Merge tag 'cgroup-for-6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:

 - cpuset isolation improvements

 - cpuset cgroup1 support is split into its own file behind the new
   config option CONFIG_CPUSET_V1. This makes it the second controller
   which makes cgroup1 support optional after memcg

 - Handling of unavailable v1 controller handling improved during
   cgroup1 mount operations

 - union_find applied to cpuset. It makes code simpler and more
   efficient

 - Reduce spurious events in pids.events

 - Cleanups and other misc changes

 - Contains a merge of cgroup/for-6.11-fixes to receive cpuset fixes
   that further changes build upon

* tag 'cgroup-for-6.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (34 commits)
  cgroup: Do not report unavailable v1 controllers in /proc/cgroups
  cgroup: Disallow mounting v1 hierarchies without controller implementation
  cgroup/cpuset: Expose cpuset filesystem with cpuset v1 only
  cgroup/cpuset: Move cpu.h include to cpuset-internal.h
  cgroup/cpuset: add sefltest for cpuset v1
  cgroup/cpuset: guard cpuset-v1 code under CONFIG_CPUSETS_V1
  cgroup/cpuset: rename functions shared between v1 and v2
  cgroup/cpuset: move v1 interfaces to cpuset-v1.c
  cgroup/cpuset: move validate_change_legacy to cpuset-v1.c
  cgroup/cpuset: move legacy hotplug update to cpuset-v1.c
  cgroup/cpuset: add callback_lock helper
  cgroup/cpuset: move memory_spread to cpuset-v1.c
  cgroup/cpuset: move relax_domain_level to cpuset-v1.c
  cgroup/cpuset: move memory_pressure to cpuset-v1.c
  cgroup/cpuset: move common code to cpuset-internal.h
  cgroup/cpuset: introduce cpuset-v1.c
  selftest/cgroup: Make test_cpuset_prs.sh deal with pre-isolated CPUs
  cgroup/cpuset: Account for boot time isolated CPUs
  cgroup/cpuset: remove use_parent_ecpus of cpuset
  cgroup/cpuset: remove fetch_xcpus
  ...

4 files changed, 59 insertions, 7 deletions

diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index ae04035b6cbe..eb0f6f349496 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -210,6 +210,14 @@ struct cgroup_subsys_state {
 	 * fields of the containing structure.
 	 */
 	struct cgroup_subsys_state *parent;
+
+	/*
+	 * Keep track of total numbers of visible descendant CSSes.
+	 * The total number of dying CSSes is tracked in
+	 * css->cgroup->nr_dying_subsys[ssid].
+	 * Protected by cgroup_mutex.
+	 */
+	int nr_descendants;
 };
 
 /*
@@ -470,6 +478,12 @@ struct cgroup {
 	/* Private pointers for each registered subsystem */
 	struct cgroup_subsys_state __rcu *subsys[CGROUP_SUBSYS_COUNT];
 
+	/*
+	 * Keep track of total number of dying CSSes at and below this cgroup.
+	 * Protected by cgroup_mutex.
+	 */
+	int nr_dying_subsys[CGROUP_SUBSYS_COUNT];
+
 	struct cgroup_root *root;
 
 	/*
diff --git a/include/linux/cpuset.h b/include/linux/cpuset.h
index de4cf0ee96f7..835e7b793f6a 100644
--- a/include/linux/cpuset.h
+++ b/include/linux/cpuset.h
@@ -99,6 +99,7 @@ static inline bool cpuset_zone_allowed(struct zone *z, gfp_t gfp_mask)
 extern int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
 					  const struct task_struct *tsk2);
 
+#ifdef CONFIG_CPUSETS_V1
 #define cpuset_memory_pressure_bump() 				\
 	do {							\
 		if (cpuset_memory_pressure_enabled)		\
@@ -106,6 +107,9 @@ extern int cpuset_mems_allowed_intersects(const struct task_struct *tsk1,
 	} while (0)
 extern int cpuset_memory_pressure_enabled;
 extern void __cpuset_memory_pressure_bump(void);
+#else
+static inline void cpuset_memory_pressure_bump(void) { }
+#endif
 
 extern void cpuset_task_status_allowed(struct seq_file *m,
 					struct task_struct *task);
@@ -113,7 +117,6 @@ extern int proc_cpuset_show(struct seq_file *m, struct pid_namespace *ns,
 			    struct pid *pid, struct task_struct *tsk);
 
 extern int cpuset_mem_spread_node(void);
-extern int cpuset_slab_spread_node(void);
 
 static inline int cpuset_do_page_mem_spread(void)
 {
@@ -246,11 +249,6 @@ static inline int cpuset_mem_spread_node(void)
 	return 0;
 }
 
-static inline int cpuset_slab_spread_node(void)
-{
-	return 0;
-}
-
 static inline int cpuset_do_page_mem_spread(void)
 {
 	return 0;
diff --git a/include/linux/sched.h b/include/linux/sched.h
index f8d150343d42..3773c1c8f099 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1243,7 +1243,6 @@ struct task_struct {
 	/* Sequence number to catch updates: */
 	seqcount_spinlock_t		mems_allowed_seq;
 	int				cpuset_mem_spread_rotor;
-	int				cpuset_slab_spread_rotor;
 #endif
 #ifdef CONFIG_CGROUPS
 	/* Control Group info protected by css_set_lock: */
diff --git a/include/linux/union_find.h b/include/linux/union_find.h
new file mode 100644
index 000000000000..cfd49263c138
--- /dev/null
+++ b/include/linux/union_find.h
@@ -0,0 +1,41 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_UNION_FIND_H
+#define __LINUX_UNION_FIND_H
+/**
+ * union_find.h - union-find data structure implementation
+ *
+ * This header provides functions and structures to implement the union-find
+ * data structure. The union-find data structure is used to manage disjoint
+ * sets and supports efficient union and find operations.
+ *
+ * See Documentation/core-api/union_find.rst for documentation and samples.
+ */
+
+struct uf_node {
+	struct uf_node *parent;
+	unsigned int rank;
+};
+
+/* This macro is used for static initialization of a union-find node. */
+#define UF_INIT_NODE(node)	{.parent = &node, .rank = 0}
+
+/**
+ * uf_node_init - Initialize a union-find node
+ * @node: pointer to the union-find node to be initialized
+ *
+ * This function sets the parent of the node to itself and
+ * initializes its rank to 0.
+ */
+static inline void uf_node_init(struct uf_node *node)
+{
+	node->parent = node;
+	node->rank = 0;
+}
+
+/* find the root of a node */
+struct uf_node *uf_find(struct uf_node *node);
+
+/* Merge two intersecting nodes */
+void uf_union(struct uf_node *node1, struct uf_node *node2);
+
+#endif /* __LINUX_UNION_FIND_H */