cgroup: remove cgroup_rstat_flush_atomic()

Previous patches removed the only caller of cgroup_rstat_flush_atomic(). 
Remove the function and simplify the code.

Link: https://lkml.kernel.org/r/20230421174020.2994750-6-yosryahmed@google.com
Signed-off-by: Yosry Ahmed <yosryahmed@google.com>
Acked-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: yosrym93

include/linux/cgroup.h

@@ -692,7 +692,6 @@ static inline void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen)
  */
 void cgroup_rstat_updated(struct cgroup *cgrp, int cpu);
 void cgroup_rstat_flush(struct cgroup *cgrp);
-void cgroup_rstat_flush_atomic(struct cgroup *cgrp);
 void cgroup_rstat_flush_hold(struct cgroup *cgrp);
 void cgroup_rstat_flush_release(void);
 

kernel/cgroup/rstat.c

@@ -171,7 +171,7 @@ __weak noinline void bpf_rstat_flush(struct cgroup *cgrp,
 __diag_pop();
 
 /* see cgroup_rstat_flush() */
-static void cgroup_rstat_flush_locked(struct cgroup *cgrp, bool may_sleep)
+static void cgroup_rstat_flush_locked(struct cgroup *cgrp)
 	__releases(&cgroup_rstat_lock) __acquires(&cgroup_rstat_lock)
 {
 	int cpu;
@@ -207,9 +207,8 @@ static void cgroup_rstat_flush_locked(struct cgroup *cgrp, bool may_sleep)
 		}
 		raw_spin_unlock_irqrestore(cpu_lock, flags);
 
-		/* if @may_sleep, play nice and yield if necessary */
-		if (may_sleep && (need_resched() ||
-				  spin_needbreak(&cgroup_rstat_lock))) {
+		/* play nice and yield if necessary */
+		if (need_resched() || spin_needbreak(&cgroup_rstat_lock)) {
 			spin_unlock_irq(&cgroup_rstat_lock);
 			if (!cond_resched())
 				cpu_relax();
@@ -236,25 +235,10 @@ __bpf_kfunc void cgroup_rstat_flush(struct cgroup *cgrp)
 	might_sleep();
 
 	spin_lock_irq(&cgroup_rstat_lock);
-	cgroup_rstat_flush_locked(cgrp, true);
+	cgroup_rstat_flush_locked(cgrp);
 	spin_unlock_irq(&cgroup_rstat_lock);
 }
 
-/**
- * cgroup_rstat_flush_atomic- atomic version of cgroup_rstat_flush()
- * @cgrp: target cgroup
- *
- * This function can be called from any context.
- */
-void cgroup_rstat_flush_atomic(struct cgroup *cgrp)
-{
-	unsigned long flags;
-
-	spin_lock_irqsave(&cgroup_rstat_lock, flags);
-	cgroup_rstat_flush_locked(cgrp, false);
-	spin_unlock_irqrestore(&cgroup_rstat_lock, flags);
-}
-
 /**
  * cgroup_rstat_flush_hold - flush stats in @cgrp's subtree and hold
  * @cgrp: target cgroup
@@ -269,7 +253,7 @@ void cgroup_rstat_flush_hold(struct cgroup *cgrp)
 {
 	might_sleep();
 	spin_lock_irq(&cgroup_rstat_lock);
-	cgroup_rstat_flush_locked(cgrp, true);
+	cgroup_rstat_flush_locked(cgrp);
 }
 
 /**