Revert "net: set proper memcg for net_init hooks allocations"

This reverts commit 1d0403d2.

Anatoly Pugachev reported that the commit 1d0403d2 ("net: set proper
memcg for net_init hooks allocations") is somehow causing the sparc64
VMs failed to boot and the VMs boot fine with that patch reverted. So,
revert the patch for now and later we can debug the issue.

Link: https://lore.kernel.org/all/20220918092849.GA10314@u164.east.ru/Reported-by: Anatoly Pugachev <matorola@gmail.com>
Signed-off-by: Shakeel Butt <shakeelb@google.com>
Cc: Vasily Averin <vvs@openvz.org>
Cc: Jakub Kicinski <kuba@kernel.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: cgroups@vger.kernel.org
Cc: sparclinux@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Tested-by: Anatoly Pugachev <matorola@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Fixes: 1d0403d2 ("net: set proper memcg for net_init hooks allocations")
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/memcontrol.h

@@ -1788,42 +1788,6 @@ static inline void count_objcg_event(struct obj_cgroup *objcg,
 	rcu_read_unlock();
 }
 
-/**
- * get_mem_cgroup_from_obj - get a memcg associated with passed kernel object.
- * @p: pointer to object from which memcg should be extracted. It can be NULL.
- *
- * Retrieves the memory group into which the memory of the pointed kernel
- * object is accounted. If memcg is found, its reference is taken.
- * If a passed kernel object is uncharged, or if proper memcg cannot be found,
- * as well as if mem_cgroup is disabled, NULL is returned.
- *
- * Return: valid memcg pointer with taken reference or NULL.
- */
-static inline struct mem_cgroup *get_mem_cgroup_from_obj(void *p)
-{
-	struct mem_cgroup *memcg;
-
-	rcu_read_lock();
-	do {
-		memcg = mem_cgroup_from_obj(p);
-	} while (memcg && !css_tryget(&memcg->css));
-	rcu_read_unlock();
-	return memcg;
-}
-
-/**
- * mem_cgroup_or_root - always returns a pointer to a valid memory cgroup.
- * @memcg: pointer to a valid memory cgroup or NULL.
- *
- * If passed argument is not NULL, returns it without any additional checks
- * and changes. Otherwise, root_mem_cgroup is returned.
- *
- * NOTE: root_mem_cgroup can be NULL during early boot.
- */
-static inline struct mem_cgroup *mem_cgroup_or_root(struct mem_cgroup *memcg)
-{
-	return memcg ? memcg : root_mem_cgroup;
-}
 #else
 static inline bool mem_cgroup_kmem_disabled(void)
 {
@@ -1880,15 +1844,6 @@ static inline void count_objcg_event(struct obj_cgroup *objcg,
 {
 }
 
-static inline struct mem_cgroup *get_mem_cgroup_from_obj(void *p)
-{
-	return NULL;
-}
-
-static inline struct mem_cgroup *mem_cgroup_or_root(struct mem_cgroup *memcg)
-{
-	return NULL;
-}
 #endif /* CONFIG_MEMCG_KMEM */
 
 #if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_ZSWAP)

net/core/net_namespace.c

@@ -18,7 +18,6 @@
 #include <linux/user_namespace.h>
 #include <linux/net_namespace.h>
 #include <linux/sched/task.h>
-#include <linux/sched/mm.h>
 #include <linux/uidgid.h>
 #include <linux/cookie.h>
 
@@ -1144,13 +1143,7 @@ static int __register_pernet_operations(struct list_head *list,
 		 * setup_net() and cleanup_net() are not possible.
 		 */
 		for_each_net(net) {
-			struct mem_cgroup *old, *memcg;
-
-			memcg = mem_cgroup_or_root(get_mem_cgroup_from_obj(net));
-			old = set_active_memcg(memcg);
 			error = ops_init(ops, net);
-			set_active_memcg(old);
-			mem_cgroup_put(memcg);
 			if (error)
 				goto out_undo;
 			list_add_tail(&net->exit_list, &net_exit_list);