[LTP] [PATCH v1 2/3] tst_cgroup: Add safe_cg_open and safe_cg_fchown functions

[Yang Xu]

safe_cg_open is used to open the sub control's file ie cgroup.procs
and returns the fd.

safe_cg_fchown is used to use fchownat to change file's uid and gid.

Signed-off-by: Yang Xu <xuyang2018.jy@fujitsu.com>
---
 include/tst_cgroup.h | 15 +++++++++++++++
 lib/tst_cgroup.c     | 39 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/include/tst_cgroup.h b/include/tst_cgroup.h
index d06847cc6..292c9baa4 100644
--- a/include/tst_cgroup.h
+++ b/include/tst_cgroup.h
@@ -188,6 +188,21 @@ ssize_t safe_cg_read(const char *const file, const int lineno,
 			 char *const out, const size_t len)
 			 __attribute__ ((nonnull));
 
+#define SAFE_CG_OPEN(cg, file_name, flags)			\
+	safe_cg_open(__FILE__, __LINE__, (cg), (file_name), (flags))
+
+int safe_cg_open(const char *const file, const int lineno,
+		 const struct tst_cg_group *const cg,
+		 const char *const file_name, int flags);
+
+#define SAFE_CG_FCHOWN(cg, file_name, owner, group)		\
+	safe_cg_fchown(__FILE__, __LINE__,			\
+			   (cg), (file_name), (owner), (group))
+
+void safe_cg_fchown(const char *const file, const int lineno,
+		    const struct tst_cg_group *const cg,
+		    const char *const file_name, uid_t owner, gid_t group);
+
 #define SAFE_CG_PRINTF(cg, file_name, fmt, ...)			\
 	safe_cg_printf(__FILE__, __LINE__,				\
 			   (cg), (file_name), (fmt), __VA_ARGS__)
diff --git a/lib/tst_cgroup.c b/lib/tst_cgroup.c
index 1cfd79243..dedc0f65b 100644
--- a/lib/tst_cgroup.c
+++ b/lib/tst_cgroup.c
@@ -1297,6 +1297,45 @@ ssize_t safe_cg_read(const char *const file, const int lineno,
 	return read_ret;
 }
 
+int safe_cg_open(const char *const file, const int lineno,
+			const struct tst_cg_group *cg,
+			const char *const file_name, int flags)
+{
+	const struct cgroup_file *const cfile =
+		cgroup_file_find(file, lineno, file_name);
+	struct cgroup_dir *const *dir;
+	const char *alias;
+	int fd;
+
+	for_each_dir(cg, cfile->ctrl_indx, dir) {
+		alias = cgroup_file_alias(cfile, *dir);
+		if (!alias)
+			continue;
+
+		fd = safe_openat(file, lineno, (*dir)->dir_fd, alias, flags);
+	}
+
+	return fd;
+}
+
+void safe_cg_fchown(const char *const file, const int lineno,
+			const struct tst_cg_group *cg,
+			const char *const file_name, uid_t owner, gid_t group)
+{
+	const struct cgroup_file *const cfile =
+		cgroup_file_find(file, lineno, file_name);
+	struct cgroup_dir *const *dir;
+	const char *alias;
+
+	for_each_dir(cg, cfile->ctrl_indx, dir) {
+		alias = cgroup_file_alias(cfile, *dir);
+		if (!alias)
+			continue;
+
+		safe_fchownat(file, lineno, (*dir)->dir_fd, alias, owner, group, 0);
+	}
+}
+
 void safe_cg_printf(const char *const file, const int lineno,
 			const struct tst_cg_group *cg,
 			const char *const file_name,
-- 
2.27.0