initd/zram.c

   1 #include <stdio.h>
   2 #include <unistd.h>
   3 #include <stdlib.h>
   4 #include <string.h>
   5 #include <errno.h>
   6 #include <fcntl.h>
   7
   8 #include <sys/utsname.h>
   9 #include <sys/mount.h>
  10 #include <sys/types.h>
  11 #include <sys/wait.h>
  12 #include <sys/stat.h>
  13
  14 #include "../log.h"
  15
  16 #include "init.h"
  17
  18 #define KB(x) (x * 1024)
  19
  20 #define ZRAM_MOD_PATH "/lib/modules/%s/zram.ko"
  21 #define EXT4_MOD_PATH "/lib/modules/%s/ext4.ko"
  22
  23 static long
  24 proc_meminfo(void)
  25 {
  26         FILE *fp;
  27         char line[256];
  28         char *key;
  29         long val = KB(16);
  30
  31         fp = fopen("/proc/meminfo", "r");
  32         if (fp == NULL) {
  33                 ERROR("Can't open /proc/meminfo: %m\n");
  34                 return errno;
  35         }
  36
  37         while (fgets(line, sizeof(line), fp)) {
  38                 key = strtok(line, ":");
  39                 if (strcasecmp(key, "MemTotal"))
  40                         continue;
  41                 val = atol(strtok(NULL, " kB\n"));
  42                 break;
  43         }
  44         fclose(fp);
  45
  46         if (val > KB(32))
  47                 val = KB(32);
  48
  49         return val;
  50 }
  51
  52 static int
  53 early_insmod(char *module)
  54 {
  55         pid_t pid = fork();
  56         char *modprobe[] = { "/sbin/modprobe", NULL, NULL };
  57
  58         if (!pid) {
  59                 char *path;
  60                 struct utsname ver;
  61
  62                 uname(&ver);
  63                 path = alloca(strlen(module) + strlen(ver.release) + 1);
  64                 sprintf(path, module, ver.release);
  65                 modprobe[1] = path;
  66                 execvp(modprobe[0], modprobe);
  67                 ERROR("Can't exec %s\n", modprobe[0]);
  68                 exit(-1);
  69         }
  70
  71         if (pid <= 0) {
  72                 ERROR("Can't exec %s\n", modprobe[0]);
  73                 return -1;
  74         } else {
  75                 waitpid(pid, NULL, 0);
  76         }
  77
  78         return 0;
  79 }
  80
  81
  82 int
  83 mount_zram_on_tmp(void)
  84 {
  85         char *mkfs[] = { "/usr/sbin/mkfs.ext4", "-b", "4096", "-F", "-L", "TEMP", "-m", "0", "/dev/zram0", NULL };
  86         FILE *fp;
  87         long zramsize;
  88         pid_t pid;
  89         int ret;
  90
  91         if (early_insmod(ZRAM_MOD_PATH) || early_insmod(EXT4_MOD_PATH)) {
  92                 ERROR("failed to insmod zram support\n");
  93                 return -1;
  94         }
  95
  96         mkdev("*", 0600);
  97
  98         zramsize = proc_meminfo() / 2;
  99         fp = fopen("/sys/block/zram0/disksize", "r+");
 100         if (fp == NULL) {
 101                 ERROR("Can't open /sys/block/zram0/disksize: %m\n");
 102                 return errno;
 103         }
 104         fprintf(fp, "%ld", KB(zramsize));
 105         fclose(fp);
 106
 107         pid = fork();
 108         if (!pid) {
 109                 execvp(mkfs[0], mkfs);
 110                 ERROR("Can't exec %s\n", mkfs[0]);
 111                 exit(-1);
 112         } else if (pid <= 0) {
 113                 ERROR("Can't exec %s\n", mkfs[0]);
 114                 return -1;
 115         } else {
 116                 waitpid(pid, NULL, 0);
 117         }
 118
 119         ret = mount("/dev/zram0", "/tmp", "ext4", MS_NOSUID | MS_NODEV | MS_NOATIME, "errors=continue,noquota");
 120         if (ret < 0) {
 121                 ERROR("Can't mount /dev/zram0 on /tmp: %m\n");
 122                 return errno;
 123         }
 124
 125         LOG("Using up to %ld kB of RAM as ZRAM storage on /mnt\n", zramsize);
 126
 127         ret = chmod("/tmp", 01777);
 128         if (ret < 0) {
 129                 ERROR("Can't set /tmp mode to 1777: %m\n");
 130                 return errno;
 131         }
 132
 133         return 0;
 134 }