[PATCH] mm/memcontrol: replace '== root_mem_cgroup' with mem_cgroup_is_root

[Hui Su]

We have supplied the inline func: mem_cgroup_is_root().
So we may use mem_cgroup_is_root() instead of using
'memcg == root_mem_cgroup' or 'memcg != root_mem_cgroup'
directly, which is more readable.

Signed-off-by: Hui Su <sh_...@163.com>
---
 mm/memcontrol.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 3dcbf24d2227..ac7af04ef88f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -868,7 +868,7 @@ void __mod_lruvec_slab_state(void *p, enum node_stat_item 
idx, int val)
        memcg = mem_cgroup_from_obj(p);
 
        /* Untracked pages have no memcg, no lruvec. Update only the node */
-       if (!memcg || memcg == root_mem_cgroup) {
+       if (!memcg || mem_cgroup_is_root(memcg)) {
                __mod_node_page_state(pgdat, idx, val);
        } else {
                lruvec = mem_cgroup_lruvec(memcg, pgdat);
@@ -1312,7 +1312,7 @@ int mem_cgroup_scan_tasks(struct mem_cgroup *memcg,
        struct mem_cgroup *iter;
        int ret = 0;
 
-       BUG_ON(memcg == root_mem_cgroup);
+       BUG_ON(mem_cgroup_is_root(memcg));
 
        for_each_mem_cgroup_tree(iter, memcg) {
                struct css_task_iter it;
@@ -2069,7 +2069,7 @@ struct mem_cgroup *mem_cgroup_get_oom_group(struct 
task_struct *victim,
        rcu_read_lock();
 
        memcg = mem_cgroup_from_task(victim);
-       if (memcg == root_mem_cgroup)
+       if (mem_cgroup_is_root(memcg))
                goto out;
 
        /*
@@ -2978,7 +2978,7 @@ __always_inline struct obj_cgroup 
*get_obj_cgroup_from_current(void)
        else
                memcg = mem_cgroup_from_task(current);
 
-       for (; memcg != root_mem_cgroup; memcg = parent_mem_cgroup(memcg)) {
+       for (; !mem_cgroup_is_root(memcg); memcg = parent_mem_cgroup(memcg)) {
                objcg = rcu_dereference(memcg->objcg);
                if (objcg && obj_cgroup_tryget(objcg))
                        break;
@@ -7027,7 +7027,7 @@ void mem_cgroup_sk_alloc(struct sock *sk)
 
        rcu_read_lock();
        memcg = mem_cgroup_from_task(current);
-       if (memcg == root_mem_cgroup)
+       if (mem_cgroup_is_root(memcg))
                goto out;
        if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && !memcg->tcpmem_active)
                goto out;
@@ -7156,7 +7156,7 @@ static struct mem_cgroup *mem_cgroup_id_get_online(struct 
mem_cgroup *memcg)
                 * The root cgroup cannot be destroyed, so it's refcount must
                 * always be >= 1.
                 */
-               if (WARN_ON_ONCE(memcg == root_mem_cgroup)) {
+               if (WARN_ON_ONCE(mem_cgroup_is_root(memcg))) {
                        VM_BUG_ON(1);
                        break;
                }
@@ -7313,7 +7313,7 @@ long mem_cgroup_get_nr_swap_pages(struct mem_cgroup 
*memcg)
 
        if (cgroup_memory_noswap || !cgroup_subsys_on_dfl(memory_cgrp_subsys))
                return nr_swap_pages;
-       for (; memcg != root_mem_cgroup; memcg = parent_mem_cgroup(memcg))
+       for (; !mem_cgroup_is_root(memcg); memcg = parent_mem_cgroup(memcg))
                nr_swap_pages = min_t(long, nr_swap_pages,
                                      READ_ONCE(memcg->swap.max) -
                                      page_counter_read(&memcg->swap));
@@ -7335,7 +7335,7 @@ bool mem_cgroup_swap_full(struct page *page)
        if (!memcg)
                return false;
 
-       for (; memcg != root_mem_cgroup; memcg = parent_mem_cgroup(memcg)) {
+       for (; !mem_cgroup_is_root(memcg); memcg = parent_mem_cgroup(memcg)) {
                unsigned long usage = page_counter_read(&memcg->swap);
 
                if (usage * 2 >= READ_ONCE(memcg->swap.high) ||
-- 
2.29.0