From e1a27d486c2374f46abd264f3fd6561815155ebd Mon Sep 17 00:00:00 2001
From: John Crispin <blogic@openwrt.org>
Date: Fri, 28 Nov 2014 01:27:57 +0100
Subject: add support for zram compressed tmpfs

Signed-off-by: John Crispin <blogic@openwrt.org>
---
 initd/zram.c | 128 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 128 insertions(+)
 create mode 100644 initd/zram.c

(limited to 'initd/zram.c')

diff --git a/initd/zram.c b/initd/zram.c
new file mode 100644
index 0000000..4dc1d2e
--- /dev/null
+++ b/initd/zram.c
@@ -0,0 +1,128 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <fcntl.h>
+
+#include <sys/utsname.h>
+#include <sys/mount.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <sys/stat.h>
+
+#include "../log.h"
+
+#include "init.h"
+
+#define KB(x) (x * 1024)
+
+#define ZRAM_MOD_PATH "/lib/modules/%s/zram.ko"
+#define EXT4_MOD_PATH "/lib/modules/%s/ext4.ko"
+
+static long
+proc_meminfo(void)
+{
+	FILE *fp;
+	char line[256];
+	char *key;
+	long val = KB(16);
+
+	fp = fopen("/proc/meminfo", "r");
+	if (fp == NULL) {
+		ERROR("Can't open /proc/meminfo: %s\n", strerror(errno));
+		return errno;
+	}
+
+	while (fgets(line, sizeof(line), fp)) {
+		key = strtok(line, ":");
+		if (strcasecmp(key, "MemTotal"))
+			continue;
+		val = atol(strtok(NULL, " kB\n"));
+		break;
+	}
+	fclose(fp);
+
+	if (val > KB(32))
+		val = KB(16);
+
+	return val;
+}
+
+static int
+early_insmod(char *module)
+{
+	pid_t pid = fork();
+
+	if (!pid) {
+		char *modprobe[] = { "/usr/sbin/modprobe", NULL, NULL };
+		char *path;
+		struct utsname ver;
+
+		uname(&ver);
+		path = alloca(sizeof(module) + strlen(ver.release) + 1);
+		sprintf(path, module, ver.release);
+		modprobe[1] = path;
+		execvp(modprobe[0], modprobe);
+		ERROR("Can't exec /usr/sbin/modprobe\n");
+		exit(-1);
+	}
+
+	if (pid <= 0) {
+		ERROR("Can't exec /usr/sbin/modprobe\n");
+		return -1;
+	} else {
+		waitpid(pid, NULL, 0);
+	}
+
+	return 0;
+}
+
+
+int
+mount_zram_on_tmp(void)
+{
+	char *mkfs[] = { "/usr/sbin/mkfs.ext4", "-b", "4096", "-F", "-L", "TEMP", "-m", "0", "/dev/zram0", NULL };
+	FILE *fp;
+	long zramsize;
+	pid_t pid;
+	int ret;
+
+	if (early_insmod(ZRAM_MOD_PATH) || early_insmod(EXT4_MOD_PATH)) {
+		ERROR("failed to insmod zram support\n");
+		return -1;
+	}
+
+	mkdev("*", 0600);
+
+	zramsize = proc_meminfo() / 2;
+	fp = fopen("/sys/block/zram0/disksize", "r+");
+	if (fp == NULL) {
+		ERROR("Can't open /sys/block/zram0/disksize: %s\n", strerror(errno));
+		return errno;
+	}
+	fprintf(fp, "%ld", KB(zramsize));
+	fclose(fp);
+
+	pid = fork();
+	if (!pid) {
+		execvp(mkfs[0], mkfs);
+		ERROR("Can't exec /sbin/mkfs.ext4\n");
+		exit(-1);
+	} else if (pid <= 0) {
+		ERROR("Can't exec /sbin/mkfs.ext4\n");
+		return -1;
+	} else {
+		waitpid(pid, NULL, 0);
+	}
+
+	ret = mount("/dev/zram0", "/tmp", "ext4", MS_NOSUID | MS_NODEV | MS_NOATIME, "errors=continue,noquota");
+	if (ret < 0) {
+		ERROR("Can't mount /dev/zram0 on /tmp: %s\n", strerror(errno));
+		return errno;
+	}
+
+	LOG("Using up to %ld kB of RAM as ZRAM storage on /mnt\n", zramsize);
+
+	return 0;
+}
-- 
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