[RFC PATCH bpf-next 4/9] bpf: add bpf rstat helpers

[Yosry Ahmed]

Add bpf_cgroup_rstat_updated() and bpf_cgroup_rstat_flush() helpers
to enable  bpf programs that collect and output cgroup stats
to communicate with the rstat frameworkto add a cgroup to the rstat
updated tree or trigger an rstat flush before reading stats.

ARG_ANYTHING is used here for the struct *cgroup parameter. Would it be
better to add a task_cgroup(subsys_id) helper that returns a cgroup
pointer so that we can use a BTF argument instead?

Signed-off-by: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
---
 include/uapi/linux/bpf.h       | 18 ++++++++++++++++++
 kernel/bpf/helpers.c           | 30 ++++++++++++++++++++++++++++++
 scripts/bpf_doc.py             |  2 ++
 tools/include/uapi/linux/bpf.h | 18 ++++++++++++++++++
 4 files changed, 68 insertions(+)

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 0f4855fa85db..fce5535579d6 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -5149,6 +5149,22 @@ union bpf_attr {
  *		The **hash_algo** is returned on success,
  *		**-EOPNOTSUP** if the hash calculation failed or **-EINVAL** if
  *		invalid arguments are passed.
+ *
+ * void bpf_cgroup_rstat_updated(struct cgroup *cgrp)
+ *	Description
+ *		Notify the rstat framework that bpf stats were updated for
+ *		*cgrp* on the current cpu. Directly calls cgroup_rstat_updated
+ *		with the given *cgrp* and the current cpu.
+ *	Return
+ *		0
+ *
+ * void bpf_cgroup_rstat_flush(struct cgroup *cgrp)
+ *	Description
+ *		Collect all per-cpu stats in *cgrp*'s subtree into global
+ *		counters and propagate them upwards. Directly calls
+ *		cgroup_rstat_flush_irqsafe with the given *cgrp*.
+ *	Return
+ *		0
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -5345,6 +5361,8 @@ union bpf_attr {
 	FN(copy_from_user_task),	\
 	FN(skb_set_tstamp),		\
 	FN(ima_file_hash),		\
+	FN(cgroup_rstat_updated),	\
+	FN(cgroup_rstat_flush),		\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 315053ef6a75..d124eed97ad7 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1374,6 +1374,32 @@ void bpf_timer_cancel_and_free(void *val)
 	kfree(t);
 }
 
+BPF_CALL_1(bpf_cgroup_rstat_updated, struct cgroup *, cgrp)
+{
+	cgroup_rstat_updated(cgrp, smp_processor_id());
+	return 0;
+}
+
+static const struct bpf_func_proto bpf_cgroup_rstat_updated_proto = {
+	.func		= bpf_cgroup_rstat_updated,
+	.gpl_only	= false,
+	.ret_type	= RET_VOID,
+	.arg1_type	= ARG_ANYTHING,
+};
+
+BPF_CALL_1(bpf_cgroup_rstat_flush, struct cgroup *, cgrp)
+{
+	cgroup_rstat_flush_irqsafe(cgrp);
+	return 0;
+}
+
+static const struct bpf_func_proto bpf_cgroup_rstat_flush_proto = {
+	.func		= bpf_cgroup_rstat_flush,
+	.gpl_only	= false,
+	.ret_type	= RET_VOID,
+	.arg1_type	= ARG_ANYTHING,
+};
+
 const struct bpf_func_proto bpf_get_current_task_proto __weak;
 const struct bpf_func_proto bpf_get_current_task_btf_proto __weak;
 const struct bpf_func_proto bpf_probe_read_user_proto __weak;
@@ -1426,6 +1452,10 @@ bpf_base_func_proto(enum bpf_func_id func_id)
 		return &bpf_loop_proto;
 	case BPF_FUNC_strncmp:
 		return &bpf_strncmp_proto;
+	case BPF_FUNC_cgroup_rstat_updated:
+		return &bpf_cgroup_rstat_updated_proto;
+	case BPF_FUNC_cgroup_rstat_flush:
+		return &bpf_cgroup_rstat_flush_proto;
 	default:
 		break;
 	}
diff --git a/scripts/bpf_doc.py b/scripts/bpf_doc.py
index 096625242475..9e2b08557a6f 100755
--- a/scripts/bpf_doc.py
+++ b/scripts/bpf_doc.py
@@ -633,6 +633,7 @@ class PrinterHelpers(Printer):
             'struct socket',
             'struct file',
             'struct bpf_timer',
+            'struct cgroup',
     ]
     known_types = {
             '...',
@@ -682,6 +683,7 @@ class PrinterHelpers(Printer):
             'struct socket',
             'struct file',
             'struct bpf_timer',
+            'struct cgroup',
     }
     mapped_types = {
             'u8': '__u8',
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 0f4855fa85db..fce5535579d6 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -5149,6 +5149,22 @@ union bpf_attr {
  *		The **hash_algo** is returned on success,
  *		**-EOPNOTSUP** if the hash calculation failed or **-EINVAL** if
  *		invalid arguments are passed.
+ *
+ * void bpf_cgroup_rstat_updated(struct cgroup *cgrp)
+ *	Description
+ *		Notify the rstat framework that bpf stats were updated for
+ *		*cgrp* on the current cpu. Directly calls cgroup_rstat_updated
+ *		with the given *cgrp* and the current cpu.
+ *	Return
+ *		0
+ *
+ * void bpf_cgroup_rstat_flush(struct cgroup *cgrp)
+ *	Description
+ *		Collect all per-cpu stats in *cgrp*'s subtree into global
+ *		counters and propagate them upwards. Directly calls
+ *		cgroup_rstat_flush_irqsafe with the given *cgrp*.
+ *	Return
+ *		0
  */
 #define __BPF_FUNC_MAPPER(FN)		\
 	FN(unspec),			\
@@ -5345,6 +5361,8 @@ union bpf_attr {
 	FN(copy_from_user_task),	\
 	FN(skb_set_tstamp),		\
 	FN(ima_file_hash),		\
+	FN(cgroup_rstat_updated),	\
+	FN(cgroup_rstat_flush),		\
 	/* */
 
 /* integer value in 'imm' field of BPF_CALL instruction selects which helper
-- 
2.36.0.512.ge40c2bad7a-goog