mm: workingset: define macro WORKINGSET_SHIFT

The magic number 1 is used in several places in workingset.c.  Define a
macro WORKINGSET_SHIFT for it to improve code readability.

Link: https://lkml.kernel.org/r/20210624122307.1759342-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/workingset.c b/mm/workingset.c
index 4f7a306..5ba3e42 100644 (file)
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -168,8 +168,10 @@
  * refault distance will immediately activate the refaulting page.
  */
 
+#define WORKINGSET_SHIFT 1
 #define EVICTION_SHIFT ((BITS_PER_LONG - BITS_PER_XA_VALUE) +  \
-                        1 + NODES_SHIFT + MEM_CGROUP_ID_SHIFT)
+                        WORKINGSET_SHIFT + NODES_SHIFT + \
+                        MEM_CGROUP_ID_SHIFT)
 #define EVICTION_MASK  (~0UL >> EVICTION_SHIFT)
 
 /*
@@ -189,7 +191,7 @@ static void *pack_shadow(int memcgid, pg_data_t *pgdat, unsigned long eviction,
        eviction &= EVICTION_MASK;
        eviction = (eviction << MEM_CGROUP_ID_SHIFT) | memcgid;
        eviction = (eviction << NODES_SHIFT) | pgdat->node_id;
-       eviction = (eviction << 1) | workingset;
+       eviction = (eviction << WORKINGSET_SHIFT) | workingset;
 
        return xa_mk_value(eviction);
 }
@@ -201,8 +203,8 @@ static void unpack_shadow(void *shadow, int *memcgidp, pg_data_t **pgdat,
        int memcgid, nid;
        bool workingset;
 
-       workingset = entry & 1;
-       entry >>= 1;
+       workingset = entry & ((1UL << WORKINGSET_SHIFT) - 1);
+       entry >>= WORKINGSET_SHIFT;
        nid = entry & ((1UL << NODES_SHIFT) - 1);
        entry >>= NODES_SHIFT;
        memcgid = entry & ((1UL << MEM_CGROUP_ID_SHIFT) - 1);