[PATCHSET] cgroup: use static_keys for subsystem enabled and on_dfl tests

[PATCHSET] cgroup: use static_keys for subsystem enabled and on_dfl tests

[Tejun Heo]

cgroup_subsys->disabled and cgroup_on_dfl() tests are likely to be
used in hot paths and seldom change.  The former is set once during
boot and the latter only when a controller is migrated between the
default hierarchy and traditional ones.

This patchset makes these tests static_key based and contains the
following four patches.

 0001-jump_label-make-static_key_enabled-work-on-static_ke.patch
 0002-cgroup-implement-static_key-based-cgroup_subsys_enab.patch
 0003-cgroup-replace-cgroup_subsys-disabled-tests-with-cgr.patch
 0004-cgroup-replace-cgroup_on_dfl-tests-in-controllers-wi.patch

0001 is a prep patch in jump_label.  0002 adds the needed static_keys.
0003-0004 convert the existing usages and drop the old tests.

This patchset is on top of v4.3-rc1 and is availalbe in the following
git branch.

 git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git review-jump-labels

diffstat follows.  Thanks.

 block/blk-throttle.c           |    2 
 block/cfq-iosched.c            |    4 -
 include/linux/cgroup-defs.h    |    1 
 include/linux/cgroup.h         |   79 +++++++---------------------
 include/linux/hugetlb_cgroup.h |    4 -
 include/linux/jump_label.h     |   18 +++---
 include/linux/memcontrol.h     |    4 -
 kernel/cgroup.c                |  113 ++++++++++++++++++++++++++++++++++++++---
 kernel/cpuset.c                |   23 ++++----
 mm/memcontrol.c                |    4 -
 10 files changed, 157 insertions(+), 95 deletions(-)

--
tejun

[PATCH 1/4] jump_label: make static_key_enabled() work on static_key_true/false types too

[Tejun Heo]

static_key_enabled() can be used on struct static_key but not on its
wrapper types static_key_true and static_key_false.  The function is
useful for debugging and management of static keys.  Update it so that
it can be used for the wrapper types too.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
Hello,

If this patch is acceptable, please let me know how it should be
routed.

Thanks.

 include/linux/jump_label.h | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index 7f653e8..c9ca050 100644
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -216,11 +216,6 @@ static inline int jump_label_apply_nops(struct module *mod)
 #define STATIC_KEY_INIT STATIC_KEY_INIT_FALSE
 #define jump_label_enabled static_key_enabled
 
-static inline bool static_key_enabled(struct static_key *key)
-{
-	return static_key_count(key) > 0;
-}
-
 static inline void static_key_enable(struct static_key *key)
 {
 	int count = static_key_count(key);
@@ -267,6 +262,17 @@ struct static_key_false {
 #define DEFINE_STATIC_KEY_FALSE(name)	\
 	struct static_key_false name = STATIC_KEY_FALSE_INIT
 
+extern bool ____wrong_branch_error(void);
+
+#define static_key_enabled(x)							\
+({										\
+	if (!__builtin_types_compatible_p(typeof(*x), struct static_key) &&	\
+	    !__builtin_types_compatible_p(typeof(*x), struct static_key_true) &&\
+	    !__builtin_types_compatible_p(typeof(*x), struct static_key_false))	\
+		____wrong_branch_error();					\
+	static_key_count((struct static_key *)x) > 0;				\
+})
+
 #ifdef HAVE_JUMP_LABEL
 
 /*
@@ -325,8 +331,6 @@ struct static_key_false {
  * See jump_label_type() / jump_label_init_type().
  */
 
-extern bool ____wrong_branch_error(void);
-
 #define static_branch_likely(x)							\
 ({										\
 	bool branch;								\
-- 
2.4.3

[PATCH 2/4] cgroup: implement static_key based cgroup_subsys_enabled() and cgroup_subsys_on_dfl()

[Tejun Heo]

Whether a subsys is enabled and attached to the default hierarchy
seldom changes and may be tested in the hot paths.  This patch
implements static_key based cgroup_subsys_enabled() and
cgroup_subsys_on_dfl() tests.

The following patches will update the users and remove duplicate
mechanisms.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
 include/linux/cgroup.h | 21 +++++++++++++++++++++
 kernel/cgroup.c        | 27 ++++++++++++++++++++++++++-
 2 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index eb7ca55..c3a9f1e 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -17,6 +17,7 @@
 #include <linux/fs.h>
 #include <linux/seq_file.h>
 #include <linux/kernfs.h>
+#include <linux/jump_label.h>
 
 #include <linux/cgroup-defs.h>
 
@@ -50,6 +51,26 @@ extern struct css_set init_css_set;
 #include <linux/cgroup_subsys.h>
 #undef SUBSYS
 
+#define SUBSYS(_x)								\
+	extern struct static_key_true _x ## _cgrp_subsys_enabled_key;		\
+	extern struct static_key_true _x ## _cgrp_subsys_on_dfl_key;
+#include <linux/cgroup_subsys.h>
+#undef SUBSYS
+
+/**
+ * cgroup_subsys_enabled - fast test on whether a subsys is enabled
+ * @ss: subsystem in question
+ */
+#define cgroup_subsys_enabled(ss)						\
+	static_branch_likely(&ss ## _enabled_key)
+
+/**
+ * cgroup_subsys_on_dfl - fast test on whether a subsys is on default hierarchy
+ * @ss: subsystem in question
+ */
+#define cgroup_subsys_on_dfl(ss)						\
+	static_branch_likely(&ss ## _on_dfl_key)
+
 bool css_has_online_children(struct cgroup_subsys_state *css);
 struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss);
 struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgroup,
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 2cf0f79..3619389 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -139,6 +139,27 @@ static const char *cgroup_subsys_name[] = {
 };
 #undef SUBSYS
 
+/* array of static_keys for cgroup_subsys_enabled() and cgroup_subsys_on_dfl() */
+#define SUBSYS(_x)								\
+	DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_enabled_key);			\
+	DEFINE_STATIC_KEY_TRUE(_x ## _cgrp_subsys_on_dfl_key);			\
+	EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_enabled_key);			\
+	EXPORT_SYMBOL_GPL(_x ## _cgrp_subsys_on_dfl_key);
+#include <linux/cgroup_subsys.h>
+#undef SUBSYS
+
+#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_enabled_key,
+static struct static_key_true *cgroup_subsys_enabled_key[] = {
+#include <linux/cgroup_subsys.h>
+};
+#undef SUBSYS
+
+#define SUBSYS(_x) [_x ## _cgrp_id] = &_x ## _cgrp_subsys_on_dfl_key,
+static struct static_key_true *cgroup_subsys_on_dfl_key[] = {
+#include <linux/cgroup_subsys.h>
+};
+#undef SUBSYS
+
 /*
  * The default hierarchy, reserved for the subsystems that are otherwise
  * unattached - it never has more than a single cgroup, and all tasks are
@@ -1319,9 +1340,12 @@ static int rebind_subsystems(struct cgroup_root *dst_root,
 
 		/* default hierarchy doesn't enable controllers by default */
 		dst_root->subsys_mask |= 1 << ssid;
-		if (dst_root != &cgrp_dfl_root) {
+		if (dst_root == &cgrp_dfl_root) {
+			static_branch_enable(cgroup_subsys_on_dfl_key[ssid]);
+		} else {
 			dst_root->cgrp.subtree_control |= 1 << ssid;
 			cgroup_refresh_child_subsys_mask(&dst_root->cgrp);
+			static_branch_disable(cgroup_subsys_on_dfl_key[ssid]);
 		}
 
 		if (ss->bind)
@@ -5483,6 +5507,7 @@ static int __init cgroup_disable(char *str)
 			    strcmp(token, ss->legacy_name))
 				continue;
 
+			static_branch_disable(cgroup_subsys_enabled_key[i]);
 			ss->disabled = 1;
 			printk(KERN_INFO "Disabling %s control group subsystem\n",
 			       ss->name);
-- 
2.4.3

[PATCH 3/4] cgroup: replace cgroup_subsys->disabled tests with cgroup_subsys_enabled()

[Tejun Heo]

Replace cgroup_subsys->disabled tests in controllers with
cgroup_subsys_enabled().  cgroup_subsys_enabled() requires literal
subsys name as its parameter and thus can't be used for cgroup core
which iterates through controllers.  For cgroup core, introduce and
use cgroup_ssid_enabled() which uses slower static_key_enabled() test
and can be indexed by subsys ID.

This leaves cgroup_subsys->disabled unused.  Removed.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
---
 include/linux/cgroup-defs.h    |  1 -
 include/linux/hugetlb_cgroup.h |  4 +---
 include/linux/memcontrol.h     |  4 +---
 kernel/cgroup.c                | 28 +++++++++++++++++++++-------
 4 files changed, 23 insertions(+), 14 deletions(-)

diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 4d8fcf2..c5d41c3 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -419,7 +419,6 @@ struct cgroup_subsys {
 		     struct task_struct *task);
 	void (*bind)(struct cgroup_subsys_state *root_css);
 
-	int disabled;
 	int early_init;
 
 	/*
diff --git a/include/linux/hugetlb_cgroup.h b/include/linux/hugetlb_cgroup.h
index bcc853e..7edd305 100644
--- a/include/linux/hugetlb_cgroup.h
+++ b/include/linux/hugetlb_cgroup.h
@@ -48,9 +48,7 @@ int set_hugetlb_cgroup(struct page *page, struct hugetlb_cgroup *h_cg)
 
 static inline bool hugetlb_cgroup_disabled(void)
 {
-	if (hugetlb_cgrp_subsys.disabled)
-		return true;
-	return false;
+	return !cgroup_subsys_enabled(hugetlb_cgrp_subsys);
 }
 
 extern int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index ad800e6..9aa7820 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -347,9 +347,7 @@ ino_t page_cgroup_ino(struct page *page);
 
 static inline bool mem_cgroup_disabled(void)
 {
-	if (memory_cgrp_subsys.disabled)
-		return true;
-	return false;
+	return !cgroup_subsys_enabled(memory_cgrp_subsys);
 }
 
 /*
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 3619389..5703ba7 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -224,6 +224,19 @@ static void kill_css(struct cgroup_subsys_state *css);
 static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
 			      bool is_add);
 
+/**
+ * cgroup_ssid_enabled - cgroup subsys enabled test by subsys ID
+ * @ssid: subsys ID of interest
+ *
+ * cgroup_subsys_enabled() can only be used with literal subsys names which
+ * is fine for individual subsystems but unsuitable for cgroup core.  This
+ * is slower static_key_enabled() based test indexed by @ssid.
+ */
+static bool cgroup_ssid_enabled(int ssid)
+{
+	return static_key_enabled(cgroup_subsys_enabled_key[ssid]);
+}
+
 /* IDR wrappers which synchronize using cgroup_idr_lock */
 static int cgroup_idr_alloc(struct idr *idr, void *ptr, int start, int end,
 			    gfp_t gfp_mask)
@@ -1482,7 +1495,7 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
 		for_each_subsys(ss, i) {
 			if (strcmp(token, ss->legacy_name))
 				continue;
-			if (ss->disabled)
+			if (!cgroup_ssid_enabled(i))
 				continue;
 
 			/* Mutually exclusive option 'all' + subsystem name */
@@ -1513,7 +1526,7 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
 	 */
 	if (all_ss || (!one_ss && !opts->none && !opts->name))
 		for_each_subsys(ss, i)
-			if (!ss->disabled)
+			if (cgroup_ssid_enabled(i))
 				opts->subsys_mask |= (1 << i);
 
 	/*
@@ -2762,7 +2775,8 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
 		if (tok[0] == '\0')
 			continue;
 		for_each_subsys_which(ss, ssid, &tmp_ss_mask) {
-			if (ss->disabled || strcmp(tok + 1, ss->name))
+			if (!cgroup_ssid_enabled(ssid) ||
+			    strcmp(tok + 1, ss->name))
 				continue;
 
 			if (*tok == '+') {
@@ -3320,7 +3334,7 @@ static int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
 {
 	int ret;
 
-	if (ss->disabled)
+	if (!cgroup_ssid_enabled(ss->id))
 		return 0;
 
 	if (!cfts || cfts[0].name[0] == '\0')
@@ -5082,7 +5096,7 @@ int __init cgroup_init(void)
 		 * disabled flag and cftype registration needs kmalloc,
 		 * both of which aren't available during early_init.
 		 */
-		if (ss->disabled)
+		if (!cgroup_ssid_enabled(ssid))
 			continue;
 
 		cgrp_dfl_root.subsys_mask |= 1 << ss->id;
@@ -5217,7 +5231,8 @@ static int proc_cgroupstats_show(struct seq_file *m, void *v)
 	for_each_subsys(ss, i)
 		seq_printf(m, "%s\t%d\t%d\t%d\n",
 			   ss->legacy_name, ss->root->hierarchy_id,
-			   atomic_read(&ss->root->nr_cgrps), !ss->disabled);
+			   atomic_read(&ss->root->nr_cgrps),
+			   cgroup_ssid_enabled(i));
 
 	mutex_unlock(&cgroup_mutex);
 	return 0;
@@ -5508,7 +5523,6 @@ static int __init cgroup_disable(char *str)
 				continue;
 
 			static_branch_disable(cgroup_subsys_enabled_key[i]);
-			ss->disabled = 1;
 			printk(KERN_INFO "Disabling %s control group subsystem\n",
 			       ss->name);
 			break;
-- 
2.4.3

[PATCH 4/4] cgroup: replace cgroup_on_dfl() tests in controllers with cgroup_subsys_on_dfl()

[Tejun Heo]

cgroup_on_dfl() tests whether the cgroup's root is the default
hierarchy; however, an individual controller is only interested in
whether the controller is attached to the default hierarchy and never
tests a cgroup which doesn't belong to the hierarchy that the
controller is attached to.

This patch replaces cgroup_on_dfl() tests in controllers with faster
static_key based cgroup_subsys_on_dfl().  This leaves cgroup core as
the only user of cgroup_on_dfl() and the function is moved from the
header file to cgroup.c.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
---
 block/blk-throttle.c   |  2 +-
 block/cfq-iosched.c    |  4 ++--
 include/linux/cgroup.h | 58 --------------------------------------------------
 kernel/cgroup.c        | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++
 kernel/cpuset.c        | 23 +++++++++++---------
 mm/memcontrol.c        |  4 ++--
 6 files changed, 76 insertions(+), 73 deletions(-)

diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index c75a263..2149a1d 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -369,7 +369,7 @@ static void throtl_pd_init(struct blkg_policy_data *pd)
 	 * regardless of the position of the group in the hierarchy.
 	 */
 	sq->parent_sq = &td->service_queue;
-	if (cgroup_on_dfl(blkg->blkcg->css.cgroup) && blkg->parent)
+	if (cgroup_subsys_on_dfl(io_cgrp_subsys) && blkg->parent)
 		sq->parent_sq = &blkg_to_tg(blkg->parent)->service_queue;
 	tg->td = td;
 }
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 04de884..1f9093e 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1581,7 +1581,7 @@ static struct blkcg_policy_data *cfq_cpd_alloc(gfp_t gfp)
 static void cfq_cpd_init(struct blkcg_policy_data *cpd)
 {
 	struct cfq_group_data *cgd = cpd_to_cfqgd(cpd);
-	unsigned int weight = cgroup_on_dfl(blkcg_root.css.cgroup) ?
+	unsigned int weight = cgroup_subsys_on_dfl(io_cgrp_subsys) ?
 			      CGROUP_WEIGHT_DFL : CFQ_WEIGHT_LEGACY_DFL;
 
 	if (cpd_to_blkcg(cpd) == &blkcg_root)
@@ -1599,7 +1599,7 @@ static void cfq_cpd_free(struct blkcg_policy_data *cpd)
 static void cfq_cpd_bind(struct blkcg_policy_data *cpd)
 {
 	struct blkcg *blkcg = cpd_to_blkcg(cpd);
-	bool on_dfl = cgroup_on_dfl(blkcg_root.css.cgroup);
+	bool on_dfl = cgroup_subsys_on_dfl(io_cgrp_subsys);
 	unsigned int weight = on_dfl ? CGROUP_WEIGHT_DFL : CFQ_WEIGHT_LEGACY_DFL;
 
 	if (blkcg == &blkcg_root)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index c3a9f1e..355bf2e 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -433,64 +433,6 @@ static inline struct cgroup *task_cgroup(struct task_struct *task,
 	return task_css(task, subsys_id)->cgroup;
 }
 
-/**
- * cgroup_on_dfl - test whether a cgroup is on the default hierarchy
- * @cgrp: the cgroup of interest
- *
- * The default hierarchy is the v2 interface of cgroup and this function
- * can be used to test whether a cgroup is on the default hierarchy for
- * cases where a subsystem should behave differnetly depending on the
- * interface version.
- *
- * The set of behaviors which change on the default hierarchy are still
- * being determined and the mount option is prefixed with __DEVEL__.
- *
- * List of changed behaviors:
- *
- * - Mount options "noprefix", "xattr", "clone_children", "release_agent"
- *   and "name" are disallowed.
- *
- * - When mounting an existing superblock, mount options should match.
- *
- * - Remount is disallowed.
- *
- * - rename(2) is disallowed.
- *
- * - "tasks" is removed.  Everything should be at process granularity.  Use
- *   "cgroup.procs" instead.
- *
- * - "cgroup.procs" is not sorted.  pids will be unique unless they got
- *   recycled inbetween reads.
- *
- * - "release_agent" and "notify_on_release" are removed.  Replacement
- *   notification mechanism will be implemented.
- *
- * - "cgroup.clone_children" is removed.
- *
- * - "cgroup.subtree_populated" is available.  Its value is 0 if the cgroup
- *   and its descendants contain no task; otherwise, 1.  The file also
- *   generates kernfs notification which can be monitored through poll and
- *   [di]notify when the value of the file changes.
- *
- * - cpuset: tasks will be kept in empty cpusets when hotplug happens and
- *   take masks of ancestors with non-empty cpus/mems, instead of being
- *   moved to an ancestor.
- *
- * - cpuset: a task can be moved into an empty cpuset, and again it takes
- *   masks of ancestors.
- *
- * - memcg: use_hierarchy is on by default and the cgroup file for the flag
- *   is not created.
- *
- * - blkcg: blk-throttle becomes properly hierarchical.
- *
- * - debug: disallowed on the default hierarchy.
- */
-static inline bool cgroup_on_dfl(const struct cgroup *cgrp)
-{
-	return cgrp->root == &cgrp_dfl_root;
-}
-
 /* no synchronization, the result can only be used as a hint */
 static inline bool cgroup_has_tasks(struct cgroup *cgrp)
 {
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 5703ba7..c24f929 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -237,6 +237,64 @@ static bool cgroup_ssid_enabled(int ssid)
 	return static_key_enabled(cgroup_subsys_enabled_key[ssid]);
 }
 
+/**
+ * cgroup_on_dfl - test whether a cgroup is on the default hierarchy
+ * @cgrp: the cgroup of interest
+ *
+ * The default hierarchy is the v2 interface of cgroup and this function
+ * can be used to test whether a cgroup is on the default hierarchy for
+ * cases where a subsystem should behave differnetly depending on the
+ * interface version.
+ *
+ * The set of behaviors which change on the default hierarchy are still
+ * being determined and the mount option is prefixed with __DEVEL__.
+ *
+ * List of changed behaviors:
+ *
+ * - Mount options "noprefix", "xattr", "clone_children", "release_agent"
+ *   and "name" are disallowed.
+ *
+ * - When mounting an existing superblock, mount options should match.
+ *
+ * - Remount is disallowed.
+ *
+ * - rename(2) is disallowed.
+ *
+ * - "tasks" is removed.  Everything should be at process granularity.  Use
+ *   "cgroup.procs" instead.
+ *
+ * - "cgroup.procs" is not sorted.  pids will be unique unless they got
+ *   recycled inbetween reads.
+ *
+ * - "release_agent" and "notify_on_release" are removed.  Replacement
+ *   notification mechanism will be implemented.
+ *
+ * - "cgroup.clone_children" is removed.
+ *
+ * - "cgroup.subtree_populated" is available.  Its value is 0 if the cgroup
+ *   and its descendants contain no task; otherwise, 1.  The file also
+ *   generates kernfs notification which can be monitored through poll and
+ *   [di]notify when the value of the file changes.
+ *
+ * - cpuset: tasks will be kept in empty cpusets when hotplug happens and
+ *   take masks of ancestors with non-empty cpus/mems, instead of being
+ *   moved to an ancestor.
+ *
+ * - cpuset: a task can be moved into an empty cpuset, and again it takes
+ *   masks of ancestors.
+ *
+ * - memcg: use_hierarchy is on by default and the cgroup file for the flag
+ *   is not created.
+ *
+ * - blkcg: blk-throttle becomes properly hierarchical.
+ *
+ * - debug: disallowed on the default hierarchy.
+ */
+static bool cgroup_on_dfl(const struct cgroup *cgrp)
+{
+	return cgrp->root == &cgrp_dfl_root;
+}
+
 /* IDR wrappers which synchronize using cgroup_idr_lock */
 static int cgroup_idr_alloc(struct idr *idr, void *ptr, int start, int end,
 			    gfp_t gfp_mask)
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index f0acff0..20eedd8 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -473,7 +473,8 @@ static int validate_change(struct cpuset *cur, struct cpuset *trial)
 
 	/* On legacy hiearchy, we must be a subset of our parent cpuset. */
 	ret = -EACCES;
-	if (!cgroup_on_dfl(cur->css.cgroup) && !is_cpuset_subset(trial, par))
+	if (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
+	    !is_cpuset_subset(trial, par))
 		goto out;
 
 	/*
@@ -879,7 +880,8 @@ static void update_cpumasks_hier(struct cpuset *cs, struct cpumask *new_cpus)
 		 * If it becomes empty, inherit the effective mask of the
 		 * parent, which is guaranteed to have some CPUs.
 		 */
-		if (cgroup_on_dfl(cp->css.cgroup) && cpumask_empty(new_cpus))
+		if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
+		    cpumask_empty(new_cpus))
 			cpumask_copy(new_cpus, parent->effective_cpus);
 
 		/* Skip the whole subtree if the cpumask remains the same. */
@@ -896,7 +898,7 @@ static void update_cpumasks_hier(struct cpuset *cs, struct cpumask *new_cpus)
 		cpumask_copy(cp->effective_cpus, new_cpus);
 		spin_unlock_irq(&callback_lock);
 
-		WARN_ON(!cgroup_on_dfl(cp->css.cgroup) &&
+		WARN_ON(!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
 			!cpumask_equal(cp->cpus_allowed, cp->effective_cpus));
 
 		update_tasks_cpumask(cp);
@@ -1135,7 +1137,8 @@ static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems)
 		 * If it becomes empty, inherit the effective mask of the
 		 * parent, which is guaranteed to have some MEMs.
 		 */
-		if (cgroup_on_dfl(cp->css.cgroup) && nodes_empty(*new_mems))
+		if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
+		    nodes_empty(*new_mems))
 			*new_mems = parent->effective_mems;
 
 		/* Skip the whole subtree if the nodemask remains the same. */
@@ -1152,7 +1155,7 @@ static void update_nodemasks_hier(struct cpuset *cs, nodemask_t *new_mems)
 		cp->effective_mems = *new_mems;
 		spin_unlock_irq(&callback_lock);
 
-		WARN_ON(!cgroup_on_dfl(cp->css.cgroup) &&
+		WARN_ON(!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
 			!nodes_equal(cp->mems_allowed, cp->effective_mems));
 
 		update_tasks_nodemask(cp);
@@ -1440,7 +1443,7 @@ static int cpuset_can_attach(struct cgroup_subsys_state *css,
 
 	/* allow moving tasks into an empty cpuset if on default hierarchy */
 	ret = -ENOSPC;
-	if (!cgroup_on_dfl(css->cgroup) &&
+	if (!cgroup_subsys_on_dfl(cpuset_cgrp_subsys) &&
 	    (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed)))
 		goto out_unlock;
 
@@ -1952,7 +1955,7 @@ static int cpuset_css_online(struct cgroup_subsys_state *css)
 	cpuset_inc();
 
 	spin_lock_irq(&callback_lock);
-	if (cgroup_on_dfl(cs->css.cgroup)) {
+	if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys)) {
 		cpumask_copy(cs->effective_cpus, parent->effective_cpus);
 		cs->effective_mems = parent->effective_mems;
 	}
@@ -2029,7 +2032,7 @@ static void cpuset_bind(struct cgroup_subsys_state *root_css)
 	mutex_lock(&cpuset_mutex);
 	spin_lock_irq(&callback_lock);
 
-	if (cgroup_on_dfl(root_css->cgroup)) {
+	if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys)) {
 		cpumask_copy(top_cpuset.cpus_allowed, cpu_possible_mask);
 		top_cpuset.mems_allowed = node_possible_map;
 	} else {
@@ -2210,7 +2213,7 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs)
 	cpus_updated = !cpumask_equal(&new_cpus, cs->effective_cpus);
 	mems_updated = !nodes_equal(new_mems, cs->effective_mems);
 
-	if (cgroup_on_dfl(cs->css.cgroup))
+	if (cgroup_subsys_on_dfl(cpuset_cgrp_subsys))
 		hotplug_update_tasks(cs, &new_cpus, &new_mems,
 				     cpus_updated, mems_updated);
 	else
@@ -2241,7 +2244,7 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
 	static cpumask_t new_cpus;
 	static nodemask_t new_mems;
 	bool cpus_updated, mems_updated;
-	bool on_dfl = cgroup_on_dfl(top_cpuset.css.cgroup);
+	bool on_dfl = cgroup_subsys_on_dfl(cpuset_cgrp_subsys);
 
 	mutex_lock(&cpuset_mutex);
 
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6ddaeba..b35c4cc 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -434,7 +434,7 @@ struct cgroup_subsys_state *mem_cgroup_css_from_page(struct page *page)
 
 	memcg = page->mem_cgroup;
 
-	if (!memcg || !cgroup_on_dfl(memcg->css.cgroup))
+	if (!memcg || !cgroup_subsys_on_dfl(memory_cgrp_subsys))
 		memcg = root_mem_cgroup;
 
 	rcu_read_unlock();
@@ -5059,7 +5059,7 @@ static void mem_cgroup_bind(struct cgroup_subsys_state *root_css)
 	 * guarantees that @root doesn't have any children, so turning it
 	 * on for the root memcg is enough.
 	 */
-	if (cgroup_on_dfl(root_css->cgroup))
+	if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
 		root_mem_cgroup->use_hierarchy = true;
 	else
 		root_mem_cgroup->use_hierarchy = false;
-- 
2.4.3

Re: [PATCH 1/4] jump_label: make static_key_enabled() work on static_key_true/false types too

[Peter Zijlstra]

On Tue, Sep 15, 2015 at 09:51:22PM -0400, Tejun Heo wrote:
> static_key_enabled() can be used on struct static_key but not on its
> wrapper types static_key_true and static_key_false.  The function is
> useful for debugging and management of static keys.  Update it so that
> it can be used for the wrapper types too.
> 
> Signed-off-by: Tejun Heo <tj@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> ---
> Hello,
> 
> If this patch is acceptable, please let me know how it should be
> routed.
> 

Yeah, no problem with this, I'm assuming there's dependencies in the
patches you didn't send me? 

Re: [PATCH 1/4] jump_label: make static_key_enabled() work on static_key_true/false types too

[Tejun Heo]

On Thu, Sep 17, 2015 at 10:59:57AM +0200, Peter Zijlstra wrote:
> On Tue, Sep 15, 2015 at 09:51:22PM -0400, Tejun Heo wrote:
> > static_key_enabled() can be used on struct static_key but not on its
> > wrapper types static_key_true and static_key_false.  The function is
> > useful for debugging and management of static keys.  Update it so that
> > it can be used for the wrapper types too.
> > 
> > Signed-off-by: Tejun Heo <tj@kernel.org>
> > Cc: Peter Zijlstra <peterz@infradead.org>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > ---
> > Hello,
> > 
> > If this patch is acceptable, please let me know how it should be
> > routed.
> > 
> 
> Yeah, no problem with this, I'm assuming there's dependencies in the
> patches you didn't send me? 

Yeap, later patches add static_keys for testing whether a controller
is enabled and whether it's on the new or old hierarchy and management
path in cgroup core needs to index the keys and test them.

Thanks.

-- 
tejun

Re: [PATCH 1/4] jump_label: make static_key_enabled() work on static_key_true/false types too

[Peter Zijlstra]

On Thu, Sep 17, 2015 at 11:27:52AM -0400, Tejun Heo wrote:
> On Thu, Sep 17, 2015 at 10:59:57AM +0200, Peter Zijlstra wrote:
> > On Tue, Sep 15, 2015 at 09:51:22PM -0400, Tejun Heo wrote:
> > > static_key_enabled() can be used on struct static_key but not on its
> > > wrapper types static_key_true and static_key_false.  The function is
> > > useful for debugging and management of static keys.  Update it so that
> > > it can be used for the wrapper types too.
> > > 
> > > Signed-off-by: Tejun Heo <tj@kernel.org>
> > > Cc: Peter Zijlstra <peterz@infradead.org>
> > > Cc: Andrew Morton <akpm@linux-foundation.org>
> > > ---
> > > Hello,
> > > 
> > > If this patch is acceptable, please let me know how it should be
> > > routed.
> > > 
> > 
> > Yeah, no problem with this, I'm assuming there's dependencies in the
> > patches you didn't send me? 
> 
> Yeap, later patches add static_keys for testing whether a controller
> is enabled and whether it's on the new or old hierarchy and management
> path in cgroup core needs to index the keys and test them.

Ok, take it through you tree then, its a small enough patch.

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Re: [PATCHSET] cgroup: use static_keys for subsystem enabled and on_dfl tests

[Zefan Li]

On 2015/9/16 9:51, Tejun Heo wrote:
> cgroup_subsys->disabled and cgroup_on_dfl() tests are likely to be
> used in hot paths and seldom change.  The former is set once during
> boot and the latter only when a controller is migrated between the
> default hierarchy and traditional ones.
>
> This patchset makes these tests static_key based and contains the
> following four patches.
>
>   0001-jump_label-make-static_key_enabled-work-on-static_ke.patch
>   0002-cgroup-implement-static_key-based-cgroup_subsys_enab.patch
>   0003-cgroup-replace-cgroup_subsys-disabled-tests-with-cgr.patch
>   0004-cgroup-replace-cgroup_on_dfl-tests-in-controllers-wi.patch
>
> 0001 is a prep patch in jump_label.  0002 adds the needed static_keys.
> 0003-0004 convert the existing usages and drop the old tests.
>
> This patchset is on top of v4.3-rc1 and is availalbe in the following
> git branch.
>
>   git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git review-jump-labels
>
> diffstat follows.  Thanks.
>
>   block/blk-throttle.c           |    2
>   block/cfq-iosched.c            |    4 -
>   include/linux/cgroup-defs.h    |    1
>   include/linux/cgroup.h         |   79 +++++++---------------------
>   include/linux/hugetlb_cgroup.h |    4 -
>   include/linux/jump_label.h     |   18 +++---
>   include/linux/memcontrol.h     |    4 -
>   kernel/cgroup.c                |  113 ++++++++++++++++++++++++++++++++++++++---
>   kernel/cpuset.c                |   23 ++++----
>   mm/memcontrol.c                |    4 -
>   10 files changed, 157 insertions(+), 95 deletions(-)
>

Acked-by: Zefan Li <lizefan@huawei.com>

Re: [PATCHSET] cgroup: use static_keys for subsystem enabled and on_dfl tests

[Tejun Heo]

On Tue, Sep 15, 2015 at 09:51:21PM -0400, Tejun Heo wrote:
> cgroup_subsys->disabled and cgroup_on_dfl() tests are likely to be
> used in hot paths and seldom change.  The former is set once during
> boot and the latter only when a controller is migrated between the
> default hierarchy and traditional ones.

Applying to cgroup/for-4.4.

Thanks.

-- 
tejun