mm: workingset: separate shadow unpacking and refault calculation

Per-cgroup thrash detection will need to derive a live memcg from the
eviction cookie, and doing that inside unpack_shadow() will get nasty
with the reference handling spread over two functions.

In preparation, make unpack_shadow() clearly about extracting static
data, and let workingset_refault() do all the higher-level handling.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 28 insertions, 28 deletions

diff --git a/mm/workingset.c b/mm/workingset.c
index 3ef92f6e41fe..f874b2c663e3 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -165,13 +165,10 @@ static void *pack_shadow(unsigned long eviction, struct zone *zone)
         return (void *)(eviction | RADIX_TREE_EXCEPTIONAL_ENTRY);
 }
 
-static void unpack_shadow(void *shadow,
-                          struct zone **zone,
-                          unsigned long *distance)
+static void unpack_shadow(void *shadow, struct zone **zonep,
+                          unsigned long *evictionp)
 {
         unsigned long entry = (unsigned long)shadow;
-        unsigned long eviction;
-        unsigned long refault;
         int zid, nid;
 
         entry >>= RADIX_TREE_EXCEPTIONAL_SHIFT;
@@ -179,29 +176,9 @@ static void unpack_shadow(void *shadow,
         entry >>= ZONES_SHIFT;
         nid = entry & ((1UL << NODES_SHIFT) - 1);
         entry >>= NODES_SHIFT;
-        eviction = entry;
-
-        *zone = NODE_DATA(nid)->node_zones + zid;
 
-        refault = atomic_long_read(&(*zone)->inactive_age);
-
-        /*
-         * The unsigned subtraction here gives an accurate distance
-         * across inactive_age overflows in most cases.
-         *
-         * There is a special case: usually, shadow entries have a
-         * short lifetime and are either refaulted or reclaimed along
-         * with the inode before they get too old.  But it is not
-         * impossible for the inactive_age to lap a shadow entry in
-         * the field, which can then can result in a false small
-         * refault distance, leading to a false activation should this
-         * old entry actually refault again.  However, earlier kernels
-         * used to deactivate unconditionally with *every* reclaim
-         * invocation for the longest time, so the occasional
-         * inappropriate activation leading to pressure on the active
-         * list is not a problem.
-         */
-        *distance = (refault - eviction) & EVICTION_MASK;
+        *zonep = NODE_DATA(nid)->node_zones + zid;
+        *evictionp = entry;
 }
 
 /**
@@ -233,9 +210,32 @@ void *workingset_eviction(struct address_space *mapping, struct page *page)
 bool workingset_refault(void *shadow)
 {
         unsigned long refault_distance;
+        unsigned long eviction;
+        unsigned long refault;
         struct zone *zone;
 
-        unpack_shadow(shadow, &zone, &refault_distance);
+        unpack_shadow(shadow, &zone, &eviction);
+
+        refault = atomic_long_read(&zone->inactive_age);
+
+        /*
+         * The unsigned subtraction here gives an accurate distance
+         * across inactive_age overflows in most cases.
+         *
+         * There is a special case: usually, shadow entries have a
+         * short lifetime and are either refaulted or reclaimed along
+         * with the inode before they get too old.  But it is not
+         * impossible for the inactive_age to lap a shadow entry in
+         * the field, which can then can result in a false small
+         * refault distance, leading to a false activation should this
+         * old entry actually refault again.  However, earlier kernels
+         * used to deactivate unconditionally with *every* reclaim
+         * invocation for the longest time, so the occasional
+         * inappropriate activation leading to pressure on the active
+         * list is not a problem.
+         */
+        refault_distance = (refault - eviction) & EVICTION_MASK;
+
         inc_zone_state(zone, WORKINGSET_REFAULT);
 
         if (refault_distance <= zone_page_state(zone, NR_ACTIVE_FILE)) {