iscsid/iscsiuio: fix OOM adjustment (#377)

* iscsid/iscsiuio: fix OOM adjustment

For both the iscsid and iscsiuio daemons, they try to modify
nice value and OOM adjustment value, so they have priority
and will not be killed by the OOM-killer.

But the code incorrectly set the value to "-17" for modern
linux systems, when the maximum is actually "-1000". While
making the changes, use "/proc/self/..." instead of
"/proc/<PID>/...", so we don't have to use getpid() nor
print out the pathname. Now we either write "-16" to
the old interface, "-1000" to the new interface, or we
print a warning.

Several "log_debug()" calls that should have been warnings
are changed to "log_warning()" calls in iscsid.

* iscsid/iscsiuio: fix OOM adjustment value for older systems

On older linux system, "-17" is the maximum, not "-16".

3 files changed, 56 insertions, 41 deletions

diff --git a/iscsiuio/src/unix/main.c b/iscsiuio/src/unix/main.c
index 0c9ad49..9a2a60c 100644
--- a/iscsiuio/src/unix/main.c
+++ b/iscsiuio/src/unix/main.c
@@ -201,35 +201,43 @@ static void daemon_init()
 	close(fd);
 }
 
-#define ISCSI_OOM_PATH_LEN 48
-
+/*
+ * make a best effort at ajusting our nice
+ * score and our OOM score, but it's not considered
+ * fatal if either adjustment fails
+ *
+ * return 0 on success of OOM adjustment
+ */
 int oom_adjust(void)
 {
 	int fd;
-	char path[ISCSI_OOM_PATH_LEN];
-	struct stat statb;
+	int res = 0;
 
-	if (nice(-10) < 0)
+	errno = 0;
+	if (nice(-10) == -1 && errno != 0)
 		LOG_DEBUG("Could not increase process priority: %s",
 			  strerror(errno));
 
-	snprintf(path, ISCSI_OOM_PATH_LEN, "/proc/%d/oom_score_adj", getpid());
-	if (stat(path, &statb)) {
-		/* older kernel so use old oom_adj file */
-		snprintf(path, ISCSI_OOM_PATH_LEN, "/proc/%d/oom_adj",
-			 getpid());
-	}
-	fd = open(path, O_WRONLY);
-	if (fd < 0)
+	/*
+	 * try the modern method of adjusting our OOM score,
+	 * then try the old one, if that fails
+	 */
+	if ((fd = open("/proc/self/oom_score_adj", O_WRONLY)) >= 0) {
+		if ((res = write(fd, "-1000", 5)) < 0)
+			LOG_DEBUG("Could not set /proc/self/oom_score_adj to -1000: %s",
+				strerror(errno));
+	} else if ((fd = open("/proc/self/oom_adj", O_WRONLY)) >= 0) {
+		if ((res = write(fd, "-17", 3)) < 0)
+			LOG_DEBUG("Could not set /proc/self/oom_adj to -16: %s",
+				strerror(errno));
+	} else
 		return -1;
-	if (write(fd, "-16", 3) < 0) /* for 2.6.11 */
-		LOG_DEBUG("Could not set oom score to -16: %s",
-			  strerror(errno));
-	if (write(fd, "-17", 3) < 0) /* for Andrea's patch */
-		LOG_DEBUG("Could not set oom score to -17: %s",
-			  strerror(errno));
+
 	close(fd);
-	return 0;
+	if (res < 0)
+		return res;
+	else
+		return 0;
 }
 
 
diff --git a/usr/iscsi_util.c b/usr/iscsi_util.c
index db1dc37..2f1de3e 100644
--- a/usr/iscsi_util.c
+++ b/usr/iscsi_util.c
@@ -65,36 +65,43 @@ void daemon_init(void)
 	close(fd);
 }
 
-#define ISCSI_OOM_PATH_LEN 48
-
+/*
+ * make a best effort at ajusting our nice
+ * score and our OOM score, but it's not considered
+ * fatal if either adjustment fails
+ *
+ * return 0 on success of OOM adjustment
+ */
 int oom_adjust(void)
 {
 	int fd;
-	char path[ISCSI_OOM_PATH_LEN];
-	struct stat statb;
+	int res = 0;
 
 	errno = 0;
 	if (nice(-10) == -1 && errno != 0)
-		log_debug(1, "Could not increase process priority: %s",
+		log_warning("Could not increase process priority: %s",
 			  strerror(errno));
 
-	snprintf(path, ISCSI_OOM_PATH_LEN, "/proc/%d/oom_score_adj", getpid());
-	if (stat(path, &statb)) {
-		/* older kernel so use old oom_adj file */
-		snprintf(path, ISCSI_OOM_PATH_LEN, "/proc/%d/oom_adj",
-			 getpid());
-	}
-	fd = open(path, O_WRONLY);
-	if (fd < 0)
+	/*
+	 * try the modern method of adjusting our OOM score,
+	 * then try the old one, if that fails
+	 */
+	if ((fd = open("/proc/self/oom_score_adj", O_WRONLY)) >= 0) {
+		if ((res = write(fd, "-1000", 5)) < 0)
+			log_warning("Could not set /proc/self/oom_score_adj to -1000: %s",
+				strerror(errno));
+	} else if ((fd = open("/proc/self/oom_adj", O_WRONLY)) >= 0) {
+		if ((res = write(fd, "-17", 3)) < 0)
+			log_warning("Could not set /proc/self/oom_adj to -16: %s",
+				strerror(errno));
+	} else
 		return -1;
-	if (write(fd, "-16", 3) < 0) /* for 2.6.11 */
-		log_debug(1, "Could not set oom score to -16: %s",
-			  strerror(errno));
-	if (write(fd, "-17", 3) < 0) /* for Andrea's patch */
-		log_debug(1, "Could not set oom score to -17: %s",
-			  strerror(errno));
+
 	close(fd);
-	return 0;
+	if (res < 0)
+		return res;
+	else
+		return 0;
 }
 
 char*
diff --git a/usr/iscsid.c b/usr/iscsid.c
index 8441037..0cf2368 100644
--- a/usr/iscsid.c
+++ b/usr/iscsid.c
@@ -621,7 +621,7 @@ int main(int argc, char *argv[])
 
 	/* oom-killer will not kill us at the night... */
 	if (oom_adjust())
-		log_debug(1, "can not adjust oom-killer's pardon");
+		log_warning("Cannot adjust oom-killer's pardon");
 
 	/* we don't want our active sessions to be paged out... */
 	if (mlockall(MCL_CURRENT | MCL_FUTURE)) {