1 files changed, 109 insertions, 20 deletions

diff --git a/kernel/cgroup/pids.c b/kernel/cgroup/pids.c
index 0e5ec7d59b4d..f5cb0ec45b9d 100644
--- a/kernel/cgroup/pids.c
+++ b/kernel/cgroup/pids.c
@@ -38,6 +38,14 @@
 #define PIDS_MAX (PID_MAX_LIMIT + 1ULL)
 #define PIDS_MAX_STR "max"
 
+enum pidcg_event {
+	/* Fork failed in subtree because this pids_cgroup limit was hit. */
+	PIDCG_MAX,
+	/* Fork failed in this pids_cgroup because ancestor limit was hit. */
+	PIDCG_FORKFAIL,
+	NR_PIDCG_EVENTS,
+};
+
 struct pids_cgroup {
 	struct cgroup_subsys_state	css;
 
@@ -49,11 +57,12 @@ struct pids_cgroup {
 	atomic64_t			limit;
 	int64_t				watermark;
 
-	/* Handle for "pids.events" */
+	/* Handles for pids.events[.local] */
 	struct cgroup_file		events_file;
+	struct cgroup_file		events_local_file;
 
-	/* Number of times fork failed because limit was hit. */
-	atomic64_t			events_limit;
+	atomic64_t			events[NR_PIDCG_EVENTS];
+	atomic64_t			events_local[NR_PIDCG_EVENTS];
 };
 
 static struct pids_cgroup *css_pids(struct cgroup_subsys_state *css)
@@ -148,12 +157,13 @@ static void pids_charge(struct pids_cgroup *pids, int num)
  * pids_try_charge - hierarchically try to charge the pid count
  * @pids: the pid cgroup state
  * @num: the number of pids to charge
+ * @fail: storage of pid cgroup causing the fail
  *
  * This function follows the set limit. It will fail if the charge would cause
  * the new value to exceed the hierarchical limit. Returns 0 if the charge
  * succeeded, otherwise -EAGAIN.
  */
-static int pids_try_charge(struct pids_cgroup *pids, int num)
+static int pids_try_charge(struct pids_cgroup *pids, int num, struct pids_cgroup **fail)
 {
 	struct pids_cgroup *p, *q;
 
@@ -166,9 +176,10 @@ static int pids_try_charge(struct pids_cgroup *pids, int num)
 		 * p->limit is %PIDS_MAX then we know that this test will never
 		 * fail.
 		 */
-		if (new > limit)
+		if (new > limit) {
+			*fail = p;
 			goto revert;
-
+		}
 		/*
 		 * Not technically accurate if we go over limit somewhere up
 		 * the hierarchy, but that's tolerable for the watermark.
@@ -229,6 +240,36 @@ static void pids_cancel_attach(struct cgroup_taskset *tset)
 	}
 }
 
+static void pids_event(struct pids_cgroup *pids_forking,
+		       struct pids_cgroup *pids_over_limit)
+{
+	struct pids_cgroup *p = pids_forking;
+	bool limit = false;
+
+	/* Only log the first time limit is hit. */
+	if (atomic64_inc_return(&p->events_local[PIDCG_FORKFAIL]) == 1) {
+		pr_info("cgroup: fork rejected by pids controller in ");
+		pr_cont_cgroup_path(p->css.cgroup);
+		pr_cont("\n");
+	}
+	cgroup_file_notify(&p->events_local_file);
+	if (!cgroup_subsys_on_dfl(pids_cgrp_subsys) ||
+	    cgrp_dfl_root.flags & CGRP_ROOT_PIDS_LOCAL_EVENTS)
+		return;
+
+	for (; parent_pids(p); p = parent_pids(p)) {
+		if (p == pids_over_limit) {
+			limit = true;
+			atomic64_inc(&p->events_local[PIDCG_MAX]);
+			cgroup_file_notify(&p->events_local_file);
+		}
+		if (limit)
+			atomic64_inc(&p->events[PIDCG_MAX]);
+
+		cgroup_file_notify(&p->events_file);
+	}
+}
+
 /*
  * task_css_check(true) in pids_can_fork() and pids_cancel_fork() relies
  * on cgroup_threadgroup_change_begin() held by the copy_process().
@@ -236,7 +277,7 @@ static void pids_cancel_attach(struct cgroup_taskset *tset)
 static int pids_can_fork(struct task_struct *task, struct css_set *cset)
 {
 	struct cgroup_subsys_state *css;
-	struct pids_cgroup *pids;
+	struct pids_cgroup *pids, *pids_over_limit;
 	int err;
 
 	if (cset)
@@ -244,16 +285,10 @@ static int pids_can_fork(struct task_struct *task, struct css_set *cset)
 	else
 		css = task_css_check(current, pids_cgrp_id, true);
 	pids = css_pids(css);
-	err = pids_try_charge(pids, 1);
-	if (err) {
-		/* Only log the first time events_limit is incremented. */
-		if (atomic64_inc_return(&pids->events_limit) == 1) {
-			pr_info("cgroup: fork rejected by pids controller in ");
-			pr_cont_cgroup_path(css->cgroup);
-			pr_cont("\n");
-		}
-		cgroup_file_notify(&pids->events_file);
-	}
+	err = pids_try_charge(pids, 1, &pids_over_limit);
+	if (err)
+		pids_event(pids, pids_over_limit);
+
 	return err;
 }
 
@@ -337,11 +372,32 @@ static s64 pids_peak_read(struct cgroup_subsys_state *css,
 	return READ_ONCE(pids->watermark);
 }
 
-static int pids_events_show(struct seq_file *sf, void *v)
+static int __pids_events_show(struct seq_file *sf, bool local)
 {
 	struct pids_cgroup *pids = css_pids(seq_css(sf));
+	enum pidcg_event pe = PIDCG_MAX;
+	atomic64_t *events;
+
+	if (!cgroup_subsys_on_dfl(pids_cgrp_subsys) ||
+	    cgrp_dfl_root.flags & CGRP_ROOT_PIDS_LOCAL_EVENTS) {
+		pe = PIDCG_FORKFAIL;
+		local = true;
+	}
+	events = local ? pids->events_local : pids->events;
+
+	seq_printf(sf, "max %lld\n", (s64)atomic64_read(&events[pe]));
+	return 0;
+}
 
-	seq_printf(sf, "max %lld\n", (s64)atomic64_read(&pids->events_limit));
+static int pids_events_show(struct seq_file *sf, void *v)
+{
+	__pids_events_show(sf, false);
+	return 0;
+}
+
+static int pids_events_local_show(struct seq_file *sf, void *v)
+{
+	__pids_events_show(sf, true);
 	return 0;
 }
 
@@ -368,9 +424,42 @@ static struct cftype pids_files[] = {
 		.file_offset = offsetof(struct pids_cgroup, events_file),
 		.flags = CFTYPE_NOT_ON_ROOT,
 	},
+	{
+		.name = "events.local",
+		.seq_show = pids_events_local_show,
+		.file_offset = offsetof(struct pids_cgroup, events_local_file),
+		.flags = CFTYPE_NOT_ON_ROOT,
+	},
+	{ }	/* terminate */
+};
+
+static struct cftype pids_files_legacy[] = {
+	{
+		.name = "max",
+		.write = pids_max_write,
+		.seq_show = pids_max_show,
+		.flags = CFTYPE_NOT_ON_ROOT,
+	},
+	{
+		.name = "current",
+		.read_s64 = pids_current_read,
+		.flags = CFTYPE_NOT_ON_ROOT,
+	},
+	{
+		.name = "peak",
+		.flags = CFTYPE_NOT_ON_ROOT,
+		.read_s64 = pids_peak_read,
+	},
+	{
+		.name = "events",
+		.seq_show = pids_events_show,
+		.file_offset = offsetof(struct pids_cgroup, events_file),
+		.flags = CFTYPE_NOT_ON_ROOT,
+	},
 	{ }	/* terminate */
 };
 
+
 struct cgroup_subsys pids_cgrp_subsys = {
 	.css_alloc	= pids_css_alloc,
 	.css_free	= pids_css_free,
@@ -379,7 +468,7 @@ struct cgroup_subsys pids_cgrp_subsys = {
 	.can_fork	= pids_can_fork,
 	.cancel_fork	= pids_cancel_fork,
 	.release	= pids_release,
-	.legacy_cftypes	= pids_files,
+	.legacy_cftypes = pids_files_legacy,
 	.dfl_cftypes	= pids_files,
 	.threaded	= true,
 };