[LTP] [PATCH v4 2/3] tst_cgroup: Add safe_cg_open and safe_cg_fchown functions

[Yang Xu]

safe_cg_open is used to open the sub controller's file ie cgroup.procs
and returns the opened fd number. The opened fd array is stored in
fds argument.

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

Reviewed-by: Richard Palethorpe <rpalethorpe@suse.com>
Signed-off-by: Yang Xu <xuyang2018.jy@fujitsu.com>
---
 include/tst_cgroup.h | 21 +++++++++++++++++++++
 lib/tst_cgroup.c     | 41 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 62 insertions(+)

diff --git a/include/tst_cgroup.h b/include/tst_cgroup.h
index d06847cc6..db959380f 100644
--- a/include/tst_cgroup.h
+++ b/include/tst_cgroup.h
@@ -89,6 +89,9 @@ enum tst_cg_ver {
 	TST_CG_V2 = 2,
 };
 
+/* This value is equal to ROOTS_MAX in tst_cgroup.c. */
+#define TST_CG_ROOTS_MAX 32
+
 /* Used to specify CGroup hierarchy configuration options, allowing a
  * test to request a particular CGroup structure.
  */
@@ -201,6 +204,24 @@ void safe_cg_printf(const char *const file, const int lineno,
 			const char *const fmt, ...)
 			__attribute__ ((format (printf, 5, 6), nonnull));
 
+#define SAFE_CG_OPEN(cg, file_name, flags, fds)			\
+	safe_cg_open(__FILE__, __LINE__, (cg), (file_name), (flags), (fds))
+
+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, int *fds)
+			__attribute__ ((nonnull));
+
+#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)
+			__attribute__ ((nonnull));
+
 #define SAFE_CG_SCANF(cg, file_name, fmt, ...)			\
 	safe_cg_scanf(__FILE__, __LINE__,				\
 			  (cg), (file_name), (fmt), __VA_ARGS__)
diff --git a/lib/tst_cgroup.c b/lib/tst_cgroup.c
index 1da3f0a5d..6c015e4f8 100644
--- a/lib/tst_cgroup.c
+++ b/lib/tst_cgroup.c
@@ -1326,6 +1326,47 @@ void safe_cg_printf(const char *const file, const int lineno,
 	}
 }
 
+int safe_cg_open(const char *const file, const int lineno,
+		      const struct tst_cg_group *cg,
+		      const char *const file_name, int flags, int *fds)
+{
+	const struct cgroup_file *const cfile =
+		cgroup_file_find(file, lineno, file_name);
+	struct cgroup_dir *const *dir;
+	const char *alias;
+	int i = 0;
+
+	for_each_dir(cg, cfile->ctrl_indx, dir) {
+		alias = cgroup_file_alias(cfile, *dir);
+		if (!alias)
+			continue;
+
+		fds[i++] = safe_openat(file, lineno, (*dir)->dir_fd, alias, flags);
+	}
+
+	return i;
+}
+
+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_scanf(const char *const file, const int lineno,
 		       const struct tst_cg_group *const cg,
 		       const char *const file_name,
-- 
2.27.0