linux-kernel - [PATCH-cgroup 2/2] cgroup: Remove nr

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Message-Id: <20240706005622.2003606-2-longman@redhat.com>
Date: Fri,  5 Jul 2024 20:56:22 -0400
From: Waiman Long <longman@...hat.com>
To: Tejun Heo <tj@...nel.org>,
	Zefan Li <lizefan.x@...edance.com>,
	Johannes Weiner <hannes@...xchg.org>
Cc: cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Waiman Long <longman@...hat.com>
Subject: [PATCH-cgroup 2/2] cgroup: Remove nr_cgrps

With the previous patch, the nr_cgrps field in the cgroup_root structure
is no longer being used. Just remove it.

Signed-off-by: Waiman Long <longman@...hat.com>
---
 include/linux/cgroup-defs.h | 3 ---
 kernel/cgroup/cgroup.c      | 5 -----
 2 files changed, 8 deletions(-)

diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 522ab77f0406..542334bf72df 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -581,9 +581,6 @@ struct cgroup_root {
 	/* must follow cgrp for cgrp->ancestors[0], see above */
 	struct cgroup *cgrp_ancestor_storage;
 
-	/* Number of cgroups in the hierarchy, used only for /proc/cgroups */
-	atomic_t nr_cgrps;
-
 	/* Hierarchy-specific flags */
 	unsigned int flags;
 
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 4a818192950f..b6854ba702ca 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -1327,7 +1327,6 @@ static void cgroup_destroy_root(struct cgroup_root *root)
 
 	cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
 
-	BUG_ON(atomic_read(&root->nr_cgrps));
 	BUG_ON(!list_empty(&cgrp->self.children));
 
 	/* Rebind all subsystems back to the default hierarchy */
@@ -2061,7 +2060,6 @@ void init_cgroup_root(struct cgroup_fs_context *ctx)
 	struct cgroup *cgrp = &root->cgrp;
 
 	INIT_LIST_HEAD_RCU(&root->root_list);
-	atomic_set(&root->nr_cgrps, 1);
 	cgrp->root = root;
 	init_cgroup_housekeeping(cgrp);
 
@@ -2159,7 +2157,6 @@ int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
 	spin_unlock_irq(&css_set_lock);
 
 	BUG_ON(!list_empty(&root_cgrp->self.children));
-	BUG_ON(atomic_read(&root->nr_cgrps) != 1);
 
 	ret = 0;
 	goto out;
@@ -5383,7 +5380,6 @@ static void css_free_rwork_fn(struct work_struct *work)
 			css_put(parent);
 	} else {
 		/* cgroup free path */
-		atomic_dec(&cgrp->root->nr_cgrps);
 		if (!cgroup_on_dfl(cgrp))
 			cgroup1_pidlist_destroy_all(cgrp);
 		cancel_work_sync(&cgrp->release_agent_work);
@@ -5693,7 +5689,6 @@ static struct cgroup *cgroup_create(struct cgroup *parent, const char *name,
 
 	/* allocation complete, commit to creation */
 	list_add_tail_rcu(&cgrp->self.sibling, &cgroup_parent(cgrp)->self.children);
-	atomic_inc(&root->nr_cgrps);
 	cgroup_get_live(parent);
 
 	/*
-- 
2.39.3