api.c: Add function to build tasks/procs path

Replace the inline logic in multiple functions that concatenates
the path and cgroup v1 tasks file with a function -
cgroup_build_tasks_procs_path() - that works for both cgroup v1
and v2.  In the v1 case, it appends tasks, and in the v2 case, it
appends cgroup.procs.

Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>

diff --git a/src/api.c b/src/api.c
index 8d9c8d17f3ca2d6af0a8c5c1a419d5649751c60b..274718bbe8f4ed1985cdb8126eeddbbbab28ad75 100644 (file)
--- a/src/api.c
+++ b/src/api.c
@@ -1497,6 +1497,50 @@ char *cg_build_path(const char *name, char *path, const char *type)
        return path;
 }
 
+/**
+ * Build the path to the tasks or cgroup.procs file
+ *
+ * @param path Output variable that will contain the path.  Must be
+              of size FILENAME_MAX or larger
+ * @param path_sz Size of the path string
+ * @param cg_name Cgroup name
+ * @param ctrl_name Controller name
+ */
+STATIC int cgroup_build_tasks_procs_path(char * const path,
+                               size_t path_sz, const char * const cg_name,
+                               const char * const ctrl_name)
+{
+       enum cg_version_t version;
+       int err = ECGOTHER;
+
+       if (!cg_build_path(cg_name, path, ctrl_name))
+               goto error;
+
+       err = cgroup_get_controller_version(ctrl_name, &version);
+       if (err)
+               goto error;
+
+       switch (version) {
+       case CGROUP_V1:
+               strncat(path, "tasks", path_sz - strlen(path));
+               err = 0;
+               break;
+       case CGROUP_V2:
+               strncat(path, "cgroup.procs", path_sz - strlen(path));
+               err = 0;
+               break;
+       default:
+               err = ECGOTHER;
+               break;
+       }
+
+error:
+       if (err)
+               path[0] = '\0';
+
+       return err;
+}
+
 static int __cgroup_attach_task_pid(char *path, pid_t tid)
 {
        int ret = 0;
@@ -1559,10 +1603,12 @@ int cgroup_attach_task_pid(struct cgroup *cgroup, pid_t tid)
                pthread_rwlock_rdlock(&cg_mount_table_lock);
                for (i = 0; i < CG_CONTROLLER_MAX &&
                                cg_mount_table[i].name[0] != '\0'; i++) {
-                       if (!cg_build_path_locked(NULL, path,
-                                               cg_mount_table[i].name))
-                               continue;
-                       strncat(path, "/tasks", sizeof(path) - strlen(path));
+                       ret = cgroup_build_tasks_procs_path(path,
+                               sizeof(path), cgroup->name,
+                               cgroup->controller[i]->name);
+                       if (ret)
+                               return ret;
+
                        ret = __cgroup_attach_task_pid(path, tid);
                        if (ret) {
                                pthread_rwlock_unlock(&cg_mount_table_lock);
@@ -1580,10 +1626,12 @@ int cgroup_attach_task_pid(struct cgroup *cgroup, pid_t tid)
                }
 
                for (i = 0; i < cgroup->index; i++) {
-                       if (!cg_build_path(cgroup->name, path,
-                                       cgroup->controller[i]->name))
-                               continue;
-                       strncat(path, "/tasks", sizeof(path) - strlen(path));
+                       ret = cgroup_build_tasks_procs_path(path,
+                               sizeof(path), cgroup->name,
+                               cgroup->controller[i]->name);
+                       if (ret)
+                               return ret;
+
                        ret = __cgroup_attach_task_pid(path, tid);
                        if (ret)
                                return ret;

diff --git a/src/libcgroup-internal.h b/src/libcgroup-internal.h
index 38a17e0ab2513e60a7c19b9cb519ac9f2c2cea27..72ddc19ea6e56133127079ac77df53d5f11792f2 100644 (file)
--- a/src/libcgroup-internal.h
+++ b/src/libcgroup-internal.h
@@ -343,6 +343,10 @@ int cgroup_chown_chmod_tasks(const char * const cg_path,
 int cgroupv2_subtree_control(const char *path, const char *ctrl_name,
                             bool enable);
 
+int cgroup_build_tasks_procs_path(char * const path,
+                                 size_t path_sz, const char * const cg_name,
+                                 const char * const ctrl_name);
+
 #endif /* UNIT_TEST */
 
 __END_DECLS