {
 enum oom_scan_t {
 	OOM_SCAN_OK,		/* scan thread and find its badness */
 	OOM_SCAN_CONTINUE,	/* do not consider thread for oom kill */
-	OOM_SCAN_ABORT,		/* abort the iteration and return */
 	OOM_SCAN_SELECT,	/* always select this thread first */
 };
 
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 83d7823..fc591a3 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2065,12 +2065,6 @@ retry:
 				/* fall through */
 			case OOM_SCAN_CONTINUE:
 				continue;
-			case OOM_SCAN_ABORT:
-				cgroup_iter_end(cgroup, &it);
-				mem_cgroup_iter_break(memcg, iter);
-				if (chosen)
-					put_task_struct(chosen);
-				return;
 			case OOM_SCAN_OK:
 				break;
 			};
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index fd6defa7..36f6454 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -358,9 +358,6 @@ retry:
 			/* fall through */
 		case OOM_SCAN_CONTINUE:
 			continue;
-		case OOM_SCAN_ABORT:
-			rcu_read_unlock();
-			return ERR_PTR(-1UL);
 		case OOM_SCAN_OK:
 			break;
 		};
@@ -890,11 +887,9 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
 	if (!p) {
 		dump_header(NULL, gfp_mask, order, NULL, mpol_mask);
 		panic("Out of memory and no killable processes...\n");
-	}
-	if (PTR_ERR(p) != -1UL) {
+	} else
 		oom_kill_process(p, gfp_mask, order, points, totalpages, NULL,
 				 nodemask, "Out of memory");
-	}
 }
 
 /*