[PATCH 2/4] cgroup: Introduce cgroup_level() helper

["Michal Koutný" <mkoutny@suse.com>]

This is a no functional change to hide physical storage of cgroup's
level and it allows subesequent conversion of the storage.

Signed-off-by: Michal Koutný <mkoutny@suse.com>
---
 block/bfq-iosched.c           |  2 +-
 block/blk-iocost.c            |  4 ++--
 include/linux/cgroup.h        | 18 +++++++++++++++---
 include/trace/events/cgroup.h |  8 ++++----
 kernel/bpf/helpers.c          |  2 +-
 kernel/cgroup/cgroup.c        |  4 ++--
 net/netfilter/nft_socket.c    |  2 +-
 7 files changed, 26 insertions(+), 14 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 4a8d3d96bfe49..f293bab068274 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -601,7 +601,7 @@ static bool bfqq_request_over_limit(struct bfq_data *bfqd,
 		goto out;
 
 	/* +1 for bfqq entity, root cgroup not included */
-	depth = bfqg_to_blkg(bfqq_group(bfqq))->blkcg->css.cgroup->level + 1;
+	depth = cgroup_level(bfqg_to_blkg(bfqq_group(bfqq))->blkcg->css.cgroup) + 1;
 	if (depth > alloc_depth) {
 		spin_unlock_irq(&bfqd->lock);
 		if (entities != inline_entities)
diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index a0416927d33dc..b4eebe61dca7f 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -2962,7 +2962,7 @@ static void ioc_cpd_free(struct blkcg_policy_data *cpd)
 static struct blkg_policy_data *ioc_pd_alloc(struct gendisk *disk,
 		struct blkcg *blkcg, gfp_t gfp)
 {
-	int levels = blkcg->css.cgroup->level + 1;
+	int levels = cgroup_level(blkcg->css.cgroup) + 1;
 	struct ioc_gq *iocg;
 
 	iocg = kzalloc_node(struct_size(iocg, ancestors, levels), gfp,
@@ -3003,7 +3003,7 @@ static void ioc_pd_init(struct blkg_policy_data *pd)
 	init_waitqueue_head(&iocg->waitq);
 	hrtimer_setup(&iocg->waitq_timer, iocg_waitq_timer_fn, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
 
-	iocg->level = blkg->blkcg->css.cgroup->level;
+	iocg->level = cgroup_level(blkg->blkcg->css.cgroup)
 
 	for (tblkg = blkg; tblkg; tblkg = tblkg->parent) {
 		struct ioc_gq *tiocg = blkg_to_iocg(tblkg);
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index bc892e3b37eea..0290878ebad26 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -525,6 +525,18 @@ static inline struct cgroup *cgroup_parent(struct cgroup *cgrp)
 	return NULL;
 }
 
+/**
+ * cgroup_level - cgroup depth
+ * @cgrp: cgroup
+ *
+ * The depth this cgroup is at.  The root is at depth zero and each step down
+ * the hierarchy increments the level.
+ */
+static inline int cgroup_level(struct cgroup *cgrp)
+{
+	return cgrp->level;
+}
+
 /**
  * cgroup_is_descendant - test ancestry
  * @cgrp: the cgroup to be tested
@@ -537,9 +549,9 @@ static inline struct cgroup *cgroup_parent(struct cgroup *cgrp)
 static inline bool cgroup_is_descendant(struct cgroup *cgrp,
 					struct cgroup *ancestor)
 {
-	if (cgrp->root != ancestor->root || cgrp->level < ancestor->level)
+	if (cgrp->root != ancestor->root || cgroup_level(cgrp) < cgroup_level(ancestor))
 		return false;
-	return cgrp->ancestors[ancestor->level] == ancestor;
+	return cgrp->ancestors[cgroup_level(ancestor)] == ancestor;
 }
 
 /**
@@ -556,7 +568,7 @@ static inline bool cgroup_is_descendant(struct cgroup *cgrp,
 static inline struct cgroup *cgroup_ancestor(struct cgroup *cgrp,
 					     int ancestor_level)
 {
-	if (ancestor_level < 0 || ancestor_level > cgrp->level)
+	if (ancestor_level < 0 || ancestor_level > cgroup_level(cgrp))
 		return NULL;
 	return cgrp->ancestors[ancestor_level];
 }
diff --git a/include/trace/events/cgroup.h b/include/trace/events/cgroup.h
index ba9229af9a343..0a1bc91754b5e 100644
--- a/include/trace/events/cgroup.h
+++ b/include/trace/events/cgroup.h
@@ -67,7 +67,7 @@ DECLARE_EVENT_CLASS(cgroup,
 	TP_fast_assign(
 		__entry->root = cgrp->root->hierarchy_id;
 		__entry->id = cgroup_id(cgrp);
-		__entry->level = cgrp->level;
+		__entry->level = cgroup_level(cgrp);
 		__assign_str(path);
 	),
 
@@ -136,7 +136,7 @@ DECLARE_EVENT_CLASS(cgroup_migrate,
 	TP_fast_assign(
 		__entry->dst_root = dst_cgrp->root->hierarchy_id;
 		__entry->dst_id = cgroup_id(dst_cgrp);
-		__entry->dst_level = dst_cgrp->level;
+		__entry->dst_level = cgroup_level(dst_cgrp);
 		__assign_str(dst_path);
 		__entry->pid = task->pid;
 		__assign_str(comm);
@@ -180,7 +180,7 @@ DECLARE_EVENT_CLASS(cgroup_event,
 	TP_fast_assign(
 		__entry->root = cgrp->root->hierarchy_id;
 		__entry->id = cgroup_id(cgrp);
-		__entry->level = cgrp->level;
+		__entry->level = cgroup_level(cgrp);
 		__assign_str(path);
 		__entry->val = val;
 	),
@@ -221,7 +221,7 @@ DECLARE_EVENT_CLASS(cgroup_rstat,
 	TP_fast_assign(
 		__entry->root = cgrp->root->hierarchy_id;
 		__entry->id = cgroup_id(cgrp);
-		__entry->level = cgrp->level;
+		__entry->level = cgroup_level(cgrp);
 		__entry->cpu = cpu;
 		__entry->contended = contended;
 	),
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index db72b96f9c8c8..b825f6e0a1c29 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -2577,7 +2577,7 @@ __bpf_kfunc struct cgroup *bpf_cgroup_ancestor(struct cgroup *cgrp, int level)
 {
 	struct cgroup *ancestor;
 
-	if (level > cgrp->level || level < 0)
+	if (level > cgroup_level(cgrp) || level < 0)
 		return NULL;
 
 	/* cgrp's refcnt could be 0 here, but ancestors can still be accessed */
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 554a02ee298ba..e011f1dd6d87f 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -5843,7 +5843,7 @@ static struct cgroup *cgroup_create(struct cgroup *parent, const char *name,
 	struct cgroup_root *root = parent->root;
 	struct cgroup *cgrp, *tcgrp;
 	struct kernfs_node *kn;
-	int i, level = parent->level + 1;
+	int i, level = cgroup_level(parent) + 1;
 	int ret;
 
 	/* allocate the cgroup and its ID, 0 is reserved for the root */
@@ -5884,7 +5884,7 @@ static struct cgroup *cgroup_create(struct cgroup *parent, const char *name,
 		goto out_stat_exit;
 
 	for (tcgrp = cgrp; tcgrp; tcgrp = cgroup_parent(tcgrp))
-		cgrp->ancestors[tcgrp->level] = tcgrp;
+		cgrp->ancestors[cgroup_level(tcgrp)] = tcgrp;
 
 	/*
 	 * New cgroup inherits effective freeze counter, and
diff --git a/net/netfilter/nft_socket.c b/net/netfilter/nft_socket.c
index 36affbb697c2f..a5b0340924efb 100644
--- a/net/netfilter/nft_socket.c
+++ b/net/netfilter/nft_socket.c
@@ -64,7 +64,7 @@ static noinline int nft_socket_cgroup_subtree_level(void)
 	if (IS_ERR(cgrp))
 		return PTR_ERR(cgrp);
 
-	level = cgrp->level;
+	level = cgroup_level(cgrp);
 
 	cgroup_put(cgrp);
 
-- 
2.52.0