[LTP] [PATCH v3 1/5] API/cgroup: Add safe_cgroup_lines_scanf

[Richard Palethorpe]

Similar to file_lines_scanf. Allows us to read a particular key-value
pair from a controller file. Can replace kselftest's cg_read_key_*
when converting tests.

Signed-off-by: Richard Palethorpe <rpalethorpe@suse.com>
Reviewed-by: Cyril Hrubis <chrubis@suse.cz>
Reviewed-by: Petr Vorel <pvorel@suse.cz>
---

V3:
* Add permissions to open
* Add needs_root to avoid TBROK when creating the FSs

V2:
* Use all filesystems
* Add new EXP macro
* Switch to strtok_r
* Increase the margin of error for exfat and ext234
* Write to the file instead of reading to populate the page cache
  (allows it to work on tmpfs)

 include/tst_cgroup.h | 12 +++++++++++-
 lib/tst_cgroup.c     | 33 +++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/include/tst_cgroup.h b/include/tst_cgroup.h
index 632050e86..561216296 100644
--- a/include/tst_cgroup.h
+++ b/include/tst_cgroup.h
@@ -188,9 +188,19 @@ void safe_cgroup_printf(const char *const file, const int lineno,
 void safe_cgroup_scanf(const char *file, const int lineno,
 		       const struct tst_cgroup_group *const cg,
 		       const char *const file_name,
-		       const char *fmt, ...)
+		       const char *const fmt, ...)
 		       __attribute__ ((format (scanf, 5, 6), nonnull));
 
+#define SAFE_CGROUP_LINES_SCANF(cg, file_name, fmt, ...)		\
+	safe_cgroup_lines_scanf(__FILE__, __LINE__,			\
+				(cg), (file_name), (fmt), __VA_ARGS__)
+
+void safe_cgroup_lines_scanf(const char *const file, const int lineno,
+			     const struct tst_cgroup_group *const cg,
+			     const char *const file_name,
+			     const char *const fmt, ...)
+			__attribute__ ((format (scanf, 5, 6), nonnull));
+
 #define SAFE_CGROUP_OCCURSIN(cg, file_name, needle)		\
 	safe_cgroup_occursin(__FILE__, __LINE__,		\
 			     (cg), (file_name), (needle))
diff --git a/lib/tst_cgroup.c b/lib/tst_cgroup.c
index c08ff2f20..c78f28112 100644
--- a/lib/tst_cgroup.c
+++ b/lib/tst_cgroup.c
@@ -1161,6 +1161,39 @@ void safe_cgroup_scanf(const char *const file, const int lineno,
 		 file_name, buf, fmt, ret, conv_cnt);
 }
 
+void safe_cgroup_lines_scanf(const char *const file, const int lineno,
+			     const struct tst_cgroup_group *const cg,
+			     const char *const file_name,
+			     const char *const fmt, ...)
+{
+	va_list va;
+	char buf[BUFSIZ];
+	ssize_t len = safe_cgroup_read(file, lineno,
+				       cg, file_name, buf, sizeof(buf));
+	const int conv_cnt = tst_count_scanf_conversions(fmt);
+	int ret = 0;
+	char *line, *buf_ptr;
+
+	if (len < 1)
+		return;
+
+	line = strtok_r(buf, "\n", &buf_ptr);
+	while (line && ret != conv_cnt) {
+		va_start(va, fmt);
+		ret = vsscanf(line, fmt, va);
+		va_end(va);
+
+		line = strtok_r(NULL, "\n", &buf_ptr);
+	}
+
+	if (conv_cnt == ret)
+		return;
+
+	tst_brk_(file, lineno, TBROK,
+		 "'%s': vsscanf('%s', '%s', ..): Less conversions than expected: %d != %d",
+		 file_name, buf, fmt, ret, conv_cnt);
+}
+
 int safe_cgroup_occursin(const char *const file, const int lineno,
 			 const struct tst_cgroup_group *const cg,
 			 const char *const file_name,
-- 
2.34.1