mm: clean up mem_cgroup_iter()

A clean up to make variable names more clear and to improve code
readability.

No functional change.

Link: https://lkml.kernel.org/r/20240905003058.1859929-6-kinseyho@google.com
Signed-off-by: Kinsey Ho <kinseyho@google.com>
Reviewed-by: T.J. Mercier <tjmercier@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Tejun Heo <tj@kernel.org>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Zefan Li <lizefan.x@bytedance.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 36cbc77307451136d327f1c9ef4709e3edbb7383..d632650c6a2bd4a6d77b56a8ca82fad49caa3819 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -987,8 +987,8 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
 {
        struct mem_cgroup_reclaim_iter *iter;
        struct cgroup_subsys_state *css;
-       struct mem_cgroup *memcg;
-       struct mem_cgroup *pos = NULL;
+       struct mem_cgroup *pos;
+       struct mem_cgroup *next;
 
        if (mem_cgroup_disabled())
                return NULL;
@@ -998,14 +998,13 @@ struct mem_cgroup *mem_cgroup_iter(struct mem_cgroup *root,
 
        rcu_read_lock();
 restart:
-       memcg = NULL;
+       next = NULL;
 
        if (reclaim) {
                int gen;
-               struct mem_cgroup_per_node *mz;
+               int nid = reclaim->pgdat->node_id;
 
-               mz = root->nodeinfo[reclaim->pgdat->node_id];
-               iter = &mz->iter;
+               iter = &root->nodeinfo[nid]->iter;
                gen = atomic_read(&iter->generation);
 
                /*
@@ -1018,29 +1017,22 @@ restart:
                        goto out_unlock;
 
                pos = READ_ONCE(iter->position);
-       } else if (prev) {
+       } else
                pos = prev;
-       }
 
        css = pos ? &pos->css : NULL;
 
-       for (;;) {
-               css = css_next_descendant_pre(css, &root->css);
-               if (!css) {
-                       break;
-               }
-
+       while ((css = css_next_descendant_pre(css, &root->css))) {
                /*
                 * Verify the css and acquire a reference.  The root
                 * is provided by the caller, so we know it's alive
                 * and kicking, and don't take an extra reference.
                 */
-               if (css == &root->css || css_tryget(css)) {
+               if (css == &root->css || css_tryget(css))
                        break;
-               }
        }
 
-       memcg = mem_cgroup_from_css(css);
+       next = mem_cgroup_from_css(css);
 
        if (reclaim) {
                /*
@@ -1048,13 +1040,13 @@ restart:
                 * thread, so check that the value hasn't changed since we read
                 * it to avoid reclaiming from the same cgroup twice.
                 */
-               if (cmpxchg(&iter->position, pos, memcg) != pos) {
+               if (cmpxchg(&iter->position, pos, next) != pos) {
                        if (css && css != &root->css)
                                css_put(css);
                        goto restart;
                }
 
-               if (!memcg) {
+               if (!next) {
                        atomic_inc(&iter->generation);
 
                        /*
@@ -1073,7 +1065,7 @@ out_unlock:
        if (prev && prev != root)
                css_put(&prev->css);
 
-       return memcg;
+       return next;
 }
 
 /**