dynamic_pager.tproj/dynamic_pager.c

   1 #define mig_external
   2
   3 #include <sys/mount.h>
   4 #include <sys/stat.h>
   5 #include <sys/sysctl.h>
   6 #include <stdio.h>
   7 #include <stdlib.h>
   8 #include <string.h>
   9 #include <unistd.h>
  10 #include <dirent.h>
  11
  12 /*
  13  * We don't exit with a non-zero status anywhere here for 2 reasons:
  14  * - the kernel can continue to create swapfiles in "/private/var/vm/swapfile<index>"
  15  * - we want this job to run only once at boot and exit regardless of whether:
  16  *      -- it could clean up the swap directory
  17  *      -- it could set the prefix for the swapfile name.
  18  */
  19
  20 static void
  21 clean_swap_directory(const char *path)
  22 {
  23         DIR *dir;
  24         struct dirent *entry;
  25         char buf[1024];
  26
  27         dir = opendir(path);
  28         if (dir == NULL) {
  29                 fprintf(stderr,"dynamic_pager: cannot open swap directory %s\n", path);
  30                 exit(0);
  31         }
  32
  33         while ((entry = readdir(dir)) != NULL) {
  34                 if (entry->d_namlen>= 4 && strncmp(entry->d_name, "swap", 4) == 0) {
  35                         snprintf(buf, sizeof buf, "%s/%s", path, entry->d_name);
  36                         unlink(buf);
  37                 }
  38         }
  39
  40         closedir(dir);
  41 }
  42
  43 int
  44 main(int argc, char **argv)
  45 {
  46         int ch;
  47         static char tmp[1024];
  48         struct statfs sfs;
  49         char *q;
  50         char fileroot[512];
  51
  52         seteuid(getuid());
  53         fileroot[0] = '\0';
  54
  55         while ((ch = getopt(argc, argv, "F:")) != EOF) {
  56                 switch((char)ch) {
  57
  58                 case 'F':
  59                         strncpy(fileroot, optarg, 500);
  60                         break;
  61
  62                 default:
  63                         (void)fprintf(stderr,
  64                             "usage: dynamic_pager [-F filename]\n");
  65                         exit(0);
  66                 }
  67         }
  68
  69         /*
  70          * set vm.swapfileprefix if a fileroot was passed from the command
  71          * line, otherwise get the value from the kernel
  72          */
  73         if (fileroot[0] != '\0') {
  74                 if (sysctlbyname("vm.swapfileprefix", NULL, 0, fileroot, sizeof(fileroot)) == -1) {
  75                         perror("Failed to set swapfile name prefix");
  76                 }
  77         } else {
  78                 size_t fileroot_len = sizeof(fileroot);
  79                 if (sysctlbyname("vm.swapfileprefix", fileroot, &fileroot_len, NULL, 0) == -1) {
  80                         perror("Failed to get swapfile name prefix");
  81                         /*
  82                          * can't continue without a fileroot
  83                          */
  84                         return (0);
  85                 }
  86         }
  87
  88         /*
  89          * get rid of the filename at the end of the swap file specification
  90          * we only want the portion of the pathname that should already exist
  91          */
  92         strcpy(tmp, fileroot);
  93         if ((q = strrchr(tmp, '/')))
  94                 *q = 0;
  95
  96         /*
  97          * Remove all files in the swap directory.
  98          */
  99         clean_swap_directory(tmp);
 100
 101         if (statfs(tmp, &sfs) == -1) {
 102                 /*
 103                  * Setup the swap directory.
 104                  */
 105
 106                 if (mkdir(tmp, 0755) == -1) {
 107                         (void)fprintf(stderr, "dynamic_pager: cannot create swap directory %s\n", tmp);
 108                 }
 109         }
 110
 111         chown(tmp, 0, 0);
 112
 113         return (0);
 114 }