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.

3 files changed, 53 insertions, 4 deletions

diff --git a/src/basic/cgroup-util.c b/src/basic/cgroup-util.c
index 33575e65ef..da4bd33d18 100644
--- a/src/basic/cgroup-util.c
+++ b/src/basic/cgroup-util.c
@@ -1684,12 +1684,13 @@ int cg_get_attribute_as_uint64(const char *controller, const char *path, const c
         return 0;
 }
 
-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;
@@ -1749,7 +1750,10 @@ 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++)
@@ -1759,6 +1763,9 @@ 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 237139fad0..6e05a8a5a1 100644
--- a/src/basic/cgroup-util.h
+++ b/src/basic/cgroup-util.h
@@ -180,9 +180,31 @@ int cg_pid_get_path(const char *controller, pid_t pid, char **path);
 
 int cg_rmdir(const char *controller, const char *path);
 
+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_get_attribute_as_uint64(const char *controller, const char *path, const char *attribute, uint64_t *ret);
 
diff --git a/src/test/test-cgroup-util.c b/src/test/test-cgroup-util.c
index daaffb5a06..5826d6ec28 100644
--- a/src/test/test-cgroup-util.c
+++ b/src/test/test-cgroup-util.c
@@ -384,22 +384,42 @@ 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]);