From 5aefc153b25b42a80942e5c367ce143817551870 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Michal=20Sekleta=CC=81r?= <msekleta@redhat.com>
Date: Wed, 29 Apr 2020 17:40:22 +0200
Subject: [PATCH] basic/cgroup-util: introduce cg_get_keyed_attribute_full()

Callers of cg_get_keyed_attribute_full() can now specify via the flag whether the
missing keyes in cgroup attribute file are OK or not. Also the wrappers for both
strict and graceful version are provided.

(cherry picked from commit 25a1f04c682260bb9b96e25bdf33665d6172db98)

Related: #1830861
---
 src/basic/cgroup-util.c     | 13 ++++++++++---
 src/basic/cgroup-util.h     | 24 +++++++++++++++++++++++-
 src/test/test-cgroup-util.c | 20 ++++++++++++++++++++
 3 files changed, 53 insertions(+), 4 deletions(-)

diff --git a/src/basic/cgroup-util.c b/src/basic/cgroup-util.c
index 92bc1f2543..4c0b73850d 100644
--- a/src/basic/cgroup-util.c
+++ b/src/basic/cgroup-util.c
@@ -2021,12 +2021,13 @@ int cg_get_attribute(const char *controller, const char *path, const char *attri
         return read_one_line_file(p, ret);
 }
 
-int cg_get_keyed_attribute(
+int cg_get_keyed_attribute_full(
                 const char *controller,
                 const char *path,
                 const char *attribute,
                 char **keys,
-                char **ret_values) {
+                char **ret_values,
+                CGroupKeyMode mode) {
 
         _cleanup_free_ char *filename = NULL, *contents = NULL;
         const char *p;
@@ -2086,7 +2087,10 @@ int cg_get_keyed_attribute(
                 p += strspn(p, NEWLINE);
         }
 
-        r = -ENXIO;
+        if (mode & CG_KEY_MODE_GRACEFUL)
+                goto done;
+        else
+                r = -ENXIO;
 
 fail:
         for (i = 0; i < n; i++)
@@ -2096,6 +2100,9 @@ fail:
 
 done:
         memcpy(ret_values, v, sizeof(char*) * n);
+        if (mode & CG_KEY_MODE_GRACEFUL)
+                return n_done;
+
         return 0;
 
 }
diff --git a/src/basic/cgroup-util.h b/src/basic/cgroup-util.h
index b414600dca..0673f4b4ce 100644
--- a/src/basic/cgroup-util.h
+++ b/src/basic/cgroup-util.h
@@ -167,9 +167,31 @@ int cg_attach(const char *controller, const char *path, pid_t pid);
 int cg_attach_fallback(const char *controller, const char *path, pid_t pid);
 int cg_create_and_attach(const char *controller, const char *path, pid_t pid);
 
+typedef enum  {
+        CG_KEY_MODE_GRACEFUL = 1 << 0,
+} CGroupKeyMode;
+
 int cg_set_attribute(const char *controller, const char *path, const char *attribute, const char *value);
 int cg_get_attribute(const char *controller, const char *path, const char *attribute, char **ret);
-int cg_get_keyed_attribute(const char *controller, const char *path, const char *attribute, char **keys, char **values);
+int cg_get_keyed_attribute_full(const char *controller, const char *path, const char *attribute, char **keys, char **values, CGroupKeyMode mode);
+
+static inline int cg_get_keyed_attribute(
+                const char *controller,
+                const char *path,
+                const char *attribute,
+                char **keys,
+                char **ret_values) {
+        return cg_get_keyed_attribute_full(controller, path, attribute, keys, ret_values, 0);
+}
+
+static inline int cg_get_keyed_attribute_graceful(
+                const char *controller,
+                const char *path,
+                const char *attribute,
+                char **keys,
+                char **ret_values) {
+        return cg_get_keyed_attribute_full(controller, path, attribute, keys, ret_values, CG_KEY_MODE_GRACEFUL);
+}
 
 int cg_set_access(const char *controller, const char *path, uid_t uid, gid_t gid);
 
diff --git a/src/test/test-cgroup-util.c b/src/test/test-cgroup-util.c
index d49356315e..60d7bb19cb 100644
--- a/src/test/test-cgroup-util.c
+++ b/src/test/test-cgroup-util.c
@@ -421,22 +421,42 @@ static void test_cg_get_keyed_attribute(void) {
         }
 
         assert_se(cg_get_keyed_attribute("cpu", "/init.scope", "cpu.stat", STRV_MAKE("no_such_attr"), &val) == -ENXIO);
+        assert_se(cg_get_keyed_attribute_graceful("cpu", "/init.scope", "cpu.stat", STRV_MAKE("no_such_attr"), &val) == 0);
         assert_se(val == NULL);
 
         assert_se(cg_get_keyed_attribute("cpu", "/init.scope", "cpu.stat", STRV_MAKE("usage_usec"), &val) == 0);
+        free(val);
+
+        assert_se(cg_get_keyed_attribute_graceful("cpu", "/init.scope", "cpu.stat", STRV_MAKE("usage_usec"), &val) == 1);
         log_info("cpu /init.scope cpu.stat [usage_usec] → \"%s\"", val);
 
         assert_se(cg_get_keyed_attribute("cpu", "/init.scope", "cpu.stat", STRV_MAKE("usage_usec", "no_such_attr"), vals3) == -ENXIO);
+        assert_se(cg_get_keyed_attribute_graceful("cpu", "/init.scope", "cpu.stat", STRV_MAKE("usage_usec", "no_such_attr"), vals3) == 1);
+        assert(vals3[0] && !vals3[1]);
+        free(vals3[0]);
 
         assert_se(cg_get_keyed_attribute("cpu", "/init.scope", "cpu.stat", STRV_MAKE("usage_usec", "usage_usec"), vals3) == -ENXIO);
+        assert_se(cg_get_keyed_attribute_graceful("cpu", "/init.scope", "cpu.stat", STRV_MAKE("usage_usec", "usage_usec"), vals3) == 1);
+        assert(vals3[0] && !vals3[1]);
+        free(vals3[0]);
 
         assert_se(cg_get_keyed_attribute("cpu", "/init.scope", "cpu.stat",
                                          STRV_MAKE("usage_usec", "user_usec", "system_usec"), vals3) == 0);
+        for (i = 0; i < 3; i++)
+                free(vals3[i]);
+
+        assert_se(cg_get_keyed_attribute_graceful("cpu", "/init.scope", "cpu.stat",
+                                         STRV_MAKE("usage_usec", "user_usec", "system_usec"), vals3) == 3);
         log_info("cpu /init.scope cpu.stat [usage_usec user_usec system_usec] → \"%s\", \"%s\", \"%s\"",
                  vals3[0], vals3[1], vals3[2]);
 
         assert_se(cg_get_keyed_attribute("cpu", "/init.scope", "cpu.stat",
                                          STRV_MAKE("system_usec", "user_usec", "usage_usec"), vals3a) == 0);
+        for (i = 0; i < 3; i++)
+                free(vals3a[i]);
+
+        assert_se(cg_get_keyed_attribute_graceful("cpu", "/init.scope", "cpu.stat",
+                                         STRV_MAKE("system_usec", "user_usec", "usage_usec"), vals3a) == 3);
         log_info("cpu /init.scope cpu.stat [system_usec user_usec usage_usec] → \"%s\", \"%s\", \"%s\"",
                  vals3a[0], vals3a[1], vals3a[2]);