[PATCH v2 bpf-next 0/4] cgroup bpf auto-detachment

[PATCH v2 bpf-next 0/4] cgroup bpf auto-detachment

[Roman Gushchin]

This patchset implements a cgroup bpf auto-detachment functionality:
bpf programs are attached as soon as possible after removal of the
cgroup, without waiting for the release of all associated resources.

Patches 2 and 3 are required to implement a corresponding kselftest
in patch 4.

v2:
  1) removed a bogus check in patch 4
  2) moved buf[len] = 0 in patch 2


Roman Gushchin (4):
  bpf: decouple the lifetime of cgroup_bpf from cgroup itself
  selftests/bpf: convert test_cgrp2_attach2 example into kselftest
  selftests/bpf: enable all available cgroup v2 controllers
  selftests/bpf: add auto-detach test

 include/linux/bpf-cgroup.h                    |   8 +-
 include/linux/cgroup.h                        |  18 +++
 kernel/bpf/cgroup.c                           |  25 ++-
 kernel/cgroup/cgroup.c                        |  11 +-
 samples/bpf/Makefile                          |   2 -
 tools/testing/selftests/bpf/Makefile          |   4 +-
 tools/testing/selftests/bpf/cgroup_helpers.c  |  57 +++++++
 .../selftests/bpf/test_cgroup_attach.c        | 145 ++++++++++++++++--
 8 files changed, 243 insertions(+), 27 deletions(-)
 rename samples/bpf/test_cgrp2_attach2.c => tools/testing/selftests/bpf/test_cgroup_attach.c (79%)

-- 
2.20.1

[PATCH v2 bpf-next 1/4] bpf: decouple the lifetime of cgroup_bpf from cgroup itself

[Roman Gushchin]

Currently the lifetime of bpf programs attached to a cgroup is bound
to the lifetime of the cgroup itself. It means that if a user
forgets (or intentionally avoids) to detach a bpf program before
removing the cgroup, it will stay attached up to the release of the
cgroup. Since the cgroup can stay in the dying state (the state
between being rmdir()'ed and being released) for a very long time, it
leads to a waste of memory. Also, it blocks a possibility to implement
the memcg-based memory accounting for bpf objects, because a circular
reference dependency will occur. Charged memory pages are pinning the
corresponding memory cgroup, and if the memory cgroup is pinning
the attached bpf program, nothing will be ever released.

A dying cgroup can not contain any processes, so the only chance for
an attached bpf program to be executed is a live socket associated
with the cgroup. So in order to release all bpf data early, let's
count associated sockets using a new percpu refcounter. On cgroup
removal the counter is transitioned to the atomic mode, and as soon
as it reaches 0, all bpf programs are detached.

The reference counter is not socket specific, and can be used for any
other types of programs, which can be executed from a cgroup-bpf hook
outside of the process context, had such a need arise in the future.

Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: jolsa@redhat.com
---
 include/linux/bpf-cgroup.h |  8 ++++++--
 include/linux/cgroup.h     | 18 ++++++++++++++++++
 kernel/bpf/cgroup.c        | 25 ++++++++++++++++++++++---
 kernel/cgroup/cgroup.c     | 11 ++++++++---
 4 files changed, 54 insertions(+), 8 deletions(-)

diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
index cb3c6b3b89c8..a0945de9ba5f 100644
--- a/include/linux/bpf-cgroup.h
+++ b/include/linux/bpf-cgroup.h
@@ -6,6 +6,7 @@
 #include <linux/errno.h>
 #include <linux/jump_label.h>
 #include <linux/percpu.h>
+#include <linux/percpu-refcount.h>
 #include <linux/rbtree.h>
 #include <uapi/linux/bpf.h>
 
@@ -72,10 +73,13 @@ struct cgroup_bpf {
 
 	/* temp storage for effective prog array used by prog_attach/detach */
 	struct bpf_prog_array __rcu *inactive;
+
+	/* reference counter used to detach bpf programs after cgroup removal */
+	struct percpu_ref refcnt;
 };
 
-void cgroup_bpf_put(struct cgroup *cgrp);
 int cgroup_bpf_inherit(struct cgroup *cgrp);
+void cgroup_bpf_offline(struct cgroup *cgrp);
 
 int __cgroup_bpf_attach(struct cgroup *cgrp, struct bpf_prog *prog,
 			enum bpf_attach_type type, u32 flags);
@@ -283,8 +287,8 @@ int cgroup_bpf_prog_query(const union bpf_attr *attr,
 
 struct bpf_prog;
 struct cgroup_bpf {};
-static inline void cgroup_bpf_put(struct cgroup *cgrp) {}
 static inline int cgroup_bpf_inherit(struct cgroup *cgrp) { return 0; }
+static inline void cgroup_bpf_offline(struct cgroup *cgrp) {}
 
 static inline int cgroup_bpf_prog_attach(const union bpf_attr *attr,
 					 enum bpf_prog_type ptype,
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index c0077adeea83..49e8facf7c4a 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -924,4 +924,22 @@ static inline bool cgroup_task_frozen(struct task_struct *task)
 
 #endif /* !CONFIG_CGROUPS */
 
+#ifdef CONFIG_CGROUP_BPF
+static inline void cgroup_bpf_get(struct cgroup *cgrp)
+{
+	percpu_ref_get(&cgrp->bpf.refcnt);
+}
+
+static inline void cgroup_bpf_put(struct cgroup *cgrp)
+{
+	percpu_ref_put(&cgrp->bpf.refcnt);
+}
+
+#else /* CONFIG_CGROUP_BPF */
+
+static inline void cgroup_bpf_get(struct cgroup *cgrp) {}
+static inline void cgroup_bpf_put(struct cgroup *cgrp) {}
+
+#endif /* CONFIG_CGROUP_BPF */
+
 #endif /* _LINUX_CGROUP_H */
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index fcde0f7b2585..65f5c482ed9d 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -22,12 +22,20 @@
 DEFINE_STATIC_KEY_FALSE(cgroup_bpf_enabled_key);
 EXPORT_SYMBOL(cgroup_bpf_enabled_key);
 
+void cgroup_bpf_offline(struct cgroup *cgrp)
+{
+	cgroup_get(cgrp);
+	percpu_ref_kill(&cgrp->bpf.refcnt);
+}
+
 /**
- * cgroup_bpf_put() - put references of all bpf programs
+ * cgroup_bpf_release() - put references of all bpf programs and
+ *                        release all cgroup bpf data
  * @cgrp: the cgroup to modify
  */
-void cgroup_bpf_put(struct cgroup *cgrp)
+static void cgroup_bpf_release(struct percpu_ref *ref)
 {
+	struct cgroup *cgrp = container_of(ref, struct cgroup, bpf.refcnt);
 	enum bpf_cgroup_storage_type stype;
 	unsigned int type;
 
@@ -47,6 +55,9 @@ void cgroup_bpf_put(struct cgroup *cgrp)
 		}
 		bpf_prog_array_free(cgrp->bpf.effective[type]);
 	}
+
+	percpu_ref_exit(&cgrp->bpf.refcnt);
+	cgroup_put(cgrp);
 }
 
 /* count number of elements in the list.
@@ -167,7 +178,12 @@ int cgroup_bpf_inherit(struct cgroup *cgrp)
  */
 #define	NR ARRAY_SIZE(cgrp->bpf.effective)
 	struct bpf_prog_array __rcu *arrays[NR] = {};
-	int i;
+	int ret, i;
+
+	ret = percpu_ref_init(&cgrp->bpf.refcnt, cgroup_bpf_release, 0,
+			      GFP_KERNEL);
+	if (ret)
+		return -ENOMEM;
 
 	for (i = 0; i < NR; i++)
 		INIT_LIST_HEAD(&cgrp->bpf.progs[i]);
@@ -183,6 +199,9 @@ int cgroup_bpf_inherit(struct cgroup *cgrp)
 cleanup:
 	for (i = 0; i < NR; i++)
 		bpf_prog_array_free(arrays[i]);
+
+	percpu_ref_exit(&cgrp->bpf.refcnt);
+
 	return -ENOMEM;
 }
 
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 217cec4e22c6..ef9cfbfc82a9 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -4955,8 +4955,6 @@ static void css_release_work_fn(struct work_struct *work)
 		if (cgrp->kn)
 			RCU_INIT_POINTER(*(void __rcu __force **)&cgrp->kn->priv,
 					 NULL);
-
-		cgroup_bpf_put(cgrp);
 	}
 
 	mutex_unlock(&cgroup_mutex);
@@ -5482,6 +5480,8 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
 
 	cgroup1_check_for_release(parent);
 
+	cgroup_bpf_offline(cgrp);
+
 	/* put the base reference */
 	percpu_ref_kill(&cgrp->self.refcnt);
 
@@ -6221,6 +6221,7 @@ void cgroup_sk_alloc(struct sock_cgroup_data *skcd)
 		 * Don't use cgroup_get_live().
 		 */
 		cgroup_get(sock_cgroup_ptr(skcd));
+		cgroup_bpf_get(sock_cgroup_ptr(skcd));
 		return;
 	}
 
@@ -6232,6 +6233,7 @@ void cgroup_sk_alloc(struct sock_cgroup_data *skcd)
 		cset = task_css_set(current);
 		if (likely(cgroup_tryget(cset->dfl_cgrp))) {
 			skcd->val = (unsigned long)cset->dfl_cgrp;
+			cgroup_bpf_get(cset->dfl_cgrp);
 			break;
 		}
 		cpu_relax();
@@ -6242,7 +6244,10 @@ void cgroup_sk_alloc(struct sock_cgroup_data *skcd)
 
 void cgroup_sk_free(struct sock_cgroup_data *skcd)
 {
-	cgroup_put(sock_cgroup_ptr(skcd));
+	struct cgroup *cgrp = sock_cgroup_ptr(skcd);
+
+	cgroup_bpf_put(cgrp);
+	cgroup_put(cgrp);
 }
 
 #endif	/* CONFIG_SOCK_CGROUP_DATA */
-- 
2.20.1

[PATCH v2 bpf-next 2/4] selftests/bpf: convert test_cgrp2_attach2 example into kselftest

[Roman Gushchin]

Convert test_cgrp2_attach2 example into a proper test_cgroup_attach
kselftest. It's better because we do run kselftest on a constant
basis, so there are better chances to spot a potential regression.

Also make it slightly less verbose to conform kselftests output style.

Output example:
  $ ./test_cgroup_attach
  #override:PASS
  #multi:PASS
  test_cgroup_attach:PASS

Signed-off-by: Roman Gushchin <guro@fb.com>
---
 samples/bpf/Makefile                          |  2 -
 tools/testing/selftests/bpf/Makefile          |  4 +-
 .../selftests/bpf/test_cgroup_attach.c        | 48 ++++++++++++-------
 3 files changed, 35 insertions(+), 19 deletions(-)
 rename samples/bpf/test_cgrp2_attach2.c => tools/testing/selftests/bpf/test_cgroup_attach.c (92%)

diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
index 4f0a1cdbfe7c..253e5a2856be 100644
--- a/samples/bpf/Makefile
+++ b/samples/bpf/Makefile
@@ -26,7 +26,6 @@ hostprogs-y += map_perf_test
 hostprogs-y += test_overhead
 hostprogs-y += test_cgrp2_array_pin
 hostprogs-y += test_cgrp2_attach
-hostprogs-y += test_cgrp2_attach2
 hostprogs-y += test_cgrp2_sock
 hostprogs-y += test_cgrp2_sock2
 hostprogs-y += xdp1
@@ -81,7 +80,6 @@ map_perf_test-objs := bpf_load.o map_perf_test_user.o
 test_overhead-objs := bpf_load.o test_overhead_user.o
 test_cgrp2_array_pin-objs := test_cgrp2_array_pin.o
 test_cgrp2_attach-objs := test_cgrp2_attach.o
-test_cgrp2_attach2-objs := test_cgrp2_attach2.o $(CGROUP_HELPERS)
 test_cgrp2_sock-objs := test_cgrp2_sock.o
 test_cgrp2_sock2-objs := bpf_load.o test_cgrp2_sock2.o
 xdp1-objs := xdp1_user.o
diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index 66f2dca1dee1..e09f419f4d7e 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -23,7 +23,8 @@ TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test
 	test_align test_verifier_log test_dev_cgroup test_tcpbpf_user \
 	test_sock test_btf test_sockmap test_lirc_mode2_user get_cgroup_id_user \
 	test_socket_cookie test_cgroup_storage test_select_reuseport test_section_names \
-	test_netcnt test_tcpnotify_user test_sock_fields test_sysctl
+	test_netcnt test_tcpnotify_user test_sock_fields test_sysctl \
+	test_cgroup_attach
 
 BPF_OBJ_FILES = $(patsubst %.c,%.o, $(notdir $(wildcard progs/*.c)))
 TEST_GEN_FILES = $(BPF_OBJ_FILES)
@@ -96,6 +97,7 @@ $(OUTPUT)/test_cgroup_storage: cgroup_helpers.c
 $(OUTPUT)/test_netcnt: cgroup_helpers.c
 $(OUTPUT)/test_sock_fields: cgroup_helpers.c
 $(OUTPUT)/test_sysctl: cgroup_helpers.c
+$(OUTPUT)/test_cgroup_attach: cgroup_helpers.c
 
 .PHONY: force
 
diff --git a/samples/bpf/test_cgrp2_attach2.c b/tools/testing/selftests/bpf/test_cgroup_attach.c
similarity index 92%
rename from samples/bpf/test_cgrp2_attach2.c
rename to tools/testing/selftests/bpf/test_cgroup_attach.c
index 0bb6507256b7..93d4fe295e7d 100644
--- a/samples/bpf/test_cgrp2_attach2.c
+++ b/tools/testing/selftests/bpf/test_cgroup_attach.c
@@ -1,3 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0
+
 /* eBPF example program:
  *
  * - Creates arraymap in kernel with 4 bytes keys and 8 byte values
@@ -25,20 +27,27 @@
 #include <sys/resource.h>
 #include <sys/time.h>
 #include <unistd.h>
+#include <linux/filter.h>
 
 #include <linux/bpf.h>
 #include <bpf/bpf.h>
 
-#include "bpf_insn.h"
+#include "bpf_util.h"
 #include "bpf_rlimit.h"
 #include "cgroup_helpers.h"
 
 #define FOO		"/foo"
 #define BAR		"/foo/bar/"
-#define PING_CMD	"ping -c1 -w1 127.0.0.1 > /dev/null"
+#define PING_CMD	"ping -q -c1 -w1 127.0.0.1 > /dev/null"
 
 char bpf_log_buf[BPF_LOG_BUF_SIZE];
 
+#ifdef DEBUG
+#define debug(args...) printf(args)
+#else
+#define debug(args...)
+#endif
+
 static int prog_load(int verdict)
 {
 	int ret;
@@ -89,7 +98,7 @@ static int test_foo_bar(void)
 		goto err;
 	}
 
-	printf("Attached DROP prog. This ping in cgroup /foo should fail...\n");
+	debug("Attached DROP prog. This ping in cgroup /foo should fail...\n");
 	assert(system(PING_CMD) != 0);
 
 	/* Create cgroup /foo/bar, get fd, and join it */
@@ -100,7 +109,7 @@ static int test_foo_bar(void)
 	if (join_cgroup(BAR))
 		goto err;
 
-	printf("Attached DROP prog. This ping in cgroup /foo/bar should fail...\n");
+	debug("Attached DROP prog. This ping in cgroup /foo/bar should fail...\n");
 	assert(system(PING_CMD) != 0);
 
 	if (bpf_prog_attach(allow_prog, bar, BPF_CGROUP_INET_EGRESS,
@@ -109,7 +118,7 @@ static int test_foo_bar(void)
 		goto err;
 	}
 
-	printf("Attached PASS prog. This ping in cgroup /foo/bar should pass...\n");
+	debug("Attached PASS prog. This ping in cgroup /foo/bar should pass...\n");
 	assert(system(PING_CMD) == 0);
 
 	if (bpf_prog_detach(bar, BPF_CGROUP_INET_EGRESS)) {
@@ -117,7 +126,7 @@ static int test_foo_bar(void)
 		goto err;
 	}
 
-	printf("Detached PASS from /foo/bar while DROP is attached to /foo.\n"
+	debug("Detached PASS from /foo/bar while DROP is attached to /foo.\n"
 	       "This ping in cgroup /foo/bar should fail...\n");
 	assert(system(PING_CMD) != 0);
 
@@ -132,7 +141,7 @@ static int test_foo_bar(void)
 		goto err;
 	}
 
-	printf("Attached PASS from /foo/bar and detached DROP from /foo.\n"
+	debug("Attached PASS from /foo/bar and detached DROP from /foo.\n"
 	       "This ping in cgroup /foo/bar should pass...\n");
 	assert(system(PING_CMD) == 0);
 
@@ -199,9 +208,9 @@ static int test_foo_bar(void)
 	close(bar);
 	cleanup_cgroup_environment();
 	if (!rc)
-		printf("### override:PASS\n");
+		printf("#override:PASS\n");
 	else
-		printf("### override:FAIL\n");
+		printf("#override:FAIL\n");
 	return rc;
 }
 
@@ -441,19 +450,26 @@ static int test_multiprog(void)
 	close(cg5);
 	cleanup_cgroup_environment();
 	if (!rc)
-		printf("### multi:PASS\n");
+		printf("#multi:PASS\n");
 	else
-		printf("### multi:FAIL\n");
+		printf("#multi:FAIL\n");
 	return rc;
 }
 
 int main(int argc, char **argv)
 {
-	int rc = 0;
+	int (*tests[])(void) = {test_foo_bar, test_multiprog};
+	int errors = 0;
+	int i;
 
-	rc = test_foo_bar();
-	if (rc)
-		return rc;
+	for (i = 0; i < ARRAY_SIZE(tests); i++)
+		if (tests[i]())
+			errors++;
+
+	if (errors)
+		printf("test_cgroup_attach:FAIL\n");
+	else
+		printf("test_cgroup_attach:PASS\n");
 
-	return test_multiprog();
+	return errors ? EXIT_FAILURE : EXIT_SUCCESS;
 }
-- 
2.20.1

[PATCH v2 bpf-next 3/4] selftests/bpf: enable all available cgroup v2 controllers

[Roman Gushchin]

Enable all available cgroup v2 controllers when setting up
the environment for the bpf kselftests. It's required to properly test
the bpf prog auto-detach feature. Also it will generally increase
the code coverage.

Signed-off-by: Roman Gushchin <guro@fb.com>
---
 tools/testing/selftests/bpf/cgroup_helpers.c | 57 ++++++++++++++++++++
 1 file changed, 57 insertions(+)

diff --git a/tools/testing/selftests/bpf/cgroup_helpers.c b/tools/testing/selftests/bpf/cgroup_helpers.c
index 6692a40a6979..4efe57c171cd 100644
--- a/tools/testing/selftests/bpf/cgroup_helpers.c
+++ b/tools/testing/selftests/bpf/cgroup_helpers.c
@@ -33,6 +33,60 @@
 	snprintf(buf, sizeof(buf), "%s%s%s", CGROUP_MOUNT_PATH, \
 		 CGROUP_WORK_DIR, path)
 
+/**
+ * enable_all_controllers() - Enable all available cgroup v2 controllers
+ *
+ * Enable all available cgroup v2 controllers in order to increase
+ * the code coverage.
+ *
+ * If successful, 0 is returned.
+ */
+int enable_all_controllers(char *cgroup_path)
+{
+	char path[PATH_MAX + 1];
+	char buf[PATH_MAX];
+	char *c, *c2;
+	int fd, cfd;
+	size_t len;
+
+	snprintf(path, sizeof(path), "%s/cgroup.controllers", cgroup_path);
+	fd = open(path, O_RDONLY);
+	if (fd < 0) {
+		log_err("Opening cgroup.controllers: %s", path);
+		return -1;
+	}
+
+	len = read(fd, buf, sizeof(buf) - 1);
+	if (len < 0) {
+		close(fd);
+		log_err("Reading cgroup.controllers: %s", path);
+		return -1;
+	}
+	buf[len] = 0;
+	close(fd);
+
+	/* No controllers available? We're probably on cgroup v1. */
+	if (len == 0)
+		return 0;
+
+	snprintf(path, sizeof(path), "%s/cgroup.subtree_control", cgroup_path);
+	cfd = open(path, O_RDWR);
+	if (cfd < 0) {
+		log_err("Opening cgroup.subtree_control: %s", path);
+		return -1;
+	}
+
+	for (c = strtok_r(buf, " ", &c2); c; c = strtok_r(NULL, " ", &c2)) {
+		if (dprintf(cfd, "+%s\n", c) <= 0) {
+			log_err("Enabling controller %s: %s", c, path);
+			close(cfd);
+			return -1;
+		}
+	}
+	close(cfd);
+	return 0;
+}
+
 /**
  * setup_cgroup_environment() - Setup the cgroup environment
  *
@@ -71,6 +125,9 @@ int setup_cgroup_environment(void)
 		return 1;
 	}
 
+	if (enable_all_controllers(cgroup_workdir))
+		return 1;
+
 	return 0;
 }
 
-- 
2.20.1

[PATCH v2 bpf-next 4/4] selftests/bpf: add auto-detach test

[Roman Gushchin]

Add a kselftest to cover bpf auto-detachment functionality.
The test creates a cgroup, associates some resources with it,
attaches a couple of bpf programs and deletes the cgroup.

Then it checks that bpf programs are going away in 5 seconds.

Expected output:
  $ ./test_cgroup_attach
  #override:PASS
  #multi:PASS
  #autodetach:PASS
  test_cgroup_attach:PASS

On a kernel without auto-detaching:
  $ ./test_cgroup_attach
  #override:PASS
  #multi:PASS
  #autodetach:FAIL
  test_cgroup_attach:FAIL

Signed-off-by: Roman Gushchin <guro@fb.com>
---
 .../selftests/bpf/test_cgroup_attach.c        | 99 ++++++++++++++++++-
 1 file changed, 98 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/test_cgroup_attach.c b/tools/testing/selftests/bpf/test_cgroup_attach.c
index 93d4fe295e7d..bc5bd0f1728e 100644
--- a/tools/testing/selftests/bpf/test_cgroup_attach.c
+++ b/tools/testing/selftests/bpf/test_cgroup_attach.c
@@ -456,9 +456,106 @@ static int test_multiprog(void)
 	return rc;
 }
 
+static int test_autodetach(void)
+{
+	__u32 prog_cnt = 4, attach_flags;
+	int allow_prog[2] = {0};
+	__u32 prog_ids[2] = {0};
+	int cg = 0, i, rc = -1;
+	void *ptr = NULL;
+	int attempts;
+
+
+	for (i = 0; i < ARRAY_SIZE(allow_prog); i++) {
+		allow_prog[i] = prog_load_cnt(1, 1 << i);
+		if (!allow_prog[i])
+			goto err;
+	}
+
+	if (setup_cgroup_environment())
+		goto err;
+
+	/* create a cgroup, attach two programs and remember their ids */
+	cg = create_and_get_cgroup("/cg_autodetach");
+	if (cg < 0)
+		goto err;
+
+	if (join_cgroup("/cg_autodetach"))
+		goto err;
+
+	for (i = 0; i < ARRAY_SIZE(allow_prog); i++) {
+		if (bpf_prog_attach(allow_prog[i], cg, BPF_CGROUP_INET_EGRESS,
+				    BPF_F_ALLOW_MULTI)) {
+			log_err("Attaching prog[%d] to cg:egress", i);
+			goto err;
+		}
+	}
+
+	/* make sure that programs are attached and run some traffic */
+	assert(bpf_prog_query(cg, BPF_CGROUP_INET_EGRESS, 0, &attach_flags,
+			      prog_ids, &prog_cnt) == 0);
+	assert(system(PING_CMD) == 0);
+
+	/* allocate some memory (4Mb) to pin the original cgroup */
+	ptr = malloc(4 * (1 << 20));
+	if (!ptr)
+		goto err;
+
+	/* close programs and cgroup fd */
+	for (i = 0; i < ARRAY_SIZE(allow_prog); i++) {
+		close(allow_prog[i]);
+		allow_prog[i] = 0;
+	}
+
+	close(cg);
+	cg = 0;
+
+	/* leave the cgroup and remove it. don't detach programs */
+	cleanup_cgroup_environment();
+
+	/* wait for the asynchronous auto-detachment.
+	 * wait for no more than 5 sec and give up.
+	 */
+	for (i = 0; i < ARRAY_SIZE(prog_ids); i++) {
+		for (attempts = 5; attempts >= 0; attempts--) {
+			int fd = bpf_prog_get_fd_by_id(prog_ids[i]);
+
+			if (fd < 0)
+				break;
+
+			/* don't leave the fd open */
+			close(fd);
+
+			if (!attempts)
+				goto err;
+
+			sleep(1);
+		}
+	}
+
+	rc = 0;
+err:
+	for (i = 0; i < ARRAY_SIZE(allow_prog); i++)
+		if (allow_prog[i] > 0)
+			close(allow_prog[i]);
+	if (cg)
+		close(cg);
+	free(ptr);
+	cleanup_cgroup_environment();
+	if (!rc)
+		printf("#autodetach:PASS\n");
+	else
+		printf("#autodetach:FAIL\n");
+	return rc;
+}
+
 int main(int argc, char **argv)
 {
-	int (*tests[])(void) = {test_foo_bar, test_multiprog};
+	int (*tests[])(void) = {
+		test_foo_bar,
+		test_multiprog,
+		test_autodetach,
+	};
 	int errors = 0;
 	int i;
 
-- 
2.20.1

Re: [PATCH v2 bpf-next 0/4] cgroup bpf auto-detachment

[Yonghong Song]

On 5/22/19 4:20 PM, Roman Gushchin wrote:
> This patchset implements a cgroup bpf auto-detachment functionality:
> bpf programs are attached as soon as possible after removal of the
typo here "attached" => "detached"?

> cgroup, without waiting for the release of all associated resources.
> 
> Patches 2 and 3 are required to implement a corresponding kselftest
> in patch 4.
> 
> v2:
>    1) removed a bogus check in patch 4
>    2) moved buf[len] = 0 in patch 2
> 
> 
> Roman Gushchin (4):
>    bpf: decouple the lifetime of cgroup_bpf from cgroup itself
>    selftests/bpf: convert test_cgrp2_attach2 example into kselftest
>    selftests/bpf: enable all available cgroup v2 controllers
>    selftests/bpf: add auto-detach test
> 
>   include/linux/bpf-cgroup.h                    |   8 +-
>   include/linux/cgroup.h                        |  18 +++
>   kernel/bpf/cgroup.c                           |  25 ++-
>   kernel/cgroup/cgroup.c                        |  11 +-
>   samples/bpf/Makefile                          |   2 -
>   tools/testing/selftests/bpf/Makefile          |   4 +-
>   tools/testing/selftests/bpf/cgroup_helpers.c  |  57 +++++++
>   .../selftests/bpf/test_cgroup_attach.c        | 145 ++++++++++++++++--
>   8 files changed, 243 insertions(+), 27 deletions(-)
>   rename samples/bpf/test_cgrp2_attach2.c => tools/testing/selftests/bpf/test_cgroup_attach.c (79%)
> 

Re: [PATCH v2 bpf-next 1/4] bpf: decouple the lifetime of cgroup_bpf from cgroup itself

[Yonghong Song]

On 5/22/19 4:20 PM, Roman Gushchin wrote:
> Currently the lifetime of bpf programs attached to a cgroup is bound
> to the lifetime of the cgroup itself. It means that if a user
> forgets (or intentionally avoids) to detach a bpf program before
> removing the cgroup, it will stay attached up to the release of the
> cgroup. Since the cgroup can stay in the dying state (the state
> between being rmdir()'ed and being released) for a very long time, it
> leads to a waste of memory. Also, it blocks a possibility to implement
> the memcg-based memory accounting for bpf objects, because a circular
> reference dependency will occur. Charged memory pages are pinning the
> corresponding memory cgroup, and if the memory cgroup is pinning
> the attached bpf program, nothing will be ever released.
> 
> A dying cgroup can not contain any processes, so the only chance for
> an attached bpf program to be executed is a live socket associated
> with the cgroup. So in order to release all bpf data early, let's
> count associated sockets using a new percpu refcounter. On cgroup
> removal the counter is transitioned to the atomic mode, and as soon
> as it reaches 0, all bpf programs are detached.
> 
> The reference counter is not socket specific, and can be used for any
> other types of programs, which can be executed from a cgroup-bpf hook
> outside of the process context, had such a need arise in the future.
> 
> Signed-off-by: Roman Gushchin <guro@fb.com>
> Cc: jolsa@redhat.com

The logic looks sound to me. With one nit below,
Acked-by: Yonghong Song <yhs@fb.com>

> ---
>   include/linux/bpf-cgroup.h |  8 ++++++--
>   include/linux/cgroup.h     | 18 ++++++++++++++++++
>   kernel/bpf/cgroup.c        | 25 ++++++++++++++++++++++---
>   kernel/cgroup/cgroup.c     | 11 ++++++++---
>   4 files changed, 54 insertions(+), 8 deletions(-)
> 
[...]
> @@ -167,7 +178,12 @@ int cgroup_bpf_inherit(struct cgroup *cgrp)
>    */
>   #define	NR ARRAY_SIZE(cgrp->bpf.effective)
>   	struct bpf_prog_array __rcu *arrays[NR] = {};
> -	int i;
> +	int ret, i;
> +
> +	ret = percpu_ref_init(&cgrp->bpf.refcnt, cgroup_bpf_release, 0,
> +			      GFP_KERNEL);
> +	if (ret)
> +		return -ENOMEM;
Maybe return "ret" here instead of -ENOMEM. Currently, percpu_ref_init
only return error code is -ENOMEM. But in the future, it could
change?

>   
>   	for (i = 0; i < NR; i++)
>   		INIT_LIST_HEAD(&cgrp->bpf.progs[i]);
> @@ -183,6 +199,9 @@ int cgroup_bpf_inherit(struct cgroup *cgrp)
>   cleanup:
>   	for (i = 0; i < NR; i++)
>   		bpf_prog_array_free(arrays[i]);
> +
> +	percpu_ref_exit(&cgrp->bpf.refcnt);
> +
>   	return -ENOMEM;
>   }
>   
[...]

Re: [PATCH v2 bpf-next 2/4] selftests/bpf: convert test_cgrp2_attach2 example into kselftest

[Yonghong Song]

On 5/22/19 4:20 PM, Roman Gushchin wrote:
> Convert test_cgrp2_attach2 example into a proper test_cgroup_attach
> kselftest. It's better because we do run kselftest on a constant
> basis, so there are better chances to spot a potential regression.
> 
> Also make it slightly less verbose to conform kselftests output style.
> 
> Output example:
>    $ ./test_cgroup_attach
>    #override:PASS
>    #multi:PASS
>    test_cgroup_attach:PASS
> 
> Signed-off-by: Roman Gushchin <guro@fb.com>
Ack except the nit below.
Acked-by: Yonghong Song <yhs@fb.com>
> ---
>   samples/bpf/Makefile                          |  2 -
>   tools/testing/selftests/bpf/Makefile          |  4 +-
>   .../selftests/bpf/test_cgroup_attach.c        | 48 ++++++++++++-------
>   3 files changed, 35 insertions(+), 19 deletions(-)
>   rename samples/bpf/test_cgrp2_attach2.c => tools/testing/selftests/bpf/test_cgroup_attach.c (92%)
> 
> diff --git a/samples/bpf/Makefile b/samples/bpf/Makefile
> index 4f0a1cdbfe7c..253e5a2856be 100644
> --- a/samples/bpf/Makefile
> +++ b/samples/bpf/Makefile
> @@ -26,7 +26,6 @@ hostprogs-y += map_perf_test
>   hostprogs-y += test_overhead
>   hostprogs-y += test_cgrp2_array_pin
>   hostprogs-y += test_cgrp2_attach
> -hostprogs-y += test_cgrp2_attach2
>   hostprogs-y += test_cgrp2_sock
>   hostprogs-y += test_cgrp2_sock2
>   hostprogs-y += xdp1
> @@ -81,7 +80,6 @@ map_perf_test-objs := bpf_load.o map_perf_test_user.o
>   test_overhead-objs := bpf_load.o test_overhead_user.o
>   test_cgrp2_array_pin-objs := test_cgrp2_array_pin.o
>   test_cgrp2_attach-objs := test_cgrp2_attach.o
> -test_cgrp2_attach2-objs := test_cgrp2_attach2.o $(CGROUP_HELPERS)
>   test_cgrp2_sock-objs := test_cgrp2_sock.o
>   test_cgrp2_sock2-objs := bpf_load.o test_cgrp2_sock2.o
>   xdp1-objs := xdp1_user.o
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index 66f2dca1dee1..e09f419f4d7e 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -23,7 +23,8 @@ TEST_GEN_PROGS = test_verifier test_tag test_maps test_lru_map test_lpm_map test
>   	test_align test_verifier_log test_dev_cgroup test_tcpbpf_user \
>   	test_sock test_btf test_sockmap test_lirc_mode2_user get_cgroup_id_user \
>   	test_socket_cookie test_cgroup_storage test_select_reuseport test_section_names \
> -	test_netcnt test_tcpnotify_user test_sock_fields test_sysctl
> +	test_netcnt test_tcpnotify_user test_sock_fields test_sysctl \
> +	test_cgroup_attach
>   
>   BPF_OBJ_FILES = $(patsubst %.c,%.o, $(notdir $(wildcard progs/*.c)))
>   TEST_GEN_FILES = $(BPF_OBJ_FILES)
> @@ -96,6 +97,7 @@ $(OUTPUT)/test_cgroup_storage: cgroup_helpers.c
>   $(OUTPUT)/test_netcnt: cgroup_helpers.c
>   $(OUTPUT)/test_sock_fields: cgroup_helpers.c
>   $(OUTPUT)/test_sysctl: cgroup_helpers.c
> +$(OUTPUT)/test_cgroup_attach: cgroup_helpers.c
>   
>   .PHONY: force
>   
> diff --git a/samples/bpf/test_cgrp2_attach2.c b/tools/testing/selftests/bpf/test_cgroup_attach.c
> similarity index 92%
> rename from samples/bpf/test_cgrp2_attach2.c
> rename to tools/testing/selftests/bpf/test_cgroup_attach.c
> index 0bb6507256b7..93d4fe295e7d 100644
> --- a/samples/bpf/test_cgrp2_attach2.c
> +++ b/tools/testing/selftests/bpf/test_cgroup_attach.c
> @@ -1,3 +1,5 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
>   /* eBPF example program:
>    *
>    * - Creates arraymap in kernel with 4 bytes keys and 8 byte values
> @@ -25,20 +27,27 @@
>   #include <sys/resource.h>
>   #include <sys/time.h>
>   #include <unistd.h>
> +#include <linux/filter.h>
>   
>   #include <linux/bpf.h>
>   #include <bpf/bpf.h>
>   
> -#include "bpf_insn.h"
> +#include "bpf_util.h"
>   #include "bpf_rlimit.h"
>   #include "cgroup_helpers.h"
>   
>   #define FOO		"/foo"
>   #define BAR		"/foo/bar/"
> -#define PING_CMD	"ping -c1 -w1 127.0.0.1 > /dev/null"
> +#define PING_CMD	"ping -q -c1 -w1 127.0.0.1 > /dev/null"
>   
>   char bpf_log_buf[BPF_LOG_BUF_SIZE];
>   
> +#ifdef DEBUG
> +#define debug(args...) printf(args)
> +#else
> +#define debug(args...)
> +#endif
> +
>   static int prog_load(int verdict)
>   {
>   	int ret;
> @@ -89,7 +98,7 @@ static int test_foo_bar(void)
>   		goto err;
>   	}
>   
> -	printf("Attached DROP prog. This ping in cgroup /foo should fail...\n");
> +	debug("Attached DROP prog. This ping in cgroup /foo should fail...\n");
>   	assert(system(PING_CMD) != 0);
>   
>   	/* Create cgroup /foo/bar, get fd, and join it */
> @@ -100,7 +109,7 @@ static int test_foo_bar(void)
>   	if (join_cgroup(BAR))
>   		goto err;
>   
> -	printf("Attached DROP prog. This ping in cgroup /foo/bar should fail...\n");
> +	debug("Attached DROP prog. This ping in cgroup /foo/bar should fail...\n");
>   	assert(system(PING_CMD) != 0);
>   
>   	if (bpf_prog_attach(allow_prog, bar, BPF_CGROUP_INET_EGRESS,
> @@ -109,7 +118,7 @@ static int test_foo_bar(void)
>   		goto err;
>   	}
>   
> -	printf("Attached PASS prog. This ping in cgroup /foo/bar should pass...\n");
> +	debug("Attached PASS prog. This ping in cgroup /foo/bar should pass...\n");
>   	assert(system(PING_CMD) == 0);
>   
>   	if (bpf_prog_detach(bar, BPF_CGROUP_INET_EGRESS)) {
> @@ -117,7 +126,7 @@ static int test_foo_bar(void)
>   		goto err;
>   	}
>   
> -	printf("Detached PASS from /foo/bar while DROP is attached to /foo.\n"
> +	debug("Detached PASS from /foo/bar while DROP is attached to /foo.\n"
>   	       "This ping in cgroup /foo/bar should fail...\n");
>   	assert(system(PING_CMD) != 0);
>   
> @@ -132,7 +141,7 @@ static int test_foo_bar(void)
>   		goto err;
>   	}
>   
> -	printf("Attached PASS from /foo/bar and detached DROP from /foo.\n"
> +	debug("Attached PASS from /foo/bar and detached DROP from /foo.\n"
>   	       "This ping in cgroup /foo/bar should pass...\n");
>   	assert(system(PING_CMD) == 0);
>   
> @@ -199,9 +208,9 @@ static int test_foo_bar(void)
>   	close(bar);
>   	cleanup_cgroup_environment();
>   	if (!rc)
> -		printf("### override:PASS\n");
> +		printf("#override:PASS\n");
>   	else
> -		printf("### override:FAIL\n");
> +		printf("#override:FAIL\n");
>   	return rc;
>   }
>   
> @@ -441,19 +450,26 @@ static int test_multiprog(void)
>   	close(cg5);
>   	cleanup_cgroup_environment();
>   	if (!rc)
> -		printf("### multi:PASS\n");
> +		printf("#multi:PASS\n");
>   	else
> -		printf("### multi:FAIL\n");
> +		printf("#multi:FAIL\n");
>   	return rc;
>   }
>   
>   int main(int argc, char **argv)

argc and argv are not used.

currently, the debug output is controlled by macro DEBUG.
you could enable debug output with command line option.
But I am okay with the current mechanism as well.

>   {
> -	int rc = 0;
> +	int (*tests[])(void) = {test_foo_bar, test_multiprog};
> +	int errors = 0;
> +	int i;
>   
> -	rc = test_foo_bar();
> -	if (rc)
> -		return rc;
> +	for (i = 0; i < ARRAY_SIZE(tests); i++)
> +		if (tests[i]())
> +			errors++;
> +
> +	if (errors)
> +		printf("test_cgroup_attach:FAIL\n");
> +	else
> +		printf("test_cgroup_attach:PASS\n");
>   
> -	return test_multiprog();
> +	return errors ? EXIT_FAILURE : EXIT_SUCCESS;
>   }
> 

Re: [PATCH v2 bpf-next 3/4] selftests/bpf: enable all available cgroup v2 controllers

[Yonghong Song]

On 5/22/19 4:20 PM, Roman Gushchin wrote:
> Enable all available cgroup v2 controllers when setting up
> the environment for the bpf kselftests. It's required to properly test
> the bpf prog auto-detach feature. Also it will generally increase
> the code coverage.
> 
> Signed-off-by: Roman Gushchin <guro@fb.com>
Looks good to me. Ack with one nit below.
Acked-by: Yonghong Song <yhs@fb.com>

> ---
>   tools/testing/selftests/bpf/cgroup_helpers.c | 57 ++++++++++++++++++++
>   1 file changed, 57 insertions(+)
> 
> diff --git a/tools/testing/selftests/bpf/cgroup_helpers.c b/tools/testing/selftests/bpf/cgroup_helpers.c
> index 6692a40a6979..4efe57c171cd 100644
> --- a/tools/testing/selftests/bpf/cgroup_helpers.c
> +++ b/tools/testing/selftests/bpf/cgroup_helpers.c
> @@ -33,6 +33,60 @@
>   	snprintf(buf, sizeof(buf), "%s%s%s", CGROUP_MOUNT_PATH, \
>   		 CGROUP_WORK_DIR, path)
>   
> +/**
> + * enable_all_controllers() - Enable all available cgroup v2 controllers
> + *
> + * Enable all available cgroup v2 controllers in order to increase
> + * the code coverage.
> + *
> + * If successful, 0 is returned.
> + */
> +int enable_all_controllers(char *cgroup_path)
> +{
> +	char path[PATH_MAX + 1];
> +	char buf[PATH_MAX];
> +	char *c, *c2;
> +	int fd, cfd;
> +	size_t len;
> +
> +	snprintf(path, sizeof(path), "%s/cgroup.controllers", cgroup_path);
> +	fd = open(path, O_RDONLY);
> +	if (fd < 0) {
> +		log_err("Opening cgroup.controllers: %s", path);
> +		return -1;
It looks like either -1 or 1 could be returned to indicate an error
in this file. Maybe, at least for the consistency of this file,
always returning 1 is preferred as setup_cgroup_environment()
has the following comments:
  * This function will print an error to stderr and return 1 if it is unable
  * to setup the cgroup environment. If setup is successful, 0 is returned.

> +	}
> +
> +	len = read(fd, buf, sizeof(buf) - 1);
> +	if (len < 0) {
> +		close(fd);
> +		log_err("Reading cgroup.controllers: %s", path);
> +		return -1;
> +	}
> +	buf[len] = 0;
> +	close(fd);
> +
> +	/* No controllers available? We're probably on cgroup v1. */
> +	if (len == 0)
> +		return 0;
> +
> +	snprintf(path, sizeof(path), "%s/cgroup.subtree_control", cgroup_path);
> +	cfd = open(path, O_RDWR);
> +	if (cfd < 0) {
> +		log_err("Opening cgroup.subtree_control: %s", path);
> +		return -1;
> +	}
> +
> +	for (c = strtok_r(buf, " ", &c2); c; c = strtok_r(NULL, " ", &c2)) {
> +		if (dprintf(cfd, "+%s\n", c) <= 0) {
> +			log_err("Enabling controller %s: %s", c, path);
> +			close(cfd);
> +			return -1;
> +		}
> +	}
> +	close(cfd);
> +	return 0;
> +}
> +
>   /**
>    * setup_cgroup_environment() - Setup the cgroup environment
>    *
> @@ -71,6 +125,9 @@ int setup_cgroup_environment(void)
>   		return 1;
>   	}
>   
> +	if (enable_all_controllers(cgroup_workdir))
> +		return 1;
> +
>   	return 0;
>   }
>   
> 

Re: [PATCH v2 bpf-next 4/4] selftests/bpf: add auto-detach test

[Yonghong Song]

On 5/22/19 4:20 PM, Roman Gushchin wrote:
> Add a kselftest to cover bpf auto-detachment functionality.
> The test creates a cgroup, associates some resources with it,
> attaches a couple of bpf programs and deletes the cgroup.
> 
> Then it checks that bpf programs are going away in 5 seconds.
> 
> Expected output:
>    $ ./test_cgroup_attach
>    #override:PASS
>    #multi:PASS
>    #autodetach:PASS
>    test_cgroup_attach:PASS
> 
> On a kernel without auto-detaching:
>    $ ./test_cgroup_attach
>    #override:PASS
>    #multi:PASS
>    #autodetach:FAIL
>    test_cgroup_attach:FAIL

I ran this problem without both old and new kernels and
both get all PASSes. My testing environment is a VM.
Could you specify how to trigger the above failure?

> 
> Signed-off-by: Roman Gushchin <guro@fb.com>
> ---
>   .../selftests/bpf/test_cgroup_attach.c        | 99 ++++++++++++++++++-
>   1 file changed, 98 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/bpf/test_cgroup_attach.c b/tools/testing/selftests/bpf/test_cgroup_attach.c
> index 93d4fe295e7d..bc5bd0f1728e 100644
> --- a/tools/testing/selftests/bpf/test_cgroup_attach.c
> +++ b/tools/testing/selftests/bpf/test_cgroup_attach.c
> @@ -456,9 +456,106 @@ static int test_multiprog(void)
>   	return rc;
>   }
>   
> +static int test_autodetach(void)
> +{
> +	__u32 prog_cnt = 4, attach_flags;
> +	int allow_prog[2] = {0};
> +	__u32 prog_ids[2] = {0};
> +	int cg = 0, i, rc = -1;
> +	void *ptr = NULL;
> +	int attempts;
> +
> +
> +	for (i = 0; i < ARRAY_SIZE(allow_prog); i++) {
> +		allow_prog[i] = prog_load_cnt(1, 1 << i);
> +		if (!allow_prog[i])
> +			goto err;
> +	}
> +
> +	if (setup_cgroup_environment())
> +		goto err;
> +
> +	/* create a cgroup, attach two programs and remember their ids */
> +	cg = create_and_get_cgroup("/cg_autodetach");
> +	if (cg < 0)
> +		goto err;
> +
> +	if (join_cgroup("/cg_autodetach"))
> +		goto err;
> +
> +	for (i = 0; i < ARRAY_SIZE(allow_prog); i++) {
> +		if (bpf_prog_attach(allow_prog[i], cg, BPF_CGROUP_INET_EGRESS,
> +				    BPF_F_ALLOW_MULTI)) {
> +			log_err("Attaching prog[%d] to cg:egress", i);
> +			goto err;
> +		}
> +	}
> +
> +	/* make sure that programs are attached and run some traffic */
> +	assert(bpf_prog_query(cg, BPF_CGROUP_INET_EGRESS, 0, &attach_flags,
> +			      prog_ids, &prog_cnt) == 0);
> +	assert(system(PING_CMD) == 0);
> +
> +	/* allocate some memory (4Mb) to pin the original cgroup */
> +	ptr = malloc(4 * (1 << 20));
> +	if (!ptr)
> +		goto err;
> +
> +	/* close programs and cgroup fd */
> +	for (i = 0; i < ARRAY_SIZE(allow_prog); i++) {
> +		close(allow_prog[i]);
> +		allow_prog[i] = 0;
> +	}
> +
> +	close(cg);
> +	cg = 0;
> +
> +	/* leave the cgroup and remove it. don't detach programs */
> +	cleanup_cgroup_environment();
> +
> +	/* wait for the asynchronous auto-detachment.
> +	 * wait for no more than 5 sec and give up.
> +	 */
> +	for (i = 0; i < ARRAY_SIZE(prog_ids); i++) {
> +		for (attempts = 5; attempts >= 0; attempts--) {
> +			int fd = bpf_prog_get_fd_by_id(prog_ids[i]);
> +
> +			if (fd < 0)
> +				break;
> +
> +			/* don't leave the fd open */
> +			close(fd);
> +
> +			if (!attempts)
> +				goto err;
> +
> +			sleep(1);
> +		}
> +	}
> +
> +	rc = 0;
> +err:
> +	for (i = 0; i < ARRAY_SIZE(allow_prog); i++)
> +		if (allow_prog[i] > 0)
> +			close(allow_prog[i]);
> +	if (cg)
> +		close(cg);
> +	free(ptr);
> +	cleanup_cgroup_environment();
> +	if (!rc)
> +		printf("#autodetach:PASS\n");
> +	else
> +		printf("#autodetach:FAIL\n");
> +	return rc;
> +}
> +
>   int main(int argc, char **argv)
>   {
> -	int (*tests[])(void) = {test_foo_bar, test_multiprog};
> +	int (*tests[])(void) = {
> +		test_foo_bar,
> +		test_multiprog,
> +		test_autodetach,
> +	};
>   	int errors = 0;
>   	int i;
>   
> 

Re: [PATCH v2 bpf-next 4/4] selftests/bpf: add auto-detach test

[Yonghong Song]

On 5/22/19 4:20 PM, Roman Gushchin wrote:
> Add a kselftest to cover bpf auto-detachment functionality.
> The test creates a cgroup, associates some resources with it,
> attaches a couple of bpf programs and deletes the cgroup.
> 
> Then it checks that bpf programs are going away in 5 seconds.
> 
> Expected output:
>    $ ./test_cgroup_attach
>    #override:PASS
>    #multi:PASS
>    #autodetach:PASS
>    test_cgroup_attach:PASS
> 
> On a kernel without auto-detaching:
>    $ ./test_cgroup_attach
>    #override:PASS
>    #multi:PASS
>    #autodetach:FAIL
>    test_cgroup_attach:FAIL
> 
> Signed-off-by: Roman Gushchin <guro@fb.com>
> ---
>   .../selftests/bpf/test_cgroup_attach.c        | 99 ++++++++++++++++++-
>   1 file changed, 98 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/bpf/test_cgroup_attach.c b/tools/testing/selftests/bpf/test_cgroup_attach.c
> index 93d4fe295e7d..bc5bd0f1728e 100644
> --- a/tools/testing/selftests/bpf/test_cgroup_attach.c
> +++ b/tools/testing/selftests/bpf/test_cgroup_attach.c
> @@ -456,9 +456,106 @@ static int test_multiprog(void)
>   	return rc;
>   }
>   
> +static int test_autodetach(void)
> +{
> +	__u32 prog_cnt = 4, attach_flags;
> +	int allow_prog[2] = {0};
> +	__u32 prog_ids[2] = {0};
> +	int cg = 0, i, rc = -1;
> +	void *ptr = NULL;
> +	int attempts;
> +
> +
Also extra line here.

> +	for (i = 0; i < ARRAY_SIZE(allow_prog); i++) {
> +		allow_prog[i] = prog_load_cnt(1, 1 << i);
> +		if (!allow_prog[i])
> +			goto err;
> +	}
> +
> +	if (setup_cgroup_environment())
> +		goto err;
> +
> +	/* create a cgroup, attach two programs and remember their ids */
> +	cg = create_and_get_cgroup("/cg_autodetach");
[...]
> +
>   int main(int argc, char **argv)
>   {
> -	int (*tests[])(void) = {test_foo_bar, test_multiprog};
> +	int (*tests[])(void) = {
> +		test_foo_bar,
> +		test_multiprog,
> +		test_autodetach,
> +	};
>   	int errors = 0;
>   	int i;
>   
> 

Re: [PATCH v2 bpf-next 4/4] selftests/bpf: add auto-detach test

[Roman Gushchin]

On Wed, May 22, 2019 at 10:47:24PM -0700, Yonghong Song wrote:
> 
> 
> On 5/22/19 4:20 PM, Roman Gushchin wrote:
> > Add a kselftest to cover bpf auto-detachment functionality.
> > The test creates a cgroup, associates some resources with it,
> > attaches a couple of bpf programs and deletes the cgroup.
> > 
> > Then it checks that bpf programs are going away in 5 seconds.
> > 
> > Expected output:
> >    $ ./test_cgroup_attach
> >    #override:PASS
> >    #multi:PASS
> >    #autodetach:PASS
> >    test_cgroup_attach:PASS
> > 
> > On a kernel without auto-detaching:
> >    $ ./test_cgroup_attach
> >    #override:PASS
> >    #multi:PASS
> >    #autodetach:FAIL
> >    test_cgroup_attach:FAIL
> 
> I ran this problem without both old and new kernels and
> both get all PASSes. My testing environment is a VM.
> Could you specify how to trigger the above failure?

Most likely you're running cgroup v1, so the memory controller
is not enabled on unified hierarchy. You need to pass
"cgroup_no_v1=all systemd.unified_cgroup_hierarchy=1"
as boot time options to run fully on cgroup v2.

But generally speaking, the lifecycle of a dying cgroup is
completely implementation-defined. No guarantees are provided.
So false positives are fine here, and shouldn't be considered as
something bad.

At the end all we want it to detach programs in a reasonable time
after rmdir.

Btw, thank you for the careful review of the patchset. I'll
address your comments, add acks and will send out v3.

Thanks!

Re: [PATCH v2 bpf-next 4/4] selftests/bpf: add auto-detach test

[Yonghong Song]

On 5/23/19 10:58 AM, Roman Gushchin wrote:
> On Wed, May 22, 2019 at 10:47:24PM -0700, Yonghong Song wrote:
>>
>>
>> On 5/22/19 4:20 PM, Roman Gushchin wrote:
>>> Add a kselftest to cover bpf auto-detachment functionality.
>>> The test creates a cgroup, associates some resources with it,
>>> attaches a couple of bpf programs and deletes the cgroup.
>>>
>>> Then it checks that bpf programs are going away in 5 seconds.
>>>
>>> Expected output:
>>>     $ ./test_cgroup_attach
>>>     #override:PASS
>>>     #multi:PASS
>>>     #autodetach:PASS
>>>     test_cgroup_attach:PASS
>>>
>>> On a kernel without auto-detaching:
>>>     $ ./test_cgroup_attach
>>>     #override:PASS
>>>     #multi:PASS
>>>     #autodetach:FAIL
>>>     test_cgroup_attach:FAIL
>>
>> I ran this problem without both old and new kernels and
>> both get all PASSes. My testing environment is a VM.
>> Could you specify how to trigger the above failure?
> 
> Most likely you're running cgroup v1, so the memory controller
> is not enabled on unified hierarchy. You need to pass
> "cgroup_no_v1=all systemd.unified_cgroup_hierarchy=1"
> as boot time options to run fully on cgroup v2.

I tested on a cgroup v2 machine and it indeed failed without
the core patch. Thanks!

> 
> But generally speaking, the lifecycle of a dying cgroup is
> completely implementation-defined. No guarantees are provided.
> So false positives are fine here, and shouldn't be considered as
> something bad.
> 
> At the end all we want it to detach programs in a reasonable time
> after rmdir.
> 
> Btw, thank you for the careful review of the patchset. I'll
> address your comments, add acks and will send out v3.
> 
> Thanks!
>