libcgroup: Better error reporting for libcgroup

From: Ankita Garg <ankita@in.ibm.com>

This patch adds human readable error messages to the configuration parser.
The error lookup is implemented as a simple table, indexed by the error.

TODO: Save errno at ECGOTHER and pass it down as cgroup_lasterror.

Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Signed-off-by: Ankita Garg <ankita@in.ibm.com>
Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>


git-svn-id: https://libcg.svn.sourceforge.net/svnroot/libcg/trunk@228 4f4bb910-9a46-0410-90c8-c897d4f1cd53

4 files changed, 45 insertions, 2 deletions

diff --git a/api.c b/api.c
index 4efb390..b5bb8ee 100644
--- a/api.c
+++ b/api.c
@@ -40,6 +40,7 @@
 #include <ctype.h>
 #include <pwd.h>
 #include <libgen.h>
+#include <assert.h>
 
 #ifndef PACKAGE_VERSION
 #define PACKAGE_VERSION 0.01
@@ -70,6 +71,31 @@ static struct cgroup_rule_list trl;
 /* Lock for the list of rules (rl) */
 static pthread_rwlock_t rl_lock = PTHREAD_RWLOCK_INITIALIZER;
 
+char *cgroup_strerror_codes[] = {
+	"Cgroup is not compiled in",
+	"Cgroup is not mounted",
+	"Cgroup does not exist",
+	"Cgroup has not been created",
+	"Cgroup one of the needed subsystems is not mounted",
+	"Cgroup, request came in from non owner",
+	"Cgroup controllers controllers are bound to different mount points",
+	"Cgroup, operation not allowed",
+	"Cgroup value set exceeds maximum",
+	"Cgroup controller already exists",
+	"Cgroup value already exists",
+	"Cgroup invalid operation",
+	"Cgroup, creation of controller failed",
+	"Cgroup operation failed",
+	"Cgroup not initialized",
+	"Cgroup trying to set value for control that does not exist",
+	"Cgroup generic error, see errno",
+	"Cgroup values are not equal",
+	"Cgroup controllers are different",
+	"Cgroup parsing failed",
+	"Cgroup, rules file does not exist",
+	"Cgroup mounting failed",
+};
+
 static int cg_chown_file(FTS *fts, FTSENT *ent, uid_t owner, gid_t group)
 {
 	int ret = 0;
@@ -2077,3 +2103,9 @@ cleanup_path:
 	free(path);
 	return ret;
 }
+
+char *cgroup_strerror(int code)
+{
+	assert((code >= ECGROUPNOTCOMPILED) && (code < ECGSENTINEL));
+	return cgroup_strerror_codes[code % ECGROUPNOTCOMPILED];
+}
diff --git a/cgconfig.c b/cgconfig.c
index fab3a72..043678a 100644
--- a/cgconfig.c
+++ b/cgconfig.c
@@ -61,8 +61,7 @@ int main(int argc, char *argv[])
 			if (ret) {
 				printf("Loading configuration file %s "
 					"failed, error: %s\n", filename,
-					strerror(errno));
-				printf("return code = %d\n", ret);
+					cgroup_strerror(ret));
 				exit(3);
 			}
 			return 0;
diff --git a/libcgroup.h b/libcgroup.h
index 2a93022..4fb99ff 100644
--- a/libcgroup.h
+++ b/libcgroup.h
@@ -94,6 +94,7 @@ enum cgroup_errors {
 	ECGROUPPARSEFAIL, /* Failed to parse rules configuration file. */
 	ECGROUPNORULES, /* Rules list does not exist. */
 	ECGMOUNTFAIL,
+	ECGSENTINEL,	/* Please insert further error codes above this */
 };
 
 #define CG_NV_MAX 100
@@ -187,6 +188,12 @@ int cgroup_init_rules_cache(void);
  */
 int cgroup_get_current_controller_path(pid_t pid, const char *controller,
 					char **current_path);
+/**
+ * Return error corresponding to @code in human readable format.
+ * @code: error code for which the corresponding error string is to be
+ * returned
+ */
+char *cgroup_strerror(int code);
 
 /* The wrappers for filling libcg structures */
 
diff --git a/libcgroup.map b/libcgroup.map
index 61ae3ba..3b55ff2 100644
--- a/libcgroup.map
+++ b/libcgroup.map
@@ -40,3 +40,8 @@ global:
 local:
 	*;
 };
+
+CGROUP_0.32.1 {
+global:
+	cgroup_strerror;
+} CGROUP_0.32;