mm, oom: rename zonelist locking functions

try_set_zonelist_oom() and clear_zonelist_oom() are not named properly
to imply that they require locking semantics to avoid out_of_memory()
being reordered.

zone_scan_lock is required for both functions to ensure that there is
proper locking synchronization.

Rename try_set_zonelist_oom() to oom_zonelist_trylock() and rename
clear_zonelist_oom() to oom_zonelist_unlock() to imply there is proper
locking semantics.

At the same time, convert oom_zonelist_trylock() to return bool instead
of int since only success and failure are tested.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 16 insertions, 20 deletions

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index b0a1e1ff0353..d33aca1552ad 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -559,28 +559,25 @@ EXPORT_SYMBOL_GPL(unregister_oom_notifier);
  * if a parallel OOM killing is already taking place that includes a zone in
  * the zonelist.  Otherwise, locks all zones in the zonelist and returns 1.
  */
-int try_set_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
+bool oom_zonelist_trylock(struct zonelist *zonelist, gfp_t gfp_mask)
 {
         struct zoneref *z;
         struct zone *zone;
-        int ret = 1;
+        bool ret = true;
 
         spin_lock(&zone_scan_lock);
-        for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
+        for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask))
                 if (zone_is_oom_locked(zone)) {
-                        ret = 0;
+                        ret = false;
                         goto out;
                 }
-        }
 
-        for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
-                /*
-                 * Lock each zone in the zonelist under zone_scan_lock so a
-                 * parallel invocation of try_set_zonelist_oom() doesn't succeed
-                 * when it shouldn't.
-                 */
+        /*
+         * Lock each zone in the zonelist under zone_scan_lock so a parallel
+         * call to oom_zonelist_trylock() doesn't succeed when it shouldn't.
+         */
+        for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask))
                 zone_set_flag(zone, ZONE_OOM_LOCKED);
-        }
 
 out:
         spin_unlock(&zone_scan_lock);
@@ -592,15 +589,14 @@ out:
  * allocation attempts with zonelists containing them may now recall the OOM
  * killer, if necessary.
  */
-void clear_zonelist_oom(struct zonelist *zonelist, gfp_t gfp_mask)
+void oom_zonelist_unlock(struct zonelist *zonelist, gfp_t gfp_mask)
 {
         struct zoneref *z;
         struct zone *zone;
 
         spin_lock(&zone_scan_lock);
-        for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask)) {
+        for_each_zone_zonelist(zone, z, zonelist, gfp_zone(gfp_mask))
                 zone_clear_flag(zone, ZONE_OOM_LOCKED);
-        }
         spin_unlock(&zone_scan_lock);
 }
 
@@ -695,8 +691,8 @@ void pagefault_out_of_memory(void)
                 return;
 
         zonelist = node_zonelist(first_memory_node, GFP_KERNEL);
-        if (try_set_zonelist_oom(zonelist, GFP_KERNEL)) {
+        if (oom_zonelist_trylock(zonelist, GFP_KERNEL)) {
                 out_of_memory(NULL, 0, 0, NULL, false);
-                clear_zonelist_oom(zonelist, GFP_KERNEL);
+                oom_zonelist_unlock(zonelist, GFP_KERNEL);
         }
 }
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index fb9908148474..578236089ec1 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2246,8 +2246,8 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
 {
         struct page *page;
 
-        /* Acquire the OOM killer lock for the zones in zonelist */
-        if (!try_set_zonelist_oom(zonelist, gfp_mask)) {
+        /* Acquire the per-zone oom lock for each zone */
+        if (!oom_zonelist_trylock(zonelist, gfp_mask)) {
                 schedule_timeout_uninterruptible(1);
                 return NULL;
         }
@@ -2285,7 +2285,7 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
         out_of_memory(zonelist, gfp_mask, order, nodemask, false);
 
 out:
-        clear_zonelist_oom(zonelist, gfp_mask);
+        oom_zonelist_unlock(zonelist, gfp_mask);
         return page;
 }