libcgroup: Introduce post order walk

With the introduction of the flags, we now actually make use of them.
This patch adds a post mode and modifies the test case to also do a post
order walk.

Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Acked-by: Bharata B Rao <bharata@linux.vnet.ibm.com>

3 files changed, 41 insertions, 4 deletions

diff --git a/src/api.c b/src/api.c
index f746bb2..2facfc8 100644
--- a/src/api.c
+++ b/src/api.c
@@ -2212,7 +2212,7 @@ int cgroup_get_last_errno()
 
 
 static int cg_walk_node(FTS *fts, FTSENT *ent, const int depth,
-			struct cgroup_file_info *info)
+			struct cgroup_file_info *info, int dir)
 {
 	int ret = 0;
 
@@ -2236,12 +2236,15 @@ static int cg_walk_node(FTS *fts, FTSENT *ent, const int depth,
 		errno = ent->fts_errno;
 		break;
 	case FTS_D:
-		info->type = CGROUP_FILE_TYPE_DIR;
+		if (dir & CGROUP_WALK_TYPE_PRE_DIR)
+			info->type = CGROUP_FILE_TYPE_DIR;
 		break;
 	case FTS_DC:
 	case FTS_NSOK:
 	case FTS_NS:
 	case FTS_DP:
+		if (dir & CGROUP_WALK_TYPE_POST_DIR)
+			info->type = CGROUP_FILE_TYPE_DIR;
 		break;
 	case FTS_F:
 		info->type = CGROUP_FILE_TYPE_FILE;
@@ -2272,7 +2275,9 @@ int cgroup_walk_tree_next(const int depth, void **handle,
 		return ECGEOF;
 	if (!base_level && depth)
 		base_level = ent->fts_level + depth;
-	ret = cg_walk_node(entry->fts, ent, base_level, info);
+
+	ret = cg_walk_node(entry->fts, ent, base_level, info, entry->flags);
+
 	*handle = entry;
 	return ret;
 }
@@ -2326,6 +2331,8 @@ int cgroup_walk_tree_begin(char *controller, char *base_path, const int depth,
 		return ECGOTHER;
 	}
 
+	entry->flags |= CGROUP_WALK_TYPE_PRE_DIR;
+
 	*base_level = 0;
 	cg_path[0] = full_path;
 	cg_path[1] = NULL;
@@ -2339,7 +2346,9 @@ int cgroup_walk_tree_begin(char *controller, char *base_path, const int depth,
 	}
 	if (!*base_level && depth)
 		*base_level = ent->fts_level + depth;
-	ret = cg_walk_node(entry->fts, ent, *base_level, info);
+
+	ret = cg_walk_node(entry->fts, ent, base_level, info, entry->flags);
+
 	*handle = entry;
 	return ret;
 }
diff --git a/src/libcgroup.map b/src/libcgroup.map
index 8d330e6..0748bb3 100644
--- a/src/libcgroup.map
+++ b/src/libcgroup.map
@@ -62,6 +62,7 @@ global:
 	cgroup_read_stats_begin;
 	cgroup_read_stats_next;
 	cgroup_read_stats_end;
+	cgroup_walk_tree_set_flags;
 	cgroup_get_controller;
 	cgroup_get_uid_gid_from_procfs;
 } CGROUP_0.33;
diff --git a/tests/walk_test.c b/tests/walk_test.c
index 2e16ecd..e09f705 100644
--- a/tests/walk_test.c
+++ b/tests/walk_test.c
@@ -41,6 +41,7 @@ int main(int argc, char *argv[])
 		exit(EXIT_FAILURE);
 	}
 	strcpy(root, info.full_path);
+	printf("Begin pre-order walk\n");
 	printf("root is %s\n", root);
 	visit_node(&info, root);
 	while ((ret = cgroup_walk_tree_next(0, &handle, &info, lvl)) !=
@@ -49,6 +50,32 @@ int main(int argc, char *argv[])
 	}
 	cgroup_walk_tree_end(&handle);
 
+	printf("pre-order walk finished\n");
+	ret = cgroup_walk_tree_begin(controller, "/", 0, &handle, &info, &lvl);
+
+	if (ret != 0) {
+		fprintf(stderr, "Walk failed\n");
+		exit(EXIT_FAILURE);
+	}
+
+	ret = cgroup_walk_tree_set_flags(&handle, CGROUP_WALK_TYPE_POST_DIR);
+
+	if (ret) {
+		fprintf(stderr, "Walk failed with %s\n", cgroup_strerror(ret));
+		exit(EXIT_FAILURE);
+	}
+
+	strcpy(root, info.full_path);
+	printf("Begin post-order walk\n");
+	printf("root is %s\n", root);
+	visit_node(&info, root);
+	while ((ret = cgroup_walk_tree_next(0, &handle, &info, lvl)) !=
+			ECGEOF) {
+		visit_node(&info, root);
+	}
+	cgroup_walk_tree_end(&handle);
+	printf("post order walk finished\n");
+
 	ret = cgroup_walk_tree_begin(controller, "/a", 2, &handle, &info, &lvl);
 
 	if (ret != 0) {